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Investigation of Physical Properties and Thi Performance of Choline
Chloride Based Deep Eutectic Solvent Using Meg as Synergetic

Compound in Gas Hydrate Formation
1Madueke, Chimezie Stanley., 2Osokogwu, Uche., 3Amieibibama, Joseph

1,2Petroleum Engineering Department, University of Port Harcourt, Nigeria

3Petroleum Engineering Department, Institute of Petroleum and Energy Studies

*Corresponding author

DOI: https://dx.doi.org/10.51244/IJRSI.2025.1210000216

Received: 20 October 2025; Accepted: 28 October 2025; Published: 15 November 2025

ABSTRACT

Flow assurance issues posed by gas hydrate to the oil industry is enormous causing economic loss, downtime
and flow line blockage. However, the use of inhibitors helps to prevent hydrate formation. This work studied the
synergy between (ChCl/Urea), (ChCl/Glycerol) in 1:2 molar ratios and ethylene glycol in a horizontal flow loop
at constant volume condition using compress natural gas as hydrate former and the physical properties (pH,
Conductivity and Turbidity) of the effluent were studied. A drop in pressure indicated that gas was used up in
forming hydrate cages. The result showed that DES of sample A with MEG as synergy in 1:1 molar ratio
performed better than all the five inhibitors studied. This was observed by lesser pressure decline in the loop.
FTIR analysis indicated that hydroxyl group (O-H stretch), Amine or Amide group (N-H bend) and carbonyl
group (C=O stretch) were the dominant functional group present in the sample and exhibited an
inhibitive/bonding effect in caging and preventing the hydrogen bond from host water from encapsulating and
forming hydrate in the presence of gaseous molecules. Sample B outperformed Sample A. However, the synergy
of Sample A with ethylene glycol performed better than sample B with ethylene glycol. The research work is
applicable in the oil and gas industry for minimizing cost and reducing toxicity of commercial inhibitors.

Keywords: Gas hydrate formation; Thermodynamic Inhibitors; Deep Eutectic Solvent; Choline Chloride;
Ethylene glycol; Ionic liquid.

INTRODUCTION

Natural gas hydrates are crystalline compounds of hydrogen bonded water lattice which engulfs sized
compounds like methane and carbon (iv) oxide gas at high pressure and lower temperature. It contains as much
as 180-unit volume of gas at standard temperature and pressure (STP) per volume of methane hydrate. (Sloan et
al., 2007). It poses serious production challenges especially with offshore exploration in deeper wells, leading
to more work for production enhancement. Hydrate plug, low efficiency of hydrate dissociation and short
production time in hydrate exploitation process has hindered the commercial availability of gas hydrate
extraction (Shen et al., 2024). Three conditions are necessary for hydrate to be form and they are: Hydrate
formation temperature and pressure usually low temperature and high pressure, presence of hydrate former e.g.
methane, ethane and carbon(iv) oxide and appreciable amount of water. (Abdulmutallib et al., 2022). Growth
rate and nucleation are of great importance in the process of gas hydrate formation. Nucleation can also be
referred as the transition from an unstable gas-liquid phase over to a stable growth phase while Induction time
is a time for the first gas-liquid contact to the first detection of hydrate phase and it is needed to predict the
nucleation period. There are various options to prevent hydrate crystallization. These options include heating,
insulation, water removal, and the use of thermodynamic hydrate inhibitors. THI’s are used to prohibit formation
of hydrates in pipelines and help in plug remediation (Odutola et al., 2022). Methanol and glycol are the most
common TI’s because of its low cost. However, gas regeneration and environmental issue poses extra cost.

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Deep eutectic solvents (DESs) are systems formed from a eutectic mixture of Lewis or Brønsted acids and bases
which can contain a variety of anionic and/or cationic species. They are partly different from ionic liquid which
are formed from systems composed primarily of one type of discrete anion and cation although the physical
properties of DESs are similar to other ILs, their chemical properties suggest application areas which are
significantly different (Barik et al., 2022).. Generally, DESs are known for a very large depression of freezing
point and are liquid at temperatures lower than 150oC. However, most of them are liquid between room
temperature and 70oC. In most cases, a DES can be obtained by mixing a quaternary ammonium salt hydrogen
Bond Acceptor (HBA) with metal salts or a hydrogen bond donor (HBD) that has the ability to form a complex
with the halide anion of the quaternary ammonium salt (Abbot et. al., 2004). They are made up of large
asymmetrical ions with low lattice energy, giving it a low melting point.

