Strong inhibition effect of sulfur impurities in alumina supports on the catalytic activity of Rh in the CH4–CO2 reforming reaction

The influence of the sulfur impurity on the CH4–CO2 reforming reaction over Rh catalyst was studied. The activity of Rh/Al2O3 varied remarkably depending on the kinds of Al2O3 support. Based on the EXAFS and TPR measurements, the variations were ascribed to the changes in the reducibility of Rh as a result of the interaction with SO42− present as impurity in the alumina support. In agreement with the assumption, the activity of Rh improved significantly as SO42− was removed from the Al2O3 support. Based on the EXAFS analysis, the role of SO42− anion was ascribed to the inhibition of the reduction of RhCl3 to give metal Rh.