U.S. patent application number 12/889807 was filed with the patent office on 2011-03-31 for process for removing nitrogen compounds from a hydrocarbon stream.
This patent application is currently assigned to UOP LLC. Invention is credited to Deng-Yang Jan, Vladislav I. Kanazirev, Michael A. Schultz.
Application Number | 20110073527 12/889807 |
Document ID | / |
Family ID | 43779121 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110073527 |
Kind Code |
A1 |
Jan; Deng-Yang ; et
al. |
March 31, 2011 |
Process for Removing Nitrogen Compounds from a Hydrocarbon
Stream
Abstract
Disclosed is a process for removing nitrogen from a hydrocarbon
feed stream by contacting the hydrocarbon feed stream with an
adsorbent at nitrogen removal conditions to produce a hydrocarbon
effluent stream having a lower nitrogen content relative to the
hydrocarbon feed stream. The hydrocarbon feed stream comprises an
aromatic compound, an organic nitrogen compound, and a diolefin
compound.
Inventors: |
Jan; Deng-Yang; (Elk Grove
Village, IL) ; Schultz; Michael A.; (Kuala Lumpur,
MY) ; Kanazirev; Vladislav I.; (Arlington Heights,
IL) |
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
43779121 |
Appl. No.: |
12/889807 |
Filed: |
September 24, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61247261 |
Sep 30, 2009 |
|
|
|
Current U.S.
Class: |
208/254R |
Current CPC
Class: |
C10G 2300/202 20130101;
C10G 2300/1096 20130101; C10G 25/05 20130101; C10G 2300/1088
20130101 |
Class at
Publication: |
208/254.R |
International
Class: |
C10G 29/16 20060101
C10G029/16 |
Claims
1. A process for removing nitrogen from a hydrocarbon feed stream
comprising an aromatic compound, an organic nitrogen compound, and
a diolefin compound, the process comprising: contacting the
hydrocarbon feed stream with an adsorbent at nitrogen removal
conditions to produce a hydrocarbon effluent stream having a lower
nitrogen content relative to the hydrocarbon feed stream; wherein
the adsorbent comprises a zeolite component, an alumina component
and a metal component (Madd); the alumina component ranging an
amount from about 40 wt % to about 90 wt % of the adsorbent, and
the metal component ranging in an amount from about 0.015 moles to
0.08 moles of the metal as the oxide per 100 g of the
adsorbent.
2. The process of claim 1 wherein the zeolite component comprises
an X zeolite.
3. The process of claim 1 wherein a mass ratio of the alumina
component to the zeolite component in the adsorbent ranges from
about 18:1 to about 2:3.
4. The process of claim 1 wherein the metal component (Madd) is an
alkali metal selected from the group consisting of sodium,
potassium, lithium, rubidium, cesium and mixtures thereof.
5. The process of claim 1 wherein the aromatic compound is benzene
and is present in an amount ranging from about 5 mass % to about
99.9 mass % of the hydrocarbon feed stream.
6. The process of claim 1 wherein the organic nitrogen compound is
selected from the group consisting of basic nitrogen compounds,
weakly basic nitriles, and combinations thereof.
7. The process of claim 6 wherein the organic nitrogen compound is
present in an amount ranging from about 30 ppb-wt to about 1 mole %
of the hydrocarbon feed stream.
8. The process of claim 6 wherein the organic nitrogen compound is
weakly basic nitriles and is present in an amount ranging from
about 30 ppb-wt to about 100 ppm-wt of the hydrocarbon feed
stream.
9. The process of claim 1 wherein the diolefin compound comprises
at least one of a C.sub.4 diolefin, a C.sub.5 diolefin, and a
C.sub.6 diolefin; and the diolefin compound is present in an amount
ranging from about 30 ppb-wt to about 3000 ppm-wt of the
hydrocarbon feed stream.
10. The process of claim 1 wherein the nitrogen removal conditions
include a temperature from about 25.degree. C. to about 300.degree.
C. and a pressure from about 34.5 kPa(g) to about 4136.9
kPa(g).
11. The process of claim 1 wherein a nitrogen to unsaturated
aliphatic compound removal is greater than 1 on a relative percent
basis.
12. The process of claim 1 wherein a nitrogen to diolefin removal
is greater than 1 on a relative mass percent basis.
13. The process of claim 1 wherein a nitrogen to diolefin removal
is at least 1.5 on a relative mass percent basis.
