Cyclohexanone — Properties, Production, Uses & Safety

What is cyclohexanone

Cyclohexanone (C₆H₁₀O, CAS 108-94-1) is a colourless to pale-yellow ketone with a peppermint/acetone-like smell. Its main industrial role is as a precursor for caprolactam and adipic acid — raw materials for nylon — and it’s also a widely used solvent in coatings, adhesives, and chemical syntheses. Below you’ll find properties, production routes, applications, handling & safety, environmental and market outlook, plus practical tips for storage and quality control.

Basic identity & key physical properties

• Name: Cyclohexanone

• Formula / M.W.: C₆H₁₀O — 98.15 g·mol⁻¹.

• Appearance / odour: Colourless to pale-yellow liquid with a peppermint/acetone-like smell.

• Boiling point: ≈ 155–156 °C (at 1 atm).

• Melting point: about −47 °C (literature varies slightly).

• Density: ≈ 0.947 g·cm⁻³ (20–25 °C). Solubility in water ≈ 2–3% (w/w) at 20 °C; miscible with many organic solvents (ketones, alcohols, ethers, aromatics).
  (These are core reference numbers used across industry and safety documents.)

Chemical behaviour — what reactions is it known for?

Cyclohexanone is a saturated cyclic ketone; its reactive carbonyl allows typical ketone chemistry:

Reduction → cyclohexanol (common in synthesis).

Oxidation → adipic acid (via further oxidation) or other ring-open products under strong oxidants — this path underlies nylon precursor production.

Formation of hydrazones/oximes, imines, acetals/ketals (acid-catalysed with diols), halogenation at α-positions, peroxidation under certain conditions. These reactions make it a flexible synthetic intermediate.

How to make cyclohexanone (overview)

Two industrially important approaches:

• Aerobic oxidation of cyclohexane (KA-oil route): industrial processes oxidize cyclohexane to a mixture called KA-oil (cyclohexanol + cyclohexanone). Conditions are typically elevated temperature/pressure with catalyst (autoxidation using air/O₂), and subsequent separation yields cyclohexanone. This is historically dominant but has tradeoffs (selectivity, safety, by-products).

• Oxidation/dehydrogenation of cyclohexanol: cyclohexanol can be selectively dehydrogenated or oxidized to cyclohexanone using catalysts; many processes use metal catalysts under controlled conditions for higher selectivity. Patented and catalyst-driven variants optimize yield and reduce side products.

There is active R&D on greener catalysts and bio-based oxidation (e.g., enzymatic or more selective oxidation systems) to reduce energy use and emissions.

Main applications — why industry cares

• Nylon intermediates: the largest single use is production of caprolactam and adipic acid (precursors for nylon 6 and nylon 6,6). A very large fraction of global cyclohexanone goes to nylon production, making downstream nylon demand the main market driver.

• Solvent & formulation uses: excellent solvency for nitrocellulose, resins, waxes and many polymers — used in paints, coatings (including shoe/leather finishes), adhesives, inks, degreasers.

• Chemical intermediate in fine chemicals: agrochemicals, pharmaceuticals, dyes, plasticizers — often used both as a reagent and solvent in multi-step syntheses.

Safety, exposure limits & handling

• Toxicology: inhalation of high concentrations produces narcotic effects; skin/eye contact is irritating. It’s not classified like classic blood-poisoners (benzene), but high exposures are dangerous.

• Occupational exposure limits: OSHA PEL (8-hr TWA) ≈ 50 ppm (200 mg/m³); NIOSH recommended exposure limit (REL) ≈ 25 ppm (100 mg/m³) TWA. ACGIH TLV historically ≈ 20–25 ppm. Use these standards when designing ventilation and PPE.

• Fire & explosion hazards: flash point ~111–116 °F (≈ 44–47 °C); vapours heavier than air and can form explosive mixtures — ensure good ventilation, avoid low spots where vapours accumulate.

• Practical controls: closed handling, local exhaust ventilation, splash goggles & gloves, flameproof equipment, leak detection, and proper waste capture. Emergency eyewash & shower recommended.

Quality, impurities & refining notes

Typical impurities: cyclohexanol, water, dicarboxylic acids (from over-oxidation). Industrial refining includes oxidation of residual alcohols, drying (e.g., Na₂SO₄), and fractional distillation; for high-purity grades, adduct formation (e.g., bisulfite addition/removal) and reactive purification steps are sometimes used. The uploaded document includes classic lab/industrial purification methods.

Environmental & regulatory considerations

Emissions from production (VOC, by-products) require control—common measures: condensers, absorber scrubbers, catalytic afterburners, solvent recovery. Regulations vary by country, but producers pursue lower-VOC processes and catalyst improvements to reduce waste. Emerging trends push toward greener catalysts and possibly bio-routes.

Market outlook

Recent market analyses (2024–2025) estimate global cyclohexanone market value in the multiple-billion USD range and project modest growth (CAGR ≈ 3–5% depending on source), driven primarily by nylon demand in automotive, textiles and packaging. Asia Pacific is a major production and demand center.

Practical tips for buyers & lab users

• Specification checklist: assay (% cyclohexanone), water content, cyclohexanol content, acid value, color (APHA), and distillation cut points.

• Storage: cool (5–30 °C), ventilated, segregated from strong oxidants and acids, in steel or compatible containers. Avoid prolonged exposure to light/air to reduce peroxide formation.

• Transport: UN classification, shipping papers, and appropriate packing group per local ADR/IMDG/IATA rules.

FAQ (brief)

Q: Is cyclohexanone carcinogenic?
A: Not listed as a classic carcinogen by OSHA lists for common grades; toxicology focuses on irritation and CNS depression from high exposures — follow SDS and workplace limits.

Q: What is KA-oil?
A: KA-oil = mixture of cyclohexanol (K) and cyclohexanone (A) produced by cyclohexane oxidation; it’s processed to separate and further convert into nylon precursors.

Conclusion

Cyclohexanone is an industrially vital ketone — chemically versatile, a cornerstone feedstock for nylon production, and a widely used solvent. While its core properties and uses are well understood, current industry focus is on improving selectivity, reducing environmental footprint, and exploring greener synthesis routes to meet tightening sustainability standards.