Objetivou-se avaliar como diferentes estratégias de manejo do pasto de azevém anual interferem na produção animal, no consumo de forragem e na emissão de metano por ovinos em sistema de integração lavoura-pecuária (SILP) (Capítulo II). Já no Capítulo III objetivou-se avaliar as técnicas dos nalcanos e do nitrogênio fecal na estimativa do consumo de forragem por ovinos em pastos de azevém anual. Os experimentos foram conduzidos nos anos de 2011 e 2012 na Estação Experimental da UFRGS. Foram utilizados ovinos em um SILP de soja e milho no verão, em rotação com azevém anual no inverno. Para ambos os Capítulos (II e III) foram estudados dois métodos de pastoreio (contínuo e rotativo) e duas intensidades de pastejo (moderada e baixa; 2,5 e 5 vezes o potencial de consumo de matéria seca, respectivamente) em um delineamento de blocos casualizados com 3 repetições. Para o Capítulo II, no primeiro experimento os animais experimentais eram cordeiros, enquanto no segundo foram ovelhas em lactação. Os resultados indicaram que o ganho médio diário (GMD) dos cordeiros foi maior (P<0,05) no método de pastoreio continuo que no método de pastoreio rotativo, independente da intensidade de pastejo. O ganho de peso vivo por área (GPV) apresentou a mesma resposta em ambos os experimentos, com maior GPV na intensidade de pastejo moderada (P<0,05). No experimento 1, o consumo de matéria seca (CMS) foi maior para o método de pastoreio continuo, enquanto no experimento 2 não houve diferenças entre métodos e intensidades. As emissões de CH4 diárias por animal não diferiram entre tratamentos em ambos os experimentos (P>0,05), porém, quando expressas em g CH4 kg GPV-1 as emissões foram em média 15,33% maiores (P<0.05) para o método de pastoreio rotativo, independente da intensidade de pastejo. Os resultados afirmam que as emissões de metano por animal não são afetadas pelos tratamentos impostos. Porém, do ponto de vista de sistema o método de pastoreio contínuo o mais eficiente, por apresentar menor emissão de metano por kg de ganho de peso vivo, independente da intensidade de pastejo. Para o Capítulo III, foram utilizados apenas cordeiros. Utilizou-se a metodologia dos n-alcanos e do nitrogênio fecal, por meio de coleta total de fezes com o auxílio de bolsas coletoras. Na avaliação entre os n-alcanos, verificou-se melhores resultados quando utilizando o par C31:C32. Para a metodologia do nitrogênio fecal, as equações propostas por Wang et al. (2009) e por Azevedo (2011) foram as melhores (P<0,05). A técnica do nitrogênio fecal mostrou-se mais acurado do que o uso dos n-alcanos, que superestimou os valores de consumo. / The aim of this study was to evaluate how different management strategies of Italian ryegrass affects animal production, forage intake and methane emissions by sheep in integrated crop-livestock system (ICLS) (Chapter II). In Chapter III, we aimed to evaluate the techniques of n-alkanes and fecal nitrogen in estimating forage intake by sheep grazing on ryegrass. The experiments were conducted in 2011 and 2012 at the UFRGS Experimental Station. The ICLS soybeans and corn crops in summer, in rotation with grazed Italian ryegrass in winter. For both chapters (II and III) two stocking methods (continuous or rotational) and two grazing intensities (moderate and low, 2.5 and 5 times the potential dry matter intake, respectively) were studied in a randomized block design with three replications. In Chapter II, in the first experiment, the experimental animals were lambs, while in the second were lactating ewes. The results indicated that the average daily gain (ADG) of lambs was higher (P<0.05) in the continuous method than in rotational grazing method, regardless of grazing intensity. The live weight gain per area (LWG) showed the same response in both experiments, with higher LWG values in moderate grazing intensity (P<0.05). In experiment I, higher dry matter intake (DMI) values were obtained under continuous grazing, while in experiment II, there no differences between methods and intensities. CH4 emissions per animal and per day did not differ between treatments in both experiments (P>0.05), but when expressed in g CH4 kg-1 LWG emissions were, on average, 15.33% higher (P<0.05) for rotational grazing method, regardless of grazing intensity. Methane emissions per animal were not affected by the treatments applied. However, from system point of view, the continuous grazing method is more efficient, since lower methane emissions per kg of LWG, regardless of grazing intensity, were obtained. In Chapter III, were used only lambs. The methodologies of n-alkanes and fecal nitrogen, were applied through total collection with dung bags. In relation to n-alkanes, better results were obtained when using the pair C31:C32. For the methodology of fecal nitrogen, the equations proposed by Wang et al. (2009) and Azevedo (2011) were the best (P<0.05). The technique of fecal nitrogen proved to be more accurate than the use of n-alkanes, which overestimated the intake.

