Method for the production of isobutene from commercial methyl tert-butyl ether

A process for preparing isobutene by acid-catalyzed dissociation of methyl tert-butyl ether (MTBE), said process comprising:

• fractionating a feed mixture comprising MTBE, C4- and C5-hydrocarbons, methanol, methyl sec-butyl ether, TBA and C4 oligomers to give
• a) a fraction a), comprising MTBE, MSBE, TBA and C4 oligomers. and
• b) a fraction b), comprising C4- and C5-hydrocarbons, MTBE and methanol,
• c) dissociating the MTBE present in the fraction a) into methanol and isobutene. and
• d) dissociating the dissociation product from c) which comprises unreacted MTBE, methanol, isobutene and low boilers and high boilers in a column into an isobutene-containing top product and a bottom product comprising the unreacted MTBE and the major part of the methanol from the dissociation, and recirculating the bottom product to the feed mixture.