1© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

Short Communication

Received January 2, 2014; revised March 8, 2014; accepted March 10, 2014

10.1002/ghg.1427Published online at Wiley Online Library (wileyonlinelibrary.com). DOI:

Correspondence to: Mohammad R.M. Abu-Zahra, The Institute Center for Energy (iEnergy), Masdar Institute of Science and Technology,

P.O.Box 54224, Masdar city, Abu Dhabi, United Arab Emirates E-mail: mabuzahra@masdar.ac.ae

Effect of moisture on the heat capacity and the regeneration heat required for CO 2 capture process using PEI impregnated mesoporous precipitated silica Dang Viet Quang , Abdallah Dindi , Aravind V Rayer , Nabil El Hadri , Abdurahim Abdulkadir , and Mohammad R.M. Abu-Zahra , Masdar Institute of Science and Technology , Abu Dhabi , United Arab Emirates

Abstract: In this study, we report the effect of the moisture of polyethylenimine (PEI) impregnated mesoporous precipitated silica used for CO 2 adsorption on the heat capacity and the heat required to regenerate the adsorbent. The results indicate that the heat capacity of the absorbent increases as its moisture content increases. The increase in moisture results in the rise of the vaporization heat of water and the elevated heat capacity results in higher sensible heat. For these reasons, the total regeneration heat required for CO 2 capture process increases signifi cantly. The adsorbent has a maxi-mum CO 2 adsorption capacity at 75 °C. CO 2 capture process using PEI impregnated mesoporous precipitated silica requires a minimum energy to regenerate the adsorbent; it reduces 46% of the energy compared to a process using an aqueous MEA 30 wt%, as the process operates at 75 °C.© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd

adsorption capacity ; CO Keywords: 2 capture ; regeneration heat ; sensible heat ; precipitated silica

Introduction

CO 2 post-combustion capture using amine solution like monoethanolamine is the most well-known technology, but it requires high

energy for the regeneration of amine solvent due to high heat capacity and vaporization heat of water. Th is causes a high energy penalty and increases the cost of electricity up to about 80% by the applica-tion of this technology to power plant. 1–6 Th erefore,

the avoidance of using liquid and volatile amine as absorbent should be taken into account in order to reduce the energy consumption of CO 2 capture pro-cess. Th us, a novel class of solid adsorbent has been investigated. 7–9 Usually a typical solid adsorbent consists of a porous substrate with or without func-tionalization. A solid adsorbent without functional-ization is named as physical adsorbent that adsorbs CO 2 by van der Walls attraction and the interaction among polar sites on its surface with CO 2 molecules.

D V Quang et al. Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process

2 © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

Chemical adsorbents are usually synthesized by modifying a substrate with functional groups such as alkaline carbonates or amine groups; the operating condition and adsorption performance of the result-ing adsorbent greatly depend on the nature of the substrate and the functional group. 10–13 Th e carbon-ate adsorbent operates at 60–100 °C for adsorption and 120–400 °C for desorption, while the amine functionalized adsorbent operates at a similar tem-perature range for adsorption, but it can be regen-erated at a much lower temperature approximately 100–130 °C. Recent reports revealed that polyethyl-enimine (PEI) impregnated adsorbent has relatively low adsorption heat (approximately 60–80 kJ/mole of CO 2 ) and high CO 2 adsorption capacity due to the high porosity of support materials that pro-vides more accessibility to CO 2 molecules. 11,14,15 Among investigated solid sorbents, PEI impregnated mesoporous silica is likely to be considered as the most eff ective solid adsorbent due to its high ad-sorption capacity, low regeneration heat, and easy preparation. 9,14,16

