Title

Part I. Destruction of environmental pollutants by microwave heating and discharge plasmas. Part II. Generation of hydrogen from water and methane using discharge plasmas

Date of Completion

January 2003

Keywords

Chemistry, Inorganic|Engineering, Environmental

Degree

Ph.D.

Abstract

Concerns about environmental pollution have caused new regulations to be implemented on a global level. Freons were shown as the principal cause of the depletion of the stratospheric ozone layer, and global action was set forth to reduce their emissions by the 1987 Montreal Protocol. Effective, environmental friendly decomposition of these pollutants is sought. In this work, the efficient destruction of two Freon species, Freon 21 and Freon 142B, using silent discharge plasmas was demonstrated. Gas chromatography was used to follow their decomposition in mixtures with oxygen, nitrogen, and water. Optical emission spectroscopy and mass spectrometry were employed to gain insight into the reaction mechanism. ^ Global warming caused by greenhouse gases such as carbon tetrafluoride is a further environmental challenge that mankind faces. The breakdown of this pollutant was achieved by gas discharges but mainly by microwave heating in this study. Activated carbon was used as a catalyst in the presence of water to decompose a mixture of nitrogen and carbon tetrafluoride. The effect of power on the conversion and catalyst deactivation were investigated. A possible reaction scheme was based on mass spectrometric results from decomposition studies. ^ Fuel cells are considered the future of transportation. In order for the fuel cells to become more competitive, the cost of hydrogen production has to become much lower than in processes used today such as steam reforming of methane. In this work, the hydrogen production from a mixture of water and nitrogen and a mixture of water and methane was examined using discharge plasmas. The influence of the reactor type and of other parameters such as input voltage and admixtures of nitrogen or argon was investigated. A reaction mechanism was proposed based on the mass spectrometric data. ^ In a related study, the metal effect of the inner electrode used in the decomposition of methane and the resulting evolution of hydrogen by discharge plasmas was investigated. The effect of the flow rate and the cleaning of the electrode were examined as further objectives of this study. A mechanism was developed using mass spectrometry and combined gas chromatography and mass spectrometry. ^