Mushrooms are one of the protein rich foods, however they have a short pro-harvest life (2 to 3 days) compared to most vegetables. The aim of this study was to evaluate whether applying an anti-browning solution using vacuum impregnation and then electron beam irradiation can be used to extend the shelf life of fresh-cut mushrooms (Agaricus bisporus). Solutions made with (a) 2% ascorbic acid + 1% calcium lactate, (b) 2% citric acid + 1% calcium lactate, (c) 1% chitosan + 1% calcium lactate, and (d) 1% calcium lactate were used to impregnate mushroom slices at different vacuum pressures, vacuum pressure times, and atmospheric restoration times. Mushrooms were also irradiated at a dose of 1 kGy using a 1.35 MeV e-beam accelerator and their quality was evaluated in terms of color, texture, and microbial growth during 15 days storage at 4 degrees C. The best vacuum impregnation treatment was the 2% ascorbic acid and 1% calcium lactate solution using a vacuum pressure of 50 mmHg for 5 minutes and an atmospheric restoration time of 5 minutes. The control (not treated) and impregnated samples lost their structure (softening) during storage. The irradiated samples lost their firmness by day 4 of storage. The addition of calcium lactate to the samples during the treatment helped to keep the product’s texture during the 15 days storage time. Color of the mushrooms changed during storage for all the control and impregnated samples and only the irradiated samples showed an acceptable color by the end of day 15. Aerobics and psychrotrophics counts were significantly reduced by irradiation; while yeast and molds population increased by day 9 and were not completely inactivated with a dose of 1 kGy. Sensory panelists preferred the treated samples over the controls. The best treatment was the combination of vacuum impregnation with irradiation according to the consumer studies.

There are many examples where creation and usage of porous substrates play important roles in various fields of application in material science and technology. In the manufacture of ceramic products, as an alternative to the plaster molds, porous resin molds are used in order to resolve the drawbacks that result A porous substrate can be produced by various ways. In this study, porous polymeric matrices of poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate-co-2-hydroxyethyl methacrylate) [poly(MMA-HEMA)] polymers were prepared by connecting the polymer microspheres to each other by an epoxy adhesive. To improve the surface properties, methyl methacrylate (MMA) was copolymerized with 2-hydroxyethyl methacrylate (HEMA). The microspheres used were synthesized by suspension polymerization and characterization was done by Nuclear Magnetic Resonance (NMR), Particle Size Analyzer and Scanning Electron Microscope (SEM). The porous samples were prepared with PMMA and poly(MMA-HEMA) copolymer microspheres with two different HEMA contents and their surface energies were measured. In addition, the effect of mean particle diameter of the microspheres used and the epoxy content of the solution used to bind the microspheres, on the impregnation capacity, morphology and the impact strength of the porous samples prepared, were studied. Inclusion of HEMA into the formulation improved the impregnation capacity of the samples. Using microspheres with narrower particle size distribution resulted in larger representative capillary radii and higher rate of impregnation of the samples. Increasing the epoxy content of the solution used to bind the beads, increased the impact strengths of the samples prepared.

