Issue 1, 2023

Birch fractionation in γ-valerolactone with the emphasis on pulp properties: prehydrolysis, acid-catalyzed, and alkaline-catalyzed concept

Abstract

Organosolv pulping represents an alternative to the traditional production of pulp, cellulosic fibrous material, allowing the utilization of other pulping streams. Pulping of resistant wood species such as Finnish silver birch (Betula pendula) is generally challenging for an uncatalyzed organosolv system. In this study, we investigate two concepts of organosolv γ-valerolactone (GVL) pulping for the production of dissolving pulp. Silver birch sawdust was fractionated in both a one-step process with sulfuric acid or sodium hydroxide-catalyzed liquor and a two-step process with a prehydrolysis step followed by an alkaline GVL digestion step. The selectivity of delignification and hemicellulose removal in one-stage alkaline-GVL pulping was less efficient compared to uncatalyzed GVL pulping due to the partial consumption of sodium hydroxide solution in the GVL pulping liquor, which hydrolyzed to 4-hydroxyvaleric acid (4-HVA) under alkaline conditions according to the equilibrium conditions. Acid-catalyzed GVL pulping at higher temperature (180 °C) resulted in a pure cellulose fraction with a low amount of lignin and hemicelluloses (<5%), but at the expense of pulp yield. Prehydrolysis removed 50% of the original hemicellulose content, but the overall performance of two-stage pulping did not improve pulping selectivity and thus pulp qualities. Optimum conditions for one-stage acid-catalyzed GVL pulping were identified as 150 °C, 120 min, and 5–10 kg H2SO4 per t for the production of dissolving pulp with specifications and macromolecular properties comparable to those of an acid sulfite dissolving pulp.

Graphical abstract: Birch fractionation in γ-valerolactone with the emphasis on pulp properties: prehydrolysis, acid-catalyzed, and alkaline-catalyzed concept

Supplementary files

Article information

Article type
Paper
Submitted
12 Sep 2022
Accepted
21 Oct 2022
First published
04 Nov 2022
This article is Open Access
Creative Commons BY-NC license

RSC Sustain., 2023,1, 97-106

Birch fractionation in γ-valerolactone with the emphasis on pulp properties: prehydrolysis, acid-catalyzed, and alkaline-catalyzed concept

M. Granatier, H. Q. Lê, E. C. González and H. Sixta, RSC Sustain., 2023, 1, 97 DOI: 10.1039/D2SU00046F

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