Nanosieve saves energy in biofuel production

Petten - a new type of membrane, developed by researchers of ECN, the University of Twente and the University of Amsterdam, is highly resistant to exposure to high temperatures. The ‘molecular sieve’ is capable of ‘dehydrating’ solvents and biofuels, which makes it a promising energy-efficient alternative for existing separation techniques. The patented discovery was published in the Chemical Communications journal of this week, and received the qualification ‘hot article’.

After 18 months of continuous testing the new membranes are still effective, even after having been exposed to a temperature of 150 degrees Celsius. Existing ceramic and polymer membranes fail at a much earlier stage (at approximately 100 degrees Celsius), because they cannot withstand the combination of high temperatures and water. In the new type of membrane researchers intercept this by selecting a ‘hybrid’ material, which combines the best features of both ceramic and polymeric membranes. They use it to create a membrane with pores so small that they allow only the smallest molecules to pass through.

Fast flow
The performance of ceramic membranes made of silica gradually decreases because of their reaction with water and steam. Therefore, in the new membrane, parts of the ceramic bonds are replaced by organic bonds that retard corrosion of the membrane by water. The manufacturing process of the new hybrid membranes is significantly simpler then that of ceramic membranes. This is due to the increased flexibility of the membrane material, which increased the resistance against cracking. At the same time the material, like ceramic membranes, enables a fast flow which allows for the use of limited membrane surface area.

Dehydration
Hybrid membranes are suitable for dehydrating solvents and biofuels: a highly demanded application. The major advantage of membrane technology is the lower amount of energy required, compared to the currently used distillation process. Moreover, researchers foresee possibilities in the separation process of hydrogen gas from gas mixtures. Based on this property, the membrane type could make an important contribution to a sustainable energy supply. An additional application can be found in desalination of water, which is currently done using polymeric membranes. The main advantage of the new 'nanosieves' is that the same result can be achieved with a much smaller membrane.

In summary, the new membrane is suitable for highly energy-efficient molecular separation techniques and is applicable at temperatures up to 150 degrees Celsius. Therefore it can be applied in many different fields, e.g. for the production of biofuels.

The research is a result of an intensive cooperation between the group Anorganic Materials of the MESA+ Institute for Nanotechnology (UT), the unit Energy Efficiency in Industry (ECN), and the University of Amsterdam (UvA). The finding is patented worldwide.

The cylinder is equipped with the hybrid membrane, a layer of several tens of nanometers thick. Inlay: the composition of the hybrid layer with the pores. From the tube (left) only the water molecules that have been ‘sieved’ from the solution are flowing.

Editorial Note
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The article ‘Hybrid ceramic nanosieves: stabilizing nanopores with organic links’ by Hessel Castricum, Ashima Sah, Robert Kreiter, Dave Blank, Jaap Vente en André ten Elshof is published in Chemical Communications, published by the Royal Society of Chemistry in the UK.

For more information: Florentine de Maar, ECN press officer, email demaar@ecn.nl, tel. +31 224 564050.