Russian scientists from the Institute of Catalysis SB RAS Federal Research Center have developed an improved method for producing zeolite crystals, which are widely used in the petrochemical industry. The researchers have modernized the vapor-phase crystallization method, in which the formation of zeolite crystals occurs under the influence of water vapor. This has made it possible to achieve a complete yield of the target product and significantly reduce the volume of toxic wastewater that is usually generated during production.
Zeolites are microporous materials with a clear structure, which are required for catalysis and adsorption processes. In oil refining, they form part of the catalysts used in oil purification and the production of various useful fractions.
Traditional synthesis methods for producing zeolite nanocrystals, such as hydrothermal treatment, require considerable resources: large volumes of water, prolonged centrifugation and expensive molding additives (templates). This makes the process energy-intensive, difficult to scale up and environmentally risky due to the formation of toxic wastewater.
The Russian researchers have proposed an improved version of vapor-phase crystallization that eliminates these drawbacks. Although the method itself has been known since the 1990s, the scientists have now added a stage involving the solid-phase mixing of reagents. The resulting gel, which contains sources of silicon, aluminum, template and water, was treated with water vapor in an autoclave without coming into direct contact with liquid. This approach allowed the researchers to increase the yield of the final product to 100%, whereas conventional methods only produce about 50%.
According to Alina Bragina, junior researcher at the Department of Unconventional Catalytic Processes, the development of these technologies is vital to closing the technological gap between Russian manufacturers and their foreign competitors. Currently, the minimum size of zeolite crystals in Russian samples stands at about 1 micrometer versus just 300–400 nanometers in foreign-made crystals.
The scientists will continue to optimize the technology at the next stage: they are exploring the possibility of synthesizing the ZSM-5 zeolite without using a template, and also plan to scale up the process and test the obtained materials in catalytic hydroisomerization and hydrocracking reactions.
