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

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O-₂,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。

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

A series of Co—V—O (meta-CoV₂O₆, pyro-Co₂V₂O₇, and ortho-Co₃V₂O₈) 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-CoV₂O₆, pyro-Co₂V₂O₇, and ortho-Co₃V₂O₈ 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 Co₃V₂O₈ and Co₂V₂O₇ showed dσ/dP_O2＞0, which implied that these were p-type semiconductor, and CoV₂O₆ reverse showed dσ/dP_O2＜0, which implied n-type semiconductor. 48.12%, 47.82% and 35.24% of C₃H₆ selectivities were obtained for p-type semiconductor Co₃V₂O₈, Co₂V₂O₇ and n-type CoV₂O₆ catalysts respectively at 10% C₃H₈ conversion, and the results showed that p-type semiconductor catalysts Co₃V₂O₈ and Co₂V₂O₇ showed higher activity than n-type catalyst CoV₂O₆. The results of FTIR, XPS, H₂-TPR and conductivity measurement indicated that transferring between non-stoichiometric and lattice oxygen that easily happened in Co₃V₂O₈ and Co₂V₂O7 catalysts might promote the oxidation-reduction 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 O-₂, 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 Co₃V₂O₈ and Co₂V₂O₇ can be attributed to the abundant oxygen species O- that existed in these catalysts.