Embora o congelamento apresente vantagens em relação a outros métodos de conservação de alimentos, o mesmo causa alterações sensoriais, principalmente em produtos de origem vegetal. O morango, uma fruta muito apreciada e com formas variadas de consumo, tem comportamento sazonal e apresenta como fator limitante para o congelamento sua estrutura frágil e sensível ao processo, o que causa alterações sensoriais. Tais alterações podem ser minimizadas com a incorporação de crioprotetores, como a trealose, um dissacarídeo que vem se destacando pelo seu efeito crioprotetor em produtos congelados e desidratados. O principal objetivo deste trabalho foi verificar o efeito crioprotetor da trealose incorporada através da impregnação a vácuo em soluções de diferentes concentrações (100, 300 e 500 g/L) em morangos submetidos ao congelamento e descongelamento. As condições de impregnação foram de 5 min, aplicando pressão de -650 mmHg e 10 min de tempo de relaxamento. As alterações provocadas pelo processo de impregnação bem como a verificação do efeito crioprotetor da trealose foram identificadas através de análise de cromatografia líquida de alta eficiência (High Performance Liquid Chromatography- HPLC), análise colorimétrica, análise de textura, determinação do teor de sólidos solúveis, determinação do teor de umidade e perda de massa (perda por gotejamento). Os resultados mostraram que a concentração da solução de trealose exerce influência significativa no teor de umidade, teor de sólidos solúveis e teor de trealose. As amostras tratadas com soluções mais concentradas não sofreram desidratação após descongelamento. O teor de trealose, após descongelamento, permaneceu constante em todas as amostras tratadas. Todas as amostras tiveram a mesma perda de massa após descongelamento (perda por gotejamento), porém a composição da massa diferiu entre elas. Amostras tratadas com a solução mais concentrada perderam sólidos enquanto que as amostras tratadas com a menos concentrada, perderam água. Na análise de textura, a introdução da trealose não influenciou a força máxima de pico nas amostras impregnadas. Após descongelamento, todas as amostras, exceto a tradada com solução de 500 g/L, sofreram amolecimento. A parte externa dos morangos não sofreu alterações de cor devido à introdução da trealose nem devido ao congelamento e descongelamento. Na parte interna dos frutos, ocorreram variações no parâmetro L* devido à impregnação e no parâmetro b*, devido ao congelamento e descongelamento. / Although freezing offers advantages to others food conservations process, it causes sensorial changes, mostly in vegetables products. The strawberry, a quite appreciated fruit, shows different ways of use, has seasonal behavior and is limited to freezing due the sensorial changes caused by its fragile structure to freezing process. These sensorial changes can be minimized by the incorporation of cryoprotectors, as trehalose, that is known by its cryoprotector effect during freezing and dehydration. The aim of this work was to verify the trehalose cryoprotector effect in frozen and thawed strawberries introduced by vacuum impregnation with different solutions (100, 300 and 500 g/L). The impregnation conditions were 5 min of applying pressure of -650 mmHg and after atmospheric pressure was restored, the sample was maintained within the solution for 10 min (these conditions were obtained from previous experiments). The alterations caused by the vacuum impregnation and the verification of the cryoprotector effect of trehalose were identified by High Performance Liquid Chromatography (HPLC), color analysis, texture analysis, soluble solids content, moisture content and drip loss. The results have shown that concentration of the trehalose solution had a significant influence on the moisture content, soluble solids and trehalose content of impregnated strawberries. The samples treated with more concentration solutions did not dehydrated after thawing. The trehalose content was the same in all treated samples after thawing. All the samples showed the same drip loss due to thawing although the composition of the mass was different among the samples. Samples treated with the most concentration solution lost trehalose while the sample treated with the least concentration solutions lost water. The introduction of trehalose did not affect the maximum peak force of the impregnated samples. The freezing and the thawing process caused the softening of the samples. This effect was not observed on the sample treated with solution of 500 g/L. The introduction of trehalose did not cause significant differences in all color parameters measured on the outside of the strawberries after impregnation and thawing. In the inside of the samples, there were variation in the L* parameter caused by the vacuum impregnations and in the b* parameter caused by the freezing and thawing process.

