Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro / A desidrogenação de hidrocarbonetos é um importante processo industrial, devido à grande demanda de hidrocarbonetos insaturados para produtos e processos industriais. Hidrocarbonetos insaturados são utilizados na manufatura de vários produtos, tais como detergentes, gasolina de alta octanagem, produtos farmacêuticos e borrachas sintéticas. Na desidrogenação de hidrocarbonetos, o catalisador comercial utilizado é à base de platina suportado em alumina. A acidez intrínseca do suporte é neutralizada por um metal alcalino ou alcalino terroso, geralmente lítio. Índio e estanho são utilizados como promotores da fase metálica. O presente trabalho teve como objetivo principal o estudo das propriedades de catalisadores de Pt modificados com adição de In e suportados em nióbia, óxido redutível sujeito ao efeito da forte interação metal-suporte (SMSI). Catalisadores Pt/Nb2O5 foram testados recentemente na desidrogenação de alcanos e apresentaram resultados promissores. Catalisadores Pt/Nb2O5 e Pt-In/Nb2O5 foram preparados por impregnação seca e caracterizados por redução à temperatura programada (TPR), espectroscopia no UV-Visível com reflectância difusa (DRS), quimissorção de H2 e CO, dessorção à temperatura programada de H2 e CO (TPD), além de oxidação à temperatura programada (TPO). A atividade catalítica desses catalisadores foi avaliada na desidrogenação do cicloexano, na hidrogenólise do metilciclopentano, na conversão do n-heptano e na reforma do metilciclopentano. A análise dos perfis de TPR permitiu concluir que há uma interação entre Pt e In nos catalisadores bimetálicos, que foi confirmada pelo decréscimo na capacidade de adsorção, medidas pelos consumos de H2 e CO. A adição de In também inibiu o efeito da forte interação metal-suporte (SMSI) entre a platina e a nióbia. A desidrogenação do cicloexano para o catalisador Pt/Nb2O5 mostrou a criação de novos sítios interfaciais. As reações de hidrogenólise foram suprimidas pela presença do efeito SMSI e pela presença do In, como foi observado na hidrogenólise do metilciclopentano. Na conversão do n-heptano, todos os catalisadores suportados em nióbia mostraram uma alta seletividade para a formação de olefinas. A presença do In suprimiu reações de hidrogenólise e favoreceu a atividade e a estabilidade do catalisador. Na reforma do metilciclopentano todos os catalisadores apresentaram boa seletividade para produtos de desidrogenação. / Hydrocarbon dehydrogenation is an important industrial process, due to the high demand of unsatured hydrocarbons for industrial processes and products. Unsatured hydrocarbons are used in the manufacture of several products, such as detergents, high octanage gasoline, pharmaceutical products and synthetic rubber. The commercial catalysts employed in the hydrocarbon dehydrogenation process is based on platinum supported on alumina. The intrinsic acidity of the support is neutralized by an alkaline or alkali earth metal, usually lithium. Indium and tin are used as promoters of the metallic phase. The present work aimed to study the property of niobia supported Pt catalysts modified by In. Nióbia is a reductible oxide, able to promote a strong metal support interaction effect (SMSI). Pt/Nb2O5 catalysts were investigated recently in the dehydrogenation of alkanes and they presented promissing results. Pt/Nb2O5 and Pt-In/Nb2O5 were prepared by incipient wetness and characterized by temperature-programmed reduction (TPR), UV-Vis diffuse reflectance spectroscopy (DRS), H2 and CO chemisorption, H2 and CO temperature-programmed desorption (TPD), besides temperature-programmed oxidation (TPO). The catalytic activity of these catalysts was evaluated in the cyclohexane dehydrogenation, methylcyclopentane hydrogenolysis, n-heptane conversion and methylcyclopentane reforming. The analysis of TPR profiles allowed to conclude that there is an interaction between Pt and In in the bimetallic catalysis, which was confirmed by the decrease in the adsorption capacity measured by the H2 and CO uptakes. In addition it also inhibited the metal support effect (SMSI) between platinum and niobia. Cyclohexane dehydrogenation results demonstrated the creation of new interfacial sites for Pt/Nb2O5 catalysts. Hydrogenolysis reactions were suppressed by the presence of the SMSI effect and by the presence of In, as observed in the methylcyclopentane hydrogenolysis. In the n-heptane conversion, all the niobia-supported catalysts displayed a high selectivity for the olefin formation. The presence of In decreased the formation of hydrogenolysis products and increased the stability of the catalyst. In the reforming methylcyclopentane all the catalysts displayed a high selectivity for the dehydrogenation products.

