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 effects of the presence of a polyelectrolyte on the polymorphism and particle size and shape of calcium carbonate crystals during reactive crystallization were investigated. Crystals were created by the single-jet reaction crystallization method. When polyacrylic acid (PAA) was added, the polymorphism and particle size and shape were different for each molecular weight of PAA and each experimental method. When sodium carboxymethylcellulose was added, the polymorph became different from those made by adding PAA and the particle sizes and shapes were different for each concentration. As a result, it is suggested that the method to achieve supersaturation, such as type of feeding, feed rate, kinds of polyelectrolyte and their concentration, may affect the polymorphism and particle size and shape of calcium carbonate. The effects of polyelectrolyte addition during reactive crystallization on the characteristics of calcium carbonate crystals were investigated. The supersaturation state, the material feed order, and the polyelectrolyte type and concentration were found to have great influence on the polymorphism, particle size and shape, and the crystal number of calcium carbonate.

Description: X-Ray diffractometry was employed to investigate the possibility of formation of non-equimolar discrete compounds in the chiral system of malic acid S - and R -enantiomers. Samples studied were mixtures of single enantiomers or an enantiomer and the various polymorphs of the racemic compound. From samples prepared via recrystallization of the melt and grinding of initial reactants, it is demonstrated that the malic acid enantiomers can form stable stoichiometric compounds in S : R ratios of 3:1 and 1:3. Compared to the known racemic and pure enantiomer phases, the corresponding compounds S 3 R / SR 3 are characterized by a proper powder diffraction pattern and melting point. Non-equimolar discrete compounds formed by malic acid S - and R -enantiomers in ratios 3:1 and 1:3 are investigated by means of X-ray powder diffraction. The corresponding S 3 R and SR 3 compounds are found to be stable or metastable phases in dependence on synthesis conditions. The phases are characterized and discussed with regard to their identity and crystallochemical nature.

Description: Acidic wastewater from industrial discharge is generally treated by neutralization. Before neutralization or water treatment, selective recovery of valuable compounds is necessary to reduce the environmental impact of this acid waste. As a contribution to the development of a novel acidic wastewater treatment, oxalic acid is set as target material which is found in acid waste from the metalworking industry. Crystallization of oxalic acid in the presence of sulfuric acid has rarely been reported. Since this acid waste also contains aluminum ions, the effect of sulfuric acid and aluminum ions on oxalic acid solubility and crystallization was clarified. As a result, sulfuric acid concentration affected the oxalic acid solubility, but aluminum ions had no influence. Oxalic acid was precipitated in columnar shape by cooling crystallization from sulfuric acid aqueous solution with aluminum ions. For effective recovery of oxalic acid from acidic wastewater by crystallization, oxalic acid solubility was investigated and found to be influenced by sulfuric acid concentration. Based on the solubility data, cooling crystallization of oxalic acid in sulfuric acid aqueous solution was conducted. Columnar-type crystals of oxalic acid precipitated in sub-mm size.

Description: A fast-dissolving solid dosage form (tablet), containing in this case paracetamol as an active pharmaceutical ingredient and modified starch as an additive, was successfully produced by means of the freeze-casting process. The structure and two key properties, namely, disintegration time and tensile strength, of freeze-casted tablets were investigated. The produced tablets exhibit a threefold faster disintegration time with equal tensile strength in comparison to the commercial compressed tablets. Sugar as a binder, however, can just improve the disintegration rate but not enhance the tensile strength due to different mechanisms working. Low tensile strength limits the applicability of freeze-casted tablets in industrial production. Modified starch may serve as a binder for solid particles of the active pharmaceutical ingredient enhancing the mechanical strength of produced tablets. Freeze-casted paracetamol tablets are able to compete with commercial compressed tablets in terms of disintegration time and tensile strength.

