CEJ2015-270-P485-495__Lij-Liu-Lzwc-Luo-LiaoHy-ID-PT CO2-DEA-1,2-PD RKT
Experimental study of the kinetics of the homogenous reaction of CO 2into a novel aqueous 3-diethylamino-1,2-propanediol solution using the stopped-?ow
technique
Jie Li a ,b ,Helei Liu a ,b ,Zhiwu Liang a ,b ,c ,?,Xiao Luo a ,b ,Huiying Liao a ,b ,Raphael Idem a ,b ,c ,Paitoon Tontiwachwuthikul a ,b ,c
a
Hunan Provincial Key Laboratory for Cost-effective Utilization of Fossil Fuel Aimed at Reducing Carbon-dioxide Emissions,College of Chemistry and Chemical Engineering,Hunan University,Changsha,Hunan 410082,PR China b
Joint International Center for CO2Capture and Storage (iCCS),Hunan University,Changsha,Hunan 410082,PR China c
Clean Energy Technology Institute at the University of Regina,Saskatchewan,Canada
h i g h l i g h t s
Kinetics was experimentally studied using the stopped-?ow technique. Establishing the VLE model and Br?nsted relationship.
DEA-1,2-PD has faster reaction rate than other conditional tertiary amines. The mechanism explains the full experimental data.
a r t i c l e i n f o Article history:
Received 28November 2014
Received in revised form 26January 2015Accepted 29January 2015
Available online 11February 2015Keywords:
Carbon dioxide Absorption Kinetics
Stopped-?ow Tertiary amine
a b s t r a c t
In this work,the stopped-?ow technique was used to determine the kinetic parameters in terms of pseudo ?rst-order rate constants (k 0)for homogenous reaction of CO 2into aqueous 3-diethylamino-1,2-propane-diol (DEA-1,2-PD)solutions as temperature ranged from 293to 313K and amine concentrations ranged from 0.20kmol/m 3to 1.00kmol/m 3.It was found that k 0increased with increasing amine concentration and temperature.Both the base-catalyzed hydration and the termolecular models were applied to inter-pret the experimental data.The results showed that the predicted CO 2absorption rates exhibited good agreement with experimental data with an absolute average deviation (AAD)of 5.7%and 3.8%with respect to base-catalyzed hydration and the termolecular model,respectively.Furthermore,the p K a of DEA-1,2-PD was experimentally determined over the temperature range from 298to 318K.The relationship between experimentally measured second-order reaction rate constants (k 2)and p K a was correlated using the Br?nsted relationship.The results suggest that the Br?nsted relationship for DEA-1,2-PD developed in this work can predict the reaction rate constant very well with an AAD of 0.8%.
ó2015Elsevier B.V.All rights reserved.
1.Introduction
The number of studies of the removal of carbon dioxide (CO 2)from gas streams generated by coal-?red power plants has explod-ed over the past two decades.The increased research attention comes as a result of the emerging problem of global warming caused by the accumulation of greenhouse gases in the atmo-sphere.Carbon capture and storage (CCS),especially post-combus-tion capture (PCC)technologies,has been identi?ed as a promising candidate for reducing the emission of CO 2,a major greenhouse gas.Normally,in processes using amine solvents,the capture and subsequent release of CO 2requires large amounts of energy,owing to the reboiler duty for the desorption process.However,the cap-tured CO 2has important utilization value,for example in the food industry and,more importantly,in the oil and gas industry for CO 2-enhanced oil recovery (EOR).If this process is to be widely used,it is important that novel technologies be developed for it so that ef?ciency is high and energy consumption is minimized.
https://www.wendangku.net/doc/5a4360654.html,/10.1016/j.cej.2015.01.128
1385-8947/ó2015Elsevier B.V.All rights reserved.
?Corresponding author at:Hunan Provincial Key Laboratory for Cost-effective
Utilization of Fossil Fuel Aimed at Reducing Carbon-dioxide Emissions,College of Chemistry and Chemical Engineering,Hunan University,Changsha,Hunan 410082,PR China.Tel.:+86136********;fax:+8673188573033.
E-mail address:zwliang@https://www.wendangku.net/doc/5a4360654.html, (Z.Liang).
Among various CO2capture technologies for PCC,which include absorption,cryogenics distillation,and membrane separation,che-mical absorption with amines is the most widely used technology. This is due to advantages in terms of the feasibility and maturity of the technology,and its operation cost and ef?ciency[1].One of the most important factors for the development of this technology is the selection and/or development of effective solvents.These sol-vents are required to have good performance in many aspects,such as fast reaction rates,high mass transfer coef?cient,high absorp-tion capacity,low heat duty for regeneration,not easily degraded, and low corrosiveness[2,3].
Tertiary amines,which are considered to be reasonable solvents for blending with primary and secondary amines due to their high absorption capacity and low energy requirement for regeneration, have received increased attention recently.Tontiwachwuthikul et al.[4]developed a new tertiary amine,4-diethylamine-2-bu-tanol(DEAB)which exhibited good performance for CO2capture and has attracted the attention of many researchers.In earlier work,Sema et al.[5]and Liu et al.[6]researched the reaction kinetics of CO2with DEAB,using a laminar jet absorber and the stopped-?ow technique,respectively.The results showed that the reaction rate of CO2absorption into DEAB was faster than for diethylmonoethanolamine(DEMEA),dimethylmonoethanolamine (DMMEA),and MDEA in terms of the forward rate constant k2. Moreover,it was also found that DEAB has a higher CO2absorption capacity and lower energy requirement for regeneration than con-ventional tertiary amines such as MDEA.
Recently,Chowdhury et al.[7]conducted a performance com-parison study of24tertiary amines for CO2capture that included synthetic amines,conventional widely used amines and some nov-el amines.Absorption rate,CO2absorption capacity,cyclic CO2 capacity,and heat of reaction were experimentally determined for each absorbent.The results were compared to MDEA and seven amine absorbents with faster kinetics,higher cyclic capacities and lower reaction heat were identi?ed.1-diethylamino-2-propanol (1DEA2P),one of the tested amines,whose chemical structure is similar to that of DEAB,was then comprehensively investigated for its reaction kinetics by Liu[8],using the stopped-?ow technique.The1DEA2P molecule contains a2-propanol group in the place of the2-butanol group in DEAB.According to the work of Liu,the capacity of CO2absorption into1DEA2P was higher than that of MEA,MDEA,AMP and DEAB at313K but the CO2absorption rate in1DEA2P was found to be slower than that in DEAB.The results correspond to the work of Couchaux et al.[9],who focused their discussions on p K a and the reaction mechanism as well as the kinetics of a series of similarly structured amines.
