Ind. Eng. Chem. Res. 2008, 47, 7375–7380
7375
Reaction Kinetics of Carbonyl Sulfide (COS) with Diethanolamine in Methanolic Solutions Rodrigo Rivera-Tinoco and Chakib Bouallou* Centre E´nerge´tique et Proce´de´s (CEP), Ecole Nationale Supe´rieure des Mines de Paris, 60 BouleVard Saint Michel, 75006 Paris, France
In this work, the kinetics of carbonyl sulfide (COS) absorption in a hybrid solvent containing diethanolamine (DEA) dissolved in methanol was studied. The amine concentrations and temperatures ranged from 380 to 2030 mol m-3 and from 298 to 323 K, respectively. With the purpose of estimating reaction rate constants for the COS-DEA system, the rigorous modeling of COS absorption was carried out based on the two-step zwitterion mechanism, used until now in the modeling of the absorption of carbon dioxide and sulfur compounds by alkanolamine aqueous solutions. A downhill simplex optimization method was developed to determine the reaction rate constants, and simultaneously an iterative procedure was followed to estimate the enhancement factor of the COS absorption. As the results show, these optimization procedures led successfully to the appropriate fitting between the experimental and modeled data and also confirm the two-step zwitterion mechanism for this absorption system. Introduction The removal of the sulfur compounds, such as the hydrogen sulfide (H2S) and carbonyl sulfide (COS), from natural and synthesis gases is an important operation in industrial processes. These compounds are eliminated because of their high toxicity and corrosive capacity, but also because of a need to reach specifications imposed by gas transport industries and to respect strict environmental standards. The sulfur compounds are eliminated by means of various processes, among which is gas absorption in specific liquid solutions. This absorption is carried out by physical and chemical solvents and currently by mixing the two in so-called hybrid solvents. Aqueous alkanolamine solutions are of great interest as chemical solvents used in natural gas sweetening processes. A wide variety of alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), diisopropanolamine (DIPA), and methyldiethanolamine (MDEA) have been used industrially for years. MDEA and DEA are example of chemical solvents used widely in gas treatment because of their chemical properties. MDEA is generally used for selective removal of H2S in the presence of CO2, whereas DEA is a common solvent for total deacidification. However, these aqueous alkanolamine solutions generally have quite low efficiencies when used for the removal of other sulfur species such as carbonyl sulfide and mercaptans.1 Moreover, when the acid gas impurities represent a significant fraction of the total gas stream, the cost for removing them by solvent absorption might be disproportionately large compared to the value of the treated gas. In contrast to the solvents mentioned previously, mixtures of chemical and physical solvents, often referred as “mixed” or “hybrid” solvents, have been developed. Industrial applications, such as the AMISOL process, show that the absorption process occurs as in a conventional alkanolamine treating unit, but the presence of the physical solvent, such as methanol, enhances the solubility capacity of the mixture, especially when the gas stream to be treated is at high pressure and has large quantities of acid compounds and/or minor gas impurities such as carbonyl * To whom correspondence should be addressed. E-mail:
[email protected]. Tel.: +331 40519111. Fax: +331 46342491.
