INDUSTRIAL AND ENGINEERING CHEMISTRY
162
loidal particles were present after several days of treatment; longer periods produced more particles. Morrell (7) points out that high acidity in an untreated drying oil may retard the thickening (bodying) or polymerization of that oil. This suggested the possibility that the presence of an acid might have some effect on the appearance of colioidal particles in an irradiated oil. Glacial acetic acid (0.04 cc.) was added to the customary volume of ArcherDaniels-Midland P. M. P. linseed oil; the sample was then subjected to ultraviolet irradiation for 24 hours. Ultramicroscopic examination of a portion of this sample revealed very few particles (Figure 4). This was in decided contrast with the results obtained upon treating the same oil 12 hours in the absence of the acid. The following experiment was performed to determine whether colloidal particles might be observed a t any point in a known polymerization reaction. Acetaldehyde that was almost optically empty was gently warmed with traces of concentrated, aqueous potassium hydroxide until a slightly yellow, more viscous, and higher boiling liquid than acetaldehyde itself was obtained. Ultramicroscopic particles were observed in this liquid. It was felt that these particles must be the aldehyde resin, still in a colloidal state of subdivision. In this connection it should be emphasized that the appearance of colloidal particles both in the aldehyde polymerization and in the ultraviolet irradiated oils does not in itself establish the identity of the processes. The mechanisms involved in the formation of the colloidal aggregates may or may not be similar. SUMMARY AND CONCLUSIONS A change that is observable under the ultramicroscope takes place in drying oils upon exposure to ultraviolet light. Colloidal particles appear in both linseed and tung oils, the
Vol. 27, No. 2
number of these particles increasing with time of treatment, While the possibility that these submicrons arise from a separation of solid oxidation products of the unsaturated acid glycerides originally present in the oils cannot be overlooked, there is evidence for believing that they arise from some form of polymerization. Several of the investigators previously cited have noted a decrease in iodine number and a thickening of drying oils upon ultraviolet treatment and have attributed these to polymerization. Addition of glacial acetic acid to linseed oil prevented a subsequent appearance of colloidal particles as a result of ultraviolet radiation. Although ordinarily the drying of oils does not proceed under the extreme conditions of ultraviolet irrddiation here used, nevertheless an implication of the results of this investigation is that a change resulting in the formation of particles of colloidal dimensions does occur during the drying process. Work is now being carried out in this laboratory in an effort t o arrive a t a satisfactory mechanism for the formation of these particles. LITERATURE CITED Black, Ph.D. dissertation, Ohio State University, 1929. Freundlich and Albu, 2.angew. Chem., 4 4 , 5 6 (1931). Jamieson, "Vegetable Fats and Oils,"p. 279 (1932). Marcusson, 2.angew. Chena., 35, 543 (1922). Morrell, J . SOC.Chem. Ind., 43, 362T (1924). Ibid., 43, B 754 (1924). Morrell, "Varnishes and Their Components," p. 55 (1923). Purdy, France, and Evans, IND. ENQ.C H ~ M22, . , 508 (1930). Slansky, 2. angew. Chem., 34,533 (1921). Stutz, IND. ENQ.CHEIM., 18, 1235 (1926). Wolff, Farben-Ztg., 34, 1119 (1919); J . Chena. SOC.,115. 916A (1919).
Wolff, 2. angew. Chem., 37, 729 (1924). RlCmviD September 1, 1934.
Phase Equilibria in Hydrocarbon Systems VII. Physical and Thermal Properties of a Crude Oil' B. H. SAGE,W. N. LACEY,AND J. G. SCHAAFSMA, California Institute of Technology, Pasadena, Calif.
P
W S I C A L and thermal properties of hydrocarbon systems, such as those found in natural reservoirs, are of value in accurate evaluation of reservoir energy and the energy relations involved in subsequent processes, such as flow from the well and through pipe lines. Before attempting an extended study of oil-gas mixtures such as are usually found in natural reservoirs, a study was made upon a crude oil from which had been taken all dissolved gas that would leave the liquid upon standing a t a pressure of one atmosphere and a temperature of 120' F. in a closed vessel. In this study a t pressures greater than one atmosphere, only the condensed liquid region could be investigated, whereas in the case of oilgas mixtures a portion of the two-phase region could be investigated as well, The data presented in this paper cover the specific values2of heat content,3 entropy, and volume of a crude oil a t temperatures from 60" t o 220" F. and pressures from the vapor pressure of the crude to 3000 pounds per square inch absolute. Application of these data is illustrated by sample calculations of some flow problems based upon assumed conditions.