Abstract Cobalt-based complexes are widely used in industry and organic synthesis as catalysts for the oxidation of hydrocarbons. The Co/Mn/Br (known as "CAB system") catalyst system is effective for the oxidation of toluene. The Co/Mn/Br/Zr catalyst system is powerful for the oxidation of p-xylene, but not for the oxidation of toluene. [Co3O(OAc)5(OH)(py)3][PF6] (Co 3+ trimer 5) is more effective than [Co3O(OAc)6(py)3][PF6] (Co 3+ trimer 6) as a catalyst in the CAB catalyst system. Higher temperatures favour the oxidation of toluene. Zr 4+ does not enhance the oxidation of toluene. Zr 4+ could inhibit the oxidation of toluene in the combination of Co/Br/Zr, Co/Mn/Zr or Co/Zr. NHPI enhances the formation of benzyl alcohol, but the formation of other by-products is a problem for industrial processes. Complex(es) between cobalt, manganese and zirconium might be formed during the catalytic reaction. However, attempts at the preparation of complexes consisting of Co/Zr or Mn/Zr or Co3ZrP or Co8Zr4 clusters failed. The oxidation of cyclohexane to cyclohexanone and cyclohexanol is of great industrial significance. For the homogeneous catalysis at 50 o C and 3 bar N2 pressure, the activity order is: Mn(OAc)3 �2H2O > Mn12O12 cluster > Co 3+ trimer 6 > [Co3O(OAc)3(OH)2(py)5][PF6]2 (Co 3+ trimer 3) > Co 3+ trimer 5 > Co(OAc)2 �4H2O > [Co2(OAc)3(OH)2(py)4][PF6]-asym (Co dimerasym) > [Co2(OAc)3(OH)2(py)4][PF6]-sym (Co dimersym); whereas [Mn2CoO(OAc)6(py)3]�HOAc (Mn2Co complex) and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. But at 120 o C and 3 bar N2 pressure, the activity order is changed to: Co dimerasym > Co(OAc)2 �4H2O > Co trimer 3 and Mn(OAc)3 �2H2O > Co 3+ trimer 6 > Mn2Co complex > Co 3+ trimer 5 > Co dimersym > Mn12O12 cluster. The molar ratio of the products was close to cyclohexanol/cyclohexanone=2/1. Mn(II) acetate and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. Among those cobalt dimers and trimers, only the cobalt dimerasym survived after the stability tests, this means that [Co2(OAc)3(OH)2(py)4][PF6]-asym might be the active form for cobalt(II) acetate in the CAB system. Metal-substituted (silico)aluminophosphate-5 molecular sieves (MeAPO-5 and MeSAPO-5) are important heterogeneous catalysts for the oxidation of cyclohexane. The preparation of MeAPO-5 and MeSAPO-5 and their catalytic activities were studied. Pure MeAPO-5 and MeSAPO-5 are obtained and characterised. Four new pairs of bimetal-substituted MeAPO-5 and MeSAPO-5(CoZr, MnZr, CrZr and MnCo) were prepared successfully. Two novel trimetal-subtituted MeAPO-5 and MeSAPO-5 (MnCoZr) are reported here. Improved methods for the preparation of four monometal-substituted MeAPO-5 (Cr, Co, Mn and Zr) and for CoCe(S)APO-5 and CrCe(S)APO-5 are reported. Novel combinational mixing conditions for the formation of gel mixtures for Me(S)APO-5 syntheses have been developed. For the oxidation of cyclohexane by TBHP catalysed by MeAPO-5 and MeSAPO-5 materials, CrZrSAPO-5 is the only active MeSAPO-5 catalyst among those materials tested under conditions of refluxing in cyclohexane. Of the MeAPO-5 materials tested, whereas CrCeSAPO-5 has very little activity, CrZrAPO-5 and CrCeAPO-5 are very active catalysts under conditions of refluxing in cyclohexane. MnCoAPO-5, MnZrAPO-5 and CrAPO-5 are also active. When Cr is in the catalyst system, the product distribution is always cyclohexanone/cyclohexanol equals 2-3)/1, compared with 1/2 for other catalysts. For MeAPO-5, the activity at 150 o C and 10 bar N2 pressure is: CrZrAPO-5 > CrCeAPO-5 > CoZrAPO-5. For MeAPO-5 and MeSAPO-5, at 150 o C and 13 bar N2 pressure, the selectivity towards cyclohexanone is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5; and the selectivity towards cyclohexanol is: MnZrAPO-5 > CrZrAPO-5 > MnCoAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5. Overall the selectivity towards the oxidation of cyclohexane is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5. The amount of water in the system can affect the performance of CrCeAPO-5, but has almost no effect on CrZrAPO-5. Metal leaching is another concern in potential industrial applications of MeAPO-5 and MeSAPO-5 catalysts. The heterogeneous catalysts prepared in the present work showed very little metal leaching. This feature, coupled with the good selectivities and effectivities, makes them potentially very useful.

