Decomposition Of Methane And Formation Of C₂ Hydrocarbons In DC Discharge Plasma

The crisis of oil has urged people to quicken the study on the effective utilization of natural gas. The synthesis of C₂ hydrocarbons through methane has become a hot item. It is one of the most important research task in China that natural gas is changed into oil products or other chemical products in plasma conditions.Depending on the lab conditions, decomposition of methane and formation of C₂ hydrocarbons are detected by photoelectrical techniques instead of normally chemical methods. Decomposition of methane is indicated with spectrum, wavelength of which is about 2.3μm; in the same way, the wavelength of formation of C₂ hydrocarbons is approximately 3.2μm. We also investigate into products of methane decomposition: H (654.3nm) and CH (431.25nm) free radicals in plasma space. It is convenient to record reaction process online by detecting the variation of spectrum intensity. These photoelectrical methods are superior to normally chemical ways due to their ability of recording fast process within milliseconds.The rules of methane plasma converted to C₂ hydrocarbons under the DC discharge conditions are researched. The experiments show: the pressure of methane and electric current density are related to decomposition of methane and formation of C₂ hydrocarbons; decomposition of methane can be divided into three periods: the period of violent decomposition, the period of transition and the period of quasi-equilibrium; methane can be decomposed very fast and mainly decomposition is completed in one minute by compared that C₂ hydrocarbons are composed slowly and the formation approach equilibrium in three minutes. High electrical field intensity is useful for methane decomposition but improper to C₂ hydrocarbons formation. According to this rule, the reaction time required and conditions of methane decomposition and C₂ hydrocarbons synthesis should be separated andoptimized respectively in order to obtain the high yield of C2 hydrocarbons.