O estudo foi realizado em área pertencente a Embrapa Pecuária Sul, Bagé, RS, com o objetivo de avaliar a emissão de metano, consumo a pasto, desempenho, e comportamento ingestivo de novilhos de corte em pastagem natural (CN), pastagem natural fertilizada com nitrogênio (CNA) e pastagem natural fertilizada com nitrogênio e sobressemeada com Lolium multiflorum e Trifolium pratense (CNM). O delineamento foi inteiramente casualizado com três repetições. Foram utilizados novilhos da raça Hereford em pastoreio contínuo com lotação variável para atingir oferta diária forragem de 12 kg MS 100 kg PV-1 (12% PV). Para o primeiro artigo, as avaliações foram feitas no verão, outono, inverno e primavera de 2013. As emissões de metano foram estimadas pela técnica do gás marcador hexafluoreto de enxofre. Para avaliação do consumo foi utilizada a técnica dos n-alcanos. Para o segundo artigo, avaliações com GPS foram feitas na primavera de 2013, outono e primavera de 2014. A localização e o deslocamento dos animais foram registrados, e avaliações visuais das atividades dos animais foram feitas a cada 10 minutos, do nascer ao pôr-do-sol, durante dois dias consecutivos em cada época. Os animais apresentaram bom desempenho ao longo do ano, com ganhos médios diários de 0,272, 0,467 e 0,514 kg para os tratamentos CN, CNA e CNM, respectivamente. As maiores emissões de metano foram durante a primavera. O CN apresentou maior quantidade de metano emitida por kg de ganho de peso (577,94, 337,69 e 387,18 g CH4 kg GPV-1 para o CN, CNA e CNM, respectivamente). Animais em CN passaram mais tempo em atividade de pastejo do que aqueles em CNA e CNM. Durante as épocas, menor atividade de pastejo foi na primavera de 2013 em comparação com outono de 2014 e primavera de 2014. Para as variáveis tempo em ruminação e em outras atividades não houve diferença nem para tratamentos nem para época de avaliação. Para o deslocamento, não houve diferença entre os tratamentos, entretanto houve efeito para as estações avaliadas, onde os animais caminharam menos no outono de 2014 comparado a primavera de 2013 e 2014. As estações do ano afetaram mais o consumo de MS e a emissão de metano que os níveis de intensificação. No entanto, considerando o desempenho dos animais, a inclusão de insumos permite menor emissão de metano por quilo de ganho de peso. / The study was conducted in an area of Embrapa Southern Region Animal Husbandry, Bagé, Rio Grande do Sul, Brazil, in order to assess the methane emission, forage intake, performance, and feeding behaviour of beef steers in natural grassland (NG), natural grassland fertilized with nitrogen (NGF) and natural grassland fertilized with nitrogen and oversown with exotic cool season species Lolium multiflorum and Trifolium pratense (NGFS). The design was completely randomized design with three replications. Hereford steers were used in continuous grazing with variable stocking rate to achieve daily supply of 12 kg DM 100 kg LW-1 (12% PV). For the first paper, evaluations were made in the summer, fall, winter and spring of 2013. Methane emissions were estimated by sulfur hexafluoride tracer gas technique. To evaluate the dry matter intake was used the n-alkanes technique. For the second paper, evaluations with GPS were made in spring 2013, fall and spring 2014. The location and the movement of animals have been recorded, and visual assessments of animal activities were made every 10 minutes, from sunrise to sunset, for two consecutive days in each season. Animals showed a good performance throughout the year, with average daily gain of 0.272, 0.467 and 0.514 kg for NG, NGF and NGFS treatments, respectively. The highest methane emissions were during spring. The NG presented a higher amount of methane emitted per kg of weight gain (577.94, 337.69 and 387.18 g CH4 kg BWG-1 to NG, NGF and NGFS, respectively). Animals in NG spent more time in grazing activity (71%) than those in NGF (63%) and NGFS (64%). During seasons, less grazing activity was in the spring of 2013 (62%) compared with fall 2014 (67%) and spring 2014 (68%). For the variables time ruminating and in other activities there was no difference either for treatments or for season. For displacement, there was no difference between treatments, however was effect on the seasons evaluated, where the animals walked less in the fall of 2014 compared to the spring of 2013 and 2014. The seasons affected more DM intake and methane emissions that intensification levels. However, considering the animals performance, the inclusion of inputs allows lower methane emissions per kilogram of weight gain.

O estudo foi realizado em área pertencente a Embrapa Pecuária Sul, Bagé, RS, com o objetivo de avaliar a emissão de metano, consumo a pasto, desempenho, e comportamento ingestivo de novilhos de corte em pastagem natural (CN), pastagem natural fertilizada com nitrogênio (CNA) e pastagem natural fertilizada com nitrogênio e sobressemeada com Lolium multiflorum e Trifolium pratense (CNM). O delineamento foi inteiramente casualizado com três repetições. Foram utilizados novilhos da raça Hereford em pastoreio contínuo com lotação variável para atingir oferta diária forragem de 12 kg MS 100 kg PV-1 (12% PV). Para o primeiro artigo, as avaliações foram feitas no verão, outono, inverno e primavera de 2013. As emissões de metano foram estimadas pela técnica do gás marcador hexafluoreto de enxofre. Para avaliação do consumo foi utilizada a técnica dos n-alcanos. Para o segundo artigo, avaliações com GPS foram feitas na primavera de 2013, outono e primavera de 2014. A localização e o deslocamento dos animais foram registrados, e avaliações visuais das atividades dos animais foram feitas a cada 10 minutos, do nascer ao pôr-do-sol, durante dois dias consecutivos em cada época. Os animais apresentaram bom desempenho ao longo do ano, com ganhos médios diários de 0,272, 0,467 e 0,514 kg para os tratamentos CN, CNA e CNM, respectivamente. As maiores emissões de metano foram durante a primavera. O CN apresentou maior quantidade de metano emitida por kg de ganho de peso (577,94, 337,69 e 387,18 g CH4 kg GPV-1 para o CN, CNA e CNM, respectivamente). Animais em CN passaram mais tempo em atividade de pastejo do que aqueles em CNA e CNM. Durante as épocas, menor atividade de pastejo foi na primavera de 2013 em comparação com outono de 2014 e primavera de 2014. Para as variáveis tempo em ruminação e em outras atividades não houve diferença nem para tratamentos nem para época de avaliação. Para o deslocamento, não houve diferença entre os tratamentos, entretanto houve efeito para as estações avaliadas, onde os animais caminharam menos no outono de 2014 comparado a primavera de 2013 e 2014. As estações do ano afetaram mais o consumo de MS e a emissão de metano que os níveis de intensificação. No entanto, considerando o desempenho dos animais, a inclusão de insumos permite menor emissão de metano por quilo de ganho de peso. / The study was conducted in an area of Embrapa Southern Region Animal Husbandry, Bagé, Rio Grande do Sul, Brazil, in order to assess the methane emission, forage intake, performance, and