Browsing by Author "Belgacem, Mohamed Naceur"
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- An integrated process to produce vanillin and lignin-based polyurethanes from Kraft ligninPublication . Silva, Eduardo A.B.; Zabkova, Miriam; Araújo, José D.; Cateto, Carolina; Barreiro, M.F.; Belgacem, Mohamed Naceur; Rodrigues, AlírioThe aim of this manuscript is to present an integrated process that includes reaction and separation steps for producing vanillin and lignin-based polyurethanes from Kraft lignin. It provides details about lignin oxidation and subsequent vanillin recovery, as well as, the synthesis of lignin-based polyurethanes. The oxidation of Kraft lignin in alkaline medium has been carried out in a batch reactor and the optimum operational conditions for vanillin production obtained. The feasibility of a continuous process for vanillin production has been analyzed using a structured bubble column reactor. The generated reaction stream (degraded lignin and sodium vanillate) was further subjected to an ultrafiltration process to recover the vanillate. An ion-exchange process allows recovering the vanillin by passing the vanillate solution through a column packed with an ion-exchange resin in H+ form. The remaining lignin can act as a raw material to produce polyurethanes and/or biofuels. In this work the first approach was explored.
- Analysis of the oxypropylation process of a lignocellulosic material, almond shell, using the response surface methodology (RSM)Publication . Pinto, João A.; Prieto Lage, Miguel A.; Ferreira, Isabel C.F.R.; Belgacem, Mohamed Naceur; Rodrigues, Alírio; Barreiro, M.F.
- Bioactivity evaluation of four technical lignins: Alcell, Indulin-AT, Sarkanda and Curan 27-11PPublication . Marques, A.; Cateto, Carolina; Calhelha, Ricardo C.; Barros, Lillian; Queiroz, Maria João R.P.; Belgacem, Mohamed Naceur; Rodrigues, Alírio; Ferreira, Isabel C.F.R.; Barreiro, M.F.In what concerns bioactive properties, and due to its phenolic character, lignin is mostly studied for their antioxidant activity. In this work four technical lignins (Alcell, Indulin-AT, Sarkanda and Curan 27-11P) have been evaluated for their antioxidant activity (DPPH radical scavenging activity, reducing power and inhibition of β-carotene bleaching) and antitumor potential against MCF-7, NCI-H460, HCT-15, HeLa and HepG2 cell lines. Additionally, the toxicity for non-tumour cells (PLP2) was also evaluated. The obtained results were correlated with the chemical and structural features of the studied lignins. Based on the achieved results, lignins of GS type, i.e. lignins rich in syringyl phenol units and poor in p-hydroxyphenyl ones result in better antitumor potential.
- Biodegradation study of I lignin-based rigid polyrethane foamsPublication . Lopretti, Mary; Cateto, Carolina; Barreiro, M.F.; Ottati, Carolina; Rodrigues, Alírio; Belgacem, Mohamed NaceurPolyurethanes are considered as one of the most versatile polymeric materials offering a wide range of products with applications in diverse sectors. Rigid polyurethane (RPU) foams belong to this class of products and represent a commercially important class of expanded materials. In the present work RPU foams have been prepared from lignin-based polyols (LP) obtained by oxypropylation of two technical lignins (Alcell and Indulin AT) and biodegradability evaluated using respirometry tests in liquid and solid media. A RPU foam produced from a commercial polyether polyol (CP) based on sorbitol (Lupranol® 3323) was used as reference. Lignin biodegradation by P. chrysogenum, T. harzianum, T. reesei, T. versicolor and P. chrysosporium fungi was tested. Respirometry tests (in liquid and solid media) were performed and foam’s biodegradation evaluated based on the produced CO2.
- Composição de biomassas residuais e avaliação da sua influência nas condições da reação de oxipropilaçãoPublication . Pinto, João A.; Belgacem, Mohamed Naceur; Rodrigues, Alírio; Barreiro, M.F.A utilização de biomassa residual para a obtenção de novos materiais é um tema de interesse no contexto atual, nomeadamente na sua avaliação como alternativa às matérias-primas provenientes do petróleo. Neste contexto, os resíduos agroindustriais são matérias-primas atrativas; na sua maioria não possuem valor económico, sendo usadas maioritariamente como fertilizantes ou mesmo na obtenção de energia pelas indústrias que os geram. Uma via de interesse para a sua valorização consiste na obtenção de polióis por processos de oxipropilação. O principal objetivo da oxipropilação consiste na obtenção de polióis líquidos (oxipropilação total) ou polióis bifásicos (oxipropilação parcial). Estes podem ser utilizados como co-monómeros na síntese de poliuretanos ou poliésteres. A oxipropilação é um processo de polimerização que conduz à formação de enxertos de poli (óxido de propileno) a partir dos grupos hidróxilo disponíveis na biomassa, levando este processo à liquefação da matéria -prima sólida. Teóricamente, qualquer biomassa contendo grupos hidroxilo (por exemplo, lenhina, polpa de beterraba, cortiça, caroço de azeitona, semente de colza, etc.) pode ser transformada, por oxipropilação, em polióis líquidos.
