U.S. patent application number 14/953800 was filed with the patent office on 2016-06-16 for hierarchical aluminophosphates as catalysts for the beckmann rearrangement.
This patent application is currently assigned to University of Southampton. The applicant listed for this patent is Honeywell International Inc.. Invention is credited to Simon R. Bare, Scott R. Keenan, Alan B. Levy, Stephanie H. Newland, Robert Raja.
Application Number | 20160167030 14/953800 |
Document ID | / |
Family ID | 56110214 |
Filed Date | 2016-06-16 |
United States Patent
Application |
20160167030 |
Kind Code |
A1 |
Levy; Alan B. ; et
al. |
June 16, 2016 |
HIERARCHICAL ALUMINOPHOSPHATES AS CATALYSTS FOR THE BECKMANN
REARRANGEMENT
Abstract
Methods for producing lactams from oximes by performing a
Beckmann rearrangement using a hierarchical porous aluminophosphate
catalyst having interconnected microporous and mesoporous networks
are provided. Exemplary catalysts include a plurality of weak
Bronsted acid active sites, including silicon-containing
aluminophosphates having the IZA framework code AFI, such as
SAPO-5, CHA, such as SAPO-34, and FAU, such as SAPO-37.
Inventors: |
Levy; Alan B.; (Randolph,
NJ) ; Raja; Robert; (Fair Oak, GB) ; Newland;
Stephanie H.; (Kintbury, GB) ; Keenan; Scott R.;
(Marlton, NJ) ; Bare; Simon R.; (Naperville,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Honeywell International Inc. |
Morris Plains |
NJ |
US |
|
|
Assignee: |
University of Southampton
Southampton
GB
|
Family ID: |
56110214 |
Appl. No.: |
14/953800 |
Filed: |
November 30, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62092471 |
Dec 16, 2014 |
|
|
|
Current U.S.
Class: |
540/464 ;
423/700; 540/535; 540/536 |
Current CPC
Class: |
C01B 39/54 20130101;
C01B 37/08 20130101; B01J 29/83 20130101; B01J 37/03 20130101; B01J
2229/183 20130101; B01J 29/84 20130101; B01J 29/89 20130101; B01J
35/1057 20130101; B01J 35/1061 20130101; C07D 225/02 20130101; C07D
223/10 20130101; B01J 35/109 20130101; B01J 29/85 20130101; B01J
29/041 20130101 |
International
Class: |
B01J 29/84 20060101
B01J029/84; C07D 223/10 20060101 C07D223/10; B01J 29/85 20060101
B01J029/85; C07D 225/02 20060101 C07D225/02 |
Claims
1. A method of performing a Beckmann rearrangement reaction
comprising the step of: reacting an oxime in the presence of a
catalyst to produce a lactam, said catalyst comprising a
hierarchical porous aluminophosphate comprising a microporous
framework and a mesoporous framework.
2. The method of claim 1, wherein the mesoporous framework has a
pore diameter from 15 .ANG. to 50 .ANG..
3. The method of claim 2, wherein the microporous framework has a
pore diameter from 3 .ANG. to 10 .ANG..
4. The method of claim 1, wherein the catalyst is a hierarchical
porous aluminophosphate catalyst isomorphously substituted with one
or two metals selected from the group consisting of: manganese,
iron, copper, magnesium, chromium, cobalt, copper, zinc, silicon,
titanium, vanadium, and tin.
5. The method of claim 1, wherein the catalyst is a hierarchical
porous aluminophosphate catalyst isomorphously substituted with one
or two metals selected from the group consisting of: cobalt,
silicon, and titanium.
6. The method of claim 1, wherein the catalyst is a hierarchical
porous silicoaluminophosphate catalyst selected from the group
consisting of: HP SAPO-5, HP SAPO-11, HP SAPO-18, HP SAPO-31, HP
SAPO-34, HP SAPO-37, HP SAPO-41, and HP SAPO-44.
7. The method of claim 6, wherein the catalyst is selected from HP
SAPO-5, HP SAPO-34, and HP SAPO-37.
