Commercial supply of ≥99.9 wt% synthetic phenol for epoxy and bisphenol A polycarbonate production is governed by impurity profiles rather than bulk assay alone. Synthetic Phenol Wholesale: Purity ≥99.9% for Epoxy & Polycarbonate normally denotes an anhydrous, solvent-free capillary gas chromatographic assay under ASTM D6142, with release parameters including solidification point by ASTM D1493, water content by ASTM E203, and molten color by ASTM D1209. The molecular weight is 94.11 g/mol, and the normal solidification point is near 40.85 °C. The product is obtained almost exclusively from cumene hydroperoxide cleavage, followed by neutralization, water washing, and vacuum distillation. The product carries CAS 108-95-2 and EC 203-632-7; within the European Union, bulk distribution is documented under REACH regulation EC 1907/2006. For epoxy and polycarbonate operations, residual carbonyls, iron, and water in the phenol feed interact with condensation catalysts and molecular weight control agents, so the ≥99.9% grade is specified as a set of impurity ceilings rather than a single assay number.

What Keeps Residual Carbonyls Below 50 mg/kg in Cumene-Derived Phenol?

Cumene oxidation yields cumene hydroperoxide at 20–25% conversion to limit by-product formation, after which acid cleavage with sulfuric acid at 50–75 °C produces phenol and acetone in approximately equimolar quantities. Residual carbonyl species such as acetone, acetophenone, hydroxyacetone, and mesityl oxide survive distillation when the acetone–phenol splitter bottoms exceed 175 °C. Continuous distillation trains use wiped-film evaporators operating at 5–10 kPa absolute pressure and reboiler skin temperatures below 200 °C to suppress aldol condensation reactions. Caustic neutralization and water washing after cleavage reduce acid carryover below 5 mg/kg as acetic acid; residual sodium is held below 1 mg/kg to avoid salt formation in downstream bisphenol A ion-exchange catalysts.

Batch-to-batch variation on bulk loading racks appears as solidification-point depression of 0.02 °C to 0.08 °C when total organic impurities rise from 500 mg/kg to 1,500 mg/kg. Liquid phenol with ≥99.9 wt% assay and ≤0.03 wt% water can still fail an epoxy-grade specification if carbonyls exceed 50 mg/kg, because carbonyls are reactive toward bisphenol A condensation catalysts and impart color. Loading pumps with mechanical seals and nitrogen-blanketed tanks reduce phenol oxidation to quinoid species, which appear as pink discoloration at 10–20 Pt-Co.

Bisphenol A synthesis for epoxy resin consumes synthetic phenol at 4:1 to 8:1 phenol-to-acetone molar ratios over sulfonated styrene-divinylbenzene ion-exchange resin at 50–90 °C. The high phenol excess drives para,para selectivity and permits downstream bisphenol A crystallization from the phenol adduct at 40–50 °C. Under these conditions, carbonyl impurities in phenol participate in acid-catalyzed condensation side reactions that produce high-boiling chromophores, raising bisphenol A color by ASTM D1209 and lowering 4,4′-bisphenol A assay. Iron above 0.5 mg/kg in the phenol feed accelerates color body formation and fouls continuous crystallizers; operating experience on 10,000 L stirred reactors indicates that iron and carbonyl levels move together when feedstock tanks are not nitrogen-blanketed.

Epoxidation of bisphenol A with epichlorohydrin in aqueous sodium hydroxide produces liquid diglycidyl ether of bisphenol A. The epoxy equivalent weight of standard low-molecular-weight resin is determined by ASTM D1652 and is typically 182–192 g/eq; dynamic viscosity at 25 °C by ASTM D2196 is 11–14 Pa·s. Residual phenolic impurities below 30 mg/kg in the final resin are required to prevent oligomer advancement during storage. Solvent-free grouts should not exceed 14 Pa·s unless the production line uses a twin-screw extruder with an L/D ratio above 24:1 and downstream static mixers.

Color stability of aqueous dilutions is checked by ASTM D1209; values above 50 Pt-Co are nonconforming for ambient-cure flooring binders. When the synthetic phenol feed contains water above 0.05 wt%, the bisphenol A condensation catalyst deactivates at the surface, reducing conversion and increasing the unreacted phenol recycle load. Vacuum stripping of the bisphenol A adduct at 5 kPa and 120–130 °C removes residual phenol; failure to hold these conditions leaves free phenol above 100 mg/kg, which disturbs subsequent epichlorohydrin stoichiometry. Fixed-bed catalyst life is sensitive to sodium and sulfur in synthetic phenol; sodium above 1 mg/kg neutralizes sulfonic acid sites and reduces catalyst productivity over a 6-month campaign.

When Polycarbonate Melt Polymerization Recycles Phenol as a Chain Stopper

In bisphenol A polycarbonate production via interfacial phosgenation, monohydric phenol is used as a chain stopper to regulate molecular weight. The stopper concentration is set relative to bisphenol A under caustic conditions; increasing end-capped chains reduces weight-average molecular weight and raises melt volume-flow rate at 300 °C and 1.2 kg load by ISO 1133-1:2022. Synthetic phenol with ≥99.9 wt% assay is preferred because o-cresol, p-cresol, and cumene impurities have different termination kinetics and generate variable polycarbonate end-groups, altering thermal stability. Residual water in the chain stopper above 0.03 wt% consumes phosgene and shifts the phosgene-to-bisphenol A molar ratio, requiring automatic pH control to hold the reaction pH at 10.5–11.0.

