Navegando por Autor "Moure, Gustavo Torres"
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Artigo Double perovskite (La2-xCa-Bax)NiO4 oxygen carriers for chemical looping reforming applications(Elsevier, 2020-01-13) Melo, Marcus Antônio de Freitas; Medeiros, Rodolfo Luiz Bezerra de Araújo; Melo, Vítor Rodrigo de Melo e; Melo, Dulce Maria de Araújo; Macedo, Heloísa Pimenta de; Moure, Gustavo Torres; Adánez-Rubio, Iñaki; Adánez, JuanDouble perovskites La2-xNiO4-δ doped with Ca and Ba were synthesized via microwave-assisted combustion method and studied as an alternative oxygen carrier (OC) for chemical looping reforming processes (CLR). The OCs, La2NiO4, La1.8Ca0.2NiO4, La1.8Ba0.2NiO4 and La1.8Ca0.1Ba0.1NiO4 were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction and oxidation (TPR/TPO) and cyclic thermogravimetric analysis (TGA). Rietveld's refinement, performed after each redox cycle, confirmed that doping allows smaller amounts of nickel to migrate from the perovskite structure. The double perovskites synthesized for the chemical looping reforming process behave as simple nickel oxide and are considered as alternative oxygen carriers to solve the problems of deactivation due to the interaction of NiO with the support. The Ca-doped OC (La1.8Ca0.2NiO4) showed lower NiO concentration outside the structure and smaller crystallite size after the redox cycles, which was associated with a change in the crystal structure, presenting superior performance and stability. The results show that all perovskites have high reactivity in both reduction and oxidation reactions, however the perovskites were not able to uncouple oxygen, which is an unsual behavior for perovskitesArtigo Study of the reactivity of Double-perovskite type oxide La1¡xMxNiO4 (M 1⁄4 Ca or Sr) for chemical looping hydrogen production(Elsevier, 2018-01-18) Melo, Marcus Antônio de Freitas; Melo, Vítor Rodrigo de Melo e; Medeiros, Rodolfo Luiz Bezerra de Araújo; Braga, Renata Martins; Macedo, Heloísa Pimenta de; Ruiz, Juan Alberto Chavez; Moure, Gustavo Torres; Melo, Dulce Maria de AraújoLa2-xMxNiO4 perovskite oxygen carriers (OC) doped with Ca and Sr (x 1⁄4 0.05 and 0.20) in the site La were prepared by microwave assisted combustion method and calcined at 800 C for 2 h. A reactivity study was carried out applying pulses of H2, O2 and CH4. The reactions involved in each step, as well as H2 production, were studied to evaluate the redox properties of each OC. The crystalline structure, morphology, reduction and oxidation profiles were determined by XRD, SEM and TPR/TPO cycles, respectively. The results indicate that the dopant (Ca or Sr) strongly affect the structure and reactivity of the OC. The increase in dopant concentration increased the degree of crystallinity and the amount of the A2BO4 phase formed. The increase in dopant concentration decreased the reducibility of the perovskite. OCs doped with Ca showed higher conversion percentages, and also higher H2 production. In carriers doped with Sr no coke formation was observed.