Assessing the effect of reducing agents on the selective catalytic reduction of NOx over Ag/Al2O3 catalysts

The selective catalytic reduction (SCR) of NOx in the presence of different reducing agents over Ag/Al2O3 prepared by wet impregnation was investigated by probing catalyst activity and using NMR relaxation time analysis to probe the strength of surface interaction of the various reducing agent species and water. The results reveal that the strength of surface interaction of the reducing agent relative to water, the latter present in engine exhausts as a fuel combustion product and, in addition, produced during the SCR reaction, plays an important role in determining catalyst performance. Reducing agents with weak strength of interaction with the catalyst surface, such as hydrocarbons, show poorer catalytic performance than reducing agents with a higher strength of interaction, such as alcohols. This is attributed to the greater ability of oxygenated species to compete with water in terms of surface interaction with the catalyst surface, hence reducing the inhibiting effect of water molecules blocking catalyst sites. The results support the observations of earlier work in that the light off-temperature and maximum NOx conversion and temperature at which that occurs are sensitive to the reducing agent present during reaction, and the proposal that improved catalyst performance is caused by increased adsorption strength of the reducing agent, relative to water, at the catalyst surface. Importantly, the NMR relaxation time analysis approach to characterising the strength of adsorption more readily describes the trends in catalytic behaviour than does a straightforward consideration of the polarity (i.e., relative permittivity) of the reducing agents studied here. In summary, this paper describes a simple approach to characterising the interaction energy of water and reducing agent so as to aid the selection of reducing agent and catalyst to be used in SCR conversions.

Cinética da transferência de calor em materiais com mudança de fase

É extensa a bibliografia dedicada a potenciais aplicações de materiais com mudança de fase na regulação térmica e no armazenamento de calor ou de frio. No entanto, a baixa condutividade térmica impõe limitações numa grande diversidade de aplicações com exigências críticas em termos de tempo de resposta curto ou com requisitos de elevada potência em ciclos de carga/descarga de calor latente. Foram desenvolvidos códigos numéricos no sentido de obter soluções precisas para descrever a cinética da transferência de calor com mudança de fase, com base em geometrias representativas, i.e. planar e esférica. Foram igualmente propostas soluções aproximadas, sendo identificados correspondentes critérios de validação em função das propriedades dos materiais de mudança de fase e de outros parâmetros relevantes tais como as escalas de tamanho e de tempo, etc. As referidas soluções permitiram identificar com rigor os fatores determinantes daquelas limitações, quantificar os correspondentes efeitos e estabelecer critérios de qualidade adequados para diferentes tipologias de potenciais aplicações. Os referidos critérios foram sistematizados de acordo com metodologias de seleção propostas por Ashby e co-autores, tendo em vista o melhor desempenho dos materiais em aplicações representativas, designadamente com requisitos ao nível de densidade energética, tempo de resposta, potência de carga/descarga e gama de temperaturas de operação. Nesta sistematização foram incluídos alguns dos compósitos desenvolvidos durante o presente trabalho. A avaliação das limitações acima mencionadas deu origem ao desenvolvimento de materiais compósitos para acumulação de calor ou frio, com acentuada melhoria de resposta térmica, mediante incorporação de uma fase com condutividade térmica muito superior à da matriz. Para este efeito, foram desenvolvidos modelos para otimizar a distribuição espacial da fase condutora, de modo a superar os limites de percolação previstos por modelos clássicos de condução em compósitos com distribuição aleatória, visando melhorias de desempenho térmico com reduzidas frações de fase condutora e garantindo que a densidade energética não é significativamente afetada. Os modelos elaborados correspondem a compósitos de tipo core-shell, baseados em microestruturas celulares da fase de elevada condutividade térmica, impregnadas com o material de mudança de fase propriamente dito. Além de visarem a minimização da fração de fase condutora e correspondentes custos, os modelos de compósitos propostos tiveram em conta a adequação a métodos de processamento versáteis, reprodutíveis, preferencialmente com base na emulsificação de líquidos orgânicos em suspensões aquosas ou outros processos de reduzidas complexidade e com base em materiais de baixo custo (material de mudança de fase e fase condutora). O design da distribuição microestrutural também considerou a possibilidade de orientação preferencial de fases condutoras com elevada anisotropia (p.e. grafite), mediante auto-organização. Outros estágios do projeto foram subordinados a esses objetivos de desenvolvimento de compósitos com resposta térmica otimizada, em conformidade com previsões dos modelos de compósitos de tipo core-shell, acima mencionadas. Neste enquadramento, foram preparados 3 tipos de compósitos com organização celular da fase condutora, com as seguintes características e metodologias: i) compósitos celulares parafina-grafite para acumulação de calor, preparados in-situ por emulsificação de uma suspensão de grafite em parafina fundida; ii) compósitos celulares parafina-Al2O3 para acumulação de calor, preparados por impregnação de parafina em esqueleto cerâmico celular de Al2O3; iii) compósitos celulares para acumulação de frio, obtidos mediante impregnação de matrizes celulares de grafite com solução de colagénio, após preparação prévia das matrizes de grafite celular. Os compósitos com esqueleto cerâmico (ii) requereram o desenvolvimento prévio de um método para o seu processamento, baseado na emulsificação de suspensões de Al2O3 em parafina fundida, com adequados aditivos dispersantes, tensioactivos e consolidantes do esqueleto cerâmico, tornando-o auto-suportável durante as fases posteriores de eliminação da parafina, até à queima a alta temperatura, originando cerâmicos celulares com adequada resistência mecânica. Os compósitos desenvolvidos apresentam melhorias significativos de condutividade térmica, atingindo ganhos superiores a 1 ordem de grandeza com frações de fase condutora inferior a 10 % vol. (4 W m-1 K-1), em virtude da organização core-shell e com o contributo adicional da anisotropia da grafite, mediante orientação preferencial. Foram ainda preparados compósitos de armazenamento de frio (iii), com orientação aleatória da fase condutora, obtidos mediante gelificação de suspensões de partículas de grafite em solução aquosa de colagénio. Apesar da estabilidade microestrutural e de forma, conferida por gelificação, estes compósitos confirmaram a esperada limitação dos compósitos com distribuição aleatória, em confronto com os ganhos alcançados com a organização de tipo core-shell.

