Abstract

Monometallic copper and bimetallic palladium–copper catalysts supported on ZnO–Al₂O₃, CeO₂–Al₂O₃ and ZrO₂–Al₂O₃ were prepared by conventional impregnation method and tested in the methanol synthesis reaction in a gradient less reactor under elevated pressure (3.5 MPa) at 220°C. The physicochemical properties of prepared catalytic systems were studied using BET, TPR-H₂, TPD-NH₃, XRD, SEM-EDS and FT-IR techniques. The results of XRD and SEM-EDS measurements showed the formation of Pd–Cu alloy during the activation of bimetallic catalysts. It was found that the formed alloy was responsible for the improved activity and selectivity of catalysts in the studied reaction. Among investigated catalysts, the highest formation rate of methanol was observed with 2%Pd–20%Cu/ZnO–Al₂O₃ system. Based on the results of FT-IR measurements it can be concluded that hydrogen molecules adsorb dissociatively on the metallic copper surface to form hydrogen atoms, increasing the hydrogen spillover effect on the metal-support interface. In contrast, CO₂ adsorb on the oxygen vacancies of the support to form carbonates, which can further undergo hydrogenation to methanol.

中文翻译：

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Cu和Pd-Cu催化剂上甲醇合成反应的机理研究

摘要

采用常规浸渍法制备了负载在ZnO-Al ₂ O ₃，CeO ₂ -Al ₂ O ₃和ZrO ₂ -Al ₂ O ₃上的单金属铜和双金属钯-铜催化剂，并在无梯度反应器中进行了甲醇合成反应的测试。在220°C的高压（3.5 MPa）下进行。使用BET，TPR-H ₂，TPD-NH ₃研究了所制备催化体系的理化性质。，XRD，SEM-EDS和FT-IR技术。XRD和SEM-EDS测量结果表明，双金属催化剂活化过程中形成了Pd-Cu合金。发现所形成的合金是所研究反应中催化剂活性和选择性提高的原因。在研究的催化剂中，使用2％Pd-20％Cu / ZnO-Al ₂ O ₃体系观察到最高的甲醇生成速率。基于FT-IR测量的结果，可以得出结论，氢分子解离地吸附在金属铜表面上形成氢原子，从而增加了氢在金属-载体界面上的溢出效应。相反，CO ₂ 吸附在载体的氧空位上形成碳酸盐，碳酸盐可进一步加氢成甲醇。