A Reactivity Test of Cu–Zn-Based Catalysts Prepared with Various Precursors and Precipitates for the Direct Synthesis of DME

Abstract

A screen test to develop Cu–Zn-based catalysts for the direct synthesis of DME from synthetic gas was performed in this study. In the screen test, commercial catalysts used for methanol synthesis and methanol dehydration were physically mixed together and their reactivity for the direct synthesis of DME was compared to each other. In addition, the Cu–Zn-based catalysts were prepared by a co-precipitation method and their reactivity was investigated in terms of the precursors used in their preparation. Experimental temperature condition was in the range of 240–290°C, pressure was 30–70 atm, molar ratio of H2/CO was 0.5–2.0 and space velocity was 3000–6000 h−1. Among various commercialized catalysts, a Siid-Chemi's catalyst in which Cu/Zn/Al were in the molar ratio 5/4/1 showed a good reactivity as well as a high DME selectivity. The optimized operating temperature of this catalyst was 270°C and the maximum CO conversion obtained at this temperature was about 43%. Comparing two different types of Cu–Zn-based catalysts, the reactivity of the CZ-A catalyst formulated from the acetate-based precursors was higher than the one of the CZ-N catalyst formulated from the nitrate-based precursors. Particle sizes of active materials on the surface of those catalysts were also calculated by Scherrer equation. While the particle size of CZ-A catalyst was smaller than CZ-N, the surface area of CZ-A was larger than CZ-N. From the experimental results, the acetate-based precursors had more advantages over the nitrate-based precursors in the preparation of the Cu–Zn-based catalysts.