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Identification of Vicinal Silanols and Promotion of Their Formation on MCM-41 via Ultrasonic Assisted One-Step Room-Temperature Synthesis for Beckmann Rearrangement
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2018-04-16 , DOI: 10.1021/acs.iecr.8b00274 Zichun Wang 1 , Yijiao Jiang 2 , Yunyao Zhang 1 , Jeffrey Shi 1 , Catherine Stampfl 3 , Michael Hunger 4 , Jun Huang 1
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2018-04-16 , DOI: 10.1021/acs.iecr.8b00274 Zichun Wang 1 , Yijiao Jiang 2 , Yunyao Zhang 1 , Jeffrey Shi 1 , Catherine Stampfl 3 , Michael Hunger 4 , Jun Huang 1
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Siliceous mesoporous MCM-41 materials were synthesized under ultrasonic treatment from 0.5 to 3 h. The obtained U-[Si]MCM-41 catalysts were applied in the Beckmann rearrangement of cyclohexanone oxime (CHO) to ε-caprolactam (CPL). The ultrasonic treatment can increase the pore wall thickness, while the density of surface SiOH groups increased slightly. Quantitative 1H MAS NMR studies of the U-[Si]MCM-41 catalysts hint at the presence of isolated and vicinal silanols. After dehydration at 393 K, 1H MAS NMR signals of poly-hydrogen-bonded vicinal silanols occurred, which are strongly reduced after dehydration at 473 K. Correspondingly, a much higher conversion of CHO to CPL was observed for U-[Si]MCM-41 dehydrated at 393 K in comparison with those dehydrated at 473 K. This finding indicates poly-hydrogen-bonded SiOH groups can promote the reaction and improve the catalytic performance of siliceous catalytic materials in the Beckmann rearrangement of CHO in an energy economic way at a suitable activation temperature.
中文翻译：
超声波辅助一步法室温合成贝克曼重排的方法鉴定了邻氨基硅烷醇并促进了它们在MCM-41上的形成
在超声处理0.5到3小时内合成了硅质中孔MCM-41材料。将获得的U- [Si] MCM-41催化剂用于环己酮肟（CHO）的贝克曼重排反应，生成ε-己内酰胺（CPL）。超声处理可以增加孔壁的厚度，而表面SiOH基团的密度则略有增加。U- [Si] MCM-41催化剂的1 H MAS NMR定量研究表明存在分离的和邻位的硅烷醇。在393 K脱水后，1发生了多氢键合邻位硅烷醇的H MAS NMR信号，在473 K脱水后强烈降低。相应地，在393 K下脱水的U- [Si] MCM-41观察到CHO向CPL的转化率更高与在473 K下脱水的那些进行比较。该发现表明，在合适的活化温度下，多氢键合的SiOH基团可以以能量经济的方式在CHO的贝克曼重排中促进反应并改善硅质催化材料的催化性能。
更新日期：2018-04-17
中文翻译：
超声波辅助一步法室温合成贝克曼重排的方法鉴定了邻氨基硅烷醇并促进了它们在MCM-41上的形成
在超声处理0.5到3小时内合成了硅质中孔MCM-41材料。将获得的U- [Si] MCM-41催化剂用于环己酮肟（CHO）的贝克曼重排反应，生成ε-己内酰胺（CPL）。超声处理可以增加孔壁的厚度，而表面SiOH基团的密度则略有增加。U- [Si] MCM-41催化剂的1 H MAS NMR定量研究表明存在分离的和邻位的硅烷醇。在393 K脱水后，1发生了多氢键合邻位硅烷醇的H MAS NMR信号，在473 K脱水后强烈降低。相应地，在393 K下脱水的U- [Si] MCM-41观察到CHO向CPL的转化率更高与在473 K下脱水的那些进行比较。该发现表明，在合适的活化温度下，多氢键合的SiOH基团可以以能量经济的方式在CHO的贝克曼重排中促进反应并改善硅质催化材料的催化性能。
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