Production of high-quality dissolving pulp from eucalyptus wood chips using deep eutectic solvent and elemental chlorine-free bleaching

Abstract

Deep eutectic solvent (DES) provides promising alternatives to conventional pulping and cellulose purification with significantly lower energy consumption and impacts on the environment. In this work, choline chloride – lactic acid (ChCl-LA DES) pulping of eucalyptus wood chips combined with several ECF bleaching sequences was investigated to produce high-grade dissolving pulps. Initially, the dependency of DES pulping yield and delignification efficiency on the moisture content (MC) of used wood chips was evaluated. The results exhibited the crucial influence of the MC of wood chips on the delignification efficiency of DES pulping. DES pulping under optimized conditions resulted in an unbleached pulp with kappa number of 42, relatively high screened yield 48.1% and viscosity 796 cm³/g, as well as very low hemicellulose content, typically less than 3.8%. Further purification of the obtained pulp using D-E_p-D and OO-D-E_p-D bleaching sequences produces several dissolving pulps characterized by a high viscosity 695 cm³/g and brightness 89.5% ISO, indicating low degradation of cellulose during DES pulping. DES pulping exhibited considerable potential to remove the hemicelluloses from wood chips and produce high-quality dissolving pulps. This could be attained through shorter pulping operations conducted at a lower temperature and a higher screened yield compared to current dissolving pulp production operations.

Highlights

• Deep eutectic solvent is able to delignify eucalyptus wood chips efficiently at moderate temperature.

• Moisture content of eucalyptus wood chips has crucial influence on pulping.

• Pulp contains very low hemicellulose.

• DES pulps are bleached easily using ECF bleaching sequences.

• DES pulping of eucalyptus wood chips followed by ECF bleaching produces high quality dissolving pulp with low energy and chemical consumption.

Keywords:

• Wood pulping
• deep eutectic solvent
• hemicellulose extraction
• dissolving pulp
• ECF bleaching

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data available on request from the authors.

Additional information

Funding

LGP₂ is part of the LabEx Tec 21 Investissements d’Avenir - grant agreement n°ANR-11-LABX-0030 and of PolyNat Carnot Institute Investissements d’Avenir - grant agreement n° ANR-16-CARN-0025-01. This study was performed under the INDES project, financed by the PolyNat Carnot Institute. Trials were made at LGP₂ and CTP, Grenoble, France. The authors gratefully acknowledge the financial support provided by PolyNat Carnot Institute, CNRS and Research Deputy of University of Tehran, Iran, and the staff of LGP₂ and CTP for technical assistance.