This is about the presentation of FYP 1.

1. SYNTHESIS AND
CHARACTERIZATION OF
DEEP EUTECTIC
SOLVENTS FOR CO2
CAPTURE AND
SEQUESTRATION
NAME: CHAN YONG SOON
SUPERVISOR: DR YIIN CHUNG LOONG
MATRIC NO: 74378

2. • Carbon dioxide, CO2, as the primary anthropogenic greenhouse gas, is
responsible for increasing sea levels, land desertification, ocean acidification and
global warming.
• Current technologies for CO2 separation consist mostly of absorption,
adsorption, membrane and cryogenic separation.
• Deep eutectic solvents (DESs) began to be investigated as novel CO2 capture
absorbents.
Project Background
WHAT IS DEEP EUTECTIC SOLVENT?

3. Deep eutectic solvents (DESs) consist of large, asymmetric ions with
low melting temperatures due to their low lattice energy.
NON-VOLATILE NON-FLAMMABLE
EXCELLENT THERMAL
AND ELECTROCHEMICAL
STABILITY
CHEAP LESS HAZARDOUS BIODEGRADABLE

4. Identifying the “optimal” mixes for CO2
capture can be troublesome
Deep eutectic solvents have not been
well characterized

5. • To synthesize a series of deep eutectic
solvents with different combinations of
natural compounds and ionic components,
focusing on achieving high CO2 absorption
capacity and low regeneration energy
requirements.
• To characterize the physicochemical
properties of the synthesized DES
formulations, including viscosity, thermal
stability and CO2 capture efficiency.
• To evaluate the performance of the DES in
CO2 capture and sequestration processes.
• Selection of the HBAs and HBDs is
carried out after a thorough literature
review.
• Obtain an optimum mixing molar
ratio of HBA to HBD.
• Physicochemical properties
characterization of the DESs is
conducted over a specified
temperature range.
• Take into account and evaluate the
factors affecting the performance of
DESs in capturing CO2.
• Provide a great deal of knowledge
about the importance and
advantages of utilizing DESs for CO2
capture application.
• Requires a great deal of effort to
justify the selection of HBAs and
HBDs to synthesize DESs that have
sufficiently high CO2 absorption
capacity.
• Gain thorough understanding about
the correlation between CO2
absorption capacity and various
specific manipulated parameters.

6. Physicochemical
Properties
Description
Melting point
• DES’s melting point is determined by nature and molar ratio of its individual components.
• Finding: The DESs consisting of polyols like glycerol or ethylene glycol had the lowest melting points among all
the choline chloride based DESs that were studied (López-Porfiri et al., 2016).
Density
• The density of DESs can be affected by nature and quantity of the HBAs and HBDs as well as temperature.
• Finding: Increasing the glycerol (HBD) content in the choline chloride (HBA) based DESs decreases the DES
density (Abbott, et al., 2011).
Viscosity
• Temperature, water content, molar ratio and chemical nature of the DES constituents affect viscosity.
• Finding: As temperature increases, the viscosity of choline chloride: urea decreases from 750 to 95 mPa‧s (D'
Agostino, Harris, Abbott, et al., 2011).
Thermal stability
• Thermal stability of DESs increases with the alkyl chain length on HBDs.
• Finding: Thermal stability of the DES consisting of allyltriphenyl phosphoniumbromide as HBA and glycerol as
HBD is the highest compared to the DESs consisting of other HBDs such as ethylene glycol, diethylene glycol
and triethylene glycol (Ghaedi, Ayoub, Sufian, et al., 2017).
Refractive index
• Refractive index of DES is affected by temperature, molar ratio of HBAs to HBDs and the types of HBDs used.
• Finding: Refractive index of DESs based on diethanolamine as HBDs increases as molar ratio of HBAs to HBDs
increases from 1:4 to 1:6 (Murshid, Mjalli, Naser, et al., 2019).

