Title: Preparation of components for transportation fuels
Abstract: Economical processes are disclosed for the production of components for refinery blending of transportation fuels by selective oxidation of feedstocks comprising a mixture of hydrocarbons, sulfur-containing and nitrogen-containing organic compounds. Oxidation feedstock is contacted with a soluble quaternary ammonium salt containing halogen, sulfate, or bisulfate anion, and an immiscible aqueous phase comprising a source of hydrogen peroxide, and at least one member of the group consisting of phosphomolybdic acid and phosphotungstic acid, in a liquid reaction mixture under conditions suitable for reaction of one or more of the sulfur-containing and/or nitrogen-containing organic compounds. Blending components containing less sulfur and/or less nitrogen than the oxidation feedstock are recovered from the reaction mixture. Advantageously, at least a portion of the immiscible acid-containing phase is recycled to the oxidation.
Patent Number: 6,881,325 Issued on 04/19/2005 to Morris, et al.
| Inventors:
|
Morris; George Ernest (Cottingham, GB);
Lucy; Andrew Richard (Brough, GB);
Gong; William H. (Elmhurst, IL);
Regalbuto; Monica Cristina (Glenview, IL);
Huff, Jr.; George A. (Naperville, IL)
|
| Assignee:
|
BP Corporation North America Inc. (Warrenville, IL)
|
| Appl. No.:
|
779287 |
| Filed:
|
February 8, 2001 |
| Current U.S. Class: |
208/212; 208/189; 208/196; 208/207; 208/211; 208/221; 208/222; 208/236; 208/243 |
| Intern'l Class: |
C10G 067//12; C10G 027//04 |
| Field of Search: |
208/189,196,207,211,212,221,222,236,243
|
References Cited [Referenced By]
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| 3551328 | Dec., 1970 | Cole et al. | 208/240.
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| 3565793 | Feb., 1971 | Herbstman et al. | 208/208.
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| 3595778 | Jul., 1971 | Smetana et al. | 208/208.
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| 3816301 | Jun., 1974 | Sorgenti | 208/208.
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| 3847798 | Nov., 1974 | Yoo | 208/209.
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| 3847800 | Nov., 1974 | Guth et al. | 208/236.
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| 3909395 | Sep., 1975 | Takacs | 208/196.
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| 4494961 | Jan., 1985 | Venkat et al.
| |
| 4723963 | Feb., 1988 | Taylor.
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| 4830733 | May., 1989 | Nagju et al.
| |
| 4990242 | Feb., 1991 | Louie et al. | 208/211.
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| 5147526 | Sep., 1992 | Kukes et al.
| |
| 5288390 | Feb., 1994 | Durante | 208/3.
|
| 5720901 | Feb., 1998 | De Jong et al. | 252/373.
|
| 5814109 | Sep., 1998 | Cook et al.
| |
| 5958224 | Sep., 1999 | Ho et al. | 208/240.
|
| 6087544 | Jul., 2000 | Wittenbrink et al.
| |
| 6217748 | Apr., 2001 | Hatanaka et al. | 208/210.
|
| 6277271 | Aug., 2001 | Kocal | 208/196.
|
| 6402939 | Jun., 2002 | Yen et al. | 204/157.
|
| Foreign Patent Documents |
| 0482841 | Apr., 1992 | EP | .
|
| 0565324 | Apr., 1993 | EP | .
|
| 0858835 | Aug., 1998 | EP | .
|
Primary Examiner: Griffin; Walter D.
Attorney, Agent or Firm: Schoettle; Ekkehard
Claims
That which is claimed is:
1. A process for the production of refinery transportation fuel or blending
components for refinery transportation fuel, which process comprises:
providing a petroleum feedstock comprising a mixture of hydrocarbons,
sulfur-containing and nitrogen-containing organic compounds, the mixture
having a gravity ranging from about 10.degree. API to about 75.degree.
API;
fractionating the petroleum feedstock by distillation to provide at least
one low-boiling blending component consisting of a sulfur-lean,
mono-aromatic-rich fraction, and a high-boiling oxidation feedstock
consisting of a sulfur-rich, mono-aromatic-lean fraction;
contacting the high-boiling oxidation feedstock with a soluble quaternary
ammonium salt containing, sulfate, or bisulfate anion, and an immiscible
aqueous phase comprising a source of hydrogen peroxide, and at least one
member of the group consisting of phosphomolybdic acid and phosphotungstic
acid, in a liquid reaction mixture under conditions suitable for reaction
of one or more of the sulfur-containing and/or nitrogen-containing organic
compounds;
separating from the reaction mixture both an essentially organic liquid and
at least a portion of the immiscible aqueous phase with oxidation products
of one or more of the sulfur-containing and/or nitrogen-containing organic
compounds;
treating at least a portion of the separated organic liquid by contact with
at least one immiscible liquid comprising a solvent having a dielectric
constant in a range from about 24 to about 80 suitable to selectively
extract oxidized sulfur-containing and/or nitrogen-containing organic
compounds; and
recovering from the treated organic liquid a product comprising a mixture
of organic compounds containing less sulfur and/or less nitrogen than the
high-boiling oxidation feedstock.