Description: In the production of beverages, cookies, and candies, citric acid is often used as preservative or flavoring agent. Due to the sensitivity in stability of saccharose concerning pH and temperature, it is necessary to know how these two parameters affect the inversion of sugar and therefore the changes in the characteristics of saccharose crystallization. It can be shown that the inversion speed increases with increasing temperature. Also, the exposure time to the acid as well as the amount of acid lead to an increased inversion and therefore need to be controlled in industrial processes. With a temperature difference of 10 °C, inversion increases by the use of 2.13 % citric acid, e.g., by more than 250 %. The metastable zone shifts, but does not change in its width while inversion takes place and the solubility and nucleation curves are shifted to lower temperatures. To control the crystallization of sugar such as saccharose in foods, knowledge of the position of the process in the phase diagram, and of the metastable zone in particular, is needed. The exposure time to citric acid and the amount of acid are shown to lead to an increased saccharose inversion. The metastable zone shifts to lower temperatures, but does not change in its width during inversion.

Description: The application of powder second harmonic generation (P-SHG), temperature-resolved SHG (TR-SHG), and SHG microscopy (SHGM) in the characterization of bulk crystalline samples is illustrated. P-SHG applied to powder samples can be an extremely sensitive approach to detect the absence of an inversion center in crystalline structures, TR-SHG serves to monitor temperature-induced phase transitions, and SHGM is used in the detection of non-centrosymmetric zones inside a heterogeneous material. These methods are of great relevance, e.g., in the pharmaceutical industry where crystalline active pharmaceutical ingredients are often made of a single enantiomer and are therefore non-centrosymmetric. Herein, several examples are provided to describe how a given SHG signal should be interpreted. A general procedure to carry out a P-SHG experiment is illustrated in detail. The application of second harmonic generation-based techniques to characterize crystalline samples is presented. Several examples are detailed for chemical purity, structural purity and polymorphism studies, with particular relevance to the pharmaceutical industry where crystalline active pharmaceutical ingredients are often made of a single enantiomer and are therefore non-centrosymmetric.

Description: Efficient and simple methods for gene integration into various plants have been studied by many researchers. The particle gun method using fine metal particles is one of the most potent technologies. However, it is difficult to control the particle size distribution and shape of the metal particles and, thus, to design and create adequate particles of suitable quality for the gene-supporting media. Here, reduction crystallization of nanometer- and submicron-sized Au was investigated in order to clarify the effects of the seeding and reaction conditions on the sizes and shapes of Au particles. The seed size has an influence on the surface roughness of the Au nanoparticles. Experiments to form Au particles were also performed using pH-controlled ascorbic acid. The pH has a great influence on the size and shape of nano/submicron Au particles and the mechanism of reduction crystallization. A simple method is suggested to control the sizes and shapes of nano/submicron-sized Au particles by reduction without additive to inhibit agglomeration. The mechanism of particle growth was analyzed by TEM-monitoring the crystallization process. The mean particle diameters of the Au particles were controlled at 6–650 nm by seeding or using pH-controlled ascorbic acid solutions.

Description: The mathematical model for hydrogen production by the photosynthetic bacterium Rhodobacter capsulatus in a batch photobioreactor is discussed. An analytical method – the homotopy perturbation method – is presented to solve the nonlinear differential equations that describe the biomass formation, substrate utilization, and hydrogen production with respect to time. Approximate analytical expressions for the concentrations of biomass, substrate and hydrogen are derived for various values of the relevant parameters. The analytical results are compared with experimental data. In addition, the sensitivity of the kinetic parameters is also analyzed. The time required to achieve the maximum growth of biomass and complete degradation of the substrate is reported. Hydrogen can be produced by the photosynthetic bacterium Rhodobacter capsulatus. Here, the mathematical model for the production in a batch photobioreactor is discussed. Approximate analytical expressions for the concentrations of biomass and substrate and the production of H 2 were obtained in terms of the kinetic parameters. The sensitivity analysis of the model parameters is also presented.

