619
Hydrocracking
The Advanced Partial Conversion Unicracking (APCU) process is a recent advancement in the
area of ultra-low-sulfur diesel (ULSD) production and feedstock pretreatment for catalytic cracking units. At low conversions (20%–50%) and moderate pressure, the Advanced Partial Conversion
Unicracking technology provides an improvement in product quality compared to traditional mild
hydrocracking. In the process, high-sulfur feeds such as vacuum gas oil and heavy cycle gas oil are
mixed with a heated hydrogen-rich recycle gas stream and passed over consecutive beds of highactivity pre-treat catalyst and distillate selective Unicracking catalyst. This combination of catalysts
removes refractory sulfur and nitrogen contaminants, saturates polynuclear aromatic compounds,
and converts a portion of the feed to ultra-low-sulfur diesel fuel. The hydrocracked products and
desulfurized feedstock for a fluid catalytic cracking unit and separated at reactor pressure in an
enhanced hot separator. The overhead products for the separator are immediately hydrogenated in
the integrated finishing reactor.
As pretreatment severity is increased, conversion increases in the fluid catalytic cracker and both
gasoline and alkylate octane-barrel output per barrel of cat cracker feedstock increase. Advanced
Partial Conversion Unicracking units can be customized to achieve maximum octane-barrel production in the cat cracker.
Another development in the Unicracking family is the HyCycle Unicracking technology that is
designed to maximize diesel production for full conversion applications.
22.3.21 unIFlex ProCess
The Uniflex process is an evolved version with significant changes (by UOP) of the former CANMET
process that used an empty vessel hydrocracking reactor in which the feedstock is processed in the
presence of an iron sulfide–based catalyst deposited on particles of coal. Because the desulfurization activity of iron is very low, molybdenum can be added at a level of tens of ppm in the form of
molybdenum naphthenate. The reaction products were fractionated and sent to the hydrotreatment
unit, while the unconverted residue (5%–10% v/v of the feedstock) can be burned or gasified.
The process uses an empty vessel hydrocracking reactor in which the feedstock is processed in
the presence of an iron sulfide–based catalyst deposited on particles of coal. Because the desulfurization activity of iron is very low, molybdenum can be added at a level of tens of ppm in the form
of molybdenum naphthenate. The reaction products are fractionated and sent to the hydrotreatment
unit (Unifining and Unicracking), while the unconverted residue (5%–10% v/v of the feedstock) can
be burned or gasified.
The flow scheme for the Uniflex process is similar to that of a conventional UOP Unicracking
process unit—liquid feedstock and recycle gas are heated to temperature in separate heaters, with
a small portion of the recycle gas stream and the required amount of catalyst being routed through
the oil heater (Gillis et al., 2010). The outlet streams from both heaters are fed to the bottom of the
slurry reactor. The reactor effluent is quenched at the reactor outlet to terminate reactions and then
flows to a series of separators with gas being recycled back to the reactor. Liquids flow to the unit’s
fractionation section for recovery of light ends, naphtha, diesel, vacuum gas oils and pitch (cracked
residuum). Heavy vacuum gas oil (HVGO) is partially recycled to the reactor for further conversion.
The heart of the Uniflex process is the upflow reactor that operates at moderate temperature
(440°C–470°C; 815°F–880°F) and 2000 psi. The feedstock distributor, in combination with optimized process variables, promotes intense back-mixing (which provides near isothermal reactor
conditions) in the reactor without the need for reactor internals or liquid recycle ebullating pumps.
The back-mixing allows the reactor to operate at the higher temperatures required to maximize
vacuum residue conversion. The majority of the products vaporize and quickly leave the reactor
(thereby minimizing the potential for secondary cracking reactions), while the residence time of the
higher boiling constituents of the feedstock is maximized.
