Abstract:

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.

Key words: alumina, methanol dehydration, dimethyl ether, acid regulation, catalyst, kinetics

摘要：

二甲醚（DME）作为一种关键的化工原料，被广泛用于合成众多重要的化学品及能源产品。在工业生产中用于从甲醇制备DME的催化剂γ-Al₂O₃因其高效的催化性能而得到普遍应用。然而，γ-Al₂O₃的合成方法和制备条件对其催化性能有着显著的影响。目前，对于工业上常用的γ-Al₂O₃合成条件如何影响其催化性能的系统研究仍然不足。特别是，作为影响催化性能的关键因素之一，酸性位点的性质尚未形成共识。通过调控双铝法成胶过程中母液的pH，成功合成了一系列具有不同孔道结构和酸性质的γ-Al₂O₃。实验结果表明，随着母液pH的增大，γ-Al₂O₃的比表面积、孔容和孔径均呈现减小趋势。同时，γ-Al₂O₃的弱酸量逐渐减小，而中强酸量呈现先增后减的趋势。进一步结合催化性能评估结果，发现中强酸数量与甲醇脱水性能密切相关。具有最高中强酸数量的γ-Al₂O₃表现出最高的DME产率，预示中强酸位点是γ-Al₂O₃催化甲醇脱水制备DME的主要活性中心。针对具有最优性能的γ-Al₂O₃开展动力学实验分析，得到甲醇脱水的反应级数为0.78，反应活化能为83.27 kJ/mol。研究可为甲醇脱水制备DME催化剂的设计提供指导，为进一步优化工业生产条件和提高催化效率夯实基础。

关键词: 氧化铝, 甲醇脱水, 二甲醚, 酸性调控, 催化剂, 动力学