Description: The circumferential overlap structure is considered as one of the key factors which influence the performances of helical baffle heat exchangers by restraining the bypass stream between adjacent baffles. The flow and thermal performances of four trisection helical baffle heat exchangers with the same angle of inclination but different circumferential overlap sizes were numerically investigated. The four schemes involve an end-to-end one and three circumferential overlap ones with triangular area covering one row (20°TCO), two rows (20°T2CO), and three rows (20°T3CO) of tubes. The flow field and combined slices with pressure contours plus velocity vectors were depicted. The 20°TCO scheme proved to be superior to other schemes since its Nusselt number as well as its comprehensive index are the highest and its secondary flow is the strongest. The circumferential overlap trisection helical baffle heat exchanger is a modification based on a quadrant baffle and anti-shortcut structure to improve heat transfer performance. The mechanisms of heat transfer enhancement for four circumferential overlap structures were investigated. Pressure contours plotted with velocity vectors on special slices reveal secondary flow and bypass stream.

Description: The growth rate of the stable polymorph A and the dissolution rate of the unstable polymorph B of L -histidine ( L -his) in aqueous solution were experimentally determined at varying temperatures. The growth and dissolution kinetics were measured by means of desupersaturation and deundersaturation techniques, respectively. Both the growth and dissolution rates increase with higher temperature. At all temperatures studied, the dissolution rate of form B is faster than the growth rate of form A, indicating that the solution-mediated transformation of the polymorphs of L -his is likely to be controlled by the growth rate of form A. Both kinetics of the polymorphs of L -his will be used to characterize the polymorphic transformations and the overall crystallization rate of L -his. The essential amino acid L -histidine has shown to exhibit polymorphism and it exists in the solid phase as a stable polymorph A and a metastable polymorph B. The kinetics of growth and dissolution of the polymorphs which contribute to the rate of transformation between the polymorphs are investigated. The results indicate that the transformation is a growth-controlled process.

Description: An adaptive dynamic search algorithm is proposed to predict the solubility of salt in a salt-water system. It is not subjected to the impact of the initial probe whether the results are convergent or not. The thermodynamic basis for the proposed algorithm is discussed in detail and the iterations of the algorithm and the calculation error are quantitatively studied. The multiple calculated results and the experimental solubility data are compared. The algorithm proves its high accuracy and efficiency in theory compared to other algorithms, such as the Newton iteration algorithm. It possesses reliable potential for application in low-salt system dissolution equilibrium calculations. A dynamic search algorithm is introduced to predict the solubility based on equilibrium equations and solubility product in salt-water systems. A comparison between the calculated results of the algorithm and the experimental solubility data proves the high accuracy and efficiency of this algorithm. It exhibits great potential for low-salt system dissolution equilibrium calculations.

Description: A multistep dry fractionation method for modification of palm oil was adopted to achieve a high iodine value (IV) of the obtained palm olein, herein denoted as top olein. The effect of the composition of palm oil top olein on the IV and on the crystallization properties was analyzed in detail. Thermal properties of a series of olein and stearin fractions were evaluated by means of differential scanning calorimetry upon cooling. The composition of triacylglycerols in the products was investigated by high-performance liquid chromatography. IV analysis was carried out to measure the degree of unsaturation in these oil samples. Finally, an innovative and reliable method was developed to determine the IV of palm oils by relating the thermal properties with IV. The results agree well with those obtained by the traditional American Oil Chemists' Society method. In the palm oil industry, the iodine value is normally determined by a titration method that uses toxic solvents. An innovative method is proposed to quickly determine the iodine value of oil samples. This approach can provide statistically similar results to those given by traditional official procedures, with the advantages of being extremely rapid and environmentally friendly.

