U.S. patent application number 11/722138 was filed with the patent office on 2008-12-18 for oxidative desulfurization process.
This patent application is currently assigned to BP Corporation North America Inc.. Invention is credited to Kenneth P. Keckler, Jeffrey T. Miller, Russell R. Simpson, Janet L. Yedinak.
Application Number | 20080308463 11/722138 |
Document ID | / |
Family ID | 36282805 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080308463 |
Kind Code |
A1 |
Keckler; Kenneth P. ; et
al. |
December 18, 2008 |
Oxidative Desulfurization Process
Abstract
Disclosed is a process which reduces the sulfur and/or nitrogen
content of a distillate feedstock to produce a refinery
transportation fuel or blending components for refinery
transportation fuel, by contacting the feedstock with an
oxygen-containing gas in an 5 oxidation/adsorption zone at
oxidation conditions in the presence of an oxidation catalyst
comprising a titanium-containing composition whereby the sulfur
species are converted to sulfones and/or sulfoxides which are
adsorbed onto the titanium-containing composition.
Inventors: |
Keckler; Kenneth P.;
(Naperville, IL) ; Yedinak; Janet L.; (Westmont,
IL) ; Simpson; Russell R.; (Batavia, IL) ;
Miller; Jeffrey T.; (Naperville, IL) |
Correspondence
Address: |
CAROL WILSON;BP AMERICA INC.
MAIL CODE 5 EAST, 4101 WINFIELD ROAD
WARRENVILLE
IL
60555
US
|
Assignee: |
BP Corporation North America
Inc.
Warrenville
IL
|
Family ID: |
36282805 |
Appl. No.: |
11/722138 |
Filed: |
December 22, 2005 |
PCT Filed: |
December 22, 2005 |
PCT NO: |
PCT/US05/46849 |
371 Date: |
February 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60640039 |
Dec 29, 2004 |
|
|
|
Current U.S.
Class: |
208/249 |
Current CPC
Class: |
B01J 29/0308 20130101;
B01J 21/063 20130101; B01J 29/89 20130101; B01J 37/036 20130101;
C10G 27/04 20130101 |
Class at
Publication: |
208/249 |
International
Class: |
C10G 29/04 20060101
C10G029/04 |
Claims
1. A process for desulfurizing a distillate feedstock to produce
refinery transportation fuel or blending components for refinery
transportation fuel wherein the feedstock contains
sulfur-containing organic impurities which process comprises: (a)
contacting the feedstock with an oxygen-containing gas in an
oxidation/adsorption zone at oxidation conditions in the presence
of an oxidation catalyst comprising a titanium-containing
composition to convert at least a portion of the sulfur-containing
organic impurities to sulfones and/or sulfoxides; (b) adsorbing the
sulfones and/or sulfoxides on to the oxidation catalyst; and (c)
recovering an oxidation/adsorption zone effluent having a reduced
amount of sulfur-containing impurities.
2. The process of claim 1 wherein the oxidation catalyst is
regenerated to produce an oxidation catalyst that contains less
adsorbed sulfones and/or sulfoxides.
3. The process of claim 2 wherein the regeneration is carried out
by contacting the catalyst with methanol under conditions to desorb
the adsorbed sulfones and/or sulfoxides.
4. The process of claim 1 wherein the titanium-containing
composition is selected from the group consisting of titanium
silicate, Ti-MCM, and Ti-HMS.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to fuels for transportation
which are derived from natural petroleum, particularly processes
for the production of components for refinery blending of
transportation fuels which are liquid at ambient conditions. More
specifically, it relates to a process for making such fuels which
includes oxidation of a petroleum distillate in order to oxidize
nitrogen and/or sulfur-containing organic impurities therein, by
contacting the petroleum distillate with an oxygen-containing gas
at oxidation conditions in the presence of a heterogeneous
catalyst.
BACKGROUND OF THE INVENTION
[0002] It is well known that internal combustion engines have
revolutionized transportation following their invention during the
last decades of the 19th century. While others, including Benz and
Gottleib Wilhelm Daimler, invented and developed engines using
electric ignition of fuel such as gasoline, Rudolf C. K. Diesel
invented and built the diesel engine which employs compression for
auto-ignition of the fuel in order to utilize low-cost organic
fuels. Development of improved diesel engines for use in
transportation has proceeded hand-in-hand with improvements in
diesel fuel compositions. Modern high performance diesel engines
demand ever more advanced specification of fuel compositions, but
cost remains an important consideration.
[0003] At the present time most fuels for transportation are
derived from natural petroleum. Indeed, petroleum as yet is the
world's main source of hydrocarbons used as fuel and petrochemical
feedstock. While compositions of natural petroleum or crude oils
are significantly varied, all crudes contain sulfur compounds and
most contain nitrogen compounds which may also contain oxygen, but
oxygen content of most crude is low. Generally, sulfur
concentration in crude is less than about 8 percent, with most
crude having sulfur concentrations in the range from about 0.5 to
about 1.5 percent. Nitrogen concentration is usually less than 0.2
percent, but it may be as high as 1.6 percent.
[0004] Crude oil seldom is used in the form produced at the well,
but is converted in oil refineries into a wide range of fuels and
petrochemical feedstocks. Typically fuels for transportation are
produced by processing and blending of distilled fractions from the
crude to meet the particular end use specifications. Because most
of the crudes available today in large quantity are high in sulfur,
the distilled fractions must be desulfurized to yield products
which meet performance specifications and/or environmental
standards. Sulfur-containing organic compounds in fuels continue to
be a major source of environmental pollution. During combustion
they are converted to sulfur oxides, which in turn, give rise to
sulfur oxyacids and, also, contribute to particulate emissions.
[0005] Even in newer, high performance diesel engines combustion of
conventional fuel produces smoke in the exhaust. Oxygenated
compounds and compounds containing few or no carbon-to-carbon
chemical bonds, such as methanol and dimethyl ether, are known to
reduce smoke and engine exhaust emissions. However, most such
compounds have high vapor pressure and/or are nearly insoluble in
diesel fuel, and they have poor ignition quality, as indicated by
their cetane numbers. Furthermore, other methods of improving
diesel fuels by chemical hydrogenation to reduce their sulfur and
aromatics contents, also causes a reduction in fuel lubricity.
Diesel fuels of low lubricity may cause excessive wear of fuel
pumps, injectors and other moving parts which come in contact with
the fuel under high pressures.
[0006] Distilled fractions used for fuel or a blending component of
fuel for use in compression ignition internal combustion engines
(Diesel engines) are middle distillates that usually contain from
about 1 to 3 percent by weight sulfur. In the past a typical
specification for Diesel fuel was a maximum of 0.5 percent by
weight. By 1993 legislation in Europe and United States limited
sulfur in Diesel fuel to 0.3 weight percent. By 1996 in Europe and
United States, and 1997 in Japan, maximum sulfur in Diesel fuel was
reduced to no more than 0.05 weight percent. This worldwide trend
must be expected to continue to even lower levels for sulfur.
[0007] The US Environmental Protection Agency is targeting a level
of sulfur less than 15 ppm in 2006 for on-road diesel. The European
Union specification will be less than 50 ppm in 2005. Further the
World Wide Fuels Charter as supported by all global automobile
manufacturers proposes even more stringent sulfur requirements of 5
to 10 ppm for the Category IV fuels for "advanced" countries. In
order to comply with these regulations for ultra-low sulfur content
fuels, refiners will have to make fuels having even lower sulfur
levels at the refinery gate. Thus refiners are faced with the
challenge of reducing the sulfur levels in fuels and in particular
diesel fuel within the timeframes prescribed by the regulatory
authorities.
