31 ISSN 2070-0504, Catalysis in Industry, 2017, Vol. 9, No. 1, pp. 31–38. © Pleiades Publishing, Ltd., 2017. Original Russian Text © Ameer Abed Jaddoa, T.R. Bilalov, F.M. Gumerov, F.R. Gabitov, Z.I. Zaripov, R.S. Yarullin, A.A. Pimerzin, P.A. Nikul’shin, 2016, published in Kataliz v Promyshlennosti. Supercritical Fluid CO 2 -Extraction Regeneration of Nickel– Molybdenum Catalyst for Hydrotreatment Ameer Abed Jaddoa a, c , T. R. Bilalov a, *, F. M. Gumerov a , F. R. Gabitov a , Z. I. Zaripov a , R. S. Yarullin b , A. A. Pimerzin d , and P. A. Nikul’shin d a Kazan National Research Technological University, Kazan, Tatarstan, 420015 Russia b OAO Tatneftekhiminvest Holding, Kazan, Tatarstan, 420061 Russia c University of Technology, Baghdad, 10066 Iraq d Samara State Technical University, Samara, 443100 Russia *e-mail: t.bilalov@yandex.ru Received July 26, 2016 Abstract⎯Results from studying the supercritical fluid СО 2 -extraction regeneration of DN-3531 industrial nickel–molybdenum hydrotreatment catalyst in the temperature range of 323.15–383.15 K, at pressures of up to 30 MPa, and with modification of the basic extragent with such polar compounds as chloroform, metha- nol, ethanol, acetone, and dimethylsulfoxide (DMSO), are presented. The order of modifiers corresponds to the increase in the solubilizing ability of modified supercritical carbon dioxide (SC-СО 2 ) with respect to cat- alyst-deactivating deposits. With DMSO as the most efficient modifier, however, not only are deactivating compounds removed but nickel and molybdenum as well, considerably reducing the final activity of a regen- erated sample. During extraction regeneration, the content of coke in the catalyst is reduced by two-thirds, while the specific surface area and the pore volume grow. The activity of the deactivated catalyst in diben- zothiophene hydrodesulfurization (HDS) and naphthalene hydrogenation grows by several hundred per cent after one-time SC-CO 2 treatment and is 2.5 times higher than for a sample regenerated using the traditional oxidative method. Keywords: Ni–Mo catalyst, hydrotreatment, extraction regeneration, supercritical carbon dioxide, diben- zothiophene, naphthalene DOI: 10.1134/S2070050417010020 INTRODUCTION Supercritical fluid technologies (SCFT) based on the use of working media in sub- and supercritical fluid states are a promising and innovative field of science. Combining the advantages of the gaseous and liquid states of working media, supercritical fluids considerably intensify heat and mass transfer processes. With supercritical fluid media, there is no phase interface, surface tension, or capillary effect. This makes them highly able to penetrate into porous structures and opens up great possibili- ties in problems of heterogeneous catalyst synthesis and regeneration. In industry, heterogeneous catalysts are tradition- ally regenerated using air–nitrogen mixtures pumped through reactors at pressures of 0.24–0.26 MPa and temperatures of up to 870 K [1]. This process is energy-intensive and leads to the gradual sintering of a catalyst’s active phase particles, which in turn limits its service life and restored activity. The SC-CO 2 extraction process studied in this work could offer an alternative to this process. The characteristics of the traditional and supercritical fluid CO 2 -extraction processes are compared in Table 1 in the context of the heterogeneous catalyst regeneration problem. The advantages of the supercritical fluid extraction (SCFE) process are quite obvious, which is why the SC-СО 2 -extraction regeneration of heteroge- neous catalysts is attracting great interest from researchers [4–13] and has already been implemented in industry [14, 15]. The deep hydrotreatment of oil fractions for the production of ultrapure fuels with sulfur contents of less than 10 ppm is currently possible only with the use of highly efficient hydrodesulfurization (HDS) cata- lysts. Since the costs of purchasing new hydrotreat- ment catalysts are very high, the maximum restoration of the catalytic activity of waste catalysts during regen- eration and their reuse have become problems of great interest. The aim of this work is to study the possibility of regenerating industrial Ni–Mo hydrotreatment cat- alyst via SC-СО 2 treatment, and the effect of organic additives (cosolvents) on the efficiency of removing coke deposits. DOMESTIC CATALYSTS