Technology Type

Overview

Methyl tert-butyl ether (MTBE) is an oxygenated fuel additive produced industrially by reacting isobutylene with methanol in the presence of an acidic catalyst. The process is widely used in refineries and petrochemical plants to enhance gasoline octane and reduce emissions.

Feedstock Sources

• Isobutylene:
  Sourced from C4 hydrocarbon streams such as those from fluid catalytic cracking (FCC), steam crackers, or via isomerization and dehydrogenation of butanes

• Methanol:
  Typically produced from natural gas or coal.

Production Methods

There are two ways to produce MTBE:

• Conventional Process:
  Which is mainly a reactor and separate distillation column with conversion range 87 - 92%. 
   
• Reactive Distillation Process:
  A more recent method for the production of MTBE dating back to the 1980s when scientist Smith recorded the first patent for the production of MTBE through this method, The reactive distillation method exhibits a lot of features that make this process attractive and practical with a conversion reaching 99⁺%.

The present description is limited to the reactive distillation process.

Core Reaction

Figure 1 - Etherification Reaction

• Catalyst: Acidic ion-exchange resin (e.g., sulfonated polystyrene-divinylbenzene)
• Typical Conditions: 40–100°C, 1–10 bar

Main Process Configurations

1. Conventional Fixed-Bed Reactor Process

• Step 1: Isobutylene and methanol are mixed and fed into a fixed-bed reactor containing acidic resin catalyst.
• Step 2: The reaction mixture exits the reactor and is sent to a distillation column.
• Step 3: MTBE is separated as the bottom product; unreacted methanol and hydrocarbons are taken overhead for recycling or further processing.

2. Reactive Distillation Process

• Step 1: Reaction and separation are combined in a single distillation column packed with catalyst.
• Step 2: As the reactants flow through the column, isobutylene and methanol react to form MTBE, which is simultaneously separated from unreacted components by distillation.
• Advantages: Higher conversion efficiency (up to 99.2%), lower energy consumption, and reduced capital costs due to fewer equipment requirements.

Process Flow Summary

1. Feed Preparation:

• C₄ stream is treated to remove impurities (e.g., butadiene, water).
• Methanol is mixed in stoichiometric or slight excess proportion to isobutylene.

2. Etherification Reaction:

• Feed enters the reactor (fixed-bed or reactive distillation column).
• Isobutylene reacts with methanol to form MTBE.

3. Separation:

• Reactor effluent is sent to a distillation column.
• MTBE is recovered as the bottom product (≥95% purity).
• Overhead contains unreacted methanol and C4 hydrocarbons, which are recycled.

4. Methanol Recovery:

• Unreacted methanol is recovered from the overhead stream, purified, and recycled.

5. Product Purification:

• Final MTBE product is further purified if necessary and sent to storage or blending.

Process Efficiency and Yields

• Isobutylene Conversion: Up to 99% (especially with reactive distillation).
• MTBE Purity: Typically ≥95%
• Energy Consumption: Lower in reactive distillation processes compared to conventional setups.
• Operational Flexibility: Modern units are designed to handle feedstock fluctuations and maintain high yields.

Alternative Routes

• Via Butane:
  n-Butane is isomerized to isobutane, then dehydrogenated to isobutylene, which is finally etherified with methanol to produce MTBE.

• From Raffinate Streams:
  MTBE can also be produced from raffinate-1 or C₄ raffinate streams via etherification with methanol.

References

1. ANIL PARS Industrial Process Company > Portfolio Item > mtbe-production-honeywell-technology - Technical Evaluation of MTBE Production with 60KTY Capacity. (Accessd 21^st Jun 2025)
2. Procurement Resource > Production Cost Report Store > Methyl Ter-butyl Ether Production Cost Report. (Accessd 21^st Jun 2025)
3. Bernhard Schleppinghoff, Martin Becker, US Patent US4503265A, Priority Date 18^th Nov 1982, Process for the production of methyl tert.-butyl ether (MTBE) and of hydrocarbon raffinates substantially freed from i-butene and from methanol, Current Assignee: Erdoelchemie GmbH, Status: Expired.
4. INTRATEC > Reports > Previews > Report MTBE E411 Cost Analysis - MTBE Production from Butane - 2021. 
5. Alan Mawlud Amin, Aree Salah Tahir, 2015 - 2016, Production of Methyl Tertiary Butyl Ether (MTBE), Slideshare