[0008] In one aspect, pending introduction of new emission
regulations in California and other jurisdictions has prompted
significant interest in catalytic exhaust treatment. Challenges of
applying catalytic emission control for the diesel engine,
particularly the heavy-duty diesel engine, are significantly
different from the spark ignition internal combustion engine
(gasoline engine) due to two factors. First, the conventional
three-way catalyst (TWC) catalyst is ineffective in removing NOx
emissions from diesel engines, and second, the need for particulate
control is significantly higher than with the gasoline engine.
[0009] Several exhaust treatment technologies are emerging for
control of Diesel engine emissions, and in all sectors the level of
sulfur in the fuel affects efficiency of the technology. Sulfur is
a catalyst poison that reduces catalytic activity. Furthermore, in
the context of catalytic control of Diesel emissions, high fuel
sulfur also creates a secondary problem of particulate emission,
due to catalytic oxidation of sulfur and reaction with water to
form a sulfate mist. This mist is collected as a portion of
particulate emissions.
[0010] Compression ignition engine emissions differ from those of
spark ignition engines due to the different method employed to
initiate combustion. Compression ignition requires combustion of
fuel droplets in a very lean air/fuel mixture. The combustion
process leaves tiny particles of carbon behind and leads to
significantly higher particulate emissions than are present in
gasoline engines. Due to the lean operation the CO and gaseous
hydrocarbon emissions are significantly lower than the gasoline
engine. However, significant quantities of unburned hydrocarbon are
adsorbed on the carbon particulate. These hydrocarbons are referred
to as SOF (soluble organic fraction).
[0011] While an increase in combustion temperature can reduce
particulate emissions, this leads to an increase in NOx emission by
the well-known Zeldovitch mechanism. Thus, it becomes necessary to
trade off particulate and NOx emissions to meet emissions
legislation.
[0012] Available evidence strongly suggests that ultra-low sulfur
fuel is a significant technology enabler for catalytic treatment of
diesel exhaust to control emissions. Fuel sulfur levels of below 15
ppm, likely, are required to achieve particulate levels below 0.01
g/bhp-hr. Such levels would be very compatible with catalyst
combinations for exhaust treatment now emerging, which have shown
capability to achieve NOx emissions around 0.5 g/bhp-hr.
Furthermore, NOx trap systems are extremely sensitive to fuel
sulfur and available evidence suggests that they would need sulfur
levels below 10 ppm to remain active.
[0013] In the face of ever-tightening sulfur specifications in
transportation fuels, sulfur removal from petroleum feedstocks and
products will become increasingly important in years to come.
[0014] Conventional hydrodesulfurization (HDS) catalysts can be
used to remove a major portion of the sulfur from petroleum
distillates for the blending of refinery transportation fuels, but
they are not efficient for removing sulfur from compounds where the
sulfur atom is sterically hindered as in multi-ring aromatic sulfur
compounds. This is especially true where the sulfur heteroatom is
doubly hindered (e.g., 4,6-dimethyldibenzothiophene). These
hindered dibenzothiophenes predominate at low sulfur levels such as
50 to 100 ppm and would require severe process conditions to be
desulfurized. Using conventional hydrodesulfurization catalysts at
high temperatures would cause yield loss, faster catalyst coking,
and product quality deterioration (e.g., color). Using high
pressure requires a large capital outlay.
[0015] In order to meet stricter specifications in the future, such
hindered sulfur compounds will also have to be removed from
distillate feedstocks and products. There is a pressing need for
economical removal of sulfur from distillates and other hydrocarbon
products.
[0016] The art is replete with processes said to remove sulfur from
distillate feedstocks and products. One known method involves the
oxidation of petroleum fractions containing at least a major amount
of material boiling above very high-boiling hydrocarbon materials
(petroleum fractions containing at least a major amount of material
boiling above about 550.degree. F.) followed by treating the
effluent containing the oxidized compounds at elevated temperatures
to form hydrogen sulfide (500.degree. F. to 1350.degree. F.) and/or
hydroprocessing to reduce the sulfur content of the hydrocarbon
material. See, for example, U.S. Pat. No. 3,847,798 (Jin Sun Yoo,
et al) and U.S. Pat. No. 5,288,390 (Vincent A. Durante). Such
methods have proven to be of only limited utility since only a
rather low degree of desulfurization is achieved. In addition,
substantial loss of valuable products may result due to cracking
and/or coke formation during the practice of these methods.
Therefore, it would be advantageous to develop a process which
gives an increased degree of desulfurization while decreasing
cracking or coke formation.
[0017] U.S. Pat. No. 6,087,544 (Robert J. Wittenbrink et al.)
relates to processing a distillate feedstream to produce distillate
fuels having a level of sulfur below the distillate feedstream.
Such fuels are produced by fractionating a distillate feedstream
into a light fraction, which contains only from about 50 to 100 ppm
of sulfur, and a heavy fraction. The light fraction is hydrotreated
to remove substantially all of the sulfur therein. The desulfurized
light fraction, is then blended with one half of the heavy fraction
to produce a low sulfur distillate fuel, for example 85 percent by
weight of desulfurized light fraction and 15 percent by weight of
untreated heavy fraction reduced the level of sulfur from 663 ppm
to 310 ppm. However, to obtain this low sulfur level only about 85
percent of the distillate feedstream is recovered as a low sulfur
distillate fuel product.
[0018] U.S. Patent Application Publication 2002/0035306 A1 (Gore et
al.) discloses a multi-step process for desulfurizing liquid
petroleum fuels that also removes nitrogen-containing compounds and
aromatics. The process steps are thiophene extraction; thiophene
oxidation; thiophene-oxide and dioxide extraction; raffinate
solvent recovery and polishing; extract solvent recovery; and
recycle solvent purification.
[0019] The Gore et al. process seeks to remove 5-65% of the
thiophenic material and nitrogen-containing compounds and parts of
the aromatics in the feedstream prior to the oxidation step. While
the presence of aromatics in diesel fuel tends to suppress cetane,
the Gore et al. process requires an end use for the extracted
aromatics. Further, the presence of an effective amount of
aromatics serves to increase the fuel density (Btu/gal) and enhance
the cold flow properties of diesel fuel. Therefore it is not
prudent to extract an inordinate amount of the aromatics.
[0020] With respect to the oxidation step, the oxidant is prepared
in situ or is previously formed. Operating conditions include a
molar ratio of H.sub.2O.sub.2 to S between about 1:1 and 2.2:1;
acetic acid content between about 5 and 45% of feed, solvent
content between 10 and 25% of feed, and a catalyst volume of less
than about 5,000 ppm sulfuric acid, preferably less than 1,000 ppm.
Gore et al. also discloses the use of an acid catalyst in the
oxidation step, preferably sulfuric acid. The use of sulfuric acid
as an oxidizing acid is problematic in that corrosion is a concern
when water is present and hydrocarbons can be sulfonated when a
little water is present.
[0021] According to Gore et al. the purpose of the thiophene-oxide
and dioxide extraction step is to remove more than 90% of the
various substituted benzo- and dibenzo thiophene-oxides and N-oxide
compounds plus a fraction of the aromatics with an extracting
solvent that is aqueous acetic acid with one or more
co-solvents.
