Jiani Zhang,Huaizhong Shi,Yue Song,Wenjing Xu,Xianyu Meng,Jiyang Li
Titanium silicalite-1 (TS-1) zeolite, as a promising shape-selective catalyst, has excellent catalytic activity in many oxidation reactions. However, there are still challenges to rapidly synthesize TS-1 and achieve a high content of Ti in TS-1 without anatase TiO2. In this work, a high-efficiency strategy has been proposed by using 1,3,5-benzenetricarboxylic acid (H3BTC) as a crystallization modifier to rapidly synthesize enhanced-Ti TS-1 zeolite without extra-framework anatase TiO2. In such a synthetic system, a mixed liquid–solid precursor phase is formed within 4.5 hours, and then TS-1 crystals can be produced within one day based on the special combination mechanism of liquid-phase and solid-phase conversion. Ti species enter into the TS-1 framework by the transformation from the liquid phase to crystals as well as by the in situ transformation of the solid phase, which makes the content of framework Ti increase significantly, and the Si/Ti ratio can reach 48.5 without any anatase TiO2. In the epoxidation of 1-hexene with H2O2 as an oxidant, the conversion of alkene over the synthesized TS-1 was improved by 8.01% compared to the traditional TS-1 (18.11% vs. 10.10%). The high-efficiency strategy reported in this paper will provide new opportunities for further promoting the industrial application of TS-1 zeolite.
Yang Xu,Dong Lin,Ze Zong,Qiuming He,Zhe Ma,Xuliang Deng,De Chen,Chaohe Yang,Xiang Feng
Demetalation-metalation method has gained prominence for its higher metal loading, efficiency and shortened synthetic period, particularly in the incorporation of metal atoms with large radii into zeolite framework in recent years. An ammonia-regulated approach has been developed for selectively evolved deep-substituted Ti precursors in dealuminized beta zeolites, which enables a controlled promotion of metalation of Ti atoms. Additionally, this ammonia-regulated approach could also enhance 1-hexene kinetic adsorption by constructing mesopores, which is demonstrated by the lower reaction order of 1-hexene. The synthesized ammonia-regulated N-Ti-beta exhibits rich framework Ti species and a high specific surface area, leading to significantly improved 1-hexene epoxidation performance (conversion of 61%, selectivity of 98%, and a high H 2 O 2 utilization efficiency of 93%). This study not only provides a new strategy to dynamically regulate evolution of Ti precursors by ammonia but also holds promise for advancing related industrial processes in demetalation-metalation methods.
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