Sulfur introduction in V–K/γ-Al2O3 catalyst for high performance in the non-oxidative dehydrogenation of isobutane

Abstract

Sulfur was introduced, for the first time, into V–K/γ-Al₂O₃ catalysts, due to which their performance in the non-oxidative dehydrogenation (DH) of isobutane was promoted remarkably. After sulfidation, the isobutene yield increased from 29.6% to 49.8%. Many attempts have been made to thoroughly explain the promoting effect of sulfidation over V–K/γ-Al₂O₃ catalysts towards DH activity. This study demonstrates that both properties of the vanadium species and the acid properties of vanadium-based catalysts are affected by sulfidation. The introduction of sulfur, which has lower electronegativity, made the bond energy of V–S lower than that of V–O. Therefore, the vanadium species can be reduced easily after sulfidation and hence, the availability of V³⁺ and V⁴⁺ species, which serve as active DH sites, increases on the catalyst surface. The increased acid strength further enables easy activation of the C–H bond in isobutane, thus contributing to an increase in isobutane conversion. Moreover, the decrease in acidic sites inhibits side reactions and confers higher isobutene selectivity to the sulfide catalyst compared to its oxidized state. The sulfide V–K/γ-Al₂O₃ catalyst, presenting ideal activity, stability and space–time yield, is a promising alternative to optimized industrial DH catalyst.