- Comprehensive insights into lignin oxypropylation reactionPublication . Cateto, Carolina; Barreiro, M.F.; Rodrigues, Alírio; Belgacem, Mohamed NaceurPolyols 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 results, together with the determined homopolymer content were analyzed with respect to the used formulations (L/PO ratio and catalyst content) and the polyol properties (IOH, viscosity and Tg).
- Development of silica-rich polyols from rice husk biomassPublication . Pinto, João A.; Belgacem, Mohamed Naceur; Rodrigues, Alírio; Barreiro, M.F.Rice (Oryza sativa) is one of the most produced and consumed cereals in the world, being the main food for more than half of the world population. It contains, by weight, about 25% of husk and 10% of bran, which represent a high volume of residues. In fact, every year about 30 million tons of solid residues (husk and pulp) are produced, most of them inadequately disposed. The rice husk ash (RHA) has proved to be an important source material for manufacturing value-added silicon carbide, silicon nitride, silicon tetrachloride, magnesium silicide, pure silicon, zeolites, fillers for rubbers and plastic composites, corrosion resistant cements, adsorbents and support of heterogeneous catalysts. The abundant presence of silica is considered an interesting feature of this lignocellulosic residue, which can be exploited in the production of silica-rich polyols. In this context, the oxypropylation of RH will enable the direct obtainment of polyols enriched with silica, which can find application as raw-materials for the synthesis of polyurethanes and other polymeric materials. The incorporation of silica in polyurethanes leads to an increase of crystallinity and polymer chain orientation. Also, the incorporation of nanofillers like silica can provide materials with higher thermal, mechanical, optical properties, and flame retardancy properties. In fact, silica nanoparticles have received much attention due to their mild synthetic preparative conditions, large surface area, smooth nanoporous surface, high adsorption capacity and large pore volume. In this context, and as a preliminary study to the topic, the oxypropylation process of RH will be presented and discussed.
- Evaluation of the almond shell oxypropylation process trough the surface response methodologyPublication . Pinto, João A.; Prieto Lage, Miguel A.; Ferreira, Isabel C.F.R.; Belgacem, Mohamed Naceur; Rodrigues, Alírio; Barreiro, M.F.The efficiency of an oxypropylation process depends on several variables and operating conditions, which may not be generalized due to the diverse nature of subtracts. In lignocellulosic biomasses, the content of each fraction (lignin, cellulose and hemicellulose) can differ, as well as, the crystalline organization, which may limit reagent’s access to biomass. Also, the hydroxyl content can vary among biomasses; high values demand higher amounts of reactants, namely catalyst content, and more severe reaction conditions. Therefore, owing to biomass variability, selection of the operating conditions for oxypropylation their optimization is a key issue. In this context, one-factor-at-a-time approaches are commonly used to optimize processes; but it is well-known that optimal operating conditions or interactions between variables cannot be predicted by this simplistic method. Both problems may be overcome by employing the response surface methodology (RSM).
- FTIR and NMR studies on lignin acetylationPublication . Cateto, Carolina; Barreiro, M.F.; Rodrigues, Alírio; Brochier-Salon, M.C.; Thielemans, Wim; Belgacem, Mohamed NaceurIn this work, a comparative study of an acetylation procedure, using four different lignin samples was performed. The chosen lignin samples, Indulin AT (Meadwestvaco), Alcell (Repap), Curan 27-11P (Borregaard LignoTech) and Sarkanda (Granit SA), represent both the guaiacyl and guaiacyl-syringyl type, and were obtained from different pulp processes (kraft and organosolv). Lignin was acetylated using an acetic anhydride-pyridine mixture and the final sample was recovered by precipitation. Final samples, with different reaction times (1 and 2 hours), were characterized by FTIR and 13C NMR analysis, and the obtained spectra were compared with the corresponding ones for non-acetylated samples. Within the used experimental conditions and samples, an incomplete acetylation yield appeared to be common. Total hydroxyl content, determined independently by titration and based on the 13C NMR results, was found to be in close agreement.
- FTIR and NMR studies on lignin acetylationPublication . Cateto, Carolina; Barreiro, M.F.; Rodrigues, Alírio; Brochier-Salon, M.C.; Thielemans, Wim; Belgacem, Mohamed NaceurIn this work, a comparative study of an acetylation procedure, using four different lignin samples was performed. The chosen lignin samples, Indulin AT (Meadwestvaco), Alcell (Repap), Curan 27-11P (Borregaard LignoTech) and Sarkanda (Granit SA), represent both the guaiacyl and guaiacyl-syringyl type, and were obtained from different pulp processes (kraft and organosolv). Lignin was acetylated using an acetic anhydride-pyridine mixture and the final sample was recovered by precipitation. Final samples, with different reaction times (1 and 2 hours), were characterized by FTIR and 13C NMR analysis, and the obtained spectra were compared with the corresponding ones for non-acetylated samples. Within the used experimental conditions and samples, an incomplete acetylation yield appeared to be common. Total hydroxyl content, determined independently by titration and based on the 13C NMR results, was found to be in close agreement.
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