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•Gamma-valerolactone is a precursor for valuable chemicals and potential fuel additive.•Non-noble metals can be used in catalytic transfer hydrogenation (CTH) to produce ...GVL.•Dispersion of metal particles on catalysts influences hydrogenation efficiency.•Lewis acid and base sites are needed for obtaining high GVL yield and selectivity.•Metal leaching from catalysts is significant in aqueous conditions.
The distinct physicochemical properties and renewable origin of gamma-valerolactone (GVL) have provided opportunities for diversifying its applications, particularly as a green solvent, excellent fuel additive, and precursor to valuable chemicals. Among the related publications found in the SCOPUS database (≈172 in the last 10 years), we focused our effort to review the conversion of levulinic acid (LA) to GVL over non-noble metal catalysts and the corresponding mechanisms (≈30 publications) as well as the applications of GVL as a solvent, fuel additive, and platform chemical (≈30 publications) mostly in the last five years (some preceding publications have also been included due to their relevance and importance in the field). The use of non-noble metals (e.g., Cu and Zr) presents a greener route of GVL synthesis than the conventional practice employing noble metals (e.g., Pd and Ru), in view of their higher abundance and milder reaction conditions needed (e.g., low pressure and temperature without H2 involved). The significance of the catalyst characteristics in promoting catalytic transfer hydrogenation of LA to GVL is critically discussed. Structural features and acid-base properties are found to influence the activity and selectivity of catalysts. Furthermore, metal leaching in the presence of water in catalytic systems is an important issue, resulting in catalyst deactivation. Various endeavors for developing catalysts using well-dispersed metal particles along with a combination of Lewis acid and base sites are suggested for efficiently synthesizing GVL from LA.
Solvents and catalysts played important roles on the selective dissolution and conversion of hemicellulose in actual biomass to produce furfural with high yield and selectivity.
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•The ...production of furfural directly from raw biomass is reviewed.•The effective utilization of raw biomass materials to its fullest is discussed.•Selective dissolution of hemicellulose keeping cellulose and lignin intact.•Effective conversion of hemicellulose to furfural with high yield and selectivity.•The important roles of solvents and catalysts in hemicellulose upgrading process.
As one main component of lignocellulosic biomass, hemicellulose is a promising alternative for the replacement of limited fossil resources to produce furfural, thus preserving a high atom efficiency. However, the complex structure of hemicellulose and the interaction between the other two components in lignocellulosic biomass (cellulose and lignin) make the effective utilization of naturally formed structure of hemicellulose challenging. This review presents an overview of the production of furfural directly from hemicellulose in lignocellulosic biomass with special emphasis on achieving the effective utilization of hemicellulose, which includes the selective dissolution of hemicellulose from lignocellulosic biomass and the selective formation of furfural from hemicellulose derivatives. Whereas the cellulose and lignin structures are retained, which can be utilized separately. Solvents and catalysts are considered as two main factors in this valorization process of hemicellulose.
The efficient valorization of lignin could dictate the success of the 2nd generation biorefinery. Lignin, accounting for on average a third of the lignocellulosic biomass, is the most promising ...candidate for sustainable production of value‐added phenolics. However, the structural alteration induced during lignin isolation is often depleting its potential for value‐added chemicals. Recently, catalytic reductive depolymerization of lignin has appeared to be a promising and effective method for its valorization to obtain phenolic monomers. The present study systematically summarizes the far‐reaching and state‐of‐the‐art lignin valorization strategies during different stages, including conventional catalytic depolymerization of technical lignin, emerging reductive catalytic fractionation of protolignin, stabilization strategies to inhibit the undesired condensation reactions, and further catalytic upgrading of lignin‐derived monomers. Finally, the potential challenges for the future researches on the efficient valorization of lignin and possible solutions are proposed.
“Lignin‐first” biorefinery: Catalytic valorization of lignin provides a promising and attractive strategy for producing value‐added phenolic monomers. The recent advances in catalytic depolymerization of technical lignin and reductive catalytic fractionation of protolignin are comprehensively summarized. The mechanism of condensation reactions and possible solutions are also discussed.
Hierarchically porous activated Starbons® derived from starch are found to make excellent adsorbents for methylene blue, even in the presence of other dyes and inorganic salts, highlighting their ...potential to be used in water purification. The optimal material (S950C90) has a methylene blue adsorption capacity (891 mg g-1) almost nine times higher than that of unactivated S800 and four times higher than that of commercial activated carbon at 298 K. The adsorption of methylene blue onto optimal materials (S950C90 and S800K4) reaches equilibrium within 5 min. Adsorption data for all the adsorbents show a good fit to the Freundlich isotherm which allows the Gibbs free energies of adsorption to be calculated. The adsorption capacities increase as the pH of the methylene blue solution increases, allowing the dye to be desorbed by treatment with acidic ethanol and the Starbon® materials reused. Porosimetry and SEM-EDX imaging indicate that methylene blue adsorbs throughout the surface and completely fills all the micropores in the Starbon® adsorbent. The methylene blue adsorption capacities show excellent correlations with both the BET surface areas and the micropore volumes of the materials.
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•Methylene blue adsorption from aqueous solution onto biomass derived carbon.•Starch derived hierarchically porous carbon adsorbent (Starbon).•Rapid adsorption which is reversible by pH swing allowing the Starbon to be reused.•Adsorption capacity correlates to the BET surface area of the Starbon material.•Adsorption capacity correlates to the micropore volume of the Starbon material.
The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the ...conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might be anticipated that neoteric solvent systems (e.g., ionic liquids) will remain niche, while renewable routes to historically established solvents will continue to grow in importance. This review discusses bio-based solvents from the perspective of their production, identifying suitable feedstocks, platform molecules, and relevant product streams for the sustainable manufacturing of conventional solvents.
Rethinking chemistry for a circular economy Kümmerer, Klaus; Clark, James H; Zuin, Vânia G
Science (American Association for the Advancement of Science),
01/2020, Letnik:
367, Številka:
6476
Journal Article
Recenzirano
Chemical complexity complicates product recycling and manufacturing sustainability
Earth is running out of resources needed for manufacturing materials such as chemicals, minerals, and petroleum. ...Thus, these components are available only at increasing economic and environmental costs. As an important contribution to a sustainable future, chemistry and its products must be adapted to a circular economy (CE)—a system aimed at eliminating waste, circulating and recycling products, and saving resources and the environment (
1
).
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