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International Journal of Greenhouse Gas Control 19 (2013) 3–12

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International Journal of Greenhouse Gas Control
journal homepage: www.elsevier.com/locate/ijggc

Analysis and predictive correlation of mass transfer coefficient KG av
of blended MDEA-MEA for use in post-combustion CO2 capture
Abdulaziz Naami a,b , Teerawat Sema a , Mohamed Edali b , Zhiwu Liang a,∗ ,
Raphael Idem a,b , Paitoon Tontiwachwuthikul a,b
a
Joint International Center for CO2 Capture and Storage (iCCS), College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR
China
b
International Test Centre for CO2 Capture (ITC), Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan S4S 0A2, Canada

a r t i c l e

i n f o

Article history:
Received 22 March 2013
Received in revised form 7 August 2013
Accepted 12 August 2013
Available online 18 September 2013
Keywords:
CO2 absorption
Packed column
Structured packing
Mass transfer coefficient
Cyclic capacity

a b s t r a c t
The mass transfer performance of the absorption of CO2 in aqueous blended MDEA-MEA solutions was
evaluated experimentally in a lab-scale absorber packed with high efficiency DX structured packing over
MDEA-MEA concentrations of 27/3, 25/5, and 23/7%wt under atmospheric pressure using a premixed
feed gas containing 15% CO2 balanced with N2 . The absorption performance was presented in terms
of overall mass transfer coefficient (KG av ) and CO2 concentration profile. The results showed that the
mass transfer performance increased as ratio of MEA in the blended solution, temperature, and liquid
flow rate increased but decreased as CO2 loading increased. In addition, it was found that the cyclic
capacity and relative solvent regeneration ability decreased as the ratio of MEA in the blended solution
increased. Based on mass transfer performance, cyclic capacity, and relative solvent regeneration ability,
23/7%wt MDEA-MEA was found to be the most effective blend ratio among the three ratios investigated
in the present work. Also, the correlation for predicting KG av for CO2 absorption into aqueous blended
MDEA-MEA was successfully developed with an AAD of 21.8%.
© 2013 Elsevier Ltd. All rights reserved.

1. Introduction
One of the options for reducing carbon dioxide (CO2 ) emissions is absorption of CO2 from gas streams using reactive amine
solvents, which has recently been considered as one of the
most mature and reliable CO2 reduction technologies (Kohl and
Nielsen, 1997; Rao and Rubin, 2002; Liang et al., 2011). The
use of an effective solvent is considered to be one of the key
parameters of this technology. Charkravarty et al. (1985) firstly
introduced blended solvent systems by mixing primary (or secondary) amines with tertiary amines in order to capitalize on
the advantages of each amine and counter the disadvantages
of one amine with another amine. Presently, several blended
conventional amines have been introduced for absorbing CO2
such as blended monoethanolamine (MEA)-methyldiethanolamine
(MDEA), diethanolamine (DEA)-MEA, triethanolamine (TEA)-MEA,
MEA-2-amino-2-methyl-1-propanol (AMP), AMP-MDEA, AMPpiperazine (PZ), and MDEA-PZ (Horng and Li, 2002; Mandal et al.,
2003; Aroonwilas and Veawab, 2004; Ramachandran et al., 2006;
Setameteekul et al., 2008; Huang et al., 2011; Samanta and

∗ Corresponding author. Tel.: +86 13618481627; fax: +86 73188573033.
E-mail address: [email protected] (Z. Liang).
1750-5836/$ – see front matter © 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.ijggc.2013.08.008

Bandyopadhyay, 2011). Blended MDEA-MEA solutions have been
widely investigated for several years. This is because, firstly, both
the single amine solvents of MEA and MDEA are mature since they
have been used for decades in fossil fuel-fired power generation,
natural gas processing, and chemical production industries. Examples of the commercial facilities that have employed these solvents
are the Warrior Run Power Plant in Maryland, USA, Shady Point
Power Plant in Oklahoma, USA, Platte River Power Authority in Colorado, USA, Searles Valley Minerals Soda Ash Plant in California,
USA, Schwarze Pumpe Pilot Plant in Germany, Salah Natural Gas
Production Facility in Algeria, Sumitomo Chemicals Plant in Japan,
and Prosint Methanol Production Unit in Brazil (Barchas and Davis,
1992; Dooley et al., 2009; Eswaran et al., 2010). Secondly, blended
MDEA-MEA can be easily used in commercial absorbers since both
MEA and MDEA have generally been used at the industrial scale.
Blended MDEA-MEA has been commercially used in large-scale
processes at Yokosuka Power Plant in Japan and, Tokyo Electric
Power Corporation in Japan (Eswaran et al., 2010). This blended
amine system capitalizes on the advantages of high absorption
capacity, high solvent stability, low corrosiveness, and low energy
requirement for regeneration of MDEA and fast reaction kinetics of
MEA.
Even though blended MDEA-MEA was introduced in 1985,
most of the investigations have focusing on the reaction kinetics

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A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

Nomenclature
AAD
AMP
Cs
CO2
DEA
GI
kL
KG
KG av
L1
MDEA
MEA
N2
P
PZ
T
TEA
xCO2
yA∗
yA,G
YA,G
Z

absolute average deviation
2-amino-2-methyl-1-propanol
concentration for amine in the solution, kmol/m3
carbon dioxide
diethanolamine
inert gas flow rate, kmol/m2 h
liquid phase mass transfer coefficient in the case of
chemical reaction, m/h
overall interfacial area gas phase mass transfer coefficient, kmol/m2 h kPa
overall volumetric mass transfer coefficients,
kmol/m3 h kPa
liquid flow rate, m3 /m2 h
methyldiethanolamine
monoethanolamine
nitrogen
total pressure of the system, kPa
piperazine
absolute temperature, K
triethanolamine
mole fraction of CO2
mole fraction of solute A at interface
mol fraction of solute A at bulk gas phase
mole ratio of solute A in gas phase
height of the absorption column, m

