Stability of gamma-valerolactone under pulping conditions as a basis for process optimization and chemical recovery

Marianna Granatier, Inge Schlapp-Hackl, Huy Quang Lê, Kaarlo Nieminen, Leena Pitkänen, Herbert Sixta*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
19 Downloads (Pure)

Abstract

This study focuses on the investigation of the extent of the γ-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of a 50 wt% GVL solution to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2 × 10–5 wt% to 6 wt%) at elevated temperatures (150–180 °C) and reaction times between 30 and 180 min caused the formation of 4 mol% 4-HVA. However, with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at a constant time (30 min) and temperature (180 °C) with the variation of the NaOH concentration (0.2 × 10–6 wt% to 7 wt%). The addition of less than 0.2 wt% of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The degree of decomposition after treatment was determined by NMR analysis. To verify the GVL stability under practical conditions, Betula pendula sawdust was fractionated in 50 wt% GVL with and without the addition of H2SO4 or NaOH at 180 °C and a treatment time of 120 min. The spent liquor was analyzed and a 4-HVA content of 5.6 mol% in a high acidic (20 kg H2SO4/t wood) and 6.0 mol% in an alkaline (192 kg NaOH/t wood) environment have been determined.

Original languageEnglish
Pages (from-to)11567-11578
Number of pages12
JournalCellulose
Volume28
Issue number18
Early online date13 Oct 2021
DOIs
Publication statusPublished - Dec 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • Biorefineries
  • Gamma-valerolactone
  • Organosolv
  • Pulping

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