2. The process according to claim 1 wherein the soluble quaternary ammonium
salt is represented by formula
CH.sub.3 N(R).sub.3 X
where X is a sulfate, or bisulfate anion, and the R's are the same or
different hydrocarbon moieties of at least 4 carbon atoms.
3. The process according to claim 1 wherein the immiscible aqueous phase
consists essentially of water, a source of hydrogen peroxide, and
phosphotungstic acid.
4. The process according to claim 3 wherein soluble quaternary ammonium
salt is represented by formula
CH.sub.3 N(R).sub.3 X
where X is a sulfate anion, and the R is a hydrocarbon moiety of about 7 to
about 10 carbon atoms.
5. The process according to claim 1 wherein the recovering of product from
the treated organic liquid includes use of at least one solid sorbent
comprising silica, and at least a portion of the separated aqueous phase
with oxidation products of one or more of the sulfur-containing and/or
nitrogen-containing organic compounds is recycled to the reaction mixture.
6. The process according to claim 5 wherein all or at least a portion of
the petroleum feedstock is a product of a hydrotreating process for
petroleum distillate consisting essentially of material boiling between
about 50.degree. C. and about 425.degree. C. which hydrotreating process
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 feedstock.
7. The process according to claim 6 further comprising treating the
immiscible aqueous phase separated from the reaction mixture to remove at
least a portion of the sulfur-containing and/or nitrogen-containing
organic compounds, recycling the treated aqueous phase to the reaction
mixture, and blending at least a portion of the low-boiling blending
component with the product containing less sulfur and/or less nitrogen
than the high-boiling oxidation feedstock to obtain a component for
refinery blending of transportation fuel.
8. The process according to claim 6 wherein the high-boiling oxidation
feedstock consists essentially of material boiling between about
200.degree. C. and about 425.degree. C.
9. The process according to claim 6 wherein the conditions of oxidation
include temperatures in a range upward from about 25.degree. C. to about
250.degree. C. and sufficient pressure to maintain the reaction mixture
substantially in a liquid phase.
10. A process for the production of refinery transportation fuel or
blending components for refinery transportation fuel, which process
comprises:
hydrotreating a petroleum distillate consisting essentially of material
boiling between about 50.degree. C. and about 425.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;
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 oxidation
feedstock consisting essentially of a sulfur-rich, mono-aromatic-lean
fraction boiling between about 200.degree. C. and about 425.degree. C.;
contacting the high-boiling oxidation feedstock with a soluble quaternary
ammonium salt containing, sulfate, or bisulfate anion, and an immiscible
aqueous phase comprising a source of hydrogen peroxide, and at least one
member of the group consisting of phosphomolybdic acid and phosphotungstic
acid, in a liquid reaction mixture under conditions suitable for reaction
of one or more of the sulfur-containing and/or nitrogen-containing organic
compounds and extraction of oxidation products from treated feedstock;
separating from the reaction mixture an essentially organic liquid and at
least a portion of the immiscible aqueous phase comprising oxidation
product of one or more of the sulfur-containing and/or nitrogen-containing
organic compounds; and
treating at least a portion of the recovered organic liquid with a solid
sorbent, an ion exchange resin, and/or a suitable immiscible liquid
containing a solvent or a soluble basic chemical compound, to obtain a
product containing less sulfur and less nitrogen than the oxidation
feedstock.
11. The process according to claim 10 wherein the soluble quaternary
ammonium salt is represented by formula
CH.sub.3 N(R).sub.3 X
where X is a sulfate anion, and the R is a hydrocarbon moiety of about 7 to
about 10 carbon atoms.
12. The process according to claim 11 wherein the immiscible aqueous phase
consists essentially of water, a source of hydrogen peroxide, and
phosphotungstic acid.
13. The process according to claim 12 wherein at least a portion of the
separated aqueous phase with oxidation products of one or more of the
sulfur-containing and/or nitrogen-containing organic compounds is treated
to remove at least a portion of the oxidation products therefrom, and
thereafter is recycled to the reaction mixture.
