U.S. patent application number 15/646889 was filed with the patent office on 2017-10-26 for production of aromatics from methanol and co-feeds.
This patent application is currently assigned to ExxonMobil Chemical Patents Inc.. The applicant listed for this patent is ExxonMobil Chemical Patents Inc.. Invention is credited to Stephen H. Brown, John S. Buchanan, Michel Daage, Lorenzo C. DeCaul, Brett T. Loveless, Stephen J. McCarthy, Mayank Shekhar, Rohit Vijay.
Application Number | 20170305810 15/646889 |
Document ID | / |
Family ID | 55583718 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170305810 |
Kind Code |
A1 |
Buchanan; John S. ; et
al. |
October 26, 2017 |
Production of Aromatics from Methanol and Co-Feeds
Abstract
Methods are provided for improving the yield of aromatics during
conversion of oxygenate feeds. An oxygenate feed can contain a
mixture of oxygenate compounds, including one or more compounds
with a hydrogen index of less than 2, so that an effective hydrogen
index of the mixture of oxygenates is between about 1.4 and 1.9.
Methods are also provided for converting a mixture of oxygenates
with an effective hydrogen index greater than about 1 with a
pyrolysis oil co-feed. The difficulties in co-processing a
pyrolysis oil can be reduced or minimized by staging the
introduction of pyrolysis oil into a reaction system. This can
allow varying mixtures of pyrolysis oil and methanol, or another
oxygenate feed, to be introduced into a reaction system at various
feed entry points.
Inventors: |
Buchanan; John S.;
(Flemington, NJ) ; Brown; Stephen H.; (Lebanon,
NJ) ; DeCaul; Lorenzo C.; (Langhorne, PA) ;
Loveless; Brett T.; (Houston, TX) ; Vijay; Rohit;
(Bridgewater, NJ) ; McCarthy; Stephen J.; (Center
Valley, PA) ; Daage; Michel; (Hellertown, PA)
; Shekhar; Mayank; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Chemical Patents Inc. |
Baytown |
TX |
US |
|
|
Assignee: |
ExxonMobil Chemical Patents
Inc.
Baytown
TX
|
Family ID: |
55583718 |
Appl. No.: |
15/646889 |
Filed: |
July 11, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14829399 |
Aug 18, 2015 |
9732013 |
|
|
15646889 |
|
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62057855 |
Sep 30, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02P 30/20 20151101;
C07C 1/2076 20130101; C10G 2400/30 20130101; C10G 3/49 20130101;
C07C 15/00 20130101; C07C 1/20 20130101; C07C 1/20 20130101; C07C
15/00 20130101; C07C 1/2076 20130101; C07C 2529/44 20130101 |
International
Class: |
C07C 1/20 20060101
C07C001/20; C07C 1/207 20060101 C07C001/207; C10G 3/00 20060101
C10G003/00 |
Claims
1. A method for converting oxygenates to aromatics, comprising:
exposing a first feed comprising a first oxygenate feed having an
effective hydrogen index of at least about 1 and a first portion of
a pyrolysis oil feed to an aromatization catalyst at a first
location under effective conversion conditions to form a first
conversion effluent comprising one or more aromatic compounds, the
volume percentage of the first portion of the pyrolysis oil feed
being about 5 vol % to about 25 vol % of the volume of the first
feed; exposing at least a portion of the first conversion effluent
and a second feed comprising a second oxygenate feed having an
effective hydrogen index of at least about 1 and a second portion
of the pyrolysis oil feed to the aromatization catalyst under
effective conversion conditions to form a second conversion
effluent comprising one or more aromatic compounds, the volume of
the second feed being less than the volume of the first feed;
wherein the volume percentage of the first and second portions of
the pyrolysis oil feed based on the total volume of the first and
second feeds is greater than the volume percentage of the first
portion of the pyrolysis oil feed, and wherein said aromatization
catalyst comprises ZSM-5 and at least one metal from Groups 8-14 of
the Periodic Table.
2. The method of claim 1, further comprising exposing at least a
portion of the second conversion effluent and a third feed
comprising a third oxygenate feed having an effective hydrogen
index of at least about 1 and a third portion of the pyrolysis oil
feed to the aromatization catalyst under effective conversion
conditions to form a third conversion effluent comprising one or
more aromatic compounds, the volume of the third feed being less
than the volume of the second feed.
3. The method of claim 1, wherein the volume percentage of the
second portion of the pyrolysis oil feed is about 25 vol % to about
70 vol % of the volume of the second feed.
4. The method of claim 1, wherein the total volume percentage of
pyrolysis oil feed exposed to the aromatization catalyst is about
15 vol % to about 70 vol % based on the total volume of the
oxygenate feeds and pyrolysis oil feed.
5. The method of claim 1, wherein the total volume percentage of
pyrolysis oil feed exposed to a conversion catalyst is at least
about 50 vol % based on the total volume of the oxygenate feeds and
pyrolysis oil feed.
6. The method of claim 1, wherein the at least one element from
Groups 8-14 is selected from the group consisting of Zn, Ga, Ag and
combinations thereof.
7. A method for converting oxygenates to aromatics, comprising:
introducing an oxygenate feed having an effective hydrogen index of
at least about 1 and a pyrolysis oil feed into a conversion
reaction system at a plurality of feed entry points, the reaction
system having a direction of flow, each of the plurality of feed
entry points being located at a different location of the reaction
system relative to the direction of flow, the plurality of feed
entry points comprising at least a first upstream entry point and a
final downstream entry point; exposing the portions of the
oxygenate feed and the pyrolysis oil feed introduced at each of the
plurality of feed entry points to an aromatization catalyst to form
a plurality of converted effluents, at least a portion of the
converted effluents from upstream feed entry points being combined
with the portions of the oxygenate feed and the pyrolysis oil feed
introduced at a downstream feed entry point; wherein the volume
percentage of the pyrolysis oil feed based on the total volume of
the oxygenate feed and the pyrolysis oil is greater than the volume
percentage of the portion of the pyrolysis oil feed introduced at
the first upstream entry point, and wherein said aromatization
catalyst comprises ZSM-5 and at least one metal from Groups 8-14 of
the Periodic Table.
8. The method of claim 7, wherein the volume percentage of the
portion of the pyrolysis oil feed introduced at each feed entry
point is greater than the volume percentage of the portion of the
pyrolysis oil feed introduced at upstream feed entry points, the
volume percentage of the portion of the pyrolysis oil feed being
based on the total volume of the portions of the oxygenate feed and
the pyrolysis oil feed introduced at the same entry point.
9. The method of claim 7, wherein the volume percentage of the
portion of the pyrolysis oil feed introduced at least two feed
entry points is substantially similar, the volume percentage of the
portion of the pyrolysis oil feed being based on the total volume
of the portions of the oxygenate feed and the pyrolysis oil feed
introduced at the same entry point.
10. The method of claim 7, wherein the volume percentage of the
portion of the pyrolysis oil feed introduced to at least one feed
entry point is about 25 vol % to about 70 vol % based on the total
volume of the portions of the oxygenate feed and the pyrolysis oil
feed introduced at the same entry point.
11. The method of claim 7, wherein the total volume percentage of
the pyrolysis oil feed exposed to the aromatization catalyst is
about 15 vol % to about 70 vol % based on the total volume of the
oxygenate feed and the pyrolysis oil feed.
12. The method of claim 7, wherein the total volume percentage of
pyrolysis oil feed exposed to the aromatization catalyst is at
least about 50 vol % based on the total volume of the oxygenate
feed and the pyrolysis oil feed.
13. The method of claim 7, wherein the at least one element from
Groups 8-14 is selected from the group consisting of Zn, Ga, Ag and
combinations thereof.
