Mobil Process
An alternative path starts by conversion of the natural gas to syngas, conversion of the syngas to methanol which is subsequently polymerized into alkanes over a zeolite catalyst. It was developed by Mobil in early 1970s.
Methanol is made from methane (natural gas) in a series of three reactions:
- Steam reforming: CH4 + H2O → CO + 3 H2 ΔrH = +206 kJ mol-1
- Water shift reaction: CO + H2O → CO2 + H2 ΔrH = -41 kJ mol-1
- Synthesis: 2 H2 + CO → CH3OH ΔrH = -92 kJ mol-1
The methanol thus formed may be converted to gasoline by the Mobil process. First methanol is dehydrated to give dimethyl ether:
- 2 CH3OH → CH3OCH3 + H2O
This is then further dehydrated over a zeolite catalyst, ZSM-5, to give a gasoline with 80% (by weight based on the organics in the product stream) C5+ hydrocarbon products.
ZSM-5 is deactivated by a carbon build-up ("coking") over time in converting methanol to gasoline. The catalyst can be re-activated by burning off the coke in a stream of hot (500 °C (930 °F)) air; however, the number of re-activation cycles is limited.
Read more about this topic: Gas To Liquids
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