Controllable interlayer hydroxyl condensation of MWW zeolite and its alkylation performance of benzene with ethylene

Abstract

MWW zeolite holds great promise in the petrochemical industry. However, achieving precise control over its dimension and interlayer hydroxyl condensation remains challenging when using a single, low-toxicity, readily available template. In this study, the rational and targeted hydrothermal synthesis of two-dimensional (2D) MCM-22(P) and three-dimensional (3D) MCM-49 using low-toxic piperidine is realized. The synergistic effect of the organic template and inorganic ions plays a crucial role in the precise synthesis of 2D and 3D MWW zeolite. In contrast to the traditional hexamethyleneimine template, piperidine introduces a distinct characteristic whereby disordered MWW layers coexist with the synthesized products. Specifically, the higher concentration of Na+ species directs more Al species to locate in the T1 site, promoting the condensation of interlayer hydroxyl and leading to the formation of 3D MWW zeolite. In contrast, a system with abundant PI can suppress the condensation of interlayer hydroxyl, resulting in the formation of 2D MWW zeolite. H-MCM-49 synthesized exhibits higher ethylene conversion and ethylbenzene selectivity than H-MCM-22 in the liquid alkylation of benzene and ethylene.