The oil and gas industry use different inhibitors to inhibit hydrate such as alcohols where high alcohol
concentration is required to thermodynamically inhibit a gas hydrate and to shift the hydrate thermodynamic
equilibrium curve to a lower temperature and higher pressure region (Najibi et al., 2022; Lu et al., 2022). 10–20
percent methanol is often used in deep water operations to prevent hydrate development in the pipelines
(Abdulmutallib et al., 2022). The rate of methanol injection depends on the water cuts and inhibitor dosage. In
brief, the inhibitory injection rate is obtained by multiplying the methanol dosage by the water generation rate.
The inhibitory effects of ethylene glycol, ethylene glycol + PVP, and Ethylene glycol + PVP + NaCl on methane
hydrate formation was studied by (Shen et al., 2025) and the influence of various temperatures, production
pressure, inhibitors combination and injection time on methane hydrate dissociation was also examined. The
author observed that a concentration of 30% ethylene glycol exhibits good synthetic inhibition. However, higher
concentrations of both ethylene glycol and PVP in synergetic combination do not necessarily lead to better
synthesis inhibition. KHIs (LDHIs) has also been used but they do not prohibit hydrate formation or alter
thermodynamics but rather postpone them by decreasing the rate of hydrate formation. A KHI concentration as
low as 1% can successfully stop the growth of crystals or nucleation. LDHI includes KHIs and anti-agglomerant
(AAs) categories and they are characterized by having low molecular weight polymers that are dispersed in a
solvent (Kelland et al., 2024). Ionic liquid and amino acid has also been used as a THIs. (Masri and Sulaimon.,
2022) developed three amino acid-based ionic liquids (AAILs), 1-ethyl-3-methyl-imidazolium-glutamate
(EMIMGlu), 1-(3-cyanopropyl)-3-methyl-imidazolium-glutamate (CPMIMGlu), and 1-butyl-3-methyl-
imidazolium-glutamate (BMIMGlu) and studied their thermodynamic inhibition performance on methane
hydrate. (Qinze et al, 2025) Investigated the effects of hydrate inhibitors on the decomposition kinetics of
hydrates and elucidated their influencing mechanisms by calculating the consumption of methane, they
quantified that the total methane consumption, the hydrate formation rate, the methane conversion rate, and the
methane recovery rate are influenced by inhibitor types and concentrations and a determinant factor in hydrate
stability. (Barik et al., 2022; Omar et al., 2022; Lomba et al., 2023; Mero et al., 2023) in different research
studied the differences in the behavior of deep eutectic solvents (DESs) and room temperature ionic liquids
(RTILs) in terms of their structure, dynamics, and intramolecular interactions and some of the physical properties
of different DES studied were listed in table 1. (Sulaiman et al., 2024) in his work formulated a DESs that worked
both as kinetic and thermodynamic inhibitor and postulated that DESs of ChCl-glycol performed better than the
DESs of ChCl-glycerol.

In recent years, research has focused on deep eutectic solvent since they are environmentally safe, cost effective,
easy to prepare and due to the current limitations on the use of conventional inhibitors like methanol and glycol,
there is need to develop a green suitable inhibitor and DESs being an environmental friendly inhibitor is being
researched. This work considers the use of Choline chloride-urea and choline chloride glycerol in 1:2 molar
ratios and a conventional inhibitor as synergy in different molar ratio in varying weight percentage of 1wt%-
5wt% so as to make flow assurance inhibitors eco-friendlier and highly effective. The use of FTIR was used to
attribute some reasons elucidated to performance of hydrate using the presence of predominant functional
groups. The physical properties (Turbidity, pH and conductivity) of solutions was studied and compared to MEG

Table 1 Physical properties of DES (Barik et al., 2022; Sulaiman et al., 2024)

Halide
Salt

HBD Viscosity/(c
p)

Conductivity
(mS Cm-1)

Density (g
Cm-3)

Surface tension
(mN m-1)

Molar ratio (Mp in oC
ratio /final mp inoC)

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ChCl Urea 632 0.75 1.24 52 1:2( 303:134/12)

ChCl Glycerol 376 1.05 1.18 55.8 1:2 (303:18/ -40)

MATERIALS AND METHODS

Deep Eutectic solvent was prepared by the addition of choline chloride + urea, and choline chloride + glycerol
both chemicals were obtained from Lobachemie Chemical Manufacturers India. The mixture was prepared in
1:2 Molar ratio respectively and the eutectic mixture was heated at 60oC in a water bath so that the resulting
mixture becomes liquid at room temperature with a melting point of 12oC and -40oC respectively. Ethylene
glycol (melting point of -12.9oC) obtained from Molychem India was added to DES in different molar ratio to
obtain the synergetic compound.

