Amine modified nano-sized hierarchical hollow system for highly effective and stable oxidative-adsorptive desulfurization

Abstract

Oxidative-adsorptive desulfurization (OADS) has become a frontier scientific topic. The main factors affecting the oxidation and adsorption performance are the polarity and size of porous catalysts. Herein, highly active and stable phosphotungstic acid immobilized on amino grafted nano-sized hierarchical hollow silica spheres (HPW-NH2-HHSS) was successfully prepared and completely characterized. The hierarchical hollow structure of HHSS support can be maintained after being functionalized with amine groups, and the active species of phosphotungstic acid H3PW12O40 (HPW) were well dispersed on the amine-modified HHSS and retained its Keggin structure of the heteropolyanions. The prepared catalyst was applied to simultaneous oxidation and adsorption of dibenzothiophene (DBT) from model fuel. The effects of contact time, the loading content of HPW, the dosage of catalyst, the [O]/[S] mole ratio, initial DBT concentration, and temperature on the removal efficiency of the OADS system were investigated. 20% HPW-NH2-HHSS demonstrated a high catalytic performance and its desulfurization efficiency could be reached to 99.36% in 30 min at a lower O/S rate (2.5). Meanwhile, the equilibrium adsorption capacity of dibenzothiophene sulfone (DBTO2) of this catalyst is about 374 mg g−1. Beside this there was no significant decline in catalyst performance after seven catalytic cycles, assigned to the chemical force between the positive charges of NH2 and the negative charges of HPW. It is the first time that this work involving the nano-sized hierarchical hollow system has been used for high-efficiency desulfurization and the theory has been advanced that the polar groups of catalysts replace polar solvents to adsorb S-oxidation products.