Macrofauna spatial differences within clam dredge-tracks and their implications for short-term fishing effect studies

In situ observations of clam dredging showed that the effects of the dredge on the benthic macrofauna may not be constant during a tow. A sand buffer forms in front of the gear approximately 10m after the beginning of a tow, and this pushes the sediment partially aside.In this study, we analyse differences in abundance, the number of taxa present, diversity, and evenness within sections of dredge-tracks in a disturbed, fished area and a non-fished area along the southern coast of Portugal. These areas were sampled by divers before and after dredge-fishing activity. At each site, three dredge-tracks were produced. These tracks were divided in three longitudinal sections 1start, middle and end) and two transverse sections 1track and edge). Six quadrats were used to sample macrofauna in each section of every track and edge. Our results show differences exist in macro- faunal distribution and abundance across sections of a dredge-track. These differences should be considered in any assessment of the short-term ecological impact of dredges on benthic macrofauna

Nanoporous carbons from sisal residues and their application in hybrid TiO2/carbon photocatalysts for the removal and degradation of phenol in solution

Tese de doutoramento, Química (Química Tecnológica), Universidade de Lisboa, Faculdade de Ciências, 2016

Laccase-assisted bio-grafting of polyhydroxy-alkanoates (PHAs) onto the ethyl cellulose (EC) backbone

In the present study, a novel enzyme-based methodology for grafting Polyhydroxyalkanoates (PHAs) onto the ethyl cellulose (EC) as a backbone polymer was developed. Laccase assisted copolymerization was carried out under mild and eco-friendly reaction conditions. The resulting homogeneous composite membranes were characterized by Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Atomic Force Microscopy (AFM). The FTIR spectra of pure PHAs and PHAs containing graft composites (PHAs-g-EC) showed their strong characteristic bands at 1721 cm1, 1651 cm-1 and 1603 cm-1 respectively. Other accompanying bands in the range of 900-1300 cm-1 correspond to C=O vibration and C-O-C bond stretching, which could be contributed from PHAs and EC, respectively. The high intensity of the 3358 cm-1 band in the graft composite may have corresponded to the degradation of the carboxylic group from PHAs and also showed an increase of hydrogen-bonded groups at that distinct band region. The morphology was examined by SEM, which showed the well dispersed PHAs crystals in the backbone polymer of EC. XRD pattern for PHAs showed distinct peaks at 2-Theta values of 28o, 32o, 34o, 39o, 46o, 57o, 64o, 78o and 84o that represent the crystalline nature of PHAs. In comparison with those of neat PHAs, the degree of crystallinity for PHAs-g-EC decreased and this reduction is mainly because of the new cross-linking of PHAs within the EC backbone that changes the morphology and destroys the crystallites. Improved mechanical properties were observed for the PHAs-g-EC as compared to the individual components due to the impregnation of EC as reinforcement into the PHAs matrix. Improved mechanical strength enhanced thermal properties, along with low crystallinity of the present PHAs-g-EC suggesting its potential for various industrial and bio-medical applications.

