Federal Water Pollution Control Administration
Division of Water Quality Research
Analytical Quality Control Laboratory
Cincinnati, Ohio
LABORATORY GUIDE FOR THE IDENTIFICATION
OF PETROLEUM PRODUCTS
January, 1969
U.S. DEPARTMENT OF THE INTERIOR
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Laboratory Guide for the Identification
of Petroleum Products
by
Fred K. Kawahara, Ph.D., F.A.I.C.
U. S. Department of the Interior
Federal Water Pollution Control Administration
Division of Water Quality Research
Analytical Quality Control Laboratory
1014 Broadway
Cincinnati, Ohio 45202
January 1969
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Contents
Page
I. INTRODUCTION 1
II. SAMPLING 2
A. Collection 2
B. Preservation of Samples 3
C. Sample Preparation for Analyses 3
D. Concentration 5
III. PRELIMINARY SOLUBILITY STUDIES 7
IV. SEPARATION, ANALYSES, AND CHARACTERIZATION 10
A. Determination of API Gravity 10
B. Doctor Test 16
C. Determination of Sulfur 18
D. Determination of Distillation Ranges 18
E. Determination of Molecular Weight by the Rast Method • .19
F. Determination of the Melting Point 20
G. Determination of the Viscosity 21
V. IDENTIFICATION 23
A. Gas Chromatography 24
B. Chromatographic Analyses 24
1. Hydrocarbons 26
2. Alkyl benzenes through C,0 27
3. Results 28
4. FIA method D 1319-61T 28
C. Infrared Analyses 29
D, Trace Constituent Analyses 36
VI. REFERENCES 40
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ii
Tables
Page
Table I. Properties of Petroleum Products 6
Table II. Solubility of Petroleum Products 9
Table III. Distinguishing Features of Petroleum 12
Products
Table IV. Petroleum Products with Similar API 14
Gravity Ranges
Table V. Properties of Petroleum Products - 22
Viscosities
Table VI. Most Frequently Used Band Assignments 32
Table VII. Ratios of Infrared Absorbances of 34
Commercial Asphalts & #6 Fuel Oils
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Laboratory Guide for the Identification
of Petroleum Products
by
Fred K. Kawahara, Ph.D.
INTRODUCTION
Oil pollution has become a major problem in the coastal and
surface waters of the United States and many other countries. Oil
discharges and spills from industrial plants and commercial ships
produce unsightly and unhealthy conditions which ruin beaches and
recreational areas, impart unpleasant taste and odor to water, and
in many cases result in harm to fish and other aquatic life. Larger
oil spills will occur more frequently as the demand for petroleum
products becomes greater and ocean oil transports become larger.
The urgency of the problem requires that detailed analytical
procedures be developed to detect and identify petroleum pollutants,
in order to establish responsibility for violations of water quality
standards and to secure abatement of the pollution.
Many oil spills occur without eye witness. In such cases
technical information and data will be necessary to facilitate
locating and identifying the sources of the pollution created by
petroleum products. Following identification, proper enforcement
for control procedures may then be exercised.
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This laboratory guide for the identification of petroleum
pollutants has been prepared to provide the analyst with specific
methods leading to a positive characterization of the waste
material.
SAMPLING
Collection
Oily materials may be collected from the surface of the water
by means of three devices. The first is a glass, wide-mouth filter-
ing funnel, connected by teflon tubing to a two-way stopcock. Volatile
oil product found upon the water surface is ladled with the aid of this
device; the lower water phase is discarded by opening the stopcock.
The upper petroleum phase is transferred to a large container. Ladling
and water-discard operation should be repeated until a sufficient
amount of oil (10 grams or more) is collected.
An alternative collector is a paint-free dustpan with a suitable
stopcock attached to the handle. Collection and concentration of
several grams of petroleum product can be achieved with this household
device. Heavy, viscous material, such as asphalts, can be collected
in a similar manner. Transfer to the final collecting jar from the
funnel, jar, or dustpan, is possible with aid of a clean spoon or stick.
The third device is a large household mop with a ringer attachment.
It is suggested that, before use, the sponge, whether derived from
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natural or synthetic materials, be rinsed thoroughly with a proper
solvent, such as chloroform. This mop is passed through the oil
pool; the absorbed materials are squeezed out and transferred by
means of a funnel into the collecting jar. The sampling operation
is facilitated by attaching the bottle, scoop, or mop to a long
pole. Where possible, reference samples of oil should also be
obtained from vessels or shore facilities.
Preservation of Samples
The samples containing oil and water are protected against
autoxidation (15) and other chemical conversions by removal of air
and exclusion of light. Carbon dioxide may be used to displace air.
If dry ice is available, a piece (approximately 0.5 cu inches) may
be added to the sample. As soon as the effervescing has stopped,
the jar is sealed with a teflon lined cap. The bottle is not capped
if unused portions of solid dry ice are visible. Samples should be
preserved in the refrigerator whenever possible.
When nitrogen or an inert gas is not available, the sample bottle
is filled carefully to the top with water to displace air.
Sample Preparation for Analyses
To prepare a volatile petroleum sample for analysis, the water
sample is extracted with distilled pentane or, if necessary, with
purified dichloromethane or chloroform. To a 500 ml separatory funnel
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200 ml of pentane is added. A portion amounting to about one-half
gram to five grams of petroleum pollutant is added to the pentane
solution. The extent to which the petroleum material dissolves in
the pentane is observed. Dichloromethane or chloroform is used, if
necessary, to dissolve the pollutant. The separatory funnel is
tilted back and forth for one minute to extract the product. The
funnel is set on a ring stand and is placed under a well ventilated
hood.
After the lower phase is drawn off, the 200 ml pentane extract
containing the petroleum pollutant is washed once with 10 ml of dis-
tilled water, and the lower aqueous layer is drawn off. (For the
dichloromethane system, the aqueous layer will be on top.)