Abstract Cobalt-based complexes are widely used in industry and organic synthesis as catalysts for the oxidation of hydrocarbons. The Co/Mn/Br (known as "CAB system") catalyst system is effective for the oxidation of toluene. The Co/Mn/Br/Zr catalyst system is powerful for the oxidation of p-xylene, but not for the oxidation of toluene. [Co3O(OAc)5(OH)(py)3][PF6] (Co 3+ trimer 5) is more effective than [Co3O(OAc)6(py)3][PF6] (Co 3+ trimer 6) as a catalyst in the CAB catalyst system. Higher temperatures favour the oxidation of toluene. Zr 4+ does not enhance the oxidation of toluene. Zr 4+ could inhibit the oxidation of toluene in the combination of Co/Br/Zr, Co/Mn/Zr or Co/Zr. NHPI enhances the formation of benzyl alcohol, but the formation of other by-products is a problem for industrial processes. Complex(es) between cobalt, manganese and zirconium might be formed during the catalytic reaction. However, attempts at the preparation of complexes consisting of Co/Zr or Mn/Zr or Co3ZrP or Co8Zr4 clusters failed. The oxidation of cyclohexane to cyclohexanone and cyclohexanol is of great industrial significance. For the homogeneous catalysis at 50 o C and 3 bar N2 pressure, the activity order is: Mn(OAc)3 �2H2O > Mn12O12 cluster > Co 3+ trimer 6 > [Co3O(OAc)3(OH)2(py)5][PF6]2 (Co 3+ trimer 3) > Co 3+ trimer 5 > Co(OAc)2 �4H2O > [Co2(OAc)3(OH)2(py)4][PF6]-asym (Co dimerasym) > [Co2(OAc)3(OH)2(py)4][PF6]-sym (Co dimersym); whereas [Mn2CoO(OAc)6(py)3]�HOAc (Mn2Co complex) and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. But at 120 o C and 3 bar N2 pressure, the activity order is changed to: Co dimerasym > Co(OAc)2 �4H2O > Co trimer 3 and Mn(OAc)3 �2H2O > Co 3+ trimer 6 > Mn2Co complex > Co 3+ trimer 5 > Co dimersym > Mn12O12 cluster. The molar ratio of the products was close to cyclohexanol/cyclohexanone=2/1. Mn(II) acetate and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. Among those cobalt dimers and trimers, only the cobalt dimerasym survived after the stability tests, this means that [Co2(OAc)3(OH)2(py)4][PF6]-asym might be the active form for cobalt(II) acetate in the CAB system. Metal-substituted (silico)aluminophosphate-5 molecular sieves (MeAPO-5 and MeSAPO-5) are important heterogeneous catalysts for the oxidation of cyclohexane. The preparation of MeAPO-5 and MeSAPO-5 and their catalytic activities were studied. Pure MeAPO-5 and MeSAPO-5 are obtained and characterised. Four new pairs of bimetal-substituted MeAPO-5 and MeSAPO-5(CoZr, MnZr, CrZr and MnCo) were prepared successfully. Two novel trimetal-subtituted MeAPO-5 and MeSAPO-5 (MnCoZr) are reported here. Improved methods for the preparation of four monometal-substituted MeAPO-5 (Cr, Co, Mn and Zr) and for CoCe(S)APO-5 and CrCe(S)APO-5 are reported. Novel combinational mixing conditions for the formation of gel mixtures for Me(S)APO-5 syntheses have been developed. For the oxidation of cyclohexane by TBHP catalysed by MeAPO-5 and MeSAPO-5 materials, CrZrSAPO-5 is the only active MeSAPO-5 catalyst among those materials tested under conditions of refluxing in cyclohexane. Of the MeAPO-5 materials tested, whereas CrCeSAPO-5 has very little activity, CrZrAPO-5 and CrCeAPO-5 are very active catalysts under conditions of refluxing in cyclohexane. MnCoAPO-5, MnZrAPO-5 and CrAPO-5 are also active. When Cr is in the catalyst system, the product distribution is always cyclohexanone/cyclohexanol equals 2-3)/1, compared with 1/2 for other catalysts. For MeAPO-5, the activity at 150 o C and 10 bar N2 pressure is: CrZrAPO-5 > CrCeAPO-5 > CoZrAPO-5. For MeAPO-5 and MeSAPO-5, at 150 o C and 13 bar N2 pressure, the selectivity towards cyclohexanone is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5; and the selectivity towards cyclohexanol is: MnZrAPO-5 > CrZrAPO-5 > MnCoAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5. Overall the selectivity towards the oxidation of cyclohexane is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5. The amount of water in the system can affect the performance of CrCeAPO-5, but has almost no effect on CrZrAPO-5. Metal leaching is another concern in potential industrial applications of MeAPO-5 and MeSAPO-5 catalysts. The heterogeneous catalysts prepared in the present work showed very little metal leaching. This feature, coupled with the good selectivities and effectivities, makes them potentially very useful.