* Parts I to VI of this series appeared, respectiqely, in January, February, June, August, November, 1934, and January, 1935. Specific values are those for one pound of the material in question. 8 Heat content is also known as "total heat" or "enthalpy."
METHODS AND M A T ~ I A L S The methods used in this work have been previously described.* They consist in measuring the isothermal change in volume with varying pressure a t a series of temperatures and in determining the specific heat a t constant pressure by the adiabatic expansion method. The crude oil was obtained from the Kettleman Hills field in California and was taken from a vent tank a t a temperature of about 120' F. and a pressure slightly below atmospheric. In order t o prevent the solution of air or the escape of volatile components, the oil was kept in a closed steel bomb until ready for use. The oil had the following characteristics: molecular weight, 188 (by freezing point lowering of benzene) ; specific gravity a t 60" F. and one atmosphere, 0.8383 (37.1" A. P. I.). Specificgravity as used in this paper refers to the ratio of the weight of a known volume of the material under the given pressure and temperature to the weight of the same volume of water a t its maximum density a t atmospheric pressure. To obtain further information concerning the characteristics of the crude oil, it was subjected to distillation. This 4 Sage, B. H., Schaafama, J. 1218 (1934).
G.,and Laoey, W. N., IND.ENG.CHQM.,
26,
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1935 0.021
,
,J
163
I
SALURATED
,
LIQUID
I
a
I
I23
100
I
I50 TEMPEHATURE
1
I
1
175
200
OF
FIGURE 2. SPECIFICHEATAT CO~STANT PRESSURE MIDO'
500
I 20m
I500
IO00 PRESSURE
~ 0 PsE R
sa
1 2500
IN
CHANGEIN SPECIFICVOLVME WITH FIGURE 1. ISOTHERMAL PRESSURE distillation was conducted in a %liter (2.1-quart) flask with a-22-inch column, 18 inches of which were packed with jack chain, An aftercondenser of acetone-carbon dioxide snow was employed to condense the more volatile constituents which were blended into the initial cut. Three gasolines were produced: start to approximately 375" F. end point, start to approximately 400' F. end point, and start to approximately 440' F. end point. A kerosene cut of 40 gravity was produced after the 400' F. end-point gasoline, and yield and characteristics of the bottoms after the kerosene cut likewise were obtained. The results are shown in full in Table I. TEMPERATURE
TABLE I. ANALYSISOF CRUDEOIL c n l_ 4 _ - .
Yield % by vol. Gravity, 'A. P.I. Mol. weight A . S. T. hl. distn., F.: Start 5% 10%
20% 30% 40% 50% 60% 70%
E#
End point
Viscosity at 130' (Universal) Viscosity at 122' (Furol) Pour point, F.
40 GR. CUT^ AFTER BOTTOMS START STARTAT AFTER 440OF. 400° F. 40 G R , 48.0 7.5 51.3 57.5 40.0 22.6 169 339 112
CUT1
START 370° F. 37.4 62.6 101
CUT^ START 400'F. 41.2 60.5 105
88 128 146 176 201 220 236 252 272 296 318 356 370 96.5 1.0 2.5
92 132 152 184 210 230 248 268 290 316 348 378 396 97.0 1.0 2.0
96 138 158 196 222 244 270 298 326 364 404 428 446 97.0 1.0 2.0
412 417 421 426 429 43 1 433 436 440 446 457 466 482 99.0 1.0 0.0
...
... ...
... ... ...
... ...
F.
F.
... ...
...
...
... ... ...
... ...
... ... ... ... ... ... ...
... ...
... ... 139 20 +60
EXPERIMENTAL RESULTS In Figure 1 are shown the isothermal changes in speciiic volume with pressure. All experimental points have been included except those used to establish the vapor pressure curve a t the bubble point. These were omitted for lack of space to plot the points close to the vapor pressure curve.
