Scientists have developed innovative materials for separating propylene

Highly selective separation of molecules? A researcher from the Karlsruhe Institute of Technology (KIT) and partners jointly developed "porous liquids": nanoparticles, which can separate gas molecules of different sizes and put them in a solvent Fine distribution
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This is because these particles have pores, and only molecules of a certain size can penetrate their openings
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These porous liquids can be used directly or processed into membranes to effectively separate propylene from the gas mixture
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Propylene is a widely used plastic material
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This will replace the energy-intensive distillation method currently commonly used
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The research team reported the findings in "Nature Materials"
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? Propylene is one of the most important raw materials in the chemical industry
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The total annual consumption of propylene in the world is about 100 million tons .
Polypropylene produced with propylene as a raw material is a real "popular plastic", which is mainly used for packaging, but can also be used in industries such as construction and automobiles
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Propylene is mainly obtained by processing crude oil or natural gas
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In this process, it is separated from other gases by distillation and then purified
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? "In the technical literature, it is assumed that the cost of using membrane gas separation in petrochemistry is only one-fifth of the energy required for distillation
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Considering the large amount of propylene required, this means that the release of a large amount of greenhouse gas carbon dioxide can be avoided
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"Dr.
Alexander Knebel, head of the junior research team from the KIT Functional Interface Institute, said that he was still conducting research at Leibniz University in Hannover and Saudi Arabia until 2019
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? This chemist is a major contributor to a research project that, for the first time, increased the petrochemical industry's interest in the use of membranes to separate propylene
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Knebel’s partners are scientists from the Leibniz University of Hannover, the King Abdullah University of Technology and the German Institute of Technology
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? It is the first time to distribute a metal organic framework in a liquid? The researchers started from the solid material ZIF-67 (zeolite imidazole framework), whose atoms form a metal organic framework with a pore width of 0.
34 nm
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In doing so, they systematically modified the surface of ZIF-67 nanoparticles
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"This allows us to finely disperse metal organic frameworks in liquids such as cyclohexane, cyclooctane or mesitylene
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" Knebel said happily
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Scientists call the resulting dispersion a "porous liquid
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" ? For example, gaseous propylene takes longer than methane to pass through a column filled with porous liquid
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This is because propylene is retained in the pores of the nanoparticles, while the smaller methane molecules pass smoothly
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"We hope to use this dispersion to produce liquid separation membranes in the future
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" Knebel said
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? Improved separation membrane? Porous liquid can also be used to produce solid separation membranes with particularly superior performance
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The researchers used a plastic material and chemically modified ZIF-67 to make a film
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They successfully increased the proportion of modified ZIF-67 in the membrane to 47.
5% without making it unstable in mechanical properties
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When scientists pass an equal amount of mixed gas composed of propylene and propane through two membranes arranged in series, even if the size of the two gas molecules differs by no more than 0.
2 nanometers, propylene with a purity of at least 99.
9% can be obtained
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In addition to its separation efficiency, the amount of gas mixture that can pass in a certain period of time is of decisive significance for the actual use of this membrane
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Compared with the previous material, the flow rate of the new membrane is at least three times higher
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With the achieved separation value, Knebel is convinced that the petrochemical industry's first use of membranes to replace traditional distillation processes for gas separation will be rewarded
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? As many metal organic particles as possible can be evenly distributed in the plastic, and the pores in the nanoparticles will not be blocked by the solvent during the film making process, that is, remain in a hollow state, which is very important to the performance of the film
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Knebel explained: “We were able to achieve these two goals because we did not incorporate solid particles directly into the membrane, but through a porous liquid, even though it seemed like a detour
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”