Description
PRIORITY CLAIM
[0001] This application is a divisional of U.S. patent application
Ser. No. 14/829,399, filed Aug. 18, 2015, which further claims
priority to and the benefit of U.S. Provisional Application No.
62/057,855, filed Sep. 30, 2014, the disclosure of each are
incorporated herein by reference in their entireties.
FIELD OF THE INVENTION
[0002] Methods are provided for the manufacture of aromatics from
oxygenate feeds.
BACKGROUND OF THE INVENTION
[0003] Conversion of methanol feeds to aromatic compounds is an
industrially valuable reaction. Conventional methods for converting
methanol to aromatics can involve exposing a methanol-containing
feed to a molecular sieve, such as ZSM-5. In addition to forming
aromatic compounds, some olefins can also be produced. Reactions
for conversion of methanol can be useful, for example, for creation
of aromatics and olefins as individual products, or for formation
of aromatic and olefin mixtures for use as naphtha boiling range or
distillate boiling range fuels.
[0004] One difficulty with methods for conversion of methanol to
aromatics is that the conversion reaction can have a relatively low
yield of aromatics. The low yields from conventional methods can
pose a variety of challenges, such as requiring large equipment
footprints relative to total product volume as well as loss of
initial reactant to various side reactions.
[0005] U.S. Pat. Nos. 4,049,573 and 4,088,706 disclose conversion
of methanol to a hydrocarbon mixture rich in C.sub.2-C.sub.3
olefins and mononuclear aromatics, particularly p-xylene, by
contacting the methanol at a temperature of 250-700.degree. C. and
a pressure of 0.2 to 30 atmospheres with a crystalline
aluminosilicate zeolite catalyst which has a Constraint Index of
1-12 and which has been modified by the addition of an oxide of
boron or magnesium either alone or in combination or in further
combination with oxide of phosphorus. The above-identified
disclosures are incorporated herein by reference.
[0006] Methanol can be converted to gasoline employing the MTG
(methanol to gasoline) process. The MTG process is disclosed in the
patent art, including, for example, U.S. Pat. Nos. 3,894,103;
3,894,104; 3,894,107; 4,035,430 and 4,058,576. U.S. Pat. No.
3,894,102 discloses the conversion of synthesis gas to gasoline.
MTG processes provide a simple means of converting syngas to
high-quality gasoline. The ZSM-5 catalyst used is highly selective
to gasoline under methanol conversion conditions, and is not known
to produce distillate range fuels, because the C.sub.10+ olefin
precursors of the desired distillate are rapidly converted via
hydrogen transfer to heavy polymethylaromatics and C.sub.4 to
C.sub.8 isoparaffins under methanol conversion conditions.
[0007] Olefinic feedstocks can also be used for producing C.sub.5+
gasoline, diesel fuel, etc. In addition to the basic work derived
from ZSM-5 type zeolite catalysts, a number of discoveries
contributed to the development of the industrial process known as
Mobil Olefins to Gasoline/Distillate ("MOGD"). This process has
significance as a safe, environmentally acceptable technique for
utilizing feedstocks that contain lower olefins, especially C.sub.2
to C.sub.5 alkenes. In U.S. Pat. Nos. 3,960,978 and 4,021,502,
Plank, Rosinski and Givens disclose conversion of C.sub.2 to
C.sub.5 olefins alone or in admixture with paraffinic components,
into higher hydrocarbons over crystalline zeolites having
controlled acidity. Garwood et al have also contributed improved
processing techniques to the MOGD system, as in U.S. Pat. Nos.
4,150,062, 4,211,640 and 4,227,992. The above-identified
disclosures are incorporated herein by reference.
[0008] Conversion of lower olefins, especially propene and butenes,
over ZSM-5 is effective at moderately elevated temperatures and
pressures. The conversion products are sought as liquid fuels,
especially the C.sub.5+ aliphatic and aromatic hydrocarbons.
Olefinic gasoline is produced in good yield by the MOGD process and
may be recovered as a product or recycled to the reactor system for
further conversion to distillate-range products. Operating details
for typical MOGD units are disclosed in U.S. Pat. Nos. 4,445,031;
4,456,779, Owen et al, and U.S. Pat. No. 4,433,185, Tabak,
incorporated herein by reference.
[0009] In addition to their use as shape selective oligomerization
catalysts, the medium pore ZSM-5 type catalysts are useful for
converting methanol and other lower aliphatic alcohols or
corresponding ethers to olefins. Particular interest has been
directed to a catalytic process ("MTO") for converting low cost
methanol to valuable hydrocarbons rich in ethene and C.sub.3+
alkenes. Various processes are described in U.S. Pat. No. 3,894,107
(Batter et al), U.S. Pat. No. 3,928,483 (Chang et al), U.S. Pat.
No. 4,025,571 (Lago), U.S. Pat. No. 4,423,274 (Daviduk et al) and
U.S. Pat. No. 4,433,189 (Young), incorporated herein by reference.
It is generally known that the MTO process can be optimized to
produce a major fraction of C.sub.2 to C.sub.4 olefins. Prior
process proposals have included a separation section to recover
ethene and other gases from by-product water and C.sub.5+
hydrocarbon liquids. The oligomerization process conditions which
favor the production of C.sub.10 to C.sub.20 and higher aliphatics
tend to convert only a small portion of ethene as compared to
C.sub.3+ olefins.
[0010] The methanol to olefin process (MTO) operates at high
temperature and near 30 psig in order to obtain efficient
conversion of the methanol to olefins. These process conditions,
however, produce an undesirable amount of aromatics and C.sub.2
olefins and require a large investment in plant equipment.
[0011] The olefins to gasoline and distillate process (MOGD)
operates at moderate temperatures and elevated pressures to produce
olefinic gasoline and distillate products. When the conventional
MTO process effluent is used as a feed to the MOGD process, the
aromatic hydrocarbons produced in the MTO unit are desirably
separated and a relatively large volume of MTO product effluent has
to be cooled and treated to separate a C.sub.2- light gas stream,
which is unreactive, except for ethene which is reactive to only a
small degree, in the MOGD reactor, and the remaining hydrocarbon
stream has to be pressurized to the substantially higher pressure
used in the MOGD reactor.
[0012] U.S. Pat. No. 3,998,898 describes a method for manufacture
of gasoline using an MTG style process. In U.S. Pat. No. 3,998,898,
a potential gasoline including aromatic compounds is manufactured
from a feed that contains two types of aliphatic compounds. The
feed can contain aliphatic compounds corresponding to a)
"difficultly convertible" compounds, such as carboxylic acids and
short chain aldehydes, and b) "easily convertible" compounds, such
as aliphatic alcohols, ketones, and aldehydes containing 3 or more
carbons, with the mixture having sufficient "easily convertible"
compounds to make up for a stoichiometric deficiency due to the
presence of any carboxylic acids in the feed. The use of a mixture
of a "difficultly convertible" compound and an "easily convertible"
compound meeting the specified criteria is described as improving
the yield of gasoline boiling range compounds at the expense of
compounds having 4 carbons or less.
[0013] U.S. Pat. No. 7,820,867 describes a variation on the methods
from U.S. Pat. No. 3,998,898. The '867 patent describes integration
of a reaction for converting synthesis gas to methanol (or other
oxygenates) with a methanol to gasoline reaction. In the integrated
system, the "difficultly convertible" compounds can be introduced
into the reaction stage for conversion of synthesis gas to
methanol. The same definition for "difficultly convertible"
compounds used in U.S. Pat. No. 3,998,898 is maintained in the '867
patent.
