U.S. patent application number 14/257789 was filed with the patent office on 2015-10-22 for combined naphtha refining and butane upgrading process.
This patent application is currently assigned to UOP LLC. The applicant listed for this patent is UOP LLC. Invention is credited to Hayim Abrevaya, Alakananda Bhattacharyya, Tom N. Kalnes, Stuart Smith, Mary Wier.
Application Number | 20150299593 14/257789 |
Document ID | / |
Family ID | 54321474 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150299593 |
Kind Code |
A1 |
Kalnes; Tom N. ; et
al. |
October 22, 2015 |
COMBINED NAPHTHA REFINING AND BUTANE UPGRADING PROCESS
Abstract
A process for refining naphtha and upgrading butanes is
described. The process involves separating a hydrotreated heavy
naphtha feed into a C.sub.7-rich fraction and a C.sub.8+-rich
fraction in a separation zone and then reacting the C.sub.7-rich
fraction with C.sub.4 paraffins to form to a low aromatic gasoline
blendstock. The C.sub.8+-rich fraction is sent to a reforming zone
to form a reformed product with higher octane and lower RVP than a
reformed product derived from heavy naphtha.
Inventors: |
Kalnes; Tom N.; (LaGrange,
IL) ; Smith; Stuart; (Lake Zurich, IL) ;
Abrevaya; Hayim; (Kenilworth, IL) ; Wier; Mary;
(Schaumburg, IL) ; Bhattacharyya; Alakananda;
(Glen Ellyn, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
54321474 |
Appl. No.: |
14/257789 |
Filed: |
April 21, 2014 |
Current U.S.
Class: |
585/304 ;
585/300 |
Current CPC
Class: |
C10G 69/02 20130101;
C10G 69/00 20130101; C10G 69/123 20130101; C10G 63/00 20130101 |
International
Class: |
C10L 1/04 20060101
C10L001/04 |
Claims
1. A process for refining naphtha and upgrading butanes comprising:
separating a hydrotreated heavy naphtha feed into a C.sub.7-rich
fraction and a C.sub.8+-rich fraction in a separation zone;
introducing the C.sub.7-rich fraction into a reaction zone;
introducing a stream comprising C.sub.4 paraffins into the reaction
zone; disproportionating a first portion of the C.sub.7-rich
fraction by contacting the first portion of the C.sub.7-rich
fraction with a catalyst in the reaction zone and reverse
disproportionating a second portion of the C.sub.7-rich fraction
and the C.sub.4 paraffins by contacting the second portion of the
C.sub.7-rich fraction and the C.sub.4 paraffins with the catalyst
in the reaction zone under reaction conditions suitable for
disproportionation and reverse disproportionation to form a
reaction product mixture; separating the reaction product mixture
in a second separation zone into at least a C.sub.3--rich stream,
an iso-C.sub.4 -rich stream, and a C.sub.6+-rich stream; and
introducing the C.sub.6+-rich stream into a hydrocarbon pool.
2. The process of claim 1 further comprising reforming the
C.sub.8+-rich fraction in a reforming zone to form a higher octane
reformed product and introducing the reformed product into the
hydrocarbon pool.
3. The process of claim 1 wherein separating the reaction product
mixture comprises separating the reaction product mixture into at
least the C.sub.3--rich stream, the iso-C.sub.4-rich stream, a
C.sub.5-rich stream, and the C.sub.6+-rich stream.
4. The process of claim 3 further comprising controlling a vapor
pressure of the C.sub.6+-rich stream by recovering at least a
portion of the C.sub.5-rich stream.
5. The process of claim 3 further comprising maximizing a gasoline
product yield by mixing at least a portion of the C.sub.5-rich
stream with the C.sub.6+-rich stream.
6. The process of claim 3 further comprising recycling at least a
portion of the C.sub.5-rich stream to the reaction zone.
7. The process of claim 1 wherein the reaction conditions include a
temperature of less than about 200.degree. C.
8. The process of claim 1 further comprising introducing the
iso-C.sub.4-rich stream and at least one olefin containing stream
into an alkylation reaction zone to produce low vapor pressure,
high octane gasoline blendstock.
9. The process of claim 1 wherein a molar ratio of C.sub.4 to
C.sub.7 is at least about 0.055.
10. The process of claim 1 further comprising recycling at least a
portion of the iso-C.sub.4 -rich stream to the reaction zone.
11. The process of claim 1 wherein at least one of the first or
second catalyst comprises HF, sulfated zirconias,
AlCl.sub.2/SiO.sub.2, zeolites, ionic solids, platinum on chlorided
Al.sub.2O.sub.3/Ga.sub.2O.sub.3 supports, supported ionic liquids,
Pt/W/Al.sub.2O.sub.3, HF/TiF.sub.4, an ionic liquid, or
combinations thereof.
12. The process of claim 1, wherein the catalyst is a liquid
catalyst comprising an ionic liquid and a carbocation promoter.
13. The process of claim 12 wherein the ionic liquid comprises an
organic cation and an anion, and wherein the organic cation is
selected from the group consisting of: ##STR00002## where
R.sup.1-R.sup.21 are independently selected from C.sub.1-C.sub.20
hydrocarbons, C.sub.1-C.sub.20 hydrocarbon derivatives, halogens,
and H.
14. The process of claim 12 wherein the ionic liquid comprises an
organic cation and an anion, and wherein the anion is derived from
halides, sulfates, bisulfates, nitrates, sulfonates,
fluoroalkanesulfonates, or combinations thereof.
15. The process of claim 12 wherein the carbocation promoter
comprises halo-alkanes, mineral acids, alkenes, or combinations
thereof.
16. The process of claim 12 further comprising mechanically mixing
while contacting the C.sub.7-rich fraction with the catalyst and
while contacting the C.sub.7-rich and the C.sub.4 paraffins with
the catalyst.