[0022] U.S. Pat. No. 6,368,495 B1 (Kocal et al.) also discloses a
multi-step process for the removal of thiophenes and thiophene
derivatives from petroleum fractions. This subject process involves
the steps of contacting a hydrocarbon feed stream with an oxidizing
agent followed by the contact of the oxidizing step effluent with a
solid decomposition catalyst to decompose the oxidized
sulfur-containing compounds thereby yielding a heated liquid stream
and a volatile sulfur compound. The subject patent discloses the
use of oxidizing agents such as alkyl hydroperoxides, peroxides,
percarboxylic acids, and oxygen.
[0023] WO 02/18518 A1 (Rappas et al) discloses a two-stage
desulfurization process which is utilized downstream of a
hydrotreater. The process involves an aqueous formic acid based,
hydrogen peroxide biphasic oxidation of a distillate to convert
thiophenic sulfur to corresponding sulfones. During the oxidation
process, some sulfones are extracted into the oxidizing solution.
These sulfones are removed from the hydrocarbon phase by a
subsequent phase separation step. The hydrocarbon phase containing
remaining sulfones is then subjected to a liquid-liquid extraction
or solid adsorption step.
[0024] The use of formic acid in the oxidation step is not
advisable. Formic acid is relatively more expensive than acetic
acid. Further, formic acid is considered a "reducing" solvent and
can hydride certain metals thereby weakening them. Therefore,
exotic alloys are required to handle formic acid. These expensive
alloys would have to be used in the solvent recovery section and
storage vessels. The use of formic acid also necessitates the use
of high temperatures for the separation of the hydrocarbon phase
from the aqueous oxidant phase in order to prevent the appearance
of a third precipitated solid phase. It is believed this
undesirable phase can be formed due to the poor lipophilicity of
formic acid. Therefore at lower temperatures, formic acid cannot
maintain in solution some of the extracted sulfones.
[0025] U.S. Pat. No. 6,171,478 B1 (Cabrera et al.) discloses yet
another complex multi-step desulfurization process. Specifically,
the process involves a hydrodesulfurization step, an oxidizing
step, a decomposition step, and a separation step wherein a portion
of the sulfur-oxidated compounds are separated from the effluent
stream of the decomposition step. The aqueous oxidizing solution
used in the oxidizing step preferably contains acetic acid and
hydrogen peroxide. Any residual hydrogen peroxide in the oxidizing
step effluent is decomposed by contacting the effluent with a
decomposition catalyst.
[0026] The separation step is carried out with a selective solvent
to extract the sulfur-oxidated compounds. Per the teachings of
Cabrera et al. the preferred selective solvents are acetonitrile,
dimethyl formamide, and sulfolane. [0027] A number of solvents have
been proposed for removing the oxidized sulfur compounds. For
example, in U.S. Pat. No. 6,160,193 (Gore) teaches the use of a
wide variety of solvents suitable for use in the extraction of
sulfones. The preferred solvent is Dimethylsulfoxide (DMSO).
[0028] A study of a similar list of solvents used in the extraction
of sulfur compounds was published by Otsuki, S.; Nonaka, T.;
Takashima, N.; Qian, W.; Ishihara, A.; Imai, T.; Kabe, T.
"Oxidative Desulfurization of Light Gas Oil and Vacuum Gas Oil by
Oxidation and Solvent Extraction" Energy & Fuels 2000, 14,
1232. That list is displayed below: [0029] N,N-Dimethylformamide
(DMF) [0030] Methanol [0031] Acetonitrile [0032] Sulfolane [0033]
Gore states that there is a relationship between the solvent's
polarity with the solvent's extraction efficiency. All of the
solvents listed in the patent and the paper are desirably
immiscible with the diesel. They are all characterized as either
polar protic or aprotic solvents.
[0034] WO 01/32809 discloses another process for selectively
oxidizing distillate fuel or middle distillates. The subject
reference discloses that oxidized distillate fuels such that
hydroxyl and or carbonyl groups are chemically bound to paraffinic
molecules in the fuel results in a reduction in particulates
generated upon combustion of the fuel versus unoxidized fuel. The
reference discloses a process for selectively oxidizing saturated
aliphatic or cyclic compounds in the fuel in the presence of
various titanium containing silicon based zeolites with peroxides,
ozone or hydrogen peroxide such that hydroxyl or carbonyl groups
are formed.
[0035] U.S. Pat. No. 6,402,939 B1 (Yen et al.) discloses a process
for the oxidative desulfurization of fossil fuels using ultrasound.
Briefly liquid fossil fuel is combined with an acidic aqueous
solution comprising water and hydroperoxide to form a multiphase
reaction mixture followed by applying ultrasound to the multiphase
reaction medium for a time sufficient to cause oxidation of
sulfides to sulfones with are subsequently extracted.
[0036] U.S. Patent Application Publication 2001/0015339 A1
(Sherman) discloses a method of removing sulfur compounds from
diesel fuel that involves forming oxidizing gas into sub micron
size bubbles and dispersing these bubbles into flowing diesel fuel
to oxidize the sulfur compounds into sulfoxides and/or
sulfones.
[0037] In view of the above, it is clear that there is a need for a
less complex, economic distillate or diesel desulfurization process
that does not employ expensive hydrotreating technologies involving
greater hydrogen useage or oxidation technologies that employ the
use of expensive chemical oxidizing agents and avoids the attendant
complex handling and corrosion issues.
[0038] The present invention provides for a relatively simple
selective desulfurization process wherein a distillate feedstock is
contacted with an oxygen-containing gas at oxidation conditions in
the presence of a heterogeneous catalyst comprising a
titanium-containing composition whereby the sulfur-containing
compounds in the distillate feedstock are converted to their
corresponding sulfones or sulfoxides a portion of which are then
adsorbed on to the titanium-containing composition.
SUMMARY OF THE INVENTION
[0039] The process of the present invention involves reducing the
sulfur content of a distillate feedstock containing
sulfur-containing organic impurities to produce a refinery
transportation fuel or blending components for refinery
transportation fuel, by contacting the feedstock with an
oxygen-containing gas in an oxidation/adsorption zone at oxidation
conditions in the presence of a heterogeneous oxidation catalyst
comprising a titanium-containing composition whereby the
sulfur-containing compounds are converted to sulfones and/or
sulfoxides a portion of which are subsequently adsorbed on to the
titanium-containing composition. A fuel or blending component
having a reduced sulfur content is then recovered from the
oxidation zone. The sulfones and/or sulfoxide can be further
removed from the catalyst for further processing whereby the
catalyst is regenerated for reuse in the process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 shows a schematic flow sheet of an embodiment of the
present invention.
[0041] FIG. 2 shows a schematic flow sheet of another embodiment of
the present invention.
[0042] FIG. 3 shows a plot of percentage desulfurization versus
hours on stream including the effect of adding an oxygen containing
gas to the process in accordance with the invention.
[0043] FIG. 4 shows desulfurization activity of fresh titanium
silicate catalyst versus the performance of regenerated titanium
silicates as a function of hours on steam.
[0044] FIG. 5 shows the desulfurization activity of two oxidation
catalysts regenerated in accordance with the invention.
[0045] FIG. 6 shows the effect of oxygen content on desulfurization
carried out in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0046] Suitable feedstocks generally include refinery streams
boiling at a temperature range from about 50.degree. C. to about
650.degree. C., preferably 150.degree. C. to about 400.degree. C.,
and more preferably between about 175.degree. C. and about
375.degree. C. at atmospheric pressure for best results. These
streams include, but are not limited to, virgin light middle
distillate, virgin heavy middle distillate, fluid catalytic
cracking process light catalytic cycle oil, coker still distillate,
hydrocracker distillate, jet fuel, vacuum distillates and the
collective and individually hydrotreated embodiments of these
streams. The preferred streams are the collective and individually
hydrotreated embodiments of fluid catalytic cracking process light
catalytic cycle oil, coker still distillate, and hydrocracker
distillate.
