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Naphtha (/ˈnæfθə/, recorded as less common or nonstandard[1] in all dictionaries: /ˈnæpθə/) is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and the fractional distillation of coal tar and peat. In some industries and regions, the name naphtha refers to crude oil or refined petroleum products such as kerosene or diesel fuel.

Naphtha is also known as Shellite in Australia.[2]

Etymology

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White gas, exemplified by Coleman Camp Fuel, is a common naphtha-based fuel used in many lanterns and stoves.

The word naphtha comes from Latin through Ancient Greek (νάφθα), derived from Middle Persian naft ("wet", "naphtha"),[3][4] the latter meaning of which was an assimilation from the Akkadian 𒉌𒆳𒊏 napṭu (see Semitic relatives such as Arabic نَفْط nafṭ ["petroleum"], Syriac ܢܰܦܬܳܐ naftā, and Hebrew נֵפְט neft, meaning petroleum).[5]

Antiquity

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The book of II Maccabees (2nd cent. BC) tells how a "thick water" was put on a sacrifice at the time of Nehemiah and when the sun shone it caught fire. It adds that "those around Nehemiah termed this 'Nephthar,' which means Purification, but it is called Nephthaei by the many."[6] This same substance is mentioned in the Mishnah as one of the generally permitted oils for lamps on Shabbat, although Rabbi Tarfon permits only olive oil (Mishnah Shabbat 2).

In Ancient Greek, it was used to refer to any sort of petroleum or pitch. The Greek word νάφθα designates one of the materials used to stoke the fiery furnace in the Song of the Three Children (possibly 1st or 2nd cent. BC). The translation of Charles Brenton renders this as "rosin."

The naphtha of antiquity is explained to be a "highly flammable light fraction of petroleum, an extremely volatile, strong-smelling, gaseous liquid, common in oil deposits of the Near East;" it was a chief ingredient in incendiary devices described by Latin authors of the Roman period.[7]

Modern period

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Since the 19th century, solvent naphtha has denoted a product (xylene or trimethylbenzenes) derived by fractional distillation from petroleum;[8] these mineral spirits, also known as "Stoddard Solvent," were originally the main active ingredient in Fels Naptha laundry soap.[9] The naphtha in Fels Naptha was later removed as a cancer risk.[10]

The usage of the term "naphtha" during this time typically implies petroleum naphtha, a colorless liquid with a similar odor to gasoline. However, "coal tar naphtha," a reddish brown liquid that is a mixture of hydrocarbons (toluene, xylene, and cumene, etc.), could also be intended in some contexts.[11]

Petroleum

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In older usage,[when?] "naphtha" simply meant crude oil, but this usage is now obsolete in English. There are a number of cognates to the word in different modern languages, typically signifying "petroleum" or "crude oil."

The Ukrainian & Belarusian word нафта (nafta), Lithuanian, Latvian, & Estonian "nafta," and the Persian naft (نفت) mean "crude oil." The Russian word нефть (neft') means "crude oil," but нафта (nafta) is a synonym of ligroin. Also, in Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Finland, Italy, Serbia, Slovenia, and Macedonia 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[12] and it generally indicates diesel fuel. In Bulgarian, nafta means diesel fuel, while neft, as well as petrol (петрол in Cyrillic), means crude oil. Nafta is also used in everyday parlance in Argentina, Uruguay and Paraguay to refer to gasoline/petrol.[13] Similarly, in Flemish, the word naft(e) is used colloquially for gasoline.[14] In Poland, the word nafta means kerosene,[15] and colloquially crude oil (the technical name for crude oil is ropa naftowa, also colloquially used for diesel fuel as ropa).

Types

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Naphtha has been divided into two types by many sources in order to differentiate between common grades more clearly:

One source[16] distinguishes by boiling point as well as carbon atom count per molecule:

  • Light naphtha is the fraction boiling between 30 and 90 °C (86 and 194 °F) and consists of molecules with 5–6 carbon atoms.
  • Heavy naphtha boils between 90 and 200 °C (194 and 392 °F) and consists of molecules with 6–12 carbon atoms.

Chemistry of Hazardous Materials differentiates light and heavy based on the carbon atom count and hydrocarbon structure:[17]

  • Light [is] a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from five to six carbon atoms per molecule.
  • Heavy [is] a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from seven to nine carbon atoms per molecule.

