Recursos de colección

Biblioteca Digital do IPB (53.442 recursos)

A Biblioteca Digital do IPB, tem por objectivo divulgar e permitir o livre acesso à produção científica produzida pela comunidade académica, promovendo a integração, partilha e a visibilidade da informação científica e garantindo a preservação da memória intelectual do Instituto Politécnico de Bragança.

DTQB - Resumos em Proceedings Não Indexados ao ISI

Mostrando recursos 1 - 20 de 188

  1. Chemical modification as a strategy to modulate properties of oxypropylated products

    Barbosa, M.; Matos, M.; Barreiro, M.F.; Gandini, A.
    Nowadays a great interest is devoted to the production and use of biobased products. The main scope of the oxypropylation process is to obtain polyols, in the form of viscous liquids, which can be interesting co-monomers to produce polyurethanes and polyesters. Due to the high hydroxyl content of natural polymers (suitable substrates to be oxypropylated), the generated polyols are multifunctional, hence most adequate to be used in rigid polyurethane foam formulations. Additionally, their properties can be modulated through chemical modification, thus opening new avenues for their exploitation. Following that strategy, an oxypropylated product (IOH of 350) used as a model polyol,...

  2. Comprehensive insights into lignin oxypropylation reaction

    Cateto, C.A.; Barreiro, M.F.; Rodrigues, A.E.; Belgacem, M.N.
    Polyols resulting from oxypropylation are a mixture of oxypropylated lignin and some low molecular weight products (polypropylene oxide oligomers). Normally these oligomers are left in the final mixture since they constitute useful co-monomers, lowering the Tg and the viscosity of the resulting liquefied lignin. In this work a series of polyols based on Alcell lignin have been produced using L/PO ratios (Lignin/propylene oxide, w/v) of 10/90, 20/80, 30/70 and 40/60 and catalyst contents (KOH) between 2-5% (C/(C+L), w/w). The produced polyols and the corresponding extracted fractions (homopolymer and oxypropylated lignin) have been analyzed by size exclusion chromatography (SEC). The obtained...

  3. Chemical composition of different oregano (origanum vulgare l.) essential oils: relevance for the activity against foodborne and spoilage bacteria

    Amaral, J.S.; Ribeiro, António E.; Alves, Sofia; Gonçalves, Alexandre; Poeta, Patrícia
    Herbs and spices have been used for centuries in culinary for seasoning and flavouring purposes. More recently, there has been a growing interest regarding the use of some plants and its essential oils (EO) for their activity against foodborne pathogens and foodspoilage bacteria. Due to its potential in extending the self-life of foods and its better acceptability by consumers who demand more “natural” foods, the use of EO can be an interesting alternative to substitute, at least partially, synthetic preservatives.

  4. Solubility of hesperetin in mixed solvents

    Ferreira, Olga; Schröder, Bernd; Coutinho, João A.P.
    The study of the solubility of flavonoids is essential to support the design of several separation processes in the food and pharmaceutical industries. Hesperetin is a flavanone with great importance for its promising biological and pharmacological properties. Our previous studies included the measurement of the solubility of this biomolecule in several pure organic solvents [1]. In this work, new solubility data is presented for hesperetin in the binary mixed solvents water + ethanol, water + methanol, and water + acetone, at 298.15 K. The isothermal shake-flask method was applied, followed by quantitative analysis by gravimetry. The three solubility phase diagrams obtained,...

  5. Effect of KCl and (NH4)2SO4 on the solubility of four amino acids in water at 298.15 K

    Ferreira, Olga; Silva, Carina; Pinho, Simão
    Amino acids (AA)are very important biomolecules, not only for their intrinsic pharmaceutical value, but also, as the building blocks of proteins. The study of their solubility in aqueous electrolyte solutions can therefore be useful for the design of the separation processees and, be related to protein chemistry, providing an important insight into the interactions present in those complex solutions.

  6. Partial molar volumes of amino acids in aqueous solutions of magnesium chloride

    Ferreira, Olga; Javornik, Ema; Pinho, Simão
    The lack of a deep molecular picture of the interactions which govern the biochemetry of vital processes is steel one critical issue in this area, which limits the development of pharmaceutical solutions for diseases induced by biochemical disorders [1]and the improvement of the efficiency of biotechnological processes [2].

  7. Multicomponent chiral separations by analytical and preparative liquid chromatography

    Ribeiro, António E.; Pais, L.S.; Rodrigues, A.E.
    This work will present a complete methodology concerning experimental, modelling and simulation results. Both the CHIRALPAK AD and CHIRALPAK IA CSP will be evaluated. The selection of the proper CSP/solvent combination for preparative operation will be fully study taking into account the screening strategy proposed by Zhang et al. Additional results include the measurement of nadolol stereoisomers solubilities, equilibrium adsorption data and fixed bed (breakthroughs) experiments. The complete screening of CSP/solvent combination will lead to the choice of the better solutions for the separation of nadolol stereoisomers, considering the target component or components to be obtained. Simulation and experimental results...

