Catalisadores de Ni suportados em óxidos sintetizados com líquido iônico: atividade catalítica na tri-reforma do metano

Abstract

Tri-reforming reaction is a new method to use and convert CO2 from industrial plants effluents. The tri-reforming involved reactions are two endothermic reactions, the steam and dry reforming and the partial methane oxidation that is an exothermic reaction. Natural gas as a feedstock to tri-reforming is an alternative to use CO2, a H2O e o O2 without any separation process. Find new materials and improve the existents catalysts that are stable during the temperature oscillations and the comprehension of active catalysts during the tri-reforming reaction are relevant. Ni catalysts are the most used in reforming reactions. However, it has low thermal and mechanic stability and as a consequence are deactivated. Looking to this way the focus of this research is to obtain Ni catalysts supported in ZrO2 and CeO2, synthesized by unusual routes owing an improvement of supports to enhance the catalytic performance of Ni. The catalysts were characterized by XRD, N2 physisorption, TPR-H2, TPD-CO2, TPD-NH3, FTIR, TGA, TEM and SEM. The catalytic performance was analyzed using the tri-reforming reaction, measuring the CH4 and CO2 and the syngas formed. The first thesis core is the ionic liquid synthesis which the objective was synthesize the organic materials. The ionic liquids were synthesized using solvothermal route and were characterized by DSC, MNR 1H and 13C, CHN elementary analysis and FTIR. The second has as objective synthesize zirconium polymorphous, in which monoclinic and tetragonal phases were obtained by ionothermal route. After analyze the synthesis conditions influence in the support phases, then nickel catalysts were synthesized by wet impregnation. TPR-H2 were performed to understand the influence of zirconium polymorphous in the Ni dispersion. In situ characterization were used to investigate the transitions states and the catalysts stability in the reaction atmosphere. According to the ionic liquid composition in the support synthesis the tetragonal ZrO2 phase stabilization occurs and an improvement in Ni dispersion was observed which improved the catalytic performance of Ni/ZrO2 catalysts. The third thesis core refers to CeO2 and Ni/CeO2 synthesis and characterization and the analysis of catalytic performance of these materials. We analyzed the influence of synthesis conditions in the CeO2 support formation. The Ni/CeO2 catalysts were obtained by wet impregnation. TPR-H2 measurements showed different Ni dispersion according with the CeO2 supports synthesized even any phase transitions were detected by XRD. In situ characterization showed different stability according to the catalysts tested and the reaction atmosphere. In the last chapter the catalysts used in this research was compared each other. For both, Ni/ZrO2 a Ni/CeO2, the support synthesis route has influence in the metal dispersion and metal crystallite size. The catalytic performance was different according synthesis route and independently of basicity and oxygen vacancies of the support used, in tri-reforming reaction the most important variable is Ni0 crystallite size.