Isobutylene
The branched C4 olefin behind butyl rubber, polyisobutylene and oxygenate fuel additives — a core building block of the C4 petrochemical stream.
Chelora Chemicals supplies isobutylene to rubber, lubricant-additive and fuel-oxygenate producers worldwide, with pressurised handling and full documentation on every consignment.
Product identity
- CAS Number
- 115-11-7
- IUPAC name
- 2-Methylprop-1-ene
- Molecular formula
- C₄H₈
- Molecular weight
- 56.11 g/mol
- Boiling point
- -6.9 °C
- Melting point
- -140.3 °C
- UN Number
- UN 1055
- HS Code
- 2901 23
Note: Isobutylene is a liquefied gas at ambient temperature and pressure — it ships and is stored under pressure. Confirm exact classification for your shipment with your regulatory affairs team.
What Isobutylene is used for
Isobutylene is a colourless, flammable gas with a mild, petroleum-like odour, handled and shipped as a liquefied gas under pressure. It is the branched-chain isomer of butene, recovered from the C4 fraction of steam cracking or refinery FCC streams, or produced on-purpose by the dehydrogenation of isobutane.
Isobutylene's largest uses are as the comonomer for butyl rubber (copolymerised with a small fraction of isoprene for innertubes, tyre liners and pharmaceutical stoppers), and as the monomer for polyisobutylene (PIB), used in lubricant viscosity modifiers, adhesives and sealants. It is also a key feedstock for the oxygenate fuel additives MTBE and ETBE, and for tert-butyl phenolic antioxidants such as BHT.
Where it sits in the petrochemical value chain
- C4 steam-cracker / FCC stream the mixed C4 feedstock isobutylene is recovered from, alongside 1-butene and butadiene.
- Isobutylene (this product) the branched olefin feedstock for the chains below.
- Butyl Rubber / Polyisobutylene / MTBE major derivative chains built on isobutylene. See 1,3-Butadiene and 1-Butene for related C4 olefins.
Handling character
Isobutylene is extremely flammable and shipped as a pressurised liquefied gas. Full hazard detail is in the Safety section below.
| Parameter | Typical value |
|---|---|
| Appearance | Colourless liquefied gas |
| Purity | 99.5% min (polymer grade) |
| Diene/sulphur content | Within producer specification (ppm level) |
| Isomer purity | Within producer specification |
Important: the figures above are indicative of commercial material and are offered for planning only. The batch certificate of analysis is the governing document.
| Property | Value |
|---|---|
| Physical state | Liquefied gas under pressure at ambient temperature |
| Boiling point | -6.9 °C |
| Melting point | -140.3 °C |
| Density (liquid) | 0.594 g/cm³ |
| Water solubility | Slightly soluble (~263 mg/L) |
| Flash point | -76 °C (extremely flammable) |
Physical constants compiled from public reference data for CAS 115-11-7 and rounded for readability. Treat them as orientation, not as a specification.
Where our customers put Isobutylene to work
The branched olefin behind butyl rubber, lubricant additives and clean-fuel oxygenates.
Butyl rubber
Copolymerised with a small fraction of isoprene into butyl rubber for innertubes, tyre liners and stoppers.
- Polymer-grade specification
- Pressurised bulk supply
- Technical desk review on request
Polyisobutylene (PIB)
Polymerised into PIB for lubricant viscosity modifiers, adhesives, sealants and chewing-gum base.
- Industrial-grade specification
- Documented batch traceability
- Contract & spot supply
MTBE & ETBE oxygenates
Reacted with methanol or ethanol into octane-boosting, clean-burning fuel oxygenates.
- Full analytical documentation available
- Retained sample held against the lot
Antioxidants & phenolics
Alkylated with phenol into tert-butyl phenolic antioxidants such as BHT.
- Documented batch traceability
- Technical desk review on request
Specialty intermediates
Feedstock for methacrylate and other fine-chemical intermediate synthesis.
- Research & process-scale quantities
- Full documentation supplied
Contract & scheduled supply
Rubber and additive plants running continuous consumption are supported with scheduled bulk delivery.
