Article pubs.acs.org/jced
Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX
DIPPR Project 851 − Thirty Years of Vapor−Liquid Critical Point Measurements and Experimental Technique Development Loren C. Wilson,*,† Louis V. Jasperson,‡ David VonNiederhausern,‡ Neil F. Giles,§ and Christian Ihmels∥ †
Former Chair of DIPPR Project 851, 25202 Hazel Ranch Drive, Katy, Texas 77494, United States Wiltec Research Company, 488 South 500 West, Provo, Utah 84601, United States § Design Institute for Physical Properties, 394A CB, Brigham Young University, Provo, Utah 84602, United States ∥ Laboratory for Thermophysical Properties LTP GmbH, Associate Institute at the University of Oldenburg, Marie-Curie-Str. 10, 26129 Oldenburg, Germany
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‡
ABSTRACT: Experimentally determined critical temperatures (Tc) and critical pressures (Pc) are reported for 64 compounds. In addition, the critical volume (Vc) has been experimentally determined for 14 of these compounds. The compounds in this study are of industrial interest in process design, simulation, and safety. These data also extend our understanding of and ability to predict these properties from group contribution methods.
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INTRODUCTION The Design Institute for Physical Properties (DIPPR) sponsored by the American Institute of Chemical Engineers was established in 1978 to provide reliable physical properties of pure compounds and mixtures to the chemical processing industry. The flagship project is Project 801 − Evaluated Process Design Data, advertised as the gold standard in reviewed physical property data for pure compounds of industrial interest. Within a few years of the start of Project 801, it became clear that an experimental effort was needed to measure the critical temperature and pressure of compounds commonly used in the chemical processing and refining industries. Project 851 was started in 1985 to sponsor experimental measurements of the critical temperature and pressure of a wide variety of compounds of industrial interest, especially those which were not thermally stable at the critical temperature. Interested companies joined this project and provided the funding to support the experimental program. Over the next 30 years, the companies supporting Project 851 have funded the measurement of critical temperatures and pressures of approximately 250 compounds and have aided in the development of three experimental methods capable of measuring the critical temperature and pressure of thermally sensitive compounds. The critical temperature and pressure of a compound are used in equations of state which are based on the corresponding states principle. This includes all the cubic equations of state used in process modeling, simulation, and design. The acentric factor is a commonly used parameter in cubic equations of state and is based on the critical temperature, critical pressure, and a reliable vapor pressure curve. Many other physical properties such as liquid density, heat of vaporization, surface tension, and liquid viscosity can also be reliably extrapolated to higher temperatures if an accurate critical point is known. Unfortunately, this property has only been measured © XXXX American Chemical Society
for a relatively few elements and compounds due to the thermal instability of most molecules at the critical temperature. This paper briefly discusses both direct and indirect methods of determining the critical point of a fluid, noting the advances which have been aided by Project 851. For a more detailed explanation of each method, the interested reader may refer to the cited papers. New data are also presented for 64 compounds.
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EXPERIMENTAL METHODS Early Work. The first documented study of the vapor− liquid critical point was by Cagniard de la Tour in 1822.1 While studying acoustics, he sealed a fluid and a flint ball in a cannon barrel. The barrel was heated and tilted and Cagniard listened to the sound of the flint ball as it rolled from one end of the barrel to the other. The sound changed as the ball passed from the vapor into the liquid phase. Cagniard noted that the change in sound ceased above a certain temperature, and he postulated that there was no longer a vapor−liquid interface inside his impromptu pressure vessel. His experimental critical temperature for water of 635 K is only 12 K below the currently accepted value. In 1869, Andrews2 studied the pressure−volume−temperature and phase behavior of carbon dioxide in a glass tube using mercury as the piston. He observed that above 304.07 K, CO2 could not be liquefied at any pressure. He used the phrase “critical point” to describe this phenomenon. The accepted value today is 304.21 K, only 0.14 K above Andrew’s early value. Andrews’ study provided greater understanding of liquids and gases and set off a significant effort to measure the critical points of many compounds. Received: April 13, 2018 Accepted: July 23, 2018