[0014] Despite numerous prior art processes, there is an ongoing
desire to improve methods of converting methanol to aromatics that
yield a higher amount of aromatics than the prior art methods.
There is a particular interest in methods that produce high yields
of paraxylene, considering paraxylene's value in industry and its
use in the manufacture of terephthalic acid, an intermediate in the
production of synthetic fibers.
SUMMARY OF THE INVENTION
[0015] The present invention provides methods for improving the
yield of aromatics, particularly paraxylene, from conversion of
oxygenate feeds including methanol. In one aspect, an oxygenate
feed having an effective hydrogen index of about 1.4 to about 1.9
is exposed to an aromatization catalyst under effective conversion
conditions to form a conversion effluent comprising one or more
aromatic compounds. The oxygenate feed contains 5 wt. % or less of
carbon-containing compounds different from CO and CO.sub.2 that
have a hydrogen index of 1 or less. Optionally, the oxygenate feed
can be substantially free of carboxylic acids, such as a feed that
comprises, consists essentially of, and/or consists of ketones,
alcohols, C.sub.3+ aldehydes, and combinations thereof.
[0016] In another aspect, methanol is reacted with a pyrolysis oil
over an aromatization catalyst in a series of steps to form
aromatics. The introduction of the pyrolysis oil is advantageously
staged to reduce or minimize the coking and/or fouling effects of
the reaction with pyrolysis oil. Thus, the total volume of the
pyrolysis oil to be reacted is split into at least two portions,
and each portion is fed, with an oxygenate feed (together "fresh
feed"), to a reactor or series of reactors at a different location
to react with an aromatization catalyst and the effluent from the
previous step. Preferably, the volume percentage of pyrolysis oil
in each successive fresh feed increases, but less fresh feed is
introduced at downstream entry points as compared to the first
entry point, and the total percentage of the pyrolysis oil in the
total amount of fresh feed is greater than the volume percentage of
the pyrolysis oil of the feed introduced at the first entry
point.
[0017] In one embodiment in which a pyrolysis oil is used as a
co-feed, a first feed comprising a first oxygenate feed having an
effective hydrogen index of at least about 1 and a first portion of
a pyrolysis oil feed is exposed to an aromatization catalyst at a
first location under effective conversion conditions to form a
first conversion effluent comprising one or more aromatic
compounds. The volume percentage of the first portion of the
pyrolysis oil feed is about 5 vol % to about 25 vol % of the volume
of the first feed. At least a portion of the first conversion
effluent, along with a second feed comprising a second oxygenate
feed having an effective hydrogen index of at least about 1 and a
second portion of the pyrolysis oil feed, is exposed to an
aromatization catalyst at a second location under effective
conversion conditions to form a second conversion effluent
comprising one or more aromatic compounds. The volume of the second
feed is less than the volume of the first feed, and the volume
percentage of the first portion of the pyrolysis oil feed based on
the total volume of the first and second feeds is greater than the
volume percentage of the first portion of the pyrolysis oil feed.
Optionally, at least a portion of the second conversion effluent,
along with a third (or fourth, or fifth, etc.) feed comprising a
third oxygenate feed having an effective hydrogen index of at least
about 1 and a third portion of the pyrolysis oil feed, is exposed
to an aromatization catalyst at a third location under effective
conversion conditions to form a third conversion effluent
comprising one or more aromatic compounds.
[0018] In still another embodiment, an oxygenate feed having an
effective hydrogen index of at least about 1 and a pyrolysis oil
feed is introduced into a conversion reaction system at a plurality
of feed entry points. The reaction system has a direction of flow,
and each of the plurality of feed entry points is located at a
different location of the reaction system relative to the direction
of flow. The plurality of feed entry points includes at least a
first upstream entry point and a final downstream entry point. The
portions of the oxygenate feed and the pyrolysis oil feed
introduced at each of the plurality of feed entry points is exposed
to at least a portion of an aromatization catalyst to form a
plurality of converted effluents, and at least a portion of the
converted effluents from upstream feed entry points are combined
with the portions of the oxygenate feed and the pyrolysis oil feed
introduced at a downstream feed entry point. The volume percentage
of pyrolysis oil feed based on the total volume of the portions of
the oxygenate feed and the pyrolysis oil feed is greater than the
volume percentage of the portion of the pyrolysis oil feed
introduced at the first upstream entry point. Optionally, the
volume percentage of the portion of the pyrolysis oil at each feed
entry point is greater than the volume percentage of the portion of
the pyrolysis oil feed introduced at upstream feed entry points,
the volume percentage of the portion of the pyrolysis oil feed
being based on the total volume of the portions of the oxygenate
feed and the pyrolysis oil feed introduced at the same entry point.
Alternatively, the volume percentage of the portion of the
pyrolysis oil feed introduced at least two feed entry points is
substantially similar.
[0019] The aromatization catalyst utilized herein comprises a
molecular sieve, preferably ZSM-5, and at least one Group 8-14
element. Effective conversion conditions for the methods provided
are a pressure of about 100 kPaa to about 2500 kPaa, a temperature
of about 300.degree. C. to about 600.degree. C., and a weight
hourly space velocity of about 0.1 hr.sup.-1 to about 20 hr.sup.-1.
The claimed methods and co-feeds provide an increased yield of
aromatics as compared to methods using methanol alone.
BRIEF DESCRIPTION OF THE FIGURES
[0020] FIG. 1 schematically shows an example of a reaction system
having multiple feed entry points for converting an oxygenate feed
to form aromatics.
[0021] FIG. 2 shows results from converting feeds with various
effective hydrogen index values to form aromatics.
[0022] FIG. 3 shows an example of a bio-oil composition.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Overview
[0023] In various aspects, methods are provided for improving the
yield of aromatics during conversion of oxygenate feeds. An
oxygenate feed can contain a mixture of oxygenate compounds,
including one or more compounds with a hydrogen index of less than
2, so that an effective hydrogen index of the mixture of oxygenates
is between about 1.4 and 1.9. Optionally, the mixture of oxygenates
can include one or more ketones or aldehydes having 3 or more
carbons. Additionally or alternately, the mixture of oxygenates can
exclude compounds having a hydrogen index of less than 1 and/or can
exclude carboxylic acids, formaldehyde, and acetaldehyde. An
example of a mixture of oxygenates having an effective hydrogen
index of between about 1.4 and 1.9 can be a mixture of acetone,
butanol (such as n-butanol), and ethanol. Such a mixture of
oxygenates can also include methanol and/or dimethyl ether.
[0024] In other aspects, a mixture of oxygenates with an effective
hydrogen index greater than about 1 can be converted with a
pyrolysis oil co-feed. Pyrolysis oils are mixtures of oxygenates
formed from pyrolysis of biomass in an atmosphere containing a
reduced amount of oxygen. Pyrolysis oils can be difficult to
process for various reasons, including an elevated content of
oxygenates and aromatics as well as the presence of substantial
amounts of carboxylic acids. However, the difficulties in
co-processing a pyrolysis oil can be reduced or minimized by
staging the introduction of pyrolysis oil into a reaction system.
This can allow varying mixtures of pyrolysis oil and methanol (or
another oxygenate feed) to be introduced into a reaction system at
various feed entry points. This type of staged addition can allow
for use of increased amounts of pyrolysis oil in the overall feed
for a conversion process while reducing or minimizing problems in a
reactor due to plugging or formation of coke.
Hydrogen Index and Effective Hydrogen Index
[0025] In various aspects, an improved feed for forming aromatic
compounds can be provided by using a feed with an effective
hydrogen index of less than 2, such as an effective hydrogen index
of about 1.4 to about 1.9. The effective hydrogen index (EHI) of a
feed can be calculated based on the hydrogen index values of the
components of a feed. In this discussion, a reference to a hydrogen
index or hydrogen index value corresponds to a value for a single
compound, while an effective hydrogen index represents a value for
a feed containing one or more components.
