Study On The Conversion Of Dimethyl Ether Through Non-equilibrium Plasma

Dimethyl ether (DME) is a kind of significant and clean fuel, a chemical intermediate as well as hydrogenous compound for fuel cell, which is independent of petroleum resource. In chemical industry, DME has been manufactured on a large scale via methanol dehydration and syngas conversion.Owning to the property of non-equilibrium, a mass of reactions could be realized directly and efficiently under non-equilibrium plasma, while they can not take place under conventional methods or technologies. It was investigated that liquid products were synthesized from DME with rotary corona discharge (RCD) plasma and dielectric-barrier discharge (DBD) plasma. Then the results of the two kinds of discharge methods were compared.Under RCD plasma, the primary products of DME conversion were H2, CO, CH4, carbon black and a few of olefins. DME flux hardly affected the conversion of DME within 50 seconds of DME retention time, and the highest value was up to 92.95%.Under DBD plasma, the products of DME conversion contained both gaseous products (H2, CO, CH4, etc) and liquid products (HCHO, CH3OH, CH3OCH2CH2OCH3, etc). Moreover, the content of CH3OCH2CH2OCH3 reached as high as 26.92%.After optimizing the parameters of DBD reactors and plasma generator, the optimum conditions were obtained as following: No.3 reaction tube(i.d.7.7mm, o.d.12.0mm, reaction length 180.0mm) as dielectric barrier, copper club of 6.0mm(o.d.) as inner electrode, aluminum foil as outer electrode, input power 50W, discharge frequency 19.0kHz, DME flux 21.0ml/min.The effects of additive gases on conversing DME into liquid products were studied with DBD plasma. The conversion of DME increased and the liquid product yield changed a little when He, Ar or H2 was introduced into the DME reactive gas. Meanwhile, the total content of low molecule products also increased. Both of DME conversions increased a little and liquid product yields decreased when CH4 and C2H6 were added into raw material, respectively. The content of hydrocarbons containing the species of CH3·/CH3O·or C2H6·/C2H6O·increased. Both of DME conversions increased obviously after air and O2 were added into raw gas, respectively. After adding air, liquid product yield changed in a small range, however, adding oxygen into DME, liquid product yield increased evidently and the highest value reached 34.43%. Moreover, the content of oxygen of the liquid product also increased.