[0047] It is also anticipated that one or more of the above
distillate streams can be combined for use as feedstock to the
process of the invention. In many cases performance of the refinery
transportation fuel or blending components for refinery
transportation fuel obtained from the various alternative
feedstocks may be comparable. In these cases, logistics such as the
volume availability of a stream, location of the nearest connection
and short-term economics may be determinative as to what stream is
utilized.
[0048] In one aspect, this invention provides for the production of
refinery transportation fuel or blending components for refinery
transportation fuel from a hydrotreated petroleum distillate. Such
a hydrotreated distillate is prepared by hydrotreating a petroleum
distillate material boiling between about 50.degree. C. and about
650.degree. C. by a process which includes reacting the petroleum
distillate with a source of hydrogen at hydrogenation conditions in
the presence of a hydrogenation catalyst to assist by hydrogenation
removal of sulfur and/or nitrogen from the hydrotreated petroleum
distillate; optionally fractionating the hydrotreated petroleum
distillate by distillation to provide at least one low-boiling
blending component consisting of a sulfur-lean, mono-aromatic-rich
fraction, and a high-boiling feedstock consisting of a sulfur-rich,
mono-aromatic-lean fraction. In accordance with one embodiment of
the process of the present invention the hydrotreated distillate or
the low-boiling component can be used as suitable feedstocks for
the process of the present invention.
[0049] Generally, useful hydrogenation catalysts comprise at least
one active metal, selected from the group consisting of the
d-transition elements in the Periodic Table, each incorporated onto
an inert support in an amount of from about 0.1 percent to about 30
percent by weight of the total catalyst. Suitable active metals
include the d-transition elements in the Periodic Table elements
having atomic number in from 21 to 30, 39 to 48, and 72 to 78.
[0050] The catalytic hydrogenation process may be carried out under
relatively mild conditions in a fixed, moving fluidized or
ebullient bed of catalyst. Preferably a fixed bed or plurality of
fixed beds of catalyst is used under conditions such that
relatively long periods elapse before regeneration becomes
necessary, for example an average reaction zone temperature of from
about 200.degree. C. to about 450.degree. C., preferably from about
250.degree. C. to about 400.degree. C., and most preferably from
about 275.degree. C. to about 350.degree. C. for best results, and
at a pressure within the range of from about 6 to about 160
atmospheres.
[0051] A particularly preferred pressure range within which the
hydrogenation provides extremely good sulfur removal while
minimizing the amount of pressure and hydrogen required for the
hydrodesulfurization step are pressures within the range of 20 to
60 atmospheres, more preferably from about 25 to 40
atmospheres.
[0052] Hydrogen circulation rates generally range from about 500
SCF/Bbl to about 20,000 SCF/Bbl, preferably from about 2,000
SCF/Bbl to about 15,000 SCF/Bbl, and most preferably from about
3,000 to about 13,000 SCF/Bbl for best results. Reaction pressures
and hydrogen circulation rates below these ranges can result in
higher catalyst deactivation rates resulting in less effective
desulfurization, denitrogenation, and dearomatization. Excessively
high reaction pressures increase energy and equipment costs and
provide diminishing marginal benefits.
[0053] The hydrogenation process typically operates at a liquid
hourly space velocity of from about 0.2 hr.sup.-1 to about 10.0
hr.sup.-1, preferably from about 0.5 hr.sup.-1 to about 3.0
hr.sup.-1, and most preferably from about 1.0 hr.sup.-1 to about
2.0 hr.sup.-1 for best results. Excessively high space velocities
will result in reduced overall hydrogenation.
[0054] Further reduction of such heteroaromatic sulfides from a
distillate petroleum fraction by hydrotreating would require that
the stream be subjected to very severe catalytic hydrogenation in
order to convert these compounds into hydrocarbons and hydrogen
sulfide (H.sub.2S). Typically, the larger any hydrocarbon moiety
is, the more difficult it is to hydrogenate the sulfide. Therefore,
the residual organo-sulfur compounds remaining after a
hydrotreatment are the larger and most structurally hindered
heteroaromatics.
[0055] Where the feedstock is a high-boiling distillate fraction
derived from hydrogenation of a refinery stream, the refinery
stream can be a material boiling between about 200.degree. C. and
about 425.degree. C. Preferably the refinery stream can be a
material boiling between about 250.degree. C. and about 400.degree.
C., and more preferably boiling between about 275.degree. C. and
about 375.degree. C.
[0056] Useful distillate fractions for hydrogenation can be any
one, several, or all refinery streams boiling in a range from about
50.degree. C. to about 650.degree. C., preferably 150.degree. C. to
about 400.degree. C., and more preferably between about 175.degree.
C. and about 375.degree. C. at atmospheric pressure. The lighter
hydrocarbon components in the distillate product are generally more
profitably recovered to gasoline and the presence of these lower
boiling materials in distillate fuels is often constrained by
distillate fuel flash point specifications. Heavier hydrocarbon
components boiling above 400.degree. C. are generally more
profitably processed as fluid catalytic cracker feed and converted
to gasoline but are amenable for use in the process of the present
invention. The presence of heavy hydrocarbon components in
distillate fuels is further constrained by distillate fuel end
point specifications.
[0057] The distillate fractions for hydrogenation can comprise high
and low sulfur virgin distillates derived from high- and low-sulfur
crudes, coker distillates, catalytic cracker light and heavy
catalytic cycle oils, and distillate boiling range products from
hydrocracker and resid hydrotreater facilities. Generally, coker
distillate and the light and heavy catalytic cycle oils are the
most highly aromatic feedstock components, ranging as high as 80
percent by weight. The majority of coker distillate and cycle oil
aromatics are present as mono-aromatics and di-aromatics with a
smaller portion present as tri-aromatics. Virgin stocks such as
high and low sulfur virgin distillates are lower in aromatics
content ranging as high as 20 percent by weight aromatics.
Generally, the aromatics content of a combined hydrogenation
facility feedstock will range from about 5 percent by weight to
about 80 percent by weight, more typically from about 10 percent by
weight to about 70 percent by weight, and most typically from about
20 percent by weight to about 60 percent by weight.
[0058] Sulfur concentration in distillate fractions useful in the
present invention is generally a function of the high and low
sulfur crude mix, the hydrogenation capacity of a refinery per
barrel of crude capacity, and the alternative dispositions of
distillate hydrogenation feedstock components. The higher sulfur
distillate feedstock components are generally virgin distillates
derived from high sulfur crude, coker distillates, and catalytic
cycle oils from fluid catalytic cracking units processing
relatively higher sulfur feedstocks. These distillate feedstock
components can range as high as 2 percent by weight elemental
sulfur but generally range from about 0.1 percent by weight to
about 0.9 percent by weight elemental sulfur.
[0059] Nitrogen content of distillate fractions useful in the
present invention is also generally a function of the nitrogen
content of the crude oil, the hydrogenation capacity of a refinery
per barrel of crude capacity, and the alternative dispositions of
distillate hydrogenation feedstock components. The higher nitrogen
distillate feedstocks are generally coker distillate and the
catalytic cycle oils. These distillate feedstock components can
have total nitrogen concentrations ranging as high as 2000 ppm, but
generally range from about 5 ppm to about 900 ppm.
