Methyl tert-butyl ether, also known as MTBE and identified by CAS 1634-04-4, is the branched ether formed by the catalytic addition of methanol to isobutylene. Neat MTBE has a normal boiling point of 55.2 °C, a closed-cup flash point of -28 °C, a density of approximately 0.740 kg/L at 20 °C, and a Reid vapor pressure of approximately 55 kPa at 37.8 °C. Commercial market data for the molecule are published in two broad series: free-on-board export cargo assessments at major load ports and domestic ex-tank or delivered assessments in local markets. The two series are sometimes compared directly under the heading MTBE FOB vs Domestic Price: Why the Two Series Cannot Be Compared. The comparison fails because the two quotes do not describe the same transfer point, grade, cost stack, or currency basis.

What is removed from an FOB cargo quote before a domestic rack price is formed?

Under ICC Incoterms 2020, a free-on-board sale at the load port transfers cost and risk when the product is placed on board the vessel nominated by the buyer. The seller clears export formalities. Once MTBE passes the vessel’s rail at the load port, ocean freight, marine insurance, destination port charges, import duty, value-added tax or consumption tax where applicable, and terminal discharge are outside the FOB quote. Domestic rack prices, by contrast, are formed at the truck loading flange of a terminal or at a refinery siding after these charges are included. A 10,000-metric-tonne vessel parcel discharged at a coastal storage terminal does not automatically become a 25-tonne road tanker price; terminal throughput fees, shore tank retention, quality testing, and local loading charges are added before the domestic truck quote is executable. Published data for some local terminal uplift components is limited because operators commonly recover these costs through throughput contracts rather than transparent spot assessments.

The Incoterms 2020 transfer boundary and bulk terminal economics

An FOB price is not a delivered price. In a typical MTBE cargo trade, the seller’s obligation terminates on the vessel at the loading port. The buyer takes title to a parcel that may require coalescing, salt-drying, or methanol adjustment after transport. MTBE is hygroscopic enough that shore tank water content can increase during humid coastal discharge unless tanks are nitrogen blanketed. Domestic grade management often requires draining water bottom using automatic water draw-off systems and confirming water content below 0.1 wt% by ASTM D6304. These actions are terminal-level tasks absent from the FOB quote. A domestic rack buyer faces a different quality assurance chain: terminal operator quality verification, contract-specific retain sample retention for 30–90 days, and possible methanol adjustment before gasoline blending. The domestic price therefore includes not only the molecule but also the terminal operator’s cost to hold and condition inventory.

Two MTBE parcels can both meet commercial specifications but not be economically identical when one is an export cargo and the other is a domestic rack lot. Export MTBE contracts often specify MTBE purity of 98.0–99.5 wt%, methanol content below 1.0 wt%, water below 0.1 wt%, and C4 hydrocarbon impurities such as isobutene, tert-butanol, and diisobutylene limited by contract. The same analytical method ASTM D5441 may be used, but the sampling point differs: marine cargo samples are drawn from shore tanks or vessel tanks before sailing, while domestic samples are drawn from terminal storage or truck loading lines. Differences in storage duration can shift methanol distribution between the ether and free methanol phases. A spread calculated between FOB and domestic quotes without comparing the exact specification range therefore compares two different quality positions. Published data for this precise comparison is limited because contract clauses and local standards vary by importer and blending season.

When a vessel flange price is compared with an ex-tank truck quote, basis and logistics dominate the spread

The numerical difference between an FOB cargo quote and a domestic ex-tank quote is not a clean arbitrage. The spread is basis risk generated by vessel scheduling, terminal tank availability, barge freight, rail freight, trucking, demurrage, and import timing. A cargo arriving at a coastal terminal can face 10–20 days of discharge and terminal storage before domestic truck uplift, depending on berth availability and tank lineup. Domestic quotes may reflect a different pricing timestamp than the FOB cargo assessment; FOB assessments are typically end-of-day or weekly cargo indications, while domestic rack prices can reset daily or after public holidays. Currency conversion between USD and CNY introduces foreign-exchange noise unless both series are normalized to the same time and currency. The appropriate comparison is an import parity formula: domestic parity equals FOB price plus ocean freight plus insurance plus import duty plus VAT plus destination terminal uplift plus local delivery. Without that cost stack, the two published numbers cannot be compared.

