U.S. patent application number 15/808035 was filed with the patent office on 2018-06-07 for combined olefin and oxygenate conversion for aromatics production.
The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to Stephen J. McCarthy, Brandon J. O'Neill.
Application Number | 20180155631 15/808035 |
Document ID | / |
Family ID | 60629798 |
Filed Date | 2018-06-07 |
United States Patent
Application |
20180155631 |
Kind Code |
A1 |
O'Neill; Brandon J. ; et
al. |
June 7, 2018 |
COMBINED OLEFIN AND OXYGENATE CONVERSION FOR AROMATICS
PRODUCTION
Abstract
Systems and methods are provided for inclusion of olefins in the
reaction environment for an oxygenate conversion process. For
conversion processes involving a metal-promoted zeolitic catalyst,
addition of olefins to an oxygenate feed can reduce or minimize
loss of aromatic selectivity as the catalyst is exposed to the
feed. Additionally or alternately, for conversion processes
involving a zeolitic catalyst including a zeolite other than an MFI
framework type zeolite, addition of olefins to an oxygenate feed
can reduce or minimize loss of activity for oxygenate conversion as
the catalyst is exposed to the feed.
Inventors: |
O'Neill; Brandon J.;
(Lebanon, NJ) ; McCarthy; Stephen J.; (Center
Valley, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Family ID: |
60629798 |
Appl. No.: |
15/808035 |
Filed: |
November 9, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62431020 |
Dec 7, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 2300/202 20130101;
Y02P 30/20 20151101; C10G 2300/1088 20130101; C10G 3/49 20130101;
C10G 3/45 20130101; C10L 1/04 20130101; C10G 3/47 20130101; C10G
2400/02 20130101; C10G 3/44 20130101 |
International
Class: |
C10G 3/00 20060101
C10G003/00 |
Claims
1. A method for forming a naphtha composition, comprising: exposing
a feed comprising oxygenates and olefins to a conversion catalyst
at an average reaction temperature of about 300.degree. C. to about
550.degree. C., a total pressure of about 10 psig (.about.70 kPag)
to about 400 psig (.about.2700 kPag), and a WHSV of 0.1 hr.sup.-1
to 20.0 hr.sup.-1 to form a converted effluent comprising a naphtha
boiling range fraction having an octane rating of at least 80, the
converted effluent further comprising less than 6.0 wt % combined
of CO, CO.sub.2, and CH.sub.4 relative to a total weight of
hydrocarbons in the converted effluent, the feed having a molar
ratio of oxygenates to olefins of about 1 to about 20, wherein the
conversion catalyst comprises at least 10 wt % of a zeolite having
MFI framework structure, the zeolite having a silicon to aluminum
ratio of 10 to 200 and an Alpha value of at least 5, the conversion
catalyst further comprising 0.1 wt % to 3.0 wt % of a transition
metal supported on the conversion catalyst.
2. The method of claim 1, wherein the naphtha boiling range
fraction comprises an octane rating of at least 90 and at least
about 40 wt % aromatics relative to a weight of the naphtha boiling
range fraction.
3. The method of claim 1, wherein the average reaction temperature
is at least about 400.degree. C.
4. The method of claim 1, wherein the 0.1 wt % to 3.0 wt % of
transition metal comprises 0.1 wt % to 3.0 wt % of Zn.
5. The method of claim 1, wherein the conversion catalyst further
comprises phosphorus supported on the conversion catalyst.
6. The method of claim 1, wherein the conversion catalyst comprises
0.5 wt % to 1.5 wt % Zn supported on the conversion catalyst.
7. The method of claim 6, wherein the conversion catalyst further
comprises phosphorus, a molar ratio of phosphorus to zinc on the
conversion catalyst being 1.5 to 3.0.
8. The method of claim 1, wherein the feed comprises a molar ratio
of oxygenates to olefins of 10 or less.
9. The method of claim 1, wherein the feed comprising oxygenates
and olefins comprises a first feedstock comprising at least a
portion of the oxygenates and a second feedstock comprising at
least a portion of the olefins, the first feedstock and the second
feedstock being combined after entering a reactor containing the
conversion catalyst.
10. The method of claim 1, wherein the feed comprises about 30 wt %
to about 95 wt % of oxygenates, about 5 wt % to about 40 wt % of
olefins, or a combination thereof.
11. The method of claim 1, wherein the feed comprises at least
about 20 wt % to about 60 wt % of components different from
oxygenates and olefins.
12. The method of claim 1, wherein the oxygenates comprises
methanol, the conversion catalyst comprising an average catalyst
exposure time of 1 grams to 2000 grams of oxygenate per gram of
catalyst.
13. A method for forming a naphtha composition, comprising:
exposing a feed comprising oxygenates and olefins to a conversion
catalyst at an average reaction temperature of about 300.degree. C.
to about 550.degree. C., a total pressure of about 10 psig
(.about.70 kPag) to about 400 psig (.about.2700 kPag), and a WHSV
of 0.1 hr.sup.-1 to 20.0 hr.sup.-1 to form a converted effluent
comprising a naphtha boiling range fraction and further comprising
at least about 30 wt % olefins and less than 15 wt % oxygenate
relative to a total weight of hydrocarbons in the converted
effluent, the feed having a molar ratio of oxygenates to olefins of
1 to 20, wherein the conversion catalyst comprises at least 10 wt %
of a 10-member ring or 12-member zeolite having a framework
structure different from MFI framework structure, the zeolite
having a silicon to aluminum ratio of 10 to 200 and an Alpha value
of at least 5, the conversion catalyst further comprising an
average catalyst exposure time of 25 grams to 200 grams of
oxygenate per gram of catalyst.
14. The method of claim 13, wherein the oxygenate comprises
methanol, and wherein the conversion catalyst comprises an average
catalyst exposure time of 50 grams to 180 grams of methanol per
gram of catalyst.
15. The method of claim 13, wherein the conversion catalyst
comprises at least 10 wt % of a zeolite having a framework
structure of MRE (ZSM-48), MTW, TON, MTT, MFS, or a combination
thereof.
16. The method of claim 13, wherein the conversion catalyst further
comprises 0.1 wt % to 3.0 wt % of Zn supported on the conversion
catalyst.
17. The method of claim 13, wherein the conversion catalyst further
comprises phosphorus supported on the conversion catalyst.
18. The method of claim 13, wherein exposing the feed comprising
oxygenates to a conversion catalyst comprises exposing the feed
comprising oxygenate to the conversion catalyst in a fluidized bed,
a moving bed, a riser reactor, or a combination thereof, the
conversion catalyst being withdrawn and regenerated at a rate
corresponding to regeneration of 0.3 wt % to 3.0 wt % of catalyst
per 1 g of oxygenate exposed to a g of conversion catalyst.
19. An oxygenate conversion effluent comprising, relative to a
total weight of hydrocarbons in the conversion effluent, at least
40 wt % aromatics, less than 6.0 wt % combined of CO, CO.sub.2, and
CH.sub.4, and less than 10 wt % olefins, a naphtha boiling range
portion of the conversion effluent having an octane rating of at
least 90, wherein less than 10 wt % of the aromatics comprise
C.sub.10 aromatics relative to a total weight of the aromatics, and
wherein less than 10 wt % of the C.sub.10 aromatics comprise durene
relative to a total weight of the C.sub.10 aromatics.
20. The oxygenate conversion effluent of claim 16, wherein the
oxygenate conversion effluent comprises less than 5.0 wt % combined
of CO, CO.sub.2, and CH.sub.4, or wherein less than 5 wt % of the
C.sub.10 aromatics comprise durene relative to a total weight of
the C.sub.10 aromatics, or a combination thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/431,020, filed on Dec. 7, 2016, the entire
contents of which are incorporated herein by reference.
FIELD
[0002] This invention relates to integrated processes for forming
naphtha boiling range products, including aromatics, by conversion
of oxygenates and olefins.
BACKGROUND
[0003] A variety of industrial processes are known for conversion
of low boiling carbon-containing compounds to higher value
products. For example, methanol to gasoline (MTG) is a commercial
process that produces gasoline from methanol using ZSM-5 catalysts.
In the MTG process, methanol is first dehydrated to dimethyl ether.
The methanol and/or dimethyl ether then react in a series of
reactions that result in formation of aromatic, paraffinic, and
olefinic compounds. The resulting product consists of liquefied
petroleum gas (LPG) and a high-quality gasoline comprised of
aromatics, paraffins, and olefins. The typical MTG hydrocarbon
product consists of about 40-50% aromatics plus olefins and about
50-60% paraffins.
[0004] U.S. Pat. No. 3,894,104 describes a method for converting
oxygenates to aromatics using zeolite catalysts impregnated with a
transition metal. Yields of aromatics relative to the total
hydrocarbon product are reported to be as high as about 58% with a
corresponding total C.sub.5+ yield as high as about 73%.
[0005] U.S. Patent Application Publication 2013/0281753 describes a
phosphorous modified zeolite catalyst. The phosphorous modification
reduces the change in alpha value for the catalyst after the
catalyst is exposed to an environment containing steam. The
phosphorous modified catalysts are described as being suitable, for
example, for conversion of methanol to gasoline boiling range
compounds.
[0006] U.S. Patent Application Publications 2015/0174561,
2015/0174562, and 2015/0174563 describe catalysts for conversion of
oxygenates to aromatics. The catalysts include a zeolite, such as
an WI or MEL framework structure zeolite, with a supported Group 12
metal on the catalyst.
[0007] U.S. Pat. No. 9,090,525 describes conversion of oxygenates
in the presence of a zeolitic catalyst to form naphtha boiling
range compounds with increased octane. A portion of the naphtha
boiling range olefins from an initial conversion product are
recycled to the oxygenate conversion process to allow for formation
of heavier naphtha boiling range compounds, including
aromatics.
SUMMARY
[0008] In some aspects, a method for forming a naphtha composition
is provided. The method can include exposing a feed comprising
oxygenates (such as methanol) and olefins to a conversion catalyst.
Examples of effective conversion conditions can include an average
reaction temperature of about 300.degree. C. to about 550.degree.