Greek letters
˛
CO2 loading, mol CO2 /mol amine

(Critchfield and Rochelle, 1987; Versteeg et al., 1990; Glasscock
et al., 1991; Rangwala et al., 1992; Hagewiesche et al., 1995; Mandal
et al., 2001; Liao and Li, 2002; Ramachandran et al., 2006; Edali et al.,
2009), solubility (Shen and Li, 1992; Li and Shen, 1993; Dawodu
and Meisen, 1994; Li and Mather, 1994; Kaewsichan et al., 2001;
Ma’mun et al., 2005), physiochemical and thermodynamics properties (Austgen et al., 1991; Li and Shen, 1992; Jou et al., 1994;
Li and Lai, 1995; Hsu and Li, 1997; Weiland et al., 1998; Bensetiti
et al., 1999; Mandal et al., 2005; Vrachnos et al., 2006), and solvent degradation (Lawal et al., 2005; Lawal and Idem, 2005, 2006;
Dawodu and Meisen, 2009). Only a few studies have investigated
the mass transfer of CO2 absorption into blends of MDEA-MEA in
packed columns.
Aroonwilas and Veawab (2004) investigated mass transfer performance for CO2 absorption into blended MDEA-MEA, MDEA-DEA,
and AMP-MEA in structured DX packing using 10% CO2 balanced
with nitrogen (N2 ) as feed gas. The mass transfer performance
was reported in terms of the overall mass transfer coefficient,
removal efficiency, and relative column height requirement. However, the experiments for the blended amines were conducted at
only 1/1 mole ratio (with total amine concentration of 3 M). It was
found that the mass transfer performance of blended AMP-MEA
is higher than those of MDEA-MEA and MDEA-DEA, respectively.
Since the reaction kinetics of CO2 absorption can be ranked as:
AMP > DEA > MDEA, (i) the mass transfer performance of AMP-MEA
then exceeds that of MDEA-MEA and (ii) that of MDEA-MEA then
exceeds that of MDEA-DEA. However, reboiler heat duty should
also be taken into consideration since it contributes about 70% of
the operating cost of the CO2 capture process (Kohl and Nielsen,
1997). Sakwattanapong et al. (2005) investigated the reboiler heat
duty for CO2 capture with blends of AMP-MEA, MDEA-MEA, and
MDEA-DEA. They reported that the reboiler heat duty of MDEADEA is lower than those of MDEA-MEA and AMP-MEA, respectively.

By taking into consideration both mass transfer performance and
heat duty requirement for solvent regeneration, blended MDEAMEA seems to be the best solvent combination among the three
because it provides good performance in both mass transfer and
reboiler heat duty requirement.
Later, Setameteekul et al. (2008) studied the mass transfer performance of blended MDEA-MEA at various MDEA-MEA blending
ratios of 1/3, 1/1, and 3/1 molar. They concluded that (i) the blending ratio of the blended MDEA-MEA has a significant effect on
the mass transfer performance, (ii) the mass transfer performance
increases as molar ratio of MEA increases, and (iii) the MDEA-MEA
of 1/3 molar ratio provided the best mass transfer performance.
Additionally, the CO2 absorption not only depends on using
an effective solvent, but the contact between gas and liquid
solvent also plays an important role in the CO2 absorption performance in a packed column. It has been over forty years since
the tray columns have been replaced by the more effective packed
columns (Aroonwilas and Tontiwachwuthikul, 1998; Aroonwilas
and Veawab, 2004). In the packed columns, the packing creates a gas–liquid contact area by generating liquid droplets. The
most promising packing should provide large surface area per
volume ratio, low pressure drop across the column, and uniform
gas–liquid distribution throughout the column. Aroonwilas and
Tontiwachwuthikul (1998) and deMontigny et al. (2001) compared
the CO2 absorption performance using randomly (IMTP#15, 0.63,
3 in. Pall Ring, 0.5 in. Berl Saddles) and structured (Gempack 4A,
Sulzer EX) packings. They concluded that the structured packing provide higher mass transfer performance than the random
packing, which is in good agreement with the results observed by
Fernandes et al. (2009).
Even though CO2 absorption technology has been industrially
used for over half a century, the most promising solvents have still
to be discovered. Recently, a number of novel solvents (e.g., 2-Nmethylamino-2-methyl-1-propanol, 2-N-ethylamino-2-methyl-1propanol, 2-(isopropylamino)ethanol, 2-(isobutylamino)ethanol,
2-(secondarybutyamino)ethanol, 2-(isopropyl)diethanolamine, 1methyl-2-piperidineethanol, 4-diethylamino-2-butanol, RITE-A
and RITE-B) has been introduced (Chowdhury et al., 2011; Goto
et al., 2011; Sema et al., 2013). The CO2 absorption performance of
these novel amines was found to exceed the conventional MEA,
AMP, DEA, and MDEA. However, the major drawbacks of these
novel solvents are (i) expense, (ii) difficult synthesis, (iii) difficult
mass production, (iv) phase separation or turning into solids under
certain conditions, and (v) undiscovered disadvantages.
Another approach for improving the CO2 absorption performance rather than working with novel solvents is to enhance and
optimize the performance of conventional solvents. In order to
achieve this, the conventional solvents have to be comprehensively investigated. Even though blended MDEA-MEA has been
widely investigated, the predictive correlation for overall mass
transfer performance of CO2 absorption into aqueous solutions of
blended MDEA-MEA has not yet been established. In the present
work, the blended MDEA-MEA ratio was selected at 27/3, 25/5,
and 23/7%wt (equivalent to MDEA-MEA molar ratio of 2.3/0.5,
2.1/0.8, and 1.95/1.16, respectively). These blend concentrations
were selected in order to capitalize on the great advantages of
both MDEA and MEA in that MDEA requires low energy for solvent regeneration and has high absorption capacity while MEA
provides fast CO2 absorption rate. Since the heat requirement for
solvent regeneration contributes about 70% of the cost of capturing CO2 (Kohl and Nielsen, 1997), MDEA was, therefore, selected
as the major component of the blended solutions in order to minimize the heat requirement for solvent regeneration. The addition
of MEA, which has fast reaction kinetics, can then enhance the CO2
absorption rate of the blended solutions. However, the total concentration of the blended solution cannot be high because MDEA

A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

itself is considered to be a slightly viscous solvent already. Thus,
the total concentration of the blended MDEA-MEA used in the
present work was then limited at 30% wt. In addition, the CO2
absorption experiments were done over ranges of temperatures
(298, 303, and 318 K), CO2 loadings at the absorber top (0.05, 0.17,
and 0.25 mol CO2 /mol amine), and liquid flow rates (2.8, 3.8, and
5 m3 /m2 h). The experiments were performed in a laboratory-scale
absorption column with DX structured packing (27.5 mm ID from
Sulzer Chemtech Canada, Inc.) at atmospheric pressure. The overall volumetric mass transfer coefficients (KG av ) at various operating
conditions were then used to establish the predictive correlation.
The data obtained from the present work will be very crucial to
further pilot plant-scale test at ITC’s technology pilot plant (diameter of 12 inches with capture capacity of 1 ton of CO2 /day). It was
mentioned by Idem et al. (2006,2011a) that only one molar ratio
of 1/4 of blended MDEA-MEA was previously tested in the pilot
plant so the results from the present work will be very useful to
(i) determine the scope of the pilot plant’s operating conditions
with blended MDEA-MEA and (ii) expand the pilot plant-scale testing to test various blended ratios other than 1/4 molar ratio of
blended MDEA-MEA. In addition, the results obtained from this
study can also lead to improvement of CO2 absorption performance of blended MDEA-MEA by addition of a third component
into the system. Up to the present, several promising amines
(e.g., AMP, PZ, 1-methyl-2-piperidineethanol, 4-diethylamino-2butanol) have been introduced for capturing CO2 (Chowdhury et al.,
2011; Goto et al., 2011; Sema et al., 2013). These solvents can
potentially enhance the performance of the well-known blended
MDEA-MEA. In order to effectively achieve this goal, a complete
understanding of blended MDEA-MEA over the range of relevant
operating conditions is required. Additionally, the third component
can also be ionic liquids, physical solvents, or even solid/liquid catalyst that can reduce the heat requirement for solvent regeneration
and improve the performance of CO2 removal as suggested by Idem
et al. (2011b) and Shannon and Bara (2012).
2. Determination of the overall mass transfer coefficient
It has been widely understood that one of the primary concerns
in removing CO2 using absorption processes is the concentration
of CO2 in the gas phase. Also, it is easier and more convenient
to measure the concentration of CO2 in gas phase than in liquid phase. Thus, for the CO2 absorption process, the gas phase
mass transfer coefficient is generally accepted to be more suitable than the liquid phase coefficient. However, it is very difficult
to measure the gas–liquid interfacial area in an absorption column. Therefore, the mass transfer coefficient in a packed column
is generally represented by overall volumetric gas phase mass
transfer coefficient (KG av ; kmol/m3 h kPa) instead of that based
on interfacial area (KG ; kmol/m2 h kPa) (Astarita et al., 1983; Kohl
and Nielsen, 1997; Aroonwilas and Tontiwachwuthikul, 1998;
deMontigny et al., 2001; Aroonwilas and Veawab, 2004; Fu et al.,
2012). The overall volumetric gas phase mass transfer coefficient
KG av can be calculated as follow:



