Study On Unconventional Direct Catalytic Oxidation Of Methane In Ionic Liquid

The using of CH4activation involved both the two aspects of the energy sources and theenvironment, which is very hot in the fields of chemical and catalysis. With the lacking of thepetroleum, the using of the natural gas is payed more and more attention. As the mainconstituent of the natural gas, the methane has a great valuable in application. The almostproducts invovles CH4are produced by converting CH4to synthetic gas in natural gaschemistry, half of the cost is expending in the production of the synthetic gas. People aresearching for the method which can directly convert CH4to the chemical products for manyyears, so far, there is no solution. There are two difficult points in this work. Firstly, as themost simple saturated hydrocarbon, the structure of the methane is especial stable （tetrahedron）comparing with other hydrocarbons. The energy of the C-H bonds in methane is439kJ/mol.Secondly, the difficult is that the products are easier to react than methane, so the selectivitycan not be ensured. Therefore, it is necessary to develope new chemical process for directconversion of methane.The Ionic liquids （ILs） are molten salt which compose with ion in room temperature.There are many good advantages such as low vapor pressure, non-volatile, non-flammable,good solubility, good phase stability, good thermal stability, good water stability of the roomtemperature ionic liquids.The ILs can instead of the traditional organic solvents. There is awide range of application such as the organic field, the synthesize of the enzymes and theanalysis field with the ILs. The ILs can be designed with a large number of species as a goodgreen solvents. Some ILs have the catalytic activity. In this paper, we studyed the conversionrate of the methane respectively with different ionic liquids in the reaction from the point ofcatalysis.a series of acidic ionic liquids were synthesized at first and then were analyzed by FT-IR.Secondly, the conversion rate of the CH4directly activation in the catalysis sistem with ILsand PdCl₂both exist and with ils only were analyzed. The reaction products were analyzed byGC、GC-MS、1HNMR and FT-IR. The experiments confirmed that:（1） The system with PdCl₂as catalysts,[mim]⁺HSO₄^-, the trifluoroacetic acid（TFA） and trifluoroacetic anhydride（TFAA） as intermedias, potassium peroxodisulfate （K₂S₂O₈） as theoxidant was investigated. In this system,[mim]⁺HSO₄^-can enhance the catalysis capability ofPdCl₂, which can convert methane to methanol direatly. The conversion rate is28%. The ILsis propitious to the reaction and the ILs is good intermedias of the reaction sistem above.（2） The system with [mim]⁺HSO₄^-as catalysts, the trifluoroacetic acid（TFA） andtrifluoroacetic anhydride（TFAA） as intermedias, potassium peroxodisulfate （K₂S₂O₈） as theoxidant was investigated. In this system,[mim]⁺HSO₄^-can activate CH4, the condition of thecatalysis system is mild, the catalyst is easy to synthesize, the cost of the methane conversionis low comparing with other catalysis system. The conversion rate is21%.（3）[mim]⁺HSO₄^-and [Bmim]⁺Cl^-are both stable in the unconventional direct catalyticoxidation system.