- Annual contracts with scheduled call-off
- Price held across the contract period
- Second source held in reserve
How we supply Isobutylene
Chelora Chemicals is a supplier and sourcing partner, not a manufacturer. Isomer purity and pressurised handling make producer selection and logistics control critical — that shapes how we manage this line.
We place your order with whichever qualified producer best matches your required grade, your price point and your delivery window, and confirm your jurisdiction's import requirements before booking.
We keep a second qualified source on this line, so a single-plant disruption never becomes your production problem.
- Isomer and diene purity confirmed before we quote. Consistency matters to downstream butyl-rubber and PIB polymerisation.
- UN 1055 documentation managed end to end. Classification, pressurised packaging approval and carrier compliance confirmed before booking.
- Scheduled call-off scheduling. We hold contracted tonnage and release it against your consumption calendar.
- Batch traceability to the producing plant. Full chain of custody documentation on request.
- Export machinery handled in-house. Classification, approved pressurised packaging, labelling, freight booking and customs paperwork are ours to manage.
- Polymer-grade material sourced to your process. Matched precisely to your rubber, PIB or oxygenate specification.
Shipped under pressure, handled with care
Pressurised cylinder, ISO tank or rail tanker — tell us your preferred format and we will quote and classify to it.
Pressurised cylinders
Steel pressure cylinders for small-volume orders and trial quantities.
Pressurised ISO tank shipment
ISO tank containers rated for liquefied-gas transport, for continuous-consumption plants.
Bulk tanker delivery
Pressurised rail cars or road tankers for large-volume domestic and regional delivery.
Incoterms to suit you
Quoted on the Incoterm your purchasing team works to, with documentation filed before booking.
Trial / sample quantities
Small pressurised packs dispatched for process trials before a commercial order is placed.
Contracted call-off supply
We hold contracted tonnage and release it against your consumption calendar.
Extremely flammable — handle accordingly
Isobutylene is an extremely flammable gas, handled under pressure, with a wide flammability range in air. The summary below is orientation only — the safety data sheet supplied with your specific batch is the authoritative document.
Classified hazards
H220Extremely flammable gas.H280Contains gas under pressure; may explode if heated.
Closed-system handling only. Isobutylene must be handled in sealed, vented systems with continuous gas detection and elimination of ignition sources; always read the SDS issued with your specific batch.
Storage
Store in pressurised vessels in a well-ventilated, bunded area away from ignition sources, oxidisers and incompatible materials, with continuous leak detection.
Handling
Handle only in closed systems with appropriate gas detection and forced ventilation; avoid any inhalation and eliminate ignition sources from the handling area.
Transport
Shipped as UN 1055 (Isobutylene), an extremely flammable liquefied gas. We confirm and document exact classification, approved pressure vessels and routing for your specific shipment and destination.
Every batch, documented
We verify documentation before dispatch so there are no surprises at your incoming-goods bench.
Specification agreed
Purity, isomer content and trace diene/sulphur levels confirmed against your process requirement before order placement.
Producer batch testing
The producing plant tests each batch against the agreed specification before release.
Documentation review
COA, SDS and pressurised-transport paperwork checked by our desk before the shipment is booked.
Traceable dispatch
Each shipment is traceable to its producing batch, with full chain-of-custody records on request.
How Isobutylene is made
Isobutylene is recovered industrially from the mixed C4 stream produced by ethylene steam cracking or refinery FCC units, separated from the linear butenes and butanes by selective reaction (historically to MTBE) or superfractionation, and increasingly produced on-purpose by the catalytic dehydrogenation of isobutane.
We do not publish operating process parameters here; this is background only. Full technical documentation accompanies every shipment, and any process-specific detail you need is best confirmed directly with our technical desk.
| Chemical family | Branched-chain olefin (alkene) |
|---|---|
| Functional groups | Carbon-carbon double bond, branched at the terminal carbon |
| Reactivity | Cationic polymerisation; etherification with alcohols (MTBE/ETBE); Friedel-Crafts alkylation |
| Related compounds | 1-Butene, 1,3-Butadiene (C4 co-products), Butyl Rubber, Polyisobutylene (downstream) |
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