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- Valorization of lignin side-streams into polyols and rigid polyurethane foams—a contribution to the pulp and paper industry biorefineryPublication . Pinto, João A.; Fernandes, Isabel P.; Pinto, Virgínia; Gomes, Elson; Oliveira, Cátia F.; Pinto, Paula C.R.; Mesquita, L.M.R.; Piloto, P.A.G.; Rodrigues, Alírio; Barreiro, M.F.Valorization of industrial low-value side-streams are of great interest, contributing to boosts in the circular economy. In this context, lignin side-streams of the pulp and paper industry were oxypropylated to produce biobased polyols and tested in the synthesis of rigid polyurethane (RPU) foams. E. globulus lignins, namely a lignin isolated from an industrial Kraft black liquor and depolymerized lignins obtained as by-products of an oxidation process, were used. RPU foams, synthesized with 100% lignin-based polyols and using a 1.1 NCO/OH ratio, were characterized concerning apparent density, morphology, thermal conductivity, thermal stability, and heat release rate (HRR). Foams containing the lignin-based polyols presented densities varying from 44.7 to 112.2 kg/m3 and thermal conductivity in the range of 37.2–49.0 mW/mK. For the reference foam (sample produced with 100% wt. Daltofoam TP 32015 polyol), values of 70.9 kg/m3 and 41.1 mW/mK were obtained, respectively. The achieved results point out the viability of using the generated lignin-based polyols at 100% content in RPU foams, mainly when depolymerized lignins are used. Moreover, fire retardancy was favored when the lignin-based polyols were introduced. The proposed strategies can contribute to establishing the integrated pulp and paper biorefinery concept where material synthesis (polyols and RPU foams) can be combined with chemical production (vanillin and syringaldehyde).
- 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.
- 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).
- Rigid polyurethane foams modified with liginin based bio-polyolsPublication . Salach, K.; Kurańska, M.; Pinto, João A.; Barreiro, M.F.; Prociak, A.Nowadays, a large number of polyurethane (PU) systems modifications relies on the use of different bio-polyols, as described in literature. Among them, one of the most important is the incorporation of bio-polyols based on plant wastes such as lignin. In this work, two bio-polyols have been synthesized from a technical lignin and applied to obtain rigid PU foams (10-30wt. in polyol premix). The lignin, obtained by an organosolv process (aqueous ethanol) proceeds from hardwoods and was converted into liquid bio-polyols by an oxypropylation process. The addition of the lignin-based bio-polyols to the PU system increased its reactivity, as confirmed by a faster decrease of the dielectric polarization and an increase of the maximum temperature in the foam core during the foaming process. The foam modified with these bio-polyols had a slightly lower apparent density and compressive strength. The obtained foams have an apparent density and a closed cell content of about 40 to 45 kg/m3 and 86-89%, respectively. The compressive strength of the foams decrease as the bio-polyol content increased. On the other hand the thermal conductivities of the obtained materials were similar ca. 23 mW/m·K. Concerning thermal stability, lignin-based foams start to degrade at lower temperatures and show a slower degradation pattern (high residue in TG).
- 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.
- Development of chitosan microspheres through a green dual crosslinking strategy based on tripolyphosphate and vanillinPublication . Correa, Rodolpho Fagundes; Colucci, Giovana; Halla, Noureddine; Pinto, João A.; Santamaria-Echart, Arantzazu; Blanco, Silvia Priscila; Fernandes, Isabel P.; Barreiro, M.F.Microencapsulation procedures have recently focused attention on designing novel mi-crospheres via green synthesis strategies. The use of chitosan (CS) as an encapsulating material has increased interest due to its unique bioactive properties and the various crosslinking possibilities offered by their functional groups. The consolidation of the microspheres by physical crosslinking using sodium tripolyphosphate (TPP) combined with chemical crosslinking using vanillin (VA) open new opportunities in the framework of green dual crosslinking strategies. The developed strategy, a straightforward technique based on an aqueous medium avoiding complex separa-tion/washing steps, offers advantages over the processes based on VA, mostly using water-in-oil emulsion approaches. Thus, in this work, the combination of TPP crosslinking (3, 5, and 10 wt.%) via spray-coagulation technique with two VA crosslinking methods (in situ and post-treatment using 1 wt.% VA) were employed in the preparation of microspheres. The microspheres were characterized concerning morphology, particle size, physicochemical properties, thermal stability, and swelling behavior. Results revealed that the combination of 5 wt.% TPP with in situ VA crosslinking led to microspheres with promising properties, being an attractive alternative for natural bioactives encapsulation due to the green connotations associated with the process.
