Catalytic theoretical

Stampfl C and Scheffler M 1997 Anomalous behavior of Ru for catalytic oxidation a theoretical study of the catalytic reaction CO+1/2 O2 to CO2 Phys. Rev. Lett. 78 1500... 

Hydrochlorination of Ethylene. The exothermic vapor-phase reaction between ethylene [74-85-1] and hydrogen chloride [7647-01-0] can be carried out at 130—250°C under a variety of catalytic conditions. Yields are reported to be greater than 90% of theoretical (14). 

The main converter, which is located downstream of the EHC, heats to functional temperature much more quickly because of catalytic combustion of exhaust gases that would otherwise pass unconverted through the catalyst during the cold start period. The EHC theoretical power required for a reference case (161) was 1600 watts to heat an EHC to 400°C in 15 s in order to initiate the catalytic reactions and obtain the resultant exotherm of the chemical energy contained in the exhaust. Demonstrations have been made of energy requirements of 15—20 Wh and 2 to 3 kW of power (160,161). Such systems have achieved nonmethane HC emissions below the California ULEV standard of 0.025 g/km. The principal issues of the EHC are system durabihty, battery life, system complexity, and cost (137,162—168). 

The catalytic method provides the basis for synthesis of carbon tubules of a large variety of forms. Straight tubules, as well as bent and helically wound tubules, were observed. The latter regular helices of fullerene diameter can be of special interest from both theoretical and practical points of view. 

Yamamoto et al. have developed a catalytic enantioselective carbo-Diels-Alder reaction of acetylenic aldehydes 7 with dienes catalyzed by chiral boron complexes (Fig. 8.10) [23]. This carbo-Diels-Alder reaction proceeds with up to 95% ee and high yield of 8 using the BLA catalyst. The reaction was also investigated from a theoretical point of view using ab-initio calculations at a RHF/6-31G basis set. 

The catalytic disproportionation of toluene (Figure 10-13) in the presence of hydrogen produces henzene and a xylene mixture. Disproportionation is an equilihrium reaction with a 58% conversion per pass theoretically possible. The reverse reaction is the transalkylation of xylenes with henzene ... 

A solution of 20.8 g. (0.1 mole) of benzalacetophenone (Note 1) (Org. Syn. 2, 1) in 150 cc. of c.p. ethyl acetate (Note 2) is placed in the reaction bottle of the catalytic reduction apparatus (p. 10) and 0.2 g. of platinum oxide catalyst (p. 92) is added. The apparatus is evacuated, then filled with hydrogen, and the mixture shaken with hydrogen until 0.1 mole has been absorbed. The time required is usually about fifteen to twenty-five minutes (Note 3). The platinum is filtered off and the solvent removed from the filtrate by distillation. The benzylacetophenone is recrystallized from about 25 cc. of alcohol and melts at 72-730. The yield is 17-20 g. (81-95 per cent of the theoretical amount). 

From a theoretical point of view the study of the kinetics of coupled catalytic reactions makes it possible to investigate mutual influencing of single reactions and the occurrence of some phenomena unknown in the kinetics of complex reactions in the homogeneous phase. This approach can yield additional information about interactions between the reactants and the surface of the solid catalyst. 

As the presumption of the identity of the function for all the reactions of the system may not be always fulfilled, this method has not met with wide application by catalytic chemists. Rather, it attracts theoretical interest (29, 30, 33-36), even though, for example, the authors of the last mentioned paper (36) used their own experimental data on the isomeriza-... 

The quantitative solution of the problem, i.e. simultaneous determination of both the sequence of surface chemical steps and the ratios of the rate constants of adsorption-desorption processes to the rate constants of surface reactions from experimental kinetic data, is extraordinarily difficult. The attempt made by Smith and Prater 82) in a study of cyclohexane-cyclohexene-benzene interconversion, using elegant mathematic procedures based on the previous theoretical treatment 28), has met with only partial success. Nevertheless, their work is an example of how a sophisticated approach to the quantitative solution of a coupled heterogeneous catalytic system should be employed if the system is studied as a whole. 

Farkas and Sherwood (FI, S5) have interpreted several sets of experimental data using a theoretical model in which account is taken of mass transfer across the gas-liquid interface, of mass transfer from the liquid to the catalyst particles, and of the catalytic reaction. The rates of these elementary process steps must be identical in the stationary state, and may, for the catalytic hydrogenation of a-methylstyrene, be expressed by ... 

Figure 5.54. Effect of sodium coverage on the change AUWR of polycrystalline Pt catalyst potential UWr and on the catalytic rates of CO oxidation (solid lines37) and C2H4 oxidation (dashed lines36). Comparison with the theoretical Na coverage required to form the Pt(l 11)-(12xl2)-Na adlayer 0 is based on the number of surface Pt atoms 09a is based on the number of surface O atoms corresponding to the Pt(l 1 l)-(2x2)-0 adlattice. Reprinted from ref. 78 with permission from Elsevier Science,...

E. Lamy-Pitara and J. Barbier The group of Professor Barbier and Dr. Lamy-Pitara was first to demonstrate NEMCA in an aqueous phase catalytic hydrogenation reaction (Chapter 10). This work is of very significant theoretical and potentially practical importance. 

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