Hydrogenolysis catalyst comparison

Comparison of the catalysts in Figure 1 demonstrates that the Ni/Re catalyst yielded the highest activity of the catalysts under the conditions tested. The Rh/Re catalyst also showed excellent conversion at 240°C as did the Ru catalyst which is also known to be an excellent hydrogenolysis catalyst for conversion of sorbitol to these products [4,5], The Ru/Re and Ru/Re+ catalysts also demonstrated high conversion, especially at high temperatures. 

On activity, comparison of runs 4 and 5 illustrates an increase by a factor of two on going from ethanol to methanol (polarity effect [3]). Addition of a catalytic quantity of sulfuric acid (run 4 compared to run 3) increases activity by a factor of ten [hydrogenolysis catalyst - [5]]. On selectivity, using alcohols in place of ether gives different intermediates (4h in EtOH, 4e in MeOH and 4g in dimethoxyethane) illustrating the concept of "reactive solvent" in the case of alcohols [6]. 

Bond rupture probabilities have also been reported by Myers and Munns (160) for hydrogenolysis reactions over a number of supported catalysts containing platinum in the range 0.1-1%. The reactions were carried out in the region of 350°-480°C. Provided one confines the comparison to nonacidic supports, these results are in tolerable agreement with the data in Table XI. 

A comparison of various metals as catalysts for the hydrogenolysis of hydrocarbons reveals a wide variation in catalytic activity, even among such closely related metals as the noble metals of group VIII of the periodic table. Striking differences in the distribution of hydrogenolysis products have also been revealed in studies on selected hydrocarbon reactants. These features are emphasized in the following discussion of activity patterns and product distributions in hydrogenolysis. 

Dehydrocyclization, 30 35-43, 31 23 see also Cyclization acyclic alkanes, 30 3 7C-adsorbed olefins, 30 35-36, 38-39 of alkylaromatics, see specific compounds alkyl-substituted benzenes, 30 65 carbene-alkyl insertion mechanism, 30 37 carbon complexes, 32 179-182 catalytic, 26 384 C—C bond formation, 30 210 Q mechanism, 29 279-283 comparison of rates, 28 300-306 dehydrogenation, 30 35-36 of hexanes over platintim films, 23 43-46 hydrogenolysis and, 23 103 -hydrogenolysis mechanism, 25 150-158 iridium supported catalyst, 30 42 mechanisms, 30 38-39, 42-43 metal-catalyzed, 28 293-319 n-hexane, 29 284, 286 palladium, 30 36 pathways, 30 40 platinum, 30 40 rate, 30 36-37, 39... 

By using ratio the number of edge (C7) atoms to the number of (111) face (Cg) atoms (Fig. 12) to define an effective particle size , the selectivity of n-butane hydrogenolysis as a function of particle size for the two surfaces could be plotted and compared to selectivities measured on supported Ir catalysts This comparison is shown in Fig. 13. Clearly, the results on single... 

I 3 Catalytic Properties of Single Site Catalysts Prepared via Surface Organometallic Chemistry Table 3.2 Comparison of initial rates in alkane hydrogenolysis". 

Two extremes emerge from comparison of the Group VIII metals Ni, Rh, Co, and Ru (the left corner of the Group VIII metal block of the periodic table) prefer terminal splitting, already show multiple splitting at rather low temperatures, are the best catalysts (with Os) in hydrogenolysis of ethane (only 2C complexes possible), and catalyze well the reaction of carbon atoms to methane. Pt is the other extreme in all of these respects, with Pd and Ir... 

Comparison of Initial Specific Rate Data for the Cyclopropane Hydrogenolysis on Platinum Catalysts... 

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