2성분계(1,2-dichloropropane + 2-ethoxyethanol)의

과잉 몰부피 및 과잉 몰엔탈피 측정

김문갑, 이영세, 김영우

국립 상주대학교 화학공학과

Excess Molar Volumes and Excess Molar Enthalpies for

{1,2-dichloropropane + 2-ethoxyethanol} at T=298.15 K.

Moon-Gab Kim, Young-Sei Lee, Young-Woo Kim

Department of Chemical Engineering, Sangju National University

Introduction

A knowledge of the excess molar properties of liquid mixture is very useful to investigate the molecular interactions between solutions and to predict the solution behavior in other organic liquids. The 1,2-dichloropropane is used as solvents for a number of industrial chemicals(synthetic resins, pigments, and waxes etc.). It has lead to an increased interest in the thermodynamic properties of mixtures of 1,2-dichloropropane with additives for the purpose of wide applications

This paper reports excess molar volumes VEm and excess molar enthalpies HEm for the binary mixture {1,2-dichloropropane+2-ethoxyethanol} at 298.15K under atmospheric pressure. The results of VEm and HEm were correlated by the model of Redlich-Kister polynomial. The NRTL, Wilson, and UNIQUAC models were used to correlate the enthalpy of mixing data. A survey of the literature reveals no studies of VEm and HEm for this mixture.

Experimental Section

Chemicals in this study were the same as those used in the previous work[1] and were used without further purification. The purity of the chemicals was checked by comparing the experimental densities and refractive indices with the literature values. The densities of the pure components were determined at 293.15 K using a vibrating-tube densimeter(Model DMA 58, Anton Paar, Graz, Austria) equipped with an automatic sample changer(model SP3, Anton Paar, Graz, Austria) with a resolution □5□10-6 g/cm3 and refractive indices were measured by a refractometer(Model RA-520, Kyoto Electronics, Japan with an accuracy of □0.00001, which are listed in Table 1  with their corresponding literature values[2,3]. The apparatus was calibrated with bi-distilled and degassed water and dry air at atmospheric pressure. The temperature in the measuring cell was regulated to □0.01K. The sample solutions of different composition were prepared by mass in a sealed vial(approximately 50cm3) using a Mettler balance(model AT-201, Switzerland) accurate to within □0.1mg.

The excess molar enthalpies, HEm, were determined at 298.15 K, using an isothermal microcalorimeter with a flow mixing cell(Model CSC-4400, Calorimetry Sciences Corporation, Utah, U.S.A). The water bath of the calorimeter provided temperature control of □0.0005K. To eliminate the uncertainties in the volumetric flow rate, liquid components were kept into the glass bottles equipped with jacket, which were pumped into the mixing cell of the calorimeter by means of digital HPLC pump(Acuflow Series Ⅱ, Fisher Scientific, U.S.A) operated in a steady-state (fixed composition) mode at atmospheric pressure.  Pressure in the calorimeter was fixed by a back- pressure regulator. The pumps were  calibrated by determining the volumetric flow rate of bi-distilled water and a empirical correction equation was fitted for each pump. The total volumetric flow rate was 0.5□·min-1 depending on the magnitude of the measured heat signal. The performance of the calorimeter was examined by means of enthalpies of mixing for the systems cyclohexane+n-hexane(particularly for the endothermic processes) and water+ ethanol(particularly for the exothermic processes) recommended as a standard reference mixture in isothermal microcalorimeter [4-6]. In all cases the smoothed results agreed within 1.6% of previously published values.

Results and Discussions

The results of excess molar volumes and excess molar enthalpies at 298.15K for (1,2-dichloropropane + 2-ethoxyethanol) are listed in Tables 2 and Table 3, respectively. The experimental data of HEm and VEm were fitted to the Redlich-Kister equation[7] to correlate the compositin dependence of both excess properties :

[eqn: Q{E} atop {m}= x ~ (1- x ) SUM from { { j}=1} to 8 { A}_{ j}(1-2 x ) ^{j-1 }],                                         (1)

where QEm = HEm/J·mol-1 or VEm/cm3·mol-1 and x is the mole fraction of 1,2-dichloropropane. Values of the coefficients Aj, determined by a Nelder-Mead simplex pattern search method[8], are given in Table 4 along with standard deviations □ :

[eqn: □= LEFT [ SUM from { { i}=0} to N LEFT { Q{E} atop {m}(expt)-Q{E} atop {m}(calc) RIGHT }^2 / LEFT ( N - r RIGHT ) RIGHT ] ^{1/2}],                              (2)

where QEm is either HEm or VEm , N is the number of experimental points and r is the number of coefficients.