14. The process of claim 1 wherein a nitrogen to diolefin removal
is at least 2 on a relative mass percent basis.
15. The process of claim 1 wherein at least about 50 wt % of the
nitrogen is removed from the hydrocarbon feed stream on an
elemental basis.
16. The process of claim 1 wherein at least about 70 wt % of the
nitrogen is removed from the hydrocarbon feed stream on an
elemental basis.
17. The process of claim 1 wherein a diolefin content of the
hydrocarbon effluent stream is at least 30% of the diolefin content
of the hydrocarbon feed stream.
18. The process of claim 1 wherein a diolefin content of the
hydrocarbon effluent stream is at least 50% of the diolefin content
of the hydrocarbon feed stream.
19. The process of claim 1 wherein a nitrogen content of the
hydrocarbon effluent stream is no more than about 50% of the
nitrogen content of the hydrocarbon feed stream and a diolefin
content of the hydrocarbon effluent stream is at least 30% of the
diolefin content of the hydrocarbon feed stream.
20. The process of claim 1 wherein a nitrogen content of the
hydrocarbon effluent stream is no more than about 50% of the
nitrogen content of the hydrocarbon feed stream and a diolefin
content of the hydrocarbon effluent stream is at least 50% of the
diolefin content of the hydrocarbon feed stream.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/247,261 filed Sep. 30, 2009.
FIELD OF THE INVENTION
[0002] This invention relates to a process for removing nitrogen
compounds from a hydrocarbon stream. More particularly, this
invention relates to the use of a selective adsorption process for
removing nitrogen compounds from a hydrocarbon stream.
BACKGROUND OF THE INVENTION
[0003] The use of molecular sieves as catalysts in aromatic
conversion processes are well known in the chemical processing and
refining industry. Aromatic conversion reactions of considerable
commercial importance include the alkylation of aromatic compounds
such as in the production of ethyltoluene, xylene, ethylbenzene,
cumene, or higher alkyl aromatics and in disproportionation
reactions such as toluene disproportionation, xylene isomerization,
or the transalkylation of polyalkylbenzenes to monoalkylbenzenes.
Often the feedstock to such an aromatic conversion process will
include an aromatic component or alkylation substrate, such as
benzene, and a C.sub.2 to C.sub.20 olefin alkylating agent or a
polyalkyl aromatic hydrocarbon transalkylating agent. In the
alkylation zone, the aromatic feed stream and the olefinic feed
stream may be reacted over an alkylation catalyst to produce
alkylated aromatics, e.g. cumene or ethylbenzene. A portion or all
of the alkylation substrate may be provided by other process units
including the separation section of a styrene process unit.
Polyalkylated benzenes are separated from monoalkylated benzene
product and recycled to a transalkylation zone and contacted with
benzene over a transalkylation catalyst to yield monoalkylated
benzenes and benzene.
[0004] Catalysts for aromatic conversion processes generally
comprise zeolitic molecular sieves. Examples include, zeolite beta
(U.S. Pat. No. 4,891,458); zeolite Y, zeolite omega and zeolite
beta (U.S. Pat. No. 5,030,786); X, Y, L, B, ZSM-5 and Omega crystal
types (U.S. Pat. No. 4,185,040); X, Y, ultrastable Y, L, Omega, and
mordenite zeolites (U.S. Pat. No. 4,774,377); and UZM-8 zeolites
(U.S. Pat. No. 6,756,030 and U.S. Pat. No. 7,091,390). It is known
in the art that the aromatic feed stream to aromatic conversion
processes often contains nitrogen compounds, including weakly basic
organic nitrogen compounds such as nitriles, that can, even at ppm
and ppb levels, cumulatively act to poison the downstream aromatic
conversion catalysts such as aromatic alkylation catalysts and
significantly shorten their useful life. Use of a variety of
zeolitic or molecular sieve guard beds to remove one or more types
of nitrogen compounds from an aromatic hydrocarbon stream upstream
of an aromatic conversion process are known in the art. Examples
include: U.S. Pat. No. 7,205,448; U.S. Pat. No. 5,220,099; WO
00/35836; WO 01/07383; U.S. Pat. No. 4,846,962; U.S. Pat. No.
6,019,887; and U.S. Pat. No. 6,107,535. U.S. Pat. No. 7,205,448
discloses an acidic molecular sieve adsorbent preferentially
adsorbs water and basic organic nitrogen compounds over weakly
basic organic nitrogen compounds such as nitrites at lower
temperatures and elevated temperatures improve the capacity of
acidic molecular sieve adsorbents to adsorb nitrites in the
presence of water.