14. The process according to claim 11 wherein the treating of recovered
organic liquid includes use of at least one immiscible liquid comprising a
solvent having a dielectric constant in a range from about 24 to about 80
suitable to selectively extract oxidized sulfur-containing and/or
nitrogen-containing organic compounds.
15. The process according to claim 14 wherein the solvent comprises a
compound selected from the group consisting of water, methanol, ethanol
and mixtures thereof.
16. The process according to claim 10 wherein the soluble quaternary
ammonium salt is represented by formula
CH.sub.3 N[(CH.sub.2).sub.7 CH.sub.3 ].sub.3 X
where X is a sulfate anion, and the immiscible aqueous phase consists
essentially of water, a source of hydrogen peroxide, and phosphotungstic
acid.
17. The process according to claim 16 wherein the treating of recovered
organic liquid includes use of at least one solid sorbent comprising
silica.
18. The process according to claim 17 further comprising treating the
immiscible aqueous phase separated from the reaction mixture to remove at
least a portion of the sulfur-containing and/or nitrogen-containing
organic compounds, recycling the treated aqueous phase to the reaction
mixture, and blending at least a portion of the low-boiling fraction with
the product containing less sulfur and less nitrogen than the oxidation
feedstock to obtain components containing less than about 50 parts per
million of sulfur for refinery blending of a transportation fuel.
19. A process for the production of refinery transportation fuel or
blending components for refinery transportation fuel, which process
comprises:
hydrotreating a petroleum distillate consisting essentially of material
boiling between about 50.degree. C. and about 425.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;
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 oxidation
feedstock consisting essentially of a sulfur-rich, mono-aromatic-lean
fraction boiling between about 200.degree. C. and about 425.degree. C.;
contacting the high-boiling oxidation feedstock with a soluble quaternary
ammonium salt represented by formula
CH.sub.3 N(R).sub.3 X
where X is a sulfate, or bisulfate anion, and the R's are the same or
different hydrocarbon moieties of at least 4 to about 10 carbon atoms, and
an immiscible aqueous phase comprising a source of hydrogen peroxide, and
at least one member of the group consisting of phosphomolybdic acid and
phosphotungstic acid, in a liquid reaction mixture under conditions
suitable for reaction of one or more of the sulfur-containing and/or
nitrogen-containing organic compounds and extraction of oxidation products
from treated feedstock;
separating from the reaction mixture an essentially organic liquid and at
least a portion of the immiscible aqueous phase comprising oxidation
products of one or more of the sulfur-containing and/or
nitrogen-containing organic compounds; and
treating at least a portion of the recovered organic liquid with a suitable
immiscible aqueous liquid containing a solvent or a soluble basic chemical
compounds to obtain a product containing less sulfur and less nitrogen
than the oxidation feedstock.
Description
TECHNICAL FIELD
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 integrated
processes which include selective oxidation of a petroleum distillate
whereby the incorporation of oxygen into hydrocarbon compounds,
sulfur-containing organic compounds, and/or nitrogen-containing organic
compounds assists by oxidation removal of sulfur and/or nitrogen from
components for refinery blending of transportation fuels which are
friendly to the environment.
The oxidation feedstock is contacted in a liquid reaction mixture with a
soluble quaternary ammonium salt and an immiscible aqueous phase
comprising a source of hydrogen peroxide and a phospho-metallic acid,
under conditions suitable for the oxidation of one or more of the
sulfur-containing and/or nitrogen-containing organic compounds. Blending
components containing less sulfur and/or less nitrogen than the oxidation
feedstock are recovered from the reaction mixture. Advantageously, at
least a portion of the immiscible phospho-metallic acid containing phase
is also recovered from the reaction mixture and recycled to the oxidation.
Integrated processes of this invention may also provide their own source
of high-boiling oxidation feedstock derived from other refinery units, for
example, by hydrotreating a petroleum distillate.
Beneficially, the instant oxidation process is very selective, i.e.
preferentially compounds in which a sulfur atom the sterically hindered
are oxidized rather than aromatic hydrocarbons. Products can be used
directly as transportation fuels, blending components, and/or
fractionated, as by further distillation, to provide, for example, more
suitable components for blending into diesel fuels.
BACKGROUND OF THE INVENTION
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 engine named for him
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.
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 crudes is low. Generally,
sulfur concentration in crude is less than about 8 percent, with most
crudes 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.
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.
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 injectors and
other moving parts which come in contact with the fuel under high
pressures.
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 specifications 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 world-wide trend
must be expected to continue to even lower levels for sulfur.
