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制备了Cu-Zn-Al (4/50/5)催化剂(Cat)和Cu-Zn-Al-Li(40/50/5/5)催化剂(Cat-Li).并将其分别用于由CO/H_2和CO_2/H_2合成甲醇。诸如TPD、TPR、TPSR、脉冲、CD3I-捕获、同位素标记、EPR及原位DRIFT等技术和方法被用来表征这两种催化剂及研究反应机理,对处于去氢、含氢及含氧态催化剂进行了对比研究以期阐明表面氧和表面氢对CO_2和CO活化所起的作用。提出了一个由甲酸根和甲醛氢化及甲醇氧化结果为证的CO/CO_2氢化机理。由于通过Li+取代CuO晶格上的Cu2+形成的氢空位,在Cat中添加Li+改善了甲醇合成活性。CO_2能被一捕获的电子(F-中心)活化,生成的CO2-能容易地被氢化成甲酸根和亚甲基双草酰,后者分解生成H2CO和表面氧。CO能被表面氧活化,生成的CO2-将遵循CO_2氢化的途径。在CD3I-捕获的实验中,我们捕获了表面氧。在无表面氧时,CO可能直接氢化成甲酸基,即CO_2氢化中的一途径。由亚甲基双草酰产生的H2CO表面模型可能与由甲醛吸附或CO氢化生成的H2CO表面模型不同。
Cu-Zn-Al (4/50/5) catalyst (Cat) and Cu-Zn-Al-Li (40/50/5/5) catalyst (Cat-Li) were prepared. And used to synthesize methanol from CO / H 2 and CO 2 / H 2, respectively. Techniques and methods such as TPD, TPR, TPSR, pulse, CD3I-capture, isotope labeling, EPR and in-situ DRIFT were used to characterize both catalysts and to investigate the reaction mechanism. A comparative study was conducted to clarify the role of surface oxygen and surface hydrogen on CO 2 and CO activation. A CO / CO 2 hydrogenation mechanism evidenced by formate and formaldehyde hydrogenation and methanol oxidation results is presented. Methanol synthesis activity was improved by adding Li + to Cat due to the hydrogen vacancy formed by the Cu2 + substitution of Li + on the CuO lattice. CO 2 can be activated by a trapped electron (F-center) and the resulting CO 2 - can easily be hydrogenated to formic acid and methylene bis-oxalyl, which decomposes to form H 2 CO and surface oxygen. CO can be activated by surface oxygen, the generated CO2- will follow the route of CO2 hydrogenation. In the CD3I-captured experiment, we captured surface oxygen. In the absence of surface oxygen, CO may be directly hydrogenated to formic acid groups, a pathway in the hydrogenation of CO 2. The H2CO surface model produced by methylene bis-oxalyl may be different from the H2CO surface model generated by formaldehyde adsorption or CO hydrogenation.