Degradation of cellulose by hydrogen chloride gas under elevated pressure in a custom-built reactor

Eero Kontturi*, Aaro Knuts, Eric Enqvist, Timo Pääkkönen

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Abstract

Acid-catalysed hydrolysis of cellulose was investigated in a custom-built reactor where dry HCl gas could be dosed at a pressure range between 0.1 - 1.0 bar. The mechanism of degradation proceeds by HCl adsorption on the fibre surface, followed by dissociation of HCl in a thin water layer covering the fibres, resulting in subsequent hydrolysis. The effect of water content was also investigated by conditioning the fibres in diverse relative humidity conditions prior to the hydrolysis. The degree of polymerisation (DP) dropped quickly to levelling-off degree of polymerisation (LODP) at room temperature, signalling that all disordered segments in cellulose microfibrils can easily be hydrolysed with HCl gas. Further hydrolysis presumably from the crystallite ends was detected at higher pressures at prolonged time periods (several days). Curiously, higher water contents (up to 10%) in the fibres resulted in significant humin formation from the glucose generated in cellulose hydrolysis. Such levels of humin are rarely detected from reaction mixtures with conventional aqueous acids. The results showed that behaviour of cellulosic fibres under pressurized HCl gas is fundamentally different from the well-established conditions in aqueous hydrolytic systems. By proper understanding on what governs the hydrolysis and its side reactions, HCl gas has potential to become a viable reagent in the future biorefinery. Moreover, gas is easier to recycle and the dry reaction product is easier to purify than in the case of aqueous systems.

Original languageEnglish
Title of host publicationNWBC 2018 - Proceedings of the 8th Nordic Wood Biorefinery Conference
EditorsEemeli Hytonen, Jessica Vepsalainen
PublisherTechnical Research Centre of Finland (VTT) and Association of Finnish Civil Engineers (RIL)
Pages179-183
Number of pages5
ISBN (Electronic)9789513886714
ISBN (Print)978-951-38-8672-1
Publication statusPublished - 2018
MoE publication typeA4 Article in a conference publication
EventNordic Wood Biorefinery Conference - Scandic Marina Congress Center, Helsinki, Finland
Duration: 23 Oct 201825 Oct 2018
Conference number: 8
http://bioeconomy.vtt.fi/NWBC2018

Publication series

NameVTT Technology
Number340
ISSN (Print)2242-1211

Conference

ConferenceNordic Wood Biorefinery Conference
Abbreviated titleNWBC
CountryFinland
CityHelsinki
Period23/10/201825/10/2018
Internet address

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