Embora o congelamento apresente vantagens em relação a outros métodos de conservação de alimentos, o mesmo causa alterações sensoriais, principalmente em produtos de origem vegetal. O morango, uma fruta muito apreciada e com formas variadas de consumo, tem comportamento sazonal e apresenta como fator limitante para o congelamento sua estrutura frágil e sensível ao processo, o que causa alterações sensoriais. Tais alterações podem ser minimizadas com a incorporação de crioprotetores, como a trealose, um dissacarídeo que vem se destacando pelo seu efeito crioprotetor em produtos congelados e desidratados. O principal objetivo deste trabalho foi verificar o efeito crioprotetor da trealose incorporada através da impregnação a vácuo em soluções de diferentes concentrações (100, 300 e 500 g/L) em morangos submetidos ao congelamento e descongelamento. As condições de impregnação foram de 5 min, aplicando pressão de -650 mmHg e 10 min de tempo de relaxamento. As alterações provocadas pelo processo de impregnação bem como a verificação do efeito crioprotetor da trealose foram identificadas através de análise de cromatografia líquida de alta eficiência (High Performance Liquid Chromatography- HPLC), análise colorimétrica, análise de textura, determinação do teor de sólidos solúveis, determinação do teor de umidade e perda de massa (perda por gotejamento). Os resultados mostraram que a concentração da solução de trealose exerce influência significativa no teor de umidade, teor de sólidos solúveis e teor de trealose. As amostras tratadas com soluções mais concentradas não sofreram desidratação após descongelamento. O teor de trealose, após descongelamento, permaneceu constante em todas as amostras tratadas. Todas as amostras tiveram a mesma perda de massa após descongelamento (perda por gotejamento), porém a composição da massa diferiu entre elas. Amostras tratadas com a solução mais concentrada perderam sólidos enquanto que as amostras tratadas com a menos concentrada, perderam água. Na análise de textura, a introdução da trealose não influenciou a força máxima de pico nas amostras impregnadas. Após descongelamento, todas as amostras, exceto a tradada com solução de 500 g/L, sofreram amolecimento. A parte externa dos morangos não sofreu alterações de cor devido à introdução da trealose nem devido ao congelamento e descongelamento. Na parte interna dos frutos, ocorreram variações no parâmetro L* devido à impregnação e no parâmetro b*, devido ao congelamento e descongelamento. / Although freezing offers advantages to others food conservations process, it causes sensorial changes, mostly in vegetables products. The strawberry, a quite appreciated fruit, shows different ways of use, has seasonal behavior and is limited to freezing due the sensorial changes caused by its fragile structure to freezing process. These sensorial changes can be minimized by the incorporation of cryoprotectors, as trehalose, that is known by its cryoprotector effect during freezing and dehydration. The aim of this work was to verify the trehalose cryoprotector effect in frozen and thawed strawberries introduced by vacuum impregnation with different solutions (100, 300 and 500 g/L). The impregnation conditions were 5 min of applying pressure of -650 mmHg and after atmospheric pressure was restored, the sample was maintained within the solution for 10 min (these conditions were obtained from previous experiments). The alterations caused by the vacuum impregnation and the verification of the cryoprotector effect of trehalose were identified by High Performance Liquid Chromatography (HPLC), color analysis, texture analysis, soluble solids content, moisture content and drip loss. The results have shown that concentration of the trehalose solution had a significant influence on the moisture content, soluble solids and trehalose content of impregnated strawberries. The samples treated with more concentration solutions did not dehydrated after thawing. The trehalose content was the same in all treated samples after thawing. All the samples showed the same drip loss due to thawing although the composition of the mass was different among the samples. Samples treated with the most concentration solution lost trehalose while the sample treated with the least concentration solutions lost water. The introduction of trehalose did not affect the maximum peak force of the impregnated samples. The freezing and the thawing process caused the softening of the samples. This effect was not observed on the sample treated with solution of 500 g/L. The introduction of trehalose did not cause significant differences in all color parameters measured on the outside of the strawberries after impregnation and thawing. In the inside of the samples, there were variation in the L* parameter caused by the vacuum impregnations and in the b* parameter caused by the freezing and thawing process.

