Tailoring of Pt particle density on the surface of dealuminated ZSM-5 and its hexane cracking performance

By acid-treating ZSM-5 zeolite to regulate its silica-to-alumina ratio (SAR) and surface acid sites, combined with loading platinum (Pt) at varying mass percentages via the Metal-Organic Solid-Phase Synthesis method, this study investigated the effect of metal-acid site ratios on the catalytic cracking of n-hexane to propane. Results demonstrated that acid treatment significantly increased the SAR of the zeolite (from 27 to 100), optimized the distribution of surface acidsites, while preserving the MFI topology. Post-Pt loading, the catalyst exhibited highly dispersed Pt nanoparticles (3.3–4.1 nm) without forming crystalline aggregates. Catalytic performance tests revealed that acid treatment enhanced the n-hexane conversion rate from 66% to 88% and propane selectivity from 50% to 57%. Pt loading exhibited a pronounced influence on performance: the medium-loaded catalyst (0.3wt%) achieved the highest propane selectivity (57%) and stability due to optimal metal-acid synergy. XPS and CO-DRIFTS analyses indicated that Pt loading reduced the electron density of oxygen species, thereby strengthening metal-acid interactions. This work provides a catalyst design strategy for the efficient and directional conversion of n-hexane.