Otimização Energética do Sistema de Refrigeração da máquina de impregnar ZELL

Esta dissertação teve como objetivo fundamental a otimização energética do sistema de refrigeração da máquina de impregnar tela ZELL e, como objetivo adicional, a avaliação da qualidade da água do circuito, justificada pela acentuada degradação dos rolos devido à corrosão provocada pela recirculação da água de arrefecimento. Inicialmente fez-se o levantamento de informações do processo produtivo para caracterizar o funcionamento do sistema de refrigeração, tendo-se selecionado duas telas de poliéster designadas neste estudo por P1 e P2 e, também, uma tela de nylon designada por N. Foram efetuados ensaios, um para cada tela, para a atual temperatura de setpoint da água à saída da torre de arrefecimento (30ºC). Realizou-se outro ensaio para a tela N mas com uma temperatura de setpoint de 37ºC, ao qual se chamou N37. Deste modo, determinou-se as potências térmicas removidas pela água de refrigeração e as potências térmicas perdidas por radiação e por convecção, tendo-se verificado que na generalidade dos rolos as referências P1 e P2 apresentam valores mais elevados. Em termos percentuais, a potência térmica removida pela água de refrigeração nos grupos tratores 1 e 3 e no conjunto de rolos de R1 a R29 corresponde a 48%, 10% e 70%, respetivamente. Com a avaliação às necessidades de arrefecimento da máquina ZELL, confirmou-se que os caudais atuais de refrigeração dos rolos garantem condições, mais que suficientes, de funcionamento dos rolamentos. Assim sendo, fez-se uma análise no sentido da diminuição do caudal total que passou de 10,25 L/s para 7,65 L/s. Considerando esta redução, determinou-se o caudal de ar húmido a ser introduzido na torre de arrefecimento. O valor determinado foi de 4,6 m3ar húmido/s, o que corresponde a uma redução de cerca de 32% em relação ao caudal atual que é de 6,8 m3ar húmido/s. Com os resultados das análises efetuadas à água do circuito de refrigeração, concluiu-se que a água de reposição e a água de recirculação possuem má qualidade para uso na generalidade dos sistemas de refrigeração, principalmente devido aos elevados valores de concentração de ferro e condutividade elétrica, responsáveis pela intensificação da corrosão no interior dos rolos.

