Reactor membranes for used in oxidation reactions of hydrocarbons involving oxygen comprising a selective oxidation catalyst on a mixed conducting, oxide ion selective ceramic membrane of the composition (Sr1-xCax)1-yAyMn1-zBzO3-delta, whereA is Ba, Pb, Na, K, Y, an element of the lanthanide group or a combination thereof,B is Mg, Al, Ga, In, Sn, an element of the 3d or 4d period or a combination thereof,x is from 0.2 to 0.8,y is from 0 to 0.4,z is from 0 to 0.6, anddelta is a number, dependent on x, y and z, that renders the composition charge neutral.