FTIR和XPS光谱分析Co-V-O催化剂的丙烷氧化脱氢活性氧物种

Active Oxygen Species of Co—V—O Catalysts in Propane Oxidative Dehydrogenation Analyzed by FTIR and XPS Spectra

制备了正钒酸钴Co3V2O8,焦钒酸钴Co2V2O7和偏钒酸钴CoV2O6三种催化剂,进行了XRD,TEM,BET,FTIR,XPS,H2-TPR和电导等表征,并测试了他们的丙烷氧化脱氢（ODH）制丙烯催化性能。对各催化剂的FTIR主要吸收峰做了经验归属,并对其O（1s）XPS谱进行了分峰拟合,计算了催化剂表面不同氧物种的含量。制得的催化剂晶粒均匀,平均粒径为20-30 nm,Co3V2O8和Co2V2O7具有p-型半导体性质,CoV2O6表现n-型半导体性质。p-型半导体Co3V2O8和Co2V2O7的丙烷ODH催化性能优于n-型半导体CoV2O6,当丙烷的转化率在10%时,在Co3V2O8,Co2V2O7,CoV2O6催化剂上丙烯选择性分别为48.12%,47.82%,35.24%。FTIR,XPS,H2-TPR和电导的研究结果表明,正、焦钒酸钴催化剂内各种价态钒之间易于进行氧化还原反应和形成氧缺位,钴含量的增加有利于丙烷转化的未充分还原的氧物种O2^-,O2^2-,O^-等增加,可以判断未充分还原的氧物种Oδ-（0〈δ〈2）是丙烷ODH活性氧物种。

A series of Co-V-O （meta-CoV2 O6, pyro-Co2 V2O7, and ortho-Co3 V2 O8 ） catalysts were prepared by microwave oxalate co-precipitation method and characterized by （XRD）, TEM, BET, FTIR, XPS, H2-TPR and conductivity measurement. The catalytic characters of the catalysts for propane oxidative dehydrogenation were investigated. The FTIR spectra of catalysts were obtained in the range of 400-1 100 cm^-1 and their major bands were assigned. The peak separation fitting of O（1s） XPS spectra was carried out and the quantity of oxygen species was calculated. The results of XRD characterization showed that pure meta-CoV2 O6, pyro-Co2 V2 O7, and ortho-Co3 V2 O8 with nice structure were obtained. The TEM images demonstrated that the catalysts showed uniform particle with the mean particle size of 20-30 nm. The diagram of the relationship between electrical conductivity and oxygen partial pressure of Co3 V2O8 and Co2 V2 O7 showed dδ/dPo2〉0, which implied that these were p-type semiconductor, and CoV2 06 reverse showed dδ/dPo2〈0, which implied n-type semiconductor. 48. 12 %, 47. 82 % and 35.24 of C3 H6 selectivities were obtained for p-type semiconductor CAD3 V2O8, Co2 V2O7 and n-type COV2O6 catalysts respectively at 10 % C3 H8 conversion, and the results showed that p-type semiconductor catalysts Co3 V2 O8 and Co2 V2 O7 showed higher activity than n-type catalyst CoV2 O6. The results of F-FIR, XPS, H2-TPR and conductivity measurement indicated that transferring between non-stoiehiometric and lattice oxygen that easily happened in Co3 V2 O8 and Co2 V2 O7 catalysts might promote the oxidationreduction reaction between different valence vanadium species, and promoted the oxygen vacancy formation. Furthermore, the forming of Co-O-V bridge bond that was easy to shift between Co and V increased the mobile oxygen species of O2^-, O2^2- and O^- and made the redox reaction among different valence V be realized. It is concluded that high catalytic properties of p-type semiconductor Co3 V2 O8 and Co2 V2 O7 can be attributed to the abundant oxygen species O that existed in these catalysts.