Commercial movement of xylene—both mixed xylene and separated C8 aromatic isomers—is treated as a high-hazard, cargo-sensitive aromatics operation in which the inquiry-to-bill-of-lading sequence determines whether a parcel meets downstream reactor or solvent formulation limits. From Inquiry to Bill of Lading: A Xylene Order Process Timeline and Document Checklist consolidates the operational steps that connect a purchase enquiry with the ocean or road transport document. Xylene, CAS 1330-20-7, has a molecular weight of 106.16 g/mol, a density of 0.860–0.875 g/cm³ at 20 °C by ASTM D4052, and a boiling range of 137–144 °C by ASTM D850. Mixed xylene is predominantly a solvent-grade blend of ethylbenzene and the three xylene isomers; para-xylene is a high-purity petrochemical intermediate for purified terephthalic acid units, while ortho-xylene feeds phthalic anhydride reactors. The order process is not a single commercial event but a controlled transfer of custody that depends on analysis, tank inspection, dangerous goods documentation, and clean bill-of-lading issuance.

What pre-shipment tests does a mixed xylene parcel require before shore tank release?

Before a terminal allows loading, the appointed cargo surveyor draws top, middle, and bottom samples from the nominated shore tank after circulation. Solvent-grade mixed xylene is commonly released against a certificate of analysis that records C8 aromatic distribution by ASTM D2306, distillation range by ASTM D850, Pt-Co color by ASTM D1209, density at 20 °C by ASTM D4052, Tag closed-cup flash point by ASTM D56, total sulfur by ASTM D5453, and copper strip corrosion by ASTM D849. Nitration-grade xylene may impose a sulfur ceiling below 1 mg/kg and a maximum acid wash color because unsaturated hydrocarbons interfere with nitration selectivity. A shore tank that has previously contained a hydrocarbon with higher sulfur or a different aromatic distribution must be stripped and circulated until laboratory analysis demonstrates the residual heel is below the contract limit. No tank should be nominated for xylene unless the previous cargo compatibility is documented in the terminal tank history and the surveyor has issued a cleanliness certificate.

Cargo readiness, tank inspection, and demurrage interfaces

Custody transfer begins when the vessel’s chief officer, shore terminal operator, and independent surveyor compare the vessel ullage report with the shore tank stock balance. The bill-of-lading quantity is normally calculated by vessel measurement under API MPMS Chapter 12.1, corrected to 15 °C against the observed density; the density-in-air basis must match the commercial contract. Xylene is classified under UN 1307, hazard class 3, packing group III, and is carried under IMDG Code 5.4.1 dangerous goods documentation. Tanks are inerted where the flash point is below 32 °C; terminal operating procedures commonly set oxygen ceilings in the vapor space based on the limiting oxygen concentration determined under IEC TS 60079-32. Road tankers and ISO tanks must be electrically bonded, and loading rates are limited to avoid static discharge—typical maximum initial fill velocity below 1 m/s until the fill pipe is submerged, after which rates may be raised according to IEC TS 60079-32 guidance. Water content is measured by ASTM E203; a typical solvent-grade water limit is <200 mg/kg. If water exceeds the contract value, the parcel may require settling, draining, or contractual adjustment. Demurrage is not resolved by INCOTERMS 2020; it falls under the shipbroker’s charterparty laytime and demurrage clauses, which specify notice of readiness requirements, surveyor attendance, and whether time counts at berth. There is no single universal laytime figure for xylene parcels; published terminal-specific data is limited.

Under a CFR or FOB sale, the inquiry phase is not separate from the analytical phase. A buyer seeking para-xylene for a purified terephthalic acid unit will request a product specification that includes para-xylene >99.7 wt% by ASTM D2306, total sulfur <0.5 mg/kg by ASTM D5453, and a bromine index below 10 mg Br₂/100 g by ASTM D1492. The seller’s terminal then nominates a shore tank and laycan. Mismatches between the purchase order specification and the last CoA of the nominated tank must be resolved before the vessel arrives; post-loading contamination claims become significantly more difficult after a clean on board bill of lading is signed. In letter-of-credit transactions, banks examine documents on their face under UCP 600 Article 14, and the bill-of-lading goods description must be identical to the credit wording. A bill of lading that states “paraxylene” where the credit states “para-xylene” may be rejected even if the CoA describes the same product.

1. Buyer inquiry and specification exchange, including target ASTM methods, lot size, and destination.
2. Quotation and Incoterms selection: FOB, CFR, or CIF for ocean parcels; EXW or DAP for road/ISO tank deliveries.
3. Purchase order issuance and terminal tank nomination referencing the CoA specification and laycan.
4. Independent surveyor sampling and shore tank inspection.
5. Laboratory analysis and CoA release against the purchase order.
6. Loading, ullage survey, tank inspection, and custody transfer signature.
7. Dangerous goods declaration and vessel cargo manifest submission.
8. Clean on board bill of lading issuance after completion of loading.

When solvent-grade xylene is replaced by nitration-grade xylene in an existing contract

Changing the product specification after tank nomination changes the analytical burden and may require re-inspection of the entire shore tank. Nitration-grade xylene is purchased for downstream nitration units where olefinic and sulfur impurities affect reaction yield and acid consumption. Compared with solvent-grade mixed xylene, the nitration-grade material typically tightens the sulfur specification below 1 mg/kg, restricts nonaromatic content, and adds an acid wash color test by ASTM D848. It may also impose a benzene limit below 0.1 wt% by ASTM D4492 because benzene is separately regulated and can affect nitration selectivity. Nitration-grade xylene requires a dedicated or cleaned tank free from residual halogenated or oxygenated solvents; even small amounts of acetone or methyl ethyl ketone may alter acid wash color and render the tank unsuitable. Do not load nitration-grade xylene into a road tanker that previously carried a high-sulfur solvent without steam washing, verification of drain-line clearance, and a documented tank entry inspection.

Once a clean on board ocean bill of lading is issued, the document package typically consists of three original negotiable B/Ls, the signed mate’s receipt, the certificate of analysis, the certificate of origin, the tanker ullage report, the dangerous goods declaration, and the commercial invoice. Electronic bills of lading reduce courier delay but require prior agreement from the carrier, shipper, and consignee, and may not be accepted by letter-of-credit banks unless the credit expressly permits an eB/L. Any amendment to the B/L after issuance must be approved by the carrier, and discrepancies in quantity or description must be corrected before the document is negotiated; carriers generally do not change a clean on board notation once the cargo has left the berth without an independent re-survey.