A horizontal constant volume gas hydrate flow loop mimicking a typical offshore gas pipeline that is exposed to
a low temperature environment that can lead to the production of gas hydrates will be used for this experiment
as shown in figure 1 and instrument functions and ranges shown in table 2. The hydrate loop is made of 316
stainless steel tubing of 0.5-inch internal diameter and 12 meters long. This steel tubing is concentrically encased
in a 4-inch polyvinylchloride (PVC) pipe, which is kept cool by regular water circulation. The PVC pipe is
insulated to avoid heat gain or loss from the system.

Figure 1 A Sketch of experimental hydrate flow loop

The experimental investigation of gas hydrate prevention using inhibitors was performed at same operating
condition of the flow loop. After the preliminary preparation, 2600ml (100%) of water was measured and turned
into the inhibitor vessel. Valve 5 and pump 3 were then turned on to build up pressure up to 25 psi and thereafter,
valve 5 and pump 3 were turn off. The compressed natural gas (CNG) was injected or pumped into the system
by turning on valve 1, valve 3 and the orifice. The valves were turned off after attaining to the maximum
operating loop pressure. Pump 2 was turned on to fill the jacket with the cooling water from the refrigerator
loaded with ice and kept running until the temperature at which hydrate was formed. At every time interval of 2
minutes for a period of 2 hours, the inlet and outlet (flow loop) pressure, inlet and outlet (flow loop) temperature,
cooling water (sub cooled) temperature and sample point (hydrate forming) pressure were recorded. The
experiment was repeated by measuring and injecting the concentration of inhibitors investigated at 26.6ml,
79.8ml, 133ml representing 1wt%, 3wt%, 5wt%, respectively with 2573.4ml, 2520.2ml and 2467ml of water
into the inhibitor vessel and allow to run.

The calculated Inhibition efficiency (IE) is given as:

IE = (1-Y) %

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Where Y is the inhibition factor given as

Y = ΔPinhibited / ΔPuninhibited (1)

ΔPinhibited = Pi - Pinhibited (2)

ΔPuninhibited = Pi - Puninhibited (3)

Table 2 Instrument used, Functions and Ranges

Instrument Functions Ranges Units

Inlet and Outlet Pressure Gauge, [P2, P1] Pressure measurement 0-500 psi

Pressure Along the Flow loop, [P3] Pressure measurement 0-500 psi

Outlet Point Temperature Gauge, [T1] Temperature measurement -50 - 50 0C

Inlet Point Temperature Gauge, [T2] Temperature measurement 0 – 100 0C

QB60 Pump, [Pump 1 &2] Circulation of fluids 0.5 hp

ATP 1.25 Pump, [Pump 3] Circulation of fluids 1 hp

Pipe internal diameter Distance 0.0127 m

A Hach 2100N Turbidimeter with parameters shown in Table 3 was used to measure the turbidity of the effluent
while Thermo-scientific Orion Star A215 Meter comprising of pH electrode and Conductivity electrode with
parameters in table 4 was used to measure the value of pH and Conductivity respectively.

Table 3 HACH 2100N Specification

Measurement method 2100N

NTU mode (decimal) 0-4000 (0-0.9999)

Accuracy ±2% of reading plus 0.01NTU from 0-40 NTU under reference condition

Operating temperature / sample
temperature

0 to 40°C (32 to 104°F)/ 0 to 95°C (32 to 203°F)

Table 4 Thermo scientific Orion star A215 Model

Measured quantity Description

pH Range: -2.000 to 20.000 Resolution: 0.1, 0.01, 0.001 Relative Accuracy: ±0.002
Calibration Points: Up to 5

Conductivity Range: 0.001 µS to 3000 mS Resolution: 0.001 μS minimum, auto ranging, up to 4
significant digits Relative Accuracy: 0.5 % of reading ±1 digit > 3 μS, 0.5 % of reading
±0.01 μS ≤ 3 μS

Inputs pH Electrode: BNC, reference pin Conductivity or ATC Probe: 8-pin mini-DIN

Fourier Transformed Infrared Spectroscopy (FTIR) was utilized for predicting the active functional group
present in the chemical inhibitor hence predicting the behavioral pattern of the inhibitor. The analysis reveals
chemical bonds in a molecule by producing an infrared absorption spectrum which is useful in examining

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functional groups of compounds. The Y axis in the graph denotes the %Transmittance while the X axis denotes
the wavelength (cm-1) and peaks in the spectrum reflect specific molecular vibrations.