The greater compressibility of the liquid a t the higher temperatures is apparent from the curves. Figure 2 shows the isobaric change in specific heat a t constant pressure with temperature. The points shown are the average of six determinations a t each temperature. The average deviation from the mean was about one per cent. The isothermal change in this specific heat with pressure was found to be quite small, even very close to the saturation line. In Figure 3 is shown the isobaric change in specific volume with temperature. The smaller change in specific volume with temperature a t the higher pressures can be seen. The data shown in Figures 1 and 2, together with the slopes of the curves shown in Figure 3, furnish the basis for the calculation of the other thermal properties.4 The results of these calcu1ationsarepresentedinTable 11. Since the isothermal changes in heat content and entropy are better known than their changes with temperature, the data were tabulated to one more significant figure than is warranted by the specific heat data. Although the temperature entropy plane is usually preferable for the graphic representation of the thermal properties of a substance, the isothermal changes in entropy are so small compared to the isobaric changes with the temperature that the former cannot be properly shown on this plane. For this reason the tabulated data are plotted upon the temperature-heat content plane shown in Figure 4. The double
TABLE11. PHYSICAL AND THERMAL PROPERTIES OF A CRUDEOIL IN -looo 0
PO
h
F,-
-130' s
V
h
F.-
Sstn.
500 1000 1500 2000 2500 3000
-
a p pressure, pounds per square inch, absolute: e per pound per F absolute.
-160' 8
-
'7.
FIGURE 3. ISOBARIC CHANGEIN SPECIFICVOLUMEWITH TEMPERATURE
11
0.02004 0.01997 0.01990 0.01983 0.01976 0.01970 0.01963
F.h 53.54 54.73 56.02 57.31 58.62 59.93 61.24
THE
CONDENSED LIQUIDREGION
-190' 8
V
0.09383 0.09296 0.09206 0.09118 0.09032 0.03949 0.08867
0.02036 0.02027 0.02019 0.02011 0.02003 0.01996 0.01989
specific volume, cubic foot per pound: h
-
F,h 8 71.22 0.12163 72.36 0.12072 73.62 0.11976 7 4 . 9 0 0.11857 7 6 . 2 0 0.11799 77.50 0.11716 78.81 0.11634
F.-
-220'
h 0.02059 89.74 0.02060 90.83 0.02049 92.07 0.02040 93.33 0.02031 94.62 0.02023 95.92 0.02016 97.22 U
heat content, B. t. u. per pound:
a
-
s 0.14948 0.14852 0.14754 0.14661 0.14573 0.14488 0.14405
entropy, B . t. u.
164
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Vol. 27, N o . 2
in going from A to B. The graphic a l l y d e t e r m i n e d value of J T d s added to the loss in h e a t c o n t e n t yields the amount of heat produced as the result of friction in the process represented by the path between A a n d B . If the change in e l e v a t i o n or the work done by or on the oil is known, it can be added to or subt r a c t e d f r o m t h e change in heat content and the same method can be used as in the foregoing to determine the friction. The p r i n c i p l e s o u t l i n e d can be i l l u s t r a t e d by a specific problem shown by the path C-D-E. This path is assumed to be that of a pumping oil well operating under a r b i t r a r i l y c h o s e n c o n d i t i o n s . Let point C represent the condition of the oil a t the e n t r a n c e to the pump cylinder 4000 feet below the surface, assuming it to be liquid a t 200.1 O F. under FIGURE 4. TEMPERATURE-HEAT CONTENT CHART saturation pressure. The outlet of the pump cylinder is represented by scale was used in order to enlarge the isothermal sections. point D, a t a pressure of 2000 pounds per square inch after An enlarged chart of the properties of the crude oil in the a frictionless adiabatic compression process. Thus the enneighborhood of 200 O F. is shown on the temperature-entropy tropy at the entrance and outlet of the pump cylinder is the plane in Figure 5 . I n both Figures 4 and 5 the five variablessame. The work done is obtained from the temperaturespecific volume, specific heat content, specific entropy, tem- heat content plot by the difference in initial and final heat perature, and pressure-were included. contents, and is found to be 7.5 B. t. u. per pound of oil. As a d p and this check, the work is calculated by evaluation of APPLICATIOK TO FLOW PROBLEMS is found t,o be 7.37 B. t. u. Let point E represent the state of The application of such data as those presented in the fore- the oil a t the surface with a temperature of 187.4" F. and going to flow calculations in the condensed region is not as im- under the corresponding saturation pressure. The path D-E portant as the application of similar information in the two- is arbitrarily chosen to represent the thermodynamic path phase region. This is because the isothermal changes in of the fluid up the flow string. However, the exact path is both heat content and entropy are so much smaller in the necessary only for evaluation of the friction, and large variacondensed region. However, the methods here applied to tions in this path are improbable. The difference in heat the condensed region can be equally well utilized for either content between