Kinetics of Catalytic Hydrogenations in the Liquid Phase

A quantitative investigation of the effect of the composition of the reaction mixture on the hydrogenation of unsaturated compounds in the liquid phase on solid catalysts must be based on an unambiguous kinetic characteristic. To obtain this quantity, it is necessary to define experimental conditions adequately and in such a way that the data reflect the effect under investigation. 

Along with dissolved hydrogen and some admixtures, a liquid reaction mixture contains one or several reactants, reaction products, and sometimes also a solvent consisting of one or several compounds. All these compounds may affect the kinetics of the hydrogenation reaction. For the purposes of this study, the aim of which consists in a quantitative description of changes in composition of the reaction mixture, it is sufficient to employ the Langmuir-Hinshelwood kinetics (7) in its simplest form, where the process of hydrogenation is characterized by the rate constant and adsorption coefficient obtained from the simplest kinetic equations. 

Catalytic hydrogenation in the liquid phase with a solid catalyst is a complex process that may be divided (2) into several steps  

absorption of hydrogen into the surface film of the liquid, which is in contact with the gas phase  

hydrogen transfer through volume of the liquid to the film at the catalyst surface  

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