Study on the binary mixtures of alkyls alfa, omega-dihalogenated (chlorine, bromine, iodine) with...

RIIIDPHU[ i$11Llllll

E L S E V I E R Fluid Phase Equilibria 109 (1995) 205-225

Study on the binary mixtures of alkyls alfa,omega-dihalogenated (chlorine, bromine, iodine) with n-alkanes. An improvement by

considering the variation of the interaction parameter with the chain length

Juan Ortega, Jose Plficido

Laboratorio de Termodin6mica y Fisicoqulmica, Escuela Superior de Ingenieros Industriales, University of Las Palmas de G.C., Canary Islands, Spain

Received 1 August 1994; accepted 15 March 1995

Abstract

The mixing enthalpies of alkyl dihalides (C1,Br,I) + n-alkanes binary liquid mixtures are examined on the basis of the UNIFAC group contribution method. All the data available in the literature for excess enthalpies and excess volumes are taken into consideration in order to interpret the behavior of the mixtures. The HEs are analyzed using several versions of the UNIFAC model using the interaction parameters already published. The predictions are acceptable in all cases for the mixtures (a,to-dichloroalkanes + n-alkanes), however, the estimations of the H E for (o~,to-dibromo or diiodoalkanes + n-alkanes) are inadequate. Therefore, a wide data base was used to recalculate new values for alkane/halide interaction in the version of the model proposed by Rupp et al., 1984 and considering different assumptions. A substantial improve in the predictions is observed when a variation of the interaction parameter values with the chain-length of the mixtures components is taken into account. In this case, the UNIFAC model predicts the HEs of a set of 82 new systems with an over all mean error lower than 4%.

Keywords: Liquid mixtures; UNIFAC model; Excess enthalpies

I. Introduction

In this paper we want to analyze the application of the UNIFAC model to the mixtures (alkyl dihalide + n-alkanes) and, therefore, an analysis of the quality and quantity of existing literature values for mixtures of (alkyl halides +n-alkanes) was undertaken, in the interest of further systematizing the program of research. Several studies have previously dealt with the HE values for systems containing n-alkanes and alkyl monohalides, namely, chlorides, bromides and iodides. Analysis of the literature values suggested a certain consistency and regularity, which led us to verify

0378-3812/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0378-3812(95)02732-7

206 J. Ortega, J. Plhcido / Fluid Phase Equilibria 109 (1995) 205-225

the results for other mixtures containing polyhalogenated components; however, the literature did not contain many values for mixtures of alkyl tri-and tetrahalides but did contain values for alkyl ot,to-dihalogenated (chlorine and bromine), which will be discussed in the following section. The analysis of the literature values for binaries ( a , w-dichloro and c~, w-dibromoalkanes + n-alkanes) were not entirely suitable for modelling such systems and thus cannot provide an appropriate frame of reference for our studies on (alkyl halides + alkane or esters), yet there is an obvious need for such values. This made redetermination of the mixing magnitudes for the binary systems { a, to-dihalides (C1,Br,I) + n-alkanes} both appropriate and necessary, to establish a suitable database for use in modelling. The experimental portion of this research has already been reported elsewhere by Ortega and Plhcido (1993a), Ortega and Pl~cido (1993b), Ortega and Plficido (1993c).

The mixtures considered were analyzed using two versions of the UNIFAC model, designated UNIFAC-1 (Rupp et al., 1984) and UNIFAC-2 (modified UNIFAC, Larsen et al., 1987; Weidlich and Gmehling, 1987), and using the interaction parameters already published in the literature. The parameter values for CH2/I unavailable in the literature, were calculated for this study, and the parameter values for CH2/C1 and CH2/Br were recalculated as necessary. The possible relationship between the interaction parameter values and the carbon chain length of the components employed was also considered.

2. Review of literature values

The error between the H E c u r v e s for (1,2-dichloroethane + n-hexane) reported by Bafios et al. (1983) and Nigam and Aggarwal (1986) was 11%. The discrepancy between the values for (1,2-dichloroethane + n-heptane) of Nigam and Aggarwal (1986) and Rhim and Bae (1979) was 26%, the same as that between the curves published by Rhim and Bae (1979) and Svejda and Demiriz (1979). There was an error of 51% between the values for (1,2-dichloroethane + n-hexadecane) presented by Bafios et al. (1983) and Svejda and Demiriz (1979). The values of Bafios et al. (1990a) for the system (1,3-dichloropropane + n-hexane) showed good agreement with the values in Polo et al. (1980); however, the differences between the curves published by those workers and those of Grolier and Kehiaian (1973) cannot be accounted for and amounted to nearly 300 Jmo1-1 at the maximum. The mean error of 27% between the data of Bafios et al. (1983) for (1,2-dichloroethane + n-hexadecane) at 308.15 K and those of Svejda and Demiriz (1979) for the same system at 313.15 K seems somewhat high. The HEs reported by Rhim and Bae (1979) at 318.15 K and Svejda and Demiriz (1979) at 313.15 K for (1,2-dichloroethane + n-heptane) likewise exhibited discrepancies, with a mean error of 71%. The values for (1,2-dichloroethane + n-hexane) by Chaudari and Katti (1990) at 303.15 K and by Nigam and Aggarwal (1986) at 298.15 K, differ by 21%, or nearly 200 Jmo1-1, at equimolar concentrations. The error for that same mixture at 303.15 K by Chaudari and Katti (1990) and Bafios et al. (1983) was 16%. The curves for (1,2-dichloroethane + n-hexane) at 308.15 K of Bafios et al. (1983) and Nigam and Aggarwal (1986) differ by 17%; the discrepancy appears to be ascribable to nonsymmetry in the shapes of these curves. The difference in the H E curves for (1,2-dichloro-ethane + n-heptane) at that same temperature, 308.15 K, of Rhim and Bae (1979) and Nigam and Aggarwal (1986) was 73%.

Turning to the literature values for mixtures with dibromides, the most significant discrepancy was a mean error of 34% between the data of (1,2-dibromoethane + n-hexane) by Delmas and Purves

J. Ortega, J. Pldcido / Fluid Phase Equilibria 109 (1995) 205-225 207

(1977) and Mor6n et al. (1985). Other values for such mixtures included H E values for (1,2-dibromoethane + n-hexane) at 288.15 K published by Baud (1915), and the values for {n-hexane + (1,3- dibromopropane to 1,8-dibromooctane)} at 298.15 K given in Artal et al. (1991).

The foregoing review cast doubt on the validity of the literature values and hence suggested that they were unsuitable an unsuitable framework for use in verifying data quality. For that reason, we believed the necessity to redetermine the H E values for a set of 70 new mixtures of {alkyls ce,w-dihalogenated (CI,Br)(a = 1, t o = 2 to 6 ) + n-alkanes (from C 5 to C17) } at 298.15 K. New values were also determined for 12 mixtures of ( a , w-diiodoalkanes + n-alkanes) that proved to be fully soluble; no literature values were found for those mixtures.

3. Analysis of the new experimental results

As stated above, the experimental portion of this study involved measuring H E values at T = 298.15 K for the binaries (a,o)-dihalogenated alkyl + n-alkanes), expressed empirically as { x l C u H E u X 2 ( X = CI,Br,I)(u = 2 to 6) + x 2 n - C v H E v + 2 (v = 5 ,7 .... 15,17)}. Because of partial miscibility of certain mixtures containing diiodoalkanes, only the systems { 1,5-diiodopentane + n-alkanes (v = 5,7 ..... 17)} could be measured. The results of the first part of this study, namely, the experimental data and their correlations for 82 mixtures, were published earlier by Ortega and Plficido (1993a), Ortega and Plficido (1993b) and Ortega and Plficido (1993c).