sulfide and mercaptans. The goal of this work was to generate new kinetic data for amine-methanol solutions, as hybrid solvent, performing the modeling of COS absorption based on the zwitterion mechanism. We used a secondary amine in these solutions: the diethanolamine. Literature The very first application of chemical solvents involved triethanolamine (TEA) in 1930. It is during this year that TEA became marketable and then other types of alkanolamines were introduced into the market for the absorption of acid gases. Since then, the use of amines in industrial processes has continued to grow, and mature applications such as the use of ethanolamines in the field of gas purification2,3 and the selective absorption of H2S in the presence of CO24 are widely available. However, knowledge of the kinetics of acid gas absorption is necessary for the modeling of new absorbers and other applications, and unfortunately, such data are not always available. Concerning the kinetic modeling of COS chemical absorption, Philipp and Dautzenberg5 performed early works on kinetics and proposed the hydrolysis of COS in water. Then, Donaldson and Nguyen6 applied the analogy of CO2 chemical absorption to COS as a hydrolysis mechanism. Validation of the reaction mechanism of COS-amine absorption occurred until AlGhawas et al.7,8 who estimated physicochemical properties and determined the reaction rate constants for COS-MDEA absorption, considering a one-step zwitterion mechanism, from 288.15 to 313.15 K at MDEA concentrations up to 0.3 wt % using a wetted-sphere absorber. Nevertheless, the modeling of COS absorption under a one-step zwitterion mechanism was replaced by the accurate two-step mechanism proposed by Littel et al.,9,10 who validated this mechanism with experimental data obtained from a stirred reactor under saturated bulk conditions. For other applications, COS absorption by aqueous solutions of MDEA and DEA has been studied by Amararene and Bouallou11 and Cadours et al.12 considering a two-step zwitterion modeling. In addition, Lammers et al.13 modeled COS absorption by MDEA-polyhydroxyalcohol solutions using the same reaction mechanism, and successfully applied their results to a natural gas sweetening plant.
10.1021/ie8002649 CCC: $40.75 2008 American Chemical Society Published on Web 09/09/2008
7376 Ind. Eng. Chem. Res., Vol. 47, No. 19, 2008
Figure 1. Flow diagram of the apparatus. Table 1. Parameters of COS Absorption by DEA-Methanol Solutionsa T (K)
CMDEA
HCOS (Pa m3 mol-1)
kL × 10-5 (m s-1)
PT,0 - PI (Pa)
ξ
298.66 299.21 299.25 313.78 313.87 323.38 323.29 323.62 323.56
387 387 2026 2029 2029 1164 1164 1164 2029
4690 4770 4780 7160 7170 7160 7150 9150 9220
3.098 3.144 1.396 1.978 1.978 2.561 2.515 2.791 2.301
19 175 20 270 58 354 25 460 26 436 93 886 29 509 23 453 15 738
65.0 64.0 106.0 164.0 174.0 110.0 102.0 110.0 168.0
a
has been considered in several works on aqueous and alcohol-aqueous systems, such as those by Littel et al.9 and Lammers et al.,13 and is frequently used because of the difficulty in measuring reactive systems directly. The physicochemical properties of COS-aqueous systems were estimated by using different correlations: the works of Pani et al.,17 Versteeg and Swaaij,18 and Tsai et al.19 were used for diffusivity estimation, and Henry constants for COS were estimated in analogy with N2O, based on the works of Wang et al.20 and Sandall.21 The viscosities of water and of amine-methanol systems are needed in these correlations; therefore, to address the methanolic system, we measured these values experimentally.
Vg (m3) ) 151 × 10-6.
