Percorrer por autor "Cateto, Carolina"
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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.
- Bio-based composite materials from olive stonePublication . Sibaja, María; Alvarado, P.; Jiménez, L.; Rojas, Orlando J.; Barreiro, M.F.; Cateto, Carolina; Rodrigues, Alírio; Lopretti, MaryThe present work describes the methodology used for the preparation and characterization of composite samples prepared by mixing various percentages of olive stone flour in a polyester resin matrix. A study on the chemical-physical properties of the olive stone is reported, as well as, a set of tests to evaluate the mechanical properties of the manufactured products obtained. Biodegradation studies were carried out on the obtained composite materials.
- Bio-based composite materials from olive stonePublication . Sibaja, María; Alvarado, P.; Jiménez, L.; Rojas, Orlando J.; Barreiro, M.F.; Cateto, Carolina; Rodrigues, Alírio; Lopretti, MaryThe present work describes the methodology used for the preparation and characterization of composite samples prepared by mixing various percentages of olive stone flour in a polyester resin matrix. A study on the chemical-physical properties of the olive stone is reported, as well as, a set of tests to evaluate the mechanical properties of the manufactured products obtained. Biodegradation studies were carried out on the obtained composite materials.
- 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.
- 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).
- 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.
- Fungal degradation of lignin-based rigid polyurethane foamsPublication . Amaral, Joana S.; Sepúlveda, Manuel Martinho Vilas Boas; Cateto, Carolina; Fernandes, Isabel P.; Rodrigues, Alírio; Belgacem, Mohamed Naceur; Barreiro, M.F.In this work, the ability of Aspergillus niger to degrade two lignin-based rigid polyurethane (RPU) foams was evaluated and compared with a control RPU foam based on a commercial polyether-polyol, Lupranol 3323. The foams degradation was studied according to different procedures, namely by setting different series of batch cultures, either using liquid media or soil conditions, for 90 days at 30 C. For the soil conditions, two different assays were performed, namely with and without A. niger addition. The changes in the morphology of the RPU foams were evaluated by optical (OM) and scanning electron microscopy (SEM), whereas the structural modifications were inspected by FTIR spectroscopy. After 90 days treatment, morphological changes were clearly visible at the surface (cell wall) of the two lignin-based foams indicating a stronger effect of the microorganisms’ activity in these samples. FTIR spectra confirmed that the chemical structure of the polymer suffered modifications after the respirometry assays due to microorganisms attack. Comparatively to the commercial foam, it was observed that both the lignin-based foams presented a higher degradation level.
- Kinetic study of the formation of lignin-based polyurethanes in bulkPublication . Cateto, Carolina; Barreiro, M.F.; Rodrigues, Alírio; Belgacem, Mohamed NaceurThe formation of lignin-based polyurethanes was monitored by Fourier transform infrared spectroscopy working in attenuated total reflectance mode (FTIR-ATR) and kinetics was analyzed according to a global second order model. The used chemical system consisted of 4,40-methylene-diphenylene diisocyanate (MDI), polycaprolactone (PCL) of three different average-molecular weights (400, 750 and 1000) and two lignin (L) samples (Alcell (A) and Indulin AT (IAT)), incorporated at different weight contents (10%, 15%, 20% and 25%) in the polyol mixture. The polymerization reaction was carried in bulk and without the presence of any catalyst. Results showed that isocyanate conversion decreases with the increase of both lignin content and PCL molecular weight. Moreover, the Indulin AT series leaded to lower isocyanate conversions compared to Alcell counterparts. The global second order treatment showed to be dependent of lignin type and content as well as PCL molecular weight. In fact, for the studied system this model was found to be more adequate for low lignin contents. After the region of linearity, a negative deviation was always observed and found to be more pronounced with increasing the lignin content.