Evaluation of Rate Parameters during Heterogeneous Catalysisin Supercritical Fluids

流体在其临界点附近的独特性质可以用来改变反应系统中的主要反应途径。超临界流体（SCF）的特殊溶剂性质可以促进在传统溶剂中无法实现的反应。这是因为超临界溶剂提供了一个环境，在这个环境中，由于溶剂的物理性质，它位于气体和液体之间，从而消除了传质限制。因此，相对于气体的高溶剂密度与相对于液体的高溶质扩散率相结合，创造了一个环境，高浓度的溶质可以溶解在溶液中，但没有严重的传质限制。本研究项目的目的是研究SCF溶剂对控制催化反应总速率的速率过程的影响。具体来说，PI将尝试测量超临界条件下催化剂的吸附速率、颗粒内扩散速率和吸附能力。他将使用色谱技术在各种实验条件下测量所需的速率参数，并通过测量转化率和产物选择性来考虑SCF对反应途径的总体影响。该技术的一个应用是通过SCF从多孔土壤中提取有机物和氧化再生溶剂相结合的危险废物修复领域。代替这种系统的潜在用途，这项工作将涉及五氧化二钒（V2O5）催化氧化1,4-二氯苯（许多有害物质的模型化合物）在超临界水和超临界氧化亚氮（N2O）中。

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).