C., a total pressure of about 10 psig (.about.70 kPag) to about 400
psig (.about.2700 kPag), and/or a WHSV of 0.1 hr.sup.-1 to 20.0
hr.sup.-1. Exposing the feed to the conversion catalyst can result
in formation of a converted effluent comprising a naphtha boiling
range fraction. The naphtha boiling range fraction can have an
octane rating of at least 80 and/or can comprise less than 6.0 wt %
combined of CO, CO.sub.2, and CH.sub.4 relative to a total weight
of hydrocarbons in the converted effluent. The feed can have a
molar ratio of oxygenates to olefins of about 1 to about 20. The
conversion catalyst can comprise at least 10 wt % of a zeolite
having MFI framework structure, the zeolite optionally having a
silicon to aluminum ratio of 10 to 200 and an Alpha value of at
least 5. The conversion catalyst can further comprise 0.1 wt % to
3.0 wt % of a transition metal supported on the conversion
catalyst, such as zinc supported on the conversion catalyst.
[0009] Optionally, the naphtha boiling range fraction can have an
octane rating of at least 90 (or at least 93, or at least 97)
and/or at least about 40 wt % aromatics relative to a weight of the
naphtha boiling range fraction. Optionally, the average reaction
temperature can be at least about 400.degree. C., or at least about
450.degree. C.
[0010] In some aspects, a method for forming a naphtha composition
is provided. The method can include exposing a feed comprising
oxygenates (such as methanol) and olefins to a conversion catalyst.
Examples of effective conversion conditions can include an average
reaction temperature of about 300.degree. C. to about 550.degree.
C., a total pressure of about 10 psig (.about.70 kPag) to about 400
psig (.about.2700 kPag), and/or a WHSV of 0.1 hr.sup.-1 to 20.0
hr.sup.-1. Exposing the feed to the conversion catalyst can result
in formation of a converted effluent comprising a naphtha boiling
range fraction and optionally further comprising at least about 30
wt % olefins and/or less than 15 wt % oxygenate relative to a total
weight of hydrocarbons in the converted effluent. The feed can have
a molar ratio of oxygenates to olefins of 1 to 20. The conversion
catalyst can comprise at least 10 wt % of a 10-member ring or
12-member ring zeolite having a framework structure different from
MFI framework structure. The zeolite can optionally have a silicon
to aluminum ratio of 10 to 200 and/or an Alpha value of at least 5.
The conversion catalyst can optionally further comprise an average
catalyst exposure time of 25 grams to 200 grams of oxygenate per
gram of catalyst. The conversion catalyst can optionally further
comprise 0.1 wt % to 3.0 wt % of a transition metal supported on
the conversion catalyst, such as Zn.
[0011] Optionally, the conversion catalyst can comprise an average
catalyst exposure time of 50 grams to 200 grams of methanol per
gram of catalyst, (or 25 grams to 180 grams, or 50 grams to 180
grams, or 50 grams to 150 grams, or 100 grams to 200 grams).
Optionally, the conversion catalyst can comprise at least 10 wt %
of a zeolite having a framework structure of MRE (ZSM-48), MTW,
TON, MTT, MFS, or a combination thereof.
[0012] In an optional aspect, exposing the feed comprising
oxygenates to a conversion catalyst comprises exposing the feed
comprising oxygenate to the conversion catalyst in a fluidized bed,
a moving bed, a riser reactor, or a combination thereof, the
conversion catalyst being withdrawn and regenerated at a rate
corresponding to regeneration of 0.3 wt % to 3.0 wt % of catalyst
per 1 g of oxygenate exposed to a g of conversion catalyst
(optionally 1.5 wt % to 3.0 wt %).
[0013] In some aspects, a conversion catalyst can further comprise
phosphorus supported on the conversion catalyst, a molar ratio of
phosphorus to zinc on the conversion catalyst optionally being 1.5
to 3.0. Additionally or alternately, the feed comprising oxygenates
and olefins comprises a first feedstock comprising at least a
portion of the oxygenates and a second feedstock comprising at
least a portion of the olefins, the first feedstock and the second
feedstock being combined after entering a reactor containing the
conversion catalyst.
[0014] In some optional aspects, a) the feed can comprise about 30
wt % to about 95 wt % of oxygenates, about 5 wt % to about 40 wt %
of olefins, or a combination thereof; b) the feed can comprise at
least about 20 wt % to about 60 wt % of components different from
oxygenates and olefins, or about 40 wt % to 60 wt %; or c) a
combination of a) and b).
[0015] In still another aspect, an oxygenate conversion effluent is
provided. The oxygenate conversion effluent can include, relative
to a total weight of hydrocarbons in the conversion effluent, at
least 40 wt % aromatics, less than 6.0 wt % combined of CO,
CO.sub.2, and CH.sub.4, and less than 10 wt % olefins. A naphtha
boiling range portion of the conversion effluent can have an octane
rating of at least 90. Optionally, less than 10 wt % of the
aromatics comprise C.sub.10 aromatics relative to a total weight of
the aromatics, and/or less than 10 wt % of the C.sub.10 aromatics
comprise durene relative to a total weight of the C.sub.10
aromatics. Optionally, the oxygenate conversion effluent can
comprise less than 5.0 wt % combined of CO, CO.sub.2, and CH.sub.4.
Optionally, less than 5 wt % of the C.sub.10 aromatics comprise
durene relative to a total weight of the C.sub.10 aromatics, or a
combination thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 schematically shows an example of a reaction system
for conversion of oxygenates to olefins.
[0017] FIG. 2 shows results from conversion of methanol in the
presence of a variety of zeolitic catalysts.
[0018] FIG. 3 shows relative yields from conversion of methanol and
methanol plus 1-pentene in the presence of a 1 wt % Zn-ZSM-5
catalyst.
[0019] FIG. 4 shows results from conversion of methanol at various
temperatures in the presence of a ZSM-5 catalyst.
[0020] FIG. 5 shows results from conversion of methanol and
1-pentene at various temperatures in the presence of a ZSM-5
catalyst.
[0021] FIG. 6 shows relative yields from conversion of methanol and
methanol plus 1-pentene in the presence of a ZSM-5 catalyst.
[0022] FIG. 7 shows another type of relative yield analysis from
conversion of methanol and methanol plus 1-pentene in the presence
of a ZSM-5 catalyst.
[0023] FIG. 8 shows relative aromatic yields from conversion of
methanol and methanol plus 1-pentene in the presence of a ZSM-5
catalyst.
[0024] FIG. 9 shows relative aromatic yields from conversion of
methanol and methanol plus 1-pentene in the presence of a 1 wt %
Zn-ZSM-5 catalyst.
[0025] FIG. 10 shows results from conversion of methanol in the
presence of a ZSM-48 catalyst.
[0026] FIG. 11 shows results from conversion of methanol plus
1-pentene in the presence of a ZSM-48 catalyst.
DETAILED DESCRIPTION
[0027] In various aspects, systems and methods are provided for
conversion of a combined feed of oxygenates (such as methanol or
dimethyl ether) and olefins to a high octane naphtha boiling range
product. For conversion processes involving a metal-promoted
zeolitic catalyst, addition of olefins to an oxygenate feed can
reduce or minimize loss of aromatic selectivity as the catalyst is
exposed to the feed. Additionally or alternately, for conversion
processes involving a zeolitic catalyst other than an MFI framework
type, addition of olefins to an oxygenate feed can reduce or
minimize loss of activity for oxygenate conversion as the catalyst
is exposed to the feed.
[0028] Natural gas, coal, and/or biomass are becoming increasingly
important sources of carbon for use in production of fuel and/or
lubricant products. A first step in conversion of carbon from a
natural gas, coal, and/or biomass source can be a conversion of
methane to methanol. Once methanol is formed, various fixed bed,
fluid bed, and moving bed processes can be used to convert methanol
to higher value products, such as fuels, aromatics, and/or olefins.
Such processes can use zeolitic catalysts, such as MFI framework
(ZSM-5) zeolitic catalysts.
[0029] Some difficulties with conversion of methanol to naphtha
boiling range products (such as aromatics) for use as gasoline can
be related to the tendency for the zeolitic catalyst to deactivate
relatively quickly. Even relatively small exposures of feed to a
zeolitic catalyst can result in loss of aromatic selectivity, with
a corresponding increase in formation of lower value paraffins. For
zeolitic frameworks other than MFI, the catalyst deactivation can
also impact the general ability of the catalyst to convert
oxygenates within a feed.
[0030] One option for increasing the aromatic selectivity of a
zeolitic catalyst can be to add a supported transition metal on the
catalyst to promote aromatic formation. Zinc is an example of a
suitable transition metal to improve aromatic selectivity. While
zinc can be effective for increasing the initial aromatic
selectivity of a zeolitic catalyst, such as MFI framework zeolitic
catalyst, exposure to an oxygenate feed can cause the catalyst to
lose aromatic selectivity due to conversion of oxygenates to carbon
oxides and paraffins.
[0031] It has been unexpectedly discovered that addition of olefins
to an oxygenate feed can reduce or minimize loss of catalyst
activity and/or selectivity during exposure to the oxygenate feed.
The olefins can correspond to any convenient type of
C.sub.2-C.sub.6 olefin. In some aspects, the olefins can correspond
to olefins generated during the oxygenate conversion process. In
such aspects, a portion of the effluent from the conversion process
can be recycled to provide olefins for the feed. In other aspects,
the olefins can be derived from any other convenient source. The
olefin feed can optionally include compounds that act as inerts or
act as a diluent in the conversion process. For example, a stream
of "waste" olefins having an olefin content of 5 vol % to 20 vol %
can be suitable as a source of olefins, so long as the other
components of the "waste" olefins stream are compatible with the
conversion process. For example, the other components of the olefin
stream can correspond to inert gases such as N.sub.2, carbon
oxides, paraffins, and/or other gases that have low reactivity
under the conversion conditions. Water can also be present,
although it can be preferable for water to correspond to 20 vol %
or less of the total feed, or 10 vol % or less.
[0032] In this discussion, octane rating is defined as (RON+MON)/2,
where RON is research octane number and MON is motor octane number.
For values reported in the examples below, RON and MON values were
determined based on a published model that determines octane
ratings for a blend of components based to determine a blended
octane. The model is described at Ind Eng Chem Res 2006, 45,
337-345. The model is believed to correlate with experimentally
determined values. In the claims below, Research Octane Number
(RON) is determined according to ASTM D2699. Motor Octane Number
(MON) is determined according to ASTM D2700.
