Hydrodesulfurization Activity of Co–Mo/Al₂O₃ Catalysts Prepared with Citric Acid: Post-treatment of Calcined Catalysts with High Mo Loading

Abstract

Co _ Mo/Al2O3 catalysts with high loading of Mo (20 wt% Mo) were prepared by the addition of citric acid (CA) using a simultaneous impregnation method or a post-treatment method. The catalyst activity was investigated for the hydrodesulfurization (HDS) of dibenzothiophene. TEM, Co K-edge XANES, NO adsorption capacity, and surface area measurements were conducted to characterize the catalysts. The catalysts were also investigated by the chemical vapor deposition technique using Co(CO)3NO to prepare Co/MoS2 and Co/Co _ MoS2 catalysts. Addition of citric acid by the post-treatment method to calcined (Co) _ Mo/Al2O3 oxide catalysts significantly enhanced the edge dispersion of MoS2 particles and the catalytic activity of Co/Mo/Al2O3 and Co _ Mo/Al2O3, whereas citric acid addition by the simultaneous impregnation method hardly affected the edge dispersion. The highest HDS activity was obtained with a CA/Mo mole ratio of 1.5-2 for the post-treatment catalysts. The posttreatment method may be applicable to the regeneration of deactivated HDS catalysts.

Analysis by Temperature-Programmed Reduction of the Catalytic System Ni-Mo-Pd/Al2o3

“…Transition metals have been widely studied due to their numerous applications, such as catalysts in a wide variety of industrial processes involving reduction atmosphere and the activation or conversion of hydrocarbons [1][2][3]. The catalytic performance is determined by the chemical structure of the catalyst and its properties [4].…”

Novel Molecular Approaches to the Structure–Activity Relationships and Unique Characterizations of Co–Mo Sulfide Hydrodesulfurization Catalysts for the Production of Ultraclean Fuels

“…175 The posttreatment was also very efficient to increase the activity for the HDS of DBT at 1.48 MPa. 176 Furthermore, it is suggested that the post-treatment method is applicable to the regeneration of deactivated HDS catalysts. 176 It was revealed with XAFS, Raman, and UVvis spectroscopic studies that CoCA and MoCA surface citrate complexes are formed by the post-treatment with citric acid at the expense of CoMoO 4 and polymolybdates.…”

“…176 Furthermore, it is suggested that the post-treatment method is applicable to the regeneration of deactivated HDS catalysts. 176 It was revealed with XAFS, Raman, and UVvis spectroscopic studies that CoCA and MoCA surface citrate complexes are formed by the post-treatment with citric acid at the expense of CoMoO 4 and polymolybdates. 174,175 In situ XAFS was used to disclose the sulfidation behaviors of Co and Mo in CoMo/B-Al 2 O 3 prepared by use of the post-treatment with citric acid for further characterizations of favorite nature of the catalyst preparation.…”