AgÃncia Nacional do PetrÃleo / O objetivo desta dissertaÃÃo foi estudar a aplicaÃÃo da sÃlica mesoporosa SBA-15 modificada com lantÃnio como catalisador heterogÃneo nas reaÃÃes de transesterificaÃÃo e esterificaÃÃo visando à produÃÃo de biodiesel. Para isso sintetizou-se o catalisador La-SBA-15 variando a razÃo molar Si/La em 25, 50 e 75. O catalisador heterogÃneo La-SBA-15 apresenta caracterÃsticas Ãcidas o qual pode ser mais tolerante a Ãgua e aos Ãcidos graxos livres presentes nos Ãleos e podem catalisar simultaneamente as reaÃÃes de transesterificaÃÃo e esterificaÃÃo. O catalisador foi caracterizado atravÃs das anÃlises de DRX, MEV e adsorÃÃo e dessorÃÃo de nitrogÃnio a 77 K. Para o estudo da aplicaÃÃo do catalisador La-SBA-15 na reaÃÃo de transesterificaÃÃo utilizou-se como matÃria-prima o Ãleo de soja e para a reaÃÃo de esterificaÃÃo o Ãcido olÃico. Ambas matÃrias-primas foram previamente caracterizadas quanto à composiÃÃo dos Ãcidos graxos por cromatografia gasosa, Ãndice de acidez, Ãndice de iodo, Ãndice de saponificaÃÃo, densidade a 20 ÂC, viscosidade cinemÃtica a 40 ÂC e teor de umidade. Primeiramente aplicou-se o catalisador La-SBA-15 com diferentes razÃes molares Si/La na reaÃÃo de esterificaÃÃo do Ãcido olÃico com etanol, verificando-se que o catalisador com razÃo molar Si/La igual a 50 apresentou a maior atividade catalÃtica na reaÃÃo com conversÃo de 91,14 %. Portanto, o catalisador La-SBA-15 com razÃo molar Si/La igual a 50 foi a melhor proporÃÃo para utilizaÃÃo da SBA-15 modificada com lantÃnio como catalisador. Em seguida utilizou-se o catalisador La-SBA-15 com razÃo molar Si/La igual a 50 na reaÃÃo de transesterificaÃÃo do Ãleo de soja com etanol obtendo-se conversÃo de 80,00 %. Com isso, verifica-se que o catalisador La-SBA-15 com razÃo molar Si/La igual a 50 pode catalisar ambas as reaÃÃes de esterificaÃÃo e transesterificaÃÃo, ou seja, catalisadores com propriedades Ãcidas podem agir sobre ambas as reaÃÃes. / The dissertation proposal to study the application of mesoporous silica SBA-15 modified with lanthanum as a heterogeneous catalyst in the esterification and transesterification reactions for biodiesel production. The catalyst lanthanum-incorporated SBA-15, La-SBA-15, with different Si/La molar ratios (75, 50, 25) were synthesized. The heterogeneous catalyst La-SBA-15 has acid characteristics which can be more tolerant of water and free fatty acids present in oils and can simultaneously catalyze the esterification and transesterification reactions. The catalyst was characterized by XRD, SEM and nitrogen isotherms at 77 K analysis. For study the application of La-SBA-15 catalyst in the transesterification reaction was used as feedstock the soybean oil and esterification reaction the oleic acid. Before the reaction, both raw materials were characterized as the fatty acid composition by gas chromatography, acid value, iodine value, saponification index, density, kinematic viscosity and water content. First applied the catalyst La-SBA-15 with different Si/La molar ratios in the esterification reaction of oleic acid with ethanol, verifying that the catalyst with Si/La = 50 molar ratio showed the highest catalytic activity in the reaction with conversion of 91,14%. Therefore, the La-SBA-15 catalyst with Si/La molar ratio of 50 was the best ratio for use of SBA-15 modified with lanthanum as a catalyst. Then used the La-SBA-15 catalyst with Si/La molar ratio of 50 in the transesterification reaction of soybean oil with ethanol resulting in conversion of 80.00%. So observed that the La-SBA-15 catalyst with Si/La molar ratio of 50 can catalyze both esterification and transesterification reactions.

No description available.

O presente trabalho teve como objetivo estudar a síntese do biodiesel por transesterificação etílica de diferentes matérias-primas lipídicas empregando catalisadores heterogêneos (químico e bioquímico). Para cumprir com os objetivos propostos foram selecionadas matérias-primas lipídicas de baixo impacto no setor alimentício, entre as quais destacam-se: óleos vegetais (andiroba, babaçu, macaúba, palma e pinhão manso) e gordura residual (sebo bovino) e catalisadores de comprovada potencialidade como óxido de nióbio impregnado com sódio (químico) e a lipase de Burkholderia cepacia imobilizada em suporte híbrido sílicaalcool polivinílico (bioquímico). O trabalho foi desenvolvido em três etapas. Inicialmente, foram determinadas as propriedades físico-químicas das diferentes matérias-primas lipídicas, algumas ainda pouco exploradas, para verificar se apresentavam potencial para serem utilizadas na reação de transesterificação. Em seguida foram preparados os catalisadores propostos por protocolos já estabelecidos, sendo obtido para o catalisador químico elevado teor de sódio impregnado no óxido de nióbio (25,43 ± 0,29%) e para catalisador bioquímico elevada atividade hidrolítica (1814 ??281 U/g). Na segunda etapa, as reações de transesterificação foram conduzidas em regime de batelada em condições adequadas para cada catalisador em termos de temperatura, tempo e proporção de catalisador. Na terceira etapa, os produtos