Enhancing effect of Mn2+ substitution in CuAl2O4 spinel for methanol steam reforming in a microreactor

Abstract

Hydrogen generation via methanol steam reforming is a promising method for producing renewable energy. In this work, a series of Mn²⁺-substituted CuAl₂O₄ spinels were prepared by solution combustion method, and the crystal structure, micromorphology, chemical constitution, reduction behavior, acidity, specific surface area and surface chemical state of the spinels were comprehensively characterized by various equipments. The obtained spinels were washcoated on Cu foams to prepare monolithic catalysts, and the catalytic performance of the catalysts was evaluated in a methanol steam reforming microreactor. Compared with the binary Cu–Al spinel, the Mn²⁺ substitution led to a decrease in the particle size, a change in the chemical composition and reduction behavior, a decline in the acidity, an increase in the specific surface area, and an improvement in the surface chemical state. As a result, the release rate of active Cu from the Mn-containing CuAl₂O₄ spinel was significantly slowed down and the formed nanoparticles were fine, which was believed to be in favor of maintaining a stable catalytic performance longer. Among the prepared catalysts, the monolithic catalyst loaded with Cu_0.4Mn_0.6Al₂O₄ exhibited the highest activity and stability. The findings of this work suggested that introducing Mn²⁺ might be a promising way to regulate the Cu releasing property for obtaining a better sustained release catalyst system.