The extract layer is then dried by permitting the solvent mixture
to pass dropwise through 5 grams of anhydrous sodium sulfate held in a
No. 12 folded filter paper seated on a filtering funnel with a 75 mm
diameter and 75 mm stem. The filtered, pollutant extract is collected
in a 300 ml round-bottom flask equipped with a standard taper 24/40
ground-glass joint.
If the petroleum product is thought to be less volatile than
gasoline or kerosene, chloroform should be used as the extracting sol-
vent. Thus, greases, asphalts, residual oils, etc., are extracted
with chloroform; the extract is washed with distilled water and is
dried over anhydrous sodium sulfate prior to the concentration step.
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Concentration
For the removal of pentane or chloroform, the distillation appa-
ratus, similar to that suggested by Fieser (10) is used. A modified
Pauly (22) receiver, made from a 125 ml Erlenmeyer flask, is attached
to the adapter which follows the water condenser. Another modifica-
tion is the use of 19/38 standard taper ground-glass joints at all
connections except the Claisen distilling head which is fitted with a
24/40 standard taper joint. The distillation flask is fitted to the
Claisen head by means of a ground-glass joint. The Claisen head is
equipped with an ebullating tube through which the nitrogen gas is bled
slowly, and the ebullating tube is fitted with a 10/30 standard taper
joint. A thermometer well is fitted at the outlet of the Claisen head.
The Pauly receiver (22) is connected by means of a foot-long
suction tubing to a dry ice trap, which is fitted with an inlet and
outlet exhaust gas stopcock. The exhaust gas stopcock is connected to
a mechanical vacuum pump or line. Heat is provided by a thermostatted
water bath. Extracting solvent (pentane, dichloromethane, or chloro-
form) is removed with aid of vacuum, from the laboratory vacuum line
or a high vacuum mechanical pump.
When the pollutant is considered to be a petroleum product other
than crude, naphtha, gasoline or jet fuel, it is recommended that the
solvent mixture containing the volatile pollutant be subjected to the
milder atmospheric distillating condition. Table I shows the high
volatility of some of the petroleum products.
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PAGE NOT
AVAILABLE
DIGITALLY
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Volatile solvents and petroleum products are recovered in the Pauly
receiver or in the dry ice trap. Distillates are analyzed to deter-
mine the presence of material other than the extracting solvents.
The refractive index of the extracting solvent should be determined
prior to the extraction procedure, using an Abbe refractometer.
During the final stages of concentration, the concentrate is
transferred to a 25 or 50 ml flask. The removal of the solvents
concentrates the oil pollutant into a small volume.
An alternative method for preparing the sample for analysis is
separation by centrifugation. This method is suitable for large
volumes of liquid petroleum pollutants admixed with water. However,
the removal by centrifugation of traces of water from the viscous
material or from minor amounts (0.1 gram) of actual liquid sample is
difficult. The extraction procedure is therefore recommended in
these instances.
PRELIMINARY SOLUBILITY STUDIES
In spite of the complex structures of petroleum products it is
possible to make some reasonable prediction as to product type by
observing the behavior in organic solvents. This preliminary obser-
vation is especially useful for identifying the heavier petroleum
products.
Mention of products and manufacturers is for identification only and
does not imply endorsement by the Federal Water Pollution Control
Administration, U. S. Department of the Interior.
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From the thoroughly dried residue, free of water and extracting
solvent, a 0.2 gram portion is taken and placed into a 20 ml vial.
Seven ml of hexane is added and the mixture is stirred with a
spatula. The solubility of the residue is observed in this solvent.
This test is repeated to determine solubility in diethyl ether and in
chloroform. If the material is soluble in each of the three solvents
in the cold, the material can be assumed to be one of the following:
light or heavy naphtha, kerosene, gas oil, white oil, certain types
of cutting oils, motor oils, paraffin, diesel oil, or jet fuel.
Vaseline or white petroleum jelly is only partly soluble in
hexane, in ether, and in chloroform. Thus, vaselines are unique.
However, greases, heavy residual oil (#6) and asphalt (feed stocks)
are insoluble in hexane and in diethyl ether, but are readily soluble
in chloroform.
These solubility characteristics of petroleum materials are
summarized in Table II.
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Table II. Solubility of Petroleum Products
Product
Light naphtha
Heavy naphtha
Gasoline
Jet fuel
Kerosene
Gas oil
Diesel oil
White oil
Cutting oil
Motor oil
Paraffin wax
White petroleum jelly
Grease
Residual fuel oil
Asphalt feed stock
Hexane
VS
VS
VS
VS
VS
VS
VS
VS
S
S
S
PS
I
I
I
Ether
VS
VS
VS
VS
VS
VS
VS
VS
S
S
S
PS
I
I
I
Chloroform
VS
VS
VS
VS
VS
VS
VS
VS
S
S
S
PS
S
S
S
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The solubility behavior of 0.2 gram of material was observed in 7 ml
of the cold organic solvent,
SEPARATION, ANALYSES, AND CHARACTERIZATION
The remaining dried residue obtained from the concentration
step is divided into two portions. One portion is used to determine
the API gravity, infrared spectra, and molecular weight. With care,
the residue may be recovered. The other portion is used to determine
the sulfur value, distillation range, and viscosity or refractive
index. For subsequent identification, the gas chromatographic anal-
yses of the more volatile petroleum products and the infrared analyses
of the less volatile products will be performed.
After the solubility behavior has been determined, the data of
Table I and II are consulted for guidance.
Determination of API Gravity
The analyst is referred to ASTM D 287 (1) for determining the API
gravity by means of the hydrometer. If the sample size is limited,
the density may be measured by the pycnometric methods, ASTM D 941 and
ASTM D 1217 for liquids. The density is referred to 60°F. Then,
degrees API = 141<5 - 131.5. If sufficient liquid is available,
sp.gr.
the use of the chainomatic specific gravity balance is convenient for
15 ml samples.
