ALBERT

Description: The search for novel chemical architectures displaying improved biological properties is a never-ending synthetic challenge. In this context many new test structures are often conceived by selecting and replicating specific design elements from naturally occurring molecules and displaying them in an alternative format by way of a new chemical assembly. Constructing these newly designed compounds can be a timely and expensive process especially when a large quantity of the target material is required for physiochemical and property testing. To permit easier scale up and safer working practice many chemical researchers are employing flow chemistry approaches to aid in their synthesis challenges. Herein we report on the preparation of a key spirocyclic lactone using flow based reaction processing techniques.

Description: Mass transfer from single CO 2 Taylor bubbles in vertical mini channels was measured for channel hydraulic diameters, D h , from 5.5 to 8.0 mm. The effects of channel geometries on the mass transfer were also investigated by using square ducts and circular pipes. Bubble rising velocities, v B , in the ducts were much faster than those in the pipes due to large liquid flow areas in the corners of the ducts. The values of mass transfer coefficients, k L , in the pipes were almost the same as those in the ducts, in spite of a large difference in v B . Sherwood numbers, Sh D , using D h as a characteristic length are well correlated in terms of the Eötvös number. The proposed Sh D correlation can well predict a long-term dissolution process of a Taylor bubble.

Description: The phase-field method coupled with the Navier-Stokes equations is a rather new approach for scale-resolving numerical simulation of interfacial two-phase flows. The intention is to implement it as finite-volume method in the open source library for computational continuum mechanics OpenFOAM® and make it freely available. An overview on the governing equations is given and the numerical method is shortly discussed. The focus is on application and validation of the code for some fundamental wetting phenomena, namely the capillary rise in a narrow channel and the spreading of a droplet on a flat surface, which is chemically homogeneous or regularly patterned. The numerical results on static meshes agree well with analytical solutions and experimental/numerical results from literature. Also, first 3D finite-volume simulations with adaptive mesh refinement near the interface are presented as a key element to achieve CPU-time efficient simulations. A phase-field method for interface resolving numerical simulations of two-phase flows is presented and implemented in OpenFOAM®. The method is validated for several capillary flows with moving contact lines and is used to study dynamic droplet spreading on a flat surface by three-dimensional simulations with adaptive mesh refinement near the interface.

Description: The influence of water on the catalysis of biphasic Heck alkynylation, a family of palladium-catalyzed carbon-carbon bond formations, was investigated. Kinetic theory derived from Hatta moduli and pseudo-stationary-state approximations discovered that water, in coordination, reductive elimination, and product dissociation reaction steps of the deprotonation catalytic cycle, increases Gibbs energy barriers compared to values previously estimated by density functional theory calculations of purely organic syntheses involving an aryl iodide. On the contrary, water reduces the energy barrier of reductive elimination in the carbopalladation catalytic cycle. Quantum tunneling in proton transfer mechanism might account for the change. Water also influenced the rate-determining steps of the catalytic cycles, and its existence potentially switches the cross-coupling’s mechanism from deprotonation, previously thought to govern the reaction, to carbopalladation. Carbopalladation theory identified the ~35% of the Pd wasted during synthesis was ~10% greater than the amount predicted by deprotonation. Our discoveries enabled E-factor predictions that could someday help reduce chemical wastes generated during materials, natural products, and pharmaceutical manufactures. Theoretical groundwork is laid that enables data-driven research in the academic laboratory and data-driven development by the process chemist.

Description: A continuous process to produce carbon supported platinum catalysts by polyol reduction was examined. The reactant dispersion was rapidly heated up to reaction temperature while flowing through a directly electrically heated tube followed by a downstream isothermic tubular reactor. Appropriate inner diameters corresponding to desired short heating-up times were calculated. A certain lower limit for the inner diameter is caused by temporary pluggings of particle agglomerates circumventing steady-state operation. Tube diameters were evaluated with respect to heating-up times and plugging. It was proved that with a tubular reactor a continuous preparation of carbon nanotube supported platinum catalysts with a low particle size and evenly distributed particles is possible.

Description: This work focussed on the mathematical modeling of the separation process in counter-current decanter centrifuges, taking the influence of the sediment build-up and the flow pattern into account. Thus far, separation processes in centrifuges are calculated by means of simplified empirical models based on the so-called sigma-theory. To reduce experimental effort, we have developed a new model, which describes the separation process by considering material functions for sedimentation and the gel point. In addition to that, an arising sediment build-up and a change in the flow conditions are taken into account. The conducted numerical simulations are validated by experiments. Simplified models such as the sigma theory usually depend on experimental data of industrial machines. Our approach shows an enhanced accuracy while not depending on such information. The proposed simulation procedure is adaptable to other types of decanter centrifuges such as co-current machines.

Description: Catalyzed reaction of sulfite with oxygen is often used by industry for corrosion protection by chemical deoxygenation. The same reaction system is considered very important as a part of atmospheric chemistry due to SO2 immission modeling. In these applications, reaction kinetic data are of crucial importance. In deoxygenation, low concentrations of sulfite close to the stoichiometric ratio to oxygen are being used. Unfortunately, the values of kinetic constants for the reaction are sparse.The reaction kinetics was investigated in a rapid-mixing apparatus, where air or pure oxygen saturated solution containing the catalyst was mixed with aqueous sulfite solution. Mixing ratios with stoichiometric excess of dissolved oxygen were tested.Analysis of literature data suggests that the reaction is of 1.5 order in sulfite, 0 order in oxygen and 0.5 order in cobalt(II) catalyst. These reaction orders had been confirmed in the concentration range tested. The apparent kinetic constant and activation energy are also presented. Crucial importance of proper mixing of the two reacting solutions is reported, which was revealed during the development of the precise experimental technique providing reliable kinetic data.

Description: Inhibitory effects of high glucose and ethanol concentrations on ethanol production from wheat enzymatic hydrolysate by zygomycetes fungus Mucor hiemalis were investigated and modeled. Ethanol yield was decreased by increasing glucose concentration from 70 to 120 g.l -1 . Among different kinetic models, i.e., linear, Emerson, and modified Williams, modified Williams model was successfully described the fungal growth kinetics. Considering the inhibitory effect of glucose, a new model was developed for describing the rate of ethanol production. Moreover, the inhibitory effect of ethanol on ethanol yield, Y p/x , was modeled. The model prediction was successfully covered the experimental data.

Description: In this study experimental mass transfer data and literature data of airlift loop reactors are analyzed concerning an effect of gas-phase residence time on the volumetric mass transfer coefficient k L a. It becomes evident that a neglect of the oxygen depletion can be regarded as a diminishment of the mass transfer driving force. The latter is found to be an important cause of the mass transfer dependency on the actual apparatus height of airlift loop reactors. Therefore a new correlation is presented which describes the volumetric mass transfer coefficients of airlift loop reactors by including the effect of gas-phase transient component concentration depletion. In this work two geometrically similar experimental apparatuses of different absolute size are utilized. Both of them are driven as airlift loop reactors with aerated concentric draft tube. The operating method is schematically illustrated in Fig. 3. The essential geometric data of the reactors is listed in Tab. 1.

Description: Monolithic honeycomb reactors are characterized by small parallel channels, which make them an interesting approach to be applied as microstructured reactors. Besides the established manufacturing of ceramic honeycombs, these structures exhibit excellent mass transfer characteristics for multiphase reactions combined with degrees of freedom in the structural design. In this contribution the potential of monolithic honeycomb reactors operated in the beneficial slug flow regime is evaluated for heterogeneously catalyzed gas-liquid reactions. Therefore, results of the Fischer-Tropsch synthesis and hydrogenation of glucose to sorbitol were analyzed in order to obtain a more generalized picture of the interaction between mass transfer and reaction in small channels operated in multiphase flow.

Description: The concept of a multi-stage microstructured (MM) reactor has been tested in the bench-scale rig for combined steam and CO 2 reforming of methane (RM). In this reactor type the RM reaction is carried out in a series of adiabatic catalytic reaction steps with heat supply through fin-plate heat exchangers placed between the stages. RM reaction has been performed over a rhodium based catalyst in form of pellets. The experimental results have been described with a reaction engineering model that can be used as basis for model-supported scale-up. This paper describes an intermediate step in the development of the integrated reactor for thermal integration of oxidative coupling and reforming of methane. Conversion and yield near thermodynamical equilibrium have been achieved. Experiments confirmed advantages of the MM reactor against wall-coated micro reactors.

Description: This short review describes photocatalytic vs photosensitizing materials to be used respectively for gas-phase photooxidation and photo-oxygenation. The reactive oxygen species specific to photocatalysis and to photosensitization are summarized. Various kinds of gas-phase reactors and of photocatalytic materials are described in order to illustrate the great number of possible configurations and conditions of use. Some efforts towards standardization of gas-phase photocatalytic reactors devoted to indoor- or outdoor-air treatment are mentioned. Some examples of use of singlet oxygen in solvent-free photooxygenation reaction of volatile sulfides are given together with the properties of silica-based photosensitizing materials.

Description: Fluorine and fluorine-containing groups are omnipresent in pharmaceuticals, agrochemicals and many other high-value chemical products like liquid crystals and organic electronics. The unique properties of fluorine resulting from its tremendously high electronegativity make this element a key player in the quest of enabling new and advanced qualities for chemical compounds and materials. With the advent of fluorinating reagents a great diversity of synthetic methodologies has been developed to incorporate fluorine or fluorine-containing groups into small molecules with high conversion and selectivity. Especially photochemically catalyzed fluorination reactions proved their potential for the synthesis of fluorine-containing fine chemicals due to their mild reaction conditions. This tutorial review gives an overview of recently published synthesis strategies that use (visible-) light-absorbing catalysts for the activation of fluorinating reagents. A special focus is made on the use of continuous-flow microreactors for photochemically catalyzed fluorination reactions due to the excellent utilization of this reactor equipment for photochemistry.