RESULTS

Physical properties of Inhibitor:

After the experimental run, 1wt% and 5wt% of the effluent samples was collected and the physical properties
(Turbidity, conductivity and pH) was checked at 25oC and the result provided in Table 5 below. The pH was
recorded to have a range of 6.01-6.68 for the six samples considered while the inhibitor conductivity increases
as synergetic compound (MEG) is added to the DESs and this is true for all studied DESs in this work. However,
the turbidity of MEG was found to be higher than the studied DESs

Table 5 Inhibitor sample and physical properties of solution after experiment run @ 25oC

DESs Inhibitor samples Molar ratio Weight% pH of solution Conductivity mS/Cm-1 Turbidity

ChCl+Urea (Sample A) 1:2 1 6.01 0.0955 3.10

5 6.48 0.609 1.44

ChCl+Glycerol (Sample B) 1:2 1 6.02 0.0497 2.54

5 6.42 0.0610 1.14

Sample A+ Ethylene glycol
(Sample C)

1:1 1 6.23 0.632 1.352

5 6.39 0.4263 3.37

Sample A + Ethylene glycol
(Sample D)

2:1 1 6.65 0.632 0.352

5 6.68 0.3003 0.922

Sample B + Ethylene glycol
(Sample E)

1:1 1 6.26 0.0830 2.28

5 6.35 0.0610 1.66

Ethylene Glycol (Sample F) 1 6.12 0.0220 9.47

5 6.15 0.0521 7.68

Hydrate Profile without Inhibitor.

For the uninhibited experiment (water and gas only) as illustrated in figure 2 the initial temperature and sub cool
final temperature was 320C and -2oC respectively with initial pressure of 150 psi. For the first 30 minutes, the
pressure drops to 120psi. After roughly an hour, the pressure dropped to 105psi. After 90 minutes, the pressure
dropped to 65 psi then to 47 psi after 120 minutes. The temperature followed the same downward pattern as the
pressure versus time curve thus, the influence of the sub cool temperature on the flow line causes a decrease in
the operating pressure. Temperature dropped from 320C to 90C in 44 minutes, then began to rise from 90C to
20.50C at 100 minutes and finally rose to 22.50C by the end of 120 minutes. The spike in temperature was due
to continuous dissolution of methane gas in the cooling water which caused a reduction in induction time. As
hydrate began to develop, the half inch inner line began to emit heat. This was due to the fact that hydrate
formation is an exothermic process (Movareji et al., 2016; Odatuwa et al., 2024). As hydrate formed in the inner
line, gas was used up, resulting in a significant drop in loop pressure (Elechi et al., 2021; Odutola et al., 2022).

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Figure 2 Pressure(psi) and Temperature 0C versus time(min.) for Uninhibited experiment

Mono ethylene glycol as an Inhibitor (Sample F):

When MEG was used as an inhibitor as indicated in figure 3 and figure 4 below for sub cool temperature range
of 32oC to -2oC gas hydrate was inhibited and from the result, it was observed that inhibitor performance was
proportional to increase in concentration. Pressure dropped to 102psi, 107psi and 110psi with effluent volume
of 850ml, 880ml and 910ml corresponding to 1wt%, 3wt% and 5wt% respectively at the end of the experimental
run. The graph illustrates that 5wt% of MEG showed a better inhibition capacity with a calculated efficiency of
61.17% while the efficiency of 3wt% and 1wt% was 58.25% and 53.4% respectively. However, 5wt% will be
regarded as the optimum wt% for this experiment since increasing the dosage significantly affected the
performance of the inhibitor. The FTIR in figure 5, showed a broad peak at point 3298cm-1 indicating the
presence of a very strong and stretched hydrogen bond. Points 2937 cm-1 and 2874 cm-1 indicated the presence
of two aliphatic C-H groups. Vibrations at points 1082 cm-1 and 1035 cm-1 showed hydrogen bonding which
was due to two primary alcohol attached and were influenced due to the presence of a strong =C-H bend at
1745cm-1. The strong hydroxyl group was responsible for the inhibitor performance and prevented hydrogen
bonding of the host water (O-H)w from encapsulating gaseous particles forming hydrate. Hence shifting the
thermodynamic equilibrium towards free water and gas zone (Odatuwa et al., 2024).

