Diffusion Dynamics in Pinus sylvestris Kraft Impregnation: Effect of Deacetylation and Galactoglucomannan Degradation

Abstract

During the impregnation stage of a Kraft cooking, dynamic changes occur in wood properties due to the alkali action. Particularly, its ion transport capacity, the effective capillary cross sectional area (ECCSA), is changed due to chemical reactions and swelling. In this work, the ECCSA in the transverse wood direction has been determined for Pinus sylvestris on the basis of the analogy between capillarity and electrical conductivity. Results show that the behavior of ECCSA can be associated with (a) the degree of removal of native acetyl groups and (b) the galactoglucomannan (GGM) losses due to peeling/stopping reactions and alkaline hydrolysis. Kinetic expressions for both reactions were discussed and a correlation between the ECCSA and both acetyl and GGM contents was established.

Molecular Modeling to Increase Kraft Pulp Yield (CRADA CRD-18-00782 Final Report)

“…The amount of GGM retained was very small even for the experiments with pretreatment at 80°C. Since primary peeling of GGM starts at about 80°C, 22 while primary peeling of cellulose is only significant at 130°C [23][24] it may be that MM stabilizes some cellulose before peeling but that the glucomannan stabilization by MM is too slow compared to primary peeling of glucomannan. The residual alkali was generally within the acceptable ranges of 4-10 g/L.…”

The limits of delignification in kraft cooking

“…The hydroxide ions will split off acetyl groups, and deacetylation is one of the main alkali-consuming reactions during kraft cooking. Acetyl groups can form strong hydrogen bonds with carboxyl groups, so deacetylation also increases the paths available for diffusion (Sjöström et al 1965;Zanuttini et al 1998;Inalbon and Zanuttini 2008;Inalbon et al 2009a;Montagna et al 2013). For fibre liberation, it would be desired if the lignin located in the middle lamellae would be specially targeted for degradation reactions and dissolution.…”

Profiles of alkali concentration and galactoglucomannan degradation in kraft impregnation of Scots pine wood: Experimental observations and modeling

“…The specific deacetylation kinetics is used and the model is refined considering: (i) the GGM degradation kinetics according to Pannanen et al (2010) and Montagna et al (2013), and (ii) the ionization of phenolic hydroxyl (OH phen ) groups of lignin. This ionization produces additional alkali consumption and generates extra immobile anionic groups.…”

“…Nevertheless, ECCSA can be better related to the degrees of reaction. Montagna et al (2013) found the following expression of ECCSA as a function of acetyl (AcG), GGM contents, and temperature for pine wood: …”