Mendeleev Russian University of Chemical Technology, Moscow, Russia
T. V. Konkova, Professor of the Department of Technologies of Inorganic Substances and Electrochemical Processes, Doctor of Technical Sciences, e-mail: kontat@list.ru
A. M. Gaydukova, Associate Professor of the Department of Technologies of Inorganic Substances and Electrochemical Processes, Candidate of Technical Sciences, e-mail: GaydukovaAM@yandex.ru
E. Yu. Liberman, Professor of the Department of Technologies of Inorganic Substances and Electrochemical Processes, Doctor of Technical Sciences, e-mail: el-liberman@mail.ru
A. D. Stoyanova, Associate Professor of the Department of Technologies of Inorganic Substances and Electrochemical Processes, Candidate of Technical Sciences, e-mail: stoyanova.a.d@mail.ru

Deactivated catalysts of diesel hydrotreating are regarded as hazardous wastes and cannot be buried in the ground; therefore, this results in a significant volume of hazardous wastes with a high content of non-ferrous metals. Developing methods of recovery and recycling of deactivated hydro treating catalysts is a currently relevant field of research in modern chemical technology. The article presents the results of studies on partial processing of deactivated Co – Mo/Al₂O₃ catalyst of diesel hydrotreating to apply it in processes of gas and waste water cleaning from toxic impurities. The authors studied nature of a leaching agent and a method of extracting molybdenum from the catalyst. A more efficient and selective leaching of molybdenum with a leaching degree of 90% or more requires treatment with a sodium carbonate solution after preliminary annealing of the deactivated catalyst to remove carbon deposits from the surface. Calcium molybdate will be separated from the leaching solution, which may be used as an alloying addition to steels. Extraction of molybdenum to the solution as sodium molybdate resulted in producing a Сo/Al₂O₃ material, whose composition was characterized by a method of energy-dispersive X-ray spectroscopy, and a porous structure — by a method of low-temperature nitrogen adsorption. Со/Al₂O₃ showed high activity and stability as a catalyst in an oxidative degradation of carmoisine azo dyes in a water solution (the dye bleeding rate was 95–97% in 30 minutes of contact), and catalytic activity in the medium-temperature degradation of carbon monoxide (temperature of 100% CO degradation was 475 ^oС). Thus, the material is promising for oxidative processes of ecological catalysis, namely degradation of toxic impurities in waste water and gas emissions.

Research was funded by the Ministry of Education and Science of the Russian Federation as part of state order No. FSSM-2023-0004.

