High thermal conductive β-SiC for selective oxidation of H2S: A new support for exothermal reactions

Abstract

Iron supported on a medium surface area silicon carbide (β-SiC) is a high efficiency catalyst for the selective oxidation of hydrogen sulphide into elemental sulphur at reaction temperatures above the sulphur dew point. The strong interaction between the topmost layer of the support and the active phase allows a high dispersion of the iron-based catalyst particles which provide a high active phase-reactants contact surface to maintain the high desulphurization activity even at high space velocity. The high thermal conductivity of the silicon carbide plays an important role in the maintenance of the high selectivity by avoiding the formation of hot spots on the catalyst surface which could favor secondary reactions. On the other hand, insulator supports such as alumina exhibits a poor selectivity due to catalyst surface temperature runaway. The thermal profile of the bed temperature calculated by a simple heterogeneous model was in agreement with the previous hypothesis. The intrinsic chemical inertness and the surface property of the material render the silicon carbide usable in very drastic conditions, i.e. in a corrosive atmosphere (2% H2S) and with a low O2/H2S ratio compared to silica and/or alumina based catalysts. In such conditions, the catalyst remains stable over 1500h on stream with high sulphur yield up to 95%. These performances make silicon carbide based catalysts the most promising catalyst support suitable for the high-temperature selective oxidation process.