In one aspect, pending introduction of new emission regulations in
California and Federal markets 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.
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.
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). Thus, the root cause of health concerns over diesel
emissions can be traced to the inhalation of these very small carbon
particles containing toxic hydrocarbons deep into the lungs.
While an increase in combustion temperature can reduce particulate, 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.
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 need would need
sulfur levels below 10 ppm to remain active.
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. While legislation on sulfur in
diesel fuel in Europe, Japan and the U.S. has recently lowered the
specification to 0.05 percent by weight (max.), indications are that
future specifications may go far below the current 0.05 percent by weight
level.
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).
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.
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.
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 a 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 in
the name of Jin Sun Yoo and U.S. Pat. No. 5,288,390 in the name of 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
desulfuriztion while decreasing cracking or coke formation.
Several different oxygenation methods for improving fuels have been
described in the past. For example, U.S. Pat. No. 2,521,698 describes a
partial oxidation of hydrocarbon fuels as improving cetane number. This
patent suggests that the fuel should have a relatively low aromatic ring
content and a high paraffinic content. U.S. Pat. No. 2,912,313 states that
an increase in cetane number is obtained by adding both a peroxide and a
dihalo compound to middle distillate fuels. U.S. Pat. No. 2,472,152
describes a method for improving the cetane number of middle distillate
fractions by the oxidation of saturated cyclic hydrocarbon or naphthenic
hydrocarbons in such fractions to form naphthenic peroxides. This patent
suggests that the oxidation may be accelerated in the presence of an
oil-soluble metal salt as an initiator, but is preferably carried out in
the presence of an inorganic base. However, the naphthenic peroxides
formed are deleterious gum initiators. Consequently, gum inhibitors such
as phenols, cresols and cresyic acids must be added to the oxidized
material to reduce or prevent gum formation. These latter compounds are
toxic and carcinogenic.
U.S. Pat. No. 4,494,961 in the name of Chaya Venkat and Dennnis E. Walsh
relates to improving the cetane number of raw, untreated, highly aromatic,
middle distillate fractions having a low hydrogen content by contacting
the fraction at a temperature of from 50.degree. C. to 350.degree. C. and
under mild oxidizing conditions in the presence of a catalyst which is
either (i) an alkaline earth metal permanganate, (ii) an oxide of a metal
of Groups IB, IIB, IIIB, IVB, VB, VIB, VIIB or VIIIB of the periodic
table, or a mixture of (i) and (ii). European Patent Application 0 252 606
A2 also relates to improving the cetane rating of a middle distillate fuel
fraction which may be hydro-refined by contacting the fraction with oxygen
or oxidant, in the presence of catalytic metals such as tin, antimony,
lead, bismuth and transition metals of Groups IB, IIB, VB, VIB, VIIB and
VIIIB of the periodic table, preferably as an oil-soluble metal salt. The
application states that the catalyst selectively oxidizes benzylic carbon
atoms in the fuel to ketones.
Recently, U.S. Pat. No. 4,723,963 in the name of William F. Taylor suggests
that cetane number is improved by including at least 3 weight percent
oxygenated aromatic compounds in middle distillate hydrocarbon fuel
boiling in the range of 160.degree. C. to 400.degree. C. This patent
states that the oxygenated alkylaromatics and/or oxygenated hydroaromatics
are preferably oxygenated at the benzylic carbon proton.
More recently, oxidative desulfurization of middle distillates by reaction
with aqueous hydrogen peroxide catalyzed by phosphotungstic acid and
tri-n-octylmethylammonium chloride as phase transfer reagent followed by
silica adsorption of oxidized sulfur compounds has been described by
Collins et al. (Journal of Molecular Catalysis (A): Chemical 117 (1997)
397-403). Collins et al. described the oxidative desulfurization of a
winter grade diesel oil which had not undergone hydrotreating. While
Collins et al. suggest that the sulfur species resistant to
hydrodesulfurization should be susceptible to oxidative desulfurization,
the concentrations of such resistant sulfur components in
hydrodesulfurized diesel may already be relatively low compared with the
diesel oils treated by Collins et al. Also see European Patent Application
0 482 841 A1 filed Oct. 18, 1991 in the name of Frances Mary Colins,
Andrew Richard Lucy, and David John Harry Smith.