[0005] It has recently been discovered that unsaturated aliphatic
hydrocarbons such as olefinic compounds, and particularly
diolefins, can shorten the effective life of adsorbents, e.g.
nitrogen adsorptive zeolites or molecular sieves, used in nitrogen
guard beds that are applied to various process streams, including
aromatic hydrocarbon feeds upstream of an aromatic conversion
process such as alkylation. These unsaturated aliphatic, e.g.
olefinic, compounds are present in aromatic process streams
contaminated with nitrogen compounds, including benzene streams
generated in styrene process separation sections and other streams
requiring removal of the nitrogen compounds prior to being
contacted with a catalyst or other material susceptible to nitrogen
poisoning. The presence, in particular, of highly unsaturated
olefinic compounds, e.g. C.sub.4-C.sub.6 diolefins, in aromatic
streams having nitrogen compound contaminants, adversely impacts
the performance of nitrogen adsorptive materials. Without being
bound by theory, it is believed that the olefinic compounds and/or
other unsaturated aliphatic compounds may shorten the life of the
nitrogen adsorbent by competing with the nitrogen compounds for the
adsorption sites and/or reacting, e.g. with aromatics such as
benzene, to form heavy reaction products that deposit on the
nitrogen guard bed adsorbent.
SUMMARY OF THE INVENTION
[0006] The invention relates to methods for removing nitrogen
compounds from a hydrocarbon stream while minimizing the adsorption
and/or reaction of unsaturated aliphatic compounds, e.g. olefins
and diolefins that are present in the hydrocarbon stream. The
invention enables longer adsorbent life which minimizes the need to
regenerate or replace the adsorbent. The invention may also be used
in existing guard bed systems without the need for additional
equipment.
[0007] In an embodiment, the invention is a process for removing
nitrogen from a hydrocarbon feed stream comprising an aromatic
compound, an organic nitrogen compound, and a diolefin compound,
the process comprising: contacting the hydrocarbon feed stream with
an adsorbent at nitrogen removal conditions to produce a
hydrocarbon effluent stream having a lower nitrogen content
relative to the hydrocarbon feed stream.
[0008] In an embodiment, the adsorbent comprises a zeolite
component, an alumina component and a metal component (Madd); the
alumina component ranging an amount from about 40 wt % to about 90
wt % of the adsorbent, and the metal component ranging in an amount
from about 0.015 moles to 0.08 moles of the metal as the oxide per
100 g of the adsorbent.
[0009] In an embodiment, the process has a nitrogen to diolefin
removal greater than 1 on a relative mass percent basis. In another
embodiment, a diolefin content of the hydrocarbon effluent stream
is at least 30% of the diolefin content of the hydrocarbon feed
stream. In a further embodiment, a nitrogen content of the
hydrocarbon effluent stream is no more than about 50% of the
nitrogen content of the hydrocarbon feed stream and a diolefin
content of the hydrocarbon effluent stream is at least 30% of the
diolefin content of the hydrocarbon feed stream.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The invention relates to methods for removing nitrogen from
a hydrocarbon feed stream comprising contacting the hydrocarbon
feed stream with an adsorbent at nitrogen removal conditions to
produce a hydrocarbon effluent stream having a lower nitrogen
content relative to the hydrocarbon feed stream. The hydrocarbon
feed stream of the invention comprises an aromatic compound, an
organic nitrogen compound and a diolefin compound. In an
embodiment, the aromatic hydrocarbon may be selected from the group
consisting of benzene, naphthalene, anthracene, phenanthrene, and
substituted derivatives thereof, with benzene and its derivatives
being preferred aromatic compounds. The aromatic compound may have
one or more of the substituents selected from the group consisting
of alkyl groups having from 1 to about 20 carbon atoms, hydroxyl
groups, and alkoxy groups whose alkyl group also contains from 1 up
to 20 carbon atoms. Where the substituent is an alkyl or alkoxy
group, a phenyl group can also be substituted on the alkyl
chain.
