A Pre-mix Synthesis Strategy for Zeolite Y-based Alkylation Catalysts: Enhanced Acidity and Stability via Zeolite-Binder Interactions

Abstract With increasingly stringent environmental regulations on gasoline composition, the replacement of hazardous liquid acid catalysts (HF and H2SO4) with solid acid alternatives for isobutane-butene alkylation has become imperative. Zeolite Y-based catalysts offer promising eco-friendly alternatives; however, their commercial application remains limited by rapid deactivation caused by insufficient Brønsted acid site (BAS) density and unfavorable oligomerization side reactions. Herein, we report a mechanism-guided pre-mix synthesis strategy that eliminates one high-temperature calcination step and maximizes zeolite-binder interactions to substantially enhance catalyst acidity and stability. The designed NH4Y-Al2O3 catalyst exhibits a total BAS density that is 1.9 times higher and a strong BAS density that is 2.6 times higher than conventionally prepared HY-Al2O3. Comprehensive characterization by XRD, MAS NMR (3Q, 27Al, 29Si), NH3-TPD, and Py-IR reveals that the enhanced acidity originates from: (i) enhanced framework Al retention and local structural stability due to reduced thermal dealumination, evidenced by increased unit cell parameter from 2.448 nm to 2.459 nm; and (ii) migration of Al species from the Al2O3 binder to ion-exchange positions and framework sites, forming distorted tetrahedral Al species. The pre-mix method reduces zeolite agglomeration, increases interfacial contact area, and lowers energy consumption. In isobutane-butene alkylation, NH4Y-Al2O3 demonstrates exceptional catalytic performance: deactivation time is extended by 70% (48 h vs. 28 h), C8 selectivity increases by 7 percentage points, and alkylate yield reaches 94.35%, surpassing conventional H2SO4 (93.10%) and HF (91.50%) systems. The hydrogen transfer rate doubles that compared to conventional catalysts, effectively suppressing oligomerization and coke formation. These findings establish design principles for zeolite-based alkylation catalysts and demonstrate an energy-efficient synthesis route that reduces carbon emissions and offers potential for industrial scale-up.