Kinetics of Catalyst Poisoning during Capillary Condensation of Reactants

The influence of the capillary condensation of reactants on the poisoning of Pt/SiO₂ catalysts by thiophene is studied experimentally for p-xylene hydrogenation at T = 60 and 80°C. The poisoning kinetics is independent of a catalyst and its rate decreases with a decrease in temperature. Poisoning during capillary condensation is 1.5–6 times slower than that in the gas phase, depending on the fraction of surface platinum in the pores filled with a liquid. The poisoning of the catalyst active sites in the pores filled with a liquid requires less sulfur at the same deactivation degree. The number of sulfur atoms per one platinum atom necessary for the complete poisoning of platinum in the gas phase is higher than that in the case of capillary condensation by a factor of 1.4–1.5.