Propylene Oxide (PO) Supply: Grades, Specs, UN 1280 Logistics and Instant Quote

Propylene oxide enters bulk chemical procurement as a low-boiling intermediate whose specification limits cannot be separated from transport classification. At 101.3 kPa, the substance boils at 34°C, and the closed-cup flash point is -37°C. The vapour pressure reaches 59.3 kPa at 20°C, producing ignitable mixtures at ambient temperature. These values place propylene oxide in the highest-hazard segment of Class 3 flammable liquids and define why storage, road tankers, isotanks, and receiving terminals are specified before a commercial quote can be issued. The molecular mass is 58.08 g/mol, the CAS registry number is 75-56-9, and the EC number is 200-879-2. Supply chains for polyether polyols, propylene glycol ethers, propylene glycol, and specialty alkoxylates consume the largest share of output; therefore, the dominant procurement specification is the polyether/polyol contract grade, not a generic commodity pool product. Since trace water, acidity, and aldehydes affect downstream alkoxylation kinetics and color stability, purchase contracts treat grade verification as a pass/fail entry condition. The unlabelled technical sections below state the grade definitions, specification data, UN 1280 logistics requirements, and the mandatory data elements for an instant quote.

What specification set governs polyether-grade Propylene Oxide (PO) procurement?

Propylene oxide is not universally sold under a single ISO specification. Commercial supply is divided into polyether/polyol grade, technical grade, and high-purity material. Polyether/polyol grade is the reference for continuous polyether polyol reactors and typically carries a purity specification of ≥99.9 wt% on a dry basis. Technical grade may be released at ≥99.5 wt% for solvents, chemical intermediates, and non-catalytic processes. High-purity grade is tendered only for pharmaceutical, electronic, or specialty applications where low aldehyde and low trace-metal profiles are required; published data for this specific configuration is limited because producer-specific methodologies control the release limits. The table below sets out representative procurement specifications and the most frequently associated test standards. The tabulated values are reference points for commercial negotiation, not harmonized normative limits.

For alkoxylation units using double metal cyanide catalysts, water is frequently tightened from ≤0.01 wt% to ≤0.005 wt% because water acts as an initiator and can shift polyether functionality and molecular weight distribution. Aldehyde limits may also be reduced to ≤20 mg/kg for odor-sensitive polyol applications. The test method for water is ASTM E203; acidity is measured by ASTM D1613; color is determined by ASTM D1209. Purity is measured by producer-validated capillary gas chromatography with flame ionization detection. No single ASTM or ISO designation covers all propylene oxide grade splits, so the certificate of analysis must state detector response factors, impurity quantification limit, and whether the sample was run on a 100 m or 60 m capillary column. Oxygenated impurities in propylene oxide tend to elute close to the main peak; therefore, a poorly resolved GC method can overstate purity and mask propionaldehyde or acetaldehyde. Receiving laboratories may reject a shipment if the certificate of analysis does not state the method detection limit for water and acids. Those data are part of the supply record because they determine whether the material can enter a continuous reactor without a downstream drying column.

UN 1280 is the dangerous goods identifier assigned to propylene oxide under the UN Model Regulations and incorporated into ADR, RID, ADN, and the IMDG Code. The proper shipping name is “Propylene oxide,” and the classification is Class 3, Packing Group I. Packing Group I applies to flammable liquids with a boiling point at or below 35°C and a flash point below 23°C, both of which propylene oxide meets. Transport equipment must be closed, pressure-resistant, nitrogen-blanketed, and equipped with flame arresters and bonding/earthing connections. Road and rail tank containers used for Packing Group I low-boiling flammables are subject to tank-code and pressure-relief requirements that differ from those for higher-boiling solvents. In marine transport under the IMDG Code, the substance appears in the Dangerous Goods List with EmS F-E and S-D; segregation from strong acids, strong bases, oxidizing agents, and anhydrous metal chlorides is required because these materials can initiate rapid ring-opening polymerization. Air freight is generally not offered through routine parcel or standard unit load device networks because the flash point and vapor pressure trigger operator approval requirements under the IATA Dangerous Goods Regulations. No standard unit load device nomination should be made without written airline approval.

