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The Chemistry and Technology of Petroleum
The boiling ranges of these fuels are subject to variation and depend upon the process used for their
production. In winter, gasoline will typically (in cold regions) have butane added to the mix (to facilitate cold starting), thereby changing the boiling range to 0°C–220°C (32°F–425°F). The fuels are
produced by thermal decomposition of a variety of hydrocarbons, including high-molecular-weight
paraffins. Less than one-third of a typical crude oil distills in these ranges, and thus the goal of
refining chemistry might be stated simply as the methods by which crude oil is converted to these
fuels. It must be recognized that refining involves a wide variety of chemical reactions, but the production of liquid fuels is the focus of a refinery.
Refining processes involve the use of various thermal and catalytic processes to convert molecules in the heavier fractions to smaller molecules in fractions distilling at these lower temperatures
(Jones, 1995). This efficiency translates into a strong economic advantage, leading to widespread
use of conversion processes in refineries today. However, in order to understand the principles of
catalytic cracking, understanding the principles of adsorption and reaction on solid surfaces is valuable (Samorjai, 1994; Masel, 1995).
A refinery is a complex network of integrated unit processes for the purpose of producing a variety of products from crude oil. Refined products establish the order in which the individual refining
units will be introduced, and the choice from among several types of units and the size of these
units is dependent upon economic factors. The trade-off among product types, quantity, and quality
influences the choice of one kind of processing option over another.
Each refinery has its own range of preferred crude oil feedstock from which a desired distribution of products is obtained. Nevertheless, refinery processes can be divided into three major types:
1. Separation: division of crude oil into various streams (or fractions) depending on the
nature of the crude material
2. Conversion: production of salable materials from crude oil, usually by skeletal alteration,
or even by alteration of the chemical type, of the crude oil constituents
3. Finishing: purification of various product streams by a variety of processes that essentially
remove impurities from the product; for convenience, processes that accomplish molecular
alteration, such as reforming, are also included in this category
The separation and finishing processes may involve distillation or even treatment with a wash
solution, either to remove impurities or, in the case of distillation, to produce a material boiling over
a narrower range, and the chemistry of these processes can be represented by simple equations, even
to the disadvantage of over-simplification of the process (Chapter 15). The inclusion of reforming
processes in this category is purely for descriptive purposes rather than being representative of the
chemistry involved. Reforming processes produce streams that allow the product to be finished as
the term applies to product behavior and utility.
Conversion processes are, in essence, processes that change the number of carbon atoms per
molecule, alter the molecular hydrogen-to-carbon ratio, or change the molecular structure of
the material without affecting the number of carbon atoms per molecule. These latter processes
(isomerization processes) essentially change the shape of the molecule(s) and are used to improve
the quality of the product (Chapter 24).
Nevertheless, the chemistry of conversion process may be quite complex (King et al., 1973), and
an understanding of the chemistry involved in the conversion of a crude oil to a variety of products
is essential to an understanding of refinery operations. It is therefore the purpose of this chapter to
serve as an introduction to the chemistry involved in these conversion processes so that the subsequent chapters dealing with refining (Chapters 17 through 22) are easier to visualize and understand.
However, understanding refining chemistry from the behavior of model compounds under refining
conditions is not as straightforward as it may appear (Ebert et al., 1987).
The complexity of the individual reactions occurring in an extremely complex mixture and the
interference of the products with those from other components of the mixture is unpredictable.
The Chemistry and Technology of Petroleum
The boiling ranges of these fuels are subject to variation and depend upon the process used for their
production. In winter, gasoline will typically (in cold regions) have butane added to the mix (to facilitate cold starting), thereby changing the boiling range to 0°C–220°C (32°F–425°F). The fuels are
produced by thermal decomposition of a variety of hydrocarbons, including high-molecular-weight
paraffins. Less than one-third of a typical crude oil distills in these ranges, and thus the goal of
refining chemistry might be stated simply as the methods by which crude oil is converted to these
fuels. It must be recognized that refining involves a wide variety of chemical reactions, but the production of liquid fuels is the focus of a refinery.
Refining processes involve the use of various thermal and catalytic processes to convert molecules in the heavier fractions to smaller molecules in fractions distilling at these lower temperatures
(Jones, 1995). This efficiency translates into a strong economic advantage, leading to widespread
use of conversion processes in refineries today. However, in order to understand the principles of
catalytic cracking, understanding the principles of adsorption and reaction on solid surfaces is valuable (Samorjai, 1994; Masel, 1995).
A refinery is a complex network of integrated unit processes for the purpose of producing a variety of products from crude oil. Refined products establish the order in which the individual refining
units will be introduced, and the choice from among several types of units and the size of these
units is dependent upon economic factors. The trade-off among product types, quantity, and quality
influences the choice of one kind of processing option over another.
Each refinery has its own range of preferred crude oil feedstock from which a desired distribution of products is obtained. Nevertheless, refinery processes can be divided into three major types:
1. Separation: division of crude oil into various streams (or fractions) depending on the
nature of the crude material
2. Conversion: production of salable materials from crude oil, usually by skeletal alteration,
or even by alteration of the chemical type, of the crude oil constituents
3. Finishing: purification of various product streams by a variety of processes that essentially
remove impurities from the product; for convenience, processes that accomplish molecular
alteration, such as reforming, are also included in this category
The separation and finishing processes may involve distillation or even treatment with a wash
solution, either to remove impurities or, in the case of distillation, to produce a material boiling over
a narrower range, and the chemistry of these processes can be represented by simple equations, even
to the disadvantage of over-simplification of the process (Chapter 15). The inclusion of reforming
processes in this category is purely for descriptive purposes rather than being representative of the
chemistry involved. Reforming processes produce streams that allow the product to be finished as
the term applies to product behavior and utility.
Conversion processes are, in essence, processes that change the number of carbon atoms per
molecule, alter the molecular hydrogen-to-carbon ratio, or change the molecular structure of
the material without affecting the number of carbon atoms per molecule. These latter processes
(isomerization processes) essentially change the shape of the molecule(s) and are used to improve
the quality of the product (Chapter 24).
Nevertheless, the chemistry of conversion process may be quite complex (King et al., 1973), and
an understanding of the chemistry involved in the conversion of a crude oil to a variety of products
is essential to an understanding of refinery operations. It is therefore the purpose of this chapter to
serve as an introduction to the chemistry involved in these conversion processes so that the subsequent chapters dealing with refining (Chapters 17 through 22) are easier to visualize and understand.
However, understanding refining chemistry from the behavior of model compounds under refining
conditions is not as straightforward as it may appear (Ebert et al., 1987).
The complexity of the individual reactions occurring in an extremely complex mixture and the
interference of the products with those from other components of the mixture is unpredictable.