Comparative Evaluation of Oxygen Delignification Processes for Low- and High-Lignin-Content Softwood Kraft Pulps

Abstract

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Bioconversion of oxygen-pretreated Kraft lignin to microbial lipid with oleaginous Rhodococcus opacus DSM 1069

“…1a and b, Kraft lignin in the current study is composed primarily of coniferyl (G) alcohol units with the β-O-4 aryl ether as the most abundant inter-unit linkage. 14,16,[21][22][23] The presence of α-carbonyl groups have been proven to improve the reactivity of non-condensed units and induce subsequent cleavage of side-chains by the C-C or C-O bonds, 14,22 thereby generating smaller molecular weight fragments that were believed to be more suitable for bacterial digestion. After pretreatment, part of the signals corresponding to the aliphatic-ether and aliphatic alcohol (lignin-interunit) moieties (e.g.…”

“…This process uses oxygen and alkali to remove the residual lignin from cellulose fibers at elevated temperatures. 14 The work of Gierer and colleagues concluded that this process is mainly attributed to the reaction of oxygen with the phenolic structures in lignin, resulting in the formation of phenoxy radicals and other oxy-radicals which can induce the fragmentation of the aromatic rings in lignin, while also causing side-chain scissions. 15 The degradation of non-phenolic structures has also been reported involving in the oxygen-process.…”

A Review on The Bioconversion of Lignin to Microbial Lipid with Oleaginous Rhodococcus opacus

“…Lignin depolymerization generates diverse low-molecular weight compounds which can be more readily processed [72]. Oxygendelignification (O 2 -delignification) is a pretreatment strategy that uses oxygen and alkali to remove the residual lignin from cellulose fibers at increased temperatures [73]. Significant structural changes appear in the lignin after O 2 -delignification [74][75][76][77] resulting in a decrease in molecular weight.…”

Investigation of the Chemistry of Oxygen Delignification of Low Kappa Softwood Kraft Pulp using an Organic/Inorganic Chemical Selectivity System

“…It was found that the elemental components were not very different from either the original pulp residual lignin or oxygen delignified pulp residual lignin; the only significant difference is that the oxygen content in the effluent lignin was higher than both other lignins due to the extensive oxidation of lignin by oxygen, a finding that has already been documented. [20] During the oxygen delignification process, part of the total methoxyl groups were depleted from lignin, that is the methoxyl group content in RL-O was less than that in RL. The methoxyl group content in dissolved lignin SL-O was even less than that in RL-O.…”