乙烷氧化脱氢制乙烯纳米Sm_2O_3催化剂的研究

Study of the Nanoscale Sm_2O_3 for the Oxidative Dehydrogenation of Ethane to Ethylene

采用XRD,TEM,BET,CO2 TPD,O2 TPD和催化剂性能评价等方法对溶胶 凝胶法制备的纳米Sm2O3的物相、颗粒度、比表面、碱性、吸附活化氧物种的能力和催化剂的ODE性能进行了表征和评价,并与常规Sm2O3进行了比较.实验结果表明,纳米Sm2O3催化剂具有较佳的低温ODE反应性能,在500～600℃的温度范围内,纳米Sm2O3的乙烷转化率和乙烯选择性均优于常规Sm2O3,其原因主要与纳米催化剂体系具有较大比表面,较多的表面缺陷位,较弱的碱性和不同于常规催化剂体系的物相结构并因此更有利于吸附和活化氧物种等因素有关.采用高温原位显微Raman光谱对纳米Sm2O3上ODE反应活性氧物种的表征结果表明,O22-是Sm2O3催化剂上ODE反应的活性氧物种.

A comparative study of the conventional Sm2O3 and the nanoscale Sm2O3 prepared by the solgel method for the oxidative dehydrogenation of ethane (ODE) to ethylene was carried out. The catalysts were characterized by XRD, SEM, TEM, BET, CO2TPD and O2TPD techniques, as well as by the catalytic performance evaluation for ODE reaction from 500 to 650 ℃. It was found that nanoscale Sm2O3 demonstrated better low temperature ODE performance than the conventional Sm2O3. C2H6 conversion of 47.7% with C2H4 selectivity of 60.1% was achieved at 500 ℃. When the reaction temperatures were lower than 600 ℃, both C2H6 conversion and C2H4 selectivity over the nanoscale Sm2O3 were higher than those over the conventional Sm2O3. The nanoscale Sm2O3 is characterized by having much higher surface area, more surface defective sites, different phase structure and weaker surface basicity as compared to the conventional Sm2O3. All of these factors will be favorable to increase catalyst's ability of oxygen activation, and to the improvement of catalyst's ODE performance at low temperature. The results of high temperature in situ microprobe Raman spectroscopic characterizations on the oxygen species over the nanoscale Sm2O3 suggest that O22- is the active oxygen species for the ODE reaction over the catalyst.