U.S. Pat. No. 5,814,109 in the name of Bruce R. Cook, Paul J. Berlowitz and
Robert J. Wittenbrink relates to producing Diesel fuel additive,
especially via a Fischer-Tropsch hydrocarbon synthesis process, preferably
a non-shifting process. In producing the additive, an essentially sulfur
free product of these Fischer-Tropsch processes is separated into a
high-boiling fraction and a low-boiling fraction, e.g., a fraction boiling
below 700.degree. F. The high-boiling of the Fischer-Tropsch reaction
product is hydroisomerizied at conditions said to be sufficient to convert
the high-boiling fraction to a mixture of paraffins and isoparaffins
boiling below 700.degree. F. This mixture is blended with the low-boiling
of the Fischer-Tropsch reaction product to recover the diesel additive
said to be useful for improving the cetane number or lubricity, or both
the cetane number and lubricity, of a mid-distillate, Diesel fuel.
U.S. Pat. No. 6,087,544 in the name of Robert J. Wittenbrink, Darryl P.
Klein, Michele S Touvelle, Michel Daage and Paul J. Berlowitz 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 product 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.
There is, therefore, a present need for catalytic processes to prepare
oxygenated aromatic compounds in middle distillate hydrocarbon fuel,
particularly processes, which do not have the above disadvantages. An
improved process should be carried out advantageously in the liquid phase
using a suitable oxygenation-promoting catalyst system, preferably an
oxygenation catalyst capable of enhancing the incorporation of oxygen into
a mixture of organic compounds and/or assisting by oxidation removal of
sulfur or nitrogen from a mixture of organic compounds suitable as
blending components for refinery transportation fuels liquid at ambient
conditions.
This invention is directed to overcoming the problems set forth above in
order to provide components for refinery blending of transportation fuels
friendly to the environment.
SUMMARY OF THE INVENTION
Economical processes are disclosed for production of components for
refinery blending of transportation fuels by selective oxidation of a
petroleum distillate whereby the incorporation of oxygen into hydrocarbon
compounds, sulfur-containing organic compounds, and/or nitrogen-containing
organic compounds assists by oxidation removal of sulfur and/or nitrogen
from components for refinery blending of transportation fuels which are
friendly to the environment. This invention contemplates the treatment of
various type hydrocarbon materials, especially hydrocarbon oils of
petroleum origin which contain sulfur at levels of about 150 ppm to about
500 ppm or even higher.
Essential elements of the invention include fractionating the petroleum
feedstock by distillation to provide at least one low-boiling blending
component consisting of a sulfur-lean, mono-aromatic-rich fraction, and a
high-boiling oxidation feedstock consisting of a sulfur-rich,
mono-aromatic-lean fraction. For the purpose of the present invention, the
term "oxidation" is defined as any means by which one or more
sulfur-containing organic compound and/or nitrogen-containing organic
compound is oxidized, e.g., the sulfur atom of a sulfur-containing organic
molecule is oxidized to a sulfoxide and/or sulfone.
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 oxidation feedstock
comprising a mixture of hydrocarbons, sulfur-containing and
nitrogen-containing organic compounds, the mixture having a gravity
ranging from about 10.degree. API to about 75.degree. API, fractionating
the petroleum feedstock by distillation to provide at least one
low-boiling blending component consisting of a sulfur-lean,
mono-aromatic-rich fraction, and a high-boiling oxidation feedstock
consisting of a sulfur-rich, mono-aromatic-lean fraction. This
high-boiling oxidation feedstock is contacted the with a soluble
quaternary ammonium salt containing halogen, sulfate, or bisulfate anion,
and an immiscible aqueous phase comprising a source of hydrogen peroxide,
and at least one phospho-metallic acid selected from the group consisting
of phosphomolybdic acid and phosphotungstic acid, in a liquid reaction
mixture under conditions suitable for oxidation of one or more of the
sulfur-containing and/or nitrogen-containing organic compounds. The
reaction mixture is separated to recover both an essentially organic
liquid and at least a portion of the immiscible aqueous phase. Product
comprising a mixture of organic compounds containing less sulfur and/or
less nitrogen than the high-boiling oxidation feedstock is recovered from
the organic liquid.
Advantageously, the high-boiling oxidation feedstock consists essentially
of material boiling between about 200.degree. C. and about 425.degree. C.
Conditions of oxidation include temperatures in a range upward from about
25.degree. C. to about 250.degree. C. and sufficient pressure to maintain
the reaction mixture substantially in a liquid phase. Beneficially, sulfur
levels of product are less than about 50 ppm, and preferably less than
about 15 ppm. This invention is particularly useful towards
sulfur-containing organic compounds in the oxidation feedstock which
includes compounds in which the sulfur atom is sterically hindered, as for
example in multi-ring aromatic sulfur compounds. Typically, the
sulfur-containing organic compounds include at least sulfides,
heteroaromatic sulfides, and/or compounds selected from the group
consisting of substituted benzothiophenes and dibenzothiophenes.
