MTBE, methyl tertiary butyl ether, being an excellent octane enhancer, is made by liquid phase reaction of methanol with isobutylene in the presence of a cation exchange resin. The reaction is reversible and exothermic and carried out in the temperature range of 311-367 K.
The acidic cation exchange resin offers many advantages over other acid catalyst. The easy elimination of the reaction medium and the possible reutilization of ion exchange catalyst make them preferable to inorganic acids and bases. These resins are cross linked three-dimensional structures of polymeric substances obtained by sulphonation of a copolymer made of polystyrene and divinyl benzene. However, these resins are very sensitive to temperature rise and start losing their activity above 393 K.
The main raw materials for the production of MTBE are isobutylene and methanol. Isobutylene can be used as a pure component or in a mixture of C4 hydrocarbons obtained from ethylene plant steam crackers or refinery catalytic crackers. Isobutylene may also be obtained from propylene oxide manufacture via the Oxirane process.
Reactor System Used at Amoco
MTBE was formerly used mainly as an octane enhancer to replace the tetraethyl lead as a fuel component. Although MTBE still has octane-enhancing properties, its main use now is as an oxygenate in gasoline blending.
This is the main reaction, to produce MTBE worldwide:
Beside the main reaction the following side reactions can take place:
|1.- Isobutylene + water ==> t-butyl alcohol|
|2.- Methanol + Methanol ==> Dimethyl ether|
|3.- Isobutylene + Isobutylene ==> Diisobutylene|
"Liquid Phase synthesis of Methyl tert-Butyl Ether Catalyzed by Ion Exchange Resin"
Subramaniam C., Bhatia S.
Department of Chemical Engineering, Indian Institute of Technology, P.O. I.I.T., Kanpur 208016, India.>
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