Preparation of mesoporous Cu/Zn/Ce/Zr/Al catalysts and activity in steam reforming of methanol

Wei Yu,Jiali Yan,Na Yang,Zhengwei Cui

doi:10.1063/5.0069568

Abstract

Ammonium carbonate-assisted mechanochemical preparation of Cu-based catalysts has been developed for steam reforming of methanol (SRM). The characteristics of the catalysts were studied by N2 adsorption–desorption, N2O titration, TEM, XRD, XPS, H2-TPR, and TG analysis. Optimized-prepared samples showed a porous structure with high surface areas due to the ammonium carbonate decomposing during the calcination. Because of the positive correlation between surface area and catalytic activity, the porous catalysts exhibited superior SRM activity, e.g., Cu1Zn1Zr1Al7 with a high surface area of 147.1 m2 g−1 reached a maximum methanol conversion of 85.2%. Furthermore, more Cu–Al spinels were introduced on Cu1Zn1Al8 by the milling process compared to wet-impregnated IM-Cu1Zn1Al8. Ascribed to the interaction of dispersed copper components with the surface oxygen vacancies of the CeO2/ZrO2, the promoted reducibility was observed with reduction peaks observed at low temperatures of 170 and 152 °C. With CexZr1−xO2 solid solution in Cu1Zn1Ce1Zr1Al6, a high surface-oxygen population was clearly formed on the surface, which suppressed CO production (0.8%) in the reaction. The ball-milled catalysts were found to have a much better catalytic time-on-stream stability, while the degradation of IM-Cu1Zn1Al8 was mainly ascribed to Cu sintering in the reaction, not the carbon deposits.

Highlights

On-board hydrogen (H2) generation from hydrocarbons is a promising approach for fuel cells, and especially suitable for high temperature polymer electrolyte membrane (HT-PEM) fuel cells, to improve fuel flexibility
A reasonable explanation for this issue could be the addition of an amount of ammonium carbonate into the mixture followed by thermal decomposition
Mechanochemical methodology for Cu-based catalysts has been developed for steam reforming of methanol (SRM)

Summary

INTRODUCTION

On-board hydrogen (H2) generation from hydrocarbons is a promising approach for fuel cells, and especially suitable for high temperature polymer electrolyte membrane (HT-PEM) fuel cells, to improve fuel flexibility. Cu-based catalysts have been reported to pose superior activity in SRM, e.g., low reforming temperature, high hydrogen selectivity, and low CO concentration. These catalysts can be deactivated for the most important factor—thermal sintering of Cu. To date, a number of studies have attempted to evaluate the effects of structural promoters on the performance of SRM. Structural promoters, e.g., ZnO, ZrO2, CeO2, and Al2O3, were introduced to evaluate the effects on the activity and stability in SRM. Detailed characterizations such as TEM, TPR, XPS, XRD, and N2O chemisorption were used to evaluate the influence of the composition, metal dispersion, and synergistic effect on the steam reforming of methanol. The real weight content calculated from the elemental chemical analysis of the inductively coupled plasma (ICP) analyzer is very close to the theoretical amounts of the catalysts during the preparation process

Catalyst characterization

Catalytic test

Activity

CONCLUSION