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A Solid‐State Combustion Method towards Metallic Cu–ZnO Catalyst without Further Reduction and its Application to Low‐Temperature Methanol Synthesis

A series of Cu–ZnO catalysts were prepared by using a solid‐state combustion method with metal nitrates and citric acid. This method was simple, waste water free, and did not require a reduction step. If the precursors were burnt in an argon atmosphere, H2 and CH4 were emitted in the decomposition of metal citrate complexes and acted as reducing agents to yield metallic Cu from Cu2+ in the chelated compounds. Analysis of XRD patterns revealed that the precursors burnt at 523 K for 1 h in the argon atmosphere were converted into pure Cu species. TPR analysis of the burnt catalysts without further reduction illustrated that almost no hydrogen was consumed. However, a part of amorphous carbon and carboxylates were left in the burnt catalysts. Compared with formerly reported Cu–ZnO catalysts prepared by the sol–gel combustion method, the catalysts prepared by the solid‐state combustion method had higher activity and methanol selectivity.