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DOI: 10.1021/acs.jced.8b00298 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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pressure vessel. However, both methods are only applicable to compounds and mixtures that are either stable or only slowly react at the critical temperature. To more accurately measure the critical properties of thermally unstable compounds, Teja, Gude, and Rosenthal3 proposed two new methods in 1989. The first was a variation of the sealed ampule method which allowed them to heat the ampules much more quickly (see Figure 1). Residence times in the range of 3−4 min are reported in their paper. The second method represented a step change in the experimental technique. Rosenthal also developed a flow technique by pumping the test fluid through a quartz tube placed in a heated oven, as shown in Figure 2. The pressure was controlled by a metering valve on the downstream side of the quartz tube. The pressure was adjusted until the critical opalescence was visible in the tube. The residence time of the test fluid could be as short as 10 s. In 1995, Wilson4 improved upon the Rosenthal technique by using two pumps instead of the metering valve. A small pressure vessel with windows on the front and back was held in a rocking mechanism inside an oven, as shown in Figure 3. The test fluid was pumped from a 1 L pump through a preheat coil in the oven and then through the pressure vessel. Then the fluid flowed out into a matching pump, which was pumping in reverse at the same rate. A small hand pump was connected to the inlet side of the preheat coil to adjust the level of the fluid in the windowed pressure vessel. The residence time for the test fluid was a function of the pumping rate and could be decreased to approximately 10 s with the advantage of much easier level and pressure control than Rosenthal’s technique. Modern Indirect Methods. The flowing visual methods for the measurement of the critical temperature and pressure made possible the measurement of these properties for a whole new set of compounds. However, many compounds of industrial interest were still too unstable to permit accurate measurement, even with a residence time of 10 s. Two indirect methods have been developed that detect the presence or lack of the liquid to vapor phase change to determine that the critical point has been reached. Nikitin5 developed an indirect method in 1993 which detects the presence or cessation of vaporization along a platinum wire submerged in the compound of interest as a function of applied
Figure 1. Critical temperature versus time of heptadecane using the sealed ampule method [taken from ref 3 with permission by the publisher].
Figure 2. Flow method developed by Teja, Anselme, and Rosenthal [taken from ref 3 with permission by the publisher].
Modern Visual Methods. The two most common methods of measuring the critical point of a thermally stable fluid are by using a pressure vessel equipped with windows or a sealed glass ampule. The glass ampule method has the advantage that the critical density can be easily measured but also the drawback that the critical pressure cannot be simultaneously measured. All three properties can be measured in a visual
Figure 3. Flow method using a small pressure vessel with windows and two motorized pumps. B
DOI: 10.1021/acs.jced.8b00298 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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fully vaporized, producing a plateau in the temperature of the fluid in the capillary as seen in Figure 6. The bath is cooled, the pressure is set incrementally higher, and the process is repeated. At some pressure, the plateau in temperature disappears, indicating that the pressure is now set above the critical pressure of the compound. With this method, the total time from room temperature to the conclusion of the measurement is approximately 0.1 s while the time within 20 K of the critical temperature is approximately 0.02 s. Another advantage of this method is that reliable vapor pressure data at high temperature and pressure are measured as part of the procedure. Often, these data are in a region where vapor pressures cannot be measured using traditional methods due to the thermal instability of the compound and are of significant value in process simulation and relief design. Safety Considerations. Four members of the acrylate family were investigated in this work. Normally, these compounds would explosively polymerize at the temperatures studied. As these were studied in the capillary flow apparatus, reactivity issues were minimized.
Figure 4. Plot of the temperature (T) of the platinum wire versus time (t) showing the boiling perturbation [taken from ref 5 with permission by the publisher].
