The use of X-ray absorption spectroscopy for developing new-generation Co-Mo catalysts of hydrotreating of diesel fuel

Abstract

The immediate problem facing the Russian petroleum refining industry is to turn to the production of gasoline complying with European standards [1]. Nowadays, only 12 of the 27 large Russian oil refinery plants have mastered the production of low-sulfur diesel fuel containing less than 0.05% sulfur [2]. Almost all diesel fuel that meets Euro 2, Euro 3, and Euro 4 standards is produced with the use of foreign catalysts since domestic catalysts do not have the required activity level. In this context, Russian industry should proceed as soon as possible to produce new-generation heterogeneous catalysts in which all surface compounds are active centers of hydrorefining reactions. According to the basic principles of the preparation of such catalysts expounded in [3], active center precursors—bimetallic Co‐Mo compounds—should be obtained when preparing an impregnating solution and the structure of these compounds should remain unaltered during the genesis of catalysts. The existence of such a structure in an oxide precursor of hydrorefining catalysts will ensure the formation of highly active disperse sulfide particles during the sulfiding step. To purposefully use this approach, the state and structure of catalyst active component precursors should be thoroughly monitored at all stages of their preparation. The most suitable for this purpose is X-ray absorption spectroscopy, which makes it possible to identify the structure of compounds synthesized in solution and on the support surface during catalyst preparation [4]. In this paper, we report the results of the EXAFS and XANES study of the structure of bimetallic oxide precursors of the active phases of hydrorefining Co‐Mo catalysts. A bimetallic compound and allied catalyst were synthesized from the ammonium salt of the tetranuclear anion [Mo 4 (e 6 c 5 O 7 ) 2 O 11 ] 4– . Solutions and cata