Directed growth of robust zeolite coatings on silicon carbide supports via microwave selective heating and silica sol pretreatment

Abstract

Structured catalysts hold considerable promise for catalytic distillation due to their enhanced mass transfer, robust mechanical/thermal stability, and facile recyclability. However, conventional synthesis methods suffer from uncontrolled bulk nucleation in the liquid phase, leading to low loading efficiency and limiting practical use. Herein, this study developed a microwave-assisted hydrothermal method for the in situ growth of NaA zeolite coatings on silicon carbide (SiC) foams. The strong microwave absorption of SiC induces localized overheating, which promotes directed crystal growth on the SiC surface while minimizing solution-phase crystallization. A silica sol pretreatment method was employed to address support dissolution and facilitate the rapid construction of a dense zeolite layer, achieving a mass variation of 1.11 after only 5 cycles, which was not attainable with other pretreatment methods under identical conditions. The resulting coating exhibited excellent adhesion, with a minimal mass loss of 0.62% under rigorous ultrasonic and solvent-flushing tests. In aldehyde-ketone condensation reactions, the structured catalyst maintained a high yield (> 90%) over three cycles. The reusability of the NaA@SiC structured catalysts, combined with uniform crystalline coatings, offers a promising approach to decrease raw materials consumption in future manufacture and applications of structured catalysts.

Graphical abstract

Keywords

microwave heating / silicon carbide foam / structured catalyst / aldol condensation

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