J. Chem. Eng. Data 1986, 1 , 391-392 39 1 Densities and Viscosities of Aqueous Maleic Acid Solutions between 25 and 90 O Demetrlo Gbmez, R afael Font,+ and Antonlo Soler Department of Technical Chemistry, Science Faculty, University of Murcia, Murcia, Spain The densities and viscosities of aqueous maleic acid soiutlons were determined in ail the possible ranges of concentrations between 25 and 90 OC. Likewise, empirical correlatlo ns were obtained to relate these properties with the concentration and the tempe ratu re. Introduction Maleic anhydride is obtained industrially by the catalytic ox- idation of hydrocarbons. One of the most widely used methods for its recovery from the gaseous flow coming from the reactor is by means of absorption with water. In the next step the resulting aqueous maleic acid solution flows to evaporators. Then the acid solution is concentrated and, afterwards, dehy- drated producing maleic anhydride vapors and water. For an adequate design of the absorption tower and the evaporators, it is necessary to know the densities and the viscosities of the maleic acid solutions as a function of concent ration and tem- perature. I t must b e add ed that the maleic acid in concentrated soh- tions and at high temperatures is isomerized to fumaric acid (in our research unit, a kinet ic study on this reaction is being carried out). This, together with the available instrumental techniques, has limited t he temperatures at which the densities and the viscosities were measured to less than 90 OC In the literat ure o nly a correlat ion bet ween th e density of aqueous maleic acid solutions and th e concentration at 2 5 OC has been found 7). Thi s c orrelat ion is based on Weiss and Downs (2) experimental data. Experimental Section The densities were measured by use of a digital densimeter Anton Paar Model DMA 45. With this instrument the mass of an exactly defined sample volume is determined from the os- cillation period of the cell which contains it, when it undergoes an undamped oscillatory movement (3). The thermostatic system incorporated in the densimeter allows the temperature to be maintained within a limit of error of f0.05 OC For each temperature the instrument constants are determined from oscillation period measurements with two samples of known density, air and water 4). The experimental error for these measurements was estimated to be g/c m3 within the range of 0.5-1.5 g/cm3. Th e average value was calculated at each temperature from a set of measurements for which the maximum difference among them was less than 0.02 . Th e viscosities were measured b y use of an automatic equipment, Viscomatic 1 of FICA, with a thermostated gl ass capillary tube, Ubbelohde-type, 0.4 mm diameter. The exper- imental techniques of this equipme nt have been described (5). Due to the wide int erval of temperatures and compositions which had to be covered, low flow times have sometimes been found (<200 ), and therefore in all th MSBS th kinetic energy corrections had to be considered in order to calculate the vis- cosities. Besides the circulation of the thermostatic liquid, the viscometer tube was covered with a regulated heating strip of 180 W which minimized heat loss and water vapor condensa- Present address: Technical Chemistry , University of Alicante, Aiicante, Spain. 0021-9568/86/1731-0391~01.5QIO Table I. Densities g/cm3) of Aqueous Solutions of Maleic Acid temp C concn, w t % 25 40 60 80 90 0.00 10.08 19.61 29.98 40.15 52.22 61.63 72.07 (0.9971) (0.9922) (0.9832) (0.9718) (0.9653) 1.0316 1.0253 1.0148 1.0069 1.0002 1.0648 1.0572 1.0456 1.0364 1.0304 1.1034 1.0945 1.0814 1.0714 1.0649 1.1434 1.1333 1.1191 1.1085 1.1000 1.1811 1.1659 1.1518 1.1446 1.2028 1.1871 1.1795 1.2192 From ref 4 . tion, giving limits of error of 0.05 OC On the other hand, given the viscosimeter charact eristic s, a sufficient amount o f the sample needed in order to make evaporation negligible was introduced. Th e maximum difference in th e viscosity values determined at each temperature and at each concentration was less than 0.1 % . The viscosimeter was calibrated with oils of known viscosity and density (6). Maleic acid with an acidity of 99.5 wt % and a content of fumaric acid less than 0.5 wt YO was used. Th e solutions were prepared by weighi ng, and then the concentration was deter- mined b y potentiometric t ritation with Na OH 0.1 N. The per- centage of fumaric acid was determined b y chromatographic analysis of the dimethyl esters of maleic and fumaric acids. The maximum error in the determination of the maleic acid con- centration by titration is less than 0.3 . In