Assessment timing also invalidates direct comparison. FOB cargo quotes are often end-of-week or end-of-day indications based on bid-offer ranges for cargoes loading 2–6 weeks ahead. Domestic rack prices may be set at a fixed time each day and apply to truck loading within 24 hours. The FOB series is therefore forward-looking relative to the vessel laycan, while the domestic series is spot or near-spot. A price change in the upstream methanol or isobutylene market can affect the two series at different speeds because the cargo series is negotiated before the vessel loads, while the domestic rack series responds to terminal inventory and prompt truck demand. Published data for this specific configuration is limited; the lag structure is not stable across trading houses.

Tax treatment further separates the two series. An FOB cargo quote is generally pre-duty and pre-value-added-tax, whereas a domestic rack quote may be quoted either tax-inclusive or tax-exclusive depending on local commercial practice. In jurisdictions where MTBE is used as a gasoline blendstock, excise or fuel tax liabilities may attach at the terminal gate or at the refinery blending point rather than at the import vessel. The domestic series can therefore embed taxes, oil product consumption fees, or terminal safety levies that do not appear in the FOB quote. Comparing the two without stripping out indirect taxes reconstructs an artificial gross margin. Published data for this specific configuration is limited where tax authorities do not publish terminal-level tax incidence. The only valid comparison uses the same invoice basis and delivery point.

Quantifying methanol, water, and sulfur drift across different MTBE sourcing channels

MTBE is not a single-component stream in commercial trade. The principal impurities are methanol, tert-butanol, water, C4 hydrocarbons, and sulfur. Methanol partitions between the ether and the water bottom; water contact during storage can extract methanol and shift the remaining liquid composition. During long-distance marine transport, a cargo containing 0.3 wt% methanol at load port may arrive with a different routine assay at discharge if vessel tanks are not fully inerted. That compositional drift affects the domestic rack price because a blender purchasing MTBE for gasoline may need to control methanol content to avoid phase separation or vapor pressure penalties. Vapor pressure is measured by ASTM D5191 or ASTM D323 for petroleum products; neat MTBE displays a Reid vapor pressure near 55 kPa at 37.8 °C. Therefore, a domestic buyer may pay for a grade with lower methanol than an export cargo; the price series embed different quality-adjusted values.

The oxygen content of neat MTBE is 18.2 wt%, but commercial grades with lower purity contain less oxygen and more C4 or methanol. Gasoline blenders using MTBE for octane and oxygen credit therefore need an accurate assay before blending. A cargo of 5,000 tonnes with 0.5 wt% methanol carries 25 tonnes of methanol. That methanol can increase the blend’s vapor pressure or contribute to water affinity in ethanol-containing gasoline. The domestic rack price may be lower or higher per tonne after normalizing for oxygen content. Therefore, the FOB-to-domestic spread cannot be calculated without oxygen balance and vapor pressure data. This is why quality-adjusted comparisons require ASTM D4814 gasoline specification tests or EN 228 in the European market.

Price reporting agencies issue FOB MTBE assessments for Rotterdam, the U.S. Gulf, and Singapore as bulk waterborne cargo indications. Domestic price series in China are often reported as ex-tank Shandong, East China, or South China in CNY per metric tonne. The FOB U.S. Gulf assessment may not be directly comparable to a Shandong domestic quote because the two locations face different feedstock positions, freight, and demand windows. The U.S. Gulf MTBE price reflects refinery and dehydrogenation economics in the United States, while a Chinese domestic quote reflects methanol import cost, steam cracker C4 availability, and local gasoline blending demand. Ocean freight and insurance alone can alter parity by the current vessel-specific freight rate, which varies with route, parcel size, and bunker fuel cost. Published data for this specific configuration is limited because freight is negotiated vessel by vessel rather than posted as a single transparent adder.

Operational boundaries also differ by supply channel. Marine cargo MTBE is stored in large shore tanks with floating roofs or fixed roofs, typically under nitrogen blanketing to reduce oxygen absorption and peroxide formation. MTBE flash point is -28 °C closed cup, lower explosive limit 1.6 vol%, and upper explosive limit 8.4 vol%. Terminal operators maintain storage below 30 °C and use equipment grounding to suppress static ignition. The domestic truck rack is designed for fast loading through bottom loading arms with vapor recovery; pump speeds and loading rates are limited to avoid static accumulation. MTBE is incompatible with strong oxidizers and may attack neoprene and nitrile rubber seals; terminal loading systems commonly use fluoropolymer-lined hoses and PTFE gaskets. These handling costs, fire protection systems, and vapor recovery compliance are incorporated into the domestic rack price but not into the FOB cargo quote. A direct price comparison that ignores terminal fire protection and vapour recovery capital costs overstates the true arbitrage between the two series.