627
Hydrocracking
constant temperature, the selectivity of the catalyst varies from about 65% to about 90% by volume.
Indeed, several catalytic systems have now been developed with a group of catalysts specifically
for mild hydrocracking operations. Depending on the type of catalyst, they may be run as a single
catalyst or in conjunction with a hydrotreating catalyst.
Precious metal catalysts, particularly catalysts incorporating platinum or platinum and palladium, are used in the latter stages of deep-desulfurization process. They have excellent performance
in hydrogenation of monocyclic aromatic hydrocarbons and are likely to become more and more
important in the years ahead and refiners seek to hydrocrack higher amounts of the heavy feedstocks. Current efforts are seeking to produce such catalysts with increased hydrogenation activity as well as resistance to sulfur and nitrogen poisoning while balancing these characteristics. In
addition, work is being done to assign appropriate cracking activity to match specific applications
using inorganic (composite) oxides, such as amorphous alumina, silica alumina, or crystalline silica
alumina, as carriers and optimization of the amount of the precious metals and highly dispersed
metal impregnation methods.
The cobalt–molybdenum, nickel–molybdenum, and precious metal catalysts are also available
for use in deep desulfurization and aromatics hydrogenation. These catalysts should be helpful in
producing diesel fuel with a sulfur content of 50 ppm or less only by substituting catalysts.
Catalysts used in residuum upgrading processes typically use an association of several kinds
of catalysts, each of them playing a specific and complementary role (Kressmann et al., 1998,
2004). The first major function to be performed is hydrodemetallization (HDM). Therefore, the
hydrodemetallization catalyst must desegregate asphaltene constituents and remove as much metals
(nickel and vanadium) as possible. One catalyst in particular has been developed by optimizing the
support pore structure and acidity (Toulhoat et al., 1990). This catalyst allows a uniform distribution
of metals deposited, and therefore, a high metal retention capacity is reached.
A specific hydrodesulfurization catalyst can be placed downstream the hydrodemetallization catalyst, and the main function is of such positioning is to desulfurize the already deeply
demetallized feedstock as well as to reduce coke precursors (1999). Thus, the main function of
the hydrodesulfurization catalyst is not the same function as that of the hydrodemetallization
catalyst. In addition, for fixed-bed processes, swing guard reactors may be used to improve the
protection of downstream catalysts and increases the unit cycle length. For example, the Hyvahl
process (q.v.) includes two swing guard reactors followed by conventional hydrodemetallization
and hydrodesulfurization reactors (DeCroocq, 1997). The hydrodemetallization catalyst in the
guard reactors may be replaced during unit operation and the total catalyst amount is replaced at
the end of a cycle.
In terms of slurry catalytic processes, metals that have been screened as potential slurry catalysts
and include transition metal-based catalysts derived from vanadium, tungsten, chromium, and iron.
Homogeneous catalyst-based hydrocracking technology [(HC)3 ™ Technology] has been developed
for upgrading of indigenous heavy crude and tar sand bitumen. In this process, the hydrocracking
catalyst is homogeneously dispersed as a colloid with particles similar in size to that of asphaltene
molecule, which results in high conversion of asphaltene constituents (Bhattacharyya and Mezza,
2010; Bhattacharyya et al., 2011).
REFERENCES
Bauman, R.F., Aldridge, C.L., Bearden, R. Jr., Mayer, F.X., Stuntz, G.F., Dowdle, L.D., and Fiffron, E. 1993.
Oil Sands—Our Petroleum Future. Preprints. Alberta Research Council, Edmonton, Alberta, Canada, p. 269.
Bearden, R. and Aldridge, C.L. 1981. Novel catalyst and process to upgrade heavy oils. Energy Progress
1: 44–48.
Bhattacharyya, A., Bricker, M.L., Mezza, B.J., and Bauer, L.J. 2011. Process for using iron oxide and alumina catalyst with large particle diameter for slurry hydrocracking. United States Patent 8,062,505,
November 22.