[0033] In this discussion, the naphtha boiling range is defined as
50.degree. F. (.about.10.degree. C., roughly corresponding to the
lowest boiling point of a pentane isomer) to 350.degree. F.
(177.degree. C.). The distillate fuel boiling range, is defined as
350.degree. F. (177.degree. C.) to 700.degree. F. (371.degree. C.).
Compounds (C.sub.4-) with a boiling point below the naphtha boiling
range can be referred to as light ends. It is noted that due to
practical consideration during fractionation (or other boiling
point based separation) of hydrocarbon-like fractions, a fuel
fraction formed according to the methods described herein may have
T5 and T95 distillation points corresponding to the above values
(or T10 and T90 distillation points), as opposed to having
initial/final boiling points corresponding to the above values.
While various methods are available for determining boiling point
information for a given sample, for the claims below ASTM D86 is a
suitable method for determining distillation points (including
fractional weight distillation points) for a composition.
Feedstocks and Products--Oxygenate Conversion
[0034] In various aspects, catalysts described herein can be used
for conversion of oxygenate feeds to aromatics and/or olefins
products, such as oxygenates containing at least one
C.sub.1-C.sub.4 alkyl group and/or other oxygenates. Examples of
suitable oxygenates include feeds containing methanol, dimethyl
ether, C.sub.1-C.sub.4 alcohols, ethers with C.sub.1-C.sub.4 alkyl
chains, including both asymmetric ethers containing C.sub.1-C.sub.4
alkyl chains (such as methyl ethyl ether, propyl butyl ether, or
methyl propyl ether) and symmetric ethers (such as diethyl ether,
dipropyl ether, or dibutyl ether), or combinations thereof. It is
noted that oxygenates containing at least one C.sub.1-C.sub.4 alkyl
group are intended to explicitly identify oxygenates having alkyl
groups containing about 4 carbons or less. Preferably the oxygenate
feed can include at least about 30 wt % of one or more suitable
oxygenates, or at least about 50 wt %, or at least about 75 wt %,
or at least about 90 wt %, or at least about 95 wt %. Additionally
or alternately, the oxygenate feed can include at least about 50 wt
% methanol, such as at least about 75 wt % methanol, or at least
about 90 wt % methanol, or at least about 95 wt % methanol. In
particular, the oxygenate feed can include 30 wt % to 100 wt % of
oxygenate (or methanol), or 50 wt % to 95 wt %, or 75 wt % to 100
wt %, or 75 wt % to 95 wt %. The oxygenate feed can be derived from
any convenient source. For example, the oxygenate feed can be
formed by reforming of hydrocarbons in a natural gas feed to form
synthesis gas (H.sub.2, CO, CO.sub.2), and then using the synthesis
gas to form methanol (or other alcohols). As another example, a
suitable oxygenate feed can include methanol, dimethyl ether, or a
combination thereof as the oxygenate.
[0035] In addition to oxygenates, the feed can also include
olefins. In this discussion, the olefins included as part of the
feed can correspond to aliphatic olefins that contain 6 carbons or
less, so that the olefins are suitable for formation of naphtha
boiling range compounds. The olefin portion of the feed can be
mixed with the oxygenates prior to entering a reactor for
performing oxygenate conversion, or a plurality of streams
containing oxygenates and/or olefins can be mixed within a
conversion reactor. The feed can include about 5 wt % to about 40
wt % of olefins (i.e., olefins containing 6 carbons or less), or
about 5 wt % to about 30 wt %, or about 10 wt % to about 40 wt %,
or about 10 wt % to about 30 wt %. Without being bound by any
particular theory, it is believed that olefins can compete
effectively for active sites on a zeolitic catalyst that have high
activity for conversion of oxygenates to paraffins or carbon
oxides, such as conversion of methanol to methane. In order to
enable this competitive effect so that olefins suppress undesirable
activity, the molar ratio of oxygenates to olefins can be 20 or
less, or 10 or less, or 6.0 or less, or 4.0 or less, such as down
to a molar ratio of about 1.0. It is noted that the weight percent
of olefins in the feed can be dependent on the nature of the
olefins. For example, if a C.sub.5 olefin is used as the olefin
with a methanol-containing feed, the wt % of olefin required to
achieve a desired molar ratio of olefin to oxygenate will be
relatively high due to the much larger molecular weight of a
C.sub.5 alkene.
[0036] In addition to oxygenates and olefins, a feed can also
include diluents, such as water (in the form of steam), nitrogen or
other inert gases, and/or paraffins or other non-reactive
hydrocarbons. In some aspects, the source of olefins can correspond
to a low purity source of olefins, so that the source of olefins
corresponds to 20 wt % or less of olefins. In some aspects, the
portion of the feed corresponding to components different from
oxygenates and olefins can correspond to 1 wt % to 60 wt % of the
feed, or 1 wt % to 25 wt %, or about 10 wt % to about 30 wt %, or
about 20 wt % to about 60 wt %. Optionally, the feed can
substantially correspond to oxygenates and olefins, so that the
content of components different from oxygenates and olefins is 1 wt
% or less (such as down to 0 wt %).
[0037] In some aspects, such as aspects related to oxygenate
conversion using an MFI or MEL framework catalyst, the yield of
aromatics relative to the total hydrocarbon product can be about 35
wt % to about 60 wt %, or about 38 wt % to about 60 wt %, or about
40 wt % to about 52 wt %, or about 38 wt % to about 45 wt %. For
example, the yield of aromatics relative to the total hydrocarbon
product can be at least about 35 wt %, or at least about 38 wt %,
or at least about 40 wt %, or at least about 45 wt %. Additionally
or alternately, the yield of aromatics relative to the total
hydrocarbon product can be about 60 wt % or less, or about 55 wt %
or less, or about 52 wt % or less, or about 50 wt % or less. In
various aspects, the yield of olefins relative to the total
hydrocarbon product can be about 2.0 wt % to about 30 wt %, or
about 2.0 wt % to 25 wt %, or about 5.0 wt % to about 20 wt %, or
about 10 wt % to about 20 wt %. For example, the yield of olefins
relative to the total hydrocarbon product can be at least about 2.0
wt %, or at least about 5.0 wt %, or at least about 10 wt %.
Additionally or alternately, the yield of olefins relative to the
total hydrocarbon product can be about 30 wt % or less, or about 25
wt % or less, or about 20 wt % or less. In various aspects, the
yield of paraffins relative to the total hydrocarbon product can be
about 20 wt % to about 45 wt %, or about 20 wt % to about 35 wt %,
or about 25 wt % to about 45 wt %, or about 25 wt % to about 40 wt
%. For example, the yield of paraffins relative to the total
hydrocarbon product can be at least about 20 wt %, or at least
about 25 wt %, or at least about 30 wt % and/or the yield of
paraffins relative to the total hydrocarbon product can be about 45
wt % or less, or about 40 wt % or less, or about 35 wt % or less.
In the claims below, the relative amounts of paraffins, olefins,
and aromatics in a sample can be determined based on ASTM D6839.
For the paraffins and olefins generated during oxygenate
conversion, at least 50 wt % of the olefins can correspond to
C.sub.3 and C.sub.4 olefins and/or at least 50 wt % of the
paraffins can correspond to C.sub.3 and C.sub.4 paraffins.
Additionally or alternately, less than 10 wt % of the paraffins can
correspond to C.sub.1 paraffins (methane).
[0038] In some aspects, such as aspects related to oxygenate
conversion using an MRE framework catalyst, the yield of aromatics
relative to the total hydrocarbon product can be about 5 wt % to
about 30 wt %, or about 10 wt % to about 30 wt %, or about 10 wt %
to about 25 wt %, or about 5 wt % to about 20 wt %. For example,
the yield of aromatics relative to the total hydrocarbon product
can be at least about 5 wt %, or at least about 10 wt %, or at
least about 15 wt %. Additionally or alternately, the yield of
aromatics relative to the total hydrocarbon product can be about 30
wt % or less, or about 25 wt % or less, or about 20 wt % or less.
In various aspects, the yield of olefins relative to the total
hydrocarbon product can be about 20 wt % to about 60 wt %, or about
25 wt % to 60 wt %, or about 20 wt % to about 40 wt %, or about 25
wt % to about 50 wt %. For example, the yield of olefins relative
to the total hydrocarbon product can be at least about 20 wt %, or
at least about 25 wt %, or at least about 30 wt %. Additionally or
alternately, the yield of olefins relative to the total hydrocarbon
product can be about 60 wt % or less, or about 50 wt % or less, or
about 40 wt % or less. In various aspects, the yield of paraffins
relative to the total hydrocarbon product can be about 20 wt % to
about 50 wt %, or about 20 wt % to about 35 wt %, or about 25 wt %
to about 45 wt %, or about 25 wt % to about 40 wt %. For example,
the yield of paraffins relative to the total hydrocarbon product
can be at least about 20 wt %, or at least about 25 wt %, or at
least about 30 wt % and/or the yield of paraffins relative to the
total hydrocarbon product can be about 50 wt % or less, or about 45
wt % or less, or about 40 wt % or less, or about 35 wt % or less.
For the paraffins and olefins generated during oxygenate
conversion, at least 50 wt % of the olefins can correspond to
C.sub.3 and C.sub.4 olefins and/or at least 50 wt % of the
paraffins can correspond to C.sub.3 and C.sub.4 paraffins.
Additionally or alternately, less than 10 wt % of the paraffins can
correspond to C.sub.1 paraffins (methane).
[0039] The total hydrocarbon product in the conversion effluent can
include a naphtha boiling range portion, a distillate fuel boiling
range portion, and a light ends portion. Optionally but preferably,
the conversion effluent can include less than 1.0 wt % of compounds
boiling above the distillate fuel boiling range (371.degree. C+),
such as having a final boiling point of 371.degree. C. or less. In
various aspects, the selectivity for forming/yield of a naphtha
boiling range portion can be at least about 35 wt % and/or about 75
wt % or less. For example, the selectivity for forming/yield of a
naphtha boiling range portion can be about 35 wt % to 75 wt %, or
40 wt % to 65 wt %, or 40 wt % to 60 wt %, or 45 wt % to 70 wt
%.
[0040] The naphtha boiling range portion formed from a conversion
process can have an octane rating of at least 80, or at least 90,
or at least 95, or at least 97, or at least 100, or at least 102,
or at least 105, such as up to 110. In particular, in aspects
involving an MFI or MEL framework catalyst, the octane rating can
be 80 to 110, or 95 to 110, or 97 to 110, or 100 to 110.
