Papers by Cristina Galacho
Fuel Processing Technology, May 1, 2008
Ordered mesoporous materials have stimulated great interest in the scientific community in the fi... more Ordered mesoporous materials have stimulated great interest in the scientific community in the fields of catalysis and materials science since their disclosure in 1992. The most important features for their use in catalysis are the extremely high surface area, which potentially allows an efficient dispersion of active sites, and the large and uniform pore diameters in the mesopore range that favour the diffusion of bulky molecules. However, the introduction of the heteroatoms into ordered mesoporous silicas to make them catalytically active can lead to a decrease in the quality of the pore structure as compared with the pure silica grades, the extent of which may depend on the preparation and calcination conditions. In this work is presented a study of the effect of calcination parameters namely, heating rate, calcination temperature, total calcination time and time at final temperature, on pore structural properties of Ti-MCM-41 materials. The materials were prepared by direct synthesis at ambient temperature and pressure, using tetraethoxysilane, titanium alcoxides, cationic surfactants and ammonia, as previously described and were characterised by X-ray diffraction, nitrogen adsorption at 77K and DR UV-Vis absorption spectroscopy. The Si/Ti values of the final calcined materials were determined by AA (Si) and ICP (Ti).The results of this study show that this method allows the preparation in a short period of time of well structured Ti-MCM-41 materials with high thermal and mechanical stabilities without necessity of external heat or pressure. Furthermore the similarity in the Si/Ti values of the synthesis gel and final calcined materials denotes an optimal compromise between synthesis performance and synthesis costs. On the other hand it can also be conclude that a heating rate of 3Kmin-1 and a calcination period of 15h at 550ºC provide middle term calcination parameters which are economically reasonable and do not affect the structural quality of Ti-MCM-41 materials.
No presente trabalho apresentam-se os resultados de estabilidade térmica, estabilidade em relação... more No presente trabalho apresentam-se os resultados de estabilidade térmica, estabilidade em relação à exposição prolongada ao vapor de água à temperatura ambiente e estabilidade mecânica de amostras de Ti-MCM-41 preparadas, com diferentes razões molares Si/Ti, segundo um novo processo realizado à temperatura ambiente a partir do Si(OEt)4 como fonte de silício e do Ti(OEt)4 como fonte de titânio, por adição directa ou em solução de 2-PrOH, usando C16TMABr ou C18TMABr como agentes estruturantes e amónia como catalisador
El objetivo principal de este proyecto es la caracterización de morteros con propiedades hidráuli... more El objetivo principal de este proyecto es la caracterización de morteros con propiedades hidráulicas utilizados en las instalaciones de almacenamiento de agua, la comprensión de sus técnicas de producción y la posible fuente de sus materias primas en el contexto histórico de la villa romana “Horta da Torre”, ubicada en el municipio de Fronteira, Portugal. Para lograrlo, será necesario el uso de una metodología multianalítica para determinar su composición mineralógica cualitativa y semi-cuantitativa, así como la caracterización de su morfología y composición elemental, siendo estos soportados por el uso de Microscopía Óptica(MO; OM), Microscopio Electrónico de Barrido-Espectrometría de Energía de Dispersión (MEBEED;SEM-EDS), Difracción de Rayos X (DRX; XRD), Termogravimetría (TR; TGA-DTA), Ataque con ácido clorhídrico y caracterización granulométrica
No seguimento da recente restruturação da Universidade de Évora, consubstanciada pela entrada em ... more No seguimento da recente restruturação da Universidade de Évora, consubstanciada pela entrada em vigor dos seus novos estatutos, coloca-se a toda a academia, em geral, e aos departamentos, em particular, uma imensa diversidade de desafios, que a todos exige grande determinação para os enfrentar e vencer. Na realidade, para além dos problemas decorrentes dos novos paradigmas do ensino superior que conduziram à recente reforma dos ensinos por força do chamado Processo de Bolonha e dos decorrentes da profunda crise financeira que tem condicionado a capacidade de acção dos departamentos, vivemos agora uma profunda mudança de modelo organizativo da Universidade de Évora que veio alterar, nalguns aspectos drasticamente, as competências dos departamentos, afastando-os dos centros de decisão internos, retirando-lhes competências nos planos científico e pedagógico, nos ensinos e na investigação, e deixando-os à míngua no plano financeiro. Apesar destas dificuldades, o Departamento de Química...