Description: A high-pressure analytic phase equilibria setup, capable of operation at 150 °C and 30 MPa, was developed. The variable-volume view cell contains two height-adjustable samplers enabling simultaneous sampling from two phases. Concurrent analysis of both samples was performed with dual online gas chromatography (GC). The GC comprises two inlets, four columns, two switch valves, and three detectors, arranged in parallel pathways. Quantitative detector calibrations were used. The setup was validated by sampling from a one-phase ternary of known composition, and comparison with binary and ternary literature data. The setup produces accurate phase composition data for supercritical systems and is well-suited to handle mixture constituents ranging from volatile gases to mid-length hydrocarbons. Supercritical fluid solvents may provide improved selectivity or solvating ability and enable the execution of difficult extractions. Ternary phase behavior data assist supercritical fluid extraction process design. A high-pressure static analytic phase equilibria setup was developed. The setup produces accurate supercritical phase composition data and can accommodate diverse mixture constituents.

Description: A fast method is proposed for determining the oxygen gas-liquid diffusion coefficient from measurements of the fluorescence quenching behind a bubble. The approach consists of capturing pictures of the concentration field at micro-scale in the laminar bubble wake. The Gaussian concentration profiles measured in the wake are demonstrated to be systematically equivalent to an instantaneous plane diffusion case. The approach permits to accurately evaluate the gas-liquid diffusivity in a very short time of around one second. Since literature data on mass diffusion coefficients are actually not sufficient, a fast method is proposed to obtain oxygen diffusion coefficients from measuring the fluorescence quenching behind a bubble. Planar laser-induced fluorescence with inhibition presents a non-intrusive alternative method to accurately evaluate the gas-liquid diffusivity in a very short time.

Description: Evidence of growth rate dispersion for symmetry-related opposite faces of centrosymmetric single crystals of ammonium perchlorate is provided. Crystallization experiments conducted by evaporation of a stagnant aqueous solution at room temperature show that some faces have high and irregular normal growth rates, in time and space, whereas the corresponding faces crystallize slowly and steadily. The faces presenting high and irregular crystal growth also form repetitive inclusions, whereas faces are not involved in any formation of vacuoles. As a consequence, it is possible to retrace the crystallization history of a single crystal by analyzing the location of series of inclusions showing the progressive displacement of its center of gravity. Crystal growth rate dispersion of ammonium perchlorate crystallized by evaporation of an aqueous solution at room temperature is evidenced by considering some Friedel pairs of faces. The relationship between the formation of inclusions and a high growth rate of crystal faces is highlighted. Considering the locations of the inclusions, the results demonstrate a high heterogeneity of crystal growth rates, from which the history of crystal growth can be retraced.

Description: In order to contribute to a better understanding of the electrostatic phenomena appearing during splash filling of liquids and to clarify the reasons why this process is suspected to increase static electrification especially due to atomization, accurate experiments of charge measurements were made on droplets of various liquids falling over a large distance (5 m). Eleven liquids of different conductivity and surface tension were tested. The results confirm that no charge evolution appears even over a long falling distance. A possible explanation of the static charge increase in splash filling is presented. Due to the generated electrostatic charges, the splash filling process poses some dangers. Here, the charge evolution of a single droplet is examined along its fall. From experiments with droplets of many different liquids, falling over 5 m, it is confirmed that the assumption that droplets are charged by friction with air, as still discussed in the explosion hazard community, does not hold true.

Description: Continuous hydrogenation reaction of ethyl benzoylformate was studied over a (–)-cinchonidine (CD)-modified Pt/Al 2 O 3 catalyst. The catalyst showed a good stability, and high enantioselectivity was achieved in the fixed-bed reactor. Chromatographic separation of ( R )- and ( S )-ethyl mandelate originating from a post-continuous hydrogenation reaction of ethyl benzoylformate over the (–)-CD-modified Pt/Al 2 O 3 catalyst was investigated in the same reaction mixture. A commercial column filled with a chiral selector resin was chosen as a perspective preparative-scale adsorbent. Since adsorption equilibrium isotherms were linear within the entire investigated range of concentrations, they were determined by pulse experiments for the isomers present in a post-reaction mixture. Breakthrough curves were measured and described successfully by the dispersive plug-flow model with linear driving force approximation. An integrated concept for the production of optically active chemicals by heterogeneous asymmetric catalysis and chromatographic separation was developed. Feasibility to conduct continuous heterogeneous catalytic enantioselective hydrogenation of ethylbenzoyl formate in the same solvent as considered optimal for chromatographic separation of the products is demonstrated.