Additionally or alternately, in aspects involving a MRE framework
catalyst, the octane rating can be 80 to 97 or 90 to 97. As defined
above, the octane rating is corresponds to (RON+MON)/2).
[0041] The conversion conditions can also result in generation of
CO and/or CO.sub.2. In some aspects, the amount of combined CO,
CO.sub.2, and CH.sub.4 can correspond to about 6.0 wt % or less of
the total hydrocarbon product in a conversion effluent, or about
5.0 wt % or less. In this discussion and the claims below, the
amounts of CO and CO.sub.2 in a conversion effluent are included
when determining the amount of the total hydrocarbon product (such
as the weight of the total hydrocarbon product).
[0042] Suitable and/or effective conditions for performing a
conversion reaction can include average reaction temperatures of
about 300.degree. C. to about 550.degree. C. (or about 350.degree.
C. to about 550.degree. C., or about 400.degree. C. to about
500.degree. C.), total pressures between about 10 psig (.about.70
kPag) to about 400 psig (.about.2700 kPag), or about 50 psig
(.about.350 kPag) to about 350 psig (.about.2400 kPag), or about
100 psig (.about.700 kPag) to about 300 psig (.about.2100 kPag),
and an oxygenate space velocity between about 0.1 h.sup.-11 to
about 10 h.sup.-1 based on weight of oxygenate relative to weight
of catalyst. For example, the average reaction temperature can be
at least about 300.degree. C., or at least about 350.degree. C., or
at least about 400.degree. C., or at least about 450.degree. C.
Additionally or alternately, the average reaction temperature can
be about 550.degree. C. or less, or about 500.degree. C. or less,
or about 450.degree. C. or less, or about 400.degree. C. or less.
In this discussion, average reaction temperature is defined as the
average of the temperature at the reactor inlet and the temperature
at the reactor outlet for the reactor where the conversion reaction
is performed. As another example, the total pressure can be at
least about 70 kPag, or at least about 350 kPag, or at least about
500 kPag, or at least about 700 kPag, or at least about 1000 kPag.
Additionally or alternately, the total pressure can be about 3000
kPag or less, or about 2700 kPag or less, or about 2400 kPag or
less, or about 2100 kPag or less.
[0043] Optionally, a portion of the conversion effluent can be
recycled for inclusion as part of the feed to the conversion
reactor. For example, at least a portion of the light ends from the
conversion effluent can be recycled as part of the feed. The
recycled portion of the light ends can correspond to any convenient
amount, such as 25 wt % to 75 wt % of the light ends. Recycling of
light ends can provide olefins, which can serve as an additional
reactant in the conversion reaction, as well as providing a
mechanism for temperature control.
[0044] Various types of reactors can provide a suitable
configuration for performing a conversion reaction. Suitable
reactors can include fixed bed reactors (such as trickle bed
reactors), moving bed reactors (such as riser reactors), and
fluidized bed reactors. It is noted that the activity and/or
selectivity of a catalyst for oxygenate conversion can vary as the
catalyst is exposed to increasing amounts of oxygenate feed. This
modification of the catalyst activity is believed to be due to the
formation of coke on the catalyst. When oxygenate conversion is
performed in a fixed bed reactor, calculating the average catalyst
exposure time can be straightforward, as the amount of oxygenate
introduced into the reactor can be compared with the amount of
conversion catalyst in the reactor. This can be used to calculate
an average catalyst exposure time as a ratio of the grams of
oxygenate (such as methanol) exposed to the catalyst divided by the
grams of catalyst.
[0045] The modification of the catalyst activity and/or selectivity
with increasing average catalyst exposure time can be reversed at
least in part by regenerating the catalyst. In some aspects, a full
regeneration can be performed on a catalyst, so that the average
amount of coke present on the regenerated catalyst is less than 0.1
wt %. In other aspects, a partial regeneration can be performed, so
that the average amount of coke present on the regenerated catalyst
after regeneration is greater than 0.1 wt %. The average amount of
coke present on a catalyst sample can be readily determined by
thermogravimetric analysis.
[0046] In aspects where a catalyst can be withdrawn from the
reactor for regeneration and recycle during operation of the
reactor, such as a moving bed reactor and/or fluidized bed reactor,
catalyst can be withdrawn and replaced with make-up (fresh) and/or
regenerated catalyst. It is noted that withdrawing catalyst from
the reactor for regeneration is distinct from removing catalyst
entirely from the reaction system and replacing the removed
catalyst with fresh make-up catalyst. In this discussion, when full
regeneration is performed on a catalyst (less than 0.1 wt % average
coke remaining on the regenerated catalyst), the average catalyst
exposure time for the regenerated catalyst is defined to be zero
for purposes of determining average catalyst exposure time for
catalyst within the reactor. In such aspects when full regeneration
is being performed, the average catalyst exposure time for catalyst
being exposed to oxygenate can be determined based on a) the flow
rate of oxygenate into the reactor relative to the amount of
catalyst in the reactor, and b) the average residence time of the
catalyst in the reactor. These values can allow for a determination
of the average grams of oxygenate per gram of catalyst in the
reactor (i.e., the average catalyst exposure time).
[0047] In a moving bed reactor, the residence time for catalyst can
correspond to the amount of time required for a catalyst particle
to travel the length of the bed to the exit, based on the average
velocity of the moving bed. As an example, the flow of methanol
into a moving bed reactor can correspond to a space velocity of 1.0
hr.sup.-1, which means 1 g of methanol per g of catalyst per hour.
In such an example, if the average residence time for catalyst in
the reactor is 48 hours (based on the average velocity of the
moving bed relative to the size of the bed), then the average
catalyst exposure time for catalyst in the moving bed would be 24 g
of methanol per g of catalyst. Similarly, in aspects involving a
fluidized bed, the catalyst residence time can be determined based
on the rate of removal of catalyst from the reactor for
regeneration. The catalyst residence time can correspond to the
amount of time required to remove an amount of catalyst that is
equivalent to the weight of the catalyst bed. Based on that
residence time, the average catalyst exposure time can be
calculated in a similar manner to the calculation for a moving
bed.
[0048] During a partial regeneration, a catalyst can be exposed to
an oxidizing environment for removal of coke from the catalyst, but
the net amount of coke remaining on the catalyst after partial
regeneration can be greater than 0.1 wt %. When a partial
regeneration is performed, the effective average catalyst exposure
time for the catalyst after regeneration will be a value other than
zero, due to the amount of remaining coke on the catalyst. When a
partial regeneration is performed, the amount of coke removal can
roughly scale in a linear manner with the effective average
catalyst exposure time of the partially regenerated catalyst. In
this discussion and the claims below, when a catalyst is partially
regenerated, the average catalyst exposure time for the partially
regenerated catalyst is determined by multiplying the average
catalyst exposure time prior to regeneration by the wt % of coke
remaining on the catalyst after partial regeneration. As an
example, a hypothetical catalyst may have an exposure time of 100 g
methanol per g catalyst prior to regeneration. In this example,
partial regeneration is used to remove 60 wt % of the coke on the
catalyst. This means that 40 wt % (or 0.4 expressed as a fraction)
of the coke remains on the catalyst after regeneration. In such an
example, the average catalyst exposure time for the regenerated
catalyst would be 0.4.times.100=40 g methanol per g catalyst.
[0049] In aspects where partial regeneration is performed, the
calculation for the average catalyst exposure time for catalyst in
the reactor can be modified based to account for the fact that any
recycled catalyst will have a non-zero initial value of catalyst
exposure time. The same calculation described above can be used to
determine an initial value. The non-zero catalyst exposure time for
the regenerated catalyst can then be added to the initial value to
determine the average catalyst exposure time within the reactor. In
the example noted above, if the average catalyst exposure time for
partially regenerated catalyst is 10 g methanol per g catalyst, and
if the amount of average exposure within the reactor is 24 g
methanol per g catalyst as calculated above, then the average
catalyst exposure time for the system when using partial
regeneration would be 34 g methanol per g catalyst. It is also
noted that a portion of the catalyst introduced into a reactor may
correspond to fresh make-up catalyst instead of partially
regenerated catalyst. In such aspects, the catalyst exposure time
for the catalyst introduced into the reactor can be a weighted
average of the fresh make-up catalyst (zero exposure time) and the
catalyst exposure time for the partially regenerated catalyst.
[0050] For a catalyst including an MFI framework zeolite, the
catalyst recycle rate can be dependent on the desired products,
with catalyst recycle rates that produce an average catalyst
exposure time/average cycle length for catalyst in the reactor of
about 1 g CH.sub.3OH/g catalyst to about 2000 g CH.sub.3OH/g
catalyst potentially being suitable, or about 50 g CH.sub.3OH/g
catalyst to about 1000 g CH.sub.3OH/g catalyst, or about 100 g
CH.sub.3OH/g catalyst to about 1500 g CH.sub.3OH/g catalyst, or
about 100 g CH.sub.3OH/g catalyst to about 1000 g CH.sub.3OH/g
catalyst. The target average catalyst exposure time can be
dependent on the specific nature of the catalyst and/or the desired
product mix. In some aspects where shorter average catalyst
exposure times are desired, the average catalyst exposure time can
be about 1 g CH.sub.3OH/g catalyst to about 200 g CH.sub.3OH/g
catalyst, or about 5 g CH.sub.3OH/g catalyst to about 150 g
CH.sub.3OH/g catalyst, or about 1 g CH.sub.3OH/g catalyst to about
100 g CH.sub.3OH/g catalyst. In other aspects where longer times
are desired, the average catalyst exposure time can be about 200 g
CH.sub.3OH/g catalyst to about 2000 g CH.sub.3OH/g catalyst, or
about 400 g CH.sub.3OH/g catalyst to about 1500 g CH.sub.3OH/g
catalyst, or about 500 g CH.sub.3OH/g catalyst to about 1000 g
CH.sub.3OH/g catalyst. The above average catalyst exposure times
can be achieved, for example, by withdrawing about 0.01 wt % to
about 3.0 wt % of catalyst per 1 g of methanol exposed to a g of
conversion catalyst, or about 0.01 wt % to about 1.5 wt %, or about
0.1 wt % to about 3.0 wt %, or about 1.0 wt % to about 3.0 wt %. It
is noted that these withdrawal rates could be modified, for
example, if only a partial regeneration is performed on withdrawn
catalyst. For catalysts other than MFI framework catalysts, a
catalyst recycle rate can be selected to produce an average
catalyst exposure time/average cycle length for catalyst in the
reactor of about 25 g CH.sub.3OH/g catalyst to about 200 g
CH.sub.3OH/g catalyst, or about 25 g CH.sub.3OH/g catalyst to about
180 g CH.sub.3OH/g catalyst, or about 50 g CH.sub.3OH/g catalyst to
about 180 g CH.sub.3OH/g catalyst, or about 50 g CH.sub.3OH/g
catalyst to about 150 g CH.sub.3OH/g catalyst, or about 25 g
CH.sub.3OH/g catalyst to about 100 g CH.sub.3OH/g catalyst, or
about 50 g CH.sub.3OH/g catalyst to about 100 g CH.sub.3OH/g
catalyst, or about 100 g CH.sub.3OH/g catalyst to about 180 g
CH.sub.3OH/g catalyst, or about 100 g CH.sub.3OH/g catalyst to
about 150 g CH.sub.3OH/g catalyst. The appropriate cycle length for
a catalyst including a non-MFI framework zeolite can depend on the
type of zeolite.