DEA-1,2-PD,another new tertiary amine of the seven amines identi?ed by Chowdhury,whose chemical structure is similar to that of1DEA2P and DEAB,showed excellent enhancement of absorption rate and CO2absorption capacity compared with MDEA as well as better performance in terms of the reaction rate and cyc-lic capacity than the other six amines.One more hydroxyl group is attached to the hydroxyalkyl in the DEA-1,2-PD molecule than that in1DEA2P,providing for a reduction of the partial pressure and increasing the water solubility of the DEA-1,2-PD.It was also found that less energy was required for the regeneration of DEA-1,2-PD than for1DEA2P,MDEA,DEA and MEA.However,no investigation of the kinetics parameters or the vapor–liquid equilibrium(VLE) model of CO2absorption into DEA-1,2-PD solutions had been car-ried out.Hence,a broad knowledge of these parameters of DEA-1,2-PD is essential in order to get a full picture of the performance of DEA-1,2-PD solvent.
On the other hand,reaction kinetics is also an essential para-meter required for simulation of the absorption process and design of the absorption column[5].So,in this work,the stopped-?ow technique,a direct method,was applied to measure the kinetics data of DEA-1,2-PD.Many amine systems[10–15],including prima-ry amine,secondary amine,tertiary amine,and the mixture of these amines,have been successfully studied through the stopped-?ow technique because of its advantages.It was found that the experimental kinetics values obtained from the stopped-?ow tech-nique compared favorably with those obtained from the indirect techniques.For example,Saha and Bandyopadhyay[16]who inves-tigated the kinetics of AMP at294–318K by gas absorption study using a wetted-wall column found that the reaction was?rst order in amine.Their results agreed closely with those of Alper[10]which
Nomenclature
1DEA2P1-diethylamino-2-propanol
1DMA2P1-dimethylamino-2-propanol
3DMA1P3-dimethylamino-1-propanol
A Arrhenius constant(m3/mol s)
AAD absolute average deviation
AEEA2-((2-aminoethyl)amino)ethanol
AMP2-amino-2-methyl-1-propanol
AmH amine
B base(amine,water or hydroxyl ion)
DEA diethanolamine
DEAB4-diethylamino-2-butanol
DEA-1,2-PD3-diethylamino-1,2-propanediol
DEMEA diethylmonoethanolamine
DMMEA dimethylmonoethanolamine
E a activation energy(kJ/mol)
k0observed pseudo?rst-order reaction rate constant(sà1) k2second-order reaction rate constant(m3/kmol s)
k H
2O
reaction rate constant of reaction8(m3/kmol s)
k OHàreaction rate constant of reaction9(m3/kmol s)
k T
DEA-1;2-PD
termolecular reaction rate constant contributed by DEA-1,2-PD,(m6kmolà2sà1)
k T H2O termolecular reaction rate constant contributed by H2O,
(m6kmolà2sà1)
K i chemical equilibrium constant for reaction i
K a,DEA-1,2-PD dissociation constant of conjugate acid of DEA-1,2-
PD(mol/m3)
MEA monoethanolamine
MDEA methyldiethanolamine
M DEA-1;2-PD molecular weight of DEA-1,2-PD
M H
2
O
molecular weight of water
n0;DEA-1;2-PD initial number of moles of DEA-1,2-PD.
n HCl number of moles of HCl
PZ piperazine
r CO
2
overall CO2reaction rate(kmol/m3s)
R universal gas constant(0.008315kJ/mol K)
T temperature(K)
t time(s)
V total total liquid volume
Y1Tconstant value of the signal(V)at equilibrium
[]concentration(Kmol mà3)
Greek letters
q
H2O
density of water
486J.Li et al./Chemical Engineering Journal270(2015)485–495
were obtained from stopped-?ow
gated the kinetics of DEAB at293–313K by found that the activity energy is62.58 those obtained in the work of Sema[5]
is62.59kJ/mol by using the laminar jet In addition,the reaction rate constant amine is not only dependent on the amine but also on its basic strength.
sted and Guggenheim[17],there is a
p K a,which is an important fundamental to quantify the solvent basicity,and the constant of the CO2–amine reaction.This validated for CO2absorption into amine by tle et al.[18]found a Br?nsted correlation tion rate constant and the corresponding p blended primary and tertiary amine
by Rochelle et al.[19]also shows that a
ory can be popularized for each category of secondary amine,hindered amine and accurate p K a value is a vital parameter physical properties of amines,but also for study[20,21].
For the new amine system,
ed reaction kinetics study is essential for PD and for properly designing an
The main objective of this work is kinetics and mechanism of the
a range of DEA-1,2-PD concentration of temperature range of293–313K.The correlated with both a termolecular catalyzed hydration mechanism.In vapor–liquid equilibrium(VLE)were Br?nsted correlation between the p K a then established.Finally,a
DEA-1,2-PD and other tertiary amines kinetics,p K a value,and the Br?nsted
2.Experimental
2.1.Chemicals
Fig.1shows the chemical structure of this work.Reagent grade
1,2-PD)with a mass purity of P98%was Reagent Co.,Ltd.and used without
cial-grade CO2cylinder gas with a volume plied by Changsha Jingxiang Gas Co.,Ltd., concentrations of aqueous DEA-1,2-PD
adding a measured volume of de-ionized water into weighed quan-tities of reagent DEA-1,2-PD.
For each experimental run,a freshly saturated CO2solution was prepared by bubbling the CO2through de-ionized water in a glass-jacketed stirred reactor used as a phase behavior cell for at least half an hour.It is important to note that the amine concentrations used were ten times greater than the CO2concentrations for each experiment.Thus,the pseudo?rst-order conditions with respect to[CO2]were ensured without the dilution of the prepared saturat-ed CO2solution.
2.2.Measurement of kinetics data from stopped-?ow apparatus
In this work,the reaction rates of the homogeneous reaction between CO2and amine with temperatures ranging from293to 313K and amine concentrations ranging from0.20kmol/m3to 1.00kmol/m3,were measured using the stopped-?ow apparatus,a standard model SF-61DX,manufactured by Hi-Tech Scienti?c, Ltd.(U.K.).It consists of four major sections:a sample handling unit,a conductivity-detection cell,A/D converter,and a micropro-cessor.The schematic diagram of the stopped-?ow equipment used in this work is exhibited in Fig.2.The amine and the CO2 solutions were placed in the seal drive syringes of the stopped-?ow equipment.The temperature for each run was controlled within ±0.1K by circulating water from a constant temperature water bath.In each experimental run,nitrogen was supplied as a pneumatic driving force to push equal volume of amine and CO2 solutions into the conductivity detection cell used to measure the intrinsic rate of the rapid homogeneous reaction by monitoring the voltage change caused by ion formation.Thus,the conductivity change versus time is measured by a circuit as described by Knipe et al.[22].The change in conductivity with respect to time is?tted according to an exponential equation resembling a?rst-order kinetic equation as below:
Fig.1.Chemical structures of some relevant amine solvents.