[0011] Although unsubstituted and monosubstituted benzenes,
naphthalenes, anthracenes, and phenanthrenes are most often used in
the practice of this invention, polysubstituted aromatics also may
be employed. Examples of suitable alkylatable aromatic compounds in
addition to those cited above include biphenyl, toluene, xylene,
ethylbenzene, propylbenzene, butylbenzene, pentylbenzene,
hexylbenzene, heptylbenzene, octylbenzene, etc.; phenol, cresol,
anisole, ethoxy-, propoxy-, butoxy-, pentoxy-, hexoxybenzene, and
so forth. Sources of benzene, toluene, xylene, and or other feed
aromatics include product streams from naphtha reforming units,
aromatic extraction units, recycle streams from styrene monomer
production units, and petrochemical complexes for the producing
para-xylene and other aromatics. The hydrocarbon feed stream may
comprise more one or more aromatic hydrocarbon compounds. In an
embodiment, the concentration of aromatic hydrocarbons in the
hydrocarbon feed stream ranges from about 5 mass % to about 99.9
mass % of the hydrocarbon feed. The hydrocarbon feed stream may
comprise between about 50 mass % and about 99.9 mass % benzene.
[0012] The hydrocarbon feed stream comprises one or more organic
nitrogen compounds. Organic nitrogen compounds typically include a
larger proportion of basic nitrogen compounds such as indoles,
pyridines, quinolines, diethanol amine (DEA), morpholines including
N-formyl-morpholine (NFM) and N-methyl-pyrrolidone (NMP). Organic
nitrogen compounds may also include weakly basic nitriles, such as
acetonitrile, propionitrile, acrylonitrile, and mixtures thereof.
The basic organic nitrogen compounds are adsorbed well on
conventional clay or resin adsorbent guard beds. Thus, the
invention does not require but encompasses use of an optional basic
nitrogen adsorption zone containing an adsorbent to remove basic
organic nitrogen compounds from the hydrocarbon stream as is known
in the art.
[0013] In an embodiment, the concentration of organic nitrogen
compounds in the hydrocarbon feed ranges from about 30 ppb-wt
(parts per billion by weight) to about 1 mole % of the hydrocarbon
feed; the concentration of organic nitrogen compounds may range
from about 100 ppb-wt to about 100 ppm-wt (parts per million by
weight) of the hydrocarbon feed. In an embodiment, the
concentration of weakly basic organic nitrogen compounds such as
nitriles in the hydrocarbon feed ranges from about 30 ppb-wt to
about 100 ppm-wt of the hydrocarbon feed;
[0014] The hydrocarbon feed stream comprises one or more diolefin
compounds, including for example diolefins having 4 to 6 carbon
atoms per molecule, i.e. C.sub.4 to C.sub.6 diolefins. In an
embodiment, the concentration of diolefin compounds in the
hydrocarbon feed ranges from about 30 ppb-wt to about 3000 ppm-wt
of the hydrocarbon feed; and the concentration of diolefin
compounds may range from about 50 ppb-wt to about 2000 ppm-wt of
the hydrocarbon feed. The hydrocarbon feed stream may comprise
other olefins such as mono-olefins. Typically, the overall
concentration of all olefins in the hydrocarbon feed stream will be
no more than 1.0 wt-% olefins. The hydrocarbon stream may contain
water up to and beyond saturation conditions.
[0015] Adsorbents used in the instant invention and methods of
making the adsorbents are disclosed in U.S. Pat. No. 6,632,766,
which is herein incorporated by reference in its entirety. In
brief, the adsorbent comprises a zeolite component, an alumina
component and a metal component wherein the alumina component is
present in an amount from about 40 to about 90 wt % of the
adsorbent and the metal component is present in an amount from
about 0.015 to 0.08 moles of the metal as the oxide per 100 g of
the adsorbent and may be referred to as a nitrogen selective
adsorbent.
[0016] Zeolites which can be used in the adsorbent have a pore
opening of about 5 to about 10 .ANG. and in general have a
composition represented by the empirical formula:
M.sub.2/nO:Al.sub.2O.sub.3:bSiO.sub.2
Where M is a cation having a valence of "n" and "b" has a value of
about 2 to about 500. In an embodiment, zeolites are those that
have a SiO.sub.2/Al.sub.2O.sub.3 molar ratio of about 2:1 to about
6:1 and/or those having the crystal structure of zeolite X,
faujasite, zeolite Y, zeolite A, mordenite, beta and ferrierite.
Preferred zeolites are zeolites X, Y and A. In an embodiment, the
zeolite is 13.times. zeolite.
