ISEP - DM – Biorrecursos
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Browsing ISEP - DM – Biorrecursos by Field of Science and Technology (FOS) "Engenharia e Tecnologia"
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- CO2 valorisation for methanol production: exploring the key role of supports in the catalytic performancePublication . Mendes, Inês Carolina de Vasconcelos; Silva, Paula Cristina Pereira; Constantino, DâniaGlobal warming, caused mainly by the increase in carbon dioxide emissions from fossil fuels, calls for sustainable solutions such as carbon capture and utilisation (CCU). CO2 can be used to produce fuels and chemicals, such as methanol, which is widely used in industrial synthesis and, recently, as a marine fuel. The production of methanol through the hydrogenation of CO2 supports the circular economy. The research community is focussing on improving cost-effectiveness through innovative catalysts, advances in reactors and better process integration. This dissertation focused on the development and study of different supported catalysts for the synthesis of methanol from CO2. Different catalysts were developed based on copper and zinc supported on alumina and alumina doped with silica using: incipient wetness impregnation and precipitation methods. Their catalytic performance was assessed in a fixed bed reactor for 8 hours, using optimum conditions obtained from a parametric study previously performed (250ºC, 30 bar, H2/CO2 ratio of 3 and GHSV of 2.8 L∙gcat -1∙h-1). The C20Z10A (P) catalyst, based on 20% by mass of copper, 10% by mass of zinc supported alumina prepared by precipitation, showed promising results, with copper-normalised time yield (CTY) values (1.04 molCO₂∙gCu -¹∙s-¹) and selectivity for methanol (7.9%). The best selectivity obtained was 12.8 per cent with the C20Z10S10 (P) catalyst, based on 20 per cent by mass of copper, 10 per cent by mass of zinc supported on alumina doped with 10 per cent by mass of silica prepared by precipitation. Although this was the material with the highest selectivity for methanol, its CTY was only 0.51 molCO₂∙gCu -¹∙s-¹. Compared to the reference material, TMC-3/1, (22.9 %), the selectivities obtained were lower. The use of aluminosilicates with 40% silica by mass as a support did not positively influence the catalyst. C20Z10A (P) should be investigated in detail, as it could be a promising catalytic system to be used in catalytic films to be integrated into a new microstructure reactor, also known as NetMIX.
- O Efeito da Combinação do Lean e Economia Circular na Performance Empresarial em PortugalPublication . Correia, Ivo Martins Correia; Sá, José Carlos Vieira de SáO avanço tecnológico e o crescimento exponencial da população atraem hoje sérias preocupações ambientais e sociais a nível global. A Economia Circular, surgiu como um conceito para abordar estas questões, propondo um sistema de ciclo fechado em contraste com o sistema linear. Embora o conceito tenha um grande potencial, ainda reside o desafio da sua adaptação nos sectores industriais e organizacionais, sobretudo nas PME. Com o avanço tecnológico surgem novos métodos e técnicas que promovem o combate aos problemas hoje apresentados, mas que exigem uma mudança completa no sistema existente assim como mão de obra qualificada. Esta investigação explora a combinação do Lean com Economia Circular e de que forma a associação dos conceitos favorece o panorama organizacional em Portugal. O estudo permite perceber em que nível se encontra a maturidade da prática circular em vários setores e se o Lean e a Economia Circular associados, algo que teoricamente colide, se complementam e formam sistemas eficazes. Através de um inquérito que resultou numa amostra pertinente para análise de 77 inquiridos de empresas portuguesas, foram validados modelos de hipótese com base nas respostas dos inquiridos, a possibilidade da associação do Lean e Economia Circular contribuírem positivamente para o Desempenho Operacional e Competitividade da Empresa. O inquérito demonstrou maioritariamente que a Economia Circular está em ascendente em Portugal, sendo que já se verifica a nível das PME’s práticas Circulares regulares. O estudo confirmou que a filosofia Lean e a Economia Circular tem um impacto positivo no Desempenho Operacional e Competitividade da Empresa sendo que através de regressão linear os resultados conferem modelos de variáveis positivos.
