Lignin recovered from the hot-water extract of sugar maple (Acer saccharum) is used in this study to synthesize adhesive blends to replace phenol-formaldehyde (PF) resin. Untreated lignin is characterized by lignin content and nuclear magnetic resonance (NMR) analysis. The molecular weight distribution of the lignin and the blends are characterized by size exclusion chromatography (SEC). The effect of pH (0.3, 0.65 and 1), ex situ furfural, and curing conditions on the tensile properties of adhesive reinforced glass fibers is determined and compared to the reinforcement level of commercially available PF resin. The adhesive blend prepared at pH = 0.65 with no added furfural exhibits the highest tensile properties and meets 90% of the PF tensile strength.
Chemical pulps are produced by chemical delignification of lignocelluloses such as wood or annual non-woody plants. After pulping (e.g., kraft pulping), the remaining lignin is removed by bleaching to produce a high quality, bright paper. The goal of bleaching is to remove lignin from the pulp without a negative effect on the cellulose; for this reason, delignification should be performed in a highly selective manner. New environmentally-friendly alternatives to conventional chlorine-based bleaching technologies (e.g., oxygen, ozone, or peroxide bleaching) have been suggested or implemented. In an attempt to find inorganic agents that mimic the action of highly selective lignin-degrading enzymes and that can be applicable in industrial conditions, the researchers have focused on polyoxometalates (POMs), used either as regenerable redox reagents (in anaerobic conditions) or as catalysts (in aerobic conditions) of oxidative delignification. The aim of this paper is to review the basic concepts of POM delignification in these two processes.
While there may be many reasons why very interesting science ideas never reach commercial practice, one of the more prevalent is that the reaction or process, which is scientifically possible, cannot be made efficient enough to achieve economic viability. One pathway to economic viability for many business sectors is the multi-product portfolio. Research, development, and deployment of viable biorefinery technology must meld sound science with engineering and business economics. It is virtually axiomatic that increased value can be generated by isolating relatively pure substances from heterogeneous raw materials. Woody biomass is a heterogeneous raw material consisting of the major structural components, cellulose, lignin, and hemicelluloses, as well as minor components, such as extractives and ash. Cellulose is a linear homopolymer of D-glucopyrano-units with β-D(14) connections and is the wood component most resistant to chemical and biological degradation. Lignin is a macromolecule of phenylpropanoid units, second to cellulose in bio-resistance, and is the key component that is sought for removal from woody biomass in chemical pulping. Hemicelluloses are a collection of heteropolysaccharides, comprised mainly of 5-and 6-carbon sugars. Extractives, some of which have high commercial value, are a collection of low molecular weight organic and inorganic woody materials that can be removed, to some extent, under mild conditions. Applied Biorefinery Sciences, LLC (a private, New York, USA based company) is commercializing a OPEN ACCESSForests 2011, 2 930 value-optimization pathway (the ABS Process™) for generating a multi-product portfolio by isolating and recovering homogeneous substances from each of the above mentioned major and minor woody biomass components. The ABS Process™ incorporates the patent pending, core biorefinery technology, -hot water extraction‖, as developed at the State University of New York College of Environmental Science and Forestry (SUNY-ESF). Hot water extraction in the absence of mineral acids and bases is preferred because of its ability to generate multiple high value output products without chemical input, recovery, or disposal costs. Instead of added chemicals in the cooking phase, the ABS Process™ relies upon an autocatalytic reaction in which acetyl groups, bound through an ester linkage to hemicellulose chains, are hydrolyzed at high temperature in water. The resulting acidic conditions (final pH ~3.5) and temperatures of 160-170 C permit further solubilization and diffusion of oligomeric 5-and 6-carbon sugars, acetic acid, aromatic substances, monomeric sugars, and other trace compounds into the extract solution. These conditions also avoid extensive degradation of monosaccharides, enabling membrane fractionation and other chemical separation techniques to be used in the following separations. A range of separation techniques are applied on the extract solution to isolate and purify fermentable sugars, acetic acid, lignin, furfural, formic acid, other hemicellulose ...
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