Densities and heat capacities of 1-butanol + n-decane from 298 K to 400 K

137

Equilibria, 27 (1986)137-151 Elsevier Science Publishers B.V.. Amsterdam -Printedin The Netherlands

FluidPhase

DENSITIES AND HEAT CAPACITIES OF l-BUTANOL + n-DECANE FROM 298

K TO 400

K

JEFFREY A. GATES and ROBERT H. WOD Department of Chemistry, University of Delaware, Newark, Delaware 19716 (USA)

JOSE CARLOS COBOS and CARLOS CASANOVA Departamento de Termologia, Universidadde Valladolid,Valladolid (Spain)

ALAINH.

ROUX, GERKVIEVE RUJX-DESGRANOESandJLAN-PIERRB E.GROLIER

Laboratoire de Thermodynamiqueet Cinetique Chimique, Universite de ClermontFerrand 2, 63170 Aubiire (France).

INTRODUCTION In our continuing effort to provide data for binary mixtures of type alcohol + an n-alkane we report here results of experimental measurements of density and heat capacity in a range of temperatures and pressures. Density measurementswere made with a new flow vibrating-tubedensimeter for operation to high temperatures and pressures constructed at the University of Delaware. Densities for pure l-butanol, pure n-decane and their binary mixtures were determined from 298 K to 400 K,

in the range of pressures 0.1 to 20 M Pa for

the pure liquid components and at pressures slightly above atmosphericpressure for the binaries. Volumetric heat capacities, Cp/V (Cp and V being the molar heat capacity at constant pressure and molar volume respectively), were measured with a new scanning calorimeter which can be operated from 278 to 358 K at atmospheric pressure ; these measurementswere made on pure components as well as their binary mixtures. EXPERIMENTAL

Densitg measurements Two flow vibrating-tubadensimeters were used. Density measurementsat pressure higher than atmospheric pressure were made at

the

University

of

Delaware with the densimeter described in details by Albert and Wood (1984). The problem of operating the densimeter in such a way to use water as the calibratingreference liquid has been solved by means of two sample-loops put in series and using an intermediate(water miscible) reference liquid (Albert

0378-3812/86/$03.50

0 1986 Elsevier Science Publishers B.V.

138 et al., 1985). A deneimeter of the Picker design (SODEV model 02D) was used at the University of Clermont-Ferrand, for measurements at 298.15 K and atmospheric pressure ;

details on this densimeter and its operation can be

found in the literature : for example Picker et al., (1974).

Voluwtric heat capacity aasuracnts Measurements of volumetric heat capacities at atmospheric pressure were made at the University of Clermont-Ferrand using a new differential scanning calorimeter (SETARAM) described elsewhere (Benoist et al., 1983 ; Roux et al., 1983). The main features are the sample size (-1 cm31 and the liquid thermostat.

A

liquid thermostat insures the thermal equilibrium of the

detection block to better than 1 m K.

The temperature of the block can be

controlled and programmedupon both heating and cooling. For a typical run the liquid sample being in the measuring cell,

the reference liquid in the

reference cell, the temperatureof the detection block containing the two cells is programmed with steps at definite values. At each step a small temperature increment is produced in order to perform the actual measurement of heat capacity.

All the operations,

e.g.

temperature scanning between steps,

temperature increments at each individual step,

data acquisition and data

hendling to obtain the volumetric heat capacity are monitored by means of a computer (H.P. 85). The apparatushas been operated in the range 278-358 K, the observed sensibility being 0.2 uW.

Liquid components used at University of Delaware were Fisher certified ACS grade ;

l-butanol with stated maximum water content 0.1 mole per cent and

n-decane with stated purity 99.4 moles per cent. Liquid components used at the University of Clermont-Ferrandwere from Fluka ;

l-butanol puriss grade with

stated purity >99 moles per cent and n-decane purum grade with stated purity >99roles per cent. All liquids were dried with molecular seive and used without further purification. Their densities and heat capacities were in all cases in good agreenantwith literature data as indicated in the following section.

