Menghui Yan,Fang Jin,Yigang Ding,Guiying Wu,Rong Chen,Luhui Wang,Yuanzhi Yan
A novel titanosilicate zeolite was synthesized by a sequential treatment of ERB-1 with deboronation and atom-planting method to develop an epoxide catalyst. The Fourier transform infrared (FTIR) and the diffuse reflectance infrared Fourier transform (DRIFT) characteristic results reveal that the silanol hydroxyl nests generated by deboronation process are further consumed by the dehydrochlorination of TiCl4 during the atom-planting treatment. At the same time, the titanium species are incorporated into the framework of MWW structure. The energy-dispersive spectroscopy (EDS), ultraviolet-visible light (UV-vis), and ultraviolet resonance Raman spectroscopy (UVRRS) characterization results reveal that the amount and coordination states of the incorporated Ti species can be controlled by the atom-planting treatment time and temperature. The catalytic performance of the new titanosilicates in the epoxidation of 1-hexene with H2O2 and of cyclohexene with tert-butyl hydroperoxide is compared for the efficiency of Ti species in the hydrophilic and hydrophobic system. The catalytic results show the framework tetrahedral coordinated titanium species are more efficient for epoxidation than extra-framework octahedral Ti species.
Although the oxidative hydration of ethylene with hydrogen peroxide (H 2 O 2 ) to ethylene glycol (EG) over Ti-MWW zeolites take advantages of step-saving and facile operation, both H 2 O 2 utilization efficiency and EG yield are relatively low, because some extra-framework octahedral Ti species are usually formed in the Ti-MWW zeolites synthesized by prevailing methods, which are detrimental to selective oxidation . In the present work, an acid-modulated isomorphous substitution method, i.e. , layered borosilicate MWW-type zeolite (ERB-1) treated with HNO 3 aqueous solution containing tetrabutyl orthotitanate (TBOT), is developed to synthesize a Ti-MWW zeolite without extra-framework octahedral Ti species under the optimized synthesis conditions. In combination with the results from extensive characterizations for the synthesized zeolites, it is found that in the zeolite prepared by the currently developed synthesis method there are more open Ti(OSi) 3 OH sites formed, resulting in the stronger Lewis acidity that is very helpful to EG production from the oxidative hydration of ethylene with H 2 O 2 , compared to the one synthesized by the prevailing method. Moreover, the developed catalyst is recyclable after the regeneration of the deactivated zeolite by calcination at high temperatures. Therefore, it is anticipated that the currently developed Ti-MWW might be industrially applicable in the one-pot synthesis of EG from ethylene with H 2 O 2 .
Bo Shuang,Wang Tianlong,Lv Tianming,Wu Huifang,Feng Ziyi,Miao Lei,Feng Zhaochi,Ren Limin,Meng Changgong
ERB-1 zeolite emerges as a key bridging material for crafting heteroatom-containing MWW for versatile catalytic applications. In this study, we developed a solvent-free strategy facilitated by high-temperature condition and seed assistance, streamlining the synthesis of ERB-1 zeolite. This novel approach not only significantly reduces the growth time to 12 h compared to the conventional 168-h hydrothermal synthesis but also enhances product yield while minimizing waste generation. Benefiting from the platelet seeds and the grinding force, a distinct non-classical growth pathway, involving nanoparticle attachment, epitaxial growth, anisotropic assembly, and crystallization, was observed in the solvent-free synthesis. Through heteroatom substitution, pillared Sn-MWW was successfully prepared, exhibiting remarkable stability and catalytic performance in the Bayer-Villiger oxidation reaction of 2-adamantanone. Our findings present a simple and cost-effective way for rapid synthesis of MWW zeolite, with implications extending to diverse catalytic applications.
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