The Mobil process
used by Methenex in New Zealand

At Motunui, Methanex New Zealand can produce 5,200 tonnes of crude methanol a day from natural gas.

Why is it called crude methanol?
The methanol, produced from synthesis gas, contains water (up to 18%), ethanol and higher alcohols, ketones, ethers.

5H₂ + CO + CO₂ ® 2CH₃OH + H₂O ^*

Despite the use of a Cu/Zn catalyst, other reactions do occur.

5H₂(g) + 2CO(g) ® C₂H₅OH(g) + 2H₂O

Even higher alcohols and some alkanes may be formed.
These by-products are removed by distillation and exchange columns.

* other sources give a different equation

2H₂(g) + CO(g) ® CH₃OH(g) 'Co or Zn/Cu catalyst

There must be many reactions within the converter.

Producing hydrocarbons from methanol
The crude methanol is transferred to the MTG( methanol to gasoline) plant.
In the conversion, a number of reactions take place.

First methanol is converted to dimethyl ether.

2CH₃OH(g) ® CH₃OCH₃(g) + H₂O(g)

The next reactions are only two of the many which follow.

2CH₃OCH₃(g) + 2CH₃OH(g) ® C₆H₁₂(g) + 4H₂O(g)

3CH₃OCH₃(g) ® C₆H₁₂(g) + 3H₂O(g)

About 80% of the resulting hydrocarbon mix is suitable for petrol production.

This petrol mixture contains:
Highly branched alkanes 53% (w/w)
Highly branched alkenes 12% (w/w)
Cycloalkanes 7% (w/w)
Aromatics 28% (w/w)

Among the aromatics is durene, a high melting point substituted benzene.

How is this compound removed from the fuel?
The molecule is rearranged to isodurene

How does all this take place?
The Mobil process depends on a zeolite catalyst.