The chemical oxidation of lignin found in Sappi Saiccor dissolving pulp mill effluent

Abstract

Sappi Saiccor (situated in Durban, South Africa) dissolving pulp mill effluent, produced from an acid bisulphite pulping process, uses acacia and eucalyptus hardwoods to produce a unique and different blend of lignin that has not been previously studied. The chemical oxidation of lignin found in Sappi Saiccor's effluent has been investigated using a number of different chemical oxidising agents, such as nitrobenzene, oxygen with and without the presence of a copper sulphate pentahydrate catalyst, and hydrogen peroxide. The reaction products were extracted with acid and identified using GC-MS and LC-MS techniques. Nitrobenzene is a good oxidising agent but tends to produce many toxic by-products and would not be acceptable on an industrial scale. Oxygen oxidation has previously been shown to produce aldehyde-type compounds, and in this work has produced good yields of both vanillin and syringaldehyde compared to previous oxygen oxidation reactions. Hydrogen peroxide is a strong oxidising agent that tends to over-oxidise the lignin during long reaction times.

Functional Hybrid Materials Based on Manganese Dioxide and Lignin Activated by Ionic Liquids and Their Application in the Production of Lithium Ion Batteries

“…Activation of the biopolymer is carried out to modify functional groups while leaving the aromatic base of the polymer intact [ 17 ]. Originally, lignin was subjected to oxidation to better understand its structure and to identify its bonds.…”

Production of Monomeric Aromatic Compounds from Oil Palm Empty Fruit Bunch Fiber Lignin by Chemical and Enzymatic Methods

“…This finding was supported by study [ 16 ], where nitrobenzene oxidation has been declared as the best oxidation method to produce high yield of aromatic aldehyde from lignin. However, study [ 27 ] reported an opposite finding. Direct oxygen oxidation has been suggested to be capable of producing higher yield of monomeric aromatic compounds than nitrobenzene oxidation when elevated temperature and pressure applied.…”

“…According to the results obtained, syringaldehyde was the sole product of OPEFBF lignin nitrobenzene oxidation, followed by hydroxybenzoic acid and vanillin. Under the commonly used temperature setting of nitrobenzene oxidation (~170°C), vanillin and syringaldehyde were always reported to be the main products, to indicate the ratio of guaiacyl and syringyl units in the lignin [ 27 ]. The work in [ 25 , 31 ] reported that OPEFBF lignin contained the highest proportion of noncondensed syringyl units with small amount of noncondensed guaiacyl units and fewer p -hydroxyphenyl units.…”

“…The reaction mixture was heated to 100°C and maintained for 30, 90, and 180 minutes. Oxygen oxidation was carried out under atmospheric pressure [ 27 ]. Experiment control was conducted as the prescribed procedure, where oxygen gas was not channeled into the reaction mixture.…”

Greener Routes to Biomass Waste Valorization: Lignin Transformation Through Electrocatalysis for Renewable Chemicals and Fuels Production

“…Moodley et al. used ECO to treat lignin and organic‐extracted mixtures from the Sappi Saiccor pulp mill effluent at a Ni electrode in KOH and NaClO 4 . Electrooxidation of the extracted organic components of the effluent, the concentrated effluent, and lignosulfonate (from Lignotech) all formed syringaldehyde and some vanillin; the product concentrations plateaued in the first 30 min, but declined steadily afterwards possibly due to overoxidation.…”