pretreatment of wheat straw using deep eutectic solvents and ultraound

Pretreatment of wheat straw using deep eutectic solvents and

ultrasound

Andrea Škulcová, MSc.

Slovak University of Technology in Bratislava, Faculty of Chemical and Food Technology,

Institute of natural and synthetic polymers, Department of wood, pulp and paper

INTRODUCTION

• new solvent systems are the great challenge in the field of green chemistry

GOAL

commercial technology - fragmentation/ isolation

biomass

lignin

others polysaccharides

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DEEP EUTECTIC SOLVENTS (DESs)

• generally – mixture of two or more components with EUTECTIC POINT

• eutectic mixture – hydrogen bonds (donors and acceptors)

• preparation of DES – temperature up to 100°C and atmospheric pressure

Fig 1: Formation of hydrogen bond between choline chloride and oxalic acid

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DEEP EUTECTIC SOLVENTS (DESs)

Tab 1: Lignin removal from biomass using different DESs in [%]

Substrate DES

Molar ratio Decrease of lignin

content by [%] Reference

HBA HBD

Wheat straw Choline chloride

Lactic acid 1:2 1:9 3.95 7.89

De Dio (2013) Malic acid 1:1 2.89

Oxalic acid 1:1 18.68

Pine wood Choline chloride

Lactic acid 1:2 1:9 4.86 9.71

De Dio (2013) Malic acid 1:1 1.71

Oxalic acid 1:1 9.71

Rice straw Lactic acid Choline chloride 2:1 5:1 9:1 64.0 75.7 74.2

Kumar et al. (2015) Betaine 2:1 5:1 65.6 70.4

Wheat straw Choline chloride

Lactic acid 1:9 1:10 14.6 29.1

Jablonský et al. (2015)

Malonic acid 1:1 3.8

Urea 1:2 1.3

Oxalic acid 1:1 57.9

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DEEP EUTECTIC SOLVENTS (DESs)

Tab 1: Lignin removal from biomass using different DESs in [%]

Substrate DES

Molar ratio Decrease of lignin

content by [%] Reference

HBA HBD

Wheat straw Choline chloride

Lactic acid 1:2 1:9 3.95 7.89

De Dio (2013) Malic acid 1:1 2.89

Oxalic acid 1:1 18.68

Pine wood Choline chloride

Lactic acid 1:2 1:9 4.86 9.71

De Dio (2013) Malic acid 1:1 1.71

Oxalic acid 1:1 9.71

Rice straw Lactic acid Choline chloride 2:1 5:1 9:1 64.0 75.7 74.2

Kumar et al. (2015) Betaine 2:1 5:1 65.6 70.4

Wheat straw Choline chloride

Lactic acid 1:9 1:10 14.6 29.1

Jablonský et al. (2015)

Malonic acid 1:1 3.8

Urea 1:2 1.3

Oxalic acid 1:1 57.9

14 h 60 °C

12 h 60 °C

24 h 60 °C

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ULTRASOUND IN BIOMASS PRETREATMENT

• modification of cell wall fibre is more flexible

• swelling better binding capacity

• fibrillation of fibre better tensile strength

Fig 2: Ultrasonic impregnation

sonotrode

suspension generator

BETTER PENETRATION

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EXPERIMENT

DELIGNIFICATION WITHOUT ULTRASOUND

• grinded wheat straw (600 mesh) laboratory experiment

• DES lactic acid: choline chloride (9:1, 10:1)

oxalic acid: choline chloride (1:1)

malonic acid: choline chloride (1:1)

urea: choline chloride (2:1)

• delignification time 24 h

• reaction temperature 60 °C

Fig 4: Prepared DES (lactic acid: choline chloride, oxalic acid: choline chloride, malonic acid: choline chloride, urea: choline chloride)

Fig 3: Grinded wheat straw 7

EXPERIMENT

DELIGNIFICATION WITHOUT ULTRASOUND

Total lignin content in grinded wheat straw was 17.3 %

Deep eutectic solvent Molar ratio

Amount of removed lignin

from total lignin [%]

Choline chloride

Lactic acid 1:9 14.6

1:10 29.1

Malonic acid 1:1 3.8

Urea 1:2 1.3

Oxalic acid 1:1 57.9

Fine extracted straw

Cellulose Hemicelluloses Lignin Ash

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DELIGNIFICATION WITH ULTRASOUND

• cut wheat straw (2 - 5 cm)

• DES lactic acid: choline chloride (10:1) • delignification time 5, 10, 20, 30, 50, 70 h • 60 °C • ultrasound 5 min

EXPERIMENT

DELIGNIFICATION WITHOUT ULTRASOUND

• cut wheat straw (2 – 5 cm)

• DES lactic acid: choline chloride (10:1)

• delignification time 5, 10, 20, 30, 50, 70 h

• 60 °C

Fig 5: Prepared wheat straw and DES (lactic acid: choline chloride)

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DELIGNIFICATION WITH ULTRASOUND

EXPERIMENT

DELIGNIFICATION WITHOUT ULTRASOUND

Total lignin content in cut wheat straw is 17.0 %

Reaction time [h]

Amount of removed lignin

from total lignin [%]

5 14.3

10 18.9

20 21.7

30 29.2

50 34.7

70 46.7

Reaction time [h]

Amount of removed lignin

from total lignin [%]

5 15.1

10 22.3

20 24.5

30 34.2

50 41.6

70 51.1

Cellulose Hemicelluloses Lignin Extractives Ash

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without US with 5 min US

CONCLUSIONS

• DESs represent promising alternative solvent systems for biomass treatment

• ultrasonic treatment increases effect of impregnation by DES

• objective properties of used DESs bring high potential in process of lignocellulosics materials fractionation

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This article was created with the support of the Ministry of Education, Science, Research and Sport of the Slovak Republic within the Research and Development Operational Programme for the project "University Science Park of STU Bratislava", ITMS 26240220084, and the project of National Centre for Research and Application of Renewable Energy Sources, ITMS: 26240120016, and the project Finalization of Infrastructure of the National Centre for Research and Application of Renewable Energy Sources, ITMS: 26240120028, and the project Competence centre for new materials, advanced technologies and energetics ITMS: 26240220073, co-funded by the European Regional Development Fund. This publication was supported by the Slovak Research and Development Agency under the contract No. APVV-0850-11, APVV-14-0393, VEGA 1/0775/13 and project Bark Extra: Study of obtaining extractive compounds and their use (Grant STU for young scientist).

ACKNOWLEDGEMENTS

Andrea Škulcová, MSc. xskulcova@stuba.sk Slovak University of Technology in Bratislava

Faculty of Chemical and Food Technology

Institute of natural and synthetic polymers Department of wood, pulp and paper

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