17. The process of claim 1 further comprising: separating the
catalyst from the reaction product mixture before separating the
reaction product mixture; regenerating the separated catalysts;
optionally, adding a carbocation promoter to the regenerated
catalyst; and recycling at least a portion of the regenerated
catalyst to the reaction zone.
18. The process of claim 1 wherein a mass ratio of the catalyst to
the C.sub.7 fraction and the butanes is less than 0.75:1.
19. The process of claim 1 wherein the hydrotreated heavy naphtha
feed is formed by separating a full range hydrotreated naphtha feed
into a hydrotreated light naphtha stream and the hydrotreated heavy
naphtha feed.
20. A process for refining naphtha and upgrading butanes
comprising: separating a hydrotreated heavy naphtha feed into a
C.sub.7-rich fraction and a C.sub.8+-rich fraction in a separation
zone; introducing the C.sub.7-rich fraction into a reaction zone;
introducing a stream comprising C.sub.4 paraffins into the reaction
zone; disproportionating a first portion of the C.sub.7-rich
fraction by contacting the first portion of the C.sub.7-rich
fraction with a liquid catalyst in the reaction zone and reverse
disproportionating a second portion of the C.sub.7-rich fraction
and the C.sub.4 paraffins by contacting the second portion of the
C.sub.7-rich fraction and the C.sub.4 paraffins with the liquid
catalyst in the reaction zone under reaction conditions suitable
for disproportionation and reverse disproportionation to form a
reaction product mixture, wherein the liquid catalyst comprises an
ionic liquid and a carbocation promoter; separating the liquid
catalyst from the reaction product mixture; separating the reaction
mixture in a second separation zone into at least a C.sub.3--rich
stream, an iso-C.sub.4-rich stream, and a C.sub.6+-rich stream;
introducing the C.sub.6+-rich stream into a hydrocarbon pool; and
reforming the C.sub.8+-rich fraction in a reforming zone to form a
reformed product and introducing the reformed product into the
hydrocarbon pool.
Description
BACKGROUND OF THE INVENTION
[0001] High octane gasoline is required for modern gasoline
engines. Previously, it was common to achieve octane number
improvement by the use of various lead-containing additives. As
lead has been phased out of gasoline for environmental reasons, it
has become increasingly necessary to rearrange the structure of the
hydrocarbons used in gasoline blending in order achieve higher
octane ratings. Catalytic reforming and catalytic isomerization are
two widely used processes for this upgrading.
[0002] The traditional gasoline blending pool normally includes
C.sub.4 and heavier hydrocarbons having boiling points of less than
205.degree. C. (400.degree. F.) at atmospheric pressure. This range
of hydrocarbons includes C.sub.4-C.sub.6 paraffins, and especially
the C.sub.5 and C.sub.6 normal paraffins which have relatively low
octane numbers. The C.sub.4-C.sub.6 hydrocarbons have the greatest
susceptibility to octane improvement by lead addition and were
formerly upgraded in this manner. With the phase out of lead
additives, octane improvement was obtained by using isomerization
to rearrange the structure of the paraffinic hydrocarbons into
branched-chain paraffins or reforming to convert the C.sub.6 and
heavier hydrocarbons to aromatic compounds. Normal C.sub.5
hydrocarbons are not readily converted into aromatics; therefore,
the common practice has been to isomerize these lighter
hydrocarbons into corresponding branched-chain isoparaffins.
Although the C.sub.6 and heavier hydrocarbons can be upgraded into
aromatics through dehydrocyclization, the conversion of C.sub.6
hydrocarbons to aromatics creates higher density species and
increases gas yields with both effects leading to a reduction in
liquid volume yields. Moreover, the health concerns related to
benzene have lead to restrictions on benzene and aromatics.
Therefore, it is preferred to change the C.sub.6 paraffins to an
isomerization unit to obtain C.sub.6 isoparaffin hydrocarbons.
Consequently, octane upgrading commonly uses isomerization to
convert C.sub.6 and lower boiling hydrocarbons.
[0003] The Reid vapor pressure (RVP) of gasoline has been utilized
by the Environmental Protection Agency as a means of regulating
volatile organic compounds emissions by transportation fuels and
for controlling the formation of ground level ozone. As these
regulations become more stringent and as more ethanol (which has a
high vapor pressure) is blended into gasoline, C.sub.5 paraffins
need to be removed from the gasoline pool. Moreover, the need to
remove components may also extend to some C.sub.6 paraffins. This
may result in refiners being oversupplied with C.sub.5 paraffins
and possibly C.sub.6 paraffins, forcing them to sell these products
at prices lower than gasoline blendstock.
[0004] Commercial refiners face a number of problems utilizing
hydrocarbons with molecular weights less than about 90 in gasoline.
Some refiners are limited in the amount of light naphtha,
particularly pentanes, they can add to gasoline in the summer
months because of more stringent regulations on vapor pressure. In
addition, some refiners cannot blend all of the high octane
reformate they produce into gasoline because of new regulations
limiting the total aromatics to 35 vol %. The growth of shale crude
oil production has increased the amount of low value butanes and
pentanes produced in refineries. Finally, some refiners need to
purchase isobutane as feedstock for C.sub.3 and C.sub.4 olefin
conversion to gasoline in existing alkylation units.
[0005] Therefore, there is a need for processes which allow better
utilization of heavy naphtha in refineries.
