Preparation of Beta zeolites with tunable porosity and acidity through piperidine-assisted desilication for facilitating melamine synthesis

The synthesis of melamine from urea represents a pivotal industrial process, which is extensively applied fine chemicals production across various industries. However, the melamine synthesis is severely hindered by conventional catalysts with poor porosity, leading to low catalytic efficiency under harsh conditions and rapid deactivation due to mass transfer limitations. Herein, a series of novel mesoporous Beta zeolite catalysts with tunable porosity and acidity were designed and fabricated for melamine synthesis through a piperidine assisted-desilication strategy. The introduction of piperidine effectively mitigated framework desilication of zeolite crystals under OH – attack, while enabling precise tuning of mesoporosity (increasing S ext from 25 to 126 cm 2 g −1 and V mes from 0.151 to 0.433 cm 3 g −1 ) and acidity (enhancing total acid sites from 0.52 to 1.14 mmol g −1 ) by modulating piperidine addition during desilication process. Among the prepared Beta zeolites, mesoporous B-7P sample (piperidine/SiO 2 molar ratio of 0.07) exhibited exceptional catalytic performance, achieving 72.3% melamine yield under mild condition (400 °C, 0.4 MPa), which represented a 67% and 15% enhancement over commercial Beta zeolite and industrial catalyst, respectively. This excellent performance could be attributed to the synergistic combination of increased active sites and well-developed mesopores that facilitating intra-crystal molecular diffusion and improved the accessibility of active centers in pores. Besides, B-7P zeolite also showed excellent recyclability (>98.5% of initial activity) over five consecutive cycles, and exhibited superior coke resistance due to its optimized pore architecture, demonstrating exceptional potential as an advanced catalyst for melamine production.