Description: Covalent immobilization of polycations onto a membrane surface has been shown to significantly improve the resistance to biofouling. The poly(vinylidene fluoride)-graft-poly( N , N -dimethylamino-2-ethylmethacrylate) (PVDF-g-PDMAEMA) copolymer was synthesized via radical grafting copolymerization and fabricated into a flat membrane. The polycation membrane surface was constructed by quaternization of PDMAEMA side chains with 1,5- dibromopentane and diquaternization of 4,4′-bipyridine. As revealed by membrane surface morphology, pore size, and porosity measurement, the polycations are distributed on the membrane surface and internal pore channel surface. Water contact angles confirm that the incorporation of polycations remarkably promotes the surface hydrophilicity of a membrane. The polycation membrane surface provides an excellent bactericidal efficiency against Escherichia coli. Biofouling is a major obstacle for ensuring long-term effectiveness of a membrane process. A strategy is proposed to construct an antibacterial poly(vinylidene fluoride) membrane surface by covalent immobilization of cations. The polycation membrane surface exhibited an excellent antibacterial activity. Irreversible fouling was converted into reversible fouling.

Description: Two sequencing batch reactors were operated to investigate the effect of influent alkalinity and reactor pH on aerobic granulation. In the first reactor R1 with high influent alkalinity the pH was adjusted in the neutral range, and in the second reactor R2 with low alkalinity the pH was held within the acidic range. The R1-dominating species were bacteria and the appearance time of granules was three weeks after reactor start-up. On the other hand, the acidic environment of R2 provided favorable conditions for fungal growth, and rapid granule formation occurred within the first week of operation. The varying microbial structure of granules resulted in different reactor performance in terms of evolution time and morphology of granules, suspended solids in the reactors, settling ability of granules, effluent quality of treated wastewater, and physical strength of the granules. Adjusting the pH of granular bioreactors has a great impact on aerobic granulation. Lowering the pH in the early stage of operation followed by a gradual increase helps in rapid formation and high strength of granules. The results are valuable for the development of full-scale aerobic granular bioreactors for wastewater treatment with rapid reactor start-up and good system stability.

Description: Pervaporation is a well-established separation technology for the production of anhydrous solvents, but its distribution in the chemical industry is still limited to a few individual applications. Besides the need of high-selective membranes, the development of membrane modules adapted to the specific requirements of this process needs more research effort. Furthermore, only few modeling tools for the pervaporation process are available. In this work, a three-step modeling approach ranging from a shortcut to a rigorous model is developed. A hydrophobic membrane is characterized in a laboratory test cell for the separation of 2-butanol from water in a wide temperature and concentration range. The identified performance data are used to simulate the same separation task with an industrial-scale membrane module. The results are validated by experiments conducted with a novel membrane module in pilot scale. Only few modeling tools for the pervaporation process are available. A three-step modeling approach for simulation of industrial-scale pervaporation modules is described. The models are based on the design of a newly developed membrane module. Performance data of a hydrophobic membrane are identified in laboratory-scale experiments. Simulations of an industrial-scale membrane module are compared to experiments in pilot scale.

Description: The chemical looping process is an alternative method to provide conventional gasification (CG) systems with the required oxygen. The syngas produced via chemical looping has a higher calorific value than that generated by a conventional process with air. For comparison, a conventional gasification unit with pure oxygen (CGPO) and a chemical looping gasification (CLG) system were simulated with Aspen Plus. The CGPO reactor consisted of a bubbling fluidized bed and sand as bed material with oxygen supplied via a pressure swing adsorption unit. The CLG comprised a bubbling fluidized-bed gasifier working in parallel with a fast fluidized-bed oxidizer. The total capital investment (TCI) of the CLG unit was higher than that of the CGPO unit but the annual operating cost of the former was less which repays the difference in TCI in less than six years. Chemical looping is an alternative method to supply conventional gasification (CG) systems with the required oxygen. As biomass gasification scenarios to produce high-concentrated syngas, CG units working with air or pure oxygen are compared techno-economically to chemical looping gasification. The latter approach is found to be a reasonable substitute for GC with oxygen.

