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Probing the methanol-assisted autocatalytic formation of methanol over Cu/ZnO/Al2O3 by high-pressure methanol and methyl formate pulses
Reaction Chemistry & Engineering ( IF 3.9 ) Pub Date : 2022-07-13 , DOI: 10.1039/d2re00185c
Philipp Schwiderowski, Sascha Stürmer, Martin Muhler

Using high-pressure methanol and methyl formate pulses as a surface-sensitive operando method for high-pressure methanol synthesis over Cu/ZnO/Al2O3, the recently found autocatalytic pathway was confirmed. The autocatalytic effect is assumed to result from the faster hydrogenation of the formed methyl formate ester at high methoxy coverages compared with the rate-determining hydrogenation of formate to dioxomethylene. When pulsing increasing amounts of methanol at 60 bar and 210 °C under kinetically controlled conditions in 13.5 vol% CO, 3.5 vol% CO2, and 73.5 vol% H2, higher amounts of methanol were observed in response. The surplus of formed methanol was found to increase exponentially as a function of the dosed amount of methanol and the applied residence time. To further investigate the methanol-assisted autocatalytic pathway, methyl formate as the predicted intermediate was pulsed, which was rapidly converted into methanol. Instead of the expected 2 : 1 stoichiometry of methanol : methyl formate, only one methanol molecule was produced per dosed methyl formate molecule. It is concluded that methyl formate is split into methoxy and formate species by dissociative adsorption, but only methoxy species are rapidly further hydrogenated to desorbing methanol, whereas formate hydrogenation to methanol is too slow on the time scale of the pulse experiments.

中文翻译:

高压甲醇和甲酸甲酯脉冲在 Cu/ZnO/Al2O3 上的甲醇辅助自催化生成甲醇

使用高压甲醇和甲酸甲酯脉冲作为表面敏感操作方法在 Cu/ZnO/Al 2 O 3上进行高压甲醇合成,证实了最近发现的自催化途径。与决定速率的甲酸酯加氢生成二氧亚甲基相比,自催化效应被认为是由于在高甲氧基覆盖率下形成的甲酸甲酯酯的加氢速度更快。在 13.5 vol% CO、3.5 vol% CO 2和 73.5 vol% H 2的动力学控制条件下,在 60 bar 和 210 °C 下脉冲增加甲醇量,响应中观察到更高量的甲醇。发现形成的甲醇的过剩量随甲醇的投药量和应用的停留时间呈指数增加。为了进一步研究甲醇辅助的自催化途径,甲酸甲酯作为预测的中间体被脉冲,甲酸甲酯迅速转化为甲醇。代替预期的 2 : 1 化学计量的甲醇:甲酸甲酯,每个剂量的甲酸甲酯分子仅产生一个甲醇分子。得出的结论是甲酸甲酯通过解离吸附分解为甲氧基和甲酸物种,但只有甲氧基物种被快速进一步氢化成解吸甲醇,而甲酸加氢成甲醇在脉冲实验的时间尺度上太慢。
更新日期:2022-07-13
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