Hydrogenolysis and Hydrogenation Reactions

3 Hydrogenolysis and Hydrogenation Reactions 6.5.3.1 Cleavage of lnterumtary Linkages 

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Hydrogen is a common reactant in the hydrogenolysis and hydrogenation reactions that show a support effect on the activity. The mode of chemisorption and the bondstrength of hydrogen on the surface of supported Pt particles is studied in chapter 5 and chapter 6. 

The action of sulphided Ni/Mo catalyst was to dramatically increase the yield of oil from the reactions of preasphaltene and asphaltenes. It is believed that the mechanism of the Ni/Mo catalyst involves a more conventional dissociative adsorption of both hydrogen and reactant molecule to the catalyst surface followed by hydrogenolysis and hydrogenation reactions. The mechanistic pathway thus differs from both iron and tin and is shown in Figure 4 by reactions 13 and 14. 

The kinetics of DBT hydrogenolysis and hydrogenation reactions is summarized with the following rate equations recommended by Broderick and Gates [121], based on a Lang-muir-Hinshelwood formulation ... 

This chapter lists hydrogenolysis and related reactions by which functional groups are replaced by hydrogen e.g. RCH2X RCH2-H or R-H. 

Hydrogenolysis and hydrogenation may occur in the absence of a catalyst but for rapid stabilization of, or effective addition of hydrogen to, the primarily formed lignin fragments, the application of a suitable catalyst is necessary The only exception to this principle are hydrogen-generating reactions which occur when primary alcohols and alkali are heated to temperatures in the vicinity of 350 °C... 

D.H. Broderick and B.C. Gates, Hydrogenolysis and Hydrogenation of Dibenzothiophene Catalyzed by Sulfided CoO/Mo03/Gamma-Al203 The Reaction Kinetics, AIChE J. 27 553-673 (1981). 

Broderick DH, Gates BC. Hydrogenolysis and hydrogenation of dibenzothiophene catalyzed by sulfided CoO-Mo03/y-Al203 the reaction kinetics. AIChE J. 1981 27 663. 

Any of these sets of computed energies can then be used for calculation of reaction enthalpies by comparing reactants and products. Table 4.4 gives some data for hydrogenation, hydrogenolysis, and isomerization reactions at several levels of theory. The table includes some data for small-ring compounds, which represent a particularly challenging test of the accuracy of the computationally based methods. 

A metal, a metal oxide, a metal sulfide, or a combination of these compounds may supply the metal function of the catalyst. The key requirement for the metal function is that it must activate hydrogen and catalyze dehydrogenation and hydrogenation reactions. In addition, metal-catalyzed hydrogenolysis (carbon-carbon breaking) is undesirable because the distribution of the hydrogenolysis products is less desirable relative to hydrocracking. 

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