Accelerated synthesis of titanium-Beta zeolites using N-methyl-2-pyrrolidone and Beta seeds

Abstract

The accelerated synthesis of titanium-Beta (Ti-Beta) zeolites is essential for improving their scalability and catalytic applicability. Here, we report a rapid hydrothermal route for the synthesis of Ti-Beta by combining N-methyl-2-pyrrolidone (NMP) as a crystallization accelerator with seed-assisted growth. It is proposed that NMP can accelerate the crystallisation by increasing the TEA⁺ concentration during the synthesis by preventing the Hofmann degradation of TEAOH at high temperatures. Using this optimized strategy, highly crystalline Ti-Beta is obtained in just 20 hours, approximately 20 times faster than conventional syntheses under otherwise identical conditions. Spectroscopic analyses confirm that the synergy of NMP and seeds enhances nucleation and crystallization kinetics while maintaining high incorporation of framework Ti species. UV-vis spectra showing the characteristic 210–220 nm charge-transfer band of tetrahedral Ti(IV) and additional features upon H₂O₂ interaction support the formation of catalytically relevant Ti-peroxo species. Raman spectroscopy rules out the presence of extra-framework TiO₂, SEM imaging reveals reduced crystal size in seeded samples, and N₂ physisorption confirms preservation of microporosity. Acid site accessibility, assessed by in situ IR spectroscopy using acetonitrile as a probe, provided direct evidence of the Lewis acidic behaviour of framework Ti sites. Overall, this work demonstrates how the combined use of organic accelerators and seeding synergistically tailors the crystallization pathway, enabling rapid production of high-quality Ti-Beta zeolites.