Catalytic impact of bimetallic Fe-Ni nanoparticles over different supports for CO2 methanation

DE PIANO, GABRIEL; ANDRADE GAMBOA J.; A. CONDÓ; F. C GENNARI

Congreso; XXIX INTERNATIONAL MATERIALS RESEARCH CONGRESS; 2021

The conversion of CO 2 to chemical products is an effective process to reduce greenhousegases. For example, the methanation of CO 2 (conversion to CH 4 ) can be conducted bymeans of nickel-based catalysts, which are the most attractive due to their high activity andrelatively low cost. To improve their performance, the modification of the support natureand the combination of nickel with another metal constitute the main approaches to beexplored. In this work, different Ni-Fe bimetallic catalysts supported on Ce 0.8 Zr 0.2 O 2 (CZ)and SiO 2 (S) were prepared by wet impregnation (total 10 wt%) in a proportion of Ni-Fe10:0 (CZ-N10), 9:1 (CZ-N9F1; S-N9F1), 3:1 (CZ-N3F1, S-N3F1) and 1:1 (CZ-N1F1; S-N1F1). The catalysts were characterized by several techniques (XRPD, N 2 -physisorption,CO-chemisorption, SEM and HR-TEM with EDS, H 2 -TPR and TPD-CO 2 ) and studied forthe methanation of CO 2 between 150 ºC and 400 °C.In the oxidized state, all catalysts show the presence of NiO, while NiFe 2 O 4 formation isonly detected for the N1F1 composition. H 2 reduction promotes the progressiveincorporation of Fe into the Ni structure, forming nanoparticles (NPs) of Ni 1-x Fe x alloy.Independently of the support nature, the catalysts with N1F1 and N3F1 compositionspossess NPs of Ni 3 Fe alloy, reaching the best metallic dispersion (CZ~4%; S~2,3%) and thesmallest particle diameter for each support. TPR and TPD-CO 2 profiles of Ni-Fe/CZ andNi-Fe/SiO 2 catalysts display different behavior. Fe-Ni/CZ catalysts show promotedreducibility at low temperature, which is related with CZ surface reduction enhanced by H 2activation onto NiO and influenced by the support oxygen vacancies. In addition, Ni-Fe/CZshows high density of weak and moderate basic sites while Ni-Fe/SiO 2 has mainly strongbasic sites. In particular, CZ-N10 catalyst shows the highest amount of CO 2 desorbed fromweak and moderate basic sites. CO 2 conversion and CH 4 selectivity increase with thedecrease of Fe content. In fact, the CZ-N10 catalyst showed the highest CO 2 conversion(~70%) and CH 4 selectivity (~100 %) at 350 °C. Superior activity of CZ-N10 wasassociated to the improved reducibility and basicity compared with other catalysts.