Description: Terutroban sodium salt (Teru-Na) is a solid active pharmaceutical ingredient initially produced in its anhydrous form. The crystallization of a new dihydrate was established using liquid-assisted grinding and the liquid-liquid interface process. The stability of the Teru-Na crystalline phases was investigated as a function of temperature and relative humidity. A combination of analytical tools (spectroscopic, thermal, and vapor sorption analyses) highlighted the remarkable stability of the dihydrate, in particular under variable storage conditions. A rationalization of the stability hierarchy was proposed by means of phase diagrams. Besides studies on the crystallization processes of active pharmaceutical ingredients, stability studies at varying temperature and relative humidity are required. With Terutroban sodium salt as an example, the appearance of a hydrate (initially undesired) during storage is rationalized and its improvements in terms of stability are demonstrated.

Description: The extraction of oils based on animal fat and vegetable oil from two types of spent bleaching earths, namely from the acidic sepiolite and the nonacidic palygorskite, was investigated by the Soxhlet method with hexane as a solvent. The yields of oil were independent of the feedstock, whereas a much lower oil yield was obtained with palygorskite exhibiting also a smaller surface area as compared to sepiolite which provided a higher yield. The glyceride compositions were very similar in bleached and extracted oils, while slightly lower melting and crystallization energies were determined by differential scanning calorimetry for the extracted oils bleached with acidic clay indicating minor hydrolysis of triglycerides. In the production of renewable diesel the feedstock is subjected to bleaching to remove undesired or harmful by-products. Oil extraction from acidic and nonacidic spent bleaching earths was investigated. The quality of the extracted oil was found to be similar to that of the bleached oil, especially considering the glyceride composition. The yields of oil were independent of the feedstock.

Description: The thermal analysis performance of evaporative fluid coolers (EFCs) is improved by replacing plain tubes by twisted oblong tubes. Results of the system are assessed by a rapid design algorithm (RDA) and compared to conventional plain-tube EFCs and other traditional algorithms including the effectiveness number of transfer units ( ϵ -NTU). Based on the RDA, a relationship between heat transfer coefficients, pressure drops, heat transfer area, and mass transfer coefficient is derived. Using the maximum allowable pressure drops in this algorithm, the minimum required heat transfer area can be determined. The algorithm is validated by comparing the plain-tube EFC design with twisted-tube design. The RDA-designed EFCs with twisted tubes provide higher efficiency compared with the traditional designs with plain tubes in such that the new design needs a lower heat transfer area for a given heat load. The application of twisted instead of plain tubes is a promising approach to increase the thermal efficiency of evaporative fluid coolers. Thermal and hydraulic analyses were performed by conventional methods and compared with an innovative rapid design algorithm. The latter minimizes the required heat transfer area, indicating a significant reduction of capital costs of such coolers.

Description: In this work, the design and optimization of different methods for propylene/propane separation in downstream of Methanol-to-Olefin (MTO) process is illustrated. Propylene and propane have similar boiling point, which requires large number of trays and energy when separating by a traditional single column with industrial low pressure steam as reboiler heat source (TRA-LPS case). Some alternatives are studied in this work, including the traditional column using waste hot water as heat resource (TRA-HW), the implement of a vapor recompression cycle (VRC) configuration, and the use of extractive distillation (ED) with acetonitrile solution as entrainer. Comparing with the case of TRA-LPS, the total annual cost can be reduced by 46.9%, 4.6%, and 47.8% for cases of TRA-HW, VRC, and ED, respectively. The required number of trays for separation is reduced by 25.6%, 10.3%, and 42.5% for three cases in the order mentioned above. It can be concluded that TRA-HW and ED cases can be two promising alternatives for this separation.