The experimental HEm data were fitted to the Wilson[9], NRTL[10], and UNIQUAC[11] models. The adjustable parameters □12=a12□a11, □21=a21□a22 in the Wilson equation, and □g12=g12□g22, □g21=g21□g11,  and □12 in the NRTL equation, and □u12 and □u21 in the UNIQUAC equation are summarized in Table 5 together with the standard deviations.

The heats of mixing, HEm equations are derived by differentiation of the Gibbs-Helmholtz relation :

[eqn: H{E} atop {m } = -RT^2 LEFT [ {□(G^E /RT) } over {□T } RIGHT ]_P,x]                                           (3)

From this equation, the following expressions(Wilson, NRTL, and UNIQUAC) can be obtained in equations (4), (5) and (6), respectively :

[eqn: {H {E } atop {m } } over {RTx_1 x_2 }= { □_12 □_12 } over {x_1 + □_12 x_2 } + { □_21 □_21 } over {x_2 + □_21 x_1 }],                                         (4)

where[eqn: □_12 = V_2 /V_1 exp(-□_12 / RT)]and[eqn: □_21 = V_1 /V_2 exp(-□_21 / RT)]

[eqn: {H {E } atop {m } } over {RTx_1 x_2 }= { x_2 + x_1 exp(□_12 □_21 )(1- □_12 □_21 ) } over {{ left {x_1 exp(□_12 □_21 ) + x_2 right } }^2 } ·□_21 + { x_1 + x_2 exp(□_12 □_12 )(1- □_12 □_12 ) } over {{ left {x_2 exp(□_12 □_12 ) + x_1 right } }^2 } ·□_12] ,                                                                         (5)

where □12=(g12□g22)/RT and □21=(g21□g11)/RT,

[eqn: H {E } atop {m } = q_1 x_1 left ( { □_2 □_21 □u_21} over {□_1 + □_2 □_21 } right ) + q_2 x_2 left ( { □_1 □_12 □u_12} over {□_2 + □_1 □_12} right )],                          (6)

where □12=exp(□□u12/RT), □21=exp(□□u21/RT), and □i=xiqi/(□xiqi).

From Fig. 1, the dependence of VEm on compositions has an S-shaped form, being negative for rich and positive for poor 2-ethoxyethanol mole fractions. This shows that a relatively high energy is needed to break hydrogen bonds of 2-ethoxyethanol with an increase of  halogenated hydrocarbon molecular during mixing. These positive deviations from ideal behavior are coincident with loosening of intermolecular interaction of a component(2-ethoxyethanol) with strong self-association.  The minimum and maximum values of this mixture are found to be about １0.016 cm3·mol-1 at x=0.12 and about 0.174 cm3·mol-1 at x=0.77, respectively. The dependence of HE on compositions has the same form as those shown in VEm , being a positive region due to the destruction of hydrogen bonding and a negative region due to the formation of complex between two liquids. The Wilson, NRTL, and UNIQUAC interaction energy parameters are given in Table 5 together with the standard deviations. The NRTL equation was found to be more suitable than the Wilson or UNIQUAC equation for this system.

References

1. Kim, M. G., Lee, Y. S., J. Kor. Soc. of Ind. Appli., 4, 2, 193(2001)

2. Lide, D. R. "CRC Handbook of Chemistry and Physics", 74th ed., CRC         Press(1993)

3. Dean, J. A., : Lange's Handbook of Chemistry, 14th ed., McGraw-Hill(1992)

4.  Tanaka, R., D'arcy, P. J., Benson, G. C., Thermochimica Acta, 11,                163-175(1975)

5. Chand, A., Fenby, D. B., J. Chem. Thermodyn., 10, 997-1001(1978)

6. Sabbah, R., Xu-wu, A, Chickos, J. S., Planas Leit　o, M. L., Roux, M. V.,        Torres, L. A., Thermochimica Acta, 331, 93-204(1999)

7. Redlich, O., Kister, A. T., Ind. Eng. Chem., 40, 345-348(1948)

8. Nelder, J. A. and Mead, R., Comp. J., 7, 308-313(1965)

9. Wilson, G. M., J. Am. Chem. Soc., 86, 127(1964)

10. Renon, H., Prausnitz, J. M., AIChE J., 14, 135(1968)

11. Abrams, D. S., Prausnitz, J. M., AIChE J., 21, 116(1975)

Table 1. Densities and refractive indices of pure components and comparison with literature values at 20□
Component	□/g·cm-3				n20D
	Expt.	Lit.[2]	Lit.[3]		Expt.	Lit.[2]	Lit.[3]
1,2-dichloropropane	1.15471	1.1560	1.1558		1.43917	1.4394	1.4390
2-ethoxyethanol	0.93030	0.9297	0.9295		1.40810	1.4080	1.4075

