QUICK NON-DESTRUCTIVE ANALYSIS OF CONDENSED LIGNIN BY FTIR. PART 2. PULP SAMPLES FROM ACID SULFITE COOKING

"In our previous work, we demonstrated how lignin condensation and precipitation taking place in kraft pulping can be detected and even quantified by Fourier Transform Infrared (FTIR) spectroscopy. Because lignin reactions in acid sulfite pulping are very different from those occurring during kraft cooking, a new analysis method is proposed to rapidly analyze the condensed lignin in acid sulfite pulp. This kind of analysis is useful for sulfite pulp mills to detect the elevated risk of black cook. This paper presents and discusses the novel method using FTIR spectroscopy to rapidly analyze lignin condensation in softwood pulp samples from acid sulfite processes. Several softwood pulp samples from acid sulfite pulping at varying levels of condensation were included in this research. According to the results, FTIR spectroscopy allows indirect quantification of lignin condensation in a difficult matrix of wood constituents, such as in incompletely delignified acid sulfite pulp."

Simultaneous pyrolysis and trimethylsilylation with N-methyl-(trimethylsilyl) trifluoroacetamide for the characterisation of lignocellulosic materials from kraft pulping

Simultaneous pyrolysis and trimethylsilylation (SPyT) withN-methyl-(trimethylsilyl)trifluoroacetamide (MSTFA) was used to characterise lignocellulosic materials from pine and eucalyptus obtained by kraft pulping. This approach protects the carboxyl groups and helps preserve the original structure of phenolic products during analytical pyrolysis, and so that pyrolysis and derivatisation occur simultaneously and the fragments of underivatised compounds are also silylatated. The SPyT products are representative for the structures present in carbohydrates and lignin of the investigated materials. The method is also suited to semi-quantitative evaluation also in terms of detection of condensed lignin structures in pulps and kraft lignins.

Preparation of a Low Reducing Effect Sulfonated Alkali Lignin and Application as Dye Dispersant

A novel grafting hydroxypropyl sulfonated and blocking condensed lignin (GSBAL) dye dispersant was prepared based on alkali lignin (AL) by sulfonation and etherification reactions. The significant increase in the sulfonic group content and the molecular weight endow GSBAL with excellent dispersity and stability at high temperatures. More importantly, the unfavorable property of the reducing effect of AL was largely reduced since over 80% of the phenolic hydroxyl groups were blocked. The functional azo groups in the dye could be mostly retained. The reducing rate of dye with GSBAL was decreased to 6.54% (25 °C), much lower than 18.62% for sulfomethylated alkali lignin (SAL) and 15.73% for sodium lignosulfonate (NaLS). The dispersity and exhaustion of the dye bath with GSBAL dispersant was significantly improved compared with that of a dye bath with SAL and NaLS.