Pyrene: vapor pressure, enthalpy of combustion, and chemical thermodynamic properties

A-166 J. Chem. Thermodynamics 1980, 12, 919-926

Pyrene : vapor of combustion, thermodynamic N. K. SMITH, R. and D. W. SCOTT

C.

pressure, enthalpy and chemical properties a,‘* ’ STEWART,

JR.,d

A.

G.

Bartlesville Energy Technology Center, Department Bartlesville, Oklahoma 74003. U.S.A.

OSBORN.

of Energy.

(Received 14 June 1979; in revised form 9 November 1979) Determinations were made of the vapor pressure of pyrene (crystal I and liquid) and of its enthalpy of combustion (crystal I). The results, with literature values of entropy, were used for compiling the chemical thermodynamic properties for the vapor state.

1. Introduction Pyrene was included in a study of polynuclear aromatic compounds of interest in advanced energy technology, primarily to obtain reliable thermodynamic quantities for the vapor state. Entropies of condensed states already were available from the low-temperature calorimetric studies of Wong and Westrum. Also, the enthalpy of formation of the crystal I had been determined by Wang”’ and earlier by Richardson and Parks.(3) Several studies of the vapor pressure had been reported, but they were inconsistent among themselves, and none appeared to be of adequate accuracy. Therefore, measurements to provide definitive vapor pressures were undertaken. The sample prepared for the vapor-pressure studies provided an opportunity for combustion calorimetry with material presumably more nearly pure than used in earlier work. The two kinds of experimental measurements, and the interpretation of the results. are discussed in what follows.

2. Sample The sample Hydrocarbon

of pyrene was provided by Professor E. J. Eisenbraun of the Synthesis Project at Oklahoma State University. It had been purified

a The research upon which this study was based was supported by the Office of Basic Energy Sciences, of Energy, and was conducted at the Bartlesville Energy Technology Center. b Contribution No. 235 from the thermodynamics research laboratory at the Bartlesville Energy Technology Center. c By acceptance of this article for publication, the publisher recognizes the Government’s (license) rights in any copyright and the Government and its authorized representatives have unrestricted right to reproduce in whole or in part said article under any copyright secured by the publisher. ’ Oral Roberts University, Tulsa, Oklahoma. Department

N. K. SMITH.

920

R. C. STEWART,

JR..

.A. G. OSBORN.

AND

D. W. SCOTT

by zone refining. The material used for the sample was a middle fraction of 29.1 g from a total charge of 162.5 g in the zone-refining tube. It was pure white, all of the yellowish color of the starting material having been concentrated in an end fraction of 22.8 g. Wong (” describes her sample as a pale yellow powder. Carbon dioxide was recovered from seven of the eight combustion experiments on pyrene; the mean percentage recovery was 99.981, with a standard deviation of the mean of +0.004. This is good evidence that the sample was free of non-isomeric impurity. Recovery ofcarbon dioxide from the calibration experiments (using benzoic acid) was (99.993 + 0.002) per cent.

3. Vapor pressure The vapor pressure was determined by inclined-piston-gauge manometry.‘4-h) Operation at the higher temperatures at which the vapor pressure of pyrene is within the range of the instrument was possible after some modification of the thermometry and control equipment. Measurements for the crystal I state were made between 398.15 and 423.15 K, and for the liquid between 425.65 and 458.15 K, with the results listed in the first two columns and footnote of table 1. The highest temperature, 458.15 K, is 35 K higher than temperatures at which vapor-pressure measurements had been made before with the inclined-piston-gauge manometer. A determination was attempted at 463.15 K, but was discontinued upon evidence of thermal decomposition of the sample. In order to deal exclusively with the liquid, the vapor pressure of the supercooled liquid was calculated from each observed value for the crystal I phase. To that end, the calorimetric values of Wong and Westrum”’ were used to derive the expression: ln(p,/p,,)

= 268.6187-6996.31(T/K)-‘-45.6846

ln(T/K)+O.O57217(T/K),

(1)

in which pL and pc, are the vapor pressures of supercooled liquid and crystal I phase, respectively, at temperature T.

