The unique properties of a fluid near its critical point can be utilized to alter principle reaction pathways within a reacting system. The unusual solvent properties of a supercritical fluid (SCF) can facilitate reactions which cannot be achieved in traditional solvents. This happens because the supercritical solvent provides an environment where mass transfer limitations are eliminated due to the solvent's physical properties, which lie intermediate between a gas and a liquid. Thus, the high solvent density relative to a gas combined with high solute diffusivity relative to diffusivity in a liquid, create an environment where high concentrations of solute can dissolve in the solution and yet severe mass transfer limitations are absent. The goal of this research project are to investigate the effect of SCF solvents on the rate processes which control the overall rate of a catalytic reaction. Specifically, the PI will attempt to measure the rate of adsorption, the rate intraparticle diffusion, and the adsorptive capacity of the catalyst under supercritical conditions. He will use chromatographic techniques to measure the desired rate parameters under a variety of experimental conditions and consider the overall effect of the SCF on the reaction pathways by measuring conversion and product selectivity. An application of this technology is in the area of hazardous waste remediation through combined SCF extraction of organics from the porous soil and solvent regeneration by oxidation. In lieu of this potential use of such systems, this work will involve the vanadium pentoxide (V2O5) catalyzed oxidation of 1,4-dichlorobenzene (a model compound for many hazardous materials) in both supercritical water and supercritical nitrous oxide (N2O).