8. The method of claim 1, wherein the catalyst is a hierarchical
catalyst comprising a microporous structure having an IZA framework
code selected from the group consisting of: AFI, CHA, and FAU.
9. The method of claim 1, wherein the catalyst is a hierarchical
porous aluminophosphate catalyst isomorphously substituted with one
or two metals selected from the group consisting of: cobalt and
titanium.
10. The method of claim 9, wherein the catalyst is selected from
the group consisting of HP Co AlPO-5, HP Ti AlPO-5, and HP Co Ti
AlPO-5.
11. The method of claim 1, wherein the oxime is selected from
cyclohexanone oxime, cyclooctanone oxime, and cyclododecanone
oxime.
12. The method of claim 1, wherein said reacting is performed in
the gas phase.
13. The method of claim 1, wherein said reacting is performed in
the liquid phase.
14. A hierarchical porous catalyst comprising: an aluminophosphate
framework with an IZA framework code selected from the group
consisting of AFI, CHA, and FAU; a plurality of interconnected
micropores, each micropore having a pore diameter from 3 to 10
.ANG.; and a plurality of mesopores interconnected with the
micropores, each mesopores having a pore diameter from 15 .ANG. to
50 .ANG..
15. The hierarchical porous catalyst of claim 14, wherein the
catalyst is a hierarchical porous aluminophosphate catalyst
isomorphously substituted with one or two metals selected from the
group consisting of: cobalt, silicon, and titanium
16. The hierarchical porous catalyst of claim 14, wherein the
catalyst is a hierarchical porous silicoaluminophosphate catalyst
selected from the group consisting of: HP SAPO-5, HP SAPO-34, and
HP SAPO-37.
17. The hierarchical porous catalyst of claim 14, wherein the
catalyst is a hierarchical porous aluminophosphate catalyst
isomorphously substituted with one or two metals selected from the
group consisting of: cobalt and titanium.
18. The hierarchical porous catalyst of claim 17, wherein the
catalyst is selected from the group consisting of HP Co AlPO-5, HP
Ti AlPO-5, and HP Co Ti AlPO-5.
19. The hierarchical porous catalyst of claim 14, wherein the
hierarchical porous catalyst is phase pure.
20. The hierarchical porous catalyst of claim 14, further
comprising a plurality of weak Bronsted acid active sites.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under Title 35, U.S.C.
.sctn.119(e) of U.S. Provisional Application Ser. No. 62/092,471
entitled HIERARCHICAL ALUMINOPHOSPHATES AS CATALYSTS FOR THE
BECKMANN REARRANGEMENT, filed on Dec. 16, 2014, the entire
disclosure of which is expressly incorporated by reference
herein.
FIELD
[0002] The present invention relates to methods of producing
lactams, such as .epsilon.-caprolactam, for example. In particular,
the present invention relates to a method producing
.epsilon.-caprolactam utilizing aluminophosphate catalysts.
BACKGROUND
[0003] Traditional approaches for producing lactams, used in the
production of nylon, include an oxime undergoing a Beckmann
rearrangement in the presence of an acid catalyst, such as fuming
sulfuric acid.
[0004] Oximes are compounds having the general formula:
##STR00001##
wherein R1 is an organic group and R2 is hydrogen or an organic
group. When R2 is hydrogen, the oxime is an oxime derived from an
aldehyde, referred to as aldoximes. When R2 is an organic group,
the oxime is an oxime derived from a ketone, referred to as
ketoximes.
[0005] Cyclic oximes are a sub-group of ketoximes having the
general formula:
##STR00002##
wherein the R1 and R2 groups form a ring.
[0006] Lactams, or cyclic amides, are compounds having the general
formula:
##STR00003##
wherein R1 and R2 form a ring.
[0007] Exemplary oximes include, but are not limited, to
cyclohexanone oxime, cyclododecanone oxime, 4-hydroxy acetophenone
oxime and oximes formed from acetophenone, butryaldehyde,
cyclopentanone, cycloheptanone, cyclooctanone, and benzaldehyde.
Exemplary lactams include those made from cyclic oximes, including
those listed above. Lactams are well known in the art as being
useful in the production of polyamides, such as nylon.
.epsilon.-caprolactam can be polymerized to form Nylon-6.
