DME, propane and CO: The oxidation, steam reforming and WGS over Pt/Al2O3. The effect of aging and presence of water

Abstract

The effect of aging in two environments (Ar at 800°C and SO2+NO+O2+H2O at 250°C) on oxidation/steam reforming reactions using dimethyl ether (DME), propane and CO were investigated on Pt/Al2O3 catalysts. Platinum dispersion as well as the changes in Pt-particles sizes were examined. The BET surface area of aged catalysts decreased compared to the fresh (degreened) sample, indicating that aging in inert gas may collapse some pores in alumina and for aging in sulfur atmosphere it may block some pores of the catalysts. Using SEM/EDX, higher sulfur amount was found in the inlet position of the aged sulfur monolith and it decreased linearly with the direction of the flow along the monolith length. The effect of water was also studied and it was found that propane and DME oxidation is negatively influenced by the presence of water, while for CO an increased activity was found. Thermal aging of the Pt/Al2O3 catalyst resulted in quite small deactivation for the examined reactions. The dispersion after the sulfur aging, and subsequent H2 reduction, was the same as after the thermal aging at 800°C, but interestingly the activity is significantly different. After the sulfur aging and hydrogen regeneration, the DME and C3H8 oxidation is promoted, while CO oxidations are slightly inhibited in the presence of water. The effect of the sulfur aging had a minor effect on DME-SR, while it completely deactivated steam reforming for propane. For the WGS reaction, the sulfur aging resulted in an overall decreased activity and in addition the conversion went through a maximum. We suggest that residues of sulfur on the alumina inhibit the water activation in the WGS reaction.