Generally, for use in this invention, the soluble quaternary ammonium salt
is represented by formula
CH.sub.3 N(R).sub.3 X
where X is a halogen, sulfate, or bisulfate anion, and the R's are the same
or different hydrocarbon moieties of at least 4 carbon atoms. Preferably,
the anion X is sulfate, or X is selected from the group consisting of
chlorine anion and bromine anion. More preferably, the anion X is a
chlorine anion or sulfate anion, and the R's are the same or different
hydrocarbon moieties of about 7 to about 10 carbon atoms. Most preferably
the anion X is a chlorine anion and the R is a hydrocarbon moiety of about
7 to about 10.
Generally, for use in this invention, the immiscible aqueous phase consists
essentially of water, a source of hydrogen peroxide, and phosphotungstic
acid.
In a further aspect of this invention, at least a portion of the immiscible
aqueous phase separated from the organic liquid phase of the reaction
mixture is recycled to the reaction mixture.
In one aspect of this invention all or at least a portion of the petroleum
feedstock is a product of a hydrotreating process for petroleum distillate
consisting essentially of material boiling between about 50.degree. C. and
about 425.degree. C. which hydrotreating process 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
feedstock.
Typically, useful hydrogenation catalysts comprises at least one active
metal, selected from the group consisting of the d-transition elements,
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. Hydrogenation
catalysts beneficially contain a combination of metals. Preferred are
hydrogenation catalysts containing at least two metals selected from the
group consisting of cobalt, nickel, molybdenum and tungsten. More
preferably, co-metals are cobalt and molybdenum or nickel and molybdenum.
Advantageously, the hydrogenation catalyst comprises at least one active
metal, each incorporated onto a metal oxide support, such as alumina in an
amount of from about 0.1 percent to about 20 percent by weight of the
total catalyst.
In one aspect, this invention provides for the production of refinery
transportation fuel or blending components for refinery transportation
fuel comprising the following steps: hydrotreating a petroleum distillate
consisting essentially of material boiling between about 50.degree. C. and
about 425.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;
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 oxidation
feedstock consisting of a sulfur-rich, mono-aromatic-lean fraction;
contacting the high-boiling oxidation feedstock with a soluble quaternary
ammonium salt containing halogen, sulfate, or bisulfate anion, and an
immiscible aqueous phase comprising a source of hydrogen peroxide, and at
least one member of the group consisting of phosphomolybdic acid and
phosphotungstic acid, in a liquid reaction mixture under conditions
suitable for oxidation of one or more of the sulfur-containing and/or
nitrogen-containing organic compounds; separating from the reaction
mixture an essentially organic liquid and at least a portion of the
immiscible aqueous phase; and treating at least a portion of the recovered
organic liquid with a solid sorbent, an ion exchange resin, and/or a
suitable immiscible liquid containing a solvent or a soluble basic
chemical compound, to obtain a product containing less sulfur and/or less
nitrogen than the oxidation feedstock.
Where the oxidation feedstock is a high-boiling distillate fraction derived
from hydrogenation of a refinery stream, the refinery stream consists
essentially of material boiling between about 200.degree. C. and about
425.degree. C. Preferably the refinery stream consisting essentially of
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.
Preferably, the soluble quaternary ammonium salt is represented by formula
CH.sub.3 N[(CH.sub.2).sub.7 CH.sub.3 ].sub.3 X
where X is selected from the group consisting of chlorine anion and sulfate
anion, and the immiscible aqueous phase consists essentially of water, a
source of hydrogen peroxide, and phosphotungstic acid. Beneficially, at
least a portion of the separated aqueous phase is recycled to the reaction
mixture.
In another aspect of this invention the treating of recovered organic
liquid includes use of at least one immiscible liquid comprising an
aqueous solution of a soluble basic chemical compound selected from the
group consisting of sodium, potassium, barium, calcium and magnesium in
the form of hydroxide, carbonate or bicarbonate. Particularly useful are
aqueous solution of sodium hydroxide or bicarbonate.
In one aspect of this invention the treating of the recovered organic phase
includes use of at least one solid sorbent comprising alumina and/or
silica, and preferably silica.
In another aspect of this invention the treating of recovered organic
liquid includes use of at least one immiscible liquid comprising a solvent
having a dielectric constant suitable to selectively extract oxidized
sulfur-containing and/or nitrogen-containing organic compounds.