Figure 3 Pressure(psi) vs time(min) Sample F

100

120

140

160

0 50 100 150

Pressure

Temperature

100

120

140

160

0 50 100 150

P
re

ss
u

Time

Pressure 1wt% MEG

Pressure 3Wt% MEG

Pressure 5Wt% MEG

Uninhibited

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Figure 4 Temp. (OC) vs Time(min) for sample F

Figure 5 FTIR analysis for Sample F

Choline chloride-urea based hydrate inhibitors with its synergetic compound:

The eutectic mixture of Choline Chloride (303OC MP) with Urea (134OC MP) formed a solvent which is liquid
at room temperature (12OC MP) and when used as an inhibitor in figure 6 below, gas hydrate was inhibited and
from the result, it was observed that inhibitor performance was not proportional to increase in concentration as
observed also by (Madueke et. al., 2023) . The pressure dropped to 105psi, 100psi and 107 psi at subcool
temperature of -2OC corresponding to 1wt%, 3wt% and 5wt% respectively at the end of the experimental run.
5wt% of DES showed a better inhibition capacity with a calculated efficiency of 58.25% while the efficiency of
3wt% and 1wt% was 51.45% and 56.31% respectively

A greater synergy was observed when MEG was used in 1:1 ratio (choline chloride Urea: MEG) in sample C
than in sample D (2:1 molar ratio). Sample C had pressure dropped to 116psi,122psi and 127psi at final subcool
temperature of -2OC by the end of the experiment corresponding to 1wt%, 3wt% and 5wt% as illustrated in
figure 7 with calculated inhibitor efficiency of 66.99%, 72.8% and 77.7% corresponding to 1wt%,3wt% and
5wt% respectively and when the pressure was compared to sample D in figure 8, it was reported to be
111psi,99psi and 99psi at the end of the 120 minutes. The calculated inhibitor efficiency was 62.13%, 50.49%
and 50.49% corresponding to 1wt%,3wt% and 5wt% respectively. However, sample D at 3wt% and 5wt% acted
as hydrate promoter with inhibitive capacity as wt% increases. The poor performance of sample D at 3wt% and
5wt% is in line with a study carried out where inhibition greater than 1% did no offer a lot of advantages (Odutola
et al., 2022).

The FTIR analysis in figure 9 for sample A indicated the presence of weak bonded (N-H) symmetric amide
functional group at point 3192cm-1 and a strong broad hydroxyl functional group (O-H) at point 3323 cm-1 which
were perfectly aligned from the eutectic mixture of choline chloride (O-H) and urea( N-H) and both compounds

0 50 100 150

Te
m

p
er

at
u

Time

Temperature1wt%

Temperature 3wt%

Temperature 5wt%

Temperature

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contributing to the hydrogen bonded network thereby preventing water from mixing with methane gas as
temperature decreases in the loop (Elechi et al., 2021). The carbonyl group on point around 1662 cm-1- 1602 cm-

1 (C=0) stretched vibration aided the stability and affected the formation of supplementary hydrogen bonding
while preserving the distinct properties in all the choline chloride-urea and its synergistic component considered.
This was supported in the research conducted by (Arkawazi et. al., 2020; Rao et. al., 2025). Point 1440 cm-1
depicted a CH2 bending or scissoring from choline moiety while point 1161 cm-1-1040 cm-1 indicated C-N and
C-O from choline and urea indicating hydrogen bonding interaction. Howbeit, confirming the presence of amide
and alcohol functional group. The strong performance of choline chloride urea and MEG (Sample C) in figure
10 can be attributed to strong broad peak at point 3329 cm-1 and 3201 cm-1 (O-H and N-H) stretch indicating
significant hydrogen bonding which is broader and more intense when compared to sample A. However, the
MEG added more HBD enhancing the hybridization. The shift to 1616 cm-1 in sample C when compared to
sample A 1662 cm-1 (figure 9) showed that the carbonyl group is more involved in hydrogen bonding due to
MEG’s hydroxyl forming abilities. Broad and slightly perfectly merged band of C-O and C-N stretching occurred
between 1332 cm-1 - 1163 cm-1 with C-O from MEG and C-N from choline. The waggling effect of C-O and C-
N at point 1038 cm-1 contributed to very strong inhibitive performance.

