Natural gas is not only playing an increasing important role in energy and chemicals supplies in 21st century but is also the second most important component of the greenhouse gases. Clean and direct conversion of methane to C 2 hydrocarbons (ethane, ethene and acetylene) through AC and DC plasma catalysis enhanced by electric field was studied at low temperature ranging from 50?℃ to 100?℃, atmospheric pressure and low power conditions. The influence of form of the electrode, distance between the electrodes, voltage, diameter of reactor, flow of inlet methane, N 2/CH 4(mole) and 20 catalysts were tested under low temperature plasma. The results indicated that best form of the electrode was plate; the better distance between the electrode was 5mm; the appropriate voltage was 38V(AC);the apparent diameter of reactor was 17mm, the likely flow range flux of inlet methane was 60—80?ml·min -1 , the suitable ratio of N 2/CH 4 (mole) was 0.5—1.0.The yield of C 2 hydrocarbons was the highest on V 2O 5,ZnO(5%)/ZSM-5-38 catalyst, the yield of ethene was the highest on La 0.8 Sr 0.2 CrO 3,ZnO catalyst. The results are better than those obtained through conventional reaction of oxidation coupling of methane.
The experiments are carried out in the system of continuous flow reactors with dielectric-barrier discharge (DBD) for studies on the conversion of natural gas to C2 hydrocarbons through plasma catalysis under the atmosphere pressure and room temperature. The influence of discharge frequency, structure of electrode, discharge voltage, number of electrode, ratio of H2/CH4, flow rate and catalyst on conversion of methane and selectivity of C2 hydrocarbons are investigated. At the same time, the reaction process is investigated. Higher conversion of methane and selectivity of C2 hydrocarbons are achieved and deposited carbons are eliminated by proper choice of parameters. The appropriate operation parameters in dielectric-barrier discharge plasma field are that the supply voltage is 20-40 kV (8.4-40 W), the frequency of power supply is 20 kHz, the structure of (b) electrode is suitable, and the flow of methane is 20-60 ml · min-1. The conversion of methane can reach 45%, the selectivity of C2 hydrocarbons
The characteristic parameters were measured with floating double probe method when cold plasma was interacting with catalysts, such as MoO3/Al2O3, NiY, Pd/Al2O3, which were used in the conversion of natural gas to C2 hydrocarbons through electrical field enhanced plasma catalysis. These parameters were compared in different input voltage, different atmosphere, before and after reaction in plasma field. The interaction between catalysts and cold plasma was also investigated. This confirm that cold plasma can enhanced catalysis effect.
Bao Wei WANG1,2, Gen Hui XU1* 1,2State Key Laboratory of C1 Chemical Technology, Tianjin University, Tianjin 300072 2School of Material Science and Engineering, Tianjin University, Tianjin 300072