[0060] Typically, sulfur compounds in petroleum fractions are
relatively non-polar, heteroaromatic sulfides such as substituted
benzothiophenes and dibenzothiophenes. At first blush it might
appear that heteroaromatic sulfur compounds could be selectively
extracted based on some characteristic attributed only to these
heteroaromatics. Even though the sulfur atom in these compounds has
two, non-bonding pairs of electrons which would classify them as a
Lewis base, this characteristic is still not sufficient for them to
be extracted by a Lewis acid. In other words, selective extraction
of heteroaromatic sulfur compounds to achieve lower levels of
sulfur requires greater difference in polarity between the sulfides
and the hydrocarbons.
[0061] By means of the heterogeneous catalyzed oxidation according
to this invention, it is possible to selectively convert these
sulfides directly to into, more polar, Lewis basic, oxygenated
sulfur compounds such as sulfoxides and sulfones which are then
adsorbed on to the titania-silica. Subsequently a desulfurized feed
stock is recovered from the oxidation/adsorption zone. It is
believed the process of the present invention also results in the
oxidation and adsorption of any nitrogen-containing species which
can be simultaneously separated with the sulfur-containing
species.
[0062] Other compounds which also have non-bonding pairs of
electrons include amines, Heteroaromatic amines are also found in
the same stream that the above sulfides are found. Amines are more
basic than sulfides. The lone pair of electrons functions as a
Bronsted-Lowry base (proton acceptor) as well as a Lewis base
(electron-donor). This pair of electrons on the atom makes it
vulnerable to oxidation in manners similar to sulfides.
[0063] In one aspect, this invention provides a process for the
production of refinery transportation fuel or blending components
for refinery transportation fuel, which includes: providing a
distillate feedstock comprising a mixture of hydrocarbons and
sulfur-containing organic impurities; contacting the feedstock with
an oxygen-containing gas such as oxygen depleted air in an
oxidation zone in the presence of an oxidation catalyst comprising
titania-silica which also serves as an adsorbent. Because oxygen
depleted air can be used in the present invention, the
concentration of oxygen can be less than about 21 vol. %. The
oxygen-containing stream preferably should have an oxygen content
of at least 0.01 vol. %. An effective concentration is from 0.5 to
10 vol. %. The gases can be supplied from air and inert diluents
such as nitrogen if required. As those skilled in the art readily
recognize, certain compositions are explosive and the composition
of oxygen containing stream should be selected to avoid explosive
regions. The oxygen-containing gas can be circulated in amounts
ranging from 200 to 20,000 standard cubic feet per barrel.
[0064] The pressure in the oxidation/adsorption zone can range from
ambient to 3000 psig preferably from about 100 psig to about 400
psig, more preferably from about 100 psig to about 300 psig.
[0065] The temperature in the oxidation/adsorption zone can range
from about 100.degree. F. to about 600.degree. F., preferably from
about 200.degree. F. to about 500.degree. F. and most preferably
from about 300.degree. F. to about 400.degree. F.
[0066] The oxidation/adsorption process of the present invention
operates at a liquid hourly space velocity of from about 0.1
hr.sup.-1 to about 100 hr.sup.-1, preferably from about 0.2
hr.sup.-1 to about 50 hr.sup.-1, and most preferably from about 0.5
hr.sup.-1 to about 10 hr for best results. Excessively high space
velocities will result in reduced overall oxidation and
adsorption.
[0067] Generally, the oxidation/adsorption process of the present
invention begins with a distillate feedstock preheating step. The
distillate feedstock is preheated in feed/effluent heat exchangers
prior to entering a furnace for final preheating to a targeted
reaction zone temperature. The distillate feedstock can be
contacted with an oxygen-containing stream prior to, during, and/or
after preheating.
[0068] Since the oxidation reaction is generally exothermic,
interstage cooling, consisting of heat transfer devices between
fixed bed reactors or between catalyst beds in the same reactor
shell, can be employed. At least a portion of the heat generated
from the oxidation process can often be profitably recovered for
use in the oxidation process. Where this heat recovery option is
not available, cooling may be performed through cooling utilities
such as cooling water or air, or through use of a quench stream
injected directly into the reactors. Two-stage processes can
provide reduced temperature exotherm per reactor shell and provide
better oxidation reactor temperature control.
[0069] The oxidation/adsorption zone effluent is generally cooled
and the effluent stream is directed to a separator device to remove
the oxygen-containing gas which can be recycled back to the
process. The oxygen-containing gas purge rate is often controlled
to maintain a minimum or maximum oxygen content in the gas passed
to the reaction zone. Recycled oxygen-containing gas is generally
compressed, supplemented if required, with "make-up" oxygen or
oxygen-containing gas (preferably air), and injected into the
process for further oxidation.
[0070] The process of the present invention can be carried out in
any sort of gas-liquid-solid reaction zone known to those skilled
in the art. For instance, the reaction zone can consist of one or
more fixed bed reactors. A fixed bed reactor can also comprise a
plurality of catalyst beds. Additionally the reaction zone can be a
fluid bed reactor, slurry, or trickle bed reactor. The
simplification implied by the use of a heterogeneous catalyst would
facilitate a range of less conventional applications for the
process of the present invention. For instance, it is contemplated
that the process of the invention can be carried out on skid
mounted units at terminals or pipelines garage fore courts and on
board fuel cell containing vehicles where sulfur sensitive
hydrocarbon reformers and fuel cells are employed.
[0071] It is believed the heterogeneous catalyzed oxidation
according to the present invention results in the direct oxidation
of a portion of the sulfur-containing organic impurities to their
corresponding sulfones and/or sulfoxides. These sulfones and/or
sulfoxides are then adsorbed on to the catalyst.
[0072] For the purposes of this disclosure the term "oxidation
catalyst" refers to titanium-containing materials such as: [0073]
1. Amorphous Titania-Silica materials. These materials are
described in the review article by Gao and Wachs in Catalysis
Today, 51, 1999, 233-254. Ti concentration from 0.001% to 50%
atomic. Any surface area, any pore volume. [0074] 2. Titanosilicate
zeolite materials. Several type of these materials are known in the
literature; TS-1, Ti-beta, Ti-ZSM-12, Ti-MCM-41, Ti-HMS, Ti-ZSM-48,
TS-2, Ti-MCM-48, Ti-MSU, Ti-SBA-15, Ti-MMM, Ti-MWW, Ti-TUD-1 and
Ti-HSM are some of those. These materials were described in the
review article entitled "Active sites and reactive intermediates in
titanium silicate molecular sieves" by Ratnasamy and Srinivas in
Advances in Catalysis 48 (2004) 1-169. [0075] 3. Titania-Silica
mixed oxides containing up to 50% titania. [0076] 4. All of the
above catalytic materials that were subjected to silylation
treatment, as described in Schoebrechts et al. in WO 02/090468.
[0077] Preferred effective titanium-containing materials can be
selected from the group consisting of titanium silicate, Ti-MCM and
Ti-HMS.
[0078] The process of the present invention can achieve
desulfurization to a level of below about 10 ppmw and can achieve
denitrogenation to a level of below about 10 ppmw.
[0079] Generally the oxygen-containing gas is contacted with the
feedstock in the presence of the oxidation catalyst in the
oxidation/adsorption zone until the oxidation/adsorption zone
effluent reaches a predetermined sulfur content or breakthrough
which indicates the catalyst has reached the desired capacity or
loading of the sulfur species, e.g. sulfones or sulfoxides.
