Microfiber, a new room for engineering solutions

Microfiber catalysts are structures that use the fibers of various materials, in particular, glass-fiber, as a carrier. Such structures show high activity and thermal resistance in various industrial processes as compared with other types. At Ruscatalysis-2021 Congress the leading researcher of Boreskov Institute of Catalysis, Dr. Andrey Zagoruiko spoke about what microfiber catalysts are developed in the Institute, how they are used, and what their prospects are.

Where the new chemical technologies come from

According to Andrey Zagoruiko, there are three drivers of the introduction of new chemical technologies. The first one is chemistry itself and new chemical reactions, but practically no new reactions can be discovered now. The second driver is the catalytic technologies and developments, when new structures are created. And the third one is engineering, i.e. creation of new catalytic reactors and new approaches to the processes.

“The basic approaches concern the factors that occur in a catalytic process, besides the reaction itself. A significant part of their efforts the scientists direct at the intensification of heat-mass exchange. And one of the variants to improve the processes is to use new geometric types on the structuring of catalysts, which would provide the optimal operation of the active components in real conditions”, said Zagoruiko.

The microfiber catalysts can serve as an example of such structuring of the systems. Instead of traditional shapes, such as monoliths and granules, these catalysts engage microfibers of glass, polymers and minerals. Noble metals or oxides of transitional metals are used as the active components.

Properties and peculiarities of microfiber catalysts

The key characteristic of the microfiber systems is their flexibility.

“We compared different types of catalysts, and microfiber showed a much higher activity that the wire structures, although their geometry is similar. The thing is that we have the flexible catalyst that can easily change its shape under the flow”, explained Zagoruiko.

The most frequently used variant of such systems is the catalysts on glass-fiber carriers. The researchers in Boreskov Institute of Catalysis developed two classes of structures with active platinum. In the first case the highly dispersed metal particles are stabilized at the outside surface of the catalyst, and the highly dispersed clusters are stabilized in the volume. The second class is simpler in terms of synthesis, they contain only finely dispersed platinum particles at the outside surface of glass fiber.

“With the platinum content less than 0.1% we obtain high activity and good thermal resistance of such systems. They bear the temperatures up to 700-800°C”, noted the scientist.

Such catalysts show high activity, stability and selectivity in oxidation of organic and chloroorganic compounds as well as sulfur dioxide. The catalyst with palladium is highly selective in the reaction of selective hydration of acetylene, in which acetylene diffuse better in the glass volume to the active sites than ethylene, due to higher dipole moment.

The microfiber catalysts based on iron and vanadium oxides show an increase in activity without a drop in selectivity in the reaction of oxidation of hydrogen sulfide into sulfur. With using the system based on nickel oxide in pyrolysis of hydrocarbons the researchers managed to obtain strong hydrophobic nanofiber carbon material with the yield of up to 65 g per 1 g of nickel.

Moreover, the main advantage of the microfiber catalytic system, according to Zagoruiko, is their engineering properties, in particular, ultralow hydraulic resistance, high intensity of mass exchange, and the possibility to make revolutionary constructions of catalytic reactors based on the systems.

“Thank you, it stopped stinking”

The scientists of Boreskov Institute of Catalysis develop the microfiber catalysts since 1990s. This direction was started and advanced by Bair Balzhinimaev. Since then the products confirmed their efficiency in the industrial applications more than once.

In 2008 in Nizhnekamsk the first load of microfiber catalyst was launched in the industrial reactor of afterburning of waste gases of isoprene manufacturing. The material designed for oxidation of isoprene, CO, isobutylene, and formaldehyde at once showed conversion higher than 99%, and it stayed this high during four years. The catalyst loaded in 2012 is still in efficient operation.

According to Andrey Zagoruiko, not only the measurements of parameters proved the efficiency of the product. An expert from the plant came up to the scientists and thanked them: “At last it stopped stinking here, thank you!”

The platinum catalysts were used for oxidation of sulfur dioxide in oleum plant in Biysk. The system allowed obtaining sulfur trioxide in the amount up to 10 m³hour, which is enough for providing the efficient operation of electrofilters due to the improvement of electrophysical properties of ash in the smoke gases of the coal boiler of 300 MWatt. The activity of the catalyst after 900 hours of operation did not drop, in fact, it increased somewhat.

In 2016 the Moscow Metro put the systems of purification and cooling of the waste gases of diesel-generators with platinum microfiber catalysts. The level of correspondence of the purification to all necessary requirements of state standards, and the residual content of CO and hydrocarbons in the purified gases was found to be significantly lower than required by the strictest global standards.

Andrey Zagoruiko summarized: the microfiber catalysts are promising for oxidation of sulfur dioxide and hydrogen sulfur, conditioning of the smoke gases of coal heat-and-power stations, utilization of organic and chloroorganic compounds, selective hydration of acetylenes and selective catalytic reduction of nitrogen oxides, environmentally friendly fuel burning, and many other catalytic processes.