Table 2. Densities, □m and excess molar volumesa, VEm for binary mixture of {x1,2-dichloropropane + (1-x)2-ethoxyethanol} at 298.15 K
x	□m	VEm	VEm	x	□	VEm	VEm	x	□m	VEm	VEm
		Expt.	R-K			Expt.	R-K			Expt.	R-K
0.000	0.92576	0	0	0.348	1.00334	0.0292	0.02836	0.698	1.07969	0.1662	0.16685
0.050	0.93714	-0.0128	-0.01272	0.398	1.01424	0.0477	0.04969	0.748	1.09060	0.1737	0.17350
0.098	0.94801	-0.0157	-0.01534	0.448	1.02521	0.0736	0.07282	0.797	1.10141	0.1735	0.17318
0.148	0.95909	-0.0132	-0.01470	0.497	1.03577	0.0945	0.09569	0.850	1.11313	0.1628	0.16267
0.198	0.97038	-0.0124	-0.01093	0.547	1.04656	0.1198	0.11788	0.898	1.12400	0.1393	0.13975
0.248	0.98132	-0.0036	-0.00277	0.597	1.05759	0.1371	0.13778	0.950	1.13595	0.0910	0.09075
0.297	0.99213	0.0118	0.01014	0.647	1.06845	0.1545	0.15438	1.000	1.14804	0	0
aUnit : cm3·mol-1

Table 3. Excess molar enthalpiesa, HEm for binary mixture of {x1,2-dichloropropane + (1-x)2-ethoxyethanol} at 298.15 K
x	HEm	HEm	HEm	HEm	HEm	x	HEm	HEm	HEm	HEm	HEm
	Expt.	R-K	Wilson	NRTL	UNIQUAC		Expt.	R-K	Wilson	NRTL	UNIQUAC
0.039	-45.4	-45.9	0.2	-35.5	-17.3	0.557	201.2	200.4	171.4	194.8	164.3
0.098	-87.7	-87.2	4.5	-73.0	-35.5	0.597	245.1	244.1	192.9	243.6	206.1
0.138	-101.9	-101.6	9.9	-87.5	-42.2	0.638	285.1	286.0	214.5	291.2	250.2
0.178	-105.5	-105.8	17.4	-93.2	-44.2	0.678	321.2	322.5	234.6	332.8	292.9
0.238	-92.3	-93.6	32.3	-86.2	-38.5	0.718	352.2	352.5	252.6	366.7	333.0
0.278	-75.9	-74.0	44.6	-71.5	-28.8	0.758	374.7	373.9	267.2	389.5	367.6
0.318	-45.8	-46.6	58.7	-49.4	-14.3	0.798	384.7	384.2	276.3	397.1	392.3
0.357	-13.0	-13.8	74.0	-21.3	4.4	0.838	380.2	379.9	276.8	384.8	401.0
0.397	23.7	24.6	91.2	13.6	28.2	0.878	356.2	355.4	263.7	347.1	384.8
0.437	66.1	66.4	109.7	53.8	56.4	0.919	296.0	298.9	227.2	275.1	328.4
0.477	109.6	110.4	129.5	98.3	88.8	0.959	196.2	194.1	152.7	164.5	213.6
0.517	156.1	155.4	150.1	145.8	124.9
aUnit : J·mol-1

Table 4. Coefficients Ai, and standard deviations □ for VEm and HEm for binary mixture of {x 1,2-dichloropropane + (1-x) 2-ethoxyethanol} at 298.15 K by equation (1)
	A0	A1	A2	A3	A4	A5	A6	A7	□
VEm	0.38826	-0.91604	0.13968	-0.09847	0.55934	0.19565	-0.08829	-0.64492	0.00123a
HEm	544.80	-2256.31	680.85	-821.09	388.10	542.55	779.16	-1314.09	1.27700b
aUnit : cm3·mol-1 bUnit : J·mol-1

Table 5. Adjustable parameters(□12 and □21, Wilson; □g12 and □g21 and □12 , NRTL; □u12 and □u21, UNIQUAC)a used in eqs. (4), (5) and (6) for correlating HEm together with standard deviations, □
Wilson			NRTL				UNIQUAC
□12	□21	□	□g12	□g21	□12	□	□u12	□u21	□
-764.7	5969.6	85.67	10746.6	-4117.1	0.11925	12.86	3579.2	-1006.6	34.1
aUnit: J·mol-1

Fig. 1. Excess molar volumes VEm for binary mixture of {x1,2-dichloropropane and (1-x)2-ethoxyethanol} at 298.15K : □, this work; □, Redlich-Kister model using parameters listed in Table 4.		Fig. 2. Excess molar enthalpies HEm for the system of {x1,2-dichloropropane and (1-x)2-ethoxyethanol} at 298.15K : □, this work; □, Redlich-Kister model using parameters listed in Table 4; and □, Wilson; □, NRTL; □, UNQUAC model using parameters listed in Table 5.