丁烯歧化制丙烯用负载型铼基催化剂

采用浸渍法制备了不同Re2O7负载量的Re2O7/Al2O3催化剂,采用XRD、XRF、低温氮吸附-脱附、NH3-TPD、FTIR和H2-TPR对催化剂进行了表征。表征结果显示,Al2O3载体负载Re2O7后在载体表面形成了新的活性物种;随Re2O7负载量的增加,Re2O7/Al2O3催化剂的BET比表面积和孔体积减小,酸性增强;焙烧过程中Re2O7是否升华与载体的比表面积有关,Re2O7单层分散阈值随载体比表面积的增大而增大。考察了Re2O7/Al2O3催化剂催化丁烯歧化制丙烯的反应性能。实验结果表明,Re2O7负载量对歧化反应的选择性影响不大,在m(2-丁烯)∶m(1-丁烯)=1.2、重时空速1h-1、60℃、2MPa的条件下,选择性始终保持在85%以上;丁烯转化率随Re2O7负载量的增加明显增大,最高达50%,接近平衡转化率;当Re2O7负载量由5%增至20%时,催化剂的寿命明显延长。

Re2O7/Al2O3 Catalysts Used in Producing Propylene by Butene Metathesis

Re2O7/Al2O3 catalysts with different Re2O7 loadings were prepared through impregnation and characterized by means of XRD,XRF,N2 adsorption-desorption,NH3-TPD,FTIR and H2-TPR.Results showed that active component on the Al2O3 support surface was formed.With increasing of Re2O7 loading,BET surface area and pore volume of the catalyst decreased,but its acidity was enhanced.Loss of Re2O7 in the catalyst in calcination process was related to the specific surface area of Al2O3 support.Threshold value of Re2O7 loading increased with the increasing of specific surface area of Al2O3 support.The catalytic properties of Re2O7/Al2O3 were evaluated in metathesis reaction of butene to propylene.Under reaction conditions:m(2-butene)∶m(1-butene)1.2,WHSV 1 h-1,60 ℃ and 2 MPa,conversion of butene rose obviously with increasing of Re2O7 loading,climax 50%,while selectivity to propylene was always over 85%,almost unchanged with different Re2O7 loadings.When Re2O7 loading increased from 5% to 20%,the catalyst lifetime evidently prolonged.