SUMMARY OF THE INVENTION
[0006] One aspect of the invention is a process for refining
naphtha and upgrading butanes. In one embodiment, a hydrotreated
heavy naphtha feed is separated into a C.sub.7-rich fraction and a
C.sub.8+-rich fraction in a separation zone. The C.sub.7-rich
fraction is introduced into a reaction zone, and a stream
comprising C.sub.4 paraffins is also introduced into the reaction
zone. A first portion of the C.sub.7-rich fraction is
disproportionated by contacting the first portion of the
C.sub.7-rich fraction with a catalyst in the reaction zone and a
second portion of the C.sub.7-rich fraction and the C.sub.4
paraffins are reverse disproportionated by contacting the second
portion of the C.sub.7-rich fraction and the C.sub.4 paraffins with
the catalyst in the reaction zone under reaction conditions
suitable for disproportionation and reverse disproportionation to
form a reaction product mixture. The reaction product mixture is
separated in a second separation zone into at least a C.sub.3--rich
stream, an iso-C.sub.4 -rich stream, and a C.sub.6+-rich stream.
The C.sub.6+-rich stream is introduced into a hydrocarbon pool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 illustrates the disproportionation reaction of a
normal heptane paraffin.
[0008] FIG. 2 illustrates the reverse disproportionation reaction
of n-butane and n-heptane.
[0009] FIG. 3 illustrates one embodiment of a disproportionation
and reverse disproportionation process.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention meets this need by providing a process
for gasoline refineries. The process involves separating a heavy
naphtha feed into a C.sub.7-rich fraction and a C.sub.8+-rich
fraction. The C.sub.7-rich fraction and butanes are reverse
disproportionated to a product mixture comprising, C.sub.5-, and
C.sub.6+ hydrocarbons. The isohexane-rich product has good octane
and a lower RVP than pentane. In some cases, the process also
produces an isopentane-rich co-product. The process forms primarily
isoparaffins, and very few naphthenes, aromatics, and alkenes are
formed. The C.sub.8+-rich fraction can be reformed in a reforming
zone to form a higher octane reformed products.
[0011] The process also forms an isobutane-rich product which can
be converted to low RVP gasoline blendstock by reaction with
propylenes and butenes in a downstream alkylation unit.
[0012] The disproportionation of paraffins (e.g., n-heptane
(n-C.sub.7)) involves reacting two moles of hydrocarbon to form one
mole each of two different products, one having a carbon count
greater than the starting material and the other having a carbon
count less than the starting material (e.g., hexane and octane), as
shown in FIG. 1. The total number of moles in the system remains
the same throughout the process, but the products have different
carbon counts from the reactants.
[0013] The microscopic reverse of heptane disproportionation is the
combination of one mole of octane and one mole of hexane to form
two moles of heptane. This type of reaction is referred herein as
reverse disproportionation. Reverse disproportionation-type
reactions can occur in which two paraffins having different carbon
numbers react to form two different paraffins having different
carbon numbers from those of the feed where the total number of
product and moles of carbon and hydrogen in the products does not
change from the total number in the feed (e.g., pentane and octane
reacting to form hexane and heptane). These reactions are sometimes
referred to as comproportionation or molecular averaging reactions.
These paraffin rearrangements have also been called alkane
metathesis. The use of any of these terms is meant to illustrate
that paraffins can react with other paraffins to form additional
paraffins different from the original feed. Another example of
reverse disproportionation involves heptane and butane reacting to
form pentane and hexane, as illustrated in FIG. 2. Utilizing the
equilibrium among the various species, the concentration of the
product can be controlled by varying the relative ratios of the
species. Consequently, two different paraffinic feed sources of
varying carbon count can be reacted to obtain a product containing
paraffins of intermediate carbon count
[0014] FIG. 3 illustrates the disproportionation and reverse
disproportionation process 100 which involves upgrading butanes to
C.sub.5+ hydrocarbons. This process also can reduce the amount of
feed going to the reformer. It also can result in a lower fraction
of aromatics in the refinery gasoline pool.
[0015] A hydrotreated heavy naphtha feed 105 is used. Heavy naphtha
is a hydrocarbon mixture typically comprising seven, eight and nine
carbon hydrocarbon molecules with the majority of the hydrocarbon
molecules being saturates as opposed to unsaturates. Heavy naphtha
is often defined by a nominal boiling point range of about
71.degree. C. (160.degree. F.) to about 204.degree. C. (400.degree.
F.), or about 82.degree. C. (180.degree. F.) to about 204.degree.
C. (400.degree. F.), or about 93.degree. C. (200.degree. F.) to
about 182.degree. C. (360.degree. F.). Carbon chain length can
extend from C.sub.6-C.sub.10 in the broadest sense depending on how
the distillation column operates.
[0016] The hydrotreated heavy naphtha feed can be formed by
separating a full range hydrotreated naphtha feed into a light
naphtha stream and a heavy naphtha stream in a naphtha splitter,
for example. Hydrotreated full range naphtha is a hydrocarbon
mixture typically comprising five, six, seven, eight and nine
carbon hydrocarbon molecules with the majority of the hydrocarbon
molecules being saturates as opposed to unsaturates. It typically
has less than about 10 wt-ppm sulfur and less than 1 wt-ppm
nitrogen. Full range naphtha is often defined by a nominal boiling
point range about 21.degree. C. (70.degree. F.) to about
204.degree. C. (400.degree. F.), or about 27.degree. C. (80.degree.
F.) to about 182.degree. C. (360.degree. F.). Carbon chain length
can extend from C.sub.4-C.sub.10 in the broadest sense depending on
how the distillation column operates.
[0017] The hydrotreated heavy naphtha feed 105 is sent to a
separation zone 110 where it is separated into a C.sub.7-rich
fraction 115 and a C.sub.8+-rich fraction 120. The separation can
take place in a heavy naphtha splitter, for example.
[0018] The C.sub.8+-rich fraction 120 (e.g., with a boiling point
range of about 99.degree. C. (210.degree. F.) to about 204.degree.
