Experiments and model for the viscosity of carbonated 2-amino-2-methyl-1-propanol and piperazine aqueous solution

Accepted Manuscript Experiments and model for the viscosity of carbonated 2-amino-2-methyl-1propanol and piperazine aqueous solution Dong Fu, Zhixin Li, Feng Liu PII: DOI: Reference:

S0021-9614(13)00305-4 http://dx.doi.org/10.1016/j.jct.2013.08.025 YJCHT 3644

To appear in:

J. Chem. Thermodynamics

Received Date: Revised Date: Accepted Date:

7 August 2013 24 August 2013 27 August 2013

Please cite this article as: D. Fu, Z. Li, F. Liu, Experiments and model for the viscosity of carbonated 2-amino-2methyl-1-propanol and piperazine aqueous solution, J. Chem. Thermodynamics (2013), doi: http://dx.doi.org/ 10.1016/j.jct.2013.08.025

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Experiments and model for the viscosity of carbonated 2-amino-2-methyl-1-propanol and piperazine aqueous solution Dong Fu*, Zhixin Li and Feng Liu

(School of Environmental Science and Engineering, North China Electric Power University, Baoding, 071003)

*

Corresponding author. Address: School of Environmental Science and Engineering, North China Electric Power University, Baoding, 071003, People's Republic of China. Tel.: +86-312-7522037; fax: +86-312-7523127. E-mail addresses: [email protected](D.Fu). 1

Abstract: The viscosities ( ) of carbonated 2-amino-2-methyl-1-propanol (AMP)piperazine (PZ) aqueous solutions were measured by using a NDJ-1 rotational viscometer, with temperatures ranging from 298.15 K to 323.15K. The total mass fraction of amines ranged from 0.3 to 0.4. The mass fraction of PZ ranged from 0.05 to 0.10. The Weiland equation was used to correlate the viscosities of both CO2-unloaded and CO2-loaded aqueous solutions and the calculated results agreed well with the experiments. The effects of temperature, mass fractions of amines and CO2 loading ( ) on the viscosities of carbonated aqueous solutions were demonstrated on the basis of experiments and calculations.

Keywords: 2-Amino-2-Methyl-1-Propanol; Piperazine; CO2 loading; Viscosity

2

1. Introduction Aqueous solutions of amines have been widely used for the removal of CO2 from a variety of gas streams [1-7]. Among the amine series, the sterically hindered amines, e.g., 2-amino-2-methyl -1-propanol (AMP), is considered to be an attractive solvents for the removal of CO2 due to its absorption capacity, absorption rate, selectivity and degradation resistance advantages [8-18]. Compared with N-methyldiethanolamine (MDEA), AMP has the same absorption capacity for CO2 (1 mol of CO2 per mol of amine) but much higher reaction rate [12]. When the aqueous solutions of AMP are used to absorb CO2, as AMP only forms bicarbonate and carbonate ions, the regeneration energy costs are relatively low. Adding small amounts of primary and secondary amines to an aqueous solution of AMP is helpful to promote the absorption of CO2, e.g., Mandal et al. [13, 14] showed that the addition of small amounts of monoethanolamine (MEA) and diethanolamine (DEA) to an aqueous solution of AMP significantly enhances the rate of absorption of CO2. For similar relative composition, the rates of absorption of CO2 in AMP-MEA and AMP-DEA aqueous solutions are higher than those in MDEA- MEA and MDEA- DEA aqueous solutions. Besides MEA or DEA, piperazine (PZ) is also considered to be an effective promoter. It has a greater capacity and higher reaction rates than MEA, e.g., 4.6 mol·L-1 PZ aqueous solution has about 75 % greater CO2 capacity than 4.91 mol·L-1 MEA aqueous solution, and CO2 reaction rates for PZ are shown to be 2-3 times faster than MEA [19]. Solution viscosity is important in the mass transfer rate modelling of absorbers

3

and regenerators because these properties significantly affect the liquid film coefficient for mass transfer. Viscosities of both CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions are required when designing or simulating an absorption column for CO2 absorption using AMP -PZ aqueous solutions. So far, there are some experiments concerning the viscosities of aqueous solutions containing AMP and PZ [20-22]. In particular, Murshid et al. [20], Samanta and Bandyopadhyay [21] measured the viscosities of aqueous solutions of PZ and aqueous blends of AMP-PZ at temperatures from 298.15 K to 333.15 K. Paul and Mandal [22] measured the viscosities of aqueous blends of AMP-PZ at the temperatures from 288 K to 333 K. Besides experiments, they [20-22] also proposed theoretical models and satisfactorily correlated their experiments as a function of temperature and concentration of amine. However, the experiments and theoretical work for the viscosities of CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions are rare. The main purpose of this work is to investigate the viscosities of carbonated AMP-PZ aqueous solutions experimentally and theoretically, so as to demonstrate the effects of temperature, mass fractions of amines and CO2 loading on the viscosities. To this end, the viscosities of CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions were measured by using a NDJ-1 rotational viscometer, with the temperatures, mass fraction of PZ and CO2 loading, respectively, ranging from 298.15 K to 323.15 K, 0.05 to 0.10 and 0 to 0.6. The Weiland equation[23] was used to correlate the viscosities of both CO2-unloaded and CO2-loaded solutions.