obtidos foram purificados e quantificados por cromatografia gasosa, RMN 1H, viscosimetria e análise termogravimétrica (TGA). O conjunto de dados obtidos demonstrou que a formação de ésteres etílicos a partir das diferentes matérias-primas é viável para os catalisadores testados. Ambos os catalisadores (químico e bioquímico) atuaram de forma eficiente convertendo os ácidos graxos presentes nas matérias-primas lipídicas nos ésteres etílicos correspondentes e apresentaram elevada estabilidade em bateladas consecutivas, com destaque para o catalisador bioquímico que revelou um tempo de meiavida de 290 h. Entretanto, a qualidade da matéria-prima lipídica interferiu a atuação dos catalisadores de maneira diferenciada. Enquanto, o catalisador químico foi sensível a presença de níveis elevados de acidez, como o constatado no óleo de macaúba, a atuação do catalisador bioquímico sofreu influência da presença de peróxidos indicativo de oxidação apresentada pelo óleo de andiroba. Com exceção dos óleos de macaúba e andiroba que apresentaram qualidade comprometida, todas as matérias-primas lipídicas originaram amostras de biodiesel com características adequadas para serem usadas como combustível, incluindo valores de viscosidade entre 3,9 a 6,0 (cSt) que atendem as especificações estabelecidas na ASTM 6751- 02. Apesar do desempenho similar dos catalisadores testados, a via química foi superior em termos de produtividade em relação à via bioquímica. Entretanto, essa baixa produtividade pode ser incrementada utilizando métodos não convencionais de aquecimento, como por exemplo, irradiação de micro-ondas e ultrassom. Os resultados obtidos neste trabalho demonstram ainda que os catalisadores heterogêneos testados possuem potencial para substituir os sistemas homogêneos normalmente empregados na síntese do biodiesel. Essa substituição oferece vantagens, que podem propiciar um aumento considerável nas perspectivas de sustentabilidade sócio-ambiental de todo o processo de produção. / The present work aimed at studying the biodiesel synthesis by transesterification reaction from several lipidic feedstocks via ethyl route employing heterogeneous catalysts (chemical and biochemical). To attain the proposed objectives non-edible feedstock having low impact in the food segment, among which stand out: vegetable oils (andiroba, babassu, macauba, palm and Jatropha curcas) and residual fat (beef tallow) and potential catalysts as niobium oxide impregnated with sodium (chemical) and lipase from Burkholderia cepacia immobilized on silica-polyvinyl alcohol matrix (biochemical) were previously selected. The work was developed in three steps. Initially, the physico-chemical properties of the different lipidic feedstocks were investigated, some of them still little explored, to identify their potential as reactants in the transesterification reactions. Then the proposed catalysts were prepared by protocols already established, being obtained for the chemical catalyst high level of sodium impregnated in the niobium oxide (25.43 ± 0.29%) and for the biochemical catalyst high hydrolytic activity (1,814± 281 U/g). In the second step, the transesterification reactions were carried out in batch reactors under appropriated conditions for each catalyst in terms of temperature, time and catalyst proportion. In the third step, the obtained products were purified and quantified by gas chromatography, 1H NMR spectroscopy, viscosimetry and thermogravimetric analysis (TGA). The dataset obtained demonstrated that the formation of ethyl esters from the different feedstocks was feasible for the tested catalysts. Both catalysts (chemical and biochemical) were efficient in converting all fatty acids present in the lipidic feedstock into the corresponding ethyl esters and showed high stability under consecutive batch runs, with emphasis for the biochemical catalyst with a half-life time of 290 h. However, the poor quality of the feedstocks strong affected the performance of the catalysts in a different way. While the chemical catalyst was sensitive to high acidity levels, as verified in the macauba oil, the biochemical catalyst performance was influenced by the presence of peroxides indicating oxidation as showed in the andiroba oil. Except for these oils, all the other feedstocks originated biodiesel samples with appropriate characteristics to be used as fuel, including viscosity values between 3.9 to 6.0 (cSt) that are in accordance with specifications recommended by ASTM 6751-02. Even though the catalysts showed similar performances, the chemical route gave higher productivity than that attained by biochemical route. However, such lower productivity can be increased using non conventional heating systems as for instance, micro-wave irradiation and ultrasound. The results obtained in this work demonstrated that the selected heterogeneous catalysts possess potential to replace the homogeneous systems usually employed in the biodiesel synthesis. Such replacement offers advantages that can provided a considerable increase in the perspectives to attain an environmental sustainability of process as a whole.

