| HS Code | |
| Product Name | Cyclohexane |
| Chemical Formula | C6H12 |
| Cas Registry Number | 110-82-7 |
| Ec Number | 203-806-2 |
| Un Number | 1145 |
| Molecular Weight | 84.16 g/mol |
| Appearance | Colorless liquid |
| Odor | Pungent, gasoline-like |
| Boiling Point | 80.7 °C |
| Melting Point | 6.5 °C |
| Density | 0.779 g/cm3 at 20 °C |
| Solubility In Water | Practically insoluble; 0.0055 g/100 mL at 20 °C |
| Flash Point | -18 °C closed cup |
| Autoignition Temperature | 245 °C |
| Vapor Pressure | 10.3 kPa at 20 °C |
| Refractive Index | 1.4266 at 20 °C |
| Viscosity | 0.894 mPa·s at 25 °C |
| Log P | 3.44 |
As an accredited Cyclohexane factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Cyclohexane packaged in 1 L amber glass bottles with solvent-resistant caps, hazard labels, and UN 1145 markings, securely sealed. |
| Container Loading (20′ FCL) | Cyclohexane in 20′ FCL: UN 1145, Class 3 flammable liquid, packed in sealed drums, properly secured, placarded, and documented. |
| Shipping | Cyclohexane ships as UN1145, Cyclohexane, Class 3, Packing Group II. It is a flammable liquid requiring approved packaging, hazard labels, and transport documents. Keep away from ignition sources and use nonsparking equipment. Follow IMDG/IATA/ADR regulations; marine-pollutant documentation may apply. |
| Storage | Store cyclohexane in a cool, dry, well-ventilated area away from heat, sparks, open flames, and strong oxidizers. Keep containers tightly closed and grounded in an approved flammable-liquid storage cabinet. Use explosion-proof equipment and avoid static discharge. Protect from direct sunlight and keep away from ignition sources. Follow local regulations and label containers clearly. Ensure secondary containment where required. |
| Shelf Life | Cyclohexane has a shelf life of at least 24 months when stored in a cool, dry, well-ventilated area away from ignition sources. |
In the caprolactam production chain, cyclohexane is consumed not as a formulation component but as the primary hydrocarbon feedstock in liquid-phase air oxidation to KA oil, which is subsequently distilled to isolate cyclohexanone and then converted to cyclohexanone oxime prior to Beckmann rearrangement. The oxidation stage operates at 140–170 °C and 0.8–1.4 MPa, using cobalt naphthenate at an addition ratio of 0.1–3 mg kg⁻¹ relative to cyclohexane feed; per-pass conversion is maintained at 4–8% to keep KA oil selectivity in the 75–85% range, because higher conversion shifts product distribution toward ring-opened acids and high-boiling residues that shorten catalyst life and increase distillation load. The cyclohexane recycle stream is typically purified by saponification and water washing to remove residual acids before recombination with fresh cyclohexane complying with benzene content <500 mg kg⁻¹ and sulfur content <2 mg kg⁻¹. Industry compliance standard for food-contact end products derived from caprolactam is FDA 21 CFR 177.1500, which covers nylon 6 resins intended for repeated-use food-contact articles; REACH registration under EC 1907/2006 is required for the cyclohexane itself, and the caprolactam REACH dossier includes dermal sensitization and respiratory irritation classifications. The downstream production process after oxidation includes vacuum distillation of KA oil, reaction of the cyclohexanone fraction with hydroxylammonium sulfate at pH 3–5 and 60–90 °C, followed by Beckmann rearrangement in oleum containing 15–25% free SO₃ at 80–120 °C; the lactam sulfate is neutralized with ammonia and extracted into a benzene or toluene stream before purification. Terminal product types from this route are polyamide 6 resin, biaxially oriented PA6 film, and continuous filament for textile and carpet fiber.
