摘要
研究了CO2氧化丙烷脱氢制丙烯高效wCr/MSU-1(w=2,4,6,8,10,质量分数,以Cr2O3计算)催化剂中Cr含量对催化剂结构和催化活性的影响.催化剂活性评价结果表明,随Cr含量的增加,催化剂的活性呈现先提高后降低的变化趋势.在600℃条件下,6.0Cr/MSU-1表现出最佳的催化反应活性,其中丙烷、CO2转化率分别达到62.6%和22.1%.为明确Cr含量对催化剂结构的具体影响,对催化剂样品进行了XRD,UV-Vis和XPS表征:催化剂样品的XRD表征发现Cr/MSU-1催化剂不仅能够保持良好的MSU-1分子筛的孔道结构,而且活性金属Cr在载体表面具有很高的分散度,随着Cr含量的增加催化剂表面形成明显的Cr2O3晶相;UV-Vis表征结果证实低Cr含量催化剂表面主要以Cr6+的形式存在,高Cr含量催化剂表面有明显的Cr3+出现;反应前后的催化剂XPS表征结果进一步证实催化剂表面的Cr6+与催化反应活性具有良好对应关系.基于上述结果,我们认为Cr6+是该催化剂重要的活性中心.
The effects of Cr content on the catalyst structure and catalytic activities have been investigated over Cr/MSU-1 catalyst for oxidative dehydrogenation of propane to propylene with CO2. The wCr/MSU-1 catalysts [w=2.0, 4.0, 6.0, 8.0, 10.0, the quality fraction in the percentage （calculated in Cr2O3）] were evaluated and characterized with X-ray diffraction （XRD）, diffuse reflectance UV-Vis and X-ray spectros- copy （XPS） techniques. The activity investigation results show that the best catalytic activity, 62.6% of pro- pane conversion with 22.1% of CO2 conversion, were obtained on 6.0Cr/MSU-1 catalyst at 600℃. The XRD characterization found that Cr/MSU-1 catalysts could maintain good MSU-1 pore structure and the high dispersion of Cr on catalyst surface. With increasing the Cr content the Cr2O3 crystal was detected on the catalyst surface. UV-Vis characterization results confirmed that Cr in the low content on the catalyst sur- face existed mainly in the form of Cr6＋, whereas it existed mainly in the form of Cr3＋ in the high Cr content catalysts. The characterization results of XPS for the fresh and used catalyst further confirmed that the content of Cr6＋ had a good relationship with the catalytic activity. Based on these studies, Cr6＋ was considered the active sites for this reaction.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2009年第15期1749-1753,共5页
Acta Chimica Sinica
基金
中国博士后科学基金面上项目(No.20080430581)
中石油科技风险创新研究项目(No.0706D01040408)
中国科学院知识创新方向性项目课题(KGCX2-YW-215-2)资助