Y?àA?expeàk0?tTtY1e1Twhere k0is the pseudo?rst-order reaction rate constant.
Then,the observed pseudo?rst-order reaction rate constant can be automatically obtained through the?tted exponential equation. All of these processes were achieved by using‘‘Kinetasyst’’soft-ware.Further details of the procedure have been reported in our previous work[6,8].
It is worth mentioning that the experimental technique used in this work has already been validated in our previous work[6,8]on the kinetics of CO2absorption into aqueous DEA solutions at298K. The results showed that the kinetics data in terms of pseudo?rst-order constant(k0)were in good agreement with the works of Ali et al.[23,24].
2.3.Measurement of dissociation constant
In this work,the dissociation constant of protonated DEA-1,2-PD(K a;DEA-1;2-PD),conjugated acid of DEA-1,2-PD,was experimental-ly measured over a temperature range of298–318K according to the method discussed in the literature[25–27].In the experiment, 5mL of1M DEA-1,2-PD solution was diluted to100mL and then a given amount of1.0M hydrochloric acid(HCl)was added into the diluted DEA-1,2-PD solution(0.05M).The pH meter was used to measure the pH values of the amine solutions.The details of the procedure and equipment used in this work as well as the valida-tion of the experimental technique and calculation procedures can be found in our published work[6,8].
2.4.CO2solubility
In this work,the method of employing the pH meter to measure the pH values of aqueous DEA-1,2-PD solution after absorbing CO2 was used to determine the equilibrium solubility of the DEA-1,2-PD-CO2-H2O system.The DEA-1,2-PD solution was diluted to 0.05M before the pH values were measured.Thus,the solution can be assumed to be ideal because of the extremely low concen-tration.The apparatus used to measure the CO2solubility of DEA-1,2-PD included a saturation cell,an absorption reactor,a mass ?ow meter,and a water bath with a temperature controller.For each run,the temperature was controlled by the water bath in which the saturated cell and the absorption reactor were enclosed. The gaseous stream,with a CO2concentration of P99.9%,was?rst passed through the water saturated cell and then bubbled into the amine solutions in the absorption reactor.The time was recorded immediately,beginning when the mixed gas streams were intro-duced into the reactor.Every few minutes,the liquid sample was taken to measure CO2loading using the titration method.The amine concentration and the CO2loading were titrated with a 1mol/L hydrochloric acid solution.At the time of obtaining CO2 solubility,the pH values of samples were measured using the pH meter.
The apparatus used in this work was validated by our previous work.The results showed a good agreement with the results reported by Maneeintr et al.and Jou et al.[28,29].The experimen-tal data obtained in this work were therefore accurate and reliable.
3.Theory
3.1.Chemical reaction scheme
The main chemical reactions involved in the DEA-1,2-PD-H2O-CO2system are shown in Eqs.(2)–(7):
R3NtHt !
K2
K a;DEA-1;2-PD
R3NHte2TCO2tR3NtH2O !
K3;k2
R3NHttHCOà
3
e3TH2OtCO2 !
K4;k H
2O HttHCOà
3
e4TCO2tOHà !
K5;k OHà
HCOà
3
e5T
HCOà
3 !
K6
HttCO2à
3
e6TH2O !
K7
HttOHàe7TR3N represents DEA-1,2-PD.Where K i is the chemical equilibrium constant for reaction i.k2is the second-order reaction rate constant
between CO2and amine.k H
2
O
is the reaction rate constant between CO2and H2O.k OHàis the reaction rate constant between CO2and OHà.
Based on this reaction scheme,an absorption rate/kinetics mod-el via base-catalyzed hydration mechanism and a vapor–liquid equilibrium model were developed.The value of p K a was also cal-culated based on this reaction scheme.
3.1.1.Base-catalyzed hydration mechanism
Donaldson and Nguyen[30]originally proposed the base-cat-alyzed hydration mechanism for the interpretation of the CO2reac-tion with tertiary amine.They suggested that the tertiary amine does not react directly with CO2,but acts as a base that catalyzes the hydration of CO2.Eqs.(3)–(5)showed the reactions of CO2with tertiary amine.
Based on the mechanism proposed by Donaldson and Nguyen above,under pseudo?rst-order conditions with respect to CO2
, Fig.2.Schematic diagram of the experimental stopped-?ow equipment(Li et al.[46]).
the overall reaction rate of CO 2absorption (kmol/m 3s)with respect to reactions 3–5can be written as:
r CO 2
?k 0?CO 2 ?k 2?R 3N tk OH à?OH à tk H 2O ?H 2O èé
?CO 2
e8T
Therefore,the overall reaction rate in terms of the CO 2con-sumption is a function of both observed pseudo ?rst-order rate constant k 0and the CO 2concentration.
Compared to reaction 3and 5,the reaction between CO 2and H 2O (as reaction 4showed)can be neglected due to the slow reac-tion rate of CO 2with H 2O [31].Therefore the simpli?ed rate expression of the overall reaction rate can be expressed as:
r CO 2?k 0?CO 2 ?k 2?R 3N tk à
OH ?OH à èé?CO 2
e9T
Several researchers [32–36]have proposed that the role of the hydroxyl ion in the observed reaction rate can be ignored especial-ly in aqueous amine solution.Moreover,Kierzkowska-Pawlak et al.[37]suggested that the contribution of reaction of CO 2with OH àto the observed reaction rate under the pseudo-?rst order reaction conditions was assumed to negligible because of the concentration of OH àions is negligible,which was caused by the fast reaction between CO 2and OH à.In the work of Kadiwala et al.[38],the cal-culated [OH à]contribution are also given,which proved that OH àcontributions on reaction kinetics of tertiary amines (1DMA2P and 3DMA1P)and CO 2are negligible.Thus,leaving the contribution of H 2O and OH àout of the observed reaction rate,the simpli?ed rate expression based on Eq.(9)can be written as:
r CO 2?k 0?CO 2 ?k 2?R 3N t?CO 2
e10T
Here,R 3N represents DEA-1,2-PD,therefore:
k 0?k 2?DEA-1;2-PD e11T
3.1.2.Dissociation constant
For an aqueous solution of DEA-1,2-PD,the dissociation reac-tion of protonated DEA-1,2-PD is the reverse reaction of Eq.(2).In present work,the dissociation constant of DEA-1,2-PD was mea-sured at a low DEA-1,2-PD concentration (0.05M),for which the solution can be assumed to be ideal (i.e.the concentration is very low and the activity coef?cient is regarded as 1)[25,26,39].The dissociation constant of DEA-1,2-PD based on Eq.(2)can be repre-sented in Eq.(12)as follows:
K a ;DEA-1;2-PD ?
