Eric M. Yezdimer, and Robert H. Wood

Transcription

1 J. Chem. hermodynamics 1997, 29, Aarent molar heat caacities of aqueous solutions of roylamine, 1,4-butanediamine, 1,6-hexanediamine, roylamine hydrochloride, roionamide, yridine, and sodium benzenesulfonate at temeratures from 300 to 525 and a ressure of 28 Americo Inglese, a Diartimento di Chimica, Universita` di Bari, rav. 200 Re David 4, Bari, Italy Josef Sedlbauer, Deartment of Chemistry, echnical University Liberec, Ha lkova 6, Liberec, Czech Reublic Eric M. Yezdimer, and Robert H. Wood Deartment of Chemistry and Biochemistry, and Center for Molecular and Engineering hermodynamics, University of Delaware, Newark, DE 19716, U.S.A. he aarent molar heat caacities of dilute aqueous solutions of roylamine, 1,4-butanediamine, 1,6-hexanediamine, roylamine hydrochloride, roionamide, yridine, and sodium benzenesulfonate were measured at and = 28. Corrections for hydrolysis or dissociation reactions and relaxation effects were alied where necessary, and the results were extraolated to infinite dilution to obtain C,2. After subtracting the heat caacity of a oint mass, the remaining heat caacity was successfully divided into functional grou contributions at all temeratures. Including the results of our revious aers on alcohols and diols and carboxylic acids and sodium carboxylates, the heat caacity contributions of the CH 2, CH 3, OH, COOH, (COOH) 2, NH 2, CONH 2, COONa, and NH 3Cl grous are now available, and these allow reasonably accurate redictions of the heat caacities of all aqueous comounds comosed of these grous in this temerature range Academic Press Limited EYWORDS: aarent molar heat caacity; roylamine; 1,4-butanediamine; 1,6- hexanediamine; roylamine hydrochloride; roionamide; yridine; sodium benzenesulfonate 1. Introduction he thermodynamic roerties of the aqueous solutions of organic secies at elevated temeratures are of key imortance in the understanding of a variety of a o whom corresondence should be addressed /97/ $25.00/0/ct Academic Press Limited

2 518 A. Inglese et al. natural henomena, such as the transformation of natural hydrocarbon deosits at high temeratures, or the interaction of aqueous solutions with minerals. In addition, there are many industrial rocesses in which the knowledge of the roerties of organic secies dissolved in hot water is essential; for instance, boiler water chemistry, or wet oxidation at both moderate and suercritical temeratures. Recent aers from this laboratory (1 3) reorted the aarent molar volumes of a variety of organic comounds, (3) and the heat caacities of alcohols and diols (1) and carboxylic acids and sodium carboxylates (2) in water at temeratures to 525, and showed that grou contribution methods were alicable from = 300 to = 525 for both these artial molar roerties. his aer concludes the series on the heat caacities of aqueous solutions of organic comounds at high temeratures. We reort here the heat caacities of several amines and other organic solutes and then exlore the utility of dividing these heat caacities into functional grou contributions. hese heat caacities allow the accurate calculation of the chemical otentials of comounds built from these grous at temeratures to 525 from chemical otentials and entroies at = ABLE 1. Aarent molar heat caacities C, of roylamine(aq). C, = C, ex + C, ; denotes the degree of hydrolysis of the amine; C, is the correction to C, ex due to hydrolysis and chemical relaxation; c,s/c,w is the ratio of massic heat caacities of solution and water, equation (1); m = 1 mol kg C, m/m c ex,s/c,w J mol C, C J mol, J mol

