Highly active and durable Pt/In2O3/Al2O3 catalysts in methanol steam reforming

Pt/In2O3/Al2O3 catalysts with extremely low Pt loading (1.0 wt%) prepared by incipient-wetness impregnation method were evaluated for methanol steam reforming (MSR) in the temperature range of 200-500 °C, and characterized by means of X-ray diffractions (XRD), high resolution transmission electronic microscopy (HRTEM), Brunauer-Emmett-Teller (BET), CO chemisorption, hydrogen temperature-programmed reduction (H2-TPR) and H2O temperature-programmed desorption (H2O-TPD). Multiple factors including Pt/In2O3 mass ratio, total In2O3 loadings, steam to carbon ratio (S/C) and gas hourly space velocity (GHSV) were found to affect the catalytic properties. Results indicated that indium oxide was homogeneously dispersed on the surface of Al2O3 and also effectively improved the dispersion of Pt nanoparticles. Meanwhile, a good correlation of water activation ability with catalytic selectivity has been established. Accordingly, the synergistic effect caused by the strong Pt-In2O3 interaction and the intimate Pt-In2O3 contact played the crucial role in effective H2O activation, thus minimizing the CO selectivity and enhancing the stability of Pt/In2O3/Al2O3 catalysts because of its high ability to activate H2O molecule. As a result, the Pt/In2O3/Al2O3 catalyst with Pt/In2O3 mass ratio at 1/30 exhibited complete methanol conversion, 99.6% H2 selectivity and extremely low CO selectivity of 3.2% at 350 °C, outperforming Pt/ZnO/Al2O3 catalyst. Furthermore, Pt/In2O3/Al2O3 catalyst displayed higher stability than Pt/ZnO/Al2O3 catalyst as evidenced by unnoticeable deactivation under continuous operation for more than 16 h.