1. Vogelaar B. M., Eijsbouts S., Bergwerff J. A., Heiszwolf J. J. Hydroprocessing catalyst deactivation in commercial practice. Catalysis Today. 2010. Vol. 154. pp. 256–263.
2. Arslanoglu H., Yaras A. Recovery of molybdenum, cobalt and nickel from spent hydrodesulphurization catalyst through oxidizing roast followed by sodium persulfate leaching. Sustainable Materials and Technologies. 2021. Vol. 28. 00286.
3. Zeng L., Cheng C. Y. A literature review of the recovery of molybdenum and vanadium from spent hydrodesulphurisation catalysts. Hydrometallurgy. 2009. Vol. 98. pp. 1–9.
4. Chen Y., Feng Q., Shao Y., Zhang G. et al. Investigations on the extraction of molybdenum and vanadium from ammonia leaching residue of spent catalyst. International Journal of Mineral Processing. 2006. Vol. 79. pp. 42–48.
5. Gao B., Jiang H., Zeng M., Peng M. et al. High-efficiency recycling method for Mo and Ni from spent catalyst via soda roasting and solvent extraction. Journal of Cleaner Production. 2022. Vol. 367. 132976.
6. Sutama D. K., Prasetya A., Petrus H., Astuti W. Recovery of cobalt and molybdenum from consumed catalyst using hydrochloric acid. IOP Conf. Series: Earth and Environmental Science. 2021. Vol. 882. 012004.
7. Arslanoglu H., Yaras A. Recovery of precious metals from spent Mo – Co – Ni/Al₂O₃ catalyst in organic acid medium: Process optimization and kinetic studies. Petroleum Science and Technology. 2019. Vol. 37. pp. 2081–2093.
8. Rezki A. S., Sumardi S., Astuti W., Bendiyasa I. M. et al. Molybdenum extraction from spent catalyst using citric acid: characteristic and kinetics study. IOP Conference Series: Earth and Environmental Science. 2021. Vol. 830. 012020.
9. Phann I., Tanaka Yu., Yamamoto Sae, Okibe N. Utilization of amino acid for selective leaching of critical metals from spent hydrodesulfurization catalyst. Frontiers in Chemistry. 2022. Vol. 10. 1011518.
10. Mishra D., Chaudhury G. R., Kim D. J., Ahn J. G. Recovery of metal values from spent petroleum catalyst using leaching-solvent extraction technique. Hydrometallurgy. 2010. Vol. 101. pp. 35–40.
11. Shalchian H., Ferella F., Birloaga I., Michelis I. D. et al. Recovery of molybdenum from leach solution using polyelectrolyte extraction. Hydrometallurgy. 2019. Vol. 190. 105167.
12. Pinto I. S. S., Soares H. MVM. Selective leaching of molybdenum from spent hydrodesulphurisation catalysts using ultrasound and microwave methods. Hydrometallurgy. 2012. Vol. 129. pp. 19–25.
13. Hamza M. F., Roux J. C., Guibal E. Metal valorization from the waste produced in the manufacturing of Co/Mo catalysts: leaching and selective precipitation. Journal of Material Cycles and Waste Management. 2019. Vol. 21. pp. 525–538.
14. Vemic M., Bordas F., Comte S., Guibaud G. et al. Recovery of molybdenum, nickel and cobalt by precipitation from the acidic leachate of a mineral sludge. Environmental Technology. 2016. Vol. 37. pp. 2231–2242.
15. Ali I., Konkova T., Belkina I., Galunin E. et al. Facile synthesis and characterization of advanced cobalt materials for degradative and adsorptive removal of carmoisine in water. International Journal of Environmental Science and Technology. 2021. Vol. 18. pp. 3221–3236.
16. Shukla P., Sun H., Wang S. et al. Nanosized Co₃O₄/SiO₂ for heterogeneous oxidation of phenolic contaminants in wastewater. Separation and Purification Technology. 2011. Vol. 77. pp. 230–236.
17. Alekhina M. B., Khabirova K. A., Konkova T. V., Prosvirin I. P. Y-type zeolites for the catalytic oxidative degradation of organic azo dyes in wastewater. Kinetics and Catalysis. 2017. Vol. 58. pp. 506–512.
18. Ivanin I. A., Krotova I. N., Udalova O. V., Zanaveskin K. L. Synergistic catalytic effect of cobalt and cerium in the preferential oxidation of carbon monoxide on modified Co/Ce/ZSM-5 zeolites. Kinetics and Catalysis. 2021. Vol. 62. pp. 798–811.
19. Grzybek G., Ciura K., Grybos J., Indyka P. et al. CO-PROX reaction over Co₃O₄/Al₂O₃ catalysts — impact of the spinel active phase faceting on the catalytic performance. The Journal of Physical Chemistry C. 2019. Vol. 123. pp. 20221–20232.
20. Kuzin E. N. Application of the method of atomic emission spectroscopy with microwave (magnetic) plasma in the processes of identifying the chemical composition of steelmaking waste. Chernye Metally. 2022. No. 10. pp. 79–82.
21. Kuzin E. N., Kruchinina N. E., Chernyshev P. I., Vizen N. S. Synthesis of titanium trichloride. Inorganic Materials. 2020. Vol. 56. pp. 507–511.
22. Konkova T. V., Prosvirin I. P., Alyokhina M. B., Skornikova S. A. Cobaltcontaining catalysts based on Al2O3 for oxidative degradation of organic dyes in the aqueous phase. Kinetics and Catalysis. 2015. Vol. 56. pp. 206–211.