摘要
对比研究了VPO和VPO/SiO2 催化剂的结构、表面元素氧化态、还原性及其对丙烷选择氧化反应的催化性能 .与VPO催化剂相比 ,VPO/SiO2 催化剂具有较大的比表面积 ;VPO主要以 (VO) 2 P2 O7的形式高度分散于SiO2 表面 ;VPO/SiO2 催化剂的还原温度较低 ;VPO/SiO2 催化剂与丙烷的相互作用较强 ;在反应条件下 ,VPO/SiO2 催化剂的活性较高 ,但产物丙烯的选择性较低 ,并有丙烯醛等C3含氧化合物生成 .这可能是由于VPO/SiO2 催化剂表面的V与Si发生了相互作用之故 .随着VPO担载量的增加 ,VPO/SiO2 催化剂的比表面积减小 ;催化剂的还原温度略有升高 ,可还原的晶格氧量增加 ;催化剂表面与丙烷的相互作用增强 ;丙烷转化率升高而丙烯选择性降低 ,丙烯醛选择性在 5 %VPO/SiO2 催化剂上最高 .这可能是由于随着VPO担载量的增加 。
VPO catalyst is one of promising catalysts for selective oxidation of C_4H_ 10 and C_3H_8. The catalysts VPO and VPO/SiO_2 with different VPO loading were prepared. Using BET, XRD, LRS, XPS, H_2-TPR and C_3H_8-TPD techniques, the physicochemical properties of the catalysts, such as structure, reducibility, vanadium oxidation states and V-O bond, as well as the interaction between C_3H_8 and the catalysts, were comparatively investigated. The catalytic performance of the catalysts in selective oxidation of C_3H_8 was also tested. VPO/SiO_2 had higher specific surface area and reducibility than VPO. In addition, the binding energy of V 2p_ 3/2 on VPO/SiO_2 was higher than that on VPO, which indicated that the coordination environment of V changed and V δ+ (4<δ<5) might exist on VPO/SiO_2. Compared with VPO, the stronger interaction between C_3H_8 and VPO/SiO_2 was observed. The interaction between Si and V occurred on VPO/SiO_2, which modified its physicochemical properties and in return changed its catalytic performance. In the case of VPO/SiO_2, (VO)_2P_2O_7 was the main phase (oxidation state) and highly dispersed on SiO_2. With the increase of VPO loading, the reduction temperature of the catalyst and binding energy of V 2p_ 3/2 changed slightly, and the intensity of V-O bond and the H_2 consumption in TPR increased, indicating that the amount of V-O species increased on the surface. On the other hand, with the increase of VPO loading, the C_3H_8 conversion increased while the C_3H_6 selectivity reduced, and the acrolein selectivity appeared the maximum value on 5%VPO/SiO_2 catalyst.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2003年第2期87-92,共6页
基金
国家重点基础研究规划项目 (G19990 2 2 40 8)