For viscous oils, the preferred method is ASTM D 70 and for solids
the ASTM D 71 method is used.
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If the residue, after concentrating and drying, is completely
soluble in each of the three solvents, the density or the API gravity
is determined. The second test will determine whether the sample is
high or low gravity naphtha, gasoline, jet fuel, kerosene, gas oil,
motor oil, fuel oil //I, fuel oil #2, or fuel oil #4. Table III shows
the distinctive properties of each petroleum product.
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Table III. Distinguishing Features of Petroleum Products
Crude Oil - most frequently sour, wide boiling range
High g. naphtha - low sulfur
Low g. naphtha - low sulfur
Gasoline - lead, halogens (phosphorus or boron?)
Jet fuel - low sulfur, API gravity - additives
Kerosene - low sulfur, API gravity
Gas oil - higher sulfur and API combination
Diesel oil - similar to Kerosene, Fuel Oil #1
White oil - paraffinic (IR), colorless
Cutting oil - glycerides, sulfur, (halogens), mineral oil
Motor oil - metals (Zn) , phosphorus, sulfur, additives,
frictional properties low
Paraffin wax - solid, paraffinic (IR)
White petroleum jelly - partly soluble in hexane, in ether, and in
chloroform
Grease - metal soaps?, low frictional properties;
hexane and ether insoluble, soluble in
chloroform
Fuel oil #1 - similar to Kerosene; low sulfur, API gravity
Fuel oil #2 - Kinematic viscosity
Fuel oil #4 - Kinematic viscosity
Fuel oil #5 - Kinematic viscosity
Fuel oil #6 - hexane and ether insoluble, soluble in chloro-
form, ratio of infrared absorbances
Asphalt - hexane and ether insoluble, soluble in chloro-
(Blown or feed) form, ratio of infrared absorbances, since
: similar to Fuel Oil- #6
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Advantage can be taken of these properties in order to distinguish the
products from each other.
Table IV groups four sets of petroleum products into similar API
gravity ranges. Since the gravity alone will not be sufficient to
produce distinctiveness, other properties are given to provide additional
evidence for characterization.
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Table IV. Petroleum Products with Similar API Gravity Ranges
Product
High gravity naphtha
Low gravity naphtha
Gasoline
High gravity naphtha
Low gravity naphtha
Jet fuel
Fuel oil #1
Kerosene
Low gravity naphtha
Gas oil
Paraffin wax
White oil
Motor oil
Fuel oil #2
Gravity
API
45
30
58
45
30
40
40
30
30
34
29
24
- 75
- 53
- 62
- 75
- 53
- 55
>35
- 46
- 53
- 33
- 39
- 32
- 30
>26
ISO. O *- J- •»•
iB.P.
95°
160°
96°
95°
160°
100°
360°
355°
160°
400°
MP =
196
370°
AU ^ -tWfc*
-eP.
- 206°F
- 410°F
- 408°F
- 206°F
- 410°F
- 500°F
- 625°F
- 575°F
- 410°F
- 8008F
1478-
°F
- 675°F
Comment
lead, colored
S <0.02%
S <0.02%
s
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Therefore, the two naphthas and gasoline can be differentiated
from each other by comparing the initial and final boiling points of
the material. Jet fuel and gasoline are different in the end point
and in the API gravity values. Jet fuel differs from the low gravity
naphtha in the initial and final boiling point range as well as in the
sulfur content. Kerosene is distinguishable from the naphtha and jet
fuel in initial and final boiling points.
In some cases the sulfur and API gravity values will help in
differentiation. Gas oil is distinguishable from the six petroleum
products mentioned above in both API gravity and boiling range or
sulfur values.
Motor oil is soluble in all three solvents, hexane, ether, and
chloroform. It is characterized by a narrow range of API values.
Motor oil differs from white oil, gas oil, and naphtha, having a
higher initial boiling point. Indeed, the motor oil has a charac-
teristic phosphorus to sulfur ratio of 0.5. Zinc is present at about
1/2 of the phosphorus value. High ash content is characteristic of
motor oil and most greases.
Fuel oil #1 can be used as a diesel fuel, in which case amyl
nitrate will be present. This product is quite similar to kerosene.
White oil is distinctively colorless. It is paraffinic as
indicated by the infrared spectrum.
Fuel oils #1, #2, #4, and #5 show distinctive kinematic viscosity
values at 100QF. Also, the latter three fuel oils have unusually high
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sulfur values, and thus may be readily distinguished from the
naphthas, gasoline, and jet fuel. The fuel oil API gravities are
distinctly lower than the API gravities of naphthas, gasoline, and
jet fuel.
Generally, crude oils contain mereaptans which can be detected
by the use of the doctor test (6) involving the reaction of sodium
plumbite and sulphur. The characteristic reaction of black precip-
itate shows the presence of mereaptans which are converted to the
dialkyl disulfide and polysulfides.
Doctor Test
One hundred and twenty-five grams of sodium hydroxide are dis-
solved in one liter of distilled water. To the mixture, 60 grams of
lead oxide are added. The entire mixture is shaken, permitted to
stand for one day, and then filtered.
A 10 ml test sample is vigorously shaken in a test tube with 5 ml
of the freshly filtered sodium plumbite solution. A pinch of sulfur
is added and the contents are shaken vigorously for 15 seconds.
Sufficient sulfur is added so that most of it floats at the interface
of the two phases. If the mixture is discolored, the test is reported
as positive. If the sulfur or the mixture remains unchanged or yellow,
the test mixture is considered sweet or mercaptan-free.
In characterizing the crudes, their wide distillation range is a
useful property.
