Methyl tert-Butyl Ether (MTBE) Storage & Tank Compatibility

Storing Methyl tert-Butyl Ether (MTBE)? Start Here

Methyl tert-butyl ether (CAS 1634-04-4, C₅H₁₂O; also called MTBE, tert-butyl methyl ether, or 2-methoxy-2-methylpropane) is a colorless, highly volatile ether best known as a gasoline oxygenate and octane booster. It is highly flammable - GHS H225, NFPA Flammability 3 - with a flash point near -14 °F, well below ordinary ambient temperature, so it readily ignites and its heavier-than-air vapor travels along the floor to remote ignition sources.

Two properties dominate the design of any MTBE storage system: extreme flammability and environmental mobility. Unlike most fuel hydrocarbons, MTBE is appreciably water soluble and resists natural breakdown, so even small leaks migrate rapidly into groundwater and drinking-water supplies - the EPA classifies MTBE as a possible human carcinogen and has documented its detection in groundwater across many parts of the United States. These twin hazards make material of construction, secondary containment, and tank design safety- and compliance-critical decisions rather than cost decisions.

Why Polyethylene Tanks Are Not Suitable for MTBE

Rotomolded polyethylene and polypropylene tanks are excellent for water, brines, and many aqueous chemicals, but they are the wrong container for MTBE. As a small, nonpolar, volatile ether, MTBE permeates the polyethylene wall and swells the polymer matrix. The result is a softened, distorted wall, extraction of resin components into the product, loss of mechanical strength, and - most dangerous of all - migration of flammable MTBE vapor through the tank shell itself.

The hazard is compounded by MTBE's behavior in the environment: it is water soluble, mobile, and persistent, so any permeation or leak through a plastic wall does not simply evaporate - it can reach and contaminate groundwater at very low taste-and-odor thresholds. For these reasons we do not recommend any polyethylene or polypropylene tank for MTBE storage. The correct primary container is grounded and bonded carbon steel or stainless steel, engineered for flammable-liquid service and placed in secondary containment.

Need a tank built for MTBE? Our custom fabrication team builds grounded, code-compliant steel and stainless vessels for flammable fuel-oxygenate and solvent service. Explore UL-142 aboveground steel tanks, compare 304 vs. 316 stainless, and review our solvent recovery systems, or call our engineers at 866-418-1777.

Material compatibility at a glance

Store MTBE in grounded and bonded carbon steel or stainless steel (304 or 316) built to a recognized aboveground flammable-liquid standard such as UL-142. Polyethylene and polypropylene are not suitable - this volatile, nonpolar ether permeates and swells them and allows flammable-vapor migration through the wall. Combine the metal vessel with rigorous ignition-source control, vapor and spill containment, and secondary containment to protect groundwater.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

Extreme flammability. MTBE ignites from a small energy input; its vapor is heavier than air and flows to low points and distant ignition sources. Eliminate ignition sources, ground and bond all transfer equipment, use intrinsically safe or explosion-proof electrical gear in the storage area, use non-sparking tools, and provide adequate ventilation.

Peroxide and reactivity concerns. Like other ethers, MTBE can form peroxides on prolonged storage, though far less readily than diethyl ether or tetrahydrofuran; it reacts violently with strong oxidizers and is decomposed by strong acids. Manage these risks:

• Store cool, away from heat, sunlight, and ignition sources, in tightly closed, vapor-tight containers; minimize air headspace.
• Keep MTBE away from strong oxidizers and strong acids, which can cause violent reaction or decomposition.
• Date long-held inventory and test for peroxides before any distillation; do not evaporate ether stocks to dryness.

Health and environment. Vapor causes drowsiness, dizziness, and respiratory, eye, and skin irritation (H335, H336, H320, H315); MTBE is suspected of causing cancer (H351) and is an aspiration hazard if swallowed (H304). Because it is water soluble, mobile, and a documented groundwater contaminant, provide robust secondary containment, spill control, and vapor recovery to protect water resources.

Common questions

Can I store MTBE in a polyethylene (poly) tank?

No. MTBE is a volatile, nonpolar ether that permeates and swells polyethylene and polypropylene, softening the wall and allowing flammable vapor to migrate through the shell. Because MTBE is also a mobile groundwater contaminant, a permeating plastic wall is both a fire and an environmental risk. Poly tanks are not suitable - use grounded, bonded carbon steel or stainless steel built for flammable-liquid service.

What is the NFPA 704 rating for MTBE?

Per published Safety Data Sheets: Health 2, Flammability 3, Instability 0. CAMEO Chemicals marks the numeric NFPA values as data unavailable but describes MTBE as a highly flammable, peroxidizable compound. The Flammability 3 reflects its very low flash point of about -14 °F, which lets it ignite under nearly all ambient conditions.

Why is MTBE such a concern for groundwater?

Unlike most fuel hydrocarbons, MTBE is appreciably water soluble, moves rapidly through soil, and resists natural breakdown, so even small leaks can reach drinking-water aquifers and impart a strong taste and odor at very low concentrations. The EPA classifies MTBE as a possible human carcinogen and has detected it in groundwater across many parts of the United States, which is why secondary containment and leak-tight steel storage are essential.

What is the best material of construction for an MTBE tank?

Grounded and bonded carbon steel or stainless steel (304 or 316), built to a recognized aboveground flammable-liquid standard such as UL-142, placed in secondary containment, with vapor and ignition-source control. Stainless is preferred where product purity, cleanability, or corrosion margin matters.