Description: This manuscript addresses the evaluation of photocatalytic efficiency using Quantum Yields (QY) and the “Photochemical Thermodynamic Efficiency Factor” (PTEF). While the QY can be considered as an early photocatalytic reactor efficiency factor, developed in the 80’s, the PTEF was first introduced by Serrano and de Lasa in 1997 [29]. The PTEF allows establishing reactor efficiency as the ratio of utilized enthalpy for the formation of consumed OH • free radicals over the absorbed photon energy. In all cases, a key consideration for the evaluation of efficiency factors is the establishment of macroscopic energy balances together with an accurate assessment of evolved and absorbed photons. Of considerable help, as well, are the experimental devices developed at the Chemical Reactor Engineering Centre (CREC)-University of Western Ontario laboratories. Furthermore, photoconversion kinetics is a required information for the calculation of the OH • consumption rates and the establishment of the related kinetic parameters. In this respect, de Lasa et al (2005) [6] postulated a unified “in series-parallel” model for the kinetics in photocatalytic conversion. Until today, both PTEFs and QYs have been used by CREC-UWO researchers for efficiency calculations in photocatalytic reactors for the decontamination of air, water and hydrogen production. This methodology is very relevant, in particular, for the assessment of the effects of reactor scale, reactor configuration, irradiation source, type of photocatalyst and model pollutant compounds.

Description: Photoinitiated crosslinking of multifunctional acrylic esters in polymeric binders was investigated based on digital imaging using the Computer to Plate (CtP) technology applying laser exposure at 830 nm in the near infrared (NIR). All coating components were applied as thin double layer film on Al-plates with an anodized surface. Materials exposed exhibit a sensitivity between 30-100 mJ/cm 2 . Processing of the exposed materials occurred in a weak aqueous alkaline bath. Generation of initiating radicals occurs by electron transfer from the excited state of the NIR-sensitizer to the radical generator – an onium salt. Several onium salts with distinct cation and anion pattern were synthesized. Iodonium salts derived from several borates and those with the bis(trifluoromethylsulfonyl)imide anion resulted in lithographic materials with high sensitivity. Photoinduced electron transfer plays a major function to generate initiating radicals by a sensitized mechanism but thermal events also influence sensitivity of the coating. Particular the radiationless deactivation of the NIR-sensitizer possesses a major function for selective release of heat. Internal conversion (〉85%) was the major deactivation pathway while a certain fraction of NIR-dye fluorescence (〈15%) was also available. Moreover, a line shape focused laser system with emission in the NIR (808 nm) was successfully used to bake the materials. This was initiated by the absorption of the NIR-dye embedded in the coating.

Description: The cover represents on opening window which represents the Novel Process Windows concept. Inside the window, a photomicroreactor can be seen. In photochemistry, photons are used to activate organic substrates for reactions. More information on the photomicroreactor design and its application can be found in the paper by Su et al. Yuanhai Su, Ali Talla, Volker Hessel, and Timothy Noël Controlled Photocatalytic Aerobic Oxidation of Thiols to Disulfides in an Energy-Efficient Photomicroreactor Chem. Eng. Technol. 2015 , 38 (10) , 1733–1742 DOI: 10.1002/ceat.201500376

Description: The optimization of installation of baffles in UV rector is investigated. The flow field is obtained by solving continuity equation and momentum equation. The radiation intensity is solved by use of radiative transfer equation. The UV dosage is obtained by coupling Lagrangian particle tracking approach with the solved radiation intensity. One unbaffled reactor and two baffled reactors are simulated. The baffled UV reactor A has the biggest residence time and the smallest UV dosage while the baffled UV reactor B has the relatively bigger residence time and the biggest UV dosage. The unbaffled reactor performs between two baffled reactors in residence time and UV dosage. The baffled UV reactor B can get the best disinfection of microorganisms. The present study shows that the optimization must be coupled the flow field and the radiation intensity to attain a harmony between them.

Description: Stable isotope proving (SIP) enables function to be linked with identity without isolating the microorganisms responsible. This culture-independent approach has been adapted to identify the microorganisms involved in the degradation of numerous environmental contaminants. SIP studies have been performed in situ or in laboratory microcosms inoculated with soil, sediment, groundwater or bioreactor samples. This review focuses on the microorganisms that have been identified in those projects. SIP studies involving the degradation of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, gasoline associated contaminants, chlorinated solvents, RDX, phenol, uranium and pentachlorophenol are discussed. This review brings to light the significant diversity of contaminant degrading microorganisms.

Description: A continuous-flow microreactor was used to synthetize II–VI semiconductor quantum dots (CdSe). In order to improve the size distribution of the nanoparticles, the synthesis was carried out in a two-step procedure. A seed solution was obtained in a separate nucleation step, followed by a controllable growth step. Quantum dots that are synthesized with the two-step method show a much narrower size distribution in comparison to those obtained in a conventional batch synthesis. Quantum dots are nanocrystalline semiconductors that differ greatly from their bulk counterparts. To obtain CdSe quantum dots with a narrow size distribution, a two-step procedure was applied, in which CdSe seeds were synthesized in a separate process prior to the nanoparticle growing procedure. The seeds were mixed into the growing solution-containing droplet by coaxial injection.

Description: The chemical process industry is paying significant attention to the intensification of processes with the main aim of achieving increased productivity, improved economic status, and enhanced sustainability. The pharmaceutical industry is moving in the same direction and, therefore, dozens of processes are in a state of change. However, it is important to note that not all processes can be intensified easily, such as slow chemical reactions, processes with solids, slurries, and on the like. This review summarizes applications of promising tools for achieving process intensification in the small-scale pharmaceutical manufacturing of so-called small molecules. The focus is on microwave radiation, microreactors, ultrasounds, and meso-scale tubular reactors. Promising tools for accelerating slow chemical reactions in organic synthesis in order to achieve process intensification are reviewed with the focus on microwave radiation, meso-scale tubular reactors, microreactors, and ultrasounds. Applications of such tools for producing small molecules in the pharmaceutical industry are discussed and illustrated with examples.

Description: Process design management system is the essential computer-aided design type of software used in design and 3D modeling of process plants. Actually, it is a management center of process plant projects which allows designers and engineers from various disciplines to concurrently create, control, and manage changes to the plant design and other related engineering data. Some methods for achieving the inherently safer designs guide the location of process equipment and utilities. Therefore, there is room for close interactions between 3D modeling and methods to assess the inherent safety. The feasibility of integration of the Fire and Explosion Index into 3D modeling of industrial chemical processes is evaluated and supported by a case study. The importance of the presented concept as key part of such management philosophies like the lean design and the building information modeling is highlighted. In conventional process plant design, safety analysis is performed at the stage when the main design decisions were already made. The presented perspective allows placing the safety considerations using the Fire and Explosion Index (F&EI) in a 3D modeling environment. Results of the F&EI assessment can be visualized and shared between all disciplines involved in plant design.

Description: Energy optimization is a hot research topic for design and operation of crude oil distillation plants. Optimum energy utilization in a multistage crude oil distillation process is achieved by optimizing the distillation load of each distillation column as well as the yield of the sidestreams of distillation columns. A generalized multistage distillation energy consumption model is proposed, and the optimal distillation load distribution is accomplished by minimizing the total energy consumption. Based on the optimal distillation loads, a nonlinear programming model is then formulated to determine the yields of sidestreams by maximizing the thermal exergy recovery for the crude oil plant. Finally, a four-stage crude oil distillation plant is investigated to demonstrate the performance of the proposed approach. The results show a decrease in energy consumption and an increase in heat recovery. The distillation load distribution of the distillation columns in a multistage crude oil distillation process is directly related to the energy consumption, and the yields of the sidestreams of these columns affect the thermal exergy recovery for the crude oil plant. These problems are formulated by an energy optimization approach combining mathematical programming and exergy analysis.

Description: Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) was employed to investigate the velocity distribution (propagator) and dispersion coefficient of a model fluidized-bed reactor of low aspect ratio containing mustard seeds. Both propagator and dispersion were found to be strongly anisotropic due to slug-flow conditions, with the vertical/axial dispersion ratio becoming smaller with increasing air flow rate. The influence of air humidity and flow rate was discussed in the gas-solid system, and the concurrent effect of electrostatic charging of particles close to the reactor wall was shown. Dispersion was generally found to increase with growing humidity and superficial gas velocity. For comparison, results are presented for a gas-liquid-solid system with a water-to-particle mass ratio of 2:1 as a function of bed height. The results indicated that the addition of water enhanced the particle motion in the bed. Velocity distribution and dispersion coefficient of a model fluidized-bed reactor of low aspect ratio was investigated by pulsed-field gradient nuclear magnetic resonance. For the first time, the feasibility is demonstrated to describe statistically the behavior in three-phase reactors with a dominating water component. Addition of water enhanced the particle motion in the bed.

Description: 1-Hexene metathesis was performed over standard and potassium-doped WO 3 /SiO 2 catalysts. The samples were tested at various reaction temperatures, molar feed compositions, and space times. Under the applied reaction conditions, doping with potassium reduced the isomerization and cracking activity of the catalyst by at least half and improved the yield of detergent-range alkenes twofold. However, increasing the potassium loading to a higher amount resulted in a significant reduction in the metathesis activity as both Brønsted and Lewis acid sites were affected. Optimum operating conditions for the yield of detergent-range alkenes were identified using response surface methodology. The metathesis of terminal linear alkenes can be applied for the valorization of secondary Fischer-Tropsch product streams. The performance of silica-supported tungsten trioxide catalysts was investigated for the gas-phase metathesis of 1-hexene in a fixed-bed reactor. Metathesis of 1-hexene yielded valuable detergent-range alkenes. Doping WO 3 /SiO 2 with potassium was found to reduce isomerization and cracking of 1-hexene.

