Preparation of propene

The present invention relates to a process for preparing propene by metathesis of olefins. The process comprises preparing propene bya) in a first reactor (R1), reacting 1-butene and 2-butene to give propene and 2-pentene in the presence of a metathesis catalyst comprising at least one compound of a metal of transition group VIb, VIIb, or VIII of the Periodic Table of elements,b) subsequently separating the propene, unreacted raffinate II, and 2-pentene formed in a) in a distillation column (D1),c) subsequently reacting the 2-pentene of b) with ethene to give propene and 1-butene in a reactor (R2) in the presence of a metathesis catalyst comprising at least one compound of a metal of transition group VIb, VIIb, or VIII of the Periodic Table of Elements,d) subsequently separating the propene and 1-butene formed in c),e) subsequently returning the 1-butene formed in d) to step a) andf) wherein unreacted raffinate II is taken off at the middle off take of column D1 in b) and partly returned to step a).