Selective Removal of Acid Sites in Mordenite Zeolite by Trimethylchlorosilane Silylation to Improve Dimethyl Ether Carbonylation Stability
Selective Removal of Acid Sites in Mordenite Zeolite by Trimethylchlorosilane Silylation to Improve Dimethyl Ether Carbonylation Stability
复制标题
DOI：
10.1021/acscatal.1c05896
复制
发表时间：
2022-04-15
期刊：
影响因子：
12.9
通讯作者：
Liu, Zhongmin
中科院分区：
文献类型：
--
作者：
Liu, Rongsheng;Zeng, Shu;Liu, Zhongmin
催化研究始终追求更高效的催化剂并实现选择性控制的转化。沸石中酸性位点的局部环境被认为是其在许多化学反应中具有催化选择性的重要原因。在此，我们证明了丝光沸石十二元环（12-MR）通道中的酸性位点可以通过三甲基氯硅烷（TMCS）硅烷化处理选择性地覆盖，从而显着提高二甲醚（DME）的羰基化性能。通过原位 DRIFT、1H MAS NMR 和 FTIR 光谱分析进行的详细机理研究表明，当氯基团被质子快速水解时，TMCS 物质取代了桥羟基中的布朗斯台德 H+，并伴随着硅氧烷键的形成。由于空间限制，硅烷化反应主要发生在12-MR通道中，并在MOR沸石的8-MR通道中产生了大部分剩余的酸位（80%），这在DME羰基化反应中提供了更好的选择性和更长的寿命。这项工作实现了一种选择性控制沸石不同约束位置内酸位点分布的概念途径，以提高催化剂的催化选择性。
Catalysis research always pursues more efficient catalystsand realizes selectivity-controlled conversion. The local environment ofacid sites in a zeolite is regarded as the vital reason for its catalyticselectivity in many chemical reactions. Herein, we have demonstrated thatthe acid sites in the 12-membered-ring (12-MR) channels of mordenitezeolite could be selectively covered by a trimethylchlorosilane (TMCS)silylation treatment, which could significantly improve the dimethyl ether(DME) carbonylation performance. Detailed mechanism studies byin situDRIFT,1H MAS NMR, and FTIR spectra analyses indicate that theTMCS species replace the Bronsted H+in the bridging hydroxyl groupswhen chloro groups are rapidly hydrolyzed by the protons, accompaniedby the formation of siloxane bonds. Due to the space limitation, thesilylation reaction mainly occurred in the 12-MR channels and createdmost of the remaining acid sites (80%) in the 8-MR channels of the MOR zeolite, which gave better selectivity and a much longerlifetime in the DME carbonylation reaction. This work realizes a conceptual pathway to selectively control the distribution of acidsites within different confinement positions of zeolites to improve the catalytic selectivity of catalysts.