Th e total energy required for the regeneration of sorbent typically includes the sensible heat, the vaporization heat of volatile components at high temperature, and the CO 2 desorption heat. Th e sensible heat is the heat that needs to raise the temperature of the sorbent to the desorption tem-perature. Th e magnitude of sensible heat depends on the specifi c heat capacity of the adsorbent, the temperature diff erence, and the mass of adsorbent. Th e most benefi t of the solid adsorbent is to reduce both the sensible heat and the vaporization of volatile components due to the reduction or avoid-ance of water and volatile amine. A previous study indicated that the regeneration energy requirement of CO 2 capture process using PEI impregnated precipitated silica can be reduced up to 46% com-pared to conventional process using an aqueous ethanolamine 30 wt%. 17 In the previous study, the heat capacity was measured and the regeneration heat was calculated for a dried sample. In fact, PEI impregnated mesoporous silica contains a large number of hydrophilic silanol and amino groups, which have a strong affi nity to water; it can easily adsorb water from its humid surroundings and therefore increase the moisture of the adsorbent. 18 As the moisture in the adsorbent increases, the specifi c heat capacity of the adsorbent will increase and this will result in the increase in the sensible

heat and the vaporization heat. However, till now the eff ect of moisture on the heat capacity and the total regeneration heat of PEI impregnated mesoporous silica has not been investigated. Th erefore, in this work, the variation in moisture content of the adsorbent as the moisturized CO 2 gas passed through the adsorbent at diff erent temperatures was measured and the eff ect of moisture on the heat capacity of adsorbent was investigated. Th e eff ect of moisture and adsorption temperature on the total energy required for the regeneration of adsorbent was reported.

Experimental Preparation of adsorbent MPS was prepared by acidizing the solution of sodium silicate in the presence of NaCl. 19–21 Typically, 152 g of sodium silicate solution (2.5SiO 2 ·NaO 2 , 26.5 wt% SiO 2 , Sigma-Aldrich, St Loius, MO) was added to 1 L beaker containing 630 g of NaCl 3.5 wt%. Th e beaker was placed in a heating mantle, which was fi rst turned on and temperature was set at 40 °C. Th en, H 2 SO 4 8 wt% was added by a drop-wise method at 40 °C. H 2 SO 4 was added to alkaline solution in two stages. Th e fi rst stage was ended as the fi rst silica aggregates were observed to prevent the formation of a strong silica gel. Th e second stage began aft er 5 min and fi nished as the pH of the solution reached 5. Th e resulting slurry was aged at 80 °C for 30 min and cooled down to room temperature. Th e slurry was fi ltered and washed with water to eliminate by-prod-uct ions, mainly Na + , SO 4 2− , and Cl − . Finally, the resulting wet silica was dried at 130 °C for 3 h to produce mesoporous precipitated silica.

Precipitated silica with average BET surface area, pore volume, and pore size are 230 m 2 /g, 0.95 cm 3 /g, and 16.7 nm, respectively, was selected to impregnate PEI. To prepare PEI impregnated precipitated silica, the desired amount of 37.5 wt% PEI in water (Branched polyethylenimine, Mw 1200, Sigma-Aldrich, St Loius, MO) was added to a 50 mL beaker containing precipitated silica with a weight ratio of 4:1 (PEI solution to silica) and mechanically mixed using a stainless steel spatula. Th e resulting wet precipitated silica was dried at 105 °C for 3 h to produce as-pre-pared adsorbent containing 60 wt% PEI that was denoted as PEI-PS-60. Moisture content in the adsor-bent (wt%) was determined by Karl Fisher titration

Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process D V Quang et al.

3© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

method using a KF-21 moisture meter (Mitsubishi Chemical Analytech Co. Ltd., Kanagawa, Japan).

Heat capacity measurement Heat capacity was determined by a Micro Reaction Calorimeter provided by Th ermal Hazard Technology (Bletchley, UK). Heat capacity was measured at temperature ranging from 30 to 90 °C. At each temperature, the heat was repeatedly measured three times with a step of ±0.5 °C. First, a blank test was conducted with an empty cell. Th en, approximate 0.3 g of adsorbent was placed in an analysis cell and the test conducted with the same condition used for the blank. Th e heat capacity of the adsorbent was calcu-lated by URC Analysis soft ware provided by Th ermal Hazard Technology (Bletchley, UK). Th e accuracy of the C p measurements is estimated to be within 3% on the basis of the measurement of the C p of water.

