(787d) Dehydrogenation of Ethylbenzene With CO2 Over Fe2O3/Al2O3-ZrO2 Catalyst: Influence of Fe2O3 Content
AIChE Annual Meeting
Friday, November 8, 2013 - 9:27am to 9:46am
Recently, styrene has been produced by ethylbenzene dehydrogenation over iron oxide catalyst with a large excess of superheated steam. In order to improve ethylbenzene conversion and enhance thermal efficiency, ethylbenzene dehydrogenation to produce styrene with CO2 (EDSC) is developed. Compared to use H2O, using CO2 is an obvious energy-saving process and conformed to the trend of green chemistry. However, the present commercial catalyst is ineffective in the presence of CO2. The indispensable requirement is to select a proper catalyst system for the EDSC process.
In our early research, we have found that Al2O3-ZrO2 (AZ) support is proper for the EDSC catalyst system, and its best performance is ZrO2 at 10 wt% (AZ10). For a catalyst, active component content affects its structure and then influences its catalytic activity. Therefore, finding the optimal addition mount of active component, then exploring catalyst characteristic performance and analyzing the reaction mechanism with this catalyst, which is meaningful for a catalyst system. Therefore, using AZ10 as the support, we prepare Fe2O3/Al2O3-ZrO2 (FAZ) catalyst, select Fe content as x (2-10) mmol in 1g AZ support and the resultant catalyst is demoted as FxAZ10.
Based on the FAZ catalyst activity evaluation result, F4AZ10 catalyst has acquired the best catalytic activity with 61.2% ethylbenzene conversion and 90.4% styrene selectivity at 550 °C. Through XRD and TEM-EDS analysis, fresh FAZ catalysts are in X-ray amorphous state or displayed only weak and broad lines of alumina, but used FAZ catalysts appear Fe3O4 (220) crystalline phase. In addition, from F4AZ10 to F10AZ10, the higher of the Fe2O3 content in FAZ catalyst, the more obvious of Fe3O4 crystalline phase after the reaction. Part of active sites reduction, agglomeration and catalyst structure change seem to cause the catalyst deactivation. N2 physical adsorption displays that both SBET and pore volume are decreased after being used for 8 hours. Raman spectroscopy indicates the carbon characteristic peaks at used F4AZ10 catalyst. These characterization results could be concluded that carbon formation and deposition is also an important factor of catalyst activity decline. According to the above analysis, the reaction mechanism of FAZ catalyst is also represented.