Nanosized “rice ball” like hierarchical beta zeolites with inter-crystalline mesopores for efficient catalytic synthesis of lactide

A series of nanosized “rice ball” like hierarchical beta zeolite aggregates (RBZxAy, x = 6, 9, 12 or 15; y = 2, 4 or 6) with hierarchical structures are successfully synthesized via gel aging and hydrothermal method without mesoporous template. The as-prepared RBZxAy zeolites possess two ranges of inter-crystalline mesoporous that formed by zeolite nanoparticles aggregation compared to the non-aged samples (B12Z4). The effects of Si/Al ratio and crystallization time on the morphology, structure and surface acidic properties of RBZxAy were systematically investigated. Meanwhile, RBZxAy as catalysts were applied in the conversion of lactic acid (LA) to lactide (LT) to investigate their catalytic performance. Benefitting from smaller crystal size, hierarchical structures and higher acid content, the representative catalyst (RBZ12A4) exhibited outstanding catalytic activity that the LA conversion was high to 98 % and the LT yield up to 94 %. In addition, RBZ12A4 presented perfect regeneration ability after 10 times recycles. This work provides an effective and facile route to directly synthesis nanocrystals aluminosilicate zeolite with hierarchal structure, and constructs an approach for efficiently converting LA to LT, it has greatly significance for the development of polylactic acid industry. Nanosized “rice ball” like hierarchical beta zeolite aggregates (RBZxAy) were synthesized via gel aging without mesoporous template. The obtained RBZ12A4 exhibited outstanding catalytic performance in the one-step synthesis of LT from LA, with the LA conversion highly to 98 %, and the LT yield up to 94 %. It provides a facile route and a cost-effective way to synthesis of nanocrystals aluminosilicate zeolite with hierarchal structure, and has greatly significance for the development of polylactic acid industry. [Display omitted] •Beta Zeolite (RBZxAy) with hierarchical structure is synthesized via gel aging.•Synthesis of RBZxAy without mesoporous template.•Aging gel could greatly reduce the nanoparticle size of RBZxAy.•Catalytic mechanism of efficient conversion of LA to LT was explored.