RgsuLTs Experimentaldensities,o,and molar heat capacities, Cp of pure liquid components at atmospheric pressure are given in Table 1 with some literature values for comparison. Experimental densities of pure components at various temperatwes and pressures are given in Table 2.

139 TABLE 1 Experimental densities, p, and molar heat capacities, C at atmospheric P' pressure of I-butanol and n-decane.

P

cP

kg.m -3

J.K-'. mol-'

T

K

This work

I-butanol

n-decane

Literature

This work

Literature

805.75a

176.67

177.02b

323.15

195.78

197.61'

348.15

217.38

368.15

234.23

298.15

805.65

298.15

726.18

726.30'

313.56

314.549

726.25d

314.47h

726.11e

313.93i

726.22f 323.15

325.77

348.15

339.18

368.15

350.96

a Hales and Ellender (1976).

b

327.00h

Counsel1 et al. (1965). ' Selected Values (1953)

d Riddick and Bunger (1970). e Goates et al. (1979) f Hutchings and Van Hook (1985). g Selected Values (1979) h Measerly et al. (1967). i Grolier et al. (1984).

P

19.8

0.7

9.7

740.95

806.02

813.20

820.06

20.5

0.2

10.2

20.5

19.8

9.7

734.01

10.2

P

0.6

FI

726.64

P k9.m-3

0.2

p1Pa

298.14 K

K P

801.40

794.16

786.74

723.11

715.52

707.44

kg.ni3

-

323.16

9.4

0.7

P

19.9

9.5

0.4

19.9

W

P

K

783.05

773.95

765.60

l-BUTANOL

20.17 20.19

10.1

0.5

20.0

10.1

696.97

706.34

a.5

P M Pa

688.17

n-DECANE

k9.ni3

-

348.16 P

K

767.55 767.59

757.86

747.52

692.95

683.40

672.39

k9i3

368.16

K

19.0 19.3

9.8 9.9

1.7

739.14 739.52

728.10 728.15

717.75

670.45 671.10

658.56 658.86 660.05 9.55 9.62 10.37

19.13 19.82

647.68

k9si3

P

399.81

1.7

P irl

Experimental densities, p, of liquid components at various temperatures and pressures.

TABLE 2

141 Excess molar volumes

(1)

VE = v - XI Vl - (1 - Xl) v2

were obtained from the densities of the mixtures according to relation

VE=xlMI

where Vi,

-1 -1 (P -PI I+

(I-

-1 -1 xl) M2 (P -P2 1

Mi and pi denote respectively the molar volume,

(2)

molar mass and

density of pure corrponenti (1 for l-butanol, 2 for n-decane) and XI is the mole fraction of l-butanol. Values of VE (Table 3) for l-butanol + n-decane for different sets of temperatures and pressures are shown in Fig. quantities were

fitted by

1.

For each set,

the excess

the method of unweighed least-squares with

a

smoothing polynomial of the type

VE = x1 (1 - xl) X Ai (1 - 2 x/ i=O

(3)

The coefficientsAi and the correspondingstandard deviations, s. are given in Table 4. These coefficientswere used to calculate the curves shown in Fig. 1. Molar heat capacities of pure components at various temperatures end atmospheric pressure are given graphically in Figs. 2 and 3. In these figures, the curves have been obtained by least-squaressmoothing of our data using the polynomial

Cp/J.K-1. mol-' = 1 Co (T/K-273.15) i=O

(4)

Correspondingcoefficientsare as follows : for l-butanol Co = 158.22; . Cl = 706.06 x 1O-3 ; C2 = 104.81 x 10-5 with standard deviation -3 o = 0.33 J.K-'.mol-' and for n-decane Co = 302.57 ; Cl = 415.46 x 10 ; C2 = 987.98 x lO-6 with standard deviation o= 0.058 J.K-'.mol-'.

