(748b) Ionic Liquids: Solvent Design for Diverse Sustainable Biomass Valorisation | AIChE

(748b) Ionic Liquids: Solvent Design for Diverse Sustainable Biomass Valorisation

Authors 

Morais, A. R. C. - Presenter, Faculty of Science and Technology, New University of Lisbon
da Costa Lopes, A. M., Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa

The
processing of residual lignocellulosic biomass within the biorefinery frames impelled
the use of green innovative technologies aiming at sustainable valorisation of
this feedstock. The main constrain is related to the complex and recalcitrant macromolecular
three-dimensional structure of biomass. The efficient and selective
pre-treatment of biomass into main constituents i.e. cellulose, hemicellulose
and lignin opens a possibility to produce diverse biofuels, biochemicals and
biomaterials as it happens in fossil refinery. Ionic liquids (ILs) are one of
the most promising solvents which offers greener solutions in biomass
conversion technologies into a great variety of products.1
The present work discloses two different scenarios of lignocellulosic biomass (wheat
straw) processing with ILs, where i) alkaline or ii) acidic character of ILs
remark biomass fractionation and subsequent product formation.

ILs with alkaline character demonstrated ability to dissolve the
entire biomass allowing fractionation of each single fraction of biomass. Such
approach produced high-purity fractions of cellulose, hemicellulose and lignin and
IL was recycled and reused with success confirming the economic and
environmental feasibility of the proposed method.2 Besides, a fraction rich in phenolic compounds was also produced by
employing polymeric resins and supercritical CO2
(scCO2) extraction. Silica C18 resin showed the highest extraction
efficiency of phenolic compounds, while Amberlite XAD-7 was the most selective
one. Nevertheless, a residual quantity of IL was found in the extracted samples
and further purification was achieved by applying scCO2 extraction. An
extract containing vanillin, tricin, syringaldehyde, p-coumaric
and vanillic acids, was produced with no IL presence.3 The discussed approach is presented in Figure 1.

Figure 1. Biomass fractionation after pre-treatment with
[emim][OAc] and further extraction and purification of phenolic compounds.

Another strategy of biomass valorisation was based on selective removal of the hemicellulose fraction of biomass solely using
acidic ILs, i.e. 1-butyl-3-methylimidazolium hydrogen sulphate ([bmim][HSO4])
and 1-ethyl-3-methylimidazolium hydrogen sulphate ([emim][HSO4]).
The acidity of [HSO4]-based ILs hydrolyses hemicellulose and produce pentoses or furfural
leaving a solid fraction constituted by cellulose and lignin for further
valorisation in the perspective of the biorefinery concept.4 The capacity of these ILs to hydrolyse and/or convert biomass into
pentoses and furfural can be attained by controlling the reaction conditions,
such as temperature, residence time and water content. A maximum pentose yield
of 81.6 mol% was obtained after processing of wheat straw at 141 °C during 1.5
hours with [emim][HSO4]/water mixture containing 58 wt. % of water.
The obtained result is for now, far the best result reported in literature for
biomass processing with ILs.

The present work demonstrates the great versatility of ILs to assist
biomass processing for the manufacture of a wide range of products.
Particularly, the ILs chemical character governing pathways in the
fractionation of biomass allowing designing specific strategies towards the
production of target chemicals.

Acknowledgments

This work was supported by the Fundação para a
Ciência e a Tecnologia (FCT/MEC, Portugal) through SFRH/BD/90282/2012,
IF/00471/2015 grants and by BBRI - Biomass and Bioenergy Research
Infrastructure (ROTEIRO/0189/2013) and the Associated Laboratory for
Sustainable Chemistry−Clean Processes and Technologies−LAQV which
is financed by national funds from FCT/MEC (UID/QUI/50006/2013) and co-financed
by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007265).
This work was done in the frame of COST EUBIS TD1203 action.

 

References

1.            R.
Bogel-Lukasik, Ionic Liquids in the Biorefinery Concept, RSC, Cambridge,
UK, 2015.

2.            S. P.
Magalhães da Silva, A. M. da Costa Lopes, L. B. Roseiro and R. Bogel-Lukasik, RSC
Adv.
, 2013, 3, 16040-16050.

3.            A. M. da
Costa Lopes, M. Brenner, P. Fale, L. B. Roseiro and R. Bogel-Lukasik, ACS
Sustain. Chem. Eng.
, 2016, 4, 3357-3367.

4.            A.
V. Carvalho, A. M. da Costa Lopes and R. Bogel-Lukasik, RSC Adv., 2015, 5,
47153-47164.