7. • Finding: An increase in molar ratio of guaiacol leads to an increase in the CO2 solubility in
the identical type of DES, indicating that guaiacol plays a significant role in the dissolution
of CO2 into DES, apparently due to its hydroxyl group (Li et al., 2016).
• Finding: The CO2 solubility in choline chloride/glycerol decreases as the molar ratio
increases from 1:3 to 1:8 (Ali, et al., 2014).
• HBD has a direct effect on CO2 absorption capacity.
• Finding: Levulinic acid-based DESs provide higher CO2 solubility compared to the furfuryl
alcohol-based DESs at the same temperature due to the presence of carbonyl group in
levulinic acid that can form stronger bonds with CO2 compared to the hydroxyl group in
furfuryl alcohol.
• HBAs are significant contributors to CO2 solubility as they have a greater ability to affect
CO2 solubility than HBDs.
• Finding: Tetrabutylammonium bromide (TBAB) based DESs show higher CO2 solubility
compared to the choline chloride based DESs due to the longer alkyl chain length of TBAB,
which increases the free volume (Haider et al., 2018); (Li, Huang, Zheng, et al., 2014).

9. • The required mass of HBA and HBD is
determined and weighed using stoichiometric
calculations and electronic balance respectively.
• The HBA and HBD are mixed in a beaker and
stirred at 80 °C for 1 hour with a hot magnetic
stirring plate to obtain a homogeneous mixture
without precipitate.
• The resulting DES is stored in gas-tight bottle at
room temperature and left overnight to ensure
that there is no precipitate formed in the bottle.
• Using a vacuum pump and desiccator, DES is
dried under vacuum for 48 hours to completely
remove the moisture.
• The resulting DESs are considered success when a
colourless and clear solution is formed.

10. Equipment Operations
Thermogravimetric
Analyzer (TGA)
• DES samples is placed in a small crucible with a cover under the nitrogen
atmosphere with a flow rate of 20 mL/min and heated at a temperature range
of 343.15 - 873.15 K with a heating rate of 5K/min.
• TGA curve of DES that shows the percentage of weight loss against the
temperature is generated and the decomposition temperature of the DES is
derived from it.
Differential Scanning
Calorimeter (DCS)
• The freezing point of DES samples are determined by heating them at a
constant heating rate of 5 K/min, from 203.15 K up to 473.15 K.
Density meter
• Density of DES is measured over the temperature range of 298.15 K up to 333.15
K at atmospheric pressure.
Viscometer
• Viscosity of DES is measured over the temperature range of 298.15 K up to
333.15 K at atmospheric pressure.
Refractometer
• Refractive index of DES is measured over the temperature range of 298.15 K up
to 333.15 K at atmospheric pressure.

11. 10 g citric acid + 10 mL
deionized water
6.50 g sodium bicarbonate + 20
mL deionized water

12. 3. The CO2 capture apparatus is set up as shown
in the left figure.
4. Short vacuum tubing is attached to the hose
barb of the vacuum flask.
5. Balloon is attached to the short vacuum tubing
to regulate pressure.
6. 5 mL of DES is measured and poured into a
reaction vial.
7. Magnetic stir bar is then added to the reaction
vial.
8. Initial mass of the reaction vial, DES and
magnetic stir bar is weighed and recorded.
9. Reaction vial is capped with a septum cap that
contains the tubing.
10. Test tube is filled with deionized water and
placed into a beaker in a slated position.
11. Hot magnetic stirrer plate is turned on and
the DES in a vial is allowed to stir at
approximately 200 rpm and 30 °C for 20
minutes.

13. 12. Using a syringe with a needle, citric acid
solution is added to the sodium bicarbonate
solution in a vacuum flask.
13. The DES in the vial is allowed to stir for 10
minutes.
14. After 10 minutes, the hot magnetic stirrer
plate is turned off and the vial is removed from
the apparatus.
15. Final mass of vial and its content is weighed
and recorded.
16. Mass of CO2 captured is calculated by
subtracting the initial mass from the final mass
of vial and its content.
17. CO2 absorption capacity of the DES is
calculated using the following equation.