U.S. patent application number 10/106579 was filed with the patent office on 2005-10-06 for hydrocarbon desulfurization process.
Invention is credited to Kalnes, Tom N..
Application Number | 20050218039 10/106579 |
Document ID | / |
Family ID | 35053114 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050218039 |
Kind Code |
A1 |
Kalnes, Tom N. |
October 6, 2005 |
Hydrocarbon desulfurization process
Abstract
A process for the production of low sulfur hydrocarbonaceous
products. The hydrocarbonaceous feedstock containing sulfur
compounds is separated into a first hydrocarbonaceous stream
containing the most refractory sulfur compounds and a second
hydrocarbonaceous stream containing the least refractory sulfur
compounds. The first stream desulfurized in a first desulfurization
zone and the effluent along with the second hydrocarbonaceous
stream is introduced into a second desulfurization zone.
Inventors: |
Kalnes, Tom N.; (LaGrange,
IL) |
Correspondence
Address: |
JOHN G TOLOMEI, PATENT DEPARTMENT
UOP LLC
25 EAST ALGONQUIN ROAD
P O BOX 5017
DES PLAINES
IL
60017-5017
US
|
Family ID: |
35053114 |
Appl. No.: |
10/106579 |
Filed: |
March 25, 2002 |
Current U.S.
Class: |
208/210 |
Current CPC
Class: |
C10G 2400/04 20130101;
C10G 65/00 20130101 |
Class at
Publication: |
208/210 |
International
Class: |
C10G 045/00 |
Claims
1-15. (canceled)
16. A process to produce an ultra low sulfur diesel stream from a
sulfur containing hydrocarbonaceous feedstock boiling in the range
of diesel fuel wherein the process comprises the steps of: (a)
separating the feedstock into a first stream containing more
refractory sulfur compounds and in an amount less than about 30
volume percent of the feedstock and a second stream containing less
refractory sulfur compounds; (b) introducing the first stream
containing more refractory sulfur compounds and hydrogen into a
first hydrodesulfurization zone containing desulfurization catalyst
at operating conditions including a temperature from about
204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.), a pressure from about 2.1 MPa (300 psig) to about
17.3 MPa (2500 psig) and a liquid hourly space velocity from about
0.1 hr.sup.-1 to about 10 hr.sup.-1 to produce a first
hydrodesulfurization zone effluent stream; (c) introducing at least
a portion of the first hydrodesulfurization zone effluent stream,
hydrogen and the second stream containing less refractory sulfur
compounds into a second hydrodesulfurizalion zone containing
hydrodesulfurization catalyst at operating conditions less severe
than those in the first hydrodesulfurization zone and including a
temperature from about 204.degree. C. (400.degree. F.) to about
482.degree. C. (900.degree. F.), a pressure from about 2.1 MPa (300
psig) to about 17.3 MPa (2500 psig) and a liquid hourly space
velocity from about 0.1 hr.sup.-1 to about 10 hr.sup.-1 to produce
a second hydrodesulfurization zone effluent; and (d) separating the
second hydrodesulfurization zone effluent to produce an ultra low
sulfur diesel stream containing less than about 50 wppm sulfur.
17. The process of claim 16 wherein the ultra low sulfur diesel
stream contains less than about 10 wppm sulfur.
Description
BACKGROUND OF THE INVENTION
[0001] The field of art to which this invention pertains is
desulfurization of a hydrocarbon feedstock to low levels of sulfur.
Hydrodesulfurization processes have been used by petroleum refiners
to produce more valuable hydrocarbonaceous streams such as naphtha,
gasoline, kerosene and diesel, for example, having lower
concentrations of sulfur and nitrogen. Feedstocks most often
subjected to hydrotreating or desulfurization are normally liquid
hydrocarbonaceous streams such as naphtha, kerosene, diesel, gas
oil, vacuum gas oil (VGO) and reduced crude, for example.
Traditionally, hydrodesulfurization severity is selected to produce
an improvement sufficient to produce a marketable product. Over the
years, it has been recognized that due to environmental concerns
and newly enacted rules and regulations, saleable products must
meet lower and lower limits on contaminants such as sulfur and
nitrogen. Recently new regulations were proposed in the United
States and Europe which basically require the complete removal of
sulfur from liquid hydrocarbons which are used as transportation
fuels such as gasoline and diesel.
[0002] Desulfurization is generally accomplished by contacting the
hydrocarbonaceous feedstock in a desulfurization reaction vessel or
zone with a suitable desulfurization catalyst under conditions of
elevated temperature and pressure in the presence of hydrogen to
yield a product containing the desired maximum limits of sulfur.
