Valorization of Lignins for Use in Multi-phase Systems

摘要

Technical lignins, are mainly used as low-value solid fuels due to their complex structures and diversity of sources. However, lignin presents multifunctionality, surface activity, nontoxicity, high heating values, etc., all of which can be considered for utilization in diverse areas.;Industrial Kraft lignins were modified by carboxymethylation, enabling their solubilization at neutral pH. The carboxymethylated lignins (CML) were characterized by elemental analysis, molecular weight (GPC), and degree of substitution (31P NMR). Surface tension analysis confirmed the suitability of the CML to reduce surface tension, given their surface activity. They presented a critical aggregation concentration in water with a minimum surface tension of 34 mN/m. The salinity and pH of the aqueous phase were adjusted as formulation variables in different (water-oil systems) Winsor-type of systems and were then emulsified following standard emulsification protocols. An ultra-high viscosity bitumen oil and other lighter fuels were used as oil phases. The drop size distribution of emulsions prepared with aqueous phases of varying pH, CML degree of substitution, and composition (water-to-oil ratio, WOR) were determined and discussed in terms of composition and formulation variables. Oil-in-water (O/W) emulsions stabilized by CMLs showed a strong shear thinning behavior (rheological behavior) with a characteristic drop size less than 2 im. They were stable for at least 1 month. CML/kerosene/water fuel emulsions were evaluated in a lab-scale fuel engine which indicated the emulsions burned effectively and displayed a relative high HHV. Compared with the pure base fuel, and under certain conditions, the O/W fuel emulsion presented lower NOx and CO emissions and maintained a relatively high combustion efficiency.;Carboxymethylated lignins were used to form liquid foams, which were produced via agitation and compressed air bubbling. The foamability and foam stability of carboxymethylated lignins in water were measured as a function of concentration, temperature, pH, mixing rate and air content. Fibers were mixed with CML solution (0.6 % solids in aqueous dispersion) under agitation to stabilize liquid foams. The foamability and stability were analyzed at varying CML and fiber concentration, pH and co-surfactant/CML ratio. After dewatering, the materials were assembled by foam-laying techniques that were further characterized for residual lignin (retention), morphology, and physical-mechanical properties (formation, density, air permeability, surface roughness, tensile and internal bond strength). The results were compared with those of similar structures obtained from foams stabilized with an anionic surfactant (SDS) as well as those from foam-free (water) systems.;A highly efficient disilazane reaction was used to substitute hydroxyls in Kraft lignin with silicone-containing vinyl groups. The SiC and SiOC bonds can improve lignin macromolecular mobility. Moreover, the modified lignin was copolymerized with acrylonitrile, and the products were used to produce composite films. The products of lignin modification and PANlignin copolymerization were characterized by FT-IR, and 1H, 13C, 31P NMR, which indicated the success of the respective procedures. Glass coating via solution casting followed by oven drying yielded films that were tested via SEM, contact angle, TGA and DSC. A good compatibility between silicone functional lignin and PAN was determined. Finally, tensile strength of the composite films were obtained via DMA.;The silicone-functionalized lignins can partially of phenol to produce lignin-based phenolic foams displaying closed-cell morphologies. Vinyl functional groups enhanced the crosslinking process during the curing step and endowed stronger bonding networks. The thermal behavior of the lignin-based resol and phenolic foams were analyzed by DSC. The morphology of the phenolic foams was observed under SEM. The mechanical properties of compression and flexural strength were tested by DMA, which indicated that the phenolic foam based on silicone-functionalized lignin is flexible and strong, properties that are otherwise difficult to attain at the same time.