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Paraffin wax ±s identifiable as a colorless solid with a wide
melting point range. It is soluble in hexane, in ether, and in
chloroform. The infrared spectrum shows only long chain paraffins.
White petroleum jelly is only partially soluble in each of the
three solvents. Its infrared spectrum shows strong paraffinic
character and little or no aromatic character.
Grease, asphaltic material, and residual fuel oil #6 are
characteristically insoluble in hexane and ether solvents. However,
the three petroleum products are soluble in chloroform.
Greases are characterized by a high metals content. Metals such
as lithium, sodium, calcium, barium, zinc or lead, may be present.
When the metals are absent, the nitrogen content may be
high. The grease will then be only partially soluble in chloroform.
Thickeners may be graphic, silica, ureas, or ammeline. Silicones
fluorocarbons, esters, or organic acid moiety, or lube oil may be
present. The infrared spectra may indicate these groups.
The two remaining petroleum products, asphalts and fuel oil #6,
have unusually low API gravity. These materials have usually higher
sulfur values and high content of nickel and vanadium. They are higher
boiling materials. These products are differentiated from one another
and also identified by use of comparative ratios of infrared absorb-
ances (12, 16), even though the products have similar infrared spectra.
Three infrared absorbances are used to yield two ratios which provide
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a linear relationship involving aromaticity, paraffinicity, and branch-
ing. This newly-developed tool shows excellent promise.
After the API gravity and solubility behavior have been determined,
additional evidence for characterization of the unknown petroleum
product may be obtained by determining the sulfur or distillation range
values.
Determination of Sulfur
The determination of volatile organic sulfur compounds may be
conducted in the manner described by Martin and Grant (18). A
satisfactory procedure for the total organic sulfur, whether volatile
or non-volatile, is that described by Belcher (A). The oxygen-bomb
method of decomposition is used and the final, almost pure solution,
is titrated with barium perchlorate-Thorin. In this method the
evaluated sample sizes varied from 10 to 30 ug of organic sulfur.
This method was selected after a lengthy study for completeness of
decomposition, and colorimetric titration of numerous methods. Special
procedures are given for interfering iodine and phosphorus. This
method has been quite successful.
Determinationxof Distillation Ranges (1)
The distillation range of naphtha petroleum products is determined
by the ASTM D 86-56, while the boiling range of the aromatics may be
determined by the ASTM D 850. A special procedure, ASTM D 216, is
highly recommended for very volatile naphthas. In the latter method
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the apparatus is identical to ASTM D 86-56 except that a lower range
thermometer is used. Also, there is a slight variation in procedure
of the ASTM D 216n54 when compared to that of ASTM D 86-56.
The ASTM D 86 method of test is intended for use in the distil-
lation of gasoline, naphtha, kerosene, and similar petroleum products.
The initial boiling point is recorded as the reading of the distillation
thermometer when the first drop falls from the end of the condenser.
The end point is the highest thermometer reading observed during the
distillation of the product under test. Appropriate distillation
apparatus and directions for the method are described. (It should be
recognized that evaporation and contamination in surface waters will
affect the readings in all determinations listed).
The determination for the molecular weight is given below since
this test is of value for low and high boiling petroleum products.
The test is not necessary in most cases.
Determination of the Molecular Weight by the Rast Method (21)
About 50 mg of the dried, retrieved material is placed into a
weighed, four-inch test tube. The weight is taken. About 500 mg of
d-camphor is added and contents are weighed. Before heating, the test
tube is stoppered. The contents are melted by placing the tube in a
heated oil bath. A clear solution results. The tube is swirled to
mix the contents as a clear solution. The mixture is heated no longer
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than one minute and cooled. The solid is powdered. (This method
may be replaced by the ebulloscopic or mass spectroscopic method
for the volatile materials.)
The melting point of the mixture is determined in a melting
point tube, using a thermometer which reads to 0.2°F. Melting points
of several samples from the mixture are determined and the average
value is calculated. The melting point of the original camphor is
taken. The difference, ZA , between these two temperatures is the
depression of the melting point of the mixture.
The molecular weight is calculated from the following formula,
„ 40 X w X 1000
M =
^A-w
in which w is the weight of the material, W is the weight of camphor,
and 40 is the molecular freezing point depression constant for camphor.
If the unknown petroleum pollutant is found to be insoluble or
partly soluble in chloroform, a melting point is determined for the
material. Ammeline, ureas, and waxes are typical solids.
Determination of the Melting Point (1)
The determination of the melting point for petrolatum and for
microcrystalline wax is the ASTM D 127-49. The ASTM petrolatum
melting point is that temperature at which the material becomes
fluid to drop from the thermometer.
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ASTM D 87-57 describes the procedure for the determination of
the melting point of paraffin wax. ASTM paraffin wax temperature
is that temperature at which the melted wax first shows a minimum
rate of temperature change when cooled under the prescribed condi-
tions. A temperature versus time cooling curve is plotted from
the periodic temperature readings. The minimum rate of temperature
change is usually represented by a plateau in the cooling curve.
The API gravity and solubility studies will not yield sufficient
information to characterize asphalt, fuel oil #6, or greases. These
products are insoluble in ether and in hexane, but are soluble in
chloroform. Greases are characterized by low frictional properties.
Metals such as lithium, barium, zinc, or lead may be present in the
greases. Since lube oils and fuel oils have distinctive viscosity
(kinematic), this measurement is suggested. Such measurements will
differentiate fuel oil #1, #2, #4, #5, and #6.
Determination of the Viscosity (1)
In Table V the wide range of viscosity of the petroleum products
is illustrated.
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Table V. Properties of Petroleum Products-
Viscosities (23)
Type of Oil
Natural gasoline
Gasoline
Water
Kerosene
Distillate
An average 1. crude oil
Average crude oil
Average crude oil
An average h. crude oil
Wyo. crude oil
ASTM Fuel 3 (max. vis.)
