METHOD FOR PRODUCING ISOBUTENE BY DECOMPOSITION OF METHYL-t-BUTYL ETHER IN VAPOR PHASE

PROBLEM TO BE SOLVED: To provide a method for producing isobutene by decomposition of methyl-t-butyl ether (MTBE) in a vapor phase. SOLUTION: The method for producing isobutene by decomposition of MTBE in a vapor phase has (a) a process for separating by distillation a stream containing MTBE composed of raw material MTBE (I) and a return stream VIII, in the operation, an MTBE-containing overhead stream (II) and a bottom stream (III) having a higher boiling point than that of MTBE are obtained, (b) a process for catalytically decomposing the overhead stream (II) obtained by the process (a) to give a decomposed product (IV), (c) a process for separating by distillation the obtained decomposed product (IV) into an overhead stream (V) containing >90 mass% isobutene and a bottom stream (VI) containing diisobutene, MTBE and >50% methanol contained in the decomposed product (IV), (d) a process for separating by distillation the obtained bottom stream under a condition to give methanol as a bottom product (VII) and >99% MTBE contained in an overhead product (VIII) and (e) a process for returning the overhead product (VIII) to the process (a). COPYRIGHT: (C)2008,JPO&INPIT