KG av =

GI
P(yA,G − yA∗ )



dYA,G
dZ

(1)

where GI is inert gas flow rate (kmol/m2 h), P is total pressure of the
system (kPa), Z is height of the absorption column (m), yA,G is mol
fraction of solute A at bulk gas phase, yA∗ is mole fraction of solute A
at interface, YA,G is the concentration (in terms of mole ratio) in gas
phase of solute A, which is CO2 in the present work, and (dYA,G /dZ) is
the solute mole ratio concentration gradient, which can be obtained
by taking a slope of YA,G versus Z plot.

5

3. Experimental
3.1. Chemicals
MDEA and MEA were purchased from Fisher Scientific, Canada,
with purities of ≥99%. The premixed 15% CO2 (balanced with N2 )
was supplied by Praxair Inc., Canada. All materials in this study were
used as received without further purification. Aqueous solutions of
blended MDEA-MEA of desired concentrations were prepared by a
known amount of deionized water and predetermined amounts of
MDEA and MEA.
3.2. CO2 absorption in packed column
The mass transfer in a packed column occurs when CO2 in the gas
phase transfers across the gas–liquid interface into the liquid phase.
In the present work, the mass transfer performance was evaluated
in terms of the overall volumetric mass transfer coefficient KG av and
the CO2 concentration profile along the height of the column. The
KG av can be calculated using Eq. (1), in which several parameters
can be obtained from the experiment. Generally, the experiments
were done at atmospheric pressure P. The inert gas flow rate GI can
be determined from the gas flow rate measurement using electronics Aalborg GFM-17 mass flow meter (ranging from 5 to 50 L/min
with a ±0.15%/◦ C accuracy). The mole fraction of CO2 in the gas
phase yA,G can be determined from an infrared CO2 gas analyzer
(model 301D, Nova Analytical System Inc., Hamilton, ON, Canada),
which is capable of measuring CO2 concentration up to 20% with
±0.5% accuracy. The measurement of CO2 concentration was done
along the height of the column through the sampling ports, which
are connected to the CO2 gas analyzer. The mole fraction of CO2 at
interface (yA∗ ) can be calculated using the Henry’s law relationship.
The Henry’s law constant of blended MDEA-MEA can be calculated
by the correlation established by Wang et al. (1992). The mole ratios
of CO2 in the gas phase (YA,G ) at various heights of the column can be
obtained from the CO2 analyze, and the, plotted against the height
of the column to get dYA,G /dZ.
The glass laboratory absorption column (diameter of
27.5 × 10−2 m and height of 2.15 m) was packed with 37 elements of stainless steel Sulzer DX structured packing (with
900 m2 /m3 packing surface area). The schematic diagram of the
experimental setup of CO2 absorption in the packed column is
presented in Fig. 1. The operational procedure of the absorption
column can be found in our previous works (Fu et al., 2012; Naami
et al., 2012). In order to validate the absorption column used in the
present work, 2 M MEA solution was tested and compared with
the results from deMontigny (2004). It was found that the results
obtained in the present work are in good agreement with those
obtained in deMontigny (2004) as shown in Fig. 2.
4. Results and discussion
The mass transfer performance of CO2 absorption into aqueous
solutions of blended MDEA-MEA was experimentally determined
in the laboratory-scale absorption column packed with DX structured packing and reported in terms of KG av and CO2 concentration
profile along the height of the column. The values of KG av are proportional to the mass transfer performance in that the higher the
KG av , the higher mass transfer performance. For the CO2 concentration profile, a lower CO2 concentration profile indicates a larger
amount of CO2 that has been removed from the gas stream resulting
in higher mass transfer performance.
The experiments were done at various MDEA-MEA concentrations of 27/3, 25/5, and 23/7%wt (which are equivalent
to MDEA-MEA molar ratios of 2.3/0.5, 2.1/0.8, and 1.95/1.16,

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A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

Fig. 1. Schematic diagram of the experimental setup of CO2 absorption in packed column.

respectively) over a range of temperatures (298, 303, and 318 K),
CO2 loadings at the absorber top (0.05, 0.17, and 0.25 mol CO2 /mol
amine), and liquid flow rates (2.8, 3.8, and 5 m3 /m2 h). A mass
balance error, which can be calculated using Eq. (2), was taken into
consideration in order to confirm the validity of each absorption
experimental run. The mass balance error compares the amount
of CO2 removed from the gas phase (which can be measured via
an infrared CO2 gas analyzer) with that added into liquid phase
(which can be measured by titration with standard 1.0 M HCl
until methyl orange end point as mentioned in Association of
Official Analytical Chemists (AOAC) methods by Horwitz (1975)).
Theoretically, these two values should be equal. However, because
of (i) experimental errors from the CO2 gas analyzer and CO2

loading measurement apparatus and (ii) an elongated liquid trap
in the packed column, the average mass balance error obtained
from the present work was found to be 4%, which is considered
to be in an acceptable range of less than 10%. Therefore, it can
be inferred from this observation that the experimental results
obtained from the present work are correct and reliable.



 absorbed CO2 − removed CO2 
 × 100% (2)
absorbed CO

Mass balance error = 

2

The total experimental data points obtained from the present
work are 600 from 30 experimental runs, which include 300 measured points of CO2 concentration and another 300 points of
temperature. From these data, the effects of MDEA-MEA blended

A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

Fig. 2. Validation of packed column using 2.0 M MEA at temperature of 294 K, CO2
loading at absorber top of 0.2 mol CO2 /mol amine, liquid flow rate of 5 m3 /m2 , inert
gas flow rate of 17.85 kmol/m2 h, and YCO2 of 0.09.

