Document Type

Thesis

Date of Award

5-31-1991

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Henry Shaw

Second Advisor

Robert J. Farrauto

Third Advisor

Ching-Rong Huang

Abstract

The catalytic oxidation of trichloroethylene(TCE) and dichloromethane (DCM) was investigated over a catalyst containing 4% PdO on Al2O3 washcoat and on a cordierite monolith with 400 channels per in2. Reactivity and selectivity of the catalyst for the destruction of 200 ppm C2HCl3 and 500 ppm CH2Cl2 in air was evaluated over the temperature range 250 to 550 °C. This research was conducted in a tubular reactor system at space velocities of 4,000 to 24,000 v/v/hr. It was found that complete oxidation occurs at 500°C for DCM and 550°C for TCE. In addition to the expected products of combustion from DCM, CH3Cl, CHCl3, and CCl4 were also found. CHCl3 was found at low temperatures and was destroyed above 500°C. The only chlorinated product produced in oxidation of TCE was C2Cl4 and was destroyed above 550°C. No significant CO formation was observed above 500°C for either compound. It was found that reaction temperature predicts conversion of the chlorocarbons and space velocity affects product distribution.

Varying the oxygen concentration over a factor of 4 showed no effect on rate, thus allowing representation of the destruction process as a first order rate law in TCE oxidation. The Arrhenius activation energy is 34 kcal/mole. The HCl selectivity in the presence of 1.5% water or 0.5% methane was also investigated. It was found that the water and methane enhance the HCl selectivity and inhibit the formation of Cl2. These two hydrogen sources also inhibited the formation of C2Cl4.

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