All mixtures were endothermic. Our H E values for (x11,2-dichloroethane +x2n-heptane) were lower than the values of Rhim and Bae (1979) with a mean error of 8%, and higher than the values of Nigam and Aggarwal (1986) (11%), and Svejda and Demiriz (1979) 8%. For the mixture (Xll,3-dichloropropane + x2n-heptane) the values were somewhat higher than those reported by Grolier and Kehiaian (1973), 6%, whereas the values for (Xll,4-dichlorobutane + x2n-heptane) and (Xll,6-dichlorohexane + x2n-heptane) were lower, 4% and 8%. The values by Grolier and Kehiaian (1973) for (x 1 1,5-dichloropentane + x 2 n-heptane) were nearly identical to ours. The curves increased regularly with n-alkane chain-length and decreased, also regularly, with a , to-dihalide chain-length sFig. 1.-3), although in the latter case the imaginary line joining the equimolar points for the a , to-dibromides exhibited a convexity, perhaps ascribable to proximity effects (Kehiaian and Marongiu, 1988), which are stronger in the case of bromi-containing molecules than chlorine-containing molecules. The endothermic effect is brought about by the breakdown in the orientational order of the n-alkane molecules, increasing with the number of -CHE-groups on the hydrocarbon. In addition, based on comparison of the results for mixtures containing other polyhalogenated components, there would also appear to be induced dipole-dipole interaction effects. Thus, the equimolar H E values increased for mixtures of n-hexane and CC14 (315 Jmol-1), CHCI 3 (756), and CH2C12 (1319) as the number of C1 atoms in the hydrocarbon molecule decreased and polar forces weakened. The literature contains no values for other alkyl polyhalogenated, but these effects have nonetheless been assumed to be applicable to dibromides and diiodides. Polar forces also weaken as the two halogen atoms become located further apart on the chain and exert a negative effect on H E values, which would account for the decrease in H E values with increasing polyhalogenated hydrocarbon chain length.

The present study also included an analysis of the V E values for the mixtures considered (Blanco and Ortega, 1993; Plficido and Ortega, 1995). Although in qualitative terms the changes in V E values were similar to those reported above for the H a values (as shown by the plots of equimolar values in

208 J. Or tega , J. Pldtcido / F l u i d P h a s e Equ i l i b r ia 109 (1995) 2 0 5 - 2 2 5

2500-

2250-

cS g

750-

50C

! . . . . ~ ~ ~ . . . - i . . ~ ~ ~. ! l ~,k ,'~ ..,.,W.- "~" j , I ~ . ~ ~ 1 ~ . k

2 "k"" .,;k~-1..,.,W,,. ' l . ..,..Ot~ ~'Fc ...--'k ~

3 ~O~'1~1"~k~l e ~ I 1 1"~t~

4 " k ' ~ 1 1 , 1 k ~ . . ~ ' ~

6 ~ f

2500-

2250"

L_ o

7 5 0

500

17 ~k~ ..,.. 15 "k~ ..,. "--.k~. 13 "k,... "~-..,. 11 "k,~."~'...,jlt. " " " ~ ' ~ .

5 .k.~. " . . , . k~ ' - - - . . ~ '~ - .~ ,~ . . . . '~ .

"*'.- C. '*

2000 1

'/'°1 i / i . . . .0""

,%

-2250 .

-3000

. . 0 _ _ _ 0 - - - - - 0 - - - 0 i . . 0 - -

2000

1250

% %

- 2 2 5 0 -

\ "-O" ~ - O r "o..

"O"- ~ - O 5

-3000 ,o b ,'4 ;6 ,8 2 ~ ; ; ; 7

v u

Fig. 1. Variation of the equimolar values of H E and V E for CvnEv+2} as a function of the number of carbon atoms of: (a), indicate v.

the mixtures {ot,tO-CuH2uC12 (or = 1; to = 2 ,3 ,4 ,5 ,6 )+n- n-alkane, labels indicate u, and (b), dichloroalkane, labels

Figs. 1-3), differences in the volumes were more pronounced, particularly for the mixtures consisting of components with markedly different molecule sizes. The increases shown in the figures with chain length of the saturated hydrocarbon were not so gradual and naturally were not linear, unlike the alterations in the enthalpy values. The important role of interstitial accommodation in the case of the molecules of the smallest hydrocarbons, such as n-pentane and n-heptane, was readily apparent and resulted in sizeable contractions in volume of around 1.5 cm 3 mo1-1 in (1,6-dichlorohexane + n- pentane), 2.3 cm 3 tool- ~ in (1,6-dibromohexane + n-pentane), and 3.0 cm 3 mol - 1 in (1,6-diiodohexane + n-pentane). Involvement of weakened polar forces, already discussed above for the enthalpies, was again evident in the V E results; in contrast, this was not the case for the orientational effects involving the n-alkanes, whose role in the V E values has not been sufficiently demonstrated.

4. Application of the UNIFAC model

Two versions of the UNIFAC group-contribution model were employed in the theoretical estimation of the mixing enthalpies, H E. The first approach, designated UNIFAC-1, was that of Rupp ct al. (1984), using temperature-independent group interaction parameter values and only restringed for

J. Ortega, J. Pl6cido / F lu id Phase Equilibria 109 (1995) 2 0 5 - 2 2 5 209

2500

2250

~o

I

7 5 0 "

500

. . ~ l - ~ j ~ -*~ _ , I . , ~ ; ~ r . ~ . . - . v t ~ "

,: x r ~ I S,, . .~ l ~ " l . k , ~ 3 " , ~ ! !

6 , I

2500

2250

cS

7 5 0 -

500

17 ,k,.,. ~ _

15 - k ~ ~"- - .k~

11 -k.-- ~ ~ ~ " ~ t ~ .~.. ~

9 " N ~ ~"'~b~. "~'"~ ~

( b )

2 0 0 0 -

1250 -

t,_

%

- 2 2 5 0 -

- 3 0 0 0

. .0 ._ . . 0 . - ~ - 0 "- - - ' 0

; i ;o ;2 ;. ;. 18 v

2( ~00

I, !50

- 2 2 5 0 -

- 3 0 0 0

\ \

u

Fig. 2. Variation of the equimolar values of H E and V E for the mixtures { a , t O - C u H 2 u B r 2 (c~ = 1; to = 2,3 ..... 6 ) + n -

C v H2v+ 2 } as a function of the number of carbon atoms of: (a), n-alkane, labels indicate u, and (b), dibromoalkane, labels indicate v.

estimation of H E . In contrast, there were two approaches to including the temperature dependence under the Modified UNIFAC model, herein designated UNIFAC-2, that of Larsen et al. (1987) and that of Weidlich and Gmehling (1987). To ensure proper application of the model, the H E were estimated for (A), the literature values, and (B), for the new values contributed by this study; in both cases, however, the interaction parameter values published for each of the respective versions of the model were employed.

4.1. Application of the UNIFAC model to the literature values

Estimation of H e values using UNIFAC-1

Mixtures of (a, to-dichloroalkanes + n-alkanes). The energetic parameters employed were those of Rupp et al. (1984) for the CH2/CI interaction. Except for certain specific mixtures, the mean errors are high. The values reported by Grolier and Kehiaian (1973), Polo et al. (1980), and Bafios et al. (1990) yielded good overall estimates. Table 1 presents the equimolar values for each of the mixtures reported in the literature, the experimental values measured for this study, and the predictions by UNIFAC-1.

210 J. Ortega, J. Pl{tcido / Fluid Phase Equilibria 109 (1995) 205-225

2500-

2250"

o

cb H

S

750"

500

i 1 " i 1 . ~ I ~

J 5 * ~

J

6~v ~

2 0 0 0 ~

1250 -

~ o

Ik

"6

-2250

-3000 , ;2 1'4 ;5 18

_ ~ ~@.__--O ---'O

6 8 10

Fig. 3. Variation of the equimolar values of H E and V E for the mixtures {a,to-C,H2,I 2 (ct = 1; to = 5,6)+ n-CvH2v + 2} as a function of the number of carbon atoms of n-alkane, labels indicate u.

Mixtures of (a, to-dibromoalkanes + n-alkanes). The first parameter values contained in the literature, for the methylene/bromide, CH2/Br , interaction, were published by Stathis and Tassios (1985). As Table 1 shows, the H E values reported by Artal et al. (1991) yielded the smallest errors.

Estimation of H e values using UNIFAC-2

Mixtures of (a, to-dichloroalkanes + n-alkanes). When applied to the mixtures of (dichloroalkanes + n-alkanes) from the literature, the versions of Larsen et al. (1987) and Weidlich and Gmehling (1987) yielded H E estimates similar to those by UNIFAC-1 model, though the errors were somewhat lower. The biggest shortcoming of both versions was the substantial increase in the error as the temperature increased. The best estimations were achieved for the values published by Grolier and Kehiaian (1973) and Polo et al. (1980); conversely, the values given by Bafios et al. (1990) yielded the highest errors as temperature increased.

