Estudo de catalisadores a base de níquel na reação de reforma seca do metano e a influência do bário nas propriedade catalíticas

Abstract

In this work a series of Ni/La2O3 catalysts were synthesized in order to assess the influence of synthesis method as well as the influence of barium on the catalytic properties. Initially, the catalytic precursors La1-xBaxNiO3 (x = 0.0; 0.05; 0.1 and 0.2) and NiO/La2O3 were prepared by the citrate and wet impregnation methods, respectively. The precursors were characterized by the techniques TGA, XRD, XRD-H2, XRD-CH4/CO2 and TPR-H2. Moreover, catalytic evaluation was realized followed by TPO analysis to evaluate carbon deposition. The XRD analysis indicated that the synthesis methods were able in obtain the desirable phases. Nonetheless, the barium presence led to BaCO3 segregation. The in situ diffraction results under reducing atmosphere indicated that the perovskite reduction mechanism occurs in two main steps. Furthermore, after reduction process, BaCO3 is a present phase in barium-based catalysts. Under reaction atmosphere, the diffraction results indicated that the catalysts are susceptible to oxidation Ni/NiO, however the barium presence makes it more resistant. The TPR results showed that barium insertion does not change the reduction process, nonetheless the higher reduction temperature for these precursors suggest a more intense metal-support interaction. The TPSR analysis and catalytic evaluation pointed out that the catalysts were active and selective to synthesis gas, being that the catalysts coming from the perovskite structure showed a better performance when compared to the catalyst synthesized by wet impregnation. The BaCO3 presence on the barium-content catalysts, although led to decreased activity of the catalysts, it suggested a higher carbon species oxidizing capacity. Such proposal was confirmed by TPO analysis, being the catalysts that presented similar performance, La0.9Ba0.1NiO3 and La0.8Ba0.2NiO3, the last one showed the highest resistance to carbon deposition.