O presente trabalho teve como objetivo estudar a síntese do biodiesel por transesterificação etílica de diferentes matérias-primas lipídicas empregando catalisadores heterogêneos (químico e bioquímico). Para cumprir com os objetivos propostos foram selecionadas matérias-primas lipídicas de baixo impacto no setor alimentício, entre as quais destacam-se: óleos vegetais (andiroba, babaçu, macaúba, palma e pinhão manso) e gordura residual (sebo bovino) e catalisadores de comprovada potencialidade como óxido de nióbio impregnado com sódio (químico) e a lipase de Burkholderia cepacia imobilizada em suporte híbrido sílicaalcool polivinílico (bioquímico). O trabalho foi desenvolvido em três etapas. Inicialmente, foram determinadas as propriedades físico-químicas das diferentes matérias-primas lipídicas, algumas ainda pouco exploradas, para verificar se apresentavam potencial para serem utilizadas na reação de transesterificação. Em seguida foram preparados os catalisadores propostos por protocolos já estabelecidos, sendo obtido para o catalisador químico elevado teor de sódio impregnado no óxido de nióbio (25,43 ± 0,29%) e para catalisador bioquímico elevada atividade hidrolítica (1814 ??281 U/g). Na segunda etapa, as reações de transesterificação foram conduzidas em regime de batelada em condições adequadas para cada catalisador em termos de temperatura, tempo e proporção de catalisador. Na terceira etapa, os produtos obtidos foram purificados e quantificados por cromatografia gasosa, RMN 1H, viscosimetria e análise termogravimétrica (TGA). O conjunto de dados obtidos demonstrou que a formação de ésteres etílicos a partir das diferentes matérias-primas é viável para os catalisadores testados. Ambos os catalisadores (químico e bioquímico) atuaram de forma eficiente convertendo os ácidos graxos presentes nas matérias-primas lipídicas nos ésteres etílicos correspondentes e apresentaram elevada estabilidade em bateladas consecutivas, com destaque para o catalisador bioquímico que revelou um tempo de meiavida de 290 h. Entretanto, a qualidade da matéria-prima lipídica interferiu a atuação dos catalisadores de maneira diferenciada. Enquanto, o catalisador químico foi sensível a presença de níveis elevados de acidez, como o constatado no óleo de macaúba, a atuação do catalisador bioquímico sofreu influência da presença de peróxidos indicativo de oxidação apresentada pelo óleo de andiroba. Com exceção dos óleos de macaúba e andiroba que apresentaram qualidade comprometida, todas as matérias-primas lipídicas originaram amostras de biodiesel com características adequadas para serem usadas como combustível, incluindo valores de viscosidade entre 3,9 a 6,0 (cSt) que atendem as especificações estabelecidas na ASTM 6751- 02. Apesar do desempenho similar dos catalisadores testados, a via química foi superior em termos de produtividade em relação à via bioquímica. Entretanto, essa baixa produtividade pode ser incrementada utilizando métodos não convencionais de aquecimento, como por exemplo, irradiação de micro-ondas e ultrassom. Os resultados obtidos neste trabalho demonstram ainda que os catalisadores heterogêneos testados possuem potencial para substituir os sistemas homogêneos normalmente empregados na síntese do biodiesel. Essa substituição oferece vantagens, que podem propiciar um aumento considerável nas perspectivas de sustentabilidade sócio-ambiental de todo o processo de produção. / The present work aimed at studying the biodiesel synthesis by transesterification reaction from several lipidic feedstocks via ethyl route employing heterogeneous catalysts (chemical and biochemical). To attain the proposed objectives non-edible feedstock having low impact in the food segment, among which stand out: vegetable oils (andiroba, babassu, macauba, palm and Jatropha curcas) and residual fat (beef tallow) and potential catalysts as niobium oxide impregnated with sodium (chemical) and lipase from Burkholderia cepacia immobilized on silica-polyvinyl alcohol matrix (biochemical) were previously selected. The work was developed in three steps. Initially, the physico-chemical properties of the different lipidic feedstocks were investigated, some of them still little explored, to identify their potential as reactants in the transesterification reactions. Then the proposed catalysts were prepared by protocols already established, being obtained for the chemical catalyst high level of sodium impregnated in the niobium oxide (25.43 ± 0.29%) and for the biochemical catalyst high hydrolytic activity (1,814± 281 U/g). In the second step, the transesterification reactions were carried out in batch reactors under appropriated conditions for each catalyst in terms of temperature, time and catalyst proportion. In the third step, the obtained products were purified and quantified by gas chromatography, 1H NMR spectroscopy, viscosimetry and thermogravimetric analysis (TGA). The dataset obtained demonstrated that the formation of ethyl esters from the different feedstocks was feasible for the tested catalysts. Both catalysts (chemical and biochemical) were efficient in converting all fatty acids present in the lipidic feedstock into the corresponding ethyl esters and showed high stability under consecutive batch runs, with emphasis for the biochemical catalyst with a half-life time of 290 h. However, the poor quality of the feedstocks strong affected the performance of the catalysts in a different way. While the chemical catalyst was sensitive to high acidity levels, as verified in the macauba oil, the biochemical catalyst performance was influenced by the presence of peroxides indicating oxidation as showed in the andiroba oil. Except for these oils, all the other feedstocks originated biodiesel samples with appropriate characteristics to be used as fuel, including viscosity values between 3.9 to 6.0 (cSt) that are in accordance with specifications recommended by ASTM 6751-02. Even though the catalysts showed similar performances, the chemical route gave higher productivity than that attained by biochemical route. However, such lower productivity can be increased using non conventional heating systems as for instance, micro-wave irradiation and ultrasound. The results obtained in this work demonstrated that the selected heterogeneous catalysts possess potential to replace the homogeneous systems usually employed in the biodiesel synthesis. Such replacement offers advantages that can provided a considerable increase in the perspectives to attain an environmental sustainability of process as a whole.

