Intensified methanol steam reforming over active and stable CeO2-Al2O3 supported catalysts

Abstract

The recent limitations imposed by the maritime rule-making units have goaded the researcher's interest towards methanol applications as near-zero emission fuel. Methanol can be either directly fed to internal combustion engineering or sent to a pre-reforming unit for hydrogen generation and further conversion in fuel cells devices. In this scenario, the optimization of the reforming unit is crucial to achieve high hydrogen yields.

This study investigates the activity, selectivity and stability of different CeO₂-Al₂O₃ supported catalysts for methanol steam reforming. Moreover, the kinetic parameters of the best performing catalyst were determined. Several mono-, bi- and trimetallic catalysts were prepared by the wet impregnation method (Ni, Cu, NiCu, CuNi, Zn-Ni-Cu, PtNi, PdNi, PtZn, PdZn, PdCu) and were preliminarily screened between 200 and 600 °C under a S/C ratio of 1.5 and WHSV = 2 h⁻¹. Looking at methanol conversion and products selectivity, the lowest CO formation was recorded over the Cu-based catalysts: the addition of 2 wt% of palladium considerably improved both CH₃OH conversion and hydrogen yield. The PdCu formulation, rarely investigated in the recent literature, appeared very promising and was also subjected to 40 h of time-on-stream test at 300 °C, observing only a 5 % reduction in terms of both conversion and H₂ yield, which were attested to 95 and 88 %, respectively, at the end of the test. Moreover, a very low coke selectivity (1.5 wt%) was recorded, with relevant deactivation resistance. Finally, based on a simplified power-law kinetic model, the activation energies for methanol steam reforming (22 kJ·mol⁻¹), methanol decomposition (71 kJ·mol⁻¹) and water gas shift reaction (84 kJ·mol⁻¹) were also developed, which further demonstrated the high activity of the developed catalyst towards MSR.