3 C,m of aqueous amines and other organic solutes to = ABLE 2. Aarent molar heat caacities C, of 1,4-butanediamine(aq). C, = C, ex + C, ; 1 and 2 denote the first and the second degree of hydrolysis of the amine, resectively; C, is the correction to C ex, due to hydrolysis and chemical relaxation; c,s/c,w is the ratio of massic heat caacities of solution and water, equation (1); m = 1 mol kg C, m/m c ex,s/c,w J mol C, C 2 J mol, J mol Exerimental wo stock aqueous solutions of roylamine, 1,4-butanediamine, 1,6-hexanediamine, roylamine hydrochloride, roionamide, yridine, and sodium benzenesulfonate were reared by mass from the solute and water. Proylamine (Aldrich: mass fraction 0.99) was used directly without further urification. he two stock solutions were reared by weighing the roylamine in a sealed syringe in order to reduce the error of the mass due to the high volatility of roylamine. he samle was then carefully transferred to a bottle containing a known mass of water. he 1,4-butanediamine (Aldrich: mass fraction 0.99) and 1,6-hexanediamine (Aldrich: mass fraction 0.98) were used without further urification. In order to determine the water content in the commercial samles, they were dissolved in methanol (Fluka: mass fraction 0.998, mass fraction of water

4 520 A. Inglese et al ) and the resulting solutions were titrated with arl-fisher solution. aking into account the water resent due to the methanol in the solution, the water contents of the analysed samle of 1,4-butanediamine and 1,6-hexanediamine were mass fractions 10 2 ( ) and 10 2 ( ), resectively. he concentrations of the aqueous solutions of 1,4-butanediamine and 1,6-hexanediamine were calculated, taking into account the water content of the samles. Proylamine hydrochloride (Aldrich: mass fraction 0.99) was further urified by crystallization from (methanol + diethylether) solution. Proionamide (Aldrich: mass fraction 0.97) was urified before use by sublimation. About 200 g of roionamide was laced in a round-bottomed flask with a long large neck connected at the to to a vacuum um. he samle was heated in a thermostat at a temerature of 333. After 24 h, about 80 er cent of the original samle had sublimed on the surface of the uer neck. he sublimed samle was collected and used to reare aqueous solutions. Pyridine (Fluka: mass fraction 0.998) was used without further urification. Sodium benzenesulfonate solutions were ABLE 3. Aarent molar heat caacities C, ex of 1,6-hexanediamine(aq). C, = C, ex + C, ; 1 and 2 denote the first and the second degree of hydrolysis of the amine, resectively; C, is the correction to C ex, due to hydrolysis and chemical relaxation; c,s/c,w is the ratio of massic heat caacities of solution and water, equation (1); m = 1 mol kg C, m/m c ex,s/c,w J mol C, C 2 J mol, J mol

5 C,m of aqueous amines and other organic solutes to = ABLE 4. Aarent molar heat caacities C, ex of roylamine hydrochloride(aq). C, = C, ex + C, ; denotes the degree of dissociation of the roylammonium ion; C, is the correction to C, ex due to dissociation and chemical relaxation; c,s/c,w is the ratio of massic heat caacities of solution and water, equation (1); m = 1 mol kg C, m/m c ex,s/c,w J mol C, C J mol, J mol reared using a samle (Fluka: mass fraction 0.99) dried for 4 d in a vacuum oven at = 323. he instrument and the exerimental rocedure used to measure the heat caacities of solutions have been described in detail by Carter and Wood, (4) with some modifications due to Sharygin. (5) he aarent molar heat caacities C, ex were calculated from: C, ex = c,w (M+1/m) (c,s /c,w )/m, (1) where c,s and c,w are the massic heat caacities of solution and water, resectively; M is the molar mass of solute; and m is the molality of the solution. he ratio of

