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Previous issue date: 2018 / A diversifica??o da matriz energ?tica, por raz?es econ?micas, ambientais e da pr?pria pol?tica
energ?tica das na??es, tem suscitado foco especial nos biocombust?veis, particularmente no
bioetanol e no biodiesel. Na ind?stria, o biodiesel (?steres de ?cidos graxos com um ?lcool de
cadeia molecular curta) ?, mais comumente, produzido pela transesterifica??o de triacilglicer?is
de ?leos vegetais ou gordura animal, com metanol ou etanol, sob cat?lise homog?nea com uma
base (KOH ou NaOH). Por representarem alternativas potencialmente mais sustent?veis, dos
pontos de vistas econ?micos e ambientais, o presente trabalho foi dedicado a avaliar a efici?ncia
qu?mica de catalisadores heterog?neos baseados em materiais de min?rios: (i) de ni?bio,
enriquecido em Nb2O5 (Geo.Nb2O5); (ii) de areia monaz?tica (Geo.Mona), uma fonte mineral
de terras raras, e (iii) de rejeitos de minera??o de fosfato, ricos em magnetita (Geo.Mag.CMT
e Geo.Mag.CMA). Os materiais minerais foram preparados em mistura com componentes
?cidos (H2SO4; HCl ou HF) ou b?sicos (KOH; , KBr, NaOH; CaO; KI; KF ou KCl). As rea??es
de transesterifica??o foram conduzidas sob refluxo, com ?leo de soja comercial e metanol, sob
a??o dos catalisadores s?lidos. A raz?o molar padr?o ?leo:metanol foi de 1:100, com 10% de
catalisador em rela??o ao ?leo, a 60 ?C. Dos testes realizados com os materiais preparados com
CaO sint?tico comercial, nas mesmas condi??es, a mistura calcinada a 800 ?C por 4 h rendeu
?steres met?licos sempre acima de 99%; o menor tempo de rea??o (2 h, para completar a
transesterifica??o) foi conseguido com o catalisador baseado na Geo.Mona, em rela??o ao
Geo.Nb2O5 (5 h), ao Geo.Mag.CMT (3 h) e o Geo.Mag.CMA tamb?m (2 h). Analisou-se o
reuso consecutivo do catalisador. Ap?s cada rea??o, o catalisador s?lido era lavado com
metanol e seco a 100 oC. O melhor resultado foi obtido com o rejeito magn?tico com CaO
calcinados a 200 ?C por 4 h, para o que se conseguiu at? 8 rea??es consecutivas. Nas
impregna??es com ?cidos e bases, os melhores resultados foram com a mistura Geo.Nb2O5 e
KOH calcinada a 600 ?C, para a qual conseguiu 8 rea??es consecutivas, com rendimento
qu?mico em ?steres met?licos de praticamente 100% e tempo reacional de 10 min, no primeiro
uso. O efeito catal?tico sin?rgico mais significativo foi conseguido com o catalisador baseado
em cada um dos tr?s materiais avaliados em mistura com CaO: nenhum efeito catal?tico
significativo na rea??o de transesterifica??o de triacilglcier?is do ?leo foi observado apenas
com o material mineral puro calcinado. O CaO puro como catalisador, tamb?m calcinado e
usado em rea??o, levou a rendimentos qu?micos pouco acima de 80%. A mistura individual do
material mineral com CaO, nas mesmas condi??es de prepara??o anteriores, levaram a
rendimentos qu?micos de efetivamente 100%. Os presentes resultados revelam a excepcional
potencialidade, dos pontos de vista qu?mico, econ?mico e ambiental, dos catalisadores mistos,
dos materiais minerais com CaO, ora avaliados, nos processos de produ??o industrial de
biodiesel. / Tese (Doutorado) ? Programa de P?s-gradua??o em Biocombust?veis, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / The diversification of the energy matrix has been drawing special attention to biofuels,
especially bioethanol and biodiesel, mainly for economic and environmental reasons and
national energy policies. In industry, biodiesel (esters of fatty acids with a short-chain alcohols)
is most commonly produced by the transesterification of triacylglycerols in vegetable oils or
animal fats with methanol or ethanol using homogeneous catalysis with a base (KOH or NaOH).