TABLE T

1. Vapor

K

p(0bs.J kPa

398.15 403.15 408.15 413.15 418.15 422.15 423.15 425.65

0.0171 0.0225 0.0299 0.0395 0.0513” 0.0633 0.0667 0.0763

Pressure

of pyrene:

61, kPa a a ’ a ’ ’

o.cQO5 0.0002 0.0002 0.0002 -0.0002 - 0.0003 -0.OcO3 0.0001

6p = (p(obs.)-p(calc.)} 4LJ) -kPa 0.00032 0.00030 0.00028 0.00026 0.00025 0.00025 0.00025 0.00025

y For supercooled liquid. The values of p/lcPa actually 0.0247, 0.0347, 0.0480, 0.0621, and 0.0661. b Not used in least-squares adjustment.

and o denotes T It

428.15 433.15 438.15 443.15 448.15 453.15 458.15

observed

PWs.) kPa 0.0865 0.1107 0.1416 0.1789 0.2246 0.2804 0.3453 b

for crystal

standard

deviation

6P

O(P)

kPa

kPa

0.0000 - 0.0002 0.0004 0.0002 0.0000 - 0.0002 - 0.0032

0.00025 0.00027 0.00027 O.CQO27 OX0027 0.00028

I state are: 0.0124,0.0175,

PROPERTIES

OF

921

PYRENE

The vapor pressure of the liquid was represented with the equation :“I lnp,

= A+B/T,-3.013 In T,+5.5121;,-3.294Ti+C(-62.646ln +77.392T,-19.424T~)+0.176p,exp{(1.65+0.8C)/T,-0.9C~,

TR (2)

in which TR = T/O, and pR = p/II,. The effective (not necessarily actual) values of critical temperature and pressure were taken as 0,/K = 954.9 and ll,/kPa = 2766. The values of the constants, with their standard deviations: A = - 10.33973i4.6. H = - 17.29997+ 1.6, C = 0.4235235 +O.lO, were obtained by a least-squares fit.“’ Values of vapor pressure from equation (2) are compared with the observed values in the third column of table 1. The measured vapor pressure at 458.15 K was slightly out of line with the rest of the measurements and was excluded from the least-squares adjustment. The discrepancy, which is too small to be revealed by the “third-law” treatment of a later section, might have arisen from experimental difficulty not necessarily related to the high temperature. Several investigators have reported vapor pressures for crystal I phase by effusion methods. The results of Malaspina, Bardi, and G&h’* and of Bradley and Cleasby!” after conversion to values for the supercooled liquid by use of equation (1). arc compared with the present results in the deviation plot of figure 1. Hoyer and Peperle”” and likewise Inokucni, Shiba, Handa, and Akamatu”” did not report original measurements, but only equations; their equations yield values, respectively, more than 30 per cent lower and 500 per cent higher than obtained by extrapolation with equations (2) and (1) and thus off scale on figure 1. These comparisons cast considerable doubt on the reliability of effusion methods for determining vapor pressure. 30

3

I

T/K lOOAp/p against temperature, FIGURE 1. Deviation plot of vapor pressures for pyrene, Ap = {p(obs.)-p(calc.)}, the calculated values of vapor pressure being obtained from equation Malaspina, Bardi, and Gigli $s) A, Bradley and Cleasby :@’ 0. this research.

with (2). 0,

The Antoine equation for liquid pyrene in the APIRP-44 tables,(12) seemingly based on the results obtained by Tsypkina’r3’ with a dynamic method, gives values more than 60 per cent lower than the observed values of this research.

