Excess enthaplies of binary mixtures toluene + propylbenzene, + butylbenzene and + hexylbenzene at 298.15, 308.15 and 318.15 K

lille ELSEVIER

Fluid Phase Eqmhbrla 102 (1994) 205-210

Excess enthaplies of binary mixtures toluene + propylbenzene, + butylbenzene and + hexylbenzene at 298.15, 308.15 and 318.15 K D.V.S.

Jain *, R. C h a d h a ~, N.S. D h a r 2

Department of Chenustry, Panjab Untverstty, Chandtgarh 160 014, hldla Recewed 29 December 1993, Accepted m final form 9 May 1994

Abstract

Excess molar enthalples of binary mixtures of toluene + propylbenzene, +butylbenzene, +lsopropylbenzene and +hexylbenzene have been determined at 298.15, 308.15 and 318.15 K using a flow mlcrocalorimeter. Mean excess heat capacities have been derived from H E values measured m the temperature range 298 15-318 15 K

Keywords" Data, Method; Density, Excess enthapies; Excess heat capacities; Mixtures

Introduction

We have previously published the excess molar enthalpies of binary mixtures of benzene + propylbenzene, + butylbenzene and + hexylbenzene (Jain and Dhar, 1989) and also ethylbenzene +propylbenzene, +butylbenzene and +hexylbenzene (Jain and Dhar, 1992) at various temperatures. In this paper we report excess enthalpies of binary mixtures of toluene +propylbenzene, +butylbenzene and +hexylbenzene at 298.15, 308.15 and 318.15 K. The H E data have been used to estimate the average CpE in the temperature range 298.15-318.15 K Woycicki and Sadowska (1977) and Woycicki (1977) have reported excess enthalpies of these mixtures at 298.15 K. As far as we know, no other C E data for these systems have been reported.

* Corresponding author ~Present address: Department of Pharmaceutmal Sciences, Panjab Umverslty, Chandlgarh 160 014, India 2 Present address: Division of Thermochemlstry, Chemical Centre, University of Lund, Sweden 0378-3812/94/$07 00 (C' 1994 - Elsevier Science B.V All rights reserved SSDI 0 3 7 8 - 3 8 1 2 ( 9 4 ) 0 2 5 3 9 - D

D V S Jam et al / Fluid Phase Equtllbrla 102 (1994) 205-210

206

Table 1 Densltms of pure components at 298 15 K Density (kg m-3)

Component

Toluene Propylbenzene Butylbenzene Hexylbenzene

Experimental

Literature a

862.20 857.80 856 09 854 60

862.25 d 857.74 b 856.07 c 854 5 a

Fortler and Benson (1979) b API Project 44 (1969) Rlddxck and Bunger (1970) d Woycmkl (1977)

2. Experimental

2.1. Materials Toluene (Glaxo, India, 99.0%), proplybenzene (Fluka 98%), butylbenzene (SISCO-Chem, India, 98%) and hexylbenzene (Fluka AG, Switzerland, 97%) were purified as described in our previous paper (Jain and Dhar, 1992). The purity of the chemicals was checked by measuring their densmes using a vibrating-tube densitimeter (DMA, Anton Paar 60/602) and comparing the experimental results with the best available literature values (Table 1).

2.2. Procedure The calorimeter used for the determination of excess enthalpy is a flow microcalorimeter of thermopile heat conduction type (LKB, Bio-Activity Monitor-2277). A general description of the instrument is given by Monk and Wadso (1968) and Suurkuush and Wadso (1982). Various aspects of design, working and calibration have been reviewed by Harsted and Thomsen (1974) and Tanaka et al. (1975). Experimental details are given in our previous paper (Jain and Dhar, 1992).

3. Results

The experimental excess molar enthalpies at 298.15, 308.15 and 318.15 K for these mixtures are given in Table 2, and Fig. 1 gives a graphical presentation of the results at 298.15 K. The experimental results were fitted by the method of least squares to the equation H E = ( 1 - - x ) x ~ h,(2x--1)' t=O

(1)

D . V S Jam et a l / Flutd Phase Equdlbrta 102 (1994) 205-210

207

Table 2 Excess molar enthalpies of toluene with propylbenzene, butylbenzene and hexylbenzene at 298 15, 308 15 and 318.15 K x

