Crude oil

1. Light products and their properties
Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas)
Also referred to as simply propane or butane, are flammable mixtures of
hydrocarbon gases used as fuel in heating appliances, cooking
equipment, and vehicles. It is increasingly used as an aerosol
propellant and a refrigerant, replacing chlorofluorocarbons in an effort to
reduce damage to the ozone layer. When specifically used as a vehicle
fuel it is often referred to as auto gas.
Varieties of LPG bought and sold include mixes that are
primarily propane (C3H 8), primarily butane (C4H10) and, most
commonly, mixes including both propane and butane. In the northern
hemisphere winter, the mixes contain more propane, while in summer,
they contain more butane. In the United States, primarily two grades of
LPG are sold: commercial propane and HD-5. These specifications are
published by the Gas Processors Association (GPA) and the American
Society of Testing and Materials (ASTM). Propane/butane blends.

2. LPG is prepared by refining petroleum or "wet" natural gas, and is almost
entirely derived from fossil fuel sources, being manufactured during the
refining of petroleum (crude oil), or extracted from petroleum or natural gas
streams as they emerge from the ground. It was first produced in 1910
by Dr. Walter Snelling, and the first commercial products appeared in 1912.
It currently provides about 3% of all energy consumed, and burns relatively
cleanly with no soot and very few sulfur emissions.
As it is a gas, it does not pose ground or water pollution hazards, but it can
cause air pollution. LPG has a typical specific calorific value of 46.1 MJ/kg
compared with 42.5 MJ/kg for fuel oil and 43.5 MJ/kg for premium
grade petrol(gasoline).
As its boiling point is below room temperature, LPG will evaporate quickly
at normal temperatures and pressures and is usually supplied in
pressurized steel vessels. They are typically filled to 80–85% of their
capacity to allow for thermal expansion of the contained liquid. The ratio
between the volumes of the vaporized gas and the liquefied gas varies
depending on composition, pressure, and temperature, but is typically
around 250:1.

4. Liquid Petroleum Gas (LPG) storage facility

5. • The pressure, at which LPG becomes liquid, called its vapour
pressure, likewise varies depending on composition and temperature;
unlike natural gas, and thus will flow along floors and tend to settle in
low spots, such as basements. There are two main dangers from this.
The first is a possible explosion if the mixture of LPG and air is
within the explosive limits and there is an ignition source. The second
is suffocation due to LPG displacing air, causing a decrease in oxygen
concentration.
Uses of LPG
• LPG has a very wide variety of uses, mainly used for cylinders across
many different markets as an efficient fuel container in the
agricultural, recreation, hospitality, calefaction, construction, sailing
and fishing sectors. It can serve as fuel for cooking, central heating
and to water heating and is a particularly cost-effective and efficient
way to heat off-grid homes.
• In the safety font LPG cylinders must be updated to new standards in
safety and user experience, giving a huge contribution for domestic
usage.

6. 1- Cooking
LPG is used for cooking in many countries for economic reasons,
for convenience or because it is the preferred fuel source.
2- Rural heating
Predominantly in Europe and rural parts of many countries, LPG
can provide an alternative to electricity and heating oil (kerosene).
LPG is most often used in areas that do not have direct access to
piped natural gas.
3- Motor fuel
When LPG is used to fuel internal combustion engines, it is often
referred to as auto gas or auto propane. LPG has a lower energy
density than either petrol or fuel-oil, so the equivalent fuel
consumption is higher, and has a high octane rating (102–108 RON
depending on local specifications). It burns more cleanly than
petrol or fuel-oil and is especially free of the particulates present in
the latter.
4- Refrigeration
LPG is instrumental in providing off-the-grid refrigeration, usually
by means of a gas absorption refrigerator.

