In chemical industry, process streams are often a complex mixture of organic components and water. These mixtures are difficult to separate. In this research project, the purpose is to study pervaporation through zeolite membranes in separating water (dehydration) or alternatively organic components from water-containing process streams. Such streams are, for example, ethanol-water, isopropylalcohol (IPA)-water, butanol-water, acetic acid-water, and formic acid-water streams.
The industry has already shown interest in taking part in the research project. Pervaporation is a membrane separation process that involves a partial vaporization of liquid mixture through membrane whose downstream side is usually under vacuum. The permeated product called permeate is, then, condensed. The separation is based on the relative affinity of the components to the membrane. Consequently, membrane separation is not limited by vapour-liquid equilibrium, which is the main advantage compared to distillation based separation processes. Therefore, since different species in the feed stream have different affinities for the membrane and different diffusion rates through the membrane, even a component of low concentration can be highly enriched in the permeate. The driving force for mass transport in pervaporation is the chemical potential gradient across the membrane. The driving force for the process is generated by the low pressure on the permeate side of the membrane, through cooling and condensing permeate vapour. Zeolites membranes are one of the novel branches in inorganic membranes. Zeolites in general are microporous aluminosilicate materials that have uniform pore system due to their porous crystalline structure. First zeolite membranes were reported by Suzuki in 1986. Since then, progress has been made to improve the quality of zeolite membranes. Nowadays, zeolite membranes are mainly polycrystalline zeolite layers that are deposited on porous inorganic supports. Zeolite membranes possess several advantages compared to polymeric membranes such as lack of swelling, high thermal and chemical stability, and also zeolite membranes can provide high flux and selectivity. In the proposed project, the following zeolite membranes will be evaluated in pervaporation application: silicalite-1, ZSM-5, FAU and SOD membranes.
The project is a collaboration between Luleå University of Technology (LTU) and University of Oulu (UO) in a PhD Polis project.