Advantageously, the solvent has a dielectric constant in a range from
about 24 to about 80. Useful solvents include mono- and dihydric alcohols
of 2 to about 6 carbon atoms, preferably methanol, ethanol, propanol,
ethylene glycol, propylene glycol, butylene glycol and aqueous solutions
thereof. Particularly useful are immiscible liquids wherein the solvent
comprises a compound that is selected from the group consisting of water,
methanol, ethanol and mixtures thereof.
In yet another aspect of this invention the soluble basic chemical compound
is sodium bicarbonate, and the treating of the organic liquid further
comprises subsequent use of at least one other immiscible liquid
comprising methanol.
In a different aspect, this invention provides a process for the production
of refinery transportation fuel or blending components for refinery
transportation fuel, which process comprises: hydrotreating a petroleum
distillate consisting essentially of material boiling between about
50.degree. C. and about 425.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; contacting the hydrotreated petroleum
distillate with a soluble quaternary ammonium salt containing halogen,
sulfate, or bisulfate anion, and an immiscible aqueous phase comprising a
source of hydrogen peroxide, and at least one phospho-metallic acid, in a
liquid reaction mixture under conditions suitable for reaction of one or
more of the sulfur-containing organic compounds; separating from the
reaction mixture both an essentially organic liquid and at least a portion
of the immiscible aqueous phase; and recovering from the organic liquid a
product comprising a mixture of organic compounds containing less sulfur
and/or less nitrogen than the high-boiling oxidation feedstock.
In other aspects of this invention, continuous processes are provided
wherein the step of contacting the oxidation feedstock and immiscible
phase is carried out continuously with counter-current, cross-current, or
co-current flow of the two phases.
In one aspect of this invention, the recovered organic liquid of the
reaction mixture is contacted sequentially with (i) an ion exchange resin
and (ii) a heterogeneous sorbent to obtain a product having a suitable
total acid number.
For a more complete understanding of the present invention, reference
should now be made to the embodiments illustrated in greater detail in the
accompanying drawing and described below by way of examples of the
invention.
BRIEF DESCRIPTION OF THE DRAWING
The drawing is a schematic flow diagram depicting a preferred aspect of the
present invention for continuous production of components for blending of
transportation fuels which are liquid at ambient conditions. Elements of
the invention in this schematic flow diagram include hydrotreating a
petroleum distillate with a source of dihydrogen (molecular hydrogen), and
fractionating the hydrotreated petroleum to provide a low-boiling blending
component consisting of a sulfur-lean, mono-aromatic-rich fraction, and a
high-boiling oxidation feedstock consisting of a sulfur-rich,
mono-aromatic-lean fraction. This high-boiling oxidation feedstock is
contacted with a soluble quaternary ammonium salt containing halogen,
sulfate, or bisulfate anion, and an immiscible aqueous phase comprising a
source of hydrogen peroxide, and at least one phospho-metallic acid in a
liquid reaction mixture maintained under conditions suitable for the
oxidation of one or more of the sulfur-containing and/or
nitrogen-containing organic compounds. Thereafter, the immiscible phases
are separated by gravity to recover a portion of the phospho-metallic acid
containing phase for recycle. The other portion of the reaction mixture is
contacted with a solid sorbent and/or an anion exchange resin to recover a
mixture of organic products containing less sulfur and/or less nitrogen
than the oxidation feedstock.
GENERAL DESCRIPTION
Suitable feedstocks generally comprise most refinery streams consisting
substantially of hydrocarbon compounds which are liquid at ambient
conditions. Suitable oxidation feedstock generally has an API gravity
ranging from about 10.degree. API to about 100.degree. API, preferably
from about 10.degree. API to about 75 or 100.degree. API, and more
preferably from about 15.degree. API to about 50.degree. API for best
results. These streams include, but are not limited to, fluid catalytic
process naphtha, fluid or delayed process naphtha, light virgin naphtha,
hydrocracker naphtha, hydrotreating process naphthas, alkylate, isomerate,
catalytic reformate, and aromatic derivatives of these streams such
benzene, toluene, xylene, and combinations thereof. Catalytic reformate
and catalytic cracking process naphthas can often be split into narrower
boiling range streams such as light and heavy catalytic naphthas and light
and heavy catalytic reformate, which can be specifically customized for
use as a feedstock in accordance with the present invention. The preferred
streams are light virgin naphtha, catalytic cracking naphthas including
light and heavy catalytic cracking unit naphtha, catalytic reformate
including light and heavy catalytic reformate and derivatives of such
refinery hydrocarbon streams.
