Comparative Effect of Organosulfur Compounds on Catalysts for the n-Heptane Isomerization Reaction at Medium Pressure: Mo_2C-Oxygen-Modified, MoO_3-Carbon-Modified, Pt/γ-Al_2O_3, and Pt/β-Zeolite Catalysts

摘要

Molybdenum oxycarbide formed from oxidized Mo_2C or reduced MoO_3 is an active and very selective catalyst for the isomerization of n-heptane compared to supported Pt. Deactivation experiments performed on the catalysts with different concentrations of organosulfur compounds show that molybdenum oxycarbide exhibits a very high resistance to deactivation, whereas with platinum-based catalysts deactivation occurs even at low sulfur concentration in the feed. Deactivation can be slowed by increasing the hydrogen partial pressure from 6 to 20 bar. In these conditions, the molybdenum oxycarbide shows no deactivation with sulfur concentrations up to 120 ppm of S. In addition, the deactivated molybdenum catalysts can be easily regenerated by mild oxidative treatment under flowing air at atmospheric pressure and 723 K for 2 h followed by a reactivation period under the hydrogen and hydrocarbon mixture.