Hydrocracking
constant temperature, the selectivity of the catalyst varies from about 65% to about 90% by volume.
Indeed, several catalytic systems have now been developed with a group of catalysts specifically
for mild hydrocracking operations. Depending on the type of catalyst, they may be run as a single
catalyst or in conjunction with a hydrotreating catalyst.
Precious metal catalysts, particularly catalysts incorporating platinum or platinum and palladium, are used in the latter stages of deep-desulfurization process. They have excellent performance
in hydrogenation of monocyclic aromatic hydrocarbons and are likely to become more and more
important in the years ahead and refiners seek to hydrocrack higher amounts of the heavy feedstocks. Current efforts are seeking to produce such catalysts with increased hydrogenation activity as well as resistance to sulfur and nitrogen poisoning while balancing these characteristics. In
addition, work is being done to assign appropriate cracking activity to match specific applications
using inorganic (composite) oxides, such as amorphous alumina, silica alumina, or crystalline silica
alumina, as carriers and optimization of the amount of the precious metals and highly dispersed
metal impregnation methods.
The cobalt–molybdenum, nickel–molybdenum, and precious metal catalysts are also available
for use in deep desulfurization and aromatics hydrogenation. These catalysts should be helpful in
producing diesel fuel with a sulfur content of 50 ppm or less only by substituting catalysts.
Catalysts used in residuum upgrading processes typically use an association of several kinds
of catalysts, each of them playing a specific and complementary role (Kressmann et al., 1998,
2004). The first major function to be performed is hydrodemetallization (HDM). Therefore, the
hydrodemetallization catalyst must desegregate asphaltene constituents and remove as much metals
(nickel and vanadium) as possible. One catalyst in particular has been developed by optimizing the
support pore structure and acidity (Toulhoat et al., 1990). This catalyst allows a uniform distribution
of metals deposited, and therefore, a high metal retention capacity is reached.
A specific hydrodesulfurization catalyst can be placed downstream the hydrodemetallization catalyst, and the main function is of such positioning is to desulfurize the already deeply
demetallized feedstock as well as to reduce coke precursors (1999). Thus, the main function of
the hydrodesulfurization catalyst is not the same function as that of the hydrodemetallization
catalyst. In addition, for fixed-bed processes, swing guard reactors may be used to improve the
protection of downstream catalysts and increases the unit cycle length. For example, the Hyvahl
process (q.v.) includes two swing guard reactors followed by conventional hydrodemetallization
and hydrodesulfurization reactors (DeCroocq, 1997). The hydrodemetallization catalyst in the
guard reactors may be replaced during unit operation and the total catalyst amount is replaced at
the end of a cycle.
In terms of slurry catalytic processes, metals that have been screened as potential slurry catalysts
and include transition metal-based catalysts derived from vanadium, tungsten, chromium, and iron.
Homogeneous catalyst-based hydrocracking technology [(HC)3 ™ Technology] has been developed
for upgrading of indigenous heavy crude and tar sand bitumen. In this process, the hydrocracking
catalyst is homogeneously dispersed as a colloid with particles similar in size to that of asphaltene
molecule, which results in high conversion of asphaltene constituents (Bhattacharyya and Mezza,
2010; Bhattacharyya et al., 2011).
REFERENCES
Bauman, R.F., Aldridge, C.L., Bearden, R. Jr., Mayer, F.X., Stuntz, G.F., Dowdle, L.D., and Fiffron, E. 1993.
Oil Sands—Our Petroleum Future. Preprints. Alberta Research Council, Edmonton, Alberta, Canada, p. 269.
Bearden, R. and Aldridge, C.L. 1981. Novel catalyst and process to upgrade heavy oils. Energy Progress
1: 44–48.
Bhattacharyya, A., Bricker, M.L., Mezza, B.J., and Bauer, L.J. 2011. Process for using iron oxide and alumina catalyst with large particle diameter for slurry hydrocracking. United States Patent 8,062,505,
November 22.