the tables where experimental data are shown, values o f percentages with four figure s are the average values obtain ed from several analysis. Density. Results and Correlation The densities o f the aqueous solutions of maleic acid were measured at temperatures of 25, 40, 0, 0, and 90 OC and at concentrations of 0 to up to 72 wt of acid, at intervals of lo , except in those cases where the solubility of the maleic acid was not total. Th e experimental average value s of the densities, related to the water density at 4 OC (4), are shown in Table I Th e differences between our experimental value s of densities at 25 O C and those which are plot ted vs. concentrat ion in the paper by Weiss and Downs (2) are less than 0.2 . Different e quat ions were tested to correlate the density p with the concentration c and the temperature f These equations were of the type Of all the correlations carried out, including the values of the densities o f pure water 4), he best one corresponds to the case where the concentration is expressed in mass fraction wA of maleic acid and the temperature t in OC. The equation obtained by multiple linear regression is p = 1.004 1.954 X 10-4t 2.44 X 10-6t2 + (3.606 X lo- 1.752 X 10-3t + 1.404 X 10-5t2)~A (8.472 X I 7.033 X 10-4t 1.262 X 10-5t2)~A2 2 ) 1986 American Chemical Society
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J. Chem. Eng. Data 1986, 1 , 391-392 39 1
Densities and Viscosities of Aqueous M aleic Acid Solutions between25 and 90 O
Demetrlo Gbmez, R afael Font,+ and Antonlo Soler
Department of Technical Chemistry, Science Faculty, University of Murcia, Murcia, Spain
The densities and viscositiesof
aqueous maleic acidsoiutlons were determined in ail the possible ranges ofconcentrations between 25 and 90 OC. Likewise,empirical correlatlons were obtained to relate theseproperties with the concentration and the temperature.
Introduction
Maleic anhydride is obtained industrially by the catalytic ox-idation of hydrocarbons. One of the most widely used methodsfor its recovery from the gaseous flow coming from the reactoris by means of absorption with water. In the next step theresulting aqueous maleic acid solution flows to evaporators.Then the acid solution is concentrated and, afterwards, dehy-drated producing maleic anhydride vapors and water. For anadequate design of the absorption tower and the evaporators,it is necessary to know the densities and the viscosities of themaleic acid solutions as a function of concentration and tem-perature.
I t must be added that the maleic acid in concentrated soh-tions and at high temperatures is isomerized to fumaric acid (inour research unit, a kinet ic study on this reaction is beingcarried out). This, together with the available instrumentaltechniques, has limited the temperatures at which the densitiesand the viscosities were measured to less than 90 OC
In the literature only a correlat ion between the density ofaqueous maleic acid solutions and the concentration at 25 OC
has been found 7 ) . This correlat ion is based on Weiss andDowns (2) experimental data.
Experimental Section
The densities were measured by use of a digital densimeterAnton Paar Model DMA 45. With this instrument the mass ofan exactly defined sample volume is determined from the os-cillation period of the cell which contains it, when it undergoesan undamped oscillatory movement (3). The thermostaticsystem incorporated in the densimeter allows the temperatureto be maintained within a limit of error of f0.05 OC For eachtemperature the instrument constants are determined fromoscillation period measurements with two samples of knowndensity, air and water 4). The experimental error for thesemeasurements was estimated to be g/cm3 within therange of 0.5-1.5 g/cm3. The average value was calculated ateach temperature from a set of measurements for which themaximum difference among them was less than 0.02 .
The viscosities were measured by use of an automaticequipment, Viscomatic 1 of FICA, with a thermostated glasscapillary tube, Ubbelohde-type, 0.4 mm diameter. The exper-imental techniques of this equipment have been described (5).
Due to the wide interval of temperatures and compositionswhich had to be covered, low flow times have sometimes beenfound (<200 ), and therefore in all th MSBS th kinetic energycorrections had to be considered in order to calculate the vis-cosities. Besides the circulation of the thermostatic liquid, theviscometer tube was covered with a regulated heating strip of180 W which minimized heat loss and water vapor condensa-
Present address: Technical Chemistry , University of Alicante, Aiicante,Spain.