ratio, temperature, CO2 loading at the absorber top, and liquid
flow rate on mass transfer performance (in terms of KG av and CO2
concentration profile along the height of the column) were then
examined.
4.1. Effect of MDEA-MEA blended ratio on mass transfer
performance
In order to examine the effect of MDEA-MEA blended ratio
on the mass transfer performance, three blended ratios of 27/3,
25/5, and 23/7%wt were tested in the packed column. The results
showed that the mass transfer performance in terms of KG av and
CO2 concentration profile increased as the weight ratio of MEA in
the blended solutions increased as presented in Figs. 3 and 4. It can
be reasoned that MEA has faster reaction kinetics of CO2 absorption
than MDEA (Kohl and Nielsen, 1997; Sema et al., 2012). The higher
the ratio of MEA in the blended solutions, the higher amounts of
the more reactive MEA molecules that can absorb CO2 ; thus, a
higher mass transfer performance was observed. Therefore, it can
be seen from Figs. 3 and 4 that 23/7%wt MDEA-MEA (molar ratio
of 1.95/1.16) provides the best mass transfer performance among
the three investigated ratios. However, by increasing the ratio of
MEA, the ratio of MDEA in the blended solutions would be reduced,

Fig. 3. Effect of MDEA-MEA blended ratio on CO2 concentration profile at temperature of 294 K, CO2 loading at absorber top of 0.25 mol CO2 /mol amine, liquid flow
rate of 5 m3 /m2 , and inert gas flow rate of 15.99 kmol/m2 h.

7

Fig. 4. Effect of MDEA-MEA blended ratio on KG av at temperature of 294 K, CO2
loading at absorber top of 0.25 mol CO2 /mol amine, liquid flow rate of 5 m3 /m2 ,
inert gas flow rate of 15.99 kmol/m2 h, and YCO2 of 0.09.

which can lead to (i) a reduction of CO2 absorption capacity and
(ii) an increment of heat requirement of solvent regeneration. This
is because MDEA has higher CO2 absorption capacity and requires
much lower heat for solvent regeneration (Kohl and Nielsen, 1997;
Sakwattanapong et al., 2005; Liang et al., 2011). It was discussed by
Kohl and Nielsen (1997) that the energy requirement for solvent
regeneration contributes about 70% of the cost of capturing CO2 .
Therefore, in order to maintain low heat requirement for solvent
regeneration and high absorption capacity characteristics of MDEA
in the blended solutions, much higher blended ratios of MDEA over
MEA were selected in this work.
4.2. Effect of temperature on mass transfer performance
In the present work, the liquid inlet temperature was varied
from 294 to 318 K. It was found that the CO2 concentration profile
became lower as temperature increased as presented in Fig. 5. The
mass transfer performance in terms of KG av was also found to correspond well with that of the CO2 concentration profile in that the
KG av increased as temperature increased as shown in Fig. 6. Therefore, it can be inferred from Figs. 5 and 6 that the mass transfer
performance of the blended MDEA-MEA increases as temperature
increases over a temperature range of 294–318 K. This is because
the reaction kinetics of blended MDEA-MEA increase as temperature increases as discussed in the works of Mandal et al. (2001),
Liao and Li (2002), and Edali et al. (2009).

Fig. 5. Effect of temperature on CO2 concentration profile of 23/7%wt MDEA-MEA at
CO2 loading at absorber top of 0.04 mol CO2 /mol amine, liquid flow rate of 5 m3 /m2 ,
and inert gas flow rate of 15.99 kmol/m3 h.

8

A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

Fig. 6. Effect of temperature on KG av of blended MDEA-MEA at blended ratios of
27/3, 25/5, and 23/7%wt, CO2 loading at absorber top of 0.04 mol CO2 /mol amine,
liquid flow rate of 5 m3 /m2 , inert gas flow rate of 15.99 kmol/m2 h, and YCO2 of 0.09.

Fig. 9. Effect of liquid flow rate on CO2 concentration profile of 23/7%wt MDEA-MEA
at temperature of 294 K, CO2 loading at absorber top of 0.2 mol CO2 /mol amine, and
inert gas flow rate of 18.65 kmol/m2 h.

4.3. Effect of CO2 loading on mass transfer performance
For the effect of CO2 loading at the absorber top on mass transfer
performance of blended MDEA-MEA, it can be found in Figs. 7 and 8
that the mass transfer performance (in terms of CO2 concentration profile and KG av ) is significantly affected by CO2 loading at the

Fig. 10. Effect of liquid flow rate on KG av of blended MDEA-MEA at blended ratios
of 27/3, 25/5, and 23/7%wt, at temperature of 294 K, CO2 loading at absorber top of
0.2 mol CO2 /mol amine, inert gas flow rate of 18.65 kmol/m2 h, and YCO2 of 0.09.

Fig. 7. Effect of CO2 loading at absorber top on CO2 concentration profile of 23/7%wt
MDEA-MEA at temperature of 294 K, liquid flow rate of 5 m3 /m2 , and inert gas flow
rate of 18.65 kmol/m2 h.

absorber top in that the mass transfer performance decreased as
CO2 loading increased over a CO2 loading range of 0.05–0.25 mol
CO2 /mol amine. This is because the amounts of active free amines
(MEA and MDEA) decreases as CO2 loading increases.
4.4. Effect of liquid flow rate on mass transfer performance

Fig. 8. Effect of CO2 loading at absorber top on KG av of blended MDEA-MEA at
blended ratios of 27/3, 25/5, and 23/7%wt, temperature of 294 K, liquid flow rate
of 5 m3 /m2 , inert gas flow rate of 18.65 kmol/m2 h, and YCO2 of 0.09.

It can be seen from Fig. 9 that the CO2 concentration profile
became lower as liquid flow rate increased over the range of
2.8–5.0 m3 /m2 h. This observation corresponds well with the mass
transfer performance in terms of KG av . As presented in Fig. 10,
the KG av increased as liquid flow rate increased. Regard to the
results observed in the present work (from Figs. 9 and 10), it
can be inferred that the liquid flow rate has a very significant
effect on the mass transfer performance for CO2 absorption into
aqueous solutions of blended MDEA-MEA in that the mass transfer
performance increases as liquid flow rate increases over the liquid
flow rate range of 2.8–5.0 m3 /m2 h. Thus, it can be reasoned that
increase of liquid flow rate results in an increase of liquid side
mass transfer coefficient (kL ), which significantly increases the
KG av in the case of liquid-phase controlled mass transfer (Astarita
et al., 1983). Additionally, by increasing the liquid flow rate, the
gas–liquid surface area is greatly increased, resulting in more liquid
spreading on the packing surface. The increase of liquid flow rate

A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

9

not only increases the mass transfer performance in the packed
column, but also leads to higher circulation and regeneration
costs; thus, it might not improve the overall system efficiency. In
addition, the range of liquid flow rate used in the present work
(2.8–5.0 m3 /m2 h) is in the effective range of using DX structured
packing, which is 0.1–5.0 m3 /m2 h, as provided by the packing
supplier (Sulzer Chemtech Canada, Inc.). The use of a liquid flow
rate higher than 5.0 m3 /m2 h can lead to a decline of mass transfer
performance.

