Seed-Assisted Synthesis of Hierarchically Structured Nano-Sized Ti-β Zeolites for the Efficient Epoxidation Reaction of Alkenes

Abstract

The development of nano-sized titanosilicate zeolites with hierarchical structures is crucial in promoting the efficient epoxidation of alkenes. In the present work, nano-sized hierarchical Ti-β (*BEA) zeolites with high crystal yield are prepared by a one-pot nanoseed-assisted approach. The influence of seed size on the resultant Ti-β zeolites is investigated by complementary characterizations, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption/desorption, UV–vis diffuse reflectance spectroscopy (DRS), and UV Raman spectroscopy. The possible process for the formation of hierarchical Ti-β nanocrystals with the assistance of nanoseeds in the synthesis gel is proposed. Consequentially, the nano-sized hierarchical material prepared by the nanoseed-assisted method shows excellent mass transportation and accessibility to active sites by reducing particle size and constructing hierarchical porosity, hence showing a remarkably enhanced catalytic activity and selectivity in the epoxidation reaction of alkenes. This work will shed light on the efficient preparation of nano-sized titanosilicate zeolites.

Acceleration of Zeolite Crystallization: Current Status, Mechanisms, and Perspectives

“…Furthermore, parallel conclusions were also derived from the preparation of other typical zeolites such as Beta, ZSM-11, and SSZ-13, which commonly employed the tetraethylammonium cations (TEA + ), tetrbuthylammonium cations (TBA + ), and 1-adamantyltrimethylammonium cations (TMAda + ) as the OSDAs. ,, However, due to the limited functions of the OSDAs, it was challenging to intelligently quicken the induction nucleation of zeolites merely by increasing the quantity of the OSDAs. In order to overcome these troubles, plenty of pioneer works that introduced the prefabricated parent zeolites into the starting gels as seeds to promote the crystallization of zeolites had been developed. ,, The earliest example that added seeds to accelerate the crystallization rate of zeolites could be dated back to before 1989, when R. D. Edelman and his collogues ascertained that seeds played important roles in a zeolite crystallization. , Afterward, the seeds were used as conventional additives to manipulate the zeolite crystallization process on a large scale, and thus the morphologies, sizes, distributions of aluminum within the frameworks, Si/Al, and ratio of the zeolites were imperceptibly regulated. − …”

Wheel-like Mordenite Nanoassemblies with Shortened Channel Lengths for Improved Catalytic Performance in Dimethyl Ether Carbonylation

“…Seed-assisted synthesis has been an efficient way to prepare zeolite nanoassemblies, which exhibit advantages of both good mass transfer and easy separation at an industrial scale. Chen and co-workers 16 prepared nanosized hierarchical Ti-BEA zeolites by a one-pot nanoseed-assisted approach. Sun et al 17 synthesized SAPO-34 nanocrystals with a short time by the seed-assisted method.…”