ASTM Fuel 5 (min. vis.)
SAE 10W lube
SAE 20W lube
Thin SAE 10 lube (100 V.I.)
Thin SAE 10 lube (0 V.I.)
Thin SAE 30 lube (100 V.I.)
Thin SAE 30 lube (0 V.I.)
ASTM Fuel 5 (Max. Vis.) or
Fuel 6 (min. Vis.)
Average SAE 50 lube
(100 V.I.)
Average SAE 50 lube
(0 V.I.)
Thick SAE 70 lube (100 V.I.)
Thick SAE 70 lube (0 V.I.)
ASTM Fuel 6
Bunker C (max.)
M.C. residium
Asphalt
Viscosity
Saybolt
37 at 100°F
33 at 100 °F
40 at 100 °F
50 at 100°F
60 at 100°F
40 at 100°F
45 at 100°F
50 at 100
10,000 at 0°F
40,000 at 0°F
90 at 130°F
90 at 130°F
255 at 130°F
255 at 1308F
(Furol)
40 at 122 °F
90 at 210°F
90 at 210°F
150 at 210°F
150 at 210°F
(Furol)
300 at 122 PF
300 at 210°F
(50 penetration)
API
76.5
57.0
10.0
42.0
35.0
48.0
40.0
35.6
32.6
36.4
26.0
15.0
200 at 100°F 31.0
320 at 100°F 29.0
160 at 100°F 30.0
180 at 100°F 27.0
70 at 210° F 26.0
58 at 210°F 21.0
800 at 100° F 11.0
986 at 100°F 25.0
2,115 at 100°F 19.0
23.0
8.0
19.8
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The API gravity is also given with the Saybolt viscosity for each
petroleum product. It should be recognized that these are examples.
As crude oils vary widely in composition and are subjected to
different processes for manufacture of petroleum products, these
figures will deviate strongly. However, a characteristic viscosi-
metric value may yield a clue as to the identity of the product type.
Consideration of the API gravity, with sulfur values, infrared data,
with boiling point range will facilitate the identification of the
product.
Viscosity is the measure of the internal resistance of an oil to
flow. Values are usually expressed as the number of seconds in time
required for a certain volume of the oil under test to pass through a
standard orifice under prescribed conditions. For kinematic viscosity
the tentative method of test is ASTM D 445-53T. It is the absolute
viscosity divided by the density, both obtained at the same temperature
of determination. The unit of measurement is the centistokes. Con-
version of the kinematic viscosity to Saybolt Universal Viscosity for
100° and 210°F values is provided in the conversion table included in
ASTM D 446-53.
IDENTIFICATION
The techniques and methods useful for the characterization of the
numerous petroleum pollutants have been outlined. To further identify
the petroleum pollutant, several additional analytical tools are avail-
able. These are principally infrared spectroscopy and gas chromatography.
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A third method involves the analyses of trace metals and other minor
constituents.
Gas Chromatography
Gas chromatography is one of the most efficient general methods
for separating components in a mixture. However, the effectiveness
of the chromatographic separation process is highly dependent upon
use of the proper column. Important parameters that govern perfor-
mance and resolution must be considered (8, 17).
Chromatographic Analyses
For the identity of classified, volatile petroleum products, such
as naphthas, gasoline (24), jet fuel, and kerosene, it is highly
recommended that the dried, recovered residual material be analyzed
by gas chromatography. As volatility is a strong characteristic of
the above products, a portion representing the volatiles of the gas
chromatographic spectrum of the reference or known sample will be
missing in the unknown petroleum sample which is exposed for long
period. Time and temperature of the environment, as well as the fuel
volatility, must be considered in matching the unknown with the
reference sample. If the gas chromatogram of the unknown shows qual-
itative and quantitative match with the reference sample, except for
reference peaks which represent compounds of high volatility or
solubility in water, the two products can be judged as being from the
same source.
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The use of the gas chromatograph as a means to identify the
heavier products, such as residual oils and asphalt, is limited.
However, gas oils, paraffins, white oils, and motor oils can be
identified by this method, if they are volatile under the condition
of analysis.
Martin and Winters (19, 20) have developed a special method
for determining saturates through C7 and alkyl-benzenes through C,0
in crude oils. The hydrocarbons to be determined are separated
from the crude oil with a packed prefractionator column, collected
in a liquid nitrogen trap, and then released into either of two
capillary columns through a stream splitter. Components through C?
are well resolved in four hours on a 500-foot capillary column with
1-octadecene. Alkyl benzenes through C,Q are resolved on an 800-foot
column coated with polyethylene glycol. Uncertainties in the results
generally are less than 6% relative.
To characterize crude oils fully, detailed knowledge of compo-
sition is needed. Conventional methods involve analyzing narrow-
boiling distillate fractions with a variety of techniques (B.P. ,
R.I., U.V., etc.). Results are usually satisfactory, but analyses
are prohibitively lengthy.
Packed columns have been used for determining individual com-
ponents in crude oil but resolution is far from ideal. However,
this method is accurate, detects trace components, and does not
involve a prior distillation. Hydrocarbons of a selected boiling
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-26-
range are separated from the crude oil by the prefractionator column
and are collected in the liquid nitrogen trap. The prefractionator,
a short packed gas chromatographic column, fractionates approximately
by boiling point differences. After the desired boiling range
fraction has been trapped, the prefractionator is bypassed by chang-
ing the position of the four-way valves. The trap is then warmed
and the hydrocarbons are carried into the capillary column through
the stream splitter. The individual components are detected by
hydrogen-flame ionization as they emerge from the column. Volatile
compounds remaining on the prefractionator are removed by back
flushing. For determining hydrocarbons through C7, a capillary column
coated with 1-octadecene is used. For alkyl benzenes through C-0, a
column coated with polyethylene glycol is used.