feeding behaviour of beef steers in natural grassland (NG), natural grassland fertilized with nitrogen (NGF) and natural grassland fertilized with nitrogen and oversown with exotic cool season species Lolium multiflorum and Trifolium pratense (NGFS). The design was completely randomized design with three replications. Hereford steers were used in continuous grazing with variable stocking rate to achieve daily supply of 12 kg DM 100 kg LW-1 (12% PV). For the first paper, evaluations were made in the summer, fall, winter and spring of 2013. Methane emissions were estimated by sulfur hexafluoride tracer gas technique. To evaluate the dry matter intake was used the n-alkanes technique. For the second paper, evaluations with GPS were made in spring 2013, fall and spring 2014. The location and the movement of animals have been recorded, and visual assessments of animal activities were made every 10 minutes, from sunrise to sunset, for two consecutive days in each season. Animals showed a good performance throughout the year, with average daily gain of 0.272, 0.467 and 0.514 kg for NG, NGF and NGFS treatments, respectively. The highest methane emissions were during spring. The NG presented a higher amount of methane emitted per kg of weight gain (577.94, 337.69 and 387.18 g CH4 kg BWG-1 to NG, NGF and NGFS, respectively). Animals in NG spent more time in grazing activity (71%) than those in NGF (63%) and NGFS (64%). During seasons, less grazing activity was in the spring of 2013 (62%) compared with fall 2014 (67%) and spring 2014 (68%). For the variables time ruminating and in other activities there was no difference either for treatments or for season. For displacement, there was no difference between treatments, however was effect on the seasons evaluated, where the animals walked less in the fall of 2014 compared to the spring of 2013 and 2014. The seasons affected more DM intake and methane emissions that intensification levels. However, considering the animals performance, the inclusion of inputs allows lower methane emissions per kilogram of weight gain.

Objetivou-se avaliar como diferentes estratégias de manejo do pasto de azevém anual interferem na produção animal, no consumo de forragem e na emissão de metano por ovinos em sistema de integração lavoura-pecuária (SILP) (Capítulo II). Já no Capítulo III objetivou-se avaliar as técnicas dos nalcanos e do nitrogênio fecal na estimativa do consumo de forragem por ovinos em pastos de azevém anual. Os experimentos foram conduzidos nos anos de 2011 e 2012 na Estação Experimental da UFRGS. Foram utilizados ovinos em um SILP de soja e milho no verão, em rotação com azevém anual no inverno. Para ambos os Capítulos (II e III) foram estudados dois métodos de pastoreio (contínuo e rotativo) e duas intensidades de pastejo (moderada e baixa; 2,5 e 5 vezes o potencial de consumo de matéria seca, respectivamente) em um delineamento de blocos casualizados com 3 repetições. Para o Capítulo II, no primeiro experimento os animais experimentais eram cordeiros, enquanto no segundo foram ovelhas em lactação. Os resultados indicaram que o ganho médio diário (GMD) dos cordeiros foi maior (P<0,05) no método de pastoreio continuo que no método de pastoreio rotativo, independente da intensidade de pastejo. O ganho de peso vivo por área (GPV) apresentou a mesma resposta em ambos os experimentos, com maior GPV na intensidade de pastejo moderada (P<0,05). No experimento 1, o consumo de matéria seca (CMS) foi maior para o método de pastoreio continuo, enquanto no experimento 2 não houve diferenças entre métodos e intensidades. As emissões de CH4 diárias por animal não diferiram entre tratamentos em ambos os experimentos (P>0,05), porém, quando expressas em g CH4 kg GPV-1 as emissões foram em média 15,33% maiores (P<0.05) para o método de pastoreio rotativo, independente da intensidade de pastejo. Os resultados afirmam que as emissões de metano por animal não são afetadas pelos tratamentos impostos. Porém, do ponto de vista de sistema o método de pastoreio contínuo o mais eficiente, por apresentar menor emissão de metano por kg de ganho de peso vivo, independente da intensidade de pastejo. Para o Capítulo III, foram utilizados apenas cordeiros. Utilizou-se a metodologia dos n-alcanos e do nitrogênio fecal, por meio de coleta total de fezes com o auxílio de bolsas coletoras. Na avaliação entre os n-alcanos, verificou-se melhores resultados quando utilizando o par C31:C32. Para a metodologia do nitrogênio fecal, as equações propostas por Wang et al. (2009) e por Azevedo (2011) foram as melhores (P<0,05). A técnica do nitrogênio fecal mostrou-se mais acurado do que o uso dos n-alcanos, que superestimou os valores de consumo. / The aim of this study was to evaluate how different management strategies of Italian ryegrass affects animal production, forage intake and methane emissions by sheep in integrated crop-livestock system (ICLS) (Chapter II). In Chapter III, we aimed to evaluate the techniques of n-alkanes and fecal nitrogen in estimating forage intake by sheep grazing on ryegrass. The experiments were conducted in 2011 and 2012 at the UFRGS Experimental Station. The ICLS soybeans and corn crops in summer, in rotation with grazed Italian ryegrass in winter. For both chapters (II and III) two stocking methods (continuous or rotational) and two grazing intensities (moderate and low, 2.5 and 5 times the potential dry matter intake, respectively) were studied in a randomized block design with three replications. In Chapter II, in the first experiment, the experimental animals were lambs, while in the second were lactating ewes. The results indicated that the average daily gain (ADG) of lambs was higher (P<0.05) in the continuous method than in rotational grazing method, regardless of grazing intensity. The live weight gain per area (LWG) showed the same response in both experiments, with higher LWG values in moderate grazing intensity (P<0.05). In experiment I, higher dry matter intake (DMI) values were obtained under continuous grazing, while in experiment II, there no differences between methods and intensities. CH4 emissions per animal and per day did not differ between treatments in both experiments (P>0.05), but when expressed in g CH4 kg-1 LWG emissions were, on average, 15.33% higher (P<0.05) for rotational grazing method, regardless of grazing intensity. Methane emissions per animal were not affected by the treatments applied. However, from system point of view, the continuous grazing method is more efficient, since lower methane emissions per kg of LWG, regardless of grazing intensity, were obtained. In Chapter III, were used only lambs. The methodologies of n-alkanes and fecal nitrogen, were applied through total collection with dung bags. In relation to n-alkanes, better results were obtained when using the pair C31:C32. For the methodology of fecal nitrogen, the equations proposed by Wang et al. (2009) and Azevedo (2011) were the best (P<0.05). The technique of fecal nitrogen proved to be more accurate than the use of n-alkanes, which overestimated the intake.

