1,3-Butadiene is an important commodity chemical and new, selective routes of catalytic synthesis using green feedstocks, such as ethanol, is of interest. For this purpose, surface chemistry of MgO/SiO₂ catalyst synthesized using wet-kneading was explored during the reaction of ethanol and the corresponding reactive intermediates, including acetaldehyde, crotonaldehyde, crotyl alcohol using temperature programmed in situ DRIFT spectroscopy combined with DFT calculations. Ethanol adsorption yielded several physisorbed and chemisorbed surface species. Acetaldehyde exhibited high reactivity to form crotonaldehyde. However, aldehyde intermediates resulted in strongly bound surface species stable even at high temperatures, assigned to surface acetate, and/or 2,4-hexadienal or polymerized acetaldehyde. Crotonaldehyde was reduced by ethanol to yield crotyl alcohol via MPV mechanism. Crotyl alcohol, on the other hand, showed to be very reactive and yield two different species on the surface, namely physisorbed and deprotonated that would further desorb as 1,3-BD. Presence of gas phase hydrogen containing molecules, such as ethanol, proved to be key in several reactive steps, including acetaldehyde condensation step and crotonaldehyde reduction. Altogether, these data suggested complex reactive interactions between the surface hydroxyl groups, gaseous reactants and surface bound reactive intermediates during the 1,3-BD formation. Future work is needed to correlate vapor phase product evolution with the transient reactive surface intermediates to examine trends leading to higher overall 1,3-BD selectivity.

中文翻译：

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MgO / SiO ₂催化剂在乙醇催化转化为1,3-丁二烯过程中的表面化学：原位DRIFTS和DFT研究

1,3-丁二烯是一种重要的商品化学，并且使用绿色原料（例如乙醇）进行催化合成的新的选择性路线也很受关注。为此，在原位编程温度下，在乙醇与相应的反应性中间体（包括乙醛，巴豆醛，巴豆醇）反应过程中，研究了湿混法合成的MgO / SiO ₂催化剂的表面化学性质。DRIFT光谱结合DFT计算。乙醇吸附产生了几种物理吸附和化学吸附的表面物质。乙醛具有高反应活性，可形成巴豆醛。然而，醛中间体导致即使在高温下也稳定的牢固结合的表面物质，被分配给表面乙酸盐和/或2，4-己二醛或聚合的乙醛。用乙醇将巴豆醛还原，通过MPV机制。另一方面，巴豆醇显示出非常高的反应性，并在表面上产生两种不同的物质，即物理吸附和去质子化，将进一步解吸为1,3-BD。气相含氢分子（例如乙醇）的存在被证明是几个反应步骤的关键，包括乙醛缩合步骤和巴豆醛还原。总而言之，这些数据表明在1，3-BD形成过程中，表面羟基，气态反应物和表面结合的反应性中间体之间存在复杂的反应性相互作用。需要进一步的工作来将气相产物的演化与瞬态反应性表面中间体相关联，以研究导致更高的整体1,3-BD选择性的趋势。