Pd-containing ionic liquid(IL) 1-hexyl-3-methylimidazolium tetrafluoroborate(C_6MIMBF_4) immobilized on 7-Al_2O_3(Pd-IL/γ-Al_2O_3) was prepared and characterized by Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM) and Brunauer-Emmett-Teller (BET) analysis.The influences of C_6MIMBF_4 loading and Pd on methane conversion to C_2 hydrocarbons under cold plasma were investigated.FTIR and SEM analyses indicated that C_6MIMBF_4 had been successfully immobilized on 7-Al_2O_3 and the C_6MIMBF_4 showed excellent stability under cold plasma.The results of BET and methane conversion showed that with the increase in immobilization amount of C_6MIMBF_4 ontoγ-Al_2O_3,the specific surface area and pore volume of IL/γ-Al_2O_3 decreased,while the selectivity and yield of C_2 hydrocarbons increased.The selectivity of C_2 hydrocarbons was 94.6%when the loading of C_6MIMBF_4 was 40%,and the percentage of C_2H_4 in C_2 hydrocarbons was as high as 64%when using Pd-IL/γ-Al_2O_3 as a catalyst with no conventional thermal reduction treatment. Optical emission spectra(OES) from the cold plasma reactor during methane conversion were also studied.The results indicated that the intensity of the C_2,CH,H,and C active species from methane and hydrogen decomposition increased when IL/γ-Al_2O_3 or Pd-IL/γ-Al_2O_3 was introduced into the plasma system.Based on the analyses of the gas product and OES spectra,it can be concluded that the surface catalyzed reactions between plasma and ionic liquid were very important for the reduction of Pd~(2+) and the formation of C_2H_4. (Pd-IL / γ-Al_2O_3) was prepared and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (C_6MIMBF_4) immobilized on 7-Al_2O_3 SEM) and Brunauer-Emmett-Teller (BET) analysis.The influences of C_6MIMBF_4 loading and Pd on methane conversion to C_2 hydrocarbons under cold plasma were investigated. FTIR and SEM analyzes showed that C_6MIMBF_4 had been successfully immobilized on 7-Al_2O_3 and the C_6MIMBF_4 showed excellent stability under cold plasma. The results of BET and methane conversion showed that with the increase in immobilization amount of C_6MIMBF_4 ontoγ-Al_2O_3, the specific surface area and pore volume of IL / γ-Al_2O_3 decreased, while the selectivity and yield of C_2 The results showed that the selectivity of C_2H was 94.6% when the loading of C_6MIMBF_4 was 40%, and the percentage of C_2H_4 in C_2H was high as 64% when using Pd-IL / γ-Al_ 2O_3 as a catalyst with no conventional thermal reduction treatment. Optical emission spectra (OES) from the cold plasma reactor during methane conversion were also studied. Results indicated that the intensity of the C_2, CH, H, and C active species from methane and hydrogen decomposition increased when IL / γ-Al 2 O 3 or Pd-IL / γ-Al 2 O 3 was introduced into the plasma system. Based on the analyzes of the gas product and OES spectra, it can be concluded that the surface catalyzed reactions between plasma and ionic liquid were very important for the reduction of Pd ~ (2+) and the formation of C_2H_4.