III International Conference

STRUCTURE FEATURES OF NANOCRYSTALLINE COBALT OXIDEREDUCTIONPP-II-18Bulavchenko O.A. 1 , Cherepanova, S.V. 2 , Tsybulya, S.V. 1, 21 Novosibirsk State University, Novosibirsk, Russia2 Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: isizy@catalysis.ruIn situ X-ray powder diffraction was used to characterize the structure of the Co catalystsupported on the γ-Al 2 O 3 and the model samples. We researched reduction process for thesupported and non-supported Co 3 O 4 . The two-stage reduction for the supported catalyst wasobserved. Co 3 O 4 was reduced to CoO and then to the metallic Co with fcc structure. On thecontrary the crystal phase of CoO wasn’t observed during the reduction of the non-supportedCo 3 O 4 sample which was reduced to the metallic Co with hcp structure in one step.The Fischer-Tropsch synthesis (FTS) is one of the processes producing synthetic liquidfuel and valued chemical compounds from syngas (i.e. mixture of CO and H 2 ). The supportedmetallic catalysts are widely used in FTS. The cobalt based catalysts are suited to producehigh yields of long alkanes in FTS [1]. Catalysts are activated by reduction of Co 3 O 4 inhydrogen. It is important to understand how the reduction conditions influence on thestructural parameters of catalyst.It is impossible to study structural parameters and phase composition of activated catalystby ex situ methods owing to reoxidation process which can take place in the air atmosphere.So the information concerning the phase composition and the crystallite size of the metallicparticles during the reduction was obtained by in situ X-ray diffraction (XRD). The XRDcamera-reactor [2] and D-500 Siemens diffractometer with CuKα-radiation were used.We have researched the supported and non-supported nanocrystalline Co 3 O 4 samples tocompare its behavior during reduction. The non-supported samples were prepared from cobaltcarbonate. Supported catalysts were prepared by the incipient wetness impregnation usingcobalt nitrate aqueous solution. The γ-Al 2 O 3 was used as the support.To carry the comparative analysis between the supported and non-supported samplescorrectly we have taken the samples with the same average size of the Co 3 O 4 crystallites(~100 Å). Therefore we did not use non-supported samples prepared from a cobalt nitratesince the average sizes of obtained Co 3 O 4 particles were essentially larger then in thesupported sample. The initial structures of the both types of the samples are similar accordingto the XRD structural analysis and contains vacancies in the cation positions. In situ X-ray195