Naturally occurring phenolic sources: monomers and polymers
TL;DR: In this article, a review article is designed to acknowledge efforts of researchers towards the 3C motto, not only trying to create but also adapting the principles to conserve and care for a sustainable environment.
Abstract: Exploration of sustainable alternatives to chemicals derived from petro-based industries is the current challenge for maintaining the balance between the needs of a changing world while preserving nature. The major source for sustainable chemicals is either the natural existing plant sources or waste generated from agro-based industries. The utility of such resources will supplement new processed materials with different sets of properties and environmental friendliness due to their biodegradability and low toxicity during preparation, usage and disposal. Amongst other polymers used on a day-to-day basis, phenolic resins account for vast usage. Replacement of petro-based monomers such as phenol and its derivatives either partly or completely utilized for the synthesis of such resins is ongoing. Extraction of natural phenolic components from cashew nut shell liquid, lignin, tannin, palm oil, coconut shell tar or from agricultural and industrial waste, and their utilization as synthons for the preparation of bio-based polymers and properties obtained are reviewed in this paper. This review article is designed to acknowledge efforts of researchers towards the “3C” motto – not only trying to create but also adapting the principles to conserve and care for a sustainable environment. This review paper describes how extraction, separation and recovery of desired phenolic compounds have occurred recently; how substituted phenol compounds, unmodified and modified, act as monomers for polymerization; and how the presence of sustainable phenolic material affects the properties of polymers. There are about 600 references cited and still there is a lot to uncover in this research area.
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TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
33,785 citations
TL;DR: This review focuses on the catalytic chemical conversion of lignocellulose and its primary ingredients into value-added chemicals and fuel products using ILs as the reaction media.
Abstract: Innovative valorization of naturally abundant and renewable lignocellulosic biomass is of great importance in the pursuit of a sustainable future and biobased economy. Ionic liquids (ILs) as an important kind of green solvents and functional fluids have attracted significant attention for the catalytic transformation of lignocellulosic feedstocks into a diverse range of products. Taking advantage of some unique properties of ILs with different functions, the catalytic transformation processes can be carried out more efficiently and potentially with lower environmental impacts. Also, a new product portfolio may be derived from catalytic systems with ILs as media. This review focuses on the catalytic chemical conversion of lignocellulose and its primary ingredients (i.e., cellulose, hemicellulose, and lignin) into value-added chemicals and fuel products using ILs as the reaction media. An outlook is provided at the end of this review to highlight the challenges and opportunities associated with this interes...
627 citations
TL;DR: The use of vanillin as a building block for the chemical industry is discussed in this article, where vanillin is one of the only molecular phenolic compounds manufactured on an industrial scale from biomass and has the potential to become a key intermediate for the synthesis of bio-based polymers, for which aromatic monomers are needed to reach good thermo-mechanical properties.
Abstract: The use of vanillin as a building block for the chemical industry is discussed in this article. Vanillin is currently one of the only molecular phenolic compounds manufactured on an industrial scale from biomass. It has thus the potential to become a key-intermediate for the synthesis of bio-based polymers, for which aromatic monomers are needed to reach good thermo-mechanical properties. After a first part dedicated to the current sourcing of vanillin, this article focuses on the alkaline oxidation lignin-to-vanillin process, reporting advantages and limits, discusses the various postdepolymerization methods for product isolation and finally examines the outlook for the wider use of vanillin as a key building block for the chemical industry.
562 citations
538 citations
TL;DR: This review covers an alternative approach, in which the lignin valorization is performed in concert with the pulping process, which enables the fractionation of all components of thelignocellulosic biomass into valorizable streams.
Abstract: Current processes for the fractionation of lignocellulosic biomass focus on the production of high-quality cellulosic fibers for paper, board, and viscose production. The other fractions that constitute a major part of lignocellulose are treated as waste or used for energy production. The transformation of lignocellulose beyond paper pulp to a commodity (e.g., fine chemicals, polymer precursors, and fuels) is the only feasible alternative to current refining of fossil fuels as a carbon feedstock. Inspired by this challenge, scientists and engineers have developed a plethora of methods for the valorization of biomass. However, most studies have focused on using one single purified component from lignocellulose that is not currently generated by the existing biomass fractionation processes. A lot of effort has been made to develop efficient methods for lignin depolymerization. The step to take this fundamental research to industrial applications is still a major challenge. This review covers an alternative approach, in which the lignin valorization is performed in concert with the pulping process. This enables the fractionation of all components of the lignocellulosic biomass into valorizable streams. Lignocellulose fractions obtained this way (e.g., lignin oil and glucose) can be utilized in a number of existing procedures. The review covers historic, current, and future perspectives, with respect to catalytic lignocellulose fractionation processes.
427 citations
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40,330 citations
"Naturally occurring phenolic source..." refers background in this paper
...Lignin hydroxyl groups can be modified to epoxy followed by treatment with diamine leading to amination.(423) Lignin undergoes structural modification on reaction with carboxylic acids, carboxylic acid 40 halides, or anhydrides....
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TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
33,785 citations
"Naturally occurring phenolic source..." refers background or methods in this paper
...ppm demonstrated the presence of stereoisomers (catechin/epicatechin; gallocatechin/ epigallocatechin).(362) The proanthocyanidin tannins in quebracho (Schinopsis lorentzii) heartwood and black wattle (Acacia mearnsii) bark showed signal at 118 or 105 ppm due to presence of catechols (quebracho) or 95 pyrogallols (wattle) respectively....
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...This technique confirms the major polymeric architecture present in willow (Salix alba) and lime leaf (Tilia 45 cordata) contain procyanidin units while for spruce needle (Pacia abie) and beech leaves (Fagus Sylvatica) have both procyanidin and prodelphinidinin varying ratios.(362) Two-dimensional chromatography (Hydrophilic Interaction Chromatography with Reversed-Phase Liquid Chromatography) coupled with MALDI50...
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TL;DR: The antiradical properties of various antioxidants were determined using the free radical 2,2-Diphenyl-1-picrylhydrazyl (DPPH*) in its radical form as discussed by the authors.
Abstract: The antiradical activities of various antioxidants were determined using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH*). In its radical form. DPPH* has an absorption band at 515 nm which dissappears upon reduction by an antiradical compound. Twenty compounds were reacted with the DPPH* and shown to follow one of three possible reaction kinetic types. Ascorbic acid, isoascorbic acid and isoeugenol reacted quickly with the DPPH* reaching a steady state immediately. Rosmarinic acid and δ-tocopherol reacted a little slower and reached a steady state within 30 min. The remaining compounds reacted more progressively with the DPPH* reaching a steady state from 1 to 6 h. Caffeic acid, gentisic acid and gallic acid showed the highest antiradical activities with a stoichiometry of 4 to 6 reduced DPPH* molecules per molecule of antioxidant. Vanillin, phenol, γ-resorcylic acid and vanillic acid were found to be poor antiradical compounds. The stoichiometry for the other 13 phenolic compounds varied from one to three reduced DPPH* molecules per molecule of antioxidant. Possible mechanisms are proposed to explain the experimental results.
18,907 citations
TL;DR: A method for the screening of antioxidant activity is reported as a decolorization assay applicable to both lipophilic and hydrophilic antioxidants, including flavonoids, hydroxycinnamates, carotenoids, and plasma antioxidants.
18,580 citations