Abstract:
A series of LiMn
2O
4/TiO
2 catalysts with spinel crystal structure were prepared by solid state reaction method, and the catalytic performance of oxidative coupling of methane on the different catalysts, such as TiO
2, Li/TiO
2, Mn/TiO
2, LiMn
2O
4 as well as LiMn
2O
4/TiO
2, was evaluated. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, CO
2 temperature programmed desorption and H
2 temperature programmed reduction. It is found that LiMn
2O
4 with spinel structure has high catalytic activity in oxidative coupling of methane reaction. 25.8% of CH
4 conversion, 43.2% of C
2 selectivity was obtained under the reaction conditions of 775℃, 0.1MPa, 7200mL·h
-1·g
-1, CH
4:O
2(volume ratio)=2.5. The introduction of TiO
2 support can not only improve CH
4 conversion and C
2 selectivity, but also restrain the deep oxidation of methane to CO
2. The LiMn
2O
4/TiO
2 with 8% loading amount showed the best activity, on which 31.6% of CH
4 conversion, 52.4% of C
2 selectivity were obtained and CO
2 selectivity was decreased to 26.3%. The effect of calcination temperature on the activity of LiMn
2O
4/TiO
2 catalysts was investigated. 850℃ is the optimal calcination temperature.