.omega.-laurolactam can be polymerized to form Nylon-12. Additional
examples of useful lactams include 11 undecanelactam, a precursor
of Nylon-11, 2-Pyrrolidone a precursor of Nylon-4, 2-Piperidone a
precursor of Nylon-5.
[0008] Exemplary reactions are shown in FIG. 1. As illustrated in
FIG. 1A, cyclohexanone oxime is reacted to form
.epsilon.-caprolactam. .epsilon.-caprolactam in turn is polymerized
to form nylon-6. As illustrated in FIG. 1B, cyclododecanone oxime
is reacted to form .omega.-laurolactam. .omega.-laurolactam in turn
is polymerized to form nylon-12. As illustrated in FIG. 1C,
cyclooctanone oxime is reacted to form the corresponding lactam
(caprylolactam), which in turn can be polymerized to form nylon-8.
Nylon-6, nylon-8, and nylon-12 are extensively used in industry and
manufacturing.
[0009] One potential reaction mechanism for the reaction of FIG. 1A
is illustrated in FIG. 1D. The mechanism generally consists of
protonating the hydroxyl group, performing an alkyl migration while
expelling the hydroxyl to form a nitrilium ion, followed by
hydrolysis, tautomerization, and deprotonation to form the
lactam.
[0010] Typically, Beckmann rearrangement reactions of oximes to
form lactams are performed using acids such as fuming sulfuric
acid. These reactions are characterized by complete or nearly
complete conversion of the oxime and very high selectivity for the
desired lactams. However, these reactions also produce byproducts
including ammonium sulfate. Although ammonium sulfate is a useful
product in itself, minimizing its production may be desirable.
[0011] Different catalysts, such as zeolites have been proposed for
use in optimizing the Beckmann rearrangement. It is widely regarded
that weak Bronsted sites are required and as such a range of
different microporous catalysts, including zeolites,
aluminophosphates (AlPO), metal substituted aluminophosphates
(MeAlPO), and mesoporous catalysts, including MCM-41 and SBA-15
have been proposed. Zeolites, such as the highly siliceous MFI
zeolite catalyst, ZSM-5, have been used in the gas-phase Beckmann
rearrangement of cyclohexanone oxime to .epsilon.-caprolactam.
[0012] However, typical microporous structures may include one or
more disadvantages, including a drop in activity over time due to
the formation of carbon deposits on the active sites that act as a
poison, reduced mass transfer, diffusion limitations, reduced
substrate versatility, and limitations on pore size. Zeotypes
having large pores, such as AlPO-8 (AET), VPI-5 (VFI), and
cloverite (CLO) may include terminal hydroxyl groups, reducing the
stability of the structure. Moreover, these larger pored zeotypes
may include strong acid sites, which are less favorable for certain
types of reactions, and may not result in increased versatility,
longevity, and activity. Mesoporous silicas and isomorphously
substituted metals in mesoporous systems, such as Mg-MCM41,
Al-MCM41, and MgAl-MCM41, may be less stable, less selective, and
less active than microporous catalysts, and their amorphous
framework may result in reduced stability.
[0013] Improvements in the foregoing processes are desired.
SUMMARY
[0014] The present disclosure provides methods for producing
lactams from oximes by performing a Beckmann rearrangement using a
hierarchical aluminophosphate catalyst. These catalysts are used in
reactions to convert oximes into lactams. High conversion of oxime
and high selectivity for the desired lactams are produced using the
disclosed methods, including improved catalyst longevity,
relatively high conversion, and relatively high selectivity for a
lactam produced from its corresponding oxime.
[0015] In some exemplary embodiments, hierarchical porous
aluminophosphate catalysts, such as metal-substituted
aluminophosphate materials, are provided. Without wishing to be
held to any particular theory, it is believed that the hierarchical
porous structure provides a microporous structure with desired weak
isolated Bronsted acid active sites and a mesoporous network aiding
in mass transfer of reactants and products. The network of
mesopores is believed to facilitate access to the active sites in
the microporous framework of the material. Additionally, in some
exemplary embodiments, the hierarchical porous (HP) AlPO materials
have large surface areas and pore volumes compared to a
corresponding microporous material due to the secondary porosity of
the mesoporous network.
