Catalysts closed reactor examinations

To examine how and why the surface ethanol reaction is assisted by the gas-phase ethanol, the following experiments were conducted in a closed circulating reactor. Ethanol vapor was first admitted onto the dioxoniobium monomer catalyst (1), Si0 2Nb(=0)2, to form the niobium ethox-ide (2), Si0 2Nb(=0)(0H)(0C2H5), at 373 K, followed by evacuation, and then the system was maintained at 523 K for 10 min, where no H2 evolution was observed because the niobium ethox-ide (2) was stable up to 600 K in vacuum. After the confirmation of no H2 formation from the preadsorbed ethanol (2), tert-butyl alcohol was introduced to the system at 523 K, which led to a stoichiometric evolution of H2 and CH3CHO. As the fert-butyl alcohol molecule has no extractable a-hydrogen, it is evident that both H2 and CH3CHO were produced from the preadsorbed ethanol by the assistance of the postdosed tert-butyl alcohol. 

A small modification of the above design, in which the catalyst in the form of granules or pellets is placed in an annular basket made of wire mesh fitted close to the reactor wall, has also been examined. The use of such an annular basket-type reactor has been reported by Tajbl et al. (1967), Relyea and Perlmutter (1968), and Lakshmanan and Rouleau (1970). The basic features of this reactor are the same as the ones described above. The reactor has been used to carry out high-pressure, high-temperature catalytic methanation of mixtures of carbon monoxide/hydrogen and carbon dioxide/hydrogen. 

Catalytic alkylation of alkylsilanes with olefinic and acetylenic compounds using solid catalysts was examined in a closed recirculation reactor at 373 - 473 K. Alkylation of diethylsilane(E2) with these compounds took place smoothly on silica-alumina (SA) and S03/Zr02 catalysts but not on alumina, which means protonic solid acid catalyzed the reaction. n-Alkylated products were the main products and the /so-alkylated ones were the minor products regardless the type of olefins. The product distribution indicates the reaction takes place via a nucleophilic attack of olefins on a Si cation. 

With aim to examine catalysts by the Bray-Liebhafsky reaction system as the matrix, two examples, one in the closed and the other in the open reactor, will be given in the following. 

With the aim to compare the activities of the two mentioned catalysts (HRP and apFe) we had to examine their kinetic properties. This is performed in the Bray-Liebhafsky reaction being in the oscillatory state. The reaction was conducted in the closed well-stirred reactor. 

A pillar structure of small rectangular posts was incorporated near the outlet of the reaction channel to retain the catalyst. The reaction was studied in the temperature range of 80-120 °C and at inlet pressures up to 5 bar. Benzyl alcohol conversion and benzaldehyde selectivity at 80 and 120 °C were very close to those from conventional glass stirred reactors. The best conversion of benzyl alcohol of 95.5% with selectivity to benzaldehyde of 78% was obtained for a micropacked bed reactors with catalyst sizes of 53-63 pm and a catalyst bed length of 48 mm at 120 °C and 5 bar. The effect of catalyst particle size on the reaction was examined with two ranges of particle size 53-63 pm and 90-125 pm. Lower conversion was obtained with particle sizes of 90-125 pm, indicating the presence of internal mass transfer resistances. In situ Raman measurements were performed and could be used to obtain the benzaldehyde concentration profile along the catalyst bed. 

The simplification made possible by the use of the reactor point effectiveness allows a close examination of the design of a reactor affected by catalyst deactivation, the characteristic of which is time-dependence. This leads to the optimal design for a reactor whose performance is time-dependent. Finally, reactor design involving multiple reactions is considered, using essentially the approach of reactor point effectiveness. 

In 2000, Itoh and Haraya constructed the first CMR and experimentally examined the performance of a dehydrogenation reaction. Asymmetric polyimide hollow fibers were pyrolyzed in a vacuum oven at 1023 K in order to obtain hollow fiber carbon membranes. Their CMR consisted of SS in which 20 carbonized hollow fibers (0.295 mm diameter and 128 mm long) and catalyst pellets (0.5 wt% Pt/Al203) were allocated. The reactor, used for cyclohexane dehydrogenation to benzene at 468 K, showed a fair improvement over equilibrium conversions. In detail, the temperature dependency of the permeation rates showed that the carbon membrane had micropores with an average diameter close to those of the gas molecules and therefore the permeation process was molecular-sieving controlled. The ideal H2/Ar... 

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