The operating conditions and the desulfurization catalysts within
the desulfurization reactor influence the quality of the
desulfurized products.
[0003] It is known that during the desulfurization of a hydrocarbon
stream as the severity of the desulfurization conditions is
increased, the level of residual sulfur containing hydrocarbons
decreases. This is due to the fact that certain sulfur compounds
are more susceptible to the desulfurization reaction with the
catalyst at given reaction conditions than are others. Not wishing
to be bound by any theory, it is believed that the location of the
sulfur atom in the compound determines if the sulfur atom will be
more readily reacted with a catalytic site. If the sulfur atom is
sterically hindered, i.e., having reduced access to the catalytic
site, more severe reaction conditions must be employed in order to
react and remove the sulfur atom from the hydrocarbonaceous
compound. An example of a difficult to desulfurize or refractory
compound is 4,6-dimethyl dibenzothiopene which has a boiling of
340.degree. C. (636.degree. F.).
[0004] Although a wide variety of process flow schemes, operating
conditions and catalysts have been used in commercial
desulfurization activities, there is always a demand for new
desulfurization methods which provide lower costs and the required
product quality. With the mandated low sulfur transportation fuels,
the process of the present invention greatly improves the economic
benefits of producing low sulfur fuels.
INFORMATION DISCLOSURE
[0005] U.S. Pat. No. 5,114,562 B1 (Haun et al) discloses a process
wherein middle distillate petroleum streams are hydrotreated to
produce a low sulfur and low aromatic product in two reaction zones
in series. The effluent of the first reaction zone is purged of
hydrogen sulfide by hydrogen stripping and then reheated by
indirect heat exchange. The second reaction zone employs a
sulfur-sensitive noble metal hydrogenation catalyst.
[0006] JP 04046993 A discloses the desulfurization of a hydrocarbon
stream by firstly fractionating the hydrocarbon into two or more
fractions and the resulting fractions are desulfurized individually
and subsequently mixed together. The reference recognizes that the
higher boiling fraction contains sulfur compounds that are
difficult to decompose while the lower boiling fraction contains
those compounds that are easier to decompose.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention is an improved process for the
production of low sulfur hydrocarbonaceous products. It has been
recognized that certain hydrocarbon boiling ranges are more easily
desulfurized than other boiling ranges. Therefore, based on this
information, the process of the present invention is able to more
easily and economically desulfurize a hydrocarbonaceous feedstock.
In accordance with the present invention, a hydrocarbonaceous
feedstock containing sulfur compounds is separated into a first
hydrocarbonaceous stream containing the most refractory sulfur
compounds and a second hydrocarbonaceous stream containing the
least refractory sulfur compounds. The first hydrocarbonaceous
stream containing the most refractory sulfur compounds is
desulfurized in a first desulfurization zone and the effluent
therefrom along with the second hydrocarbonaceous stream containing
the least refractory sulfur compounds is introduced into a second
desulfurization zone. This permits the selection and use of the
most suitable desulfurization catalysts and operating conditions to
achieve ultra low residual sulfur in the hydrocarbon product
stream.
[0008] In accordance with one embodiment, the present invention
relates to a process to produce a low sulfur hydrocarbon stream
from a sulfur containing hydrocarbonaceous feedstock wherein the
process comprises the steps of: (a) separating the feedstock into a
first stream containing more refractory sulfur compounds and a
second stream containing less refractory sulfur compounds; (b)
introducing the first stream containing more refractory sulfur
compounds and hydrogen into a first hydrodesulfurization zone
containing desulfurization catalyst to produce a first
hydrodesulfurization zone effluent stream; (c) introducing at least
a portion of the first hydrodesulfurization zone effluent stream,
hydrogen and the second stream containing less refractory sulfur
compounds into a second hydrodesulfurization zone containing
hydrodesulfurization catalyst to produce a second
hydrodesulfurization zone effluent; and (d) separating the second
hydrodesulfurization zone effluent to produce a low sulfur
hydrocarbon product stream.
[0009] In accordance with another embodiment, the present invention
is a process to produce an ultra low sulfur diesel stream from a
sulfur containing hydrocarbonaceous feedstock boiling in the range
of diesel fuel wherein the process comprises the steps of: (a)
separating the feedstock into a first stream containing more
refractory sulfur compounds and a second stream containing less
refractory sulfur compounds; (b) introducing the first stream
containing more refractory sulfur compounds and hydrogen into a
first hydrodesulfurization zone containing desulfurization catalyst
to produce a first hydrodesulfurization zone effluent stream; (c)
introducing at least a portion of the first hydrodesulfurization
zone effluent stream, hydrogen and the second stream containing
less refractory sulfur compounds into a second hydrodesulfurization
zone containing hydrodesulfurization catalyst to produce a second
hydrodesulfurization zone effluent; and (d) separating the second
hydrodesulfurization zone effluent to produce an ultra low sulfur
diesel stream containing less than about 50 wppm sulfur.