4.5. Effect of MDEA-MEA blending ratio on cyclic capacity
Astarita et al. (1983) and Maneeintr et al. (2009) described the
cyclic capacity concept in which cyclic capacity is defined as the
difference of moles of CO2 absorbed in the solution per unit volume
of solution in the absorption step and that in the regeneration step,
which is, then, crucial to the CO2 absorption process. With the
same volume of solvent, the solvent with higher cyclic capacity
can carry a higher amount of absorbed CO2 than that with lower
cyclic capacity. Therefore, it can be inferred from this concept that
for a solvent that has high cyclic capacity, a low liquid circulation
rate can be applied, which results in (i) a lower operation cost
for pumping liquid and (ii) a smaller volume of solvent can be
used in the packed column. In order to investigate the effect of
MDEA-MEA blended ratio on the cyclic capacity, three blended
ratios of 27/3, 25/5, and 23/7%wt were tested in the present work.
The experimental and calculation procedures for cyclic capacity
can be found in our previous work (Maneeintr et al., 2009). The
results showed that the cyclic capacity of the blended MDEA-MEA
increased as the ratio of MDEA in the blended solution increased
and can be ranked as: 27/3%wt MDEA-MEA > 25/5%wt MDEAMEA > 23/7%wt MDEA-MEA, as presented in Fig. 11. Based on this
observation, this result occurred because MDEA has higher cyclic
capacity than MEA (Chowdhury et al., 2011); thus, by increasing
the ratio of MDEA (in another words, decreasing the ratio of MEA)
in the blended solution, the cyclic capacity of the blended solution
was then found to be increased.

Fig. 11. Effect of MDEA-MEA blended ratio on cyclic capacity.

4.6. Relative solvent regeneration ability
One of the key points for the CO2 absorption process using
chemical solvent is the ability of solvent to be generated. It has
been generally accepted that good/promising solvents for this technology should be easy to regenerate; in other words, they should
require low heat for solvent regeneration. This is because the majority (about 70%) of the cost of CO2 capture comes from the solvent
regeneration unit.
In the present work, the relative solvent regeneration ability
of the blended MDEA-MEA was determined and compared with
those of 2 M MDEA and 5 M MEA. The experiment was conducted
at 80 ◦ C in a temperature controlled bath (Cole-Parmer; the temperature can range from -20 to 200 ◦ C with ±0.01 ◦ C accuracy).
3000 ml of the solutions, which include 27/3%wt (or 2.3/0.5 molar
ratio) MDEA-MEA, 2 M MDEA, and 5 M MEA, at the same initial
CO2 loading of 0.5 were introduced into round-bottom flasks

Fig. 12. Experimental set up for determining relative solvent regeneration ability.

10

A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

Fig. 13. Relative solvent regeneration ability of 5 M MEA, 2 M MDEA, and 2.3/0.5 M
(27/3%wt) MDEA-MEA.

connected with condensers as shown in Fig. 12. Within the same
operating conditions, the CO2 loadings of the three tested solvents
were then measured as the experiment proceeded by titrating
with standard 1.0 M HCl using methyl orange as an indicator.
The results obtained from this experiment suggest the solvents’
relative regeneration ability in that the CO2 loading of a solution that has high relative solvent regeneration ability (in other
words, one that is relatively easy to regenerate) would decrease
more rapidly than one that has lower relative solvent regeneration
ability. It was found that the CO2 loadings of the three testing solutions decreased as the operational time increased as presented in
Fig. 13. Even though the results observed from Fig. 13 can generally be understood as showing that the relative regeneration ability
of blended MDEA-MEA would fall in between those of MDEA and
MEA, the results obtained from the present work clearly show
how close the relative regeneration ability of 27/3%wt (or 2.3/0.5
molar ratio) blended MDEA-MEA is to that of 2 M MDEA. This new
observation is considered to be very useful in order to (i) use the
blended MDEA-MEA more effectively in the pilot plant-scale testing and (ii) enhance the performance of the blended MDEA-MEA
by addition of the third component (e.g., amine or additive). In
addition, at the end of the experiment, the total amine concentrations of the three testing solutions were determined (by titration
with standard 1.0 M HCl (Horwitz, 1975)) and compared with the
initial concentrations. It was found that the total amine concentrations were very close to the initial concentrations. Thus, it can
be said that the experimental set up as shown in Fig. 12 is effective. More importantly, the results obtained from this study are
reliable.
In the present work, the mass transfer performance of CO2
absorption into aqueous solutions of blended MDEA-MEA was comprehensively investigated in a DX structured packed column at
various operating conditions of MDEA-MEA blend ratio, temperature, CO2 loading at the absorber top, and liquid flow rate. The
mass transfer performance was evaluated in terms of KG av and CO2
concentration profile along the height of the column. It was found
that the mass transfer performance increased as the ratio of MEA in
the blended solution, temperature, and liquid flow rate increased
but decreased as CO2 loading increased (as presented in Figs. 3–10)
over the testing conditions. In addition, the mass transfer performance (in terms of both KG av and CO2 concentration profile) of
blended MDEA-MEA increased as the ratio of MEA in the blended
solution increased as shown in Figs. 3, 4, 6, 8 and 10. This is because
MEA has faster reaction kinetics of CO2 absorption than MDEA (Kohl
and Nielsen, 1997; Sema et al., 2012). The higher the ratio of MEA in

the blended solutions, the higher the amounts of the more reactive
MEA molecules that can absorb CO2 ; thus, a higher mass transfer
performance was observed. By comparing the three MDEA-MEA
blend ratios (27/3, 25/5, and 23/7%wt MDEA-MEA), it was observed
that the 23/7%wt MDEA-MEA provided the best mass transfer performance among the three as shown in Figs. 3, 4, 6, 8 and 10.
However, in order to effectively use blended MDEA-MEA, not only
mass transfer performance, but also the cyclic capacity and relative
regeneration ability should be taken into consideration.
In summary, by increasing the ratio of MEA in the blended solution, the mass transfer performance would be increased but the
cyclic capacity and the relative solvent regeneration ability would
be decreased. As shown in Figs. 3, 4, 6, 8 and 10, it can be observed
that the mass transfer of 23/7%wt MDEA-MEA is much higher than
those of 25/5 and 27/3%wt MDEA-MEA, respectively. On the other
hand, the cyclic capacities of the three blend ratios are considerably close to each other as presented in Fig. 11. Therefore, it can be
reported that the effect of ratio of MEA in the blended MDEA-MEA
solutions on mass transfer performance is more significant than
that on cyclic capacity. As a result, based on above discussion, it
is reasonable to conclude that the 23/7%wt MDEA-MEA provides
the best CO2 absorption performance among the three blending ratios over the operating conditions conducted in the present
work.
4.7. Empirical predictive correlation for KG av of blended
MDEA-MEA
Liang et al. (2011) mentioned that in order to effectively
design an absorption column, the KG av is required. However, it
is an expensive and time consuming process to experimentally
determine the KG av in a packed column. Thus, the predictive correlation for KG av is then found to be important since it can be
used to determine the KG av from operating conditions without
experimental work. Dey and Aroonwilas (2009) proposed a predictive correlation for blended AMP-MEA. The model was tested
with the experimental mass transfer data of blended AMP-MEA
in a laboratory-scale absorption column packed with DX structural packing. They concluded that the predictive results were
found to be in good agreement with the experimental results.
For the MDEA-MEA system, the predictive correlation can be seen
in Eq. (3).
KG av = K × eA(MDEA/MEA) × eB˛ × eCxCO2 × L1D × eECs × eF/T