CO 2 adsorption studies CO 2 loading capacity of adsorbents at CO 2 atmosphere was also determined by the Micro Reaction Calorim-eter operating under a gas fl ow mode. An analysis cell containing approximately 0.2 g of adsorbent, which had been treated at 110 °C for 30 min, was placed in an analysis cell as shown in Fig. 1 . Gas supplied from cylinders was regulated by mass fl ow controllers

(MFC1 and MFC 2) to control the volume fraction of CO 2 . Th e gas could enter the analysis cell aft er remov-ing water using a desiccant column (C) or adding water using a moisturizer (A) Th e fl ow rate of CO 2 intro-duced into the analysis cell was adjusted by MFC3. Th e valve V6 was used to control the total gas pressure of the system, which was indicated by a transducer (T4). Th e CO 2 concentration in the outlet gas from the analysis cell was monitored by a CO 2 Transmitter Series GMT220 (Vaisala group, Helsinki, Finland).

Th e test was run by URC control soft ware under the isothermal mode and result was displayed as the variation of power (mW) with time (s). When the power signal becomes constant, CO 2 gas was intro-duced at the rate of 1 mL/min. Since the reaction between CO 2 gas and the adsorbent is exothermic, the power signal increased right aft er the gas contacted with adsorbent. Test was completed when the power signal became constant again. Th e obtained data can be used to calculate the adsorption heat. Th e integral heat (Q) was computed by using URC analysis soft -ware provided by Th ermal Hazard Technology (Bletchley, UK). Th e heat of adsorption ΔH (kJ/mole of CO 2 ) was calculated by dividing the integral heat by the mole of CO 2 absorbed. Th e CO 2 loading capacity of adsorbent (mg/g) was calculated by dividing the quantity of CO 2 adsorbed per the mass of adsorbent. To reaffi rm the CO 2 loading capacity of adsorbent,

Figure 1. Schematic illustration of CO 2 adsorption experiments.

D V Quang et al. Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process

4 © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

CO 2 was analyzed by a CO 2 analytical system designed by the Masdar Institute (Abu Dhabi, UAE). Accord-ingly, CO 2 loading samples were brought to react with H 3 PO 4 acid in a three-neck fl ash at about 110 °C to release CO 2 gas, which was carried by N 2 gas to a CO 2 detector, where CO 2 concentration was detected and recorded by computer soft ware. Th e CO 2 adsorption capacity was calculated by dividing the total amount of CO 2 released from sample per the mass of sample.

Results and discussion Effect of moisture on the heat capacity of adsorbent Before determining the heat capacity, the adsorbent was exposed to diff erent conditions to adjust its moisture content. To reduce the moisture to less than 3%, the sample was heated in a drying oven for about 20 min at 110 °C, whereas the sample was exposed to highly humid air at room temperature to increase its moisture. Th e heat capacity of the adsorbent containing diff erent moisture content is shown in Fig. 2 . Th e obtained results indicated that the heat capacity of PEI-PS-60 is relatively low and it increases along with the increase of moisture content. Th e average heat capacity of the adsorbent containing about 3% moisture is 1.9 J/g·°C and it increases to 2.2 and 2.4 J/g·°C as the moisture increases to 10 and 15%, respectively (Table 1 ). From

the results, it is obvious that the moisture has a great eff ect on the heat capacity of the adsorbent. Th e heat capacity increases 17.09% and 26.4% as the moisture increases from 3 to 10 and 15%, respectively. However, although, the heat capacity of PEI-PS-60 increases considerably as its moisture content increases to 15%, it is much lower than that of an aqueous solution of MEA 30 wt% (3.98 J/g·°C). Th e high heat capacity of the aqueous MEA solution is mostly due to the large fraction of water, which have high heat capacity (about 4.2 J/g·°C), while PEI and mesoporous silica in PEI-PS-60 has low heat capacity. Apparently, impregnating PEI onto mesoporous silica is a promising method to reduce the heat capacity of adsorbent.

