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HDS, HDN, hydrocracking, HDM, etc. Catalyst activity is usually measured in
terms of the reaction temperature at which it produces products meeting the required
specifications for a given feed while all other process parameters are unchanged.
For a specific feedstock, a catalyst that gives the required product quality or conversions at lower operating temperature is the best ones in terms of activity. Selectivity
expresses the ability of the catalyst to favor the desired chemical transformations in
comparison with other reactions to produce selected products with specified properties. For example, FCC naphtha HDS requires a catalyst that needs to perform selective HDS with minimum saturation of olefins in order to retain octane number. The
stability of the catalyst is defined as a change in the activity or performance of the
catalyst with time-on-stream when the feedstock and process conditions are stable.
The catalyst stability is measured in terms of the cycle length. Catalyst stability or
life is affected by several factors such as the following:
• Presence of poisons in the feedstock such as metals.
• Inactivation by one or more of the products.
• Loss of a volatile agent from the catalyst.
• Loss of activity due to a change in the crystal phase.
Selection of hydrotreating catalysts is mostly based on the comparison between
required start-of-run (SOR) temperatures to achieve certain product quality in terms
of product sulfur or yields. Apart from catalyst activity and selectivity, catalyst stability is also an important factor to be considered during catalyst selection. A catalyst that performs well under SOR conditions may have poor stability and deactivate
faster than other catalysts that performed slightly less under those conditions. Based
on the initial activity, selectivity, and overall life, economic comparison needs to be
performed incorporating product value based on specific conversion and yields,
energy cost, cost of catalyst, etc., and a suitable catalyst needs to be selected using
economic considerations for those catalysts that meet the conversion or product
quality or product yield requirements.
7.1 Selection of Hydrotreating Catalysts for Gasoline
and Gas Oils
The choice of the catalyst depends on the specific process requirement such as
hydrodesulfurization, hydrodenitrogenation, aromatics hydrogenation, olefin saturation, and hydrocracking. Table 4 presents the selection of common catalysts for
different hydrotreating applications. In general, the Co-Mo catalyst is the best
choice for hydrodesulfurization of straight-run feedstock such as virgin naphtha,
kerosene, and gas oils. Although it is true that Co-Mo catalysts are well suited for
HDS of straight-run feeds, high-activity Ni-Mo catalysts also exhibit substantially
high activity for the HDS of petroleum fractions, but with higher hydrogen
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part II—Catalyst…
HDS, HDN, hydrocracking, HDM, etc. Catalyst activity is usually measured in
terms of the reaction temperature at which it produces products meeting the required
specifications for a given feed while all other process parameters are unchanged.
For a specific feedstock, a catalyst that gives the required product quality or conversions at lower operating temperature is the best ones in terms of activity. Selectivity
expresses the ability of the catalyst to favor the desired chemical transformations in
comparison with other reactions to produce selected products with specified properties. For example, FCC naphtha HDS requires a catalyst that needs to perform selective HDS with minimum saturation of olefins in order to retain octane number. The
stability of the catalyst is defined as a change in the activity or performance of the
catalyst with time-on-stream when the feedstock and process conditions are stable.
The catalyst stability is measured in terms of the cycle length. Catalyst stability or
life is affected by several factors such as the following:
• Presence of poisons in the feedstock such as metals.
• Inactivation by one or more of the products.
• Loss of a volatile agent from the catalyst.
• Loss of activity due to a change in the crystal phase.
Selection of hydrotreating catalysts is mostly based on the comparison between
required start-of-run (SOR) temperatures to achieve certain product quality in terms
of product sulfur or yields. Apart from catalyst activity and selectivity, catalyst stability is also an important factor to be considered during catalyst selection. A catalyst that performs well under SOR conditions may have poor stability and deactivate
faster than other catalysts that performed slightly less under those conditions. Based
on the initial activity, selectivity, and overall life, economic comparison needs to be
performed incorporating product value based on specific conversion and yields,
energy cost, cost of catalyst, etc., and a suitable catalyst needs to be selected using
economic considerations for those catalysts that meet the conversion or product
quality or product yield requirements.
7.1 Selection of Hydrotreating Catalysts for Gasoline
and Gas Oils
The choice of the catalyst depends on the specific process requirement such as
hydrodesulfurization, hydrodenitrogenation, aromatics hydrogenation, olefin saturation, and hydrocracking. Table 4 presents the selection of common catalysts for
different hydrotreating applications. In general, the Co-Mo catalyst is the best
choice for hydrodesulfurization of straight-run feedstock such as virgin naphtha,
kerosene, and gas oils. Although it is true that Co-Mo catalysts are well suited for
HDS of straight-run feeds, high-activity Ni-Mo catalysts also exhibit substantially
high activity for the HDS of petroleum fractions, but with higher hydrogen
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part II—Catalyst…