Thermal Properties of Cobalt and Molybdenum Containing Citrate Systems

Citrate complexes of transition metals, namely cobalt and molybdenum, used as active components in the synthesis of catalytic systems supported on alumina for hydrotreatment of heavy oil fractions have been studied. Cobalt nitrate hexahydrate and polyoxomolybdate (molybdenum blue) obtained by mechanical activation of molybdenum disulphide (MoS2) powder were used as initial compounds. Thermogravimetric analysis of the samples was carried out during their heating from 25 to 750 & DEG;C at a rate of 15 & DEG;C/min in air. Thermogravimetric analysis shows that the order in which the active components are introduced significantly affects the thermal stability of the sample. Despite the general similarity of the profiles, a shift of the temperature range of citrate complex decomposition is observed, depending on the order of active components introduction. Presumably, this may be due to the different degrees of Mo and Co availability for the formation of compounds with citrate ligands. It is shown that the most thermally stable system is the one in which the Co-containing component and citric acid are introduced first, and then the alcohol solution of molybdenum blue; the least stable system is the reverse one, in which the alcohol solution of molybdenum blue is introduced first, then citric acid and the Co-containing component are added.