1-Butene (n-Butylene)
The linear terminal C₄ alkene. A colourless, flammable gas used as a comonomer in LLDPE and HDPE manufacture, and as a building block for butylene oxide, sec-butanol, and MEK.
Molecular Structure
What is 1-Butene (n-Butylene)?
1-Butene (but-1-ene) is a linear four-carbon alpha-olefin with a terminal C=C double bond. It is the most widely used C₄ comonomer for polyethylene, incorporated at 2–10 mol% to control branch density and density.
As a short-chain alpha-olefin, 1-butene inserts into growing polyethylene chains under metallocene or Ziegler–Natta catalysis to introduce ethyl side-branches. These branches reduce crystallinity and density, converting HDPE to LLDPE with improved toughness, flexibility, and impact resistance. 1-Butene selectivity versus 1-hexene or 1-octene comonomers depends on the catalyst system and target film properties.
Chelora sources 1-butene separated from C₄ fractions or on-purpose, with low levels of isobutylene, 2-butenes, and 1,3-butadiene — critical for comonomer grade. Full CoA and logistics support.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
1-Butene (n-Butylene)'s reactivity is defined by its CH₂=CH– (terminal α-olefin) — the site of polymerisation and other industrially important reactions.
Lewis structure — sp² at C1, C2
Structural Identity
- IUPAC NameBut-1-ene
- Molecular FormulaC₄H₈
- Molecular Weight56.11 g/mol
- Hybridisationsp² at C1, C2
- Bond typeCH₂=CH– (terminal α-olefin)
- C=C bond length1.34 Å
- GeometryPlanar at C=C; tetrahedral C3, C4
- CAS Number106-98-9
- InChI KeyVXNZUUAINFGPBY-UHFFFAOYSA-N
Product Specifications
Chelora supplies 1-Butene (n-Butylene) in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | 1-Butene (n-Butylene) |
|---|---|
| CAS Number | 106-98-9 |
| Molecular formula | C₄H₈ |
| Molecular weight | 56.11 g/mol |
| Purity (standard grade) | ≥ 99.0 mol% |
| Purity (commercial grade) | ≥ 98.5 mol% |
| Physical state (ambient) | Gas (ambient) |
| Boiling point | −6.3 °C at 1 atm |
| Melting point | −185.4 °C |
| Flammable limits | 1.6 – 9.3% v/v v/v in air |
| Isobutylene (max, comonomer grade) | ≤ 500 ppm vol |
| 1,3-Butadiene (max) | ≤ 10 ppm vol |
| 2-Butenes (max) | ≤ 1000 ppm vol |
| Moisture (max) | ≤ 10 ppm wt |
| Critical temperature | 146.4 °C |
| Critical pressure | 39.7 bar |
| UN Number | UN 1012 |
| IMO / IMDG Class | Class 2.1 (Flammable Gas) |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of 1-Butene (n-Butylene).
LLDPE Comonomer
The primary use: copolymerisation with ethylene at 2–10 mol% gives LLDPE with controlled branch density, crystallinity, and density (0.915–0.940 g/cm³) for films, stretch wrap, and flexible packaging.
HDPE Comonomer
Used at low levels (0.5–3 mol%) in bi- and trimodal HDPE pipe and blow-moulding grades to improve ESCR (environmental stress cracking resistance) while maintaining stiffness.
Butylene Oxide (1,2-Epoxybutane)
Peracid epoxidation of 1-butene gives butylene oxide — used as a reactive diluent in epoxy systems, a stabiliser for chlorinated solvents, and a building block for specialty glycols.
sec-Butanol & MEK
Acid-catalysed hydration of 1-butene (or 2-butenes via isomerisation) gives sec-butanol, which is dehydrogenated to methyl ethyl ketone (MEK) — a widely used industrial solvent.