[0010] In another embodiment, the present invention is a process to
produce an ultra low sulfur diesel stream from a sulfur containing
hydrocarbonaceous feedstock boiling in the range of diesel fuel
wherein the process comprises the steps of: (a) separating the
feedstock into a first stream containing more refractory sulfur
compounds and in an amount less than about 30 volume percent of the
feedstock and a second stream containing less refractory sulfur
compounds; (b) introducing the first stream containing more
refractory sulfur compounds and hydrogen into a first
hydrodesulfurization zone containing desulfurization catalyst at
operating conditions including a temperature from about 204.degree.
C. (400.degree. F.) to about 482.degree. C. (900.degree. F.), a
pressure from about 2.1 MPa (300 psig) to about 17.3 MPa (2500
psig) and a liquid hourly space velocity from about 0.1 hr.sup.-1
to about 10 hr.sup.-1 to produce a first hydrodesulfurization zone
effluent stream; (c) introducing at least a portion of the first
hydrodesulfurization zone effluent stream, hydrogen and the second
stream containing less refractory sulfur compounds into a second
hydrodesulfurization zone containing hydrodesulfurization catalyst
at operating conditions less severe than those in the first
hydrodesulfurization zone and including a temperature from about
204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.), a pressure from about 2.1 MPa (300 psig) to about
17.3 MPa (2500 psig) and a liquid hourly space velocity from about
0.1 hr.sup.-1 to about 10 hr.sup.-1 to produce a second
hydrodesulfurization zone effluent; and (d) separating the second
hydrodesulfurization zone effluent to produce an ultra low sulfur
diesel stream containing less than about 50 wppm sulfur.
[0011] Other embodiments of the present invention encompass further
details such as types and descriptions of feedstocks,
desulfurization catalysts and preferred operating conditions
including temperatures and pressures, all of which are hereinafter
disclosed in the following discussion of each of these facets of
the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0012] The drawing is a simplified process flow diagram of a
preferred embodiment of the present invention. The drawing is
intended to be schematically illustrative of the present invention
and not be a limitation thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0013] It has been discovered that a more efficient and economical
production of ultra low sulfur hydrocarbon products including ultra
low sulfur diesel stock can be achieved and enjoyed in the
above-described integrated hydrodesulfurization process.
[0014] Although the present invention is particularly useful for
the production of ultra low sulfur diesel, any suitable
hydrocarbonaceous feedstock may be used in the present invention.
Illustrative hydrocarbon feedstocks include naphtha and kerosene
and those containing components boiling above 288.degree. C.
(550.degree. F.), such as atmospheric gas oils, vacuum gas oils,
deasphalted vacuum and atmospheric residua, mildly cracked residual
oils, cracked gas oils, coker distillates, straight run
distillates, solvent-deasphalted oils, pyrolysis-derived oils, high
boiling synthetic oils, cycle oils and cat cracker distillates. A
preferred feedstock is a gas oil or other hydrocarbon fraction
having at least about 50% by weight, and most usually at least
about 75% by weight of its components boiling at a temperature
between about 315.degree. C. (600.degree. F.) and 538.degree. C.
(1000.degree. F.).
[0015] The selected feedstock is separated by fractionation or any
other convenient method to produce a first hydrocarbonaceous stream
containing more refractory sulfur compounds and a second stream
containing less refractory sulfur compounds. The first stream
containing more refractory sulfur compounds preferably comprises
less than about 30 volume percent of the hydrocarbonaceous
feedstock. Hydrocarbonaceous sulfur compounds are graded according
to the difficulty in removing sulfur from the hydrocarbonaceous
sulfur compounds. Certain hydrocarbonaceous compounds due to their
physical characteristics are more resistant to desulfurization than
other hydrocarbonaceous compounds having different characteristics.
Therefore, the hydrocarbonaceous sulfur compounds, which are more
difficult to desulfurize, are considered to be refractory. In many
cases, the higher boiling hydrocarbonaceous sulfur compounds are
found to be more refractory than the lower boiling
hydrocarbonaceous sulfur compounds. In the case of diesel boiling
range hydrocarbons, the higher boiling hydrocarbons are more
refractory to desulfurization. The separation of diesel boiling
range hydrocarbons for the present invention is conveniently
performed in a splitter or a fractionation zone.