C. (400.degree. F.)), which can include some aromatic compounds,
can be sent to a reformer for further processing as discussed
below, and the reformate can be sent to a hydrocarbon pool, such as
a gasoline pool.
[0019] The C.sub.7-rich fraction (e.g., with a boiling point range
of about 82.degree. C. (180.degree. F.) to about 99.degree. C.
(210.degree. F.)) 115 is sent to reaction zone 125. A stream 130
comprising C.sub.4 paraffins is also introduced into the reaction
zone 125. The C.sub.4 paraffins can include n-C.sub.4 paraffins,
iso-C.sub.4 paraffins, or mixtures thereof. In some embodiments, a
liquid catalyst stream 132 is also introduced into the reaction
zone 125. In other embodiments, the catalyst will be contained in
the reaction zone.
[0020] A portion of the C.sub.7-rich fraction is contacted with a
catalyst in the reaction zone 125 and disproportionated. The
C.sub.4 paraffins and at least a second portion of the C.sub.7-rich
fraction are contacted with the catalyst in the reaction zone 125
and reverse disproportionated. By a portion of the C.sub.7-rich
fraction we mean that some of the C.sub.7-rich fraction reacts in
the stated way. The portions are not physically separated. There
will also be some disproportionation of the C.sub.4 paraffins. In
addition, other reactions will occur, such as isomerization of the
various paraffins. If the C.sub.4 paraffins are present in excess
of their equilibrium amount, equilibrium favors the reverse
disproportionation reaction.
[0021] The molar ratio of C.sub.4 to C.sub.7 is at least about
0.055, or at least about 0.1, or at least about 0.2, or at least
about 0.5, or at least about 0.75, or at least about 1, or at least
about 5, or at least about 10, or at least about 15. As the C.sub.4
to C.sub.7 ratio increases, additional butanes are consumed and the
reaction product becomes richer in pentanes and hexanes. If the
ratio is too low, C.sub.4 paraffins will be generated by
disproportionation of C.sub.7.
[0022] Where a liquid catalyst is used, a spent liquid catalyst
stream 134 is removed from the reaction zone 125. It can be
regenerated and recycled to the reaction zone 125.
[0023] The reaction mixture 135 includes the disproportionation
products and reverse disproportionation products. The reaction
mixture 135 is separated in a second separation zone 140 into at
least a C.sub.3--rich stream 145, an iso-C.sub.4-rich stream 150,
and a C.sub.6+-rich stream 155. Additional product streams can be
taken, if desired. One example of a suitable separation process is
distillation.
[0024] When a liquid catalyst is used, the liquid catalyst is also
present in the reaction mixture. The liquid catalyst can be
separated from the reaction mixture by phase separation due to the
density difference between the hydrocarbons and the liquid catalyst
before separation into the various hydrocarbon streams.
[0025] The C.sub.3--rich stream 145 can be recovered and further
processed. The C.sub.3--rich stream can be used in a variety of
processes. It can be used as a refinery fuel instead of natural
gas. Alternatively, it could be purified and recovered as a high
purity liquid propane product. It could be used as a feedstock for
a hydrogen plant. It could also be used as a feedstock for a
chemical plant, such as an ethylene cracker, although this would be
less common.
[0026] The iso-C.sub.4-rich stream 150 can be recovered. In some
embodiments, a portion 160 of the iso-C.sub.4-rich stream 150 is
recycled to reaction zone 125 and used in the reverse
disproportionation reaction. The iso-C.sub.4-rich product can be
used in alkylate production as discussed below
[0027] In some embodiments, a n-C.sub.4-rich stream is recovered
and recycled to the reaction zone 125 (not shown).
[0028] The C.sub.6+-rich stream 155 is sent to the hydrocarbon
pool, such as a gasoline pool.
[0029] In some embodiments, the reaction mixture 135 is separated
into at least a C.sub.3--rich stream 145, an iso-C.sub.4-rich
stream 150, a C.sub.6+-rich stream 155, and a C.sub.5-rich stream
165, which can be recovered. In some embodiments, a portion 170 of
the C.sub.5-rich stream 165 is mixed with the C.sub.6+-rich stream
155 and sent to the hydrocarbon pool. In some embodiments, all or a
portion of the C.sub.5-rich stream 165 could be recycled to the
reaction zone 125 (not shown). Alternatively, all or a portion of
the C.sub.5-rich stream 165 could be recovered and used a feedstock
for a chemical plant.
[0030] If a separate C.sub.5-rich stream is not recovered, the
C.sub.5 hydrocarbons will be included in the C.sub.6+-rich
stream.
[0031] In some embodiments, the vapor pressure of the C.sub.6+-rich
stream can be controlled by controlling the amount of the
C.sub.5-rich stream included in the C.sub.6+-rich stream. By
forming a separate C.sub.5-rich stream and mixing only a portion of
the C.sub.5-rich stream (or none) with the C.sub.6+-rich stream,
the vapor pressure can be controlled as needed.
[0032] In some embodiments, the gasoline product yield can be
maximized by mixing at least a portion of the C.sub.5-rich stream
with the C.sub.6+-rich stream.
[0033] The iso-C.sub.4-rich stream and at least one olefin
containing stream (containing olefins such as an ethylene,
propylene, or butene stream, or mixtures thereof) can be introduced
into an alkylation reaction zone to produce additional gasoline
blendstock.
[0034] Suitable reaction conditions include a temperature of about
200.degree. C. or less, or about 175.degree. C. or less, or about
150.degree. C. or less, or about 125.degree. C. or less, or about
100.degree. C. or less, or about 90.degree. C. or less, or about
80.degree. C. or less, or about 70.degree. C. or less, or about
60.degree. C. or less, or in the range of about 0.degree. C. to
about 200.degree. C., or about 0.degree. C. to about 175.degree.