Description: A microreactor system was developed to investigate the cyclization of pseudoionone (PI) catalyzed by sulfuric acid. The conversion of PI and selectivities of α -ionone and β -ionone were explored under various conditions. The effects of residence time, molar ratio of acid/PI (M-ratio), reaction temperature and sulfuric acid concentration on the reaction were investigated. It was found that sulfuric acid concentration played a vital role in the reaction system, which could greatly influence the conversion and selectivities. 77% β -ionone yield and up to 93% total yield of α -ionone and β -ionone were achieved under optimized conditions. In addition, the formation of byproducts was investigated in detail and the side reactions could be restrained by optimizing the reaction parameters.

Description: The micro-particle image velocimetry (micro-PIV) is a quantitative full field technique for the velocity measurement for flows in microfluidics. The flow fields of both Newtonian and non-Newtonian fluids in microchannels were investigated by micro-PIV. The velocity profiles in various PMMA square microchannels were measured. Different concentrations of various polyacrylamide (PAAm) aqueous solutions were used as non-Newtonian fluids. Two viscous Newtonian fluids were also employed to serve as reference, in particular to validate a lattice Boltzmann (LB) simulation. The results show that satisfactory flow measurements could be realized by the micro-PIV technique. The experimental velocity profile compares favourably with the LB simulation and an approximate solution. The experimentally measured velocity profile can lead to the quantification of the flow index of non-Newtonian fluids as an in-line rheological characterisation.

Description: The spontaneous polymerization, i.e, runaway, of acrylic acid during storage is a serious problem which may endanger life and facilities. In respond to a starting polymerization, effective emergency measures are necessary. For these investigations, a polytropic reactor setup, namely, an isoperibolic reactor is introduced to offer a rational access to restabilization studies. Furthermore, safety diagrams are created where the used amount of stabilizer is plotted against the polymerization progress in terms of the rising temperature. Such diagrams display the minimum required amount of the shortstopper (RESTAB™) for terminating a runaway polymerization. The suitability of the reaction setup is investigated using unstabilized acrylic acid. The restabilization of monomers in tanks is necessary to prevent a spontaneous polymerization, a so-called runaway, which in case of acrylic acid cannot only lead to a shut-down and damage of chemical plants, but also cause casualties. The necessary amount to terminate the undesired starting polymerization immediately is investigated in especially developed isoperibolic reactors.

Description: Saturated branched fatty derivatives are of great interest for the lubricants and cosmetics industry due to their improved temperature and viscosity behavior compared to the corresponding linear homologues. One way to produce saturated branched derivatives is the homogeneously rhodium catalyzed conjugation and co-oligomerization of linoleic compounds based on renewable resources (e.g. sunflower oil) with ethene. The paper studies the catalyst extraction behavior of the homogeneous rhodium catalyst RhCl 3 *3H 2 O from saturated branched fatty derivatives for catalyst recycling. Investigation of the extraction parameters was performed using the model substance isostearic acid. Additionally extraction of rhodium from co-oligomer mixtures with different grade of saturation was carried out successfully. Also the influence of solvent residues from prior reaction steps has been investigated.

Description: 2,4,5-Trifluorobromobenzene is a valuable intermediate with important application in the synthesis of biologically active peptides and fluorescent reagents. In this paper, a continuous-flow system has been successfully developed for the synthesis of 2,4,5-trifluorobromobenzene in microreactor using FeBr 3 as a catalyst, which is steadily generated in situ from the reaction of Br 2 and Fe. The procedure is efficient and easy-to-handle, and 2,4,5-trifluorobromobenzene can be obtained in minutes in high yields.

