GaN-ZnO/MCM-41的制备及其催化CO_(2)氧化丙烷脱氢制丙烯反应

Synthesis of GaN-ZnO/MCM-41 for catalyzing CO_(2)-based oxidative dehydrogenation of propane to propene

二氧化碳氧化丙烷脱氢制丙烯(CO_(2)-OPDH)工艺是丙烯生产路线中较为理想的途径,而高性能催化剂的研制是该工艺取得突破的关键。以介孔分子筛MCM-41为载体,GaN-ZnO固溶体为活性组分,通过固相氮化法构筑具有双功能活性中心的GaN-ZnO/MCM-41催化剂,并对其催化CO_(2)-OPDH反应性能进行了研究。结合X射线衍射光谱(XRD)、氮气吸脱附测试、场发射扫描电镜-能谱(SEM-EDX)、透射电子显微镜(TEM)、热重-质谱联用(TG-MS)以及拉曼光谱(Raman),对催化剂的物理化学性质进行了表征分析。研究表明,固相氮化法能够制备出固溶体催化剂,且该催化剂表现出有效的催化丙烷脱氢性能,优于相同反应条件下负载的单组分氮化镓或氧化锌催化剂。在600℃,CO_(2)气氛下,Ga0.5-Zn0.5/MCM-41-800的丙烷转化率为21%,丙烯选择性高达92%。固溶体结构有利于活性组分的分散,能够产生更多的活性位点,而焙烧温度影响固溶体的组成结构,进而影响其催化活性。此外,CO_(2)不仅能提高催化剂的活性,而且能够减少积炭的生成,改善催化剂的稳定性。

The oxidative dehydrogenation of propane to propene in the presence of CO_(2)(CO_(2)-OPDH)is considered as a desirable route for propene production,and the development of catalyst with high performance is the key to get a breakthrough in this process.Here,the GaN-ZnO/MCM-41 catalysts with dual-function active sites were constructed via a solid-state nitridation method with GaN-ZnO solid solution as the active component supporting on mesoporous MCM-41.Their catalytic performances for CO_(2)-OPDH reaction were further evaluated.The physicochemical properties of obtained catalysts were characterized by a series of techniques such as X-ray diffraction spectroscopy(XRD),N_(2)adsorption-desorption measurements,field-emission scanning electron microscopy equipped with an energy dispersive X-ray instrument(SEM-EDX),transmission electron microscopy(TEM),thermogravimetric-mass spectra(TGMS)and Raman spectra.It is found that the solid solution catalyst can be successfully prepared in a solid-state nitridation method,the propane dehydrogenation activity of which is superior to that of the supported single-component GaN or ZnO catalysts under the same testing conditions.Among them,the Ga_(0.5)-Zn_(0.5)/MCM-41 catalyst delivers a propane conversion of 22%with the selectivity of 92%towards propene at 600℃in the CO_(2)atmosphere.This excellent catalytic performance could be attributed to the formation of solid solution structure,which was beneficial to the dispersion of active components and the generation of more active sites.The calcination temperature influenced the structure of solid solution and thus affected its catalytic activity.In addition,CO_(2)can not only increase the activity of the catalyst,but also improve its stability by declining the coke formation in PDH reaction.