3rd Post Combustion Capture Conference (PCCC3)
CO2 enthalpy and heat capacity measurements in aqueous Piperzine
blends with different Alkanolamines
Abdurahim Abdulkadir, Khalid Al-Ali, Ahmed Al Hajaj, Enas Nashef, Mohammad Abu
Zahra *
Separation Technology Laboratory, Masdar Institute of Science and Technology, P.O.Box 54424, Masdar City,UAE
Keyword: Micro-Reaction Calorimeter; Enthalpy; Heat capacity; Post-Combustion Carbon Capture; MEA; PZ;MDEA;AMP
1. Introduction
One of the most matured technology to capture CO2 from industrial gases is the chemical absorption technology
using a reactive solvent such as aqueous amines. Screening of the solvent for the capture process is quite a complex
process due to the varying characteristics such as reactivity, cyclic loading, temperature stability, stability towards
oxygen[1, 2]. Alkanolamines such as monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA),
diisopropanolamine (DIPA), triethanolamine (TEA), and N-methyldiethanolamine (MDEA), 2-amino-2-methyl-lpropanol (AMP), and 2-piperidineethanol (2-PE) were widely used as absorbent for the acid gas removal
processes[2]. The most recent mixed solvents (e.g. primary or secondary amines + tertiary or sterically hindered
amines) which have two or more solvents attracted the attention due to their combined effect of faster kinetics
(associated with primary or secondary amines) and high absorption capacity with lower regeneration energy
(associated with tertiary amines)[3] . Piperazine activated aqueous alkanolamine solutions have such advantages and
they have been extensively studied and proposed as a more efficient bulk removal solvent[3, 4]. The heat of
absorption and specific heat of MEA blended with 3PM has been reported using micro-reaction calorimeter[5]. In
this work the thermodynamic properties of the blend of different alkanolamines with PZ were investigated. Adeosun
et al. studied four PZ blends (MEA + PZ + H 2O; DEA + PZ + H2O; AMP + PZ + H2O; MDEA + PZ + H2O) for
their absorption capacity with absorption rate and suggested for further thermodynamic studies for the feasibility of
such blends for post-combustion capture applications[6].
In this work a micro-reaction calorimeter was used to measure the heat of absorption and the heat capacity of PZ
blended with different alkanolamines. The heat of absorption was measured at 313.150K while the heat capacities of
aqueous mixtures were measured from 303.15 to 353.15 K. The enthalpies of 20wt% of piperzine, 10wt% of Methyl
diethanolamine (MDEA), 10wt% of 2-Amino-2-methyl-1-propanol (AMP), 10/20wt% of MDEA/PZ and 10/20wt%
* Corresponding author. Tel.: +971-2810-9181.
E-mail address: [email protected].
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of AMP/PZ blends were measured. Moreover, the heat capacity of Monoethanolamine (MEA) blended with
Piperzine (PZ) was measured using the micro-reaction calorimeter (µRC) at an interval of 5 0K. The heat capacities
of PZ, MEA, (MEA + H2O), (PZ + H2O), (MEA + PZ) and (MEA + PZ + H2O) were studied. The samples of the
binary blends ((MEA + H2O), (PZ + H2O), (MEA + PZ) ) and the ternary blend ((MEA + PZ + H2O)) were prepared
at different mole fractions of X = 0.2,0.4,0.6 & 0.8 as shown in table1.
2. Experimental Section
The alkanolamine materials were supplied by Sigma-Aldrich chemical Co. They were used without any further
purification. The aqueous amine solutions were prepared using distilled water on the basis of mole fraction for PZ
and MEA while for other alkanolamines it is in weight percentage. The enthalpy and heat capacity were measured
using a micro Reaction Calorimeter provided by Thermal Hazard Technology (UK). Heat capacity was measured at
temperature ranging from (303.1 to 353.15) K. The measurement of the heat capacity was achieved by making a
“step-change” in the temperature of the cell in comparison to the reference cell of the empty vial. At each
temperature, the heat was repeatedly measured 3 times with a step of ± 0.5 K. First, blank test was conducted with
an empty vial. Then, the absorbent of 0.5-1 g was placed in the vial and the experiment was conducted with the
same condition used for the blank. The calibration has been made using the water heat capacities in the temperature
range of interest. The absorption enthalpies of CO2 in the aqueous blends were measured at 313.150K.
Fig 1. Micro-Reaction Calorimeter Experimental Set-up for measuring the heat of absorption.
3. Results and Conclusions
The Preliminary results for the heat capacity obtained for blends of MEA and PZ at temperatures range from
303.15 to 353.15 K and different mole fractions of piperzine (0.2 ≤ X ≤ 0.8) is shown in table 1. Also, the heat
capacity of these pure amines of MEA & PZ obtained from this work is compared with the literature values [7, 8].
The absolute average deviations (AAD %) were found to be 0.4 % and 1.2%. Chen and Li et al.[8] extrapolated the
heat capacity values of PZ from the experimental results of higher temperatures to the lower temperatures, whereas
in this work the experimental values were obtained at the lower temperature range. Moreover, the absorption
enthalpies of CO2 in the aqueous blends of pure PZ, MDEA & AMP with their blends were measured at 313.15 0K.
The maximum loading capacity of these amine blends is also reported. The blend of 10/20wt% of AMP/PZ
exhibited the highest heat of absorption. While the pure piperzine of 20wt% shows the highest heat of absorption of
115 (KJ/mole CO2) at a maximum loading capacity of CO2 at 0.62 (mol CO2/mol Amine). Further report on the
heat capacity of PZ, MEA, (MEA + H2O), (PZ + H2O), (MEA + PZ) and (MEA + PZ + H2O) will be studied at
Author name / Energy Procedia 00 (2015) 000–000
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different mole fractions X = (0.2, 0.4, 0.6 & 0.8). Table 2, shows the heat of absorption of PZ, MDEA, AMP and
their blends at 10/20wt%.
T/K
x1 = 0.2
x1 = 0.4
x1 = 0.6
x1 = 0.8
Cp
Cp
Cp
Cp
303.15
147.0
155.4
162.6
167.2
308.15
149.3
158.5
164.8
169.4
313.15
151.7
160.5
166.9
170.7
318.15
154.1
162.2
168.5
172.0
323.15
156.6
164.3
170.5
173.5
328.15
159.1
166.3
172.5
175.2
333.15
160.8
168.2
174.4
176.8
338.15
163.4
170.8
176.7
178.8
343.15
166.1
173.0
178.5
180.7
348.15
168.1
175.7
180.2
182.2
353.15
170.1
178.0
182.0
183.6
Table 1: Heat Capacities (J*mol-1*K-1) of (MEA + PZ) blends at different mole fractions of piperzine.
AMINES
PZ
MDEA
AMP
MDEA/PZ
AMP/PZ
CONCENTARION
20wt%
10wt%
10wt%
10/20wt%
10/20wt%
HEAT of
ABSORPTION
(KJ/mole CO2)
115.15
56.76
70.25
79.75
93.4
LOADING CAPACITY
(molCO2/mol Amine)
0.62
0.63
0.72
0.78
0.82
Table 2: Heat of absorption for stand-alone and blends of MDEA and AMP with PZ at 313.15 0K.
4. References
1.
2.
3.
4.
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8.
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Chen, Y.-R., et al., Liquid heat capacity of the solvent system (piperazine+ 2-amino-2-methyl-l-propanol+
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