922

N. K. SMITH.

R. C. STEWART,

TABLE

2. Entropy

JR..

of pyrene

T/K

423.81

S,/J K-’ mol-’ ’ AfH/T J K-’ mol-’ (R/J K- ’ mol-‘)ln(p/p’)

367.7+0.7 182.0+0.9 -60.6rtO.O

S”(expt)/J K-’ mol-’ S”(calc.)/J K-’ mol-’ {S”(expt)-S”(calc.)}/J

489.1+1.1 488.7 0.4

’ Wong

K-’

mol-’

A. G. C,,H1O

OSBORN.

AND

in the ideal-gas 440

D. W. SCOTT state 460

381.2kO.8 172.5f0.4 -53.9kO.O 499.8 + 0.9 499.7 0.1

480

397.4+0.x 161.9k1.3 -46.5fO.O

413.3kO.8 152.2+ 2.2 -39.8+0.0

512.8k1.5 513.2 -0.4

525.7 + 2.3 526.6 -0.9

and Westrum.“’

Equation (2) was used to calculate the entropy of vaporization at the triple-point temperature and three other temperatures at which Wong and Westrum”) reported values of the entropy of the liquid. In calculating the enthalpy of vaporization by means of the Clapeyron equation, crude estimates were made of the almost negligible effects of gas imperfection and liquid volume. The calculation of the entropy in the ideal-gas state is summarized in table 2. 4. Thermodynamic

functions

As an aid in interpreting the experimental results, thermodynamic functions were calculated by the rigid-rotator harmonic-oscillator approximation. For an assumed TABLE

T it

3. Standard

-{G"(T)-H"(O)}/T

0 200 273.15 298.15 300 400 500 600 a The standard by the reaction:

J K-’

-

mol-’

0

0

269., 294., 302., 303.0 336,s 370., 404.,

69., 92., lOO., lOl., 135.6 169., 200.,

0

mol-’

of pyrene

ClhHIO(g)

H'(T)-H"(O) -

kJ mol-’

0 13.8, 25.1, 29.9, 30.3, 54.2, 84.5, 120.,

c;

S J K-’

properties

~H"V)-H"(O)~IT

JK-‘mol-’

200 273.15 298.15 300 400 500 600

T K

thermodynamic

J K-’

mol-’

0

0

338., 386., 402.9 404.2 472., 539., @x5

128., 183., 201.8 203., 213., 331., 378.,

enthalpy, Gibbs energy, 16C(c, graphite)+5H,(g)

and common = C,,H,,(g).

255., 234., 227., 225., 225., 218., 212., 208.,

255., 295., 318., 327., 328., 363., 40% 438.,

logarithm

of the equilibrium

~~.l - 60.9; - 57.3, -57.1, -41.4, -41.8, -38.1, constant

of formation

PROPERTIES

OF

923

PYRENE

structure with 2rc/3 bond angles and C-C and C-H bond distances 0.141 nm and 0.108 nm, respectively, the product of the principal moments of inertia is 2.875 x lo-“’ g3 cm’. The symmetry number is 4. Bree, Kidd, Mistra, and Vilkos (14) have made a vibrational assignment for pyrene based on molecular spectra for the crystalline and solution states. With five fundamentals of wavenumber less than 300 cm-i, most or all of which must have significantly lower wavenumbers in the vapor state than in the condensed state, the assignment as it stands is not suitable for calculating vapor-state thermodynamic functions. The expedient adopted was to lump all effects of lower wavenumbers in the vapor state into the lowest B,, fundamental. Bree and coworkers’ assignment was used for the remaining 71 fundamentals, their calculated values being used if observed values were lacking. Then 82 cm-’ was used for the lowest B,, fundamental instead of 126 cm-’ observed in a condensed state to fit the experimental values of entropy. The standard thermodynamic functions were calculated at 273.15 and 298.15 K and at 100 K intervals between 200 and 600 K, so values at intermediate temperatures can be obtained by 5-point Lagrangian interpolation. The results are in table 3. Final digits retained for smoothness and internal consistency are subscripted as a reminder that they may not be justified by the absolute accuracy. The calculated values of entropy are compared with the experimental values in table 2.

