Researchers at the Karlsruhe Institute of Technology (KIT) have developed "porous liquids". These porous liquids are nanoparticles, that are capable of separating gas molecules of different sizes from each other in a solvent. The particles have empty pores, allowing only molecules of a certain size to penetrate. The porous liquids can be used directly or processed into membranes efficiently to separate propene from gaseous mixtures. This could replace the energy-intensive distillation that has been the common procedure up to now. The team reports on the results in Nature Materials.
Propene, also known as propylene, is one of the most important raw materials for the chemical industry. Polypropylene is produced from propene and mainly used for packaging in the construction and automotive industries. Propene is primarily obtained by processing crude oil or natural gas. In this process, it is separated from other gases by distillation and then purified.
"In the technical literature, it is assumed that gas separation in petrochemistry using membranes would only cost one-fifth of the energy required for distillation. In view of the required high quantities of propene, this means that the release of huge amounts of the greenhouse gas CO2 can be avoided", says Dr. Alexander Knebel from the KIT Institute of Functional Interfaces. Knebel's collaborative partners were scientists from Leibniz Universität Hannover, King Abdullah University of Science and Technology and the Deutsches Institut für Kautschuktechnologie.
The researchers began their work with the solid material ZIF-67, zeolitic imidazole framework with 0.34 nanometer-wide pore openings. They were then able to systematically modify the surface of ZIF-67 nanoparticles.
"This enabled us to finely disperse a metal-organic framework in liquids such as cyclohexane, cyclooctane or mesitylene," says Knebel joyfully. Scientists call the resulting dispersion "porous liquid".