Mixtures o f (t~, to-dibromoalkanes + n-alkanes. The version of Larsen et al. (1987) did not contem- plate the CH2/Br interaction, which was, however, included in the paper by Gmehling et al. (1993). Application of this latter version of the model to the literature values produced very high errors. For

J. Ortega, J. Pl(lcido / Fluid Phase Equilibria 109 (1995) 205-225 211

Table 1 N

Average errors, ~=Y'~(IHi,Eexp- HiE.call/HiE, exp)lOO/N, and equimolar values, (H~/2/J mo1-1) at T / K , obtained in i

application of UNIFAC model to the binaries (Xlalkyldihalides + x 2n-alkanes), for UNIFAC-1 by Rupp et al. (1984) 1 or Stathis and Tassios (1985) 1, and UNIFAC-2 by Larsen et al. (1987) 2 and Gmehling et al. (1993) 3, and UNIFAC-1 with the parameters calculated in this work 4 using eqs. in Appendix A

M i x t u r e Experiment UNIFAC- 1 UNIFAC-2 UNIFAC- 1 T / K (H~/2) e I(H1E/2) ~ 2 (HE/2) ~. 3 (HE/z) ~ 4 (HE/2)

xal,2-Dichloroethane + x2n_C5 a 298.1(1588) 21(1348) 9(1601 12(1582) 6(1548) x z n _ C 6 b 288.1(1592) 16(1482) 8(1589) 11(1669) 5(1644) n.C6 c 298.1(1550) 13(1486) 13(1737) 11(1725) 7(1484) n_C6 b 298.1(1607) 16 10 11 4 n_C6 d 298.1(1468) 10 19 17 13 n_C6 e 303.1(1754) 16(1481) 6(1812) 3(1751) 10(1636) n_C6 b 308.1(1569) 14(1474) 18(1887) 13(1776) 3(1628) n.C6 d 308.1(1497) 2 29 18 12 n_C6 b 318.1(1567) 13(1449) 26(2038) 12(1825) 2(1605) x2n-C 7 f 288.1(1716) 13(1610) 3(1701) 6(1794) 2(1721) n-C 7 g 293.1(1696) 16(1612) 12(1822) 14(1885) 5(1720) n-C 7 f 298.1(1840) 16(1609) 4(1857) 5(1850) 11(1717) n_C7 h 298.1(1563) 16 19 18 10 n.C7 d 298.1(1521) 15 19 18 11 n_C7 a 298.1(1715) 17 7 7 2 n_C7 e 303.1(1838) 15(1601) 9(1935) 7(1875) 13(1710) n-C 7 f 308.1(2007) 26(1593) 7(2015) 13(1902) 21(1701) n.C7 d 308.1(1228) 23 57 47 34 n.C7 h 313.1(1561) 19(1578) 39(2095) 26(1926) 12(1690) n_C7 e 318.1(2176) 36(1562) 11(2176) 20(1950) 31(1677) xzn_C8 e 303.1(1936) 14(1712) 14(2045) 12(1986) 17(1773) x2n_C9 a 298.1(1863) 14(1822) 12(2057) 9(2057) 4(1836) xzn-Clo g 293.1(1904) 11(1925) 7(2054) 9(2118) 2(1894) n.Ca ° h 298.1(1586) 20(1914) 29(2141) 28(2145) 15(1888) n.C1 ° h 313.1(1689) 11(1861) 35(2409) 23(2219) 7(1855) xzn_Cl a a 298.1(1993) 14(1822) 12(2057) 9(2057) 4(1836) x2n-Cl2 f 293.1(1996) 13(2092) 9(2197) 11(2269) 2(1999) x2n_C13 a 298.1(2105) 12(2149) 12(2350) 10(2359) 3(2049) xzn-C14 g 293.1(2029) 14(2234) 11(2313) 14(2119) 4(2119) n.C14 h 298.1(1541) 51(2215) 65(2408) 63(2418) 45(2110) n_C14 h 313.1(1670) 29(2134) 64(2703) 50(2486) 27(2071) xzn_C15 a 298.1(2213) 11(2276) 10(2461) 9(2471) 3(2176) x2n-C16 g 293.1(2137) 17(2357) 8(2495) 10(2497) 4(2249) ~n_C16 h 298.1(1532) 56(2334) 70(2511) 69(2521) 53(2239) n_C16 b 298.1(2121) 12 15 14 3 n_C16 b 308.1(2106) 13(2275) 28(2712) 20(2566) 5(2213) n_Cl 6 h 313.1(1659) 68(2240) 110(2815) 91(2588) 64(2198) n_C16 b 318.1(2077) 10(2202) 38(2918) 25(2608) 5(2180) n_C16 b 328.1(2070) 7(2119) 46(3130) 23(2646) 6(2134) x 2 n _ C 1 7 a 298.1(2306) 9(2387) 12(2556) 11(2566) 3(2283)

212 J. Ortega, J. Pldcido / Fluid Phase Equilibria 109 (1995) 205-225

Table 1 (continued)

Mixture Experiment T // K (H1E/2)

UNIFAC- 1 a '(HE~a)

UNIFAC-2 "~ 2 (HE~2) E3 (HE~2)

UNIFAC- 1 4 (HE/2)

x, 1,3-Dichloropropane + x2n_C5 a x2n_C6 i n_C6 c

n .C6 i

n_C6 i

n_C6 i

x2n_C7 a n-C7 J

x 2 n . C 9 a

x2n_C9 a

x2n .C1 ' a

x2n_C15 a x2n_CD i n.C, 6 n_C, 6 i n C,6 i xan_C17 a

298.1(1423) 20(1182) 11(1319) 11(1324) 9(1382) 288.1(1250) 13(1316) 5(1321) 11(1416) 16(1493) 298.1(1254) 8(1306) 13(1438) 12(1449) 16(1484) 298.1(1255) 11(1306) 12(1438) 11(1449) 15(1484) 308.1(1253) 10(1283) 21(1557) 14(1479) 14(1465) 318.1(1256) 7(1250) 30(1679) 16(1506) 12(1437) 298.1(1564) 16(1417) 6(1544) 6(1559) 4(1569) 298.1(1460) 8 7(1544) 8 8 298.1(1676) 11(1611) 3(1723) 3(1744) 2(1707) 298.1(1820) 10(1773) 3(1868) 4(1894) 1(1826) 298.1(1960) 10(1911) 2(1990) 3(2017) 2(1949) 298.1(2099) 8(2030) 2(2092) 2(2120) 1(2084) 298.1(1877) 10(2083) 12(2138) 12(2166) 12(2152) 308.1(1832) 9(2015) 25(2303) 18(2188) 15(2110) 318.1(1798) 9(1936) 40(2472) 24(2208) 17(2061) 328.1(1756) 7(1850) 57(2648) 32(2225) 20(2007) 298.1(2192) 6(2133) 3(2180) 4(2208) 2(2205)

X 11,4-Dichlorobutane + x2n.C5 a x2n_C6 c x2n-C7 J n_C7 a x2n_C9 a x2n_C1 ' a

x2n_C, 3 a

x2n_C , 5 a

x2n_C17 a

298.1(1303) 17(1043) 12(1109) 11(1121) 7(1220) 298.1(1245) 10(1155) 13(1215) 13(1231) 6(1320) 298.1(1468) 8(1256) 11(1310) 11(1329) 6(1405) 298.1(1436) 13 7(1309) 6 4 298.1(1553) 11(1433) 6(1470) 5(1495) 2(1548) 298.1(1693) 11(1582) 6(1603) 5(1631) 2(1672) 298.1(1833) 11(1710) 7(1714) 5(1743) 3(1798) 298.1(1968) 10(1820) 7(1809) 6(1838) 2(1936) 298.1(2068) 9(1917) 7(1890) 6(1920) 2(2068)