[0017] The alumina component is an activated alumina that may be
obtained by rapid dehydration of aluminum hydroxides, e.g., alumina
trihydrate, gibbsite, or hydrargillite in a stream of hot gasses or
solid heat carrier. Dehydration may be accomplished in any suitable
apparatus using the stream of hot gases or solid heat carrier.
Generally, the time for heating or contacting with the hot gases is
typically from a fraction of a second to 4 or 5 seconds. The
temperature of the gases normally varies between 400.degree. C. and
1000.degree. C. The process is commonly referred to as flash
calcination and is disclosed, for example in U.S. Pat. No.
2,915,365. However, other methods of calcination may be employed.
One source of activated alumina is gibbsite which is one form of
alumina hydrate derived from bauxite using the Bayer process.
However, alpha alumina monohydrate, pseudoboehmite or the alumina
trihydrate may be used if sufficiently calcined. Other sources of
alumina may also be utilized including clays and alumina alkoxides.
Activated aluminas include aluminas having a surface area usually
greater than 100 m.sup.2/g and typically in the range of 100 to 400
m.sup.2/g.
[0018] The metal component (Madd) is selected from the group
consisting of alkali, alkaline earth metals, and mixtures thereof.
The metal component (Madd) is in addition to the metal cation (M)
present in the exchange sites of the zeolite. Additionally, the
metal component can be the same or different than the M metal. For
example, the M metal in a zeolite can be potassium whereas the
metal component (Madd) can be sodium. Examples of the metal
component (Madd) include but are not limited to sodium, potassium,
lithium, rubidium, cesium, calcium, strontium, magnesium, barium,
zinc and copper. In an embodiment, the metal component (Madd) is
selected from the group consisting of sodium, potassium, lithium,
rubidium, cesium and mixtures thereof. The source of the metal
component can be any compound which decomposes to the metal oxide
at activation conditions. Examples of metal component sources are
the nitrates, hydroxides, carboxylates, carbonates and oxides of
the metals. The shaped adsorbent can be prepared by combining the
three components in any order and forming into a shaped article.
Without wishing to be bound by any particular theory, it is
believed that the metal component (Madd) decreases the acidity of
zeolite and/or alumina components. Thus, the acidity/basicity of
the adsorbent may be varied by the amount and type of metal
component (Madd). For example having more metal component (Madd)
and/or using metals that provide more basic metal oxides such as
potassium and cesium will increase the basicity, i.e. reduce the
acidity, of the adsorbent. Excessive amounts of the metal component
(Madd) may be detrimental if sufficient to accelerate the double
bond shift reaction of the olefins.
[0019] In one method, the alumina, zeolite and an aqueous solution
of the desired metal compound are mixed and formed into a shaped
article. For example, gamma alumina, zeolite X and a solution of
sodium acetate can be combined into a dough and then extruded or
formed into shapes such as pellets, pills, tablets or spheres (e.g.
by the oil drop method) by means well known in the art. A preferred
method of forming substantially rounded shapes or bodies involves
the use of a pan nodulizer. This technique uses a rotating pan or
pan nodulizer onto which is fed the alumina component, zeolite
component and a solution of the metal component thereby forming
substantially rounded particles.
[0020] Another method of forming the shaped article is to mix
powders of the alumina, zeolite and metal compound followed by
formation of pellets, pills, etc. A third method is to combine the
alumina and zeolite components (powders), form them into a shaped
article and then impregnate the shaped article with an aqueous
solution of the metal compound. The forming step is carried out by
any of the means enumerated above.
[0021] In preparing a solution of the desired metal compound, pH
may be adjusted to a value from about 7 to about 14. In an
embodiment, the pH ranges from about 9 to about 13.5. The pH of the
solution may be controlled by adding the appropriate amount of the
desired metal hydroxide. For example, if sodium is the desired
metal, sodium acetate can be used to form the aqueous solution and
the pH may be adjusted using sodium hydroxide.
[0022] Having obtained the shaped articles, they are cured or dried
at ambient temperature up to about 200.degree. C. for a time of
about 5 minutes to about 25 hours. The shaped articles can be cured
in batches e.g. bins or trays or in a continuous process using
conventional equipment such as a moving belt oven, or rotating
kiln. Once the shaped articles are cured, they are activated by
heating the cured articles at a temperature of about 275.degree. C.
to about 600.degree. C. for a time of about 5 to about 70 minutes.