[0026] The hydrogen index (HI) of a compound containing only
carbon, hydrogen, and oxygen can be expressed as HI=[n-2p]/m, where
m, n, and p refer to the stoichiometric values in a chemical
formula expressed as C.sub.mH.sub.nO.sub.p. Based on this
definition, examples of hydrogen index values for oxygenate
compounds are: aliphatic alcohols have a hydrogen index of 2;
acetone and propanal have a hydrogen index of 1.33 (C4+ ketones and
aldehydes have HI values between 1.5 and 2); acetaldehyde has a
hydrogen index of 1; aromatic oxygenates (such as phenols) have
hydrogen index values less than 1; and formaldehyde and sugars have
a hydrogen index of 0. Carboxylic acids have a wide range of HI
values, ranging from -1 for formic acid to greater than 1 for C5+
carboxylic acids. It is noted that benzene has an HI value of 1,
while C7+ single ring aromatic hydrocarbons have HI values slightly
greater than 1. After determining the hydrogen index values for the
components in a feed, the effective hydrogen index for the feed can
be determined based on a mole weighted average of the hydrogen
index values of the individual components.
Mixtures of Oxygenates with Hydrogen Index of at Least 1
[0027] Hydrogen index can assist in characterizing a feed for
conversion of oxygenates to aromatics. For example, the formula for
methanol (HI=2) is CH.sub.4O. During a conversion reaction, the
oxygen in the methanol typically forms water. After removing a
water unit, the remaining atoms in methanol correspond to a
CH.sub.2 unit. In order to form a C6 aromatic compound (HI=1) from
CH.sub.2 units (HI=2), 6 additional hydrogen atoms (or 3H.sub.2
molecules) have to be accounted for, such as by reaction with other
compounds. In other words, for an oxygenate to aromatics conversion
reaction, a comparison of the hydrogen index for feed and products
indicates the amount of excess hydrogen atoms that have to be
accounted for. In a reaction environment for forming aromatics from
methanol (or other oxygenates), these additional hydrogens have to
be incorporated into other products from the conversion reaction.
Conventionally, the additional hydrogen atoms are accounted for by
forming short chain aliphatic compounds, such as ethane and
propane, which have a stoichiometry of C.sub.nH.sub.2n+2. Based on
stoichiometry, in an idealized reaction for forming benzene from
methanol, this means at least three alkanes (ethane) have to be
formed for each aromatic formed. This can result in a substantial
reduction in the yield of aromatics from the conversion process, as
at least as many carbon atoms have to be incorporated into alkane
products as are incorporated into aromatic products.
[0028] Instead of forming substantial amounts of alkanes, the
additional H.sub.2 units can be consumed by hydrogenating compounds
(such as oxygenate compounds) with lower HI values. For example,
formaldehyde has an HI value of 0. From a stoichiometry standpoint,
3 methanols plus 3 formaldehydes can be used to form a C6 aromatic
without requiring formation of additional alkanes. More generally,
any compounds present within a feed can potentially react with the
excess hydrogen, including compounds that are not directly involved
with formation of aromatic compounds.
[0029] Under conventional methods, such as the methods in U.S. Pat.
No. 7,820,867, increasing the yield of aromatics from an oxygenate
feed was believed to require mixing of "easily convertible"
compounds (having HI values greater than 1) with "difficultly
convertible" compounds having HI values less than 1. In such
conventional methods, ketones and C3+ aldehydes were considered
"easily convertible" compounds, while all carboxylic acids were
defined as "difficultly convertible" regardless of HI value.
However, it has been unexpectedly determined that the yield of
aromatics can be improved using mixtures of oxygenates to form a
feed having an effective hydrogen index of 1.4 to 1.9, where
substantially all of the oxygenates in the feed have an HI value of
greater than 1. Preferably, substantially none of the oxygenates in
the feed are carboxylic acids. An example of such an oxygenate feed
can be a feed composed of alcohols, ketones, and C.sub.3+ aldehydes
that have a hydrogen index of greater than 1. In such a feed,
substantially all of the components in the feed can represent
compounds that are conventionally believed to be "easily
convertible" compounds. However, an improved yield of aromatics
relative to feed with an EHI value of 2 (i.e., a feed of alcohols
and/or dialkyl ethers) can still be obtained. A feed with
substantially all components being "easily convertible" is defined
herein as a feed containing about 5 wt. % or less of components
that have a hydrogen index less than 1 and/or that are carboxylic
acids. For example, a feed with substantially all components being
easily convertible can contain about 3 wt. % or less of components
that have a hydrogen index less than 1 and/or that are carboxylic
acids, or about 1 wt. % or less, or about 0.5 wt. % or less, or
about 0.1 wt. % or less.
[0030] One example of a feed that can have substantially all
components that are "easily convertible" compounds is a mixture of
acetone, butanol (preferably n-butanol), and ethanol. Mixtures of
acetone, n-butanol, and ethanol are an example of a type of
fermentation product that can be formed from fermentation of starch
by some biological processes. A typical yield from such a
fermentation process (on a dry basis) can be about 30 vol %
acetone, about 60 vol % n-butanol, and about 10 wt. % ethanol in
the product. This type of mixture of acetone, n-butanol, and
ethanol can be not only suitable for use in synthesis of aromatics,
but can in fact provide an improved yield relative to a pure
alcohol feed. More generally, a variety of biological processes
(such as fermentation processes) can produce mixtures of alcohols
and ethers that also include ketones and C.sub.3+ aldehydes. Such
mixtures can have an EHI of less than about 1.9, thus allowing for
use of the mixtures for conversion to aromatics with an improved
yield of aromatics relative to a feed with an EHI of 2.
Mixtures of Oxygenates with Pyrolysis Oils (Staged Addition)
[0031] Another option for providing a process with improved
aromatics yield can be to use a traditionally lower value stream as
a source of compounds with low hydrogen index. Pyrolysis oils are
an example of a potential feed stream containing low hydrogen index
compounds. Pyrolysis oils can include a large variety of oxygenate
and/or aromatic compounds, and the composition of pyrolysis oils
can vary depending on the nature of the original feed and the
pyrolysis conditions. From an effective hydrogen index standpoint,
pyrolysis oils are a potentially useful co-feed for an oxygenate
conversion process, as typical pyrolysis oils can have an effective
hydrogen index of less than 1. However, pyrolysis oils are
conventionally viewed as less desirable for use as a co-feed during
conversion of oxygenates to aromatics due to an increased tendency
for pyrolysis oils to coke and/or foul the conversion reactor. This
coking is believed to increase with increasing concentrations of
pyrolysis oil in a feed for conversion.
[0032] An illustrative example of a possible pyrolysis oil
composition is shown in FIG. 3. The composition in FIG. 3 was
described in "Exploratory Studies of Fast Pyrolysis Oil Upgrading",
F. H. Mahfud, Rijksuniversiteit Groningen, Nov. 16, 2007, ISBN
978-90-367-3226-9.
[0033] As shown in FIG. 3, a pyrolysis oil can contain a
substantial portion of aromatic compounds, such as syringols,
furans, phenols, and guaiacols. Due in part to the presence of the
aromatic compounds, incorporating pyrolysis oils into a feed for an
oxygenate conversion process is conventionally believed to lead to
substantial coking of the catalyst. This coking can foul a
conversion reactor and potentially prevent operation of the reactor
at higher concentrations of pyrolysis oil in a feed.