Few works have dealt with the COS absorption by hybrid solvents. Alper et al.14 studied this type of system using equipment manufactured by Hi-Tech Scientific Ltd. (Bradford on Avon, U.K.) consisting of a standard SF-51 stopped-flow spectrofluorimeter with a conductivity cell attachment. The kinetics study of the reaction of COS with primary amines (MEA, diglycolamine, 2-amino-2-methyl-1-propanol) and secondary amines (DEA) in alcoholic solutions was carried out for a concentration range from 100 to 1500 mol m-3 and a temperature range from 278 to 298 K. The results showed that the reaction rate of COS is higher in the alcoholic solutions than in water, because of the higher physical solubility of COS. The partial reaction order with respect to the amine was found to vary from 1 to 2.14 To make progress in these hybrid systems and their application in COS absorption, we decided to determine accurately the reaction rate constants of COS-DEA-methanol absorption by modeling the two-step zwitterion mechanism, at temperatures from 298 to 323 K. By analogy to CO2 absorption and according to the works of Danckwerts15 and Blauwhoff et al.,16 the first stage of the mechanism is assumed to be the zwitterion formation, followed by the stage of deprotonation of this zwitterion by any base present in the system. Nevertheless, the physicochemical properties of COS-methanol systems needed to model the gas absorption are not available in the open literature, so as a first approach, we estimated the properties of COS assuming the COS-N2O analogy in aqueous systems, validated experimentally by Al-Ghawas et al.7 This assumption
Experimental Section The apparatus (Figure 1) is the same as used by Amararene and Bouallou11 and consists of a thermostatted Lewis-type reactor with a constant gas-liquid interface (15.34 ( 0.05) × 10-4 m2. The reactor is closed at both ends by two metallic flanges. The temperature was controlled by circulating a thermostatic fluid through the glass double jacket. A six-bladed Rushton turbine (4.25 × 10-2 m diameter) and a propeller (4 × 10-2 m diameter), driven magnetically by a variable-speed motor, were used to agitate the liquid and gas phases, respectively. Also, four vertical baffles were placed inside the cell in order to avoid the formation of a vortex. A Druck pressure gauge (0-250 kPa) was mounted on the upper flange and was calibrated at a temperature higher than the experimental temperature to avoid liquid condensation in its measuring chamber. A tube was mounted through the upper flange and allowed the cell to be either degassed or connected to a tank of COS gas. The lower flange was equipped with a temperature probe and a nonrotating stem valve. The pressure transducer was calibrated to within (42 Pa against a pressure calibration device. The temperature in the reactor was known to within 0.02 K and was calibrated against a 25 Ω platinum probe. A microcomputer was used to record both pressure and temperature signals. Methanol and alkanolamine were degassed independently, and methanolic solutions were prepared under vacuum. The masses of these compounds were determined by differential weighing.
Ind. Eng. Chem. Res., Vol. 47, No. 19, 2008 7377
Figure 2. Experimental and modeled data of COS absorption by DEA-methanol solutions.
Figure 3. Representation of estimated reaction rate constants vs the inverse of the experimental temperature for COS absorption by DEA-methanol solutions. Table 2. Logarithmic Values of Reaction Constants Presented in Figure 3 T (K)
-ln k1,1
-ln k1,2
-ln k2,1
298.66 299.21 313.78 313.87 313.57 323.62
6.359 8.195 5.967 6.359 7.064 5.461
10.612 8.798 8.386 8.775 9.505 7.899
9.730 11.622 10.434 11.364 9.793 8.831
The flask containing the solution was connected to the reactor to allow the solution to transfer by gravity under vacuum. Accurate weighing of the flask before and after transfer yielded the mass of solution actually introduced into the cell. The liquidphase volume was calculated considering its density. At a given temperature and vapor pressure PI, pure COS was introduced for a very short time into the upper part of the cell; the pressure could not exceed 2.5 × 105 Pa in order to avoid damaging the Lewis cell. Once the gas was in the cell, stirring was started, and the pressure drop resulting from absorption was recorded. The estimated average experimental error in the COS absorption rate is 8% and was estimated by measuring the known absorption of CO2 by MDEA aqueous solutions and evaluating the slopes of the different measurements. The methanol was purchased from Prolabo and had a minimum purity of 99.8%. DEA was from Aldrich and had a certified minimum mass purity of 99%. Carbonyl sulfide, with a certified volume purity of 99.997%, was from L’Air Liquide. Solutions