Effect of moisture on the total regeneration energy Th e total energy required for the regeneration of adsorbent is stated in Eqn (1).

Q Q Q Qreg des sen vap= + + (1) where Q reg is the regeneration energy of the process. Q des is the heat of CO 2 desorption, which has the same absolute value as the heat of adsorption. Th e heat of CO 2 adsorption on aqueous MEA 30 wt% and PEI impregnated silica were reported elsewhere. 17 Q sen is the sensible heat that must be supplied to increase temperature of sorbent to regeneration temperature.

Figure 2. Heat capacity of adsorbent with different moisture contents.

Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process D V Quang et al.

5© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

Th e sensible heat is calculated by the following equation:

= ΔQ Cp* Tsen (2) in which Cp is heat capacity and ΔT is temperature diff erence between CO 2 rich adsorbent entering stripper and regeneration temperature.

Q vap is the latent heat of the vaporization of water in sorbent. Q vap is given as:

Q q *mvap i i=

(3)

where q i and m i are the specifi c heat of vaporization and the amount of water (i), respectively.

According to Eqns (1), (2), and (3), the variation in moisture not only infl uences the heat capacity of adsorbent, but also the total energy required of CO 2 capture process. As the moisture increases from 3 to 10 and 15%, the sensible heat required to raise tem-perature from 75 to 110 °C increases from 527.3 to 566.9 and 719.1 kJ/kg of CO 2 , respectively (Table 2 ). Th is indicates that the sensible heat increases 7.5 and 36.4% as the moisture increases from 3 to 10 and 15%. Moreover, when the adsorbent is moisturized, the latent heat of the vaporization of water needs to be taken into account. In general, the heat of vaporiza-tion of water depends on the moisture content in the

Temperature (°C)

Heat capacity (J/g°C)

MEA 30 wt% PEI-PS-60 (3% moisture)

PEI-PS-60 (10% moisture)

PEI-PS-60 (15% moisture)

30 3.93 1.90 2.13 2.27

35 3.93 1.86 2.15 2.30

40 3.91 1.85 2.16 2.31

45 3.92 1.85 2.14 2.32

50 3.93 1.87 2.15 2.33

55 3.94 1.87 2.18 2.36

60 3.95 1.86 2.18 2.38

65 3.97 1.89 2.22 2.39

70 3.99 1.88 2.24 2.42

75 4.01 1.93 2.28 2.46

80 4.05 1.97 2.33 2.52

85 4.07 1.99 2.35 2.55

90 4.10 1.95 2.37 2.56

Average 3.98 1.90 2.22 2.40

Table 1. Variation in the heat capacity of adsorbent with moisture.

Type of heat

Regeneration heat requirement (kJ/kg of CO 2 )

Aqueous MEA 30 wt%

PEI-PS-60 3 wt% moisture

PEI-PS-60 10 wt% moisture

PEI-PS-60 15 wt% moisture

Sensible heat 1505.3 527.3 566.9 719.1

Desorption heat 1931.8 1568.2 1568.2 1568.2

Heat of water vaporization 462.3 0 — —

50 wt% of moisture in PEI-PS-60 — — 831.9 1451.0

70 wt% of moisture in PEI-PS-60 — — 1164.7 2031.3

Total heat requirement 3899.4 2095.5 — —

50 wt% of moisture in PEI-PS-60 — — 2967.0 3738.2

70 wt% of moisture in PEI-PS-60 — — 3222.5 4168.8

Table 2. Regeneration heat requirement for aqueous MEA 30 wt% and PEI-PS-60 with different moisture content.