Boletim da Sociedade Portuguesa de Química, 2021
as well. The success of these networking breakfasts, involving students, young researchers, and s... more as well. The success of these networking breakfasts, involving students, young researchers, and scientists, encouraged its further organization in Portugal, annually since 2019. This article describes the interventions of Portuguese women scientists, coming from Institutions throughout Portugal, in the Global Women's Breakfast as partners in their mission as scientists, creative and open to international collaborations.
Sustainability, 2020
The research focuses on identifying the way in which Romanian universities managed to provide kno... more The research focuses on identifying the way in which Romanian universities managed to provide knowledge during the Coronavirus pandemic, when, in a very short time, universities had to adapt the educational process for exclusively online teaching and learning. In this regard, we analyzed students’ perception regarding online learning, their capacity to assimilate information, and the use of E-learning platforms. An online survey based on a semi-structured questionnaire was conducted. Data was collected from 762 students from two of the largest Romanian universities. The results of the research revealed that higher education institutions in Romania were not prepared for exclusively online learning. Thus, the advantages of online learning identified in other studies seem to diminish in value, while disadvantages become more prominent. The hierarchy of problems that arise in online learning changes in the context of the crisis caused by the pandemic. Technical issues are the most impor...
Adsorption Science & Technology, 2000
Activated carbons were prepared from olive stones either by the addition of zinc chloride (25–50 ... more Activated carbons were prepared from olive stones either by the addition of zinc chloride (25–50 wt%) or by gasifying non-activated carbon with steam to burn-offs between 25% and 49%. The adsorption of nitrogen at 77 K was investigated and the adsorption data interpreted by the application of the Langmuir equation, the BET equation and the αS-method. The adsorption of carbon dioxide at 273 K was also followed and the data analyzed using the DR and DA equations. The adsorption of iodine from aqueous potassium iodide solution, and of Methylene Blue and p-nitrophenol from aqueous solutions at 298 K was also determined. Activation with zinc chloride produced physical and chemical changes which modified the thermal degradation process. Carbonization with zinc chloride restricted the formation of tars with the subsequent formation of solid carbon, the amount of zinc chloride incorporated in the precursor governing the porosity of the resulting carbon. The atmosphere under which activation...
Determination of sugar content in soft drinks. Simple, Safe and Sustainable! Soft drinks are one ... more Determination of sugar content in soft drinks. Simple, Safe and Sustainable! Soft drinks are one of the food products that most contribute to the intake of sugar by the Portuguese population, assuming the first position in adolescents. Facing such excessive consumption, it is essential to raise the awareness of the society, in general, and of young people, in particular, for this type of consumption and its potential risks! This article presents a practical laboratory work that aims to determine the amount of sugar in soft drinks. The main objectives are to promote the knowledge, skills and competences related to the measurement of masses and volumes, as basic operations in chemistry laboratories, as well as plotting graphs and fitting lines to experimental results. In addition, the work presented contributes to integrate Chemical education within the scope of the Green Chemistry paradigm and to promote reflection and action within the scope of the Sustainable Development Goals, pro...
Over the last decades the literature has shown the possibility of producing activated carbons (AC... more Over the last decades the literature has shown the possibility of producing activated carbons (AC) from a wide variety of raw materials and to use them as one of the most environment-friendly solutions for waste disposal. Additionally it has been shown that the adsorption of pollutants from different media by AC is one of the most efficient techniques for remediating or solving this type of problem [1]. In this context, the presence of pesticides in water can cause serious problems in the environment and to human health; their removal from wastewaters is a crucial concern. The work presented here focuses these two problematic areas (solid waste reduction and wastewater treatment). The main idea was to develop low cost and efficiently adsorbent materials for hazardous compounds removal from aquatic media, to level admitted in drinking water [2]. In this perspective, we present a study involving the production of AC, by chemical activation with KOH, from wastes PET (PET-2-700), the op...