Le carbure de silicium (SiC) est un matériau léger possédant de nombreuses propriétés avantageuses : forte résistance mécanique, bonne conductivité et faible expansion thermiques, ainsi que chimiquement inerte sur une large gamme de températures. Ces caractéristiques font de lui un matériau de choix pour de nombreuses applications dans des conditions extrêmes, allant de la catalyse au gainage de combustible nucléaire de génération IV. Pour satisfaire aux spécificités de ces applications, le SiC se doit de posséder une surface spécifique élevée, et une porosité contrôlée.Nous avons étudié la faisabilité de la synthèse de SiC mésoporeux par une voie dite de « soft templating » utilisant des semifluoroalcanes (SFA) linéaires pour structurer un précurseur moléculaire du SiC, le 1,3,5-trisilacyclohexane (TSCH). En effet, la polymérisation du TSCH en polycarbosilane autour d’assemblages de SFA permet de structurer la matrice, puis de créer de la porosité lors du retrait du template. Le polycarbosilane est ensuite converti en SiC par un processus de calcination au cours duquel la porosité doit être conservée.Dans un premier temps, nous avons temps étudié les capacités d’auto assemblage des SFA dans le cyclohexane comme solvant modèle, puis dans le TSCH, par des techniques de diffusion des rayons X et des simulations des diagrammes de diffusion. Nous en avons appréhendé le comportement et déterminé les paramètres contrôlant la taille des objets. Nous avons ensuite réalisé la synthèse de SiC à partir du TSCH en présence de SFA.Les matériaux obtenus ne présentant pas les caractéristiques de surface spécifique et de porosité visées, nous avons élargi nos recherches à d’autres templates, dont un copolymère tribloc styrène-butadiène-styrène, qui a permis d’obtenir des SiC mésoporeux, amorphes ou cristallins, par une voie impliquant le greffage des précurseurs de SiC sur le copolymère. / Silicon carbide (SiC) is a light material with numerous interesting properties: strong mechanical resistance, weak thermal expansion, good heat conductivity and chemically inert on a large range of temperatures. These characteristics make SiC an appropriate material for various applications in extreme conditions, from catalyst to generation IV nuclear fuel cladding material. Nevertheless, to fulfill these application specificities, SiC has to show high specific surface area, and a controlled porosity.We have studied the possibility to synthetize mesoporous SiC by a soft templating approach using semifluorinated alkanes (SFA) to structure a SiC molecular precursor, the 1,3,5-trisilacyclohexane (TSCH). The TSCH polymerization into polycarbosilane around SFA aggregates can structure the matrix, that will create porosity after the template removal. Then polycarbosilane is converted into a SiC by a calcination process conserving the porosity.In a first time, we studied the self-aggregation capacities of SFA in cyclohexane as model solvent, and then in TSCH, by X-ray scattering techniques and simulations of scattering patterns. We discussed the behavior of SFA and determined the parameters controlling the size of the aggregates. Then, we proceeded to SiC synthesis from TSCH in presence of SFA.As resulting materials didn’t show the expected specific surface area and porosity characteristics, we enlarged our studies to other templates such as a triblock copolymer styrene-butadiene-styrene, which finally allowed us to obtain mesoporous SiC, amorphous or crystalline, by an approach involving the grafting of the SiC precursor onto the copolymer.

