Estudo de catalisadores de cobalto suportados em matrizes de La2O3-CeO2-SiO2 para a produção de hidrogênio a partir da reforma a vapor do etanol

Abstract

This research reports studies with Co/SiO 2 catalysts modified with La 2 O 3 and CeO 2 by steam reforming of ethanol (SRE) in order to increase the catalytic activity and reduce the carbon formation on the catalyst. The amount of Co used was 10%, already of La and Ce were 10% CoLa x Ce 50-x Si 50 , where X = 2%, 4% and 6%. The supports were prepared according co-precipitation and impregnation methods in order to evaluate the effect on the catalytic performance. The active phase was incorporated by impregnation method. All were characterized by Energy Dispersive X Ray Spectroscopy (EDX), X Ray Diffraction (XRD), Temperature-Programmed Reduction (TPR) and Specific Surface Area (BET) and those prepared by coprecipitation were also analyzed by X Ray Diffraction in Situ. Thereafter, the catalysts were applied in the SRE and the highest selectivity against H 2 in each method was selected for studies of variation of the mass content of active phase (10% and 20%) and temperature reaction. The performance was compared with catalysts without additive in the holder. After tests, the coke formed was determined by Elemental Analysis and characterized by Scanning Electron Microscopy (SEM) and XRD. From the XRD and TPR results was possible identify the presence of Co 3 O 4 phase in all catalysts. In the mixed catalyst (Co/Ce-La-Si) was identified, by XRD, the formation of solid solutions between the cerium and lanthanum. Was observed that the catalyst with higher concentrations of La 3+ , in both methods of preparation, were more selective against H 2 , furthermore the temperature affected the performance of the catalysis. After characterization and quantification of the produced carbon during SRE, only catalysts supported in pure La 2 O 3 , for both methods, showed the formation of La 2 O 2 CO 3, which minimizes coke formation and was identified by XRD. Through of SEM analysis of the catalyst after the reaction, it was found that coke formed a filamentous-like structure, allowing the exposure of the metallic cobalt for a longer period of time with the support.