44
HDS catalysts. The NiMo/δ-Al 2 O 3 catalyst was found to exhibit higher HDS activity for model compounds compared to the NiMo/γ-Al 2 O 3 catalyst prepared using
the same mesoporous material. Also, the NiMo/δ-Al 2 O 3 catalyst showed higher
hydrogenation activity and removed sulfur predominantly by the HYD route. Higher
HDS activity and selectivity of the NiMo/δ-Al 2 O 3 catalyst prepared using mesoporous alumina were attributed to the balanced acidity, MSI, and suitable dispersion/
stacking of the active phases along with its favorable textural characteristics.
Braggio et al. [30] prepared two NiMo catalysts with different methods, coimpregnation and post-treatment using citric acid as a chelating agent to study the
effect of catalyst preparation method on the HDS and hydrogenation of DBT. In the
post-treatment method, impregnation of citric acid was done on the calcined CoMo
catalyst. HDS reactions were carried out in a three-phase reactor with and without
quinolone to understand the inhibition effects. DDS was found to be the favored
route for the HDS of the DBT molecule. The catalyst prepared using the posttreatment method was more effective for hydrotreating compared to the coimpregnation catalyst due to higher density of active sites on the catalyst and better
sulfidation behavior. The inhibition effect of quinolone was more for the catalyst
prepared by post-treatment, but this was offset by the higher activity of the catalyst
than that of the co-impregnation catalyst.
Singh et al. [31] reported the preparation of ultrasmall bimetallic NiMo oxidic
nanoclusters supported on alumina to carry out HDS reactions. Colloidal synthesis
was used to prepare the metal oxide nanoclusters with oleic acid and oleylamine as
ligands, and subsequently the nanoclusters were incorporated into the pores of alumina support. The ligands were removed later through calcination of the supported
catalysts followed by sulfidation. HDS activity of the nanocolloidal-based catalyst
was found to be better compared to the catalyst prepared using the conventional wet
impregnation method with DBT and diesel as feedstocks due to ultrasmall size of
the metal oxide nanoclusters on the support and better dispersion (Fig. 2).
Liu et al. [32] synthesized hexagonal, ordered, and highly dispersed mesoporous
NiMo-Al 2 O 3 catalysts with 20 wt% MoO 3 and varying NiO contents using a one-pot
evaporation-induced self-assembly (EISA) method with P123 as a structuredirecting agent and anhydrous ethanol as a solvent. High activity was observed
using the catalyst prepared with Ni/Mo molar ratio of 1:1 for the HDS of DBT due
to the formation of an easily reducible form of molybdate in the octahedral site and
better dispersion of MoS 2 nanoparticles. Also, the ordered mesoporous NiMo-Al 2 O 3
catalysts removed sulfur predominantly through the DDS route, as shown by the
formation of biphenyl in the product.
Dong et al. [33] synthesized hierarchically structured alumina hollow microspheres with high specific surface area and favorable pore volume and acidity via a
citric-acid-modulated hydrothermal method and prepared highly active NiMobased catalysts and tested for HDS of DBT.
Cheche et al. [34] utilized waste rubber tires to make activated carbon for subsequent preparation of NiMo-based bimetallic HDS catalysts through the wetness coimpregnation method subjecting to various calcination temperatures. The highest
activity for HDS of DBT was observed for the catalyst calcined at 300 °C due to
G. Valavarasu and B. Ramachandrarao
HDS catalysts. The NiMo/δ-Al 2 O 3 catalyst was found to exhibit higher HDS activity for model compounds compared to the NiMo/γ-Al 2 O 3 catalyst prepared using
the same mesoporous material. Also, the NiMo/δ-Al 2 O 3 catalyst showed higher
hydrogenation activity and removed sulfur predominantly by the HYD route. Higher
HDS activity and selectivity of the NiMo/δ-Al 2 O 3 catalyst prepared using mesoporous alumina were attributed to the balanced acidity, MSI, and suitable dispersion/
stacking of the active phases along with its favorable textural characteristics.
Braggio et al. [30] prepared two NiMo catalysts with different methods, coimpregnation and post-treatment using citric acid as a chelating agent to study the
effect of catalyst preparation method on the HDS and hydrogenation of DBT. In the
post-treatment method, impregnation of citric acid was done on the calcined CoMo
catalyst. HDS reactions were carried out in a three-phase reactor with and without
quinolone to understand the inhibition effects. DDS was found to be the favored
route for the HDS of the DBT molecule. The catalyst prepared using the posttreatment method was more effective for hydrotreating compared to the coimpregnation catalyst due to higher density of active sites on the catalyst and better
sulfidation behavior. The inhibition effect of quinolone was more for the catalyst
prepared by post-treatment, but this was offset by the higher activity of the catalyst
than that of the co-impregnation catalyst.
Singh et al. [31] reported the preparation of ultrasmall bimetallic NiMo oxidic
nanoclusters supported on alumina to carry out HDS reactions. Colloidal synthesis
was used to prepare the metal oxide nanoclusters with oleic acid and oleylamine as
ligands, and subsequently the nanoclusters were incorporated into the pores of alumina support. The ligands were removed later through calcination of the supported
catalysts followed by sulfidation. HDS activity of the nanocolloidal-based catalyst
was found to be better compared to the catalyst prepared using the conventional wet
impregnation method with DBT and diesel as feedstocks due to ultrasmall size of
the metal oxide nanoclusters on the support and better dispersion (Fig. 2).
Liu et al. [32] synthesized hexagonal, ordered, and highly dispersed mesoporous
NiMo-Al 2 O 3 catalysts with 20 wt% MoO 3 and varying NiO contents using a one-pot
evaporation-induced self-assembly (EISA) method with P123 as a structuredirecting agent and anhydrous ethanol as a solvent. High activity was observed
using the catalyst prepared with Ni/Mo molar ratio of 1:1 for the HDS of DBT due
to the formation of an easily reducible form of molybdate in the octahedral site and
better dispersion of MoS 2 nanoparticles. Also, the ordered mesoporous NiMo-Al 2 O 3
catalysts removed sulfur predominantly through the DDS route, as shown by the
formation of biphenyl in the product.
Dong et al. [33] synthesized hierarchically structured alumina hollow microspheres with high specific surface area and favorable pore volume and acidity via a
citric-acid-modulated hydrothermal method and prepared highly active NiMobased catalysts and tested for HDS of DBT.
Cheche et al. [34] utilized waste rubber tires to make activated carbon for subsequent preparation of NiMo-based bimetallic HDS catalysts through the wetness coimpregnation method subjecting to various calcination temperatures. The highest
activity for HDS of DBT was observed for the catalyst calcined at 300 °C due to
G. Valavarasu and B. Ramachandrarao