Isobutylene
The branched four-carbon olefin supplied by Chelora Chemicals — the monomer behind butyl rubber and polyisobutylene, and the feedstock for oxygenate fuel additives — exported from Indonesia by pressurised cylinder or ISO tank with full batch documentation on every shipment.
What Isobutylene is, and why buyers source it
A working overview of the compound's chemistry, its central role in butyl rubber and oxygenate chemistry, and the grade Chelora Chemicals keeps in regular supply.
Isobutylene is a branched four-carbon olefin: a terminal double bond carried on a carbon that also bears two methyl groups. That branched, trisubstituted double bond is more electron-rich and more nucleophilic than a straight-chain olefin's, which is what makes isobutylene unusually reactive in cationic polymerisation and acid-catalysed addition — the chemistry behind both polyisobutylene and the oxygenate fuel additives built from it.
At room temperature and atmospheric pressure it is a colourless, flammable gas with a faint, mild odour. Like the other C4 olefins, it is transported and stored either as a compressed gas in cylinders and tube trailers or as a pressurised liquid in bulk vessels.
Where it fits in the value chain
Isobutylene's best-known end use is copolymerisation with a small proportion of isoprene to give butyl rubber (IIR), prized for its exceptionally low gas permeability and used in tyre inner liners and pharmaceutical stoppers. Cationic homopolymerisation gives polyisobutylene (PIB), used in adhesives, sealants and lubricant viscosity modifiers. Reaction with methanol or ethanol gives the oxygenate fuel additives MTBE and ETBE, while catalytic oxidation gives methacrolein and methacrylic acid, precursors to methyl methacrylate monomer, and reaction with phenol gives the hindered-phenol building blocks of antioxidants such as BHT.
Grade we supply
Chelora Chemicals offers Isobutylene in polymer grade (99.5%+ purity), suited to butyl rubber and polyisobutylene polymerisation and the oxygenate and methacrylate chemistry described above. The grade is supplied with a batch-wise certificate of analysis.
How Isobutylene is produced
An overview of the production route for orientation purposes. Our manufacturing partners' own process parameters and in-process controls are proprietary and are not disclosed beyond what is needed to interpret the certificate of analysis.
Isobutylene is recovered from the mixed C4 fraction of steam crackers and of refinery fluid catalytic cracking (FCC) units, where it occurs alongside 1-butene, 2-butenes, butadiene and butanes. Because its boiling point is close to that of the linear butenes, it is historically separated by selective reaction rather than straight distillation: the classic route reacts the C4 stream with methanol over an acid catalyst to form MTBE, which is then separately decomposed back to high-purity isobutylene and methanol once the linear butenes have been left behind in the raffinate.
A second major route is catalytic dehydrogenation of isobutane, which is itself recovered from natural gas liquids or produced by isomerising normal butane; this on-purpose route gives isobutylene directly without needing to separate it from a mixed olefin stream, and has grown in importance as a dedicated supply source for butyl rubber and polyisobutylene manufacture.
Industries and processes that use it
Isobutylene is consumed across butyl rubber, polyisobutylene and oxygenate-fuel-additive chemistry, with significant secondary demand from methacrylate and antioxidant intermediate manufacture. The fields below account for most of the demand we see through our export desk.
Butyl Rubber (IIR)
Copolymerised with a small proportion of isoprene to give butyl rubber, valued for its very low gas permeability in tyre inner liners and pharmaceutical closures.
Polyisobutylene (PIB)
Cationically homopolymerised to polyisobutylene, used in adhesives, sealants, chewing-gum base and lubricant viscosity-index improvers.
Oxygenate Fuel Additives
Reacted with methanol or ethanol to give MTBE or ETBE, octane-boosting oxygenate components of gasoline.
Methacrylate & Antioxidant Intermediates
Catalytically oxidised to methacrolein/methacrylic acid for methyl methacrylate, or reacted with phenol to build hindered-phenol antioxidants such as BHT.
How the molecule is typically carried forward
The electron-rich, branched double bond governs almost all of this molecule's further reaction chemistry, favouring cationic and acid-catalysed pathways. Reaction classes below account for most of the ways Isobutylene is converted into a finished polymer or intermediate.
Cationic Polymerisation
The electron-rich double bond opens readily under a Lewis-acid initiator, adding repeatedly to itself (with a little isoprene for butyl rubber) to build the polymer chain.
Acid-Catalysed Etherification
Reaction with methanol or ethanol over an acid catalyst adds the alcohol across the double bond, giving MTBE or ETBE.
Catalytic Oxidation
Stepwise catalytic oxidation of the methyl groups and double bond gives methacrolein and then methacrylic acid, the route to methyl methacrylate.