6 522 A. Inglese et al. massic heat caacities c,s /c,w is related to the ratio of owers in the heater by the relation: c,s /c,w =( w / s ) SL 1+f ( s w )/ w, (2) where ( w / s ) SL is the ratio of densities of water and solution at the temerature and ressure of the samle loo; f is the calibration factor for heat loss; and s and w are the owers that kee the temerature rise ex constant when water is relaced by the solution in the samle cell. he value of s that gives the same ex was found by calculation from a ower that gave the same ex and the measured sensitivity of to small changes in ower. he calibration factor for heat loss f equation (2) was determined by changing (with an auxiliary ISCO um) the base flow rate in the samle cell in order to mimic a change in heat caacity. he resulting values of f for the resent exeriments have ABLE 5. Aarent molar heat caacities C, = C ex, of roionamide(aq). c,s/c,w is the ratio of massic heat caacities of solution and water, equation (1); m = 1 mol kg C, ex m/m c,s/c,w J mol

7 C,m of aqueous amines and other organic solutes to = ABLE 6. Aarent molar heat caacities C, = C ex, of yridine(aq). c,s/c,w is the ratio of massic heat caacities of solution and water, equation (1); m = 1 mol kg C, ex m/m c,s/c,w J mol been reorted by Inglese and Wood. (1) he temerature rise of the liquid in the samle cell ex was determined by measuring the temeratures after the samle cell heater, before and after turning on the heater. he temerature reorted is (block) + (1/2) ex. he ratio of densities, at the temerature and ressure of the samle loo, ( w / s ) SL, was calculated for all solutes included in this study from the aarent molar volumes V determined by Criss and Wood (3) at m 0.1 mol kg, by means of the equation: ( w / s ) SL =(1+m w V )/(1 + m M), (3) where M is the molar mass of the solute. Here, V was assumed constant in the investigated range of molalities for the urose of this calculation. he obtained ratios of densities ( w / s ) SL at = and = 28 for roylamine are (m = mol kg ) and (m = mol kg ); for 1,4-butanediamine, (m = mol kg ) and (m = mol kg ); for 1,6-hexanediamine, (m = mol kg ) and (m = mol kg ); for roylamine hydrochloride, (m = mol kg ) and (m = mol kg ); for roionamide, (m = mol kg ) and (m = mol kg ); for yridine, (m = mol kg ) and (m = mol kg ); and for sodium benzenesulfonate, (m = mol kg ) and (m = mol kg ).

8 524 A. Inglese et al. ABLE 7. Aarent molar heat caacities C, = C ex, of sodium benzenesulfonate(aq). c,s/c,w is the ratio of massic heat caacities of solution and water, equation (1); m = 1 mol kg C, ex m/m c,s/c,w J mol Although assuming V is not deendent on molality could cause a small error at higher molalities (erhas 6 J mol at m = 0.7 mol kg, as estimated from the molality deendence of alcohols), the error is roortional to the molality, so it will not result in areciable error in the extraolated value of C,2. At each temerature the calorimeter was tested by measuring the heat caacity of NaCl(aq) at m = mol kg. he exerimental results obtained for this solution were in satisfactory agreement with the earlier measurements (1) and the literature results. (6) 3. Results he ratio of secific heat caacities c,s /c,w, from equation (2), and the exerimental aarent molar heat caacities C ex,, see equation (1), at constant ressure for