Some sources also define petroleum naphtha, which contains both heavy and light naphtha, and typically consists of 15-30% of crude oil by weight.[18]

Uses

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Heavy crude oil dilution

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Naphtha is used to dilute heavy crude oil to reduce its viscosity and enable/facilitate transport; undiluted heavy crude cannot normally be transported by pipeline, and may also be difficult to pump onto oil tankers. Other common dilutants include natural-gas condensate and light crude. However, naphtha is a particularly efficient dilutant and can be recycled from diluted heavy crude after transport and processing.[19][20][21] The importance of oil dilutants has increased as global production of lighter crude oils has fallen and shifted to exploitation of heavier reserves.[20]

Fuel

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Light naphtha is used as a fuel in some commercial applications. One notable example is wick-based cigarette lighters, such as the Zippo, which draw "lighter fluid"—naphtha—into a wick from a reservoir to be ignited using the flint and wheel.

It is also a fuel for camping stoves and oil lanterns, known as "white gas", where naphtha's low boiling point makes it easy to ignite. Naphtha is sometimes preferred over kerosene because it clogs fuel lines less. The outdoor equipment manufacturer MSR published a list of trade names and translations to help outdoor enthusiasts obtain the correct products in various countries.[22]

Naphtha was also historically used as both a fuel and a working fluid in some small boats where steam technology was impractical; most were built to circumvent safety laws relating to traditional steam launches.[23]

As an internal combustion engine fuel, petroleum naphtha has seen very little use and suffers from lower efficiency and low octane ratings, typically 40 to 70 RON. It can be used to run unmodified diesel engines, though it has a longer ignition-delay than diesel. Naphtha tends to be noisy in combustion due to the high pressure rise rate. There is a possibility of using naphtha as a low-octane base fuel in an octane-on-demand concept, with the engine drawing a high-octane mix only when needed. Naptha benefits from lesser emissions in refinement: fuel energy losses from "well-to-tank" are 13%; lower than the 22% losses for petroleum.[18]

Plastics

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Naphtha is a crucial component in the production of plastics.[24]

Health and safety considerations

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The safety data sheets (SDSs) from various naphtha vendors indicate various hazards such as a flammable mixture of hydrocarbons: flammability, carcinogenicity, skin and airway irritation, etc.[25][2][26][27]

Humans can be exposed to naphtha in the workplace by inhalation, ingestion, dermal contact, and eye contact. The US Occupational Safety and Health Administration (OSHA) has set the permissible exposure limit for naphtha in the workplace as 100 ppm (400 mg/m3) over an 8-hour workday. The US National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 100 ppm (400 mg/m3) over an 8-hour workday. At levels of 1000 ppm, which equates to 10 times the lower exposure limit, naphtha is immediately dangerous to life and health.[28]

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Naphtha

View on Grokipedia
from Grokipedia
Naphtha is a flammable liquid hydrocarbon mixture obtained as a fraction from the distillation of crude oil or from natural gas condensates, typically consisting of hydrocarbons with carbon numbers ranging from C5 to C12 and boiling points between approximately 30°C and 200°C. This versatile petroleum distillate appears as a clear to pale yellow or brownish liquid with a gasoline-like odor and is characterized by its volatility and solubility in organic solvents. Naphtha is broadly classified into light and heavy types based on boiling range and composition. Light naphtha boils between 30°C and 90°C, primarily comprising C5-C6 paraffins and cycloparaffins, while heavy naphtha boils from about 90°C to 200°C and contains a higher proportion of C7-C12 hydrocarbons, including more aromatics and naphthenes. Its composition varies depending on the source crude oil and refining process, but typically includes 40-60% paraffins, 30-50% naphthenes, and 5-20% aromatics such as and . Physically, naphtha has a of 0.63-0.78 g/cm³ at 20°C and a ranging from -40°C to 60°C, making it highly flammable and requiring careful handling. In industry, naphtha serves as a critical feedstock in the sector, where it undergoes to produce olefins like and for plastics manufacturing, or to yield high-octane components and aromatics such as , , and . It is also widely used as a in paints, varnishes, adhesives, inks, and rubber processing, as well as a in asphalt production and a in tanks. Due to its and potential carcinogenic effects from prolonged exposure, naphtha is regulated under occupational safety standards, with permissible exposure limits set at 100 ppm over an 8-hour period.