- Maximizing Spirulina's value in a biorefinery approachPublication . Santos, Carolina Ascenso dos; Caetano, Nídia de SáWith the pressing global environmental challenges there is an increasing need for sustainable and circular bioresource management. This thesis explores the multifaceted potential of Spirulina in various sectors, leading to the idealisation of a biorefinery. The study begins by assessing Spirulina’s properties, culture conditions and applications that boost its potential for a sustainable biorefinery development, emphasizing its versatility in producing high-value compounds and its contributions to several industrial sectors. Experimentally, Spirulina was cultivated and high-value compounds, such as lipids, phycocyanin and antioxidants, were obtained with the use of eco-friendly extraction methods. Additionally, Spirulina was incorporated as a functional ingredient in butter. Sensorial analyses were conducted revealing positive consumer acceptance and the potential for Spirulina to enhance the nutritional profile of everyday foods. Then, Spirulina was tested as an organic soil corrective. Through comparative tests, it was shown that Spirulina improved germination, by 150%, and plant growth, underscoring its potential in promoting sustainable agricultural practices. Finally, aggregating the results and inputs from the literature, the concept of a Spirulina-based biorefinery was explored, identifying viable process routes and multiple processes integration, such as the reuse of waste streams. The results indicate that with strategic process optimization, Spirulina-based biorefineries could contribute significantly to reducing environmental negative impact while offering economically viable solutions, supporting a circular bioeconomy.
- Potential of marine macroalgae as a source of iodine and natural antioxidants: their use in inhibiting lipid peroxidation reactions in food productsPublication . Santos, Francisca Filipa Pereira Leite dos; Soares, Cristina Maria DiasThe deterioration of food quality due to lipid peroxidation poses a significant challenge in the food industry. This study evaluates the effectiveness of seaweed extracts as natural antioxidants in preventing lipid oxidation during the accelerated ageing of oils used in canned fish. Ten seaweeds were selected: four brown (Fucus vesiculosus, Himanthalia elongata, Eisenia bicyclis, and Undaria pinnatifida); two green (Ulva Lactuca, and Codium tomentosum); and 4 red (Palmaria palmata, Gracilaria gracilis, Chondrus cripus, and Porphyra dioica). Solid-liquid extraction (SLE) was used to optimize extraction conditions, followed by subcritical water extraction (SWE) at 140°C and 190°C, and ultrasound-assisted extraction (UAE) for 10 and 20 minutes. The extracts were analyzed for phenolic compounds and antioxidant capacity. Olive and sunflower oils were tested for lipid oxidation and accelerated ageing tests were conducted on sunflower oil with the seaweed extracts. The results were compared to a control and BHTtreated oil. Brown seaweeds consistently showed the best antioxidant performance, significantly reducing lipid oxidation, while red seaweeds were less effective. Sensory analysis indicated less rancidity in oils treated with brown macroalgae. These findings suggest that brown seaweeds have strong potential as natural antioxidants, offering a possible replacement for synthetic antioxidants in food preservation. Further research is needed to optimize extract concentration, assess nutritional impacts, and examine long-term effects on the shelf life of canned fish.
- Valorização do resíduo industrial carbonato de cálcio numa perspetiva de sustentabilidade e economia circularPublication . Vila Cova, Cláudia Filipa Silva; Morais, Simone BarreiraNum cenário marcado pela crescente produção de resíduos e pelo uso insustentável de recursos naturais, a busca por alternativas circulares torna-se cada vez mais urgente. A indústria do açúcar enfrenta o desafio de gerir os seus resíduos de forma eficaz, minimizando os impactos ambientais e otimizando os seus processos. Neste contexto, a presente tese dedica-se a investigar estratégias, alinhadas com os princípios da sustentabilidade e da economia circular, para a valorização do carbonato de cálcio nas lamas de carbonatação obtidas durante a produção de açúcar. Para tal, foram caracterizadas as propriedades físico-químicas do resíduo, avaliados métodos de processamento e de reutilização em diferentes contextos industriais. O estudo sobre o aproveitamento das lamas de carbonatação da RAR revelou que estas atendem aos requisitos legais para uso agrícola e como corretivo alcalinizante, embora o seu teor médio de humidade de 29% limite as aplicações industriais. A opção mais viável é o uso como corretivo de solos ácidos. Diversos setores industriais demonstraram interesse, mas as lamas precisam de pré-tratamento, especialmente secagem, para cumprir às especificações desses setores. Testes laboratoriais reduziram a humidade para 0,57%, próximo do valor requerido por algumas indústrias, com um secador rotativo sendo adequado para este processo. A viabilidade económica mostrou ganhos anuais significativos ao vender as lamas ao natural para uso agrícola, eliminando custos de gestão de resíduos. Contudo, a secagem requer investimentos e sua viabilidade depende fortemente do preço de venda do produto final. Recomenda-se, assim, manter as parcerias para uso agrícola, realizar testes piloto de secagem e aprofundar estudos de mercado para identificar setores que valorizem o carbonato de cálcio seco. Explorar a integração energética e otimização de processos também é essencial. Há potencial para transformar as lamas de um passivo ambiental num produto de valor agregado, começando pelo uso agrícola e avançando conforme a procura do mercado. Trabalhos futuros devem focar-se em estudos de mercado, otimização do pré-tratamento das lamas, estratégias de marketing eficazes e parcerias para promover a valorização de resíduos e a economia circular na indústria do açúcar.