9 C,m of aqueous amines and other organic solutes to = ABLE 8. Standard aarent molar heat caacities C,2 of roylamine, 1,4-butanediamine, and 1,6-hexanediamine in aqueous solutions, where b is defined in equation (4), and is the difference between exerimental C,2 and that calculated from the functional grou additivity scheme, equation (8) C,2 b J mol J mol roylamine a ,4-butanediamine ,6-hexanediamine a he uncertainties are estimated 95 er cent confidence limits of C,2 from the fit. aqueous solutions of roylamine, 1,4-butanediamine, 1,6-hexanediamine, roylamine hydrochloride, roionamide, yridine, and sodium benzenesulfonate are given in tables 1 to 7, resectively. Results obtained when the calorimeter occasionally exhibited a noisy baseline are not reorted. Values of C ex, were calculated using initial and final baselines, and both are reorted in tables 1 to 7. When the baseline shift was high ( 12 J mol for a m = 0.4 mol kg solution), only values that agreed with the other measurements were reorted. Because the hydrolysis of the amines and dissociation of the roylammonium ion might make areciable contributions to C ex, under the conditions of our measurements, we alied corrections due to these reactions and also due to the chemical relaxation effect. (7) Because of a lack of the data required for calculations, we could not make the corrections for sodium benzenesulfonate. Calculated corrections C,, the degree of hydrolysis or dissociation, and the final corrected aarent molar heat caacity C, = C, ex C, are reorted in tables 1 to 4. he method of calculating the corrections was described in detail in the revious aer. (2) he data used to calculate the heat caacities of ions at infinite dilution at = 28 were those of Sharygin (8) for HCl, Archer (6) for NaCl, and Simonson (9) for NaOH (corrected from the ressure = 7 ). Reaction roerties for all hydrolysis or dissociation reactions at standard temerature and ressure were calculated from the volumetric data of Ho iland (10) ( r Vm ), from Robinson and Stokes (11) ( r Hm and ln ), and from Oloffson and Heler (12) ( r Hm and ln for water dissociation). he corrections were never much larger than the estimated

10 526 A. Inglese et al. ABLE 9. Standard aarent molar heat caacities C,2 of roionamide, yridine, roylamine hydrochloride, and sodium benzenesulfonate in aqueous solutions, where b is defined in equation (4), and is the difference between the exerimental C,2 and that calculated from the functional grou additivity scheme, equation (8) C,2 b J mol J mol roionamide a yridine roylamine hydrochloride b b 1 sodium benzensulfonate b b 1 a he uncertainties are estimated 95 er cent confidence limits of C,2 from the fit. b Due to the neglect of the second virial coefficient in the extraolation, extra uncertainties ( 5 J mol at = 448 and 10 J mol at = 523 ) were added to the 95 er cent confidence limits. exerimental uncertainties; the largest corrections are 3 er cent at = 303 (roylamine), and 1 er cent at = 523 (roylamine hydrochloride). he resulting aarent molar heat caacities for the amines were fitted with the equation: C, = C,2 +b (1 ) (m/m ), (4) with m = 1 mol kg, to obtain the values of the artial molar heat caacity at infinite dilution C,2, its estimated uncertainty, and the sloe b (see table 8). he Pitzer ion-interaction treatment (13) with C (1) = 0 was used for the extraolation of the heat caacities of roylamine hydrochloride and sodium benzenesulfonate: C, = C,2 +(A C /1.2) ln{ (I/I ) 1/2 } +2R C (0) (1 ) (m/m ), (5) where I = 1/2 i m i zi 2 is the ionic strength (m i and z i are the actual molality and charge of ion i, resectively), A c is the Debye Hückel limiting sloe (calculated here from Archer and Wang, (14) with roerties of water given by Hill s (15) equation of state), and C (0) is a constant. We have found reviously (2) that the estimated

11 C,m of aqueous amines and other organic solutes to = er cent confidence limits of C (0) were always higher for the carboxylates than the value itself and the fits were almost undistinguishable with or without this arameter. he same was found for both salts included in this study; so C (0) = 0 was used in all extraolations. he resulting C,2 of roylamine hydrochloride and sodium benzenesulfonate and their estimated uncertainties are given in table 9. In the same table, the values of C,2 for roionamide and yridine may be found, for which the linear extraolation, equation (4) with = 0, was used. It has been shown in revious aers from this laboratory (1 3) that functional grou methods work quite well for V2 and C,2 at temeratures to 525. he functional grou equation is: C,2 = C, (std. state) + n j C j, (6) j where is the number of articles (1 for a non-electrolyte, 2 for a 1 1 electrolyte); C, (std. state) is the standard state heat caacity of a single article; and C j is the contribution to the heat caacity of the functional grou j. he standard state heat caacity is the artial molar heat caacity roduced by adding a oint mass to a mass of 1 kg of solution at constant ressure: (16 18) C, (std. state) = 2 R w +R 2 ( w / ) + (3/2) R, (7) where w = (1/V m ) ( V m / ) for ure water. For convenience in calculating C, (std. state), a table of w values at = 28 and is given by Inglese and Wood. (1) he form used for rediction of the temerature deendence of C,2 was that introduced in a revious aer: (2) C,2 =C, (std. state) + n j [a j + b j (/) + c j / (/) ]. (8) j able 10 gives the functional grou arameters resulting from a weighted least-squares fit of equation (8) to the calculated values of C,2 from tables 8 and 9 (amines, roylamine hydrochloride, and roionamide) and from the revious ABLE 10. Functional grou arameters in equation (8) Grou j a j b J mol j 10 J mol 6 c j J mol CH CH CONH COOH (COOH) COONa NH NH 3Cl OH BzSO 3Na Pyridine

