Procurement of cyclohexanone (CAS 108-94-1) for large-volume downstream conversion requires supplier certification around three analytical nodes: ketone purity, cyclohexanol carry-over, and water content. This cyclohexanone (CAS 108-94-1) supplier and manufacturer guide treats commercial material as a process intermediate rather than a generic solvent, meaning the certificate of analysis must be read against the catalytic and thermodynamic demands of downstream oximation, nitric acid oxidation, and polymer solution preparation. The molecule is a six-membered cyclic aliphatic ketone with a molecular weight of 98.15 g/mol, a normal boiling point of 155.6 °C at 101.3 kPa, a relative density of 0.947 at 20 °C, a water solubility of approximately 87 g/L at 20 °C, and a closed-cup flash point of 44 °C. Commercial distribution occurs under UN 1915, Class 3, Packing Group III. The European REACH registration lists industrial solvent and monomer-synthesis exposure scenarios; EC No is 203-631-1.

The supplier-selection process differs for oxidation-grade and solvent-grade material. Oxidation-grade cyclohexanone is typically specified at ≥ 99.5 % purity by gas chromatography with flame ionization detection, while solvent-grade material may allow higher cyclohexanol content because residual alcohol participates in resin hydrogen-bonding interactions. Total purity alone is not sufficient for qualification. Batch-to-batch variance in low-boiling impurities such as cyclohexene and 2-cyclohexen-1-one can shift downstream catalyst deactivation rates even when total purity remains within specification. Supplier quality systems should include ISO 9001:2015, ISO 14001:2015, and transport-compliance records aligned with the International Maritime Dangerous Goods Code.

What process variables control the cyclohexanone-to-cyclohexanol ratio in air oxidation?

The dominant production route begins with liquid-phase air oxidation of cyclohexane at 150–170 °C and 0.8–1.5 MPa. Per-pass cyclohexane conversion is deliberately limited to 4–6 % to preserve selectivity toward the mixed alcohol-ketone stream known as KA oil. Under these conditions, the combined selectivity to cyclohexanol and cyclohexanone typically falls in the range of 70–85 %. The ketone-to-alcohol ratio is governed by catalyst selection: soluble cobalt salts favour higher ketone yields, while boric acid processes generate cyclohexyl borate esters that hydrolyse to cyclohexanol and require a separate dehydrogenation step. Unconverted cyclohexane is recovered by distillation and recycled; the recycle stream concentrates acidic byproducts, so suppliers operating air-oxidation plants must control naphthenic acids and low-molecular-weight carboxylic acids to avoid downstream corrosion in carbon steel distillation columns.

Boric acid-modified cyclohexane oxidation improves selectivity by trapping cyclohexanol as a non-oxidizable borate ester. The hydrolysis step regenerates cyclohexanol and releases boric acid, which must be recovered by crystallization or ion exchange to avoid downstream fouling. Plants using this route often produce a more alcohol-rich intermediate and therefore require larger dehydrogenation capacity. Supplier audits for boric acid-route material should request boron and borate residue data in finished cyclohexanone, because carry-over can promote haze in solvent applications and catalyst poisoning in downstream hydrogenation.

The cyclohexanol-rich fraction from boric acid or cobalt-catalysed oxidation is converted to cyclohexanone by catalytic dehydrogenation in a shell-and-tube reactor. Copper-zinc oxide and copper-chromite catalysts are operated with heat-transfer oil at 220–280 °C; the reaction is endothermic and requires close approach to isothermal operation. High hydrogen partial pressure suppresses catalyst fouling but shifts equilibrium toward the alcohol. Manufacturers therefore maintain a low-pressure stripping loop to remove hydrogen from the reactor effluent. Supplier audits for this route should examine whether the plant publishes cyclohexanol content in feed and product, because residual alcohol in finished cyclohexanone above 0.10 wt% affects downstream oximation mass balance.