[0051] It is noted that the oxygenate feed and/or conversion
reaction environment can include water in various proportions.
Conversion of oxygenates to aromatics and olefins results in
production of water as a product, so the relative amounts of
oxygenate (such as methanol or dimethyl ether) and water can vary
within the reaction environment. Based on the temperatures present
during methanol conversion, the water in the reaction environment
can result in "steaming" of a catalyst. Thus, a catalyst used for
conversion of oxygenates to aromatics is preferably a catalyst that
substantially retains activity when steamed. Water may also be
present in a feed prior to contacting the zeolite catalyst. For
example, in commercial processing of methanol to form gasoline, in
order to control heat release within a reactor, an initial catalyst
stage may be used to convert a portion of the methanol in a feed to
dimethyl ether and water prior to contacting a zeolite catalyst for
forming gasoline.
Catalysts for Oxygenate Conversion
[0052] In various aspects, a transition metal-enhanced zeolite
catalyst composition can be used for conversion of oxygenate feeds
to naphtha boiling range fractions and olefins. In this discussion
and the claims below, a zeolite is defined to refer to a
crystalline material having a porous framework structure built from
tetrahedra atoms connected by bridging oxygen atoms. Examples of
known zeolite frameworks are given in the "Atlas of Zeolite
Frameworks" published on behalf of the Structure Commission of the
International Zeolite Association", 6.sup.th revised edition, Ch.
Baerlocher, L. B. McCusker, D. H. Olson, eds., Elsevier, N.Y.
(2007) and the corresponding web site,
http://www.iza-structure.org/databases/. Under this definition, a
zeolite can refer to aluminosilicates having a zeolitic framework
type as well as crystalline structures containing oxides of
heteroatoms different from silicon and aluminum. Such heteroatoms
can include any heteroatom generally known to be suitable for
inclusion in a zeolitic framework, such as gallium, boron,
germanium, phosphorus, zinc, and/or other transition metals that
can substitute for silicon and/or aluminum in a zeolitic
framework.
[0053] A suitable zeolite can include a 10-member or 12-member ring
pore channel network, such as a 1-dimensional 10-member ring pore
channel or a 3-dimensional 10-member ring pore channel. Examples of
suitable zeolites having a 3-dimensional 10-member ring pore
channel network include zeolites having an MFI or MEL framework,
such as ZSM-5 or ZSM-11. ZSM-5 is described in detail in U.S. Pat.
Nos. 3,702,886 and Re. 29,948. ZSM-11 is described in detail in
U.S. Pat. No. 3,709,979. Preferably, the zeolite is ZSM-5. Examples
of suitable zeolites having a 1-dimensional 10-member ring pore
channel network include zeolites having a MRE (ZSM-48), MTW, TON,
MTT, and/or MFS framework. In some aspects, a zeolite with a
3-dimensional pore channel can be preferred for conversion of
methanol, such as a zeolite with an MFI framework.
[0054] Generally, a zeolite having desired activity for methanol
conversion can have a silicon to aluminum molar ratio of about 10
to about 200, or about 15 to about 100, or about 20 to about 80, or
about 20 to about 40. For example, the silicon to aluminum ratio
can be at least about 10, or at least about 20, or at least about
30, or at least about 40, or at least about 50, or at least about
60. Additionally or alternately, the silicon to aluminum ratio can
be about 300 or less, or about 200 or less, or about 100 or less,
or about 80 or less, or about 60 or less, or about 50 or less.
[0055] Typically, reducing the silicon to aluminum ratio in a
zeolite will result in a zeolite with a higher acidity, and
therefore higher activity for cracking of hydrocarbon or
hydrocarbonaceous feeds, such as petroleum feeds. However, with
respect to conversion of oxygenates to aromatics, such increased
cracking activity may not be beneficial, and instead may result in
increased formation of residual carbon or coke during the
conversion reaction. Such residual carbon can deposit on the
zeolite catalyst, leading to deactivation of the catalyst over
time. Having a silicon to aluminum ratio of at least about 40, such
as at least about 50 or at least about 60, can reduce or minimize
the amount of additional residual carbon that is formed due to the
acidic or cracking activity of a catalyst.
[0056] It is noted that the molar ratio described herein is a ratio
of silicon to aluminum. If a corresponding ratio of silica to
alumina were described, the corresponding ratio of silica
(SiO.sub.2) to alumina (Al.sub.2O.sub.3) would be twice as large,
due to the presence of two aluminum atoms in each alumina
stoichiometric unit. Thus, a silicon to aluminum ratio of 10
corresponds to a silica to alumina ratio of 20.
[0057] In some aspects, a zeolite in a catalyst can be present at
least partly in the hydrogen form. Depending on the conditions used
to synthesize the zeolite, this may correspond to converting the
zeolite from, for example, the sodium form. This can readily be
achieved, for example, by ion exchange to convert the zeolite to
the ammonium form followed by calcination in air or an inert
atmosphere at a temperature of about 400.degree. C. to about
700.degree. C. to convert the ammonium form to the active hydrogen
form.
[0058] Additionally or alternately, a zeolitic catalyst can include
and/or be enhanced by a transition metal. Preferably the transition
metal is a Group 12 metal from the IUPAC periodic table (sometimes
designated as Group IIB) selected from Zn, Cd, or a combination
thereof. More generally, the transition metal can be any convenient
transition metal selected from Groups 6-15 of the IUPAC periodic
table. The transition metal can be incorporated into the
zeolite/catalyst by any convenient method, such as by impregnation,
by ion exchange, by mulling prior to extrusion, and/or by any other
convenient method. Optionally, the transition metal incorporated
into a zeolite/catalyst can correspond to two or more metals. After
impregnation or ion exchange, the transition metal-enhanced
catalyst can be treated in air or an inert atmosphere at a
temperature of about 400.degree. C. to about 700.degree. C. The
amount of transition metal can be expressed as a weight percentage
of metal relative to the total weight of the catalyst (including
any zeolite and any binder). A catalyst can include about 0.05 wt %
to about 20 wt % of one or more transition metals, or about 0.1 wt
% to about 10 wt %, or about 0.1 wt % to about 5 wt %, or about 0.1
wt % to about 2.0 wt %. For example, the amount of transition metal
can be at least about 0.1 wt % of transition metal, or at least
about 0.25 wt % of transition metal, or at least about 0.5 wt %, or
at least about 0.75 wt %, or at least about 1.0 wt %. Additionally
or alternately, the amount of transition metal can be about 20 wt %
or less, or about 10 wt % or less, or about 5 wt % or less, or
about 2.0 wt % or less, or about 1.5 wt % or less, or about 1.2 wt
% or less, or about 1.1 wt % or less, or about 1.0 wt % or
less.
[0059] In some optional aspects, a zeolitic catalyst can be
substantially free of phosphorous. A catalyst composition that is
substantially free of phosphorous can contain about 0.01 wt % of
phosphorous or less, such as less than about 0.005 wt % of
phosphorous, or less than about 0.001 wt % of phosphorous. A
zeolitic catalyst that is substantially free of phosphorous can be
substantially free of intentionally added phosphorous or
substantially free of both intentionally added phosphorous as well
as phosphorous present as an impurity in a reagent for forming the
catalyst composition. In some aspects, a zeolitic catalyst can
contain no added phosphorous, such as containing no intentionally
added phosphorous and/or containing no phosphorous impurities to
within the detection limits of standard methods for characterizing
a reagent and/or a resulting zeolite.
[0060] Optionally, a zeolitic catalyst for methanol conversion can
include added phosphorus, such as phosphorus added by impregnation,
ion exchange, mulling prior to extrusion, or another convenient
method. The amount of phosphorus can be related to the amount of
transition metal in the catalyst composition. In some aspects, the
molar ratio of phosphorus to transition metal can be 0.5 to 5.0, or
1.5 to 3.0, or 1.0 to 2.5, or 1.5 to 2.5. At higher molar ratios of
phosphorus to transition metal, the phosphorus can be beneficial
for maintaining a relatively stable selectivity for aromatics
formation during an oxygenate conversion process. Additionally or
alternately, a catalyst can include about 0.05 wt % to about 10 wt
% of phosphorus, or about 0.1 wt % to about 10 wt %, or about 0.1
wt % to about 5 wt %, or about 0.1 wt % to about 2.0 wt %. For
example, the amount of phosphorus can be at least about 0.1 wt %,
or at least about 0.25 wt %, or at least about 0.5 wt %, or at
least about 0.75 wt %, or at least about 1.0 wt %. Additionally or
alternately, the amount of phosphorus can be about 10 wt % or less,
or about 5 wt % or less, or about 2.0 wt % or less, or about 1.5 wt
% or less, or about 1.2 wt % or less, or about 1.1 wt % or less, or
about 1.0 wt % or less.