[0034] In various aspects, the difficulties with coking in a
conversion reactor when using a pyrolysis oil as a co-feed can be
reduced or minimized by staging the addition of the pyrolysis oil
in a reaction system by using a plurality of feed entry points. For
example, in a reaction system using a series of reactors (or
alternatively a series of feed entry points within a single
reactor), the ratio of methanol (or another high EHI feed) to
pyrolysis oil can be set separately for each reactor and/or feed
entry point. The ratio of methanol to pyrolysis oil in the first
reactor can be set to a relatively low value, so that 25 vol % or
less of the feed corresponds to pyrolysis oil. This can reduce or
minimize the coking in the initial reactor. The feed to the second
reactor can then correspond to the effluent from the first reactor
plus an additional amount of both the methanol and the pyrolysis
oil. Based on the presence of the effluent from the first reactor,
a higher percentage of the fresh feed in the second reactor (feed
entry point) can correspond to the pyrolysis oil. In an example
using three feed entry points, the volume percentage of pyrolysis
oil in the fresh feed to the second reactor can be at about 25 vol
% to about 70 vol %, or about 25 vol % to about 50 vol %. The
effluent from the second reactor can then be used as a portion of
the feed to a third reactor. The fresh feed to the third reactor
can include a still larger percentage of pyrolysis oil, such as
about 40 vol % to about 80 vol %.
[0035] More generally, staging of addition of the pyrolysis oil in
the feed to the conversion reaction can be used with any convenient
reaction system configuration. The concept of staging is based on
introducing a total feed to a reaction system by splitting the feed
across multiple feed entry points at different locations relative
to the direction of flow within the reaction system. Additionally,
the composition of the feed at each feed entry point will typically
be different from the total composition for the feed. The staging
can be performed by using multiple reactors, with different
concentrations of pyrolysis oil in the feed to each reactor.
Additionally or alternately, the staging can be performed by
introducing feed in multiple locations (feed entry points) in a
reactor, with downstream locations in the reactor receiving greater
percentages of pyrolysis oil in the feed. The staging of addition
of the feed can be used with fixed bed reactors, fluidized bed
reactors, moving bed reactors, or any other convenient type of
reactor. In some preferred aspects, the reactors used can be
fluidized bed reactors or other reactors that can facilitate
regeneration and recycle of catalyst within the reactor.
[0036] In this discussion, references to introducing a feed or a
co-feed at a feed entry point are understood as including any
convenient method for introducing a feed. For example, a high EHI
feed (such as a methanol feed) and a pyrolysis oil feed can be
mixed prior to entering a reaction system via a feed entry point,
or the high EHI feed and the pyrolysis oil feed can be introduced
into a reaction system separately at similar locations relative to
the direction of flow within the reaction system.
[0037] The number of feed entry points in a reaction system having
staged (different) amounts of pyrolysis oil in the fresh feed can
be any convenient number. At least two different feed entry points
are needed in order to have staged addition of the pyrolysis oil.
In various aspects, introducing the pyrolysis oil co-feed using
three to eight feed points having different concentrations can be
preferred. In order to avoid fouling, the highest pyrolysis oil
volume percentage (concentration) at any feed entry point can be
about 80 vol % or less.
[0038] When using multiple feed entry points for a feed including a
pyrolysis oil, higher amounts of pyrolysis oil can be introduced
into the later (downstream) feed entry points. Preferably, the
amount of feed introduced into a reaction system at all prior
upstream feed entry points can be at least as great as the amount
of feed introduced at any single downstream feed entry point. This
can assist with providing a sufficient volume of previously reacted
feed so that production of coke due to downstream introduction of
pyrolysis oil is reduced or minimized.
[0039] In various aspects, the combined amount of feed (high EHI
feed plus pyrolysis oil feed) introduced at the first entry point
can be at least 20 vol % of the total amount of feed (high EHI feed
plus pyrolysis oil feed) introduced into the conversion reaction
system, such as at least about 25 vol %, or at least about 30 vol
%, or at least about 35 vol %. Additionally or alternately, the
combined amount of feed introduced at the first entry point can be
about 75 vol % or less of the total amount of feed introduced into
the conversion reaction system, such as about 65 vol % or less, or
about 50 vol % or less. In some aspects, after the initial feed
entry point, the combined amount of feed introduced at each
subsequent feed entry point can preferably be at least about 5 vol
% of the total amount of feed introduced into the conversion
reaction system, or at least about 10 vol %. By staging the
introduction of the pyrolysis oil, the net concentration of
pyrolysis oil in the total feed across all feed entry points can be
as high as 70 vol %, such as about 15 vol % to about 70 vol %,
preferably about 25 vol % to about 70 vol %, and most preferably 50
vol % to 70 vol % of the feed.
[0040] In some alternative aspects, a single feed entry point can
be used for introduction of a pyrolysis oil co-feed. In such
aspects, the amount of pyrolysis oil used as a co-feed can be about
5 vol % to about 50 vol %, preferably about 10 vol % to about 40
vol %, and more preferably about 15 vol % to about 30 vol %.
[0041] For a reaction system with a plurality of feed entry points,
such as two to eight feed entry points, or three to eight feed
entry points, the pyrolysis oil concentration can vary at each feed
entry point. For the first or initial feed entry point, the
pyrolysis oil concentration can be from 5 vol % to 25 vol %
relative to the total weight of feed introduced at the first feed
entry point, preferably from 10 vol % to 25 vol %, and more
preferably from 15 vol % to 20 vol %. For the final feed entry
point, the pyrolysis oil concentration can be from about 30 vol %
to about 80 vol %, preferably about 40 vol % to about 80 vol %,
more preferably about 40 vol % to about 70 vol %, and even more
preferably about 50 vol % to about 70 vol %. If three or more feed
entry points are used, in some aspects at least one intermediate
feed entry point can have a pyrolysis oil concentration of about 25
vol % to about 50 vol %, preferably about 25 vol % to about 45 vol
%, and more preferably about 30 vol % to about 40 vol %.
Additionally or alternately, if three or more feed entry points are
used, in some aspects at least one intermediate feed entry point
can have a pyrolysis oil concentration of about 35 vol % to about
60 vol %, preferably about 40 vol % to about 60 vol %, and more
preferably 40 vol % to about 55 vol %.
[0042] In some aspects, two or more of the feed entry points can
have a substantially similar concentration of pyrolysis oil. In
other aspects, each subsequent feed entry point can have a higher
concentration of pyrolysis oil than the prior feed entry point,
such as at least 5 vol % greater, or at least 10 vol % greater. Any
convenient method or scheme can be used for varying the relative
amounts of high EHI feed and pyrolysis oil feed at the various feed
entry points. For example, one option can be to introduce the same
amount of pyrolysis oil at each feed entry point while varying the
amount of methanol (or other high EHI feed) at the feed entry
points to achieve the desired variation in pyrolysis oil
concentration. Another option can be to introduce the same total
weight of feed at each feed entry point while varying the amounts
of high EHI feed and pyrolysis oil feed.
[0043] By using staged addition of pyrolysis oil, an increased
amount of pyrolysis oil can be used as a co-feed for conversion of
oxygenates to aromatics while reducing or minimizing the amount of
additional coke formed in the reaction system. For the first
reactor and/or first feed entry stage of the reaction system, the
amount of coke generated in the reactor can roughly correspond to
the amount of coke expected based on the percentage of pyrolysis
oil in the feed. However, for a second (or other subsequent)
addition locations for the feed, the amount of coke can correspond
to an amount less than would be expected based on addition of all
of the pyrolysis oil with the initial feed. Instead, the effluent
from the earlier reactors (or upstream locations) can act as a
diluent so that the amount of coke generated is comparable to what
would be expected based on the concentration of the fresh pyrolysis
oil in the total input flow to a given reactor stage or location.