with fixed amine concentrations ranging from 380 to 2030 mol m-3 were prepared. Results and Discussion Following Littel et al.,9 we assumed the saturation of the bulk by COS. As a consequence, the pressure decrease in the cell is proportional to the overall reaction rate, as expressed in eq 1. -RCOSVL ) -Vg
dCCOSg
(1)
dt The initial conditions of COS gas are given by CCOSg(t)0) ) CCOSg°
(2)
The variation in the COS concentration of the gas phase can be represented by eq 3.9 However, values for the dimensionless solubility coefficient, mCOS, are not available for the experimental conditions under which this work was performed. Therefore, an equivalence between the terms of eqs 3 and 4 was considered. Equation 4 was used by Amararene and Bouallou11 in the modeling of COS absorption by aqueous amine solutions. dCCOSg dt
) -kLa ′ (mCOSCCOSg - CCOSL) dCCOSg dt
)-
kLaξCCOSint Vg
VL Vg
(3) (4)
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Figure 4. Experimental and modeled data of COS absorption by DEA-methanol solutions using the Arrhenius law for the reaction rate constants and the correlation of the enhancement factor. Table 3. Experimental and Modeled Pressure Values (Pa) of COS Absorption by DEA-Methanolic Solutions at Three Different Concentrations and Temperatures 323 K, 2008 mol m-3
313 K, 2029 mol m-3
298 K, 387 mol m-3
time (s)
experimental
modeled
experimental
modeled
experimental
modeled
100 200 300 400 500
5730.1 2086.3 759.6 276.6 100.7
5809.0 2144.2 791.5 292.1 107.8
8642.9 2825.7 923.8 302.0 98.7
9843.1 3665.1 1364.7 508.2 189.2
7179.1 2687.9 1006.3 376.8 141.1
7408.0 2872.5 1114.8 433.0 168.3
The volumetric surface area, a′, was substituted by the enhancement factor, ξ, and the interfacial surface area, a, divided by the volume of the gas phase. The enhancement factor ξ, the mass transfer coefficient kL, and the gas volume Vg are needed to describe the absorption rate correctly; therefore, as was done by Rivera-Tinoco and Bouallou,22 we assumed that the COS-amine reaction did not change the amine concentration in the bulk significantly, leading to constant values for kL, HCOS, and ξ with respect to time. Including these constants in the integration of eq 4 leads to a linear representation of global absorption (eq 5), which additionally uses the initial COS pressure value at t0, PT,0.
(
)
kLξaRT PT - PI ln )(t - t0) ) -β(t - t0) PT,0 - PI VgHCOS
( ) ( )
DCOS FNdag2 dcell µ
0.618
µ FDCOS
0.434
βVgHCOS kLaRT
PCOS - CCOSL HCOS
(8)
At any time, PCOS can be obtained from the measured total (PT) and inert (PI) pressures (eq 9). The COS absorption is modeled assuming ideal behavior of the gas phase and the COS concentration in the bulk liquid phase as a function of time, which is equal to zero at t ) ∞, meaning complete COS consumption by the chemical reaction. PCOS ) PT - PI
(9)
The reaction mechanism proposed for DEA-amine systems by Alper et al.14 was considered as four chemical reactions, involving the reaction rates R1,1, R1,2, R2,1, and R2,2, represented as a chemical balance by eqs 10 and 11.
(6)
COS + C4H11NO2 798 C4H10O2N+HCOS-
The mass-transfer coefficient, kL, was calculated using the Sherwood (Sh), Reynolds (Re), and Schmidt (Sc) correlations, as was done by Amararene and Bouallou,11 and the initial values of the enhancement factor ξ were determined using eq 7, in which the β values correspond to the slope of the linear representation of the experimental data by eq 5. Then, the enhancement factor value was increased iteratively until a minimum value for the objective function was reached. ξ)
CCOSint )
(5)
In this case, kL is given by kL ) 0.352
Henry’s law constant, as shown in eq 8, which is equivalent to the term (mCOSCCOSg - CCOSL) in eq 3.