X, 1,5 -Dichloropentane +

x 2 n . C 5 a x2n_C6 c

x2n-C 7 J n_C7 a x2n_C9 a x2n_C11 a x2n_C13 a x2n.C15 a x2n_C, 7 a

298.1(1131) 15(926) 14(949) 14(961) 5(1076) 298.1(1160) 12(1027) 12(1043) 11(1059) 5(1170) 298.1(1280) 12(1120) 12(1128) 10(1146) 2(1252) 298.1(1262) 12 11 10 1 298.1(1380) 7(1282) 6(1273) 5(1296) 2(1391) 298.1(1541) 10(1420) 9(1394) 8(1419) 2(1515) 298.1(1660) 9(1539) 9(1497) 7(1522) 2(1640) 298.1(1781) 10(1642) 10(1585) 8(1610) 2(1777) 298.1(1910) 12(1732) 12(1661) 10(1685) 2(1916)

x a 1,6-Dichlorohexane + x2n_C5 a x2n_C6 c

x 2 n - C 7 J

n_C7 a

x2n_C9 a

x2n_C11 a

x2n_C13 a x2n_C15 a

x2n_C17 a

298.1(939) 10(828) 11(822) 11(832) 3(952) 298.1(990) 6(920) 6(907) 4(919) 5(1040) 298.1 (1190) 15(1005 ) 17(983 ) 16(998) 6(1117) 298.1(1097) 8 10 9 2 298.1(1210) 6(1154) 8(1116) 6(1133) 3(1248) 298.1(1356) 6(1282) 9(1227) 8(1246) 2(1367) 298.1(1496) 8(1392) 11(1322) 9(1341) 1(1490) 298.1(1595) 8(1488) 11(1403) 10(1422) 2(1624) 298.1(1721) 10(1573) 12(1474) 11(1493) 3(1766)

J. Ortega, J. Pl~cido / Fluid Phase Equilibria 109 (1995) 205-225 213

Table 1 (continued)

Mixture Experiment T/K (H~/O

UNIFAC- 1 I (HE/2)

UNIFAC-2

-~ 2 (HE/z) F3 (HE/z)

UNIFAC-1 4 (H~2)

X 11,2-Dibromoethane + x2n_C5 n 298.1(1525) x2n_C6 k 288.1(1458) n_C6 k 298.1(1492) n-C 6 ! 298.1(1408) n_C6 k 308.1(1481) n_C6 k 318.1(1522) x2n_C7 n 298.1(1661) x2n_Cs 1 298.1(1670) x2n_C9 n 298.1(1833) x2n-Clo ! 298.1(1798) x2n_C11 n 298.1(1963) x2n_C13 n 298.1(2100) x2n_C15 n 298.1(2264) x2n_C16 l 298.1(2020)

n_C16 k 298.1(2033)

n.C16 I 308.1(2032) n_C16 k 308.1(1975) n_C16 1 318.1(2068) n_C16 k 318.1(1972) n-C16 | 328.1(1990) n_C16 k 328.1(1969) xEn_C17 n 298.1(2395) x 11,3-Dibromopropane + x2n_C5 n 298.1(1456) x2n_C6 m 298.1(1344) x2n_C7 n 298.1(1599) x2n_C9 n 298.1(1761) x2n_C11 n 298.1(1906) x2n.C13 n 298.1(2054) x2n_Ca 5 n 298.1(2180) x2n_C17 n 298.1(2329) x 11,4-Dibromobutane + x2n_C5 n

x2n_C6 m

x2n_C7 n

x 2 n . C 9 n

x2n_C11 n

x2n_C13 n

x2n_C15 n

x2n_C17 n

298.1(1372) 298.1(1302) 298.1(1510) 298.1(1684) 298.1(1813) 298.1(1970) 298.1(2107) 298.1(2236)

x11,5-Dibromopentane + x2n_C5 n

x2n_C6 m

x2n_C7 n

x2n_C9 n

x2n_C11 n x2n_C13 n

x2n.C15 n x2n_C17 n

298.1(1255) 298.1(1196) 298.1(1417) 298.1(1579) 298.1(1706) 298.1(1853) 298.1(1994) 298.1(2133)

19(1472) 17(1629) 13(1616) 13 11(1588) 3(1551) 14(1743) 23(1860) 11(1961) 13(2058) 12(2141) 10(2292) 8(2421) 19(2478) 21 24(2405) 18 13(2322) 15 12(2230) 11 11(2531)

16(1269) 10(1396) 11(1511) 8(1709) 6(1874) 6(2113) 5(2132) 7(2235)

22(1106) 8(1220) 16(1324) 14(1504) 11(1655) 12(1783) 12(1894) 13(1990)

19(972) 10(1075) 18(1170) 17(1335) 16(1474) 17(1592) 17(1695) 17(1785)

38(1061) 25(1142) 26(1193) 46 23(1241) 17(1285) 32(1316) 33(1430) 30(1536) 20(1635) 29(1727) 25(1895) 2(2043) 15(2111) 18 12(2161) 21 8(2207) 2O 13(2247) 2O 26(2175)

33(979) 22(1101) 29(1215) 25(1420) 23(1599) 23(1756) 22(1896) 22(2020)

35(903) 22(1016) 28(1123) 25(1314) 24(1482) 25(1630) 21(1761) 20(1879)

29(834) 20(940) 25(1039) 24(1218) 23(1375) 23(1515) 23(1639) 21(1751)

7(1465) 6(1500) 9(1602) 3O 9(1605) 8(1598) 3(1710) 15(1798) 3(1871) 7(1932) 2(1992) 1(2103) 2(2219) 12(2266) 12 19(2331) 13 17(2311) 13 12(2285) 12 2(2347)

7(1278) 12(1515) 3(1627) 2(1800) 2(1940) 2(2080) 3(2231) 2(2368)

11(1275) 7(1403) 5(1508) 3(1675) 1(1820) 2(1970) 2(2136) 4(2268)

10(117o) 7(1286) 4(1382) 4(1538) 4(1679) 3(1833) 2(2005) 2(2123)

214

Table 1 (continued)

J. Ortega, J. PlScido / Fluid Phase Equilibria 109 (1995) 205-225

Mixture Experiment T / K (H~/:)

UNIFAC-1 ~(n~/~)

UNIFAC-2

: (HI~/:) F. 3 (H~2)

UNIFAC-1 4 ( H E / 2 )

X 11,6-Dibromohexane + x2n.C5 n 298.1(1082) 16(862) x2n.C6 m 298.1(1046) 10(956) x2n_C7 n 298.1(1228) 14(1042) x2n_C9 n 298.1(1382) 14(1193) x2n_C11 n 298.1(1518) 14(1321) x2n_C13 n 298.1(1660) 15(1432) x2n_C15 n 298.1(1796) 16(1528) xzn_Ca 7 n 298.1(1932) 18(1612) X 11,8-Dibromooctane + x2n_C6 m 298.1(848) x 11,5 -Diiodopentane + x2n_C5 o 298.1(1407) x2n_C7 o 298.1(1600) x2n_C9 o 298.1(1798) x2n.Cn o 298.1(1932) x2n_C13 o 298.1(2077) x 11,6-Diiodohexene +

10(769)

25(772) 10(1070) 18(871) 10(1173) 20(963) 5(1259) 19(1131) 2(1402) 19(1279) 2(1537) 18(1410) 2(1689) 18(1528) 3(1865) 19(1634) 2(1967)

18(752) 22(968)

24(1026) 2(1281) 21(1244) 2(1554) 22(1426) 2(1776) 22(1582) 2(1961) 20(1716) 3(2119)

x2n_C5 o 298.1(1186) 20(910) 2(1158) x2n_C7 o 298.1(1396) 20(1109) 2(1390) x2n_C9 o 298.1(1554) 18(1277) 7(1580) x2n.C11 o 298.1(1728) 18(1421) 2(1739) x2n_C13 o 298.1(1837) 16(1546) 4(1874) x2n.C15 o 298.1(1999) 17(1656) 3(1989) x2n_C17 o 298.1(2140) 18(1752) 3(2090)

a Ortega and Pl~cido (1993a); b Bafios et al. (1983); c, Polo et al. (1980); d Nigam and Aggarwal (1986); ~ Chaudari and Katti (1990); f Rhim and Bae (1979); g Hahn and Svejda (1985); h Svejda and Demiriz (1979); i Bafios et al. (1990); J Grolier and Kehiaian (1973); k Mor6n et al. (1985); i Delmas and Purves (1977); m Artal et al. (1991); n Ortega and Phlcido (1993b); o Ortega and Pl~cido (1993c).

the set of 20 mixtures included in Table 1, the mean overall error exceeded 20%, which indicated that the actual parameters are unsuitable for estimating the H E for this type of mixture.

4.2. Application of the UNIFAC model to the values of this study

Estimation of H E values using UNIFAC-1

Mixtures of (a, oJ-dichloroalkanes + n-alkanes). Table 1 gives the individual errors for each mixture.

