Ethene−Norbornene Copolymerization Using Homogenous Metallocene and Half-Sandwich Catalysts:  Kinetics and Relationships between Catalyst Structure and Polymer Structure. 1. Kinetics of the Ethene−Norbornene Copolymerization Using the [(Isopropylidene)(η5-inden-1-ylidene-η5-cyclopentadienyl)]zirconium Dichloride/Methylaluminoxane Catalyst

1998 ◽  
Vol 31 (15) ◽  
pp. 4669-4673 ◽  
Author(s):  
Dieter Ruchatz ◽  
Gerhard Fink
1981 ◽  
Vol 46 (7) ◽  
pp. 1577-1587 ◽  
Author(s):  
Karel Jeřábek

Catalytic activity of ion exchangers prepared by partial sulphonation of styrene-divinylbenzene copolymers in reesterifications of ethyl acetate by methanol and propanol, hydrolysis of ethyl acetate and in synthesis of bisphenol A has been compared with data on polymer structure of these catalysts and with distribution of the crosslinking agent, divinylbenzene, calculated from literature data on kinetics of copolymerisation of styrene with divinylbenzene. It was found that the polymer structure of ion exchangers influences catalytic activity predominantly by changing the local concentration of acid active sites. The results obtained indicated that the effect of transport phenomena on the rate of catalytic reactions does not depend on the degree of swelling of the ion exchangers in reaction medium but it is mainly dependent on the relative affinity of reaction components to the acid groups or to the polymer skeleton.


1998 ◽  
Vol 550 ◽  
Author(s):  
Stephen E. Rankin ◽  
Alon V. McCormick

AbstractHydrolytic polycondensation of silicon alkoxides and organically modified alkoxides shows promise as a route to new materials for medicine. Mathematical models of this polymerization accelerate the development of these materials and processes for their production. With a reliable model, one can rapidly explore a wide variety of options for controlling material properties. Here we describe a model for kinetics of sol-gel copolymerization of a simple pair of ethoxysilanes: (CH3)3Si(OC2H5) and (CH3)2Si(OC2H5)2. We then describe how reactor configuration alone can be used to control of polymer structure by choosing how to mix the reactants. An example is shown of maximizing homogeneity at any reactor residence time of interest in the model copolymer system by using the time of addition of the faster-reacting monomer.


1995 ◽  
Vol 418 ◽  
Author(s):  
H. Arisawa ◽  
T. B. Brill

AbstractFlash pyrolysis of polyethyleneglycol by T-Jump/FTIR spectroscopy to temperatures of the surface during combustion reveals that volatile products arise from approximately equal amounts of C-O and C-C homolysis. Nine volatile products are discussed. The average number of repeating units in the volatile oligomers is 2.5. A shift in product distribution occurs at 420–480°C resulting from a change in the polymer structure. Below 420°C, di- and mono-ether oligomers and diethyleneglycol dominate. Above 480°C, the mono-ethers and ethyleneglycol dominate. The Arrhenius constants for decomposition reflect this difference: Ea=8.8 kcal mol−1, In (A, s−1) =2.0 at 370–420°C and Ea=19 kcal mol−1, In (A, s−1)=10 at 480–550°C.


1982 ◽  
Vol 60 (21) ◽  
pp. 2749-2754 ◽  
Author(s):  
Craig Fairbridge ◽  
James R. MacCallum ◽  
Robert A. Ross

The oxygen/ethane and oxygen/1-butene reactions have been investigated in a continuous flow system at atmospheric pressure over a manganese oxide/carbon fibre catalyst. The products of reaction were carbon dioxide and water. Apparent activation energies were 108 ± 4 kJ mol−1for the former reaction from 673 to 573 K, and 81 ± 4 kJ mol−1 for the latter from 573 to 473 K. Kinetic data for both reactions were best described by the rate equation:[Formula: see text]The surface mechanism may be complex and it is proposed that reactants interact as adsorbed species each of which is adsorbed on two surface sites. Both oxygen and the hydrocarbon gas appear to be directly involved in further steps. Scanning electron microscopy, X-ray photoelectron spectroscopy, and low temperature krypton adsorption were used to assess the catalyst structure.


1981 ◽  
Vol 59 (14) ◽  
pp. 2232-2238
Author(s):  
R. A. Ross ◽  
C. Fairbridge

The catalytic reaction between ethane and nitric oxide over manganese(III) oxide has been investigated in a continuous flow system from 673 to 573 K at atmospheric pressure. The products of catalysis were nitrogen, carbon dioxide, nitrous oxide, and water. The rate of nitrous oxide formation was constant over this temperature region, while the apparent activation energies for nitrogen and carbon dioxide formation increased from 32 ± 4 and 22 ± 4 kJ mol−1, respectively, at 573 to 613 K, to 78 ± 4 and 63 ± 4 kJ mol−1 between 613 and 673 K. The kinetic results were best described by the rate equation:[Formula: see text]The surface mechanism appears to be complex and has been interpreted by a scheme involving interaction of the reactants in an absorbed layer. Both nitric oxide and ethane are believed to be involved further in subsequent steps. Infrared evidence indicates the possibility of a surface nitrate intermediate consistent with the mechanistic proposal. Scanning electron microscopy and X-ray powder diffraction techniques were used to assess the catalyst structure.


1995 ◽  
Vol 28 (11) ◽  
pp. 3771-3778 ◽  
Author(s):  
William J. Gauthier ◽  
John F. Corrigan ◽  
Nicholas J. Taylor ◽  
Scott Collins

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