k1,1
k2,1
C4H11NO2 + C4H10O2N+HCOS- 798 C4H10O2NCOS- + k2,2
C4H11NO2H+(11) Considering the mass-transfer balance and the zwitterion reaction mechanism, the modified differential equations for the COS gas and liquid concentrations presented by Littel et al.9 are given by
(7)
At the interface, vapor-liquid equilibrium was assumed. The COS partial pressure, PCOS, is related to the concentration of unreacted dissolved COS, as a function of the COS concentrations at the interface (CCOSint) and in the bulk (CCOSL) and the
(10)
k1,2
dCCOSg dt dCCOSL dt
(
) -kLaζ
(
) kLaξ
)
PCOS VL - CCOSL 2 HCOS Vg
)
PCOS 1 - CCOSL - R1,1 + R1,2 HCOS Vg
(12)
(13)
Ind. Eng. Chem. Res., Vol. 47, No. 19, 2008 7379
Neglecting the diffusion of ionic molecules, the differential equations for the other chemical species are similar to those presented by Littel et al.9 and Rivera-Tinoco and Bouallou22 for COS-MDEA reactions. dCC4H11NO2 dt
) -R1,1 + R1,2 - R2,1 + R2,2
dCC4H10O2N+HCOS-
) R1,1 - R1,2 - R2,1 + R2,2 dt dCC4H10O2NCOS) R2,1 - R2,2 dt dCC4H11NO2H+ ) R2,1 - R2,2 dt
(14) (15) (16) (17)
with R1,1 ) k1,1CCOSLCC4H11NO2
(18)
R1,2 ) k1,2CC4H10O2N+HCOS-
(19)
R2,1 ) k2,1CC4H10O2N+HCOS-CC4H11NO2
(20)
R2,2 ) k2,2CC4H10O2NCOS-CC4H11NO2H+
(21)
The differential equations were solved by using a fourth-order Runge-Kutta procedure.22 Parallel reactions were not considered. The optimum values for reaction rate constants for modeling the COS-DEA absorption were estimated using a downhill simplex multivariable method, minimizing the difference between the experimental and modeled COS pressure data, as represented in eq 22. Moreover, an iterative sequence of values for the enhancement factor ξ was obtained simultaneously in order to improve the model. The estimation of the Arrhenius law coefficients for the reaction constants was carried out considering all experimental data at temperatures from 298 to 323 K. The experimental conditions for these data sets are presented in Table 1. n
∆P )
∑ (P t)0
COSg,experimental - PCOSg,calculated)t
2
(22)
In Figure 2, we present the experimental and modeled data for different temperatures and concentrations. Results of reaction rate constant estimations are presented in Figure 3. Between 298 and 323 K, we observed that reaction rate constants k1,1 and k1,2 values ranged between 5.69 × 10-4 and 2.28 × 10-3 and k2,1 values ranged from 1.89 × 10-5 to 7.71 × 10-5 for the studied temperatures. In agreement with Littel et al.9 and Rivera-Tinoco and Bouallou,22 we validated that reaction rate constant k2,2 has a value of zero. We estimated the coefficients of the Arrhenius law equation, using a quasi-Newton minimization method based on the values presented in Table 2 and Figure 3, as a function of the inverse temperature. The Arrhenius laws for the three nonzero reaction rate constants are -5346 + 10.468 (23) T -5319 + 7.951 (24) ln k1,2 ) T -5406 + 7.268 (25) ln k2,1 ) T In the latest work about COS absorption by DEA aqueous solutions, Amararene and Bouallou11 presented an activation energy (Ea × R) of 47.9 kJ mol-1. Alper et al.14 presented some ln k1,1 )
activation energy values for alcoholic solutions of the same order, e.g., 46.0 kJ mol-1 for a DEA-propanol system. These values correspond well with the activation energies for k1,1, k1,2, and k2,1 estimated in this work, which are 44.4, 44.2, and 44.9 kJ mol-1, respectively, although a decrease in the activation energy is noted in this methanolic system. The calculated values of the pre-exponential coefficients for the Arrhenius laws are greater than those published by Amararene and Bouallou11 for free alcohol solutions, which can be related to the positive effect of methanol on the COS-DEA reaction. For k1,1, this coefficient is 3.48 × 104, which is 34 times greater than the value predicted for DEA aqueous solutions by Amararene and