The heating can be done with the articles in a moving pan or in a
moving belt oven or a rotating kiln where the articles may be
direct fired or indirect fired to provide the finished solid
adsorbent.
[0023] The relative amount of the three components can vary
considerably over a wide range. Usually the amount of alumina
varies from about 40 to about 90 wt % of the adsorbent. In an
embodiment, the mass ratio of the alumina component to the zeolite
component in the adsorbent ranges from about 18:1 to about 2:3; and
may range from about 9:1 to about 2:3. The amount of zeolite may
vary from about 5 to about 60 wt % of the adsorbent. The amount of
metal component, Madd, can also vary considerably, but must be
present in an amount equal to at least 10% of the stoichiometric
amount of the metal cation, M, present in the exchange sites of the
zeolite. For practical reasons, the maximum amount of Madd should
be no more than 50% of the stoichiometric amount of M. In absolute
terms, it is preferred that the amount of Madd be present from
about 0.015 to about 0.08 moles of Madd per 100 grams of adsorbent.
The amounts of M and Madd are reported or expressed as the oxide of
the metal, e.g. Na.sub.2O.
[0024] The hydrocarbon feed stream to be purified is contacted with
the above described adsorbent at nitrogen removal conditions to
reduce the nitrogen content of the hydrocarbon stream. The process
produces an effluent hydrocarbon stream having a lower nitrogen
content relative to the nitrogen content of the hydrocarbon feed
stream. In general, nitrogen removal conditions include a
temperature from about 25.degree. C. to about 300.degree. C. and a
pressure from about 34.5 kPa(g) to about 4136.9 kPa(g). In an
embodiment, the temperature ranges from about 50.degree. C. to
about 200.degree. C.; and the temperature may range from about
75.degree. C. to about 175.degree. C. The effluent hydrocarbon
stream from the adsorption zone, may then be introduced into a
downstream processing unit such as an alkylation zone or
transalkylation zone.
[0025] It may be desirable to use a first bed of an alkylation zone
or transalkylation zone as an adsorbent zone for the removal of
nitrogen. In such an event, the adsorbent and the alkylation or
transalkylation catalyst should be spaced apart. The alkylation
agent, e.g. olefin, should bypass the adsorption zone and be
delivered to an interbed space to mix with the denitrogenated
hydrocarbon stream exiting the adsorption zone. However, it may be
preferable to contain the nitrogen adsorption zone and the
alkylation zone in separate vessels.
[0026] In an embodiment, the invention removes a greater amount of
nitrogen from the hydrocarbon feed stream than the amount of
unsaturated aliphatic compounds removed on a relative percent
basis. The relative percent basis is determined by the nitrogen
content and Bromine Index of the hydrocarbon feed and effluent
streams. Bromine Index is commonly used to assess the olefin
content, including diolefins, of hydrocarbon mixtures. That is, in
this embodiment, the percent decrease in nitrogen content on a mass
percent basis is greater than the percent decrease of the Bromine
Index between the hydrocarbon feed and effluent streams. For
example, if the hydrocarbon feed stream contains 4 ppm-wt nitrogen
and has a Bromine Index of 300 and the hydrocarbon effluent stream
contains 1 ppm-wt nitrogen and has a Bromine Index of 150, the
nitrogen content is decreased by 75% ((4-1)/4) and the Bromine
Index is decreased by 50% ((300-150)/300). Therefore, in this
example, the process has a nitrogen to unsaturated aliphatic
compound removal of 1.5 (75%/50%) on a relative percent basis.
Since the nitrogen to unsaturated aliphatic compound removal is
greater than 1, the amount of nitrogen removed from the hydrocarbon
feed stream is greater than the amount of unsaturated aliphatic
compounds removed from the hydrocarbon feed stream on a relative
percent basis. In another embodiment, the nitrogen to unsaturated
aliphatic compound removal is at least 1.5 on a relative percent
basis, and the nitrogen to unsaturated aliphatic compound removal
may be at least 2 on a relative percent basis. In a further
embodiment, the nitrogen to unsaturated aliphatic compound removal
is at least 2.5 on a relative percent basis, and the nitrogen to
unsaturated aliphatic compound removal may be at least 3 on a
relative percent basis.
