Production of isobutene by decomposition of MTBE

The subject of the present invention is a process for the production of isobutene by the decomposition of MTBE, which comprises the following steps: a) MTBE synthesis; isobutene-containing hydrocarbon mixture (II) is added to one or more methanol-containing streams (VIII IX) and reacting with methanol (III) contained in the acid ion exchanger to obtain MTBE- and TBA-containing stream (IV), b) MTBE separation; from stream (IV) , Distilling off stream (V) containing MTBE and TBA, c) MTBE cracking; stream (V) is cracked in the gas phase using a heterogeneous catalyst to provide at least isobutene, methanol, MTBE and Obtaining a stream (VI) containing water and optionally TBA; d) isobutene separation; the stream (VI) is separated by distillation and more than 50% by weight each contained in the stream (VI). Obtaining a stream (VII) containing methanol, TBA and water, and a stream (XVII) containing isobutene; e) water separation; distilling water from stream (VII) to a proportion of less than 1% by weight. Separating and obtaining stream (VIII), f) return; returning methanol-containing stream (VIII) completely or partially to MTBE synthesis. Furthermore, the subject of the present invention is the following members: i) tube bundle, ii) tube plate, iii) deflection plate, iv) inner jacket, v) pressure-resistant outer jacket containing at least one inlet and outlet. vi) In a tube bundle device having a jacket space containing a liquid that emits or absorbs heat, the inner jacket is connected to the deflector plate and the tube plate attached over the length of the tube bundle with or without a gap In this case, the tube bundle device is characterized in that the liquid existing in the jacket space surrounds the inner jacket on both sides.