5. Enthalpy of sublimation The individual values of vapor pressure from table 1, Wong and Westrum’s”’ values of -{G”(T)-H”(O)}/T for liquid and crystal I state, and values calculated for the vapor were used to calculate values of the enthalpy of sublimation ArHo at T = 0. The calculations are summarized in table 4. TABLE

TIK 398.15 403.15 408.15 413.15 418.15 422.15 423.15 425.65 428.15 433.15 438.15 443.15 448.15 453.15 458.15

52

4. Enthalpy -R

of sublimation

of pyrene

kPa)

-A[{G”(T)-H”(O)}/71

ln(pllOl.325 J K-’

mol-’ 74.90 72.05 69.18 66.35 63.65 61.50 60.98 59.80 58.75 56.70 54.65 52.71 50.81 48.97 47.24

J K-’

C16H10

at T = 0 A:

H"(O)

mol-’

kJ mol-’

185.91 185.68 185.43 185.15 184.88 184.67 184.61 184.31 183.94 183.21 182.48 181.74 181.01 180.30 179.61 Accepted

103.8 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9 103.9

value :

924 TABLE

N. K. SMITH,

5. Enthalpy

R. C. STEWART,

of sublimation

of pyrene

T ..K

A:H (77 kJ mol-’

348 361 364 369 317 384 393 402 411 419

98.97 98.72 98.47 98.22 97.91 97.69 97.34 97.00 96.64 96.26

JR..

A. G. OSBORN.

AND

at T = 0 from microcalorimetric and GigI?*’

D. W. SCOT1

results of Malaspina,

- A{H’(T)-H”(0);

A:H”(O)

kJ mol-’

kJ mol.

5.28 5.82 5.95 6.19 6.58 6.93 7.41 7.97 8.59 9.21

104.3 104.5 104.4 104.4 104.5 104.6 104.7 105.0 105.2 105.5 104.7

Mean

:

Bard].

’

Malaspina, Bardi, and Gigli@’ reported experimental values of enthalpy of sublimation determined with a Calvet microcalorimeter. Their results were used in a similar manner to calculate AEH”(O) as shown in table 5. The values of A;Zf”(O) show a slight trend with the temperature of the calorimetric measurement and more scatter than those in table 4. However, the mean value is only 0.8 per cent higher than the one obtained from the vapor pressure. With 103.9 kJ mall’ taken for AEH”(O), the enthalpy of sublimation at 298.15 K is calculated to be (100.2 f 0.4) kJ mol - ‘. The assigned uncertainty arises largely from uncertainty in the approximate thermodynamic functions.

6. Enthalpies of combustion and formation Experimental procedures used for the combustion calorimetry of hydrocarbons by this laboratory have been described. (15, 16) Rotating-bomb calorimeter BMR II”” and platinum-lined bomb Pt-3b, (18) internal volume 0.349, dm3, were used without bomb rotation. For each experiment, 1.0 cm3 of water was added to the bomb, and the bomb was flushed and charged to 3.04 MPa with pure oxygen. Because the oxygen was pure, nitric acid formation was negligible. Each experiment was started at 296.15 K, and the final temperatures were very nearly 298.15 K. The material for combustion was compressed into pellets, and a platinum baffle was placed over the crucible to reduce soot formation to a negligible level. Temperatures were measured by quartz crystal thermometry. A programmable calculator controlled the combustion experiments and recorded the results. The quartz thermometer was calibrated with a platinum resistance thermometer. Counts of the crystal oscillation were taken over 100 s periods throughout .the experiments ; integration of the time-temperature curve is inherent in the quartz thermometer reading.” 9, National Bureau of Standards sample 39i benzoic acid was used for calibration ; its specific energy of combustion is - (26.434kO.003) kJ g- ’ under certificate conditions. Conversion to standard conditions’20’ gives - (26413.68 + 3.01) J g-’ for

