ИСТИНА

The Fischer-Tropsch synthesis (FTS) is an industrial-scale process of synthesis gas (CO+H2) transformation into valuable chemicals, such as liquid fuels, lubricants, and light olefins. Cobalt- and iron-based catalysts can be used in this reaction, while cobalt ones are more stable and necessary for the production of long-chain hydrocarbons. To obtain high metal dispersion Co is usually supported on different oxides, such as silica, alumina, titania, zirconia, etc. At the same time, Co can react with such oxides forming inactive unreducible complex oxides, and the expensive noble metal structural promotors are required to prevent the formation of such complex oxides. Structural carbon materials have been intensively investigated in the past decade as alternative supports for FTS catalysts. Among such materials carbon nanotubes (CNTs) were found to be the most promising since they are thermally conductive, inert, stable, and can be easily modified. In addition, their production tends to grow from year to year. However, application of CNTs as an FTS support is limited because of their reaction with both hydrogen and air at high temperatures during annealing, reduction, and regeneration stages of the catalyst lifecycle. Thus, careful optimization of the preparation technique is required to preserve the support structure. The lack of information on the stability of carbon-based catalysts in the FTS hinders the integration of CNTs into the catalytic industry. This work is devoted to the study of the structure evolution of Co-based CNT-supported catalyst during its preparation, activation, long-term FTS tests at relevant conditions, and regeneration. We studied Co/CNT system by TEM, Raman spectroscopy, nitrogen adsorption, XPS, and thermal analysis after different stages of the catalyst lifecycle and revealed the sintering of Co particles and their waxing. But, interestingly, no strong deactivation was observed. Careful optimization of annealing and reduction of the catalyst precursor allowed preserving the support integrity.