[0061] A catalyst composition can employ a transition
metal-enhanced zeolite in its original crystalline form or after
formulation into catalyst particles, such as by extrusion. A
process for producing zeolite extrudates in the absence of a binder
is disclosed in, for example, U.S. Pat. No. 4,582,815, the entire
contents of which are incorporated herein by reference. Preferably,
the transition metal can be incorporated after formulation of the
zeolite (such as by extrusion) to form self-bound catalyst
particles. Optionally, a self-bound catalyst can be steamed after
extrusion. The terms "unbound" and "self-bound" are intended to be
synonymous and mean that the present catalyst composition is free
of any of the inorganic oxide binders, such as alumina or silica,
frequently combined with zeolite catalysts to enhance their
physical properties.
[0062] The transition metal-enhanced zeolite catalyst composition
employed herein can further be characterized based on activity for
hexane cracking, or Alpha value. Alpha value is a measure of the
acid activity of a zeolite catalyst as compared with a standard
silica-alumina catalyst. The alpha test is described in U.S. Pat.
No. 3,354,078; in the Journal of Catalysis, Vol. 4, p. 527 (1965);
Vol. 6, p. 278 (1966); and Vol. 61, p. 395 (1980), each
incorporated herein by reference as to that description. The
experimental conditions of the test used herein include a constant
temperature of about 538.degree. C. and a variable flow rate as
described in detail in the Journal of Catalysis, Vol. 61, p. 395.
Higher alpha values correspond with a more active cracking
catalyst. For an oxygenate conversion catalyst, Alpha values of at
least 15 can be suitable, with alpha values greater than 100 being
preferred. In particular, the Alpha value can be about 15 to about
1000, or about 50 to about 1000, or about 100 to about 1000.
[0063] As an alternative to forming self-bound catalysts, zeolite
crystals can be combined with a binder to form bound catalysts.
Suitable binders for zeolite-based catalysts can include various
inorganic oxides, such as silica, alumina, zirconia, titania,
silica-alumina, cerium oxide, magnesium oxide, yttrium oxide, or
combinations thereof. For catalysts including a binder, the
catalyst can comprise at least about 10 wt % zeolite, or at least
about 30 wt %, or at least about 50 wt %, such as up to about 90 wt
% or more. Generally, a binder can be present in an amount between
about 1 wt % and about 90 wt %, for example between about 5 wt %
and about 40 wt % of a catalyst composition. In some aspects, the
catalyst can include at least about 5 wt % binder, such as at least
about 10 wt %, or at least about 20 wt %. Additionally or
alternately, the catalyst can include about 90 wt % or less of
binder, such as about 50 wt % or less, or about 40 wt % or less, or
about 35 wt % or less. Combining the zeolite and the binder can
generally be achieved, for example, by mulling an aqueous mixture
of the zeolite and binder and then extruding the mixture into
catalyst pellets. A process for producing zeolite extrudates using
a silica binder is disclosed in, for example, U.S. Pat. No.
4,582,815. Optionally, a bound catalyst can be steamed after
extrusion.
[0064] In some aspects, a binder can be used that is substantially
free of alumina, such as a binder that is essentially free of
alumina. In this description, a binder that is substantially free
of alumina is defined as a binder than contains about 10 wt %
alumina or less, such as about 7 wt % or less, or about 5 wt % or
less, or about 3 wt % or less. A binder that is essentially free of
alumina is defined as a binder that contains about 1 wt % or less,
such as about 0.5 wt % or less, or about 0.1 wt % or less. In still
other aspects, a binder can be used that contains no intentionally
added alumina and/or that contains no alumina within conventional
detection limits for determining the composition of the binder
and/or the reagents for forming the binder. Although alumina is
commonly used as a binder for zeolite catalysts, due in part to
ease of formulation of alumina-bound catalysts, in some aspects the
presence of alumina in the binder can reduce or inhibit the
activity of a transition metal-enhanced zeolite for converting
methanol to aromatics. For example, for a catalyst where the
transition metal is incorporated into the catalyst after
formulation of the bound catalyst (such as by extrusion), the
transition metal may have an affinity for exposed alumina surfaces
relative to exposed zeolite surfaces, leading to increased initial
deposition and/or migration of transition metal to regions of the
bound catalyst with an alumina surface in favor of regions with a
zeolite surface. Additionally or alternately, alumina-bound
catalysts can tend to have low micropore surface area, meaning that
the amount of available zeolite surface available for receiving a
transition metal may be undesirably low.
[0065] As an example of forming a bound catalyst, the following
procedure describes a representative method for forming silica
bound ZSM-5 catalyst particles. ZSM-5 crystal and a silica binder,
such as an Ultrasil silica binder, can be added to a mixer and
mulled. Additional deionized water can be added during mulling to
achieve a desired solids content for extrusion. Optionally, a
caustic solution can also be added to the mixture and mulled. The
mixture can then be extruded into a desired shape, such as 1/10''
quadralobes. The extrudates can be dried overnight at about
250.degree. F. (121.degree. C.) and then calcined in nitrogen for
about 3 hours at about 1000.degree. F. (538.degree. C.). The
extrudates can then be exchanged twice with an about IN solution of
ammonium nitrate. The exchanged crystal can be dried overnight at
about 250.degree. F. (121.degree. C.) and then calcined in air for
about 3 hours at about 1000.degree. F. (538.degree. C.). This
results in a silica bound catalyst. Based on the exchange with
ammonium nitrate and subsequent calcinations in air, the ZSM-5
crystals in such a bound catalyst can correspond to ZSM-5 with
primarily hydrogen atoms at the ion exchange sites in the zeolite.
Thus, such a bound catalyst is sometimes described as being a bound
catalyst that includes H-ZSM-5.
[0066] To form a transition metal-enhanced catalyst, a bound
catalyst can be impregnated via incipient wetness with a solution
containing the desired metal for impregnation, such as Zn or P. The
impregnated crystal can then be dried overnight at about
250.degree. F. (121.degree. C.), followed by calcination in air for
about 3 hours at about 1000.degree. F. (538.degree. C.). More
generally, a transition metal can be incorporated into the zeolitic
catalyst at any convenient time, such as before or after ion
exchange to form H-form crystals, or before or after formation of a
bound extrudate. In some aspects that are preferred from a
standpoint of facilitating manufacture of a bound zeolite catalyst,
the transition metal can be incorporated into the bound catalyst
(such as by impregnation or ion exchange) after formation of the
bound catalyst by extrusion or another convenient method.
Example of Reaction System Configuration
[0067] FIG. 1 shows an example of a reaction system configuration
for performing oxygenate conversion to form a naphtha boiling range
product. It is noted that the reactors shown in FIG. 1 are depicted
as fixed bed, downflow reactors (such as trickle-bed reactors) for
convenience. It is understood that any or all of the reactors shown
in FIG. 1 can alternatively be moving bed reactors and/or fluidized
bed reactors. In FIG. 1, a feed 105 can correspond to an
oxygenate-containing feed. In a particular example, feed 105 can
correspond to 96 wt % methanol and 4 wt % water. A second feed 106
can correspond to an olefin-containing feed. Optionally, oxygenate
feed 105 can be introduced into a reactor as a plurality of input
flows, such as a first input flow containing a mixture of methanol
and water and a second input flow containing a mixture of nitrogen
and hydrogen. Optionally, oxygenate feed 105 and olefinic feed 106
can be combined prior to entering the reactor 110.
[0068] The feed 105 (or alternatively a combination of oxygenate
feed 105 and olefinic feed 106) can optionally be introduced into
an initial dehydration reactor 110. Initial dehydration reactor 110
can include an acidic catalyst, such as an acidic alumina catalyst,
that can facilitate an equilibrium reaction between methanol,
water, and dimethyl ether. This can result in production of an
effluent 115 that includes both methanol and dimethyl ether. Those
of skill in the art will recognize that dimethyl ether and methanol
can often be used in similar manners when performing an oxygenate
conversion reaction. The dehydration of methanol to form dimethyl
ether is highly exothermic. By performing an initial dehydration,
the amount of heat generated in the conversion reactor(s) can be
reduced, which can allow for improved temperature control in the
conversion reactor. Optionally, a portion of the oxygenate feed 105
can bypass the dehydration reactor and can be input directly into
conversion reactor 120. In aspects where other oxygenates are used
as a feed, such as C.sub.2+alcohols or larger ethers, dehydration
reactor can be omitted so that feed 105 (or a combination of
oxygenate feed 105 and olefinic feed 106) is an input flow for
conversion reactor 120.
[0069] The oxygenate feed 105 and olefinic feed 106 (and/or the
effluent 115 containing both dimethyl ether and methanol) are then
passed into conversion reactor 120. The input to conversion reactor
120 can be exposed to a conversion catalyst under effective
conditions for forming a conversion effluent 125. The conversion
effluent 125 can then be separated, such as by using a 3 phase
separator 130. One phase generated by separator 130 can be an
aqueous phase 133 that includes a substantial majority of the water
present within the conversion effluent 125. Another phase generated
by separator 130 can correspond to a hydrocarbon liquid product
137. The hydrocarbon liquid product can correspond to naphtha
boiling range compounds formed during the conversion reaction.
Optionally, the hydrocarbon liquid product can include a portion of
hydrocarbon-like compounds that include one or more heteroatoms,
such as oxygen, sulfur, nitrogen, and/or other heteroatoms that are
commonly found in petroleum or bio-derived feeds.
[0070] A third phase generated by separator 130 can correspond to a
hydrocarbon gas product 135. The hydrocarbon gas product 135 can
include C.sub.4-compounds corresponding to light paraffins and
light olefins. Optionally, a recycle portion 122 of hydrocarbon gas
product 135 can be recycled as part of the input flows to
conversion reactor 120. In some configurations where the amount of
recycle portion 122 is sufficiently large, a bleed or waste flow
(not shown) can also be present to reduce or minimize the build-up
of C.sub.4-paraffins in conversion reactor 120.
EXAMPLE 1
Methanol Conversion Using Zeolitic Catalysts
[0071] Various conversion catalysts were tested in an isothermal
fixed-bed reactor without recycle. In this example, the feed
corresponded to 100 wt % methanol. The feed was exposed to
conversion catalyst at a temperature of 450.degree. C., a pressure
of 15 psig, and a weight hourly space velocity of 2 hr.sup.-1.
[0072] The ZSM-5 conversion catalysts used in this example were
based on small crystal, self-bound MFI framework (ZSM-5) zeolite.
The ZSM-5 had a silicon to aluminum ratio of 20 to 40 and an Alpha
value of at least 100. For the catalyst with added Zn, after making
an H-form extrudate of the self-bound zeolite, Zn was added via
aqueous impregnation of Zn(NO.sub.3).sub.2.
