Naphtha ( or ) normally refers to a number of different flammable liquid mixtures of hydrocarbons, i.e. a distillation product from petroleum or coal tar boiling in a certain range and containing certain hydrocarbons. It is a broad term covering the lightest and most volatile fraction of the liquid hydrocarbons in petroleum.
In petroleum engineering, full range naphtha is defined as the fraction of hydrocarbons in petroleum boiling between 30°C and 200°C It consists of a complex mixture of hydrocarbon molecules generally having between 5 and 12 carbon atoms. It typically constitutes 15–30% of crude oil, by weight. 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.
Naphtha is used primarily as feedstock for producing high octane gasoline (via the catalytic reforming process). It is also used in the petrochemical industry for producing olefins in steam crackers and in the chemical industry for solvent (cleaning) applications. Common products made with it include lighter fluid, fuel for camp stoves, and some cleaning solvents.
Etymology
The word
naphtha came from Latin and Greek where it derived from
Persian. In
Ancient Greek it was used to refer to any sort of
petroleum or
pitch. It appears in Arabic as "nafţ" (نَفْط) ("petroleum"), and in Hebrew as "neft" (נֵפְט). Arabs and Persians have used and distilled petroleum for tar and fuel from ancient times, as attested in local Greek and Roman histories of the region.
There is a conjecture that the Greek word
naphtha came from the
Indo-Iranian god name
Apam Napat, which occurs in
Vedic and in
Avestic.
Naphtha is the root of the word naphthalene. The second syllable of "naphtha" can also be recognised in phthalate.
It also enters the word napalm from "naphthenic acid and palmitic acid", as the first napalm was made from a mixture of naphthenic acid with aluminium and magnesium salts of palmitic acid.
In older usage, "naphtha" simply meant crude oil, but this usage is now obsolete in English.
The Ukrainian word нафта (lit. nafta), the Russian word нефть (lit. neft') and the Persian naft ( نفت) mean "crude oil". Also, in Italy, Czech Republic, Slovakia, Serbia, Bosnia-Herzegovina, Croatia, Slovenia nafta (нафта in Serbian Cyrillic transcription) is colloquially used to indicate diesel fuel and crude oil; in Bulgarian, nafta means diesel fuel, while neft means crude oil. "Nafta" is also used colloquially in Argentina and Uruguay to refer to gasoline.
Health and safety considerations
Forms of naphtha may be
carcinogenic, and frequently products sold as naphtha contain some impurities which may also have harmful properties of their own.
Like many
hydrocarbon products, they are products of a refining process in which a complex soup of chemicals is
broken into another range of chemicals, which are then graded and isolated mainly by their
specific gravity and
volatility. There is, therefore, a range of distinct chemicals included in each product. This makes rigorous comparisons and identification of specific carcinogens difficult, especially in our modern environment where exposure to a great number of such products occurs on a daily basis, and is further complicated by exposure to a significant range of other known and potential carcinogens (e.g., see).
Below are linked some Material Safety Data Sheet (MSDS) specifications for different "naphtha" products containing varying degrees of naphtha, as well as various other chemicals. As well as giving health guidelines, these are some of the few ways to determine what a given product contains.
JT Baker VM&P; Naphtha MSDS.
Diggers Shellite MSDS
Shell Ronsonol MSDS source1 source2 formula developed for Ronson
Links to more MSDS for various camping-stove fuels including several that include naphtha
Benzene in particular is a known high-risk carcinogen, so benzene content is typically specified in the MSDS when it is present in the mixture due to the specifics of the feedstock and distilling process used. Specific detailing of other hydrocarbon species is less common.
Properties
Physical
Naphtha's molecular weight is 100–215 g/mol. Its specific gravity is 0.75–0.785 g/cm
3, and boiling point is 160–220 °C (320–430 °F). Vapor pressure is less than 5 torr (5 mm Hg). Naphtha is colorless (kerosene odor) or red-brown (aromatic odor) liquid and is insoluble in water. It is incompatible with strong oxidizers.
Production in refineries
Naphtha is obtained in
petroleum refineries as one of the intermediate products from the
distillation of crude oil. It is a liquid intermediate between the light gases in the crude oil and the heavier liquid
kerosene. Naphthas are volatile, flammable and have a
specific gravity of about 0.7. The generic name 'naphtha' describes a range of different refinery intermediate products used in different applications. To complicate the matter further, similar naphtha types are often referred to by different names.
The different naphthas are distinguished by:
Density (g/ml or specific gravity)
PONA, PIONA or PIANO analysis, which measures (usually in volume percent but can also be in weight percent):
* Paraffin content (volume percent)
* Isoparaffin content (only in a PIONA analysis)
* Olefins content (volume percent)
* Naphthenes content (volume percent)
* Aromatics content (volume percent)
Different types
Paraffinic
Generally speaking, less dense ("lighter") naphthas will have a higher
paraffin content. These are therefore also referred to as
paraffinic naphtha. The main application for these naphthas is as a feedstock in the petrochemical production of
olefins. This is also the reason they are sometimes referred to as "light distillate feedstock" or
LDF (These naphtha types can also be called "straight run gasoline"/
SRG or "light virgin naphtha"/
LVN).
