Characterization of the spent industrial catalyst Co-Mo/Al2O3 for fine hydrotreatment of diesel fuel

Abstract

Physicochemical properties of the spent industrial catalyst Co-Mo/Al₂O₃ for hydrotreatment of diesel fuel were studied. IR, TG, DTA and SEM techniques were used to establish that the catalyst surface is covered uniformly by a coke film; the soft coke consists predominantly of a mixture of slightly branched saturated hydrocarbons. Coke is oxidized at 190–375 °C (soft coke) and 375–525 °C (hard coke) and was removed quantitatively by calcining in air at 550 °C for 3 hours. XRD and SEM techniques, low temperature nitrogen adsorption, and chemical analysis were used to demonstrate considerable changes in the structure of the spent catalyst (phases Co₃O₄, CoCO₃ and CoSO₄·6H₂O); the Mo content decreased by 7.7 %; Fe, Na and V impurities were accumulated; sintering resulted in a decrease in the specific surface area and total pore volume by 31.5 and 28.4 %, respectively. The data obtained are necessary for developing methods for the catalyst utilization.