It is also noted that using staged addition of the pyrolysis oil
can reduce or minimize the amount of methanol that is consumed in
alkylation of the pyrolysis oil instead of being converted to the
desired aromatic compounds.
[0044] FIG. 1 schematically shows an example of a reaction system
suitable for introducing pyrolysis oil in a stage manner during an
oxygenate to aromatics conversion process. For convenience in
illustrating the concept, FIG. 1 shows examples of both using
multiple reactors for staged addition as well as introducing feeds
at multiple locations within a reactor. Of course, any convenient
combination of additional reactors and additional feed entry points
can be used, such a reaction system using separate reactors for
each feed entry point and/or a reaction system comprising a single
reactor with multiple feed entry points. The reactors in FIG. 1 can
correspond to any convenient type of reactor for stage addition of
feed. For convenience, the reactors in FIG. 1 are shown as fixed
bed reactors, but fluidized bed reactors or riser reactors could
also be used.
[0045] In FIG. 1, two sources of feed for the reaction system are
shown. One feed source 105 of feed is a feed with an effective
hydrogen index greater than 1, such as a feed comprising methanol
and/or dimethyl ether, or a feed comprising a mixture of alcohols
and ethers. A second feed source 107 can provide a pyrolysis oil
feed to the reaction system. FIG. 1 shows these feed sources
schematically as corresponding to multiple instances of feed
sources for convenience. In other aspects, a single high hydrogen
index feed source 105 and/or pyrolysis oil feed source 107 could be
used. FIG. 1 also depicts introducing feed streams derived from
feed source(s) 105 and 107 as separate feed streams into a reaction
system at various feed entry locations. Of course, a feed stream
comprising a mixture of feeds from a feed source 105 and a feed
source 107 can be mixed together prior to entering a reactor.
Mixing a pyrolysis oil with a methanol (or other high effective
hydrogen index stream) could be beneficial, for example, to provide
better mixing prior to entering a reactor or to improve the flow
properties of the pyrolysis oil feed for delivery to a reaction
system.
[0046] In FIG. 1, feed streams 115 and 117 (from feed sources 105
and 107, respectively) are delivered to a first conversion reactor
120. Second conversion reactor 140 similarly receives feed streams
135 and 137, along with first conversion reactor effluent 122. The
feed streams 135 and 137, along with first conversion reactor
effluent 122, are introduced into second conversion reactor 140
prior to an initial catalyst bed 143. Feed streams 155 and 157 are
introduced into reactor 140 between initial catalyst bed 143 and
final catalyst bed 144. At the location where feed streams 155 and
157 are introduced, the feed streams are at least partially mixed
with effluent from initial catalyst bed 143 prior to passing
through final catalyst bed 144.
[0047] For a configuration such as the reaction system shown in
FIG. 1, the relative amounts of feed from feed sources 105 and 107
at each feed entry location can be varied so that the percentage of
feed from feed source 107 increases at later feed entry locations.
For example, for a combined amount of feed delivered to the first
conversion reactor 120, 80 vol % of the feed can correspond to feed
stream 115 from source 105, while 20 vol % can correspond to feed
stream 117 from source 107. At the second feed entry location, 50
vol % of the fresh feed can be in feed stream 135 while the other
50 vol % can be in feed stream 137. At the third (final) feed entry
location, 30 vol % of the fresh feed can be in feed stream 155
while the remaining 70 vol % can be in feed stream 157.
Conversion Conditions
[0048] One option for performing an oxygenate to aromatics
conversion reaction, such as a methanol to gasoline type process,
can be to use a moving or fluid catalyst bed with continuous
oxidative regeneration. The extent of coke loading on the catalyst
can then be continuously controlled by varying the severity and/or
the frequency of regeneration. In a turbulent fluidized catalyst
bed the conversion reactions are conducted in a vertical reactor
column by passing hot reactant vapor upwardly through the reaction
zone at a velocity greater than dense bed transition velocity and
less than transport velocity for the average catalyst particle. A
continuous process is operated by withdrawing a portion of coked
catalyst from the reaction zone, oxidatively regenerating the
withdrawn catalyst and returning regenerated catalyst to the
reaction zone at a rate to control catalyst activity and reaction
severity to effect feedstock conversion. Preferred fluid bed
reactor systems are described in Avidan et al. (U.S. Pat. No.
4,547,616); Harandi et al. (U.S. Pat. No. 4,751,338); and Tabak et
al. (U.S. Pat. No. 4,579,999), each of which is incorporated herein
by reference in its entirety. In other aspects, other types of
reactors can be used, such as fixed bed reactors, riser reactors,
fluid bed reactors, and/or moving bed reactors.
[0049] A suitable feed can be converted to aromatics by exposing
the feed to an aromatization catalyst under effective conversion
conditions. General conversion conditions include a pressure of
about 100 kPaa to about 2500 kPaa, preferably about 100 kPaa to
about 2000 kPaa, more preferably about 100 kPaa to about 1500 kPaa,
and ideally about 100 kPaa to about 1200 kPaa. The amount of feed
(weight) relative to the amount of catalyst (weight) can be
expressed as a weight hourly space velocity (WHSV). Suitable weight
hourly space velocities include a WHSV of about 0.1 hr.sup.-1 to
about 20 hr 1, preferably about 1.0 hr.sup.-1 to about 10
hr.sup.-1. A wide range of temperatures can be suitable, depending
on the desired type of aromatics-containing product. Thus,
temperatures of about 300.degree. C. to about 600.degree. C.,
preferably about 300.degree. C. to about 500.degree. C., and more
preferably about 350.degree. C. to about 450.degree. C.
Aromatization Catalyst
[0050] The catalyst used herein is a composition of matter
comprising a molecular sieve and a Group 8-14 element, or
combination of metals from the same group of the Periodic Table.
The composition of matter can optionally further comprise
phosphorus and/or lanthanum and/or other elements from Group 1-2
and/or Group 13-16 of the Periodic Table that provide structural
stabilization. In this sense, the term "comprising" can also mean
that the catalyst can comprise the physical or chemical reaction
product of the molecular sieve and the Group 8-14 element or
combination of elements from the same group (and optionally
phosphorus and/or lanthanum and/or other elements from groups 1-2
and/or group 13-16). In this description, reference to a group
number for an element corresponds to the current IUPAC numbering
scheme for the periodic table. Optionally, the catalyst may also
include a filler or binder and may be combined with a carrier to
form slurry.
[0051] In various aspects, the molecular sieve comprises
.gtoreq.10.0 wt. % of the catalyst, such about 10.0 to 100.0 wt. %,
preferably about 25.0 to 95.0 wt. %, and more preferably about 50.0
to 90.0 wt. %.
[0052] As used herein the term "molecular sieve" refers to
crystalline or non-crystalline materials having a porous structure.
Microporous molecular sieves typically have pores having a diameter
of .ltoreq.about 2.0 nm. Mesoporous molecular sieves typically have
pores with diameters of about 2 to about 50 nm. Macroporous
molecular sieves have pore diameters of >50.0 nm.
[0053] Particular molecular sieves are zeolitic materials. Zeolitic
materials are crystalline or para-crystalline materials. Some
zeolites are aluminosilicates comprising [SiO4] and [AlO4] units.
Other zeolites are aluminophosphates (AlPO) having structures
comprising [AlO4] and [PO4] units. Still other zeolites are
silicoaluminophosphates (SAPO) comprising [SiO4], [AlO4], and [PO4]
units.