?DEA-1;2-PD ?H t ?DEA-1;2-PDH t
e12T
Brie?y,the concentration of H +occurring in Eq.(12)can be directly obtained by measuring the pH values of the amine solu-tions after adding a given mass of 1.0M hydrochloric acid (HCl)into the prepared aqueous DEA-1,2-PD solution.Bear in mind that the concentration of DEA-1;2-PDH tcan be calculated using the mass balance of protons of the reaction between H +and DEA-1,2-PD to form DEA-1;2-PDH t:
n HCl àH t??V total ?DEA-1;2-PDH t??
V total
e13T
Then,the concentration of free DEA-1,2-PD can be calculated using the DEA-1,2-PD balance equation as follows:
DEA-1;2-PD ? tDEA-1;2-PDH t??à
á
V total ?n 0;DEA-1;2-PD
e14T
where n HCl is number of moles of HCl added during the titration;V total is the total liquid volume after titration;n 0;DEA-1;2-PD is the ini-tial number of moles of DEA-1,2-PD.
Finally,the K a ;DEA-1;2-PD can be calculated based on Eq.(12),and the value of p K a of the aqueous DEA-1,2-PD solution can be calcu-lated by the following equation:
p K a ?àlog K a ;DEA-1;2-PD eTe15T
It is generally accepted that the dissociation constant is a func-tion of temperature.Therefore,the dissociation constant obtained for DEA-1,2-PD at a low concentration can be applied directly to calculate the p K a value,and thus,establish the VLE model of 1M DEA-1,2-PD solution.
3.1.3.Vapor–liquid equilibrium model
Liquid bulk concentrations of all chemical species are required for kinetic analysis.For the system of DEA-1,2-PD-CO 2-H 2O,based on the reactions 2–7,the concentration of DEA-1,2-PD,DEA-1,2-PDH +,HCO à3,CO 2à
3
can be obtained by solving the mass balance equations,the equilibrium constant equations,the pH equation and charge balance equations as shown below:The total DEA-1,2-PD balance
?DEA-1;2-PD 0??DEA-1;2-PD t?DEA-1;2-PDH t
e16T
The charge balance:
?DEA-1;2-PDH t t?H t ??OH à t?HCO à3 t2?CO 2à
3
e17T
The equilibrium constants for reactions (2)–(7)can be presented as follows:
K 2?
DEA-1;2-PDH t
?
?
DEA-1;2-PD ? H t
??e18T
K 6?
H t
??CO 2à3
h
i
HCO à3
?
?
e19TK 7??H t ?OH à
e20T
The pH values:
PH ?àlog eH tT
e21T
The input parameters for this calculation are the initial concen-tration of DEA-1,2-PD in the solution ([DEA-1,2-PD]0;mol/L),equi-librium constants of involved reactions (K 2,K 6,K 7)and pH values.The chemical equilibrium constant K 2can be obtained via the value of the dissociation constant of DEA-1,2-PD as determined above.The values of K 6and K 7can be obtained from the literature [38–40].pH values can be measured by using the pH meter.3.2.Termolecular mechanism
The termolecular mechanism was originally proposed by Crooks and Donnellan [41]and recently revisited by da Silva and Svendsen [42].It assumes that an amine (denoted here as AmH )reacts simultaneously with one molecule of CO 2and one molecule of a base to form a loosely-bound encounter complex as interme-diate via a single step rather than in two steps.This is represented as follows:
CO 2tAmH áááB $AmCOO àáááBH t
e22T
This complex then breaks up to form reactant molecules such as CO 2and amine species,while its small fraction reacts with a sec-ond molecule of the amine or a water molecule to give ionic prod-ucts (carbamate for primary and secondly amines,and protonated amine and bicarbonate for tertiary amines).The forward reaction rate based on this termolecular mechanism where H 2O,OH à,and AmH were considered as the dominating bases,is given by:
r CO 2?k 0?CO 2 ?f k AmH ?AmH tk OH à?OH à tk H 2O ?H 2O g?CO 2 ?AmH
e23T
J.Li et al./Chemical Engineering Journal 270(2015)485–495489
It has been generally accepted that in
deprotonation of the intermediate is and amine.When the contribution of water of amine,Eq.(20)can be rewritten as r CO 2?k 0?CO 2 ?f k AmH ?AmH tk H 2O ?H 2O g?CO where,therefore,k 0is given by:
k 0?ek AmH ?AmH tk H 2O ?H 2O T?AmH
When the amine concentration becomes tration of water is so much greater than tion that it can be assumed to be can be rearranged as follows:
k 0
?AmH
?k AmH ?AmH tk H 2O ?H 2O Thus,the kinetic parameters k AmH and k H 2were obtained by using a straightforward graphical method.In this work,where k AmH denotes k DEA-1;2-PD .
4.Results and discussion
4.1.Vapor–liquid equilibrium model for CO 2-DEA-1,2-PD-H 2O system The bulk concentration of all chemical species (DEA-1,2-PD,
DEA-1,2-PDH +,HCO à3;CO 2à
3)of a given loading of aqueous DEA-1,2-PD solutions,which is required for the CO 2absorption kinetic model,was successfully obtained via the vapor–liquid equilibrium (VLE)model for aqueous DEA-1,2-PD solution developed in this work.In order to present the VLE plots of the DEA-1,2-PD-H 2O-CO 2system,the pH values and CO 2loading of DEA-1,2-PD solution are experimentally obtained in this study and shown in Table 1.The results for the bulk concentrations obtained from the VLE model developed in the present work are shown in Fig.3.It can be observed from Fig.3that the DEA-1,2-PD concentration decreases as CO 2loading increases.To the contrary,the protonated DEA-1,2-PD concentration increases as the CO 2loading increases.This is because of the reactions between CO 2and aqueous DEA-1,2-PD solutions in CO 2-DEA-1,2-PD-H 2O system as shown in Eqs.(2)and (3),respectively.The concentration of bicarbonate ions increased with increasing CO 2loading because the higher the CO 2loading,the more CO 2was introduced to react with DEA-1,2-PD-H 2O,H 2O,and OH àto form HCO à3,resulting in increasing the
concentration of HCO à
3.It can be also seen in Fig.3that the concen-tration of CO 2à
3increased with CO 2loading and reached a maxi-mum due to the CO 2à3formation by HCO à3when CO 2loading less than 0.4.This can also be explained by Eq.(6).Whereas,at CO 2loading higher than 0.4,the acidity of the solution increased and then the concentration of CO 2à
3began to decrease due to the reverse reaction of Eq.(6)to form HCO à3from CO 2à3.Thus,it can be suggested that the VLE model developed in this work is applica-ble for predicting the bulk concentration of all species of the CO 2-DEA-1,2-PD-water system,and the predictions can then be applied for establishing a CO 2absorption kinetics model.
