Pulsed corona discharge oxidation of aqueous lignin: decomposition and aldehydes formation

Abstract

Lignin is the mass waste product of pulp and paper industry mostly incinerated for energy recovery. Lignin is, however, a substantial source of raw material for derivatives currently produced in costly wet oxidation processes. The pulsed corona discharge (PCD) for the first time was applied to lignin oxidation aiming a cost-effective environmentally friendly lignin removal and transformation to aldehydes. The experimental research into treatment of coniferous kraft lignin aqueous solutions was undertaken to establish the dependence of lignin oxidation and aldehyde formation on the discharge parameters, initial concentration of lignin and gas phase composition. The rate and the energy efficiency of lignin oxidation increased with increasing oxygen concentration reaching up to 82 g kW-1 h-1 in 89% vol. oxygen. Oxidation energy efficiency in PCD treatment exceeds the one for conventional ozonation by the factor of two under the experimental conditions. Oxidation at low oxygen concentrations showed a tendency of the increasing aldehydes and glyoxylic acid formation yield.

Epoxy thermosets from model mixtures of the lignin-to-vanillin process

“…Extensive details concerning these conditions can be found in literature, from early patents [17][18][19][20][21][22] to more recent works. 8,[14][15][16][23][24][25][26][27][28][29] The cleavage of a guaiacyl unit (G, Figure 1) leads to the vanillate ion, which gives vanillin 1 after protonation. As mentioned earlier, G units are predominant in lignins from softwoods (G lignins).…”

Non-thermal gas-phase pulsed corona discharge for lignin modification

“…Previous research [32] has reported that the highest lignin conversion to aldehydes was obtained by increasing initial lignin concentration to 600 mg/L for a reaction in a 5-7 % volumetric oxygen gas phase. With the aim of improved conversion rate, lignin concentration was raised to 1400 mg/l and the volumetric oxygen content was reduced to 2-3 %.…”

“…Panorel et al [32] investigated implementation of PCD for lignin removal from water and for conversion of lignin into aldehydes. The PCD method was found to be an energyefficient form of wastewater treatment, including for lignin removal from water.…”

Plasma technology for lignocellulosic biomass conversion toward an electrified biorefinery

“…165 Ring-opening occurred upon subsequent alkali treatment. Panorel et al 153 used pulsed corona discharges to oxidize kraft lignin in aqueous NaOH solutions and studied the effects of pulse repetition frequency, oxygen content in air mixtures, and initial lignin concentration on the lignin oxidation and aldehyde formation. Pulsed corona discharges were more efficient than conventional ozonation processes, giving an optimum 70% degradation of lignin with low fractions of vanillin and syringaldehyde products.…”