Microsoft Word - 16.01 Talibov.docx HUNGARIAN JOURNAL OF INDUSTRY AND CHEMISTRY Vol. 44(1) pp. 33–38 (2016) hjic.mk.uni-pannon.hu DOI: 10.1515/hjic-2016-0004 VAPOUR PRESSURE OF ETHANOL AND 1-PROPANOL BINARY MIXTURES MISIRKHAN TALIBOV1 AND JAVID SAFAROV1,2 1 Department of Heat and Refrigeration Techniques, Azerbaijan Technical University, H. Javid Ave. 25, AZ1073 Baku, AZERBAIJAN 2 Institute of Technical Thermodynamics, University of Rostock, Albert-Einstein Str. 2, D-18059 Rostock, GERMANY The vapour pressure of binary mixtures containing ethanol and 1-propanol were investigated at temperatures ranging from 274.15 to 443.15 K using two different setups with static methods. The measured values were fitted to a Clausius-Clapeyron type relationship. The heat of evaporation of mixtures was determined from the vapour-liquid equilibria data. Keywords: vapour pressure, ethanol, 1-propanol, static method, pressure transmitters, Clausius- Clapeyron equation 1. Introduction Investigation of thermodynamic properties of pure liquids and their mixtures is important in various fields of science, chemical engineering, economy and industry. Aliphatic alcohols are commonly applied in chemical, biological, and medical uses as solvents for fats, oils, resins, paints, and nitrocellulose with regard to the manufacture of goods from perfumes to brake fluids [1]. In addition, the studied solutions of ethanol (C2H5OH) and 1-propanol (C3H7OH) are also used as heat transfer fluids in heat reservoirs, solar heating systems, oxygenates in fuels, and cryogenic power generation systems [2]. For the design and modelling of such applications, the determination of flow in pipes, heat transfer, and mass transfer operations requires the knowledge of thermophysical properties. Density, vapour pressure, speed of sound, viscosity, and heat capacity often need to be defined for these purposes. This work is a continuation of our previous publications in the field of thermophysical properties of alcohol and their solutions [3–6]. Hereby, the vapour pressure of binary solutions of (1-x) C2H5OH + x C3H7OH were investigated. The vapour pressure data of binary solutions of ethanol and 1-propanol at different temperatures and concentrations were determined. After the analysis of the literature using “ThermoLit” from NIST, we concluded that only a few vapour pressure values for these systems have been reported to date [7–11]. *Correspondence: javid.safarov@uni-rostock.de Early studies by Parks and Schwenk [7] reported the vapour pressure of a (1-x) C2H5OH + x C3H7OH mixture at 298.15 K using glass apparatus and the differential method. A good commercial grade ethanol (w = 99.9%) and "refined" commercial 1-propanol (w = 99.34%) were used during the preparation of solutions. Later, Udovenko and Frid [8] investigated the vapour pressure of the same mixture, but within a higher temperature range (323.15 to 353.15 K) using the dynamic method. The vapour liquid equilibria (VLE) of these systems were analysed using a refractometer. The activity coefficients γ of both pure components were calculated. A series of studies in the early 90s included the work of Zielkiewicz [9], who studied the vapour pressure at 313.15 K using the static method. Dried ethanol and 1-propanol were used during the preparation of solutions. The temperature and pressure were controlled within ±0.001 K and ±0.004 kPa, respectively. Binary samples were prepared by weighing within an uncertainty of ±0.0005 mole fractions. Solution preparations were carried out using the dry nitrogen process. Furthermore, Pradhan et al. [10] investigated the vapour pressures of ethanol and 1- propanol solutions at 303.15 K using the static method. For the fitting of obtained values a modified NRTL equation was used. Quite recently, Cristino et al. [11] carried out high temperature VLE measurements for the system of ethanol and 1-propanol solutions within a temperature range of 403.2 to 423.2 K using a flow apparatus. Alcohols used during the preparation of solutions had a