Methyl Tertiary Butyl Ether (MTBE) (CAS No. 1634-04-4)

Methyl tertiary butyl ether, commonly known as MTBE, is a volatile, oxygenated hydrocarbon ether widely utilized as a high-octane gasoline additive and extraction solvent. With the chemical formula C₅H₁₂O, it is a colorless, flammable liquid with a distinctive, mild ether-like odor. This compound enhances fuel performance by improving combustion efficiency and reducing emissions, while also serving as an effective medium for separating polar compounds in chemical processes. Its low water solubility and high blending stability make it a preferred choice for refining and laboratory applications.

CAS Number: 1634-04-4 Molecular Weight: 88.15 g/mol Synonyms: tert-Butyl methyl ether, Methyl tert-butyl ether, 2-Methoxy-2-methylpropane

Key Properties

Methyl tertiary butyl ether offers consistent physical and chemical characteristics that support its role in fuel and solvent applications. The table below details primary specifications:

Property Value/Description
Appearance Colorless liquid
Purity ≥99.0% (GC)
Density (20°C) 0.740 g/cm³
Boiling Point 55-56°C
Melting Point -108.6°C
Flash Point -33°C (closed cup)
Refractive Index (20°C) 1.369
Solubility in Water 42 g/L at 20°C (sparingly soluble)
Vapor Pressure (20°C) 245 mmHg

These properties highlight MTBE’s volatility, low density, and compatibility with hydrocarbons, ensuring seamless integration in gasoline blends.

Applications and Uses

MTBE’s oxygen content and solvency properties enable its versatile deployment in energy and chemical sectors:

  • Fuel Additives: Blended into gasoline at 5-15% to boost octane rating, reduce engine knock, and lower carbon monoxide emissions in reformulated fuels.
  • Solvent in Extractions: Employed as a green alternative for liquid-liquid extractions in pharmaceutical and fine chemical purification, effectively isolating organics from aqueous phases.
  • Chemical Synthesis: Used as a reaction medium in Grignard reactions, alkylations, and polymerizations due to its aprotic nature and low boiling point for easy recovery.
  • Industrial Cleaning: Serves in degreasing formulations for electronics and precision parts, leveraging its non-corrosive profile and rapid evaporation.
  • Other Uses: Incorporated in biodiesel production as a co-solvent and in analytical chemistry for sample preparation in chromatography.

Its renewable production potential from bio-isobutylene positions MTBE as a bridge to sustainable fuel technologies.

Safety and Handling

Methyl tertiary butyl ether is highly flammable and volatile, with potential to form explosive vapors; it is mildly irritating to skin and eyes and poses environmental persistence risks in groundwater. Key guidelines include:

  • Storage: Store in cool, well-ventilated areas below 25°C in grounded, approved containers away from ignition sources and strong oxidizers. Use stainless steel or carbon steel tanks.
  • Handling: Wear PPE including flame-retardant gloves, goggles, and respirators. Avoid inhalation and use explosion-proof equipment; monitor for vapor accumulation.
  • Environmental Impact: Highly mobile in soil and water; implement spill containment and bioremediation to mitigate contamination risks.
  • Regulatory Compliance: UN 2398 (Class 3, PG IA); complies with REACH, TSCA, and EPA standards for oxygenates, with restrictions in some regions due to leaching concerns.

Consult the Safety Data Sheet (SDS) for exposure limits and spill response.

Frequently Asked Questions (FAQs)

What is the primary use of MTBE?

MTBE is mainly used as an octane booster and oxygenate in gasoline, enhancing engine performance and reducing harmful emissions in automotive fuels.

Is MTBE safe for fuel applications?

It is flammable and requires careful handling, but when blended properly, it improves fuel safety by minimizing knock; environmental monitoring is advised due to solubility issues.

What is the shelf life of MTBE?

Stored in sealed, dry conditions away from light and contaminants, MTBE remains stable for 1-2 years, with minimal degradation in purity.

Can MTBE be shipped internationally?

Yes, it is shipped worldwide under UN 2398 regulations, in tankers, drums, or isotanks for volumes from 200 L to bulk, with proper labeling for flammables.

How does MTBE compare to ethanol as a gasoline additive?

MTBE provides higher blending energy (less volume needed for oxygen) and better phase stability than ethanol, though ethanol is more renewable and less prone to groundwater persistence.

Is MTBE soluble in water?

MTBE has limited water solubility (42 g/L), allowing it to act as an effective extraction solvent while posing challenges for environmental cleanup due to slow dissolution.

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