Naphtha

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Not to be confused with naphthalene, a solid benzene derivative which is the main ingredient in mothballs.

Naphtha (/ˈnæfθə/ or /ˈnæpθə/) normally refers to a number of flammable liquid mixtures of hydrocarbons, i.e. a component of natural gas condensate or a distillation product from petroleum, coal tar, or peat boiling in a certain range and containing certain hydrocarbons. It is a broad term covering among the lightest and most volatile fractions of the liquid hydrocarbons in petroleum. Naphtha is a colorless to reddish-brown volatile aromatic liquid, very similar to gasoline.

In Petroleum Refinery Engineering, full range naphtha is defined as the fraction of hydrocarbons in petroleum boiling between 30 °C and 200 °C.[1] 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 bitumen mining industry as a diluent, the petrochemical industry for producing olefins in steam crackers, and the chemical industry for solvent (cleaning) applications. Common products made with it include lighter fluid, fuel for camp stoves, and some cleaning solvents. Light naphtha is also used directly as a blending component in the production of gasoline.

Etymology[edit]

The word naphtha came from Latin and Greek where it derived from Persian.[2] In Ancient Greek, it was used to refer to any sort of petroleum or pitch. It appears in Arabic as نَفْط nafṭ ("petroleum"), and in Hebrew as נֵפְט neft. Persians have used and distilled petroleum for tar and fuel from ancient times, as attested in local Greek and Roman histories of the region.[citation needed]

The second book of the Maccabees in the Septuagint, part of the Old Testament canon in the major Christian denominations: Latin and Greek Catholic, and Greek and Russian Orthodox, uses the word "naphtha" to refer to a miraculously flammable liquid. This account says that Nehemiah and the levitical priests associated with him called the liquid "nephthar", meaning "purification", but "most people" call it naphtha (or Nephi).[3]

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 and Belarusian word нафта (lit. nafta), Lithuanian, Latvian and Estonian "nafta", the Russian word нефть (lit. neft') and the Persian naft ( نفت) mean "crude oil". Also, in Italy, Serbia, Bosnia and Herzegovina, Croatia, Slovenia, Bulgaria nafta (нафта in Cyrillic) is colloquially used to indicate Diesel fuel and crude oil. In the Czech Republic and Slovakia, nafta was historically used for both Diesel fuel and crude oil, but its use for crude oil is now obsolete[4] and it generally indicates diesel fuel (crude oil is referred to as ropa[5]). In Bulgarian, nafta means diesel fuel, while neft, as well as "petrol" (петрол in Cyrillic), means crude oil. "Nafta" is also used in Argentina, Paraguay and Uruguay to refer to gasoline. In Poland, the word "nafta" means kerosene.

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.;[6] the name means "grandson of (the) waters", and the Vedas describe him as fire emerging from water.

Health and safety considerations[edit]

Forms of naphtha may be carcinogenic, and frequently products sold as naphtha contain some impurities which may also have harmful properties of their own.[7][8] 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 people are daily exposed to many such products, and is further complicated by exposure to a significant range of other known and potential carcinogens.[9]

"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."[10] "Almost all volatile, lipid-soluble organic chemicals cause general, nonspecific depression of the central nervous system or general anesthesia."[11] 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.

Below are linked few 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 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.[citation needed]

Naphtha is also extremely volatile and can explode on exposure to high temperature surfaces. In 1999, such an explosion led to four deaths at the Avon Refinery in Martinez, California.

Properties[edit]

Physical[edit]

Naphtha's molecular weight is 100–215 g/mol. Its density is 750–785 kg/m3, and boiling point is 160–220 °C (320–428 °F). Vapor pressure is less than 666 Pa (5 torr; 5 mmHg). Naphtha is colorless (kerosene odor) or red-brown (aromatic odor) liquid and is insoluble in water. It is incompatible with strong oxidizers.[citation needed]

Production in refineries[edit]

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.[12] 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, measured by detailed capillary gas chromatography (usually in volume percent but can also be in weight percent):

Different types[edit]

Paraffinic[edit]

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 terephthalate PET feedstock and paint and coating solvents.

Heavy[edit]

White gas, by Coleman Camp Fuel, is a common naphtha fuel in North America, used in many stoves, lanterns and torches

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[edit]

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

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.[citation needed]

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.

Examples in daily life[edit]

Procter & Gamble naphtha soap, c. 1919

Shellite (Australia), also known as white gas (North America), or Coleman fuel, is a white liquid with a hydrocarbon odor. Shellite has a freeze point lower than −30 °C (−22 °F), and a boiling point of 47 °C (117 °F). 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 flash point, it is often used in low pressure camping stoves. Shellite is also a fast-drying solvent used for cleaning metal, hard plastic, and painted surfaces.

See also[edit]

References[edit]

Further reading[edit]

  • McDermott, Henry J. (2004). Air Monitoring for Toxic Exposures (Second Edition) John Wiley & Sons, Inc.

External links[edit]