Mechanochemistry-Induced Surface Acidity Modulation to Boost Selective Hydrogenative Ring Opening of Anthracene

Abstract The poor combustion performance of polycyclic aromatic hydrocarbons (PAHs) in heavy oil produced by direct coal liquefaction hinders the efficient utilization of coal-derived fuels. The hydrogenation and ring opening of PAHs into alkylnaphthalenes, which are promising components for high-density aviation fuels, are important approaches. In this study, a mechanochemical strategy to regulate HY zeolite was proposed, enabling surface modification to tune the exposed acidity and strength preserving the FAU framework structure and original pore size. The surface of HY noticeably changed from a smooth to angular morphology after ball milling with different agents. Pyridine-adsorbed Fourier transform infrared (Py-IR) spectra revealed a significant decrease in acid sites after direct ball milling without any agent. After carbon nanotubes (CNTs) were introduced during ball milling (Y-CBM-1.5), the number of acid sites (in Py-IR) increased substantially, resulting in a higher Brønsted/Lewis (B/L) acidity ratio in weak acidity and a lower B/L ratio in strong acidity. Pt-Y-CBM-1.5 resulted in almost 100% conversion of anthracene with the highest selectivity for hydrogenated ring-opening products (61%) in the liquid products, benefiting from the increase of the B/L ratio in weak acidity that facilitated ring opening and decreased B/L in strong acidity that prevented overcracking and alkylation. This work reports a simple but effective strategy for modulating the acidity of zeolites without changing their pore structure, which significantly promotes the selective cracking of large alkane molecules in chemical industry production.