D V Quang et al. Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process

6 © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

adsorbent and the regeneration temperature and operating time of process. With the increase in temperature and operating time, the amount of water vaporized will increase and therefore the heat of vaporization will increase. Figure 3 shows the varia-tion in the moisture content and regeneration heat of the adsorbent with the fraction of water vaporized. Th e adsorbent containing 10% moisture was used to calculate the regeneration heat. During the regenera-tion process, water in the adsorbent vaporizes and the moisture content of the adsorbent decreases along with the increase in the amount of vaporized water. Th e decrease in the moisture of the adsorbent causes the reduction in the sensible heat due to the lower heat capacity, but the vaporization of the water requires more energy, therefore, the total required energy to regenerate adsorbent increases as the percentage of vaporized water increases. As can be seen in Fig. 4 , although the sensible heat contributes a considerable part to the total regeneration energy, the increase in the total regeneration heat is mostly attributed to the increase in the vaporization heat of water. As the moisture of adsorbent is less than 3%, the vaporization heat is negligible and the regenera-tion heat calculated is 2095.5 kJ/kg of CO 2 that is contributed by the sensible heat and the desorption heat. Th is is relatively small and reduced up to 46%

compared to the regeneration heat required for an aqueous MEA 30 wt% process where operating conditions such as lean loading (0.25 mole of CO 2 /mole of MEA), molar ratio of H 2 O/CO 2 (0.5), regen-eration temperature (100 °C) and CO 2 capture effi -ciency (90%) were estimated according to the data from references. 22–24 However, the vaporization of water is signifi cant as the moisture of adsorbent is greater than 3%. As 50 and 70 wt% of water in the adsorbent containing 10% moisture vaporizes, the regeneration heat increases 41.6 and 53.8% compared to that of PEI-PS-60 containing 3% moisture. It reduces 23.9 and 17.4% the required energy compared to that of an aqueous MEA 30 wt%. Th e regeneration heat of the adsorbent is higher than that of liquid absorbent as the 70 wt% of water in PEI-PS-60 containing 15% moisture is vaporized.

Recent studies indicated that the humidity in fl ue gas has a signifi cant infl uence on the adsorption capacity of amine based mesoporous silica. Hiyoshi et al. reported that the CO 2 adsorption capacity of amine graft ed SBA-15 did not change, but that of amine impregnated SBA-15 increased in the presence of moisture. 25 Whereas, most of the recent studies revealed that the CO 2 adsorption capacity of amine-based mesoporous silica increased in the presence of moisture. 18,26–29 In our work, we found that as the

Figure 3. Variation in the regeneration heat and moisture in adsorbent with water vaporization.

Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process D V Quang et al.

7© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

moistures in the adsorbent are 3, 10, and 15%, the CO 2 loading measured are 139.9, 150.9, and 129.8 mg CO 2 /g of moisture included adsorbent (Table 3 ). Th e amount of CO 2 adsorbed per gram of dry adsorbent in the moisturized samples containing 3, 10, and 15% water increased 5.0, 18.2, and 11.2% compared to that in a dry sample (137.2 mg/g). It is evident that CO 2 adsorption capacity of the adsorbent increased as adsorption experiments were conducted in a humid condition. However, the increase in the CO 2 loading was reduced as the moisture increased from 10 to 15%. Th is is most likely due to the variation in the dispersion state of the adsorbent at the higher

moisture in which the PEI impregnated silica particles stick together and reduced the accessibility of amino groups to CO 2 molecules.

Th e increase in the CO 2 adsorption capacity as moisture increases from 3 to 10% helps to reduce 7.3% adsorbent quantity required to capture 1 kg of CO 2 . Although the amount of adsorbent reduces, the sensible heat required for the adsorbent with 10% moisture (566.9 kJ/kg of CO 2 ) is little higher than that of adsorbent with 3% moisture (527.3 kJ/kg of CO 2 ). Moreover, as discussed above, the moisturized adsorbent requires a signifi cant amount of heat to vaporize water, which results in a higher energy

Figure 4. Comparison of the regeneration heat required for solid adsorbent containing moisture with that of an aqueous MEA 30% solution.