Hydrocarbons
The column is a 500 feet by 0.001 inch stainless steel capillary
coated with 1-octadecene. All hydrocarbons through C_ and 10 lowest
boiling Co are well resolved, when the column is operated at 30°C with
helium-exit flow of 0.85 ml per minute at a gauge pressure of 35 p.s.i.
A temperature of 30°C gives optimum resolution. With a change of
temperature on the octadecene column, the elution position of some
hydrocarbons will change. An increase or decrease of only 3eC causes
at least one pair of compounds to elute together. With an increase in
temperature, cycloparaffins and aromatics are retained on the column
longer relative to paraffins.
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-27-
Alkyl benzenes through C
10
Determination of alkylbenzenes through CIQ is complicated by the
presence of saturates that accompany the alkyl benzenes from the pre-
fractionator column. The saturates would elute with the alkylbenzenes
if a column separating compounds in order of the boiling point were
used. However, interference is minimized by using a polar liquid phase
that selectively retains alkylbenzenes while saturates of similar boil-
ing points are separated first.
Good separations were obtained with an 800-foot by 0.01-inch
column, coated with polyethylene glycol. This column has high separating
power for individual alkylbenzenes and is selective in retaining the
alkylbenzene past saturates. The column is operated at 60°C with a
helium exit flow of 0.20 ml per minute at a gauge pressure of 45 p.s.i.
To perform the analysis, the double four-way valve is positioned
so helium flows through the prefractionator into the liquid nitrogen
trap. Helium flow is adjusted to 40 ml per minute.
The trap is immersed about two inches into liquid nitrogen. One
to 20 pi of crude oil, which contains about 1.5% of one or more of the
reference standards, is added. Elution is continued until the desired
components are in the trap; the time needed must be precisely determined
with prior runs. With this apparatus, four minutes are needed for
elution of components through toluene; 6.5 minutes are needed for
alkylbenzenes through 1, 3-dimethylbenzene; 15 minutes are needed for
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alkylbenzenes through Cg. Similarly, gasoline and other volatile
components may be analyzed and identified.
After the desired components have been typed, the position of the
double four-way valve is switched. Helium pressure to the capillary
column is adjusted. After equilibrium, current is applied to the
stainless steel trap heater so that its portion of trap outside of
liquid nitrogen reaches 130°C, after which the sample is introduced
into the capillary column by removing the liquid nitrogen. Three
seconds are required to vaporize the sample.
Results
Accuracy was estimated by analyzing synthetic blends made to
simulate crude oil and by analyzing crude oils previously examined
with packed columns. Average deviations from mean values are only
3% relative.
FIA method D 1319-61T (1)
This older method describes the procedure for the determination
of the saturates, olefins, and aromatics (Including aromatic olefins)
in petroleum fractions that distill below 600°F. Gasoline is an example.
About 3/4 ml of sample containing traces of fluorescent dye (Sudan
III) is introduced into a small glass adsorption column of 154 cm X 1.5
mm dimensions. Silica gel of 100 to 200 mesh size is used. When all
the sample has been adsorbed on the gel, alcohol is added to desorb
and develop the sample. The hydrocarbons are separated according to
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-29-
their adsorption affinities into aromatics (including aromatics with
olefinic side chains plus any sulfur, nitrogen, and oxygen compound),
olefins, and saturates. The fluorescent dyes are also selectively
separated with the sample fractions, and mark the boundaries of the
aromatics, olefins, and saturates clearly visible under ultraviolet
light. Ultraviolet light source with radiation at 3650A0 is required.
The volume percentage of each hydrocarbon type is determined by
measuring the length of each zone in the long, narrow extension of
the column. Reproducibility for experienced operators is about 3%
for determining aromatics, olefins, and saturates.
A more defined characterization of the saturated fraction could
be obtained by determination of the naphthenes in the saturated
fraction. The ASTM D 2002-62T method covers the isolation of sat-
urated hydrocarbons by shaking a measured amount of sample with a
solution of PO^S *n concentrated H_SO,. The unreacted hydrocarbons,
when separated, recovered and washed from the sulfonation acid, are
representative of the saturates in the sample.
Infrared Analyses
A suitable tool for the identification of heavier petroleum pro-
ducts is the infrared spectrophotometer. As greases, heavy residual
fuel oil, and asphalt are less volatile, the unknown infrared spectrum
can be compared with the reference spectrum. If the unknown has been
exposed unduly to environmental factors, such as air, sunlight, or
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-30-
temperature, peroxidative (15) changes are considered. Useful infor-
mation cannot be obtained from the infrared spectrum of the volatile
petroleum products, such as naphthas and gasoline, unless an on-the-spot
collection is made of the sample immediately following the spill.
Though each petroleum product is a mixture of numerous types of
organic compounds, a peak-by-peak correlation qualitatively and
quantitatively of an unknown sample against that of an authentic
source sample is excellent evidence for identity. Certain group
frequency bands permit the chemist to obtain useful information with
reference to known functional group frequencies. These characteristic
group frequencies may afford partial or complete characterization
(5, 7, 25).
Infrared spectra may be obtained for gases, liquids, or solids.
Because water sampling normally involves liquids or solids, the dis-
cussion on sample handling will involve the latter two items. Liquids
may be examined in solution or neat. Liquids (neat) are tested between
plates; the amount of material is several mg. Mobile liquids may be
also handled in cells from 0.1 to 1 mm in thickness. However, when
solutions are used, the selection of solvent is critical. The spectrum
obtained from examination of a solution should be that of the solute
except in regions where the solvent absorbs strongly.