Polybutene-1 (PB-1)
Isotactic polymerisation of 1-butene gives poly(1-butene) — a slow-crystallising polyolefin with outstanding creep resistance for pressure pipes and hot-water plumbing systems.
C₄ Alkylation
1-Butene can be used in refinery alkylation units or as feedstock for specialty chemical synthesis requiring a linear terminal alkene building block.
Why source 1-Butene (n-Butylene) through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market supply.
Grade Flexibility
Standard and custom grades available. Impurity specifications can be tailored to your process and catalyst system.
Full Documentation
CoA, SDS, UN transport docs, REACH compliance, and destination-market certificates with every shipment.
Logistics Support
Experienced in specialised chemical logistics for compressed gases and volatile liquids — Indian and international delivery.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Store in a well-ventilated, dedicated area away from ignition sources, heat, and sunlight.
- All electrical equipment in storage and handling areas must be ATEX/IECEx rated for the applicable zone.
- Ensure full bonding and earthing of all transfer equipment during any transfer operation.
- Never store with strong oxidisers, halogens, or materials that generate static.
- Install continuous gas detection with audible and visual alarms set below the LEL.
- Use only approved pressure-rated piping, valves, and fittings with compatible materials.
- Conduct pre-use and post-use leak checks with suitable gas detection equipment.
- Maintain inhibitor levels where applicable; check on receipt and periodically during storage.
Hazard Summary
Classification: Flammable Gas/Liquid · Flammable limits 1.6 – 9.3% v/v v/v · UN 1012.
Flammability: Highly flammable — never rely on odour to detect leaks. Use continuous gas monitoring below LEL.
Health: Asphyxiant in enclosed spaces. Oxygen monitoring mandatory in confined areas. Follow occupational exposure limits (OELs) per SDS.
PPE minimum: Chemical goggles, appropriate gloves, flame-retardant clothing, and supplied-air respirator where oxygen deficiency is possible.
Consult the full SDS for exposure limits, spill containment, emergency response, and disposal before any use.
Frequently Asked Questions
Technical and commercial questions about 1-Butene (n-Butylene) sourcing and specifications.
What is 1-butene used for?
1-Butene is primarily used as a comonomer in LLDPE and HDPE polymerisation. It is also a feedstock for butylene oxide, sec-butanol, MEK, poly(1-butene) pressure pipe resin, and various C₄ specialty chemicals.
Why is 1-butene preferred as a comonomer over 1-hexene or 1-octene?
1-Butene is lower-cost and widely available from C₄ cracker streams. It delivers shorter ethyl branches versus the butyl (1-hexene) or hexyl (1-octene) branches. C₄-LLDPE typically has lower dart-drop impact and haze compared with C₆/C₈ grades, but is cost-competitive and adequate for many blown film applications.
How is comonomer-grade 1-butene specified?
Comonomer grade requires very low isobutylene (which poisons certain catalysts), ultra-low 1,3-butadiene (irreversible catalyst poison at ppm levels), controlled 2-butene isomers, and low moisture. Chelora supplies to agreed comonomer specifications with batch CoA.
How is 1-butene produced and separated?
1-Butene is recovered from mixed C₄ streams by superfractionation and/or extractive distillation after removal of butadiene and isobutylene. It can also be produced on-purpose by ethylene dimerisation (Alphabutol or similar processes).
What is the CAS number for 1-butene?
1-Butene has CAS number 106-98-9, IUPAC name but-1-ene, molecular formula C₄H₈, and molecular weight 56.11 g/mol. The terminal C=CH₂ double bond distinguishes it from the internal isomers cis- and trans-2-butene.
What documentation does Chelora provide?
Each shipment includes a Certificate of Analysis, Safety Data Sheet (GHS/REACH), UN 1012 Class 2.1 transport documentation, and any required destination-market certificates.
Request a quote or specification sheet
Talk to Chelora's sourcing team about 1-Butene (n-Butylene) grade, volume, logistics, documentation, and lead times. We respond within one business day.