The poor performance of sample D in figure 11 can be attributed to the reduction on the influence of the strong
hydroxyl bond at point 3333 cm-1 (lesser O-H influence) and the consistent appearance of weak to moderate
band N-H bond in the region of 3201 cm-1 and 3416 cm-1 when compared to sample C in figure 10, thus leading
to reduction in hydrogen bond density due to higher choline chloride and urea concentration Point 1662 cm-1-
1614 cm-1 in figure 11 showed C=0 stretch which had more intensity than in sample C indicating the presence
of excess urea which was less involved in hydrogen bonding while point 1165 cm-1-1041 cm-1 in fig 10-11
showed C-O and C-N vibration and indicated that sample C which had more intensity, had more complex
interactive network due to higher availability of hydroxyl group from MEG when compared to sample D and it
is attributed to some reasons for the poor performance of sample D.

Figure 6 pressure(psi) vs time(min) Sample A

Figure 7 Pressure(psi) vs time(min) Sample C

100

120

140

160

0 50 100 150

P
re

ss
u

Time

Pressure 1wt%

Pressure 3wt%

pressure for 5wt%

Uninhibited

100

120

140

160

0 50 100 150

P
re

ss
u

Time

Pressure 5wt%

Pressure 3wt%

Pressure 1wt%

Uninhibited

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Figure 8 Pressure(psi) vs time(min) sample D

Figure 9 FTIR analysis for sample A

Figure 10 FTIR analysis for sample C

100

120

140

160

0 50 100 150

p
r
e
ss

u
r
e

Time

Pressure 1wt%

Pressure 3wt%

Pressure 5wt%

Uninhibited

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Figure 11 FTIR analysis for Sample D

Choline chloride-glycerol based hydrate inhibitors with its synergetic compound:

The eutectic mixture of Choline Chloride (303OC MP) with glycerol (18OC MP) in 1:2 molar ratio formed a DES
solvent which is (-40OC MP) and when it was used as an inhibitor as indicated in figure 12 below, gas hydrate
was inhibited. However, from the result, it was observed that inhibitor performance was proportional to increase
in concentration. There was pressure drop from 150psi to 104psi, 108psi and 110psi at subcool temperature of -
2OC whereas effluent volume of 860ml, 890ml and 900ml was collected corresponding to 1wt%, 3wt% and 5wt
% respectively at the end of the experiment. 5wt% of DES showed a better inhibition capacity with a calculated
efficiency of 61.17% while the efficiency of 3wt% and 1wt% was 59.22% and 55.34% respectively. However,
5wt% will be regarded as the optimum wt% for this study since increasing the dosage significantly affected the
performance of the inhibitor. MEG is a poor synergy for DES comprising of Choline chloride and Glycerol. All
the wt% of Choline chloride and glycerol in sample B performed better when compared with its synergy (Sample
E). However, at increased wt%, The inhibition performance of sample E decreases indicating it acted more as
hydrate promoter than inhibitor as concentration increases. The calculated efficiency of 51.5%, 40.8 % and 35
% for 1wt%, 3wt% and 5wt% respectively indicated that choline chloride-glycerol is not a good synergy with
MEG and this was also indicated with effluent volume of 790ml, 760ml and 730ml corresponding to 1wt%,
3wt% and 5wt% respectively at the end of the experimental. However, the effect of volume of hydrate was not
studied but the volume of effluent recorded at the end of every experimental run decreases as the concentration
of inhibitor increases. This phenomenon shows that the higher the volume of effluent recorded the better the
performances and effectiveness of inhibitor used (Nwaibu et al., 2018). During the experimental run for sample
E, it was observed that gas was almost used up to form hydrate cages or crystals which was visible as it began
appearing in tiny observable crystals when the effluent was collected for 3wt% and 5wt% since the influence of
the sub cooling temperature of the flow line causes a decrease in the operating pressure and gas hydrate formation
temperature. Figure 13 illustrates the graph of pressure versus time for sample E with a pressure drop from
150psi to 113psi, 101psi and 97psi at subcool temperature of 4OC and final pressure of 100psi, 89psi and 83psi
corresponding to 1wt%,3wt% and 5wt% respectively at the end of 120minutes. The poor performance of the
synergetic compound in higher weight % can be attributed to the increase in molecular weight. and poor
intermolecular interaction. This view was supported by (Scong et al., 2017) whose work illustrated that
molecular weight affects the performance of hydrate inhibitor.