Engineering bio-based polymers using alternative solvents and processes

The work presented in this thesis explores novel routes for the processing of bio-based polymers, developing a sustainable approach based on the use of alternative solvents such as supercritical carbon dioxide (scCO2), ionic liquids (ILs) and deep eutectic solvents (DES). The feasibility to produce polymeric foams via supercritical fluid (SCF) foaming, combined with these solvents was assessed, in order to replace conventional foaming techniques that use toxic and harmful solvents. A polymer processing methodology is presented, based on SCF foaming and using scCO2 as a foaming agent. The SCF foaming of different starch based polymeric blends was performed, namely starch/poly(lactic acid) (SPLA) and starch/poly(ε-caprolactone) (SPCL). The foaming process is based on the fact that CO2 molecules can dissolve in the polymer, changing their mechanical properties and after suitable depressurization, are able to create a foamed (porous) material. In these polymer blends, CO2 presents limited solubility and in order to enhance the foaming effect, two different imidazolium based ILs (IBILs) were combined with this process, by doping the blends with IL. The use of ILs proved useful and improved the foaming effect in these starch-based polymer blends. Infrared spectroscopy (FTIR-ATR) proved the existence of interactions between the polymer blend SPLA and ILs, which in turn diminish the forces that hold the polymeric structure. This is directly related with the ability of ILs to dissolve more CO2. This is also clear from the sorption experiments results, where the obtained apparent sorption coefficients in presence of IL are higher compared to the ones of the blend SPLA without IL. The doping of SPCL with ILs was also performed. The foaming of the blend was achieved and resulted in porous materials with conductivity values close to the ones of pure ILs. This can open doors to applications as self-supported conductive materials. A different type of solvents were also used in the previously presented processing method. If different applications of the bio-based polymers are envisaged, replacing ILs must be considered, especially due to the poor sustainability of some ILs and the fact that there is not a well-established toxicity profile. In this work natural DES – NADES – were the solvents of choice. They present some advantages relatively to ILs since they are easy to produce, cheaper, biodegradable and often biocompatible, mainly due to the fact that they are composed of primary metabolites such as sugars, carboxylic acids and amino-acids. NADES were prepared and their physicochemical properties were assessed, namely the thermal behavior, conductivity, density, viscosity and polarity. With this study, it became clear that these properties can vary with the composition of NADES, as well as with their initial water content. The use of NADES in the SCF foaming of SPCL, acting as foaming agent, was also performed and proved successful. The SPCL structure obtained after SCF foaming presented enhanced characteristics (such as porosity) when compared with the ones obtained using ILs as foaming enhancers. DES constituted by therapeutic compounds (THEDES) were also prepared. The combination of choline chloride-mandelic acid, and menthol-ibuprofen, resulted in THEDES with thermal behavior very distinct from the one of their components. The foaming of SPCL with THEDES was successful, and the impregnation of THEDES in SPCL matrices via SCF foaming was successful, and a controlled release system was obtained in the case of menthol-ibuprofen THEDES.

Second Welland Canal - Book 1, Survey Map 4 - Through Grantham Township

Survey map of the Second Welland Canal created by the Welland Canal Company showing a portion of the Grantham Township. Identified structures associated with the Canal include the floating tow path and the canal itself. The surveyors' measurements and notes can be seen in red and black ink and pencil. Features of the First Welland Canal are noted in red ink and include the old towing path. Local area landmarks are also identified and include streets and roads (ex. Line between Wood and Tenbroeck), an unnamed bridge, a poplar tree and walnut tree along the east shore. Properties and property owners of note are: Concession 4 Lot 22, Samuel Wood, and John R. Tenbroeck.

Second Welland Canal - Book 1, Survey Map 5 - Through Grantham Township

Survey map of the Second Welland Canal created by the Welland Canal Company showing a portion of the Grantham Township near Port Dalhousie. Identified structures associated with the Canal include the tow path and floating tow path. The surveyors' measurements and notes can be seen in red and black ink and pencil. Features of the First Welland Canal are noted in red ink and include the old towing path, the Old Canal, two unnamed bridges traversing the Old Canal, and the bed of the Twelve Mile Creek. Local area landmarks are also identified and include streets and roads (ex. Old Road, Side Line, Road to Port Dalhousie), Samuel Wood's house, Peter Weaver's house, J. R. Tenbroeck's house, a poplar and walnut tree along the east shore, an oak and hickory tree along the west shore, and a walnut tree stump along the west shore. Properties and property owners of note are: Concession 3 Lots 21, 22, and 23, Concession 4 Lots 21, 22, and 23, Adam Gould, Samuel Wood, Peter Weaver, and John R. Tenbroeck.

Second Welland Canal - Book 1, Survey Map 6 - Through Grantham and Louth Townships

Survey map of the Second Welland Canal created by the Welland Canal Company showing the area between the Townships of Grantham and Louth. Identified structures associated with the Canal include the floating tow path. The surveyors' measurements and notes can be seen in red and black ink and pencil. Features of the First Welland Canal are noted in red ink and include the old towing path, and the original bed of the Twelve Mile Creek. Local area landmarks are also identified and include streets and roads (ex. New Road, 1st Concession Road, and an unnamed road in the top right corner), an unnamed bridge along New Road, J. Martindale's House, an Old Saw Mill, Richardsons Creek, Georges Point, and an oak tree at Georges Point. Properties and property owners of note are: Concession 2 Lot 23 and Concession 3 Lot 23 in the Grantham Township, Concession 2 Lots 1 and 2, and Concession 3 Lots 1 and 2 in the Louth Township, Peter Weaver, J. Martindale, and John Bonner. A property belonging to the Board of Works is outlined in red at Georges Point.

