Effect of sulphur on the performance of Rh–LaCoO3 based catalyst for tar conversion to syngas

The effect of sulphur addition on the catalytic activity of 1%Rh/Al2O3, LaCoO3/Al2O3 and 1%Rh–LaCoO3/Al2O3 catalysts in reforming of tar produced by biomass pyrolysis has been investigated by adding 20 or 200 ppm H2S in a fixed bed reactor at 700 °C using a S-free biomass slowly pyrolyzed. The catalysts have been characterized by ICP-MS and BET analyses. The poisoning effect of sulphur has been also studied by in situ DRIFT and TPR analyses. A very high sulphur exposure of the catalysts leads to the partial inhibition of the reforming properties related to the poisoning of dispersed rhodium sites. The LaCoO3 layer effectively preserves rhodium from sulphur poisoning in the 1%Rh–LaCoO3/Al2O3, the catalyst containing both phases showing mostly unchanged catalytic properties also upon 200 ppm S-treatment under reaction conditions. The LaCoO3/Al2O3 catalyst shows reduced reforming properties coupled to an increase of cracking and total oxidation reactions associated to the partial destruction of the perovskite structure.

The high sulphur tolerance of a Rh–LaCoO3/Al2O3 catalyst has been shown in tar conversion to syngas at 700 °C. The protective effect of the perovskite layer under reaction conditions preserving the reforming properties of rhodium has been demonstrated.Figure optionsDownload as PowerPoint slideHighlights
► Rh–LaCoO3/Al2O3 performance in tar conversion is poorly affected by S.
► At high S levels reforming is inhibited, cracking and oxidation are less influenced.
► The perovskite layer preserves rhodium from S poisoning.
► Alumina protects rhodium but at lower extent with respect to the perovskite.
► S causes a partial loss of LaCoO3 structure and a limited formation of Rh(SO4)x.