Friedel-Crafts Alkylation of Phenol
Reaction with phenol over an acid catalyst substitutes tert-butyl groups onto the aromatic ring, building hindered-phenol antioxidant intermediates.
Isobutylene against other olefins we supply
Buyers sourcing isobutylene for butyl rubber or oxygenate chemistry often need the related linear C4 olefin or the parent C3 olefin from the same cracker/refinery streams. A quick reference to what else is on our regular supply list.
| Product | CAS Number | Category | Notes |
|---|---|---|---|
| Isobutylene | 115-11-7 | C4 olefin | The product on this page — the monomer behind butyl rubber and polyisobutylene. |
| 1-Butene | 106-98-9 | C4 olefin | A related linear C4 olefin recovered from the same mixed cracker/FCC C4 stream — see its product page. |
| Propylene | 115-07-1 | C3 olefin | A related olefin co-produced in the same steam-cracking chain — see its product page. |
| Isoprene | 78-79-5 | C5 diolefin | The diolefin copolymerised with isobutylene to make butyl rubber — see its product page. |
Exact physical constants and purity specifications are confirmed per batch on the certificate of analysis — treat the notes above as a sourcing guide, not a specification sheet, for products other than Isobutylene.
Safety classification at a glance
Based on GHS classification as commonly listed for this substance. This is a summary for orientation only — always work from the current safety data sheet supplied with your specific batch.
Extremely flammable gas.
Contains gas under pressure; may explode if heated.
Simple asphyxiant in enclosed or poorly ventilated spaces by displacing oxygen.
Keep away from heat, sparks, open flame and all other ignition sources.
Flame-resistant workwear, gas detection and appropriate respiratory protection in confined-space work are the baseline for routine handling.
Handled as a compressed or liquefied gas; standard pressurised-gas handling precautions apply throughout.
Bond and ground all transfer equipment to prevent static discharge during loading and offloading.
Danger — GHS02 flammable and GHS04 gas-under-pressure pictograms apply.
This compound is an extremely flammable gas supplied under pressure, which may explode if heated, and acts as a simple asphyxiant in enclosed spaces by displacing oxygen. It must be handled with ignition-source control, gas detection and grounded/bonded transfer equipment at all times. Full first-aid, storage, spill and PPE guidance is in the MSDS issued with every shipment, and should be read in full before this material is handled.
Keeping it on spec between delivery and use
General storage guidance for this grade. Site-specific storage rules, segregation requirements and re-test intervals should follow your own EHS procedures and the MSDS issued with your batch.
Store and handle as a compressed or liquefied gas, in pressure-rated cylinders, tube trailers or ISO tanks, away from heat, sparks, open flame and oxidising gases, with adequate ventilation at all times. Cylinders and pressure vessels should be inspected and re-certified on the schedule required by local pressure-equipment regulations. Re-check purity on any material held beyond its agreed retest interval before use.
How it ships from Indonesia
Standard packing and export terms for this product. Confirm exact figures against your order — they vary slightly by destination and quantity.
What travels with every batch
Specification is agreed before the purchase order, not discovered on arrival. Every shipment of Isobutylene leaves with a documented, checkable paper trail.
Certificate of Analysis
Batch-wise assay, colour and key physical constants, issued against the agreed specification so your QC team can check it, not just file it.
Safety Data Sheet
GHS-format SDS in English covering hazard classification, handling, storage, first-aid and spill response for the exact grade shipped.
Technical Data Sheet
Reference physical and chemical properties, recommended storage and typical applications, for internal circulation to your process or R&D teams.
Certificate of Origin
Confirms Indonesian origin for customs clearance and any preferential-duty claim at your destination port.
Dangerous Goods Declaration
UN packing group, classification and shipper's declaration prepared ahead of loading so documentation never holds up customs.
Third-Party Inspection
Independent pre-shipment inspection and re-sampling can be arranged on request, at your cost, for buyers who require it as a matter of policy.
Frequently asked questions
What buyers most often ask our sales desk about this grade.
01What is Isobutylene used for?+
02What is the CAS number of Isobutylene?+
03How is Isobutylene produced?+
04What purity grade does Chelora Chemicals supply?+
05Is Isobutylene hazardous?+
06Why does isobutylene polymerise so differently from the other C4 olefins?+
07What packing options are available?+
08How long does delivery take?+
09Can I get a sample before placing a bulk order?+
10Do you supply other C4 and C3 olefins as well?+
Need Isobutylene on spec, on time?
Send us your required purity, quantity, packing preference and destination port. Our desk quotes most enquiries within one working day.