Etymology and History

Origins in antiquity

The term "naphtha" derives from the ancient Persian word "naft," referring to an inflammable liquid, with etymological roots in the "napta," meaning damp or moist, as preserved in Zoroastrian texts composed around 1500–1000 BCE. This linguistic origin reflects early Iranian recognition of volatile products as distinct from heavier bitumens, emphasizing their flammable properties in pre-modern contexts. In the BCE, the Greek historian provided one of the earliest Western accounts of naphtha, describing it as a highly volatile oil extracted from wells in the region near Ardericca in Susiana (modern-day southwestern ), then part of the Persian Empire. He noted its extraction using ropes from a pit near a river and its oily nature, suitable for anointing beards and hair to promote growth, and other applications. While Herodotus does not detail its flammability on water, later ancient sources highlight naphtha's ability to spread and burn on water, underscoring its potential as an incendiary material. Ancient Mesopotamians utilized naphtha-like fractions from natural seeps as a for lamps and torches, as evidenced by records detailing its collection and application in daily lighting. In Greek and later Byzantine contexts, it served as a key component in incendiary weapons, notably contributing to the composition of —a Byzantine naval incendiary deployed from the CE onward, combining naphtha with and to create unquenchable flames that adhered to surfaces and burned on . Additionally, across Mesopotamian and Greco-Roman traditions, naphtha and were incorporated into medicinal ointments for their qualities, treating ailments such as wounds, skin conditions, and respiratory issues, with valued as a and . Archaeological findings in ancient Persia reveal evidence of bitumen processing, including heating and separation techniques akin to rudimentary , dating back 5000–6000 years in southern Iranian sites, where natural seeps were exploited to isolate lighter fractions like naphtha for and uses in and artifacts. In ancient , similar processing of from Himalayan and Indus Valley sources is attested through residue analysis on and tools from the BCE, indicating its refinement for sealing boats, jewelry, and architectural elements, though direct evidence remains limited to simple thermal methods.

Development in the modern era

In the , during the Enlightenment and the onset of the , European chemists began adopting the ancient term "naphtha" to describe volatile, flammable distillates derived from sources such as wood and , marking a shift toward more systematic chemical classifications of organic materials. These distillates were recognized for their properties and low boiling points, distinguishing them from heavier tars and oils in early industrial processes. By the , the rise of further refined the concept of naphtha, classifying it as a light oil fraction produced during the of in , which proliferated from the onward to supply illuminating gas for urban lighting. In these operations, naphtha emerged as a key byproduct from the of , valued for its volatility and utility in early chemical applications, reflecting the era's growing emphasis on techniques. The 1859 oil boom in , triggered by Edwin Drake's successful well in Titusville, significantly expanded naphtha's role as a of kerosene refining, where it was the initial light fraction separated during to produce lamp fuel. This surplus naphtha found immediate industrial uses as a in varnishes and rubber processing; for instance, it was employed to dissolve raw rubber in preparations leading to Charles Goodyear's 1839 vulcanization breakthrough, which stabilized the material for practical applications despite challenges with solvent-induced stickiness. Toward the late 19th century, efforts to standardize naphtha's definition accelerated with the formation of organizations like the American Society for Testing Materials (ASTM) in 1898, which established specifications based on boiling range—typically 30–200°C—to ensure consistency in industrial and commercial products. These standards, evolving from early testing protocols, solidified naphtha's identity as a defined fraction rather than a vague volatile substance. In the early , naphtha emerged as a key straight-run distillate fraction from the atmospheric of crude oil in refineries, serving as a precursor to amid rising demand from automobiles and . The advent of thermal cracking processes in the revolutionized its production; the Burton process, patented in 1912 and first commercialized in 1913 at Standard Oil's , applied high temperatures (around 425°C) and pressures (5-7 kg/cm²) to heavier gas oils, effectively doubling and naphtha yields from crude oil compared to prior methods. By the and , naphtha's role expanded with the introduction of thermal reforming and early catalytic processes, which upgraded low-octane straight-run naphtha into higher-value components through dehydrogenation and , laying the groundwork for modern blending. This evolution proved critical during , as naphtha feedstocks enabled and to produce high-octane aviation (avgas) with ratings up to 100/130; in the United States, production scaled rapidly in the via processes like the Houdry catalytic cracking (deployed from 1936) and (introduced 1942), culminating in 28.4 million tons of leaded avgas output by 1945 to power Allied aircraft. Postwar globalization accelerated naphtha's trade, with expanding refinery infrastructure worldwide—particularly in the —positioning it as a vital intermediate for and fuels, as evidenced by increasing exports from regional facilities amid booming global demand. The oil crises, precipitated by OPEC's embargo and production restrictions starting in , dramatically impacted naphtha markets by driving petroleum product prices upward (with oil quadrupling from $3 to $12 per barrel) and redirecting flows, thereby establishing Middle Eastern refineries as dominant exporters to support international needs. By the 1950s, as of supplanted older methods, industry standards formalized the terminology "" to specify this crude (boiling range typically 35-200°C), clearly differentiating it from coal tar naphtha variants that had dominated earlier aromatic production but were largely phased out by the due to inefficiency.

