Optimal Pt load of a Pt/La2O3·SiO2 highly selective WGS catalyst used in a Pd-membrane reactor

Abstract

Pt(wt%)/La2O3(27)·SiO2 catalysts with wt% = 0.02 up to 1.2 were synthesized and tested in a conventional fixed-bed reactor. In differential mode, the Pt(0.1)/La2O3(27)·SiO2 catalyst showed higher activity per gram of Pt than the other solids. XPS showed the presence of only surface metallic platinum, in both the fresh and used Pt(0.1 wt%) formulation, which could be responsible for the high catalytic activity. At higher Pt loads both Ptδ+ and Pt° species were present at the surface. The presence of La2Si2O7 in all solids was detected by XRD. Graphitic carbon in the used catalysts was not detected through laser Raman spectroscopy. Different catalytic tests were carried out in a tubular Pd-membrane reactor feeding a reformer outlet type stream with a molar composition of 40% H2, 40% H2O, 12% CO2 and 8% CO. They were performed between 673 and 723 K and at pressures ranging from 100 kPa to 800 kPa. At 723 K and 800 kPa, the CO conversion and H2 recovery values were 96% and 88%, respectively. A stability test including several start-up and shut-down cycles showed high stability of the Pt(0.1) catalyst.