confirmed purity greater than 99.9 weight percent. The pressure was controlled using two pressure transducers within ranges of 0 – 0.4 (uncertainty of ±0.0002 MPa) and 0–1.7 MPa (uncertainty of ±0.0009 MPa). The TALIBOV AND SAFAROV Hungarian Journal of Industry and Chemistry 34 temperature was measured using a platinum resistance thermometer with an uncertainty of ±0.1 K. The statistical associating fluid theory for potentials of variable range (SAFT-VR) was used to model the systems and found to accurately reproduce the experimental data. Using this analytical method the uncertainty of solution preparation was ±0.0001 mole fractions. The outcome of a literature survey summarised in Table 1 is that only small temperature, pressure, and concentration intervals were investigated to date in addition to older literature examples decades ago that may have used out-dated measurement techniques. In this work, the vapour pressures of binary (1-x) C2H5OH + x C3H7OH solutions were investigated using two highly accurate, fully automatic static experimental setups and ultrapure Merck quality chemicals. 2. Experimental 2.1. Samples and Measurements Ultra-pure ethanol EMPLURA® (w = 99.995%, CAS No. 71-36-3, Art. Nr. 8.22262.2500) and 1-propanol Analyse EMSURE® ACS, Reag. Ph Eur (w = 99.995%, CAS No. 71-23-8, Art. Nr. 1009971000) were purchased from Merck Schuchardt OHG, Germany. The samples were used without further purification. They were carefully degassed in glass flasks with special vacuum leak-proof valves before measurements were taken. The water content is determined by Karl Fischer titration and was determined to be less than a mass fraction of 20 ppm. 2.2. Experimental Procedure The vapour pressure measurements of binary solutions of (1-x) C2H5OH + x C3H7OH were measured using two high-accuracy static experimental seweups [12–14]. The glass cells were used for vapour pressure measurements lower than ambient pressure at temperatures from 274.15 to 323.15 K. The metal cell was used for the higher temperature range of 323.15–433.15 K using the static method [12–14]. The glass cell method consists of absolute and differential parts (if the vapour pressure is smaller than the uncertainty of the absolute cell, 30 Pa). The vapour pressure of the solution was always higher than the uncertainty of measurements between 274.15 and 323.15 K. The measurements within this temperature range were carried out only using the absolute cell of installation. The internal volume of the glass cell in absolute measurements is approximately 78.56 cm3, and the volume of steel tube cells is 1 cm3. The glass cell static method consists of a bolted-top cell in a water-bath kept at constant temperature (± 0.01 K) using a thermostat. The vapour pressure was measured using a calibrated high accuracy sensor head [Type 615A connected to the signal conditioner Type 670A, MKS Baratron, USA] attached to the top of the cell of various Keller pressure transmitters: maximum pressure of 300,000 Pa with an uncertainty of ΔP = ±(400 to 1,500) Pa, maximum pressure of 1,000,000 Pa with an uncertainty of ΔP = ±(1,000 to 5,000) Pa and maximum pressure of 1,600,000 Pa with an uncertainty of ΔP = ±(2,000 to 8,000) Pa. The experimental uncertainty of the pressure in the absolute vapour pressure measurement using the glass cell is ±10–30 Pa. The internal volume of the measurement cell is approximately 140 cm3. Temperatures were measured using two different platinum resistance thermometers, PT-100. The second platinum resistance thermometer, PT-100, transfers the measured temperature in the computer via an Omega PT-104A Channel RTD Input Data Acquisition Module (Omega Engineering, Inc., USA) for the measuring of temperature, with an accuracy of ±0.001 K. Experiments were carried out starting from a low temperature (333.15 K) to a high temperature (433.15 K) at 10 K intervals. Before the experiments, the measurement cells were washed with water, methanol and acetone and then all residual fluids were removed. This procedure requires