12 528 A. Inglese et al. aers (1,2) (alcohols, diols, carboxylic acids, and carboxylates). he weights were (1/ ) 2, where is the estimated standard deviation of C,2 from extraolation. Because of a lack of data for related comounds, yridine and sodium benzenesulfonate were evaluated searately, i.e., one comound as one grou. In the main fit, the average [ C,2(ex) C,2(calc) / ] was 0.78, and the maximum was 2.5. he average relative error was 2.0 er cent, which was mainly due to the high relative error in the sodium acetate measurement (2) at = 448. he reason for searate evaluation of the (COOH) 2 grou and the evidence of steric, or near-neighbor effects, or both, were already discussed. (2) For diamines included in this work, these effects were found to be much less than the exerimental uncertainties; the same holds true for diols reorted in the revious aer. (1) FIGURE 1. Comarison of C,2 redictions with exerimental data:, exerimental results;, HF equation of state; (21), redictions of the grou contribution method, equation (8). (a), 1-roanol; (b), acetic acid; (c), roylamine; (d), sodium acetate; (e), roanoic acid; (f), sodium roanoate.

13 C,m of aqueous amines and other organic solutes to = here are no direct exerimental results at = 28 with which to comare the measurements ublished in this series of aers. On the other hand, there are systematic redictions of the standard-state artial molar roerties at elevated temeratures and ressures, based on the revised Helgeson irkham Flowers equation of state (anger and Helgeson, (19) Shock et al. (20) ). Among almost 300 organic and inorganic secies included in the SUPCR92 software ackage, (21) six match our comounds: 1-roanol, roylamine, roanoic acid, acetic acid, sodium acetate, and sodium roanoate. he comarison, as summarized in figure 1, shows that the redictions are excellent, considering the narrow range of temeratures on which they were usually based. Figure 2 dislays the grou contributions C j, see equation (8), now available as a function of temerature for all functional grous, including three new ones (CONH 2,NH 2, and NH 3 Cl). he new curves for CH 2,CH 3, COOH, (COOH) 2, FIGURE 2. Functional grou heat caacities C j as a function of temerature.

14 530 A. Inglese et al. COONa, and OH grous are not significantly different from those in the revious aer, (2) although there are differences in the coefficients of the fit. We may not be sure about actual uncertainties in functional grou fits because there are not enough results for most grous, but some facts are encouraging: there is good consistency of functional grous found in several comounds (esecially CH 2 and CH 3 ) and the behavior of the temerature deendencies of the C j s is always hysically reasonable. As derived from the behavior of the limiting activity coefficient of the solute in the solvent critical region, (22) the artial molar heat caacity of the solute should aroach infinity at the solvent critical oint. As the temerature increases, the divergence is either ositive, in the case when the solute molecules reel the solvent molecules or attract them weakly; or negative, when the solute attracts the solvent sufficiently strongly. hese effects may be seen in the whole temerature range for our functional grous: for non-olar grous (CH 2,CH 3 ), the lot of C j against remains concave at all temeratures, and the sloe is ositive at the highest temeratures, while for olar grous CONH 2, NH 2, COOH, (COOH) 2, OH the lot is convex at all temeratures, and the sloe is negative at the highest temeratures, which indicates sufficiently strong attractive interactions. For the FIGURE 3. C,2 calculated from functional grou additivity, equation (8), lotted against exerimental C,2.