Description: A preliminary study based on a conceptual process design methodology that includes a technical evaluation and an economic study has been carried out for the use of the metal-organic framework NH 2 -MIL-53(Al) as adsorbent for the separation of carbon dioxide from methane. Among the alternatives considered, a vacuum pressure swing adsorption was chosen in the detailed design phase. The combination of a design with columns in parallel and the possibility of recirculating some of the streams ensures a high degree of separation and a final product with high quality without compromising the operation costs. A comparison with the state-of-the-art technology, amine scrubbing, and with a process based on membranes demonstrates that the proposed process is competitive as a result of its low operation costs and the energy demand. A vacuum pressure swing adsorption process, based on the usage of the metal-organic framework NH 2 -MIL-53(Al) for the separation of CO 2 from CH 4 , is proposed based on a conceptual process design methodology. The analysis includes a technical evaluation, an economic study, and a comparison with the most widely applied technologies, proving the competitiveness of the proposed process.

Description: The broken-and-intact-cell model is conventionally used for interpretation of overall extraction curves (OECs) observed in supercritical fluid extraction (SFE) of ground oilseeds. Another possibility, considered here, assumes that the packed beds of the ground material always contain a significant amount of very small particles, i.e., dust, which control the initial extraction rates. The bidisperse representation of particle ensembles allows accurate description of OECs on the basis of the modified shrinking core model. A simple asymptotic solution has been derived for bidisperse granulometric distributions under typical SFE conditions. Special microscopic observations have been performed to reveal and examine the dust fraction in ground seed substrates. A generalization of the shrinking core model for supercritical fluid extraction is introduced which takes into account the polydisperse nature of ground plant material. Model simplification adjusted for common extraction conditions, resulting in bidisperse approximation and simple asymptotic formulas is developed and successfully verified on experimental data from literature.

Description: An industrial-scale dead-end ultrafiltration system was optimized using statistically designed experiments. Given a certain level of pollutant, a two-level full factorial design and a central composite design were used to optimize the filtrate production of a single 8-inch industrial ultrafiltration membrane while manipulating the levels of four factors: feed pressure, backwash pressure, forward filtration time, and backwash time. Analysis of variance and residual analysis were used to validate and check the adequacy of the developed regression models. The optimal levels were later validated experimentally. The predicted filtrate production was in reasonable agreement with the experimental data. A two-level full factorial design and a central composite design were used to optimize the filtrate production of an industrial ultrafiltration membrane while manipulating the feed pressure, backwash pressure, forward filtration time, and backwash time. The obtained regression models were validated by analysis of variance and residual analysis. The optimal levels were then validated experimentally.

Description: The solubility behavior of salicylic acid (SAA)/4,4′-dipyridyl (4,4′-dipy) cocrystals is investigated in an ethanol solvent. The phase solubility diagram (PSD) of SAA/4,4′-dipy cocrystals is determined which are formed in a 2:1 stoichiometric ratio in ethanol. The objective is to improve the fundamentals of the formation mechanisms, solution behavior, and solid-state properties of SAA/4,4′-dipy cocrystals. The solubility behavior and solution chemistry of cocrystals are studied. It was found that the thermodynamic stability regions of the cocrystals and its components are defined by the phase solubility diagram. Besides the kinetic also the thermodynamic factor turned out to be important for the crystallization of cocrystals. Physical properties of active pharmaceutical ingredients can be tuned by pharmaceutical cocrystals without changing the chemical identity. The solubility behavior of salicylic acid/4,4′-dipyridyl (SAA/4,4′-dipy) cocrystals is investigated in an ethanol solvent to improve the fundamentals of the formation mechanisms, solution behavior, and solid-state properties of these cocrystals.

Description: The polymorphic formation of taltirelin (TTL) was monitored inline by Raman spectroscopy in batch cooling crystallization. The concentrations of the polymorphic forms and supersaturation were measured during crystallization and transformation processes. Polymorphic transformation was detected by monitoring the Raman spectra of the two polymorphs in slurry state. The effect of cooling rate and concentration on the polymorphic crystallization was assessed. At a slow cooling rate and a low concentration, the stable form, i.e., the β -form, was nucleated directly without transformation from the α -form. The nucleation mechanism of the two TTL polymorphs was studied using the supersaturation profile tracked by Raman spectroscopy. In cooling crystallization, supersaturation can be controlled by the cooling rate. Profiles of concentration are helpful for understanding polymorphic crystallization. At a low cooling rate, the α -form of taltirelin is nucleated and then transformed to the β -form. The α -form is formed at a high cooling rate, while the β -form is generated at a very slow cooling rate.

Description: Atorvastatin calcium (AC) spherical crystals were prepared by spherical agglomeration. CH 2 Cl 2 acting as bridging liquid was added together with the drug solution or after the antisolvent precipitation process. Polymorph transformation in antisolvent crystallization and agglomeration processes was observed by focused-beam reflectance measurement (FBRM). The results suggested the occurrence of an immediate agglomeration when CH 2 Cl 2 was added together with the drug solution. Size-controllable AC spherical crystals with improved flowability and compressibility can be obtained by adjusting the amount of CH 2 Cl 2 and the stirring speed. The improved compaction behavior of the AC particles can be applied for direct tableting. A higher stirring speed can reduce the amount of bridging liquid which is required for effective agglomeration. It was a prerequisite for fine particles to be wetted by the bridging liquid in the spherical agglomeration process. Spherical agglomeration is an effective method to improve the flowability and compressibility of Atorvastation calcium particles. A polymorph transformation occurred during the antisolvent precipitation and agglomeration process. The final size distribution of the particles is controllable by adjusting the amount of bridging liquid and stirring speed.

Description: The performance of a modified bioreactor inside a light enclosure for carbon dioxide (CO 2 ) bio-fixation by Chlorella vulgaris was investigated. The influence of different light intensities on CO 2 bio-fixation and biomass production rates was evaluated. The results showed that the photon flux available to microalgal cultures can be a key issue in properly optimizing microalgae photobioreactor performance, particularly at high cell concentrations. Although the optimal pH values for C. vulgaris range from 6-8, cell growth can take place even at pH 4 and 10. Batch microalgal cultivation in a photobioreactor was used to investigate the effect of different light intensities, including 30, 50, 100, 185 and 300 μmol m -2 s -1 . The maximum biomass concentration of 1.83 g L -1 was obtained at a light intensity of 100 μmol m -2 s -1 and 2 L min -1 of 2% CO 2 enriched air aeration. The performance of a modified bioreactor inside a light enclosure for carbon dioxide (CO 2 ) bio-fixation by Chlorella vulgaris was investigated. The influence of different light intensities on CO 2 bio-fixation and biomass production rates was evaluated. The results showed that the photon flux available to microalgal cultures can be a key issue in properly optimizing microalgae photobioreactor performance, particularly at high cell concentrations. Although the optimal pH values for C. vulgaris range from 6-8, cell growth can take place even at pH 4 and 10. Batch microalgal cultivation in a photobioreactor was used to investigate the effect of different light intensities, including 30, 50, 100, 185 and 300 μmol m -2 s -1 . The maximum biomass concentration of 1.83 g L -1 was obtained at a light intensity of 100 μmol m -2 s -1 and 2 L min -1 of 2% CO 2 enriched air aeration.

Description: Controlled silver particle geometries require at least a synthesis in two steps which strongly differ in their reaction kinetics. For the first step, the very fast seed formation, chaotic advection-based micromixers are tested in combination with a batch reactor for the growth step. Nanoparticles with narrow size distribution and excellent shape uniformity can be prepared in large batches. To achieve a highly reproducible and homogeneous particle solution, a microfluidic system containing three different micromixers for optimal mixing of the chemical precursors is established, allowing stringent control of every synthesis step. The produced silver particles can be used as seeds for forming anisotropic particles. Their further potential is demonstrated by preparation of anisotropic silver triangles. The thus generated seed particles are better suited for growing to triangles than those from conventional batch synthesis. The synthesis of silver nanoprisms is realized in a novel microfluidic platform consisting of three different micromixers. Uniform crystalline particles were prepared, acting as seed particles for a second batch reactor-based synthesis. This reproducible synthesis platform allows for large-scale synthesis of plasmonic nanoparticles with defined dimension and plasmon resonance.

Description: Fluid flow patterns and associated concentration fields in Y-mixers are investigated using lattice Boltzmann method (LBM) -based models. The focus lies on the impact of mixing angle on flow and concentration fields, which is varied between acute (θ = 10°) and obtuse (θ = 130°) angles. Residence time distributions are determined to study the effect of the angles on mixing and velocity patterns, in particular, different flow regimes, namely, stratified laminar, vortex and engulfment. The results from the simulations are validated with literature data and found to be in good agreement. Maximum mixing occurs in the 100 o -obtuse angle Y-mixer, attributed to the extensive engulfment of flows in the mixing channel.