The mean error for all of the 35 mixtures included in the Table was 11%, which can be considered acceptable in light of the fact that not too many values for (monochloroalkanes + n-alkanes) were employed in calculating the values of the CH2/C1 interaction. The H E values for these same 35 mixtures were also estimated for the interaction in the form CH2/CC1 using the values proposed by Ortega et al. (1988). The resulting errors were practically the same as in the preceding case and therefore have not been included in Table 1.

J. Ortega, J. Pl6cido / Fluid Phase Equilibria 109 (1995) 205-225 215

Mixtures of (a, to-dibromoalkanes + n-alkanes). The percentage errors obtained are presented in Table 1. They were on the order of the errors obtained for the dichloroalkanes, 13%. As was the case for the dichloroalkanes, the predictions for the alkyl dibromides considered here were lower than the experimental values in all cases except for the (1,2-dibromoethane + n-alkanes).

Estimation of H e values using UNIFAC-2 The UNIFAC model was applied to all the above-mentioned binary mixtures using the tempera-

ture-dependent interaction parameters published in the literature. Accordingly, the version of Larsen et al. (1987) was used to estimate the H E values of ( a , to-dichloroalkanes + n-alkanes) only, whereas the version of Weidlich and Gmehling (1987) was applied to all the sets of mixtures. Further comments on the treatments applied to each family of systems follow below.

Mixtures of (a, oo-dichloroalkanes + n-alkanes). The methylene/chloride interaction was represented here as C H J C C 1 . The results achieved using the values reported by the Lyngby and Dortmund groups were identical, with a mean error of 8% for the set of 35 mixtures. In both cases the results were three percentage points better than the results produced by the UNIFAC-1 model. The availability of a broader data base including values for other thermodynamic magnitudes, as G E and y=, improved the model 's predictions.

Mixtures of (a, to-dibromoalkanes + n-alkanes). Here the H E w e r e estimated using the version of Weidlich and Gmehling (1987) only, with the parameter values by Gmehling et al. (1993) for the C H 2 / B r interaction. The overall mean error for the 35 mixtures was on the order of 25%, duplicating the error obtained with UNIFAC-1. Table 1 presents the percentage differences for each mixture, which in this case can be seen to diminish with n-alkane chain length.

Mixtures of (a, to-diiodoalkanes + n-alkanes). As in the preceding case, the version of the Dortmund group was used to analyze these mixtures, and the errors for each system are given in Table 1. Although to date the literature contains few values for mixtures of alkyl iodides, the estimations were not so poor. The overall mean error for the 12 mixtures considered here was less than 20%, though qualitatively the discrepancies between the curves appeared to be much larger.

5. Discussion of the UNIFAC model results

The values set out in Table 1 provide a quantitative evaluation of the predictions achieved using the different versions of the UNIFAC model. Analysis of the results obtained can be summarized as follows.

The application of the UNIFAC-1 and UNIFAC-2 models to the literature values for the mixtures of (dichloroalkanes + n-alkanes) was quite similar, with an overall mean error of around 15% in all cases. However, it should be noted the greater differences presented in the estimations of H E using UNIFAC-2 at temperatures higher than 298.15 K, whereas this fact does not appear so relevant with UNIFAC-1. The UNIFAC-1 model was able to represent the endothermic process of (dibromoalkanes + n-alkanes) mixtures reasonably well. The UNIFAC-2 model did not yield such good results when the parameter values of Gmehling et al. (1993) were employed, and no explanation has been found for the large errors obtained for the values published by Delmas and Purves (1977).

216 J. Ortega, J. Pl6cido / Fluid Phase Equilibria 109 (1995) 205-225

The following comments can be made concerning application of the model to the new values collected in the framework of this study.

The UNIFAC-1 version yielded similar estimates for the mixtures of both the a , w-dichloro and the a,to-dibromoalkanes and the n-alkanes, with errors of around 12%. The values for the CH2/C1 and CH2/Br interactions used in that model were calculated using a data base comprising values almost exclusively of monochloroalkanes.

Using the version of Larsen et al. (1987), H E values could be estimated only for the (a,to-dichloroalkanes + n-alkanes), because the literature does not contain parameter values for the interactions involving bromine and iodine. The estimates for the a, to-dichloroalkanes were acceptable, with an error of less than 9%, though the solid line plotting of equimolar H E values on n-alkane chain length presented an unexpected convexity. The version of Weidlich and Gmehling (1987) yielded estimates similar to those of the version of Larsen et al. (1987) for the ( a , to-dichloroalkanes + n-alkanes), but the errors for the mixtures of the a,o~-dibromoalkanes and a,to-diiodoalkanes with n-alkanes were much higher, at 20%. The data base of literature values for these mixtures, not only HE values but also VLE, LLE, and Cp E, was much smaller.

The preceding analyses revealed that certain literature values used to calculate the interaction parameters for the model were not sufficiently precise. We therefore decided to recalculate new parameters for the UNIFAC model for the interactions between chlorine, bromine, and iodine and the methylene group, employing a larger data base comprising values for mixtures of both alkyl monohalides and alkyl dihalides with n-alkanes, for the UNIFAC-1 version of Rupp et al. (1984) only, although, as it was mentioned above, their parameters can only be used for H E . It was considered inadvisable to perform such a recalculation for the UNIFAC-2 versions because other thermodynamic values for the mixtures considered were not available (VLE and LLE data, ~/o~, CpE).

6. Estimation of new parameters for the UNIFAC-1 model

Pursuant to the discussion presented in the preceding section, new parameter values for the methylene/halide interaction were calculated following several different approaches, in all cases employing the largest possible number of experimental values. The algorithm of Marquardt (1963) was used in the recalculus, minimizing the overall mean error of the values introduced. In order to reduce the problem of multiplicity of roots in the regression, the database did not comprise the actual values obtained by direct experimentation but rather estimates obtained by correlation of the ( x , H E) values (Ortega and Plficido, 1993a, Ortega and Plficido, 1993b, Ortega and Plficido, 1993c). Optimization of the parameter value estimates was based on the three cases discussed below. The first two cases differed with respect to the type of data base employed, namely, values for alkyl monohalide and alkyl dihalides combined or values for dihalogenated with alkanes only. The results obtained for these two cases led to a third approach.

7. First ease

7.1. Combined data base for (alkyl monohalides and alkyl dihalides + n-alkanes)

CH2/CI interaction: A database was established consisting of values for 100 pairs of ( x l , H E) values for seven mixtures of (xlot,to-dichloroalkanes + x2n-alkanes) and for certain binary mixtures


of (Xll-chloroalkanes + x2n-alkanes) that appeared to exhibit a certain level of consistency and hence to afford greater reliability, namely, values for (1-chlorobutane + n-dodecane) reported by Valero et al. (1980a), (1-chlorohexane + n-octane) reported by Paz-Andrade and Bravo (1977), and (1-chlorododecane + n-octane) reported by Valero et al. (1980a). The interaction parameter values found were:

acn2/Cl = 68.4 a C l / C H 2 ---- 6.1

Reapplying the UNIFAC-1 model to the experimental values for ( a, to-dichloroalkanes + n-alkanes) published by Ortega and Plficido (1993a), Ortega and Plficido (1993b) and Ortega and Plficido (1993c) yielded an overall mean error of 7%, 4 points less than the error obtained using the original parameters by Rupp et al. (1984) given in Table 1. Re-estimation of the H E values of (1-chloroalkanes + n-alkanes) considered in the literature yielded a mean error of 6%. The percentage differences for each system appear in Table 2. That table also compares the quality of the predictions obtained with the version by Rupp et al. (1984) and those of UNIFAC-2.

CHz/Br interaction: The computation procedure was as described above, this time using alkyl monobromides and dibromides. The binary mixtures containing monobromides in the literature employed in the calculations were (1-bromoethane + n-dodecane), (1-bromobutane + n-hexane), and (1-bromododecane + n-hexadecane) reported in Valero et al. (1980b). The following parameter values were calculated using 100 pairs of (x i ,H E) for the said mixtures as well as for the mixtures of (a,to-dibromoalkanes + n-alkanes) published by Ortega and Plficido (1993a), Ortega and Plficido (1993b) and Ortega and Plficido (1993c).

aCH2/Br = 63.0 a B r / C H 2 ---- 6.0

Application of the model to the set of 35 new mixtures considered in this study using these recalculated interaction parameters yielded a mean error of 10%, a decrease of 3 points over the error obtained using the values for the methylene/bromide interaction given by Stathis and Tassios (1985). Nevertheless, the mean error increased slightly, from 12 to 15%, for the series of mixtures containing 1,2-dibromoethane, whereas the errors for the other mixtures improved. UNIFAC-2 model does not predict well the excess enthalpies of these mixtures.