Orientador: Florencia Cecilia Menegalli / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-10T02:57:51Z (GMT). No. of bitstreams: 1 Sousa_Severinade_D.pdf: 3233199 bytes, checksum: c69375c3baa9b4be2e41470f3792f663 (MD5) Previous issue date: 2008 / Resumo: O processo de desidratação osmótica figos (Fícus carica, L.) em soluções de sacarose foi investigado com base em um planejamento experimental completo e metodologia de superfície de resposta (RSM). As variáveis independentes foram a concentração de sacarose, variando de 35,9 a 64,1% p/p e a temperatura da solução desidratante de 32,9 a 47,0ºC, a fim de avaliar a cinética da perda de umidade, da incorporação de açúcares e da atividade de água durante o processo. As condições ótimas de desidratação osmótica que geraram dois tipos de produtos, ou seja, figos com maior conteúdo de açúcares e figos com menor conteúdo de açúcares, ambos com menor atividade de água e menor conteúdo de umidade, foram encontradas respectivamente, na temperatura de 39,7ºC e concentração de 63,1% p/p de sacarose, e temperatura de 35,3ºC e concentração de sacarose de 64,1% p/p. A cinética de incorporação de ácido ascórbico foi estudada durante o processo de desidratação osmótica a 44ºC e 36% p/p de concentração da solução, com adição de ácido ascórbico de 100 e 200mg/100g de solução, obtendo-se coeficientes de difusão para a incorporação da vitamina através do modelo difusional de Fick. A avaliação da degradação de vitamina C durante subseqüente secagem mostrou que as perdas de vitamina C podem ser compensadas através de sua incorporação à fruta durante o processo de desidratação osmótica. As isotermas de sorção e a cinética da secagem convectiva foram determinadas às diferentes temperaturas (40, 50, 60 e 70ºC). Para o ajuste dos dados de secagem foram utilizados o modelo difusional de Fick, o modelo de Page e o modelo exponencial com dois termos. Durante a secagem observou-se que a difusividade não foi constante durante todo o período, considerando-se três difusividades distintas ao longo da curva de secagem. As amostras in natura apresentaram maiores coeficientes de difusão de umidade que as amostras desidratadas osmoticamente com sacarose. O tempo de secagem foi reduzido com o processo de desidratação osmótica em todas as temperaturas, especialmente para obtenção da fruta em umidades intermediárias / Abstract: A full experimental design and response surface methodology (RSM) were used to study osmotic dehydration process of figs (Ficus carica, L.) in sucrose solutions. The independent variables were: the sucrose concentration, varying from 35,9 to 64,1% w/w and the solution temperature, varying from 32,9 to 47,0ºC, in order to study the kinetic of water loss, sugars incorporation and water activity during the process. The optimized conditions in osmotic dehydration to obtain two kinds of products: figs with higher content of sugars and figs with lower content of sugars, both of them with lower water activity and water content, had been found respectively, at 39,7ºC and 63,1% w/w and 35,3ºC and 64,1% w/w of temperature and sucrose concentration. The kinetic of ascorbic acid incorporation was studied during osmotic dehydration process at 44ºC, using a solution of 36% of sucrose concentration with an addition of 100 or 200mg of ascorbic acid /100g of solution. The diffusion coefficients for the vitamin incorporation were obtained fitting data with the Fick¿s second law of diffusion. The evaluation of vitamin C degradation during the subsequent drying process showed that the losses of vitamin C can be compensated with the addition of this vitamin in the fruit during osmotic dehydration process. The sorption isotherms and the kinetic of the convective drying were determined at different temperatures (40, 50, 60 and 70ºC). The drying data was fitted with Fick¿s second law of diffusion, the Page model and the Exponential model with two terms. During the drying was observed that the diffusivity was not constant during all period, therefore, were considered three different diffusivities along of the drying curves. The fresh samples had presented higher water diffusion coefficients compared with the samples osmotically dehydrated with sucrose. The drying time was reduced with the use of osmotic dehydration as pretreatment for the several temperatures, especially when the intermediate moisture of fruit was obtained / Doutorado / Doutor em Engenharia de Alimentos

This research project, funded by the Federal Highway Administration (FHWA Project DTFH61-02-C-0097), focuses mainly on alkali-silica reaction (ASR) and techniques to mitigate the effects of alkali-silica reaction in hardened concrete. A large portion of this report discusses the construction and design of an outdoor exposure site built at the University of Texas at Austin where the goal was to cast field representative concrete elements with laboratory precision and expose them to real environmental conditions. The elements were monitored for expansion and deterioration. At discrete expansion levels a range of mitigation methods were implemented on the structures. After the concrete elements were treated, long-term monitoring was conducted to determine the best approach to provide effective suppression of alkali-silica reaction in the various element types. / text

