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RESEARCH PRODUCT

Influence of Sodium on the Structure and HDS Activity of Co–Mo Catalysts Supported ON Silica and Aluminosilicate

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Abstract Structural changes and catalytic performances of hydrodesulfurization (HDS) Co–Mo catalysts, supported on amorphous aluminosilicate (ASA) and amorphous SiO 2 were investigated as a function of the amount of sodium ions added to the supports. The catalysts were prepared according to the incipient wet impregnation method using (NH 4 ) 6 Mo 7 O 24 as molybdenum precursor and CoCl 2 or Co(NO 3 ) 2 as cobalt precursor. Structural and morphological characterisations of the materials were performed with X-ray diffraction (XRD) and surface area measurements (BET). In the case of the ASA-supported catalysts, increasing the amount of sodium resulted in a gradual decrease of the catalyst surface areas and allowed formation of the β-CoMoO 4 phase. In the SiO 2 -supported catalysts, the β-CoMoO 4 phase formed in the absence of sodium. Moreover, addition of the alkali ions to the amorphous silica induced the phase transition to cristobalite resulting in a drastic decrease of the surface area. The catalytic behaviour of the materials was tested in the HDS of thiophene carried out in a continuous-flow system at atmospheric pressure, in a range of temperature between 603 K and 673 K. Unlike the silica-supported catalysts that were strongly inhibited by the addition of sodium, the ASA-supported catalysts exhibited a maximum of the HDS activity in correspondence with a specific amount of sodium. A correlation between structure and activity is proposed.