Adipic acid synthesis from cyclohexane begins with the same liquid-phase air oxidation route used for KA oil, but the downstream nitric acid oxidation imposes stricter control on the ratio of cyclohexanone to cyclohexanol in the KA oil feed, because the two species differ in nitric acid demand and influence N₂O generation. The nitric acid oxidation stage is carried out at 50–90 °C with 40–60% HNO₃, copper(II) and vanadium catalyst concentrations of 0.1–0.5 wt% relative to KA oil, and a HNO₃:KA oil molar feed ratio of 2.0–2.4:1; the stoichiometric requirement is approximately 2 mol HNO₃ per mole of cyclohexanone or cyclohexanol. Industry compliance standard for the sector includes the EU Industrial Emissions Directive 2010/75/EU and the associated BAT conclusions for large volume organic chemicals, which require thermal or catalytic abatement of N₂O emissions from adipic acid plants with destruction efficiencies above 99.0%; US EPA 40 CFR Part 98 also requires annual greenhouse gas reporting from adipic acid production. The production process isolates KA oil by saponification and distillation, oxidizes it with nitric acid under controlled aeration, then crystallizes adipic acid from the aqueous reaction mass, followed by centrifugation, rinsing, and recrystallization to achieve specifications of 99.8–100.0% purity and moisture below 0.3 wt%. Terminal product types include nylon 66 salt produced with hexamethylenediamine, polyester polyols for polyurethane elastomers, and ester plasticizers such as di-2-ethylhexyl adipate.
The oxidation of cyclohexane to KA oil is deliberately held at low per-pass conversion because the cyclohexyl hydroperoxide intermediate decomposes selectively in the presence of dissolved metal catalysts, but the absence of stabilizers or excessive residence time shifts selectivity toward ring-opening products such as adipic, glutaric, and succinic acids. In derivative production for cyclohexanone-formaldehyde resins, the cyclohexanone fraction is condensed with aqueous formaldehyde at a cyclohexanone:formaldehyde molar ratio of 1.0:1.0–1.5 and an alkaline catalyst dosage of 0.5–2.0 wt% sodium hydroxide relative to cyclohexanone; the condensation is run at 60–90 °C under nitrogen, followed by vacuum dehydration to a softening point of 85–115 °C; published data for specific condensation recipes is limited. Industry compliance standard for resins intended for food-contact coatings is FDA 21 CFR 175.300, and manufacture is conducted under REACH Annex VI and VII registration obligations for cyclohexane as a registered intermediate. In finished nitrocellulose lacquer applications, the cyclohexanone-formaldehyde resin is incorporated at 5–20 wt% of total nonvolatile binder to modify film hardness and solvent release. Terminal product types include cyclohexanone-formaldehyde resin as a film-forming modifier in nitrocellulose lacquers, wood grain sealers, and gravure ink vehicles.
Within solventborne chlorinated rubber coating lines, cyclohexane is introduced as a low-density aliphatic diluent in the let-down stage, not as a primary grinding solvent, to adjust evaporation rate and viscosity without increasing aromatic content. The cyclohexane addition level is 5–18 wt% of total coating mass, with total solvent content typically 40–65 wt% depending on application method; in a representative chlorinated rubber primer formulation, the solvent blend may contain cyclohexane at 10–15 wt%, xylene at 35–50 wt%, and methyl ethyl ketone at 10–20 wt%; published data for specific customer formulations is limited. The manufacturing process involves high-speed disperser premixing of pigment and plasticizer at 3,000–5,000 rpm, followed by horizontal bead mill grinding to Hegman 5–6, then let-down with chlorinated rubber pre-dissolved in the cyclohexane-containing solvent blend under low-shear stirring. The low flash point of cyclohexane, approximately -18 °C closed cup, requires explosion-proof motors, grounding, and solvent vapor extraction; the material is handled below 25 °C and in closed transfer lines to limit vapor escape. Industry compliance standard for VOC content is Directive 2004/42/EC Annex IIB for marine and protective coatings, and test method ASTM D3960 is used for VOC determination; REACH Annex XVII restrictions on benzene and toluene carry over into solvent blend specifications. Terminal product types include chlorinated rubber primers, intermediate coats for steel and concrete, and solventborne traffic marking paints.
