Direct synthesis of hollow single-crystalline zeolite beta using a small organic lactam as a recyclable hollow-directing agent

Abstract

Hollow zeolites are widely investigated as catalysts and nanoreactors in the petrochemical and fine chemical industries because they offer fast mass transfer along with a hollow core for encapsulation of functional components. However, the synthesis of hollow zeolites still remains a significant challenge due to the complexity and restrictions of currently available synthetic strategies. Herein, a direct and efficient approach for constructing hollow zeolite beta with simultaneously a low Si/Al ratio (∼19) and high yield (above 89 wt%), based on some cost-effective and recyclable pentacyclic lactams, is reported. Meanwhile, a unique formation mechanism involving the selective decomposition of the tetraethylammonium (TEA⁺) cations locating at internal Al sites, and dissolution and recrystallization of the internal activated aluminosilicate species from the core to outer surface is proposed for the first time. In addition, the hollow beta catalyst exhibits better catalytic performance in the alkylation of benzene with isobutylene compared with the conventional solid beta sample.