Temperature (°C)

CO 2 adsorption capacity (mg/g)

Aqueous MEA 30 wt% PEI-PS-60 (dry)

PEI-PS-60 (3 wt% moisture)

PEI-PS-60 (10 wt% moisture)

PEI-PS-60 (15 wt% moisture)

25 — 66.7 — — —

40 118.8 107.1 — — —

75 — 137.2 139.9 150.9 129.8

100 — 135.7 — — —

110 — 118.7 — — —

Table 3. Variations in CO 2 loading with temperature and moisture.

D V Quang et al. Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process

8 © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

requirement for adsorbent regeneration. Obviously, the heat required to regenerate PEI impregnated mesoporous silica using for CO 2 capture increases along with the increase in moisture content. Th ere-fore, the PEI-PS-60 can be an eff ective CO 2 adsorbent only when the moisture content in the adsorbent is controlled at a minimum extent.

Effect of CO 2 adsorption temperature Previous studies indicated that the adsorption tem-perature plays a signifi cant role in the CO 2 adsorption performance of PEI impregnated mesoporous sil-ica. 14,16,30 In this study, we found that the CO 2 adsorp-tion capacity of the dry adsorbent increases from 66.7 to 137.3 mg/g as the adsorption temperature increases from 25 to 75 °C. It attains a maximum adsorption capacity (137.3 mg/g) at 75 °C and decreases to 118.7 mg/g as temperature increases to 110 °C (Fig. 5 and Table 3 ). Th is is likely due to the change of the structure of PEI molecules inside the pores of silica with temperature. At low temperature, the PEI molecules inside the pores displays as nanoparticles, the majority of amino groups are wrapped in the nanoparticles and the accessibility of CO 2 is limited to those amino groups, which causes a low adsorption capacity. As temperature increases, the PEI molecules become fl exible and expandable, more amino groups are exposed and therefore the accessibility of the CO 2

to amino groups increases, which help the increase in CO 2 adsorption capacity.

Flue gas usually contains a signifi cant amount of water ranging from 6 to 15% ( v/v ), its volume depends on the source of fuel and technology of power plant. 16 When the fl ue gas comes into contact with silica-based adsorbent, the adsorbent may adsorb the water and this will result in the increase in its moisture content. Depending on the water concentration of the fl ue gas and the adsorption temperature of CO 2 adsorption process, the water absorbed by the adsor-bent will be varied. In this work, the change in the moisture of PEI-PS-60 was investigated at 40 and 75 °C. Th e mixture of CO 2 and N 2 gas was passed through a moisturizer and entered a reactor contain-ing adsorbent as illustrated in Fig. 1 . Th e average moistures of the adsorbent aft er contacting with the gas at 40 and 75 °C are about 9 and 3%, respectively. Obviously, the moisture adsorption of the adsorbent reduces at the higher adsorption temperature. It is likely that water adsorption by the adsorbent is an exothermal process, which could be attributed to the reduction in the moisture adsorption performance of the adsorbent at high temperature. Th e results indicates that the equilibrium moisture of adsorbent at 75 °C is 3%, where the rate of moisture adsorption and desorption is similar and therefore any change in the adsorption temperature or humidity of gas may

Figure 5. Effect of the operating temperature on the CO 2 adsorption capacity of the adsorbent.

Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process D V Quang et al.

9© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

cause the change in the moisture content of the adsorbent.

It is apparent that the adsorption temperature has a signifi cant role in controlling both CO 2 adsorption capacity and the moisture of the adsorbent. PEI-PS-60 has a maximum CO 2 adsorption capacity and lower moisture content (≈3%) at 75 °C. Th erefore, the energy required to regenerate the adsorbent is minimum as the CO 2 capture process operates at 75 °C. At this temperature, the regeneration energy of a process using PEI-PS-60 can be reduced up to 46% compared to that of a process using an aqueous MEA 30 wt%.