Suitable oxidation feedstocks generally include refinery distillate steams
boiling at a temperature range from about 50.degree. C. to about
425.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, 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.
It is also anticipated that one or more of the above distillate steams can
be combined for use as oxidation feedstock. 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.
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.
By means of liquid phase oxidation according to this invention it is
possible to selectively convert these sulfides into, more polar, Lewis
basic, oxygenated sulfur compounds such as sulfoxides and sulfones. A
compound such as dimethylsulfide is a very non-polar molecule, whereas
when oxidized, the molecule is very polar. Accordingly, by selectively
oxidizing heteroaromatic sulfides such as benzo- and dibenzothiophene
found in a refinery streams, processes of the invention are able to
selectively bring about a higher polarity characteristic to these
heteroaromatic compounds. Where the polarity of these unwanted sulfur
compounds is increased by means of liquid phase oxidation according to
this invention, they can be selectively extracted by a polar solvent
and/or a Lewis acid sorbent while the bulk of the hydrocarbon stream is
unaffected.
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.
Generally for oxidation reactions according to the invention, the hydrogen
peroxide concentration in the aqueous phase is in the range of about 3 to
about 15 percent by weight. Preferably, the hydrogen peroxide
concentration in the aqueous phase during the oxidation reaction is in the
range of about 5 to about 10 percent by weight.
Broadly, the appropriate amount of hydrogen peroxide used herein is the
stoichiometric amount necessary for oxidation of one or more of the
sulfur-containing and/or nitrogen-containing organic compounds in the
oxidation feedstock and is readily determined by direct experimentation
with a selected feedstock. With a higher concentration of hydrogen
peroxide, the selectivity generally tends to favor the more highly
oxidized sulfone which beneficially is even more polar than the sulfoxide.
The statement that oxidation according to the invention in the liquid
reaction mixture comprises a step whereby an oxygen atom is donated to the
divalent sulfur atom is not to be taken to imply that processes according
to the invention actually proceeds via such a reaction mechanism.
By contacting the oxidation feedstock with a soluble quaternary ammonium
salt and an immiscible aqueous phase of hydrogen peroxide and
phospho-metallic acid, the tightly substituted sulfides are oxidized into
their corresponding sulfoxides and sulfones with negligible if any
co-oxidation of mononuclear aromatics. These oxidation products due to
their high polarity, can be readily removed by separation techniques such
as sorption, extraction and/or distillation. The high selectivity of the
oxidants, coupled with the small amount of tightly substituted sulfides in
hydrotreated streams, makes the instant invention a particularly effective
deep desulfurization means with minimum yield loss. The yield loss
corresponds to the amount of tightly substituted sulfides oxidized. Since
the amount of tightly substituted sulfides present in a hydrotreated crude
is rather small, the yield loss is correspondingly small.
Broadly, the liquid phase oxidation reactions are rather mild and can even
be carried out at temperatures as low as room temperature. More
particularly, the liquid phase oxidation will be conducted under any
conditions capable of converting the tightly substituted sulfides into
their corresponding sulfoxides and sulfones at reasonable rates.
In accordance with this invention conditions of the liquid mixture suitable
for oxidation during the contacting, the oxidation feedstock with the
organic peracid-containing immiscible phase include any pressure at which
the desired oxidation reactions proceed. Typically, temperatures upward
from about 10.degree. C. are suitable, and sufficient pressure to maintain
the reaction mixture substantially in a liquid phase. Preferred
temperatures are between about 25.degree. C. and about 250.degree. C.,
with temperatures between about 50.degree. and about 150.degree. C. being
more preferred.
Integrated processes of the invention can include one or more selective
separation steps using solid sorbents capable of removing sulfoxides and
sulfones. Non-limiting examples of such sorbents, commonly known to the
skilled artisan, include activated carbons, activated bauxite, activated
clay, activated coke, alumina, and silica gel. The oxidized sulfur
containing hydrocarbon material is contacted with solid sorbent for a time
sufficient to reduce the sulfur content of the hydrocarbon phase.
Integrated processes of the invention can include one or more selective
separation steps using an immiscible liquid containing a soluble basic
chemical compound. The oxidized sulfur containing hydrocarbon material is
contacted with the solution of chemical base for a time sufficient to
reduce the acid content of the hydrocarbon phase, generally from about 1
second to about 24 hours, preferably from 1 minute to 60 minutes. The
reaction temperature is generally from about 10.degree. C. to about
230.degree. C., preferably from about 40.degree. C. to about 150.degree.
C.
Generally, the suitable basic compounds include ammonia or any hydroxide,
carbonate or bicarbonate of an element selected f