Det elektriska isolationssystemet för stora roterande maskiner består av ett kompositmaterial av glimmertejp och ett värmehärdande harts. Hartset hjälper till att mekaniskt stabilisera lindningsstrukturen i statorn samt ersätter luftinneslutningar i isolationssystemet för att undertrycka bildandet av elektriska urladdningar. Vakuumtryckimpregneringsprocessen (VPI) är den föredragna tekniken för att impregnera glimmerisolationen med det värmehärdande hartset. Hartset som används i VPI-processen är sammansatt av flera nyckelkomponenter, inklusive den härdbara polymeren, härdare som deltar i tvärbindning, reaktiva utspädningsmedel för förbättrade processegenskaper och ytterligare tillsatser som katalysatorer och stabilisatorer. Olika hartskemier har använts under åren för VPI-processen. Det finns dock betydande farhågor när det gäller påverkan på miljö- och arbetshälsa för några av dessa komponenter. Den ökade medvetenheten om de skadliga effekterna av olika kemikalier har drivit på arbetet med att utveckla hartser med reducerade flyktiga organiska föreningar som kan vara skadliga för såväl miljön som de som hanterar hartset i stora mängder. Dessutom har stränga EU-regler klassificerat vissa härdare och reaktiva utspädningsmedel som ’substances of very high concern’, vilket har lett till ett stort behov av att hitta alternativ för dessa föreningar. Detta examensarbete består av en litteraturstudie som har genomförts med hänsyn till de önskade egenskaperna för VPI-hartser för att utvärdera potentiella kandidater som alternativ till härdare och reaktiva utspädningsmedel. Fyra olika impregneringshartser har tagits i beaktande som alternativ. Olika härdningskinetikparametrar har uppmätts med olika karakteriseringstekniker såsom infraröd spektroskopi av Fouriertransform i realtid, reologi och differentiell scanningkalorimetri. Eftersom de termiska, elektriska och mekaniska egenskaperna är nödvändiga för att säkerställa långvarig livslängd för industriellt nyttjade roterande maskiner, har olika egenskaper studerats genom att utföra dynamisk mekanisk analys, drag- och böjningstestning samt dielektrisk spektroskopi, genom att härda hartserna under lämpliga tids- och temperaturförhållanden. Alla de fyra hartserna visade varierande härdningskinetikparametrar och egenskaper som har korrelerats till hartskemin samt att hartsernas egenskaper har utvärderats i jämförelse med varandra. / The electrical insulation system for large rotating machines consists of a composite material of mica tape and a thermosetting resin. The resin helps in mechanically stabilizing the winding structure in the stator as well as replaces air inclusions in the insulation system to suppress the formation of discharges. Vacuum pressure impregnation (VPI) is the preferred technique to impregnate this mica tape with the thermosetting resin. The resin used in VPI process is composed of several key components, including the thermoset polymer, a hardener that participates in crosslinking, reactive diluents for improved processability and and additional additives like catalysts and stabilizers. Different chemistries have been used over the years for the VPI process. However, there are significant concerns regarding the environmental and occupational health and safety of some of these components.  The increasing awareness of the harmful effects of various chemicals has driven efforts to develop resins with reduced volatile organic compounds which can be detrimental to both the environment as well as those who are handling the resin in large quantities. Furthermore, stringent EU regulations have classified some hardeners and reactive diluents as substances of very high concern which has resulted in pressing need to find alternatives for these compounds.  This thesis, thus, consists of a literature study which has been performed taking the desired properties for VPI resins into consideration to evaluate potential candidates as alternatives for hardeners, and reactive diluents. Four different chemistries of impregnation have been taken into consideration as alternatives. Different curing kinetics parameters have been measured by different characterization techniques such as real time Fourier transform infrared spectroscopy, rheology, and differential scanning calorimetry. As the thermal, electric, and mechanical factors are necessary to ensure long term lifespan of industrial machines, different properties have been studied by performing dynamic mechanical analysis, tensile and flexural testing as well as dielectric spectroscopy by curing the resins under appropriate time and temperature conditions. All the four resins showed varied curing kinetics parameters and properties which have been correlated to the chemistry involved in the resin as well as evaluated in comparison to each other.

