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

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

Methyl tert-butyl ether (MTBE), formula C₅H₁₂O, is a colorless, highly volatile ether best known as a gasoline-blending oxygenate and high-octane component. It is a low-molecular-weight ether that is only slightly soluble in water but fully miscible with hydrocarbons and most organic solvents, and it carries a sharp anesthetic-like odor. With a flash point near -28 C and a vapor pressure of roughly 245-250 mmHg at 25 C, MTBE forms ignitable vapor-air mixtures readily at ambient temperature, and its vapors are heavier than air. Because it behaves as an aggressive hydrocarbon solvent, MTBE permeates, swells and environmentally stress-cracks polyethylene and most common plastics. For that reason it is a metal-and-fluoropolymer chemical: stainless steel, carbon steel, PTFE and Viton handle it well, while HDPE and XLPE tanks do not.

Is MTBE Compatible With Polyethylene (HDPE / XLPE) Tanks?

No. MTBE is not compatible with polyethylene storage tanks, and we do not recommend HDPE or crosslinked (XLPE) tanks for it. Polyethylene resists aqueous salts, acids, bases, glycols and many water-based chemistries, but it has poor resistance to low-molecular-weight ethers, aromatics and fuel solvents. MTBE is exactly that class of chemical: a small, nonpolar ether and gasoline oxygenate that the polymer absorbs. The result is swelling, softening, weight gain, loss of yield strength and, critically, environmental stress cracking of the tank wall and fittings over time. Published polyethylene resistance charts rate the closely related aromatic and fuel solvents (xylene, benzene, gasoline) as limited-to-not-recommended for PE, and aromatic and ether hydrocarbons are known to plasticize polyethylene even without chemical degradation. For MTBE service, specify stainless steel (304/316) or grounded carbon steel with PTFE/PVDF or Viton (FKM) seals instead. If you must use a plastic, use a fluoropolymer-lined system, never a bare PE or PP tank.

Material compatibility at a glance

Store and handle MTBE in stainless steel (304/316) or properly grounded carbon steel with fluoropolymer (PTFE/PVDF) or Viton (FKM) seals. Polyethylene (HDPE/XLPE), polypropylene, PVC/CPVC, EPDM and nitrile are all unsuitable: this low-molecular-weight ether and gasoline oxygenate permeates and stress-cracks plastic tanks. Bond and ground all equipment, keep the system dry and oxygen-controlled to limit peroxide buildup, and confirm every wetted component against a current chemical-resistance chart and the supplier SDS before service.

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

• Extremely flammable: flash point about -28 C and high vapor pressure mean ignitable vapors form at room temperature. Eliminate ignition sources, bond and ground all containers, and use explosion-rated equipment.
• Vapors are heavier than air and can travel to a distant ignition source and flash back; provide low-level ventilation and store in a cool, well-ventilated area away from heat and oxidizers.
• Suspected carcinogen (H351) and a central-nervous-system depressant (H336): control vapor exposure, use proper respiratory protection, and avoid inhalation of mist or vapor.
• Aspiration hazard (H304): may be fatal if swallowed and enters the airways. Do not induce vomiting; seek medical attention immediately.
• Irritant to skin, eyes and respiratory tract (H315, H320, H335): wear chemical-resistant gloves (Viton/nitrile-laminate per glove-permeation data), splash goggles and protective clothing.
• Forms explosive organic peroxides on prolonged air contact: keep containers tightly closed and oxygen-limited, date inventory, and test for peroxides before distillation or evaporation.

Common questions

Can I store MTBE in a polyethylene (HDPE or XLPE) tank?

No. MTBE is a low-molecular-weight ether and gasoline oxygenate that permeates, swells and environmentally stress-cracks polyethylene. HDPE and XLPE tanks are rated unsuitable for it. Use stainless steel, grounded carbon steel, or a fluoropolymer-lined system instead.

What tank and seal materials are recommended for MTBE?

Stainless steel (304/316) and properly grounded carbon steel are the standard choices, with PTFE or PVDF and Viton (FKM) for gaskets and O-rings. Avoid EPDM, nitrile, PVC/CPVC and all bare polyolefin (PE/PP) components.

Why is MTBE such a fire hazard?

MTBE has a flash point of about -28 C and a vapor pressure near 245-250 mmHg at 25 C, so it gives off ignitable vapor at ordinary temperatures. Its vapors are heavier than air and can flash back from a remote ignition source, which is why it carries an NFPA flammability rating of 3 and signal word Danger.

Does MTBE form dangerous peroxides like other ethers?

Yes. Like most ethers, MTBE can slowly form explosive organic peroxides on prolonged contact with air. Keep containers tightly sealed and oxygen-limited, rotate inventory, and test for peroxides before any distillation or evaporation step. This peroxide tendency is reflected in the SDS instability rating.