The transformations of a molecule containing two adjacent epoxide rings, 2,2'-bioxirane that is, were studied over various acidic aluminosilicates (HZSM-5, HY-FAU, AlMCM-41), for the first time, In the 373 - 473 K temperature range, in a pulse reactor, a ring-opening -ring-enlargment reaction producing furan only occured over the zeolites and it was the predominant reaction on AlMCM-41 as well. The driving force of this transformation route is water formation via elimination from 2,2'-bioxirane. Suprising is the lack of the mono- or dialdehyde, the would-be products of the cleavage of the sterically more hindered C - O bonds - an acid-catalysed reaction typical for alkyl-substituted oxiranes.