Naphtha

Not to be confused with Naphthalene.

Coleman camp fuel, also known as white gas, is a common naphtha fuel used in many lanterns and torches.

Naphtha is a name given to several mixtures of liquid hydrocarbons that are extremely volatile and flammable. Each such mixture is obtained during the distillation of petroleum or coal tar, and occasionally by the distillation of wood. Accordingly, it is known by different names, such as petroleum naphtha, coal-tar naphtha, or wood naphtha.

Naphtha is used primarily as feedstock for producing a high-octane gasoline component 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.

Alternative names

Naphtha is known by various names, including ligroin, VM&P Naphtha (Varnish Makers and Painter's Naphtha), Benzin, Petroleum Naphtha, Naphtha ASTM, Petroleum Spirits, white spirit, shellite, and ronsonol.

Etymology

The origin of the word naphtha is unclear. It was an ancient Greek word that referred to any type 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 god Apam Napat, the god of freshwater, sometimes described as a fire god.

Physical properties

Naphthas have a molecular weight range of 100-215, a specific gravity range of 0.75-0.85, and a boiling point range of 70-430 °F. Their vapor pressure is generally less than 5 mm mercury. Naphthas are insoluble in water. They are colorless (with a kerosene odor) or red-brown (with an aromatic odor). They are incompatible with strong oxidizers.

“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.”

Health and safety considerations

Forms of naphtha may be carcinogenic, and frequently products sold as naphtha contain some impurities that may have deleterious properties of their own. 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.

Below are linked some Material Safety Data Sheet (MSDS) specifications for different "naphtha" products, which contain varying proportions of naphtha and other chemicals. Besides giving health guidelines, they provide one 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.

“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).

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 vapor 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), and 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 off guitars when preparing "relic" instruments.
• to remove oil from the aperture blades of camera lenses, which if present can cause slow the movement of the blades, leading to overexposure.

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 degrees Celsius, and a boiling point of 47 degrees Celsius. 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.

Air sampling for naphthas

Air sampling is conducted to identify and evaluate employee or source exposures of potentially hazardous gases or particulates; assess compliance; and evaluate process or reformulation changes.

Two categories of air sampling equipment exist, they are: direct reading and sample collection.

• Direct reading equipment provides immediate measurement of exposure concentration.
• Sample collection equipment takes samples of air over a period of time, and these samples are then weighed and analyzed in a laboratory.

Sample collection involves active and passive air monitoring methods. Active sampling relies on sampling pumps to draw air and chemical vapors or gases to adsorbent filter materials. Passive monitors rely on the collection of gases and vapors through passive diffusion to allow personal sampling without use of pumps.

Sampling types

Various types of sampling may be used, as noted below.

• Personal sampling: Personal sampling is used to evaluate employee exposure to naphtha. The employee wears the sampling device that collects an air sample representative of air exposure for a specific period of time.

• Area Sampling: Area Sampling is used to evaluate background exposure to leaks and implement control measures.

• Grab Sampling: Grab sampling is used to monitor extremely toxic environments over a short period of time, or to determine if additional air monitoring is required for over-exposure.

• Integrated Sampling: Integrated exposure sampling is used to determine the 8-hour time weighted average exposure because various exposure concentrations are integrated during the sampling period.

Complications

Complications with air sampling can occur in the form of interference with chemicals (alcohols, ketones, ethers, and halogenated hydrocarbons), vapors, sampling media, humidity, temperature, barometric pressure, atmospheric dust, water vapor, and container.

Toxicity

Toxicity dose response exposures may be impacted (either decreased or increased) by the following factors. Chemical factors impact toxicity such as: concentration or quantity (harm in dose) times duration, hormesis (low dose stimulation), additivity, competition, synergism, antagonism, dispersability, water solubility, heavier or lighter than air, media exposure (liquid, gas, vapor, aerosol), molecule or particle size, toxicity of dose, toxicodynamics (what the chemical does to the body), progressive, permanent and reversible effects, bioavailability (binding or interference with the chemical), persistence, psychological impact, metals in different oxidative state, mechanism of action, sub cellular level, nanotechnology, receptors, and free radicals.

Individual biological factors such as stress, respiratory rate, gender, age, race, sweating, individual susceptibility, route of entry (injection, dermal, ingestion, inhalation, ocular), perfusion, affinity (binding, lipophilicity, storage) toxicokinetics (what body does to chemical), rate of uptake, detoxification excretion, elimination, transport, metabolism or biotransformation, water solubility, absorption, digestion or adsorption, systemic impact or local impact on body systems. Environmental factors impact chemical and particulate exposures such as: heat, cold, precipitation, inversions versus clear days and air pressure.

Exposure Control

Primary health prevention methods focus on chemical exposures prior to occurrence. Engineering prevention controls would be substitution, automation, enclosure, elimination, isolation and change of process. Ventilation controls would be local exhaust ventilation and vacuum operations. Administrative prevention controls would include work practice changes, education, training, job rotation, job reduction, work schedules, substitution, job reassignment, wet work methods, maintenance, and housekeeping. Secondary health prevention methods focus on early identification and treatment of chemical exposures for cure and treatment. Personal protective equipment could be air-purifying cartridge and powered air-purifying cartridge and supplied (air hose, self contained or re-breather) respirators; gloves (PVA, viton, neoprene). Tertiary health prevention methods are treatment and rehabilitation of employees exposed to chemical overexposure in the work place.

See also

• Benzene
• Hexane
• Naphthalene
• Oil refinery
• Organic chemistry
• Petroleum

References

ISBN links support NWE through referral fees

• Burton, D. J. 2002. Burton Field Guide for Industrial Hygiene. Fairfax, VA: AIHA. ISBN 1931504326.

• McDermott, Henry J. 2004. Air Monitoring for Toxic Exposures. 2nd ed. Hoboken, NJ: Wiley-Interscience. ISBN 0471454354.

• Meyer, Eugene. 2004. Chemistry of Hazardous Materials. 4th ed. Upper Saddle River, NJ: Pearson Prentice Hall. ISBN 0131127608.

External links

• 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

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