- Valorization of almond agro-industrial residues: production of biopolyols from almond shellPublication . Pinto, João A.; Barreiro, M.F.The almond is a nut, well-known and quite produced in Portugal, especially in the region of Trás-os-Montes e Alto Douro and Algarve. Almond (Prunus dulcis) is a mid-size tree of the Rosaceae family (rose family). Almond fruit consists of the hull, shell, and kernel (nut). The edible kernel or nut is separated and collected for commercial uses and is widely used for food applications purposes. At global level almond production and processing generates millions of tons of residues in addition to almond nuts. Almond residues, including shells, hulls, pruning, leaves, skin and discharged inedible kernel, are viable feedstocks for a wide range of products. In this context, this work aims at review the uses of almond processing residues and related industries (e.g. sweet almond oil extraction) and open new avenues for their exploitation by suggesting new applications. The work comprises the identification and evaluation of the almond industry residues, their characterization and traditional uses. Additionally novel utilizations are proposed in the field of chemicals and materials. A special emphasis is given to the development of biopolyols from the almond shell by means of oxypropylation processes. In this last case, conventional synthesis using a high pressure reactor was attempted. The almond shell residue used in this work was characterized in what concerns lignocellulosic composition, moisture, ash contents and extractables. It comprises cellulose, hemicellulose and lignin at contents of 30.2%, 12.3% and 34.5%, respectively. Moreover it presents a moisture content of 6.0%, 2.2% of ashes and 8.1% of total extractables with predominance of the polar ones. Oxypropylation was successfully conducted under moderate conditions of temperature, pressure and time giving rise to liquid polyols with a homopolymer content ranging from 5-75%, a hydroxyl number between 250-520 mg KOH/g and viscosities up to 750 Pa.s. The unreacted almond shell residues varied between 5.0 and 37.3%, results in accordance with published data for other biomass substrates. In a general way it was observed that low AS/PO ratios (i.e. 10/90) give rise to polyols with low unreacted AS residue, low viscosity (due to a high homopolymer content), and the lowest IOH number. Moreover the polyols based on this formulation presented the highest thermal stability, especially the one with the formulation 10/90/5. The polyols based on the AS/PO ratio of 30/70 presented high unreacted AS residues, low homopolymer content, high IOH number (the highest value correspond to the formulation 30/70/5, 518.2 mgKOH/g) and high viscosity.
- Thermal properties and molecular interactions of alginate/gelatin hydrogel microparticlesPublication . Pilipenko, Nadezhda; Sorita, Guilherme Dallarmi; Pinto, João A.; Fernandes, Isabel P.; Gonçalves, Odinei Hess; Leimann, Fernanda Vitória; Barreiro, M.F.Hydrogels are attractive materials for several engineering applications. They can be obtained, for example, from the combination of alginate and gelatin, and have been widely used in microencapsulation processes. In this work alginate/gelatin hydrogel microparticles were prepared based on the enzymatic crosslinking of gelatin (transglutaminase, TGase), and alginate gelation induced by calcium chloride (CaCl2). The evaluated conditions to study thermal properties, and molecular interactions between microparticle’s components where: gelatin amount (%wt, polymeric mixture-basis), TGase amounts (active units/ ggelatin) and contact time with CaCl2 (min). Four samples were obtained. For sample 1 the evaluated conditions were: gelatin amount 25 %wt; TGase amounts 10 U/g and contact time with CaCl2 81 min. For samples 2, 3 and 4: gelatin amount 75 %wt, 75 %wt and 75 %wt; TGase amounts 10 U/g, 30 U/g and 30 U/g and contact time with CaCl2 81 min, 21 min and 81 min, relatively. One formulation composed only by alginate (MAlginate) was also produced for comparison. The contact time with CaCl2 was 240 min. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) confirmed that the studied variables influence both, thermal properties and the developed molecular interactions between the two polymers (alginate and gelatin) (fig.1). FTIR results show that a higher contact time with CaCl2 led to an increased level of alginate crosslinking. The use of TGase results in the increasing of the hydrogen bounded N-H groups. According to DSC results the use of TGase increases the thermal stability of crosslinked microparticles.
- Polyols and rigid polyurethane foams derived from lignin side-streams of the pulp and paper industryPublication . Fernandes, Isabel P.; Pinto, João A.; Gomes, Elson; Oliveira, Cátia F.; Pinto, Paula C.R.; Mesquita, L.M.R.; Piloto, P.A.G.; Rodrigues, Alírio; Barreiro, M.F.Lignin is one of the major components of the side-streams of the pulp and paper industries and of the emerging lignocellulosic biore neries. Find new strategies for lignin valorisation, apart from e vironmental issues, will contribute to close the lignocellulosic value-chain. In this context, this work will focus on the synthesis of polyols through oxypropylation and their subsequent incorporation into rigid polyurethane (RPU) foam formulations. Two E. globulus lignin streams were tested: (i) lignin isolated from industrial kraft liquor and (ii) depolymerized lignin resulting from an oxidation process developed at the LA LSRE-LCM to produce vanillin and syringaldehyde. This work is therefore part of the LA LSRE-LCM global strategy towards the consolidation of the integrated process to valorise lignin from the kraft pulp industry, which accounts with more than 25 years of experience.
- Valorisation of brazilian pine-fruit shell residue (araucaria angustifolia) in the production of biopolyolsPublication . Rezende, Stephany; Pinto, João A.; Leimann, Fernanda Vitória; Barreiro, M.F.The valorisation of agro-forestry residues, namely the ones which do not have commercial value, have attracted the interest of academia and industrials contributing to generate new alternatives in the eld of chemicals and materials. The purpose is not only promoting their reuse to generate value- added products, but also highlight the production of bio-based products from renewable resources. Araucaria angustifolia is a coniferous tree native of South America, found in the South and Southwest of Brazil, part of a whole vegetation of the Atlantic Forest. The Brazilian pine-fruit shell (PFS) is an attractive lignocellulosic residue with potential to be used as a raw material to produce polymeric materials. In this context, this work comprises the characterization of PFS and their use to produce polyols trough oxypropylation