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• Chemistry  (20)
• 1
Electronic Resource
Hoboken, NJ : Wiley-Blackwell
AIChE Journal 35 (1989), S. 1445-1456
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 kinetics of a semibatch melt transesterification of dimethyl terephthalate (DMT) with ethylene glycol (EG) is studied with zinc acetate as a catalyst. This paper quantifies the effect of various reactor operating conditions on the transesterification rate and the product composition distribution. Our experiments support the assumption that the methylesters in DMT and growing oligomer chains have the same reactivities for transesterification with EG and that the reactivity of hydroxyl groups in pure EG for esterification with DMT is twice that of the hydroxyl group in oligomers. With a molecular species model in which various oligomers are identified by the type of functional end groups, the progress of the transesterification and the oligomer concentration distribution were estimated and the agreement between the model predictions and the experimental data were excellent. It has also been shown that 30 wt. % of oligomers are produced for [EG]/[DMT] molar ratio of three, and up to 70 wt. % oligomers are produced at the [EG]/[DMT] molar ratio of one.
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• 2
Electronic Resource
Stamford, Conn. [u.a.] : Wiley-Blackwell
Polymer Engineering and Science 26 (1986), S. 975-981
ISSN: 0032-3888
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Notes: The steady state structure of non-isothermal free radical solution polymerization in a continuous stirred tank reactor is analyzed. With mean residence time as a bifurcation parameter, five regions of steady states are identified. The effect of reactor operating conditions on the structure and the stability of steady state is discussed.
Type of Medium: Electronic Resource
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• 3
Electronic Resource
Hoboken, NJ : Wiley-Blackwell
AIChE Journal 33 (1987), S. 2067-2076
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: A detailed kinetic model for the bulk styrene polymerization initiated by symmetrical diperoxyester bifunctional initiators is presented. When chain termination occurs via a combination termination mechanism, six distinct polymeric species are identified in accordance with the nature of the polymer end units. It is shown that the unequal thermal decomposition characteristics of the peroxides of the bifunctional initiator system lead to the formation of polymers having considerably higher molecular weight than those obtained by the monofunctional intiator systems. It has also been found that high monomer conversion, high molecular weight, and narrow molecular weight distribution can be obtained simultaneously by using the bifunctional initiators at high reaction temperatures. This is due to the reinitiation and propagation of inactive polymers carrying undecomposed peroxides. The molecular-weight-increasing effect of the bifunctional initiator is more pronounced at high reaction temperatures. The new possibilities of increasing the monomer conversion and controlling the polymer molecular weight properties more effectively through the use of bifunctional initiators are discussed.
Type of Medium: Electronic Resource
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• 4
Electronic Resource
Hoboken, NJ : Wiley-Blackwell
AIChE Journal 43 (1997), S. 196-211
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Plausible stoichiometries for solvation and association complexes in binary mixtures of chloroform and one of six organic diluents (n-hexane, p-dioxane, acetone, diethyl ether, tri-n-butyl phosphate, or triethylamine) are examined parametrically. A range of stoichiometric assumptions based on hydrogen bonding are examined, but only a few such combinations yield statistically significant fits to the experimental vapor-liquid equilibria and NMR chemical shift data. Hydrogen bonding considerations and the “true” chemical species are much more important than nonspecific physical factors such as molecular sizes, shape differences, and regular solution terms. Thermodynamic equilibrium constants are presented for the most significant chloroform solvation complexes. Nonspecific dilution shift is important and more helpful in fitting NMR data than the assumption of a chloroform dimer. Physical effects and an orientation factor are used to predict excess enthalpy in chloroform/n-hexane mixtures where no solvation or association reactions occur. Model parameters are used to predict excess molar volumes and enthalpies. Commonly reported stability constants are concentration dependent.
