RELATIONSHIP BETWEEN SELECTIVITY AND HYDROGEN SORPTION OF CARBON-SUPPORTED PALLADIUM CATALYSTS

The relationship between the catalytic activity, selectivity and the hydrogen content of carbon-supported palladium catalysts was studied by examining how certain parameters such as the duration and medium (liquid or gas phase) of the prehydrogenation of the catalyst control the amount of hydrogen sorbed on 10% Pd/C catalysts. The hydrogenation of allyl alcohol at room temperature and 1 bar in 0.05 mol dm-3 sulphuric acid or sodium sulphate solution was investigated. The measurement of the electrode potential of the catalyst was also used to monitor the process during hydrogenation. The sorption properties (hydrogen content) of catalysts were calculated from the results of equilibrium galvanostatic polarization measurements. It was found that there is a relationship between the hydrogen content of a catalyst and the proportions of reduction and isomerization. Surfaces poor in hydrogen favour isomerization and those rich in hydrogen favour reduction. Under certain conditions the proportion of isomerization may be as high as 70%. © 1990.