For examining trace amounts of material, microcavity cells are
used with a beam condenser. The cell may have a path length of 0.05 mm
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-31-
and a capacity of 0.8 microliter. The solvent and sample should be dry
and transparent in range of measurement. Carbon tetrachloride, carbon
disulfide, and chloroform are the solvents frequently used. It is
suggested that solutions analyzed with matched cells be dilute. Con-
centrated solutions will render useless the advantage of matched cells.
Solids are examined as a mull which are prepared by grinding
several mg of the solid with a drop of Nujol. This mull is placed
between two plates as a film. Solids may also be examined as discs
made from 1 mg of material mixed, by vibration, with 100 mg of dried
o
potassium bromide. In a die under pressure of about 30,000 Ib per in
discs are pressed.
Before a sample is examined with a suitable infrared spectrometer,
the following are required: (1) the instrument, e.g., Perkin Elmer 137,
must be calibrated so that the absorption bands of the instrument's
spectrum coincide with those established for a standard polystyrene
film; (2) the sample to be examined should be free of moisture and
solvents which may interfere with the unknown spectrum.
The two important areas for a preliminary examination are in the
region below 7.4y and in the 11.1 to 15.4y region. Important absorp-
tion bands are interpreted after what has been observed in the high
and low energy regions of the spectrum. The most frequently used band
assignments for petroleum products derived directly from crude oil are
given in Table IV.
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-32-
Table VI. Most Frequently Used Band Assignments
Paraffins (s)CH3 (a)CH3 (s)CH3 (a)CH3
3.38y 3.48v 6.8y 7.28y
(s)CH2 (a)CH2
3.42p 3.51u
13.9y
Olefins O=C _. .. _
Cis 14.5u
6.0-6.ly Trans 10.4y
Vinyl 10u, lly
Aromatic 3.23-3.33y 6.2-6.29y; 6.7-6.76y
11.1-15.4p
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-33-
The following functional groups should be considered in the more
complex products, such as chemicals or peroxidized material: carbonyl,
acidic, ester, ether, peroxido, hydrox/1, sulfoxides, sulfones, sulfides,
phosphates, etc. Group frequency assignments are found in Bellamy (5)
and other texts on infrared spectroscopy (7, 25).
To aid in identification, the dried grease is analyzed by infrared
spectrometry and matched with the known or reference sample. The two
spectra are compared. A match of peak-by-peak correlation is necessary
for the entire spectrum, unless loss of certain group frequencies occurs
due to solubilization of certain compounds in the aqueous medium or due
to changes effected by the autoxidation process.
The nearly ash-free residue, after drying, is considered to be
heavy residual fuel oil or asphalt when soluble only in chloroform.
Measurement of the infrared absorbances at six group frequencies is
made. These are 3050 cm" , 2925 cm~ , 1600 cm" , 1375 cm" , 810 cm" ,
and 720 cm . Absorbances are determined by the base-line technique.
The length of the vertical line, which intersects the line tangential
to the two proximate inflections, is measured. Ratio of intensity of
the infrared absorption (RIA) at one frequency to that intensity of
the absorption at another frequency is considered. These ratios are
given in Table VII.
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-34-
Table VII. Ratios of Infrared Absorbances
of Commercial Asphalts & #6 Fuel Oils (16)
KIA
720 cm'1
1375 cm'1
3050 cm'1
2925 cm"1
810 cm"1
1375 cm'1
810 cm'1
720 cm'1
1600 cm'1
1375 cm"1
1600 cm"1
720 cm"1
Asphalt
.28
.20
.25
.87
.54
1.97
#6 Fuel Oil
.20
.25
.46
2.42
.73
4.18
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-35-
In addition, the average values of ratios of seven commercial asphalts
and #6 fuel oils are given.
The #6 fuel oils are found to contain more aromatics that absorb at
800 cm than the asphaltic products, according to the plot of points
810 cm versus 810 cm . Asphalt ratios are located near the origin
1375 cm7"1 720 cm'1
of the plot and have values less than 0.4 for the former ratio and less
than 1.3 for the latter ratio. The heavy residual oils, or #6 fuel oils,
lie on the same common line expressed by the equation Y = 0.13 X +0.125.
In contrast to asphalts, residual oils are characterized by a smaller
proportion of carbon methyls and methylene chains. The absorbance due
to carbon methyl branching is about four times the absorbance due to
the methylene chains.
The identity of the classified petroleum product, whether asphalt
or residual oil, can be established by comparative evaluation of the
above two ratios. Further, the identity of the unknown with the known
is confirmed by comparing the remaining four ratios of the unknown with
the known. All values should check.
Autoxidation (16) of the residual oil in water at ambient temper-
atures will show increases in the ratios
-1 -1 -1 1
1030 cm . 1155 cm . 1300 cm" . and 1695 cm" . These increases that
1375 cm'1 1375 cm'1 1375 cm'1 1375 cm'1
occur within one week are due to increase formation of sulfoxides, alkyl
ethers, secondary alcohols, and carbonyls. These small changes at the
representative group frequencies should be considered when establishing
the identity or source of pollutant with a fresh reference sample.
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-36-
A point to consider in the evaluation of the vessels carrying
or using foreign residual fuel oil is that this product normally
contains less cracked stock than domestic fuel. The reason is that
domestic residual fuel is the product obtained after numerous
catalytic and thermal processes that are responsible for aromaticity
and olefinic formation. Foreign residual fuel oils are products of
straight-run distillation. The set of values may form a distinct
linear relationship.
Trace Constituent Analyses
Many metals are found in trace quantities in petroleum (11).
Some are in solution, some in suspension, and others are associated
or chelated with the porphyrin molecules in petroleum. Generally,
nickel and vanadium are present in highest quantity. The crude oil
or residual fuel oil is washed, dry ashed, and analyzed by emission,
absorption spectroscopy or by x-ray fluorescence.