4

2. Experimental 2.1 Materials AMP and PZ were purchased from the Huaxin Chemical Co. The provenance and sample purity are shown in table 1. They were used without further purification. Aqueous solutions of AMP-PZ were prepared by adding doubly distilled water. The uncertainty of the electronic balance is ± 0.1 mg. 2.2 Apparatus and procedure The carbonated AMP-PZ aqueous solutions were prepared according to the methods mentioned in the work of Weiland et al. [23], Amundsen et al. [24], and our previous work [25-27]: CO2-unloaded AMP -PZ aqueous solutions were put into a volumetric flask immersed in the thermostatic bath with a built-in stirrer for uniform temperature distribution. CO2 from a high-pressure tank was inlet into the volumetric flask at certain temperatures (CO2 pressure is atmosphere). Once the carbonated solution was prepared, varying proportions of the unloaded and loaded solutions were mixed together to produce a set of samples having a fixed ratios of AMP /PZ -to-water, but with varying CO2 loading. The CO2 loading is defined as = n CO / (nAMP 2

+nPZ), in which n CO is the mole of loaded CO2, nAMP and nPZ are, respectively, the 2

moles of AMP and PZ in the unloaded aqueous solutions. The uncertainty of CO2 loading is less than 2 % [23-27]. The viscosities of the carbonated AMP-PZ aqueous solutions were measured at temperatures from 298.15 K to 323.15 K by using a NDJ-1 rotational viscometer produced by the Shanghai Hengping instrument factory. The measurement ranges for

5

temperature and viscosity are respectively (273.15-383.15) K and (0.1-100) mPa s. The uncertainty of temperature is 0.05 K, and the uncertainty for viscosity is 0.01 mPa s

3. Results and discussion The viscosities of CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions are shown in table 2. Besides experiments, theoretical work is also presented in this work. The Weiland equation [23] was applied to correlate the viscosities of both CO2-loaded and CO2-unloaded solutions. Compared with the widely used Eyring equation [28] and the Grunberg-Nissan equation [29], the Weiland equation [21] can simultaneously describe the temperature, mass fraction of amine and CO2 loading dependences. When applied to carbonated AMP-PZ aqueous solutions, the Weiland equation can be expressed as:

η mix =

w1 w2 η1 + η2 w1 + w2 w1 + w2

where

mix

(1)

is the viscosity of the carbonated aqueous solution, w1 and w2 respectively

stand for the mass fractions of AMP and PZ. The

1

and 2 are expressed as:

⎧ [(ai w + bi )T + (ci w + d i )]w ⎫ × f (α , w)⎬ , 2 T ⎩ ⎭

η i / η water = exp⎨ where amines

water

(2)

is the viscosity of pure water, w= w1+ w2 is the total mass fraction of

The f (α , w) refers to the contribution of CO2 loading:

f (α , w) = α (ei w + f i T + g i ) + 1

(3)

6

where ai, bi, ci, di, ei, fi and gi are adjustable parameters. The parameters ai, bi, ci and di were regressed by fitting to the viscosities of CO2-unloaded AMP-PZ aqueous solutions measured in this work. The objective function was expressed as: n

[

]

(4)