In polychloroprene-based contact adhesives, cyclohexane is not used as the sole solvent because polychloroprene requires a balanced solubility parameter blend; cyclohexane typically comprises 20–40 wt% of the solvent fraction, with the total solvent content between 70 and 85 wt% of the adhesive formulation for sprayable grades. The remaining solvent fraction is commonly split among ethyl acetate, acetone, toluene, or hexane, selected to control evaporation rate and to achieve a Brookfield viscosity of 1,500–4,000 mPa·s at 25 °C. Manufacturing involves dissolving milled polychloroprene in the cyclohexane-containing blend under low-speed planetary mixing at 20–60 °C, adding magnesium oxide and zinc oxide as acid scavengers and vulcanizing aids, then adding tackifier resin dispersion; the batch is filtered through 100–200 μm mesh and deaerated before packaging. Compliance standard for occupational exposure to cyclohexane is the ACGIH TLV of 100 ppm 8-hour TWA, and EU CLP classification requires H225, H304, H315, H336, and H410 label elements; adhesive performance is tested to ASTM D6862 for peel strength under specified application. Terminal products are contact adhesives for laminate panels, footwear, automotive interior trim, and construction sandwich panels.
Residual solvent control in pharmaceutical intermediate purification places cyclohexane under ICH Q3C(R8) Class 2 limits: the permitted daily exposure is 38.8 mg day⁻¹, corresponding to a concentration limit of 3,880 ppm in pharmaceutical products. As a recrystallization solvent, cyclohexane is charged at 5–15 mL per gram of dry crude intermediate, depending on solubility gradient and impurity rejection; the process stream is heated to 60–80 °C, hot-filtered through 0.45 μm cartridge media, and cooled to 0–5 °C at a controlled rate of 0.2–0.5 °C min⁻¹ to avoid oiling-out and solvent inclusion. The wet cake is vacuum-dried at 40–60 °C and residual cyclohexane is quantified by gas chromatography following USP <467> residual solvent procedures, with acceptance criteria aligned to ICH Q3C. Industry compliance standard for the final active pharmaceutical ingredient includes USP <467> and Ph. Eur. Chapter 5.4, with batch release documentation required for the cyclohexane residual level. Terminal products are purified pharmaceutical intermediates and fine chemical actives used in registered API processes; cyclohexane is selected only when the target compound is stable in aliphatic hydrocarbons and no peroxide-forming solvent is required.
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Cyclohexane, CAS 110-82-7, EC 203-806-2, is a saturated six-membered cycloparaffin with molecular formula C6H12 and molar mass 84.16 g/mol. It is produced commercially by liquid-phase catalytic hydrogenation of benzene over supported nickel or platinum catalysts, followed by distillation or extractive finishing to control unconverted benzene and close-boiling hydrocarbons. The compound is supplied as a clear, colorless liquid with a boiling point of 80.7 °C at 101.3 kPa, freezing point of 6.5 °C, density of 0.778–0.779 g/mL at 20 °C, refractive index n20/D of 1.426–1.427, and closed-cup flash point of −18 °C. Commercial product models are generally purity-tier grades rather than discrete part numbers; specifications for industrial, high-purity, and extraction/UV grades are shown in Table 1.
| Property | Method | Industrial grade | High purity grade | Extraction/UV grade |
|---|---|---|---|---|
| Purity, GC area% | GC-FID, ASTM D5134-13(2020) framework | ≥99.5 | ≥99.9 | ≥99.95 |
| Benzene | GC-FID, ASTM D5134-13(2020) framework | ≤0.1 wt% | ≤0.01 wt% | ≤0.002 wt% |
| Methylcyclopentane | GC-FID, internal method | ≤0.3 wt% | ≤0.05 wt% | ≤0.01 wt% |
| Sulfur | ASTM D5453-19 | ≤5 mg/kg | ≤1 mg/kg | ≤0.5 mg/kg |
| Water | ASTM E203-16 | ≤100 mg/kg | ≤50 mg/kg | ≤30 mg/kg |
| Density at 20 °C | ASTM D4052-18 | 0.778–0.779 g/mL | 0.778–0.779 g/mL | 0.778–0.779 g/mL |
| Distillation range | ASTM D86-20a | 80.0–81.5 °C | 80.0–81.0 °C | 80.5–81.0 °C |
| Color APHA | ASTM D1209-00 | ≤10 | ≤5 | ≤5 |
| Residue on evaporation | ASTM D1353-13 | ≤10 mg/kg | ≤5 mg/kg | ≤2 mg/kg |
The tabulated limits are representative certificate-of-analysis values for bulk supply; individual manufacturers may narrow or widen residual parameters. The GC-FID method uses NIST-traceable calibration blends and is executed under ISO 17025 accredited laboratory procedures. The industrial grade is typically specified for chemical intermediate use where downstream purification or reaction consumes residual benzene. The high-purity grade is selected for closed-loop solvent recovery units in adhesive lines because lower residue protects heat exchangers from fouling. The extraction/UV grade is used in analytical laboratories and pharmaceutical isolation where non-volatile residue must remain below 2 mg/kg and water below 30 mg/kg to avoid extractive interference. These grade definitions are not governed by a single ASTM product specification, and purchasers should align the certificate-of-analysis parameters with the intended unit operation.