0021-9568/86/1731-0391~01.5QIO
Table I. Densities g/cm3) of Aqueous Solutions of MaleicAcid
temp Cconcn,w t % 25 40 60 80 90
0.0010.0819.6129.9840.1552.2261.6372.07
(0.9971) (0.9922) (0.9832) (0.9718) (0.9653)1.0316 1.0253 1.0148 1.0069 1.00021.0648 1.0572 1.0456 1.0364 1.03041.1034 1.0945 1.0814 1.0714 1.06491.1434 1.1333 1.1191 1.1085 1.1000
1.1811 1.1659 1.1518 1.14461.2028 1.1871 1.1795
1.2192
From ref 4 .
tion, giving limits of error of 0.05 OC On the other hand, giventhe viscosimeter characteristics, a sufficient amount of thesample needed in order to make evaporation negligible wasintroduced. The maximum difference in the viscosity valuesdetermined at each temperature and at each concentration wasless than 0.1 % . The viscosimeter was calibrated with oils ofknown viscosity and density (6).
Maleic acid with an acidity of 99.5 wt % and a content offumaric acid less than 0.5 wt YOwas used. The solutions wereprepared by weighing, and then the concentration was deter-mined by potentiometric tritation with NaOH 0.1 N. The per-centage of fumaric acid was determined by chromatographicanalysis of the dimethyl esters of maleic and fumaric acids. Themaximum error in the determination of the maleic acid con-centration by titration is less than 0.3 . In the tables whereexperimental data are shown, values of percentages with fourfigures are the average values obtained from several analysis.
Density. Results and Correlation
The densities of the aqueous solutions of maleic acid weremeasured at temperatures of 25, 40, 0, 0, and 90 OC andat concentrations of 0 to up to 72 wt of acid, at intervalsof l o , except in those cases where the solubility of themaleic acid was not total.
The experimental average values of the densities, related tothe water density at 4 OC ( 4 ) ,are shown in Table I
The differences between our experimental values of densitiesat 25 O C and those which are plotted vs. concentration in thepaper by Weiss and Downs (2) are less than 0.2 .
Different equations were tested to correlate the density p with
the concentrationc
and the temperaturef
These equationswere of the type
Of all the correlations carried out, including the values of thedensities of pure water 4 ) , he best one corresponds to thecase where the concentration is expressed in mass fraction w Aof maleic acid and the temperature t in OC. The equationobtained by multiple linear regression is
p = 1.004 1.954 X 10-4t 2.44 X 10-6t2 +(3.606 X lo- 1.752 X 10-3t + 1.404 X 1 0 - 5 t 2 ) ~ A(8.472 X I 7.033 X 10-4t 1.262 X 1 0 - 5 t 2 ) ~ A 22 )
1986 Amer i can Chem ica l Soc i ety
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392 J. Chem. Eng ata 1986 , 392-395
Table 11. Viscosities mPa 8 ) of Aqueous Solutions ofMaleic Acid
temp, O Cconcn,w t 25 40 60 80 90
0.0010.0819.6129.9840.1552.2261.0072.07
(0.890) (0.653) (0.467) (0.355) (0.315)1.092 0.792 0.595 0.450 0.4081.349 0.968 0.696 0.528 0.4771.775 1.255 0.861 0.649 0.5842.459 1.702 1.115 0.832 0.741
2.540 1.571 1.144 1.0092.245 1.557 1.357
2 080
From ref 4.
The coefficient of the multiple correlation is 0.999 5, nd thestandard devlatkn of the experimental points from this equationis 0.000 87 g/cm3.
Vlscodty. Resutts and Correlatlon
The viscosities of the aqueous maleic acid solutions for ex-perimental conditions similar to those in the determination ofdensities were measured. The experimental resutts are tabu-lated in Table 11.