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• 5
Electronic Resource
New York, NY [u.a.] : Wiley-Blackwell
Journal of Applied Polymer Science 31 (1986), S. 2231-2265
ISSN: 0021-8995
Keywords: Chemistry ; Polymer and Materials Science
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Notes: Propylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. External boundary layer heat and mass transfer effects are investigated for various catalysts and operating conditions. For high-activity catalysts used in slurry, external film mass transfer effects may be significant. For gas-phase polymerization of propylene or ethylene, the model predicts significant particle overheating at short times, which may explain the particle sticking and agglomeration problems sometimes observed in industrial reactors.
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• 6
Electronic Resource
New York, NY [u.a.] : Wiley-Blackwell
Journal of Applied Polymer Science 37 (1989), S. 1429-1433
ISSN: 0021-8995
Keywords: Chemistry ; Polymer and Materials Science
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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• 7
Electronic Resource
New York, NY [u.a.] : Wiley-Blackwell
Journal of Applied Polymer Science 37 (1989), S. 707-728
ISSN: 0021-8995
Keywords: Chemistry ; Polymer and Materials Science
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Notes: The steady-state and transient behavior of a continuous stirred-tank reactor for melt transesterification of dimethyl terephthalate with ethylene glycol in the presence of metal acetate catalyst is presented. The kinetic model includes the main transesterification reactions and side reactions leading to diethylene glycol and carboxylic acid end groups. The effect of various reactro operating parameters such as [EG]/[DMT] mole ratio and feed catalyst concentration on the product distribution under steady-state reactor operating conditions is analyzed. The dynamic process model has also been solved and the reactor transients to step changes in various reactor parameters are reported.
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• 8
Electronic Resource
New York, NY [u.a.] : Wiley-Blackwell
Journal of Applied Polymer Science 41 (1990), S. 2987-3024
ISSN: 0021-8995
Keywords: Chemistry ; Polymer and Materials Science
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Notes: A semibatch melt prepolymerization of poly(ethylene terephthalate) (PET) is studied. Being characterized by complex reaction pathways leading to various functional end groups and side products, PET prepolymerization process poses a challenging modeling problem. Ten distinct polymeric species have been defined in accordance with the type of functional end groups and the corresponding mass balance and moment equation are developed to estimate the progress of reaction and polymer molecular weight. The effect of various reactor operating conditions on the performance of the polymerization process has been examined through numerical simulation of the molecular species model developed. In particular, the effect of incomplete transesterification of methyl ester groups on the polymer molecular weight has been investigated in detail.
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• 9
Electronic Resource
New York, NY [u.a.] : Wiley-Blackwell
Journal of Applied Polymer Science 44 (1992), S. 1759-1778
ISSN: 0021-8995
Keywords: Chemistry ; Polymer and Materials Science
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Notes: The optimal control policies for batch free radical polymerization of styrene catalyzed by a binary mixture of monofunctional initiators have been determined using a multiobjective dynamic optimization technique. The process objectives considered in the optimization include monomer conversion, polymer molecular weight, initiator residue level, and total reaction time. It is illustrated through model simulations and experiments that the performance of the batch polymerization process can be improved significantly through the use of optimal initiator mixture and polymerization temperature programming. This paper also illustrates how the multiobjection optimization technique can be used effectively to solve complex polymerization reactor optimization problems with detailed reaction models.
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• 10
Electronic Resource
New York, NY [u.a.] : Wiley-Blackwell
Journal of Applied Polymer Science 30 (1985), S. 1065-1081
ISSN: 0021-8995
Keywords: Chemistry ; Polymer and Materials Science
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Notes: Propylene was polymerized in gas phase over a \documentclass{article}\pagestyle{empty}\begin{document}${\rm TiCl}_3 \cdot \frac{1}{3}{\rm AlCl}_3$\end{document} (Stauffer Type AA) Catalyst with AlEt2Cl cocatalyst both with and without H2 present. The effects of polymerization temperature, monomer concentration, catalyst composition, and hydrogen were investigated. The experiments were carried out at operating conditions approaching industrial practice.
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