[0080] The oxidation/adsorption zone is then taken out of service
and regenerated. The oxidation catalysts can then be regenerated by
a number of procedures. These methods include high temperature
oxidation at conditions including a temperature of about 500 to
about 1000 degrees C. and a pressure of about 0 to about 100 psia
in the presence of an oxygen-containing gas; high temperature
pyrolysis at conditions including a temperature of about 500 to
about 1000 degrees C. and a pressure of about 0 to about 100 psia;
high temperature hydrotreatment at conditions including a
temperature of about 500 to about 700 degrees C. and a pressure of
about 25 to about 40 atmospheres in the presence of a
hydrogen-containing gas; and solvent regeneration.
[0081] An effective solvent is methanol. It is believed other polar
solvents such as acetonitrile, dimethyl sulfoxide, sulfolane,
acetic acid may be similarly effective in restoring the oxidation
catalyst essentially back to its initial activity. The solvent
regeneration is generally carried out at conditions including a
temperature of about 50 to about 400 degrees F. and a pressure of
about 0 to about 300 psig pressure, and a contact time with the
catalyst such that the liquid hourly space velocity of solvent is
maintained until sulfur concentration in the effluent extract
stream becomes constant indicating that the regeneration has been
essentially completed.
[0082] Additionally a pressure swing operation can be carried out
to regenerate the catalyst at the following conditions including a
temperature of about 100 to about 500 degrees F. and a pressure of
0 to about 50 psia pressure. Ideally, one oxidation/adsorption zone
will be used to desulfurize the feedstock while another
oxidation/adsorption zone is being regenerated after
desulfurization service.
[0083] In order to better communicate the present invention,
another preferred aspect of the invention is depicted schematically
in FIG. 1. Referring to the schematic flow diagram depicted in FIG.
1, a liquid feedstock from Feed Tank 10 is passed through conduit
15 where it is preheated and mixed with a diluted air stream 16
which air stream contains about 7 mole percent oxygen or preferably
3 mole percent oxygen.
[0084] The preheated mixture of diluted air and feed is then passed
to oxidation/adsorption zone 20. Oxidation/adsorption zone 20 may
be operated at 325.degree. F., 200 psig pressure and a liquid
hourly space velocity of 0.7 hr.sup.-1 or preferably 1.0 hr.sup.-1.
The zone can be a fixed bed downflow reactor where the fixed bed
contains titania-silica. In the reactor sulfur-containing organic
species in the feedstock are oxidized to their corresponding
sulfones and/or sulfoxides. These sulfones and/or sulfoxides are
then adsorbed to the titania-silica in the oxidation/adsorption
zone. The reaction is exothermic and the oxidation/adsorption zone
is operated in a manner such that the rise in temperature across
the oxidation/adsorption zone preferably does not exceed 25.degree.
F. The oxidation/adsorption zone can be sized to handle a 24 hour
cycle operation with a feedstock containing up to 500 ppmw sulfur
and a product sulfur specification not to exceed 10 ppmw. After a
24-hour operation cycle, oxidation/adsorption zone 20 would be
switched off-line in order to regenerate the oxidation catalyst.
The effluent stream 21 from Oxidation/adsorption zone 20 is then
passed to Reactor effluent separator 30 where a low sulfur product
or blending component is recovered in stream 31. A recycle gas
stream 32 is passed to Knockout Drum 50 where additional low sulfur
product is recovered in stream 53 and gas recycle stream 52 is
dried in Dryer 60 and recompressed (Compressor 70) and recycled to
the oxidation/adsorption zone after appropriate additions of
make-up oxygen.
[0085] FIG. 2 depicts oxidation/adsorption zone 40 in regeneration
mode. In this case methanol is passed through stream 71 from fresh
methanol tank 70 to the Oxidation Reactor Vessel 40 in regeneration
40 in order to desorb the adsorbed sulfones and/or sulfoxides. This
regeneration process can remove in excess of 99% of the adsorbed
sulfones and/or sulfoxides and essentially restore the oxidation
activity and adsorption capacity of the catalyst. The methanol- and
sulfone and/or sulfoxides-containing stream, 41 is then passed to a
spent methanol tank before it is passed to column 90 where the
methanol is recovered in stream 92 from a waste sulfone and/or
sulfoxides methanol stream 91. This waste stream is relatively low
in volume and can be sent to a hydrocracker, coker, or a distillate
hydrotreater or off-site for further processing. The desorption
regeneration can be carried out at the same pressure as the
oxidation/adsorption. Preferrably the desorption regeneration is
carried out at a low pressure equivalent to the pressure in the
distillation step. The methanol feed rate can be the same feed rate
as the hydrocarbon feedstock is fed to the oxidation/adsorption
zone. It is believed at least ten times the catalyst volume in
solvent is required to carry out the desorption/regeneration
process. Subsequent to the desorption step the oxidation/adsorption
zone can be dried out to remove any free remaining methanol. After
the drying step the catalyst in the oxidation/adsorption zone can
be calcined at 800.degree. F. using a 3% oxygen stream and
ultimately put back in service.
[0086] For a more complete understanding of the present invention,
reference should be now be made to the embodiments illustrated in
greater detail in the Examples described below.
EXAMPLE 1
[0087] A titanium silicate used in the present invention as the
oxidation catalyst and sulfone/sulfoxide adsorbent was prepared as
follows: 350 grams of tetraethylorthoslicate were added to 500
grams of water. The tetraethylorthosilicate is immiscible with
water and formed two layers with the top layer being the
tetraethylorthosilicate: 139 grams of 10% in HCl was added which
was soluble in the water layer. The two layers were heated with
stirring to about 70.degree. C. The initial reaction with the
tetraethylorthosilicate formed a single layer which upon further
heating formed a clear violet-gel. The gel was dried at room
temperature to produce a solid. The solid was washed with 3 liters
of water to reduce the amount of Cl. The catalyst was then dried
overnight at 100.degree. C. The solid can optionally be calcined at
500.degree. C. for 4 hours. The yield of catalyst was 82 grams.
[0088] Three titania-silica catalysts prepared as described above
were analyzed and were mostly amorphous), but Catalyst A and
Catalyst C contained small concentrations of the anatase polymorph
of TiO.sub.2 as shown in Table 1.
TABLE-US-00001 TABLE 1 Catalyst Wt % anatase Avg. cryst. Size,
.ANG. A 1.4(1) 85 B -- -- C 1.7(1) 98
The three catalysts were ground in a mortar and pestle. The X-ray
powder patterns were measured on a Rigaku diffractometer using the
standard configuration. Catalyst A was blended with a known
concentration of quartz internal standard in a Spex 8000
mixer/mill, and the pattern re-measured. Quantitative phase
analysis was carried out by the Rietveld method using GSAS.
EXAMPLE 2
Experimental Equipment
[0089] Pilot-scale units were used to evaluate the performance of
the catalyst with a 350 ppm-sulfur-containing diesel feed. The
pilot-scale reactor consists of a 10.5 inch length 0.75
O.D..times.0.438 inch I.D..times.0.065 inch wall 316 Stainless
Steel tubing. The reactor temperatures were maintained by three
electrically heated sections of the reactor wall inside an
insulated furnace box. The temperatures of these sections were
controlled by a programmable computer with the use of single point
thermocouples on each of the reactor wall sections. In addition, a
0.125 inch O.D. stainless steel thermowell that runs through the
middle of the reactor from the top housed a multi-point
thermocouple (three multi-point thermocouple with 2'' spacing) to
monitor internal reaction temperature.