Densities and volumetric heat capacities of pure liquids as well as of binary mixtures have been combined to capacities,C

generate a

series of

molar heat

at 298.15. 323.15, 348.15 and 368.15 K and atmosphericpressure P' E as well as the corresponding excess molar heat capacitie8.C given in P' Table 5.

142 TABLE 3 Excess molar volumes VE for I-butanol (I) + n-decane (2) at different temperaturesand pressures.

298.15 K

323.16 K

348.16 K

368.16 K

0.1 kl Pa

0.7 M Pa

0.4

0.5 PI Pa

VE

Xl

The

VE

Xl

-1 Ul13.11101

MPa

VE

VE

-1 Cll13.1d

-1 Cli13.11101

-1 cm3.nl,l

0.0456

0.0842

0.0489

0.1617

0.3530

0.4988

0.1387

0.2385

0.1358

0.3667

0.6276

0.9094

0.2551

0.3195

0.2456

0.5004

0.7955

1.1697

0.2910

0.3432

0.2748

0.5343

0.8118

1.1835

0.3925

0.3707

0.3933

0.5283

0.8846

1.2598

0.5475

0.3494

0.5538

0.5426

0.8307

1.1638

0.6553

0.3131

0.6555

0.4448

0.7142

1.0079

0.8564

0.1626

0.8671

0.2224

0.3357

0.4831

CpE

values were obtained according to CE P

=cP-x1 cPl -

(1 - x,1 co

(5)

where C refers to the mixture and subscripts 1 and 2 refer to l-butanol and P n-&cane respectively. At each temperatureand for each mixture, the excess quantities were fitted by the method of unweighed

least-squares with a

smoothingpolynomialof the type CE P

=

x1

(1 - xl)

!

i-0

Bi

(,‘+

(6)

143

Fig. I. Excess molar volumes Vg of I-butanol (1) + n-decane (2). Points are our experimntal data :V, at 298.15 K and 0.1 M Pa ;

0

,at 323.16 K and 0.7 M Pa ;A,

0

, at368.16K

at 348.16 K and 0.4 M Pa ;

and0.5MPa.

Curves represent the smoothing equation (3) with the coefficients given in Table 4.

240

16

Fig. 2. Hofar heat capacity of I-butanal aa a function of tamllerature. r)oint;s are our experimental data : l Using our density niewumments ;

0 using densities Literature

(2X%).

data : Z5 from Counsel1 et ax. (1965).

Curve represents +??Xt.

of Wales and Ellen&r

the smootking eqtiatian (4) witb the coefficients

given in the

145

50

0

Fig. 3. Molar heat capacity of n-decane

as a function

of temperature.

Points are our experimental data : l using our density measurements ; 0

using densities from Selected Values (1953).

Literature data

: A from Messerly et al. (1967).

Curve revesents the smoothing equation (4) with the coefficients given in the text.

146 TABLE 4 CoefficientsAi and standard deviations s for least-squaresrepresentations by smoothing equation (3), of ?

of I-butanol (1) + n-decane (2) at

different temperaturesand pressures.

A2

Al

*0

*3

A4

s

*5

&l-l

.~___________-.____-___-_~---~-~~-298.15 K

$)

1.4510

6.3827

0.3369

0.0072

2.2222

0.8048

0.5132

0.0011

3.4753

1.0472

4.8807

1.6693

3.1 M Pa

323.16 K 3.7 M Pa

348.16 K

2.4459

2.3390

0.0065

2.3586

3.0329

0.014

0.4 M Pa

368.16 K

9.1721

-

0.5 M Pa

The corresponding coefficients and standard deviations are given

in

Table 6. The C E curves are shown graphicallyin Fig. 4. P As can be seen from Fig. 1, althagh proper effects due to small pressure changes may not

be

negligible,

temperature, the maximum of

the

VE(x)-curve E

alcohol concentrations. At first, C

VE

appears to

increase with

being slightly shifted toward low increases strongly with increasing

temperature(see Fig. 4). However, fromThe measurementsat 369 K, the onset of a decrease of this quantity is evident.