Phenol hydrogenation is an alternative route selected when low sulfur and low chloride profiles are required for electronic-grade or high-purity solvent markets. Supported palladium catalysts at 120–180 °C and 0.2–1.0 MPa hydrogen partial pressure deliver high cyclohexanone selectivity, but over-hydrogenation to cyclohexanol becomes significant when phenol conversion exceeds 95 %. Manufacturer qualification for phenol-based material should include a residual phenol specification, typically below 0.01 wt%, and trace sulfate and chloride analysis because catalyst residues can migrate into downstream formulations. The advantage of this route is that feedstock phenol is a commoditized aromatic with established residual chloride and sulfur specifications, enabling low-odor and low-color solvent use without additional caustic washing.

Specification, sampling, and certificate-of-analysis benchmarking

Commercial specifications vary by production route, but the following table summarizes common benchmark limits used in supplier qualification for large-volume cyclohexanone (CAS 108-94-1). Values should be verified against the supplier’s current certificate of analysis because no single standard imposes the full set.

ASTM D1078 provides boiling-range data but does not resolve trace impurity identity. For supplier certification, gas chromatographic impurity profiling is more informative than distillation range, particularly when cyclohexanone is used in caprolactam or adipic acid operations. No single ASTM purity method for cyclohexanone exists; purchasers should request raw chromatographic integration data for peaks in the 0.01–0.10 % range and compare retention-time libraries against certified reference materials. Gas chromatographic method parameters for cyclohexanone typically include a polyethylene glycol capillary column of 30 m length, 0.32 mm internal diameter, and 0.25 µm film, with split injection at 250 °C and flame ionization detection at 300 °C. Area normalization without internal standard can hide detector non-linearity; therefore calibration by an internal standard such as n-nonane or n-hexadecane is preferred. Peaks below 0.01 % are often not reported, but buyers should request them if the material feeds catalyst-sensitive processes.

Sampling for cyclohexanone should follow the supplier’s documented procedure, but reproducibility improves when samples are taken under nitrogen or into pre-dried glass bottles and analyzed within 24 h. Water content can increase by 0.01–0.02 wt% during transfer if the receiving vessel is not purged. Acidity is reported as acetic acid because many industrial pH probes lack resolution in non-aqueous systems. The acidity test method ASTM D1613 uses a methanolic titrant; chlorinated solvents are not required. Distillation range by ASTM D1078 is adequate for detecting high-boiling condensation products, but narrow-range specifications between 153.0 °C and 156.5 °C provide limited differentiation among modern suppliers.

For caprolactam synthesis, the critical supplier-controlled parameter is not bulk purity alone but the concentration of cyclohexanol and alkali metals in the feed. Cyclohexanone oximation with hydroxylamine sulfate proceeds at 70–90 °C and pH 4–6; residual cyclohexanol above 0.10 wt% survives the oximation loop and appears as an inert in the Beckmann rearrangement, reducing carbon efficiency. Transition metals including iron and chromium are controlled in the low mg/kg range in oxidation-grade material because they accelerate tar formation in the oleum-catalysed rearrangement at 80–110 °C. Published single-value metal limits remain route-specific and are not harmonized across caprolactam producers. Sampling procedures for oxidation-grade cyclohexanone should include dedicated stainless steel or PTFE-lined containers because moisture pickup from ambient air can raise water content by 0.01–0.02 wt% during transfer in humid environments.

The oximation stage consumes hydroxylamine sulfate, and the resulting cyclohexanone oxime is separated from ammonium sulfate by extraction or crystallization. If cyclohexanone contains high water, the oxime yield drops due to hydrolysis. The Beckmann rearrangement uses oleum or a zeolite-based catalytic route; in the oleum route, the reaction mass is quenched with ammonium hydroxide, and the caprolactam is extracted with organic solvent. Supplier qualification for large-volume caprolactam consumers often includes a color stability test because color bodies in cyclohexanone can carry into polymer-grade caprolactam and require additional hydrogenation.

