Ethylene CAS 74-85-1

What is Ethylene?

Ethylene is the simplest olefin: two carbon atoms joined by a double bond, formula C₂H₄. At normal temperature and pressure it is a colourless, flammable gas with a faintly sweet odour, and it is the largest-volume organic chemical made anywhere in the world.

Its commercial importance comes from that double bond. It opens readily under catalysts, radicals or oxidants, which lets ethylene polymerise into polyethylene or add chlorine, oxygen, water, benzene or acetic acid to build a long list of intermediates. Most of the world's plastics, antifreeze, PVC and styrene trace back to it.

Ethylene is supplied in grades set by purity and by the impurities that matter to the downstream catalyst. Polymer grade, at or above 99.9%, is made for Ziegler-Natta, metallocene and chromium polyethylene catalysts, which are poisoned by parts-per-million levels of acetylene, carbon monoxide, oxygen, water and sulphur compounds. Chemical grade tolerates more.

Commercially, ethylene is mostly produced and consumed on the same site or through pipeline networks, because it is hard to store and transport. Merchant supply by cylinder, tube trailer and refrigerated tank serves the producers and users who sit outside those networks.

Why ethylene specifically

• A reactive double bond with a simple structure. Ethylene polymerises and adds reagents cleanly without the selectivity problems that larger olefins bring.
• The base of the polyethylene family. HDPE, LDPE and LLDPE together are the most-used plastics, and all start from ethylene.
• A route to many intermediates. Ethylene oxide, ethylene dichloride, ethylbenzene, vinyl acetate and ethanol all come from the same feed.
• A mature, well-documented supply chain. Specifications, test methods and handling rules are established, so qualification is a question of impurities rather than basic suitability.

How Ethylene is Manufactured

Almost all ethylene is made by steam cracking of hydrocarbons. The feedstock determines the by-product slate, and the purification train determines the grade.

• Feedstock selection. Ethane, propane, naphtha or gas oil. Ethane gives the highest ethylene yield and the fewest co-products; naphtha gives a wider slate including propylene, butadiene and aromatics.
• Steam cracking. Feed is diluted with steam and heated in furnace tubes to around 800 to 850 °C for a fraction of a second, breaking saturated hydrocarbons into olefins, hydrogen and methane.
• Quench and compression. Furnace effluent is cooled rapidly to stop further reaction, water and heavy oils are removed, and the gas is compressed in stages.
• Acid gas and water removal. Caustic washing removes CO₂ and H₂S, and molecular-sieve driers remove water so cryogenic equipment does not freeze.
• Cryogenic separation. Fractionation separates hydrogen, methane, ethylene and ethane, and heavier cuts. A C2 splitter column separates ethylene from ethane.
• Acetylene removal and polishing. Selective hydrogenation converts acetylene, a catalyst poison, back to ethylene. Guard beds remove residual CO, oxygen and sulphur to polymer-grade levels.

Typical Commercial Specification

Figures below are representative of polymer-grade ethylene. Tell us your polymerisation process and catalyst type and we will advise on the grade and trace-impurity limits you should specify.

Physical & Chemical Properties

Behaviour in the process

Ethylene behaves as a reactive, flammable gas that is close to its critical point at ambient temperature, and that shapes how it is stored and handled:

• Low critical temperature. At 9.2 °C it cannot be liquefied by pressure alone at normal ambient temperature, which is why merchant ethylene is either held as a compressed gas or as a cryogenic refrigerated liquid.
• Wide flammable range. A mixture of ethylene with air between about 2.7 and 36% is flammable, which is far wider than propane or butane and means leaks need rapid detection.
• Polymerisation chemistry. Under heat, pressure and initiators it forms polyethylene, so uncontrolled conditions in a vessel can start exothermic polymerisation.
• Ripening hormone. At very low concentrations ethylene acts as a plant hormone that ripens fruit, a use and a storage concern in produce chambers.
• Catalyst sensitivity of downstream plants. It is the trace contaminants, not the ethylene itself, that decide whether a feed behaves well in a polymerisation reactor.

Polymer Grade vs Chemical Grade and Related Olefins

Ethylene is bought by grade, and it is often compared with the other light olefins that share its supply chain.

Stated plainly: polymer grade is a specification of impurities as much as of purity, chemical grade is cheaper because the downstream chemistry is more forgiving, and the other olefins are not substitutes but partners — butene, hexene and octene are fed alongside ethylene to tune polymer density.

Industries We Supply Ethylene To

The same gas goes to a polyethylene plant, an ethylene oxide unit and a produce ripening facility. What changes is the purity, the packing and the paperwork each requires.

Where Ethylene is Used

Ethylene is bought overwhelmingly to make polyethylene, with a broad chemical tail behind it. These are the end uses our customers buy it for.

In polyethylene manufacture

Ethylene is fed with a catalyst and, for LLDPE and HDPE, a comonomer such as butene or hexene into a gas-phase, slurry or solution reactor. Melt index, density and molecular weight distribution are set by the catalyst, comonomer and hydrogen levels. Trace impurities in the feed cut catalyst productivity, which is why the specification limits CO, acetylene and oxygen.

In ethylene oxide manufacture

Ethylene is oxidised over a silver catalyst with oxygen or air. Selectivity depends on the ethylene being free of sulphur and halogen contaminants, and the process is very sensitive to ethylene composition and to inhibitors. Most EO goes on to make monoethylene glycol.

