The present invention relates to composite ceramic membranes for use in chemical processes such as the separation of molecules, sometimes referred to as molecular sieving, preferably in combination with chemical conversion of molecules selected from a composition of different molecules, e.g. the selective partial or full oxidation. The composite membrane of the invention offers a combination of molecular sieving and oxygen transport that makes the composite membrane suitable for the selective oxidation of hydrocarbons from a feed comprising a mixture hydrocarbons. The composite membrane of the invention comprises a first layer containing an oxygen transporting material (OTM), e.g. perovskite, and, in association with the first layer, a second layer, containing a molecular sieve layer, e.g. a zeolite.