Controllable construction of highly active Ti species in TS-1 zeotype by organic base treatment†

IF 4.2 3区化学 Q2 CHEMISTRY, PHYSICAL Catalysis Science & Technology Pub Date : 2024-12-16 DOI:10.1039/d4cy01313a

Shiqing Li , Jie Tuo , Rusi Peng , Xianchen Gong , Ying Ma , Hao Xu , Peng Wu

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Abstract

Regulating the microenvironment of Ti active centers in titanosilicates is of great significance in both theoretical research and practical application of titanosilicate/H₂O₂ systems. Herein, a novel six-coordinated Ti species containing an organic amine ligand, Ti(OSi)₂(OH)₂(H₂O)TPA, was constructed in the TS-1 zeotype in the process of dissolution and recrystallization by hydrothermal post-treatment with tetrapropylammonium hydroxide and ammonium chloride. The newly formed hexa-coordinated Ti species promoted the activation of H₂O₂ significantly, responsible for the superior catalytic activity in 1-hexene epoxidation with a conversion of 35.5% compared with the untreated TS-1 (18.0%). After removal of organics by calcination, Ti(OSi)₂(OH)₂(H₂O)TPA was transformed into Ti(OSi)₂(OH)₂(H₂O)₂ sites, which also exhibited higher epoxidation activity compared to the original framework Ti(OSi)₄ sites. In addition, the acid sites of Si–OH in TS-1 zeotype were quenched by the basic amine molecules, which effectively inhibited the occurrence of side reactions such as epoxide ring opening, leading to a high epoxide selectivity of 98.6%. With the construction of highly active Ti(OSi)₂(OH)₂(H₂O)TPA sites and without further calcination process, the obtained catalyst (denoted as TS-PN-am) exhibited not only excellent catalytic capacity but also application potential in continuous liquid-phase epoxidation.

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有机碱处理对TS-1型高活性钛的可控构建

调控钛酸盐中钛活性中心的微环境对钛酸盐/H2O2体系的理论研究和实际应用都具有重要意义。在四丙基氢氧化铵和氯化铵的水热后处理下，在TS-1型中构建了一个含有有机胺配体Ti(OSi)2(OH)2(H2O)TPA的新型六配位Ti物种。新形成的六配位Ti明显促进了H2O2的活化，导致1-己烯环氧化的催化活性优于未经处理的TS-1(18.0%)，转化率为35.5%。煅烧去除有机物后，Ti(OSi)2(OH)2(H2O)TPA转化为Ti(OSi)2(OH)2(H2O)2位点，与原始框架Ti(OSi)4位点相比，其环氧化活性也更高。此外，Si-OH在TS-1型中的酸位被碱性胺分子淬灭，有效抑制了环氧化合物开环等副反应的发生，环氧化合物选择性高达98.6%。通过构建高活性Ti(OSi)2(OH)2(H2O)TPA位点，无需进一步煅烧，得到的催化剂（记为TS-PN-am）不仅具有优异的催化性能，而且在连续液相环氧化中具有应用潜力。

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来源期刊

Catalysis Science & Technology CHEMISTRY, PHYSICAL-

CiteScore

8.70

自引率

6.00%

发文量

587

审稿时长

1.5 months

期刊介绍： A multidisciplinary journal focusing on cutting edge research across all fundamental science and technological aspects of catalysis. Editor-in-chief: Bert Weckhuysen Impact factor: 5.0 Time to first decision (peer reviewed only): 31 days