Residual benzene in cyclohexane is not reduced to low levels by simple distillation because benzene and cyclohexane form a minimum-boiling azeotrope at approximately 77.8 °C at 101.3 kPa. Low-benzene grades therefore require either near-complete benzene hydrogenation upstream of the main fractionator or extractive distillation using a polar solvent such as sulfolane. In a two-stage hydrogenation train, the finishing reactor is operated at a lower space velocity and a temperature of 150–180 °C to reduce benzene to below 0.01 wt%. Sulfur compounds in the benzene feed, typically thiophenes, poison supported nickel catalysts; a sustained feed sulfur level above 1 mg/kg lowers conversion and produces batch-to-batch variation in the benzene content of the crude product. The low-odor coating grade is therefore a separate fractionation cut with benzene at ≤0.01 wt% or ≤0.002 wt% depending on grade, verified by capillary GC rather than by odor panel testing.
Methylcyclopentane, formed by isomerization during hydrogenation, remains a close-boiling impurity and is controlled in high-purity grades to ≤0.05 wt% because its accumulation influences distillation-range narrowness and can alter solvency in adhesive formulations. Water is limited to ≤50 mg/kg for high-purity material because free water at lower ambient temperatures separates and promotes corrosion in carbon steel storage; for moisture-sensitive organometallic applications, extraction/UV grade at ≤30 mg/kg is specified.
In resin thinning and extraction operations, cyclohexane is metered at 5–30 wt% of formulation mass to reach target viscosity. Its Kauri-butanol value of 54 under ASTM D1133-21 places it between n-hexane at 33 and toluene at 105; it is therefore used where aromatic solvency would cause excessive swelling of rubber seals or where a non-aromatic alternative is required. With a Hildebrand solubility parameter of 16.8 MPa1/2, cyclohexane is less polar than esters or ketones and is unsuitable for high-nitrocellulose solvency unless blended with oxygenated solvents. For vegetable oil extraction, the density difference between the cyclohexane-rich phase and aqueous phase permits phase disengagement in countercurrent columns, but the flash point of −18 °C requires nitrogen blanketing on storage tanks and vapor monitoring to below 20% of the lower explosive limit by EN 60079-10-1 area classification.
Substitution is controlled by volatility, freeze point, and solvency differences. Cyclohexane has a higher boiling point than n-hexane by 12.0 °C and a higher density by 0.120 g/mL, which reduces evaporative loss in unsealed extraction vessels but increases concentration time in downstream solvent recovery. Against methylcyclohexane, cyclohexane has a lower boiling point by 20.2 °C and a lower flash point by 14 °C, requiring stricter control of headspace vapor in heated crystallizers. The freeze point of cyclohexane at 6.5 °C is a processing constraint in cold crystallization: cooling below 10 °C in unjacketed lines risks solidification, whereas n-hexane remains liquid below −95 °C. In contrast, cyclohexane has a higher Kauri-butanol value than n-hexane and methylcyclohexane, providing greater solvent power for low-polarity resins and waxes in recrystallization. Table 2 compares key parameters.
