Hong Zhe, Wang Xin, Fang Yingsen, Deng Lihua, Li Lei, Zhu Zhirong
College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing 314001, Zhejiang, China.
School of Chemical Science and Engineering, Tongji University, Shanghai 200092, China.
Inorg Chem. 2024 Feb 19;63(7):3258-3266. doi: 10.1021/acs.inorgchem.3c03454. Epub 2024 Feb 6.
Toluene side-chain alkylation with methanol for the styrene monomer formation remains a great challenge. An optimal synergy between acidic and basic sites on zeolites is required for an efficient catalysis process. It is important to modulate the surface Lewis acid-base pairs precisely. Herein, we report a strategy to restructure the surface Lewis acid-base pairs in cesium-modified X zeolite (CsX) by N doping. In the process of toluene side-chain alkylation, the CsX-BN-600 catalyst, where N species is doped into the framework of the X zeolite, exhibits 2.7 times the styrene formation rate and a much better selectivity of 85.7% in comparison to the parent CsX of 70.1% selectivity to styrene at the same reaction conditions. The introduction of N species into zeolites acts as a new Lewis base site and optimizes the Lewis sites due to its ability of electron donation. Meanwhile, the frustrated Lewis pair (FLP) between the deprotonated framework nitrogen in X zeolite and positively polarized C species in the side-chain alkylation reaction is created. Furthermore, the N doping contributes to the generation of the active intermediates of HCOO* and HCO*. These reasons favor the superiority of the catalyst through N doping.
甲苯与甲醇进行侧链烷基化反应以生成苯乙烯单体仍然是一个巨大的挑战。沸石上的酸性位点和碱性位点之间需要达到最佳协同作用才能实现高效催化过程。精确调节表面路易斯酸碱对非常重要。在此，我们报告了一种通过氮掺杂来重构铯改性X沸石（CsX）表面路易斯酸碱对的策略。在甲苯侧链烷基化过程中，CsX-BN-600催化剂（其中氮物种掺杂到X沸石骨架中）在相同反应条件下，与母体CsX相比，苯乙烯生成速率提高了2.7倍，选择性也更好，达到85.7%，而母体CsX对苯乙烯的选择性为70.1%。将氮物种引入沸石中可作为新的路易斯碱位点，并因其电子给予能力优化路易斯位点。同时，在侧链烷基化反应中，X沸石中去质子化的骨架氮与带正电的极化碳物种之间形成了受阻路易斯对（FLP）。此外，氮掺杂有助于生成HCOO和HCO活性中间体。这些原因使得通过氮掺杂的催化剂具有优势。