Chemical Composition and Properties

Hydrocarbon constituents

Naphtha is a complex mixture of hydrocarbons primarily composed of aliphatic hydrocarbons, known as paraffins or alkanes, which typically constitute 40-70% by weight. These include straight-chain examples such as n-pentane (C₅H₁₂) and branched isomers like (2-methylbutane). Cycloalkanes, or naphthenes, make up 20-50% of the mixture and are exemplified by (C₆H₁₂). Aromatic hydrocarbons account for 10-30%, with representative compounds including benzene (C₆H₆) and toluene (C₇H₈). The hydrocarbons in naphtha generally range from C₅ to C₁₂ carbon atoms, though variations occur depending on the source material. Unsaturation levels are low in straight-run naphtha, with olefins typically comprising less than 5% by weight. A specific example of composition in petroleum-derived naphtha includes approximately 41% paraffins, 54% naphthenes, and 5% aromatics. Naphtha also contains trace impurities, including sulfur compounds at levels of 0.1-1%, along with minor amounts of - and oxygen-containing compounds. These impurities vary by crude oil origin and processing but are generally present in low concentrations. The molecular makeup of naphtha is analyzed using for detailed constituent profiling. The ASTM D5134 standard provides a method for simulated and identification of paraffins, naphthenes, and monoaromatics through capillary . These constituents contribute to the overall physical properties of naphtha observed in subsequent analyses.

Physical and chemical characteristics

Naphtha exhibits a range of physical properties that reflect its status as a volatile mixture derived from . Its boiling range typically spans 30–200 °C, with light naphtha boiling between 30–90 °C and heavy naphtha between 90–200 °C, allowing for separation based on volatility during processes. The of naphtha lies between 0.65 and 0.80 g/cm³ at 20 °C, influenced by the proportion of aliphatic and aromatic hydrocarbons, while its ranges from 1.40 to 1.45, and remains low at 0.5–1.0 cP, contributing to its flow characteristics as a . Chemically, naphtha is highly flammable, with an autoignition temperature of 200–300 °C, making it prone to ignition under elevated temperatures without an external flame source. It demonstrates low solubility in water, typically less than 0.1 g/L, which limits its miscibility with aqueous systems but enhances compatibility with organic solvents. Naphtha shows reactivity toward oxidation, particularly in the presence of air or oxygen, forming peroxides and hydroperoxides that can lead to gum formation during storage or processing. Thermally, it maintains stability up to approximately 400 °C, beyond which cracking into lighter hydrocarbons begins, a property critical for its use in high-temperature petrochemical operations. In terms of fuel-related metrics, straight-run naphtha has a research octane number (RON) of 40–70, which can be enhanced to over 90 through , improving its suitability as a blending component. Its vapor pressure ranges from 50–100 kPa at 38 °C, affecting volatility and rates in applications like fuel formulation.
PropertyTypical RangeNotes
Boiling Range30–200 °C (light: 30–90 °C; heavy: 90–200 °C)Determines fractions
Density (20 °C)0.65–0.80 g/cm³Varies with aromatic content
Refractive Index1.40–1.45Indicates optical purity
Viscosity0.5–1.0 cPLow for easy handling
Autoignition Temperature200–300 °CHigh flammability risk
Water Solubility<0.1 g/LHydrophobic nature
RON (straight-run)40–70Boostable via reforming
Vapor Pressure (38 °C)50–100 kPaInfluences volatility
Environmentally, naphtha displays low biodegradability, with a half-life exceeding 30 days in under aerobic conditions, due to its complex structure that resists microbial breakdown. Its lipophilic nature promotes in aquatic organisms, potentially leading to trophic magnification in food chains. These traits necessitate careful management to mitigate ecological persistence.

