Influence of precipitation method on the properties of precursors of CuO/ZnO/Al2O3 catalysts
加料方式对CuO/ZnO/Al2O3系催化剂前驱体性质的影响

The influence of precipitation method on the precursors of CuO/ZnO/Al_2O_3 catalysts were studied by X-ray Diffraction, Thermogravimetry-Differential Thermogravimetry and Temperature Programmed Reduction techniques. The catalytic activity of the catalysts for methanol synthesis was tested using a differential fixed-bed reactor. It is found that the feeding method has strong influence on the Cu precursors in CuO/ZnO/Al_2O_3 catalyst. In case of base to salt, the initial precipitate was crystal Cu_2(OH)_3NO_3; while in the case of co-current, the initial phase was mainly amorphous Cu_2CO_3(OH)_2. The feed method has no effect on the initial phase composition and crystallinity of Zn-precursor and Zn_5(CO_3)_2(OH)_6 was the unique phase in the precursors. The phases of (Cu, Zn)_2CO_3(OH)_2 and (Cu, Zn)_5(CO_3)_2(OH)_6 in the precursors of the catalyst were produced from the substitution of Cu_2CO_3(OH)_2 (amorphous) and Zn_5(CO_3)_2(OH)_6. The activity of the catalyst was in the order of co-current>salt to base >base to salt.