In addition,

an

increasingly

significantnegative region of CpE(x) at low alcohol concentrationis observed. This negative region is a consequenceof the strong non-idealitywhich results from the formation of hydrogen bonds between alcohol molecules in both the pure liquid and the solution. The rather umymmetrical behavior of excess properties of alcohol + n-alkane solutions was predicted by Kehiaian and Treszczanowicz (19691,

using a simple association model and experimentally

shown by the early measurementsof Woycicka and Recko (1972) and Kalinowskaand

0

0.2

0.4

0.6

0.6

1 Xl

Fig. 4. Excess molar heat capacities CpE at atmospheric pressure of butanol (1)

t n-decane (2). Points are our experimentaldata

A,

et 348.15 K

; 0,

: V , at 298.15 K ; 0,

at 323.15 K

;

at 368.15 K. Curves represent the moothing equation (6)

with the coefficientsgiven in Table 6.

148 Modem

Woycicka

(1973).

capacities

have

permitted

solutions.

In

particular,

extremums (Roux-Desgranges the strong

self

the

concentration

terms

self

association

present

work

calorimetry

in

investigations

confirms

partial

of

that

of association

in

for

accurately

the very

and apparent 1985

the

Costas

and Patterson

alcohol ccupled

heat

flow

temperature

through

densitorretry

range

is

phenomena in alcohol

likely

of

show sharp

with

the

aid

molar heat

+ n-decane

(2)

capacities

at different

of

heat

to the

capacities

hydrogen and to

bonds.

(heat boost

in Our

capacity) theoretical

solutions.

E -1 C in J.K . mol -’ for 1-butanol (1) P temperatures and atmospheric pressure.

298.15 K

323.15 K

348.15 K

358.15 K

0.0456

8.96

8.20

2.65

0.16

0.1387

13.23

17.70

17.19

9.88

0.2551

14.61

20.86

23.50

20.23

0.2910

14.70

21.09

24.19

21.70

0.3925

14.81

21.20

25.04

24.31

0.5475

13.44

19.22

22.94

23.06

0.6553

11.58

16.81

20.13

20.23

0.8564

5.48

8.58

10.59

11.05

Xl

of

have quantitatively

TABBLE 5 Excess

heat

alcohol

1985) attributed

(1985)

dependence

solutions

region

capacities

Recently ,

alcohol.

measuring

dilute

; Tanaka et al.,

and temperature in

an extended

data

et al.,

model,

explained

techniques

take

association

Kehiaian-Treszczanowicz

of

flow to

I

498.40 182.23

-827.12

-245.90

298.15

323.15

348.15 368.75 7640.52

-2466.13

-26626.7

-2296.24

399.84

8262.07

3550.07

-2008.84

1173.91

40847.3

3083.11

-2867.59

0.22

0.27

-30545.4

8988.5

0.27

0.10

-1308.62

869.62

(CpE) J.K-' .mol -'

s

Coefficients Bi and standard deviationss for least-squares representations by smoothing equation E of I-butanol (1) + n-decane (2) at different temperatures and atmospheric pressure. of c P

TABLE 6 (6),

150

We gratefully ackmwledge the assistance of the France-American Commissionof the Directionde la Cooperationet des RelationsInternationales (Ministere de 1'EducationNaticnale) and of the Cormnission des Relations Internationales (Universitdde Clermont-Ferrand 2) during the realizationof this work. This work was supportedby the NationalScience Fundationunder grant numberCHE 800 96 72. Financialsupportreceivedwithin the frameworkof the Spanish-Frenchprogram for scientificand technicalcooperation("Action IntigrQ" between UniversiM

de

Clermont-Ferrand2

and Universidad de

Valladolid)is also gratefullyacknowledged.

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589-593.

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Cc&as,

M.

:

240-243.

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Hydrocarbons and

Related Corrpounds, 1953. American Petroleum InstituteReserach Project 44. Carnegie Press. Pittsburg. Table 20d (part 11, p. 288.

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Thermodynamic Research

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