Process for isolating tetrahydrofuran

A process which isolates tetrahydrofuran from a stream of tetrahydrofuran, alkanol and high boilers, by: (a) separating off a first stream of tetrahydrofuran and alkanol as azeotrope in a first distillation stage; (b) feeding part of the first stream into a reactor for esterifying maleic anhydride, giving a second stream of tetrahydrofuran and monoalkyl maleate; (c) separating the second stream into a third stream of monoalkyl maleate and a fourth stream of tetrahydrofuran in a second distillation stage; (d) feeding the fourth stream of tetrahydrofuran from the second distillation stage and the part of the first stream from (a) which is not fed to the reactor into a third distillation stage to obtain a product stream of tetrahydrofuran and a sixth stream of tetrahydrofuran and alkanol; (e) recirculating the sixth stream from the third distillation stage into the first distillation stage or the reactor in (b).