Description: Pretreatment of lignocellulosic biomass is essential for overcoming its inherent recalcitrance prior to enzymatic hydrolysis and fermentation of its carbohydrate components into biofuels and bioproducts. Among the myriad of existing pretreatment methods, the hot water pretreatment with no-chemical usage is a particularly attractive approach due to its fewer safety and environmental concerns, as well as relative low cost. The hydronium ions dissociated from water at elevated temperatures can catalyze the deconstruction of lignocellulosic biomass into fermentable sugars, digestible cellulose, and lignin fragments. However, a prohibitive amount of sugar degradation products particularly generating in conventional batch systems limit the efficiency of hot water pretreatment. Although the advanced continuous reaction systems like flowthrough systems are prone to reduce the sugar degradation compounds thereby enhancing the sugar recovery, excessive water consumption accompanied with the over dilute sugar streams still impede the implementation of hot water pretreatment to be an economical viable pathway. These limitations of hot water pretreatment are considered to be associated with the scant attention of water-biomass interaction mechanism, as well as the engineering aspects regarding kinetic modeling and reactor configurations. Thus, extrapolating this information from scattered literatures would play a vital role to complete the comprehensive understanding of the hot water pretreatment. This review aims to fill in the blank of those critical factors influencing hot water pretreatment of lignocellulosic biomass, in terms of chemistry and engineering fundamentals to understand the correct axiomatic approaches needed to advance this technology. In particular, various reactor configurations and kinetic models are evaluated herein to explore the optimization strategies of hot water pretreatment toward application.

Description: During the past years cost pressure on the European chemical companies grew dramatically by increased competition from low-labor-cost BRIC countries on the one side and the U.S., favored by decreased energy costs due to shale gas exploitation, on the other side. Raising costs for energy consumption and wages come on top. Lonza, as a mid-sized chemical company located in a high-income-country, faced the need of cost reduction long time before and established highly efficient procedures in both, development and production, with the aim to decrease costs and already successfully applied since years. The paper describes some of the applied techniques in detail and shows their potential in terms of time and cost reduction. Furthermore, Lonza works with great emphasis on future solutions.

Description: Solid-liquid extraction using a laboratory robot, where anthocyanins are leached from dried red vine leaves ( vitis vinifera ), is evaluated with respect to precision and accuracy. The solid handling of the robot results in standard deviations between ± 0.6 and ± 1.8 depending on the particle size (max. 630 µm). For liquid handling standard deviations are from ± 0.8 to ± 2.6 depending on the volatility of the solvents. The validated, fully automated natural plant extraction-robot shows yields based on dry matter from 1.3 % to 0.8 %, 1.15 % to 0.55 % and 0.4 to 0.15 % for methanol, water (HCl, pH = 2.5) and ethanol and is improving with increasing particle size. Manually performed extraction kinetics experiments are compared with the robot and indicate a variance of 0.1 %. With respect to process intensification, a comparison of yields obtained by microwave and ultrasonic supported extraction in comparison to laboratory robot shaking and stirred single-stage batch experiments was performed.

Description: Aerial view of pipes of the thermal power plant. © Nickolay Vinokurov/Shutterstock

Description: The electrochemical reduction of CO 2 is a promising method for its conversion which still suffers from important challenges that have to be solved before industrial realization becomes attractive. This study describes the optimization of gas diffusion electrodes with respect to catalyst dispersion and mass transport limitations allowing solubility issues to be circumvented and current densities to be increased to industrially relevant values. Consequently, the transfer of the promising results from semi-batch experiments into continuous mode of operation is demonstrated, and it is shown how the energetic efficiency can be significantly improved by the choice of electrolyte, in terms of concentration and type. Thereby ohmic losses can be decreased and the intrinsic activity improved.

Description: In a future energy system, flexible reactor operation may be needed if renewable electricity is converted to chemical energy carriers (synfuels). Limiting factors for the flexibility in a synfuel process can occur on different scales (catalyst, reactor, process). The present study addresses transient catalyst and reactor effects in 3-phase catalytic synthesis reactors with low-temperature Fischer-Tropsch synthesis as example reaction. A method was developed based on lab-scale experiments with step-changes and periodic-changes of inlet variables and mathematical models for experimental design and data analysis. Changes of feed gas flow, syngas H 2 /CO-ratio and temperature as inlet variables led, in some cases, to transient effects caused by catalyst changes or by reactor characteristics (e.g. residence times of gas components affected by their solubility in liquid hydrocarbon products). Catalyst changes include the reversible storage of carbon species during CO-rich intervals and hydrogenation of these carbon species during H 2 -rich intervals. The approach will help to scale-up for industrial applications and can be applied to other synthesis reactions.

Description: Profile measurements in a catalytic gauze reactor are conducted for catalytically assisted methane combustion over platinum. The reactor combines a capillary sampling technique with a novel fiber-optic Laser-Induced Fluorescence (LIF) Spectroscopy method for detection and quantification of gas phase OH[[[Wingdings;F09E]]] radicals serving as indicator species for gas phase reactions. The steep spatial gradients in the vicinity of the gauze are resolved at submillimeter scale. Experimental profiles are compared with three dimensional numerical reactor simulations including flow, mass transport, heat transport and microkinetic models for both surface and gas phase chemistry. The results provide insight into the interaction of chemistry and transport upstream, at and downstream the catalytic gauze and the interaction of surface and gas phase reactions by exchange of heat and radicals released from the catalyst surface.

Description: A packed bed algae biofilm reactor was developed using porous and non-porous dual packings. The biofilm was cultivated on reticulated polyurethane foam cubes of 0.01 m dimension. The non-porous glass raschigs were used as bed support that helps the removal of generated gas from the system. The effect of variables such as column L/D ratio, catalyst cube dimension and feed flow rate on the treatment of sewage water was studied. The reaction kinetics indicates that the nutrients uptake rate is dependent on both pore and film diffusion. The kinetics of uptake of nutrients follows a pseudo-first order reaction. From the pseudo reaction rate constant, Thiele Modulus and effectiveness factor were calculated and a kinetic model equation for fractional nutrients uptake was developed in terms of operating variables. It was observed that the model can predict the reaction rate with ±5% deviation. The packed bed column was operated continuously for 90 days with 76-83% of TN and 70-76% TP removal in 24 h of residence time and the results obtained may be useful for large-scale treatment of sewage water.

Description: With the high interest in renewable resources, the field of biosorption has undergone a huge leap in importance in recent years. The arsenic contamination in water causes many diseases. Various biosorbent materials have been tested for their ability to remove the two inorganic arsenic species commonly found in water; arsenite As (III) and arsenate As (V). The review evaluates source and various biosorbent used for arsenic removal from wastewater. The arsenic biosorption is influenced by the pH of aqueous phase, the concentration of arsenic, the presence of competing ions and arsenic speciation. The biosorption kinetic of As (III) and As (V) by biosorbents has been reported to be rapid, with greater than 80 % biosorption occurring between 30- 60 min, followed by second step which may take up several hours. The pseudo-second order model showed the best fit for kinetics of arsenic, which corresponds to a chemisorption process. Langmuir equation is widely used in a large number of equilibrium studies; this finding indicates that most arsenic ions are adsorbed in monolayer form and removal is better for As (III) than for As (V).

Description: Ionotropic alginate microgels are commonly used for bioencapsulation applications and the air extrusion system is one of the common methods employed to produce these microgels. Although there have been many individual studies, no single report to date has comprehensively summarized the findings and results of the use of this system. Our review gives insight into the air extrusion methods, covering the setup, type and characteristics of the system, focussing on their innovative aspects. Characterization techniques for the resulting microgels are presented, along with the influence of process variables on their product size, and the development of empirical models for size prediction.

Description: For the purpose of a long-term heat storage system based on water sorption, a composite material consisting of 15 wt.% CaCl 2 and zeolite Ca-X (prepared by ion-exchange with Ca 2+ and subsequent impregnation with CaCl 2 of a binder-free granulated zeolite Na-X) was prepared on a technical scale. In a lab-scale apparatus, the heat storage density of the composite material reaches values up to 260 kWh m -3 for water vapor partial pressures up to 33 mbar. As compared to the pure zeolites Ca-X and Na-X, this corresponds to an increase in heat storage density of 45 % and 68 %, respectively. An engineering concept based on the mechanical transport of the composite heat storage material through a pre- and a main reactor was demonstrated in a “hardware in the loop” test bench.

Description: A model of the steam gasification of a single char particle driven by high intensity radiation was developed and experimentally verified with available measurements in literature. This was used to explore the sensitivity of particle surface temperature and heat transfer mechanisms to variations in particle diameters (100m to 1900m), radiative heat flux (1MW/m 2 to 4MW/m 2 ) and the concentration of the gasification agent, H 2 O (0.2 to 0.8 mole fraction) under typical conditions for solar gasification reactors. The results highlight the importance of particle diameter in influencing solar to chemical energy conversion efficiency and assist in the selection of appropriate feedstock particles to match the conditions in specific solar gasification reactors.

Description: Distillation of hydrocarbons was investigated to decrease energy consumption by applying the columns with the coupled heat and material flows. The elements of downstream processes were considered such as separation of the catalytic cracking gas and the recovery of benzene from petroleum and coking coal products by extractive distillation with N-methylpyrrolidone. It was found that the thermally coupled columns applied for the separation reduced energy consumption for the catalytic cracking gas separation up to 13.1% and for the benzene recovering up to 28.7%.

Description: Rapid granulation of biomass and reactor start-up has been studied in a novel denitrifying reactor. The effect of wastewater characteristics, reactor operating conditions and reactor geometry on microbial granulation has been studied. It was possible to achieve granulation in just 15 days of reactor start-up. In 15 days the settling velocity of the granules was 1.5 cm s -1 , which is almost 10 folds higher than that of seed sludge. The reactor was able to handle a nitrate loading rate of 50 g NO 3 -N m -3 day -1 in 3 days of reactor start-up with rates reaching up to 460 g NO 3 -N m -3 day -1 in just 30 days of reactor start-up with a removal efficiency of almost 100%. Based on the experimental observation, a hypothesis for the cause of rapid granulation has been proposed.

