Pressure separates water-ethanol mixtures in zeolite pores (cover)
What is it about?
What happens to a liquid mixture when it is driven by pressure into an initially empty matrix? What if the matrix has an ordered pattern of molecular-sized pores? To answer this question, we injected an ethanol-water solution into one of such porous materials by using a diamond anvil cell. In this apparatus, the sample is compressed between the tips of two opposing diamonds and experiences huge pressures - about 10.000 times the normal atmospheric pressure. At these conditions, matter is subjected to forces which are comparable to internal atomic forces. New unexpected phenomena could show up. Now, let’s combine the use of high-pressures with the ordering effect of the empty pore matrix and see what happens to our mixture.
Why is it important?
How it is difficult to separate alcohol-water mixtures into their components, it is certainly well known. This is a problem also for sustainable processes - such as the production of biofuels. Thanks to high pressure and to the porous matrix, here we observed the separation of ethanol and water, leading to a beautiful pattern of clusters. The clusters – rows of ethanol dimers, and square water tetramers - occupy different regions of the host matrix and alternate like tiles forming a nice molecular mosaic – a “two-dimensional architecture” – inside the porous host. What’s really exciting is that the ordered pattern, created by high pressure, also remained stable by bringing the material back to atmospheric pressure. This means that using high pressures and porous hosts, we can obtain new materials, which are stable at normal conditions, and could be exploited in applications.
The following have contributed to this page: Gloria Tabacchi
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