[pt] A avaliação do aporte continental de hidrocarbonetos para a zona costeira pelos corpos hídricos é de grande importância para melhor compreensão das características regionais quanto à ocupação do solo e do impacto que a urbanização exerce sobre um estuário. As distribuições de hidrocarbonetos alifáticos (n-C12 a n-C40) e hidrocarbonetos policíclicos aromáticos (46 HPAs) foram investigadas no material particulado em suspensão (MPS) e sedimentos ao longo de onze meses em seis dos principais rios e dois canais da bacia da Baía de Guanabara. O ΣHPAs variou de 27,59 a 11.514 ng L-1 no MPS e de 14,60 a 64.961 ng g-1 para as amostras de sedimento. Foram determinadas a taxa de exportação média dos rios dos rios e canais, indo de 0,03 t ano-1 observada para o rio Suruí a 1,87 t ano-1 observada para o rio Iguaçu; a contribuição de HPAs para o sedimento parte norte da baía na e as principais fontes de hidrocarbonetos. Avaliações de tipologia e estatísticas permitiram demonstrar a proporção da contribuição de fontes petrogênicas e pirolíticas nas diferentes regiões e quantificar estas contribuições. A taxa de exportação de HPAs dos cinco principais rios ao norte da baía equivale a 3 t ano-1, representando 30 porcento do aporte total anual de HPAs nesta área da Baía de Guanabara. O estudo geocronológico mostra a evolução histórica do aporte de HPAs apontando para a transição da predominância das fontes de combustão no passado para fontes petrogênicas nos anos recente e mostrou que dentre os NHPAs avaliados, apenas os compostos 2-nitrofluoranteno, 3-nitrofluoranteno e 7-nitrobenzo(a)antraceno foram observados na região noroeste enquanto 2-nitronaftaleno, 5-nitroacenafteno e 2-nitrofluoreno foram observados ao sul da baía, sugerindo a deposição preferencial de subprodutos de reações atmosféricas. Pela primeira vez foi estimada a massa de HPAs depositada ao longo do tempo no sedimento da Baía de Guanabara e realizado o estudo de NHPAs servindo como base para estudos futuros. / [en] The evaluation of the hydrocarbons continental input by end members is of great importance for a better understanding the regional characteristics in terms of land use and the impact that urbanization has on an estuary. Aliphatic (n-C12 to n-C40) and polycyclic aromatic hydrocarbons (46 PAH) were investigated in suspended particulate matter (SPM) and sediments for eleven months in six major rivers and two canals in the basin of Guanabara Bay. The ΣPAH ranged 27.59 to 11,514 ng L-1 for SPM and of 14.60 to 64,961 ng g-1 for the sediment samples. PAH flow rates of the most contaminated rivers and channels ranging of 0,03 t year-1 for Suruí river to 1,87 t year-1 to Iguaçu river; the contribution to the PAH sediment load of the receiving bay, and the main sources of hydrocarbons were determined. Typology and statistical evaluation demonstrated contribution of distinct sources in different regions and allowed quantification of these contributions. Total flow rate for the five major rivers to the bay north amounts to 3 tons year-1 and responds for 30 percent of the total PAH annual input into the northern area of the Guanabara Bay. Geochronological study shows the historical evolution of the PAH contribution pointing to the transition from the predominance of combustion sources in the past to petrogenic sources in recent years and showed that among the nitrated polycyclic aromatic hydrocarbons (NPAHs) evaluated only, 2-nitrofluoranthene, 3-nitrofluoranthene and 7-nitrobenzo(a)anthracene compounds were observed in the region NW while 2-nitronaphthalene, 5-nitroacenaphthene and 2-fluoranthene were observed south of the bay, suggesting preferential deposition of atmospheric reactions byproducts. For the first time PAH mass deposited in the bay sediments has been estimated and conducted the study about NPAHs shall serve as base for future studies.

Unspecific peroxygenase (EC 1.11.2.1) represents a group of secreted hemethiolate proteins that are capable of catalyzing the selective mono-oxygenation of diverse organic compounds using only H2O2 as a cosubstrate. In this study, the peroxygenase from Agrocybe aegerita (AaeUPO) was found to catalyze the hydroxylation of various linear (e.g n-hexane), branched (e.g. 2,3-dimethylbutane) and cyclic alkanes (e.g. cyclohexane). The size of n-alkane substrates converted by AaeUPO ranged from gaseous propane (C3) to n-hexadecane (C16). They were mono-hydroxylated mainly at the C2 and C3 position, rather than at the terminal carbon, and the corresponding ketones were formed as a result of overoxidation. In addition, a number of alkenes were epoxidized by AaeUPO, including linear terminal (e.g. 1-heptene), branched (2-methyl-2-butene) and cyclic alkenes (e.g. cyclopentene), as well as linear and cyclic dienes (buta-1,3-diene, cyclohexa-1,4-diene). Furthermore, the conversion of terminal alkynes (e.g. 1- octyne) gave the corresponding 1-alkyn-3-ol in low yield. Some of the reactions proceeded with complete regioselectivity and - in the case of linear alkanes, terminal linear alkenes and alkynes - with moderate to high stereoselectivity. The conversion of n-octane gave (R)-3-octanol with 99% enantiomeric excess (ee) and the preponderance of the (S)-enantiomer reached up to 72% ee of the epoxide product for the conversion of 1-heptene. Catalytic efficiencies (kcat/ Km) determined for the hydroxylation and respectively epoxidation of the model compounds cyclohexane and 2-methyl-2-butene were 2.0 × 103 M-1 s-1 and 2.5 × 105 M−1 s−1. The results obtained in the deuterium isotope effect experiment with semideuterated n-hexane and the radical clock experiment with norcarane clearly demonstrated that the hydroxylation of alkanes proceeds via hydrogen abstraction, the formation of a substrate radical and a subsequent oxygen rebound mechanism. Moreover, stopped-flow experiments and substrate kinetics proved the involvement of a porphyrin radical cation species (compound I; AaeUPO-I) as reactive intermediate in the catalytic cycle of AaeUPO, similar to other hemethiolate enzymes (e.g. cytochrome P450 monooxygenases, P450s). / Die Gruppe der Unspezifischen Peroxygenasen (EC 1.11.2.1) umfasst extrazelluläre Häm-Thiolat-Enzyme, die mittels H2O2 als Cosubstrat die selektive Monooxygenierung unterschiedlicher organischer Verbindungen katalysieren. In der vorliegenden Arbeit konnte gezeigt werden, dass die von Agrocybe aegerita sekretierte Peroxygenase (AaeUPO) verschiedene