Solid oxide fuel cells (SOFCs) are electrochemical energy conversion devices that directly transform the chemical energy of fuel into electrical energy. They generate electricity far more efficiently and with fewer emissions per megawatt-hour compared to any combustion-based power generation system. More remarkably, SOFCs can directly use hydrocarbon fuels without requiring external fuel reforming, employing low-cost Ni catalyst instead of noble-metal catalysts used for low-temperature fuel cells. However, the conventional SOFCs using Ni-based anodes fed with carbon-containing fuels have one pitfall; the carbon produced by hydrocarbon cracking is deposited on the Ni surface, thereby precluding the surface of the Ni-based anodes from being available for further fuel oxidation and consequently impeding SOFC operation. This dissertation focuses on overcoming this critical drawback to allow for the simultaneous use of Ni-based anodes and hydrocarbon fuels. Further work focuses on improving SOFC performance to provide the highest efficiencies possible. To boost the power densities of SOFCs, a novel, facile approach to modify the surface structure of anode powders and thereby enlarge the three-phase boundary (TPB) regions of anodes is presented. One such powder preparation method based on the electric charge variation of oxides depending upon the pH of the solution results in significantly extended TPB regions and thus a remarkable increase in power densities of SOFCs. Another method involves the formation of Ce₁₋[subscript x]Gd₁₋[subscript y]Ni[subscript x+y]VO₄₋[subscript delta] at the phase boundaries between NiO and Ce₀.₈Gd₀.₂O₁.₉ (GDC) by V⁵⁺-incorporation onto NiO surface; this method improves the microstructure of Ni-GDC-based anodes and considerably lowers GDC electrolyte sintering temperature, thereby enhancing the SOFC performance. With these high performance anodes, natural gas-fueled SOFCs are studied through two strategies to alleviate coking: incorporation of catalytic materials onto the Ni surface and the introduction of catalytic functional layers (CFLs) to the outer surface of an anode-supported single cell. Hydrogen tungsten bronze and hydroxylated Sn formed on the Ni surface provide hydroxyls for the deposited solid carbon, removing it from the anodes as CO₂. Moreover, the use of hydrophilic Sn or Sb-incorporated Ni-GDC CFLs prevents the anode from being exposed directly to hydrocarbon fuels and controls the solid carbon accumulation similarly to the former strategy. / text

Submitted by José Henrique Lazaro de Carvalho (jose.carvalho@fc.unesp.br) on 2018-04-26T14:52:46Z No. of bitstreams: 1 merged.pdf: 3543516 bytes, checksum: 94a6da42fee42b5469644d670ca0dddc (MD5) / Approved for entry into archive by Minervina Teixeira Lopes null (vina_lopes@bauru.unesp.br) on 2018-04-26T17:33:49Z (GMT) No. of bitstreams: 1 carvalho_jhl_me_bauru.pdf: 3133645 bytes, checksum: 07b206851bb163d2aab65e55f0340aea (MD5) / Made available in DSpace on 2018-04-26T17:33:49Z (GMT). No. of bitstreams: 1 carvalho_jhl_me_bauru.pdf: 3133645 bytes, checksum: 07b206851bb163d2aab65e55f0340aea (MD5) Previous issue date: 2018-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os hidrocarbonetos se constituem na função mais simples da química orgânica. Mesmo sendo formados apenas por carbono e hidrogênio, esta classe é uma das mais diversas, onde se destacam os hidrocarbonetos alquil aromáticos (HAA) e os hidrocarbonetos aromáticos policíclicos (HAP). Por possuírem baixa reatividade e serem lipossolúveis, os HAA e HAP tendem a se acumular na natureza e nos tecidos vivos podendo levar a mutações genéticas e ao câncer. Funcionalizações oxigenadas nestes hidrocarbonetos ampliam suas aplicações industriais e auxiliam na sua remediação ambiental. A oxidação radicalar utilizando radicais hidroxila via TBHP (t-butil-hidroperóxido) é uma rota promissora devido à ausência de resíduos metálicos nocivos no processo. Paralelamente, o uso de metais do bloco-d, como o nióbio, como catalisadores heterogêneos, que são conhecidos por apresentarem boa estabilidade térmica, porosidade, maior superfície de contato e podendo ser recuperado e reutilizado, vem sendo descrito como bons catalisadores para a reação, permitindo rendimentos maiores e condições reacionais mais brandas. O nióbio tem despertado o interesse de muitos grupos de pesquisa devido às suas propriedades e aplicabilidades na metalurgia, supercondutores e supercapacitores, e na síntese orgânica. Este trabalho focou no estudo da aplicação do óxido de nióbio como catalisador heterogêneo em reações de oxidação de HAA e HAP usando o TBHP como oxidante. Diferentes variáveis reacionais como o solvente, a concentração e morfologia do catalisador, temperatura, dentre outras, foram investigadas a fim de otimizar a reação para a melhor conversão no derivado oxigenado. A melhor condição obtida foi utilizando Nb2O5 amorfo em 10% em mol de reagente, em acetonitrila e em refluxo com mais de 40 % de conversão em derivado oxigenado para qualquer substrato de hidrocarboneto estudado. / Hydrocarbons are the simplest function of organic chemistry. Although formed only by carbon and hydrogen, this class is one of the most diverse, in which the alkyl aromatic hydrocarbons (AAHs) and the polycyclic aromatic hydrocarbons (PAHs) stand out. These substances are mostly fossil raw materials widely used in industry in diverse applications. Because they have low reactivity and are liposoluble, AAHs and PAHs tend to accumulate in nature and in living tissues, leading to genetic mutations and cancer. Oxygenated functionalities in these hydrocarbons broaden their industrial applications