[0090] The pilot plant reactor consisted of a preheat zone filled
with alumina chips, sieved to a Tyler screen mesh size of -20 +40
(USA Standard Testing Sieve by W. S. Tyler). The second and third
heated zones were loaded with 10 cc catalyst crushed to a Tyler
screen mesh size of -20 +40 (USA Standard Testing Sieve by W. S.
Tyler). The remainder of the reactor (temperature zone 4) was
filled with alumina chips, sieved to a Tyler screen mesh size of
-20 +40 (USA Standard Testing Sieve by W. S. Tyler) and used as a
cool-down zone and to support the catalyst. The reactor was
predominately operated in the down-flow mode, but was also been
operated in an up-flow configuration.
[0091] A Brooks flow controller was used to deliver 250 ml min-17%
oxygen diluted in nitrogen feed gas to the reactor. An oxygen
analyzer installed downstream of the reactor measured the oxygen
content of the off-gas at ambient pressure.
[0092] A precision syringe-metering pump (ISCO) delivered liquid
feed to the reactor. The feed was preheated to the reaction
temperature in the reactor preheat zone, and the temperature was
measured along the centerline by thermocouples in various
positions. The liquid product from the reactor flowed into a cooled
high-pressure separator/receiver where 7% oxygen in nitrogen was
used to maintain the outlet pressure of the reactor at operating
pressure. Reactor pressure was maintained at 200 psig by a GO back
pressure regulator on the off-gas from the separator/receiver.
Liquid samples were drained from the high-pressure
receiver/separator and analyzed for sulfur content by a Spectro
XEPOS XRF analyzer, Model XEP01. Nitrogen was determined by
chemiluminescence. Sulfur specification was determined with a
capillary GC, with a sulfur specific detector
[0093] For these experiments, 10 cc of catalyst were charged to the
reactor. Feed flow rates were operated to achieve a liquid
hydraulic space velocity (standard volume of feed in cc/hour
divided by charged volume of catalyst in cc) to range between 1.0
and 2.0 hr.sup.-1. The reaction zone temperature was maintained at
320.degree. F.+/-5.degree. F.
[0094] Experimental Procedure
[0095] After the reactor was charged with catalyst, it was
pressurized with 7% oxygen diluted in nitrogen gas at 200 psig and
gas flow was established at 250 ml min.sup.-1. The catalyst bed was
saturated with approximately 50 ml feed. A feed rate of 10-50 ml
hour.sup.-1 was then initiated. With the gas and liquid feed
established, the reactor was slowly heated to the operating
temperature of 300-400.degree. F. After the desired operating
temperature was achieved, the test begins and liquid product is
collected at hourly intervals. The liquid product was then analyzed
for sulfur content by a Spectro XEPOS model XEP01 XRF analyzer. The
reaction was continued until deactivation of the catalyst or
breakthrough occurred.
[0096] Procedure for Spent Catalyst Evaluation:
[0097] One to two microliters of the methanol extract of spent
catalyst were injected via a split injection port at 30.degree. C.
onto a 30 meter by 0.32 mm i.d. fused silica column with a 0.1
micron film of polydimethylsilicone (DB1). Column temperature was
held at 40.degree. C. for 2 minutes then programmed to increase to
300.degree. C. at 10.degree. C./minute intervals. The transfer line
from the end of the column to the mass spectrometer ion source was
held at 300.degree. C. Mass spectra were obtained at a scan rate of
0.7 seconds per mass decade at either 3000 mass resolving power or
1000 mass resolving power.
[0098] Results and Discussion:
[0099] Experiments were conducted with a titanium-silicate catalyst
using diesel fuel as the feed having the properties set forth in
Table 2 below. While the diesel feed was flowing through the
catalyst bed, in the beginning of the experiment, only pure
nitrogen gas was fed into the reactor. Results in Table 4 below
indicate that with no oxygen present in the system, sulfur
concentration in the reactor effluent was reduced by 12.92 percent.
After several hours on stream, the gas flow was switched to a gas
flow made up of 7% volume oxygen in nitrogen. As can be clearly
seen from the results, the gaseous molecular oxygen was efficiently
utilized by the catalyst to reduce the sulfur content in the
reactor effluent by 74.72 percent. These experimental results
clearly demonstrate that the titanium-silicate catalyst was
effective in removing sulfur from the feed stream when gaseous
oxygen was present in the feed gas. FIG. 3 graphically depicts the
results of the experimental run.
[0100] Additionally, Table 3 below indicates the same sulfur
compounds were present in the product as were present in the feed
but at a lower concentration. However, GC-MS analysis of methanol
extracted hydrocarbons from the spent catalyst revealed the
presence of sulfoxides and sulfones in addition to unreacted C1-C4
dibenzothiophenes. Because acid washing would be expected to
selectively remove sulfones and sulfoxides from product and
essentially none were removed, one can conclude that there were no
sulfoxides or sulfones in the product and that they had been
adsorbed on to the catalyst.
TABLE-US-00002 TABLE 2 Distillate Feed Composition Analytical Tests
Feed Inspection XRF Sulfur, ppm-w 356 Chemiluminescence (ASTM 4629)
Nitrogen, ppm-w 233 Sulfur Speciation 1- C1 Benzothiophenes, ppm S
0.30 2- C2 Benzothiophenes, ppm S 2.36 3- C3 Benzothiophenes, ppm S
9.56 4- C4 Benzothiophenes, ppm S 25.42 5- Dibenzothiophene, ppm S
9.31 6- C1 Dibenzothiophenes, ppm S 79.78 7- C2 Dibenzothiophenes,
ppm S 115.01 8- C3 Dibenzothiophenes, ppm S 60.47 9- C4
Dibenzothiophenes, ppm S 65.73 total S ppm 367.94
TABLE-US-00003 TABLE 3 Acid washed Feed Product Product Total
sulfur, ppm-w 356 90 70 Sulfur Speciation 1- C1 Benzothiophenes,
ppm S 0.30 0.00 0.00 2- C2 Benzothiophenes, ppm S 2.36 0.02 0.11 3-
C3 Benzothiophenes, ppm S 9.56 1.25 1.23 4- C4 Benzothiophenes, ppm
S 25.42 5.90 5.43 5- Dibenzothiophene, ppm S 9.31 0.00 0.00 6- C1
Dibenzothiophenes, ppm S 79.78 17.80 16.14 7- C2 Dibenzothiophenes,
ppm S 115.01 25.05 22.67 8- C3 Dibenzothiophenes, ppm S 60.47 16.28
14.98 9- C4 Dibenzothiophenes, ppm S 65.73 19.54 16.72 total S ppm
367.94 85.84 77.28
TABLE-US-00004 TABLE 4 gas add flow washed Catalyst press. temp,
feed rate, product product product product product Feed Feed hrs on
% % type psig .degree. F. LHSV gas sccm S, ppm N, ppm O, wt % TAN
S, ppm S, ppm N, ppm stream desulf denitrog Ti silicate 200 322 1
N2 250 310 128 356 233 6.63 12.92% 45.06% Ti silicate 200 322 1 N2
250 310 174 <0.10 356 233 22.00 12.92% 25.32% Ti silicate 200
323 1 7% O.sub.2 250 180 176 <0.10 356 233 22.92 49.44% 24.46%
Ti silicate 200 323 1 7% O.sub.2 250 90 137 <0.10 356 233 23.67
74.72% 41.20% Ti silicate 200 322 1 7% O.sub.2 250 120 134 <0.10
356 233 24.34 66.29% 42.49% Ti silicate 200 322 1 7% O.sub.2 250
130 138 <0.10 356 233 25.09 63.48% 40.77% Ti silicate 200 323 1
7% O.sub.2 250 170 143 0.10 356 233 25.84 52.25% 38.63% Ti silicate
200 322 1 7% O.sub.2 250 200 148 0.10 356 233 26.59 43.82% 36.48%
Ti silicate 200 322 1 7% O.sub.2 250 230 156 0.10 356 233 27.34
35.39% 33.05% Ti silicate 200 322 1 7% O.sub.2 250 250 164 0.10 356
233 28.09 29.78% 29.61% none 200 305 1 7% O.sub.2 250 346 246 0.10
0.03 253 356 233 17.00 2.81% -5.58% none 200 329 1 7% O.sub.2 250
345 243 0.10 0.03 266 356 233 43.00 3.09% -4.29%
EXAMPLE 3
[0101] Two different methods were tried for regenerating the
deactivated Ti-silicate catalyst. The first regeneration ("A")
included heat treating the spent catalyst in flowing nitrogen
(572.degree. F.) followed by air (950.degree. F.) for at least
several hours; see Table 5 below. The second regeneration ("B")
method involved soaking the catalyst in methanol in a sealed
reactor at 310.degree. F. for at least several hours followed by
calcinations in flowing 7% oxygen in nitrogen at 800.degree. F. for
at least several hours. These regenerated catalysts were then used
to carry out the process of the invention. Results are graphically
depicted in FIG. 4 and set forth in Table 6 below.
