Improving Efficiency

The key to increasing the efficiency of chemical processes is the use of membranes for product separation and product purification in downstream processing.

The driving force for membrane separation is not the temperature difference, but rather the gradient in the chemical or electrochemical potential, which, depending on the membrane process, is expressed as a gradient in pressure, partial pressure (or fugacity), electrical charge or substance concentration. Membrane processes are therefore significantly cheaper than thermal processes and, for example, use 80% less energy than distillation (Materials for Separation Technologies: Energy and Emission Reduction Opportunities, DOE report 4 May 2005).

In developed industrial countries, around 16% of energy consumption goes to material separation in chemistry, around half of which is achieved through distillation. Replacing distillation with membrane separation could save around 10% of total energy consumption (Nature 532 (2016) 435-437).

Membrane processes have already proven their advantages in the following applications (position paper from Dechema, VDI and DGMT, 2022):

• Separation of dissolved by-products and concentration of dissolved dyes, pigments and nanoparticulate products (NF, UF, MF)
• Recycling suspended and homogeneous catalysts (NF, UF, MF), usually closely combined with the reaction stage
• Separation of valuable materials from synthesis output and return to the synthesis stage (NF, UF, MF)
• Fractionation or residual monomer separation of polymers (UF)
• Cell separation, product concentration and product purification (UF, MF) as well as release of organic acids (bipolar ED) in the context of white biotechnology
• Hydrogen separation and recycling in ammonia synthesis, adjustment of synthesis gas compositions, CO₂ separation from methane and O₂ separation from air (GT)
• Wastewater concentrations (UO, NF, UF, MF) and concentrate treatment for wastewater-free production processes (zero liquid discharge (ZLD))
• Separation of organic vapors from waste and process gas streams to close material cycles

As energy prices increase and energy supply security decreases, interest in membrane processes is growing. The prerequisite is the availability of selective and stable membranes.

Institutes of the Fraunhofer Society are developing and testing new membranes. This applies to polymer membranes, mixed matrix membranes and inorganic membranes and ranges from liquid filtration (micro, ultra and nanofiltration, reverse osmosis and osmosis) to pervaporation, vapor permeation and gas separation. Membrane samples are available on an industrial scale. Processes with the new membranes are being developed and tested. Systems from laboratory to pilot scale are available for this purpose.