Improvement of Cu/Zn-based catalysts by nickel additive in methanol decomposition

A series of Cu/Zn/M catalysts, prepared by co-precipitation method, have been studied for methanol decomposition reaction. CO and H-2 are the major products. Cu/Zn catalysts show low initial activity and poor stability. The formation of CuZn alloys was observed in the deactivated Cu/Zn catalysts which had been used in methanol decomposition at 250 degreesC. If one adds small amounts of Ni in the catalyst, the Cu/Zn/Ni (5/4/X) catalysts show high activity at low temperature. The catalyst activity and stability are affected by nickel content, the activity of Cu/Zn/Ni catalysts maintained a relatively stable values with 78% conversion of methanol, 95% selectivity of H-2, 93% selectivity of CO, and more than 70% yield of hydrogen was obtained at 250 degreesC when X greater than or equal to 1. The stability of the Cu/Zn/Ni (5/4/X) catalysts was dependent on Ni contents. The most stable catalyst is Cu/Zn/NTi (5/4/1). The stabilization effect of nickel on Cu/Zn-based catalysts was studied by XRD, TPR and copper surface area measurements. The roles of nickel may be attributed to the increase of the dispersion of active Cu species and the prevention of formation of CuZn alloy. (C) 2002 Elsevier Science B.V. All rights reserved.