Os pictogramas de perigo presentes nos rótulos dos produtos químicos de uso diário informam sobre... more Os pictogramas de perigo presentes nos rótulos dos produtos químicos de uso diário informam sobre os perigos físicos e os potenciais efeitos nocivos dos mesmos para a saúde humana e para o meio ambiente
Adsorção de metformina em carvões activado
Na presente comunicação apresenta-se um estudo referente à estabilidade mecânica de materiais Ti-... more Na presente comunicação apresenta-se um estudo referente à estabilidade mecânica de materiais Ti-MCM-41 preparados, por substituição isomórfica durante a síntese, segundo um processo realizado à temperatura e pressão ambiente, tendo sido avaliado o efeito do aumento progressivo de uma pressão externa unidireccional nas propriedades estruturais dos referidos materiais. A título comparativo são também estudadas amostras constituídas unicamente por sílica
No presente trabalho apresenta-se um estudo referente à síntese, caracterização e resistência à a... more No presente trabalho apresenta-se um estudo referente à síntese, caracterização e resistência à aplicação do aumento progressivo de pressão externa unidireccional de amostras de Ti-MCM-41 e de Ti-SBA-15, contendo diferentes teores de metal (5≤Si/Ti≤100), preparadas por substituição isomórfica durante a síntese
Neste trabalho apresentam-se os resultados da determinação de calores de adsorção, de adsortivos ... more Neste trabalho apresentam-se os resultados da determinação de calores de adsorção, de adsortivos com dimensões e polaridades diferentes, em alguns negros de fumo e nos carvões superactivados (M25 e M30) por IGC. A determinação de calores de adsorção relativamente elevados nas amostras M25 e M30 pôs em evidência a presença de microporosidade estreita até então desconhecida
On the basis of the studies performed, the activated carbons (AC) prepared from recycled PET, by ... more On the basis of the studies performed, the activated carbons (AC) prepared from recycled PET, by chemical activation with KOH (PET-2-700), can be successfully used on the removal of MCPA and MB from aqueous medium. In order to improve the pollutant adsorption capacity removal, the PET-2-700 was submitted to different post treatment. The oxidised AC (PET-2-700HN) exhibits an increase on the MB adsorption capacity but show a MCPA decrease adsorption removal. The PET-2-700 was submitted to different reduction post treatments. The high temperature treatment, PET-2-700T, was not favourable for increasing the MB or MCPA adsorption capacity. However the PET-2-700N and the PET-2-700U show a significant increase on the MCPA adsorption capacity. The results prove the influence of chemical characteristics of the AC on the MB and MCPA removal. The MB and MCPA adsorption isotherm were analyzed according to the Langmuir and Freundlich models, and calculated parameters reflect with good accuracy t...
his PhD thesis presents studies on the preparation, characterisation, thermal stability, stabilit... more his PhD thesis presents studies on the preparation, characterisation, thermal stability, stability during long term exposure to water vapour at 298K and evaluation of the catalytic properties of Ti-MCM-41 materials. Studies related to the synthesis and structural characterisation of Si-MCM-41 materials, prepared at room temperature, from structure directing agents with different chain lengths and by direct addition of the silica source or by its addition in alcoholic solution, allowed selection of tetra-, hexa- and octadecyltrimethylammonium bromides as the most suitable structure directing agents for the preparation of M41S type materials of high quality and exclusion of BuOH as the alcohol in the process of synthesis of the these materials. After developing and implementing a new method for the synthesis of Ti-MCM-41 materials, carried out at room temperature and based on the procedure for preparing Si-MCM-41 solids, a systematic studied of the effect of the principal synthesis pa...
Neste trabalho apresentam-se os estudos de preparação, caracterização e estabilidade hidrotérmica... more Neste trabalho apresentam-se os estudos de preparação, caracterização e estabilidade hidrotérmica de materiais Ti-SBA15. Para o efeito, desenvolveu-se um novo método de síntese, processo hidrótermico por via directa, que permitiu a obtenção de materiais com elevado teor de Ti e de acordo com as razões molares de síntese, Si/Ti, pré-definidas. Os materiais foram caracterizados por DRX e adsorção de N2 a 77K o que permitiu verificar que todas as amostras com razão molar Si/Ti10 apresentam uma estrutura hexagonal mesoporosa, regular e uniforme. Por outro lado, os ensaios de estabilidade hidrotérmica, realizados por imersão das amostras em água à temperatura de 373,15K e durante 24 horas, revelaram que os materiais em causa exibem uma boa estabilidade hidrotérmica
Neste artigo de divulgação sobre a cafeína (parte I) apresenta-se, numa perspetiva de “Química pa... more Neste artigo de divulgação sobre a cafeína (parte I) apresenta-se, numa perspetiva de “Química para Todos”, as principais designações, fórmulas e caraterísticas físico-químicas, a sua ocorrência e história, e, ainda um breve resumo sobre os processos de isolamento, síntese e produção
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Papers by Cristina Galacho