  8. Methodologies for the separation of chiral drugs by liquid chromatography: from analytical to preparative scale

    Ribeiro, António E.; Rodrigues, A.E.; Pais, L.S.
    The main goal of the present work is to clear demonstrate that the selection of the proper solvent composition is a key step for both analytical and preparative separations. A complete methodology developed in the last years inside the LSRE group will be described. Three real optimization case-studies will be presented: two non-steroidal anti-inflammatory drugs (the separation of ketoprofen and flurbiprofen enantiomers) and one antihypertensive drug (the separation of nadolol stereoisomers).

  9. Monolith technology in isolation of human immunoglobulin G subclasses

    Leblebici, P.; Rodrigues, A.E.; Pais, L.S.
    In the present study, a method was developed for the separation of hIgG into its subclasses with the advantages of monolithic technology. pH elution was applied using Protein A monolith column in a stepwise method and conditions were optimized. Since IgG3 has very low affinity to Protein A, elution was occurred immediately upon injection of the sample. IgG1 and IgG4 were eluted simultaneously under the applied conditions. Furthermore, IgG2 was separated with significant purity. According to the present results, monolithic Protein A column could be proposed as a time efficient separation media for the enrichment of IgG2 which is the...

  10. Synthesis of 1,1-dibutoxyethane in a simulated moving bed adsorptive reactor

    Graça, N.S.; Pais, L.S.; Silva, V.M.T.M.; Rodrigues, A.E.
    The synthesis of 1,1-Dibutoxyethane was carried out in a Simulated Moving Bed pilot unit LICOSEP 12-26 (Novasep, France) with 12 columns packed with the commercial ionexchange resin Amberlyst 15 (Rohm & Haas, France). Experimentally it was obtained a raffinate purity of 85% with a productivity of 5,04 Kg.L-1.d-1 and a desorbent consumption of 15, 5 L.Kg-1. The influence of the different operation parameters was studied by simulation. The results showed that the SMBR process presents a potential to be a competitive, efficient and environmentally friendly way to produce 1,1- Dibutoxyethane and other acetals.

  11. Multicomponent chiral separations by multicolumn and simulated moving bed adsorption processes

    Ribeiro, António E.; Graça, Nuno S.; Ferreira, Alexandre P.; Rodrigues, A.E.; Pais, L.S.
    This work will present a complete methodology concerning experimental, modelling and simulation results. Both the CHIRALPAK AD and CHIRALPAK IA CSP will be evaluated. The selection of the proper CSP/solvent combination for preparative operation will be fully study taking into account the screening strategy proposed by Zhang et al. Additional results include the measurement of nadolol stereoisomers solubilities, equilibrium adsorption data and fixed bed (breakthroughs) experiments. The complete screening of CSP/solvent combination will lead to the choice of the better solutions for the separation of nadolol stereoisomers, considering the target component or components to be obtained. Simulation and experimental results...

  12. Optimization of simulated moving bed processes for multicomponent chiral separations

    Ribeiro, António E.; Rodrigues, A.E.; Pais, L.S.
    This work will present and discuss the experimental and simulation results obtained for the analytical and preparative separation of the four stereoisomers of nadolol, an important example of a non-selective beta-adrenergic receptor antagonist (beta-blocker) pharmaceutical drug, widely used in the treatment of cardiovascular system diseases, such as hypertension, ischemic heart disease (angina pectoris), congestive heart failure and certain arrhythmias. The main focus will be placed in the selection of the proper CSP/solvent combination for SMB operation. Experimental results will be presented using Chiralpak AD and Chiralpak IA CSP (Daicel, Europe) and different mixtures of alkanes, alcohols and acetonitrile as solvent.

  13. Chiral separation of nadolol stereoisomers by liquid chromatography : screening of mobile phase composition and SMB separation

    Ribeiro, António E.; Pais, L.S.; Rodrigues, A.E.
    This work describes a systematic approach to rapid development of simulated moving bed (SMB) chiral chromatographic separations. The presented methodology involves several pulse experiments using a single-column to screen the best mobile phase composition using a Chiralpak AD stationary phase and equilibrium adsorption data used to specify the initial flow rates of the SMB operation.

  14. Choosing the right solvent for preparative liquid chromatography

    Ribeiro, António E.; Graça, Nuno S.; Gomes, P. Sá; Pais, L.S.; Rodrigues, A.E.
    In this work we pretend to clear demonstrate that the choice of the proper solvent is crucial for both analytical and preparative separations. The work developed in the last years by the LSRE group will be described with three real optimization case-studies: two non-steroidal anti-inflammatory drugs (the separation of ketoprofen and flurbiprofeno enantiomers) and one antihypertensive drug (the separation of nadolol stereoisomers).

