One would think that acceleration of chemical reactions and absorption of toxic substances are two different tasks. But both can be solved by a material created at the Scientific Center "Catalysis in Chemical Technology" of the Russian Chemico-Technological University named after D. Mendeleyev (Moscow)--the porous ceramic matrix is easily transformed both into a catalyst and a sorbent. The project "Directed Synthesis of Highly Porous and Highly Permeable Catalytic Systems of Cellular Structure for Processes of Catalytic Cleaning of Waste Gases of Chemical and Metallurgical Productions from CO, CH and NO_x" was realized within the framework of the Federal Target Program "Studies and Elaboration under priority directions of the development of scientific-technological complex of Russia in 2007-2013". Mikhail Petrov, a journalist, told about this work, which has perspectives of diverse application, on the pages of an electron edition "Science and Technologies of Russia-STRF.ru".

"The basis of the system proposed by us is a highly durable ceramic frame,--explains the project manager Vladimir Grunsky, Dr. Sc. (Tech.) and demonstrates samples of the materials--in appearance they look like rough stocky cylinders resembling a pumice-stone or a petrified coral sponge.--In order to get it, we take a foam polyurethane matrix and saturate it with slip--a suspension for getting of ceramic items. Then in complex thermal conditions we remove polymer and at the same time bake slip's hard phase. As a result the frame duplicates the porous structure of the matrix and

From polyurethane matrices. Ceramic frame duplicates the system of pores of these blanks.

becomes uninterrupted in gaseous and hard phase. In a word, all cells and cavities in it are running."

As ceramics scientists prefer corund--it is stable in any media (including acid and alkaline) and can endure high temperatures. That's why it is not easy to bake it. "Usually corund is baked under 1,700 °C, but we managed this under 1,500 °C. Though it was rather difficult.-- Prof. Grunsky recollects all difficulties connected with the search.--This is our know-how--due to connecting, reinforcing and other additives, crafty temperature modes we won 200 degrees."

But this was only beginning of our difficulties with corund. For efficient catalysis or sorbtion the material should have a big area of specific surface, while corund has only approximately 2 m²/g, i.e. practically zero as compared, for example, with active carbon (1,000 m²/g). Therefore, at the last stage of preparation of a ceramic frame, it is modified with various carbon materials. And, so, with the use of nanotubes the area of specific surface increases up to 600 m²/g.

"After such development of the surface we have only to determine priorities,--Prof. Grunsky concludes as a culmination of the project, where small unattractive cylinders of different colors try to find their place in the real world.--If we want to get a catalytic system, we add appropriate catalytic complexes into the ceramic matrix, and if we speak about filters-sorbents, we cover the frame surface with a sorbtion-active material. And here, by the way, we have very interesting proposals related to our work. Now imagine, 30 °C heat, a diesel locomotive going along the railway, suddenly a spark from its engine falls on dry grass and it blazes up. Our filters-neutralizers of exhaust gases are made to avert such situations-- they will catch soot with other toxic substances and simultaneously prevent inflammation. Recently we have signed a contract with Kolomensky Diesel-Construction Works (near Moscow) on industrial tests of this device."

The new approach proved its efficiency also in tests on diesels of KamAZ cars, and it is planned to carry out tests on the factory stand. At the same time the scientists are working to create sorbtion filters to catch radionuclides from processing of nuclear fuel.

The system proposed by specialists of the Russian Chemico-Technological University advantageously differs from the existing analogs by the fact that reactions in it are uninterrupted and reagents are not mixed with catalytic substances. On the basis of this system a great number of technological processes of the synthesis of substances can be simplified and, for example, exclude from them a stage of filtration. But, as it often happens, administrative difficulties hamper introduction of novelties into the technological process.

"Today the main problem is that enterprises are not sufficiently interested in new works,--Prof. Grunsky cannot conceal his anxiety.--Manufacturers prefer ready, though often obsolete, solutions from abroad. So, as long as there are no powerful engineering centers to promote perspective national know-how created in our country, all will remain as before."

M. Petrov, Two-Faced and Useful, Both Catalyst and Sorbent.--Electronic edition "Science and Technologies of Russia--STRF.ru", April 22, 2013

Illustrations from STRF.ru site

Prepared by Sergei MAKAROV