Description: K-solubilizing bacteria were isolated from solar salt pans of CSIR-CSMCRI’s experimental salt farm and Sambhar lake, mining areas of Naseerabad and wastewater from marble cutting machinery. Seven promising bacterial isolates from Makrana, three from Sambhar lake and three from Naseerabad were found to have comparatively better potassium solubilizing capacity. Out of these, three potential bacterial isolates were identified as Acinetobacter soli (MTCC 5918), Enterobacter xiangfangensis (MTCC 5917) and Acinetobacter baumannii (MTCC 5916). Thereafter, Acinetobacter soli was found to have maximum potassium releasing capacity of 80 mg/l in supernatant, which may be further applied as a biofertilizer.

Description: The development of floating liquefied natural gas (FLNG) plants has resulted in a focus on reducing the weight and size of the topside processing facilities for these units. The conventional fractionation of natural gas liquids (NGL) in LNG plants implies a direct sequence of three or more conventional distillation columns requiring different levels of refrigeration. The results of a feasibility study are described, indicating that a packed three-product dividing-wall column (DWC) could replace conventional de-ethanizer and depropanizer columns. This could provide significant energy, hardware, weight, and footprint benefits, but, very likely, at the expense of an unaffordable cold utilities demand. 1) A conventional demethanizer combined with a three-product dividing-wall column operated at moderate pressure appears to be a promising alternative for the conventional three-column sequence as encountered in natural gas liquids fractionation plants. In addition to the overall energy saving, such a configuration enables also weight, hardware, and footprint reduction.

Description: A 3D numerical model was developed for studying the multiphase flow and heat transfer process in a radiant syngas cooler (RSC). Realizable k-ϵ turbulent and discrete random walk models were adopted to simulate gas phase and particle phase flow fields, respectively. The surface temperature of the membrane wall was calculated by heat flux balance equations. The calculated temperature distribution was validated by comparing calculated values with measured data of an industrial RSC. Four different membrane wall arrangements of RSC, namely, ordinary membrane wall (OMW), partial division wall (PDW), annular division wall (ADW), and fin division wall (FDW), were designed for a specific condition. The radiant syngas cooler is one of the critical and expensive components of power plants. A three-dimensional numerical model was developed to predict the complex multiphase flow and heat transfer process in such a cooler of entrained-flow coal gasification for optimization. Four different membrane wall arrangements were designed and evaluated for a specific condition.

Description: In order to improve the flow uniformity in plate-fin heat exchanger (PFHE), a modified header structure with a plain baffle inside is proposed in this study. Flow distribution and pressure drop in header were studied by using numerical method. Results show that the modified header is high-efficient in improving the flow uniformity in header of PFHE with negligible pressure drop increase. Then, a performance effectiveness factor was introduced to predict the effects of the modified structure on the performance of PFHE. Finally, influences of baffle structure parameters on modified structure performances were further discussed. Conclusions of this paper indicate that the modified header structure can effectively improve the performance of PFHE.

Description: Continuous manufacturing of fine chemical, life science, and pharmaceutical products is under recent investigation in R&D. As cooling crystallization is an important unit operation for purification of products, continuously operated, scalable devices are required for process development on lab-scale. A tubular crystallizer was developed, based on the coiled flow inverter (CFI) design. Experimental characterization proved a narrow residence time distribution (RTD) of the liquid phase close to ideal plug flow. Counter-current air cooling allows for adjusting linear and curved temperature profiles. Unseeded operation with the l-alanine (water) system demonstrated that nucleation has to be actively controlled to successfully apply intensified continuous cooling crystallization processes.

Description: The stability of a polymorph and the rate of polymorphic transformation are usually affected by solvent, and thus a molecular level understanding of the solvent effect on the nucleation of stable form during the polymorphic transfomration process is necessary to effectively control the whole process. In this work, the role of water in the nucleation of the stable β form of L-glutamic acid (L-Glu) on three typical surfaces of the metastable α form is investigated via molecular dynamics simulation. By comparing the simulation results on the surfaces in contact with solution with those on the surfaces in vacuum, it is revealed that water molecules have not made any change in the order of the adsorption energies for the solute molecules on the three surfaces, but reduced the absolute values of the adsorption energies with the extent increasing in the order of {011} 〈 {111} 〈 {001}, and retarded the clustering behavior of solute molecules with the same order. In addition, water molecules also weaken the inductive effects of the surfaces on the conformational change of α to β. In general, the effect of water on the nucleation of the β form on the surfaces of α form unraveled here will aid the understanding of polymorphic transformation of L-Glu in solution.

Description: In view of a kind of stripping column used widely in chemical industry, being in operation of total cold reflux and without top light product, a new stripping process is suggested in this paper. It takes dual feeds of the hot plus the cold by replacing partial cold reflux with a part of cold feed, resulting in significant reduction of energy consumption and simplification of the overhead vapor route. Due to no any change on the column’s body and only a pipe needed, this new process can be promoted conveniently in retrofitted projects. Further an optimization study is developed for choosing proper flow rate of cold feed and column’s running pressure. An application in a stripper of pre-hydrotreating resultant of oil catalytic reformer shows that the new process is valid.

Description: In the present study, efforts have been made for replacing sodium bicarbonate with ammonium bicarbonate (recovered from effluent of the pigment industry) for cultivation of CSMCRI’s Chlorella variabilis (ATCC PTA 12198) with enhanced biomass and lipid productivity. Utilizing ammonium bicarbonate in the medium (instead of sodium bicarbonate) yielded better biomass and productivity having less production age of 9 days as compared to Zarrouk’s medium in 5 L flask. Also, the modified medium containing ammonium bicarbonate yielded comparatively better total reducing sugar content which may be used for bioethanol production or may serve as the carbon source for further mixotrophic growth of Chlorella variabilis (PTA 12198).

Description: Bioremediation of environments, polluted with hydrocarbons, is among the most important and challenging technological and environmental issues. The use of plants and microbes is one of the most efficient methods for bioremediation. A new combination of grasses, Kentucky bluegrass ( Poa pratensis ) and Bermuda grass ( Cynodon dactylon ), and bacteria, Rhodococcus erythropolis , was hypothesized for the bioremediation of naturally polluted soils with hydrocarbons around Isfahan refinery, Iran. A 90-day greenhouse experiment, as a factorial design with 12 treatments including soil inoculation with bacteria as well as soil sterilization using both plants in three replicates were examined. Both grasses significantly decreased the concentration of soil hydrocarbons compared with the control polluted soil, although Kentucky grass was the more effective one. The bacteria enhanced the bioremediation abilities of both plants, especially Kentucky grass. Soil sterilization significantly decreased the rate of hydrocarbons in the soil. The positive effects of bacteria on the process of bioaugmentation, specifically, due to their adaptability potential with the grasses examined in this research work, make this method of bioremediation strongly recommendable. However, more research is essential to illuminate the new details on the role of R. erythropolis in polluted soils with hydrocarbons.

Description: The generation of gaseous singlet oxygen by gas-liquid reaction of chlorine with alkaline solution of hydrogen peroxide in spray form was studied experimentally on the originally designed device with a fast separation of reacted liquid from gas. The singlet oxygen yield, residual chlorine, and water vapor content in gas were measured under different experimental conditions of the centrifugal spray singlet oxygen generator (CSSOG) using nitrogen as a dilution gas. A characteristic feature of the CSSOG is a high utilization of the chemicals and production of singlet oxygen at a very high total pressure even near the atmospheric pressure. This generator developed originally for driving a chemical oxygen-iodine laser (COIL) could be employed also as an efficient singlet oxygen source in material science, chemical synthesis, and others. A centrifugal spray generator of singlet oxygen was optimized for operation with nitrogen buffer gas and high total pressure. This generator is able to successfully operate at much higher pressure compared to other types. Due to the very high hydrogen peroxide utilization the consumption of input liquid chemicals is substantially reduced.

Description: Ionic liquids (ILs) are recyclable acid catalysts for transesterification reactions. In the present study, different acidic ILs were examined in this reaction, with special focus on their recyclability. Furthermore, the IL-catalyzed transesterification reaction was realized in continuous operation. A miniplant reactor with technically representative design and operating characteristics was used for this study. The applied rig has a volume of 5 L and an external thermosyphon reboiler. The miniplant reactor can be operated in batch and in continuous mode. ILs functionalized with a sulfonic acid group were found to be the most suitable IL catalysts for the transesterification reactions under investigation. Using these ILs, reaction rates as high as for H 2 SO 4 could be realized. Moreover, the IL catalyst was demonstrated to be active for at least 1000 h of operation time. Ionic liquids are suitable catalysts for acid-catalyzed transesterifications. Acidic ionic liquids were used as recyclable and durable catalysts for this reaction. The performances of the benchmark catalysts were obtained for at least 1000 h of operation in a miniplant reactor, which is representative of industrial processes.

Description: A mathematical model based on 34 days continuous operation of an industrial isomerization unit was developed. The unit involves a radial-flow reactor with a catalyst capable of converting xylenes and ethylbenzene to mixed xylenes. The catalyst contains EU-1 zeolite, platinum, and alumina as binder. Two reactions are considered, i.e., ethylbenzene isomerization and xylene isomerization. The rates are based on the Hougen-Watson model according to the literature. An optimization procedure based on the trust-region-reflective algorithm was carried out in order to obtain new kinetic constants that minimize the difference between the actual and the calculated values. The standard error of the parameters estimated was calculated through the deleted-one Jackknife method. A simplified mathematical model for simulating the reactor operation of an industrial isomerization unit was developed. A relatively new type of catalyst allowed milder conditions to reduce side reactions. The kinetic constants were obtained through an optimization procedure. The model may be applied to simulate larger systems due to its simplicity.