PROPERTIES

OF PYRENE

925

A, V/M, the specific energy of the idealized combustion reaction. Eight benzoic acid calibration experiments interspersed among the experiments with pyrene gave e(calor) = (16772.05kO.32) J K-’ (mean and standard deviation of the mean). For the cotton thread fuse, empirical formula CH1,77400,887, A,Un/M was - 16945 J g-l. The results are based on the 1961 molar masses of the elements.‘2” For reducing apparent mass in air to mass, converting the energy of the actual bomb process to that of the isothermal bomb process, and reducing to standard states,“@ the following values were used for the properties of pyrene : density, 1.277 g cmm3 :(22’ specific heat capacity, 1.134 J g-l K-l z(2)and (ae/ap),, 0.79 J kg-’ Pa-1.(23) TABLE 6. Summary of a typical calorimetric experiment at 298.15 K a 0.862804 0.001758 0.05535 1.99610 - 33478.7 - 36.3 0.8

m’(pyreneVg mm(fuse)/g n’(H,O)/mol AL/K .s(calor.)( - Af,)/J s(cont.)( - Af, )/J b

A&,/J AE,,WNO, )/J A&m tostsi ,,,,jJ ’

( - m’(ACU/M)(fuse)}/J (m’(A, U”/M)(pyrene)}/J

(A,U“lM)(pyreneYJ g-’ (4 U”/M)(pyrene)lJ

g-’

22.0 29.8 - 33462.4 - 38783.4 -(38785.0+0.8) experiments

mean and standard deviation of the mean. eight

a The symbols and abbreviations of this table are those of reference 20 except as noted. b s’(cont.)(ti -298.15 K) +E’(cont.)(298.15 K)- t,+At,). ’ Items 81 to 85. 87 to 90, 93, and 94 of the computation form of reference 20.

Results of the combustion experiments are summarized in table 6. Values of A, V/M refer to the reaction of unit mass of sample ; the equation for the reaction is C16Hlo(c)+

W/2)02(g)

= 16C02k)+

5H2W).

(3)

The derived value for the standard molar energy of the combustion reaction, ACU”, is - (7844.59 &- 1.OO) kJ mol- ’ ; for the standard molar enthalpy of combustion, Ai,H", ---(7850.79) 1.OO) kJ mol- ’ ; and for the standard molar enthalpy of formation, &,H”, (125.49 + 1.24) kJ mol-‘. These uncertainties are the uncertainty intervals.‘24’ The standard enthalpies of formation of CO,(g) and H,O(l) were taken to be -393.51 kJ mol-’ and -285.83 kJ mol-‘, respectively;‘25’ corresponding uncertainties assigned were 0.046 kJ mol-’ and 0.042 kJ mol-1.(26) Combining this value for the standard enthalpy of formation of the solid with the value for the enthalpy of sublimation, reported previously in this paper, gives a value of (225.7 &- 1.3) kJ mol- ’ for the standard enthalpy of formation of gaseous pyrene at 298.15 K. Wong (2) found the value -(7840.1,f0.3,) kJ mol-’ for AcH”, and previously Richardson and Parksf3) reported a value of - (7836.5, A2.9,) kJ mol-‘. No

926

N. K. SMITH,

R. C. STEWART,

JR., A. G. OSBORN.

AND

D. W. SCOTT

explanation has been found for the rather large discrepancy between these values and the result, - (7844.59 + 1.O), reported here.

7. Standard thermodynamic properties The experimental value of the standard enthalpy of formation at 298.15 K, standard thermodynamic functions for pyrene vapor from table 3, and standard thermodynamic functions for C(c, graphite) and H,(g) from the JANAF tablest2” were used to calculate values of the standard enthalpy, entropy, and common logarithm of the standard equilibrium constant of formation. The results are in table 3. Although not as accurate as ones usually compiled for compounds of lower molar mass, which are more susceptible to calorimetric and spectroscopic investigation, they should suffice for many practical chemical-thermodynamic applications.