fs = ∑ 1 − η cal / η exp × 100% / n i =1

where the superscripts ‘exp’ and ‘cal’ respectively stand for the experimental and calculated values, n represents the number of data points. The optimized values are a1= 2.8095, b1= 11.5916, c1= -12.4734 and d1= -5.4592; a2= 1.3581, b2= 7.1575, c2= -1.0848 and d2= 5.1024. The average relative deviation is 4.05 %. It is worth noting that besides our experimental work on the viscosities of CO2-unloaded AMP-PZ aqueous solutions, many other experimental results can also be found from the work of Murshid et al.[20], Samanta and Bandyopadhyay [21], and Paul and Mandal [22]. Using the Weiland equation and the optimized parameters, we predict the viscosities of CO2-unloaded AMP-PZ aqueous solutions with the temperatures ranging from 298.15 K to 333.15 K, and w1 and w2 respectively ranging from 0 to 0.30 and 0 to 0.1035. The average relative deviation between the predictions and experiments [20-22] is 9.74 %. Thus, the regressed parameters are applicable when the temperature ranges from 298.15 K to 333.15 K, w1 ranges from 0 to 0.35 and w2 ranges from 0 to 0.1035. Figures 1 and 2 show the viscosities of the CO2-unloaded AMP-PZ aqueous solutions calculated from the Weiland equation, and the comparison with experiments. The viscosity increases with the increase of w1 at a given temperature and given w2, and exponentially decreases with the increase of temperature at given w2 and w1. The 7

Weiland equation correctly captures the mass fraction of amine and temperature dependence of the viscosities, and satisfactorily fits the experimental results. The agreement between the experiments [20-22] and predictions is also good, despite the fact that viscosities under high temperatures were overestimated. The temperature dependence of the viscosity can also be well described by the Eyring model, = 1exp( 2T), however,

1

and

2

are dependent on both temperature and the mass

fraction of amines. To describe the viscosity of CO2-loaded AMP-PZ aqueous solutions using the Weiland equation, one should first determine the adjustable parameters ei, fi and gi. They were regressed by fitting to the viscosities of CO2-loaded AMP-PZ aqueous solutions from this work. The objective function is the same as that in Eq.(4). The optimized values are e1=-5.3842, f1=7.5248 and g1=-2.0137; e2=-3.9256, f2=7.2418 and g2=1.1880. The average relative deviation is 5.81%. Figure 3 shows the CO2 loading dependence of the viscosity of carbonated AMP-PZ aqueous solutions. One finds from this figure that at a given temperature and given w2 and w1, the viscosities of carbonated aqueous solutions increase monotonously with the increase of CO2 loading. The Weiland equation correctly captures the CO2 loading dependence of the viscosities and the calculated results match the experiments satisfactorily. Figure 4 shows the effect of the mass fraction of amines on the viscosity of carbonated AMP-PZ aqueous solutions under series of temperatures, indicating that the higher is the total mass fraction of amines of the CO2 unloaded solution, the higher is the viscosity of the CO2 loaded solution. It is worth

8

noting that the composition of CO2 loaded AMP-PZ aqueous solution is different from that of the CO2 unloaded solution, in particular, there are many bicarbonate and carbonate ions in the CO2 loaded solution. With the increase of CO2 loading, the concentration of ions tends to increase, thus leading to the increase of the viscosity of carbonated solution. Figure 5 shows the temperature dependence of the viscosity. One finds that at given CO2 loading, given w2 and w1, the viscosity exponentially decreases with increasing temperature. The temperature dependence of the viscosity of carbonated solution can also be well described by the Eyring model, = 1exp( 2T), however, in this case,

1

and

2

are dependent on the temperature, the mass fraction of amines and the

CO2 loading. Compared with the Eyring model, the Weiland equation can simultaneously describe the influence of temperature, mass fraction of amine and CO2 loading on the viscosity of carbonated solution.

4. Conclusions In this work, the viscosities of carbonated AMP-PZ aqueous solutions were measured over wide ranges of CO2 loading, temperature and mass fraction of amines. The Weiland equation was used to correlate the viscosities. Our results showed that: (1) For CO2-unloaded AMP-PZ aqueous solutions, the viscosity increases with the increase of the w1 at a given temperature and given w2, and exponentially decreases with the increase of temperature at a given w2 and w1; (2) For CO2-loaded AMP-PZ aqueous solutions, the viscosity increases monotonously

9

with the increase of CO2 loading and exponentially decreases with increasing temperature; (3) The Weiland equation can correctly capture the effects of CO2 loading, mass fraction of amines and temperature on the viscosities, and satisfactorily fit the experimental data.

Acknowledgments The authors appreciate the financial support from the National Natural Science Foundation of China (Nos. 21276072 and 21076070), the Natural Science Funds for Distinguished Young Scholar of Hebei Province (No. B2012502076), the Fundamental Research Funds for the Central Universities (No. 13ZD16) and the 111 project (B12034).