lineare (z. B. n-Hexan), verzweigte (z. B. 2,3-Dimethylbutan) und zyklische Alkane (z. B. Cyclohexan) hydroxyliert. Die Größe der von der AaeUPO umgesetzten Substrate reichte vom gasförmigen Propan (C3) bis hin zu n-Hexadekan (C16). Die Alkane wurden bevorzugt am zweiten und dritten Kohlenstoffatom (C2 und C3) hydroxyliert; eine Hydroxylierung am terminalen Kohlenstoff konnte nur vereinzelt und in geringem Umfang beobachtet werden. Die Überoxidationen der primär gebildeten, sekundären Alkohole führte außerdem zur Entstehung der entsprechenden Ketonderivate. Darüber hinaus wurde eine Vielzahl linearer terminaler (z. B. 1-Hepten), verzweigter (z. B. 2-Methyl-2-Buten) und zyklischer Alkene (z. B. Cyclopenten) sowie linearer und zyklischer Diene (1,3-Butadien, 1,4-Cyclohexadien) durch die AaeUPO epoxidiert. Die Umsetzung terminaler Alkine (z. B. 1-Octin) führte zur Entstehung der jeweiligen 1-Alkin-3-ole. Manche dieser Reaktionen verliefen ausgeprägt regioselektiv und, im Falle der linearen Alkane sowie der linearen terminalen Alkene und Alkine, mit mittlerer bis hoher Stereoselektivität. So ergab beispielsweise die Umsetzung von n-Octan einen Enantiomerenüberschuss größer 99% für (R)-3-Octanol; die Epoxidierung von 1-Hepten lieferte einen Enatiomeerenüberschuss (ee) von bis zu 72% für das (S)-Enantiomer. Die katalytischen Effizienzen, die für die Hydroxylierung bzw. Epoxidierung der Modellverbindungen Cyclohexan und 2-Methyl-2-Buten ermittelt wurden, betragen 2.0 × 103 M-1 s-1 und 2.5 × 105 M−1 s−1. Der ausgeprägte Deuterium-Isotopen-Effekt, der im Zuge der Umsetzung von semideuteriertem n-Hexan beobachtet wurde sowie die Ergebnisse des Radical-Clock-Experiments mit Norcarane als Substrat bestätigten, dass die Hydroxylierung von Alkanen über Wasserstoffabstraktion, die Bildung eines Substratradikals und anschließende direkte Sauerstoffrückbindung verläuft. Die Stopped-Flow-Experimente belegen zudem das Auftreten eines Porphyrin-Kationradikal-Intermediates (Compound I; AaeUPO-I) im katalytischen Zyklus der AaeUPO (vergleichbar mit dem reaktiven Intermediat der P450-Monooxygenasen).

No description available.

In this work the relationships between penetrant structure, its transport properties, and its effects on the mechanical properties of a polymer matrix were investigated. Although there is a vast amount of data on the diffusion of low molecular weight molecules into polymeric materials and on the mechanical properties of various polymer-penetrant systems, no attempts have been made to inter-relate the two properties with respect to the chemical structure of the diffusant. Therefore, two series of penetrants - n-alkanes and esters - were examined in this context, with the goal of correlating molecular size, shape, and chemical nature of the penetrant to its final transport and matrix mechanical properties. These correlations have been demonstrated to allow quantitative prediction of one property, given a reasonable set of data on the other parameters. A series of n-alkanes (C6-C17) and esters (C5-C17) have been used to separate the effects of penetrant size and shape, from those due to polymer-penetrant interactions, in the diffusion through a polyamide polymeric adhesive. These effects have been taken into account in order to yield a qualitative relationship that allows for prediction of diffusivity based upon penetrant structural information. Transport properties have been analyzed using mass uptake experiments as well as an in-situ FTIR-ATR technique to provide detailed kinetic as well as thermodynamic information on this process. The phenomenon of diffusion and its effects on the resulting dynamic mechanical response of a matrix polymeric adhesive have been studied in great detail using the method of reduced variables. The concept of a diffusion-time shift factor (log aDt) has been introduced to create doubly-reduced master curves, taking into account the effects of temperature and the variations in the polymer mechanical response due to the existence of a low molecular weight penetrant. / Ph. D.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Data on the process performance at different operating conditions are required to determine the feasibility of a separation process. Such data can be experimentally measured, but due to the time and costs associated with pilot plant scale experiments, the use of predictive process models are often preferred. The main aim of this project is to establish a working process model in Aspen Plus® that can be used to predict the separation performance of a supercritical fluid fractionation process aimed at the separation of mixtures of detergent range alkanes and alcohol isomers where similar boiling points or low relative volatilities can occur. Currently, an azeotropic distillation process is employed for the separation of detergent range alkanes and alcohols. Although this process shows good separation performance, some concerns regarding the operating conditions are raised: the preferred entrainer, diethylene glycol, is toxic to humans; very low operating pressures of 0.016 – 0.031 MPa and high temperatures of 473 K are required; additional processing units and materials are required to remove the entrainer from the product streams. An alternative process, supercritical fluid fractionation, is proposed in this work after previous studies have reported that this process have potential for the separation of alkanes and alcohols. The supercritical fluid fractionation process addresses the concerns of the azeotropic distillation process in the following ways: a non-toxic solvent, CO2, is used as the separating agent; mild temperatures of 344 K is proposed, but at the cost of the low operating pressures of the azeotropic process; and a single process unit and no additional material is required to separate the solvent from the product streams. A process model was developed in Aspen Plus® to evaluate the separation performance of the newly proposed supercritical fluid fractionation process and compare it to the current azeotropic distillation process. The development of the process model included the development of an accurate thermodynamic model in Aspen Plus®. After thorough evaluation of a number of cubic equations of state, the RK-ASPEN model was found to be superior in its representation and prediction of phase transition pressures for multi-component mixtures of detergent range alkanes and alcohols