Rapid synthesis of nano-sized Beta zeolite via guar gum assistance: Tailoring particle morphology for improved diffusion in lactide production

Beta zeolite serves as a crucial catalyst for the direct one-step synthesis of lactide from lactic acid, yet its application encounters persistent challenges including prolonged synthesis duration and excessive crystal ripening, which substantially compromise the efficient and high-quality production of zeolites at industrial scale. To address this, we developed a rapid hydrothermal synthesis route at 180 °C, employing an inexpensive bio-derived polysaccharide, guar gum, as a crystal growth modulator. By systematically optimizing key parameters (guar gum/SiO 2 ratio, aging temperature/duration, crystallization time), we successfully tailored the zeolite's texture. The introduction of guar gum effectively suppressed Ostwald ripening, yielding Beta zeolite with significantly reduced primary crystal size (<100 nm) and developed intercrystalline porosity within a remarkably short period of 8 hours. Compared to a rapidly synthesized counterpart without guar gum, the optimized catalyst exhibited a substantially higher specific surface area (586 vs. 384 m 2 g –1 ) and a mesopore population centered at 20–60 nm. In the conversion of lactic acid to lactide, this nano-structured catalyst delivered a markedly higher lactide yield of 79.2%, a 51% improvement over the control sample (52.5%). Gel permeation chromatography and thermogravimetric analysis confirmed that the tailored particle architecture shortened diffusion paths, effectively mitigating oligomer overpolymerization and coking. This work provides a facile and scalable strategy for controlling zeolite crystal growth at the nanoscale, demonstrating the significant impact of particle morphology engineering on catalytic process efficiency.