The storage and transport problem

This deserves its own section because ethylene's critical temperature of 9.2 °C complicates logistics. It cannot be held as a liquid at ambient temperature under pressure, so merchant volumes move as compressed gas in cylinders or tube trailers, or as a cryogenic liquid at about −104 °C in insulated tanks. Container choice follows volume, distance and the receiving facility's equipment.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis based on gas chromatography, with trace impurities reported to the limits you specify.

• Ethylene content — measured by gas chromatography with flame ionisation detection.
• Acetylene and carbon monoxide — the catalyst poisons, reported in ppmv against the polymer-grade limits.
• Oxygen, CO₂ and hydrogen — analysed by GC with thermal conductivity or specialised detectors.
• Total sulphur — by sulphur chemiluminescence or equivalent, with detection to ppb levels.
• Moisture — by dew point or capacitive analyser, critical for cryogenic and catalytic use.
• Methane, ethane and heavier hydrocarbons — defining grade and checking for contamination from cracking.
• Cylinder and tank condition — valve integrity, pressure and cleanliness confirmed before filling.

Common Process Problems & Likely Causes

When ethylene causes trouble, it is usually trace poisons, moisture or a handling and pressure problem. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. High-pressure steel cylinders and tube trailers for compressed gas, and cryogenic ISO tank containers for refrigerated liquid ethylene. The format follows your volume and receiving equipment.
• Pressure and temperature control. Compressed ethylene is held under pressure in tested cylinders. Refrigerated liquid ethylene is held at around −104 °C in vacuum-insulated tanks with pressure relief.
• Storage. Outdoors or in well-ventilated, fire-resistant stores, away from heat, ignition sources and oxidisers, with cylinders secured upright.
• Segregation. Keep apart from oxidising gases such as oxygen and chlorine, and from halogens and strong acids.
• Electrical and ignition control. Earth and bond all transfer equipment, use flameproof electrical equipment in classified zones and ban ignition sources.
• Shelf life. Stable gas with no fixed expiry in sound, leak-free packaging. Cylinder retest dates apply, and purity should be re-checked after long storage.
• Transport classification. UN 1962 ethylene (compressed) and UN 1038 ethylene, refrigerated liquid; Class 2.1 flammable gas.

Hazards & Safe Handling

Ethylene is an extremely flammable gas and a simple asphyxiant with mild anaesthetic effects at high concentration. It is not classified as carcinogenic or toxic, but fire, pressure and oxygen displacement are the real hazards.

• Fire and explosion. Wide flammable range of about 2.7 to 36% in air. Control ignition sources, fit gas detection and earth all equipment.
• Pressure hazard. Cylinders and vessels can rupture in fire or if overheated. Protect from heat and use pressure relief.
• Asphyxiation. High concentrations in enclosed spaces displace oxygen. Provide ventilation and oxygen monitoring before entry.
• Narcotic effects. Inhalation at high concentration can cause dizziness and drowsiness. Remove the person to fresh air.
• Cold burns. Refrigerated liquid ethylene causes severe frostbite on contact. Use insulated gloves and a face shield.
• PPE. Flame-resistant clothing, safety glasses, leather gloves and portable gas detection where leaks are possible.
• Leak response. Shut off the source if safe to do so, evacuate and ventilate, and keep ignition sources away until the area is confirmed gas-free.
• Environment. Not persistent and not significantly bioaccumulative. Vent only through approved flare or recovery systems.

Regulatory & Compliance Notes

Ethylene is a commodity with well-established regulatory handling. Because obligations differ by territory and use, the notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser.

• REACH and chemical inventories. Ethylene is registered under EU REACH and listed on major inventories, with the supplier's role confirmed in the quotation.
• GHS classification. Flammable gas (Category 1), gas under pressure and STOT SE 3 (narcotic effects). The SDS carries the full hazard statements.
• Dangerous goods transport. UN 1962 or UN 1038, Class 2.1. ADR, IMDG, IATA and DOT requirements apply to labelling, vehicle and container design.
• Process safety. Storage and use fall under major-hazard and flammable-gas rules in many jurisdictions, including zoning and hazardous area classification.
• Food and agricultural use. Ethylene used for ripening must meet the local horticultural rules on permitted concentrations and exposure.
• Quality agreements. Polymer producers commonly expect documented specification, test methods and change control. Tell us what your agreement requires.

We Supply Ethylene Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Ethylene from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, dangerous-goods 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 the dangerous-goods rules and routing allow.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the dangerous-goods declaration issued as a complete set.
• Flexible volumes. From specialty cylinder quantities through tube trailers up to repeat ISO tank loads 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 Ethylene from Chelora

We are an independent sourcing and supply partner. For ethylene that means settling three things at enquiry: the grade and trace-impurity limits, the packing and connection format you can receive, and the dangerous-goods route to your site — because for this product the logistics are as much a part of the specification as the purity.

• Documentation on every lot. Batch-specific COA with ethylene content and trace impurities, plus SDS and dangerous-goods paperwork.
• Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the gas.
• Quantities. From specialty cylinders through to full ISO tank loads on contract supply.
• Grade range. Polymer grade and chemical grade, with tighter limits on acetylene, CO or sulphur where your catalyst needs them.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related olefins. Propylene, 1-butene, isobutylene and 1,3-butadiene alongside ethylene 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 and dangerous-goods document set, and tracked through to arrival.

Related Olefins & Petrochemical Feedstocks

Buyers of ethylene often source other olefins alongside it — polyethylene plants typically buy a butene comonomer on the same programme. Consolidating them cuts freight cost and gives you a single point of contact for documentation.