C., or about 0.degree. C. to about 150.degree. C., or about
10.degree. C. to about 150.degree. C. , or about 25.degree. C. to
about 150.degree. C., or about 30.degree. C. to about 150.degree.
C., or about 40.degree. C. to about 150.degree. C., or about
50.degree. C. to about 150.degree. C., or about 55.degree. C. to
about 150.degree. C.
[0035] The pressure in the reaction zone is typically in the range
of about 0 MPa to about 13.8 MPa, or about 0 MPa to about 8.1 MPa,
or about 0 MPa to about 5 MPa, or about 0 MPa to about 3.5 MPa. The
pressure should be sufficient to ensure that the reaction product
is in a liquid state. Small amounts of vapor may also be present,
but this should be minimized.
[0036] The reaction can take place in the presence of a gas.
Suitable gases include, but are not limited to methane, ethane,
propane, hydrogen, hydrogen chloride, nitrogen, and the like.
[0037] The residence time in the reaction zone is generally less
than about 12 hr, or less than about 10 hr, or less than 7 hr, or
less than 5 hr, or less than 4 hr, or less than 3 hr, or less than
2 hr, or less than 1 hr. The reaction time can be selected so that
a predetermined conversion can be obtained. When the catalyst is an
ionic liquid, the reaction time is a function of the degree of
mixing, and the reaction temperature. Where a liquid catalyst is
used, the reaction time is also a function of the concentration of
the carbocation promoter (if present), the molar ratio of the
catalyst promoter (if present) to liquid catalyst, and the
mass/volume ratio of liquid catalyst to hydrocarbon being reacted.
Generally, increasing any of these conditions will increase the
reaction rate.
[0038] When a liquid catalyst is used, the reaction will proceed
simply by contacting the hydrocarbon feed and the liquid catalyst,
the reaction rate is generally too slow to be commercially viable.
When mass transfer rate is controlling, the reaction rate can be
substantially increased by increasing the mixing intensity of
hydrocarbon feed and liquid catalyst. After a certain point,
increasing the mixing intensity will not provide any additional
benefit. Mixing intensity can be controlled using pumps, flow
configurations, and baffles. Baffles help to prevent a vortex from
forming in the reactor, which would reduce the amount of
mixing.
[0039] The contacting step may be practiced in laboratory scale
experiments through full scale commercial operations. The process
may be operated in batch, continuous, or semi-continuous mode. The
contacting step can take place in various ways, with both
concurrent and co-current flow processes being suitable. The order
of addition of the reactants may not always be critical. For
example, the reactants can be added individually, or some reactants
may be combined or mixed before being combined or mixed with other
reactants.
[0040] Suitable catalysts include, but are not limited to, HF,
sulfated zirconias, AlCl.sub.2/SiO.sub.2, zeolites, ionic solids,
platinum on chlorided Al.sub.2O.sub.3/Ga.sub.2O.sub.3 supports,
supported ionic liquids, Pt/W/Al.sub.2O.sub.3, HF/TiF.sub.4, ionic
liquids, or combinations thereof.
[0041] If the catalyst is an ionic liquid, when the ionic liquid
catalyst is separated from the reaction product mixture, it can
include deactivated catalyst after being used in the process. The
ionic liquid catalyst can become deactivated as a result of the
buildup of a heavy hydrocarbon, which will be referred to as
conjunct polymer herein. This conjunct polymer is a byproduct of
the disproportionation and reverse disproportionation reactions.
The deactivated catalyst can be regenerated using any known
regeneration process. Suitable regeneration methods include, but
are not limited to the following. The ionic liquid containing the
conjunct polymer could be contacted with a reducing metal (e.g.,
Al), an inert hydrocarbon (e.g., hexane), and hydrogen and heated
to about 100.degree. C. The deactivating polymer will be
transferred to the hydrocarbon phase, allowing for the conjunct
polymer to be removed from the ionic liquid phase. See e.g., U.S.
Pat. No. 7,651,970; U.S. Pat. No. 7,825,055; U.S. Pat. No.
7,956,002; and U.S. Pat. No. 7,732,363. Another method involves
contacting the ionic liquid containing the conjunct polymer with a
reducing metal (e.g., Al) in the presence of an inert hydrocarbon
(e.g. hexane) and heating to about 100.degree. C. The conjunct
polymer will be transferred to the hydrocarbon phase, allowing for
the conjunct polymer to be removed from the ionic liquid phase. See
e.g., U.S. Pat. No. 7,674,739 B2. Still another method of
regenerating the ionic liquid involves contacting the ionic liquid
containing the conjunct polymer with a reducing metal (e.g., Al),
HCl, and an inert hydrocarbon (e.g. hexane), and heating to about
100.degree. C. The conjunct polymer will be transferred to the
hydrocarbon phase, allowing for the conjunct polymer to be removed
from the IL phase. See e.g., U.S. Pat. No. 7,727,925. The ionic
liquid can be regenerated by adding a homogeneous metal
hydrogenation catalyst (e.g., (PPh.sub.3).sub.3RhCl) to the ionic
liquid containing the conjunct polymer and an inert hydrocarbon
(e.g. hexane). Hydrogen would be introduced, and the conjunct
polymer would be reduced and transferred to the hydrocarbon layer.
See e.g., U.S. Pat. No. 7,678,727. Another method for regenerating
the ionic liquid involves adding HCl, isobutane, and an inert
hydrocarbon to the ionic liquid containing the conjunct polymer and
heating to about 100.degree. C. The conjunct polymer would react to
form an uncharged complex, which would transfer to the hydrocarbon
phase. See e.g., U.S. Pat. No. 7,674,740. The ionic liquid could
also be regenerated by adding a supported metal hydrogenation
catalyst (e.g. Pd/C) to the ionic liquid containing the conjunct
polymer and an inert hydrocarbon (e.g. hexane). Hydrogen would be
introduced and the conjunct polymer would be reduced and
transferred to the hydrocarbon layer. See e.g., U.S. Pat. No.
