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In this work, we studied the effect of CO2 in the feed stream of the TRM process performance of nickel supported on LaFeO3 perovskite for hydrogen production compared to the POM reaction. The perovskite and nickel supported on LaFeO3 were synthesized and characterized by Thermogravimetric Analysis (TGA/DTA), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Programmed Reduction Temperature (TPR). The catalytic tests were carried out in temperatures varying from 700 to 800°C with feed flow of 350 cm3/min and 200 cm3/min for TRM and POM, respectively. The hydrogen selectivity for the tri-reforming was 78%, while for the partial oxidation reaction, only 55% H2 at 700°C. Results showed that the hydrogen selectivity for the Ni/LaFeO3 catalyst is significantly higher for the tri-reforming process, suggesting that CO2 enhanced the hydrogen selectivity compared to the partial oxidation of methane. Analyses by Raman spectroscopy and thermogravimetric calculations showed structural modifications of the catalysts after the reaction. The Raman spectrum showed segregated NiO and Fe3O4 and low carbon formation at 700°C. The proposed mechanism suggests methane and oxygen adsorbed preferentially on metallic Ni0 sites and CO2 on Fe2O3 sites.

Resumo Catalisador monolítico comercial de níquel foi selecionado com o objetivo de se determinar o regime cinético da reação de oxidação parcial do metano (OPM). As estruturas cristalinas deste catalisador foram identificadas por DRX. A composição química superficial e o estado químico dos elementos presentes na superfície da amostra foram determinados por EDX. A técnica de microscopia (MEV) com emissão de campo foi utilizada neste trabalho com as finalidades de análise morfológica do catalisador antes de sua utilização nas reações de oxidação parcial. Análises de TG-DTA foram realizadas com o objetivo de se estudar o comportamento térmico do catalisador. A área superficial e a área metálica foram determinadas por BET e Quimissorção, respectivamente. A temperatura de redução do catalisador foi determinada através de TPR. Foi utilizada uma unidade experimental para realização de testes catalíticos. Antes das reações, os catalisadores pulverizados na faixa granulométrica < 0,150 mm foram submetidos a uma etapa de redução para ativar os sítios de níquel metálico. As análises dos produtos de saída do reator e das cargas reagentes foram realizadas por cromatografia gasosa, utilizando-se um Cromatógrafo VARIAN CP3800. Foi determinado o regime cinético na OPM utilizando as massas de catalisador 65, 80 e 95 mg. Palavras-chave: Regime Cinético; Catalisadores; Níquel; Alumina; Oxidação Parcial. KINETIC REGIME OF AN NI/AL2O3 CATALYST IN PARTIAL METHANE OXIDATION REACTIONS Abstract Commercial monolithic nickel catalyst was selected with the objective of determining the kinetic regime of the partial oxidation reaction of methane (OPM). The crystalline structures of this catalyst were identified by XRD. The surface chemical composition and the chemical state of the elements present on the sample surface were determined by EDX. The microscopy technique (SEM) with field emission was used in this work with the purpose of morphological analysis of the catalyst before its use in partial oxidation reactions. TG-DTA analyzes were performed with the objective of studying the thermal behavior of the catalyst. The surface area and the metallic area were determined by BET and Chimimetry, respectively. The catalyst reduction temperature was determined by TPR. An experimental unit was used to carry out catalytic tests. Before the reactions, the pulverized catalysts in the granulometric range <0.150 mm were subjected to a reduction step to activate the metallic nickel sites. Analyzes of the reactor output products and the reagent loads were performed by gas chromatography using a VARIAN CP3800 Chromatograph. The kinetic regime at OPM was determined using the catalyst masses 65, 80 and 95 mg.

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