Conclusion Th is study indicated that the heat capacity of PEI impregnated mesoporous silica increases as its moisture content increases. Th e increase in the moisture results in the rise of the vaporization heat of water and the increase in the heat capacity results the increase in the sensible heat. Th ese cause a signifi cant increase in the total regeneration heat required for CO 2 capture process in which the vaporization heat plays a crucial role in the increase in the total regen-eration heat. Th e moisture of the adsorbent, however, can be controlled by adjusting the adsorption tem-perature of CO 2 capture process; the moisture of adsorbent can be maintained at about 3% at the adsorption temperature of 75 °C. Th e adsorbent has a maximum CO 2 adsorption capacity (137.3 mg/g) at 75 °C. Th e obtained results indicated that the adsor-bent requires a minimum energy to regenerate as the CO 2 capture process is operated at 75 °C. A process using PEI-PS-60 can be reduced up to 46% the regeneration energy compared to that of a process using an aqueous MEA 30 wt%.

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Dang Viet Quang

Dr. Dang Viet Quang is a postdoctoral researcher at Masdar Institute of Science and Technology, UAE. He received his PhD degree in Chemical Engineering from Hanyang University, Republic of Korea in 2012. His studies focus on the synthesis of nanopar-ticles, mesoporous material, functional-

ized silica and their application to water and air purifi ca-tion, CO 2 capture and utilization.

Abdallah Dindi

Abdallah Dindi is currently a graduate student in Masdar Institute of Science and Technology, Abu Dhabi. He earned his Bachelors in Chemical Engineering from the University of Lagos, Nigeria. His current research interests include CO 2 Capture and Utilization.

Aravind V Rayer

Aravind V Rayer is a postdoctoral researcher at the Masdar Institute of Science and Technology, Abu Dhabi, UAE. His main research is focused on the chemical thermodynamics and kinetics of the absorbents used in the fi eld of CO 2 capture technologies.

Nabil El Hadri

Nabil EL Hadri is currently a post-doc researcher in Masdar Institute of Sciences and Technology in Abu Dhabi. He graduated from IFP Energies nouvelles and University of Claude Bernard in Lyon (France) with a PhD in CO 2 capture by amine solution in post-combustion process. His current

research deal with the development of new sorbents for CO 2 post-combustion capture.

Abdurahim Abdulkadir

Abdurahim Abdulkadir is a graduate student in the department of Chemical and Environmental Engineering program at Masdar Institute of Science and Technology. He earned his B.Sc.in Mechanical Engineering from the University of Asmara. His current research interests include Thermody-

namic measurements and evaluations for amine blend sorbent systems for post-combustion CO 2 Capture.

Short Communication: Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process D V Quang et al.

11© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd | Greenhouse Gas Sci Technol. 1–11 (2014); DOI: 10.1002/ghg

Mohammad R.M. Abu-Zahra

Dr. Mohammad Abu Zahra is currently an associate professor in the depart-ment of Chemical and Environmental Engineering. He joined Masdar Institute of Science & Technology as assistant professor in May 2011. Prior to joining, he worked for the International Energy Agency Greenhouse Gas R&D Pro-

gramme (IEAGHG) as a project manager in the capture and integrated system team. He was responsible of initiating and managing various projects and technical studies with a major focus on carbon dioxide capture. Dr. Abu Zahra worked (2005–2009) for the Separation technology department in the Dutch research institute (TNO) in the Netherlands as a senior research engineer. His R&D activities were in the areas of process develop-ment and gas treatment technologies In 2009, he was awarded the degree of Doctor from Delft University of Technology after defending his PhD thesis entitled “Carbon dioxide capture from fl ue gas: development and evaluation of existing and novel process concepts”. Dr. Abu Zahra is the editor for Asia in the Current Environmental Engineering and serves in the editorial board of the International Journal of Greenhouse Gas Control. His current research focuses on the develop-ment of novel separation technologies aiming to reduce GHG emissions and seek solutions for environmental problems. He is leading the Siemens-Masdar Institute CCS collaboration, the Masdar-Masdar Institute-RTI project and the coordinator of the CCS research activities within Masdar Institute.