[0073] FIG. 2 shows the aromatics yield from conversion of a
methanol feed versus the amount of feed processed for various types
of zeolitic catalysts. The catalysts include self-bound ZSM-48;
yttria bound ZSM-48 (65:35 zeolite to binder ratio); alumina bound
ITQ-13 (65:35 zeolite to binder ratio); self-bound ZSM-5; and
self-bound ZSM-5 with 0.5 wt % Zn supported on the catalyst. The
ZSM-5 catalysts were similar to the catalyst used in Example 1. As
shown in FIG. 2, for all of the zeolitic catalysts, the selectivity
for aromatics formation starts out at an initial level for each
catalyst and then steadily declines as greater amounts of feed are
processed. FIG. 2 also shows that addition of 0.5 wt % Zn to a
catalyst can increase the initial level of aromatics selectivity,
but the decline in aromatics selectivity with exposure to feed
remains similar.
EXAMPLE 2
Conversion of Methanol and Olefins with Zeolitic Catalyst Having
Supported Transition Metal
[0074] A self-bound ZSM-5 catalyst similar to the catalyst in
Example 1 was impregnated with zinc nitrate via incipient wetness
to form a 1 wt % Zn/ZSM-5 catalyst. As shown in FIG. 2, addition of
Zn to a zeolitic catalyst can improve the initial aromatic
selectivity of a catalyst. The 1 wt % Zn/ZSM-5 catalyst was exposed
to two types of feeds to determine the impact of addition of
olefins in the presence of a metal-enhanced zeolitic catalyst. A
first type of feed corresponded to 100 wt % methanol, similar to
Example 1. A second type of feed corresponded to about 70 wt %
methanol and about 30 wt % of 1-pentene. This corresponded to a
feed with a oxygenate to olefin molar ratio of about 5. In this
example, the feeds were exposed to the conversion catalyst in an
isothermal reactor at a temperature of 450.degree. C., a pressure
of 90 psig, and a weight hourly space velocity of 2 hr.sup.-1. The
data shown in FIG. 3 corresponds to data taken after 46 hours of
exposure of each feed to the catalyst, or at roughly 90 grams of
feed per gram of catalyst.
[0075] FIG. 3 shows the product distribution for the hydrocarbon
products generated from conversion of the methanol and the
methanol/1-pentene feeds. Substantially all of the methanol and/or
dimethyl ether in the feed was converted under these conditions.
Due to the presence of 1 wt % Zn on the zeolitic catalyst,
conversion of the methanol feed resulted in formation of at least
.about.15 wt % (relative to the total hydrocarbon product) of
carbon oxides (CO, CO.sub.2) and methane. By contrast, the feed
including both olefins and methanol had a carbon oxide plus methane
yield of less than 4 wt %. This substantial reduction in the amount
of methane and carbon oxides produced when using a combined feed of
methanol and olefins resulted in a corresponding increase in
aromatics production (i.e., aromatics selectivity). Although the
ratio of aromatics versus paraffins or the ratio for aromatics
versus olefins appeared to be unchanged when using the combined
oxygenate plus olefins feed, the ability to avoid formation of
methane and carbon oxides appeared to increase aromatics
selectivity by more than 5 wt % (relative to the total hydrocarbon
yield). Thus, it appears that using a combined feed of oxygenates
and olefins provides an unexpected shift upward in aromatic
selectivity for a conversion catalyst that includes a supported
metal, as compared with the aromatic selectivity for a feed
including only oxygenates.
EXAMPLE 3
Conversion of Methanol and Olefins with Zeolitic Catalyst (No
Metal)
[0076] The decline in selectivity to carbon oxides and methane with
exposure to feed was further investigated using the self-bound
ZSM-5 catalyst without an additional supported metal. A feed
corresponding to 100 wt % methanol was processed over self-bound
ZSM-5 catalyst in an isothermal reactor at a total pressure of 15
psig (.about.100 kPag) and a space velocity of 2 hr.sup.-1. The
temperature for the conversion was 325.degree. C., 350.degree. C.,
or 375.degree. C. FIG. 4 shows results from conversion of the
methanol feed over the conversion catalyst at the three
temperatures. In FIG. 4, the initial portion of the conversion
reaction was performed at 350.degree. C., followed by a reduction
to 325.degree. C., and then the temperature was increased to
375.degree. C.
[0077] FIG. 4 shows the relative yield of paraffins, aromatics,
olefins, and "other" in comparison with the total converted
hydrocarbon yield, as determined by gas chromatography. Similar to
FIG. 2, the selectivity of the ZSM-5 catalyst for aromatics starts
at an initial higher level and then declines with increasing feed
exposure. This trend is visible at 350.degree. C., and resumes when
the conversion temperature is returned to 375.degree. C.
Additionally, while the trend of decreasing aromatics selectivity
is visible at 325.degree. C., the selectivity for aromatics
formation is further shifted to lower values at this temperature.
This is believed to be due to a substantial portion of
(unconverted) methanol and/or dimethyl ether being present in the
total hydrocarbon product. In other words, for the
methanol/dimethyl ether that is converted at 325.degree. C., it is
believed that the selectivity remains the same, but the presence of
a substantial amount of unconverted methanol/dimethyl ether in the
total hydrocarbon product means that the yield of aromatics is
lower.
[0078] FIG. 5 shows results from performing a similar conversion
reaction using the ZSM-5 catalyst, but with a feed that included
about 70 wt % methanol and about 30 wt % 1-pentene (similar to the
oxygenate plus olefin feed used in Example 2). The combined
methanol/1-pentene feed was converted under the same conditions as
the methanol feed in FIG. 5, including using a sequence of
conversion temperatures of 350.degree. C., followed by 325.degree.
C., followed by 375.degree. C. As shown in FIG. 5, the addition of
1-pentene reduced or minimized the difference in aromatics
selectivity at 325.degree. C. However, the addition of 1-pentene
did not appear to impact the overall aromatics selectivity at
350.degree. C. or 375.degree. C. relative to the aromatics
selectivity for the methanol feed. Thus, for a zeolitic catalyst
without a supported metal, addition of olefins to the feed did not
appear to modify overall aromatics selectivity at temperatures that
were high enough to allow for full conversion of oxygenates in the
feed.
[0079] Without being bound by any particular theory, it is believed
that in addition to undergoing conversion, the olefins in the feed
can also assist with conversion of oxygenates in the feed. This is
demonstrated in FIG. 6, which shows the distribution of hydrocarbon
products (including "products" corresponding to unreacted
methanol/dimethyl ether) from the conversion runs in FIGS. 4 and 5.
In FIG. 6, the left bar for each product type corresponds to the
methanol feed, while the right bar corresponds to the methanol plus
olefin feed. As shown in FIG. 6, exposing the methanol feed to the
conversion catalyst at 325.degree. C. resulted in a substantial
amount of methanol/dimethyl ether that was not converted. By
contrast, only a minimal amount of methanol was unconverted for the
feed including both methanol and 1-pentene.
[0080] FIG. 7 shows additional details for product yields from the
conversion reactions corresponding to FIGS. 4 and 5 at each of the
studied temperatures (325.degree. C., 350.degree. C., and
375.degree. C.).
[0081] FIG. 7 includes data for both the methanol feed and the
mixed methanol plus 1-pentene feed. For each product type shown in
FIG. 7 (water, C5+, C3-C4, C1-C2), the left three bars correspond
to the methanol feed, while the right three bars correspond to the
methanol plus olefin feed. Each series of three bars corresponds to
325.degree. C., 350.degree. C., and 375.degree. C. from left to
right. For the yields in FIG. 7, any unreacted methanol/dimethyl
ether is not included as part of the yield calculation. As shown in
FIG. 7, addition of olefins to the methanol feed resulted in a
lower amount of C.sub.1 and/or C.sub.2 production (such as
production of methane). The amount of water generated was reduced,
but that is at least partially explained by the reduction in
oxygenates in the feed. Similarly, the apparent increase in olefins
for the feed including both methanol and olefins may be related to
the additional olefins that were present in the feed.
EXAMPLE 4
Reduction in Durene Formation
[0082] FIG. 8 shows additional details regarding the types of
aromatics that were produced during conversion of the methanol feed
and the methanol/1-pentene feed using the ZSM-5 catalyst (no
metal). The results in FIG. 8 were obtained at the reaction
conditions listed in conjunction with FIGS. 4 and 5. In FIG. 8,
"A6" corresponds to an aromatic compound that includes 6 carbon
atoms (i.e., benzene). In other words, "A6" refers to a C.sub.6
aromatic compound. The "A7", "A8", and "A9" columns are believed to
correspond to various alkyl-substituted benzenes. The "A10" and
"A11" columns can potentially include both alkyl substituted
benzenes, naphthalene, and substituted naphthalenes. For each
product type shown in FIG. 8, the left three bars correspond to the
methanol feed, while the right three bars correspond to the
methanol plus olefin feed. Each series of three bars corresponds to
325.degree. C., 350.degree. C., and 375.degree. C. from left to
right. As shown in FIG. 8, addition of olefins to the methanol feed
resulted in a substantial reduction in the amount of durene
produced at all temperatures (325.degree. C., 350.degree. C.,
375.degree. C.). Durene corresponds to 1, 2, 4, 5
tetramethylbenzene, and therefore represents a substantial portion
of the aromatics present in the "A10" aromatics column. Durene is a
compound that can crystallize at relatively low temperatures, and
that can potentially affect gasoline performance and appearance.
The ability to suppress durene formation while maintaining a
similar overall selectivity for aromatics formation is another
unexpected advantage of using a combined feed of oxygenates and
olefins as the conversion feed.
[0083] FIG. 9 shows that a similar reduction in durene formation
was achieved when performing conversion of the methanol/1-pentene
feed using a 1 wt % Zn/ZSM-5 catalyst. The results in FIG. 9 were
generated by conversion of a methanol feed or a methanol/1-pentene
feed in an isothermal reactor at a temperature of 450.degree. C., a
pressure of 90 psig, and a WHSV of 2 hr.sup.-1. In FIG. 9, the left
bar for each product type corresponds to the methanol plus olefin
feed, while the right bar corresponds to the methanol feed. It is
noted that the increased temperature used for the results in FIG. 9
also contributed to reducing the amount of durene production.