Production Methods

Petroleum distillation processes

Naphtha is primarily obtained through atmospheric distillation, the initial stage in crude refining where the feedstock is separated into various fractions based on points. In this process, desalted crude oil is preheated in a network of heat exchangers to recover heat from product streams, then further heated in a furnace to approximately 350°C before entering the fractionation column. The column operates at , with vaporized components rising and condensing at different trays, allowing the naphtha fraction—characterized by a range of roughly 40–180°C—to be collected from the top sections as a light overhead product. This fraction typically constitutes 10–20% of the crude oil by volume, depending on the feedstock composition. For heavier crudes with lower , vacuum distillation is integrated downstream to enhance overall recovery, where the atmospheric residue is further processed under reduced pressure to distill additional lighter components without thermal cracking. In such units, any remaining naphtha-like light ends can be recovered from the topping of the vacuum residuum, though the primary naphtha yield still originates from the atmospheric stage. Yields are significantly influenced by crude type; for light crudes like Brent (API gravity around 38°), naphtha recovery can reach 15–25% by weight, reflecting higher proportions of low-boiling hydrocarbons. Yield optimization in these systems employs side strippers on the column to remove entrained gases and improve purity, alongside advanced integration via preheat trains that can recover up to 80% of the input. Typical crude units in modern refineries operate at capacities of 100,000–500,000 barrels per day, with amounting to about 1–2% of the crude oil's inherent content, primarily as for the furnace. Post- quality control for naphtha involves hydrotreating, a catalytic process that reduces content to below 10 ppm by reacting compounds with over cobalt-molybdenum catalysts at 300–400°C and 30–60 bar. This step ensures the naphtha meets specifications for downstream or applications while minimizing environmental impacts.

Alternative production sources

Naphtha can be obtained from condensates through processes in (LNG) plants or facilities, where the condensates are separated into component hydrocarbons. This method typically yields 50-60% naphtha from the condensate feedstock, primarily light naphtha fractions suitable for use. In major production areas such as U.S. fields, where associated natural gas liquids (NGLs) are abundant, and Qatar's LNG operations like the Pearl GTL facility, which converts into liquid products including naphtha, this source contributes notably to supply. Global output from natural gas condensates represents a secondary but growing alternative to refinery production. Coal-tar naphtha, rich in aromatic hydrocarbons, is produced as a by-product of coke oven operations in via of . The process separates the light oil fraction from , achieving yields of approximately 5-10% naphtha relative to the tar input. Historically, this was the primary source of naphtha before the mid-20th century, with production dating back to the in the 1780s when provided most industrial solvents and feedstocks. Today, however, coal-tar naphtha accounts for less than 5% of global naphtha supply due to the dominance of and declining coke production in developed economies. Emerging synthetic routes from involve to produce , followed by Fischer-Tropsch synthesis to generate naphtha-like hydrocarbons, offering a renewable alternative at pilot and demonstration scales. These processes achieve overall efficiencies of 30-50% (on a lower heating value basis) for liquid products from biomass input, with demonstrations in facilities producing up to several hundred barrels per day of Fischer-Tropsch products including naphtha-range hydrocarbons. As of 2025, the bio-naphtha market continues to expand, with production capacities increasing through new facilities focused on sustainable feedstocks. Additionally, shale oil retorting serves as a minor source, where of yields crude containing 20-30% naphtha fractions, though commercial scale remains limited due to high energy requirements. Compared to petroleum-derived naphtha, production from these alternative sources generally incurs 20-50% higher costs owing to specialized processing and lower , positioning them primarily for niche applications like high-purity or bio-based specialty grades rather than bulk commodity supply.

