Porous Materials and Membranes

Abstract

The sol-gel process has been recognised as a very attractive, simple and versatile way for the preparation of catalysts, adsorbents and inorganic membranes [1, 2]. The two conventional routes, colloidal or polymeric, usually described in sol-gel chemistry, have been now widely used to prepare membranes which consist of thin meso (2 nm < pores < 50 nm) or microporous (pores < 2 nm) solgel layers coated on macroporous (pores > 50 nm) supports as shown in figure 1. Sol formulation, coating from formulated sols, and membrane layer consolidation by drying and firing are the three main steps involved in this method. Several coating methods can be used depending on the geometry of the support. Supports for ceramic membranes consist of macroporous materials (carbon, metal or ceramic) produced under different shapes. Flat supports are used at the laboratory scale for the filtration of small quantities of fluids. Tubular, multichannel, and honeycomb extruded pieces are preferred in industrial plants treating larger quantities of fluids.