Study On Methane Converted To C₂ Hydrocarbons By Radio Frequency Plasma In The Presence Of Carbon Dioxide

C2 hydrocarbons are important raw material for organic chemical industry. And using natural gas to produce C2 hydrocarbons is their main source. With the continuous decrease of petroleum resources, more and more attention has been focused on the exploitation of natural gas that is high effectiveness, cleanness and abundant worldwide. To convert natural gas into C2 hydrocarbons and study the conversion rule was the main aim in this article.The experiments were at room temperature and atmospheric pressure by low temperature plasma--- Radio Frequency Plasma. Natural gas containing 99.99% methane was converted at the T-type reactor and the cannula-type reactor in the presence of CO2. And the main products were C2H2, C2H4, C2H6, H2 and C and a little of liquid. The article studied the effects of discharge voltage, total flow, discharge area and reactor structure on methane conversion and the yield and selectivity of goal products. Compared with reactions of pure methane by RF plasma, the effect of CO2 on methane reaction was also studied in the article. The results showed: with the increase of discharge voltage, conversion ratio of methane also increased but the selectivity of C2 decreased. The effect of total flow was changed with different reactors and whether CO2 existed, too much or too little was both bad for reactions. To a certain extent, the increase of discharge area was good for methane conversion. And the effects on selectivity of C2 were different from reactors. In the T-type reactor, the selectivity increased with the increase of discharge area, and at the condition that voltage was 800 V, total flow was 500:50, and four electrodes, the total selectivity value was up to 45.583%. And in the cannula-type reactor, the total selectivity was biggest at the condition of three electrodes, which was 29.6%. From the distributing of C2 hydrocarbons, the T-type reactor was good for the formation of C2H4, and its selectivity is up to 33.6%, at the condition that voltage was 800V, flow was 400:40, and four electrodes. At this condition, the total selectivity value was 43.9% while C2H6 was 7.0% and C2H2 was 3.3%. The cannula-type reactor was good for the formation of C2H6, and its selectivity value is up to 27.6%, at the condition that voltage was 1200V, flow was 300:30, and four electrodes. At this condition, the total selectivity value was 50.7% while C2H4 was 11.9% and C2H2 was 11.2%.According to experimental data and relevant literature, the macro-kinetics model of CH4 by RF plasma has been studied. And the kinetic parameters have been calculated by FORTRAN. The macro-kinetics equation has been obtained:This was fit for the condition that vacuum degree was between 0.090~0.095MPa, the temperature was about 293.15K, and the voltage was not more than 900V.By analyzing reaction mechanism of the methane conversion by RF plasma, the main fragments of methane in low-pressure RF capacitive discharge were CH3?, CH2?, CH?, C? and H?, which were further formed the goal products C2H6, C2H4 and C2H2.