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Naphtha



Naphtha (CAS No.: 8032-32-4, 8030-30-6, 8002-05-9; aka petroleum ether, white spirit (though in the UK white spirit is something completely different), Ligroin; VM&P Naphtha (CAS No. 64742-89-8); Varnish Makers and Painter's Naphtha [1]; Benzin; Petroleum Naphtha, Naphtha ASTM, Petroleum Spirits, Shellite, Ronsonol, Energine; not to be confused with Naphthalene) is a group of various liquid hydrocarbon intermediate refined products of varying boiling point ranges from 20 to 75 °C (68 to 167 °F), which may be derived from oil or from coal tar, and perhaps other primary sources.

Naphtha is used primarily as feedstock for producing a high octane gasoline component via the catalytic reforming process. Naphtha is also used in the petrochemical industry for producing olefins in steam crackers and in the chemical industry for solvent (cleaning) applications.

Additional recommended knowledge

Contents

Health and safety considerations

Forms of naphtha may be carcinogenic, and frequently products sold as naphtha contain some impurities, which may also have deleterious properties of their own. [2] [3] Like many hydrocarbon products, because they are products of a refractory process where 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 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 [4]).

Below are linked some Material Safety Data Sheet (MSDS) specifications for different "naphtha" products, which contain 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
  • Links to more MSDS for various camping-stove fuels including several that include naphtha

Benzene in particular is a known high-risk carcinogen, and so benzene content is typically specified in the MSDS. But more specific breakdown of particular forms of hydrocarbon is not as common.

Properties of Naphthas

    • Health Hazards

“Light naphtha, 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.”[1] “Almost all volatile, lipid-soluble organic chemicals cause general, nonspecific depression of the central nervous system or general anesthesia.” [2] 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).

    • Physical Properties

Molecular weight is 100-215; specific gravity is 0.75- 0.85; boiling point is 320-430 F; vapor pressure is < 5 mm HG. Naphtha’s are insoluble in water; colorless (kerosene odor) or red-brown (aromatic odor) liquid; incompatible with strong oxidizers.

Production of naphtha in refineries and uses

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 further complicate the matter, 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)

Paraffinic naphthas

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, the naphtha is heated in the presence of water vapour and the absence of oxygen or air until the hydrocarbon molecules fall apart. The primary products of the cracking process are olefins (ethylene / ethene, propylene / propene and butadiene) and aromatics (benzene and toluene). These are used as feedstocks for derivative units that produce plastics (polyethylene and polypropylene for example), synthetic fiber precursors (acrylonitrile), industrial chemicals (glycols for instance).

Heavy naphthas

  The "heavier" or rather denser types are usually richer in naphthenes and aromatics and therefore also referred to as N&A's. 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 / descriptions

Naphthas are also used in other applications such as:

  • (as an unprocessed component - in contrast to reforming above) in the production of petrol/motor gasoline.
  • industrial solvents and cleaning fluids
  • an oil painting medium
  • the sole ingredient in the home cleaning fluid Energine, which has been discontinued. You can purchase this type of naphtha at any hardware store.
  • 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 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 oil from the aperture blades of camera lenses, which if present can slow the movement of the blades, leading to overexposure.
  • in medieval times, pots containing naphtha were used in battle as a form of primitive grenade.

Examples

Shellite (Australia), also known as white gas (North America), white spirit or Coleman fuel, is a water white liquid with a hydrocarbon odour. Shellite has a flashpoint less than -30 °C, and a boiling point of 47 °C. 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, and is marketed principally as a refill fluid for cigarette lighters and has a flashpoint of about 6 °C.

Etymology

The origin of the word Naphtha is unclear. It is an Ancient Greek word that was used to refer to any sort of petroleum or pitch. The Greeks themselves borrowed the word from the Old Persian words nafata, naft or neft, which were used to describe bubbling oil. Naphtha may also have been derived from the name of the Vedic Hindu and Avestic god Apam Napat, a form of Agni, or fire god.

Naphtha is the root of the words naphthalene and napalm, which is derived from naphtha by mixing under controlled conditions with aluminium salts of palmitic acid (a type of soap).

References

  1. ^ “Chemistry of Hazardous Materials, Third Edition”, Meyer, E., Prentice Hall, 1998, page 458.
  2. ^ “Occupational and Environmental Medicine, Third Edition”, LaDou, J. , MS., MD. Lange Medical Books, McGraw Hill, 2004, page 508.

See also

Additional Sources

  • McDermott, Henry J. (2004). Air Monitoring for Toxic Exposures (Second Edition) John Wiley & Sons, Inc.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Naphtha". A list of authors is available in Wikipedia.
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