approximately 2 to 3 h or more to reach the Table 1. Summary of the vapour pressure P literature investigations of a (1-x) C2H5OH + x C3H7OH mixture. Reference Method Properties Temperature (T in K) Concentration (x mole fraction) Uncertainty ΔP Fitted density equation Purity Source Parks [7] 1924 GA P, T, ∆H 298.15 0.0000 to 1.0000 99.9% (Et) 99.34% (Pr) CS Udovenko [8] 1948 DM P, T, γ 323.15 – 353.15 0.0000 to 1.0000 CC ARG (Et) ARG (Pr) R Zielkiewicz [9] 1993 SM P, T 313.15 0.0436 to 0.9291 ±0.004 kPa POCh Pradhan [10] 1993 SM P, T 303.15 0.0306 to 0.9700 ±0.001 kPa 99.9% (Et) 99.6% (Pr) AC Cristino [11] 2015 FA P, T, VLE 403.20 – 423.20 0.0017 to 0.9993 ±0.0002 – ±0.0009 MPa SAFT-VR 99.9% (Et) 99.9% (Pr) P (Et) FS (Pr) GA, glass apparatus; ∆H, heat of mixing; P, vapour pressure; T, temperature; x, mole fraction; Et, Ethanol; Pr, 1-Propanol; CS, commercial sample; DM, dynamic method; γ, activity coefficient; CC, Clapeyron-Clausius equation; ARG, analytical reagent grade; R, Reachim, USSR; SM, static method; POCh, Avantor Performance Materials Poland S.A.; AC, Aldrich Chemical; FA, flow apparatus; SAFT-VR, statistical associating fluid theory; VLE, vapour-liquid equilibrium; P, Panreac; FS, Fisher Scientific. VAPOUR PRESSURE OF ETHANOL AND 1-PROPANOL BINARY MIXTURES 44(1) pp. 33–38 (2016) DOI: 10.1515/hjic-2016-0004 35 desired minimal pressure (20–30 Pa). Equilibration of the cells is a rapid process and a constant pressure in the stationary regime is reached within 15 minutes. Equilibrium pressure readings are performed in triplicate approximately 10 to 20 min intervals. Specific quantities of ethanol and 1-propanol were evacuated, degassed in two separate flasks and connected using an adapter [12]. Ethanol flowed into a flask containing 1-propanol and the concentration of the solution was determined using the weight of the flask containing the solution on an electronic scale (Sartorius ED224S, Germany) with an uncertainty of 0.0001 g. A quantity of the solution was injected into the equilibrium cells up to approximately 50% of their volume. The vapour pressures of the water, methanol, acetone, toluene, 1-butanol, etc. were measured as reference substances for testing both setups [12–14]. The experimental vapour pressure results were assessed to be reliable to within an average uncertainty of ±0.05% according to test measurements. 3. Results and Discussion The measured experimental vapour pressures for an ethanol/1-propanol mixture within the temperature range of 274.15 to 433.15 K are listed in Table 2, and are also shown in Fig.1. The vapour pressures of pure alcohols were taken from Refs. [15–16]. The experimental vapour pressure results, P in Pa of investigated solutions were fit to the Antoine equation: ln (P) = AA – BA / ( T/K + CA ) (1) Table 2. Experimental mole fraction x of 1-propanol, and vapour pressure P (in Pa) of a solution of (1-x)C2H5OH + x C3H7OH a Temperature mole fraction of 1-propanol (x) (K) 0.0000b 0.0989 0.1918 0.4034 0.5935 0.7971 0.9038 1.0000c 274.15 1684 1490 1374 1116 897 672 530 515 278.15 2248 1980 1843 1498 1219 902 739 697 283.15 3155 2810 2620 2149 1761 1330 1102 1008 293.15 5842 5390 5023 4186 3442 2670 2260 2034 303.15 10458 9762 9180 7780 6521 5150 4402 3854 313.15 18054 16872 15880 13558 11502 9260 8030 7048 323.15 29356 27918 26430 22909 19560 15890 13873 12273 333.15 46796 44590 42200 36700 31777 26000 22992 20472 343.15 71902 68812 65321 57200 49784 41400 36903 32867 353.15 108174 103196 98000 86256 75504 63400 56954 50997 363.15 157911 150535 143157 126500 111128 94202 85257 76746 373.15 224798 214272 203797 180800 159521 136296 123958 113402 383.15 313786 298327 284000 252345 223518 192294 176009 161109 393.15 429264 407124 387678 345105 306612 265259 244002 223982 403.15 576481 545340 519543 462803 412430 358865 331402 305477 413.15 759512 718454 684376 610504 545107 476594 441754 408702 423.15 982342 932045 887923 792004 708954 622271 578714 539077 433.15 1254038 1191945 1135123 1012845 907984 800473 746309 702376 443.15 