TABLE-US-00005 TABLE 5 Heated in N2 ramping T to 300 C. Collected
Condensate and weighed catalyst. Catalyst further Regeneration
procedure calcined in air to 950 F. for 4 hr. Spent cat before
regeneration Sulfur, wt % by ICP 0.154 Carbon, wt % 22.12 Hydrogen,
wt % 3.06 Nitrogen, wt % 0.22 Spent cat after regeneration Sulfur,
wt % by ICP 0.0066 Carbon, wt % 1.07 Hydrogen, wt % 0.59 Nitrogen,
ppm-w 72 Spent catalyst before regen, g 34.56 Condensate collected
during 4.68 regen, wt Condensate sulfur, ppm-wt Condensate oxygen,
wt %
TABLE-US-00006 TABLE 6 Regeneration A Regeneration B regenerate
with nitrogen at 572 F. regenerate with methanol at 310 F. Fresh
followed by calcination at 950 F. in air followed by calcination at
800 F. in 7% oxygen product S, Feed S, hrs on % product Feed hrs on
% product Feed hrs on % ppm ppm stream desulf S, ppm S, ppm stream
desulf S, ppm S, ppm stream desulf 30 356 0.75 91.57% 60 356 1.50
83.15% 35 356 1.00 90.17% 70 356 2.33 80.34% 62 356 2.00 82.58% 70
356 3.00 80.34% 100 356 3.33 71.91% 70 356 3.00 80.34% 87 356 4.00
75.56% 130 356 4.08 63.48% 108 353 4.00 69.66% 106 356 5.00 70.22%
160 356 4.83 55.06% 138 356 5.00 61.24% 136 356 6.00 61.80% 210 356
5.58 41.01% 173 356 6.00 51.40% 220 356 6.33 38.20%
[0102] Results indicate that it is possible to regenerate the
catalyst after it is deactivated in the oxidation/adsorbtion zone.
At this time, it is believed that the strongly adsorbed oxidized
sulfur compounds on the surface of the catalyst are responsible for
the catalyst deactivation. It is believed nitrogen compounds that
are present in the feed oil and the oxidized nitrogen compounds (in
the catalyst assisted oxidation reaction) may also play a role in
the catalyst deactivation.
EXAMPLE 3
[0103] In this example three separate deactivation runs were
carried out.
[0104] Table 7 shows that essentially all of the sulfur was either
deposited on the catalyst or recovered in the liquid product.
TABLE-US-00007 TABLE 7 Three separate deactivation runs at 1.5 hr,
3 hr, and 4.5 hr to mass balance sulfur and determine S, N levels
on catalyst. Run Description 1.5 hr test 3.0 hr test 4.5 hr test
Catalyst Catalyst Description Ti silicate Ti silicate Ti silicate
Age of Catalyst, hrs lineout 1.50 lineout 3.00 lineout 4.50
Operating Conditions Reaction Temperature, .degree. F. 325 325 325
Pressure, psig 200 200 200 Gas Feed 7% O2/N2 7% O2/N2 7% O2/N2 Gas
Flow Rate, sccm 250 250 250 Feed Description finished diesel
finished diesel finished diesel Feed LHSV 1.0 1.0 1.0 Analytical
Results Feed sulfur, ppm-w 335 335 335 335 335 335 Feed total
nitrogen, ppm-w 73 73 73 73 73 73 Product nitrogen, ppm-w 55 22 50
16 58 20 Product sulfur, ppm-w 286 60 276 70 284 90 Product weight,
g 84.43 17.19 84.02 32.73 83.77 50.96 Absolute sulfur in product, g
0.0241 0.0010 0.0232 0.0023 0.0238 0.0046 Spent Catalyst Sulfur,
ppm-w 580 1230 1130 Carbon, wt % 21.83 16.47 24.27 Hydrogen, wt %
3.08 2.36 3.33 Nitrogen, wt % <0.10 <0.10 <0.10 Carbon,
Hydrogen, and nitrogen, combined % 24.91 18.83 27.60 Calculations
wet catalyst wt, calculated, g 12.41 11.36 12.80 Total sulfur on
wet catalyst, g 0.0072 0.0140 0.0145 Total feed processed, g 101.62
116.75 134.73 Total sulfur processed, g 0.03404 0.03911 0.04513
Total sulfur in all product cuts, g 0.0252 0.0255 0.0284 Sulfur
mass balance, % 95.11% ###### 94.93% hrs on stream 1.5 3.0 4.5 %
desulfurization 82.09% 79.10% 73.13% % denitrogenation 69.86%
78.08% 72.60%
EXAMPLE 4
[0105] Additional runs were carried out using amorphous titanium
silicate and a mixture of Ti/MCM and Ti/HMS molecular sieves. Table
8 below and FIG. 5 show the results of these runs.
TABLE-US-00008 TABLE 8 hrs on press. gas flow product product Feed
S, Feed N, stream Catalyst type psig temp, .degree. F. LHSV feed
gas rate, sccm S, ppm N, ppm ppm ppm % desulf 2.00 Ti/MCM &
Ti/HMS soigel 200 318 1 3% O.sub.2 250 92 203 356 233 74.16% 4.00
Ti/MCM & Ti/HMS soigel 200 318 1 3% O.sub.2 250 166 160 356 233
53.37% 6.00 Ti/MCM & Ti/HMS soigel 200 318 1 3% O.sub.2 250 177
163 356 233 50.28% 2.25 Ti silicate 200 321 1 3% O.sub.2 250 74 44
356 233 79.21% 3.75 Ti silicate 200 321 1 3% O.sub.2 250 50 28 356
233 85.96% 6.00 Ti silicate 200 321 1 3% O.sub.2 250 106 47 356 233
70.22%
EXAMPLE 5
[0106] FIG. 6 shows the results of various runs carried out in
accordance with the invention wherein oxygen levels were varied and
temperatures were varied.
* * * * *