Selective production of hydrogen by partial oxidation of methanol over Cu/Cr catalysts

Abstract

Hydrogen production by partial oxidation of methanol (CH 3OH+(1/2)O 2→2H 2+CO 2) over a series of binary Cu/Cr catalysts and ternary Cu/Cr/M (M=Fe, Zn, Ce, etc.) catalysts prepared by co-precipitation method was studied. The results show that Cu60Cr40 catalyst exhibits high CH 3OH conversion and H 2 selectivity as compared with other binary catalysts and the introduction of Zn promoter not only helps to increase the activity of Cu60Cr40 catalyst but also improves the stability of the catalyst, the highest of the activity of the ternary Cu/Cr/Zn is obtained with a relative composition of Cu/Cr (6:4)/Zn (10%). The results obtained by XRD, H 2-TPR, BET methods and the measurement of the copper surface area by decomposition of N 2O reveal that catalyst performance for methanol conversion is dependent on the metallic copper surface area in the catalyst. Binary Cu/Cr catalysts containing less than 40% Cr enhance the dispersion of the metallic copper. Higher Cr content in the catalyst would lead to the formation of copper chromate that, on the contrary, decreases the surface area of the metallic copper. The stability results suggest that a rapid drop of activity of binary Cu60Cr40 catalyst during 100 h operation is due to the sintering of Cu species and the introduction of Zn helps to prevent Cu60Cr40 catalyst from being sintered to some extent.