NiMo/Alumina Hydrodesulphurization Catalyst Modified by Saccharose: Effect of Addition Stage of Organic Modifier

NiMo/Al2O3 catalysts, obtained by one-pot simultaneous impregnation, were modified by saccharose (SA, at Ni/SA = 1 mol ratio) addition. To address the influence of stage of saccharide impregnation on the hydrodesulphurization activity of sulphided catalysts, three different preparation methodologies were followed: (a) modification of already calcined (400 degrees C) NiMo/Al2O3 by SA impregnation; (b) SA deposition directly onto the alumina support, prior to Ni + Mo impregnation; (c) simultaneous Ni + Mo + SA deposition. Materials were characterized by N-2 physisorption, X-ray diffraction, infrared (IR) spectroscopy, UV-vis spectroscopy, and temperature-programmed reduction (TPR), and tested on liquid-phase dibenzothiophene (DBT) conversion (batch reactor, T = 320 degrees C, P =7.2MPa, n-hexadecane as solvent). The last methodology resulted in the catalyst with the highest DBT hydrodesulphurization (HDS) activity, on a pseudo-first order kinetic constant basis. A decreased proportion of tetrahedral Mo6+ species due to diminished interaction with the carrier, increased reducibility of octahedral Mo6+, and Ni complexation as well seemed to play determining roles in the trends of the activity observed. Simultaneous saccharose addition during NiMo phase impregnation required no additional preparation steps to efficiently integrate the organic modifier.