Bouallou.11 The second step of the zwitterion mechanism limits the reaction, which confirms the deprotonation role presented by Alper et al.14 Moreover, the two-step zwitterion model of COS absorption applied in this work confirms that the reaction is second-order with respect to the amine, as reported by the same authors. The pre-exponential coefficients of k1,2 and k2,1 are 2.84 × 103 and 1.43 × 103, respectively. Their values are less than 3 times higher than the pre-exponential values presented by Amararene and Bouallou.11 The values of the reaction rate constants are higher than those presented for aqueous DEA systems, confirming the role of alcohol as a physical solvent that enhances the COS-amine reaction, which is improved by the increase of the hybrid solvent solubility. We assume that the reaction rates constants for COS absorption by amine-water-alcohol solutions would present intermediate values between those observed for amine-water and amine-alcohol absorption. Following Rivera-Tinoco and Bouallou,22 we estimated an optimized value for the enhancement factor ξ. An iterative procedure was used to estimate the enhancement factor that allowed for the modeling of COS absorption at temperatures up to 323 K. In our work, we found that the ξ value is strongly affected by the amine concentration, as was also the case for COS absorption by MDEA systems studied in our previous work.22 Nevertheless, a single mathematical expression is able to predict the values of the enhancement factor as a function of the system temperature and amine concentration, contrary to MDEA aqueous solutions. Further studies would extend the validity range for this expression (eq 26). ξ ) 0.51T0.6 - 0.21CDEA0.5 + 1.83 × 10-6T2.5CDEA0.5 4.44 × 10-12(26) Comparing the enhancement factor values estimated in this work with those presented by Amararene and Bouallou,11 we note that the presence of methanol increases them and enhances the absorption of COS. Considering a temperature of 313 K and an amine concentration of approximately 2000 mol m-3, the enhancement factor for DEA aqueous solutions is ∼13, whereas DEA methanolic solutions showed values of ∼150. Finally, we carried out the modeling of pressure profiles for COS absorption at the experimental conditions listed in Table 1, using the reaction rate constants estimated by the Arrhenius law determined in this work and the enhancement factor described by eq 26. The results are represented in Figure 4 and Table 3. The experimental and modeled data exhibit a successful fitting for the whole range of amine concentrations and temperatures, with an 8% error that is near the accuracy of the pressure sensors of the Lewis reactor used in the experiments. Conclusion For the first time, kinetic data are presented for COS absorption in DEA methanolic solutions assuming each of the
7380 Ind. Eng. Chem. Res., Vol. 47, No. 19, 2008
two steps of zwitterion mechanism. The results of the optimization procedures developed in this work allowed the estimation of Arrhenius expressions for the reaction rate constants and the equations to describe the behavior of the enhancement factor as a function of the amine concentration. Comparing aqueous DEA systems to DEA-methanolic solutions, it is noted that this alcohol enhances the pre-exponential coefficients of the Arrhenius laws and the enhancement factor. COS-DEAmethanol absorption follows the zwitterion mechanism, and the results show that accurate modeling can be performed with the constants and coefficients determined in this work. Nomenclature a ) interfacial area (m2) a′ ) volumetric surface area (m2 m-3) C ) concentration (mol m-3) DCOS ) diffusion coefficient of COS (m2 s-1) dcell )Lewis cell inside diameter (m) dag ) propeller diameter (m) ξ ) enhancement factor H ) molar-scale Henry’s law constant (Pa m3 mol-1) k1,1, k1,2 ) reaction rate constants (m3 mol-1 s-1) k2,1, k2,2 ) reaction rate constants (s-1) kL ) liquid-side mass-transfer coefficient of unreacted COS (m s-1) N ) stirring speed (s-1) PI, PT ) inert and total pressures, respectively (Pa) R ) gas constant (8.3143 J.K-1 mol-1) Ri,j ) reaction rate (mol s-1) T ) absolute temperature (K) t ) time (s) V ) volume (m3) Greek Letters β ) slope (s-1) µ ) solution viscosity (Pa s) F ) solution density (kg m-3) Subscripts g ) gas int ) interface I ) inert L ) liquid T ) total 0 ) initial
