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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
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/12698 |
| Date | 07 January 2011 |
| Creators | Peres, Ana Paula da Silva |
| Contributors | CPF:06117988320, http://lattes.cnpq.br/3318871716111536, Martinelli, Ant?nio Eduardo, CPF:15724520800, http://lattes.cnpq.br/0022988322449627, Barros, Br?ulio Silva, CPF:00735018405, Ruiz, Juan Alberto Chavez, CPF:00744293456, http://lattes.cnpq.br/5051286289341242, Melo, Dulce Maria de Ara?jo |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Ci?ncia e Engenharia de Materiais, UFRN, BR, Processamento de Materiais a partir do P?; Pol?meros e Comp?sitos; Processamento de Materiais a part |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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