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Previous issue date: 2015-01-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / As emiss?es de compostos sulfurados pela ind?stria do refino de petr?leo v?m
sendo sujeitas a legisla??es cada vez mais restritivas devido aos impactos ambientais e na
sa?de humana. A remo??o de compostos de enxofre pode ocorrer atrav?s de rea??es de
hidrotratamento (HDT) as quais s?o catalisadas por s?lidos, geralmente ?xidos ou sulfetos
met?licos normalmente suportados em alumina. Para a remo??o de enxofre (HDS)
catalisadores de Co(Ni)-Mo(W)/Al2O3 s?o os mais utilizados, por?m novos materiais vem
sendo desenvolvidos para esse fim. Carbetos de metais refrat?rios foram identificados como
potenciais candidatos para essa aplica??o, a dopagem destes pode ser uma alternativa para a
cat?lise dessa rea??o. Os precursores para obten??o de Mo2C foram heptamolibdato de
molibd?nio [(NH4)6[Mo7O24].4H2O] e nitrato de cobalto [Co(NO3)2.6H2O] e foram
cominu?dos manualmente em propor??es estequiom?tricas anteriormente ? rea??o. Os
precursores foram caracterizados por TG/DTA, MEV, FRX e DRX. Os carbetos de
molibd?nio com adi??o de cobalto foram obtidos atrav?s de rea??o g?s-s?lido com atmosfera
de metano (CH4) e hidrog?nio (H2) utilizando reator de leito fixo. Foi utilizada vaz?o total da
mistura gasosa de 15L/h com 5% de CH4 e taxa de aquecimento de 5?C/min at? a temperatura
de rea??o (700 ou 750?C). Dois percentuais de cobalto foram empregados: 2,5 e 5%. Foi
notada a presen?a de fase CoMoO4 e MoO3 nos percursores calcinados, o que indica o ?ntimo
contato entre os metais. Para os produtos da rea??o de carboneta??o a 700?C,
independentemente do teor de cobalto adicionado, foi formado Mo2C-ortorr?mbica e MoO2-
monocl?nica. A 750?C somente Mo2C foi detectada por DRX. N?o foi poss?vel a identifica??o
de fase contendo Co pelos difratogramas em nenhuma das condi??es. Nessa temperatura, a
an?lise de TOC indicou a completa convers?o dos ?xidos a carbeto, com forma??o de 8,9%
de carbono livre para a amostra com 2,5% de Co, para a amostra com 5% a convers?o foi
incompleta (86%). Os produtos de rea??o foram caracterizados por FRX, DRX, MEV, TOC,
BET e granulometria a laser / Sulfur compounds emissions have been, on the late years, subject to more severe
environmental laws due to its impact on the environment (causing the acid rain phenomena)
and on human health. It has also been object of much attention from the refiners worldwide
due to its relationship with equipment?s life, which is decreased by corrosion, and also with
products? quality, as the later may have its color, smell and stability altered by the presence of
such compounds. Sulfur removal can be carried out by hydrotreating (HDT) which is a
catalytic process. Catalysts for HDS are traditionally based on Co(Ni)-Mo(W)/Al2O3.
However, in face of the increased contaminants? content on crude oil, and stricter legislation
on emissions, the development of new, more active and efficient catalysts is pressing.
Carbides of refractory material have been identified as potential materials for this use. The
addition of a second metal to carbides may enhance catalytic activities by increasing the
density of active sites. In the present thesis Mo2C with Co addition was produced in a fixed
bed reactor via gas-solid reaction of CH4 (5%) and H2(95%) with a precursor made of a mix
of ammonium heptamolybdate [(NH4)6[Mo7O24].4H2O] and cobalt nitrate[Co(NO3)2.6H2O]
at stoichiometric amounts. Precursors? where analyzed by XRF, XRD, SEM and TG/DTA.
Carboreduction reactions were carried out at 700 and 750?C with two cobalt compositions
(2,5 and 5%). Reaction?s products were characterized by XRF, XRD, SEM, TOC, BET and
laser granulometry. It was possible to obtain Mo2C with 2,5 and 5% cobalt addition as a
single phase at 750?C with nanoscale crystallite sizes. At 700?C, however, both MoO2 and
Mo2C phases were found by XRD. No Co containing phases were found by XRD. XRF,
however, confirmed the intended Co content added. SEM images confirmed XRD data. The
increase on Co content promoted a more severe agglomeration of the produced powder. The
same effect was noted when the reaction temperature was increased. The powder synthesized
at 750?C with 2,5% Co addition TOC analysis indicated the complete conversion from oxide
material to carbide, with a 8,9% free carbon production. The powder produced at this
temperature with 5% Co addition was only partially converted (86%)
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19690 |
| Date | 30 January 2015 |
| Creators | Ara?jo, Camila Pacelly Brand?o de |
| Contributors | 13681389420, http://lattes.cnpq.br/1030834608582624, Fontes, Francisco de Assis Oliveira, 20300190468, http://lattes.cnpq.br/9043538628554844, Silva, Gilson Garcia da, 56634161453, http://lattes.cnpq.br/8681275097040450, Souza, Carlson Pereira de |
| Publisher | Universidade Federal do Rio Grande do Norte, P?S-GRADUA??O EM ENGENHARIA QU?MICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| 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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