REFERENCES 1. Wang, W-K; Westrum, E. F., Jr. J. Chem. Thermodynamics 1971, 3, 105. 2. Wong, S-W. S. Diss. Abstr. B 1%7, 28(6), 2383. 3. Richardson, W.; Parks, G. S. J. Am. Chem. Sot. 1939, 61, 3543. 4. Douslin, D. R.; McCullough, J. P. U.S. Eur. Mines, RI 6149, 1963. 5. Douslin, D. R.; Osbom, A. G. J. Sci. Instr. 1965, 42, 369. 6. Osbom, A. G.: Douslin, D. R. J. Chem. Eng. Data 1975, 20. 229. I. Scott, D. W.; Ohm, A. G. J. Phys. Chem. 1979, 83,2714. 8. Malaspina, L.; Bardi, G.; Gigli, R. J. Chem. Thermodynamics 1974, 6, 1053. 9. Bradley, R. S.; Cleasby, T. G. J. Chem. Sot. London 1%3,2, 1690. 10. Hoyer, H.; Peperle, W. Z. Elektrochem. 1958, 62, 61. 11. Inokucni, H.; Shiba, S.; Handa, T.; Akamatu, H. Bull. Chem. Sot. Jpn 1952, 25, 299. 12. American Petroleum Institute Research Project 44 at Texas A&M University, Selected Values of Properties of Hydrocarbons and Related Compounds Table 23-2-(33.6050)-k, Looseleaf, issued October 31. 1975. 13. Tsypkina, 0. ?a. Zhur. P&lad. Khim. 1955,28, 185; J. Appl. Chem. (U.S.S.R.) 1955,28, 167 (English translation). Compare Chem. Abs. 49, 9976g. 14. Bree, A.; Kidd, R. ; Mistra, T. N.; Vilkos, V. V. Spectrochimica Acta 1971, 27, 2315. 15. Good, W. D.; Scott, D. W. J. Chem. Eng. Dnrn 1969, 14, 102. 16. Good, W. D. ; Smith, N. K. J. Chem. Eng. Data 1969, 14, 231. 17 Good, W. D.; Scott, D. W.; Waddington, G. J. Phys. Chem. 1956, 60, 1080. 18. Good, W. D.; Douslin, D. R.; Scott, D. W.; George, A.; Lacina, J. L.; Dawson, J. P.; Waddington, G. J. Phys. Chem. 1959, 63, 1133. 19. Goldberg, R. N.; Nuttall, R. L.; Prosen, E. J.; Brunetti, A. P. NBS Report 10437, June 9, 1971. U.S. Department of Commerce, National Bureau of Standards. 20. Hubbard, W. N.; Scott, D. W.; Waddington, G. In Experimental Thermochemisfry. Rossini, F. D.: editor. Interscience: New York. 1956, chapter 5, pp. 75-128. 21. Cameron, A. E.; Withers, E. J. Am. Chem. Sot. 1962, 84, 4175. 22. Robertson, J. M.; White, J. G. J. Chem. Sot. 1947, 358. 23. McLaughlin, E.; Ubbelohde, A. R. Trans. Faraday Sot. 1957, 53, 628. 24. Rossini, F. D. In Experimenral Thermochemisrry. Rossini, F. D.: editor. Interscience: New York. 1956, chapter 14, pp. 297-320. 25. Wagman, D. D.; Evans, W. H.; Halow, I.; Parker, V. B.: Bailey, S. M.; Schumm, R. H. Nar. Eur. Stand. U.S. Tech. Note 270-3. 1968. 26. Rossini, F. D. J. Res. Nut. Bur. Stand. 1931, 6, 1. 27. JANAF Thermochemical Tables, NSRDS-NBS 37. Second edition. 1971.