Diffusion of benzene through water film confined in silica mesopores: Effect of competitive adsorption of solvent

Abstract

To understand the partial hydrogenation of benzene on Ru particles coated with hydrophilic materials, the diffusion of benzene through the water film confined in silica mesopores was studied by molecular dynamics simulation. There is an unconventional hydrogen bond between benzene and the surface hydroxyl group, which was previously supposed to retard benzene diffusion in hydrophilic mesopores. Driven by stronger hydrogen bonding, solvent water, however, is preferentially adsorbed onto the hydroxylated silica surface. Benzene dissolved in the water film has to diffuse away from the interfacial region, thereby weakening its interaction with the surface. Benzene may diffuse faster in hydroxylated mesopores than in bare mesopores, and the difference depends on the pore diameter. With a pore diameter of 4 to 6 nm, the diffusion coefficient of benzene along the pore axis, varying from 0.04 × 10−8 to 0.12 × 10−8 m2/s, could be adjusted by surface hydroxylation.