H E (J mol -I) 298 15 K

x 308.15 K

318 15 K

H E (J mo1-1) 298 15 K

308 15 K

318 15 K

Toluene + propylbenzene 0 0000 0.1340 0 2339 0 2790 0.3753 0 4329

00 2.3 35 38 45 46

00 2.2 32 3.5 40 4.1

00 19 30 32 3.7 39

0.4923 0 6010 0.6563 0.7902 0 8272 1 0000

45 42 39 28 2.4 00

42 3.9 38 2.6 22 00

3.8 37 32 24 2 1 00

00 8.9 13 3 14 7 16.7 16 8

0.0 79 12.3 13 2 14.8 15 2

0.4647 0.5738 0.6311 0 7711 1 0000

19 5 17 8 16.4 11 3 00

16 8 15 5 14.4 10.2 0.0

15 1 14 2 13 2 90 00

0.0 22.5 25 9 39.9 44 4 50.2 51.6

00 19.2 22.9 35.4 40 5 46 0 46 9

0 3610 0.4154 0 5284 0 5859 0.7412 0.7827 1.0000

55 8 55 3 51 5 48 3 35 3 31.1 0.0

52 2 51 8 48 5 46 7 33 1 29.2 0.0

47 0 47 2 44 5 41 8 30.3 26 5 00

Toluene + butylbenzene 0 0000 0 1215 0 2145 0.2570 0.3492 0 3883

0.0 95 14 3 16 3 18.6 19 3

Toluene + hexylbenzene 0.0000 0.0814 0 1003 0 1810 0 2217 0.3099 0.3428

0.0 23.7 28.0 42.4 47 2 54 1 55.0

Here x represents the mole fraction of the second component. The values of the coefficients h, and the standard deviations are listed in Table 3. The coefficients are used to obtain the calculated solid curves in Fig. 1. As far as we know, only Woycicki and Sadowska (1977) and Woycicki (1977) have reported H E for these systems at 298.15 K. Their values of H E at 298.15 K are compared m Fig. 1 with these in the present work. It can be seen that the literature values of H E for toluene +propylbenzene and + hexylbenzene at 298.15 K are about 5% higher than our results and for toluene + butylbenzene the H E results of Woycicki and Sadowska (1977) show (a little above their experimental error) triple extrema, in contrast with the present results which show a single maximum. The H E values for mixtures o f toluene and isopropylbenzene are negative (Jain et al., 1992) while they are positive for toluene + propylbenzene. The difference in H E between the two sets o f results cannot be attributed to the free volume effect because propylbenzene and isopropylbenzene have almost the same free volume. However, the difference in H E is consistent with the differences in their physical properties, i.e. density and heat o f vaporization. For all the mixtures H E decreases with temperature. Mean excess heat capacities for the three mixtures have

D. V S. Jain et a/ /Flutd Phase Equihbrta 102 (1994) 205-210

208

56 48

7

~o

E 32 z

24 )6 8

0.2

0.4

0.6

0.8

!.0

x

Fig 1 Excess molar enthalples of binary mixtures, toluene + propylbenzene (©), +butylbenzene ( ~ ) , and +hexylbenzene ([]) at 298 15 K (hnes are the smoothed representations of the data) 0 , toluene + propylbenzene at 298 15 K (Woyclckl and Sadowska, 1977), A, toluene + butylbenzene at 298.15 K (Woyclckl and Sadowska, 1977), II, toluene + hexylbenzene at 298 15 K (Woycackl, 1977) Table 3 Values of parameters h, m Eq. (1) along with the standard deviations of H E for various mixtures at 298 15, 308 15 and 318 15 K System

T (K)

h, (J tool l) ho

~ (J tool i) hi

h2

Toluene + propylbenzene

298.15 308 15 318 15

18 17 16.83 15 59

- 2 42 --1 66 -- 1 71

0.03 - 0 19 -0.68

0 06 006 0 06

Toluene + butylbenzene

298.15 308.15 318.15

76 56 66.42 60.07

--20 56 - 19.21 - 17.29

- 6 90 4 78 4.01

0.14 0 10 0 37

Toluene + hexylbenzene

298 15 308.15 318.15

212 06 200.61 182 87

-84.28 - 75 91 --68 04

51 51 44.00 32 78

0 32 0 41 0 37

been derived from the H E results in the temperature range 298.15-318.15 K and these are given m Table 4 while Fig. 2 gives a graphical presentation of the data. It can be seen from Fig. 2 that C E for these systems is negative and C~ becomes more negative as the chain length difference between the two components increases.

