The purpose of this work is to enhance the performance of ceramic membranes with large porosity. This objective can be get both by a controlled reduction of pore diameter and/or, by a controlled modification of the surface of the upper layer of the ceramic membrane. A typical modification is a thin film deposition using hybrid material prepared from TiO2-SiO2 and silicone (poly-dimethyl-siloxane) using the sol-gel technique. The aging time of the initial solution is an important parameter for the elaboration of efficient silica membranes. The SEM observation of the deposited thin films shows a formation of rather homogeneous spheres of mean diameter of about 1 mum. These spheres are supporting a top thin 'silicone layer' when the aging time (t(ag)) is under 20 h but are without any top thin film when tag is higher than 24 h. Gas flows measurements were done using C3H8, N-2, He and CO2 gases. The best membranes in terms of permeability/selectivity are ones obtained with a t(ag) of about 48 h. The silicone-silica membrane was also tested with alkane gases and the efficiency for alkanes gas separation deduced.