4.2.CO 2absorption kinetics of DEA-1,2-PD
The kinetics of the homogenous reaction of CO 2into aqueous DEA-1,2-PD solution were experimentally measured using the stopped-?ow apparatus,over a DEA-1,2-PD concentration range of 0.20–1.00kmol/m 3,and a temperature range of 293–313K.In the present work,the amine concentration was kept at least 10times higher than the concentration of CO 2.Therefore,the pseudo ?rst-order conditions were ensured and then the values of observed pseudo ?rst-order rate constant (k 0)occurred in Eqs.(10)and (25)were directly obtained through ‘‘Kinetasyst’’soft-ware.Fig.4shows a typical result of the stopped-?ow experiment at 298K and DEA-1,2-PD concentration of 1kmol/m 3.From Fig.4,it can be seen that the the experimental data can been ?tted with Eq.(1)very well,the ?tted parameter R occurred in the de?nition in Fig.4is represented the pseudo ?rst-order reaction rate con-stant k 0occurred in Eq.(1).The values of k 0as a function of tem-perature and DEA-1,2-PD concentration,obtained in this work,are listed in Table 2,and plotted against DEA-1,2-PD concentration (kmol/m 3)in Fig.5.As expected,for a given amine concentration,the reaction kinetics,in terms of k 0,were increased with the increase of temperature.The increase of amine concentration also resulted in the increase of the k 0values within a given temperature.
The experimentally measured pseudo ?rst-order rate constants k 0were then correlated by the empirical power law relationship in Fig.5to determine the order of the reaction.The results showed that the reaction orders were 1.14,1.11,1.05,1.05and 1.01,with respect to [DEA-1,2-PD]for 293,298,303308and 313K,respec-tively.All values were extremely close to 1and with an average reaction order of 1.07.Thus,the values of k 0at various concentra-tions and temperatures of DEA-1,2-PD (from Table 2)were then interpreted by the base-catalyzed hydration mechanism (as Eq.(1)showed)to determine the second-order reaction rate constants.Table 3showed all the results of ?tted values of second-order reac-tion rate constant k 2,which was a strong temperature dependency parameter.It has been generally accepted that second-order reac-tion rate constant k 2can be ?tted to the following Arrhenius expression:
k 2?A exp eàE a =RT Te27T
where A ,E a ,and R represent the Arrhenius constant (m 3/mol s),the activation energy (kJ/mol),and the universal gas constant (0.008315kJ/mol K),respectively.
Table 1
Experimental pH values and CO 2loading in aqueous DEA-1,2-PD solutions at initial DEA-1,2-PD concentration of 1.0kmol/m 3and 313K.CO 2loading (mol CO 2/mol Amine)0.210.290.380.490.600.63pH
9.83
9.6
9.4
9.23
9
8.88
Fig.3.Liquid phase speciation and concentration in aqueous DEA-1,2-PD solutions as a function of CO 2loading at initial DEA-1,2-PD concentration of 1.0kmol/m 3and 313K.
490
Fig.6displays the corresponding Arrhenius equation for the second-order reaction rate constant k 2of DEA-1,2-PD.The value of activation energy (E a )of DEA-1,2-PD obtained from the slope of the Arrhenius plot is 47.18kJ/mol.The regression of the k 2val-ues (from Table 3)results in the following Arrhenius equation:
?1:17?1010exp eà5673:9=T T
e28It can be seen in Fig.5that the Arrhenius equation (Eq.(28)obtained in this work can predict the second-order reaction rate constants k 2very well over the whole temperature range investi-gated,with an acceptable AAD of 5.67%.
In this work,the termolecular mechanism was also applied correlate the experimentally observed pseudo ?rst-order reaction
Fig.4.A typical result of the stopped-?ow experimental at 298K and DEA-1,2-PD concentration of 1kmol/m 3.
(in terms of k 0)of DEA-1,2-PD obtained from stopped-?ow concentration ranged from 0.20kmol/m 3to 1.00kmol/m 3,293to 313K).Pseudo ?rst-order rate constant (k 0,s à1)293K 298K 303K 308K 313K 8.0811.6316.9423.9632.8617.8424.3734.3445.6857.4520.8128.9739.4657.2773.2926.8836.0551.1566.6186.9436.9451.7171.7596.33124.1144.4861.6979.59113.10145.0951.57
69.17
92.25
131.32
165.26
Fig.5.Effect of DEA-1,2-PD concentration and temperature on kinetics data (in terms of k 0)over a DEA-1,2-PD concentration range of 0.20–1.00kmol/m 3,and temperature range of 293–313K.
Table 3
Second-order reaction rate constants for CO 2absorption into aqueous DEA-1,2-PD solution.T (K)
Reaction order (n )
Term
[DEA-1,2-PD]/kmol m à30.200
0.3990.5010.6020.7990.883 1.002293 1.14k 2/m 3kmol à1s à1
40.344.741.544.646.250.351.4298 1.1158.061.057.859.864.769.869.0303 1.0584.586.078.884.989.790.192.0308 1.05119.6114.4114.4110.6120.5128.1131.0313
1.01
164.1
143.9
146.4
144.4
155.3
164.3
164.9
Fig.6.Arrhenius plot for the kinetics constant of CO 2absorption into aqueous DEA-1,2-PD solutions over a temperature range of 293–313K.
4.3.pKa of the aqueous DEA-1,2-PD solutions
It has been generally accepted that p K a is a key parameter in the screening of an amine solvent for the removal of acid waste gas,represents the basicity of the solvent.It is also an important parameter for kinetic analysis.In tertiary amines,the reaction rate shows a strong dependence on p K a because of the base-catalyzed hydration mechanism.In general,the higher the p K a value,the higher the basicity,the faster the absorption kinetics [43].In the present work,the p K a values of DEA-1,2-PD over a temperature range of 293–318K were successfully obtained through the experi-ment described in the experimental part.The temperature depen-dency pKa can be written as following relation:
K a ?