Description: Fuzzy-based approaches like fuzzy chance constrained programming (FCCP) and fuzzy expected value model (FEVM) have been applied to a multi-objective optimization problem of the industrial grinding process to carry out the uncertainty analysis. Results are compared with respect to the power of risk averseness adopted in the approaches used. The extent of constraint satisfaction due to the presence of uncertain parameters can be accommodated assuming credibility of constraint satisfaction under the FCCP framework whereas the robust set of parameters in the FEVM approach is determined by considering the expectation terms for objectives and constraints. Nonlinear relation of uncertain parameters has been handled by adopting simulation-based approaches while computing the credibility. These approaches are very generic and can be applied for the study of parametric sensitivity for any process model in a novel manner. Multi-objective optimization of an industrial grinding process under uncertainties in various process parameters was performed. The uncertain optimization problem was converted into an equivalent deterministic optimization problem by credibility-based fuzzy chance constrained programming. The proposed approaches can be applied to study parametric sensitivity for any process model.

Description: There are many approaches to face the issue of agent encapsulation as method to protect sensitive substances against outer influences. The possibility of the use of inclusion containing crystals as encapsulation material was investigated. Since many products are water-based media the low water soluble substance salicylic acid (SA) was chosen to investigate its qualities as a container substance. Therefore, the solubility of SA was investigated in dependence on the composition of the antisolvent water and the solvent ethanol by means of a ternary phase diagram. Moreover, SA container crystals were generated and filled by means of an antisolvent crystallization method. Copper sulfate and ascorbic acid could successfully be encapsulated in two case studies.

Description: The phase equilibria of supercritical CO 2 + alkane + alcohol mixtures were studied using online gas chromatography. Gas chromatograph design criteria and quantitative detector calibration methods are presented. An adapted manual calibration injection technique eliminated liner overload and pressure wave effects. Observation of the cell contents has proven essential for accurate vapor phase sampling. Visuals, often not visible to the naked eye, show that sampling can disrupt an equilibrated high-pressure system even though pressure and temperature remain constant to within 0.1 bar and 0.01 °C. Such disruptions may manifest in one of three phenomena: global mist formation, localized mist formation, or no-warning droplet formation.

Description: Natural gas is a primary source of energy and most of the natural gas reserves are contaminated with high percentages of CO 2 . Removal of CO 2 from natural gas is necessary to purify the gas and to enhance the calorific value of gas. Different processes are used for CO 2 removal from natural gas, but all these processes have several limitations. Membrane technology is an efficient technique for CO 2 removal from natural gas due to its ease of operation and low cost. Among different types of membranes used for gas separation, polymeric membranes exhibit excellent separation performance. In polymeric membranes, the separation performance is affected by plasticization and swelling in the membrane. Recent technological advancements and major problems in polymeric membranes are reported in this review. Separation performance of polymeric membranes is highlighted in terms of permeability and selectivity. Moreover, techniques to overcome the major problems in polymeric membranes are highlighted. Among all these techniques, crosslinking and thermal treatment are commonly used to minimize the effect of plasticization and swelling in the membrane. For future perspectives, it can be concluded that there is a need to find more efficient methods to overcome the problems of plasticization and swelling in the polymeric membrane.

Description: Selective acetylene hydrogenation over a commercial Pd-Ag/Al 2 O 3 catalyst was carried out under industrial operation conditions that correspond to the “tail-end” process. Pyrolysis gas chromatography-mass spectrometry was used to analyze the composition of the green oil. C8–C30 linear hydrocarbons with even carbon-numbered chains were detected as the main components of the green oil. Its chain length increased with operating time, temperature, and hydrogen partial pressure, and decreased with acetylene partial pressure. The composition of the green oil deviates from the Anderson-Schulz-Flory distribution. Both coupling-hydrogenation and hydrogenation-coupling mechanisms are involved in green oil formation. The composition evolution of green oil which is formed during acetylene selective hydrogenation over a commercial Pd-Ag catalyst is investigated by pyrolysis gas chromatography-mass spectrometry and other methods and reaction routes are proposed. The results are valuable to avoid green oil formation in industrial processes and for the development of new catalysts.