7,691,771. Still another method involves adding a suitable
substrate (e.g. pyridine) to the ionic liquid containing the
conjunct polymer. After a period of time, an inert hydrocarbon
would be added to wash away the liberated conjunct polymer. The
ionic liquid precursor [1-butyl-1-methylpyrrolidinium][Cl] would be
added to the ionic liquid (e.g.
[1-butyl-1-methylpyrrolidinium][Al2Cl7]) containing the conjunct
polymer followed by an inert hydrocarbon. After a given time of
mixing, the hydrocarbon layer would be separated, resulting in a
regenerated ionic liquid. The solid residue would be converted to
ionic liquid by adding AlCl.sub.3. See e.g., U.S. Pat. No.
7,737,363 and U.S. Pat. No. 7,737,067. Another method involves
adding the ionic liquid containing the conjunct polymer to a
suitable substrate (e.g. pyridine) and an electrochemical cell
containing two aluminum electrodes and an inert hydrocarbon. A
voltage would be applied and the current measured to determine the
extent of reduction. After a given time, the inert hydrocarbon
would be separated, resulting in a regenerated ionic liquid. See,
e.g., U.S. Pat. No. 8,524,623.
[0042] In some embodiments, after the ionic liquid has been
regenerated, a carbocation promoter is added to the regenerated
ionic liquid so the liquid catalyst can be recycled to the reaction
zone.
[0043] The molar ratio of the carbocation promoter to the ionic
liquid in the liquid catalyst is typically in the range of about
0:1 to about 3:1, or about 0.1:1 to about 1:1. This relates to
forming the carbocation promoter from the halo-alkane or mineral
acid. This ratio is important relative to the specific type of
anion. For example, if the anion is AlCl.sub.4.sup.-, a reaction is
unlikely to occur or will be poor because the aluminum is fully
coordinated. However, if the anion is Al.sub.2Cl.sub.7.sup.-, there
is some aluminum present that can coordinate to the carbocation
promoter's anion, assisting in generating the carbocation from the
carbocation promoter.
[0044] When an ionic liquid catalyst is used, the mass or volume
ratio of liquid catalyst (ionic liquid and carbocation promoter) to
hydrocarbon feed is typically less than about 1:1. This is
desirable because the ionic liquid is an expensive component in the
process. In some embodiments, the mass ratio of ionic liquid to
hydrocarbon feed is not more than about 0.75:1, or not more than
about 0.7:1, or not more than about 0.65:1, or not more than about
0.60:1, or not more than about 0.55:1, or not more than about
0.50:1. In some embodiments, the volume ratio of ionic liquid to
hydrocarbon feed is not more than about 0.8:1, or not more than
about 0.7:1, or not more than about 0.6:1, or not more than about
0.5:1, or not more than about 0.45:1, or not more than about 0.4:1,
or not more than about 0.35:1, or not more than about 0.3:1, or not
more than about 0.25:1. In some embodiments, the mass or volume
ratios of liquid catalyst to hydrocarbon feed can be about 1:1 or
more.
[0045] When an ionic liquid catalyst is used, there can be one or
more ionic liquids in the liquid catalyst.
[0046] In some embodiments, the liquid catalyst comprises an ionic
liquid and a carbocation promoter. The ionic liquid is in liquid
form. In some embodiments, it is not supported on an oxide support.
In addition, in some embodiments, the ionic liquids do not contain
Bronsted acids, so the acid concentration within these systems is
less than prior art processes using ionic liquids which are
Bronsted acidic organic cations. In some embodiments, the acid
concentration is less than about 2.5 M, or less than about 2.25 M,
or less than about 2.0 M, or less than about 1.75 M, or less than
about 1.5 M.
[0047] The ionic liquid comprises an organic cation and an anion.
Suitable organic cations include, but are not limited to:
##STR00001##
[0048] where R.sup.1-R.sup.21 are independently selected from
C.sub.1-C.sub.20 hydrocarbons, C.sub.1-C.sub.20 hydrocarbon
derivatives, halogens, and H. Suitable hydrocarbons and hydrocarbon
derivatives include saturated and unsaturated hydrocarbons, halogen
substituted and partially substituted hydrocarbons and mixtures
thereof. C.sub.1-C.sub.8 hydrocarbons are particularly
suitable.
[0049] The anion can be derived from halides, sulfates, bisulfates,
nitrates, sulfonates, fluoroalkanesulfonates, and combinations
thereof. The anion is typically derived from metal and nonmetal
halides, such as metal and nonmetal chlorides, bromides, iodides,
fluorides, or combinations thereof. Combinations of halides
include, but are not limited to, mixtures of two or more metal or
nonmetal halides (e.g., AlCl.sub.4.sup.- and BF.sub.4.sup.-), and
mixtures of two or more halides with a single metal or nonmetal
(e.g., AlCl.sub.3Br). In some embodiments, the metal is aluminum,
with the mole fraction of aluminum ranging from 0<Al<0.25 in
the anion. Suitable anions include, but are not limited to,
AlCl.sub.4.sup.-, Al.sub.2Cl.sub.7.sup.-, Al.sub.3Cl.sub.10.sup.-,
AlCl.sub.3Br.sup.-, Al.sub.2Cl.sub.6Br.sup.-,
Al.sub.3Cl.sub.9Br.sup.-, AlBr.sub.4.sup.-, Al.sub.2Br.sub.7.sup.-,
Al.sub.3Br.sub.10.sup.-, GaCl.sub.4.sup.-, Ga.sub.2Cl.sub.7.sup.-,
Ga.sub.3Cl.sub.10.sup.-, GaCl.sub.3Br.sup.-,
Ga.sub.2Cl.sub.6Br.sup.-, Ga.sub.3Cl.sub.9Br.sup.-,
CuCl.sub.2.sup.-, Cu.sub.2Cl.sub.3.sup.-, Cu.sub.3Cl.sub.4.sup.-,
ZnCl.sub.3.sup.-, FeCl.sub.3.sup.-, FeCl.sub.4.sup.-,
Fe.sub.3Cl.sub.7.sup.-, PF.sub.6.sup.-, and BF.sub.4.sup.-.