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[7] Y. Maham, A. E. Mather, C. Mathonat, J. Chem. Thermodyn. , 32(2) (2000), 229-236. [8] F. H. Al-Masabi, M. Castier, Int. J. Greenh. Gas Con., 5(6)(2011), 1478-1488. [9] S. Xu, Y. W. Wang, F. D. Otto, A. E. Mather, Chem. Eng. Sci., 51(6) (1996), 841-850. [10] Z. Pei, S. Yao, W. Jian, Z. Wei, Y. Qing, J. Environ. Sci., 20(1) (2008), 39-44. [11] J. Xiao, C. W. Li, M. H. Li, Chem. Eng. Sci., 55(2000), 161-175. [12] G. Sartori, D. W. Savage, Ind. Eng. Chem. Fund. , 22(2) (1983), 239-249. [13] B. P. Mandal, A. K. Biswas, S. S. Bandyopadhyay, Chem. Eng. Sci., 58(18) (2003), 4137- 4144. [14] B. P. Mandal, S. S. Bandyopadhyay, Chem. Eng. Sci., 61(16) (2006), 5440-5447. [15] A. K. Saha, S. S. Bandyopadhyay, A. K. Biswas, Chem. Eng. Sci., 50(22) (1995), 3587-3598. [16] B. P. Mandal, M. Guha, A. K. Biswas, S. S. Bandyopadhyay, Chem. Eng. Sci., 56(21) (2001), 6217-6224. [17] B. P. Mandal, S. S. Bandyopadhyay, Chem. Eng. Sci., 60(22) (2005), 6438-6541. [18] B. P. Mandal, M. Kundu, S. S. Bandyopadhyay, J. Chem. Eng. Data., 50(2) (2005), 352-358. [19] S. Kadiwala, A. V. Rayer, A. Henni, Fluid Phase Equilibr., 292(1-2) (2010), 20-28. [20] G. Murshid, A. M. Shariff, L. K. Keong, M.A. Bustam, (5) (2011), 2660-2663

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J.Chem. Eng. Data, 56

[21] A.Samanta, S. S. Bandyopadhyay, J. Chem. Eng. Data, 51 (2) (2006), 467–470 [22] S.Paul,B. Mandal, J. Chem. Eng. Data, 51 (5) (2006),1808-1810. [23] R. H. Weiland, J. C. Dingman, D. B. Cronin, G. J. Browning, J. Chem. Eng. Data, 43(3) (1998), 378-382. [24] T. G. Amundsen, L. E. Oi, D. A. Eimer, J. Chem. Eng. Data, 54(11) (2009), 3096-3100. [25] D. Fu, Y. F. Xu, X. Y. Hua, Fluid Phase Equilibr., 314(25) (2012), 121-127. [26] D. Fu, L. H. Chen, L. G. Qin, Fluid Phase Equilibr., 319(14) (2012), 42-47. [27] D. Fu, L. Wei, S. T. Liu, Fluid Phase Equilibr., 337(2013), 83-88. [28] S. Glasstone, K. J. Laidler, H. Eyring, The theory of rate process. New York: McGraw-Hill(1941). [29] L.

Grunberg,

A.

H.

Nissan,

Mixture

164(1949),799-800.

12

law

for

viscosity,

Nature,

Figure legends FIGURE 1 Effect of the mass fractions of AMP (w1) and PZ (w2) on the viscosity ( ) of CO2–unloaded AMP-PZ aqueous solution. w2=0.10 and w2=0.05(insert). Symbols: experimental data from this work. z T=298.15K; { T=303.15K; „ T=313.15K. … T=323.15K. Lines: calculated results.

FIGURE 2 Temperature dependence of the viscosity of AMP-PZ aqueous solution. Symbols: Main plot, experimental data from this work, w2=0.10, z w1=0.20, { w1 =0.25, „ w1=0.30; Insert plot, experimental data from refs. [20, 21], z w2=0.0174, w1=0.2826 [20], { w2=0.1035, w1=0.1965 [21]; Lines:

calculated results.

FIGURE 3 CO2 loading ( ) dependence of the viscosity of carbonated AMP-PZ aqueous solution at w2/w1=0.05/0.30 and w2/w1=0.10/0.30(insert). z T=298.15K, { T=303.15K, „ 313.15K, … T=323.15K; Lines: calculated results.

FIGURE 4 Effect of the mass fraction of amines on the viscosity of carbonated AMP-PZ aqueous solution. Main plot, w2/w1=0.10/0.30 (z =0.1; „ =0.3; ) and w2/w1=0.05/0.30 ({ =0.1; … =0.3; ---); Insert plot, w2 /w1=0.10/0.30 (zT=303.15K; „ T=323.15K; ) and w2/w1=0.05/0.30 ({T=303.15K; … 323.15K; ---). Symbols: experimental data from this work. Lines: calculated 13

results.

FIGURE 5 Temperature dependence of the viscosity of carbonated AMP-PZ aqueous solution

at

w2/w1=0.05/0.30

and

w2/w1=0.10/0.30(insert).

