One-Pot Synthesis of Amorphous Aluminosilicates with Tunable Aluminum Coordination for Enhanced Cracking Performance

Abstract

Amorphous aluminosilicates represent a class of important solid acid catalysts. Herein, a series of amorphous aluminosilicate catalysts with tunable Si/Al molar ratios were synthesized via a facile hydrothermal method. Silicon incorporation was found to modulate transformation of alumina into sheet-like assemblies while suppressing their crystallinity, promote formation of an amorphous Al-O-Si network, and enhance mesoporosity, resulting in increased surface area (up to 305.6 m2/g) and pore volume (up to 0.78 cm3/g). Silicon introduction induced the transformation of octahedral Al (AlVI) to tetrahedral (AlIV) and pentahedral (AlV) species, thereby increasing the abundance of surface hydroxyl groups, particularly bridging Si–(OH)–Al species, which significantly enhanced the Brønsted acid site (BAS) density from 8.12 to 26.41 µmol/g. This enhancement in BAS led to superior cumene cracking performance, with the Si/Al = 0.37 (Si-4) sample achieving 27% conversion. These findings underscore the critical role of silicon in tuning aluminum coordination and acidity, providing a rational design strategy for efficient solid acid catalysts.