MTBE is the most widely produced oxygenate. Its raw materials are isobutylene and methanol. An important reason for the widespread use of MTBE is feedstock flexibility. MTBE can be made inside the refinery, using petroleum-derived raw materials, or it can be produced externally, using natural gas feedstocks, thereby ensuring ready availability and reducing dependence on crude oil for the production of automotive fuels.

Isobutylene can be obtained from:
1. steam cracker operation
2. fluid catalytic cracker (FCC) operation
3. butane dehydrogenation
4. dehydration of tertiary butyl alcohol

1. Steam cracker

Steam cracker operations produce isobutylene cost-effectively, but availability is limited. Only a small percentage of the cracker feed is converted into a C4 fraction, the main products being ethylene and propylene. Most of the contained butadiene is extracted and the remaining raffinate-1 is an important source of isobutylene. The premium uses for isobutylene are isobutyl rubber and polyisobutylenes, but it is also an intermediate for a wide range of specialty chemicals. The remainder is mainly used as MTBE feedstock.

More recent technologies convert other C4 components into isobutylene. Notable are the partial hydrogenation of butadiene and the skeletal isomerisation of normal butylenes.

2. FCC

FCC off gases are another source of isobutylene. With the continued requirement for upgrading heavy refinery fractions, more isobutylene is becoming available from this source and a logical use for this stream is an onsite MTBE unit. In Europe there are about fourteen such refinery MTBE units.

3. Butane dehydrogenation

The dehydrogenation route is very capital intensive. Normal-butane needs to be isomerised into isobutane, which is then dehydrogenated into isobutylene. The capital investment for a grassroots 700 kilotonnes/year unit is about 500 million dollars. Most of the current dehydrogenation units are built in areas where infrastructure is already available or in places where raw materials are available at low costs, e.g. the U.S. Gulf Coast, Saudi Arabia, Canada, Malaysia.

4. TBA

Tertiary butyl alcohol (TBA) is produced as a co-product of propylene oxide in dedicated plants. TBA is dehydrated into isobutylene to produce MTBE. It can also be sold directly as an octane-enhancing component for gasoline. Dehydration of TBA is a very cost-effective method of producing MTBE in large quantities.

Production capacity

Commercial production of MTBE started in Europe in 1973 and in the US in 1979. Total worldwide production capacity in 1998 was 23.5 million tonnes and the actual production was 18 million tonnes. The estimated annual production of MTBE in the EU today is 3 million tonnes.

The distribution of the production capacity for MTBE (and other ether oxygenates) in Europe is shown in the table below. There are more than 50 production plants for ether oxygenates in Europe, the majority of which produce MTBE. The production capacity of the plants ranges from 15,000 tonnes to over 600,000 tonnes per annum and the output of the plants is either used within the company producing the chemical (captive) or is sold on the open market (merchant). 

MTBE & ETBE Production capacities Europe 2004:

Source: Lyondell

Demand

Over the past decade, worldwide demand for fuel ethers overall has grown rapidly. 

The world market can be approximated by using MTBE figures as the volume of ETBE and TAME combined is far less than MTBE. The MTBE market grew strongly in the 1990's. The 1999 consumption of 20,700 kt/a was about double that of 1992. However the US Energy Bill passed in July 2005 will cause a significant drop in US consumption, as it creates a new mandate for a national renewable fuel standard for ethanol-blending, whilst removing the 2% oxygen content. 

In Europe, the demand is today approximately equal to the production capacity, i.e. around 2.6 million tonnes. In the last few years Europe was a net exporter of MTBE (either as a straight component or blended into gasoline), but the implementation of stricter gasoline quality requirements has recently increased the demand for alternative high octane blending components. The consumption of MTBE is expected to remain fairly stable in Europe over the next few years.