pressure. The platinum wire serves simultaneously as heater and temperature sensor. When a pulse of electricity is passed through the wire, the wire and the fluid immediately adjacent to it warms. When the fluid reaches the boiling point and begins to boil, the heat transfer rate from the wire to the fluid changes, and this produces a perturbation in the plot of temperature versus time, as seen in Figure 4. The pulses are very short, ranging from 10−5 to 10−3 seconds. The bulk of the fluid is maintained at a lower temperature, usually where it is thermally stable. Only the thin film of fluid around the wire is subjected to temperatures approaching the critical temperature of the fluid. This method has been used to measure the critical properties of fluids such as 1,2,3propanetriol, 1,2-ethanediol, tetracontane, and hexacontane. In 2000, Wilson and co-workers6 developed a subsecond flow method also based on the detection of boiling of the liquid flowing through a capillary tube at constant pressure in a bath that is being heated. The apparatus is shown in Figure 5. The pressure is set at a constant value in the nitrogen ballast tank at the beginning of the experiment. The test fluid is pumped through the capillary, and the bath is heated at a constant rate. Below the liquid−vapor phase transition, the temperature of the fluid closely follows the temperature of the bath as the bath is heated. If the applied pressure is below the critical pressure, the fluid will begin to boil once the bath and capillary tube reach the bubble point temperature of the fluid. The temperature of the fluid then remains approximately constant while the bath continues heating until the stream is
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RESULTS AND DISCUSSION For historical reference, Table 1 presents the principal investigator, their institution or company, and citation of the published data for each project year of DIPPR Project 851. The Chemical Abstract Service reference number, source, and analyzed purity of each compound are given in Table 2. The analyzed purity was measured by gas chromatography and reported on a water-free basis. The concentration of water in each compound was measured by Karl Fischer titration. Table 3 reports measured critical temperature (Tc), critical pressure (Pc), and critical volume (Vc) data for 64 compounds, along with values from the literature if available. This table includes the research group and method used to measure these values. For 40 compounds, no measured values of the critical temperature, pressure, or volume were available in the literature. Many of these compounds come from classes of compounds for which there are very little data available, and the results from this work represent a significant addition to the literature. In cases where other measured values were available, agreement was usually good, and in some cases these results reduced the uncertainty of the measured value significantly. The estimates of uncertainty of the new results presented in Tables 3 and 4 are based on the authors’ estimates of
Figure 5. Capillary flow method developed by Wilson.6 C
DOI: 10.1021/acs.jced.8b00298 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Figure 6. Temperature of the test fluid in the capillary versus bath temperature at several pressures for diphenylmethane in the critical region.
Table 1. DIPPR Project 851 Principal Investigators and Citations of the Resulting Data project year
principal investigator
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2000 2001 2002 2003 2004 2004 2005 2006 2007 2007
A. Teja A. Teja A. Teja A. Teja A. Teja A. Teja A. Teja G. Wilson G. Wilson G. Wilson G. Wilson G. Wilson G. Wilson G. Wilson G. Wilson G. Wilson E. Nikitin G. Wilson N. Giles N. Giles N. Giles E. Nikitin N. Giles L. Jasperson L. Jasperson C. Ihmels
2008 2008
L. Jasperson E. Nikitin
institution or company Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Institute of Thermal Physics Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Institute of Thermal Physics Wiltec Research Co. Wiltec Research Co. Wiltec Research Co. Laboratory for Thermophysical Properties Wiltec Research Co. Institute of Thermal Physics
Table 1. continued project year
citation 8 9 10 11 12 13 14 4 15 15 16 16 17 18 19 19 20 21 this this this 22 this this this this
principal investigator
2008
C. Ihmels
2009 2009
E. Nikitin C. Ihmels
2010 2011 2011
E. Nikitin C. Ihmels
2012 2013
none L. Jasperson
institution or company
citation
Laboratory for Thermophysical Properties Institute of Thermal Physics Laboratory for Thermophysical Properties
this work
Institute of Thermal Physics Laboratory for Thermophysical Properties
22 this work
Wiltec Research Co.