FTIR analysis in figure 14 indicated the presence of a strong hydrogen bonding stretch at peak point covered
around point 3321 cm-1. This was due to multiple hydroxyl group associated with glycerol aiding hydrogen bond
formation. Peak point of 2930cm-1-2840cm-1 showed an aliphatic C-H stretched vibration likely from methyl
and methylene group of choline and glycerol respectively while a C-N/N-CH3 asymmetry stretch from 1475cm-

1-1467cm-1 is related to a quaternary ammonium group (N+(CH3)3) from choline chloride. C-O stretch/C-O-C
vibration at point 1037cm-1 confirms strong interaction between choline chloride and glycerol respectively. This
was supported by the peak shift and change in intensity from free glycerol conducted by (syahputra et. al., 2023)
indicating strong intermolecular hydrogen bonding with choline chloride. Sample E FTIR graph in figure 15
indicated strong broad hydrogen bonding from glycerol and MEG at point 3360cm-1. The aliphatic C-H stretch
occurred at point 2937 cm-1-2874 cm-1 but the presence of slightly intensed C=O stretch at point 1708 cm-1 likely

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from oxidation of MEG into a different functional group (e.g. Aldehyde group absorption range) with strong
absorption affecting the hydrogen bonding and overall inhibition performance of sample E but when compared
to sample B in figure 14, it was reported to be less significant with different insignificant absorption range. the
poor performance due to oxidation was supported by a study conducted by (Khalifa et. al., 2015) whose study
reported that thermally degraded MEG undergo oxidation reaction and was a poor hydrate inhibitor when
compared to MEG at normal condition. There was CH2 bending / N⁺(CH₃)₃ symmetric bend at point 1411 cm-1-
1255 cm-1. from the choline group. Sample E possess similar characteristics to Sample B e.g. C-O stretch on
point 1032 cm-1 which appeared on point 1082 cm-1. in sample E. The slight shift is due to interaction of the
hydroxyl group from MEG.

Figure 12 Pressure(psi) vs time(min)Sample B

Figure 13 Pressure(psi) vs time(min) sample D

Figure 14 FTIR analysis for sample B

0
20
40
60
80

100
120
140
160

0 50 100 150

P
re

ss
u

Time

Sample B 1wt%

Sample B 3wt%

Sample B 5wt%

Uninhibited

0
20
40
60
80

100
120
140
160

0 50 100 150

P
re

ss
u

Time

Pressure1%

Pressure3%

Pressure 5%

Uninhibited
Pressure

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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue X October 2025

Figure 15 FTIR analysis for sample E

Temperature profile with DES inhibitor and without Inhibitor:

It was observed from figure 16, that loop temperature decreased uniformly when inhibitors was used indicating
that the inhibitors were successful in preventing hydrate formation which is accompanied by an increase in
temperature. However, there was hydrate formation when no inhibitors were used, this can be observed by the
sudden increase in loop temperature at 58 minutes from 13.5oC to 14oC and at the end of the 120 minutes, the
temperature rose to 22oC.

Figure 16 Temp. (OC) vs Time(min) for DES samples considered

DISCUSSION

From the experimented result, The five DESs and MEG considered were able to inhibit hydrate at different
weight percentage of 1wt %, 3wt% and 5wt% and acted by altering water molecules (O-H)w with the strong (O-
H)a and weak to medium (N-H) bond making it unfavorable for hydrate formation to occur while pushing the
equilibrium position towards a hydrate free zone. However, Sample D and sample E acted as a hydrate promoter
in higher weight percentage since increasing the inhibitor weight percentage reduces the hydrate inhibition
performance indicating that ethylene glycol is not a good synergetic compound for choline chloride- urea based
DES in 2:1 ratio (sample D) likely due to excess urea which was less involved in hydrogen bonding and Choline-
glycerol based DES in 1:1 molar ratio (sample E). This was similar to the result gotten by (Odutola et al., 2022)
when PVP was used as a synergy in a thermodynamic under inhibited system. More research will be needed to
determine the molar ratio for effective synergy for choline chloride-glycerol based DES in the future since
oxidation of MEG in sample E played an important role in hydrogen bond linkage (Khalifa et. al., 2015). The
synergetic effect of Choline Chloride-urea and ethylene glycol in 1:1 ratio (sample C) performed better and was
able to inhibit hydrate formation more effectively. This can be observed with the volume of effluent of
980ml,1040ml and 1080ml at the end of the experiment and the inhibitor efficiency of 66.99%, 72.8% and 77.7%
corresponding to 1wt%, 3wt% and 5wt% respectively. The higher the volume of effluent, the greater the inhibitor
efficiency in preventing the gas engulfed by water molecules forming hydrate (Nwaibu et al., 2018). From the