Det elektriska isolationssystemet för stora roterande maskiner består av ett kompositmaterial av glimmertejp och ett värmehärdande harts. Hartset hjälper till att mekaniskt stabilisera lindningsstrukturen i statorn samt ersätter luftinneslutningar i isolationssystemet för att undertrycka bildandet av elektriska urladdningar. Vakuumtryckimpregneringsprocessen (VPI) är den föredragna tekniken för att impregnera glimmerisolationen med det värmehärdande hartset. Hartset som används i VPI-processen är sammansatt av flera nyckelkomponenter, inklusive den härdbara polymeren, härdare som deltar i tvärbindning, reaktiva utspädningsmedel för förbättrade processegenskaper och ytterligare tillsatser som katalysatorer och stabilisatorer. Olika hartskemier har använts under åren för VPI-processen. Det finns dock betydande farhågor när det gäller påverkan på miljö- och arbetshälsa för några av dessa komponenter. Den ökade medvetenheten om de skadliga effekterna av olika kemikalier har drivit på arbetet med att utveckla hartser med reducerade flyktiga organiska föreningar som kan vara skadliga för såväl miljön som de som hanterar hartset i stora mängder. Dessutom har stränga EU-regler klassificerat vissa härdare och reaktiva utspädningsmedel som ’substances of very high concern’, vilket har lett till ett stort behov av att hitta alternativ för dessa föreningar. Detta examensarbete består av en litteraturstudie som har genomförts med hänsyn till de önskade egenskaperna för VPI-hartser för att utvärdera potentiella kandidater som alternativ till härdare och reaktiva utspädningsmedel. Fyra olika impregneringshartser har tagits i beaktande som alternativ. Olika härdningskinetikparametrar har uppmätts med olika karakteriseringstekniker såsom infraröd spektroskopi av Fouriertransform i realtid, reologi och differentiell scanningkalorimetri. Eftersom de termiska, elektriska och mekaniska egenskaperna är nödvändiga för att säkerställa långvarig livslängd för industriellt nyttjade roterande maskiner, har olika egenskaper studerats genom att utföra dynamisk mekanisk analys, drag- och böjningstestning samt dielektrisk spektroskopi, genom att härda hartserna under lämpliga tids- och temperaturförhållanden. Alla de fyra hartserna visade varierande härdningskinetikparametrar och egenskaper som har korrelerats till hartskemin samt att hartsernas egenskaper har utvärderats i jämförelse med varandra. / The electrical insulation system for large rotating machines consists of a composite material of mica tape and a thermosetting resin. The resin helps in mechanically stabilizing the winding structure in the stator as well as replaces air inclusions in the insulation system to suppress the formation of discharges. Vacuum pressure impregnation (VPI) is the preferred technique to impregnate this mica tape with the thermosetting resin. The resin used in VPI process is composed of several key components, including the thermoset polymer, a hardener that participates in crosslinking, reactive diluents for improved processability and and additional additives like catalysts and stabilizers. Different chemistries have been used over the years for the VPI process. However, there are significant concerns regarding the environmental and occupational health and safety of some of these components.  The increasing awareness of the harmful effects of various chemicals has driven efforts to develop resins with reduced volatile organic compounds which can be detrimental to both the environment as well as those who are handling the resin in large quantities. Furthermore, stringent EU regulations have classified some hardeners and reactive diluents as substances of very high concern which has resulted in pressing need to find alternatives for these compounds.  This thesis, thus, consists of a literature study which has been performed taking the desired properties for VPI resins into consideration to evaluate potential candidates as alternatives for hardeners, and reactive diluents. Four different chemistries of impregnation have been taken into consideration as alternatives. Different curing kinetics parameters have been measured by different characterization techniques such as real time Fourier transform infrared spectroscopy, rheology, and differential scanning calorimetry. As the thermal, electric, and mechanical factors are necessary to ensure long term lifespan of industrial machines, different properties have been studied by performing dynamic mechanical analysis, tensile and flexural testing as well as dielectric spectroscopy by curing the resins under appropriate time and temperature conditions. All the four resins showed varied curing kinetics parameters and properties which have been correlated to the chemistry involved in the resin as well as evaluated in comparison to each other.