[0016] In accordance with the present invention, the first
hydrocarbonaceous stream containing more refractory sulfur
compounds is introduced along with hydrogen into a desulfurization
zone containing desulfurization catalyst and operated at
desulfurization conditions. Preferred desulfurization conditions
include a temperature from about 204.degree. C. (400.degree. F.) to
about 482.degree. C. (900.degree. F.) and a liquid hourly space
velocity of the hydrocarbonaceous feed from about 0.1 hr.sup.-1 to
about 10 hr.sup.-1.
[0017] Suitable desulfurization catalysts for use in the present
invention are any known conventional hydrotreating catalysts and
include those which are comprised of at least one Group VIII metal,
preferably iron, cobalt and nickel, more preferably cobalt and/or
nickel and at least one Group VI metal, preferably molybdenum and
tungsten, on a high surface area support material, preferably
alumina. Other suitable desulfurization catalysts include zeolitic
catalysts, as well as noble metal catalysts where the noble metal
is selected from palladium and platinum. It is within the scope of
the present invention that more than one type of desulfurization
catalyst be used in the same reaction vessel. The Group VIII metal
is typically present in an amount ranging from about 2 to about 20
weight percent, preferably from about 4 to about 12 weight percent.
The Group VI metal will typically be present in an amount ranging
from about 1 to about 25 weight percent, preferably from about 2 to
about 25 weight percent. Typical desulfurization temperatures range
from about 204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.) with pressures from about 2.1 MPa (300 psig) to
about 17.3 MPa (2500 psig), preferably from about 2.1 MPa (300
psig) to about 13.9 MPa (2000 psig).
[0018] The resulting effluent from the first desulfurization zone
is introduced into the second desulfurization zone along with
hydrogen the second stream containing less refractory sulfur
compounds. The second desulfurization zone contains desulfurization
catalyst which may be the same or different from the
desulfurization catalyst used in the first desulfurization zone and
may be selected from any known desulfurization catalyst such as
those described hereinabove for example. Preferred desulfurization
conditions may be selected from those ranges taught for the first
desulfurization zone and may be more, less or equal to the severity
of reaction conditions selected for the first desulfurization
zone.
[0019] The resulting effluent from the second desulfurization zone
is partially condensed and introduced into a vapor-liquid separator
operated at a temperature from about 21.degree. C. (70.degree. F.)
to about 60.degree. C. (140.degree. F.) to produce a hydrogen-rich
gaseous stream containing hydrogen sulfide and a liquid
hydrocarbonaceous stream. The resulting hydrogen-rich gaseous steam
is preferably passed through an acid gas scrubbing zone to reduce
the concentration of hydrogen sulfide to produce a purified
hydrogen-rich gaseous stream, a portion of which may then be
recycled to either one or both of the desulfurization zones. The
liquid hydrocarbonaceous stream is preferably introduced into a
cold flash drum to remove dissolved hydrogen and normally gaseous
hydrocarbons and subsequently sent to a fractionation zone. It is
preferred that the low sulfur hydrocarbon product stream contains
less than about 50 wppm sulfur, more preferably 10 wppm sulfur. The
make-up hydrogen may be introduced into the process at any
convenient location, but in a preferred embodiment, the make-up
hydrogen is introduced into the first desulfurization zone.
DETAILED DESCRIPTION OF THE DRAWING
[0020] In the drawing, the process of the present invention is
illustrated by means of a simplified schematic flow diagram in
which such details as pumps, instrumentation, heat-exchange and
heat-recovery circuits, compressors and similar hardware have been
deleted as being non-essential to an understanding of the
techniques involved. The use of such miscellaneous equipment is
well within the purview of one skilled in the art.
[0021] With reference now to the drawing, a feed stream comprising
a heavy diesel boiling range distillate fraction enters the process
through line 1 and is introduced into fractionation zone 2. A
hydrocarbonaceous stream containing the more refractory sulfur
compounds is removed from the bottom of fractionation zone 2 via
line 4 and is introduced into desulfurization zone 8 via line 7
along with a make-up hydrogen stream which is introduced via lines
6 and 7, and a hydrogen-rich gaseous stream provided via lines 18
and 7. Another hydrocarbonaceous stream containing less refractory
sulfur compounds is removed from fractionation zone 2 via line 3
and is introduced via line 3 into heat-exchanger 13 and the
resulting heated effluent is transported via lines 5 and 10 and is
introduced into desulfurization zone 11 along with the effluent
from desulfurization zone 8 which is carried via lines 9 and 10.