15 C,m of aqueous amines and other organic solutes to = COONa and NH 3 Cl grou (comosed of the charged grous Na +, COO,NH + 3, and Cl ), ( 2 C j / 2 ) is negative and large at all temeratures, and the sloe at the highest temeratures is also negative and large, as exected from the strong long-range attractive forces between the charged grous and water. Figure 3 (the lot of the calculated against exerimental values of C,2) gives an overall indication of the accuracy of our fit. Figure 3 indicates that reasonably accurate redictions of C,2 at temeratures u to 525 may be obtained with equation (8) for alcohols, olyols, mono- and olyfunctional carboxylic acids, sodium carboxylates, amines and olyamines, amides, and hydrochlorides. he reliability of the redictions should be slightly less than the recision of our fit, with somewhat larger uncertainty in the case of olyfunctional comounds and comounds with strong steric or near-neighbor effects. he authors thank Cecil M. Criss and Everett L. Shock for helful discussions. his work was suorted by the Deartment of Energy (DOE) under grant number DEFG02-89ER and by the National Science Foundation (CHE ). Such suort does not constitute endorsement by DOE of the views exressed in this article. REFERENCES 1. Inglese, A.; Wood, R. H. J. Chem. hermodynamics 1996, 28, Inglese, A.; Sedlbauer, J.; Wood, R. H. J. Solution Chem. 1996, 25, Criss, C. M.; Wood, R. H. J. Chem. hermodynamics 1996, 28, Carter, R. W.; Wood, R. H. J. Chem. hermodynamics 1991, 23, Sharygin, A.; Wood, R. H. J. Chem. hermodynamics 1996, 28, Archer, D. G. J. Phys. Chem. Ref. Data 1992, 21, Woolley, E. M.; Heler, L. G. Can. J. Chem. 1977, 55, Sharygin, A. V. Ph.D. Dissertation, St. Petersburg State University, Russia Simonson, J. M.; Mesmer, R. E.; Rogers, P. S. Z. J. Chem. hermodynamics 1989, 21, Ho iland, H. hermodynamic Data for Biochemistry and Biotechnology. Cha. 2. Hinz, A.-J.: editor. Sringer-Verlag: Berlin Robinson, R. A.; Stokes, R. H. Electrolyte Solutions. 2nd edition. Academic Press: New York Olofsson, G.; Heler, L. G. J. Solution Chem. 1975, 4, Rogers, P. S. Z.; Pitzer,. S. J. Phys. Chem. Ref. Data 1982, 11, Archer, D. G.; Wang, P. J. J. Phys. Chem. Ref. Data 1991, 19, Hill, P. G. J. Phys. Chem. Ref. Data 1990, 19, Neff, R. O.; McQuarrie, D. A. J. Phys. Chem. 1973, 77, Ben Naim, A. Solvation hermodynamics. Plenum Press: New York Wood, R. H.; Crovetto, R.; Majer, V.; Quint, J. R. Proerties of Water and Steam. Proceedings of the 11th International Conference. Pichal, M.; Sifner, O.: editors. Hemishere: New York, anger, J. C.; Helgeson, H. C. Am. J. Sci. 1988, 288, Shock, E. L.; Oelkers, E. H.; Johnson, J. W.; Sverjensky, D. A.; Helgeson, H. C. J. Chem. Soc. (London) Faraday rans. 1992, 88, Johnson, J. W.; Oelkers, E. H.; Helgeson, H. C. Comuters & Geosciences 1992, 18, Wheeler, J. C. Ber. Bunsenges. Phys. Chem. 1972, 76, O-638 (Received 2 July 1996; in final form 7 October 1996)