A T
tB e31As Fig.10demonstrates,p K a values tend to decrease with increasing temperature.The experimentally measured p K a values were correlated with Eq.(31)and then a predictive correlation for p K a of aqueous DEA-1,2-PD solutions was established as follow:
7.Arrhenius plot of the kinetic rate constants of DEA-1-2-PD and H 2O for termolecular mechanism.
Fig.8.The correlation between the measured and predicted pseudo ?rst-order rate constant based on base-catalyzed hydration mechanism.
Fig.9.The correlation between the measured and predicted pseudo ?rst-order rate constant based on termolecular mechanism.
pK a ;DEA-1;2-PD ?
1878:2
T
t3:75e32T
The values of p K a of DEA-1,2-PD calculated from Eq.(32)were found to be in very good agreement with the experimental results with an AAD of 0.07%.The temperature dependency correlations p K a for MDEA,DMMEA,DEMEA,and DEA2P,obtained from the work of Hamborg and Versteeg [43],Kamps and Maurer [25],and Liu [8],are also displayed in Fig.10.Fig.10shows that DEA-1,2-PD has a higher p K a value than MDEA,DMMEA,DEMEA,and DEA2P with respect to the investigated temperature range of 293–318K.
Versteeg and van Swaaij [44],who ?rstly proposed the Br?nsted relationship,suggested that the relationship between the natural logarithm of second-order reaction rate constant k 2and p K a appears to be a linear relationship.This relationship was studied by several researchers and found to provide a signi?cant contribu-tion to the comprehensive understanding of CO 2absorption kinet-ics.In the present work,the Bronsted relationship of DEA-1,2-PD,which is plotted in Fig.11,was correlated by using the experimen-tal measured p K a and k 2.The developed Br?nsted relationship of DEA-1,2-PD can be expressed as:
ln k 2;DEA-1;2-PD eT?à3:14p K a ;DEA-1;2-PD eTt35:64
e33As can be seen in Fig.11,it is worth noticing that the Br?nsted relationship of DEA-1,2-PD,which is expressed as Eq.(33),can be used to predict the k 2of DEA-1,2-PD effectively,with an AAD of 0.8%.In addition,the Br?nsted relationships of nes,whose experimental data were collected works of Hamborg and Versteeg [43],Henni [46],Liu et al.[8]is also plotted in Fig.10.The of comparative performance among these sented in Section 4.4.
https://www.wendangku.net/doc/5a4360654.html,parison of aqueous solution of tertiary A comprehensive investigation of reaction tertiary amine DEA-1,2-PD,including the VLE relationship,and reaction rate constant,are Because DEA-1,2-PD,the amine studied in amine,it is therefore reasonable to conduct performance with other conventional MDEA,DEMEA,and DMMEA,as well as novel vents (i.e.1DMA2P,3DMA1P,1DEA2P,and its potential for CO 2removal.
As presented in Fig.10,the p K a of with that of MDEA,DEMEA,DMMEA,temperature ranging from 293to 318K.The general conclusion that can be drawn from Fig.10is that the value of p K a decreases with increasing temperature for all these amines.However,at each temperature,there are different p K a values for the different amines.The p K a of DEA-1,2-PD is higher than for MDEA,DEMEA,DMMEA,and 1DEA2P,respectively.It can be ranked in the order of DEA-1,2-PD >1DEA2P >DEMEA >DMMEA >MDEA.This is due to the presence of the alkyl group and the hydroxyl group which are considered to be electron donors.It is expected that more elec-tron donor groups in the molecule results in an increased density of the nitrogen electron cloud and consequently a higher p K a value [38].
In general,the relationship between the reaction kinetics of CO 2absorption into tertiary amine and p K a value has shown that the high p K a,value indicates fast reaction kinetics.This phenomenon was observed by Bentiez-Garcia et al.[47],who studied the effect of basicity on CO 2absorption rates for four tertiary amines (TEA,MDEA,DEMEA and triethylamine).It can therefore be concluded from the p K a results presented in Fig.9that DEA-1,2-PD has better reaction kinetics performance than conventional tertiary amines.It is important to mention that the p K a value can only give a guidance to preliminary estimation of the reaction kinetics.The reaction kinetics cannot be fully con?rmed by the p K a value but only the reaction rate constant.This is because the reaction kinet-ics is directly interpreted by the reaction rate constant:the higher the reaction rate constant,the faster the reaction kinetics.Hence,in order to analyze the CO 2absorption reaction kinetics compre-hensively,both the Br?nsted relationships,which exhibit the rela-tionship between k 2and p K a,and Arrhenius relationships,which exhibit the temperature dependency k 2,are also presented in Figs.11and 12for these tertiary amines,respectively.
It can be seen from Fig.11that at the same temperature,although DEA-1,2-PD has a higher p K a value than that of DEAB,1DEA2P,DEMEA,DMMEA,and MDEA,the reaction kinetics of DEA-1,2-PD in terms of second-order reaction rate constant is low-er than those of DEAB,1DEA2P,and DEMEA.This result is in good agreement with the Arrhenius relationships (as Fig.12shows)obtained in this work.The kinetics parameters of tertiary amines at 298K are listed in Table 5.It was found that the reaction kinetics of CO 2absorption into DEA-1,2-PD is faster than for MDEA,Fig.10.The p K a values of some tertiary amines over a temperature of 293–318K.
Fig.11.Bronsted plots of tertiary amines (for DEA-1,2-PD,dots are experimental data measured from present work,and the straight line is the ?tted results from Eq.(33)).
Journal 270(2015)485–495493
5.Conclusions
In the present work,the kinetics of CO 2absorption into unload-ed aqueous solutions were experimentally measured using the stopped-?ow apparatus with DEA-1,2-PD concentrations ranging between 0.20and 1.00kmol/m 3and a temperature range of 293–313K.Both the experimental equipment and method were validat-ed in our previous works.The results show that the reaction rate increases with both increasing DEA-1,2-PD concentration and increasing temperature.Both the base-catalyzed hydration and termolecular mechanisms were applied to interpret the experimental data and gave identical results for all practical purposes.
The reaction order with respect to the DEA-1,2-PD concentra-tion is found to vary slightly with temperature,and varies between 1.01and 1.14with an average of about 1.07.This can be approximated to 1for the range of temperatures studied.
In addition,the p K a of aqueous solution of DEA-1,2-PD was experimentally determined with temperature ranging from 293to 318K.Results suggest both the Arrhenius relationship and Br?n-sted relationship obtained in this work can predict the second-order reaction rate constant well.
