Infludnce of metal loading and temperature on hydrogen chemisorption and hydrogenation activity of Ry/γ-Al₂O₃ catalyststs†

Abstract

Ry/γ-Al₂O₃ catalysts with Ru loadings from 0.5% to 5.0% prepared by the incipient wetness method are characterized by hydrogen chemisorption, and benzene hydrogenation in the temperature range from 85°C to 200°C under differential conditions with the objective of studying the influence of metal loading on the physico-chemical characteristics of the catalysts. Ru surface area calculated from irreversible H₂ uptake is found to increase steadily with Ru loading upto 2.5% above which the increase is minimal, while Ru particle size increases upto 7.1 nm and Ru dispersion decreases with Ruγ loading. Effect of temperature is studied on hydrogen chemisorption on 5.0% Ru catalyst and on benzene hydrogenation on all the catalysts. Hydrogen chemisorption as well as the activity of the catalysts increase with temperature upto 125°C and decrease above this temperature signifying the important role played by the reversibly adsorbed hydrogen in enhancing the activity of the catalysts. Hydrogenation activity of the catalyst is observed to increase proportionately with metal area while the turnover frequency of the reaction remains fairly constant over the range of Ru particle size from 2.7 nm to 7.1 nm.