[0027] In an embodiment, the invention removes a greater amount of
nitrogen from the hydrocarbon feed stream than the amount of
diolefin compounds removed from the hydrocarbon feed stream on a
relative mass percent basis. That is, in this embodiment, the
percent decrease in nitrogen content on a mass percent basis is
greater than the percent decrease of the diolefin content on a mass
percent basis between the hydrocarbon feed and effluent streams,
i.e. the nitrogen to diolefin removal is greater than 1 on a
relative mass percent basis. In another embodiment, the nitrogen to
diolefin removal is at least 1.5 on a relative mass percent basis;
and the nitrogen to diolefin removal may be at least 2 on a
relative mass percent basis. In a further embodiment, the nitrogen
to diolefin removal is at least 2.5 on a relative mass percent
basis; and the nitrogen to diolefin removal may be at least 3 on a
relative mass percent basis.
[0028] Removal of the unsaturated aliphatic compounds such as
olefin and/or diolefin compounds may result from various mechanism
including adsorption and reaction. The nitrogen content of the
hydrocarbon feed stream to and effluent stream from the adsorption
zone may be determined by standard lab methods such as UOP269 or
ASTM D5762 or ASTM D4629 depending on the nitrogen concentration.
Likewise, the diolefin content of the streams may be determined by
method UOP980, and the Bromine Index of the streams may be
determined using method UOP304. Unless otherwise noted, the
analytical methods used herein such as ASTM D5762 and UOP980 are
available from ASTM International, 100 Barr Harbor Drive, West
Conshohocken, Pa., USA.
[0029] In another embodiment, at least 50 wt % of the nitrogen is
removed from the hydrocarbon feed stream on an elemental basis; and
the invention may remove at least about 70 wt % of the nitrogen in
the hydrocarbon feed stream on an elemental basis. In another
embodiment, at least about 80 wt % of the nitrogen is removed from
the hydrocarbon feed stream on an elemental basis, that is, the
hydrocarbon effluent stream from the contacting step has a nitrogen
content that is no more than about 20% of the nitrogen content of
the hydrocarbon feed stream.
[0030] In a further embodiment, the hydrocarbon effluent stream
from the contacting step has a diolefin content of at least 30% of
the diolefin content of the hydrocarbon feed stream; and the
hydrocarbon effluent stream may have a diolefin content of at least
50% of the diolefin content of the hydrocarbon feed stream. In
another embodiment, the hydrocarbon effluent stream has a diolefin
content of at least 70% of the diolefin content of the hydrocarbon
feed stream.
[0031] In another embodiment, the hydrocarbon effluent stream from
the contacting step has a nitrogen content no more than about 50%
of the nitrogen content of the hydrocarbon feed stream, and
hydrocarbon effluent stream has a diolefin content of at least 30%
of the diolefin content of the hydrocarbon feed stream. In a
further embodiment, the hydrocarbon effluent stream from the
contacting step has a nitrogen content no more than about 50% of
the nitrogen content of the hydrocarbon feed stream, and
hydrocarbon effluent stream has a diolefin content of at least 50%
of the diolefin content of the hydrocarbon feed stream. The
hydrocarbon effluent stream from the contacting step may have a
nitrogen content no more than about 30% of the nitrogen content of
the hydrocarbon feed stream, and hydrocarbon effluent stream may
have a diolefin content of at least 30% of the diolefin content of
the hydrocarbon feed stream. The hydrocarbon effluent stream from
the contacting step may have a nitrogen content no more than about
30% of the nitrogen content of the hydrocarbon feed stream, and
hydrocarbon effluent stream may have a diolefin content of at least
50% of the diolefin content of the hydrocarbon feed stream.
Example 1
[0032] An adsorbent according to the invention was prepared
following Example 2 of U.S. Pat. No. 7,115,154. The resulting
adsorbent was found to have 0.142 total moles of Na.sub.2O per 100
g of adsorbent. The total moles includes the metal component (Madd)
added of 0.036 moles of Na.sub.2O per 100 g of adsorbent.
Example 2
[0033] A commercially available acid treated clay was obtained from
Sud-Chemie under the product name TONSIL CO 630 G for use as a
comparative adsorbent.
