Benzene CAS 71-43-2

What is Benzene?

Benzene is the simplest aromatic hydrocarbon, formula C₆H₆, a six-carbon ring with delocalised electrons that give it exceptional stability. It is a clear, colourless, highly flammable liquid with a characteristic sweet odour, boiling at about 80 °C.

That stability is the point. The aromatic ring survives substitution reactions intact, so benzene can be alkylated, nitrated, chlorinated and hydrogenated to build almost the entire aromatic derivatives chain.

Nearly all benzene goes to four derivatives: ethylbenzene for styrene, cumene for phenol and acetone, cyclohexane for nylon, and nitrobenzene for aniline. Those four routes account for the overwhelming majority of global demand.

Benzene is a regulated carcinogen. It is classified Category 1A for carcinogenicity in the EU and controlled under specific occupational standards in most jurisdictions, which shapes how it is stored, sampled and documented.

Why Benzene specifically

• An aromatic platform. The stable ring accepts electrophilic substitution cleanly, making it the entry point to most aromatic derivatives.
• The styrene chain. Alkylation with ethylene gives ethylbenzene, and dehydrogenation gives styrene for polystyrene and ABS.
• The phenol chain. Alkylation with propylene gives cumene, whose oxidation yields phenol and acetone together.
• The nylon chain. Hydrogenation to cyclohexane leads to caprolactam and adipic acid for nylon 6 and nylon 66.

How Benzene is Manufactured

Benzene comes from refining and from steam cracking. The route determines the impurity profile more than the headline purity.

• Catalytic reforming. Naphtha is reformed to raise aromatics content, producing a reformate rich in benzene, toluene and xylenes.
• Pyrolysis gasoline recovery. The pygas from naphtha steam crackers is hydrotreated to remove dienes and sulphur, then fed to aromatics extraction.
• Aromatics extraction. Benzene is separated from non-aromatic hydrocarbons by extractive distillation or liquid-liquid extraction with sulpholane, NMP or similar solvents.
• Toluene hydrodealkylation. Toluene is converted to benzene and methane where benzene demand exceeds reformate supply.
• Toluene disproportionation. Toluene is converted to benzene plus xylenes, favoured where para-xylene is also wanted.
• Finishing and clay treating. Final distillation and clay treatment deliver nitration grade: 99.9% purity with a freezing point above 5.45 °C.

Typical Commercial Specification

Figures below are representative of commercial nitration-grade benzene. Tell us the downstream reaction and we will advise on the grade you should specify.

Physical & Chemical Properties

Behaviour in the process

Benzene is chemically stable but has handling behaviours that matter in practice:

• Freezes near room temperature. At 5.5 °C benzene solidifies, so winter storage and transfer lines need heating or tracing in cold climates.
• High volatility and low flash point. Vapour forms readily at ambient and is heavier than air, pooling in pits and sumps.
• Carcinogenic vapour. Exposure control, not just fire control, drives closed sampling and vapour recovery on loading.
• Excellent solvency. Benzene attacks many elastomers and coatings; seal and gasket selection matters.

Benzene Grades and Related Aromatics

Benzene is bought by grade, and nitration grade is the commercial default. Where a cheaper aromatic will do the job, toluene and xylene are the usual alternatives.

Stated plainly: nothing substitutes for benzene in the styrene, phenol and nylon chains. Where benzene appears only as a solvent, toluene or xylene almost always replaces it, and regulation has pushed that substitution almost to completion.

Industries We Supply Benzene To

The same nitration-grade liquid goes to a styrene complex, a phenol plant and a nylon intermediate unit. What changes is the impurity ceiling and the exposure-control documentation each site requires.

Where Benzene is Used

Benzene is bought almost entirely as a chemical intermediate. Solvent use has largely disappeared under exposure regulation.

In ethylbenzene manufacture

Benzene is alkylated with ethylene over a zeolite catalyst in liquid or vapour phase. Excess benzene suppresses polyalkylation, and the unconverted benzene is recycled, so feed purity and water content directly affect catalyst life and the recycle loop.

In cumene and phenol manufacture

Benzene is alkylated with propylene to cumene, which is oxidised to the hydroperoxide and cleaved with acid to phenol and acetone. The cleavage produces both products in fixed ratio, which is why phenol economics are permanently tied to the acetone market.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis, with the freezing point reported alongside GC purity because it is the traditional and most sensitive measure of benzene quality.

• Purity — by gas chromatography against the nitration-grade specification.
• Freezing point — the classic indicator of total impurity content.
• Non-aromatics — reported because they survive downstream reactions as inerts.
• Total sulphur and thiophene — measured because sulphur poisons alkylation and hydrogenation catalysts.
• Water content — relevant to zeolite catalyst life in alkylation units.
• Acid wash colour and Pt-Co colour — indicators of oxidation and contamination.
• Copper corrosion — confirming absence of corrosive sulphur species.

