New Adsorbents for Purification: Selective Removal of Aromatics

Adsorption of benzene and cyclohexane on ®arious Y-zeolites was in®estigated to de®elop sorbents for the purification of aliphatics by remo®al of aromatics. Ag-Y showed superior benzenercyclohexane selecti®ities to Na-Y, Pd-Y, and H-USY. Separation factors greater than 10 5 were obtained with Ag-Y at low concentrations of benzene. High selecti®ities were achie®ed by the strong interaction between benzene and Ag-Y, while the interaction with cyclohexane was not influenced by the cations. Molecular orbital calculation re®ealed that benzene formed a classic -complexation bond with Ag-Y: donation of electron charges from the p-orbitals of benzene to the ®acant s-orbital of the ( ) sil®er donation and, simultaneously, back donation of electron charges from d( ) orbitals of sil®er to -orbital of benzene d back donation . Grand canonical Monte Carlo simulations were also performed for adsorption isotherms. Potential parameters of benzene on Ag-Y, including -complexation, were de®eloped first. Simulation and experiments of GCMC agreed excellently for adsorption of benzene on Yzeolites.