Non-oxidative dehydrogenation of hydrocarbons is an attractive alternative route for the production of CO- and CO2-free hydrogen. It will satisfy a major requirement for successful utilization of polymer electrolyte membrane (PEM) fuel cells (< 10 ppm CO) and sequestering carbon as a potentially valuable by-product, carbon nanotubes (CNTs). Due to the deposition of carbon on the surface of catalyst particles during the reaction, catalyst performance, life-time, and purification of the generated carbon product, are significant issues to solve in order to make the process practically feasible. The scope of this thesis includes: the development of novel Fe, Ni, and Fe-Ni catalysts supported on a Mg(Al)O support to achieve improved catalytic performance with easily-purified CNTs; evaluation of catalysts for ethane/methane dehydrogenation at moderate reaction temperatures; and study of activation and deactivation mechanisms by a variety of characterization techniques including TEM, HRTEM, XRD, Mössbauer spectroscopy, and x-ray absorption fine structure (XAFS) spectroscopy. The Mg(Al)O support was prepared by calcination of synthetic MgAl-hydrotalcite with a Mg to Al ratio of 5. The catalysts were prepared either by conventional incipient wetness method or by a novel nanoparticle impregnation method, where the monodisperse catalyst nanoparticles were prepared in advance by thermal decomposition of a metal-organic complex in an organic-phase solution and then dispersed onto the Mg(Al)O support. Dehydrogenation of undiluted methane was conducted in a fix-bed plug-flow reactor. Before reaction, the catalysts were activated by reduction in hydrogen. Fe-based catalysts exhibit a higher hydrogen yield at temperature above 600ºC compared with monometallic Ni catalyst. FeNi-9 nm/Mg(Al)O, Fe-10 nm/Mg(Al)O and Fe-5 nm/ Mg(Al)O nanoparticle catalysts show much improved performance and longer life-times compared with the corresponding FeNi IW/Mg(Al)O and Fe IW/Mg(Al)O catalysts prepared by incipient wetness. 10 nm is the optimum particle size for methane dehydrogenation. Addition of Ni to Fe forming a bimetallic FeNi alloy catalyst enhances the catalytic performance at the temperatures below 650ºC. Metallic Fe, Ni, FeNi alloy and Fe-Ni-C alloy, unstable iron carbide are all catalytically active components. Catalysts deactivation is due to the carbon encapsulation. The carbon products are in the form of stack-cone CNTs (SCNTs) and multi-walled CNTs (MWNTs), depending on the reaction temperature and catalyst composition. The growth of CNTs follows a tip growth mechanism and the purity of cleaned CNTs is more than 99.5%.

<p>Samples of SCR catalysts were impregnated with the following alkali salts; KCl, K2SO4 and ZnCl2 at two different concentrations in a wet impregnation method. The activities of the six samples were measured in a test reactor and at different temperatures between 250-350 ºC. Compared to fresh catalyst, the impregnated samples all had lower activity. It seems like KCl is the most poisoning salt, depending on the lowest value of the activity. The experimental results are expected as compared to earlier articles, which reports that all alkali salts has deactivating effects on a catalyst and that KCl is among the most poisoning ones. By making a cross-section SEM analysis, the penetration of the metals at different depths in to the catalyst material wall was evaluated. An ICP-AES analysis was carried out in order to see the concentration of K and Zn of the test samples. Finally, the pore diameter and active surface was measured by BET method. Since the values of the active surface didn’t change compared to a fresh catalyst and the pore diameter was only slightly decreased we can suppose that the alkali salts deactivates the catalyst by coating of the catalyst pore structure and not as a pore blocking.</p>