in the temperature range 318 – 348 K. Phase transition pressures could be predicted with an error of less than 6 % with the inclusion of regressed polar parameters and binary solute-solvent interaction parameters for two multi-component mixtures: CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) and CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol). Polar parameters were regressed from pure component vapour pressure data predicted with correlations available in Aspen Plus®. Binary interaction parameters were regressed from experimental bubble and dew point data. Binary bubble and dew point data were measured for a number of systems containing ethane or CO2 and a C10-alkane or C10-alcohol isomer at temperatures between 308 K and 353 K, and compositions ranging between 0.01 and 0.7 mass fraction solute. A comparison between the phase equilibrium data measured for these systems revealed that the structure of the molecule, and not only the molecular weight, influences its solubility in the supercritical solvent. The phase transition pressures of n-decane, 2-methylnonane, 3-methylnonane and 4-methylnonane did not differ significantly in CO2 or ethane, and these compounds will in all likelihood not be separated in a supercritical fluid fractionation process. The phase transition pressures measured for the C10-alcohol isomers decreased in both CO2 and ethane in the following order: 1-decanol, 3,7-dimethyl-1-octanol, 2-decanol, 2,6-dimethyl-2-octanol and 3,7-dimethyl-3-octanol. The position of the hydroxyl group and the number, length and position of the side branches, all influence the solubility behaviour and phase transition pressures of the isomeric alcohols in the supercritical solvent. Since the use of ethane did not show any significant benefits with regard to selectivity, the use of the less harmful and less expensive solvent, CO2, in further investigations was justified. The RK-ASPEN thermodynamic model, with the inclusion of the regressed polar and binary solute-solvent interaction parameters, was implemented in the process model and the separation performance of the process was simulated at different operating conditions for the CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) mixture. A comparison to experimental pilot plant data revealed that the model cannot be used to predict the separation performance at low fractionation temperatures (316 K) due to shortcomings in the thermodynamic model. However, the performance of the process at high fractionation temperatures (344 K) could be predicted well, with an error of 10 – 36 %. Simulations for the CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) mixtures showed that the composition of the feed mixture have a significant effect on the location and size of the operating window and optimum operating conditions. The optimum operating conditions were defined as the conditions where an acceptable selectivity ratio and alcohol recovery occurred simultaneously. Since the selectivity ratio and alcohol recovery have opposing optimization approaches, a number of possible optimum operating conditions exist, based on the product specifications. When an alcohol and an alkane with similar phase behaviour exist in a mixture, a distinct minimum selectivity ratio will occur at a point within the extract-to-feed ratio limits of the process. When the alkanes and alcohols present in a mixture do not have similar or overlapping phase transition pressures, the minimum selectivity ratio will typically cover a small range of extract-to-feed ratios at the high end limit of the extract-to-feed ratio range. To summarize: A process model was established in Aspen Plus® that can be used to determine the feasibility and separation performance of a supercritical fractionation process for a feed mixture of detergent range alkane and alcohol isomers. The model was used to prove that an SFF process is a feasible alternative process to consider for the removal of alkanes from mixtures of detergent range alcohol isomers, even where overlapping boiling points or low relative volatilities occur. During the development of the process model, the following significant novel contributions were made: · New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in supercritical ethane, as published in The Journal of Supercritical Fluids 58 (2011) 330 – 342. · New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in supercritical CO2, as published in The Journal of Supercritical Fluids 59 (2011) 14 – 26. · A thermodynamic model was developed in Aspen Plus® that can accurately predict the phase transition pressures of binary, ternary and multi-component mixtures of detergent range alkanes and alcohols in supercritical CO2, as published in The Journal of Supercritical Fluids 84 (2013) 132 – 145. · A process model was developed in Aspen Plus® that can be used to predict the separation performance of a supercritical fluid fractionation process for the separation of mixtures of detergent range alkanes and alcohols. · Experimental and simulated results indicated that a supercritical fluid fractionation process can be implemented successfully to separate an alkane from a mixture of alcohol isomers, as was shown for two mixtures: CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol). / AFRIKAANSE OPSOMMING: Data oor die omvang van skeiding by verskillende bedryfstoestande word benodig om die lewensvatbaarheid van ’n skeidingsproses te bepaal. Sulke data kan eksperimenteel gemeet word, maar as gevolg van die tyd en kostes geassosieer met eksperimente op loodsaanlegskaal, word die gebruik van prosesmodelle verkies. Die hoofdoel van hierdie projek is om ’n werkende prosesmodel, wat daarop gemik is om C8 – C20 alkane en alkohol isomere te skei, in Aspen Plus® tot stand te bring om die omvang van die skeiding van ’n superkritiese fraksioneringsproses te meet. Tans word azeotropiese distillasie gebruik vir die skeiding van C8 – C20 alkane en alkoholisomere. Alhoewel goeie skeiding met hierdie proses bewerkstellig word, is daar sekere eienskappe van die proses wat aandag vereis: die voorgestelde skeidingsagent, dietileen glikol, is giftig vir mense; baie lae bedryfsdrukke van 0.016 – 0.031 MPa en hoë temperature van 473 K word benodig; addisionele proseseenhede en materiaal is nodig om die skeidingsagent van die produkte te verwyder. Die gebruik van ’n alternatiewe proses - superkritiese fraksionering - word in hierdie