this work
22, 23 this work
the standard uncertainty. These estimates are based on three criteria: replicate measurements, the agreement between the experimental technique and other researchers for the same compound, and the underlaying uncertainties of the equipment used to measure the reported values. Where available, the published uncertainty associated with a result from the literature was also included. Squalane (a C30 branched alkane) represents a special opportunity to investigate the uncertainty associated with the capillary flow and heat pulse experimental techniques, since this compound was investigated by the same research group twice: once in 1997 and reported in 20006 and again in 2013 and reported in this work. This compound has also been investigated by Nikitin using his pulse heating technique7 and reported in 2005. These three sets of measured values are given in Table 4. The critical temperatures are within a spread of approximately 3%. Considering that this compound was well beyond the ability of existing static methods, this is reasonable
work work work work work work work
this work 22 D
DOI: 10.1021/acs.jced.8b00298 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 2. Source and Purity of Materials analyzed purity, mass %a,b compound
CASRN
supplier
researcher
supplier
water, mass %c
2,4,4-trimethyl-1-pentene p-tolualdehyde dimethyl terephthalate N-methyl ethanamide diphenylmethane dimethyl carbonate methoxyacetone 2-methylthiophene 3-methylthiophene 2-phenoxyethanol 2-methylpropanal 2-methoxy-1-propanol 2-ethoxyethanol tetrahydrothiophene methyl acetoacetate ethylene glycol diacetate benzenethiol ethyl prop-2-enoate methyl 2-methylprop-2-enoate 1-methoxy-2-(2-methoxyethoxy)ethane cyclohexanethiol 2-Pyrrolidone ethyl 2-methylprop-2-enoate (2-methoxy-1-methylethyl) propanoate 1-azacyclopenta-2,4-diene N,N-dimethyl methanamide 2-ethylhexyl prop-2-enoate 1-methoxy-2-[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]ethane 1,4-(hydroxymethyl)cyclohexane (1-methyl)ethenyl ethanoate piperidine butyl 2-methylprop-2-enoate 3-methoxypropanenitrile 1-methoxy-2-[2-(2-methoxyethoxy)ethoxy]ethane N-methyl methanamide 1,3-Dioxolan-2-one (1R,3S)-1,3-dimethylcyclohexane trans-1,2-dimethylcyclohexane ethylcyclohexane isopropylcyclohexane methyl prop-2-enoate diethyl carbonate N-methylpiperidine N-methylpyrrole N,N-dimethylethanamide 2,2,4-trimethyl-1,3-pentanediol t-butylcyclohexane n-butylcyclohexane n-Butylbenzene sec-butylbenzene t-butylbenzene carbon disulfide trans-1,4-dimethylcyclohexane cis-1,2-dimethylcyclohexane 1,2-dimethoxyethane N-methylpyrrolidine diethylaminoethanol 1-(2-hydroxyethyl)piperazine squalane
107-39-1 104-87-0 120-61-6 79-16-3 101-81-5 616-38-6 5878-19-3 554-14-3 616-44-4 122-99-6 78-84-2 1589-47-5 110-80-5 110-01-0 105-45-3 111-55-7 108-98-5 140-88-5 80-62-6 111-96-6 1569-69-3 616-45-5 97-63-2 148462-57-1 109-97-7 68-12-2 103-11-7 143-24-8 105-08-8 108-22-5 110-89-4 97-88-1 110-67-8 112-49-2 123-39-7 96-49-1 638-04-0 6876-23-9 1678-91-7 696-29-7 96-33-3 105-58-8 626-67-5 96-54-8 127-19-5 144-19-4 3178-22-1 1678-93-9 104-51-8 135-98-8 98-06-6 75-15-0 2207-04-7 2207-01-4 110-71-4 120-94-5 100-37-8 103-76-4 111-01-3
Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich sponsor Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich sponsor Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich TCI TCI Sigma-Aldrich TCI Sigma-Aldrich Sigma-Aldrich Sponsor TCI Sigma-Aldrich TCI Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich TCI Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich ChemSampCo ChemSampCo Acros ABCR Fluka Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Acros Sigma-Aldrich Acros Acros Sigma-Aldrich Sigma-Aldrich ChemSampCo ChemSampCo ABCR Fluka Sigma-Aldrich Sigma-Aldrich TCI
99.98% 98.7% 99.0% 99.5% 99.8% 99.97% 99.6% 99.7% 99.9% 99.99% 99.5% 99.8% 99.6% 99.6% 99.98% 99.5% 99.9% 99.8%d 99.9%d 99.7% 99.6% 97.7% 99.3%d 99.6% 99.7% 99.8% 99.3%d 98.9% 99.9%e 98.5% 99.8% 99.5% 98.8% 99.9% 99.4% 99.9% 99.4% 98.5% 99.6% 99.3% 99.5%d 99.0% 99.4% 99.5% 99.8% 99.9% 99.7% 99.4% 99.7% 99.8% 99.9% 99.9% 99% 99% 99% 99% 99.5% 99.4% 99.8%
99.2% 99.4% 100.0% 99.9% 99.8% 99.95% 99.8% 98.7% 98.9% 99.70% 99.62% 99.7% 99.98% 99.9% 99.69% 99.75% 99.8% 99.9% 99.9% 99.95% 98+% 99.6% 99.3% 99.7% 99.95% 99.94% 99% 99.9% 99.9%e 99.2% 99.3% 99.6% 99.9% 99.6% 99.6% 99.8%