Second Welland Canal - Book 1, Survey Map 8 - Through Grantham and Louth Townships

Survey map of the Second Welland Canal created by the Welland Canal Company showing the area between the Townships of Louth and Grantham. Identified structures associated with the Canal include the floating tow path. It is not labelled, but runs along the bottom of the map. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks that are identified include streets and roads (ex. New Road, and Road to Port Dalhousie), and an unnamed bridge along New Road. Richardson's Creek is identified in pencil. Properties and property owners of note are: Lot 23 in Grantham Township, Lots 1 and 2 in Louth Township, John Bonner, John Martindale, Geo. E. Read, Thomas Read, N. Pawling, and the Board of Works.

Second Welland Canal - Book 1, Survey Map 7 - Through Grantham Township

Survey map of the Second Welland Canal created by the Welland Canal Company showing a portion of the Grantham Township. Identified structures associated with the Canal include the floating tow path. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks are also identified and include streets and roads (ex. Road to Port Dalhousie, and Road to St. Catharines), Georges Point, Browns Island, and an unnamed island. Properties and property owners of note are: Concession 2 Lots 21 and 22, Concession 3 Lots 21 and 22, John Clark, C. May, George May, and J. R. Tenbroeck.

Second Welland Canal - Book 1, Survey Map 10 - St. Catharines

Survey map of the Second Welland Canal created by the Welland Canal Company along the western edge of the Town of St. Catharines. Although not labelled, the Second Welland Canal can be seen running through the map along with its tow path, which is located on the southwestern edge of the waterway. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks are identified and include streets and roads (ex. Ontario Street and Road to Hamilton), Artesian Mineral Well, Dr. Mack's Artesian Well, Stephenson House Mineral Well and Gas Works, New Brewery, Old Brewery, Welland House Mineral Well, L. Shickluna's Shipyard, Vinegar Manufactory, Merritt's Covered Race, Mitchels Wharf, Sail Loft, an office, a tavern, two barns, a boathouse, a structure belonging to T. Nihan (or P. Nihen), and some store houses. Properties and property owners of note are: Concession 6 Lot 20, William H. Merritt, E. S. Adams, William Chace, Jacob Hainer, J. Taylor, and J. P. Merritt.

Second Welland Canal - Book 1, Survey Map 11 - St. Catharines and Locks 3 and 4

Survey map of the Second Welland Canal created by the Welland Canal Company showing the Town of St. Catharines. Identified structures associated with the Canal include Lock 3 and its Lock House, Lock 4 and its Lock House, Hydraulic Race, and a floating tow path. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks are also identified and include streets and roads (ex. Geneva Street, Ontario Street, St. Paul Street, and Merritville Road), Lincoln Mills and its Store House, T. M. Merritt's Store House, Cooper Shop, L. Shickluna's Dry Dock, Peter McGill's Grist Mill, J. Flint's Saw Factory, T. Hosteter's Gristing Mill, J. Dougan Builder's shop or office, Norris and Nelson Mill, G. N. Oil Foundry and its Machine Shop and Boiler, a barrel shed, woolen factory, Estate of P. Nihen (or T. Nihan), Norris and Nelson's Wharf, the W. C. Office, and structures (possibly houses) or small properties belonging to T. Adams, and A. K. Boomer. Properties and property owners of note are: Concession 6 Lots 16, 17, and 18, Concession 7 Lots 16, 17, and 18, Alva Dittrick, James R. Benson, W. B. Robinson, and C. Phelps.

Second Welland Canal - Book 1, Survey Map 12 - St. Catharines and Lock 4

Survey map of the Second Welland Canal created by the Welland Canal Company showing the Town of St. Catharines. Identified structures associated with the Canal include Lock 4, Hydraulic Race, floating tow path, and the Canal waterway itself. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks are also identified and include streets and roads (ex. Geneva Street, St. Paul Street, Queenston Street, Niagara Street and Mill Street), C. Phelp's Grist Mill and Store House, Stinson's Distillery, and several unnamed bridges. Properties and property owners of note are: Concession 6 Lot 16, J. R. Benson, Calvin Phelps, J. Hudson, David Gray, A. Roberts, Mrs. McDonell, J. S. McDonell, T. B. Wragg, J. Donaldson, W. Barr Jr., C. L. Hall, G. Ward, Ridout Bros and Co., and the St. Catharines Grass Co.