The Chemistry of Delignification - A General Concept - Part II

Gierer, Josef

doi:10.1515/hfsg.1982.36.2.55

Cited by 90 publications

(55 citation statements)

References 20 publications

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“…In acidic media, it forms a hydroxonium cation (Lachenal 1996;Gierer 1982), which is an electrophile and attacks the electron-rich sites of lignin, initiating such reactions as: ring hydroxylation, oxidative demethylation, oxidative ring opening, displacement of side chains, cleavage of β-aryl ether bonds, and epoxidation (Gierer 1982). The reduced viscosity of the pulps from hydrogen peroxide-aided treatments is presumably due to the formation of harmful radicals induced by high temperature and transition metals present in wood (Lachenal 1996).…”

Section: Hydrotropic Treatmentmentioning

confidence: 99%

Hydrotropic Fractionation of Birch Wood into Cellulose and Lignin: A New Step Towards Green Biorefinery

2013

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Hydrotropic treatment is an attractive process that uses water-soluble and environmentally friendly chemicals. Currently, this method is practically unexploited on a large scale due to the long treatment times required. In this study, the hydrotropic process was modified by the addition of hydrogen peroxide, formic acid, or both. The modified treatments were more selective than the reference, and the pulps obtained using the modified treatments had lower lignin contents. After bleaching, the resultant pulps were comparable to dissolving pulps with respect to the content of hemicelluloses and viscosity. Cellulose solutions were successfully obtained in a 7% NaOH/12% urea aqueous solvent after pretreating the bleached pulp with a HCl/EtOH mixture. Hydrotropic lignin was recovered from the spent solution by precipitation in water. The lignin had very low contents of carbohydrates and sulphur. The preliminary results show that a hydrotropic process can be used for such biorefinery applications as fractionation of fibres, cellulose polymer, and lignin from birch wood. The green cellulose and lignin biopolymers can potentially be used for shaping biomaterials or production of biobased chemicals.

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Section: Hydrotropic Treatmentmentioning

confidence: 99%

Hydrotropic Fractionation of Birch Wood into Cellulose and Lignin: A New Step Towards Green Biorefinery

2013

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“…6). The subsequent steps include a reaction with the superoxide anion radical (O2· -) forming a hydroperoxide anion structure and its rearrangement to the primary oxidation products (oxirane, muconic acid ester, or carbonyl structures) (Chang and Gratzl 1980;Gierer 1982;Sixta et al 2006). The hydroperoxide structure, with a pKa value of 12 to 13, plays a crucial role, and has lately been shown to be the key intermediate in the course of phenolic lignin oxidation (Ji et al 2009a,b).…”

Section: Alkali-o2 Oxidationmentioning

confidence: 99%

Experiences of Kraft Lignin Functionalization by Enzymatic and Chemical Oxidation

Kalliola¹,

Asikainen²,

Talja³

et al. 2014

BioResources

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Linear hydrophilic derivatives are expected to soften lignin and improve its utilization in composite applications. Oxidation by means of laccase in the presence of oxygen was employed in an attempt to functionalize commercial kraft lignin by vanillic acid-PEG ester and ether derivatives. Thielavia arenaria and Melanocarpus albomyces laccases at pH 6 and 8 were used. According to O2 consumption and the increase in molar mass, the tested laccases were active toward the lignin and the vanillic acid derivatives and also formed corresponding phenoxyl radicals. However, homogenous polymerization instead of cross-coupling and functionalization took place. As an alternative, lignin functionalization by the ester derivative by chemical oxidation under alkali-O2 conditions was also tested. Efficient lignin polymerization was observed. However, functionalization was not detected. Interestingly, a clear decrease in lignin glass transition temperature was obtained by an isolation procedure that included freeze-drying. This suggests that functionalization may not be necessary to induce the desired softening effect.

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“…During peroxyformic acid treatment, electrophilic HO + ions are formed (HCOOOH + H + = HCOOH + HO + ). According to model compound studies the main reactions for the HO + ions with lignin are expected to be ring hydroxylation, oxidative ring opening, substitution of side chains, cleavage of β-aryl ether bonds, and epoxidation (Gierer et al 1982;Hortling et al 1991;Strumila and Rapson 1975;Yuan et al 1998b).…”

Section: Papermaking Propertiesmentioning

confidence: 99%

Comparative study on the prebleaching of bamboo and hardwood pulps produced in Kharnaphuli Paper Mills

Jahan¹,

Hosen²,

Rahman³

2013

Turk J Agric For

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The Chemistry of Delignification - A General Concept - Part II

Cited by 90 publications

References 20 publications

Hydrotropic Fractionation of Birch Wood into Cellulose and Lignin: A New Step Towards Green Biorefinery

Hydrotropic Fractionation of Birch Wood into Cellulose and Lignin: A New Step Towards Green Biorefinery

Experiences of Kraft Lignin Functionalization by Enzymatic and Chemical Oxidation

Comparative study on the prebleaching of bamboo and hardwood pulps produced in Kharnaphuli Paper Mills

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