[0050] The ionic liquid is typically combined with one or more
carbocation promoters. In some embodiments, the carbocation
promoter is added to the ionic liquid. In other embodiments, the
carbocation promoter is generated in situ. However, in situ
production might not provide reproducible results if it is not
controlled.
[0051] Suitable carbocation promoters include, but are not limited
to, halo-alkanes, mineral acids alone or combined with alkenes, and
combinations thereof. Suitable halo-alkanes include but are not
limited to 2-chloro-2-methylpropane, 2-chloropropane,
2-chlorobutane, 2-chloro-2-methylbutane, 2-chloropentane,
1-chlorohexane, 3-chloro-3-methylpentane, perchloroethylene,
hydrogen chloride, or combinations thereof. In some embodiments,
the carbocation promoter is not a cyclic alkane.
[0052] Suitable mineral acids include, but are not limited to, HCl,
HBr, H.sub.2SO.sub.4, and HNO.sub.3. Although HF can also be used,
it is less desirable due to safety issues. If the mineral acid is
not strong enough to protonate off a hydrogen from a C--H bond,
isobutene or another alkene can be added with the mineral acid to
produce the desired carbocation promoter. The mineral acid can be
generated in situ by the addition of a compound that reacts with
the ionic liquid. In situ acid generation can also occur as a
result of reaction with water present in the system. The mineral
acid may also be present as an impurity in the ionic liquid. The
C.sub.8+-rich fraction can be sent to a reforming zone. The
reforming zone upgrades the octane number of the reforming feed
stream through a variety of reactions including naphthene
dehydrogenation and paraffin dehydrocyclization and
isomerization.
[0053] Reforming operating conditions may include a pressure of
from about atmospheric to about 6080 kPa(a), with the preferred
range being from atmospheric to about 2026 kPa(a) and a pressure of
below 1013 kPa(a) being especially preferred. Hydrogen is generated
within the reforming zone, but additional hydrogen may be directed,
if necessary, to the reforming zone in an amount sufficient to
correspond to a ratio of from about 0.1 to 10 moles of hydrogen,
both generated and added, per mole of hydrocarbon feedstock. The
volume of the contained reforming catalyst corresponds to a liquid
hourly space velocity of from about 1 to 40 hr.sup.-1. The
operating temperature generally is in the range of 260.degree. to
560.degree. C.
[0054] Reforming catalysts may comprise a supported platinum-group
metal component which comprises one or more platinum-group metals,
with a platinum component being preferred. An illustrative platinum
component generally comprises from about 0.01 to 2 mass of the
catalytic composite, preferably 0.05 to 1 mass %, calculated on an
elemental basis. Reforming catalysts may contain other metal
components known to modify the effect of the preferred platinum
component. Such metal modifiers may include Group IVA (14) metals,
other Group VIII (8-10) metals, rhenium, indium, gallium, zinc,
uranium, dysprosium, thallium and mixtures thereof. A preferred
metal modifier is a tin component. Catalytically effective amounts
of such metal modifiers may be incorporated into the catalyst by
any means known in the art.
[0055] The reforming catalyst may be a dual-function composite
containing a metallic hydrogenation-dehydrogenation component on a
refractory support which provides acid sites for cracking and
isomerization. The refractory support of the reforming catalyst
should be a porous, adsorptive, high-surface-area material which is
uniform in composition without composition gradients of the species
inherent to its composition. Examples of suitable refractory
supports are those containing one or more of: (1) refractory
inorganic oxides such as alumina, silica, titania, magnesia,
zirconia, chromia, thoria, boria or mixtures thereof; (2)
synthetically prepared or naturally occurring clays and silicates,
which may be acid-treated; (3) crystalline zeolitic
aluminosilicates, either naturally occurring or synthetically
prepared such as FAU, MEL, MFI, MOR, MTW (IUPAC Commission on
Zeolite Nomenclature), in hydrogen form or in a form which has been
exchanged with metal cations; (4) non-zeolitic molecular sieves as
disclosed in U.S. Pat. No. 4,741,820, incorporated by reference;
(5) spinels such as MgAl.sub.2O.sub.4, FeAl.sub.2O.sub.4,
ZnAl.sub.2O.sub.4, CaAl.sub.2O.sub.4 ; and (6) combinations of
materials from one or more of these groups.
[0056] Reforming catalysts may optimally contain a halogen
component. The halogen component may be fluorine, chlorine, bromine
or iodine or mixtures thereof. Chlorine is the preferred halogen
component.
[0057] The reforming catalyst may comprise a large-pore molecular
sieve such as a molecular sieve having an effective pore diameter
of about 7 angstroms or larger. Examples of large-pore molecular
sieves which might be incorporated into the present catalyst
include LTL, FAU, AFI and MAZ (IUPAC Commission on Zeolite
Nomenclature) and zeolite-beta. Or, the reforming catalyst may
contain a nonacidic L-zeolite (LTL) and an alkali-metal component
as well as a platinum-group metal component. It is often necessary
to composite the L-zeolite with a binder in order to provide a
convenient form. Any refractory inorganic oxide binder is suitable.
