Effect of Cr Content on Catalytic Performance of Cr/MSU-1 Catalysts in Oxidative Dehydrogenation of Propane to Propylene with CO2

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 spectroscopy (XPS) techniques. The activity investigation results show that the best catalytic activity, 62.6% of propane conversion with 22.1% of CO2 conversion, were obtained on 6.0Cr/MSU-1 catalyst at 600 degrees C. 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 surface 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