正压、低温脉冲微波等离子体裂解天然气直接转化制C2烃的研究

Study on the Direct Conversion of Natural Gas to C2 Hydrocarbons at Atmospheric or Higher Pressure via Low- temperature Pulsed Microwave Plasma

利用脉冲微波强化、扩展丝光等离子体反应装置,在常压和正压条件下,对低温脉冲微波等离子体裂解甲烷和氢气混合气制C2烃的反应进行了研究.考察了压力、微波功率、脉冲通/断时间以及氢气/甲烷比例、流量等参数对反应的影响.结果表明,在脉冲微波的作用下,常规高压放电形成的在空间呈非连续分布的丝状等离子体被强化和扩展成为连续分布的伞状等离子体,等离子体利用率和活性均得以大幅度提高;利用这种低温等离子体可以获得高的甲烷转化率,而且产物纯净,只有乙烯和乙炔;通过改变压力,还可以调节产物中C2H2/C2H4的物质的量比值.当气体总流量为300 mL/min、物质的量比n(H2)/n(CH4)=2:1、压力为O.13 MPa、微波峰值功率为120 W、脉冲通/断比=400/400 ns时,甲烷转化率可达59.2%,C2烃单程收率可达52%,其中乙炔单程收率达42.7%.

A conventional high voltage wire-like plasma can be greatly enhanced and spread by pulsed microwave to form an umbrella-like plasma continuously distributed in reactor. By use of this plasma, methane is directly converted to C-2 hydrocarbons at high yield under the condition of atmospheric or higher pressure. The effect of pressure, microwave power, pulse duration, molar ratio of H-2/CH4 and flow rate on the methane conversion was investigated. Higher conversion of methane is achieved by proper choice of parameters, and the products only comprise ethylene and acetylene; The molar ratio of C2H2/C2H4 could be adjusted through changing the pressure. With total flow rate of 300 mL/min, H-2/CH4 molar ratio of 2, pressure of 0.13 MPa, peak microwave power of 120 W, pulse duty factor of 400/400 ms, conversion of methane and yield of C-2 could reached up to 59.2% and 52% respectively.