When nitric acid oxidation demands low ketone-peroxide precursors

Adipic acid production consumes cyclohexanone in nitric acid oxidation at 60–90 °C and 0.5–1.0 MPa. The reaction system uses continuous stirred-tank reactors with external cooling loops because the oxidation is strongly exothermic. Copper and vanadium salts act as homogeneous catalysts; impurity-driven side reactions generate glutaric and succinic dicarboxylic acids, which are separated by crystallization from the dibasic acid stream. Manufacturer audits for this route should focus on trace levels of cyclohexane, cyclohexene, and peroxide-active impurities because unsaturated compounds can initiate local radical decomposition products that complicate off-gas treatment. Published data for a single peroxide limit in cyclohexanone feedstock is limited; suppliers typically report peroxide index by iodometric titration, and buyers should establish lot-specific acceptance baselines.

The nitric acid oxidation process generates nitrous oxide off-gas; modern plants install abatement systems for N2O decomposition. Feed cyclohexanone purity influences the formation of lower dicarboxylic acids, which affect adipic acid recovery by crystallization. A supplier change can shift the glutaric-to-succinic acid ratio in the dibasic acid purge stream, so manufacturer audits should compare historical impurity fingerprints before qualification. In continuous plants, the cyclohexanone feed is metered with positive displacement pumps; density and viscosity variation due to water or cyclohexanol can alter mass flow calibration by 0.5–1.0 % if volumetric metering is used without density compensation.

For vinyl chloride-vinyl acetate copolymer coatings and printing inks, cyclohexanone is typically used at 5–30 wt% of the solvent blend. Its evaporation rate is slower than methyl ethyl ketone, governed by the normal boiling point of 155.6 °C, and its viscosity of approximately 2.2 mPa·s at 25 °C influences resin-cut viscosity and transfer. In rotogravure ink control, flow time is measured by ASTM D4212; formulators adjust cyclohexanone content to maintain a Zahn cup flow time range suitable for gravure cylinder engraving depths. Supplier qualification for solvent-grade cyclohexanone should include a color hold test because aldehyde and ketone condensation products can raise Pt-Co color above 10 during storage in unlined steel drums.

In coated fabrics and PVC plastisols, cyclohexanone acts as a fusion solvent that can lower the gelation temperature of a plastisol by 5–15 °C depending on resin and plasticizer. Solvent retention in cast films can increase volatile organic compound emissions; production lines use forced-air ovens at 150–190 °C to remove the ketone before final fusion. Electrical properties of vinyl films are influenced by residual solvent; surface resistivity measurements by ASTM D257 are used to verify that solvent removal is complete. Supplier certification for solvent-grade cyclohexanone should include halide residue data because halide carry-over can corrode doctor blades and gravure cylinders; published universal halide limits are formulation-specific rather than fixed by a single standard.

Storage and transport limits for flammable-liquid classification

Cyclohexanone is classified as a flammable liquid under Regulation (EC) No 1272/2008 with the hazard statements Flam. Liq. 3, H226; Acute Tox. 4, H332; Skin Irrit. 2, H315; Eye Irrit. 2, H319; and STOT SE 3, H335. Storage should use grounded and bonded tanks with nitrogen padding if product is held longer than 30 days. The material can form peroxides under prolonged air exposure, although at a lower rate than ethers; periodic peroxide monitoring by iodometric titration is included in supplier stability programs. Avoid contact with strong oxidizers, nitric acid, and strong bases because exothermic condensation and oxidation reactions may generate pressure in closed systems.

Cyclohexanone is transported in 200 L steel drums, 1000 L intermediate bulk containers, and dedicated stainless steel road tankers. The International Maritime Dangerous Goods Code assigns UN 1915, Class 3, Packing Group III; marine packaging for flammable liquids follows packing instruction P001. For bulk storage, nitrogen blanketing at low positive pressure prevents moisture ingress and lowers headspace oxygen concentration. Tank materials should be reviewed against the supplier’s safety data sheet; stainless steel and lined carbon steel are common for bulk terminals, while zinc, copper, and aluminium components should be avoided in service because they can accelerate condensation reactions. Internal tank temperature is often specified below 35 °C to limit acid-catalysed self-condensation and color development.