The resulting effluent from desulfurization zone 11 is transported
via line 12 and introduced into heat-exchanger 13 and the resulting
cooled stream is carried via line 14 and introduced into
heat-exchanger 15. The resulting partially condensed stream from
heat-exchanger 15 is carried via line 16 and introduced into
high-pressure separator 17. A hydrogen-rich gaseous stream is
removed from high-pressure separator 17 via line 18 and recycled as
described hereinabove. A liquid hydrocarbonaceous stream having low
concentrations of sulfur compounds is removed from high-pressure
separator 17 via line 19 and recovered.
[0022] The process of the present invention is further demonstrated
by the following illustrative embodiment. This illustrative
embodiment is, however, not presented to unduly limit the process
of this invention, but to further illustrate the advantage of the
hereinabove-described embodiment. The following data were not
obtained by the actual performance of the present invention but are
considered prospective and reasonably illustrative of the expected
performance of the invention.
ILLUSTRATIVE EMBODIMENT
[0023] A distillate feedstock having the characteristics presented
in Table 1 is hydrodesulfurized in accordance with the prior art in
a single stage reaction zone utilizing a commercially available
hydrodesulfurization catalyst operated at the conditions presented
in Table 3 under "Prior Art" to produce a 149.degree. C.+diesel
product having a residual sulfur level of 5 wppm. The product
yields from the desulfurization reactor are presented in Table
4.
[0024] Another portion of the feedstock having the characteristics
presented in Table 1 is separated by fractionation into two
fractions as presented in Table 2. The heavier fraction containing
essentially all of the refractory sulfur compounds is
hydrodesulfurized in a first reaction zone utilizing the same type
of commercially available hydrodesulfurization catalyst and the
resulting effluent is introduced into a second hydrodesulfurization
reaction zone along with the lighter fraction to produce a reactor
yield presented in Table 4. The reaction zone conditions are
presented in Table 3 under "Invention" and a 149.degree. C.+diesel
product having a residual sulfur level of 5 wppm is produced.
[0025] From Table 3, it can be seen that the present invention
requires only 78% of the catalyst in the prior art process which
means that less catalyst is required to perform the same level of
desulfurization shown in Tables 4 and 5 and the reactor volume is
less as well. Since the recycle gas rate for the present invention
is only 50% of the prior art rate, the recycle gas circuit
equipment is smaller while maintaining comparable yields and
product qualities with the same catalyst cycle length. These
overall results translate to lower investment and operating costs
for a desulfurization unit to produce ultra low sulfur product.
1TABLE 1 Distillate Feedstock Analysis 20% Straight Run Distillate
40% Light Coker Gas Oil 40% Light Cycle Oil Distillation, .degree.
C. (.degree. F.) Initial Boiling Point 180 (356) 10 226 (439) 30
261 (501) 50 285 (545) 70 311 (592) 90 346 (656) 95 364 (687) End
Point 376 (709) Sulfur, weight percent 1.31 Nitrogen, weight ppm
1100
[0026]
2TABLE 2 Separated Feedstock Lighter Fraction Heavier Fraction
Volume Percent 75 25 Sulfur, weight percent 1.16 1.75 Nitrogen,
weight ppm 700 2200 Refractory Sulfur Trace 4x Feed Concentration
Distillation, .degree. C. (.degree. F.) Initial Boiling Point 180
(355) 310 (590) 50% 271 (520) 343 (650) End Point 321 (610) 376
(710)
[0027]
3TABLE 3 Comparison of Operating Conditions Prior Art Invention
Pressure, kPa (psig) 6650 (950) 6650 (950) Catalyst Volume Base
0.78 Base Recycle Gas Rate Base 0.5 Base Reactor Temperature 360
(680) <357 (675) Requirement, .degree. C. (.degree. F.)
[0028]
4TABLE 4 Comparison of Desulfurization Reactor Yields Prior Art
Invention Base Base Hydrogen Consumption Weight Percent of
Feedstock Hydrogen Sulfide 1.39 1.39 Ammonia 0.13 0.13
C.sub.1-C.sub.4 0.37 0.37 C.sub.5-149.degree. C. 4.09 4.09
149.degree. C.+ 95.70 95.70
[0029]
5TABLE 5 Comparison of Product Quality 149.degree. C. + Diesel
Prior Art Invention Sulfur, weight ppm 5 5 Nitrogen, weight ppm 1
1
[0030] The foregoing description, drawing and illustrative
embodiment clearly illustrate the advantages encompassed by the
process of the present invention and the benefits to be afforded
with the use thereof.
* * * * *