Influence of precipitation temperature on phase composition of precursor of CuO/ZnO/Al2O3 catalyst and its catalytic activity for water gas shift reaction

The CuO/ZnO/Al2O3 catalyst was prepared by the Cu-Zn-Al ternary co-current coprecipitation method at pH 7. The effect of precipitation temperature on the phase composition of the catalyst precursor was studied by XRD, DTG, TPR, N-2 adsorption and N2O titration methods. The catalyst activity for the water gas shift reaction (WGSR) was tested in a differential fixed-bed reactor at atmospheric pressure. The results demonstrated that Cu2CO3(OH)(2), (Cu,Zn)(2)CO3(OH)(2) and (Cu,Zn)(6)Al-2(OH)(16)CO3.4H(2)O were the main phases in the catalyst precursor and the amounts of the latter two phases increased with increasing precipitation temperature. In the calcined catalyst, CuO-ZnO solid solution formed and its amount increased as the precipitation temperature increased. No spinel-like phase of (Cu,Zn)Al2O4 was detected by XRD in the calcined catalyst. There was a linear relationship between the low-temperature (200 degreesC) catalytic activity for WGSR and the Cu surface area of the catalyst. WGSR was a structure-insensitive reaction.