Description: An industrial-scale reactor for ethylene production was modeled using the oxidative dehydrogenation of ethane (ODHE) in a multi-tubular reactor system, examining a variety of parameters affecting reactor performance. The model showed that a double-bed multi-tubular reactor with intermediate air injection scheme was superior to a single-bed design, due to the increased ethylene selectivity while operating under lower oxygen partial pressures. The optimized reactor length for 100 % oxygen conversion was theoretically determined for both reactor designs. The use of a distributed oxygen feed with a limited number of injection points indicated a significant improvement on the reactor performance in terms of ethane conversion and ethylene selectivity. This concept also overcame the reactor runaway temperature problem and enabled operations over a wider range of conditions to obtain enhanced ethylene production. High demands for ethylene call for more efficient reactor designs. This model for the oxidative dehydrogenation of ethane for a Ni-Nb-O mixed-oxide catalyst showed that a double-bed multi-tubular reactor with air injection is superior to a single-bed design, due to an increased ethylene selectivity while operating under lower oxygen partial pressures.

Description: Pilot Setup for Dynamically Enhanced Membrane Emulsification This setup allows the production of emulsions with narrow drop size distributions. A disperse liquid phase is pushed through a porous membrane into another immiscible fluid phase. A rotor above the membrane induces laminar shear flow, which detaches the drops from the membrane pores. A narrow shear gap and micro engineered membranes help to maintain good control over drop detachment. The sub pictures show drops detaching from membrane pores (top) at different shear flow conditions acquired in a separate visualization setup. The bottom picture shows a cut through a micro engineered silicon membrane, which was specifically designed and fabricated at ETH Zurich for the emulsification setup. The apparatus was designed and built by the Bühler AG, Uzwil, Switzerland in close collaboration with the ETH Zurich, Switzerland. DOI: 10.1002/ceat.201300256 Drop Detachment from a Micro-Engineered Membrane Surface in a Dynamic Membrane Emulsification Process S. Holzapfel*, E. Rondeau, P. Mühlich, E. J. Windhab* Chem. Eng. Technol. 2013 , 36 (10) , 1785–1794

Description: Typically, the product fineness in a dispersion process is determined by the strength of the agglomerates and aggregates, the properties of the homogeneous phase and its interaction with the surface of the disperse phase, the stress mechanism itself as well as its intensity and frequency acting on the particles. The objective of this study is to characterize the efficiency of a dispersion process in terms of stress frequency and intensity using a newly developed dispersing machine called dispermeter. This dispersing machine is capable of processing suspensions with a broad range of viscosities. Furthermore, due to highly defined geometries, the rheological behavior of suspensions as an important parameter for processability and suspension stability can be characterized during the dispersion process. By utilizing the rheological properties the dispermeter can be used for the selection of an applicable electrostatic or steric stabilizer for an optimal dispersion process. With the dispermeter two different types of pyrogenic metallic oxide particles, nanosized alumina and silica, are processed. The progress in deagglomeration is monitored by particle size analysis and compared with that in a dissolver. A theoretical process model is used to characterize both processes. Moreover, this model is used to predict the dispersion results obtained in the dissolver. To characterize the rheological properties and dispersion stability as well as the efficiency of a dispersion process in terms of stress frequency and intensity, a new dis-persing machine was developed. A theoretical process model was used to characterize the dispersion process in the dispermeter and in a dissolver. Moreover, this model was used to predict the dispersion results obtained in the dissolver.

Description: Visualization of local mass transfer coefficients over the dry surface of corrugated-sheet structured packing is essential for optimizing the existing geometry of structured packing and for improving mass transfer efficiency to develop new structured packing. The local flow patterns between packing sheets and the gas-phase mass transfer coefficient at each point over the surface are illustrated by employing a wall-surface reaction model. Different turbulence models are utilized, i.e., a standard κ-ϵ model and three different low-Re-κ-ϵ models. The numerical calculation results with the Lam-Bremhorst low-Re-κ-ϵ turbulence model is found to agree well with experimental data. There are three similar regions with enhanced mass transfer efficiency in each mass transfer unit cell of structured packing. Local mass transfer coefficients at each point over the dry surface in a symmetric mass transfer unit cell of corrugated-sheet structured packings were determined. Computational fluid dynamics simulation results with a Lam-Bremhorst low-Re-κ-ϵ turbulence model and a wall-surface reaction model corresponded well with previous experimental data.

Description: The drying process of organic solid waste is investigated, based on an experimental study involving its drying kinetics. The experiments were conducted in a thin-layer fixed-bed dryer under various operational conditions. The problem of selecting the best fit for solid waste moisture content as a function of time is addressed as well, using artificial neural network (ANN) models and four well-known drying kinetics correlations commonly applied to biological materials. According to the statistical analysis employed, the simulations showed good results for the ANN, and the Overhults model provided optimum agreement with experimental data among all other models evaluated. Empirical correlations between the Overhults model parameters and the drying operational conditions using nonlinear regression techniques were determined. The kinetics of the drying process of solid citrus wastes in a thin-layer fixed-bed dryer under different operational conditions is investigated. By means of artificial neural networks and four well-known drying kinetics correlations, the problem of selecting the best fit for solid waste moisture content as a function of time is addressed as well.

Description: Lavandin essential oil has been encapsulated in poly-(ϵ-caprolactone) (MW: 4000 g mol –1 ) by means of the particles from gas saturated solutions (PGSS) process. The influence of process conditions, i.e., pre-expansion temperature and pressure, and oil/polymer mass ratio, on the morphology of particles and the efficiency of encapsulation has been analyzed. Spherical particles with particle sizes of 100–700 μm were obtained, with increasing particle sizes and more agglomeration as the oil/polymer ratio was increased. The efficiency of encapsulation was increased by conditions that favored a fast solidification of the polymer shell, including high pre-expansion pressures, reaching efficiencies up to 50 % with oil loads up to 120 mg oil/g particles. Essential oils can be used as natural cattle growth promoters or biocides, but a formulation is required in order to protect the essential oil from evaporation and degradation, and to provide a controlled delivery. The encapsulation of lavandin essential oil in polycaprolactones by a particles from gas saturated solutions (PGSS) process is presented, analyzing the influence of process parameters on the morphology of particles and the efficiency of encapsulation.

Description: CO 2 /N 2 gas separation was performed over a nanocrystalline zeolite tetraethylammonium (TEA)-beta membrane prepared on a stainless-steel porous disc by repeated hydrothermal crystallization. Two to three consecutive hydrothermal syntheses were required to form a membrane comprised of a continuous and compact layer of zeolite beta nanocrystals on the support. The membrane TEA-BEA3 obtained by three consecutive syntheses, in which the membrane from two consecutive syntheses was used as support, exhibited the highest structural order. When the separation experiment was performed over this membrane without applying any external applied pressure, 100 % selectivity of CO 2 over N 2 was observed. The separation was driven by differences in chemical potentials of the molecules generated only by the adsorption-desorption behavior of the gases into the membrane. The novel zeolite TEA-beta membrane provided promising results for the separation of small gas molecules due to the combined influence of diffusion and sorption selectivity. Nanocrystalline zeolite tetraethylammonium (TEA)-beta membranes were prepared by repeated coating of zeolite nanocrystals via hydrothermal crystallization from a colloidal solution over a porous stain-less-steel disc support. When the separation experiment was performed without applying any external pressure, a CO 2 selectivity over N 2 of 100 % could be achieved.

Description: Ad- and desorption are common techniques for the purification of natural substances. The main drawback is the tedious experimental procedure for resin and solvent screening. An approach of fully automated batch experiments is presented. In order to fulfill all requirements like automation of flexible dosing of loose resins, handling organic solvents, and providing reproducible conditions, these experiments are performed on a custom-built modular robotic platform. The batch ad- and desorption experiments were fully automated for the determination of essential process parameters like kinetics, isotherms, and thermodynamic parameters without the need of manual intervention. Thus, the hands-on time could be significantly reduced by more than 90 % which contributes to improved health and safety outcome by preventing the contact of operators to potentially hazardous materials. A fully automated and highly flexible ad- and desorption method for batch resin, solvent, and condition screening experiments was developed and implemented on a robotic platform, enabling the determination of essential process parameters without manual intervention. The hands-on time was significantly reduced, contributing to improved health and safety outcome for operators.

Description: In situ radio-frequency heating (ISRFH) combined with soil vapor extraction was demonstrated at a contaminated field site of a former hydrotreatment plant in Zeitz near Leipzig. The project was carried out in several phases including cold soil vapor extraction for comparison. During the test, a soil volume of about 300 m 3 was heated to an average temperature of 54 °C. As expected, the extraction rate for hydrocarbons (especially the main contaminant benzene) was markedly enhanced by soil heating. Furthermore, microbial degradation of organic compounds was supported. Although a total amount of approximately 1.4 t of hydrocarbons was removed from the soil, the demonstration project was not aimed at complete remediation of the site. Conditions limiting the extent of cleanup are discussed in detail and conclusions for an efficient application of ISRFH in soil remediation are derived whereas experiences from other sites are also implied. Potential and limitations of the combination of in situ radio-frequency heating (ISRFH) and soil vapor extraction are exemplarily discussed for a demonstration project carried out at a former industrial site. Conditions restricting the extent of cleanup are discussed and conclusions for an efficient application of ISRFH in soil remediation are deduced.

Description: The physical stability of emulsions can be related to changes in the droplet size distribution over time. Stability control of emulsions used as metal working fluids is an important factor for the machining industry due to the decreased performance of aged and broken emulsions. Results of turbidimetric spectra measurements of metal working fluids for process control purposes and emulsion stability monitoring are discussed. Metal working emulsions were artificially destabilized by admixing salts which resulted in droplet coagulation. The destabilization process was investigated by measuring the droplet size distribution and the turbidity spectra over time. The results were evaluated based on quantitative criteria proposed in the literature. The applicability of these criteria to evaluate metal working fluids during machining operations is discussed. The destabilization process of a commercial metal working fluid (MWF) emulsion artificially aged with CaCl 2 was characterized by UV-Vis-NIR spectroscopy. The wavelength exponent proved as a quantitative criterion in monitoring of the emulsion destabilization. This simple method can be applied to in situ characterization of MWF quality in machining processes.

