Extraction of wheat straw with aqueous tetra-n-butylphosphonium hydroxide

Uula Hyväkkö, Alistair W.T. King, Ilkka Kilpeläinen

Research output: Contribution to journalArticleScientificpeer-review

26 Citations (Scopus)


The stability of tetra-n-butylphosphonium hydroxide ([P4444][OH](aq)) solutions and their potential for wheat straw extraction are investigated. Under certain concentration ranges, aqueous [P4444][OH](aq) is known to rapidly dissolve up to 20 wt% of cellulose at 25°C. However, at elevated temperatures and at the high concentration ranges required for cellulose dissolution, [P4444][OH](aq) irreversibly decomposes. This was determined by following the kinetics of decomposition at different temperatures and concentrations, using 31P NMR analysis of the solutions. A lower concentration range of 40 wt% [P4444][OH](aq) was observed for fractionation of wheat straw, avoiding significant decomposition of the expensive phosphonium component. Herein, the possibilities for producing cellulose-rich fractions with reduced lignin contents and hemicellulose-rich extracts are discussed. A proposal is given for a full process cycle using [P4444][OH](aq), where the phosphonium salt is used in fractionation and recovered by anion metathesis as a chloride salt. Although not demonstrated in this article, the chloride salt may be converted back to the hydroxide by means of, e.g., ion exchange.

Original languageEnglish
Pages (from-to)1565-1577
Number of pages13
Issue number1
Publication statusPublished - Feb 2014
MoE publication typeA1 Journal article-refereed


  • Biomass
  • Cellulose
  • Electrolyte
  • Fractionation
  • Hemicellulose
  • Hydroxide
  • Ionic liquid
  • Lignin
  • Phosphonium
  • Wheat straw


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