Yuqing Ouyang,Ningning Du,Xiaoyun Xiong,Qingxun Hu,Hongman Sun,Tingting Li,Jie Zhong,Youhe Wang,Zifeng Yan
The combination of titanium silicalite-1 (TS-1) zeolite and H 2 O 2 oxidant provides an excellent alternative to many highly toxic and polluting olefin oxidation processes due to the by-product being water-only and without deep oxidation. However, the diffusion of bulky reactants and products suffers from the inherent micropores of conventional TS-1 zeolites. Herein, we designed a reticulated ordered macroporous carbon material with uniform and coherent mesopores, and successfully synthesized ordered hierarchical TS-1 zeolites containing intracrystalline macroporous-mesoporous-microporous by dry gel method. The fully interconnected intracrystalline macroporous-mesoporous-microporous hierarchical TS-1 improves the accessibility of the active site and the diffusion efficiency of bulky compounds. It showed excellent catalytic performance during the epoxidation reaction of chloropropene, and its epichlorohydrin yield and H 2 O 2 effective utilization were 70.11% and 77.05%, which were 2.2 and 1.9 times of the catalytic performance of commercial TS-1 zeolites, respectively, and significantly better than the ultrafine TS-1 synthesized by conventional methods. The high catalytic performance was maintained after three cycles of use. This offers a good opportunity for the design and synthesis of efficient zeolite catalysts in the future.
Simultaneous achievement of constructing mesopores and eliminating anatase is a long-term pursuit for enhancing the catalytic performance of TS-1. Here, we developed an aromatic compounds-mediated synthesis method to prepare anatase-free and hierarchical TS-1 for olefin epoxidation. A series of hierarchical TS-1 zeolites were prepared by introducing aromatic compounds containing different functional groups via the crystallization process. The formation of intercrystalline mesopores and insertion of titanium into framework were facilitated at different extent. The synergistic coordination of carboxyl and hydroxyl in aromatic compounds with Ti(OH) 4 realizes the uniform distribution of titanium species and eliminates the generation of anatase. Noteworthily, eight machine learning models were trained to reveal the mechanism of additive functional groups and preparation conditions on anatase formation and microstructure optimization. The prediction accuracy of most models can reach more than 80%. Benefiting from the larger mesopore volumes (0.37 cm 3 ·g −1 ) and higher content of framework Ti species, TS-DHBDC-48h samples exhibit a higher catalytic performance than other zeolites, giving 1-hexene conversion of 49.3% and 1,2-epoxyhenane selectivity of 99.9%. The paper provides a facile aromatic compounds-mediated synthesis strategy and promotes the application of machine learning toward the design and optimization of new zeolites.
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