Example 3
[0034] A sample of Y-74 zeolite was slurried in a 15 wt %
NH.sub.4NO.sub.3 aqueous solution and the solution temperature was
brought up to 75.degree. C. (167.degree. F.). Y-74 zeolite is a
stabilized sodium Y zeolite with a bulk Si/Al.sub.2 ratio of
approximately 5.2, a unit cell size of approximately 24.53, and a
sodium content of approximately 2.7 wt % calculated as Na.sub.2O on
a dry basis. Y-74 zeolite is prepared from a sodium Y zeolite with
a bulk Si/Al.sub.2 ratio of approximately 4.9, a unit cell size of
approximately 24.67, and a sodium content of approximately 9.4 wt %
calculated as Na.sub.2O on a dry basis that is ammonium exchanged
to remove approximately 75% of the Na and then steam de-aluminated
at approximately 600.degree. C. (1112.degree. F.) by generally
following steps (1) and (2) of the procedure described in col. 4,
line 47 to col. 5, line 2 of U.S. Pat. No. 5,324,877. After 1 hour
of contact at 75.degree. C. (167.degree. F.), the slurry was
filtered and the filter cake was washed with an excessive amount of
warm de-ionized water. These NH.sub.4.sup.+ ion exchange,
filtering, and water wash steps were repeated two more times, and
the resulting filter cake had a bulk Si/Al.sub.2 ratio of 5.2, a
sodium content of 0.13 wt % calculated as Na.sub.2O on a dry basis,
a unit cell size of the 24.572 .ANG. and an absolute intensity of
96 as determined X-ray diffraction. The resulting filter cake was
dried to an appropriate moisture level, mixed with
HNO.sub.3-peptized Pural SB alumina to give a mixture of 80 parts
by weight of zeolite and 20 parts by weight Al.sub.2O.sub.3 binder
on a dry basis, and then extruded into 1.6 mm diameter cylindrical
extrudate. The extrudate was dried and calcined at approximately
600.degree. C. for one hour in flowing air. This catalyst was
representative of the existing art. This catalyst had a unit cell
size of 24.494 .ANG., an XRD absolute intensity of 61.1, and 57.2%
framework aluminum as a percentage of the aluminum in the modified
Y zeolite.
Example 4
[0035] A sample of a commercial benzene recycle stream (>99 wt %
benzene) containing olefin, diolefin and nitrogen compounds was
used as the hydrocarbon feed to evaluate the effectiveness of the
adsorbents of Examples 1-3 to remove nitrogen and the unsaturates.
The analysis of the feed is reported in Table 1 with the analysis
of the effluent or product from each test. The unsaturated
aliphatic, i.e., total olefin content was determined by UOP304. The
nitrogen content was determined by D4629, and the diolefin content
was determined by UOP980 as modified to improve the sensitivity of
the method to detect lower levels of diolefins. UOP980 was followed
except that sample size was altered and standard solutions of lower
concentrations were used during calibration of the instrument as
known by those skilled in the art to improve detection of lower
concentrations of the diolefins in the samples. The modification of
UOP980 does not alter the relative measurements between different
samples, but improves and/or enables quantification of
concentrations of less than 500 ppm-wt and especially less than 100
ppm-wt of diolefins.
[0036] Prior to the test, the adsorbent was pre-dried at
250.degree. C. for 4 hours in flowing nitrogen. The adsorption
experiment was done in an autoclave, which was first purged with
nitrogen followed by charging 0.6 g of adsorbent and 30 g of the
hydrocarbon feed. The autoclave was then pressurized to about 400
psig and ramped to the temperature listed in Table 1 for each test.
The autoclave includes a mixer which was set at 100 rpm. When the
specified temperature was reached, the autoclave was held at
temperature for one hour with mixing. Thereafter, the heat was cut
to allow the autoclave to cool to room temperature and mixing
stopped. The spent adsorbent was separated from the liquid product
or effluent, which was sampled and analyzed.
TABLE-US-00001 TABLE 1 Feed Example 1 Example 2 Example 3
Temperature, .degree. C. 100 125 150 100 125 150 25 75 125
Nitrogen, ppm-wt 3.1 0.7 0.7 0.6 1.32 1.06 0.7 0.9 1.41 0.6 Bromine
Index, 292 225 209 258 138 91 47 114 91 23 mg Br per 100 g
Diolefins, ppm-wt 825 614 621 613 25 3 1 NA 247 5
[0037] Example 1 according to the invention exhibited unexpected
effectiveness in removing nitrogen while leaving the olefin and
diolefin compounds relatively intact. The ability to selectively
adsorb nitrogen components over olefin components makes the
adsorbent particularly useful in commercial services, where both
types of contaminants are present in aromatic streams. By
minimizing adsorption and/or reaction of the olefins a higher
nitrogen capacity and longer adsorbent life are expected.
* * * * *