Preparation of Copper-Based Catalysts for Methanol Synthesis by Acid–Alkali-Based Alternate Precipitation Method

A new copper-based catalyst for methanol synthesis was prepared by the acid-alkali-based alternate precipitation (AP) method. The catalyst activity is the highest when the pH value of the mother solution alters three times in the range of 5.0 to 9.5. Compared with the catalysts prepared by other methods, the activity and thermal stability of the catalyst prepared by the AP method are the best. About 88% activity of the catalyst is remained after the thermal test, which is 8%–20% higher than those of other catalysts. Furthermore, the activity of this catalyst after the thermal test is higher than those of other catalysts before the thermal test. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption, differential thermogravimetric analysis (DTG), and scanning electron microscopy (SEM). XRD patterns show that the characteristic peaks of CuO and ZnO are far more broadened for the catalyst prepared by the AP method. From SEM photographs it is found that the grains of the catalyst prepared by the AP method are smaller, and the distribution of the grains is symmetrical. The crystal size of this catalyst is small. DTG patterns show that this catalyst requires the lowest reduction temperature. The primary reason for the high activity and thermal stability of the catalyst prepared by the AP method is that an amorphous sosoloid of CuO and ZnO is formed, which can increase the dispersion of the active components and the BET surface area of the catalyst.