Dynamic Acid Synergy in Y-Embedded Hβ Zeolite: Structural Tailoring and Acid Cooperativity for Enhanced Friedel-Crafts Acylation Towards 2-Ethylanthraquinone

Abstract

To address the bottleneck of insufficient catalytic activity at single acidic sites in traditional Friedel-Crafts acylation reactions, this study innovatively proposes a novel synergistic catalytic strategy combining Lewis and Brønsted acids. A Y-Hβ catalyst with dual-acid functionality and hierarchical pore structure was successfully constructed by precisely introducing yttrium ions (Y³⁺) into the Hβ zeolite framework through an equal-volume impregnation method. Structural characterization confirms that Y³⁺ is anchored in the framework as [YO₄] tetrahedra, establishing strong Lewis acid sites while maintaining the structural integrity of Hβ zeolite. Mechanistic studies reveal that Y³⁺ promotes C = O bond cleavage in anhydride molecules through adsorption polarization to generate C⁺ intermediates, while simultaneously enhancing the proton acidity of adjacent Brønsted acid sites via electronic induction effects. Under Lewis acid regulation, neighboring Si-OH-Al sites precisely donate protons to the α-position of anthraquinone, forming C₁₀H₇⁺ intermediates. The synergistic cooperation between dual acids reduces the acylation reaction energy barrier to 32.8 kcal/mol (a 24.1 kcal/mol reduction compared to Hβ zeolite), significantly accelerating reaction kinetics. Under optimized conditions (250 °C, 5 h), the reaction achieves 82.6% conversion and 80.6% selectivity, demonstrating 50.6% improvement in catalytic efficiency over Hβ zeolite. Regeneration tests verify that the Y-Hβ catalyst maintains over 90% initial activity after 5 cycles, attributed to the high stability of Y-O-Si bonds and exceptional anti-coking performance, highlighting its promising industrial application potential.

Graphical Abstract