The estimates carried out using the recalculated values for (monobromoalkanes + n-alkanes) in the literature yielded an error of 11%, similar to that of Stathis and Tassios (1985), as shown in the forth column of Table 2.

CH2/I interaction: Following the same procedure described above, a data base was established using the values for the mixtures of ( a , to-diiodoalkanes + n-alkanes) compiled in this study and those for the binary mixtures (1-iodobutane + n-hexadecane), (1-iodooctane + n-hexane), and (1-iodohexane + n-dodecane) from Mufioz-Embid et al. (1987). Regression yielded the following values.

a C H E / I = 53.3 al/CH z = 37.0

Re-applying the UNIFAC-1 model to the twelve miscible mixtures of (diiodoalkanes + n-alkanes) yielded an overall mean error of around 7%. The mean error for the set of mixtures of (monoiodoal- kanes + n-alkanes) in the literature was 9%. The discrepancies for each individual mixture appear in Table 2 along to the prediction errors for the UNIFAC-2, which estimates well the H E.

In summary, the differences between the H E estimates for (alkyls a , to-dihalogenated + n-alkanes) and the experimental values were greatest when the model was applied using the parameters values calculated solely from data for alkyl monohalides, e.g., the original values presented in Rupp et al.


Table 2 Average errors, ~, obtained in 1-Iodo)alkanes + n-alkanes

the application of UNIFAC model on the binary mixtures of (1-Chloro, l -Bromo,

Binary mixture ~ a ~ b E c E d E ~ Ref

1-Chlorobutane + n-hexane 6 5 4 4 9

3 8 7 1 5 + n-heptane 24 11 13 22 28

9 7 7 5 4 + n-octane 11 4 5 8 14 + n-nonane 4 7 7 3 7 + n-decane 7 8 8 3 2 + n-dodecane 4 8 8 3 7 + n-hexadecane 3 14 14 6 3

5 17 17 8 4 1-Chloropentane + n-hexane 3 12 12 3 3 + n-heptane 2 13 13 3 2 + n-octane 3 10 10 1 5 + n-nonane 2 10 10 2 4 + n-decane 2 11 11 3 4 1-Chlorohexane + n-hexane 5 9 10 2 7 + n-heptane 4 10 10 1 6 + n-octane 4 11 11 1 5 + n-nonane 4 10 12 1 6 + n-decane 3 11 11 1 5 + n-undecane 8 17 18 8 10 1-Chlorooctane + n-hexane 1 15 17 4 10 + n-octane 3 14 16 2 8 1-Chlorododecane + octane 9 17 20 8 8 + dodecane 21 8 11 12 19 + hexadecane 14 13 16 6 13 1-Chlorohexadecane + octane 28 42 46 33 29 + dodecane 2 21 25 8 2 + hexadecane 16 8 13 7 14 1-Bromoethane + n-hexane 2 10 7 13 + n-dodecane 5 8 11 5 + n-hexadecane 5 7 4 9 1-Bromobutane + n-hexane 2 13 8 5 + n-dodecane 5 14 8 3 + n-hexadecane 10 13 8 8 1-Bromohexane + n-hexane 2 6 5 1

Valero et al. (1980a) Doan-Nguyen et al. (1978) Mufioz Embid et al. (1987) Grolier et al. (1983) Valero et al. (1980a) Doan-Nguyen et al. (1978) Grolier et al. (1983) Valero et al. (1980a) Valero et al. (1980a) Grolier et al. (1983)

Paz-Andrade and Bravo (1977) Paz-Andrade and Bravo (1977) Paz-Andrade and Bravo (1977) Nufiez et al. (1989) Nufiez et al. (1989)

Paz-Andrade and Bravo (1977) Paz-Andrade and Bravo (1977) Paz-Andrade and Bravo (1977) Nufiez et al. (1989) Nufiez et al. (1989) Nufiez et al. (1989)

Doan-Nguyen et al. (1978) Doan-Nguyen et al. (1978)

Valero et al. (1980a) Valero et al. (1980a) Valero et al. (1980a)

Valero et al. (1980a) Valero et al. (1980a) Valero et al. (1980a)

Valero et al. (1980b) Valero et al. (1980b) Valero et al. (1980b)


de Torres et al. (1980)


Table 2 (continued)

Binary mixture ~ a ~ b ~ c ~ d E e Ref

1-Bromododecane +hexane + dodecane +hexadecane 1-Bromohexadecane +hexane + dodecane + hexadecane 1-Iodomethane + n-hexane +n-dodecane + n-hexadecane 1-Iodoetane +n-hexane + n-dodecane + n-hexadecane 1-Iodopropane + n-hexane + n-dodecane +n-hexadecane 1-Iodobutane +n-hexane + n-dodecane +n-hexadecane 1-Iodopentane + n-hexane +n-dodecane +n-hexadecane 1-Iodohexane +n-hexane +n-dodecane + n-hexadecane 1-Iodoheptane + n-hexane +n-dodecane +n-hexadecane 1-Iodooctane +n-hexane + n-dodecane + n-hexadecane 1-Iodododecane +n-hexane + n-dodecane + n-hexadecane 1-Iodohexadecane + n-hexane +n-dodecane +n-hexadecane

22 19 19 16 8 37 9 15 6 38 5 20

43 19 40 10 5 43 5 16 9 56 11 17

7 12 20 2 17 26 2 14 21

6 12 21 2 14 23 3 10 18

5 12 22 2 12 22 4 8 15

2 9 19 7 9 18 5 4 13

6 11 19 3 4 14 7 6 8

6 7 17 2 5 15 7 5 7

5 2 12 3 6 18 6 5 7

5 3 12 3 5 16 4 2 10

20 20 11 10 10 23 8 8 19

4 37 30 6 6 16 13 11 24



Mufioz Embid et al. (1987) Mufioz Embid et al. (1987) Mufioz Embid et al. (1987)


Mufioz Embid et al. (1987) Mufioz Embid et al. (1987) Mu~oz Embid et al. (1987)



Mufioz Embid et al. (1987) Mu~oz Embid et al. (1987) Mufioz Embid et al. (1987)





220 J. Ortega, J. Pld~cido / Fluid Phase Equilibria 109 (1995) 205-225

(1984), instead of using a more comprehensive data base containing values for both mono and dihalides. The discrepancies were more pronounced for the mixtures containing Br than for the mixtures containing C1. This would suggest that the methylene /ha l ide interactions differ for mono or dihalogenated components; there are no values for other polyhalogenated components that can be used to verify this. However, with a view to obtaining confirmation, we decided to calculate new inter action parameters from a data base consisting of values for (alkyls a , to-dihalogenated + n-alkanes) only. The results are discussed in the following case.

8. Second case

8.1. Database for (alkyl dihalides + n-alkanes)

CH2/C1 interaction: The following new values were calculated using the H E values for the ( a , to-dichloroalkane + n-alkane) systems.

aCHE/C1 = 7 1 . 1 aC1/CI4 ~ = 6 . 3

The mean overall error for the set of 35 mixtures was 6%, somewhat lower than in the preceding case. The estimates for the systems containing 1,2-dichloroethane and 1,3-dichloropropane were somewhat higher, while the estimates for all the other systems were lower, resulting in a net improvement. Using these parameters to estimate the values for the mixtures of (monochloroalkanes + n-alkanes) yielded a mean error of 8% (Table 2).

C H 2 / B r interaction: Only employing the H E of ( a , to-di-bromoalkanes + n-alkanes) the following parameter were obtained herein:

aCHE/Br = 6 5 . 7 aBr /CH2 = 7 . 7

Application of these values to the set of binary mixtures measured for this work yielded H E estimates with a mean error of 9%. For the binary mixtures containing monobromides, the error increased to 12% (Table 2).

C H 2 / I interaction: The database consisted only of pairs o f (x1 ,H E) values for the twelve mixtures of (x 1 c~, to-diiodoalkanes + xEn-alkanes) contemplated in this study and yielded the following interaction parameter values:

acn2/I = 58.0 a l / C H 2 = 45.5

The mean error in the recalculation of the H E for the said twelve mixtures using those values was

Note to Table 2: N

~= ~(IHi,Eexp - HiEcall/HiE, exp)lOO/N, N number of experimental points, aVersion by Rupp et al. (1984) for i ~ l

monochloroalkanes and Stathis and Tassios (1985) for monobromoalkanes, b Version by Larsen et al. (1987). c Version by Gmehling et al. (1993). d Version by Rupp et al, (1984) with parameters recalculated using (mono and dichloro or mono and dibromo or mono and diiodo)alkanes + n-alkanes (first case), e Version by Rupp et al. (1984) with parameters recalculated using only (dichloro or dibromo or diiodo)alkanes + n-alkanes (second case).

