Kinetics of the oxidative ammonolysis of lignin

Ewellyn A. Capanema*, Mikhail Balakshin

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterScientificpeer-review

Abstract

The effect of reaction variables on the oxidative ammonolysis of technical lignins was studied in the range of 0.4-0.8 M NH4OH, reaction temperature of 70 - 130°C, oxygen pressure of 0.5 - 1.2 MPa and pH 9- 12.7. The kinetics of nitrogen incorporation consists of two phases, both of which follow a pseudo-first order reaction law. The reaction is 1st and 0.5 order with respect to oxygen and NH4OH concentration, respectively. The effective activation energy of nitrogen incorporation is rather low, 33-43 kJ/mol. The dependence of the reaction rate on pH of the reaction solution goes through a maximum. Linear correlation between nitrogen incorporation and O-demethylation, CO2 formation, oxygen uptake as well as oxygen incorporation were observed. Structural analyses of the soluble N-modified lignins by FTIR and 1H NMR spectroscopic techniques showed only qualitative differences of the spectra obtained under different reaction conditions indicating that the reaction conditions do not affect the reaction pathways. A scheme of possible reaction mechanisms is postulated based on the experimental results.

Original languageEnglish
Title of host publicationWhat to Know about Lignin
PublisherNova Science Publishers, Inc.
Pages303-328
Number of pages26
ISBN (Electronic)978-1-5361-9222-3
Publication statusPublished - 28 Jan 2021
MoE publication typeA3 Part of a book or another research book

Keywords

  • Lignin
  • N-modified lignin
  • Oxidative ammonolysis
  • Reaction kinetics

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