[0054] Non-limiting examples of SAPO and AlPO molecular sieves
useful herein include one or a combination of SAPO-5, SAPO-8,
SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34,
SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44,
SAPO-47, SAPO-56, AlPO-5, AlPO-11, AlPO-18, AlPO-31, AlPO-34,
AlPO-36, AlPO-37, AlPO-46, and metal containing molecular sieves
thereof. Of these, particularly useful molecular sieves are one or
a combination of SAPO-18, SAPO-34, SAPO-35, SAPO-44, SAPO-56,
AlPO-18, AlPO-34 and metal containing derivatives thereof, such as
one or a combination of SAPO-18, SAPO-34, AlPO-34, AlPO-18, and
metal containing derivatives thereof, and especially one or a
combination of SAPO-34, AlPO-18, and metal containing derivatives
thereof.
[0055] Additionally or alternatively, the molecular sieves useful
herein may be characterized by a ratio of Si to Al. In particular
embodiments, the molecular sieves suitable herein include those
having a Si/Al ratio of about 0.05 to 0.5.
[0056] In an embodiment, the molecular sieve is an intergrowth
material having two or more distinct crystalline phases within one
molecular sieve composition. In particular, intergrowth molecular
sieves are described in U.S. Patent Application Publication No.
2002-0165089 and International Publication No. WO 98/15496,
published Apr. 16, 1998, both of which are herein fully
incorporated by reference.
[0057] Particular molecular sieves useful in this invention include
ZSM-5 (U.S. Pat. No. 3,702,886 and Re. 29,948); ZSM-11 (U.S. Pat.
No. 3,709,979); ZSM-12 (U.S. Pat. No. 3,832,449); ZSM-22 (U.S. Pat.
No. 4,556,477); ZSM-23 (U.S. Pat. No. 4,076,842); ZSM-34 (U.S. Pat.
No. 4,079,095) ZSM-35 (U.S. Pat. No. 4,016,245); ZSM-48 (U.S. Pat.
No. 4,397,827); ZSM-57 (U.S. Pat. No. 4,046,685); and ZSM-58 (U.S.
Pat. No. 4,417,780). The entire contents of the above references
are incorporated by reference herein. Other useful molecular sieves
include MCM-22, PSH-3, SSZ-25, MCM-36, MCM-49 or MCM-56, with
MCM-22. Still other molecular sieves include Zeolite T, ZKS,
erionite, and chabazite.
[0058] Another option for characterizing a zeolite (or other
molecular sieve) is based on the nature of the ring channels in the
zeolite. The ring channels in a zeolite can be defined based on the
number of atoms included in the ring structure that forms the
channel. In some aspects, a zeolite can include at least one ring
channel based on a 10-member ring. In such aspects, the zeolite
preferably does not have any ring channels based on a ring larger
than a 10-member ring. Examples of suitable framework structures
having a 10-member ring channel but not having a larger size ring
channel include EUO, FER, IMF, LAU, MEL, MFI, MFS, MTT, MWW, NES,
PON, SFG, STF, STI, TON, TUN, MRE, and PON.
[0059] In some aspects, the catalyst can also optionally include at
least one metal selected from Group 8-14 of the Periodic Table,
such as at least two metals (i.e., bimetallic) or at least three
metals (i.e., trimetallic). Typically, the total weight of the
Group 8-14 elements is from about 0.1 to 10 wt. % based on the
total weight of the catalyst, preferably from about 0.1 to 2.0 wt.
%, and more preferably from about 0.1 to 1.0 wt. %. Of course, the
total weight of the Group 8-14 elements shall not include amounts
attributable to the molecular sieve itself.
[0060] Additionally or alternatively, in some aspects, the catalyst
can also include at least one of phosphorous and/or lanthanum
and/or other elements from groups 1-2 and/or group 13-16, such as
at least two such elements or at least three such elements.
Typically, the total weight of the phosphorous and/or lanthanum
and/or other elements from groups 1-2 and/or groups 13-16 is about
0.1 to 1.0 wt. % based on the total weight of the catalyst. Of
course, the total weight of the phosphorous and/or lanthanum and/or
other elements from groups 1-2 and/or groups 13-16 shall not
include amounts attributable to the molecular sieve itself.
[0061] For the purposes of this description and claims, the
numbering scheme for the Periodic Table Groups corresponds to the
current IUPAC numbering scheme. Therefore, a "Group 4 metal" is an
element from Group 4 of the Periodic Table, e.g., Hf, Ti, or Zr.
The more preferred molecular sieves are SAPO molecular sieves, and
metal-substituted SAPO molecular sieves. In particular embodiments,
one or more Group 1 elements (e.g., Li, Na, K, Rb, Cs, Fr) and/or
Group 2 elements (e.g., Be, Mg, Ca, Sr, Ba, and Ra) and/or
phosphorous and/or Lanthanum may be used. One or more Group 7-9
element (e.g., Mn, Tc, Re, Fe, Ru, Os, Co, Rh, and Ir) may also be
used. Group 10 elements (Ni, Pd, and Pt) are less commonly used in
applications for forming olefins and aromatics, as the combination
of a Group 10 element in the presence of hydrogen can tend to
result in saturation of aromatics and/or olefins. In some
embodiments, one or more Group 11 and/or Group 12 elements (e.g.,
Cu, Ag, Au, Zn, and Cd) may be used. In still other embodiments,
one or more Group 13 elements (B, Al, Ga, In, and Tl) and/or Group
14 elements (Si, Ge, Sn, Pb) may be used. In a preferred
embodiment, the metal is selected from the group consisting of Zn,
Ga, Cd, Ag, Cu, P, La, or combinations thereof. In another
preferred embodiment, the metal is Zn, Ga, Ag, or a combination
thereof.
[0062] Particular molecular sieves and Group 2-13-containing
derivatives thereof have been described in detail in numerous
publications including for example, U.S. Pat. No. 4,567,029 (MeAPO
where Me is Mg, Mn, Zn, or Co), U.S. Pat. No. 4,440,871 (SAPO),
European Patent Application EP-A-0 159 624 (ElAPSO where El is Be,
B, Cr, Co, Ga, Fe, Mg, Mn, Ti, or Zn), U.S. Pat. No. 4,554,143
(FeAPO), U.S. Pat. Nos. 4,822,478, 4,683,217, 4,744,885 (FeAPSO),
EP-A-0 158 975 and U.S. Pat. No. 4,935,216 (ZnAPSO, EP-A-0 161 489
(CoAPSO), EP-A-0 158 976 (ELAPO, where EL is Co, Fe, Mg, Mn, Ti, or
Zn), U.S. Pat. No. 4,310,440 (AlPO4), U.S. Pat. No. 5,057,295
(BAPSO), U.S. Pat. No. 4,738,837 (CrAPSO), U.S. Pat. Nos.
4,759,919, and 4,851,106 (CrAPO), U.S. Pat. Nos. 4,758,419,
4,882,038, 5,434,326, and 5,478,787 (MgAPSO), U.S. Pat. No.
4,554,143 (FeAPO), U.S. Pat. Nos. 4,686,092, 4,846,956, and
4,793,833 (MnAPSO), U.S. Pat. Nos. 5,345,011 and 6,156,931 (MnAPO),
U.S. Pat. No. 4,737,353 (BeAPSO), U.S. Pat. No. 4,940,570 (BeAPO),
U.S. Pat. Nos. 4,801,309, 4,684,617, and 4,880,520 (TiAPSO), U.S.
Pat. Nos. 4,500,651, 4,551,236, and 4,605,492 (TiAPO), U.S. Pat.
