New sorbents for purification and bulk separation by pi-complexation: Aromatic /aliphatic separation, diene /olefin separation, and desulfurization.

Abstract

Separation by pi-complexation is promising in industrial realization, because the interaction is stronger than Van der Waals interaction, leading to higher selectivities, yet weak enough to be reversible. In this dissertation, it was demonstrated that pi-complexation was applicable to three important bulk separation or purification: aromatics/aliphatic separation, diene/olefin separation, and desulfurization. The work presented here involves the preparation of sorbents, isotherm measurement, and simulation of adsorption states. Several characterization techniques such as XPS and EPR were used on the sorbents. The sorbents in this work are transition metal salts dispersed on high surface area substrates, or cation-exchanged zeolites. PdCl₂ or AgNO₃ dispersed on SiO₂ gel exhibited high equilibrium adsorption ratios of benzene over cyclohexane. Ag<super>+</super>-Y and Cu<super>+</super>-Y showed excellent purification capabilities for various purifications. Molecular orbital calculations revealed classical pi-complexation in most cases, and theoretical bonding energies were in good agreement with experimental results. Grand canonical Monte Carlo simulations are discussed for the adsorption of benzene. Poisoning resistance to H₂S and H₂ was evaluated for diene/olefin purification.