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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 409-419 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The formation of aerosol particles by gas-phase chemical reaction in the presence of seed particles has been studied experimentally and theoretically. Titanium tetraisopropoxide (TTIP) vapor containing ultrafine TiO2 seed particles was introduced into a laminar flow aerosol reactor, and the properties of produced TiO2 aerosol were measured. By comparing the particle numbers and size distributions of the resulting aerosol with those of the seed particles and those of homogeneously nucleated particles in the absence of seed particles, the effects of initial concentrations of TTIP vapor, reaction temperatures, and properties of seed particles on the suppression of homogeneous nucleation were experimentally clarified. In the theoretical analysis, the population balance equation expressing simultaneous generation of TiO2 monomer, Brownian coagulation and diffusive deposition of TiO2 monomer and aerosols was solved. The observed suppression of homogeneous nucleation by the seed particles is explained qualitatively by the theoretical analysis.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1249-1256 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of powders by aerosol routes spans a wide range of operating temperatures depending on the type of aerosol reactors used. The dominant mechanism of particle growth and evolution depends highly on the rate at which the reactions producing the condensible species are carried out. Numerical solutions of the discrete-sectional aerosol general dynamic equation that accounts for the interactions of the discrete clusters were obtained for conditions representative of the different types of aerosol reactors used for powder production today. Simplified reaction and coagulation equations that give fast and useful prediction of the evolution of aerosols associated with chemical reactions were derived, and a simple reaction-coagulation model was developed. The effects of reaction rate, initial vapor concentration, residence time, seed particles, and temperature profile on the properties of tine particles produced by gas-phase chemical reactions were evaluated using both models. Results show good agreement between the two.
    Additional Material: 9 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 9 (1992), S. 19-27 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Agglomerates of uniformly sized primary spheres are found in many aerosol and colloidal systems. Such particles have been described as fractal although they possess selfsimilarity over only a narrow range of length scales. Previous work suggests that, for such objects, ideal fractal scaling laws may require substantial corrections. The problem is particularly acute for measurements of particle structure from 2d images. The relation between the structure of an agglomerate and the characteristics of its projection is investigated using simple analytical models and clusters generated by a modified cluster cluster aggregation simulation. The morphology of the simulated clusters is varied by changing the ratio of masses of the colliding clusters. The fractal dimensions Df3 of the simulated clusters were typically 10-20% higher than those measured for the projections, Df2, even though Df3 〉 2. This difference decreases as the cluster size increases. It was found that the fraction of primary particles visible in the 2d image is more sensitive to cluster size than to fractal dimension for clusters with less than several thousand primary particles.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 29 (1997), S. 523-525 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants for three dimethylbenzaldehydes and two trimethylphenols have been determined for the OH reactions at 298±2 K and atmospheric pressure using a relative rate method. The OH reaction rate constants were placed on an absolute basis using the literature rate constant for 1,2,4-trimethylbenzene of (3.25±0.5)×10-11 cm3 molecule-1s-1). The measured rate constants were (in units of cm3 molecule-1 s-1) 2,4-dimethyl-benzaldehyde, (4.32±0.67)×10-11; 2,5-dimethylbenzaldehyde, (4.37±0.68)×10-11; 3,4-dimethylbenzaldehyde, (2.14±0.34)×10-11; and 2,3,5- trimethylphenol, (12.5±1.9)×10-11, 2,3,6-trimethylphenol, (11.8±1.8)×10-11. Using an average OH concentration of 8.7×105 molecule cm-3, the estimated atmospheric lifetimes are ca. 7.5 h for 2,4- and 2,5-dimethylbenzaldehydes, ca. 15 h for 3,4-dimethylbenzaldehyde, ca. 2.5 h for 2,3,5- and 2,3,6-trimethylphenols. The reactivities of the trimethylphenols exceed those of the dimethyl-benzaldehydes by more than a factor of 3. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 523-525, 1997.
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 17 (1985), S. 177-216 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An experimental investigation of the gas-phase photooxidation of toluene-NOx-air mixtures at part-per-million concentrations has been carried out in a 65-m3, outdoor smog chamber to assess our understanding of the atmospheric chemistry of toluene. In addition, six CO—NOx-air irradiations were conducted to characterize the chamber with regard to any wall radical sources. Measured parameters in the toluene-NOx experiments included O3, NO, NO2, HNO3, peroxyacetyl nitrate (PAN), CO, toluene, benzaldehyde, o-cresol, m-nitrotoluene, peroxybenzoyl nitrate (PBZN), temperature, relative humidity, aerosol size distributions, and particulate organic carbon. Predictions of the reaction mechanism of Leone and Seinfeld [7] are found to be in good agreement with the data under a variety of initial conditions. Additional simulations are used to investigate various mechanistic pathways in areas where our understanding of toluene chemistry is still incomplete.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 79-101 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The OH reaction with isoprene is studied. Methyl nitrite photolysis experiments were carried out in an outdoor smog chamber in an attempt to identify as completely as possible OH-isoprene product distribution. Emphasis was placed on identification and quantification of oxygenated products. A Tenax-based cryo-trap thermal desorber used to trap, concentrate, and dry chamber samples for identification on a GC/MS is described. Analysis of the products revealed that O(3P) can form in reaction systems designed to study OH reactions that include high concentrations of NO, and consequently NO2, hence, this reaction is also examined. The yields of methacrolein and methyl vinyl ketone are determined as 25 ± 3 and 35.5 ± 4%, respectively, with an additional 4 ± 2% as 3-methyl furan, totaling 65 ± 4%. These results, combined with those of previous studies allow 80% of isoprene's products to be explicitly identified, and the general structure of the remaining products to be ascertained. The O(3P) reaction produces 84 ± 8% epoxides, and 8 ± 3% species which result in production of HO2, and subsequently, OH. A heretofore unidentified product of the O(3P) reaction, 2-methyl 2-butenal, is identified. The rate constant of the NO2-isoprene reaction is measured.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 103-125 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of experiments have been performed to study the ozone-isoprene reaction in a smog chamber by adding externally produced O3 to the hydrocarbon in the dark. A chemical tracer, methyl cyclohexane, was added to probe the OH formation in the system. O(3P) formation was also examined using the known distribution of products that are unique to the O(3P)-isoprene reaction (part I). The results provide clear evidence that both OH and O(3P) are produced by the O3-isoprene reaction directly in large quantities; about 0.68 ± 0.15 and 0.45 ± 0.20 per O3-isoprene reaction, respectively. These additional radicals severely complicate the analysis of the O3 reaction, hence, computer kinetic modeling was necessary to ascertain the products of the O3 reaction itself, corrected for OH and O(3P) reactions. The product distribution, which differs dramatically from that published previously, is: 67 ± 9% methacrolein, 26 ± 6% methyl vinyl ketone, and 7 ± 3% propene, accounting for 100 ± 10% of the reacted isoprene. Applicability of these results to the gas-phase O3 reaction with other unsaturated hydrocarbons is briefly discussed.
    Additional Material: 8 Ill.
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