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(4) Kohl, A.; Nielsen, R. Gas Purification; Gulf Publishing Company: Houston, TX, 1997. (5) Philipp, B.; Dautzenberg, H. Kinetische Untersuchungen zur Bildung and Zetsetzung von Monothiocarnonat in wa¨ssrige Lo¨sung. Z. Phys. Chem. 1965, 229, 210. (6) Donaldson, T. L.; Nguyen, Y. N. Carbon dioxide reaction and transportation in aqueous amine membranes. Ind. Eng. Chem. Fundam. 1980, 19, 260. (7) Al-Ghawas, H. A.; Sandall, O. C. Simulation Absorption of Carbon Dioxide Carbonyl Sulfide and Hydrogen Sulfide in Aqueous Methyldiethanolamine. Chem. Eng. Sci. 1991, 2, 665. (8) Al-Ghawas, H. A.; Ruis-lbanez, G.; Sandall, O. C. Absorption of Carbonyl Sulfide in Aqueous Methyldiethanolamine. Chem. Eng. Sci. 1989, 44, 631. (9) Little, R. J.; Versteeg, G. F.; van Swaaij, W. P. M. Kinetics Study of COS with Tertiary Alkanolamine Solutions. 1. Experiments in an Intensely Stirred Batch Reactor. Ind. Eng. Chem. Res. 1992, 31, 1262. (10) Little, R. J.; Versteeg, G. F.; van Swaaij, W. P. M. Kinetics Study of COS with Tertiary Alkanolamine Solutions. 2. Modeling and Experiments in a Stirred Cell Reactor. Ind. Eng. Chem. Res. 1992, 31, 1269. (11) Amararene, F.; Bouallou, C. Kinetics of carbonyl sulfide (COS) absorption with aqueous solutions of diethanolamine and methyldiethanolamine. Ind. Eng. Chem. Res. 2004, 43, 6136. (12) Cadours, R.; Magne´-Drisch, J.; Normand, L.; Roquet, D.; Perdu, G. COS removal from natural gases by absorption in alkanolamine solutions. Presented at the 85th Annual GPA Convention, Grapevine, TX, Mar 5-8, 2006. (13) Lammers, J. N. J. J.; Haringa, J.; Littel, R. J. Effect of polyhydroxyalcohols on COS absorption in aqueous methyldiethanolamine. Chem. Eng. J. Biochem. Eng. 1995, 60, 123. (14) Alper, E.; AI-Roweih, M.; Bouhamra, W. Reaction kinetics of COS with primary and secondary amines in alcoholic solutions. Chem. Eng. J. 1994, 55, 53. (15) Danckwerts, P. V. The reaction of CO2 with ethanolamines. Chem. Eng. Sci. 1979, 34, 443. (16) Blauwhoff, P. M. M.; Versteeg, G. F.; van Swaaij, W. P. M. A study in the reaction between CO2 and alkanolamines in aqueous solutions. Chem. Eng. Sci. 1984, 39, 207. (17) Pani, F.; Gaunand, A.; Cadours, R.; Bouallou, C.; Richon, D. Kinetics of Absorption of CO2 in Concentrated Aqueous Methyldiethanolamine in Solutions the Range 296 K to 343 K. J. Chem. Eng. Data 1997, 42, 353. (18) Versteeg, G. F.; van Swaaij, W. P. M. Solubility and Diffusivity of Acid Gases (CO2, N2O) in Aqueous Alkanolamine Solutions. J. Chem. Eng. Data 1988, 33, 29. (19) Tsai, T. C.; Ko, J. J.; Wang, H. M.; Lin, C. Y.; Li, M. H. Solubility of Nitrous Oxide in Alkanolamine Aqueous Solutions. J. Chem. Eng. Data 2000, 45, 341. (20) Wang, Y. W.; Xu, S.; Otto, F. D.; Mather, A. E. Solubility of N2O in Alkanolamines and in Mixed Solvents. Chem. Eng. J. 1992, 48, 31. (21) Sandall, O. C. Kinetics of Sulfur Species-Hydrocarbon-Aqueous Amine Systems; Project 962 RR-182; Gas Processors Association: Tulsa, OK, 2002. (22) Rivera-Tinoco, R.; Bouallou, C. Kinetic study of COS absorption by Methyldiethanolamine aqueous solutions from 415 to 4250 mol m-3 and 313 to 353 K. Ind. Eng. Chem. Res. 2007, 31, 12.
ReceiVed for reView February 15, 2008 ReVised manuscript receiVed June 23, 2008 Accepted July 8, 2008 IE8002649
