Study On Ce-based Catalyst In The Dehydrogenation Of Ethylbenzene Ce-Based Catalyst With Cartbon Dioxide

Styrene as the basis for the petrochemical industry products, synthetic rubber and plastics is an important raw material. In industry, it mainly obtained by the catalytic dehydrogenation of ethylbenzene. This process have some disadvantages, such as high energy consumption, low equilibrium conversion and catalyst deactivation. In the process of oxidative dehydrogenation, CO2is an effective way to reduce energy consumption and decrease CO2pollution. It is important to develop the high conversion and high selectivity catalysts, this paper choose the CeO2to solve the lack of lattice oxygen and carbon deposition on the catalyst. The Ce-based catalyst can improve the self-regeneration capacity of catalyst and the reaction activity can be increased by the supplement of lattice oxygen. Finally, this paper obtain the reaction mechanism of catalyst.In this paper, the hydrothermal method was used to prepare the different components of Ce-based catalysts and the catalysts were applied with ethylbenzene dehydrogenation in the presence of carbon dioxide at550℃. By N2-adsorption, XRD, Raman scattering, TEM analysis, the fresh and used catalysts were characterized. Catalysts were associated with the characterization results, to find the important factor of catalysts. Several results and conclusions were obtained as follows:(1) To investigate the influence of the Ce/Fe and Ce/Zr atomic ratio on the reaction of ethylbenzene dehydrogenation. Approximately20%of Fe3+could dissolve into the CeO2lattice while portions of Fe2O3were highly dispersed on the surface of the Ce1-xFexO2solid solution. The formation of solid solutions could create more oxygen vacancies to promote the absorption and activation of CO2, which improves the activity of Ce-Fe catalyst and increased ethylbenzene conversion by as much as13%, and the activity of Ce-Zr catalyst was more than Ce-Fe catalyst. As the increase of catalyst surface, the activity of Fe2O3/CexZr1-xO2and Fe2O3/CexZr1-xO2/Al2O3increased, however, the activity of supported catalysts still is in decline.(2) By the XRD, TEM, Raman, it is confirmed the Fe ion-substituted CeO2and the formation of oxygen vacancy. The reduction capacity and oxygen storage capacity (OSC) was tested by the TPR and H2-O2titration, the order of OSC was Ceo.8Feo.202> Ceo.9Feo.1O2> CeO2and Ceo.3Zro.7O2> Ce0.5Zr0.5O2> Ce0.7Zr0.3O2, the order of catalyst activity can correspond to the the order.(3) After regenerated using CO2, Combined with the analysis of X-ray diffraction, Transmission electron microscopy, Thermogravimetric analysis, Kaman spectroscopy, CO2temperature-programmed oxidation, Temperature Programmed Surface Reaction and X-Ray Photoelectron Spectrometer, the reason for the deactivation of catalysts was discussed. In the reaction process, the rate of carbon deposition elimination was less than the rate of generating carbon. The generated coke occupied the active sites, preventing the adsorption and activation of CO2on the catalyst, thus the actived oxygen can not be added and the catalyst activity declined.