Types of Naphtha

Light naphtha

Light naphtha is a volatile fraction of distillates, primarily composed of hydrocarbons with five to six carbon atoms (C₅–C₆), including straight-chain and branched paraffins such as and , as well as cycloparaffins (naphthenes). It boils in the narrow range of 30–90 °C and typically contains 30–50% paraffins, with low levels of aromatics (less than 10%) and minimal olefins. This composition distinguishes it as a lighter, more paraffinic stream compared to broader naphtha cuts. Produced mainly through the of condensates or as the initial light overhead product from topping crude units, light naphtha emerges early in the process before heavier fractions like . These sources yield a high-purity stream with minimal impurities from heavier crudes. Key physical and chemical properties include high volatility, evidenced by a exceeding 60 kPa (typically 80–90 kPa), a research octane number (RON) of 50–60, and a of approximately 0.65–0.70 g/cm³ at 15 °C. Its inherently low content, often below 200 ppm, supports applications requiring cleaner feedstocks for environmental compliance. Market prices fluctuate between $400 and $600 per metric ton depending on regional supply dynamics and crude oil benchmarks. Its primary industrial application is as feedstock for units, where straight-chain paraffins are rearranged into branched isomers to boost ratings. Due to its lower average molecular weight (around 72–86 g/mol), light naphtha evaporates more rapidly than heavier variants, rendering it less ideal for or reforming processes that favor denser feeds.

Heavy naphtha

Heavy naphtha is a fraction primarily composed of hydrocarbons with carbon numbers ranging from C7 to C12, boiling in the range of 90–200°C, and typically containing 30–50% naphthenes along with higher levels of aromatics at 20–40%. It is derived from the higher-boiling portions of atmospheric crude oil , serving as a key intermediate in refining processes. Key physical and chemical properties of heavy naphtha include a density of 0.75–0.80 g/cm³, an untreated number (RON) of 40–50, and a higher heating value of –44 MJ/kg, reflecting its greater molecular weight compared to lighter fractions. Due to its relatively low and potential instability from unsaturated components, heavy naphtha often requires to enhance stability and suitability for downstream applications. Market prices typically range from $500–700 per ton amid fluctuations in crude oil supply. It is particularly valued for its richness in BTX (benzene, toluene, xylene) precursors, such as naphthenes that can be converted to aromatics through reforming, making it a preferred feedstock for . Prior to use in synthesis, heavy naphtha is frequently pretreated via to remove olefins, which can otherwise cause in catalytic processes and ensure compatibility with reforming units. This step enhances its role as a precursor in producing high-value aromatics for plastics, , and other chemicals.

Specialized variants

naphtha represents a specialized variant of naphtha enriched with aromatic hydrocarbons through extraction processes applied to fractions, typically achieving aromatic contents of around 60% or higher depending on the grade. This enrichment enhances its solvency properties, making it suitable for applications in paints, coatings, and adhesives where strong dissolving power is required. A representative example is Solvesso 100, a light aromatic naphtha with a range of 140–165°C, primarily composed of C9 and C10 aromatics such as trimethylbenzenes and ethylmethylbenzenes. Coal-tar naphtha, derived from the light oil fraction of produced during processes, is distinguished by its higher content of (typically 5–10%) and polycyclic aromatic hydrocarbons (PAHs) compared to petroleum-based naphthas. The phenol-rich composition arises from the of , resulting in a fraction that includes cresols and xylenols alongside and derivatives. Global production of this variant remains limited, estimated at less than 1 million tons per year, primarily as a of metallurgical coke manufacturing. Due to elevated PAH levels, which pose environmental and health risks, its use is subject to stringent regulations, including restrictions under frameworks like the EU REACH and U.S. EPA guidelines on hazardous air pollutants. Reformate naphtha emerges as the output of units in refineries, where heavy naphtha feedstocks undergo dehydrogenation and to yield a high-octane product rich in C6–C10 hydrocarbons, including 40–60% aromatics such as , , and xylenes. This process typically produces reformate with a research number (RON) of 95–100, enabling direct blending into without further treatment to boost overall quality. Unlike straight-run naphthas, reformate's enhanced branching and aromatic profile provides superior antiknock properties, making it a key component in high-performance fuels. Bio-naphtha constitutes a renewable variant produced via hydroprocessing of oils, animal fats, or organic waste, yielding a drop-in compatible product that mirrors fossil naphtha in composition and performance. This process involves hydrodeoxygenation and to generate hydrocarbons in the C5–C10 range, achieving up to 80% compatibility with existing infrastructure for seamless integration. The market for bio-naphtha has a global supply capacity of approximately 0.75–1 million metric tons per year as of 2025, driven by demand for sustainable feedstocks in plastics and chemicals production.