  15. Separation of nadolol stereoisomers by liquid chromatography : screening of the mobile phase composition

    Ribeiro, António E.; Gomes, P. Sá; Pais, L.S.; Rodrigues, A.E.
    The screening of the most convenient mobile phase composition is presented for the chiral separation of the four stereoisomers of the beta-blocker drug nadolol. When the final goal is the preparative chiral separation, this selection is critical, since solubility, selectivity and retention are all parameters very sensitive with mobile phase composition. Experimental results will show that the best mobile phase composition is, generally, very different if we consider an analytical or a preparative separation point of view.

  16. Chiral separation of non-steroidal anti-inflammatory drugs by preparative and simulated moving bed chromatography

    Ribeiro, António E.; Gomes, Pedro Sá; Pais, L.S.; Rodrigues, A.E.
    The work presents modelling, simulation and experimental results for the chiral separation of non-steroidal anti-inflammatory drugs, particularly, the optimization of mobile phase composition under preparative and simulated moving bed chromatography. The experimental separation of two chiral systems (ketoprofen and flurbiprofen enantiomers) will be presented to show how compounds of the same family can lead to different solutions.

  17. Nanotubos de carbono para processos de tratamento de águas

    Ribeiro, Rui; Gomes, Helder; Silva, Adrián; Silva, Cláudia; Figueiredo, Joaquim; Faria, José
    Oxidantes como o oxigénio molecular, o ozono e o peróxido de hidrogénio são utilizados nos tratamentos de águas residuais por via química oxidativa podendo atuar por si próprios, ou ser ativados por meio de um catalisador, ou fotocatalisador, adequado. Sendo os tratamentos químicos processos definitivos por natureza, é possível apontar à mineralização completa dos poluentes presentes. Contudo, raramente é esse o caso, quando se procura uma solução racional do ponto de vista económico. No caso de efluentes industriais recorre-se muitas vezes a tratamentos diferenciados, com vista a uma degradação oxidativa parcial.

  18. Towards the development of water purification technologies using carbon materials and metal oxides

    Silva, Adrián; Gomes, Helder; Pereira, Manuel; Faria, Joaquim; Órfão, José; Figueiredo, José
    The abatement of environrnental pollutants, and especially the availability of clean water in sufficient amounts, are important issues in large and industrialized cities as well as in less developed regions. Advanced oxidation processes (AOPs) can decisively contribute to water purification. As a consequence, the development of effective catalysts has prompted enormous attention in materiais science. Carbon materiais have been widely employed in AOPs, usually as catalyst supports and less commoniyas catalysts on their OWD. An overview ofthe different steps involved in the development of suitable catalysts from the nano- to the macro-scale will be presented in this work, with particular emphasis on the use of carbon materiais...

  19. Materiais de carbono para processos de oxidação catalítica com peróxido de hidrogénio

    Ribeiro, Rui; Silva, Adrián; Faria, Joaquim; Gomes, Helder
    A crescente complexidade das águas residuais tem levado ao aumento do número de poluentes que são refractários aos processos convencionais de tratamento biológico. Tipicamente, a transferência deste tipo de poluentes para uma fase sólida – via adsorção – tem sido um método bastante utilizado; contudo, no sentido de promover a sua efetiva destruição, com especial incidência em águas residuais de origem industrial, surgem os processos avançados de oxidação (AOP, Advanced Oxidation Processes) – baseados na geração, e subsequente utilização, de radicais hidroxilo (HO•), conhecidos fortes agentes oxidantes. A oxidação catalítica com peróxido de hidrogénio (CWPO, Catalytic Wet Peroxide Oxidation) é um AOP que utiliza peróxido de hidrogénio...

  20. Carbon nanotubes as base materials for water treatment processes

    Faria, Joaquim; Ribeiro, Rui; Silva, Adrián; Silva, Cláudia; Figueiredo, José; Gomes, Helder
    Chemical wastewater treatments are dependent on the addition of auxiliary oxidants, which may include molecular oxygen, ozone, and hydrogen peroxide, working on their own, or activated by means of a specialized catalyst or photocatalyst. Chemical treatments are by nature definitive processes, since they can lead to complete mineralization of the existing pollutants. However, this is seldom the case, when looking for a rational solution from the socio-economical point of view. In the case of industrial effluents, special treatments are often required, even when only a partial oxidative degradation is targeted, due to the complex nature of the pollutants (e.g. dyes, pharmaceuticals, oils, organics, inorganics and bio-compounds). Some...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.