Department of Chemical and Biomolecular Engineering, University of Houston, 4226 Martin Luther King Boulevard, Houston, Texas 77204, United States.
Green Carbon Research Center, Korea Research Institute of Chemical Technology (KRICT), 141 Gajeongro, Yuseong, Daejeon 34114, Republic of Korea.
J Am Chem Soc. 2022 May 4;144(17):7861-7870. doi: 10.1021/jacs.2c01975. Epub 2022 Apr 20.
Identifying zeolite catalysts that can simultaneously optimize -xylene selectivity and feed utilization is critical to toluene alkylation with methanol (TAM). Here, we show that zeolite MCM-22 (MWW) has an exceptional catalyst lifetime in the TAM reaction at high operating pressure, conversion, and selectivity. We systematically probe the catalytic behavior of active sites in distinct topological features of MCM-22, revealing that high -xylene yield and catalyst stability are predominantly attributed to sinusoidal channels and supercages, respectively. Using a combination of catalyst design and testing, density functional theory, and molecular dynamics simulations, we propose a spatiotemporal coke coupling phenomenon to explain a multistage -xylene selectivity profile wherein the formation of light coke in supercages initiates the deactivation of unselective external surface sites. Our findings indicate that the specific nature of coke is critical to catalyst performance. Moreover, they provide unprecedented insight into the synchronous roles of distinct topological features giving rise to the exceptional stability and selectivity of MCM-22 in the TAM reaction.
鉴定能够同时优化二甲苯选择性和进料利用率的沸石催化剂对于甲苯与甲醇烷基化反应（TAM）至关重要。在这里，我们表明，在高操作压力、转化率和选择性下，MWW 型 MCM-22 沸石在 TAM 反应中具有出色的催化剂寿命。我们系统地研究了 MCM-22 不同拓扑特征中活性位的催化行为，揭示了高二甲苯收率和催化剂稳定性主要归因于正弦通道和超笼，分别。通过催化剂设计和测试、密度泛函理论和分子动力学模拟的结合，我们提出了一种时空焦炭偶联现象来解释多阶段二甲苯选择性分布，其中超笼中轻焦炭的形成引发了非选择性外表面位的失活。我们的研究结果表明，焦炭的特定性质对于催化剂性能至关重要。此外，它们为不同拓扑特征的同步作用提供了前所未有的见解，这些作用导致了 MCM-22 在 TAM 反应中具有出色的稳定性和选择性。