1582042 1505202 1432927 1278187 1147706 1015139 949123 893968 a Standard uncertainties u are u(T) = 0.01 K and u(x) = 0.0001 mole fractions and the combined expanded uncertainties Uc are Uc(P) = 30 Pa for P < 0.1 MPa, Uc(P) = 1500 Pa for P < 3 MPa, and Uc(P) = 8000 Pa for P < 16 MPa (level of confidence = 0.95); b The vapour pressure values of ethanol were taken from Ref. [15]; c The vapour pressure values of 1- propanol were taken from Ref. [16]. Figure 1. Plot of vapour pressure P (in kPa) of a (1-x) C2H5OH + x C3H7OH solution mixture as a function of 1-propanol mole fraction x. ¿, 274.15 K; ¢, 278.15 K; ▲, 283.15 K; �, 293.15 K; ▼, 303.15 K; Ò, 313.15 K; Ì, 323.15 K; ¯, 333.15 K; £, 343.15 K; r, 353.15 K; �, 363.15 K; s, 373.15 K; °, 383.15 K; ⊕, 393.15 K; «, 403.15 K; ¶, 413.15 K, ◐, 423.15 K; x, 433.15 K; ◑, 443.15 K; lines fit to Eqs.(3) and (4). TALIBOV AND SAFAROV Hungarian Journal of Industry and Chemistry 36 The fitted constants AA, BA, and CA for the investigated solutions are summarised in Table 3 with the standard mean deviation defined as follows: δP/P =100/n ⋅ (P exp. −P cal. )/P exp. ⎡ ⎣ ⎤ ⎦ i=1 n ∑ (2) From Table 3, it can be seen that coefficients AA, BA, and CA exhibit non-trivial dependence from the mole fraction of 1-propanol. Fitting of these coefficients was a challenging task. Thus, we also used a Clausius– Clapeyron-type equation to obtain the vapour pressure results of the investigated solutions from mole fractions of 1-propanol: ln p= ACC + BCC T +CCClnT +DCCT , (3) where P is vapour pressure in Pa; T is the temperature in K; and ACC, BCC, CCC, and DCC are the coefficients of the equation, depending on the mole fraction of the solvent as follows: ACC = aix j BCC = bix j i=0 3 ∑ CCC = cix j DCC = dix j i=0 3 ∑ i=0 3 ∑ i=0 3 ∑ (4) The coefficients ai, bi, ci, and di for the investigated ethanol/1-propanol mixtures are tabulated in Table 4. The uncertainty of fitting was approximately ur(ΔP/P) = 0.7678. The plots of deviation of experimental Pexp and calculated Pcal vapour pressure values as a function of Figure 2. Deviation of experimental Pexp and calculated Pcal vapour pressure values versus pressure P using Eqs.(3) and (4) at various temperatures and mole fractions. Figure 3. Deviation of experimental Pexp and calculated Pcal vapour pressure values versus temperature T using Eqs.(3) and (4) at various pressures P and mole fractions. Figure 4. Deviation of experimental Pexp and calculated Pcal vapour pressure values versus mole fraction x using Eqs.(3) and (4) at various pressures P and temperatures T. Table 4. Clausius - Clapeyron equation fitting parameters ai, bi, ci, and di from Eqs.(3) and (4). ai bi ci di a0 = 103.156 b0 = -7994.80 c0 = -12.3406 d0 = 0.0098481 a1 = 251.788 b1 = -8366.78 c1 = -42.1398 d1 = 0.0527419 a2 = 222.344 b2 = -7727.52 c2 = -36.8168 d2 = 0.0438405 a3 = -446.740 b3 = 14403.70 c3 = 74.8888 d3 = -0.0951465 Table 3. Antoine parameters AA, BA, CA and percent deviations (ΔP/P in %) as a function of 1-propanol mole fraction. mole fraction A A BA CA ΔP/P 0.0000a 23.1773 3461.23 -54.3818 0.6234 0.0989 22.8524 3275.81 -63.4603 0.0742 0.1918 22.7353 3228.33 -65.9886 0.0689 0.4034 22.4745 3118.11 -72.4808 0.1652 0.5935 22.3425 3077.68 -76.1926 0.2204 0.7971 22.2692 3064.56 -79.8646 0.3263 0.9038 22.1582 3009.02 -84.6711 0.1983 1.0000b 22.7515 3373.18 -70.0769 0.8270 a from Ref. [15]; b from Ref. [16]. VAPOUR PRESSURE OF ETHANOL AND 1-PROPANOL BINARY MIXTURES 44(1) pp. 33–38 (2016) DOI: 10.1515/hjic-2016-0004 37 pressure, temperature, and mole fraction using Eqs.(3) and (4) are shown in Figs.2-4, respectively. The enthalpies of vaporisation, ΔHvap in J mol -1, for the (1-x) C2H5OH + x C3H7OH mixture at the four middle temperatures (293.15, 333.15, 373.15, and 423.15 within temperature ranges of 274.15–313.15 K, 313.15–353.15 K, 353.15–393.15 K, and 373.15–443.15 K, respectively) were defined using Eq.