Oxidative dehydrogenation of ethane to ethylene over LiCl/SO42--ZrO2 catalyst

Sulfated zirconia (SO 2-_4-ZrO_2) samples were prepared by a modified two-step method (refluxing ZrO-(OH)_2 precursor in basic solution followed by drying and (NH_4)_2SO_4 impregnation) and then impregnated with a LiCl solution to give the SO 2-_4-ZrO_2-supported LiCl catalysts with Li mass content of 0.5%～15%. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, N_2 adsorption, temperature-programmed desorption-mass spectrometry, and X-ray photoelectron spectroscopy. The results show that with increasing LiCl loading, the specific surface area and acidity of the catalysts as well as the volume fraction of tetragonal zirconia in the catalysts decrease, while the catalytic performance of the catalysts for oxidative dehydrogenation of ethane (ODHE) to ethylene increases. Over the LiCl/SO 2-_4-ZrO_2 catalyst with a Li content of 15%, the ethylene yield of 77.8% with an ethane conversion of 90.6% is achieved at 650 ℃, and the yield higher than 71% is maintained over a period of 24 h. The textural structure of ZrO_2 has little effect on the catalytic behavior of the LiCl/SO 2-_4-ZrO_2 catalysts. The specific surface area of SO 2-_4-ZrO_2 samples prepared by the modified two-step method is much bigger than that of the SO 2-_4-ZrO_2 samples made by the method reported in literature, and therefore more LiCl can be loaded on unit mass of support. This is favorable to improve the catalyst stability and slow down catalyst deactivation during the ODHE reaction due to the loss of LiCl.