One or more of silica, alumina or magnesia may be preferred binder
materials. The L-zeolite and binder may be composited to form the
desired catalyst shape by any method known in the art. An alkali
metal component is part of the alternative reforming catalyst. One
or more of the alkali metals, including lithium, sodium, potassium,
rubidium, cesium and mixtures thereof, may be used, with potassium
being preferred. The alkali metal optimally will occupy essentially
all of the cationic exchangeable sites of the nonacidic
L-zeolite.
[0058] The iso-C.sub.4-rich product can be sent to an alkylation
zone. Alkylation is typically used to combine light olefins, for
example mixtures of alkenes such as propylene and butylene, with
isobutane to produce a relatively high-octane branched-chain
paraffinic hydrocarbon fuel, including isoheptane and isooctane.
Similarly, an alkylation reaction can be performed using an
aromatic compound such as benzene in place of the isobutane. When
using benzene, the product resulting from the alkylation reaction
is an alkylbenzene (e.g. toluene, xylenes, ethylbenzene, etc.). For
isobutene alkylation, typically, the reactants are mixed in the
presence of a strong acid catalyst, such as sulfuric acid or
hydrofluoric acid. The alkylation reaction is carried out at mild
temperatures, and is typically a two-phase reaction. Because the
reaction is exothermic, cooling is needed. Depending on the
catalyst used, normal refinery cooling water provides sufficient
cooling. Alternatively, a chilled cooling medium can be provided to
cool the reaction. The catalyst protonates the alkenes to produce
reactive carbocations which alkylate the isobutane reactant, thus
forming branched chain paraffins from isobutane. Aromatic
alkylation is generally now conducted with solid acid catalysts
including zeolites or amorphous silica-aluminas.
[0059] The alkylation reaction zone is maintained at a pressure
sufficient to maintain the reactants in liquid phase. For a
hydrofluoric acid catalyst, a general range of operating pressures
is from about 200 to about 7100 kPa absolute. The temperature range
covered by this set of conditions is from about -20.degree. C. to
about 200.degree. C. For at least alkylation of aromatic compounds,
the volumetric ratio of hydrofluoric acid to the total amount of
hydrocarbons entering the reactor should be maintained within the
broad range of from about 0.2:1 to about 10:1, preferably from
about 0.5:1 to about 2:1
[0060] Any suitable alkylation catalyst may be used. Typically, the
catalysts are acidic. Suitable alkylation catalysts include, but
are not limited to, hydrofluoric acid, sulfuric acid and acidic
ionic liquids. Other catalysts include zeolites having a zeolite
framework type selected from the groups consisting of beta, MOR,
MWW, FAU and NES. Suitable zeolites include mordenite, ZSM-4,
ZSM-12, ZSM-20, offretite, gmelinite, beta, NU-87, UZM-8, MCM-22,
MCM-36, MCM-49, zeolite Y, zeolite X, and gottardite. Another class
of acidic, solid catalysts are acidified refractory oxides such as
chlorided, fluorided, or sulfated alumina, gallia, boria, molybdia,
ytterbia, titania, chromia, silica, zirconia, and the like and
combinations thereof. Clays and amorphous catalysts may also find
utility. Further discussion of alkylation catalysts can be found in
U.S. Pat. Nos. 5,196,574; 6,315,964B1 and 6,617,481B1. Newer
alkylation catalysts can also be used in this process. For example,
one such catalyst comprises a mixture of two types of zeolitic
materials, where the zeolites are mixed and produced to have two
zeolites within a single catalyst pellet. With the new catalysts,
the first zeolite is also characterized by its acidity, wherein the
acidity is characterized by having less than 70% of NH.sub.3
desorption off the zeolite at temperatures greater than 400.degree.
C. An example of the first zeolite is UZM-8. The second zeolite
having a silica to alumina molar ratio less than 8, and includes a
rare earth element incorporated into the zeolitic framework in an
amount greater than 16.5 wt %. The first zeolite component is in an
amount between 10 and 90% by weight of the catalyst, and the second
zeolite component is in an amount between 10 and 90% by weight. The
zeolites are intermingled into single catalyst particles. An
example of the second zeolite is a rare earth substituted X
zeolite, Y zeolite, or a zeolite having an EMT/FAU intergrowth. The
incorporation of rare earth exchanged ions in a low ratio zeolite
reduces the acidity due to an increase in the number of framework
alumina at low ratios, and also reduces geometric space in the
supercage.
EXAMPLE
[0061] A refinery model was used to estimate the yields that could
be achieved when processing a feedstock composed of 50 wt-% butanes
and 50 wt-% heptanes at reverse disproportionation conditions that
included a pressure of 2.8 MPa(g) (400 psig), a temperature of
100.degree. C., and a residence time of greater than 4 hours using
an ionic liquid catalyst. To maximize the combined yield of C6+
blendstock and iC4 for use as alkylation feedstock, the normal
butane and pentane co-products produced by the process were
recovered and recycled to the reactor. The mass ratio of recycle
flow to feedstock was 0.5. Sufficient mechanical mixing was assumed
to allow the reactants to approach an equilibrium product mixture.
The resultant process mass balance is illustrated in Table 1
below.
TABLE-US-00001 TABLE 1 Estimated Process Mass Balance Wt-% Feed nC4
50 nC7 50 Products C3- 3.0 iC4 40.0 nC4 0.1 C5 0.2 C6+ 56.7
[0062] While at least one exemplary embodiment has been presented
in the foregoing detailed description of the invention, it should
be appreciated that a vast number of variations exist. It should
also be appreciated that the exemplary embodiment or exemplary
embodiments are only examples, and are not intended to limit the
scope, applicability, or configuration of the invention in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention. It being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended
claims.
* * * * *