When used as feedstock in petrochemical steam crackers, naphtha is heated in the presence of water vapour and the absence of oxygen or air until the hydrocarbon molecules break apart. The primary products of the cracking process are olefins (ethylene / ethene, propylene / propene and butadiene). When naphtha is used as a feedstock in catalytic reforming the primary products are aromatics including benzene, xylene, and toluene. The olefins are used as feedstocks for derivative units that produce plastics (polyethylene and polypropylene for example), synthetic fiber precursors (acrylonitrile), industrial chemicals (glycols for instance) while the aromatics are used for octane boosting in fuel blending as well as polyethylene terphthalate PET feedstock and paint and coating solvents.
Heavy
The "heavier" or rather denser types are usually richer in naphthenes and aromatics and therefore also referred to as N&As.; These can also be used in the petrochemical industry but more often are used as a feedstock for refinery catalytic reformers where they convert the lower
octane naphtha to a higher octane product called
reformate. Alternative names for these types are Straight Run Benzene (SRB) or Heavy Virgin Naphtha (HVN).
Other applications
Naphthas are also used in other applications such as:
An unprocessed component (in contrast to reforming above) in the production of petrol/motor gasoline;
Industrial solvents and cleaning fluids;
A commonly available general purpose solvent designated as "VM&P;" naphtha, which stands for "varnish makers' and painters'";
An oil painting medium;
The sole ingredient in the home cleaning fluid Energine, which has been discontinued;
An ingredient in shoe polish;
An ingredient in some lighter fluids for wick type lighters such as Zippo lighters;
An adulterant to petrol;
A fuel for portable stoves and lanterns, sold in North America as white gas, camp fuel or Coleman fuel;
Historically, as a probable ingredient in Greek fire (together with grease, oil, sulfur, and naturally occurring saltpeter from the desert);
A fuel for fire spinning, fire juggling, or other fire performance equipment which creates a brighter and cleaner yet shorter burn;
To lightly wear the finish (polish) off guitars when preparing "relic" instruments;
To remove from the aperture blades of camera lenses any oil which, if present, could slow the movement of the blades, leading to overexposure;
As a coating for elemental lithium metal, to prevent oxidation (mineral oil is also used for this purpose);
As a fuel in gas turbine unit;
As the working fluid (and sometimes, fuel) in the naphtha (external combustion) engine.
In medieval times, pots containing naphtha were used in battle as a form of primitive grenade. In Ancient China, monks used forms of Naphtha to prepare in religious ceremonies such as Chimbohduh.
Naphtha is used in the furniture industry on "works in progress" to see temporarily (until the naphtha evaporates) how the patina will look when the piece is oiled and/or aged. It is useful in matching adjacent boards for a join, primarily with tabletops, panels and shelves.
Health hazards
"Light naphtha [is] a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from five to nine carbon atoms per molecule. Heavy naphtha, a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from seven to nine carbons per molecule." "Almost all volatile, lipid-soluble organic chemicals cause general, nonspecific depression of the
central nervous system or general
anesthesia." The OSHA PEL TWA = 100 parts-per-million (ppm); Health Hazards/Target Organs = eyes, skin, RS, CNS, liver, kidney. Symptoms of acute exposure are dizziness and
narcosis with loss of
consciousness. The
World Health Organization categorizes health effects into three groups: reversible symptoms (Type 1), mild chronic
encephalopathy (Type 2) and severe chronic toxic encephalopathy (Type 3).
Topical exposure to naphtha can cause a burning sensation on the skin within a period of minutes to an hour, followed by contact dermatitis—a rash—that can last for days to weeks.
Examples in daily life
Shellite (
Australia), also known as
white gas (
North America),
white spirit (outside the UK) or
Coleman fuel, is a white liquid with a hydrocarbon odour. Shellite has a
freeze point lower than , and a
boiling point of . The composition of shellite is 95%
paraffins and naphthenes, less than 5% aromatic hydrocarbons and less than 0.5%
benzene. It is highly flammable and due to its low
flashpoint is used in many low pressure camping stoves. Shellite is also a fast drying solvent used for cleaning metal, hard plastic and painted surfaces.
Ronsonol is a brand name used in North America, for a product marketed principally as a refill fluid for cigarette
lighters and having a flashpoint of about .
See also
Benzene
Fluid catalytic cracking
Gasoline gallon equivalent
n-Hexane
Naphthalene
Oil refinery
Olefin
Petroleum naphtha
References
Further reading
McDermott, Henry J. (2004). Air Monitoring for Toxic Exposures (Second Edition) John Wiley & Sons, Inc.
External links
Petroleum naphtha A Citizendium article.
NIOSH Pocket Guide to Chemical Hazards from the US National Institute for Occupational Safety and Health
Search a number of sites for MSDS
Different names with different meanings in different countries, for some naphtha-containing camping-stove products
Cooper Basin naphtha manufacturer's description
Lists of many chemical manufacturer's MSDS sites
The Physical and Theoretical Chemistry Laboratory Oxford University Chemical and Other Safety Information
NLM Hazardous Substances Databank – Naphtha
Category:Petroleum products
Category:Chemical engineering
Category:Hydrocarbon solvents