(3)

where KG av is the overall volumetric mass transfer coefficient
(kmol/m3 h kPa), (MDEA/MEA) is the molar ratio of MDEA and MEA,
xCO2 is the mole fraction of CO2 , ˛ is the CO2 loading (mol CO2 /mol
amine), Cs is the concentration of amine in the solution (kmol/m3 ),
L1 is the liquid flow rate (m3 /m2 h), T is the absolute temperature
(K), and K, A, B, C, D, E, and F are the coefficients for the respective
parameters modeled in the proposed equation.
The experimental values of KG av obtained in the present work at
various operating conditions of MDEA-MEA blending ratios (27/3,
25/5, and 23/7%wt), temperatures (298, 303, and 318 K), CO2 loadings at the absorber top (0.05, 0.17, and 0.25 mol CO2 /mol amine),
and liquid flow rates (2.8, 3.8, and 5 m3 /m2 h) were then used to
correlate the predictive correlation in Eq. (3) using the nonlinear
regression analysis package NLREG (with a minimum confidence
level of 97%). The coefficients (K, A, B, C, D, E, and F) obtained
from the NLREG program are presented in Table 1. By comparing the predicted and experimental results in the parity chart,
as shown in Fig. 14, it can be seen that the predicted values of
KG av calculated from Eq. (3) are in fairly good agreement with
the experimental values with an absolute average deviation (AAD)
of 21.8%.

A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

11

Table 1
Summary of parameters for predictive equation presented in Eq. (3).
Concentration of
blended
MDEA-MEA (% wt)

Confidential level

A

B

C

D

E

F

K

AAD

27/3
25/5
23/7

0.97
0.97
0.99

−0.0032
0
0.04

−4
−1.1
−3.65

−10.325
−14.3
−11.4

0.8531
0.559
0.91

0.1438
0.3665
0.2

−595.211
−511.5
−443

0.9254
1
1

20.9%
21.7%
22.8%

“Project 985” in Hunan University – Novel Technology Research and
Development for CO2 Capture as well as Hunan University to
the Joint International Center for CO2 Capture and Storage (iCCS)
is gratefully acknowledged. In addition, we would also like to
acknowledge the research supports over the past many years of
the Industrial Research Consortium – Future Cap Phase II of the
International Test Center for CO2 Capture (ITC) at the University of
Regina. We would also like to acknowledge the research support
from the following organizations: Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for
Innovation (CFI), Saskatchewan Ministry of Energy & Resources,
Western Economic Diversification, Saskatchewan Power Corporation, Alberta Energy Research Institute (AERI), and Research
Institute of Innovative and Technology for the Earth (RITE).

References
Fig. 14. Parity chart compares predicted and experimental values of KG av for CO2
absorption into blended MDEA-MEA solutions.

5. Conclusions
The mass transfer performance of CO2 absorption into aqueous
solutions of blended MDEA-MEA was experimentally determined
(in terms of KG av and CO2 concentration profile) in a laboratoryscale absorption column packed with DX structured packing. The
experiments were conducted at various operating conditions of
MDEA-MEA blending ratios (27/3, 25/5, and 23/7%wt), temperatures (298, 303, and 318 K), CO2 loadings at the absorber top
(0.05, 0.17, and 0.25 mol CO2 /mol amine), and liquid flow rates
(2.8, 3.8, and 5 m3 /m2 h). The results show that the mass transfer
performance increases as ratio of MEA in the blended solution, temperature, and liquid flow rate increase but decreases as CO2 loading
increases within the range of conditions using in the present work.
On the other hand, the cyclic capacity and the relative solvent
regeneration ability decrease as the ratio of MEA in the blended
solution increases. However, after taking into consideration all
three parameters (i.e., mass transfer performance, cyclic capacity, and relative solvent regeneration ability), it can be concluded
that 23/7%wt MDEA-MEA provides the best CO2 absorption performance among the three blend ratios over the operating conditions
conducted in the present work.
Acknowledgments
The first author (A. Naami) would like to acknowledge and
appreciate the scholarship support from the Libyan Higher Educational studies through the cultural section of the Libyan Embassy
in Ottawa, Canada. The financial support from the National Natural
Science Foundation of China (NSFC No. 21276068, 21250110514,
and 21376067), Ministry of Science and Technology of the People’s of Republic of China (MOST No. 2012BAC26B01), Ministry
of Education of the People’s of Republic of China-Supported Program for Innovative Research Team in University (No. IRT1238),
Shaanxi Yanchang Petroleum (Group) Co., LTD, China’s State

