Catalytic wet air oxidation of phenol in the presence of catalysts based on highly dispersed Ru supported on carbon nanotubes

The large volumes of organic pollutants formed by various industrial plants are very dangerous for the environment and human health. Phenol and its derivatives are particularly harmful substances. An important problem in the field of phenol utilization is the impossibility of PhOH conversion by traditional biotechnologies due to phenol's high toxicity with respect to microorganisms. This makes necessary to develop a new, efficient technology for processing ofphenol pollutants. Catalytic wet air oxidation is proposed as a method of utilization ofphenols. Both soluble (based on salts and complexes of transition metals) and solid (for example, highly dispersed platinum group metals supported on inert carbon substrates) catalysts are proposed for wet air oxidation of organic substrates, but solid catalytic systems are more promising than soluble ones due to easy regeneration and separation from the reaction medium. The purpose of this work was the preparation of catalysts based on ruthenium na-noparticles supported on carbon nanotubes modified by nitrogen and testing of the catalysts prepared in the wet air oxidation of organic pollutants. The work is a logical development of our research aimed at creating methods for the environmentally friendly disposal of organic pollutants in the presence of highly dispersed ruthenium catalysts deposited on various types of carbon carriers (graphite-like material, sibunite, and carbon nanofibers). Bamboo-like carbon nanotubes doped with nitrogen (N-MCNT) with a modifying additive content of 0, 2, 3 and 6 wt. % were synthesized. N-MCNT supports were prepared by catalytic decomposition of the ethylene-ammonia mixture in the presence of the 62Fe-8Ni-30AhO3 catalyst, and 3 wt. % of Ru nanoparticles were precipitated onto the prepared supports. The catalysts of 3%Ru/N-MCNT and their supports were investigated by a number of physico-chemical methods, namely TEM, nitrogen adsorption, XPS, and ACP-ICP. The composition of the catalysts was confirmed, the size of the Ru nanoparticles was found to be 1.4-1.9 nm, and no change in the structure of N-MCNTs occurred during the metal deposition. Precipitation of Ru did not lead to a significant change in the textural characteristics of the supports. The size of the metal nanoparticles was inversely proportional to the nitrogen content, i.e., nitrogen promoted the stabilization of small nanoparticles. An XPS study showed that 3% of Ru/N-MCNTs also contains atoms of Fe (up to 2 wt. %), which are the remains of the 62Fe-8Ni-30AhO3 catalyst that was not removed during washing. Developed 3 %Ru /N-MCNT catalysts and their N-MCNT supports were tested in the wet air oxydation of phenol used as an example organic pollutant at 160°C. Three percent Ru/N-MCNT catalysts was found to be highly effective in the utilization of phenol. In the presence of the catalytic systems created, 100% conversion ofphenol was achieved, with a residual balance of total organic carbon of 25-30% of the initial value. At the same time, the presence of iron impurities made it impossible to clearly show the impact of nitrogen modification of nanotubes on the catalytic activity of N-MCNT supports and, consequently, on the activity of 3% Ru/N-MCNT catalysts. Further efforts in this field of research will be concentrated, among other things, on improving the quality of the catalyst composition.

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