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The Chemistry and Technology of Petroleum
most logical means of refining or correlation of various properties to structural types present and
hence attempted classification of the petroleum (Chapter 2). Indeed, careful evaluation of petroleum from physical property data is a major part of the initial study of any petroleum destined
as a refinery feedstock. Proper interpretation of the data resulting from the inspection of crude
oil requires an understanding of their significance. In the following section, an indication of the
physical properties that may be applied to petroleum, or even petroleum product, evaluation will
be presented.
10.3 PHYSICAL PROPERTIES
For the purposes of this text, a physical property is any property that is measurable and
the value of which describes the physical state of petroleum that do not change the chemical nature of petroleum. The changes in the physical properties of a system can be used to
describe its transformations (or evolutions between its momentary states). Physical properties
are contrasted with chemical properties, which determine the way a material behaves in a
chemical reaction.
10.3.1 elementAl (ultImAte) AnAlysIs
The analysis of petroleum for the percentages of carbon, hydrogen, nitrogen, oxygen, and sulfur
is perhaps the first method used to examine the general nature, and perform an evaluation, of a
feedstock. The atomic ratios of the various elements to carbon (i.e., H/C, N/C, O/C, and S/C) are
frequently used for indications of the overall character of the feedstock. It is also of value to determine the amounts of trace elements, such as vanadium, nickel, and other metals, in a feedstock
since these materials can have serious deleterious effects on catalyst performance during refining
by catalytic processes.
However, it has become apparent, with the introduction of the heavier feedstocks into refinery
operations, that these ratios are not the only requirement for predicting feedstock character before
refining. The use of more complex feedstocks (in terms of chemical composition) has added a
new dimension to refining operations. Thus, although atomic ratios, as determined by elemental
analyses, may be used on a comparative basis between feedstocks, there is now no guarantee that
a particular feedstock will behave as predicted from these data. Product slates cannot be predicted
accurately, if at all, from these ratios.
The ultimate analysis (elemental composition) of petroleum is not reported to the same
extent as for coal (Speight, 1994). Nevertheless, there are ASTM procedures for the ultimate
analysis of petroleum and petroleum products but many such methods may have been designed
for other materials.
For example, carbon content can be determined by the method designated for coal and coke
(ASTM D3178) or by the method designated for municipal solid waste (ASTM E777). There are
also methods designated for
1. Hydrogen content (ASTM D1018, ASTM D3178, ASTM D3343, ASTM D3701, and ASTM
E777)
2. Nitrogen content (ASTM D3179, ASTM D3228, ASTM D3431, ASTM E148, ASTM E258,
and ASTM E778)
3. Oxygen content (ASTM E385)
4. Sulfur content (ASTM D124, ASTM D1266, ASTM D1552, ASTM D1757, ASTM D2662,
ASTM D3177, ASTM D4045, and ASTM D4294)
The Chemistry and Technology of Petroleum
most logical means of refining or correlation of various properties to structural types present and
hence attempted classification of the petroleum (Chapter 2). Indeed, careful evaluation of petroleum from physical property data is a major part of the initial study of any petroleum destined
as a refinery feedstock. Proper interpretation of the data resulting from the inspection of crude
oil requires an understanding of their significance. In the following section, an indication of the
physical properties that may be applied to petroleum, or even petroleum product, evaluation will
be presented.
10.3 PHYSICAL PROPERTIES
For the purposes of this text, a physical property is any property that is measurable and
the value of which describes the physical state of petroleum that do not change the chemical nature of petroleum. The changes in the physical properties of a system can be used to
describe its transformations (or evolutions between its momentary states). Physical properties
are contrasted with chemical properties, which determine the way a material behaves in a
chemical reaction.
10.3.1 elementAl (ultImAte) AnAlysIs
The analysis of petroleum for the percentages of carbon, hydrogen, nitrogen, oxygen, and sulfur
is perhaps the first method used to examine the general nature, and perform an evaluation, of a
feedstock. The atomic ratios of the various elements to carbon (i.e., H/C, N/C, O/C, and S/C) are
frequently used for indications of the overall character of the feedstock. It is also of value to determine the amounts of trace elements, such as vanadium, nickel, and other metals, in a feedstock
since these materials can have serious deleterious effects on catalyst performance during refining
by catalytic processes.
However, it has become apparent, with the introduction of the heavier feedstocks into refinery
operations, that these ratios are not the only requirement for predicting feedstock character before
refining. The use of more complex feedstocks (in terms of chemical composition) has added a
new dimension to refining operations. Thus, although atomic ratios, as determined by elemental
analyses, may be used on a comparative basis between feedstocks, there is now no guarantee that
a particular feedstock will behave as predicted from these data. Product slates cannot be predicted
accurately, if at all, from these ratios.
The ultimate analysis (elemental composition) of petroleum is not reported to the same
extent as for coal (Speight, 1994). Nevertheless, there are ASTM procedures for the ultimate
analysis of petroleum and petroleum products but many such methods may have been designed
for other materials.
For example, carbon content can be determined by the method designated for coal and coke
(ASTM D3178) or by the method designated for municipal solid waste (ASTM E777). There are
also methods designated for
1. Hydrogen content (ASTM D1018, ASTM D3178, ASTM D3343, ASTM D3701, and ASTM
E777)
2. Nitrogen content (ASTM D3179, ASTM D3228, ASTM D3431, ASTM E148, ASTM E258,
and ASTM E778)
3. Oxygen content (ASTM E385)
4. Sulfur content (ASTM D124, ASTM D1266, ASTM D1552, ASTM D1757, ASTM D2662,
ASTM D3177, ASTM D4045, and ASTM D4294)