Vapor Phase Decomposition of Aromatic Hydrocarbons by Electric Discharge

Abstract

Vapor phase decomposition of aromatic and hydroaromatic hydrocarbons by electric discharge in hydrogen was inves tigated in electric discharge sustained in a narrow gap between two dielectric barriers. Alternating current, 10,000 hertz, was used as a power source. Hydrogen containing a certain concentration of the organic vapor was preheated and fed into the discharge zone. The reactor temperature was maintained at about 300°C. and the reactor pressure was varied from 70 to 760 mm. Hg. Condensable decompo sition products were analyzed by use of mass spectroscopy and vapor phase chromatography. "p\ecomposition of organic compounds in an electric discharge generally involves fragmentation and polymerization induced by inelastic collision with high energy electrons. When hydrogen is added, active hydrogen atoms produced by electric discharge also participate in the decomposition reactions. The reaction mechanisms are complex involving excited molecules, free radicals, and ions. In this laboratory hydrocracking of coal, coal volatiles, and related materials by electric discharge in hydrogen was studied. It is postulated by Given ( I ) that coal ( vitrinite ) molecules contain aromatic and hydroaromatic structures and probably fused aromatic ring nuclei linked together by methylene or ethylene groups forming hydroaromatic rings. Many of the replaceable hydrogens in the structure are substituted by hydroxyl or carbonyl groups. Short alkyl groups and alicyclic rings may also be attached as side chains. In pyrolysis at 500°-600°C., dissociation of hydroxyl groups and dehydrogenation of naphthenic rings take place. These acts lead to formation of OH and H radicals which in turn help to break the linkages between aromatic nuclei, forming smaller, partly 316 Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on August 24, 2015 |