Nos. 4,824,554, 4,744,970 (CoAPSO), U.S. Pat. No. 4,735,806
(GaAPSO) EP-A-0 293 937 (QAPSO, where Q is framework oxide unit
[QO2]), as well as U.S. Pat. Nos. 4,567,029, 4,686,093, 4,781,814,
4,793,984, 4,801,364, 4,853,197, 4,917,876, 4,952,384, 4,956,164,
4,956,165, 4,973,785, 5,241,093, 5,493,066, and 5,675,050, all of
which are herein fully incorporated by reference. Other molecular
sieves include those described in R. Szostak, Handbook of Molecular
Sieves, Van Nostrand Reinhold, New York, N.Y. (1992), which is
herein fully incorporated by reference. In some aspects, the
molecular sieve as modified by the Group 8-14 element and/or a
Group 1-2, Group 13-16, lanthanum, and/or phosphorous is a ZSM-5
based molecular sieve.
[0063] Various methods for synthesizing molecular sieves or
modifying molecular sieves are described in U.S. Pat. No. 5,879,655
(controlling the ratio of the templating agent to phosphorus), U.S.
Pat. No. 6,005,155 (use of a modifier without a salt), U.S. Pat.
No. 5,475,182 (acid extraction), U.S. Pat. No. 5,962,762 (treatment
with transition metal), U.S. Pat. Nos. 5,925,586 and 6,153,552
(phosphorus modified), U.S. Pat. No. 5,925,800 (monolith
supported), U.S. Pat. No. 5,932,512 (fluorine treated), U.S. Pat.
No. 6,046,373 (electromagnetic wave treated or modified), U.S. Pat.
No. 6,051,746 (polynuclear aromatic modifier), U.S. Pat. No.
6,225,254 (heating template), International Patent Application WO
01/36329 published May 25, 2001 (surfactant synthesis),
International Patent Application WO 01/25151 published Apr. 12,
2001 (staged acid addition), International Patent Application WO
01/60746 published Aug. 23, 2001 (silicon oil), U.S. Patent
Application Publication No. 2002-0055433 published May 9, 2002
(cooling molecular sieve), U.S. Pat. No. 6,448,197 (metal
impregnation including copper), U.S. Pat. No. 6,521,562 (conductive
microfilter), and U.S. Patent Application Publication No.
2002-0115897 published Aug. 22, 2002 (freeze drying the molecular
sieve), which are all herein incorporated by reference in their
entirety.
Example--Improved Aromatics Yield Using Easily Convertible
Oxygenates
[0064] Four different oxygenate feeds were used as feeds for an
oxygenate to aromatic conversion reaction. A first feed (diamond
symbols in FIG. 2) was a conventional methanol (100%) feed with an
effective hydrogen index of 2. A second feed (triangle symbols in
FIG. 2) was a mixture of about 70 vol % methanol and about 30 vol %
acetone with an effective hydrogen index of about 1.8. A third feed
(circle symbols in FIG. 2) was a mixture of about 30 vol % acetone,
about 55 vol % n-butanol, about 10 vol % ethanol, and about 5 vol %
water, which also had an effective hydrogen index of about 1.8.
This feed is believed to be representative of a type of
acetone/n-butanol/ethanol mixture that could be generated from a
suitable fermentation process. The fourth feed (square symbols in
FIG. 2) was a mixture of about 55 vol % acetone, about 30 vol %
n-butanol, about 10 vol % ethanol, and about 5 vol % water,
resulting in an effective hydrogen index of between about 1.5 and
1.6. In the feeds with effective hydrogen index of between 1.4 and
1.9, all of the feed components have a hydrogen index of greater
than 1.
[0065] The feeds were exposed to one of two types of aromatization
catalysts under effective conditions for conversion of oxygenates
to aromatics. The conditions included a temperature of about
450.degree. C., a weight hourly space velocity of about 2
hr.sup.-1, and a pressure of about 15 psig (about 100 kPag). At the
conversion conditions, between 90 wt. % and 100 wt. % of each feed
was converted. One aromatization catalyst used for performing the
conversion reaction was a phosphorous stabilized ZSM-5 catalyst.
The phosphorous content on the catalyst was about 1.2 wt. %
relative to the total weight of the catalyst. The other
aromatization catalyst was a ZSM-5 catalyst with 1 wt. % of Zn
deposited on the catalyst.
[0066] FIG. 2 shows aromatic selectivities for the products
generated from converting each of the four feeds in the presence of
the two types of aromatization catalysts. In the results shown in
FIG. 2, the Zn-ZSM-5 catalyst had generally higher aromatics
production, but the same trend of dependence of aromatic
selectivity on the feed was present for both catalysts. As shown in
FIG. 2, using a mixture of oxygenates with an effective hydrogen
index of less than 1.9 resulted in improved aromatics selectivity
(yield) relative to a conventional 100% methanol feed. Altering the
mixture of oxygenates at the same feed effective hydrogen index did
not appear to alter the aromatics selectivity. Additionally, it is
noted that further reducing the effective hydrogen index from about
1.8 to between about 1.5 and 1.6 resulted in still further
increases in aromatics yield. This demonstrates that improvements
in aromatics yield can be obtained from oxygenate mixtures that are
conventionally believed to correspond to only "easily convertible"
compounds.
Example--Improved Aromatics Yield with Pyrolysis Oil Co-Feed
[0067] A feed containing methanol and a feed including about 80 vol
% methanol and 20 vol % pyrolysis oil were exposed to a fixed bed
of an aromatization catalyst (ZSM-5) under effective conditions for
conversion of oxygenates to aromatics. The weight hourly space
velocity was about 6 hr.sup.-1 and the pressure was about 1 atm
(100 kPag). The conversion was performed at both 400.degree. C. and
500.degree. C. The conversion conditions were effective for
substantially complete conversion of oxygenate compounds in the
feeds.
[0068] At 400.degree. C., conversion of the methanol feed resulted
in a hydrocarbon product where 17.2 wt. % of the products were
C.sub.6-C.sub.9 aromatics. Using the feed with 80 vol % methanol
and 20 vol % pyrolysis oil, performing a conversion at 400.degree.
C. resulted in a hydrocarbon product where 26.4 wt. % of the
products were C.sub.6-C.sub.9 aromatics. Similar results were
observed at a conversion temperature of 500.degree. C. Conversion
of the methanol feed at 500.degree. C. resulted in a hydrocarbon
product with 19.4 wt. % C.sub.6-C.sub.9 aromatics, while conversion
of the methanol/pyrolysis oil feed resulted in 26 wt. %
C.sub.6-C.sub.9 aromatics. It is noted that attempting to process
just the pyrolysis oil feed under the conversion conditions
resulting in plugging of the catalyst bed.
[0069] In addition to improving the yield of aromatics, the
co-processing of the methanol and pyrolysis feed also resulted in
conversion of substantially all of the oxygenates in the pyrolysis
oil into hydrocarbons. After separation of any desirable portions
of the conversion effluent, such as a desired aromatics and/or
naphtha fraction, another valuable portion of the effluent can be
an upgraded pyrolysis oil that is more suitable for further
processing in conventional refinery processes.
[0070] This example demonstrates the benefits of co-processing a
pyrolysis oil feed with a high EHI oxygenate feed for aromatics
production (such as gasoline production). By staging the addition
of pyrolysis oil to a reaction system as described herein, the
benefits of co-processing of pyrolysis oil can be achieved while
reducing or minimizing the amount of coke production and/or fouling
in the reaction system.
[0071] Although the present invention has been described in terms
of specific embodiments, it is not so limited. Suitable
alterations/modifications for operation under specific conditions
should be apparent to those skilled in the art. It is therefore
intended that the following claims be interpreted as covering all
such alterations/modifications as fall within the true spirit/scope
of the invention. Ranges disclosed herein include combinations of
any of the enumerated values.
* * * * *