The Destructive Hydrogenation of Hydrocarbons

A great many substances have been described as catalysts for the conversion of heavy hydrocarbons into those of lower boiling point, by treatment with hydrogen under pressure. Most of the publications on these processes are not concerned with the precise chemical composition of the catalysts but only with their rough classification into groups of the periodic system, so that it is not possible to gain much information from them which is useful for the present discussion. 

The molybdenum catalysts, unlike nickel, are not poisoned by sulfur compounds, and when such compounds are present in the hydrocarbon undergoing treatment, partial conversion of M0O2 to M0S2 will take place. For this reason, as well as because of the particularly high activity of the disulfide, it is of interest to consider the structure of M0S2 with reference to the adsorption of organic molecules on its surface. 

Molybdenum disulfide eonsists of a layer lattice ivith hexagonal S3nnmetry. 

Each plane of molybdenum atoms is held by covalent bonds between two planes of sulfur atoms part of the structure is shown in Fig. 8. The important feature of this lattice is that the molybdenum atoms are arranged triangularly 3.15A. apart. Such planes could readily be exposed in a crystalline M0S2 catalyst from which one layer of outer sulfur atoms had been removed by reaction with hydrogen. On this lattice, with the Mo—C bond 2.14A. it can be seen that two-point adsorption of an olefin would take place with an angle of 112° for the Mo—C—C bonds. This fit is not 

It must be remembered that an important step in the destructive hydrogenation process is a reduction in the molecular weight of the hydrocarbons. This involves rupture of a C—C bond. 

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Although his governmental duties occupied much of Ipatieff s time, he still was able to continue his scientific work and to study the destructive hydrogenation of hydrocarbons. 

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