Water/2-Amino-2-ethyl-1-3-propanediol계의 밀도, 점도,

표면장력 측정

윤상준, 이현송, 이 흔

한국과학기술원 화학공학과

Density, Viscosity and Surface Tension Measurements of Water / 2-Amino-2-ethyl-1-3-propanediol System

Sang Jun Yoon, Hyun-Song. Lee, Huen. Lee

Department of Chemical Engineering, KAIST

Introduction

Alkanolamine solutions are widely used in synthesis, refinery and any other gas stream industry for the removal of acidic compound such as CO2 and H2S. Especially, after we knew that global warming effect is primarily due to CO2, separation of CO2 from every industries have been of great interest. The species of widely used alkanolamines are monoethanolamine(MEA), diethanolamine(DEA), N-methyldiethanolamine(MDEA), di-2-propanolamine (DIPA). These materials are studied by many researchers and have been used industrially.(1,2) Because of more good characteristics for absorption capacity, selectivity, absorption rate, and degradation than previous absorbents, sterically hindered amines are proposed to removal of acid gases.(3) Already experimented sterically hindered amines are 2-amino-2-methyl-1-propanol(AMP), 2-piperidineethanol(PE) and 2-amino-2-methyl-1,3- propanediol(AMPD). Physical properties such as density, viscosity and surface tension are required for design of the acid gases removing plant. Research for AEPD has not appeared in the literature.

In present study, we provide the density, viscosity and surface tension of the binary water + AEPD mixtures at temperatures ranging from 303.15 to 343.15K using a pycnometer, various viscometer and a capillary tube, respectively.

Experimental Apparatus and Method

2-Amino-2-ethyl-1-3-propanediol (97%+ purity) was purchased from Acros Organics and was used without further purification. AEPD solution was prepared using triple-distilled water.

Density measurement of binary solution mixture was performed using pycnometer. A water bath was used to maintain the mixture temperature within a pycnometer. Water bath can be controlled temperature constantly within 0.05K. Temperature of solution was measured by mercury-filled glass thermometer. A Satorius R120S balance with a precision of 0.0001g was used for weight measurements of liquid mixtures. Primary we check the volume of pycnometer using water.

Viscosities of binary mixture were measured by appropriate Ubbelohde type viscometers (Witeg) of various capillary sizes. Temperature of solution in viscometer was maintained by water bath, in which controlled to within 0.05K. Electronic stopwatch was used to measure the efflux times of liquid solutions with an accuracy of 0.01s. The kinematic viscosity of solution was calculated by multiplication of efflux time with viscometer constant that was given from manufacturing company. If we knew the density of solution, the dynamic viscosity was estimated by multiplication of kinematic viscosity with density value. The efflux time of each data set was measured at least three times and averaged.

The surface tension measurement apparatus consists of cathetometer, capillary tube, water bath, liquid circulator, and thermometer. The detailed figure of apparatus was described elsewhere.(4) Thermometer was immersed into the sample so that was measured the temperature directly with a precision of 0.1K. The height of liquid rise in the capillary tube was determined by the cathetometer (N.O.W. NCM 30) with an accuracy of 10-5m. The diameter of capillary tube was calibrated with benzene at various temperatures and averaged value of diameter was used to calculate the surface tension.

Results and Discussion

1. Density

For the check of reliability of our experiment, the density of pure AEPD was measured at 293.15K. Only one data was founded in the literature.(5) Density of pure AEPD was good agreement with literature data. Experimented data of binary mixture were measured over the temperature ranging from 303.15 to 343.15K and the AEPD concentration of 20, 40, 60, 70, 80, and 100wt%. Each data set was repeated more than three times and averaged. Maximum deviation of the average value is less than 0.3%.

The experimented data were regressed using the following polynomial:

(1)

where x is weight fraction of AEPD. In Figure 1, the experimented and calculated density of water/AEPD mixture were plotted to temperature at various weight percents of AEPD. Each data were good agreed well with a 0.07% ADD value. While the temperature increased, the density of binary mixture decreased linearly. Especially the difference of density decreased with the weight percent of AEPD increased.

2. Viscosity

The viscosity of binary mixture at temperature of 303.15, 313.15, 323.15, 333.15, 343.15K were studied at various different AEPD compositions of 20, 40, 60, 70, 80wt%. The following equation was used to fit the studied viscosity data.

(2)     The maximum deviation value was found about 1%. The measured and calculated viscosity data were compared graphically in Figure 3. As the composition of AEPD increased, the viscosity of water/AEPD mixture increased dramatically.

3. Surface tension

To verify the reliability of experimental apparatus and procedure used in this work, the surface tension of water was measured and compared with an appropriate literature value.(6) Every data point was repeated more than six times and the maximum deviation of data at the same condition is less than 0.7%. After that, surface tension of water + AEPD binary mixture system was obtained at the same condition with viscosity measurement. These experimental results were correlated as a function of temperature and concentration of AEPD in water by the same expression with equation (1) used in density correlation. The average absolute deviation value was found to be 0.423%.

Experimented and calculated surface tension data were plotted in Figure 4 at various temperatures and compositions. As can be seen in Figure 4, surface tension of binary mixture decreased with increasing temperature and concentration of AEPD. In the case of 20wt% AEPD condition, the decreasing slop is slightly different with others. But its slop is almost similar to the shape of water. Because the state of 20wt% AEPD is more resemble to water than AEPD.

Reference

(1) Li, M.-H.; Lie, Y.-C. Densities and Viscosities of Solutions Monoethanolamine + N-Methyldiethanolamine + Water and Monoethanolamine + 2-Amino-2-methyl-1- propanol + Water. J. Chem. Eng. Data 1994, 39, 444-447.

(2) 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, 29-34

(3) Sartori, G.; Savage, D. W. Sterically Hindered Amines for CO2 Removal from Gases. Ind. Eng. Chem. Fundam. 1983, 22, 239-249.

(4) Lee, J.-W.; Park, S.-B.; Lee, H. Density, Surface tension, and Refractive Indices of the Water + 1,3-Propanediol System. J. Chem. Eng. Data 2000, 45, 166-168.

(5) Susan, B. The Merck Index, 12th ed.; Merck & Co., Inc.: Whitehouse Station, NJ, 1996.

(6) David, R. L. CRC Handbook of Chemistry and Physics, 76th ed.; CRC Press: Boca Raton, FL, 1995-1996.

Figure 1. Densities of water+AEPD             Figure 2. Viscosities of water + AEPD

system as a function of temperature             system as a function of temperature

at various weight fraction of AEPD             at various weight fraction of AEPD

: (●) 0.2; (○) 0.4; (■) 0.6; (□) 0.7;         : (●) 0.2; (□) 0.4; (▲) 0.6; (▽) 0.7;

(▲) 0.8; (◇) 1.0; (◆) reference               (◆) 0.8 ; (―) calculated.

(―) calculated.

Figure 3. Surface tensions of water+AEPD

system as a function of temperature

at various weight fraction of AEPD

: (●) 0.2; (○) 0.4; (▼) 0.6; (▽) 0.7;

(■) 0.8; (◆) water; (□) reference;

(―) calculated.