Influence of Precipitation Methods on Precursors and Properties of Cu-Based Catalyst for Methanol Synthesis

Cu/ZnO/Al2O3 catalyst samples for methanol synthesis were prepared by co-precipitation (CP), two-stage precipitation (TP), and fractional precipitation (FP) methods, respectively. The evaluation results showed that the methanol yields over the catalyst prepared by FP is the best, which is 46.3% higher than that over the catalyst prepared by CP and 9.3% higher than that over the catalyst prepared by TP. The catalyst samples and their precursors were characterized by X-ray diffraction, thermogravimetry, infrared spectroscopy, N-2 adsorption-desorption, temperature-programmed reduction, and N2O titration. The results revealed that the precursor prepared by FP has higher amounts of (Cu,Zn)(2)CO3(OH)(2) and (Zn,Cu)(5)(CO3)(2)(OH)(6) phases and a lower amount of the (Cu,Zn)(6)Al-2(OH)(16)CO3 center dot 4H(2)O phase. Therefore, after calcination the catalyst has a higher amount of CuO-ZnO solid solution and carbonate formed at high temperature.