The process employs a proprietary, dual-function nano-sized solid catalyst that is blended with
the feed to maximize conversion of heavy components and inhibit coke formation. Specific catalyst
Hydrocracking
The Advanced Partial Conversion Unicracking (APCU) process is a recent advancement in the
area of ultra-low-sulfur diesel (ULSD) production and feedstock pretreatment for catalytic cracking units. At low conversions (20%–50%) and moderate pressure, the Advanced Partial Conversion
Unicracking technology provides an improvement in product quality compared to traditional mild
hydrocracking. In the process, high-sulfur feeds such as vacuum gas oil and heavy cycle gas oil are
mixed with a heated hydrogen-rich recycle gas stream and passed over consecutive beds of highactivity pre-treat catalyst and distillate selective Unicracking catalyst. This combination of catalysts
removes refractory sulfur and nitrogen contaminants, saturates polynuclear aromatic compounds,
and converts a portion of the feed to ultra-low-sulfur diesel fuel. The hydrocracked products and
desulfurized feedstock for a fluid catalytic cracking unit and separated at reactor pressure in an
enhanced hot separator. The overhead products for the separator are immediately hydrogenated in
the integrated finishing reactor.
As pretreatment severity is increased, conversion increases in the fluid catalytic cracker and both
gasoline and alkylate octane-barrel output per barrel of cat cracker feedstock increase. Advanced
Partial Conversion Unicracking units can be customized to achieve maximum octane-barrel production in the cat cracker.
Another development in the Unicracking family is the HyCycle Unicracking technology that is
designed to maximize diesel production for full conversion applications.
22.3.21 unIFlex ProCess
The Uniflex process is an evolved version with significant changes (by UOP) of the former CANMET
process that used an empty vessel hydrocracking reactor in which the feedstock is processed in the
presence of an iron sulfide–based catalyst deposited on particles of coal. Because the desulfurization activity of iron is very low, molybdenum can be added at a level of tens of ppm in the form of
molybdenum naphthenate. The reaction products were fractionated and sent to the hydrotreatment
unit, while the unconverted residue (5%–10% v/v of the feedstock) can be burned or gasified.
The process uses an empty vessel hydrocracking reactor in which the feedstock is processed in
the presence of an iron sulfide–based catalyst deposited on particles of coal. Because the desulfurization activity of iron is very low, molybdenum can be added at a level of tens of ppm in the form
of molybdenum naphthenate. The reaction products are fractionated and sent to the hydrotreatment
unit (Unifining and Unicracking), while the unconverted residue (5%–10% v/v of the feedstock) can
be burned or gasified.
The flow scheme for the Uniflex process is similar to that of a conventional UOP Unicracking
process unit—liquid feedstock and recycle gas are heated to temperature in separate heaters, with
a small portion of the recycle gas stream and the required amount of catalyst being routed through
the oil heater (Gillis et al., 2010). The outlet streams from both heaters are fed to the bottom of the
slurry reactor. The reactor effluent is quenched at the reactor outlet to terminate reactions and then
flows to a series of separators with gas being recycled back to the reactor. Liquids flow to the unit’s
fractionation section for recovery of light ends, naphtha, diesel, vacuum gas oils and pitch (cracked
residuum). Heavy vacuum gas oil (HVGO) is partially recycled to the reactor for further conversion.
The heart of the Uniflex process is the upflow reactor that operates at moderate temperature
(440°C–470°C; 815°F–880°F) and 2000 psi. The feedstock distributor, in combination with optimized process variables, promotes intense back-mixing (which provides near isothermal reactor
conditions) in the reactor without the need for reactor internals or liquid recycle ebullating pumps.
The back-mixing allows the reactor to operate at the higher temperatures required to maximize
vacuum residue conversion. The majority of the products vaporize and quickly leave the reactor
(thereby minimizing the potential for secondary cracking reactions), while the residence time of the
higher boiling constituents of the feedstock is maximized.
The process employs a proprietary, dual-function nano-sized solid catalyst that is blended with
the feed to maximize conversion of heavy components and inhibit coke formation. Specific catalyst