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Titel:
Hydrothermal stable pervaporation membranes. Development of Hybrid silica -hybSi
 
Auteur(s):
 
Gepubliceerd door: Publicatie datum:
ECN Efficiency & Infrastructure 6-2-2009
 
ECN publicatienummer: Publicatie type:
ECN-M--09-013 Conferentiebijdrage
 
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Gepresenteerd op: 12th Aachener Membran Kolloquium, Aachen, Germany, 29-30 oktober 2008.

Samenvatting:
Thermal separation processes like distillation consume a large amount of energy in the process industry. Replacing these processes by membrane pervaporation will lead to much lower energy consumption. The expected high chemical and thermal stability of inorganic membranes compared to polymer membranes has resulted in a growing research activity with the first aim of replacing polymer membranes with inorganic ones. The superior separation performance, i.e. selectivity and flux, of silica-based membranes in the dehydration of alcohols and solvents at elevated temperatures has raised the interest even further. The application depends on a reliable and good long-term performance. Unfortunately, information on this topic is still very limited. We have shown that silica and methylated silica membranes are not stable at temperatures above 100oC and the application window of state-of-the-art Me-SiO2 membranes for use in dehydration processes is limited to 95°C [1]. For methanol separation from organic solvents the Me-SiO2 membranes can be used at higher temperatures [2]. Hybrid silica materials are expected to have a much higher hydrothermal stability than (methylated) silica. The superior separation performance, i.e. selectivity and flux, of these hybrid membranes in the dehydration of alcohols and solvents at elevated temperatures has raised the interest [3]. High flux performance is required to decrease the membrane area needed and thereby the price to become competitive against the well know distillation technique. It is proven that the required water flux of at least 3 kg/m2h, for the dehydration of 5wt. % water in butanol as a representative standard application, can be achieved easily. The profitable application of the membranes depends on a reliable, stable long-term behaviour and the broad applicability especially at temperatures above 100°C. We will report on the development of organic/inorganic hybrid silica membranes with selectivities and fluxes, that are comparable with the silica based membranes in dehydration by pervaporation. Details of test results will be given in different dehydration applications up to 150°C including the dehydration of aprotic solvents. Further, results will be given on long term stability testing up to 150°C and up to 2 years of continuous operation in the dehydration of organic mixtures. The results show that a completely new class of hybrid materials is available that opens new markets for dehydration processes by pervaporation.


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