For melt transesterification plants, phenol is generated as a by-product from diphenyl carbonate and bisphenol A; low-boiling impurities in recycled phenol depress vacuum and require a phenol purification train combining distillation at 5–15 kPa and crystallization or adsorption. Operating data from a 30,000 t/year line indicate that the recycle phenol stream can accumulate diphenyl carbonate, phenyl benzoate, and residual catalyst, which must be rejected to maintain ≥99.9 wt% phenol purity. This recovered phenol is not always suitable as chain stopper without re-distillation due to color from oligomeric species; published data for this specific configuration is limited when tetraphenylphosphonium salt catalysts are used.

Trace iron in phenol affects polycarbonate color through metal-catalyzed oxidation of bisphenol A during high-temperature extrusion. Compounding on a 37 mm twin-screw extruder with L/D 40:1 and barrel temperature profile 280–320 °C increases yellowness index by ASTM E313 when phenol-derived bisphenol A contains iron above 0.1 mg/kg. Therefore polycarbonate producers require iron below 0.05 mg/kg in synthetic phenol used for bisphenol A feedstock. The melt reaction temperature is maintained within ±5 °C at the die to avoid thermal branching. Interfacial polycarbonate washing at 35–40 °C uses methylene chloride and water; residual phenol in the polymer is reduced to below 5 mg/kg by steam precipitation. Chain stopper impurities above 0.1 wt% create bimodal molar mass distributions detectable by gel permeation chromatography.

Gas Chromatographic Assay Is Reported on Anhydrous, Solvent-Free Basis

The release protocol for wholesale synthetic phenol with ≥99.9 wt% purity requires simultaneous conformance to all specified methods because assay alone misses polymeric color precursors. The table summarizes the standard release matrix used for bulk marine parcels and ISO tank containers. Results are reported on an anhydrous, solvent-free basis, with water and solidification point determined on the molten sample at 45 °C.

Typical release matrix for ≥99.9 wt% synthetic phenol

Parameter	Limit	Test method
Purity (anhydrous, solvent-free)	≥99.9 wt%	ASTM D6142
Solidification point	≥40.85 °C	ASTM D1493
Water content	≤0.03 wt%	ASTM E203
Color, molten	≤10 Pt-Co	ASTM D1209
Distillation range at 101.325 kPa	181.1–182.6 °C	ASTM D1078

Each bulk shipment is normally accompanied by a certificate of analysis that states the actual capillary GC purity, water content, and solidification point. Because phenol is hygroscopic, the water content can increase during sampling at relative humidity above 60% unless the sample loop is purged with dry nitrogen. Capillary GC conditions for ASTM D6142 typically use a 30 m × 0.32 mm fused-silica column with 0.25 µm phenyl methyl siloxane stationary phase, split injection at 250 °C, flame ionization detection at 300 °C, and oven programming from 60 °C to 280 °C at 8 °C/min. Quantification is performed by area normalization; impurities eluting after phenol are confirmed by mass spectrometry when total unknowns exceed 500 mg/kg.

During heated transfer and storage, molten synthetic phenol is maintained at 50–60 °C through 316L stainless steel piping with steam tracing. Solidification at 40.85 °C is the dominant operational risk in unheated tank farms. Crystallized phenol can be rewarmed, but localized hot spots above 120 °C accelerate oxidation and should be avoided. Dry nitrogen blanketing at 0.5–1.0 kPa gauge prevents moisture uptake and color formation. PTFE-lined diaphragm pumps are specified because centrifugal pumps with carbon steel internals can introduce iron contamination. Storage tanks should not share vents with acetone or formaldehyde because backdiffusion of reactive vapors generates resinous solids.

Compatibility with elastomers is limited. EPDM, neoprene, and natural rubber absorb phenol and swell; PTFE or 316L gaskets are used for loading arms and manways. For bulk marine parcels, phenol is often shipped as a mixture of molten and crystallized product, requiring shore tanks at 55–65 °C to liquefy before discharge. Phenol reacts with strong oxidizers, aluminum chloride, and concentrated nitric acid; storage near sodium hypochlorite or formaldehyde is incompatible. The ACGIH threshold limit value for phenol is 5 ppm with skin notation, and bulk handling areas require vapor monitoring with alarm setpoints below 2 ppm.

Melt-phase polycarbonate manufacturing recovers phenol from the polymerization reactor as a vapor at 280–300 °C and 1–5 kPa absolute pressure with unreacted diphenyl carbonate. A wiped-film evaporator with internal condenser recovers phenol at 99.5 wt% before a downstream rectification column polishes it to 99.9 wt%. The recycled phenol is returned to light-colored polycarbonate grades only if ASTM D1209 color remains below 10 Pt-Co and water remains below 0.02 wt%. Higher moisture in the recycle stream hydrolyzes diphenyl carbonate back to phenol and carbon dioxide, shifting the melt polymerization equilibrium and lowering molecular weight. The melt volume-flow rate measured by ISO 1133-1:2022 increases with moisture-dependent molecular weight depression; the quantitative slope is resin-specific and published data for this specific configuration is limited.