The present work was devoted to the evaluation of the chemical efficiency of heterogeneous
catalysts based on mineral materials: (i) niobium, enriched in Nb2O5 (Geo.Nb2O5); (ii) monazite
sand (Geo.Mona), a mineral source of rare earths, and (iii) phosphate mining tailings, rich in
magnetite (Geo.Mag.CMT e Geo.Mag.CMA). The mineral materials were prepared in
admixture with acidic (H2SO4, HCl or HF) or basic (KOH, KBr, NaOH, CaO, KI, KF or KCl)
components. The transesterification reactions were conducted under reflux with commercial
soybean oil and methanol in the presence of the solid catalysts. The standard molar ratio of
oil:methanol was 1:100, using 10% catalyst relatively to the quantity of oil, at 60 ?C. According
to the tests performed with the materials prepared with commercial synthetic CaO under the
same conditions, the yield of methyl esters with the mixture calcined at 800 ?C for 4 h was
always greater than 99%. The shortest reaction time (2 h to complete the transesterification)
was achieved with the Geo.Mona catalyst; the reaction times with Geo.Nb2O5 (5 h), the
Geo.Mag.CMT (3 h) and the Geo.Mag.CMA also (2 h) were longer. The consecutive reuse of
the catalyst was also verified. After each reaction, the solid catalyst was washed with methanol
and dried at 100 ?C. The best result was obtained with the magnetic waste with CaO calcined
at 200 ?C for 4 h, with which up to eight consecutive reactions were achieved. On impregnating
with acids or bases, the best results are obtained with the Geo.Nb2O5 and KOH mixture calcined
at 600 ?C, with which eight consecutive reactions were completed. Virtually 100% yields of
methyl esters were obtained in a reaction time of 10 min in the first use. The most significant
synergistic catalytic effect was achieved with each of the three minerals mixed with CaO. No
significant catalytic effect on the transesterification reaction of triacylglycerols in the oil was
observed with the pure calcined minerals. When the calcined CaO is used alone as catalyst, the
reaction yielded just over 80%. For the mixture of the individual minerals with CaO under the
same preparation conditions described above, the transesterification reaction led to virtually
100% yields. The present results reveal an outstanding potential regarding the chemical,
economic and environmental aspects of the mixed catalysts (the mineral material with CaO) for
chemical processes leading to the industrial production of biodiesel.
| Identifer | oai:union.ndltd.org:IBICT/oai:acervo.ufvjm.edu.br/jspui:1/1732 |
| Date | 18 December 2017 |
| Creators | Rocha, B?rbara Gon?alves |
| Contributors | Fabris, Jos? Domingos, Nelson, David Lee, Pereira, M?rcio C?sar, Teixeira, Ana Paula de Carvalho, Cavalcante, Luis Carlos Duarte, Ferreira, Giovana Ribeiro, Roa, Juan Pedro Bretas, Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Fabris, Jos? Domingos |
| Publisher | UFVJM |
| Source Sets | IBICT Brazilian ETDs |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFVJM, instname:Universidade Federal dos Vales do Jequitinhonha e Mucuri, instacron:UFVJM |
| Rights | A concess?o da licen?a deste item refere-se ao ? termo de autoriza??o impresso assinado pelo autor, assim como na licen?a Creative Commons, com as seguintes condi??es: Na qualidade de titular dos direitos de autor da publica??o, autorizo a Universidade Federal dos Vales do Jequitinhonha e Mucuri e o IBICT a disponibilizar por meio de seus reposit?rios, sem ressarcimento dos direitos autorais, de acordo com a Lei n? 9610/98, o texto integral da obra disponibilizada, conforme permiss?es assinaladas, para fins de leitura, impress?o e/ou download, a t?tulo de divulga??o da produ??o cient?fica brasileira, e preserva??o, a partir desta data., info:eu-repo/semantics/openAccess |
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