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以层状铜锰铝水滑石为前躯体制备Cu-MnO双功能催化剂,实现了甲醇水蒸气重整制氢与苯甲酸甲酯气相加氢反应耦合制备苯甲醛,选择性可达93.34%,要明显优于传统的外加氢方法。X射线衍射和热重-差热分析表明合成的CuMnAl-LDHs、Cu2Al-LDHs、Mn2Al-LDHs具有典型的层状水滑石结构。层状前躯体经氢气还原后,催化剂CuMnAl-500具有Cu、MnO两种活性组分。结合单活性组分催化剂Cu2Al-500、Mn2Al-500的结构表征和催化性能评价,推测了气相耦合加氢的反应机制:首先通过甲醇在活性Cu组分上发生水蒸气重整反应得到活化氢,然后活化氢转移到MnO表面上,苯甲酸甲酯发生脱氧加氢生成苯甲醛;同时,加氢反应产生的副产物甲醇又可以进入新一轮的水蒸气重整制氢反应。
Cu-MnO bifunctional catalyst was prepared by using layered copper manganese aluminum hydrotalcite as precursor, and the reaction of methanol steam reforming and hydrogenation of methyl benzoate to form benzaldehyde was achieved. The selectivity was up to 93.34% Significantly better than the traditional external hydrogen method. X-ray diffraction and TG-DTA analysis show that the synthesized CuMnAl-LDHs, Cu2Al-LDHs and Mn2Al-LDHs have the typical layered hydrotalcite structure. After the layered precursor was hydrogen reduced, the catalyst CuMnAl-500 with Cu, MnO two active components. Combining the structural characterization and catalytic performance evaluation of catalysts Cu2Al-500 and Mn2Al-500, the reaction mechanism of gas-phase coupling hydrogenation was presumed. Firstly, activated hydrogen was obtained by the steam reforming reaction of methanol on the active Cu component, Then, the activated hydrogen is transferred to the surface of MnO and the methyl benzoate undergoes deoxygenation and hydrogenation to form benzaldehyde. At the same time, the by-product methanol produced by the hydrogenation reaction can enter into a new round of steam reforming hydrogen production reaction.