werk voorgestel nadat vorige studies getoon het dat hierdie proses die potensiaal het om alkane en alkohole te skei. Die superkritiese fraksioneringsproses spreek al die kommerwekkende eienskappe van azeotropiese distillasie aan soos volg: ’n veilige oplosmiddel, CO2, word as die skeidingsagent gebruik; gemiddelde temperature van 344 K word voorgestel, maar ten koste van lae bedryfsdrukke; ’n enkele proseseenheid en geen addisionele materiaal word benodig om die oplosmiddel van die produkte te skei nie. ’n Prosesmodel is in Aspen Plus® ontwikkel om die omvang van die skeiding wat deur die voorgestelde superkritiese fraksioneringsproses teweeggebring is, te evalueer en te vergelyk met die azeotropiese distillasieproses wat tans in gebruik is. Die ontwikkeling van die prosesmodel sluit die ontwikkeling van ’n akkurate termodinamiese model in Aspen Plus® in. Na deeglike evaluasie van ’n aantal kubiese toestandsvergelykings is gevind dat die RK-ASPEN-model die faseoorgangsdrukke van multi-komponentmengsels van C8 – C20 alkane en alkohole die beste voorspel binne die temperatuurbereik van 318 – 348 K. Faseoorgangsdrukke kon voorspel word met ’n fout van minder as 6 % met die insluiting van voorafbepaalde polêre parameters en binêre interaksie-parameters vir twee multi-komponentmengsels: CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) and CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol). Polêre parameters is bepaal met dampdruk data, wat voorspel is met korrelasies in Aspen Plus®. Binêre interaksieparameters is van eksperimentele faseoorgangsdata bepaal. Binêre faseoorgangsdata is vir ’n aantal sisteme wat uit etaan of CO2 en ’n C10-alkaan- of C10-alkohol-isomeer bestaan, gemeet by temperature tussen 308 K en 353 K en samestellings van tussen 0.01 en 0.7 massafraksie van die opgeloste stof. ’n Vergelyking tussen die gemete fase-ewewigsdata het onthul dat die struktuur van die molekuul, en nie net die molekulêre massa nie, die oplosbaarheid van die stof in die superkritiese oplosmiddel beïnvloed. Die faseoorgangsdrukke van n-dekaan, 2-metielnonaan, 3-metielnonaan en 4-metielnonaan het geen skynbare verskille getoon in etaan of CO2 nie en dus sal hierdie stowwe in alle waarkynlikheid nie met ’n superkritiese fraksioneringsproses geskei kan word nie. Die faseoorgangsdrukke wat vir die C10-alkohol gemeet is, het in beide etaan en CO2 afgeneem in die volgende volgorde: 1-dekanol, 3,7-dimetiel-1-oktanol, 2-dekanol, 2,6-dimetiel-2-oktanol en 3,7-dimetiel-3-oktanol. Die posisie van die hidroksielgroep en die aantal, lengte en posisie van die sytakke beïnvloed die oplosbaarheidsgedrag van die alkohol-isomere in die superkritiese oplosmiddel. Aangesien die gebruik van etaan nie enige voordele ten opsigte van selektiwiteit inhou nie, is die gebruik van die minder skadelike en goedkoper oplosmiddel, CO2, vir verdere ondersoeke geregverdig. Die ontwikkelde termodinamiese model, met die insluiting van die polêre parameters en binêre interaksieparameters, is in die prosesmodel ingesluit en die omvang van die skeiding van die proses is gesimuleer by verskillende bedryfstoestande vir die CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) mengsel. ’n Vergelyking tussen die gesimuleerde data en die eksperimentele loodsaanlegdata het onthul dat die model nie die omvang van die skeiding kan voorspel by lae fraksioneringstemperature (316 K) nie as gevolg van die tekortkominge in die termodinamiese model. Die omvang van die skeiding by hoë temperature (344 K) kon egter goed voorspel word met ’n fout van 10 – 36 %. Simulasies van die CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) en CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) mengsels het getoon dat die samestelling van die voermengsel ’n beduidende effek op die grootte van die bedryfsvenster en optimum bedryfstoestande het. Die optimum bedryfstoestande word gedefinieer as die toestande waar ’n aanvaarbare selektiwiteitsverhouding en alkoholherwinning terselfdertyd voorkom. Aangesien die selektiwiteitsverhouding en alkoholherwinning teenstrydige optimeringsbenaderings het, bestaan daar ’n aantal optimum bedryfstoestande gebaseer op die produkspesifikasies. Wanneer ’n alkohol en ’n alkaan met ooreenstemmende fasegedrag saam in ’n mengsel voorkom, bestaan daar ’n duidelike minimum selektiwiteitsverhouding by ’n punt binne die ekstrak-tot-voer-verhoudingslimiete van die proses. Wanneer die alkane en alkohole in ’n mengsel nie ooreenstemmende fasegedrag toon nie, sal die minimum selektiwiteitsverhouding oor ’n reeks ekstrak-tot-voer-verhoudings voorkom, tipies by die hoë limiet van die ekstrak-tot-voer-verhoudingsreeks. Om op te som: ’n Prosesmodel is in Aspen Plus® tot stand gebring wat die lewensvatbaarheid en omvang van die moontlike skeiding van ’n superkritiese fraksioneringsproses vir voermengsels van C8 – C20 alkane en alkohol-isomere kan voorspel. Die model is gebruik om te bewys dat ’n superkritiese proses ’n lewensvatbare alternatiewe proses is om te oorweeg vir die verwydering van alkane uit mengsels van alkohol-isomere, self waar ooreenstemmende kookpunte of lae relatiewe vlugtigheid tussen komponente voorkom. Tydens die ontwikkeling van die prosesmodel is die volgende beduidende nuwe bydraes gemaak: · Nuwe fase-ewewigsdata is gemeet vir C10-alkaan- en C10-alkohol-isomere in superkritiese etaan, soos gepubliseer in The Journal of Supercritical Fluids 58 (2011) 330 – 342. · Nuwe fase-ewewigsdata is gemeet vir C10-alkaan and C10-alkohol isomere in superkritiese CO2, soos gepubliseer in The Journal of Supercritical Fluids 59 (2011) 14 – 26. · ’n Termodinamiese model is ontwikkel in Aspen Plus® wat die faseoorgangsdrukke van binêre, ternêre en multi-komponent mengsels van C8 – C20 alkane en alkohol-isomere in superkritiese CO2 akkuraat kan voorspel, soos gepubliseer in The Journal of Supercritical Fluids 84 (2013) 132 – 145. · ’n Prosesmodel is ontwikkel in Aspen Plus® wat die omvang van die moontlike skeiding van ’n superkritiese fraksioneringsproses, gemik op die skeiding van mengsels van C8 – C20 alkane en alkohol-isomere, kan voorspel. · Eksperimentele en gesimuleerde resultate toon aan dat ’n superkritiese fraksioneringsproses suksesvol geïmplementeer kan word vir die skeiding van ’n alkaan vanuit ’n mengsel van alkohol-isomere, soos bewys vir twee mengsels: CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) en CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol).