A pirólise rápida é uma tecnologia promissora para a conversão de biomassa. O principal produto desse processo é o bio-óleo, um líquido com elevada densidade energética, com potencialidades para a aplicação na produção de combustíveis e compostos renováveis. No entanto, existem ainda algumas barreiras para a sua utilização direta e um pós-processamento pode ser necessário. O uso de catalisadores no pós-processamento de bio-óleo, ou durante o processo de pirólise rápida, configura-se como alternativa para a produção direta de combustíveis e de produtos químicos com valor agregado, pois o processamento catalítico, além de elevar o rendimento, melhora a qualidade do bio-óleo produzido. O presente trabalho apresenta uma contribuição para o desenvolvimento do processo de pirólise rápida como uma rota viável de processamento de biomassas residuais, visando a obtenção de bio-óleo com propriedades adequadas a sua aplicação direta como combustível ou ainda para o fracionamento em produtos de interesse na indústria química. Este estudo compreende a síntese e avaliação do desempenho de diferentes catalisadores para o processo de pirólise rápida, bem como o projeto de uma unidade flexível para o processamento de biomassas através do processo de pirólise rápida catalítica. Catalisadores foram sintetizados através de diferentes metodologias e a sua atividade para a pirólise rápida foi avaliada através de ensaios utilizando moléculas representativas dos produtos da pirólise. O emprego de catalisadores a base de HZSM-5 modificada por metais permitiu, em alguns casos, o aumento na eficiência da reação de pirólise. A incorporação de zinco, gálio e nióbio resultou em aumento da atividade, elevando a produção de compostos aromáticos a partir da conversão catalítica de furanos. Os catalisadores de zinco apresentaram melhores resultados, possivelmente devido à maior incorporação do zinco nos sítios ácidos da zeólita, produzindo novos sítios capazes de elevar a taxa da reação de aromatização. Uma avaliação das alterações superficiais dos catalisadores permitiu correlacionar algumas propriedades do catalisador com sua atividade para a pirólise rápida e distribuição de produtos, permitindo também, em alguns casos, a identificação de possíveis rotas reacionais. As variáveis de processo, tais como temperatura de reação, velocidade espacial e presença de diferentes teores de água, simulando teores de água presentes em biomassas típicas, foram avaliadas. Verificou-se a importância da co-alimentação de água nos ensaios padrão para verificação da atividade de catalisadores para aplicação em pirólise rápida de biomassa. A água produz uma nova rota reacional na presença de HZSM-5 (reação de hidrólise), o que altera significativamente a distribuição de produtos da pirólise. / Fast pyrolysis is a promising technology for converting biomass into liquid fuels and chemicals. The main product of this process is bio-oil, a liquid with high energy density, which enables its use as a renewable source for the production of energy, fuels and chemicals. However, there are some barriers to its direct use as a fuel, and a post-processing may be needed. The use of catalysts for bio-oil upgrading or combined with the fast pyrolysis process is an alternative to the direct production of fuels, since the catalyst improves the quality and stability of bio-oil, as well as improving the pyrolysis yield. This work presents a contribution to the development of the fast pyrolysis process as a viable processing route for biomass conversion into fuels and chemicals. This study involves the synthesis and evaluation of different catalysts for the fast pyrolysis process, as well as the design of a flexible unit for the processing of biomass by catalytic fast pyrolysis. Catalysts were synthesized using different methods and their activity was evaluated by using furans as representative compounds of pyrolysis-derived products. Studies were conducted to identify catalysts with desirable properties for biofuel production. The incorporation of metals on HZSM-5 resulted in a promoting effect on catalytic conversion of furans. Zinc, niobium and gallium showed better activity than unmodified HZSM-5, increasing the aromatics production. Zinc catalysts presented the best result among samples, possibly due to a greater incorporation of zinc in the zeolite acid sites, producing new sites that are capable of increasing the rate of the aromatization reaction. An evaluation of the catalyst surface changes allowed the determination of the correlation between certain catalyst properties and their activity. It also allowed the identification of possible reaction pathways. Process variables such as reaction temperature, space velocity and water vapour pressure were also evaluated. The importance of water co-feeding in standard tests for catalysts activity evaluation was studied. Water produces a new reaction pathway in the presence of HZSM-5 (hydrolysis reaction), which significantly changes the distribution of pyrolysis products.

Made available in DSpace on 2014-12-17T14:08:49Z (GMT). No. of bitstreams: 1 AruzzaMMA_DISSERT.pdf: 1774693 bytes, checksum: a3fe2aad8bc5ee5d62f0d84e6a4733c6 (MD5) Previous issue date: 2011-07-01 / The use of biofuels remotes to the eighteenth century, when Rudolf Diesel made the first trials using peanut oil as fuel in a compression ignition engine. Based on these trials, there was the need for some chemical change to vegetable oil. Among these chemical transformations, we can mention the cracking and transesterification. This work aims at conducting a study using the thermocatalytic and thermal cracking of sunflower oil, using the Al-MCM-41 catalyst. The material type mesoporous Al-MCM-41 was synthesized and characterized by Hydrothermical methods of X-ray diffraction, scanning electron microscopy, nitrogen adsorption, absorption spectroscopy in the infrared and thermal gravimetric analysis (TG / DTG).The study was conducted on the thermogravimetric behavior of sunflower oil on the mesoporous catalyst cited. Activation energy, conversion, and oil degradation as a function of temperature were estimated based on the integral curves of thermogravimetric analysis and the kinetic method of Vyazovkin. The mesoporous material Al-MCM-41 showed one-dimensional hexagonal formation. The study of the kinetic behavior of sunflower oil with the catalyst showed a lower activation energy against the activation energy of pure sunflower oil. Two liquid fractions of sunflower oil were obtained, both in thermal and thermocatalytic pyrolisis. The first fraction obtained was called bio-oil and the second fraction obtained was called acid fraction. The acid fraction collected, in thermal and thermocatalytic pyrolisis, showed very high level of acidity, which is why it was called acid fraction. The first fraction was collected bio-called because it presented results in the range similar to petroleum diesel / O uso dos biocombust?veis remota ao s?culo XVIII, quando Rudolf Diesel realizou os primeiros ensaios utilizando o ?leo de amendoim como combust?vel em um motor de igni??o por compress?o. Com base nesses ensaios, constatou-se a necessidade de realizar algumas transforma??es qu?micas ao ?leo vegetal. Dentre essas transforma??es qu?micas, pode-se citar a transesterifica??o e o craqueamento. Este trabalho tem como objetivo, realizar um estudo utilizando-se o craqueamento t?rmico e termocatal?tico do ?leo de girassol, utilizando o Al-MCM-41 como catalisador. O material mesoporoso tipo Al-MCM-41 foi sintetizado hidrotermicamente e caracterizado pelos m?todos de difra??o de raios-X, microscopia eletr?nica de varredura, adsor??o de nitrog?nio, espectroscopia de absor??o na regi?o do infravermelho e an?lise termogravim?trica (TG/DTG). Ainda foi realizado o estudo do comportamento termogravim?trico do ?leo de girassol sobre o catalisador mesoporoso citado. Com base nas curvas integrais das an?lises termogravim?tricas e o m?todo cin?tico de Vyazovkin, foram estimados a energia de ativa??o, a convers?o e a degrada??o do ?leo em fun??o da temperatura. O material mesoporoso Al-MCM-41 apresentou forma??o hexagonal unidimensional. O estudo do comportamento cin?tico do ?leo de girassol com o catalisador mostrou uma menor energia de ativa??o frente ? energia de ativa??o do ?leo de girassol puro. Na pir?lise t?rmica e termocatal?tica do ?leo de girassol foram obtidas duas fra??es l?quidas. A primeira fra??o obtida foi denominada de bio?leo e a segunda fra??o obtida foi denominada de fra??o ?cida. A fra??o ?cida coletada tanto na pir?lise t?rmica como na termocatal?tica apresentou ?ndice de acidez muito elevado, raz?o pela qual foi denominada fra??o ?cida. A primeira fra??o coletada foi denominada de bio?leo porque apresentou resultados na faixa semelhante ao diesel de petr?leo

A pirólise rápida é uma tecnologia promissora para a conversão de biomassa. O principal produto desse processo é o bio-óleo, um líquido com elevada densidade energética, com potencialidades para a aplicação na produção de combustíveis e compostos renováveis. No entanto, existem ainda algumas barreiras para a sua utilização direta e um pós-processamento pode ser necessário. O uso de catalisadores no pós-processamento de bio-óleo, ou durante o processo de pirólise rápida, configura-se como alternativa para a produção direta de combustíveis e de produtos químicos com valor agregado, pois o processamento catalítico, além de elevar o rendimento, melhora a qualidade do bio-óleo produzido. O presente trabalho apresenta uma contribuição para o desenvolvimento do processo de pirólise rápida como uma rota viável de processamento de biomassas residuais, visando a obtenção de bio-óleo com propriedades adequadas a sua aplicação direta como combustível ou ainda para o fracionamento em produtos de interesse na indústria química. Este estudo compreende a síntese e avaliação do desempenho de diferentes catalisadores para o processo de pirólise rápida, bem como o projeto de uma unidade flexível para o processamento de biomassas através do processo de pirólise rápida catalítica. Catalisadores foram sintetizados através de diferentes metodologias e a sua atividade para a pirólise rápida foi avaliada através de ensaios utilizando moléculas representativas dos produtos da pirólise. O emprego de catalisadores a base de HZSM-5 modificada por metais permitiu, em alguns casos, o aumento na eficiência da reação de pirólise. A incorporação de zinco, gálio e nióbio resultou em aumento da atividade, elevando a produção de compostos aromáticos a partir da conversão catalítica de furanos. Os catalisadores de zinco apresentaram melhores resultados, possivelmente devido à maior incorporação do zinco nos sítios ácidos da zeólita, produzindo novos sítios capazes de elevar a taxa da reação de aromatização. Uma avaliação das alterações superficiais dos catalisadores permitiu correlacionar algumas propriedades do catalisador com sua atividade para a pirólise rápida e distribuição de produtos, permitindo também, em alguns casos, a identificação de possíveis rotas reacionais. As variáveis de processo, tais como temperatura de reação, velocidade espacial e presença de diferentes teores de água, simulando teores de água presentes em biomassas típicas, foram avaliadas. Verificou-se a importância da co-alimentação de água nos ensaios padrão para verificação da atividade de catalisadores para aplicação em pirólise rápida de biomassa. A água produz uma nova rota reacional na presença de HZSM-5 (reação de hidrólise), o que altera significativamente a distribuição de produtos da pirólise. / Fast pyrolysis is a promising technology for converting biomass into liquid fuels and chemicals. The main product of this process is bio-oil, a liquid with high energy density, which enables its use as a renewable source for the production of energy, fuels and chemicals. However, there are some barriers to its direct use as a fuel, and a post-processing may be needed. The use of catalysts for bio-oil upgrading or combined with the fast pyrolysis process is an alternative to the direct production of fuels, since the catalyst improves the quality and stability of bio-oil, as well as improving the pyrolysis yield. This work presents a contribution to the development of the fast pyrolysis process as a viable processing route for biomass conversion into fuels and chemicals. This study involves the synthesis and evaluation of different catalysts for the fast pyrolysis process, as well as the design of a flexible unit for the processing of biomass by catalytic fast pyrolysis. Catalysts were synthesized using different methods and their activity was evaluated by using furans as representative compounds of pyrolysis-derived products. Studies were conducted to identify catalysts with desirable properties for biofuel production. The incorporation of metals on HZSM-5 resulted in a promoting effect on catalytic conversion of furans. Zinc, niobium and gallium showed better activity than unmodified HZSM-5, increasing the aromatics production. Zinc catalysts presented the best result among samples, possibly due to a greater incorporation of zinc in the zeolite acid sites, producing new sites that are capable of increasing the rate of the aromatization reaction. An evaluation of the catalyst surface changes allowed the determination of the correlation between certain catalyst properties and their activity. It also allowed the identification of possible reaction pathways. Process variables such as reaction temperature, space velocity and water vapour pressure were also evaluated. The importance of water co-feeding in standard tests for catalysts activity evaluation was studied. Water produces a new reaction pathway in the presence of HZSM-5 (hydrolysis reaction), which significantly changes the distribution of pyrolysis products.

A pirólise rápida é uma tecnologia promissora para a conversão de biomassa. O principal produto desse processo é o bio-óleo, um líquido com elevada densidade energética, com potencialidades para a aplicação na produção de combustíveis e compostos renováveis. No entanto, existem ainda algumas barreiras para a sua utilização direta e um pós-processamento pode ser necessário. O uso de catalisadores no pós-processamento de bio-óleo, ou durante o processo de pirólise rápida, configura-se como alternativa para a produção direta de combustíveis e de produtos químicos com valor agregado, pois o processamento catalítico, além de elevar o rendimento, melhora a qualidade do bio-óleo produzido. O presente trabalho apresenta uma contribuição para o desenvolvimento do processo de pirólise rápida como uma rota viável de processamento de biomassas residuais, visando a obtenção de bio-óleo com propriedades adequadas a sua aplicação direta como combustível ou ainda para o fracionamento em produtos de interesse na indústria química. Este estudo compreende a síntese e avaliação do desempenho de diferentes catalisadores para o processo de pirólise rápida, bem como o projeto de uma unidade flexível para o processamento de biomassas através do processo de pirólise rápida catalítica. Catalisadores foram sintetizados através de diferentes metodologias e a sua atividade para a pirólise rápida foi avaliada através de ensaios utilizando moléculas representativas dos produtos da pirólise. O emprego de catalisadores a base de HZSM-5 modificada por metais permitiu, em alguns casos, o aumento na eficiência da reação de pirólise. A incorporação de zinco, gálio e nióbio resultou em aumento da atividade, elevando a produção de compostos aromáticos a partir da conversão catalítica de furanos. Os catalisadores de zinco apresentaram melhores resultados, possivelmente devido à maior incorporação do zinco nos sítios ácidos da zeólita, produzindo novos sítios capazes de elevar a taxa da reação de aromatização. Uma avaliação das alterações superficiais dos catalisadores permitiu correlacionar algumas propriedades do catalisador com sua atividade para a pirólise rápida e distribuição de produtos, permitindo também, em alguns casos, a identificação de possíveis rotas reacionais. As variáveis de processo, tais como temperatura de reação, velocidade espacial e presença de diferentes teores de água, simulando teores de água presentes em biomassas típicas, foram avaliadas. Verificou-se a importância da co-alimentação de água nos ensaios padrão para verificação da atividade de catalisadores para aplicação em pirólise rápida de biomassa. A água produz uma nova rota reacional na presença de HZSM-5 (reação de hidrólise), o que altera significativamente a distribuição de produtos da pirólise. / Fast pyrolysis is a promising technology for converting biomass into liquid fuels and chemicals. The main product of this process is bio-oil, a liquid with high energy density, which enables its use as a renewable source for the production of energy, fuels and chemicals. However, there are some barriers to its direct use as a fuel, and a post-processing may be needed. The use of catalysts for bio-oil upgrading or combined with the fast pyrolysis process is an alternative to the direct production of fuels, since the catalyst improves the quality and stability of bio-oil, as well as improving the pyrolysis yield. This work presents a contribution to the development of the fast pyrolysis process as a viable processing route for biomass conversion into fuels and chemicals. This study involves the synthesis and evaluation of different catalysts for the fast pyrolysis process, as well as the design of a flexible unit for the processing of biomass by catalytic fast pyrolysis. Catalysts were synthesized using different methods and their activity was evaluated by using furans as representative compounds of pyrolysis-derived products. Studies were conducted to identify catalysts with desirable properties for biofuel production. The incorporation of metals on HZSM-5 resulted in a promoting effect on catalytic conversion of furans. Zinc, niobium and gallium showed better activity than unmodified HZSM-5, increasing the aromatics production. Zinc catalysts presented the best result among samples, possibly due to a greater incorporation of zinc in the zeolite acid sites, producing new sites that are capable of increasing the rate of the aromatization reaction. An evaluation of the catalyst surface changes allowed the determination of the correlation between certain catalyst properties and their activity. It also allowed the identification of possible reaction pathways. Process variables such as reaction temperature, space velocity and water vapour pressure were also evaluated. The importance of water co-feeding in standard tests for catalysts activity evaluation was studied. Water produces a new reaction pathway in the presence of HZSM-5 (hydrolysis reaction), which significantly changes the distribution of pyrolysis products.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nowadays, one of the major challenges worldwide is the reduction of greenhouse gas emissions, whose contribution to climatic changes was comproved. The emissions of carbon dioxide from the burning of fossile fuels are the main factor that increases the global warming. Biodiesel is a biodegradable fuel derived from renewable sources that can be obtained by different processes such as pyrolysis, esterification or even transesterification. The pyrolysis reactions refer to the rupture of carbon-carbon binding in hydrocarbons molecules. This reaction is an endothermic process and, therefore, thermodynamically favored by high temperatures and low pressures. The present work has as objective to studiy the thermal and catalytic pyrolysis of soy oil, using acid mesoporosous heterogeneous catalysts (HAlMCM-41). The synthesis and characterization of AlMCM-41 and HAlMCM-41 was performed with different Si/Al ratios. The sample of AlMCM-41 was synthesized by hydrothermal method after that it was submitted to a process of ion exchange to generate the acidic form HAlMCM-41. The catalysts were characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). Based on the results obtained by infrared spectroscopy analysis, it was possible to indentify the main bands on the structure of AlMCM-41, demonstrating that the calcination method was promising in the elimination of the organic activating substituent. The results of X-ray diffraction showed that the AlMCM-41 was synthesized successfully and with high degree of hexagonal ordination to different Si/Al ratios. A comparative study between thermal pyrolysis and catalytic pyrolysis of refined soybean oil, over catalyst HAlMCM-41 synthesized with different Si/Al ratios, was carried out aiming to study the influence of this catalyst on the conversion rates and in the pyrolysis reaction s activation energy. The results show that mesoporosos catalysts were obtained and that the Si/Al rate of best catalytic activity was equal to 60. / Um dos principais desafios mundiais está relacionado à redução dos gases causadores do efeito estufa, cuja contribuição nas mudanças climáticas já foi comprovada. A emissão de dióxido de carbono proveniente da queima de combustíveis fósseis é o principal fator que contribui para o aumento do aquecimento global. O biodiesel é um combustível biodegradável derivado de fontes renováveis, que pode ser obtido por diferentes processos tais como a pirólise, a esterificação ou pela transesterificação. As reações de pirólise referem-se à ruptura da ligação carbono-carbono dos hidrocarbonetos mediante a ação de energia térmica. Essa reação constitui um processo endotérmico, sendo favorecida termodinamicamente por altas temperaturas e baixas pressões. O presente trabalho tem como objetivo estudar a pirólise convencional e catalítica de óleo de soja, utilizando catalisadores heterogêneos mesoporosos ácidos (HAlMCM-41). Foi realizada a síntese e caracterização do AlMCM-41 e HAlMCM-41 com diferentes razões de Si/Al. A amostra de AlMCM-41 foi sintetizada pelo método hidrotérmico, e em seguida, submetida a um processo de troca iônica para geração da forma ácida HAlMCM-41. Os catalisadores obtidos foram caracterizados por difração de raios-X (DRX) e espectroscopia na região do infravermelho (IV). Com base nos resultados obtidos na análise de espectroscopia na região do infravermelho, foi possível identificar as principais bandas relativas à estrutura do AlMCM-41, demonstrando que o método de calcinação foi promissor na eliminação do direcionador orgânico. Os resultados das análises de difração de raios-X mostraram que o AlMCM-41 foi sintetizado com sucesso e com alto grau de ordenação hexagonal nas diferentes razões Si/Al. Um estudo comparativo entre a pirólise convencional e a catalítica de óleo de soja refinado, sobre catalisador HAlMCM-41, foi realizado com o objetivo de estudar a influência desse catalisador nas taxas de conversão e na energia de ativação das reações de pirólise. Os resultados mostram que se obteve catalisadores mesoporosos e que a razão Si/Al de melhor atividade catalítica foi a de 60.

Biomass liquefaction by fast pyrolysis is considered to be a key technology in future biorefineries for the production of low-carbon renewable liquids. These liquids may be used as a fuel for heat and power, as an intermediate for catalytic upgrading to distillate transportation fuels (such as renewable diesel or biojet) and as a raw material for advanced bioproducts. With the estimated supply of bioenergy required to meet international GHG reduction targets, the use of high ash (mineral-containing) biomass sources, such as harvest residues, hog fuels, and other unmerchantable wood sources is also expected to increase. However, the elevated presence of suspended char particulate (solids), as well as minerals and other ash components contained in pyrolytic liquids resulting from the conversion of these lower quality biomass residues may create new challenges for end-users. In light of this, two treatment pathways were investigated in this work: biomass pretreatment through sieving and acid washing, and post-condensation microfiltration of fast pyrolysis bio-oils. Selection of these two pathways was prioritized based on scarcity of published data, as well as the technical potential of both approaches for suspended char particulate and ash reduction in fast pyrolysis bio-oils. For biomass sieving and acid washing carried out at pilot scale, it was found that removing up to 80% of the ash contained in a hog fuel feedstock was possible by sieving out a fraction of the fines and subsequently washing with 0.1M nitric acid provided up to 40% increase in organic liquid yield after fast pyrolysis. Reaction water in the product was minimized when acid leaching was performed, while the solids content and ash content of the produced liquids were reduced by up to 80% and 87%, respectively. Cross-flow microfiltration of fast pyrolysis bio-oils produced principally from non-pretreated mill and harvest residues in the 1-40 µm range was performed. Microfiltration was found to remove between 80-95% of suspended solid particles, while only removing 4-45% of ash, presumably in the solid phase. To achieve high ash removal (>90%), microfiltration was combined with use of solid-phase adsorbents, such as Amberlyst 15, to remove cationic ash elements such as magnesium, calcium, iron, etc. The flux profiles from bio-oil cross-flow microfiltration were analyzed and consistently demonstrated a transient rapid and intermediate decline operating region, followed by a pseudo steady-state operating region. It was found that the initial flux of permeate in the transient operating region ranged from 100-1000 L m-2 h-1, while the pseudo steady-state flux ranged from 20-50 L m-2 h-1 for the experimental trials included in this study. It was determined that bio-oil temperatures of 50-60 ˚C, transmembrane pressures less than 1 bar and the addition of diluent solvents provided the highest pseudo steady-state fluxes of such a process. To improve the throughput of the process, different fouling remediation strategies were experimentally evaluated. The use of permeate, solvent and air backflushing confirmed that on-line cleaning strategies are suitable for active flux remediation, as fouling was found to be reversible over continuous operating periods up to 10 hours. Furthermore, it was found that the use of non-optimized on-line air backflushing resulted in increased throughput of low solids fast pyrolysis bio-oil from cross-flow microfiltration by 100%. Ultimately, the data produced from this work is intended to be used to generate design parameters and associated cost estimates for biomass washing and post-condensation microfiltration as processing strategies to generate high quality bio-oils from low cost biomass feedstocks.

No description available.

La pyrolyse douce est un procédé prometteur et largement utilisé, mené à une température de 200 à 300 °C dans une atmosphère inerte afin de produire des matériaux durables (bois traité thermiquement) ou des combustibles solides (bois torréfié). Le but de cette étude est d’étudier les bois traités thermiquement dans un réacteur à l’échelle semi-industrielle pour une production durable de matériaux. Deux essences de bois européennes différentes, une essence de feuillus (peuplier, Populus nigra) et une essence de résineux (sapin, Abies pectinata), sont utilisées pour réaliser les expériences. La présente recherche est divisée en trois parties. Dans la première partie, le comportement thermique des planches de bois est étudié dans un réacteur à l’échelle semi-industrielle. Les expériences sont effectuées à 200-230 °C avec une vitesse de chauffe de 0.2 °C min-1 dans un environnement sous vide (200 hPa) pour intensifier la dégradation thermique. Quatre étapes différentes de dégradation thermique lors du traitement thermique du bois sont définies, en fonction de l'intensité de la perte de masse différentielle (DML). Les caractéristiques de dévolatilisation du bois traité sont évaluées à l'aide de l'indice de dévolatilisation (ID) basé sur les résultats de l'analyse immédiate. La corrélation de l'ID par rapport à la perte de masse des deux essences de bois est fortement caractérisée par une distribution linéaire, ce qui permet de fournir un outil simple et utile pour prédire la perte de masse du bois. Dans la seconde partie de l’étude, plusieurs analyses (spectroscopie infrarouge à transformée de Fourier, diffraction des rayons X, mesure du changement de couleur, teneur en humidité à l’équilibre et angle de contact) ont été réalisées. Les résultats obtenus démontrent clairement la dégradation thermique lors des réactions de déshydratation, de désacétylation, de dépolymérisation et de condensation au cours du traitement thermique. Les phénomènes de changement de couleur et de transformation hygroscopique observés sont illustrés et discutés en détail. La décarbonisation (DC), la déshydrogénation (DH) et la désoxygénation (DO) des bois traités sont également évaluées. Il s'avère que les trois indices peuvent être bien corrélés à la variation de couleur totale et à l'étendue de la réduction de l'hygroscopicité (HRE). Dans la dernière partie de l'étude, une modélisation cinétique du traitement thermique du bois est développée sur la base d’un schéma cinétique en deux étapes. La cinétique obtenue permet de prédire avec succès le rendement en solide de planches de bois lors du traitement dans un réacteur à l’échelle semi-industrielle. Dans le même temps, une prévision de la composition élémentaire est proposée. Celle-ci est basée sur les analyses élémentaires (ultimes) du bois non traité et du bois traité, ainsi que sur les rendements instantanés en solides. Les résultats indiquent que la prédiction des profils C, H et O est en bon accord avec les changements de composition attendus dans le matériau au cours du traitement. En résumé, les résultats obtenus et la cinétique établie sont propices à l’identification des mécanismes de dégradation thermique du bois et peuvent être utilisés pour le traitement thermique et la conception de réacteurs dans l'industrie afin de produire des matériaux bois adaptés à diverses applications. / Mild pyrolysis is a promising and widely applied process conducted at 200-300 °C in an inert condition to produce sustainable materials (i.e. heat treated wood) or solid fuel (i.e. torrefied wood). The aim of this study is to investigate the woods heat treated in a semi-industrial scale reactor for sustainable material production. Two different European wood species, a hardwood species (poplar, Populus nigra) and a softwood species (fir, Abies pectinata), are used to perform the experiments. The present research is divided into three parts. In the first part, the thermal behavior of wood boards is studied in a semi-industrial scale reactor. The experiments are carried out at 200-230 °C with a heating rate of 0.2 °C min-1 in a vacuum condition (200 hPa) to intensify the thermal degradation. Four different stages of thermal degradation during wood heat treatment are defined based on the intensity of differential mass loss (DML). The devolatilization characteristics of treated woods are evaluated by the devolatilization index (DI) based on the results of proximate analysis. The correlation of DI with respect to mass loss of the two wood species is strongly characterized by linear distribution, which is able to provide a simple tool to predict the mass loss of wood. In the second part of the study, a number of analyses, such as Fourier-transform infrared spectroscopy, X-ray diffraction, measurement of color change, equilibrium moisture content, and contact angle) are performed to evaluate the property changes of treated woods. The obtained results clearly demonstrate the thermal degradation through dehydration, deacetylation, depolymerization, and condensation reactions during the heat treatment. The observed phenomena of color change and hygroscopic transformation are illustrated and discussed in detail. The decarbonization, dehydrogenation, and deoxygenation of the treated woods are also evaluated. It is found that the three indexes can be well correlated to the total color difference and hygroscopicity reduction extent (HRE). In the last part of the study, the kinetic modeling of wood heat treatment is developed based on a two-step kinetic scheme. The obtained kinetics successfully predict dynamic solid yield of wood boards during the treatment in the semi-industrial reactor. Meanwhile, the prediction of elemental composition is also performed by a direct method based on the elemental analyses of untreated and treated woods at the end of the treatment, as well as the instantaneous solid yield. The results point out that the prediction of C, H, and O profiles are in good agreement with expected composition changes in the wood materials during treatment. In summary, the obtained results and established kinetics are conducive to recognizing the mechanisms of wood thermal degradation and can be used for heat treatment process and reactor design in industry to produce wood materials for various applications.

Mineral matter affect various coal properties as well as the yield and composition of products released during thermal processes. This necessitates investigation of the effect of the inherent minerals on the products derived during pyrolysis, as pyrolysis forms the basis of most coal utilisation processes. A real challenge in this research has been quantifying the changes seen and attributing these effects to specific minerals. Thus far it has been deemed impossible to predict product yields based on the mineral composition of the parent coal. Limited research regarding these aspects has been done on South African coal and the characterisation of pyrolysis products in previous studies was usually limited to one product phase. A novel approach was followed in this study and the challenges stated were effectively addressed. A vitrinite-rich South African coal from the Highveld coal field, was prepared to an undersize of 75 μm and divided into two fractions. HCl/HF acid washing reduced the ash yield from 14.0 wt% d.b. to 2.0 wt% d.b. (proximate analysis). Pyrolysis was carried out with the North-West University (NWU) Fischer Assay setup at 520, 750 and 900°C under N2 atmosphere and atmospheric pressure. The effect of acid washing and the addition of minerals on the derived pyrolysis products were evaluated. Acid washing led to lower water and tar yields, whilst the gas yields increased, and the char yields were unaffected. The higher gas yield can be related to increased porosity after mineral removal as revealed by Brunauer-Emmett-Teller (BET) CO2 adsorption surface area analysis of the derived chars. Gas chromatography (GC) analyses of the derived pyrolysis gases indicated that the acid washed coal fraction (AW TWD) derived gas contained higher yields of H2, CH4, CO2, C2H4, C2H6, C3H4, C3H6 and C4s when compared to the gas derived from the raw coal fraction (TWD). The CO yield from the TWD coal was higher at all final pyrolysis temperatures. Differences in gas yields were related to increased tar cracking as well as lower hydrogen transfer and de-hydrogenation of the acid washed chars. Analyses of the tar fraction by means of simulated distillation (Simdis), gas chromatography mass spectrometry (GC-MS) –flame ionization detection (–FID) and size exclusion chromatography with ultraviolet (SEC-UV) analyses, indicated that the AW TWD derived tars were more aromatic in nature, containing more heavier boiling point components, which increased with increasing final pyrolysis temperature. The chars were characterised by proximate, ultimate, X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance infrared Fourier-transform (DRIFT) and BET CO2 analyses. Addition of either 5 wt% calcite, dolomite, kaolinite, pyrite or quartz to the acid washed fraction (AW TWD) was done in order to determine the effect of these minerals on the pyrolysis products. These minerals were identified as the most prominent mineral phases in the Highveld coal used in this study, by XRD and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) analyses. It was found that mineral activity decreased in the order calcite/dolomite>pyrite>kaolinite>>>quartz. Calcite and dolomite addition led to a decrease in tar yield, whilst the gas yields were increased. Markedly, increased water yields were also observed with the addition of calcite, dolomite and pyrite. Kaolinite addition led to increased tar, char and gas yields at 520°C, whilst the tar yield decreased at 750°C. Pyrite addition led to decreased tar and gas yields. Quartz addition had no noteworthy effect on pyrolysis yields and composition, except for a decrease in char yield at all final pyrolysis temperatures and an increased gas yield at 520°C. Regarding the composition of the pyrolysis products, the various minerals had adverse effects. Calcite and dolomite affected the composition of the gas, tar and char phases most significantly, showing definite catalytic activity. Tar producers should take note as presence of these minerals in the coal feedstock could have a significant effect on the tar yield and composition. Kaolinite and pyrite showed some catalytic activity under specific conditions. Model coal-mineral mixtures confirmed synergism between coal-mineral and mineral-mineral interactions. Although some correlation between the pyrolysis products derived from the model coal-mineral mixtures and that of TWD coal was observed, it was not possible to entirely mimic the behaviour of the coal prior to acid washing. Linear regression models were developed to predict the gas, tar and char yields (d.m.m.f.) with mineral composition and pyrolysis temperature as variables, resulting in R2 coefficients of 0.837, 0.785 and 0.846, respectively. Models for the prediction of H2, CO, CO2 and CH4 yields with mineral composition and pyrolysis temperature as variables resulting in R2 coefficients of 0.917, 0.702, 0.869 and 0.978, respectively. These models will serve as foundation for future work, and prove that it is feasible to develop models to predict pyrolysis yields based on mineral composition. Extending the study to coals of different rank can make the models universally applicable and deliver a valuable contribution in industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Mineral matter affect various coal properties as well as the yield and composition of products released during thermal processes. This necessitates investigation of the effect of the inherent minerals on the products derived during pyrolysis, as pyrolysis forms the basis of most coal utilisation processes. A real challenge in this research has been quantifying the changes seen and attributing these effects to specific minerals. Thus far it has been deemed impossible to predict product yields based on the mineral composition of the parent coal. Limited research regarding these aspects has been done on South African coal and the characterisation of pyrolysis products in previous studies was usually limited to one product phase. A novel approach was followed in this study and the challenges stated were effectively addressed. A vitrinite-rich South African coal from the Highveld coal field, was prepared to an undersize of 75 μm and divided into two fractions. HCl/HF acid washing reduced the ash yield from 14.0 wt% d.b. to 2.0 wt% d.b. (proximate analysis). Pyrolysis was carried out with the North-West University (NWU) Fischer Assay setup at 520, 750 and 900°C under N2 atmosphere and atmospheric pressure. The effect of acid washing and the addition of minerals on the derived pyrolysis products were evaluated. Acid washing led to lower water and tar yields, whilst the gas yields increased, and the char yields were unaffected. The higher gas yield can be related to increased porosity after mineral removal as revealed by Brunauer-Emmett-Teller (BET) CO2 adsorption surface area analysis of the derived chars. Gas chromatography (GC) analyses of the derived pyrolysis gases indicated that the acid washed coal fraction (AW TWD) derived gas contained higher yields of H2, CH4, CO2, C2H4, C2H6, C3H4, C3H6 and C4s when compared to the gas derived from the raw coal fraction (TWD). The CO yield from the TWD coal was higher at all final pyrolysis temperatures. Differences in gas yields were related to increased tar cracking as well as lower hydrogen transfer and de-hydrogenation of the acid washed chars. Analyses of the tar fraction by means of simulated distillation (Simdis), gas chromatography mass spectrometry (GC-MS) –flame ionization detection (–FID) and size exclusion chromatography with ultraviolet (SEC-UV) analyses, indicated that the AW TWD derived tars were more aromatic in nature, containing more heavier boiling point components, which increased with increasing final pyrolysis temperature. The chars were characterised by proximate, ultimate, X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance infrared Fourier-transform (DRIFT) and BET CO2 analyses. Addition of either 5 wt% calcite, dolomite, kaolinite, pyrite or quartz to the acid washed fraction (AW TWD) was done in order to determine the effect of these minerals on the pyrolysis products. These minerals were identified as the most prominent mineral phases in the Highveld coal used in this study, by XRD and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) analyses. It was found that mineral activity decreased in the order calcite/dolomite>pyrite>kaolinite>>>quartz. Calcite and dolomite addition led to a decrease in tar yield, whilst the gas yields were increased. Markedly, increased water yields were also observed with the addition of calcite, dolomite and pyrite. Kaolinite addition led to increased tar, char and gas yields at 520°C, whilst the tar yield decreased at 750°C. Pyrite addition led to decreased tar and gas yields. Quartz addition had no noteworthy effect on pyrolysis yields and composition, except for a decrease in char yield at all final pyrolysis temperatures and an increased gas yield at 520°C. Regarding the composition of the pyrolysis products, the various minerals had adverse effects. Calcite and dolomite affected the composition of the gas, tar and char phases most significantly, showing definite catalytic activity. Tar producers should take note as presence of these minerals in the coal feedstock could have a significant effect on the tar yield and composition. Kaolinite and pyrite showed some catalytic activity under specific conditions. Model coal-mineral mixtures confirmed synergism between coal-mineral and mineral-mineral interactions. Although some correlation between the pyrolysis products derived from the model coal-mineral mixtures and that of TWD coal was observed, it was not possible to entirely mimic the behaviour of the coal prior to acid washing. Linear regression models were developed to predict the gas, tar and char yields (d.m.m.f.) with mineral composition and pyrolysis temperature as variables, resulting in R2 coefficients of 0.837, 0.785 and 0.846, respectively. Models for the prediction of H2, CO, CO2 and CH4 yields with mineral composition and pyrolysis temperature as variables resulting in R2 coefficients of 0.917, 0.702, 0.869 and 0.978, respectively. These models will serve as foundation for future work, and prove that it is feasible to develop models to predict pyrolysis yields based on mineral composition. Extending the study to coals of different rank can make the models universally applicable and deliver a valuable contribution in industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015