Obten??o de ?xidos a base de n?quel e cobalto para rea??o de oxida??o parcial do metano

• Main Author: Peres, Ana Paula da Silva
• Other Authors: CPF:06117988320
• Format: Others
• Language: Portuguese
• Published: Universidade Federal do Rio Grande do Norte 2014
• Subjects: NiCo2O4; Gelatina; Catalisador; Oxida??o parcial de metano; Gelatin; Catalyst; Partial oxidation of methane; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Online Access: http://repositorio.ufrn.br:8080/jspui/handle/123456789/12698

Made available in DSpace on 2014-12-17T14:06:55Z (GMT). No. of bitstreams: 1 AnaPP.pdf: 5176837 bytes, checksum: 9d8890c4a2dd055dfe7d581f34a7f4e8 (MD5) Previous issue date: 2011-01-07 === Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior === Nickel-based catalysts supported on alumina have been widely used in various reactions to obtain synthesis gas or hydrogen. Usually, higher conversion levels are obtained by these catalysts, however, the deactivation by coke formation and sintering of metal particles are still problems to be solved. Several approaches have been employed in order to minimize these problems, among which stands out in recent years the use of additives such as oxides of alkali metals and rare earths. Similarly, the use of methodologies for the synthesis faster, easier, applicable on an industrial scale and to allow control of the microstructural characteristics of these catalysts, can together provide the solution to this problem. In this work, oxides with spinel type structure AB2O4, where A represents divalent cation and B represents trivalent cations are an important class of ceramic materials investigated worldwide in different fields of applications. The nickel cobaltite (NiCo2O4) was oxides of spinel type which has attracted considerable interest due to its applicability in several areas, such as chemical sensors, flat panel displays, optical limiters, electrode materials, pigments, electrocatalysis, electronic ceramics, among others. The catalyst precursor NiCo2O4 was prepared by a new chemical synthesis route using gelatine as directing agent. The polymer resin obtained was calcined at 350?C. The samples were calcined at different temperatures (550, 750 and 950?C) and characterized by X ray diffraction, measurements of specific surface area, temperature programmed reduction and scanning electron microscopy. The materials heat treated at 550 and 750?C were tested in the partial oxidation of methane. The set of techniques revealed, for solid preparations, the presence of the phase of spinel-type structure with the NiCo2O4 NixCo1-xO solid solution. This solid solution was identified by Rietveld refinement at all temperatures of heat treatment. The catalyst precursors calcined at 550 and 750?C showed conversion levels around 25 and 75%, respectively. The reason H2/CO was around 2 to the precursor treated at 750?C, proposed reason for the reaction of partial oxidation of methane, one can conclude that this material can be shown to produce synthesis gas suitable for use in the synthesis Fischer-Tropsch process === Catalisadores a base de n?quel suportados em alumina, t?m sido amplamente empregados nas diversas rea??es para obten??o de g?s de s?ntese ou hidrog?nio. Normalmente, altos n?veis de convers?o s?o obtidos por estes catalisadores, entretanto, a desativa??o por forma??o de coque e sinteriza??o das part?culas met?licas s?o ainda problemas a serem solucionados. Diversas abordagens t?m sido empregadas com a finalidade de minimizar estes problemas, dentre as quais tem se destacado nos ?ltimos anos a utiliza??o de aditivos como ?xidos de metais alcalinos e metais terras raras. Paralelamente, o uso de metodologias de s?nteses mais r?pidas, f?ceis, aplic?veis em escala industrial e que permitam o controle das caracter?sticas microestruturais destes catalisadores, pode em conjunto, prover a solu??o para este problema. Neste trabalho, ?xidos com estrutura tipo espin?lio AB2O4, onde A representa c?tions divalentes e B representa c?tions trivalentes, s?o uma classe importante de materiais cer?micos mundialmente investigados em diferentes campos de aplica??es. As cobaltitas de n?quel (NiCo2O4) s?o ?xidos do tipo espin?lio que tem atra?do consider?vel interesse devido a sua aplicabilidade em diversas ?reas, como em sensores qu?micos, monitores de tela plana, limitadores ?pticos, materiais para eletrodos, pigmentos, eletrocat?lise, cer?micas eletr?nicas, entre outras. O precursor catal?tico NiCo2O4 foi preparado por uma nova rota de s?ntese qu?mica usando a gelatina como agente direcionador. A resina polim?rica obtida foi tratada termicamente a 350?C. As amostras foram calcinadas em diferentes temperaturas 550, 750 e 950?C e caracterizadas por difra??o de raios X, medidas de ?rea superficial espec?fica, redu??o a temperatura programada e microscopia eletr?nica de varredura. Os materiais tratados termicamente a 550 e 750?C foram testados na oxida??o parcial do metano. O conjunto de t?cnicas revelaram, nos s?lidos preparados, a presen?a da fase de estrutura espin?lio do tipo NiCo2O4 juntamente com a solu??o s?lida NixCo1-xO. Esta solu??o s?lida foi identificada atrav?s do refinamento Rietveld em todas as temperaturas de tratamento t?rmico. Os precursores catal?ticos calcinados a 550 e 750?C apresentaram n?veis de convers?o em torno de 25 e 75%, respectivamente. A raz?o H2/CO foi em torno de 2 para o precursor tratado a 750?C, raz?o proposta pela rea??o de oxida??o parcial do metano, pode-se concluir que este material pode ser indicado para produzir g?s de s?ntese adequado para ser utilizado na s?ntese de Fischer-Tropsch