Industrial Uses

Solvent and diluent applications

Naphtha serves as a key in rubber processing, particularly in where it dissolves raw rubber to form cements and facilitates mixing with other compounds during compounding and molding stages. In the United States, this application accounts for a notable share of naphtha consumption in the rubber industry, supporting the production of rubber cements used in assembly and repair. Additionally, naphtha is employed in adhesives formulation, where it acts as a carrier to blend resins and polymers, enhancing in industrial bonding processes. In the paints and varnishes sector, naphtha functions as a thinning agent, particularly for resins, by reducing and promoting even application while enabling rapid through . Light naphtha variants are preferred in these formulations due to their higher volatility and faster rates compared to heavier grades, which minimizes times in coatings production. This property makes light naphtha ideal for oil-based enamels and varnishes, where quick release ensures efficient film formation without prolonged tackiness. As a diluent, naphtha is blended with heavy crude oils, such as from Canadian , to reduce and enable pipeline transport. Typically, diluent comprises 25-30% of the mixture by volume, transforming the non-flowable into a pumpable fluid known as dilbit. In operations like those along the , naphtha-based diluents from condensates are commonly used to meet transportation specifications for exports. A specific application of naphtha occurs in asphalt production for road paving, where it is incorporated into cutback asphalts as a to liquefy the binder for easier mixing with aggregates and application at ambient temperatures. Rapid-curing cutback grades, utilizing light naphtha or similar distillates, evaporate quickly after laying, allowing the asphalt to set for immediate traffic use in patching and resurfacing. Naphtha's advantages in these roles include its low cost, typically ranging from $0.50 to $1.00 per , making it economically viable for large-scale industrial use. Its can be tuned by adjusting the aromatic content, with higher aromatics enhancing dissolution of polar resins and polymers while aliphatics provide milder action. Globally, for naphtha in and applications is driven by ongoing needs in and sectors.

Petrochemical feedstock

Naphtha serves as a primary feedstock in the petrochemical industry for producing key olefins and aromatics through thermal and catalytic processes. Heavy naphtha is particularly suited for steam cracking, where it is preheated and mixed with steam before being heated to 750–900°C in pyrolysis furnaces under low pressure to break down hydrocarbons into lighter molecules. This endothermic reaction, diluted with steam to reduce coking and improve selectivity, typically yields about 30% ethylene (C₂H₄), 15% propylene (C₃H₆), and byproducts such as 4–5% butadiene, alongside hydrogen, methane, and heavier residues. Steam cracking supports the production of these olefins essential for downstream chemicals. In , light naphtha is processed to generate high-octane components and valuable aromatics. The feedstock, pretreated to remove impurities like , is passed over a bifunctional platinum-on-alumina catalyst at 450–550°C and 10–30 bar in a series of reactors, promoting dehydrogenation, , and cyclization reactions. This process yields reformate with an octane number exceeding 100, including about 40% BTX aromatics (, , and xylenes), which are extracted for use. These olefins from naphtha cracking form the basis for plastics production, with and polymerized into and . Approximately 50% of is directed toward synthesis, while supports and other polymers. For instance, of 1 ton of naphtha generates roughly 0.3 tons of , enabling the indirect production of about 0.25 tons of after . Naphtha dominates global ethylene feedstock, accounting for about 50–60% of production, compared to 30–40% from natural gas liquids like , reflecting regional preferences such as naphtha's prevalence in and .

