In‐situ IR Spectroscopy Study of Reactions of C3 Oxygenates on Heteroatom (Sn, Mo, and W) doped BEA Zeolites and the Effect of Co‐adsorbed Water
In‐situ IR Spectroscopy Study of Reactions of C3 Oxygenates on Heteroatom (Sn, Mo, and W) doped BEA Zeolites and the Effect of Co‐adsorbed Water
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DOI：
10.1002/cctc.202001424
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发表时间：
2020-11
期刊：
影响因子：
4.5
通讯作者：
Sean Najmi;Jungseob So;E. Stavitski;William P. McDermott;Yimeng Lyu;S. Burt;Ive Hermans;D. Sholl;Carsten Sievers
中科院分区：
文献类型：
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作者：
Sean Najmi;Jungseob So;E. Stavitski;William P. McDermott;Yimeng Lyu;S. Burt;Ive Hermans;D. Sholl;Carsten Sievers
本文用红外光谱法研究了在水蒸气存在和不存在的条件下，丙酮和羟基丙酮在掺杂锡、钼和钨的ZSM-5分子筛上的反应。丙酮仅在Sn-2 O3上转化为异亚丙基丙酮。在较高的温度下，形成较大的含氧化合物，如佛酮、芳烃和焦炭。Sn-12中共吸附水的存在抑制了互变异构化。H2O蒸汽也有利于使高温下的焦炭形成最小化。羟基丙酮在Sn-Cu上转化为2-羟基丙醛，在高达400 °C下对Sn位点表现出高亲和力。在不存在H2O的情况下，Sn-Al 2 O3催化羟基丙酮转化为烯醇，但暴露于H2O诱导形成2-羟基丙醛并随后转化为丙烯醛。使用刘易斯酸描述符来合理化反应途径。对于羟基丙酮异构化为2-羟基丙醛，酸中心的硬度影响反应，并分别与催化剂的总刘易斯酸性相关。然而，交换金属的大小显着影响羟醛缩合，其中酮和烯醇形式的丙酮同时吸附到活性位点。
The reactions of acetone and hydroxyacetone over heteroatom doped BEA zeolites (Sn, Mo, and W) in the presence and absence of H2O vapor are investigated using infrared spectroscopy. Acetone is converted to mesityl oxide over Sn‐BEA exclusively. At higher temperatures, larger oxygenates such as phorones, aromatics, and coke form. The presence of co‐adsorbed water in Sn‐BEA suppresses tautomerization. H2O vapor is also beneficial for minimizing coke formation at high temperatures. Hydroxyacetone is converted into 2‐hydroxypropanal over Sn‐BEA, exhibiting high affinity to Sn sites up to 400 °C. Sn‐BEA catalyzes conversion of hydroxyacetone into the enol in the absence of H2O, but exposure to H2O induces the formation of 2‐hydroxypropanal and subsequent conversion to acrolein. The Lewis acid descriptors are used to rationalize the reaction pathways. For the isomerization of hydroxyacetone into 2‐hydroxypropanal, the hardness of acid sites influences the reaction and correlates with the overall Lewis acidity of the catalysts, respectively. However, the size of the exchanged metal significantly affects aldol condensation, where keto and enol forms of acetone adsorb to active sites simultaneously.