7. LPG Properties

8. The contaminants of liquefied petroleum gas are:
1- The contaminants of liquefied petroleum gas are controlled at a level at
which they do not corrode fittings and appliances or impede the flow of
the gas. For example, hydrogen sulfide (H2S) and carbonyl sulfide
(COS) should be absent but Organic sulfur such as dimethyl sulfide
(CH3SCH3) and ethyl mercaptan (C2H5SH) are commonly used at a
concentration of up to 50 ppm, required for adequate odorization.
2- Liquefied petroleum gas may also be contaminated by higher-boiling
constituents such as the constituents of middle distillates to lubricating
oil must be prevented from reaching unacceptable levels.
3- Olefins and especially diolefins are prone to polymerization and should
be removed.
Gasoline blending components, and naphtha
• Technology exists to make gasoline from coal, shale oil, oil sands, and
exotic sources such as recycled plastics and rubber tires. These
processes are complicated and expensive. Petroleum crude, also called
crude oil or crude continues to be the most economical source of
gasoline.

9. • The first step of gasoline refining is to isolate the gasoline naturally
present in crude, much as the first refiners did. Then, in more
complex steps, non-gasoline components of crude are converted into
gasoline and gasoline molecules are rearranged to improve their
characteristics. Understanding the various conversion steps requires
knowing something about the hydrocarbon (HC) building blocks that
make up gasoline and crude. This chapter first discusses the
composition of gasoline and the nature of hydrocarbons. Then it
explains the various refining steps and how the resulting products are
blended to create a finished gasoline. Finally, it describes gasoline
specification properties and the tests used to measure them.
• Composition
There are two ways to describe a material, by its chemical
composition and by its properties. Both viewpoints can be
instructive. Gasoline is a complex mixture of hundreds of
hydrocarbons that vary by class, including paraffins, olefins,
naphthenes, and aromatics. Within each class, hydrocarbons also
vary by size. The mixture of hydrocarbons (and oxygenates) in a
gasoline determines its physical properties and engine performance
characteristics.

10. • Gasoline is manufactured to meet property limits prescribed by
specifications and regulations, not to achieve a specific distribution of
hydrocarbons by class and size. To varying degrees, property limits
define chemical composition.
• Each individual hydrocarbon boils at a specific temperature, or boiling
point, and in general, the boiling point increases with molecular size.
Consequently, requiring a distillation profile is equivalent to requiring a
population of hydrocarbons with a range of sizes. The temperature
limits of a distillation profile exclude smaller hydrocarbons with lower
boiling points and larger hydrocarbons with higher boiling points.
• Octane number is another example of how property limits define
chemical limits. Table (6) illustrates how Research octane number
(RON) varies with class for hydrocarbons of the same carbon number.
So, an octane number limit requires greater representation of some
classes and less of others. Octane number differentiation goes beyond
class, however. Different isomers of the same hydrocarbon can have
different octane numbers. The RON of isooctane (2, 2, 4-
trimethylpentane) is 100 by definition while the RON of normal octane
is estimated to be less than zero. Other properties, such as volatility,
also are influenced by isomer structure.

12. Components for Gasoline
1- Catalytic Naphtha Reforming: Saturated, low octane hydrocarbons
converted into higher octane product containing about 60% aromatics.
2- Fluidized Catalytic Cracking (FCC): Breaks larger hydrocarbons into
a product containing 30% aromatics and 20-30 olefins.
3- Isomerisation: Straight chain HCs converted into branched isomers.
4- Alkylation: gaseous olefins streams reacted with isobutene to produce
liquid high octane iso-alkanes.
5- The first two are most commonly used to produce gas blending high
octane components.
Gasoline Blending
Despite the diversity and ingenuity of the processes within a modern
petroleum refinery, no single stream meets all the requirements of
gasoline. Thus, the final step in gasoline manufacture is blending
various streams into a finished product. It is not uncommon for finished
gasoline to be made up of six or more streams see Figure (9).
Sometimes, to provide more flexibility, a stream is distilled into several
fractions and each fraction is used as a separate blending component
(for example, FCC light and FCC heavy gasoline).

