Removal of siloxanes from landfill gases with the application of dielectric barrier discharge plasma

M.M. Tahiyat, S. Hoque, T.I. Farouk
University of South Carolina,
United States

Keywords: siloxane, DBD, plasma, PDMS

Summary:

Usage of Landfill gas as renewable energy has garnered immense interest in recent times due to its enrichment in methane. But this gas also contains organosilicate compounds: volatile methyl siloxanes (VMS) as a contaminant. When silicates undergo oxidation in internal combustion engines, these form silicate deposits that erode both engines and when released into the environment causes pollution. Current techniques of VMS removal incorporate adsorption beds like activated carbon filters, silica gel, alumina and others. All of these techniques, however, suffer from limited regeneration capability, low adsorption capacity, and and the need to recycling. Temperature also plays a crucial factor in affecting adsorption and thus a high overhead cost is also associated in some of these cases. In this study, a typically dominant VMS, D4 (C8H24O4Si4), was removed from a helium carrier gas by application of dielectric barrier discharge (DBD) plasma. D4 siloxane was bubbled into a helium carrier gas stream and passed through an annulus DBD reactor. GCMS analysis of the treated gas stream showed traces of CO and CH4 implying dissociation of Si-C bonds. A white solid residue was also found to deposit on reactor walls. X-ray photoelectron spectroscopy and two-dimensional NMR spectroscopy confirmed the residue to be polydimethylsiloxane, suggesting that both bond dissociation and recombination are instigated by the DBD plasma. Further study is underway to shed light on how a combination of different siloxanes can be treated with the proposed method.