Targeted applications

On the basis of detailed analyses of chemical processes and assessments of the potential impact of alternative technologies we have selected a number of applications and membrane process options for our developments. The main selection criteria are the potential energy and cost savings of using membranes in these processes.

Pervaporation

The theme pervaporation covers a wide range of applications and includes the separation of water from organic solvents. The principle of this technology is selective evaporation of the minor compound of liquid mixture using a membrane. By doing so it is not necessary to evaporate the complete feed mixture but only the minor component. This drastically reduces the energy demand of these separations. This is especially true for azeotropic separations such as a water/ethanol mixture at 4/96 vol%.

For this purpose, ECN has developed Ceramic-Supported Polymer (CSP) membranes (J. Membr. Sci. 2008, 319, 126). and sol-gel membranes consisting of (modified) silica (Chem. Commun. 2004, 834), zirconia, and titania (J. Sol-Gel Sci. Techn. 2008, 48, 203). Currently, we focus on organic-inorganic hybrid silica’s, scaling up of the membranes and processes, and demonstrations. More information on these so-called HybSi® membranes can be found on www.HybSi.com.

Oxygen production

Large scale production of oxygen is currently done by cryogenic distillation. This is a very energy demanding process, but has the advantage of the simultaneous production of pure nitrogen. Large consumers of pure oxygen include the oxy-steel process, production of a variety of chemicals, and partial oxidation of methane. A strong increase in the use of high purity oxygen is expected in processes like gas-to-liquid, i.e. the production of liquid transportation fuels from natural gas through Fischer-Tropsch reaction, and low CO2 emission power plants. For these applications a membrane that operates at high temperatures (700-900 °C) will result in a significant increase in energy efficiency. Currently, we are concentrating our development on two key limiting factors:

• Stable and high performance supported tubular perovskite membranes,

• Functional sealing technology based on our proprietary technology.

Hydrogen production

Hydrogen is one of the most commonly used chemicals is in the (petro)chemical industry. It is used in cracking of crude-oil streams, in the production of ammonia, and in many other processes. Hydrogen also plays a key-role in many long term views on a secure, reliable, and clean energy supply. The largest gains in efficiency can be achieved by the application of so-called membrane reactors. These reactors, used for steam reforming, or for water gas shift reactions, provide higher efficiencies by integration of the catalytic reaction with a hydrogen selective membrane. ECN is currently focusing on noble metal alloys and reactor design for the steam reforming of natural gas. Multi-tube separation modules are available through www.HYSEP.com.

Natural gas upgrading

World wide, natural gas is abundantly available. Still winnable reserves are dwindling. Soon all remaining reserves will either be situated in remote locations, requiring liquefaction or gas to liquid (GTL) to make them transportable, or contain large amounts of CO₂ and H₂S, or even both. New technologies are required to make the utilization of these fields profitable. Currently, ECN is looking into breakthrough membrane principles to remove the impurities that are found in these gas fields.

Nanofiltration

Nanofiltration is a pressure driven permeation process in which the continuous phase (the solvent) passes the membrane, while other components are retained. Typical examples of nanofiltration are the separation of dyes from textile industry waste streams, removal of particles from fuel, and the recovery of homogeneous catalysts from product streams. The common feature of all of these processes is that species in the size range of macromolecules or nanoparticles are retained by the membrane. This means that the membrane should selectively block the permeance of species in the range of a few hundred to a few thousand Daltons. ECN concentrates on the development of inherently solvent resistant membrane materials for selected processes.