Common Process Problems & Likely Causes

When benzene causes trouble, it is usually sulphur, non-aromatics, water or freezing in cold weather. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. ISO tank containers, road tankers, rail cars and bulk parcel tankers; drums for small quantities.
• Closed handling. Closed sampling and vapour recovery on loading and discharge are standard because of the carcinogen classification.
• Temperature control. Keep above 7 °C to prevent freezing; tracing and lagging are needed in cold climates.
• Storage. Fixed or floating roof tanks with nitrogen blanketing or vapour control, earthed and bunded, with gas detection.
• Material compatibility. Carbon steel and stainless steel are standard. Benzene attacks many elastomers; check seal and hose specifications.
• Segregation. Keep apart from oxidisers, halogens and acid mixtures.
• Shelf life. Indefinite in sealed, dry, blanketed storage. Water bottoms and colour are the practical checks.
• Transport classification. UN 1114, benzene, Class 3 flammable liquid, packing group II, with carcinogen subsidiary labelling where required.

Hazards & Safe Handling

Benzene is a highly flammable liquid and a confirmed human carcinogen. Fire risk is manageable with standard controls, but long-term exposure control is the central health issue and drives most of the handling rules.

• Carcinogenicity. Classified Category 1A carcinogen and Category 1B mutagen; causally linked to leukaemia. Exposure must be kept as low as technically possible.
• Occupational exposure limits. Limits are very low, commonly around 1 ppm as an 8-hour average with action levels below that. Confirm the limit applicable in your jurisdiction.
• Medical surveillance. Many jurisdictions require biological monitoring and health surveillance for benzene-exposed workers.
• Fire and explosion. Flash point about −11 °C with a flammable range of roughly 1.2 to 7.8%. Earth and bond all transfer equipment.
• Heavy vapour. Vapour pools at low points. Ventilate and monitor at low level.
• Aspiration hazard. Swallowing and aspirating liquid can cause chemical pneumonitis. Never induce vomiting.
• PPE. Flame-resistant clothing, chemical-resistant gloves, eye protection and appropriate respiratory protection for any breach of containment.
• Environment. Prevent entry to drains, soil and groundwater; benzene is a regulated groundwater contaminant.

Regulatory & Compliance Notes

Benzene is one of the most heavily regulated industrial chemicals, with specific occupational standards in most jurisdictions. The notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser.

• GHS classification. Flammable liquid Category 2, carcinogenicity Category 1A, germ cell mutagenicity Category 1B, STOT RE Category 1 and aspiration hazard.
• Occupational exposure regulation. Dedicated benzene standards covering monitoring, medical surveillance, regulated areas and exposure limits apply in the US, EU and many other jurisdictions.
• REACH authorisation and restriction. Listed as a substance of very high concern and restricted in consumer products and in preparations above low thresholds in the EU.
• Gasoline content limits. Benzene content in motor fuel is capped in most markets, which affects reformate handling and benzene balances.
• Dangerous goods transport. UN 1114, Class 3, PG II. ADR, IMDG, IATA and DOT rules apply to tank design, labelling and routing.
• Quality agreements. Downstream producers commonly expect documented freezing point, sulphur and non-aromatics limits with change control.

We Supply Benzene Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Benzene from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork and freight so the material arrives ready to use.

• Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
• Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where routing and cargo rules allow.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
• Flexible volumes. From a single ISO tank up to repeat bulk shipments on a supply contract.
• Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.

Buying Benzene from Chelora

We are an independent sourcing and supply partner. For benzene that means settling three things at enquiry: the grade and freezing point, the closed-handling route into your tankage, and the carcinogen and dangerous-goods paperwork your site and your regulator require.

• Documentation on every lot. Batch-specific COA (GC purity, freezing point, non-aromatics), plus SDS and the full transport paperwork.
• Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
• Quantities. From a single ISO tank through to full bulk shipments on contract supply.
• Grade matching. Nitration grade to the freezing point, sulphur and non-aromatics limits your downstream catalyst requires.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related products. Toluene, Ethylbenzene, Cumene and other feedstocks alongside Benzene from one supplier.

How ordering works

• Send the enquiry. Product, grade or purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
• We quote. Price, lead time, packing format and a sample COA, normally within one working day.
• Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
• Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.

Related Products

Buyers of benzene often source other aromatics alongside it — styrene producers typically buy ethylene and ethylbenzene, and phenol plants need cumene and propylene on the same programme.