Aroonwilas, A., Tontiwachwuthikul, P., 1998. Mass transfer coefficients and correlation for CO2 absorption into 2-amino-2-methyl-1-propanol (AMP) using
structured packing. Industrial and Engineering Chemistry Research 37 (2),
569–575.
Aroonwilas, A., Veawab, A., 2004. Characterization and comparison of the
CO2 absorption performance into single and blended alkanolamines in a
packed column. Industrial and Engineering Chemistry Research 43 (9),
2228–2237.
Astarita, G., Savage, D.W., Bisio, A., 1983. Gas Treating with Chemical Solvents. John
Wiley, NY, USA.
Austgen, D.M., Rochelle, G.T., Chen, C.C., 1991. Model of vapor-liquid equilibria for
aqueous acid gas-alkanolamine systems. 2. Represetation of hydrogen sulfide
and carbondioxide solubility in aqueous MDEA and carbon dioxide solubility
in aqueous mixtures of MDEA with MEA or DEA. Industrial and Engineering
Chemistry Research 30 (3), 543–555.
Barchas, R., Davis, R., 1992. The Kerr-McGee/ABB Lummus Crest technology for the
recovery of CO2 from stack gases. Energy Conversion and Management 33 (5–8),
333–340.
Bensetiti, Z., IIiuta, I., Larachi, F., Gradjean, B.P.A., 1999. Solubility of nitrus oxide
in amine solutions. Industrial and Engineering Chemistry Research 38 (1),
328–332.
Charkravarty, T., Phuken, U.K., Weilund, R.H., 1985. Reaction of acid gases with
mixtures of amines. Chemical Engineering Progress 40, 32–36.
Chowdhury, F.A., Okabe, H., Yamada, H., Onoda, M., Fujioka, Y., 2011. Synthesis and
selection of hindered new amine absorbents for CO2 capture. Energy Procedia
4, 201–208.
Critchfield, J., Rochelle, G.T., 1987. CO2 absorption into aqueous MDEA and
MDEA/MEA solutions. In: Paper No. 43e, Presented at the AIChE National Meeting, Houston, TX.
Dawodu, O.F., Meisen, A., 1994. Solubility of carbon dioxide in aqueous mixtures of
alkanolamines. Journal of Chemical and Engineering Data 39 (3), 548–552.
Dawodu, O.F., Meisen, A., 2009. Degradation of alkanolamine blends by carbon dioxide. Canadian Journal of Chemical Engineering 74 (6), 960–966.
deMontigny, D., 2004. Comparing Packed Columns and Membrane Absorbers for CO2
Capture. University of Regina, Regina, Saskatchewan, Canada, Ph.D. Dissertation.
deMontigny, D., Tontiwachwuthikul, P., Chakma, A., 2001. Parametric studies of carbon dioxide absorption into highly concentrated monoethanolamine solutions.
Canadian Journal of Chemical Engineering 79, 137–142.
Dey, A., Aroonwilas, A., 2009. CO2 absorption into MEA-AMP blended: mass transfer
and absorber height index. Energy Procedia 1, 211–215.
Dooley, J.J., Davidson, C.L., Dahowski, R.T., 2009. An Assessment of the Commercial
Availability of Carbon Dioxide Capture and Storage Technology as of June 2009.
Office of Scientific and Technical Information, US Department of Energy, TN,
USA.
Edali, M., Aboudheir, A., Idem, R., 2009. Kinetics of car carbon dioxide absorption into
mixed aqueous solutions of MDEA and MEA using a laminar jet apparatus and a
numerically solved 2D absorption rate/kinetics model. International Journal of
Greenhouse Gas Control 3, 550–560.
Eswaran, S., Wu, S., Nicola, R., 2010. Advanced amines-based CO2 Capture for coalfired power plant. In: Proceeding of the Coal-Gen 2010 Conference, Pittsburgh,
PA, USA, August 10–12.

12

A. Naami et al. / International Journal of Greenhouse Gas Control 19 (2013) 3–12

Fernandes, J., Lisboa, P.F., Simoes, P.C., Mota, J.P.B., Saatdjian, E., 2009. Application of
CFD in the study of supercritical fluid extraction with structured packing. Journal
of Supercritical Fluids 50, 61–68.
Fu, K., Sema, T., Liang, Z., Liu, H., Na, Y., Shi, H., Idem, R., Tontiwachwuthikul, P., 2012.
Investigation of mass-transfer performance for CO2 absorption into diethylenetriamine (DETA) in a ramdomly packed column. Industrial and Engineering
Chemistry Research 51 (37), 12058–12064.
Glasscock, D.A., Critchfirlf, J.E., Rochelle, G.T., 1991. CO2 absorption/desorption in
mixtures of methyldiethanolamine with monoethanolamine or diethanolamine.
Chemical Engineering Science 46, 2829–2845.
Goto, K., Okabe, H., Chowdhury, A.F., Shimizu, S., Fujioka, Y., Onoda, M., 2011. Development of novel absorbents for CO2 capture from blast furnace gas. International
Journal of Greenhouse Gas Control 5, 1214–1219.
Hagewiesche, D.P., Ashour, S.S., Al-Ghawas, H.A., Sandall, O.C., 1995. Absorption of carbon dioxide into aqueous blendeds of monoethanolamine
N-methyldiethanolamine.
and
Chemical
Engineering
Science
50,
1071–1079.
Horng, S.Y., Li, M.H., 2002. Kinetics of absorption of carbon dioxide into aqueous
solutions of monoethanolamine + triethanolamine. Industrial and Engineering
Chemistry Research 41 (2), 257–266.
Horwitz, W., 1975. Association of Official Analytical Chemists (AOAC) Methods, 12th
ed. George Bant, Gaithersburg, MD, USA.
Hsu, C.H., Li, M.H., 1997. Densities of aqueous blends amines. Journal of Chemical
and Engineering Data 42 (3), 502–507.
Huang, Y.M., Soriano, A.N., Caparanga, A.R., Li, M.H., 2011. Kinetics of absorption
of carbon dioxide in 2-amino-2-methyl-1-propanol + N-methyldiethanolamine.
Journal of the Taiwan Institute of Chemical Engineers 42, 76–85.
Idem, R., Tontiwachwuthikul, P., Gelowitz, D., Wilson, M., 2011a. Latest research on
fundamental studies of CO2 capture process technologies at the International
Test Centre for CO2 Capture. Energy Procedia 4, 1707–1712.
Idem, R., Shi, H., Gelowitz, D., Tontiwachwuthikul, P., 2011b. Catalytic Method and
Apparatus for Separating a Gaseous Component from an Incoming Gas Stream.
International Patent Application PCT/CA2011/000328 filed 29/03/2011.
Idem, R., Wilson, M., Tontiwachwuthikul, P., Chakma, A., Veawab, A., Aroonwilas, A.,
Gelowitz, D., 2006. Aqueous MEA and mixed MEA/MDEA solvents at the University of Regina CO2 capture technology development plant and the Boundary
Dam CO2 capture demonstration plant. Industrial and Engineering Chemistry
Research 45 (8), 2414–2420.
Jou, F.Y., Otto, F.D., Mather, A.E., 1994. Vapor-liquid equilibrium of carbon dioxide in
aqueous mixtires of monoethanolamine and methyldiethanolamine. Industrial
and Engineering Chemistry Research 33 (8), 2002–2005.
Kaewsichan, L., Al-Boferson, O., Yesavage, V.F., Selim, M.S., 2001. Prediction of the
solubility of acid gases in monoethanolamine (MEA) and methyldiethanolamine
(MDEA) solutions using the electrolyte-UNIQUAC model. Fluid Phase Equilibria
183–184, 157–171.
Kohl, A.L., Nielsen, R.B., 1997. Gas Purification, 5th ed. Gulf Publishing Company,
Houston, USA.
Lawal, A.O., Bello, A., Idem, R.O., 2005. The role of methyl diethanolamine (MDEA) in
preventing the oxidative degradation of CO2 loaded and concentrated aqueous
monoethanolamine (MEA)-MDEA blends during CO2 absorption from flue gases.
Industrial and Engineering Chemistry Research 44 (6), 1874–1896.
Lawal, A.O., Idem, R.O., 2005. Effects of operating variables on the product distribution and reaction pathways in the oxidative degradation of CO2 -loaded aqueous
MEA-MDEA blends during CO2 absorption from flue gas streams. Industrial and
Engineering Chemistry Research 44 (4), 986–1003.
Lawal, A.O., Idem, R.O., 2006. Kinetics of the oxidative degradation of CO2 loaded
and concentrated aqueous MEA-MDEA blends during CO2 absorption from flue
gas streams. Industrial and Engineering Chemistry Research 45 (8), 2601–2607.
Li, M.H., Lai, M.D., 1995. Solubility and diffusivity of N2 O and CO2 in (monoethano
lamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2amino-2-methyl-1-propanol + water). Journal of Chemical and Engineering Data
40 (2), 486–492.
Li, Y.G., Mather, A.E., 1994. Correlation and Prediction of the solubility of carbon dioxide in a mixed alkanolamines solution. Industrial and Engineering Chemistry
Research 33 (8), 2006–2015.
Li, M.H., Shen, K.P., 1992. Densities and solubilities of solutions of carbon dioxide
in water + monoethanolamine + N-methyldiethanolamine. Journal of Chemical
and Engineering Data 37 (3), 288–290.
Li, M.H., Shen, K.P., 1993. Calculation of equilibrium solubility of carbon dioxide
in aquous mixtures of monoethanolamine with methyldiethanolamine. Fluid
Phase Equilibria 85, 129–140.