D . V S Jam et al / Flutd Phase Equtlibrta 102 (1994) 205 210

209

Table 4 Mean excess molar heat capacities for the binary mixtures m the temperature range 298.15-318 15 K Toluene + propylbenzene

Toluene + butylbenzene

Toluene + hexylbenzene

x

CE(JK

x

C E ( J K -1 mol l)

x

C E ( J K -1 mol -I)

0 10 0 20 0.30 0 40 0 50 0 60 0 70 0 80 0 90

--0 02 --0.03 --0 03 - 0.03 --0 03 - 0 03 --0 03 --0 02 --0 01

0 10 0.20 0.30 0 40 0.50 0.60 0 70 0.80 0 90

- 0 05 -0.12 -0.17 - 0.20 -0.21 - 0 18 -0.14 - - 0 08 --0 03

0 10 0.20 0 30 0.40 0.50 0 60 0.70 0 80 0.90

- 0 24 - 0 37 - 0 41 - 0.40 - 0 36 --0 32 --0 27 - 0 21 --0 13

i mol l)

o.0

-o,F\ i~¢

ti71

- 0.3

,2 0.5

0

!.0

x

Fig 2. Mean C E for the binary mixtures of toluene + propylbenzene ( A ) , +butylbenzene ( ©) and + hexylbenzene ([2]) m the temperature range 298.15-318.15 K (lines are the smoothed representations of the data)

Table 5 Coefficients c, for Eq. (2) along with standard devmtlons of CpE for various binary mixtures in the temperature range 298 15--318 15 K System

Toluene + propylbenzene Toluene + butylbenzene Toluene + hexylbenzene

c , ( J K -1 mo1-1)

s ( J K 1 mol ~)

CO

C1

C2

-0.124 --0 827 -- 1 457

0 354 0.184 0 818

-0.085 0.578 -0.970

0.003 0 004 0 004

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210

T h e C ~ - x d a t a were fitted to Eq. (2) b y the m e t h o d o f the least squares: CpE = ( 1 - x )

x

~ c,(2x-1)'

(2)

t--0

T h e values o f the p a r a m e t e r s c, a n d the s t a n d a r d d e v i a t i o n s s are given in T a b l e 5.

List of symbols h, coefficients in Eq. (1) H E excess m o l a r e n t h a l p y c, coefficients in the Eq. (2) CpE excess heat c a p a c i t y x mole fraction of c o m p o n e n t 2

References API project 44, 1969. Thermodynamic Research Centre, Texas A&M University, College Station, TX Fortler, J L and Benson, G C, 1979. Heat capacities of some aromatic hydrocarbon mixtures containing benzene or toluene J Chem. Eng Data, 24. 34 Harsted, B S and Thomsen, E.M., 1974 Excess enthalples from flow mlcrocalorlmetry. J. Chem Thermodyn, 6 549 Jam, D V S and Dhar, N S., 1989. Excess enthalples of binary mixtures benzene + propylbenzene, +butylbenzene, +hexylbenzene at 298.15, 308 15, 318.15 K , 1989 Fluid Phase Equilibria, 47" 89. Jam, D.V S, and Dhar, N S., 1982 Excess molar enthalples of binary mixtures ethylbenzene + propylbenzene, +propylbenzene, +butylbenzene, and +hexylbenzene at 298.15, 308.15, 318 15 K Fluid Phase Equlhbrla, 81 231 Jam, D V.S, Chadha, R and Dhar, N S., 1992. Excess molar enthalples of (benzene or methylbenzene or ethylbenzene + 2-methylethylbenzene) at 298.15, 308 15 and 318 15 K. J Chem. Thermodyn., 24:1027 Monk, P and Wadso, I, 1968. A flow micro-reaction calorimeter. Acta Chem Scand, 22 1842. Rlddlck, J and Bunger, W B, 1970 Organic Solvents Wdey, New York. Suurkuush, J. and Wadso I, 1982 A multlchannel mlcrocalorametry system Chem. Scr, 20 155 Tanaka, R D'Arcy, P J and Benson, G C, 1975. Apphcatlon of a flow m~crocalorlmeter to determine the excess enthalples of binary mixtures of non-electrolytes. Thermochlm Acta, 11' 163 Woyclcki, W, 1977. Excess enthalples of alkylbenzene mixtures. Bull Acad. Pol Sc~, Ser Scl Chim, 25 553 Woyclckk W , and Sadowska, K W, 1977 Excess enthalples and excess volumes of alkylbenzene mixtures Bull. Acid Pol Sci., Ser Scl Chlm., 25 115