Description: A scale-down study of an industrial reactor for the production of polyvinyl chloride (PVC) via an emulsion polymerization process was performed in order to understand the source of batch-to-batch variations in product quality. In Part 2 of this series of three papers, it is demonstrated that a large excess of base is required to control the particle size distribution of the seed process. Although differences exist between the critical micelle concentration and the surface area occupied by a surfactant molecule for linear and branched isomers of the surfactant sodium dodecyl benzene sulfonate, the characteristics of the molecules from different suppliers were reasonably similar. A scale-down study of an industrial reactor for PVC production by means of emulsion polymerization is presented with the aim to identify the source of batch-to-batch variations in product quality. In Part 2 of this series of papers, the necessity of a large excess of base to control the particle size distribution of the seed process is demonstrated.

Description: SO 2 and NO are the main precursors for acid precipitation. Experimental studies on desulfurization and denitrification were carried out using microwave irradiation over activated carbon carried catalyst. The results show that adsorption capacities and removal efficiencies of activated carbon carried Cu-based catalyst were higher than Mn-based or Zn-based ones. The adsorption capacity of SO 2 improved with the increasing moisture in flue gas, but the adsorption capacity of NO had a peak at 6.23 mg g –1 and then began to drop. The desulfurization efficiency increased with O 2 content in flue gas, but no noticeable change of denitrification efficiency was observed from the experimental data. The desulfurization efficiency descended with the increase of moisture in flue gas, while the denitrification efficiency augmented earlier and reached a plateau later with the addition of the water steam. In addition, characterization of activated carbon confirmed that the main active component of Cu-based catalyst is CuO. The addition of a catalyst can improve the removal efficiencies for SO 2 and NO and lower the reaction temperatures. Optimum experimental parameters were determined. The characterization of activated carbon by X-ray diffraction confirmed that the main active component of the catalyst is CuO, which has different valences in the reductive atmosphere, resulting in high microwave absorption ability.

Description: A scale-down study of an industrial reactor for the production of polyvinyl chloride (PVC) via an emulsion polymerization process was carried out in order to understand the cause of batch-to-batch variations in product quality. The results in Part 2 of this series of papers indicated that a large excess of base is required to control the particle size distribution (PSD) of the seed process. Here, it is demonstrated that the flow rate of the initiator and the second-stage surfactant are the most important parameters for PSD control. Altering the time point at which the initiator and surfactant are injected allows controlling the relative volume fractions of large and small particles. In Part 3 of a scale-down study on an industrial reactor for PVC production, the flow rate of initiator and second-stage surfactant proved to be the most important parameters for particle size distribution control. Changing the time point of injection of initiator and surfactant enables controlling the volume fractions of large and small particles.

Description: The potential of binderless briquetting as a means of transforming low-rank coals into low moisture high grade solid fuel products has been studied. Using two dried low-rank coals, binderless briquettes with high mechanical strength have been successfully produced through mechanical compression. An increase in heating value was achieved as a result of moisture reduction in the briquettes compared to as-received coals. The residue moisture content in the briquettes had a predominant effect on briquetting characteristics and there existed an optimum moisture content for the maximum briquettes strength. The chemical structure and wettability of binderless briquettes were analyzed using FTIR and contact angle measurement. The results showed that hydrophobicity and chemical structure significantly affected the briquette properties. High mechanical strength binderless briquettes using two dried low-rank coals were successfully produced. Drying of low-rank coals prior to briquetting resulted in 30–50 % increase in calorific value. The optimum moisture content for high compressive strength was 12–15 %. The aromaticity of the briquettes was higher than raw coals as a result of decomposition of oxygen functionalities and aliphatic hydrogen groups.

Description: The effect of pressure on the possible existence of multiple steady states in bubble column reactors is investigated. A mathematical model involving fast pseudo first-order kinetics is employed to describe the performance of non-isobaric, non-isothermal reactors. The numerical analysis reveals that the existence of multiplicity is sensitive to pressure variation, yet high-pressure operating conditions do not necessarily lead to a higher likelihood of multiplicity in these contactors. Bubble column reactors are widely used in industry for a variety of gas-liquid and biochemical reactions. The occurrence of steady-state multiplicity in non-isobaric bubble column reactors is examined using a mathematical model and the sensitivity of the reactor performance to pressure variation is investigated.

Description: The present work reports the effect of bentonite clay on methane hydrate formation and dissociation in synthetic seawater of salinity 3.55 % of total dissolved salts. Extensive observations of pressure-temperature equilibrium during formation and decomposition of methane hydrate under different conditions have been made. It is observed that phase equilibrium conditions of hydrate are affected on changing the concentration of bentonite clay in synthetic seawater. Induction time for hydrate nucleation has been measured under different concentrations of clay and subcooling conditions. The presence of bentonite clay in synthetic seawater reduces the induction time of hydrate formation. Enthalpy of hydrate dissociation is calculated by Clausius-Clapeyron equation using measured phase equilibrium data. The amount of gas consumed during hydrate formation has been calculated using real gas equation. It is found that a larger amount of gas is consumed upon addition of bentonite clay in synthetic seawater. Bentonite clay is used for methane hydrate formation in synthetic seawater. Reaction kinetics and hydrate formation pressure and temperature are studied under different conditions. Bentonite clay is further-more investigated in terms of surface morphology, chemical changes due to hydrate formation and particle size distribution in suspension.

Description: An engineered process for scalable manufacture of a calcium aluminum carbonate CO 2 sorbent with production amounts of about 1000 g per hour has been developed. The process includes mixing and heating, solid-liquid separation, drying and extrusion, crushing and conveying, and calcined molding steps. The sorbent preparation involves the coprecipitation of Ca 2+ , Al 3+ , and CO 3 2– under alkaline conditions. By adjusting the Ca:Al molar ratio, a series of Ca-rich materials could be synthesized for use as CO 2 sorbents at 750 °C. A calcium acetate-derived sorbent exhibited better cyclic stability than sorbents originating from CaCl 2 and Ca(NO 3 ) 2 . The initial sorption capacity increased with CaO concentration. High stability of more than 90 % was maintained by the Ca:Al sorbents after 40 looping tests. The main advantages using CaO-based sorbents for high-temperature CO 2 capture are their high capacity and advanced CO 2 uptake characteristics. A novel process for scalable manufacture of a calcium aluminum carbonate CO 2 sorbent is introduced. Using this method, CO 2 sorbents with significantly improved performance can be produced in kg-batches.

Description: Amine solutions were applied in carbon dioxide removal from a model mixture of biogas, carried out in a loop reactor system. In addition, the effect of CO 2 absorption acceleration in the presence of piperazine was confirmed and quantified, relating the obtained CO 2 loading with the piperazine concentration. Further, the interactions of CO 2 and water in aqueous amine solutions were discussed. The obtained acid gas loadings were accurately described taking into account the effect of the dissolved CO 2 on the equilibrium constant. A logarithmic absorption isotherm that follows from such considerations and a saturation-type isotherm were compared. In describing the experimental data, advantages and disadvantages of both approaches are discussed. The absorption performance of piperazine-containing amine solutions to be used for biogas upgrading was investigated in terms of CO 2 capture. The suggested approach was utilized to describe the non-ideality of the absorption isotherms and proved to be suitable also for data reported by other research groups.

Description: An ultrasonic enhanced salt-containing hydrodistillation (UESHD) method for separating essential oil from lavender ( Lavandula angustifolia ) flowers was investigated using response surface methodology (RSM). The experimental data obtained from a 27-run experiment were fitted to a second-order polynomial equation. The optimal conditions were determined by the 3D response surface and the contour plots derived from the models. The efficiency of UESHD and conventional hydrodistillation (HD) was compared. The extraction yield of UESHD was two-fold higher than that of HD. In addition, GC-MS results indicated some differences in composition and content between the two essential oils from UESHD and HD. An ultrasonic enhanced salt-containing hydro-distillation (UESHD) method was developed to separate lavender essential oil. The extraction yield of the oil was optimized by statistical software, the separation conditions by the Box-Behnken design. UESHD enabled a more than two-fold yield of essential oil than conventional hydrodistillation.

Description: The effects of operating conditions on radial variation of gas holdups, bubble swarm rising velocity, and Sauter mean diameter were investigated in a bubble column reactor under elevated pressures using a conductivity probe method. Air served as gas phase and tap water as liquid phase with varying gas velocity and pressure. All three parameters increased constantly with higher superficial gas velocity. Maximum holdup, velocity, and Sauter mean diameter were found at the center of the cross section. Two different cases for Sauter mean diameter distribution were observed. The gas holdups increase continuously with higher system pressure, but decrease for bubble swarm rising velocity and Sauter mean diameter. According to experimental results, an empirical correlation of the gas holdup profiles is presented. Experimental data on the distribution of gas holdup, bubble swarm rising velocity, bubble size distribution, and Sauter mean bubble diameter in an air-water system are presented. The effects of operating conditions were evaluated in a bubble column reactor under elevated pressures and churn-turbulent flow regime applying a conductivity probe method.