Symbols:

experimental data from this work. z =0.0; { =0.2; „ =0.4; …= =0.6. Lines: calculated results. : from the Weiland equation, ----: from the Eyring model.

14

FIGURE 1 16 8

12

/(mPa s)

6

4

/(mPa s)

2

0 0.20

0.24

0.28

0.32

0.36

w1

8

4

0 0.20

0.24

0.28

w1

15

0.32

0.36

FIGURE 2 12 5

/(mPa s)

4

8

3

/(mPa s)

2

1 290

300

310

320

330

340

T/K

4

0 290

300

310

T/K

16

320

330

FIGURE 3 16

14

12

/(mPa s)

12

10

8

/(mPa s)

6

4 0.1

0.2

0.3

0.4

0.5

0.6

8

4

0 0.1

0.2

0.3

0.4

17

0.5

0.6

FIGURE 4 12

16

/(mPa s)

12

10

8

4

8

/(mPa s)

0 0.1

0.2

0.3

0.4

0.5

0.6

T/K

6

4

2 290

300

310

T/K

18

320

330

FIGURE 5 12

16

12

/(mPa s)

10

8

4

/(mPa s)

8 0 290

300

310

320

330

T/K

6

4

2 290

300

310

T/K

19

320

330

TABLE 1. Provenance and purity of the samples studied

Chemical

CAS No.

Mass fraction

Molar mass

Density/(g cm-3) (293.15 K)

purity

PZ Huaxin

110-85-0

0.995

86.14

0.8760

AMP Huaxin

124-68-5

0.995

89.14

0.9172

21

TABLE 2 Viscosities

a

(mPa s) of carbonated AMP-PZ aqueous solutions under

different mass fractions of AMP (w1) and PZ (w2), and different CO2 loadings (mol CO2 per mol amines) /(mol CO2 per mol w1/ w2

0.25/0.05

0.30/0.05

0.35/0.05

/ mPa·s

amines)

T = 298.15 K

303. 15 K

313. 15 K

323. 15 K

0

3.92

3.31

2.43

1.87

0.10

5.63

4.87

4.63

3.50

0.20

6.09

5.05

4.84

3.84

0.30

6.25

5.54

4.93

4.03

0.40

6.68

6.03

4.99

4.23

0.50

7.19

6.28

5.51

4.90

0.60

7.84

6.39

5.86

5.42

0

4.83

4.01

3.18

2.75

0.10

6.42

6.05

5.00

3.92

0.20

6.91

6.71

5.78

4.16

0.30

7.78

7.32

6.51

5.03

0.40

8.48

7.89

6.80

5.94

0.50

9.04

7.94

7.09

6.31

0.60

9.92

8.54

7.86

6.75

0

6.08

5.14

4.22

3.35

0.10

8.27

7.99

6.91

5.35

22

0.20/0.10

0.25/0.10

0.30/0.10

0.20

9.54

8.76

7.34

5.77

0.30

10.12

9.44

7.84

6.48

0.40

10.56

9.76

8.23

7.06

0.50

11.24

10.28

8.63

7.66

0.60

12.18

10.86

9.26

8.28

0

3.93

3.47

2.50

1.99

0.10

6.80

6.06

4.83

4.12

0.20

6.98

6.25

5.24

4.40

0.30

7.23

6.34

5.37

4.54

0.40

7.46

6.64

5.68

4.63

0.50

7.82

7.06

5.99

4.82

0.60

8.35

7.63

6.24

5.24

0

5.38

4.73

3.82

3.08

0.10

7.56

7.41

5.85

4.34

0.20

7.95

7.73

6.25

4.56

0.30

8.46

7.99

6.67

4.94

0.40

8.68

8.38

7.08

5.47

0.50

9.26

8.74

7.41

5.73

0.60

9.62

8.94

7.78

6.56

0

7.31

6.54

5.21

3.96

0.10

8.57

7.90

7.06

5.31

0.20

9.09

8.68

7.35

5.39

23

0.30

9.45

9.02

7.86

6.10

0.40

10.42

9.99

8.19

6.79

0.50

11.35

10.96

8.75

7.11

0.60

12.85

12.22

9.89

7.82

a

Standard uncertainties are (T)= 0.05 K; (w)= 0.0001; ( )= 0.02 mol CO2 per mol amines; ( )= 0.01 mPa s

24

Research highlights

The viscosities of the carbonated AMP-PZ aqueous solutions were measured;

The experiments were modeled satisfactorily by using the Weiland equation; . The influence of the mass fractions of amines on the viscosity was illustrated;

The temperature and CO2 loading dependences of the viscosity were demonstrated.

25