The aim of the investigations is the development of new nanoporous ceramic membranes (pore size < 1 nm) for gas separation with a significantly higher chemical and hydrothermal resistance than the generally used silica membranes. In selecting mixed-oxide systems as well as suitable calcination conditions, the favoured microporous properties and the corrosion resistance should be obtained. An increase of the crystallization temperature is necessary to keep the nanoporosity up to higher temperatures. TiO2-ZrO2 mixed-oxide membranes with varying compositions were prepared via sol-get technique. At first tubular a-alumina supports (pore size 60nm) were coated with mixed-oxide (TiO2-ZrO2) intermediate layers using the colloidal sol-gel route. The formed UF-membranes are applied as supports for subsequent coating experiments. The nanoporous TiO2-ZrO2 mixed-oxide membranes were prepared via a polymeric sol-gel method. The composition of the membranes is already predefined during the preparation of the sols by using the corresponding quantities of the starting alkoxides. The influence of the chemical composition and sintering parameters onto crystalline phases, pore size and surface area of the systems was investigated. SEM, filtration and corrosion tests as well as structural investigations like O-17 NMR spectroscopy were carried out and discussed. (c) 2006 Elsevier B.V. All rights reserved.