A cobalt-doped silica (Co-SiO2) layer was successfully synthesized in a sol-gel process as the mesoporous layer overlaid in three-, six-, and ten-step coating on a mullite support. The microporous layer was coated over the mesoporous layer in six steps by adopting the sol-gel method. The membranes were applied in pervaporation experiments to dehydrate dimethyl amino ethyl azide (DMAZ) containing 5 wt % water. In dehydration tests, the membrane permeate flux decreased and its separation factor increased. During the first initial hours, it reached a steady state and subsequently remained constant.