27
and metal phosphides). They also compared the RVA of HDN and HDS reactions
for mixed first-row transition metals with W supported on Al 2 O 3 versus Ni-Mo reference catalysts with RVA of 100 in VGO hydrotreating application. Based on their
study, the authors concluded that it would be difficult to replace the conventional
Co-Mo, Ni-Mo, and Ni-W catalysts for HDS/HDN applications based on the activity, selectivity, stability, and economics, and the status quo would continue for the
near future.
Song et al. [89] used a new and simple method to prepare bulk and supported
nickel phosphide (Ni 2 P) using thermal treatment of a solid mixture containing
Na(H 2 PO 3 ) 2 and NiCl 2 .6H 2 O in certain molar ratio as precursors. In this method,
bulk Ni 2 P was formed by heating the physical mixture of the precursors at
200–300 °C for 1 h in a nitrogen atmosphere. Nickel phosphide was formed by
decomposition of NaH 2 PO 3 to release phosphine and subsequent reduction of nickel
ions. The activity of supported Ni 2 P/SiO 2 catalysts for HDS of DBT was found to be
good at different temperatures.
Varakin et al. [90] synthesized unsupported molybdenum disulfide catalysts
(MoS 2 /Al 2 O 3 and MoS 2 /C/Al 2 O 3 ) and compared their HDS performance for DBT
with the catalysts prepared from ammonium tetrathiomolybdate with and without
structural agents. Bulk MoS 2 catalysts prepared by etching of the MoS 2 /Al 2 O 3
showed higher selectivity for the HDS of DBT, and sulfur was predominantly
removed through the hydrogenation pathway. The high HYD/DDS activity of the
bulk catalysts was attributed to the high ratio of HYD sites on spatial angles relative
to centers on the rim and edges due to the low slab length and minimal average
number of MoS 2 layers.
Li et al. [91] studied gasoline HDS with minimum olefin saturation using an
unsupported Co-Mo catalyst and compared the performance with the CoMo/γ- -
Al 2 O 3 catalyst. The HDS activity of the unsupported catalyst was reported to be
fourfold compared to the supported catalyst for model compounds and full range
FCC gasoline due to differences in MoS 2 slab morphologies such as curvature, slab
length, and stacking number. Curved MoS 2 structure was found to promote olefin
isomerization reaction without saturation resulting in improved octane rating.
Alhough increased slab length and higher stacking number of MoS 2 in the unsupported catalyst resulted in higher desulfurization selectivity, the effect of slab length
was predominant in influencing the HDS selectivity compared to the stacking number.
Xie et al. [93] showed improved activities for MoS 2 -Co 3 S 4 hollow polyhedrons
for the hydrogen evolution reaction and HDS compared to the pure MoS 2 , Co 3 S 4 and
MoS 2 -Co 3 S 4 nanoparticles prepared by conventional coprecipitation methods due to
the better morphology and synergy between Co 3 S 4 and MoS 2 . Synthesis of MoS 2 -
Co 3 S 4 hollow polyhedrons was reported by the vulcanization of Mo-doped ZIF-67.
Li et al. [92] synthesized Co-Mo sulfide with a hollow structure using a combination
of co-precipitation and low-temperature sulfurization in ethanol solution. Formation
of porous Co-Mo sub-microtubes was reported with high specific surface area, more
active sites, and active component exposure in order to obtain a higher degree of
HDS for DBT.
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part I: Nature…
and metal phosphides). They also compared the RVA of HDN and HDS reactions
for mixed first-row transition metals with W supported on Al 2 O 3 versus Ni-Mo reference catalysts with RVA of 100 in VGO hydrotreating application. Based on their
study, the authors concluded that it would be difficult to replace the conventional
Co-Mo, Ni-Mo, and Ni-W catalysts for HDS/HDN applications based on the activity, selectivity, stability, and economics, and the status quo would continue for the
near future.
Song et al. [89] used a new and simple method to prepare bulk and supported
nickel phosphide (Ni 2 P) using thermal treatment of a solid mixture containing
Na(H 2 PO 3 ) 2 and NiCl 2 .6H 2 O in certain molar ratio as precursors. In this method,
bulk Ni 2 P was formed by heating the physical mixture of the precursors at
200–300 °C for 1 h in a nitrogen atmosphere. Nickel phosphide was formed by
decomposition of NaH 2 PO 3 to release phosphine and subsequent reduction of nickel
ions. The activity of supported Ni 2 P/SiO 2 catalysts for HDS of DBT was found to be
good at different temperatures.
Varakin et al. [90] synthesized unsupported molybdenum disulfide catalysts
(MoS 2 /Al 2 O 3 and MoS 2 /C/Al 2 O 3 ) and compared their HDS performance for DBT
with the catalysts prepared from ammonium tetrathiomolybdate with and without
structural agents. Bulk MoS 2 catalysts prepared by etching of the MoS 2 /Al 2 O 3
showed higher selectivity for the HDS of DBT, and sulfur was predominantly
removed through the hydrogenation pathway. The high HYD/DDS activity of the
bulk catalysts was attributed to the high ratio of HYD sites on spatial angles relative
to centers on the rim and edges due to the low slab length and minimal average
number of MoS 2 layers.
Li et al. [91] studied gasoline HDS with minimum olefin saturation using an
unsupported Co-Mo catalyst and compared the performance with the CoMo/γ- -
Al 2 O 3 catalyst. The HDS activity of the unsupported catalyst was reported to be
fourfold compared to the supported catalyst for model compounds and full range
FCC gasoline due to differences in MoS 2 slab morphologies such as curvature, slab
length, and stacking number. Curved MoS 2 structure was found to promote olefin
isomerization reaction without saturation resulting in improved octane rating.
Alhough increased slab length and higher stacking number of MoS 2 in the unsupported catalyst resulted in higher desulfurization selectivity, the effect of slab length
was predominant in influencing the HDS selectivity compared to the stacking number.
Xie et al. [93] showed improved activities for MoS 2 -Co 3 S 4 hollow polyhedrons
for the hydrogen evolution reaction and HDS compared to the pure MoS 2 , Co 3 S 4 and
MoS 2 -Co 3 S 4 nanoparticles prepared by conventional coprecipitation methods due to
the better morphology and synergy between Co 3 S 4 and MoS 2 . Synthesis of MoS 2 -
Co 3 S 4 hollow polyhedrons was reported by the vulcanization of Mo-doped ZIF-67.
Li et al. [92] synthesized Co-Mo sulfide with a hollow structure using a combination
of co-precipitation and low-temperature sulfurization in ethanol solution. Formation
of porous Co-Mo sub-microtubes was reported with high specific surface area, more
active sites, and active component exposure in order to obtain a higher degree of
HDS for DBT.
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part I: Nature…