J. Ortega, J. Plfcido / Fluid Phase Equilibria 109 (1995) 205-225 221

smaller than 2%. Application of the model to the (1-iodoalkane + n-alkane) systems yielded a mean error of 17% (Table 2).

The partial conclusion drawn from the results for the two preceding cases was that there was practically no improvement for the CI and Br-containing components using the recalculated parameter as compared with the existing literature values, though the errors did improve for the estimates for the alkyl a,to-dihalogenated with the most carbon atoms. Accordingly, the errors improved for the long-chain dihalides, whereas they increased for the short-chain dihalides. The error improved for all the a , to-diiodoalkane systems, since there were no values for low-molecular-weight diiodides. This result suggested that the parameters for the CHz/C1, CH2/Br, and CH2/ I interactions in the mixtures of (alkyls a,to-dihalogenated + n-alkanes) were dependent upon the number of carbons in both components, and we therefore decided to study that dependence by means of a third case, discussed below.

9. T h i r d case

9.1. Data base for (alkyl dihalides + n-alkanes)

CH2/C1 interaction: The values for the CH2/CI and CI /CH 2 interactions were recalculated separately for each of the binary mixtures represented empirically {Xla,to-CuH2uCl 2 ( a = 1; to = 2,3,4,5,6; u = to) + x2n-CvH2v+2 (v = 5,7,...,17)} using eleven pairs of (Xl HE) values for each mixture. This enabled the different parameters to be recalculated according to the number of carbon atoms either in the dihalide, u, or in the n-alkane, v. Plotting the u or v values obtained yielded a hyperbolic paraboloid whose analytical expression, acH2/Cl = @(u,v), had to be solved, as discussed below. This function, that is f(v), applied only to mixtures of a , to-dichloroalkanes with a single n-alkane, i.e., constant v, took the form of an exponential function that approached its maximum value as the number of carbons in the dihalide increased, such that it was nearly constant from u = 5, indicative of diminishing proximity effects. Accordingly, the shape of the surface can be represented analytically as:

acn2/cl = f (v) [1 - exp{ g(v)}u] (1)

The functions f(v) and g(v) are parabolas, the former being more concave than the latter is convex, thereby offsetting the larger differences between the theoretical estimates and the experimental values for the mixtures containing long-chain n-alkanes.

The inverse interaction parameters, aCI/CH2 , correspond to a ruled surface that exhibited a deformation in the region of the values for long-chain n-alkanes. A more detailed examination of these functions falls outside the scope of the present study. Therefore, the expressions obtained for the different interaction are shown in an appendix of this paper.

Summarizing, the results obtained in this third case reflects a good predictions for different mixtures studied, with errors close to 3% in all cases.

Because the mixing enthalpies were available only for the long-chain diiodides due to their partial miscibility with the n-alkanes, the method was therefore validated by extrapolating the parameter values, naturally considering a similar behavior for all the alkyl a , to-dihalides. Accordingly, Fig. 4 presents plots of the values of aCH2/A (A = C1,Br,I) on the number of carbon atoms in the


75-

z...

L.,

30

/ A/ diiodides

U

Fig. 4. Variation o f the parameters aCH2/A (A = C1,Br,I) as a function of the number of carbon atoms of a , to-CuH2uA 2 in the mixtures ( or, to-C u H 2u A 2 + n-C 7 H 17). ( • ), est imated values.

a , to-dihalide for mixtures of ( a , og-dihalides + n-heptane). The similarity in the trends followed by all the curves indicates that extrapolation for mixtures of ( a , to-CuH2uI 2 + n-heptane) [where u = 2,3,4] is feasible. The corresponding values for CH 2/I interaction at the respective values of u were 36.0, 46.0, and 52.5. As an example, these values were applied to estimate the H E of (Xll,4-diiodobutane + xEn-heptane) at a concentration miscibility totally. At x 1 = 0.228 the error in the prediction was 3.8%, and the interaction parameter used w e r e aCHE/I = 52.5 and a i / c n 2 = 34.3, the former obtained by extrapolation as explained above, the latter using the corresponding function.

I0. Conclusions

N e w H E and V E values reported in the literature for 35 mixtures of dichlorides, 35 mixtures of dibromides, and 12 mixtures of completely miscible diiodides were used here for describing its behavior in terms of UNIFAC. Several versions of UNIFAC were applied to the new values, and the results are summarized in Table 1. The version of Rupp et al. (1984) produced acceptable predictions, with an error of 11% for mixtures of (ce,to-dichloroalkanes+n-alkanes) and 13% for (a,to-dibromoalkanes + n-alkanes). The version of Larsen et al. (1987) could only be used for the 35 mixtures of ( a , to-dichloroalkanes + n-alkanes), for which it yielded a mean error of 8.%. Application of the version of Weidlich and Gmehling (1987) produced good results, with an error of less than 8%; however, its application to the mixtures containing dibromides and diiodides gave place to errors of, respectively, 25% and 21%.

New interaction parameters were calculated for the version of Rupp et al. (1984) using different databases. The best results were achieved using the parameter calculated by UNIFAC-1 from a set of (Xl H E) values for (Xlalkyl mono and dihalides + x 2 n-alkanes); the parameters w e r e : a CH2/C! = 68.4, aCI/CH2 = 6.1, a c u 2 / B r = 63.0, aBr/CH2 = 6.0, a c n 2 / I = 53.3, and a i / C H 2 = 37.0. These values yielded good estimates, with overall mean errors of 7% for mixtures of a,to-dichloroalkanes + n-alkanes, 10% for mixtures of a , to-dibromoalkanes + n-alkanes, and 7% for mixtures of a , to-diiodoalkanes + n-alkanes considered in this study. In addition, variable interaction parameters that changed with the chain-length of the mixture components were also determined. This procedure improved the predictions of the H E for all the systems, yielding an overall mean error of less than 3%. However, we

J. Ortega, J. Pldcido / Fluid Phase Equilibria 109 (1995) 205-225 223

believe that this method needs to be refined by further study using other primary systems in order to get a better definition.

A representation, for each of the different cases considered, of the percentage errors obtained by applying the Rupp et al. (1984) version of the UNIFAC to each mixture versus the chain-length of the saturated hydrocarbon can be summarized as follows. The errors achieved in the third case were lower and more constant with changing n-alkane chain length. The lowest molecular-weight n-alkanes were exceptions to this general rule, because experimental errors were somewhat higher due to evaporation, which exerted a significant effect on the H E results. Nevertheless, the mean error of around 3% achieved for the H E in the third case warrants further consideration of this method in future applications of the UNIFAC to other types of mixtures, to test the method's general validity.

Acknowledgements

The authors are grateful to DGICYT (MEC) of Spain for the financial support for the research project PB92-0559.

Appendix A

Equations to estimate the interaction parameters as a function of the number of carbon atoms of the mixture components: {or, to-CuH2uA2 (ot = 1; to = 2,3,4,5,6; u = to; A = C1,Br,I) + n-CvHev+2 (v = 5,7 ..... 17)}

aCH2/C~ = ( 7 5 . 0 - 1.165V + 0.085V2)[1 - -exp( - -0 .914 + 0 . 0 5 3 v - 0.002v2)u]

aCl/CH~ = ( 5 3 . 0 - 6 .81U)+ ( - -0 .5 + 1.2U)V + [(3.1 + 1.45u)10-7]exp(v)

aCH:/Br = (94.73 -- 5.53V + 0.25V2)[ 1 - - e x p ( - - 0 . 0 2 2 - 0.094v + 0.004vZ)u]

aBr/CH2 = 40 + (6.03 -- 0.8U -- 0.02U2)V + [(-- 100 + 35U + 4ua)10-8]exp(v)

acn2/1 = (26.8 + 2.89V) + (5.22 -- 0.46V)U

al /ca 2 = ( - -98 .6 + 22.54u) + (12.9 -- 1.70u)v

References

Artal, M., Fernandez, J. and Mufioz-Embid, J., 1991. Excess enthalpies of some a,to-dibromoalkanes(C3-C s) + hexane or cyclohexane. Int. Data Ser. Sel. Data Mixtures, Ser. A, pp. 77-86.

