Petroleum naphtha is an intermediate hydrocarbon liquid stream derived from the
refining of
crude oil with
CAS-no 64742-48-9. It is most usually
desulfurized and then
catalytically reformed, which rearranges or restructures the
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-
octane component of
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organi ...
(or
petrol
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic c ...
).
There are hundreds of different petroleum crude oil sources worldwide and each crude oil has its own unique composition or
assay. There are also hundreds of petroleum refineries worldwide and each of them is designed to process either a specific crude oil or specific types of crude oils. Naphtha is a general term as each refinery produces its own naphthas with their own unique initial and final boiling points and other physical and compositional characteristics.
Naphtha
Naphtha ( or ) is a flammable liquid hydrocarbon mixture.
Mixtures labelled ''naphtha'' have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat. In different industries and regions ' ...
s may also be produced from other material such as
coal tar
Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas from coal. It is a type of creosote. It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psorias ...
,
shale deposits,
tar sands
Oil sands, tar sands, crude bitumen, or bituminous sands, are a type of unconventional petroleum deposit. Oil sands are either loose sands or partially consolidated sandstone containing a naturally occurring mixture of sand, clay, and wate ...
, and the
destructive distillation
Destruction may refer to:
Concepts
* Destruktion, a term from the philosophy of Martin Heidegger
* Destructive narcissism, a pathological form of narcissism
* Self-destructive behaviour, a widely used phrase that ''conceptualises'' certain kind ...
of wood.
Source
The first unit operation (after being desalinated) in a petroleum refinery is the
crude oil distillation unit. The overhead liquid distillate from that unit is called ''virgin'' or ''straight-run'' naphtha and that distillate is the largest source of naphtha in most petroleum refineries. The naphtha is a mixture of many different hydrocarbon compounds. It has an initial
boiling point (IBP) of about 35 °C and a final boiling point (FBP) of about 200 °C, and it contains
paraffins,
naphthene
In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containing ...
s (cyclic paraffins) and
aromatic hydrocarbon
Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past groupin ...
s ranging from those containing 4
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, ...
s to those containing about 10 or 11 carbon atoms.
The virgin naphtha is often further
distilled into two streams:
* a virgin ''light'' naphtha with an IBP of about 30 °C and a FBP of about 145 °C containing most (but not all) of the hydrocarbons with six or fewer carbon atoms
* a virgin ''heavy'' naphtha containing most (but not all) of the hydrocarbons with more than six carbon atoms. The heavy naphtha has an IBP of about 140 °C and a FBP of about 205 °C.
The virgin heavy naphtha is usually processed in a catalytic reformer, because the light naphtha has molecules with six or fewer carbon atoms—which, when reformed, tend to crack into butane and lower molecular weight hydrocarbons that are not useful as high-octane gasoline blending components. Also, the molecules with six carbon atoms tend to form aromatics, which is undesirable because the environmental regulations of a number of countries limit the amount of aromatics (most particularly
benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
) in gasoline.
Types of virgin naphthas
The table below lists some typical virgin heavy naphthas, available for catalytic reforming, derived from various crude oils. It can be seen that they differ significantly in their content of paraffins, naphthenes and aromatics:
:
Cracked naphthas
Some refinery naphthas also contain some
olefinic hydrocarbons, such as naphthas derived from the
fluid catalytic cracking,
visbreakers and
coking processes used in many refineries. Those olefin-containing naphthas are often referred to as ''cracked'' naphthas.
In some (but not all) petroleum refineries, the cracked naphthas are desulfurized and catalytically reformed (as are the virgin naphthas) to produce additional high-octane gasoline components.
Other uses
Some petroleum refineries also produce small amounts of specialty naphthas for use as solvents, cleaning fluids and dry-cleaning agents, paint and varnish diluents,
asphalt
Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
diluents, rubber industry solvents, recycling products, and
cigarette-lighter, portable-camping-stove and lantern fuels. Those specialty naphthas are subjected to various purification processes which adjusts chemical characteristics to suit specific needs.
Specialty naphtha comes in many varieties and each are referred to by separate names such as ''petroleum ether'', ''petroleum spirits'', ''mineral spirits'', ''paraffin'', ''benzine'', ''hexane'', ''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 point and other compositional characteristics of any of the specialty naphtha is to read the
Safety Data Sheet (SDS) for the specific naphtha of interest. Safety Data Sheets can be found on a chemical suppliers websites or by contacting the supplier directly.
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
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
(which may be and is converted into
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
for fertilizers),
ethylene, and other olefins. Natural gas is also used as feedstock to steam reformers and steam crackers.
Safety
People can be exposed to petroleum naphtha in the workplace by breathing it, swallowing it, skin contact, and eye contact. The
Occupational Safety and Health Administration
The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) set the legal limit (
permissible exposure limit) for petroleum naphtha exposure in the workplace as 500 ppm (2000 mg/m
3) over an 8-hour workday. The
National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH) has set a
recommended exposure limit
A recommended exposure limit (REL) is an occupational exposure limit that has been recommended by the United States National Institute for Occupational Safety and Health. The REL is a level that NIOSH believes would be protective of worker safet ...
(REL) of 350 mg/m
3 over an 8-hour workday and 1800 mg/m
3 over 15 minutes. At levels of 1100 ppm, 10% of the lower explosive limit, petroleum naphtha is
immediately dangerous to life and health.
References
:
External links
CDC - NIOSH Pocket Guide to Chemical Hazards - Petroleum distillates (naptha)
{{DEFAULTSORT:Petroleum Naptha
Petroleum products