578
The Chemistry and Technology of Petroleum
from DAOs. The wax hydrofining option processes low oil content (<1% by weight) wax from conventional solvent lube plant dewaxing-deoiling units under moderate hydroprocessing conditions.
Thus, liquefied wax and hydrogen are preheated to reaction temperature in a conventional coil
furnace and fed to a fixed bed reactor containing a supported hydrotreating catalyst. Sulfur and
nitrogen compounds are converted to hydrogen sulfide and ammonia, multiring aromatics are saturated, and trace acids and solvent residues are removed. The reactor effluent is flashed to separate
hydrogen, hydrogen sulfide and ammonia, and the wax is steam stripped and dried to improve
volatility and color. Both crystalline and microcrystalline waxes can be processed in the same unit,
although the types of oil molecules in microcrystalline waxes typically require more severe operating conditions. SCANfining (q.v.) is the next step up from hydrofining and is used to meet environmental requirements for sulfur in gasoline using a proprietary RT-225 catalyst to treat gasoline
from a fluid catalytic cracking unit. The process is specially designed to achieve high selectivity for
sulfur removal without excessive olefin saturation and octane loss. Along similar paths, the diesel
oil deep desulfurization (DODD) process for removing sulfur to very low levels and the GO-fining
and residfining processes are used for upgrading gas oils and residua, respectively, for feedstocks to
a catalytic cracking unit and also to use as low sulfur fuel oil (Song, 2002).
Finally, as an additional option, most feedstocks to a fluid catalytic cracking unit are high sulfur with a high ratio of residue blended. This type of feedstocks results in high sulfur high-olefin
gasoline. This kind of gasoline can be treated in a hydrofiner and the hydrofined naphtha is of good
quality containing more saturated hydrocarbons, through which high sulfur content problem of
gasoline is resolved. Typical operating conditions are: (280°C–320°C; 535°F–610°F), 290–1160 psi
with a liquid hourly space velocity (LHSV) in the range 1.5 to −3.0 h −1 and a hydrogen-oil ratio (v/v)
of 200–400.
The catalysts for hydrofining typically contain tungsten oxide and/or molybdenum oxide, nickel
oxide and cobalt oxide supported on an alumina carrier. Catalysts with a lower metal content may
exhibit higher activity at low-temperature (Xia et al., 2000; Tanaka, 2004; Kumagai et al., 2005).
21.3.5 IsomAx ProCess
The Isomax process is a two-stage, fixed-bed catalyst system that operates under hydrogen pressures from 500 to 1500 psi in a temperature range of 205°C–370°C (400°F–700°F), for example,
with middle distillate feedstocks. Exact conditions depend on the feedstock and product requirements, and hydrogen consumption is of the order of 1000–1600 ft 3 /bbl of feed processed. Each
stage has a separate hydrogen recycling system. Conversion may be balanced to provide products
for variable requirements, and recycling can be taken to extinction if necessary. Fractionation can
also be handled in a number of different ways to yield desired products.
21.3.6 ultrAFInIng ProCess
Ultrafining is a regenerative, fixed-bed, catalytic process to desulfurize and hydrogenate refinery
stocks from naphtha up to and including lubricating oil. The catalyst is cobalt–molybdenum on alumina and may be regenerated in situ using an air–stream mixture. Regeneration requires 10–20 h
and may be repeated 50–100 times for a given batch of catalyst; catalyst life is 2–5 years depending
on feedstock.
21.3.7 unIFInIng ProCess
This is a regenerative, fixed-bed, catalytic process to desulfurize and hydrogenate refinery distillates of any boiling range. Contaminating metals, nitrogen compounds, and oxygen compounds
are eliminated, along with sulfur. The catalyst is a cobalt–molybdenum–alumina type that may be
regenerated in situ with steam and air.
The Chemistry and Technology of Petroleum
from DAOs. The wax hydrofining option processes low oil content (<1% by weight) wax from conventional solvent lube plant dewaxing-deoiling units under moderate hydroprocessing conditions.
Thus, liquefied wax and hydrogen are preheated to reaction temperature in a conventional coil
furnace and fed to a fixed bed reactor containing a supported hydrotreating catalyst. Sulfur and
nitrogen compounds are converted to hydrogen sulfide and ammonia, multiring aromatics are saturated, and trace acids and solvent residues are removed. The reactor effluent is flashed to separate
hydrogen, hydrogen sulfide and ammonia, and the wax is steam stripped and dried to improve
volatility and color. Both crystalline and microcrystalline waxes can be processed in the same unit,
although the types of oil molecules in microcrystalline waxes typically require more severe operating conditions. SCANfining (q.v.) is the next step up from hydrofining and is used to meet environmental requirements for sulfur in gasoline using a proprietary RT-225 catalyst to treat gasoline
from a fluid catalytic cracking unit. The process is specially designed to achieve high selectivity for
sulfur removal without excessive olefin saturation and octane loss. Along similar paths, the diesel
oil deep desulfurization (DODD) process for removing sulfur to very low levels and the GO-fining
and residfining processes are used for upgrading gas oils and residua, respectively, for feedstocks to
a catalytic cracking unit and also to use as low sulfur fuel oil (Song, 2002).
Finally, as an additional option, most feedstocks to a fluid catalytic cracking unit are high sulfur with a high ratio of residue blended. This type of feedstocks results in high sulfur high-olefin
gasoline. This kind of gasoline can be treated in a hydrofiner and the hydrofined naphtha is of good
quality containing more saturated hydrocarbons, through which high sulfur content problem of
gasoline is resolved. Typical operating conditions are: (280°C–320°C; 535°F–610°F), 290–1160 psi
with a liquid hourly space velocity (LHSV) in the range 1.5 to −3.0 h −1 and a hydrogen-oil ratio (v/v)
of 200–400.
The catalysts for hydrofining typically contain tungsten oxide and/or molybdenum oxide, nickel
oxide and cobalt oxide supported on an alumina carrier. Catalysts with a lower metal content may
exhibit higher activity at low-temperature (Xia et al., 2000; Tanaka, 2004; Kumagai et al., 2005).
21.3.5 IsomAx ProCess
The Isomax process is a two-stage, fixed-bed catalyst system that operates under hydrogen pressures from 500 to 1500 psi in a temperature range of 205°C–370°C (400°F–700°F), for example,
with middle distillate feedstocks. Exact conditions depend on the feedstock and product requirements, and hydrogen consumption is of the order of 1000–1600 ft 3 /bbl of feed processed. Each
stage has a separate hydrogen recycling system. Conversion may be balanced to provide products
for variable requirements, and recycling can be taken to extinction if necessary. Fractionation can
also be handled in a number of different ways to yield desired products.
21.3.6 ultrAFInIng ProCess
Ultrafining is a regenerative, fixed-bed, catalytic process to desulfurize and hydrogenate refinery
stocks from naphtha up to and including lubricating oil. The catalyst is cobalt–molybdenum on alumina and may be regenerated in situ using an air–stream mixture. Regeneration requires 10–20 h
and may be repeated 50–100 times for a given batch of catalyst; catalyst life is 2–5 years depending
on feedstock.
21.3.7 unIFInIng ProCess
This is a regenerative, fixed-bed, catalytic process to desulfurize and hydrogenate refinery distillates of any boiling range. Contaminating metals, nitrogen compounds, and oxygen compounds
are eliminated, along with sulfur. The catalyst is a cobalt–molybdenum–alumina type that may be
regenerated in situ with steam and air.