Atmospheric pressure dielectric barrier discharge for siloxane reformation

Atmospheric pressure dielectric barrier discharge (DBD) plasma operating in octamethylcyclotetrasiloxane (D4)-helium gas mixture was studied as a prospective method for the reformation of the organosilicon compounds in the carrier stream. It was found that with the application of DBD, a significant amount of D4 precipitates out of the carrier stream in the form of a white residue on the reactor walls. Structural characterization of this residue with x-ray photoelectron and nuclear magnetic resonance spectroscopy revealed that the deposits are primarily composed of a linear chained polymerized form of D4 referred to as polydimethylsiloxane. The dependency of the carrier gas flow rate on the removal rate of D4 from the helium carrier gas was investigated for five different flow conditions. Solvent absorption with gas chromatography and mass spectrometry were used to deduce the concentration of D4 in the effluent from the reactor and hence the siloxane reformation ratio. A maximum of  80% conversion of D4 in the helium stream was achieved.