However, the benefit of using a combined oxygenate/olefin feed for
reducing durene production is still evident in FIG. 9. Based on
FIG. 9, addition of olefins when performing oxygenate conversion
can allow for formation of a conversion effluent that includes less
than 10 wt % C.sub.10 aromatics relative to the total weight of
hydrocarbons in the conversion effluent. Additionally or
alternately, less than 10 wt % of the C.sub.10 aromatics (or less
than 5 wt %) can correspond to durene.
EXAMPLE 5
Conversion Using Non-MFI Zeolitic Catalysts
[0084] The results in Example 1 show the relatively short
processing lifetimes for non-MFI zeolitic catalysts for conversion
of oxygenates to olefins and/or aromatics. In particular, as the
amount of oxygenate exposed to the catalyst increases, such as to
more than about 100 g oxygenate per gram of catalyst, the
selectivity of non-MFI catalysts for oxygenate conversion rapidly
falls off. It has been unexpectedly discovered that using a
combined oxygenate and olefin feed can reduce or minimize this fall
off in conversion activity for non-MFI zeolitic catalysts.
[0085] FIG. 10 shows results from conversion of a methanol feed
(similar to the feed in Example 1) for a ZSM-48 catalyst. The
ZSM-48 catalyst did not include an additional metal supported on
the catalyst. The conversion reaction was performed in an
isothermal reactor at 350.degree. C., 15 psig (.about.100 kPag),
and a WHSV of about 2 hr.sup.-1. A similar conversion reaction
using the ZSM-48 catalyst was also performed using the combined
methanol/1-pentene feed described above. The results from
conversion of the combined methanol/1-pentene feed are shown in
FIG. 11.
[0086] FIG. 10 appears to show that a substantial portion of the
loss in selectivity for olefins formation when using a methanol
feed is due to a loss in ability to convert the methanol feed. For
example, the amount of unconverted methanol corresponds to about 20
wt % of the feed at an exposure of only 100 grams of methanol per
gram of catalyst. By contrast, when an olefin is also present in
the feed, FIG. 11 shows that at least 90 wt % conversion of the
feed is maintained until at least an exposure of 150 grams of feed
per gram of catalyst. Based on extrapolation, it further appears
that roughly 90 wt % conversion of feed could be maintained until
at least an exposure of 200 grams of feed per gram of catalyst.
Surprisingly, the aromatics selectivity in FIGS. 10 and 11 appears
to be similar, even as FIG. 10 shows substantially lower amounts of
overall feed conversion. Thus, for non-MFI zeolitic catalysts,
inclusion of olefins in an oxygenate feed appears to provide a
benefit by allowing for increased feed conversion to olefins, while
maintaining a somewhat similar selectivity for aromatics formation.
Based on the data in FIG. 11, addition of olefins can allow for
operation of a conversion reactor at an average catalyst exposure
to feed of between about 50 grams of feed per gram of catalyst to
about 200 grams of feed per gram of catalyst, (or about 50 grams to
about 150 grams, or about 75 grams to about 200 grams, or about 75
grams to about 175 grams, or about 75 grams to about 150 grams, or
about 100 grams to about 200 grams), while still maintaining at
least 85 wt % conversion of oxygenate in the feed, or at least 90
wt %. In other words, the oxygenate in the conversion effluent can
be 15 wt % or less of the total hydrocarbon product, or 10 wt % or
less.
Additional Embodiments
[0087] Embodiment 1. A method for forming a naphtha composition,
comprising: exposing a feed comprising oxygenates and olefins to a
conversion catalyst at an average reaction temperature of about
300.degree. C. to about 550.degree. C., a total pressure of about
10 psig (.about.70 kPag) to about 400 psig (.about.2700 kPag), and
a WHSV of 0.1 hr.sup.-1 to 20.0 hr.sup.-1 to form a converted
effluent comprising a naphtha boiling range fraction having an
octane rating of at least 80, the converted effluent further
comprising less than 6.0 wt % combined of CO, CO.sub.2, and
CH.sub.4 relative to a total weight of hydrocarbons in the
converted effluent, the feed having a molar ratio of oxygenates to
olefins of about 1 to about 20, wherein the conversion catalyst
comprises at least 10 wt % of a zeolite having MFI framework
structure, the zeolite having a silicon to aluminum ratio of 10 to
200 (or 20 to 40) and an Alpha value of at least 5 (or at least
15), the conversion catalyst further comprising 0.1 wt % to 3.0 wt
% of a transition metal supported on the conversion catalyst.
[0088] Embodiment 2. The method of Embodiment 1, wherein the
naphtha boiling range fraction comprises an octane rating of at
least 90 (or at least 93, or at least 97) and at least about 40 wt
% aromatics relative to a weight of the naphtha boiling range
fraction.
[0089] Embodiment 3. The method of any of the above embodiments,
wherein the average reaction temperature is at least about
400.degree. C., or at least about 450.degree. C.
[0090] Embodiment 4. The method of any of the above embodiments,
wherein the oxygenates comprises methanol, the conversion catalyst
comprising an average catalyst exposure time of 1 gram to 2000
grams of oxygenate per gram of catalyst, or 1 gram to 200 grams, or
400 grams to 1500 grams.
[0091] Embodiment 5. A method for forming a naphtha composition,
comprising: exposing a feed comprising oxygenates and olefins to a
conversion catalyst at an average reaction temperature of about
300.degree. C. to about 550.degree. C., a total pressure of about
10 psig (.about.70 kPag) to about 400 psig (.about.2700 kPag), and
a WHSV of 0.1 hr.sup.-1 to 20.0 hr.sup.-1 to form a converted
effluent comprising a naphtha boiling range fraction and further
comprising at least about 30 wt % olefins and less than 15 wt %
oxygenate relative to a total weight of hydrocarbons in the
converted effluent, the feed having a molar ratio of oxygenates to
olefins of 1 to 20, wherein the conversion catalyst comprises at
least 10 wt % of a 10-member ring or 12-member zeolite having a
framework structure different from WI (optionally different from WI
or MEL) framework structure, the zeolite having a silicon to
aluminum ratio of 10 to 200 (or 20 to 40) and an Alpha value of at
least 5 (or at least 15), the conversion catalyst further
comprising an average catalyst exposure time of 25 grams to 200
grams of oxygenate per gram of catalyst, the conversion catalyst
optionally further comprising 0.1 wt % to 3.0 wt % of a transition
metal (preferably Zn) supported on the conversion catalyst.
[0092] Embodiment 6. The method of Embodiment 5, wherein the
oxygenate comprises methanol, or wherein the conversion catalyst
comprises an average catalyst exposure time of 50 grams to 200
grams of methanol per gram of catalyst, (or 25 grams to 180 grams,
or 50 grams to 180 grams, or 50 grams to 150 grams, or 100 grams to
200 grams); or a combination thereof.
[0093] Embodiment 7. The method of Embodiment 5 or 6, wherein the
conversion catalyst comprises at least 10 wt % of a zeolite having
a framework structure of MRE (ZSM-48), MTW, TON, MTT, MFS, or a
combination thereof.
[0094] Embodiment 8. The method of any of Embodiments 5 to 7,
wherein exposing the feed comprising oxygenates to a conversion
catalyst comprises exposing the feed comprising oxygenate to the
conversion catalyst in a fluidized bed, a moving bed, a riser
reactor, or a combination thereof, the conversion catalyst being
withdrawn and regenerated at a rate corresponding to regeneration
of 0.3 wt % to 3.0 wt % of catalyst per 1 g of oxygenate exposed to
a g of conversion catalyst (optionally 1.5 wt % to 3.0 wt %).
[0095] Embodiment 9. The method of any of the above embodiments,
wherein the 0.1 wt % to 3.0 wt % of transition metal comprises 0.1
wt % to 3.0 wt % of Zn, or 0.5 wt % to 1.5 wt % Zn.
[0096] Embodiment 10. The method of any of the above embodiments,
wherein the conversion catalyst further comprises phosphorus
supported on the conversion catalyst, a molar ratio of phosphorus
to zinc on the conversion catalyst optionally being 1.5 to 3.0.
[0097] Embodiment 11. The method of any of the above embodiments,
wherein the feed comprises a molar ratio of oxygenates to olefins
of 10 or less, or 6.0 or less.
[0098] Embodiment 12. The method of any of the above embodiments,
wherein the feed comprising oxygenates and olefins comprises a
first feedstock comprising at least a portion of the oxygenates and
a second feedstock comprising at least a portion of the olefins,
the first feedstock and the second feedstock being combined after
entering a reactor containing the conversion catalyst.
[0099] Embodiment 13. The method of any of the above embodiments,
a) wherein the feed comprises about 30 wt % to about 95 wt % of
oxygenates, about 5 wt % to about 40 wt % of olefins, or a
combination thereof; b) wherein the feed comprises at least about
20 wt % to about 60 wt % of components different from oxygenates
and olefins, or about 40 wt % to 60 wt %; or c) a combination of a)
and b).
[0100] Embodiment 14. An oxygenate conversion effluent comprising,
relative to a total weight of hydrocarbons in the conversion
effluent, at least 40 wt % aromatics, less than 6.0 wt % combined
of CO, CO.sub.2, and CH.sub.4, and less than 10 wt % olefins, a
naphtha boiling range portion of the conversion effluent having an
octane rating of at least 90, wherein less than 10 wt % of the
aromatics comprise C.sub.10 aromatics relative to a total weight of
the aromatics, and wherein less than 10 wt % of the C.sub.10
aromatics comprise durene relative to a total weight of the
C.sub.10 aromatics.
[0101] Embodiment 15. The oxygenate conversion effluent of
Embodiment 14, wherein the oxygenate conversion effluent comprises
less than 5.0 wt % combined of CO, CO.sub.2, and CH.sub.4, or
wherein less than 5 wt % of the C.sub.10 aromatics comprise durene
relative to a total weight of the C.sub.10 aromatics, or a
combination thereof.
[0102] Embodiment 16. A conversion effluent made according to any
of Embodiments 1-13.
[0103] While the present invention has been described and
illustrated by reference to particular embodiments, those of
ordinary skill in the art will appreciate that the invention lends
itself to variations not necessarily illustrated herein. For this
reason, then, reference should be made solely to the appended
claims for purposes of determining the true scope of the present
invention.
* * * * *
References