Ball et al. (2,3) made a comprehensive examination of a California
crude oil containing appreciable quantities of nitrogen, sulfur, and
oxygen. Concentrated in the asphalt fraction are the nitrogen com-
pounds of high molecular weight. Small amounts are found in the
distillates. These are suspected to be pyrroles, indoles, and
carbazoles.
Of the oxygenated types of compounds, phenols and organic acids
have been isolated. Investigation in this area will provide an
addition to fundamental knowledge and an aid to economic processing
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-37-
of the crude. If one applies a suitable method (13, 14) of minor
constituent analyses, such information obtained will serve as an
aid to identification. Types and amounts of acids, phenols, and
mercaptans may serve to identify one crude oil from another.
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-38-
Characterization Scheme
Soluble
Naphthas
Gasoline
Jet fuel
Kerosene
Fuel oil #1
Gas oil
White oil
Motor oil
Fuel oil #2
Fuel oil #4
Wax
Residue - Dried
(hexane)
Insoluble
#6
Jelly, Grease, Fuel oil/Asphalt
(CHC13)
Grease
Metals
Ba, Li, Ca
acids
Fuel oil
Asphalt
IR - RIA
partly sol.
Jelly
partly sol.
in hexane,
in ether,
in CHC13
(IR)
Hi aromatic Lower aromatic
#6 Fuel oil Asphalt
Grease
High
nitrogen
AMIDE-Type
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-39-
Resldue - Dried
Soluble
High gravity naphtha
Gasoline
Low gravity naphtha
Jet fuel
Kerosene
Fuel Oil #1
Gas oil
v.
White oil
Motor oil
Fuel oil #2
Fuel oil #4
Wax
(hexane)
I.B.P.-e.P. API
95° - 206 °F 45
96° - 408°F 58
160° - 410°F 30
100° - 5008F 40
355° - 575°F 40
- gravity
- 75
- 62
- 52
- 55
- 46
360° - 625°F >35
400° - 800 °F 30
29
24
370° - 625°F
(90%)
420° - 683°F 9
MP = 145°-
190°F 34
- 33
- 32
- 30
>26
- 36
- 39
Comment
k. vis.
I.R.-
paraffin
Zn, P, S
k. vis.
k. vis.
Solid-IR
paraffinic
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-40-
REFERENCES
1. "ASTM Standards on Petroleum Products and Lubricants," Prepared
by ASTM Committee D-2 on Petroleum Products and Lubricants,
November 1957. Published by the American Society for Testing
and Materials, Philadelphia, Pennsylvania.
2. Ball, J. S., Raines, W. E., and Helm, R. V., Fifth World
Petroleum Congress Proceedings. June 1-5, 1959, Section V,
Paper 14, p. 175, Published by Fifth World Petroleum
Congress, Inc. , New York.
3. Ball, J. S., Wenger, W. J., Hyden, H. J., Horr, C. A., and Myers,
A. T., Preprints, Division of Petroleum Chemistry, American Chem-
ical Society, ],, No. 1, 241-6 (1956).
4. Belcher, R., "Submicromethods of Organic Analysis," Elsevier
Publishing Co., New York, 1966, p. 70.
5. Bellamy, L. J., "The Infrared Spectra of Complex Organic Mole-
cules," 2nd ed., John Wiley and Sons, New York, 1958.
6. Boyd, G. A., Oil and Gas J.. 32(8). 16, 31 (1933).
7. Colthup, N, B., Daly, L. H., and Wiberly, S. E., "Introduction
to Infrared and Raman Spectrescopy," Academic Press, New York,
1964.
8. Dal Nogare, S. and Juvet, R. S., Jr., "Gas Liquid Chromatography,
Theory and Practice," Interscience Publishers, New York, 1962.
9. Encyclopedia of Science and Technology, Volume 10, p.66, Table 4,
McGraw-Hill Book Co., Inc.
10. Fieser, L. F., Experiments in Organic Chemistry," 2nd ed. D. C.
Health and Company, New York, 1941, p. 244.
11. Gamble, L. W. and Jones, W. H., Anal. Chem.. 27, 1456 (1955).
12. Johnson, W. D. , Kawahara, F. K., Fuller, F. D., Scarce, L. E.,
Risley, C., Jr., Proceedings of the Eleventh Conference on Great
Lakes Research. April 18, 1968.
13. Kawahara, F. K., Anal. Chem. 40, 1009 (1968).
14. Kawahara, F. K., ibid., 40, 2073 (1968).
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-41-
15. Kawahara, F. K., Ind. Eng. Chem. Prod. Res. Develop. 4^ 7 (1965)
16. Kawahara, F. K., Environmental Science and Technology, to be
published.
17. Littlewood, A. B., "Gas Chromatography," D. H. Desty, ed.,
Academic Press., New York, 1958,
18. Martin, R. L. and Grant, J. A., Anal. Chem. . 37., 644 (1965).
19. Martin, R. L. and Winters, J. C., Anal. Chem.. 31, 1954 (1959).
20. Martin, R. L. and Winters, J. C., ibid, 35_, 1930 (1963).
21. McElvain, S. M., "The Characterization of Organic Compounds,"
The MacMillan Company, New York, 1945, pp. 36-37.
22. Morton, A. A., "Laboratory Technique in Organic Chemistry,"
1st. ed., McGraw-Hill Book Company, Inc., New York, 1938,
p. 110.
23. Nelson, W. L., "Petroleum Refining Engineering," McGraw-Hill
Book Company, Inc., New York, 1958, p. 143.
24. Sanders, W. N. and Maynard, J. B. , Anal. Chem. . 40_, 527 (1968).
25. Silverstein, R. M., and Bassler, G. C., "Spectrometric Identi-
fication of Organic Compounds," John Wiley and Sons, Inc., New
York, 1964, pp. 49-70.
US GOVERNMENT PRINTING OFFICE. 1973- 759-S5Z/10B1
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