UPTAKE OF S-35 BY PD, IR, RU PROMOTED MO-OXIDE CATALYSTS AND THEIR ACTIVITY IN CYCLOHEXANOL TRANSFORMATION

Initial stages of sulphurization of Pd, Ir, Ru-promoted Mo/Al2O3 have been investigated using H2 S-35 in a microcatalytic pulse system. Sulphur uptake of the catalysts as well as its effect on the transformation of cyclohexanol were monitored. Two types of retained sulphur can be distinguished: reversible which can be removed by hydrogen and/or by cyclohexanol pulses and irreversible which cannot. Hardly any sulphur was incorporated into an unpromoted Mo--Al2O3 causing practically no change in tbe catalytic behaviour. The hydrogenation and dehydrogenation selectivity of promoted catalysts decreased sharply as a function of the retained sulphur and did not change further after ca. 30-40% of the promoter atoms are sulphided.