Large three-dimensional porous zeolite for water and gas purification

An international team of researchers succeeded in developing the most stable and porous zeolite known so far composed entirely of silica, which they named ZEO-3

[Translation by Dr. Moshe Nachmani]

This zeolite was created by the unprecedented compression of a one-dimensional silicate chain with a three-dimensional zeolite. This process does not change the composition of the silicate chain. Such zeolite could be applied for the removal and recovery of volatile organic compounds from a gas stream that can even contain water. The findings of this study have long been published in the prestigious scientific journal Science.

Zeolites are microporous silicates used in a variety of applications, such as catalysts, adsorbents and cation exchangers. Stable zeolites based on silica with increased porosity are sought-after materials that allow the adsorption and processing of large molecules, "however, they represent a challenge to our synthetic capabilities," explains Miguel Camblor, one of the authors of the article. In light of the fact that the size of the pores in zeolites is similar to that of small molecules, there is a limit to the size of the molecules that can be processed. This is why zeolites with larger pores have always been in high demand, especially those with pores in all three dimensions. "If there are pores in only one direction (length/width/height), even if they are large, the zeolite may clog easily, while if there are pores in all dimensions, it is more difficult," says the researcher.

After more than eighty years of extensive international research in this field, the research team succeeded in developing the most stable and porous zeolite known to date. "Until now, the zeolites with very large pores were not stable, since they were formed by germanium instead of silicon" says the researcher. Previous stable zeolites reached seven angstroms in size.

Last year, this research team published a previous paper about a novel zeolite composed of aluminum and large pores dubbed ZEO-1. Now, the same researchers have succeeded in developing a zeolite composed of only pure silica called ZEO-3. "In these two types of zeolites, the pores reached a size of more than ten angstroms," explains the researcher. The new zeolite has two unique properties: extremely large pores in all three directions, and the zeolite is produced with the help of calcination of a one-dimensional silicate chain within a compression process, that is, without changing the composition of the chain. "Such an approach has never led to the production of such zeolite," explains the researcher. "Such a two- and three-dimensional compression process was known in the field, but a one-dimensional chain has never been expanded into a three-dimensional structure," adds the researcher. In view of the fact that the zeolite consists of silicon only, it is able to adsorb large chemical substances. The zeolite can be applied for the removal and recovery of volatile organic compounds from a stream of gas. "For example, at a site where harmful volatile organic compounds are produced, this zeolite can be used to purify the area and not just to recycle the pollutants," says the researcher. As part of further research, this zeolite could also be used as a catalyst and to transfer drugs.

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