The reaction kinetics of DEA-1,2-PD was found to be faster than those of 3DMA1P,1DMA2P,DMMEA,and MDEA,but slower than those of DEAB,1DEA2P,and DEMEA.This can be explained by the coef?cient of the steric hindrance and supply electronic effect of the electron donor.Therefore,these results provide guidelines for development of new blended DEA-1,2-PD –activator absorbent systems for CO 2capture.Acknowledgments
The ?nancial support from National Natural Science Foundation of China (NSFC Nos.U1362112,21376067,21476064and
21406057),Ministry of Science and Technology of the People’s of Republic of China (MOST No.2012BAC26B01and 2014BAC18B04),Innovative Research Team Development Plan-Ministry of Educa-tion of China (No.IRT1238),Specialized Research Fund for the Doc-toral Program of Higher Education (No.20130161110025),Key project of international ®ional scienti?c and technology plan (2014WK2037),Institutions of higher learning professional com-prehensive reform pilot projects,China Excellent Engineer Training Plan for Students of Chemical Engineering and Technology in Hunan University,and China’s State ‘‘Project 985’’in Hunan University–Novel Technology Research &Development for CO 2Capture are all gratefully acknowledged.
I also greatly appreciate Wilfred Olson and Wichitpan Rong-wong for their great contribution to help me correct any grammar mistakes and insightful inputs to my research work.
References
[1]T.Sema, A.Naami,Z.Liang,R.Idem,P.Tontiwachwuthikul,H.Shi,P.
Wattanaphan,A.Henni,Analysis of reaction kinetics of CO 2absorption into a novel 4-diethylamino-2-butanol solvent,Chem.Eng.Sci.81(2012)251–259.[2]F.A.Chowdhury,H.Yamada,T.Higashi,Y.Matsuzaki,S.Kazama,Synthesis and
characterization of new absorbents for CO 2capture,Energy Procedia 37(2013)265–272.
[3]H.Yamada,F.A.Chowdhury,K.Koto,T.Higashi,CO 2solubility and species
distribution in aqueous solutions of 2-(isopropylamino)ethanol and its structure isomers,Int.J.Greenhouse Gas Control 17(2013)99–105.
[4]P.Tontiwachwuthikul,A.G.H.Wee,R.Idem,K.Maneeintr,G.J.Fan,A.Veawab,
A.Aroonwilas, A.Chakma,Method for capturing carbon dioxide from gas https://www.wendangku.net/doc/5a4360654.html, Patent Application,Patent US 2008/0050296A1(2008).
[5]T.Sema,A.Naami,Z.Liang,R.Idem,H.Ibrahim,P.Tontiwachwuthikul,1D
absorption kinetics modeling of CO 2-DEAB-H 2O system,Int.J.Greenhouse Gas Control 12(2013)390–398.
[6]H.Liu,T.Sema,Z.Liang,K.Fu,R.Idem,Y.Na,P.Tontiwachwuthikul,CO 2
absorption kinetics of 4-diethylamine-2-butanol solvent using stopped-?ow technique,Sep.Purif.Technol.136(2014)81–87.
[7]F.A.Chowdhury,H.Yamada,T.Higashii,K.Goto,M.Onoda,CO 2capture by
tertiary amine absorbents,a performance comparison study,Ind.Eng.Chem.Res.52(2013)8323–8331.
[8]H.Liu,Z.Liang,T.Sema,W.Rongwong, C.Li,Y.Na,R.Idem,P.
Tontiwachwuthikul,Kinetics of CO 2absorption into a novel 1-diethylamino-2-propanol solvent using stopped-?ow technique,AIChE J.60(2014)502–3510.
[9]G.Couchaux,D.Barth,M.Jacquin,A.Faraj,J.Grandjean,Kinetics of carbon
dioxide with amines.I.Stopped-?ow studies in aqueous solutions:a review,Oil Gas Sci.Technol.(2013),https://www.wendangku.net/doc/5a4360654.html,/10.2516/ogst/2013150.
[10]E.Alper,Reaction mechanism and kinetics of aqueous solutions of 2-amino-2-methyl-1-propanol and carbon dioxide,Ind.Eng.Chem.Res.29(1990)1725–1728.
[11]A.Jensen,R.Christensen,Determination of some inorganic substances in the
labyrinthine ?uids,Acta Chem.Scand.9(1955)486.
[12]R.H.Weiland,O.Trass,Absorption of carbon dioxide in ethylenediamine
solutions,Can.J.Chem.Eng.49(1971)767–772.
[13]H.Hikita,S.Asai,H.Ishikawa,M.Honda,The kinetics of reactions of carbon
dioxide with monoisopropanolamine,diglycolamine and ethylenediamine by a rapid mixing method,Chem.Eng.J.14(1977)27–30.
[14]S.H.Ali,Kinetic of the reaction of carbon dioxide with blends of amines in
aqueous media using the stopped-?ow technique,Int.J.Chem.Kinetics 37(2005)391–405.
[15]A.V.Rayer, A.Henni,J.Li,Reaction kinetics of 2-((2-aminoethyl)
amino)ethanol in aqueous and non-aqueous solutions using the stopped-?ow technique,Can.J.Chem.Eng.91(2013)190–498.
[16]A.K.Saha,S.S.Bandyopadhyay,Kinetics of absorption of CO 2into aqueous
solutions of 2-amino-2-methyl-1-propanol,Chem.Eng.Sci.22(1995)3587–3598.
[17]J.N.Br?nsted,E.A.Guggenheim,Contribution to the theory of acid and basic
catalysis:the mutarotation of glucose,J.Am.Chem.Soc.49(1927)2554–2584.[18]R.J.Little,G.F.Versteeg,Kinetics of CO 2with primary and secondary amines in
aqueous solutions –I.Zwitterion deprotonation kinetics for DEA and DIPA in aqueous blends of alkanolamines,Chem.Eng.Sci.47(1992)2027–2035.
[19]G.T.Rochelle,S.Bishnoi,Research needs for CO 2capture from ?ue gas by
aqueous absorption/stripping.Final report for P.O.No.DE-AF26-99FT01029.F.E.T.C.U.S.Department of Energy,Pittsburgh,PA 15236,Austin,Texas 78712,The University of Texas at Austin,2001.
[20]F.Khalili,A.Henni,A.L.L.East,p K a values of some piperazines at (298,303,
313,and 323)K,J.Chem.Eng.Data 54(2009)2914–2917.
[21]A.L.Kohl,R.B.Nielsen,Gas Puri?cation,?fth ed.,Gulf Publishing Company,
Houston,1997.
[22]A.C.Knipe,D.McLean,N.L.Tranter,A fast response conductivity ampli?er for
chemical kinetics,J.Phys.E 7(1974)586–590
.
Fig.12.Arrhenius plots of different tertiary amines.
Table 5
Second order reaction rate constant (k 2)at 298K and activation energy of tertiary amines.
