INHIBITING EFFECT OF H2S ON TOLUENE HYDROGENATION OVER A MOS2 AL2O3 CATALYST

The influence of hydrogen sulfide partial pressure on the activity of a model MoS2/gamma-Al2O3 catalyst for toluene hydrogenation has been investigated over a wide range of hydrogen sulfide partial pressure, from 0 to 0.3 MPa, under a total pressure of 6 MPa, reaction temperature between 320 and 410-degrees-C, and liquid hourly space velocity between 0.5 and 7.5 h-1. A moderate inhibiting effect of H2S on the hydrogenation activity is found for H2S partial pressure up to 60 000 Pa with an order of reaction relative to H2S comprised between 0 and -1/2. For H2S partial pressure higher than 60 000 Pa, no apparent inhibiting effect of H2S on the hydrogenation activity is detected. The results have been best interpreted in term of a kinetic model whereby the reaction occurs on a surface containing two sites, one unsaturated Mo ion and one stable sulfur ion host of the proton generated by the heterolytic dissociative adsorption of hydrogen and hydrogen sulfide.