Effects of Citric Acid Addition Method on the Activity of NiMo/γ-Al₂O₃ Catalysts in Simultaneous Hydrodesulfurization and Hydrodenitrogenation Reactions

Abstract

Two NiMo catalysts were prepared by different methods using citric acid to assess the effects of preparation method on dibenzothiophene hydrodesulfurization (HDS) and simultaneous HDS and hydrodenitrogenation: co-impregnation and post-treatment. Characterization of oxide catalysts was performed by nitrogen physisorption, X-ray diffraction, and temperature-programmed sulfidation, while sulfided samples were characterized by temperature-programmed reduction (TPR-S) and NO chemisorption. The catalytic evaluation for HDS reaction was performed in a three-phase reactor, with and without quinoline. The direct desulfurization is the preferred route for the HDS of dibenzothiophene. The post-treatment method was more efficient in achieving higher catalytic activity than co-impregnation. Furthermore, TPR-S and NO chemisorption results show an enhancement in the density of active sites on the catalyst prepared by post-treatment, being more hydrogenating than the one synthesized by co-impregnation. Although the catalyst prepared by post-treatment was more inhibited by quinoline, it remained more active than the one synthesized by co-impregnation.

Catalytic Hydrotreatment of Algal HTL Bio‐Oil over Phosphide, Nitride, and Sulfide Catalysts

“…[20] Moreover, these catalysts can also be boosted by adding another element, such as phosphorus [21,22] or a chelating agent (e. g., citric acid). [23,24] Biller et al [25] employed NiMo/Al 2 O 3 and CoMo/Al 2 O 3 sulfide catalysts to upgrade algal HTL bio-oils and reported that both catalysts showed similar activity during hydroprocessing. Later, Guo et al [26] compared commercial NiMo/Al 2 O 3 and NiW/Al 2 O 3 and concluded that NiMo performed better in removing oxygen and nitrogen.…”

“…These nanomaterials are usually supported on γ‐alumina and are promoted by nickel or cobalt [20] . Moreover, these catalysts can also be boosted by adding another element, such as phosphorus [21,22] or a chelating agent (e. g., citric acid) [23,24] …”

Alumina-Supported NiMo Hydrotreating Catalysts─Aspects of 3D Structure, Synthesis, and Activity

“…In the early 2000s, a modified workflow gained traction since it yielded catalysts of higher activity. In this workflow, organic additives, such as glycols, ethylenediaminetetraacetic acid (EDTA), or nitrilotriacetic acid (NTA), were added to the catalyst formulation. − Since these additives would decompose or oxidize under typical calcination conditions (400 °C in air), the calcination step was omitted. The effect of organic additives on catalytic performance has been explored in numerous studies, linking changes in structure, density, and stability of the active phase to performance. ,− These uncalcined catalyst types show a low tendency to form Mo–O–Al bonds, which advances the formation of type II catalysts.…”

Single-Pot Synthesis of NiMo-Al2O3 Catalyst for Quinoline Hydrodenitrogenation

“…Typically, the supported NiMo catalysts are prepared by conventional wetness impregnation. − The active metal species are simultaneously or sequentially loaded on premade supports. The improved dispersion of metal oxide at high metal loading resulting from strong metal–support interaction may decrease the sulfidation degree of metal species, which is unfavorable for the HDN reaction.…”