Several empirical equations have been tested to correlateviscosity in function with concentration and with temperature.The best obtained equation which relates the viscosity p to theabsolute temperature r and the mole fraction of malelc acid x Ais the following
log p = -1.0375 2.810 X 107T-3 - 5.284 X IOl3T-(3.740 1.974 X 107T-3 1.534 X 1015T-e)xA
(-3.151 X 10aT 3 4.966 X 1015T-')xA2 (3)
The multiple correlation coeffic ient is 0.9992, and thestandard deviation of the experimental polnts from this equationis 0.0227 mPa.s.
This equation has been selected because we had observedthat the relationship between log p and the composition and thtemperature was almost in accordance to the equations pro-posed by Litovitz (7 ) and Suryanarayana and Venkatesan (8).
Glossary
t temperature, O C
T temperature, KWA
XA
Greek Letters
density, g/cm3c absolute viscosity, mPa-s
Reglstry No. Maleic acid, 110-16-7.
mass fraction of maleic acidmole fraction of maleic acid
Llterature Clted
International Cr/t/ca/ Tables; McGraw-Hill:New York, 1928; Vol. 3, pp11 1-1 14.Weiss, J. M.; Downs, C. R. J A m . C h e m . SOC. 1823, 4 5 , 1003.Delmas, G.; Saint-Romaln. P.; Purves, P. J Chem. Soc. , FaradayTrans. 11875, 7 1 , 1181-1187.Handbook of Chemistry and Physlcs; CRC Press: Boca Raton, FL,
Soler, A.; B aal o, A.; Gdmez, D. Invest . T6c. Pap. 1878, 16, 61,
Ruiz, J.; &m er, D.; iiiana, A.; Soler, A. An. Ouim. 1884, 80 , 573.L l o v l z ,T. A. J . Chem. Phys. 1852, 20, 1088.Suryanarayana, C . V.; Venkatesan, V. K. Mnat sh . Chem. 1858, 89,824.
198 1-82.
596-62 1.
Recelved for revlew January 27, 198 4. Revised manusc ript recelved January21, 1986. Acc epted April 7, 1986.
Determ ination of Activity Coefflcientsof Oxygenated Hydrocarbonsin Squ alane by Gas-Liquid Chrom atograph y
Layla A. Qaddora and George M. Janlni'
Department of Chemistty, Kuwait lJniversi@, Kuwait
A study he thermodynamics oxygenatedh y d r o end aromatlc solute8 In eqwl ane wasconducted wing gaa-llquld chromatography. Wu t eInlInJt- acthrity c t8 ere determined atfour temperatures In the range of 30-45 OC. Thecor rospomhg excess thermodynamic properties werecalculated and the results were ex ml ned and dlscussedaccordbtg to the regular solution theory and thepertwbatbn theory of eolutlons.
Knowiedge of th thermodynamics of nonelectiolytlc solutionsis of great theoretical and pract ical importance in physicalchemistry and chemical engineering. Static methods are ac-curate, but in most cases, time consuming. I n contrast GLChas been shown to be rapM, efficient, and capable of I-2accuracy in the determination of infinitedlu tion activity coef-ficients and reiated solution hermodynamic properties ( 1 ) . Theaccuracy of actMty coefficients as measured by GLC dependson the type of systems studied, careful control of the experi-mental parameters, and the availability of accurate physicaldata. For systems where the only retention mechanism op-erative is solute absorption in the bulk of the stationary phase,
0021-9568/86/1731-0392$01.50/0
the accuracy can be as good as 1 or better.I n this study we sought to apply the GLC method with
squalane as stationary phase for the determination of the so-lution properties of oxygenated aliphatic and aromatic hydro-carbons. The solutes were selected to represent differentfunctional groups. Squalane was chosen because It has beenextensively studied by GLC and by static techniques and con-siderable quantities of thermodynamic properties of a wide
range of solutes have been accumulated (2-8). Although mostof the studies in the cited literature were conducted at tem-peratures exceeding those studied here, an attempt was madeto compare our results with independent measurements.
Solute activity coefficients were determined at four temper-atures. The corresponding thermodynamic properties werecalculated and the results were examined and dlscussed ac-cording to the regular solution th ory and the perkKbation th oryof solutions.
Theory
Solute activity coefficients at infinite dllution in the stationaryphase are related to GLC measured specific retention volumeby the expression (9)
1986 Am er i can Chemica l Soc i e ty
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