59
utilization of the active surface. To overcome the limitations of high-pressure drop
due to the utilization of smaller particles, ring-shaped or polylobe particles are used
in residue HDT units to provide high surface and improved accessibility of feed
molecules into the interior of the catalyst with reduced pressure drop. A chestnutbur-type catalyst with a specific pore structure design was reported to be beneficial
to increase the accessibility of feed molecules to the catalyst interiors [63].
The HDS and HDM reactivity of molecules and diffusion limitations depend on
the size of the resid molecules [64]. Ancheyta et al. [65] explained various aspects
of heavy petroleum feed hydroprocessing, including catalysts, in a brief tutorial.
Takahashi et al. [66] prepared a HDM catalyst with low activity and used a combination of HDM and HDS catalysts with medium-pore Al 2 O 3 as a support material
for the HDT of atmospheric residue under deep HDS conditions to study the influence of chemical composition on the life of the HDM catalyst. Their study suggested that use of low temperature in the guard bed reactor resulted in lower coke
deposition and improved catalyst life.
For residue hydroprocessing, especially for HDM, large-pore supports such as
alumina are required due to the large molecules present in the residue. Stanislaus
et al. [67] prepared a large-pore HDM catalyst using Al 2 O 3 as a support and studied
the pore enlargement mechanism through changes in the alumina phase during
hydrothermal treatment of γ-alumina with and without additives. They used different additives such as phosphorous, fluorine, phenol, and acetic acid. The reason for
pore enlargement was attributed to the formation and growth of boehmite into large
crystallites due to rehydration of γ- Al 2 O 3 . Evaluation of a wide-pore NiMo/γ-Al 2 O 3
catalyst showed higher activity for HDM and asphaltenes conversion during vacuum residue hydrotreating. Also, the use of wide-pore catalysts resulted in the uniform distribution of the deposited metals within the catalyst pellet compared to that
of a conventional HDM catalyst. Kressmann et al. [68] and Rana et al. [69] reviewed
the advances in heavy oil upgradation processes and catalysts.
8 Commercial HDT/HDS Catalysts
There are several commercial catalysts available in the market for the HDT/HDS of
petroleum fractions, starting from naphtha to heavy residue. However, the catalyst
market is predominantly captured by selective major catalyst manufacturing companies with a proven track record. Improved catalysts are being continuously developed and deployed by these companies based on improvements in catalyst
preparation methods, addition of modifiers, improvements in supports, etc. Most of
the new-generation commercial hydrotreating catalysts are made of CoMo or NiMo
type supported on alumina with application for deep HDS and aromatic hydrogenation of petroleum fractions. Some catalyst suppliers also provide trimetallic catalysts of NiCoMo or NiMoW type either supported on alumina or as an unsupported
bulk metal catalyst (e.g., Nebula catalyst supplied by Albemarle). In certain applications where high aromatic hydrogenation activity is required in a clean sulfur-free
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part II—Catalyst…
utilization of the active surface. To overcome the limitations of high-pressure drop
due to the utilization of smaller particles, ring-shaped or polylobe particles are used
in residue HDT units to provide high surface and improved accessibility of feed
molecules into the interior of the catalyst with reduced pressure drop. A chestnutbur-type catalyst with a specific pore structure design was reported to be beneficial
to increase the accessibility of feed molecules to the catalyst interiors [63].
The HDS and HDM reactivity of molecules and diffusion limitations depend on
the size of the resid molecules [64]. Ancheyta et al. [65] explained various aspects
of heavy petroleum feed hydroprocessing, including catalysts, in a brief tutorial.
Takahashi et al. [66] prepared a HDM catalyst with low activity and used a combination of HDM and HDS catalysts with medium-pore Al 2 O 3 as a support material
for the HDT of atmospheric residue under deep HDS conditions to study the influence of chemical composition on the life of the HDM catalyst. Their study suggested that use of low temperature in the guard bed reactor resulted in lower coke
deposition and improved catalyst life.
For residue hydroprocessing, especially for HDM, large-pore supports such as
alumina are required due to the large molecules present in the residue. Stanislaus
et al. [67] prepared a large-pore HDM catalyst using Al 2 O 3 as a support and studied
the pore enlargement mechanism through changes in the alumina phase during
hydrothermal treatment of γ-alumina with and without additives. They used different additives such as phosphorous, fluorine, phenol, and acetic acid. The reason for
pore enlargement was attributed to the formation and growth of boehmite into large
crystallites due to rehydration of γ- Al 2 O 3 . Evaluation of a wide-pore NiMo/γ-Al 2 O 3
catalyst showed higher activity for HDM and asphaltenes conversion during vacuum residue hydrotreating. Also, the use of wide-pore catalysts resulted in the uniform distribution of the deposited metals within the catalyst pellet compared to that
of a conventional HDM catalyst. Kressmann et al. [68] and Rana et al. [69] reviewed
the advances in heavy oil upgradation processes and catalysts.
8 Commercial HDT/HDS Catalysts
There are several commercial catalysts available in the market for the HDT/HDS of
petroleum fractions, starting from naphtha to heavy residue. However, the catalyst
market is predominantly captured by selective major catalyst manufacturing companies with a proven track record. Improved catalysts are being continuously developed and deployed by these companies based on improvements in catalyst
preparation methods, addition of modifiers, improvements in supports, etc. Most of
the new-generation commercial hydrotreating catalysts are made of CoMo or NiMo
type supported on alumina with application for deep HDS and aromatic hydrogenation of petroleum fractions. Some catalyst suppliers also provide trimetallic catalysts of NiCoMo or NiMoW type either supported on alumina or as an unsupported
bulk metal catalyst (e.g., Nebula catalyst supplied by Albemarle). In certain applications where high aromatic hydrogenation activity is required in a clean sulfur-free
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part II—Catalyst…