Liang, Z.H., Sanpasertpanich, T., Tontiwachwuthikul, P., Gelowitz, D., Idem, R., 2011.
Design, modelling and simulation of post-combustion CO2 capture systems
using reactive solvents. Carbon Management 2, 265–288.
Liao, C.H., Li, M.H., 2002. Kinetics of absorption of carbon dioxide into aqueous solutions of monoethanolamine + N-methyldiethanolamine. Chemical Engineering
Science 57, 4569–4582.
Ma’mun, S., Nilsen, R., Svendsen, H.F., Juliussen, O., 2005. Solubility of carbon dioxide
in 30% mass monoethanolamine and 50% mass methyldiethanolamine solutions.
Journal of Chemical and Engineering Data 50 (2), 630–634.
Mandal, B.P., Guha, M., Biswas, A.K., Bandyopadhyay, S.S., 2001. Removal of carbon
dioxide by absorption in mixed amines: modelling of absorption in aqueous MDEA/MEA and AMP/MEA solutions. Chemical Engineering Science 56,
6217–6224.
Mandal, B.P., Biswas, A.K., Bandyopadhyay, S.S., 2003. Absorption of carbon dioxide into aqueous blends of 2-amino-2-mthyl-1-propanol and diethanolamine.
Chemical Engineering Science 58, 4137–4144.
Mandal, B.P., Kundu, M., Bandyopadhyay, S.S., 2005. Physical solubility
and diffusivity if CO2 and N2 O into aqueous solutions of (2-amino-2and
(N-methyldiethanolamine
methyl-1-propanol + monoethanolamine)
+ monoethanolamine). Journal of Chemical and Engineering Data 50 (2),
352-258.
Maneeintr, K., Idem, R.O., Tontiwachwuthikul, P., Wee, A.G.H., 2009. Synthesis, solubilities, and cyclic capacity of amino alcohols for CO2 Capture from flue gas
streams. Energy Procedia 1, 1327–1334.
Naami, A., Edali, M., Sema, T., Idem, R., Tontiwachwithikul, P., 2012. Mass transfer
performance of CO2 absorption into aqueous solutions of 4-diethylamine2-butanol, monoethanolamine, and N-methyldiethanolamine. Industrial and
Engineering Chemistry Research 51 (18), 6470–6479.
Ramachandran, N., Aboudheir, A., Idem, R., Tontiwachwuthikul, P., 2006. Kinetics of the absorption of CO2 into mixed aqueous loaded solutions of
monoethanolamine and methyldiethanolamine. Industrial and Engineering
Chemistry Research 45 (8), 2608–2616.
Rangwala, H.A., Morrell, B.R., Mather, A.E., Otto, F.D., 1992. Absorption of CO2 into
aqueous tertiary amine/MEA solutions. Canadian Journal of Chemical Engineering 70, 482–490.
Rao, A.B., Rubin, E.S., 2002. A technical, economical, and environmental assessment
of amine based CO2 capture technology for power plant greenhouse gas control.
Environmental Science and Technology 36, 4467–4475.
Samanta, A., Bandyopadhyay, S.S., 2011. Absorption of carbon dioxide into
piperazine activated aqueous N-methyldiethanolamine. Chemical Engineering
Science 171, 734–741.
Sakwattanapong, R., Aroonwilas, A., Veawab, A., 2005. Behavior of reboiler heat duty
for CO2 capture plants using regenerable single and blended alkanolamines.
Industrial and Engineering Chemistry Research 44 (12), 4465–4473.
Sema, T., Naami, A., Liang, Z., Idem, R., Ibrahim, H., Tontiwachwuthikul, P., 2013. 1D
absorption kinetics modeling of CO2 -DEAB-H2 O system. International Journal
of Greenhouse Gas Control 12, 390–398.
Sema, T., Naami, A., Liang, Z., Shi, H., Rayer, A.V., Sumon, K.Z., Wattanaphan, P., Henni,
A., Idem, R., Saiwan, C., Tontiwachwuthikul, C., 2012. Reaction kinetics of CO2
absorption into reactive amine solutions. Carbon Management 3 (2), 201–220.
Setameteekul, A., Aroonwilas, A., Veawab, A., 2008. Statistical factorial design analysis for parametric interaction and empirical correlations of CO2 absorption
performance in MEA and blended MEA/MDEA processes. Separation and Purification Technology 64, 16–25.
Shannon, M.S., Bara, J.E., 2012. Properties of alkylimidazoles as solvents for CO2
capture and comparisons to imidazoliun-based ionic liquids. Industrial and Engineering Chemistry Research 50 (14), 8665–8677.
Shen, K.P., Li, M.H., 1992. Solubility of carbon dioxide in aqueous mixtures of
monoethanolamine with methyldiethanolamine. Journal of Chemical and Engineering Data 37 (1), 96–100.
Versteeg, G.F., Kuipers, J.A.M., van Beckum, F.P.H., van Swaaij, W.P.M., 1990. Mass
transfer with the complex recersible chemical reactions-II. Parallel reversible
chemical reactions. Chemical Engineering Science 45, 183–197.
Vrachnos, A., Kontogeorgis, G., Voutsas, E., 2006. Thermodynamics modeling of
acidic gas solubility in aqueous solutions of MEA, MDEA, and MEA-MDEA blends.
Industrial and Engineering Chemistry Research 45 (14), 5148–5154.
Wang, Y.W., Xu, S., Otto, F.D., Mather, A.E., 1992. Solubility of N2 O in alkanolamines
and mixed solvents. Chemical Engineering Journal 48, 31–40.
Weiland, R.H., Dingman, J.C., Cronin, D.B., Browning, G.J., 1998. Density and viscosity
of some partially carbonated aqueous alkanolamines solutions and their blends.
Journal of Chemical and Engineering Data 43 (3), 378–382.