Fuel and energy applications

Naphtha serves as a key component in blending, particularly light naphtha, which is incorporated into reformulated to adjust volatility and contribute to enhancement after processing such as . Typically blended at ratios up to 5% directly due to its low number (around 50-55 RON) and high , it helps meet specifications for modern s while complying with emission standards like Euro 5 and Euro 6 through controlled aromatic and olefin content. In processes, naphtha is restructured into higher- components (up to 95-100 RON) that boost the overall pool , enabling blends that satisfy regulatory requirements for environmental performance. In specialty fuels, naphtha functions as white gas or for portable camping stoves and lanterns, prized for its clean-burning properties and low residue. This refined variant has a of approximately -4°C, allowing reliable ignition in cold conditions while minimizing sooting in wick-based appliances. Historically, naphtha-based formulations powered early applications, including military and engines via , a wide-cut naphtha-type with a low freezing point (-58°C) suited for high-altitude operations. Within refineries, excess or off-spec naphtha is combusted in fired heaters to generate process heat, supporting operations like and cracking with thermal efficiencies typically ranging from 80% to 90% through optimized heat recovery systems. This approach recycles diluents from heavy oil upgrading, reducing and enhancing overall site by capturing heat. The segment is pressured by rising priorities and policy-driven transitions to lower-carbon . In 2024, total naphtha use stood at around 277 million tons, with the segment projected to further decline its share by 2025.

Health and Safety Considerations

Toxicity and health risks

Acute of naphtha vapors can irritate the , leading to symptoms such as coughing, , , and . In rats, the 4-hour inhalation LC50 is 16 mg/L (approximately 3,400 ppm), indicating moderate at high concentrations. Prolonged or repeated skin contact with naphtha can cause defatting, dryness, irritation, and due to its properties. Ingestion of naphtha presents a significant aspiration ; if aspirated into the lungs during or , it can cause and severe pulmonary damage, including . Chronic exposure to naphtha through repeated as a may contribute to neurological damage, manifesting as chronic or "painters' ," with symptoms including persistent headaches, fatigue, memory impairment, and reduced cognitive function. Naphtha is not classifiable as to its carcinogenicity to humans (IARC Group 3). However, it may contain trace amounts of benzene (IARC Group 1), typically less than 1%, which can increase risks of leukemia and other cancers with prolonged exposure. Occupational exposure limits for naphtha include an OSHA permissible exposure limit (PEL) of 100 ppm (400 mg/m³) as an 8-hour time-weighted average (TWA) and a NIOSH immediately dangerous to life or health (IDLH) value of 1,000 ppm. Biomonitoring of naphtha exposure often involves measuring urinary metabolites like , a primary indicator of absorption from naphtha components. Workers in refining and industries face heightened risks from routine handling, , and potential leaks, with studies linking such exposures to respiratory and systemic effects. Intentional misuse through abuse, including incidents in the involving volatile hydrocarbons like those in naphtha-based products, has led to acute neurological and cardiac complications in vulnerable populations.

Flammability and environmental hazards

Naphtha, particularly light grades, is classified as a Class IA under the (NFPA) 30 standard due to its below 23°C and under 35°C for the lightest fractions, making it highly susceptible to ignition. The vapors form explosive mixtures with air within a concentration range of 1% to 6% by volume, posing significant fire and explosion risks during storage and handling. NFPA 30 mandates stringent storage requirements, including approved containers, ventilation to prevent vapor accumulation, and separation from ignition sources to mitigate these hazards. Safe handling protocols emphasize prevention of and vapor ignition; equipment must be grounded and bonded during transfer to avoid sparks, while inerting with is recommended for enclosed systems to displace oxygen and reduce potential. In the event of spills, immediate response involves containing the liquid with non-combustible absorbents such as or , as naphtha evaporates approximately 10 times faster than , accelerating vapor release but limiting long-term pooling. As a major source of volatile organic compounds (VOCs), naphtha emissions contribute to the formation of and photochemical through atmospheric reactions with oxides under . It exhibits high aquatic toxicity, with median lethal concentrations (LC50) for typically ranging from 1 to 10 mg/L, indicating severe impacts on marine and freshwater ecosystems even at low exposure levels. Certain components, such as aromatic hydrocarbons, demonstrate persistence in , where they can migrate and contaminate aquifers due to low and slow rates. Regulatory frameworks address these risks through targeted controls; under the European Union's REACH regulation, naphtha must limit aromatic content, particularly , to below 0.1% by weight to avoid carcinogenic classification and ensure safe use. In the United States, under the Planning and Community Right-to-Know Act (EPCRA) Section 313 (Toxics Release Inventory), facilities must report annual releases exceeding 10,000 pounds of listed toxic chemicals, such as present in naphtha, to facilitate environmental tracking and risk management. As of 2025, updates in both regions promote bio-based naphtha alternatives, with EU efforts seeking clearer to accelerate adoption in feedstocks and reduce reliance on fossil-derived variants.

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