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In a first step the intrinsic kinetics of acetophenone hydrogenation on a Rh/C catalyst was studied in a semi-batch reactor. Tiny catalyst grains of 17 μm in average diameter were used in order to avoid any intraparticle diffusion limitation. Experiments were performed over a wide range of operating conditions and various Langmuir–Hinshelwood kinetic equations were discriminated over the complete conversion range. The model based on nondissociative adsorption of hydrogen and noncompetitive adsorption of the organic species with the gas molecules was found to fit better all the experimental data. The relevance of its optimized parameters was then discussed. In a second step the intraparticle diffusion limitations were also studied in a semi-batch reactor by varying the particle size. Two models based on the complex kinetics previously established were developed, taking into account the catalyst grain size and shape. After an additional adjustment of one of the adsorption constants ratios, they were found to provide a good representation of the data in terms of activity and selectivity.

The hydrogenation of acetone was investigated in basic aqueous solutions with undoped and chromium-doped catalysts. The reaction was carried out under pressure in an autoclave equipped with a reference electrode. The consumption of hydrogen and the electrode potential were measured during the course of the reaction. A mathematical model was applied which fits the experimental kinetic data well. It allows the computation of the rate constant and the adsorption equilibrium constants. The kinetics obey a Langmuir-Hinshelwood mechanism with competitive adsorption. The metallic catalyst particles behave like a dispersed electrode and an electrochemical double layer is formed at their surface. In the presence of hydrogen alone, the metal potential obeys the Nernst law for the hydrogen electrode. During acetone hydrogenation, the double layer is modified and the measured potential goes to the positive region for several tens of millivolts, depending on whether the catalyst is doped or not. In all cases an experimental correlation was found between this experimental potential rise and the reaction rate.

IR emission spectra obtained with a Fourier transform spectrometer at 110/sup 0/C revealed that pyridine adsorbed on platinum Y zeolite by coordination to the Na ion and by formation of pyridinium ions with bands at 755 and 685 cm/sup -//sup 1/; the formation of pyridinium ions suggested the presence of acidic OH groups formed during platinum reduction with hydrogen. Bands observed at 465 and 2070 cm/sup -//sup 1/ in the spectra of adsorbed carbon monoxide were attributed to linearly adsorbed species, and a band at 1850 cm/sup -//sup 1/ to carbon monoxide bonded to two platinum atoms. The experimental technique and its scope are discussed.