14. Figure (9) Crude oil modern refinery

15. Figure (10) Products of different using from crude oil refining

16. Gasoline Additives
Additives are gasoline-soluble chemicals mixed with gasoline to enhance certain
performance characteristics or to provide characteristics not inherent in the gasoline.
Typically, they are derived from petroleum-based raw materials and their function
and chemistry are highly specialized. They produce the desired effect at the parts-
per-million (ppm) concentration range. (One ppm is 0.0001 mass percent or
1mg/kg.).
1- Oxidation inhibitors, including aromatic amines and hindered phenols, are also
called antioxidants. They prevent gasoline components from reacting with oxygen in
the air to form peroxides or gums.
2- Corrosion inhibitors are carboxylic acids and carboxylates. The tank and pipeline
facilities of gasoline distribution and marketing systems are constructed primarily of
uncoated steel.
3- Silver corrosion inhibitors are substituted thiadiazole. Combinations of trace
amounts of elemental sulfur, hydrogen sulfide, and mercaptans can cause the silver
used in vehicle fuel gauge sender units to corrode and fail.
4- Metal deactivators are chelating agents, that is, chemical compounds that capture
specific metal ions. The more active metals such as copper and zinc effectively
catalyze the oxidation of gasoline.
5- Demulsifies are polyglycol derivatives. An emulsion is a stable mixture of two
mutually insoluble materials.

17. 6- Antiknock compounds increase the antiknock quality of gasoline. They
include materials based on:
• Lead alkyls, such as tetraethyl lead (TEL) and tetramethyl lead (TML).
• Manganese, called methylcyclopentadienyl manganese tricarbonyl
(MMT).
• Iron, called ferrocene.
Because only a small amount of additive is needed, using antiknock
compounds is a lower-cost method to increase octane number than
changing gasoline chemistry.
Naphtha
Naphtha is a general term that has been used for over two thousand years
to refer to flammable liquid hydrocarbon mixtures. Mixtures labeled
naphtha have been produced from natural gas condensates, petroleum
distillates, and the distillation of coal tar and peat. It is used differently in
different industries and regions to refer to gross products like crude oil or
refined products such as kerosene.

20. Types of naphtha:
• Various qualifiers have been added to the term "naphtha" by various
sources in an effort to make it more specific:
• One source differentiates by boiling point:
• Light naphtha is the fraction boiling between 30 °C and 90 °C and
consists of molecules with 5–6 carbon atoms.
• Heavy naphtha boils between 90 °C and 200 °C and consists of
molecules with 6–12 carbons.
• Another source differentiates light and heavy based on
hydrocarbon structure:
• Light is a mixture consisting mainly of straight-chained and cyclic
aliphatic hydrocarbons having from five to nine carbon atoms per
molecule.
• Heavy is a mixture consisting mainly of straight-chained and cyclic
aliphatic hydrocarbons having from seven to nine carbons per
molecule.
• Both of these are useful definitions, but they are in conflict with one
another, so these terms are also sufficiently broad that they are not
widely useful.

21. Other uses of Naphtha
• Some petroleum refineries also produce small amounts of specialty
naphthas for use as solvents, cleaning fluids, paint and varnish
diluents, asphalt diluents, rubber industry solvents, dry-cleaning,
cigarette lighters, and portable camping stove and lantern fuels. Those
specialty naphthas are subjected to various purification processes.
• Sometimes the specialty naphthas are called petroleum
ether, petroleum spirits, mineral
spirits, paraffin, benzine, hexanes, ligroin, white oil or white
gas, painters naphtha, refined solvent naphtha and Varnish makers' &
painters' naphtha (VM&P) . The best way to determine the boiling
range and other compositional characteristics of any of the specialty
naphthas is to read the Material Safety Data Sheet (MSDS) for the
specific naphtha of interest.
• On a much larger scale, petroleum naphtha is also used in
the petrochemicals industry as feedstock to steam reformers and steam
crackers for the production of hydrogen (which may be and is
converted into ammonia for fertilizers), ethylene and other olefins.
Natural gas is also used as feedstock to steam reformers and steam
crackers.

22. Table (7): Straight-Run Distillates