Description: Drying is considered as an intensive operation that consumes large quantities of energy. Usually, baker's yeast is obtained using freeze drying or fluidized-bed drying, both of which are considered as expensive technologies. So, exploring other techniques such as contact drying could limit this disadvantage. In addition, no work dealing with contact drying of baker's yeast has been accomplished yet. Therefore, here, the behavior of baker's yeast during vacuum agitated contact drying is presented. The results show that the drying process can be divided into three phases: the pasty phase, the lumpy phase, and the granular phase. The influence of the drying parameters, such as the temperature, the impeller velocity, and the initial mass, was also studied. It was found that the wall temperature and the impeller velocity have a positive effect on the drying kinetics, as their increase allows a reduction in the drying time. Nevertheless, an increase in the pressure level or the initial mass of the product caused the drying time to increase. The behavior of baker's yeast during vacuum agitated contact drying is studied. The wall temperature and the impeller velocity have a positive effect on the drying kinetics, as their increase leads to a reduction in the drying time, whereas an increase in the pressure level or the initial mass of the product increases the drying time.

Description: Nucleation kinetics and a growth model of penicillin sulfoxide in butyl acetate were studied. Nucleation parameters such as energy per unit volume, radius of critical nucleus, critical free energy barrier, and nucleation rate were evaluated. A laser method was selected to detect the first crystal in induction period studies. By means of scanning electron microscopy and surface entropy factor, the growth model of penicillin sulfoxide developed from butyl acetate could be determined. According to the results of nucleation kinetics and the growth model of penicillin sulfoxide in butyl acetate, production process parameters can be optimized. The products of penicillin sulfoxide exihibit high purity and provide long-lasting forms of storage. The results are essential for crystallization process control of penicillin sulfoxide in industry.

Description: Oxygen mass transfer from air to the liquid phase in bioreactors with aerobic cultures has long been a serious impairment to the productivity of various bioprocesses. An increase of the oxygen mass transfer rate (OTR) can be the key to overcome oxygen limitation. The influence of higher air pressure on OTR was measured and a significantly enhanced OTR could be obtained. The oxygen volumetric mass transfer coefficient ( k L a ) was described by a function of the air pressure in a stirred lab-scale pressurized bioreactor. The correlation obtained proved that k L a slightly decreased with higher air pressure, following a power function. The oxygen mass transfer rate (OTR) and oxygen volumetric mass transfer coefficient ( k L a ) must be known to achieve optimum design operation and avoid oxygen transfer limitations. An increased air pressure is an important approach to enhance OTR and k L a . The proposed correlation could be valuable for further process optimizations where oxygen transfer is a limiting factor.

Description: A MnCu-mixed oxide catalyst supported on a cordierite monolith was synthesized. The catalyst showed very good stability and high homogeneity and presented an excellent catalytic activity in the combustion of ethyl acetate, n- hexane, and its mixture. The total conversion temperature of the mixture was determined by the temperature at which the most difficult molecule was oxidized. An excellent catalytic activity in the combustion of ethyl acetate, n- hexane and its mixture was obtained with a MnCu/cordierite monolith catalyst. The monolithic catalyst was synthesized using a simple and reproducible method. Catalysts with homogeneous and well-adhered coatings were obtained. The simplicity of the method used favors scaling for industrial applications.

Description: Nano-alumina powders containing yttrium oxide were synthesized via the sol-gel method using aluminum chloride hexahydrate as catalyst precursor. Fourier transform infrared analysis showed the presence of Al-O and Al-O-Al bands in the powder structure and X-ray diffraction spectra proved that the alumina was in the amorphous phase. The amorphous nano-alumina powders were shown to be mesoporous with a high surface area, and both spherical and slit-shaped particles were found in the calcined powder. A high percentage of conversion of oil to biodiesel was obtained in the transesterification reaction and the synthesized nano-alumina powders could be easily regenerated for further use. The amorphous nano-alumina powder can thus be recommended for use as active catalyst in the transesterification reaction for biodiesel production on the industrial scale. A novel catalyst for use in the transesterification reaction for biodiesel production was synthesized and characterized. A simple, reliable and cost-efficient sol-gel technique is proposed, leading to amorphous alumina powders with high surface area and nano-sized particles, appropriate for industrial applications.

Description: A series of Mg-modified SBA-15 mesoporous silicas with different MgO contents were successfully synthesized by a simple one-pot synthesis method and further impregnated with Ni. The Mg-modified SBA-15 materials and supported Ni catalysts were characterized by N 2 physisorption (BET), X-ray diffraction (XRD), temperature-programmed desorption of CO 2 (CO 2 -TPD), temperature-programmed H 2 reduction (H 2 -TPR), and temperature-programmed hydrogenation (TPH) techniques and used for methane dry reforming with CO 2 . CO 2 -TPD results proved that the addition of Mg increased the total amount of basic sites which was responsible for the enhanced catalytic activity over the Mg-modified Ni catalyst. The excellent catalytic stability of Ni/8Mg-SBA-15 was ascribed to less coking and higher stability of the Ni particle size due to the introduction of Mg. Mg-modified SBA-15 mesoporous materials with varying Mg contents were successfully synthesized by a one-pot approach and applied as support for Ni-based catalysts. The incorporation of Mg to Ni/SBA-15 catalyst remarkably decreased the active Ni particle size via metal-support interaction and yielded a high resistance ability to coke deposition.

Description: Methanation of CO under unsteady-state operation conditions was studied systematically based on a simplified mathematical model for an integral reactor using steady-state kinetics available in the literature. The inlet composition of CO and H 2 was changed stepwise and the step response of the system was monitored in order to study the dynamic behavior of the reactor. Furthermore, periodic changes were applied with different cycling times. It was observed that the time average reaction rate could not be improved by cycling the feed composition. Moreover, the reactor appears to be self-stabilizing, since the amplitude at the outlet is reduced, leading to a steady state for high cycling frequencies. The results allow conclusions on principles to design a methanation reactor for unsteady-state operation. However, it also becomes obvious that unsteady-state kinetics is mandatory in order to describe the experimental results obtained under dynamic conditions. Methane is one important backbone for the energy supply in today's western world. Methanation under unsteady-state operation conditions was studied based on a mathematical model. The inlet composition of CO and H 2 was varied stepwise to study the dynamic behavior of the reactor for different cycle periods. It was observed that the reactor behaves in a self-stabilizing manner.

Description: Polyethersulfone (PES) dope solutions were prepared from mixtures of two solvents containing N , N -dimethylformamide (DMF) as core solvent and acetone as co-solvent (CS) in a closed heating system. PES asymmetric membranes were cast by a dry/wet phase inversion process. Complete miscibility of PES with the fixed mixture of acetone and DMF under atmospheric pressure could be achieved. The kinetic and thermodynamic properties indicated that interaction of DMF and acetone is strongest when their mole ratio is unity, pointing to the phenomenon of true co-solvency for PES dissolution. These results were supported by determination of the water uptake, contact angle measurement, and SEM analyses. Membrane performance, pore volume, and total pore volume on the membrane surface were also investigated. From mixtures containing N , N -dimethylformamide (DMF) as core solvent and acetone as co-solvent, polyethersulfone (PES) dope solutions were prepared. Membranes produced from such dope solutions containing acetone turned out to be superior in terms of permeation flux rates, rejection rates, and quality compared to membranes prepared without acetone.

Description: Alginate hydrogel beads are widely used as an encapsulation medium for biomedical, bioprocessing, and pharmaceutical applications. The size and shape of the beads are often critically controlled since in many usages the beads are monodisperse in size and spherical in shape. Extrusion dripping is a well-known method to produce alginate beads. Nevertheless, the production of beads of desired size and spherical shape is often achieved based on one's experience or trial and error. An overview is provided on alginate properties, formulation and preparation of alginate and gelling solutions, production conditions, and post-production treatment that may influence the bead size and shape. Various methods of bead size and shape measurement are also discussed. The influence of significant process variables like alginate properties, formulation and preparation of alginate and gelling solutions, production conditions, and post-production treatment on size and shape of Ca-alginate beads is reviewed. Various methods for bead size determination and shape analysis are described in detail and discussed.

Description: The influence of mechanical stress on the crystal size distribution of lysozyme crystal slurries in a dynamic cross-flow device is discussed. The reduction of crystal size may have an influence on mass and resistance of the fouling layer. A filter test device with a filter area of 130 cm 2 is used for thickening. After thickening, a model impurity, namely bovine serum albumin, is washed out of the suspension. A reduction of crystal size due to stirring and a reduced fouling layer with increasing stirrer speed is observed. Furthermore, a higher stirring speed increases the specific filtrate flux. In the presence of the impurity, more crystal aggregates than single isometric crystals are formed and, hence, the decrease of crystal size due to shear forces is more pronounced than without impurity. Protein crystals are in comparison to other organic and nonorganic crystals very soft and fragile. During separation in a dynamic cross-flow device a decrease of the crystal size is observed due to crystal breakage which could influence the separation and following product formulation steps. The impact of stirring speed and residence time is discussed for lysozyme crystals.

Description: The kinetics of bioethanol production using mono- and co-cultures of Saccharomyces cerevisiae and Pichia stipitis with glucose, xylose, and glucose-xylose sugar mixtures were investigated. A MATLAB® program was formulated for simulation of experimental results in order to get predicted values of ethanol production and sugar consumption and for kinetic parameter estimation. Kinetic parameters implied less extent of substrate and/or product inhibition when the co-culture scheme of immobilized S. cerevisiae and free P. stipitis was employed for fermentation of mixed sugars. In addition, a high ethanol yield was achieved by applying this co-culture strategy to wheat straw hydrolysates. The kinetics of bioethanol production with single and mixed-sugar fermentation employing mono- and co-cultures of Saccharomyces cerevisiae and Pichia stipites were determined. Bioconversion of concentrated wheat straw hydrolysates to ethanol was successfully performed using a co-culture of immobilized S. cerevisiae and free P. stipitis .