Novel Approach to Detoxification of Polychlorinated Solvents A Waste-to-Useful Fuel ConversionEPA Grant Number: R823179
Title: Novel Approach to Detoxification of Polychlorinated Solvents A Waste-to-Useful Fuel Conversion
Investigators: Timmons, Richard B.
Institution: The University of Texas at Arlington
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 1995 through September 1, 1998 (Extended to May 31, 2000)
Project Amount: $303,082
RFA: Exploratory Research - Engineering (1995) Recipients Lists
Research Category: Engineering and Environmental Chemistry , Land and Waste Management
Description:The purpose of this project is to evaluate the utility of a heterogeneous catalytic hydrodechlorination process as a viable disposal route for hazardous chlorinated waste liquids. In contrast with the numerous catalytic oxidation and combustion studies of chlorinated waste destruction, there have been few investigations of reductive processes as an alternate route to detoxification of these materials. Most importantly, the proposed hydrodechlorination process would lead to useful hydrocarbons and HCl as reaction products. This can be contrasted with typical oxidative processes which are known to produce a wide range of undesirable by-products including, in some cases, potential carcinogenic compounds (such as furans and dioxins). The chemical thermodynamics for these proposed hydrodechlorination processes are extremely favorable, including conversion of heavily polychlorinated molecules, as driven mainly by the large, negative free energy of formation of HCl.
The current project is predicated on preliminary data, from our laboratory, in which complete catalytic hydrodechlorination has been demonstrated with several of the most commonly used industrial chlorinated solvents. However, despite favorable thermodynamic considerations, undesirable chemical kinetic factors led to slow coking of the catalyst and, ultimately, to catalyst deactivation. Thus, a primary focus of the present project is to improve significantly catalyst activity and longevity for these hydrodechlorination processes. To achieve this goal, systematic evaluation of a wide range of potential catalyst materials will be conducted. In particular, the work centers on preparation and evaluation of selected bifunctional catalysts in which active hydrogenolysis metals (e.g., Ni, Pt, etc.) are supported on materials which are known to provide good resistance to coking (e.g., small pore shape selective zeolites). These catalyst evaluation studies are accompanied by detailed catalyst characterization, including in situ spectroscopic analysis of the hydrodechlorination reaction processes. In this way, the current detailed microscopic level exploratory research work will hopefully lead to the identification of a specific catalyst formulation which is sufficiently promising for future, much larger scale, conversion experiments.