0
5

10
15
20
25
30
35
40

0 50 100 150

Te
m

p
er

at
u

Time

Sample B
Temp.1wt%

Sample B Temp.
3wt%

Sample B Temp.
5wt%

uninhibited

Sample D Temp.
1wt %

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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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FTIR result in figure 10, the performance of sample C can be attributed to the increase surface area of the strong
hydrogen bond (O-H)a and its successive effect in interacting with water molecules. The conventional inhibitor
ethylene glycol is used to compare and validate the performance of each DES inhibitor and it was observed that
ethylene glycol performed slightly better than sample A, while sample B performed better than ethylene glycol
(sample F) in 1wt% and 3wt% but as wt% increases, the calculated inhibition efficiency of ethylene glycol
increases surpassing sample B. Graph of figure 17 and figure 18 represent the calculated inhibitor efficiency of
the 6 samples considered and the pressure drop (Pf-Pi) in relation to time respectively. The figures showed that
1wt%, 3wt% and 5wt% of sample C performed more than all the inhibitors considered when studied individually
and the experiment without inhibitor (uninhibited) had the highest pressure drop with a value of 103psi.
However, 5wt% is the optimum dosage for sample C. Moreover, 1 wt% of Sample C performed better than all
wt% of MEG considered, therefore the addition of sample C will greatly reduce the percentage of MEG needed
in the industry for hydrate inhibition and overall cost associated with MEG regeneration.

Figure 17 Inhibition Efficiency of Samples

Figure 18 Differential pressure drop (Pf-Pi) (Psi) vs time(min)

CONCLUSION

This work investigated the inhibitive performance of choline chloride based deep eutectic solvents using MEG
as synergetic compound on a constant volume flow loop mimicking an offshore transport line. Various inhibitors
were validated and compared with the Conventional MEG. The physical properties of the inhibitors were
determined at 25oC. The pH was recorded to have a range of 6.01-6.68 for the six samples considered while the

56.31 55.34

66.99
63.11

51.5 53.451.45

59.22

72.8

50.49

40.8

58.2558.25
61.17

77.7

50.49

61.17

Sample A Sample B Sample C Sample D Sample E MEG

In
h

ib
it

o
r
E

ff
ic

ie
n

c
y

Inhibitor Sample

Efficiency
1wt%

Efficiency
3wt%

Efficiency
5wt%

100

120

0 50 100 150

P
f-

P
i

Time

Sample B 1wt%
Sample B 3wt%
Sample B 5wt%
Sample D 1wt%
Sample D 3wt%
Sample D 5wt%
Uninhibited
Sample A 1wt%
Sample A 3wt%
Sample A 5wt%
Sample F 1wt%
Sample F 3wt%
Sample F 5wt%
Sample C 5wt%
Sample C 3wt%
Sample C 1wt%
Sample E 1wt%
Sample E 3wt%
Sample E 5wt%

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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue X October 2025

inhibitor conductivity increases as synergetic compound (MEG) was added to the DESs. Turbidity of MEG was
found to be higher than the studied DESs. FTIR was used to predict the active functional group, bond interaction
and behavior of DES properties present in the mixture. The poor performance of Sample D is likely due to excess
urea which was less involved in hydrogen bonding while the oxidation of MEG into a different functional group
in Aldehyde absorption range affected the hydrogen bonding and overall inhibition performance of sample E.
This research work will be recommended for field trial since sample C will reduce the toxicity and wt% of MEG
required for hydrate inhibition. 1 wt% of sample C synergy performed better than 5wt% of MEG (sample F).
However, the cost associated with regeneration of MEG will be greatly reduced since all DESs considered with
the exception of sample E altered only the physical interaction while the chemical morphology of each
component remained intact with little shift, bend or waggling (Juric et. al., 2021). Hence no new product was
formed as illustrated from the FTIR results.

Ethics declarations

The authors declare no conflict of interest and all authors agreed and approved the manuscript

ACKNOWLEDGEMENT

I am grateful for God for giving me the strength and knowledge to compute this article and to my dear wife for
her support. A special Thanks to my HOD Petroleum Engineering Dr. Osokogwu Uche and the assistance
director for Institute for petroleum Studies Associate Prof. Amieibibama, Joseph for their supervision, guidance
and support.

Grants and Funds

The author declares that there are no grants and funds received during the preparation of this manuscript

Statement and Declaration

The authors declare that they all contributed to this manuscript and they all read and approved the final
manuscript

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