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No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) alice_lopes_macedo.pdf: 2851693 bytes, checksum: 6e7032a0575fb31a58f4ce49e26fe1a5 (MD5) Previous issue date: 2013 / Os catalisadores heterog?neos desenvolvidos pelo grupo de pesquisa a base de ?cidos de Lewis suportados em diferentes ?xidos inorg?nicos, como por exemplo o ZnCl2/SiO2 e FeSO4/SiO2, tem se mostrado excelentes na esterifica??o de ?cidos graxos livres, por?m ineficazes quando aplicados na transesterifica??o de ?leos vegetais. Este trabalho prop?e o estudo e a s?ntese de um catalisador produzido a partir da substitui??o dos ?cidos de Lewis por ?cido de Bronsted-Lowry, tais como, o ?cido sulf?rico e o ?cido clor?drico. ?leos e gorduras residuais geralmente cont?m um alto ?ndice de ?cidos graxos livres (AGL) e um elevado teor de ?gua em sua constitui??o. Essas subst?ncias dificultam a a??o dos catalisadores b?sicos como NaOH ou KOH que s?o amplamente empregados nestes processos, levando tamb?m a inibi??o de alguns catalisadores a base de ?cidos minerais. A nova mistura catal?tica (H2SO4/SiO2) foi sintetizada a partir de ?cido sulf?rico 10 M imobilizado em s?lica 24 mesh, previamente preparada a partir de areia de constru??o e carbonato de s?dio e caracterizada pelas seguintes t?cnicas anal?ticas: Microscopia Eletr?nica de Varredura, Espectrometria de Dispers?o de Energia, Infravermelho e Termogravimetria. O catalisador foi inicialmente aplicado com ?xito em rea??es de transesterifica??o de ?leos vegetais refinados e de ?leos e gorduras residuais purificados, por?m o grande desafio foi realizar a transesterifica??o de ?leos vegetais de baixa qualidade, os chamados ?leos e gorduras residuais, que al?m de possu?rem em sua constitui??o ?leos vegetais misturados ? gordura animal e ?cidos graxos livres, s?o muitas vezes contaminados por at? 1% de ?gua, em que propor??es acima de 0,5% m/m podem levar a total desativa??o do catalisador. O emprego de s?lica sint?tica 24 mesh na constitui??o do catalisador objetivou aumentar a ?rea de superf?cie, favorecendo o processo de adsor??o de ?gua oriunda da esterifica??o de ?cidos graxos livres e tamb?m a contida nos ?leos e gorduras residuais, evitando uma maior perda da atividade catal?tica por lixivia??o. O rendimento obtido em biodiesel foi acima de 99%, calculado a partir dos dados obtidos por Cromatografia Gasosa acoplada a Espectr?metro de Massa. O catalisador utilizado no processo foi recuperado por lavagem em ?ter et?lico e ativado em estufa 150? C por 3 horas e utilizado em outros processos reacionais. O glicerol obtido como subproduto da transesterifica??o foi utilizado sem pr?via purifica??o na rea??o de catalisa??o com acetona empregando H2SO4/SiO2, formando o cetal 2,2-dimetil-1,3-dioxolano-4-il metanol em 93% de rendimento, o qual foi determinado por CG/EM. Este produto ? caracterizado por sua grande aplica??o como aditivo para combust?veis pela ind?stria automobil?stica. A mistura catal?tica (H2SO4 10M/SiO2) utilizada possui uma capacidade de carga de 1,91x10-3 mols H+/g, ou aproximadamente 9,4% m/m de H2SO4 no catalisador e equivalente a 0,94% m/m de H2SO4 em rela??o ao ?leo vegetal empregado nos diferentes processos reacionais. Essas propor??es se mostraram bem abaixo das propor??es normalmente empregadas em rea??es de transesterifica??o catalisadas por ?cido sulf?rico, que variam de 4 a 5%. O emprego deste catalisador nos processos de transesterifica??o e de catalisa??o, permitiu a sua recupera??o e reutiliza??o por 2 ciclos, sendo que ap?s o ?ltimo ciclo a s?lica resultante foi acidificada novamente, seca e empregada em novos processos catal?ticos. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2013. / ABSTRACT The heterogeneous catalysts developed by our research group based Lewis acid supported on various inorganic oxides such as: ZnCl2/SiO2 and FeSO4/SiO2, has proved excellent for esterification of free fatty acids, but ineffective when applied in the transesterification vegetable oils. This paper proposes the synthesis and study of a catalyst produced from the Br?nsted-Lowry acids sulfuric acid in replacement of previously employed Lewis acids. Waste oils and fats generally contain a high content of free fatty acids (FFA), as well as a high water content, these substances hinders the action of basic catalysts such as NaOH or KOH which are widely used in these processes, taking also inhibition of some catalysts from the mineral acids. The new catalyst mixture (H2SO4/SiO2) was synthesized from 10 M sulfuric acid immobilized on silica 24 mesh, previously prepared from construction sand and sodium carbonate. Later this material was characterized using the following analytical techniques, Scanning Electron Microscopy, Spectroscopy Dispersion Energy, Infrared and thermogravimetric analysis. Initially, the catalyst was applied in transesterification of vegetable oils and refined oils and waste fats purified. However, the most challenge was to perform the transesterification of vegetable oils of low quality, they called residual oils and fats, over to have in their constution vegetable oils mixed with animal fat and free fatty acid are often contaminated by 1% water, in proportions up to 0.5% w/w can lead to complete deactivation of the catalyst. The use of synthetic silica 24 mesh aimed to increase the surface area, favoring the adsorption of water from the esterification of free fatty acids and also contained in the waste oils and fats, preventing further loss of catalytic activity by leaching. The yield obtained in biodiesel was above 99%, calculated from the data obtained by GC/MS. The catalyst used in the process was recovered by washing using ethyl ether and activated in an oven 150 ?C for 3 hours and used in the process of ketalization of glycerol, as well as in subsequent transesterification reactions. The glycerol obtained as a byproduct of the transesterification was used without purification in the previous reaction of ketalization with acetone employing H2SO4/SiO2 ketalization with acetone forming the ketal 2,2-dimethyl-1 ,3-dioxolan-4-yl methanol in 93% yield, which was determined by GC/MS. This product is characterized by its wide application as a fuel additive for the automotive industry. The catalytic mixture (H2SO410 M/SiO2) used has a capacity of 1.91 x10-3mol H+/g, or about 9,4% w/w of H2SO4 in the catalyst, equivalent to 0.94% w/w of H2SO4 in compared to vegetable oil employed in the different reaction processes, these proportions were below the proportions normally used in transesterification reactions catalyzed by sulfuric acid ranging from 4 to 5%. The use of this catalyst in processes of transesterification and ketalization allowed the recovery and reuse during two cycles. After the last cycle, the resulting silica was acidified, dried and used in another catalytic process