Bulk unloading requires a receiving system that can keep the product under dry nitrogen at an oxygen concentration below the locally validated limiting oxygen concentration. The receiving tank should be designed for 34°C boiling liquid and a flash point below -35°C; low-pressure storage tanks with open vents are not suitable. Transfer pumps should be canned-motor or mechanical-seal units rated for the vapor pressure of propylene oxide, and lines should be closed-loop with vapor return to the supply tank. For isotank shipments, terminal operators require a dangerous goods declaration, the tank certificate, the certificate of analysis, and a safety data sheet aligned to GHS and, where applicable, REACH. The table below summarizes the principal transport instruments and document controls for UN 1280.

The selection of packaging and mode is not independent of grade. High-purity material for pharmaceuticals may move in smaller stainless steel or phenolic-lined steel containers under nitrogen, while bulk polyether-grade material moves in dedicated stainless steel isotanks or road tankers. If a receiving tank cannot maintain a nitrogen pad or closed-loop vapor return, the supply is normally shifted to drums or intermediate bulk containers with UN-approved closures. Published data for the maximum permissible storage period in all container types is limited; therefore, the shipper and receiver must agree on the maximum shelf-life after loading and the required revalidation of water and color before use.

When UN 1280 logistics constrain isotank nominations at coastal distribution terminals

Coastal distribution terminals with multiple Class 3 services may be unable to accept propylene oxide unless the tank pit is configured for high-vapour-pressure polar flammables. The terminal must confirm that the un-loading manifold is segregated from amines, aqueous ammonia, strong bases, and oxidizing acids. Simultaneous unloading with these materials is not permitted. The receiving tank should be stainless steel or lined carbon steel with a nitrogen pad, pressure/vacuum relief, and a closed-loop vapour connection. The transfer pump should be a canned-motor or mechanical-seal design with a shut-off head compatible with the isotank maximum allowable working pressure. The unloading line should be electrically continuous and bonded to the isotank before hoses are connected. Portable flammability monitoring should be calibrated for propylene oxide vapor; standard catalytic sensors may require correction for the oxygenated structure, so the terminal should verify sensor response against the supplier’s calibration gas. Published data for this specific configuration is limited; site-specific safety assessments control the final acceptance.

Isotank nominations for UN 1280 normally require the consignee to provide the terminal’s dangerous goods acceptance number, tank pit location, allowable unloading window, and vapour return pressure. The shipper’s logistics provider must verify that the tank container is approved for Packing Group I low-boiling liquid and that the relief device set pressure and start-to-discharge rating are stated on the tank certificate. Container cleanliness is critical: residues of previous cargoes, especially amines or acids, can catalyze oligomerization or cause a pressure rise. Therefore, the tank must be cleaned, dried, and nitrogen-blanketed before loading. The maximum water content after cleaning should be checked against the required COA limit; if the prepared tank dew point is above -30°C, the first fill may fail the water specification. These operational constraints add cost and lead time, which is why an instant quote requires terminal acceptance before a firm transport price can be returned.

Instant quote inputs: grade, packaging, UN 1280 transport mode, and terminal validation

An instant quote for propylene oxide is operationally useful only when the request contains the following data elements: the grade required by COA, the annual or per-lot volume, the packaging and unloading mode, the origin and destination port or warehouse, the requested Incoterms 2020 rule, and the receiving terminal’s ability to handle UN 1280 Class 3 Packing Group I. For bulk supply, the quote should state whether the movement is FOB, CFR, or DAP, because dangerous goods surcharges, tank cleaning, vapor-return charges, and terminal acceptance fees vary by terminal and route. For drum supply, the quote should state the UN-approved drum specification, the maximum fill ratio at 20°C, and whether the drum is palletized under an open or closed shed. A request that omits grade or terminal compatibility cannot return an enforceable transport or commercial offer because the UN 1280 logistics cost is conditional on packaging, mode, and acceptance.

No quote should be treated as a transport approval. The bill of lading, dangerous goods declaration, and terminal acceptance records are the controlling documents. If the receiving terminal imposes a lower unloading pressure or a narrower moisture limit than the shipper’s tank, the quote must be revised after a technical review. Volatility and reactivity make propylene oxide procurement a specification-first transaction; the instant quote is therefore an input-validation tool, not a substitute for dangerous goods planning or producer COA review.