Tertiary amines k 2(m 3kmol à1s à1)E a (kJ/mol)References MDEA 1241.93Versteeg [37]DMMEA 27.253.63Henni [44]DEMEA 79.850.50Li [45]
1DMA2P 2162.55Kadiwala [38]3DMA1P 3275.55Kadiwala [38]1DEA2P 91.594.18Liu [8]DEAB
416.562.59Liu [6]
DEA-1,2-PD
63
47.18
In this work
Journal 270(2015)485–495
[23]S.H.Ali,S.Q.Merchant,M.A.Fahim,Kinetic study of reactive absorption of
some primary amines with carbon dioxide in ethanol solution,Sep.Purif.
Technol.18(2000)163–175.
[24]S.H.Ali,S.Q.Merchant,M.A.Fahim,Reaction kinetics of some secondary
alkanolamines with carbon dioxide in aqueous solutions by stopped?ow technique,Sep.Purif.Technol.27(2002)121–136.
[25]A.P.Kamps,G.Maurer,Dissociation constant of N-methyldiethanolamine in
aqueous solution at temperatures from278K to368K,J.Chem.Eng.Data41 (1996)1505–1513.
[26]H.Shi,T.Sema,A.Naami,Z.Liang,R.Idem,P.Tontiwachwuthikul,13C NMR
spectroscopy of a novel amine species in the DEAB-CO2-H2O system:VLE model,Ind.Eng.Chem.Res.51(2012)8608–8615.
[27]H.Shi, A.Naami,R.Idem,P.Tontiwachwuthikul,1D NMR analysis of a
quaternary MEA-DEAB-CO2-H2O amine system:liquid phase speciation and vaporàliquid equilibria at CO2absorption and solvent regeneration conditions, Ind.Eng.Chem.Res.53(2014)8577–8591.
[28]K.Maneeintr,R.Idem,P.Tontiwachwuthikul, A.G.H.Wee,Synthesis,
solubilities,and cyclic capacity of amino alcohols for CO2capture from?ue gas streams,Energy Procedia1(2009)1327.
[29]F.Y.Jou, A.E.Mather, F.D.Otto,Solubility of H2S and CO2in aqueous
methyldiethanolamine solutions,Ind.Eng.Chem.Process Des.Dev.21 (1992)539.
[30]T.L.Donaldson,Y.N.Nguyen,Carbon dioxide reaction kinetics and transport in
aqueous amine membrane,Ind.Eng.Chem.Fundam.19(1980)260–266. [31]D.P.Hagewiesche,S.S.Ashour,H.A.Al-Ghawas,O.C.Sandall,Absorption of
carbon dioxide into aqueous blends of monoethanolamine and N-methyldiethanolamine,Chem.Eng.Sci.50(1995)1071–1079.
[32]G.F.Versteeg,L.A.J.VanDijck,W.P.M.Van Swaaij,On the kinetics between CO2
and alkanolamines both in aqueous and non aqueous solutions,Chem.Eng.
Commun.144(1996)113–158.
[33]R.J.Little,W.P.M.Van Swaaij,G.F.Versteeg,Kinetics of carbon dioxide with
tertiary amines in aqueous solution,AIChE J.36(1990)1633–1640.
[34]H.Bosch,G.F.Versteeg,W.P.M.Van Swaaij,Kinetics of the reaction of CO2with
the sterically hindered amine2-amino-2-methylpropanol at298K,Chem.Eng.
Sci.45(1990)1167–1173.
[35]S.Xu,Y.W.Wang,F.D.Otto,A.E.Mather,Kinetics of the reaction of carbon
dioxide with2-amino-2-methyl-1-propanol solutions,Chem.Eng.Sci.51 (1996)841–850.[36]S.Ma’mun,V.Y.Dindore,H.F.Svendsen,Kinetics of the reaction of carbon
dioxide with aqueous solutions of2-((2-aminoethyl)amino)ethanol,Ind.Eng.
Chem.Res.46(2007)385–394.
[37]H.Kierzkowska-Pawlak,M.Siemieniec,A.Chacuk,Reaction kinetics of CO2in
aqueous methyldiethanolamine solutions using the stopped-?ow technique, Chem.Process Eng.33(2011)7–18.
[38]S.Kadiwala,A.Henni,Kinetics of carbon dioxide(CO2)with ethylenediamine,
3-amino-1-propanol in methanol and ethanol,and with1-dimethylamino-2-propanol and3-dimethylamino-1-propanol in water using stopped-?ow technique,Chem.Eng.J.179(2012)262.
[39]R.L.Kent,B.Eisenberg,Better data for amine treating,Hydrocarbon Process
(1976).
[40]Y.C.Chang,R.B.Leron,M.H.Li,Equilibrium solubility of carbon dioxide in
aqueous solutions of(diethylenetriamine+piperazine),J.Chem.Thermodyn.
64(2013)106–113.
[41]J.E.Crooks,J.P.Donnellan,Kinetics and mechanism of the reaction between
carbon dioxide and amine in aqueous solution,J.Chem.Thermodyn.II(1989) 331–333.
[42]E.F.da Silva,H.F.Svendsen,Ab initio study of the reaction of carbamate
formation from CO2and alkanolamines,Ind.Chem.Eng.Res.43(2004)3413–3418.
[43]E.S.Hamborg,G.F.Versteeg,Dissociation constants and thermodynamic
properties of alkanolamines,Energy Procedia1(2009)1213–1218.
[44]G.F.Versteeg,W.P.M.Van Swaaij,On the kinetics between CO2and
alkanolamines both in aqueous and non-aquous solutions–tertiary amines, Chem.Eng.Sci.43(1988)587–591.
[45]A.Henni,J.Li,P.Tontiwachwuthikul,Reaction kinetics of CO2in aqueous1-
amino-2-propanol,3-amino-1-propanol,and dimethylmonoethanolamine solutions in the temperature range of298–313K using the stopped-?ow technique,Ind.Eng.Chem.Res.47(2008)2213–2220.
[46]J.Li,A.Henni,P.Tontiwachwuthikul,Reaction kinetics of CO2in aqueous
ethylenediamine,ethylethanolamine and diethylmonoethanolamine solutions in the temperature range(298–313)K using the stopped-?ow technique,Ind.
Eng.Chem.Res.46(2007)4426–4434.
[47]J.Benitez-Garcia,G.Ruiz-Ibanez,H.A.Al-Ghawas,O.C.Sandall,On the effect of
basicity on the kinetics of CO2absorption in tertiary amines,Chem.Eng.Sci.11 (1991)2927–2931.
J.Li et al./Chemical Engineering Journal270(2015)485–495495