Ozone storage in solid form by cyclodextrins

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A French research consortium (Institut National Polytechnique de Toulouse, Ecole D’ingenieurs de Purpan, Universite Paul Sabatier Toulouse, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique) elaborated a technology to store ozone gas in solid cyclodextrin matrix. The process served a basis of a recent PCT patent application [1].

Due to its strong oxidizing power, ozone is currently used for many applications, such as oxidizing and disinfection. Ozone is a gas in ambient conditions which cannot be stored due to its chemical instability. Thus, this molecule must be produced as needed by an ozonator, a device also called an “ozone generator”, which produces an electrical discharge in a flow of oxygen (O2) and which creates the ozone molecule (O3). Ozone can also be produced by other processes involving plasma or UV light, in particular at the wavelength of 185 nm. Ozone molecule has a limited lifespan, in the order of about twenty minutes in water under ambient conditions. It cannot be stored for example in a bottle in the pure state or as a mixture. It should be noted that the risks of explosion are high when the mixture envisaged is a mixture of dioxygen at several dozen Bars. 

Amonst the tested cyclodextrins (alpha-, beta-, gamma-CD, HPBCD, SBECD, BCD-polymer), HPBCD proved to be the most potent ozone gas storing host as approximately 1% guest content could be achieved within the complex (clathrate). This means that the solid cyclodextrin host is able to capture 100-1000 times higher concentration than water. The obtained ozone-HPBCD complex showed significant antibacterial and antifungal efficacy since the guest gas molecule was released upon contact with aqueous environment. The stability of the solid HPBCD complex is moderate at room tempreature (each day 20% ozone loss was observed) which could be overcome by storing at refrigerated conditions.

The international search report of the application is favorable for the applicants. The cloest prior art of the invention is an earlier patent application of Oxytec LLC [2] proposing a method for reducing contamination in water or soil, by injecting an aqueous solution of an ozone complex (clathrate) containing cyclodextrin – without isolating any solid complex.

[1] Method for preparing a solid material for storing ozone, the material and the uses thereof. PCT patent application WO2020148497

[2] Chemical oxidation method and compounds. US patent application 2018/0178263

credits: ozone by Hamish from the Noun Project

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