Bafios, I., Valero, J., Gracia, M. and Gutierrez-Losa, C., 1983. Conformational equilibrium and calorimetric behaviour of systems containing 1,2 dichloroethane. Ber. Bunsenges. Phys. Chem., 87: 866-871.

Bafios, I., Valero, J., Perez, P., Gracia, M. and Gutierrez-Losa, C., 1990. Excess molar enthalpies of mixtures containing 1,3-dichloropropane. J. Chem. Thermodyn., 22: 67-72.

Baud, E., 1915. Analyze thermique des m61anges binaries. Bull. Soc. Chim. Fr., 17: 329-345.


Blanco, A.M. and Ortega, J., 1993. Excess volumes of alpha, omega-dichloroalkanes (C2-C6)+ some normal alkane (C5-C17) mixtures. Int. Data Ser., Sel. Data Mixtures, Ser. A. 21 (3): 195-231.

Chaudari, S.K. and Katti, S.S., 1990. Excess enthalpies of n-alcohols (C 1 to C a) and alkanes (C 6 to C 8) with 1,2-dichloroethane at 303.15 K. Thermochimica Acta, 158: 99-106.

Delmas, G. and Purves, P., 1977. Thermodynamic properties of Mixtures of linear and branched alkanes with 1,2-dibromoethane and tetrahydronaphthalene, J. Chem. Soc Faraday Trans., 73: 1828-1837.

Doan-Nguyen, T.H., Vera J.H. and Ratcliff, G.A., 1978. Heats of mixing of binary chloroalkane-n-alkane and chloroalkane-n-alcohol systems at 25°C, J. Chem. Eng. Data, 23: 218-221.

Gmehling, L, Li, J. and Schiller, M., 1993. A modified UNIFAC model. 2. Present parameter matrix and results for different thermodynamic properties, Ind. Eng. Chem. Res., 32: 178-193.

Grolier, J.-P.E. and Kehiaian, H.V., 1973. Enthalpies de m61ange des or, to-dichloroalcanes avec des hydrocarbures. J. Chim. Phys., 70: 807-810.

Grolier, J-P.E., Sosnkowska, K. and Kehiaian, H.V., 1983. Enthalpies de melange des chlorures organiques avec des hydrocarbures, J. Chim. Phys. 70: 367-373.

Hahn, G. and Svejda, P., 1985. Excess enthalpies of 1,2-dichloroethane + some normal alkanes (C7-C16). Int. Data Ser., Sel. Data Mixtures, Ser. A: 143-147.

Kehiaian, H.V. and Marongiu, B., 1988. A comparative study of thermodynamic properties and molecular interactions in mono-and polychloroalkane + n-alkane or + cyclohexane mixtures. Fluid Phase Equilibria, 40: 23-78.

Larsen, B.L, Rasmussen, P. and Fredenslund, Aa., 1987. A modified UNIFAC group-contribution model for predicting of phase equilibria and heat of mixing. Ind. Eng. Chem. Res., 26: 2274-2286.

Marquardt, D.W., 1963. An algorithm for least-squares estimation of non-linear parameters. J. Soc. Ind. Appl. Math., 11: 431-441.

Mor6n, M.C., Perez, P., Gracia, M. and Gutierrez-Losa, C., 1985. Excess molar enthalpies of mixtures containing 1,2-dibromoalkanes. J. Chem. Thermodyn., 17: 733-737.

Mufioz-Embid, J., Otin, S., Velasco, I., Gutierrez-Losa, C. and Kehiaian, H.V., 1987. Excess enthalpies of 1-iodoalkane + n- alkane mixtures. Measurement and analysis in terms of group contributions (DISQUAC). Fluid Phase Equilibria, 38: 1-17.

Nigam, R.K. and Aggarwal, S., 1986. Thermodynamic and spectroscopic evidence in binary mixtures of nonelectrolytes. Fluid Phase Equilibria, 26: 181-200.

Nuflez, L., Miguelez, F., Barral, L. and Paz-Andrade, M.I., 1989. Excess molar enthalpies at 298.15 K of (1-chloropentane + nonane or decane) and of (1-chlorohexane + nonane or decane or undecane) J. Chem. Thermodyn., 21: 495-497.

Ortega, J., Matos, J.S., Paz-Andrade, M.I., Fernandez, J. and Pias, L., 1988. Analysis of excess enthalpies of ester+ 1- chloroalkanes with two group contribution models: primary parameters. Fluid Phase Equilibria, 43: 295-316.

Ortega, J. and Pl~cido, J., 1993a. Excess enthalpies of some alpha,omega-dichloroalkane (C2-C6)+normal alkane (Cs-C17) mixtures. Int. Data Ser., Sel. Data Mixtures Ser. A, 21(1): 1-37.

Ortega, J. and Plficido, J. 1993b. Excess enthalpies of some alpha,omega-dibromoalkane (C2-C6)+normal alkane (C5-C17) mixtures. Int. Data Ser., Sel. Data Mixtures, Ser. A., 21(1): 48-84.

Ortega, J. and Plficido, J., 1993c. Excess enthalpies of 1.5-diiodopentane or 1,6-diiodohexane+some normal alkane (C5-C17) mixtures. Int. Data Ser., Sel. Data Mixtures, Ser. A., 21(3): 232-245.

Paz-Andrade, M.I. and Bravo, R., 1977. Excess enthalpies of 1-chloroalkane (C5-C 6) + n-alkane (C6-C s) mixtures. Int. Data Ser., Sel. Data Mixtures, Ser. A, 1: 71-76.

Plficido, J. and Ortega, J., 1995. Excess volume of alpha,omega-dibromo (C2-C 6) or diiodoalkane ( C s - C 6) + some normal alkane (C5-C17) mixtures. Int. Data Ser., Sel. Data Mixtures, Ser. A., in press.

Polo, C., Gutierrez-Losa, C., Kechavarz, M.R. and Kehiaian, H. V., 1980. Excess enthalpies of liquid a , to-dichloroalkanes + n-heptane mixtures. A group contribution study of the CI-C1 proximity effect. Ber. Bunsenges. Phys. Chem., 84: 525-529.

Rhim, J.N. and Bae, S.Y., 1979. Heats of mixing for the binary liquid mixtures 1,2-dichloroethane + n-heptane, 1,2-dichloroethane-n-butanal, n-heptane-n-butanal. Hwahak Konghak, 17: 201.

Rupp, W., Hetzel, S., Ojini, I and Tassios, D.P., 1984. Prediction of enthalpies of mixing with group-contribution models: primary parameters. Ind. Eng. Chem. Process Des. Dev., 23: 391-400.

Stathis, P.J. and Tassios, D.P., 1985. Prediction of enthalpies of mixing for systems containing alcohols with an UNIFAC/Association model. Ind. Eng. Chem. Process Des. Dev., 24: 701-707.


Svejda, P. and Demiriz, A.M., 1979. Determination of the excess enthalpies of mixing of the liquid systems: 1,2-dichloroethane + n-alkanes by flow microcalorimetry. I International Conference on Non-Electrolytes Solutions., University of Santiago de Compostela, p. 137.

de Torres, A., Velasco, I. and Otin, S., and Gutierrez-Losa, C., 1980. Excess enthalpies of some binary mixtures. Contribution to the study of the Br-O specific interaction, J. Chem. Thermodynamics, 12: 87-93.

Valero, J., Gracia, M. and Gutierrez-Losa, C., 1980a. Excess enthalpies of some (chloroalkane + n-alkane) mixtures. J. Chem. Thermodyn., 12: 621-625.

Valero, J., Lopez, M.C., Gracia, M. and Gutierrez-Losa, C., 1980b. Excess enthalpies of some (bromoalkane + n-alkane) mixtures, J. Chem. Thermodyn., 12: 627-633.

Weidlich, U. and Gmehling, J., 1987. A modified UNIFAC model 1. Prediction of VLE, h E and 3, =. Ind. Eng. Chem. Res., 26: 1372-1381.

Study on the binary mixtures of alkyls alfa, omega-dihalogenated (chlorine, bromine, iodine) with...

Documents

Transcript of Study on the binary mixtures of alkyls alfa, omega-dihalogenated (chlorine, bromine, iodine) with...