One-Pot Ethanol-Mediated Synthesis of Surface Si-Zoned ZSM-5 Zeolites

Abstract

Passivation of external surface acid sites in zeolites is a widely used strategy to enhance catalytic stability and to mitigate undesired non-shape-selective reactions. However, synthesizing zeolites with a uniform and thickness-controllable Si-zoned shell in a true one-pot manner remains highly challenging. Here, we develop an ethanol-mediated one-pot route to synthesize surface Si-zoned ZSM-5 zeolites. Ethanol establishes a favorable synthesis environment that promotes a classical, layer-by-layer crystallization pathway and enables the near-quantitative utilization of aluminosilicate species during the initial crystallization stage. This complete consumption of framework-forming species allows soluble silicate species to be subsequently added directly into the mother liquor, where they are selectively incorporated onto the preformed ZSM-5 crystals to build a thickness-tunable silica-rich shell. Notably, bulk and surface analyses together with bulky-probe reactions confirm that the silica-rich shell is structurally continuous and catalytically inert. This ethanol-assisted strategy offers a facile, high-yield, and scalable one-pot platform for engineering surface compositions in zeolites. The resulting surface Si-zoned ZSM-5 offers a versatile basis for the design of catalysts with improved stability and shape-selectivity.