Alumina structure and surface property regulation for catalyzing methanol dehydration to dimethyl ether

Dimethyl ether (DME), as a key chemical raw material, is widely used in the synthesis of a multitude of important chemical products and energy commodities. In the industrial production, γ -Al2O3 used for the preparation of DME from methanol has been widely applied due to its high catalytic efficiency. However, the synthesis methods and preparation conditions of γ-Al2O3 have a significant impact on its catalytic performance. At present, there is still insufficient systematic research on how the synthesis conditions of γ-Al2O3 commonly used in industry affect its catalytic performance. This study successfully prepared γ-Al2O3 with different pore structures and acidic properties by adjusting the pH of the mother liquor during the sol-gel process using the double aluminum method. The influence of acidic site properties of γ-Al2O3 on the performance of methanol-to-DME synthesis was systematically investigated. Characterization results revealed that, with an increase in the pH of the mother liquor, the specific surface area, pore volume, and pore size of γ -Al2O3 exhibited a decreasing trend. Furthermore, as the pH increased, the weak acidity of γ-Al2O3 gradually decreased, while the moderate-strong acidity showed an initial increase followed by a decrease. Combining the results of catalytic performance evaluation, it was found that the quantity of moderate-strong acidic sites is closely related to methanol dehydration performance. γ-Al2O3 with the highest quantity of moderate-strong acidic sites exhibited the highest DME yield, suggesting that moderate-strong acid sites are the primary active centers for γ-Al2O3 catalyzing methanol dehydration to produce DME. Kinetic experiments were conducted on γ -Al2O3 with optimal performance, and the reaction order of methanol dehydration was 0.78, and the reaction activation energy was 83.27 kJ/mol. This study provides important guidance for the design of catalysts for methanol dehydration to produce DME, laying the foundation for further optimization of industrial production conditions and improvement of catalytic efficiency. © 2024 Materials China. All rights reserved.