| Parameter | Cyclohexane | n-Hexane | Methylcyclohexane | Cyclohexene |
|---|---|---|---|---|
| CAS number | 110-82-7 | 110-54-3 | 108-87-2 | 110-83-8 |
| Boiling point at 101.3 kPa | 80.7 °C | 68.7 °C | 100.9 °C | 83.0 °C |
| Flash point, closed cup | −18 °C | −22 °C | −4 °C | −6 °C |
| Density at 20 °C | 0.779 g/mL | 0.659 g/mL | 0.770 g/mL | 0.811 g/mL |
| Refractive index n20/D | 1.426 | 1.375 | 1.423 | 1.446 |
| Molar mass | 84.16 g/mol | 86.18 g/mol | 98.19 g/mol | 82.14 g/mol |
| Kauri-butanol value | 54 | 33 | 44 | not commonly specified |
| Lower explosive limit | 1.3 vol% | 1.2 vol% | 1.1 vol% | 1.0 vol% |
Cyclohexene differs functionally despite a similar boiling range; its unsaturated double bond allows epoxidation, hydration to cyclohexanol, and polymerization, whereas cyclohexane remains inert under the same conditions. Cyclohexene has a higher density of 0.811 g/mL and a flash point of −6 °C, but its peroxide formation on exposure to air requires stabilizer addition; cyclohexane does not form peroxides at comparable rates. The selection between cyclohexane and cyclohexene is therefore not based on boiling range but on whether saturation is required in downstream synthesis.
Cyclohexane is the primary feedstock for cyclohexanol/cyclohexanone mixtures, referred to as KA oil, used in adipic acid and caprolactam synthesis. In production-scale liquid-phase oxidation, air or oxygen-enriched air is sparged into a bubble-column or stirred autoclave at 150–165 °C and 0.8–1.2 MPa. Conversion per pass is deliberately limited to 4–6% to preserve selectivity toward KA oil; higher conversion increases ring-opening acids and esters. Soluble cobalt or cobalt-chromium salts are used as homogeneous catalysts, and the resulting cyclohexyl hydroperoxide intermediate is decomposed to cyclohexanol and cyclohexanone in post-oxidation cleavage. The reactor effluent is cooled and flashed to recover unreacted cyclohexane for recycle; this recycle stream accumulates low-reactivity impurities such as methylcyclopentane and must be purged or separated to avoid suppressing oxygen uptake. The cyclohexanone/cyclohexanol ratio in KA oil, typically 1:1 to 1.5:1 depending on catalyst and temperature, is a critical control point for downstream adipic acid quality.
Cyclohexanol/cyclohexanone mixtures are further oxidized with 50–65 wt% nitric acid in the presence of copper/vanadium catalysts to adipic acid at 60–80 °C and 0.1–0.5 MPa; adipic acid is then polymerized with hexamethylenediamine to nylon 6,6. Alternatively, cyclohexanone is converted to cyclohexanone oxime using hydroxylamine sulfate, followed by Beckmann rearrangement in oleum at 80–110 °C to produce caprolactam, the monomer for nylon 6. These downstream conversions impose tight limits on cyclohexane impurities because color and trace organic content in caprolactam are affected by residual sulfur and unsaturated hydrocarbons. In integrated nylon complexes, the cyclohexane oxidation train is operated with continuous online analysis of off-gas oxygen and dissolved hydroperoxide to avoid explosive oxygen concentrations; the lower explosive limit of 1.3 vol% for cyclohexane vapor applies to the reactor headspace and recovery lines.
In bulk storage, cyclohexane is maintained under a nitrogen pad to exclude moisture and oxygen. Transfer equipment is grounded because the liquid has low conductivity and can accumulate static charge; grounding and bonding are required under NFPA 77. Transport classification is UN 1145, Class 3, Packing Group II. The REACH registration for cyclohexane includes exposure scenarios for industrial use as an intermediate, formulation, and solvent; risk management measures include local exhaust ventilation for drumming operations and closed-transfer loops for bulk loading. In humid environments, water ingress above 100 mg/kg in industrial grade can separate as a lower water phase when stored below 6.5 °C; tanks are fitted with bottom water draws and desiccant breathers when relative humidity exceeds 60%. For analytical use, packaging in 2.5 L glass bottles or 20 L pails under nitrogen is common, with lot-specific certificates reporting density, distillation range, and residue. Published data for high-vacuum semiconductor-grade cyclohexane is limited; electronics-grade users typically require additional particle, trace-metal, and total organic carbon data not covered by the standard grades in Table 1.