(5) from Ref. [12]: d lnP d 1 T ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ = − ΔHv R (5) If we plot ln(P) as a function of 1/T, we can define ΔHv from the gradient of the line: ΔHv = −R ⋅ d lnP d 1 T ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ . (6) After the integration of Eq.(6) we can find ln p= − ΔHv R ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 1 T ⎛ ⎝ ⎜ ⎞ ⎠ ⎟+ intercept (7) ΔHv = RT(intercept− lnP) (8) The calculated enthalpy of vaporisations ΔHv in J mol-1 for the (1-x)C2H5OH + x C3H7OH mixture within the temperature range of 274.15–443.15 K are listed in Table 5 and compared to the available literature results [7–11] shown in Fig.5. When the measured values by Parks [7] at T = 298.15 K are compared to our values, we obtain ∆P = ±242 Pa or ∆P/P = ±5.24% deviations. The maximum deviation is ∆P = 394 Pa at x = 0.759 mole fractions of 1-propanol. The Parks’ values [7] are higher than our results and the vapour pressures of ethanol exhibit small deviations compared to ours and all other literature values presented in Ref. [15]. The vapour pressure of 1- propanol published in Ref. [7] exhibits a large deviation from ours and all other literature values presented in Ref. [16]. We hypothesise that the vapour pressure values of 1-propanol with high deviation from the literature were used during the analysis of concentration dependence in Ref. [7]. The 44 data points of Udovenko and Frid [8] measured within the range of 323.15 – 353.15 K are mostly higher than our values. The average deviations of both sources are ∆P = ±242 Pa and ∆P/P = ±5.24% with maximum deviations of ∆P = 2952 Pa at T = 343.15 K and x = 0.5 mole fractions of 1-propanol. The 11 data points of Zielkiewicz [9] at T = 313.15 K exhibit small deviations from our results with ∆P = ±33 Pa and ∆P/P = ±0.2631% mean deviation. The maximum obtained deviation in ∆P = -59 Pa at x = 0.2793 mole fractions of 1-propanol. The next 22 data points of Pradhan et al. [10] are mostly higher than our values. The average mean deviation of this comparison is ∆P = ±143 Pa and ∆P/P = ±2.2378%. The maximum obtained deviation in ∆P = 209 Pa and ∆P/P = ±3.5182% at T = 303.15 K and x = 0.7002 mole fractions of 1-propanol. The last 18 experimental values from the recent work of Cristino et al. [11] measured at high vapour pressure intervals of 304.2–967.4 kPa also exhibit small differences from our values as the mean deviation between two experimental sources is ∆P = ±5698 Pa and ∆P/P = ±0.9227%. The maximum deviation of this comparison is ∆P = -21134 Pa at T = 413.2 K and x = 0.0002 mole fractions of 1-propanol. 4. Conclusion Vapour pressure measurements for the binary mixture of ethanol and 1-propanol over a wide range of temperatures from 274.15 K to 468.15 K were studied. The Antoine and Clausius–Clapeyron equations were used to fit the experimental results. The enthalpies of vaporisation at four various temperatures were calculated. The available literature values were compared with measured values and small deviations were observed. Figure 5. Deviation of experimental Pexp and literature Plit vapour pressure values for the ethanol/1-propanol mixture versus 1-propanol mole fraction using Eqs.(3) and (4) at various pressures P and temperatures T. Table 5. Enthalpy of vaporisation, ΔHv in kJ mol -1 for a (1-x) C2H5OH + x C3H7OH mixture at various temperatures. x 293.15 K 333.15 K 373.15 K 423.15 K 0.0000 43.245 41.210 39.579 37.457 0.1574 43.905 41.300 39.542 37.576 0.2876 44.499 41.416 39.425 37.553 0.5351 45.768 41.989 39.707 37.718 0.7130 46.768 42.811 40.157 38.002 0.8699 47.809 43.815 40.965 38.613 0.9411 47.887 44.441 41.546 39.125 1.0000 47.908 45.052 42.330 39.963 TALIBOV AND SAFAROV Hungarian Journal of Industry and Chemistry 38 Acknowledgement The research was supported by University of Rostock and Azerbaijan Technical University REFERENCES [1] Cano-Gómez, J.J.; Iglesias-Silva, C.A.; Ramos- Estrada, M.; Hall, K.R.: Densities and viscosities for binary liquid mixtures of ethanol + 1-propanol, 1-butanol, and 1-pentanol from 293.15 to 328.15 K at 0.1 MPa, J. Chem. Engng. 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