and assist in their environmental remediation. Radical oxidation using hydroxyl radicals via TBHP (t-butylhydroperoxide) is a promising route due to the absence of noxious metal residues in the process. At the same time, the use of d-block metals, such as niobium, as heterogeneous catalysts, which are known to have good thermal stability, porosity, larger contact surface and be able to be recovered and reused, have been described as good catalysts for the reaction, allowing for higher yields and softer reaction conditions. Niobium has attracted the interest of many research groups because of its properties and applications in metallurgy, superconductors and supercapacitors, and in organic synthesis. This work focused on the study of the application of niobium oxide as a heterogeneous catalyst in oxidation reactions of AAHs and HAP using TBHP as oxidant. Many reactional variables like the solvent, the catalyst concentration and morphology, as well as temperature have been investigated in order to optimize the reaction for the better conversion to oxygen derivatives. The best obtained condition was using 10 % in mol amorphous Nb2O5 in acetonitrile under reflux with a conversion yield of more than 40 % for any studied hydrocarbon substrate.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / O atual cenÃrio de recursos limitados de combustÃveis fÃsseis, o aumento da demanda por energia e o aquecimento global tem levado a um aumento expressivo na produÃÃo de biocombustÃveis na Ãltima dÃcada. O biodiesel emergiu como uma alternativa econÃmica e ambientalmente viÃvel para reduzir as emissÃes de gases responsÃveis pelo efeito estufa e a dependÃncia de combustÃveis derivados de petrÃleo. O glicerol à o principal subproduto da indÃstria de biodiesel e à tambÃm uma matÃria-prima muito versÃtil, podendo ser utilizado na produÃÃo de produtos quÃmicos, polÃmeros e combustÃveis. Recentemente vÃrios autores tÃm relatado a conversÃo de glicerol em Ãcido lÃtico, um importante composto com ampla aplicaÃÃo na indÃstria quÃmica, farmacÃutica e alimentÃcia. Um dos processos de destaque à a sÃntese hidrotÃrmica alcalina, que à vantajosa por permitir utilizar o glicerol contendo Ãgua originado na produÃÃo de biodiesel, mas que requer altas temperaturas que, aliadas Ãs condiÃÃes alcalinas em que a reaÃÃo acontece, podem provocar severa corrosÃo nos equipamentos. Neste trabalho foi possÃvel sintetizar e caracterizar um catalisador de palÃdio suportado em carbono ativado (Pd/C) e verificar sua influÃncia na conversÃo de glicerol em Ãcido lÃtico em condiÃÃes hidrotÃrmicas alcalinas. AtravÃs de uma tÃcnica de deposiÃÃo foi possÃvel obter um catalisador com teor mÃdio de 2,52% em massa do metal, presente como espÃcies catiÃnicas (Pd2+) e metÃlicas (Pd0). Este catalisador foi testado em reator de batelada, partindo-se de uma soluÃÃo 0,5 M de glicerol e 0,55 M de NaOH (razÃo molar NaOH:glicerol de 1,1) e carga de catalisador de 0,5 g/100 mL de soluÃÃo, nas temperaturas de 200 ÂC e 230ÂC. A conversÃo de glicerol, a seletividade a Ãcido lÃtico e o rendimento de Ãcido lÃtico foram monitorados durante 240 minutos de reaÃÃo. O melhor desempenho ocorreu na temperatura de 230 ÂC e 180 minutos de reaÃÃo. Nestas condiÃÃes foi possÃvel obter 95,9% de conversÃo de glicerol e 52,3% de seletividade a Ãcido lÃtico, resultando em um rendimento em Ãcido lÃtico de 50,1%. AlÃm disso, o catalisador apresentou estabilidade diante das condiÃÃes de reaÃÃo empregadas, sendo reutilizado por cinco ciclos de reaÃÃo sem perda significativa de atividade ou seletividade. / The current scenario of limited resources of fossil fuels, increased energy demand and global warming has led to a significant increase in biofuel production in the last decade. Biodiesel has emerged as an economic and environmentally viable alternative to reduce emissions of greenhouse gases and dependence on petroleum-based fuels. Glycerol is the main by-product of the biodiesel industry and also is a very versatile raw material, being used in the production of chemicals, fuels and polymers. Recently several authors have reported the conversion of glycerol into lactic acid, an important compound with wide application in the chemical, pharmaceutical and food industry. One of the prominent process is the alkaline hydrothermal synthesis, which is advantageous for allowing the use of glycerol containing water originated from biodiesel process, but requires high temperatures which, combined with the alkaline reaction conditions, can cause severe corrosion in equipment. In this study it was synthesized and characterized a palladium catalyst supported on activated carbon (Pd/C) and evaluated its influence in the conversion of glycerol to lactic acid. Using a deposition technique it was possible to obtain a catalyst with an average metallic content of 2.52%, present as cationic (Pd2+) and metallic (Pd0) species. This catalyst was evaluated in a batch reactor, operating with a 0.5 M glycerol and 0.55 M NaOH solution (NaOH:glycerol mole ratio of 1.1), catalyst loading of 0.5 g per 100 mL solution, at temperatures of 200ÂC and 230ÂC. The glycerol conversion, the selectivity to lactic acid and lactic acid yield were monitored for 240 minutes of reaction. The best performance was obtained at 230 ÂC and 180 minutes of reaction time. Under these conditions it was possible to obtain 95.9% conversion of glycerol and 52.3% selectivity to lactic acid, resulting in a lactic acid yield of 50.1%. Furthermore, the catalyst showed excellent stability in the reaction conditions employed in this study, being reused for five reaction cycles without significant loss of activity or selectivity.