D and E (14.80 B. t. u.) yields the heat lost the superheated or the two-phase regions for hydrocarbon to the surroundings-in this case, 9.66 B. t. u. per pound of oil. The value of J'T d s over the given path from D to E is found systems. I n Figure 4 the difference between the gain in heat content by graphical integration t o be -7.78 B. t. u. per pound. of the oil during isothermal and during adiabatic compression Then the energy lost as a result of friction during flow is is shown. TCe frictionless adiabaiic compression follows along a line of c o n s t a n t e n t r o p y from the initial to the final state, while the isothermal c o m p r e s s i o n follows a horizontal path from the initial state to the final pressure. The work done in the adiabatic compression is given either by the gain in heat content of the fluid or by graphical e v a l u a t i o n of d p over the constant entropy path. The isothermal gain in heat content is given by Figure 4, and, when the process is f r i c t i o n l e s s , the heat rejected is determined by a s c e r t a i n i n g T(S1 - SI) for the path. T h e s u m g i v e s t h e a m o u n t of w o r k done. The evaluation of the heat lost by the oil in a flowing process, whether there is friction or not, can be directly obtained as differences in initial and final heat content of the oil, when there is no work done on the system and the change in elevation is negligible. In Figure 5 the random path A-B could represent any one of a number of processes. If there is no I4 0.11 0.1 2 0.13 work done on or by the system or no change in ENTROPY B.TU. PER LB. P E R 9. elevation, the difference in initial and final heat FIGURE5 . TEMPERATURE-ENTROPY DIAGRAM contents will give the loss of heat from the oil
sv
sv
Februar). 1935
1NDUSTRIAL AND ENGINEERING CHEMISTRY
equal to the algebraic sum of f T d s and the heat lost by the system, and is in this case equal to 1.88 B. t. u. per pound.
165
tute. Acknowledgment is made to the institute for its assistance. Thanks are due to the Standard Oil Company of California for their cooperation in furnishing the sample of crude oil used and for all the data included in Table I, except the molecular
ACKNOWLEDGMENT This investigation was carried out as a part of the work of Research Project 37 of the American Petroleum Insti-
RECEIVED September 13,
1934.
Pressure -Volume- Temperature Relations for Fractions of an Oil Study of Fractionation:
Physical Properties of Fractions a t Normal and High Pressures
R. B. Dow Harvard 1-niversity, Cambridge, Mass.
The results of fractionation of a light mineral oil f r o m a Midcontinent source are presented. The densities, viscosities, and indices of refraction have been studied f o r the unfractionated oil, nine cuts, and the bottoms at atmospheric pressure and, in most cases, at two temperatures. -/lbreoz'er, the pressure-volume-temperature relations have been investigated u p to pressures approaching apparent solidification f o r the eleven samples. Curves for the change of volume with pressure and for the variation of the thermal expansion with pressure are included f o r several samples.
AND
RI. R. FEKSKE The Pennsylvania State College, State College, Pa.
T
HIS investigation is a result of the interest of the Special Research Committee on Lubrication, American Society of Mechanical Engineers, in the physical properties of lubricants at high hydrostatic pressures. The thermodynamic properties of several lubricating oils were examined ( 3 ) at high pressures, and the viscosities of similar oils a t high pressures were studied by other investigators (6-8). Consequently a fair knowledge of these properties exists for mineral and fixed oils under the different conditions of p r e s s u r e and tern p e r a t u r e. In order to study t h e dependence of some of the thermo-
o 883
FIGURE1. RELATIVEVOLUMES AS FUNCTION OF PRESSURE AT 40" C.
orqm
dynamic properties on composition for a hydrocarbon oil, a light mineral oil' from a hfidcontinent source was fractionated, and the fractions or cuts were examined a t normal and high pressures. There appears to be no mention of a similar investigation a t high pressures in the literature. VACUUM FRACTIONATION The vacuum fractionating column of special design is 15 cm. (6 inches) in diameter and 3 meters (10 feet) in height. A noteworthV feature of operation is the low-pressure drop through the column for efficient fractionation, the pressure at the top being 0.2 to 0.3 mm. of mercury and the drop through the column amounting to 3 or 4 mm. These pressures are read on hlcCleod gages attached to the top and bottom of the column. The still, on the other hand, is designed to obtain good circulation in the oil by using t h e r m o s i p h o n effects. It is capable of holding a charge of about 19 liters (5 gallons). The assembly is electrically heated. I
4
8
'2
16
20
Number o f Cuf
14
I 9 8 3 2
BOfhVnS
FIGURE. 2. RELATIVE VOLUMESOF VARIOUSCUTS
1 Thia oil wae obtained from the Atlantic Refining Company, Philadelphia, a n d is known t o t h e t r a d e as Renown Engine oil.