[0016] In one exemplary embodiment, a method of performing a
Beckmann rearrangement reaction is provided. The method comprises
reacting an oxime in the presence of a catalyst to produce a
lactam, said catalyst comprising a hierarchical aluminophosphate.
In a more particular embodiment, the catalyst comprises a plurality
of weak Bronsted acid active sites. In a still more particular
embodiment, the catalyst does not include any Lewis acid sites.
[0017] In one more particular embodiment of any of the above
embodiments, the catalyst comprises a microporous framework and a
mesoporous framework. In one exemplary embodiment, the microporous
framework and the mesoporous framework are interconnected. In a
more particular embodiment of any of the above embodiments, the
mesoporous framework having a pore diameter from 15 .ANG. to 50
.ANG.. In one more particular embodiment of any of the above
embodiments, the microporous framework having a pore diameter from
3 .ANG. to 10 .ANG..
[0018] In one more particular embodiment of any of the above
embodiments, the catalyst is a hierarchical porous aluminophosphate
catalyst isomorphously substituted with one or two metals selected
from the list consisting of: manganese, iron, copper, magnesium,
chromium, cobalt, copper, zinc, silicon, titanium, vanadium, and
tin. In a more particular embodiment of any of the above
embodiments, the catalyst is a hierarchical porous aluminophosphate
catalyst isomorphously substituted with one or two metals selected
from the list consisting of: cobalt, silicon, and titanium. In a
more particular embodiment of any of the above embodiments, the
catalyst is a hierarchical porous aluminophosphate catalyst
isomorphously substituted with silicon. In a more particular
embodiment of any of the above embodiments, the catalyst is a
hierarchical porous aluminophosphate catalyst isomorphously
substituted with one or two metals selected from the list
consisting of: cobalt and titanium. In a still more particular
embodiment, the metal is isomorphously substituted as a Type I or
Type II substitution.
[0019] In one more particular embodiment of any of the above
embodiments, the catalyst comprising a microporous structure having
the IZA framework code AFI, CHA, or FAU.
[0020] In one more particular embodiment of any of the above
embodiments, the catalyst is a hierarchical porous
silicoaluminophosphate catalyst. In a still more particular
embodiment, the catalyst is selected from the group consisting of:
HP SAPO-5, HP SAPO-11, HP SAPO-18, HP SAPO-31, HP SAPO-34, HP
SAPO-37, HP SAPO-41, and HP SAPO-44. In a still more particular
embodiment, the catalyst is selected from the group consisting of
HP SAPO-5, HP SAPO-34, and HP SAPO-37. In a still more particular
embodiment, the catalyst is selected from the group consisting of
HP SAPO-5 and HP SAPO-34. In one even more particular embodiment,
the catalyst is HP SAPO-5. In another even more particular
embodiment, the catalyst is HP SAPO-34. In another even more
particular embodiment, the catalyst is HP SAPO-37.
[0021] In one more particular embodiment of any of the above
embodiments, the catalyst is a hierarchical porous aluminophosphate
catalyst selected from the group consisting of HP Co AlPO-5, HP Ti
AlPO-5, and HP Co Ti AlPO-5. In one more particular embodiment of
any of the above embodiments, the catalyst is HP Co AlPO-5. In one
more particular embodiment of any of the above embodiments, the
catalyst is HP Ti AlPO-5. In one more particular embodiment of any
of the above embodiments, the catalyst is HP Co Ti AlPO-5.
[0022] In one more particular embodiment of any of the above
embodiments, the oxime is selected from the group consisting of:
cyclohexanone oxime, cyclododecanone oxime, 4-hydroxy acetophenone
oxime and oximes formed from acetophenone, butryaldehyde,
cyclopentanone, cycloheptanone, cyclooctanone, and benzaldehyde. In
another more particular embodiment of any of the above embodiments,
the lactam is selected from the group consisting of:
.epsilon.-caprolactam .omega.-laurolactam 11-undecanelactam,
2-Pyrrolidone, and 2-Piperidone. In one more particular embodiment
of any of the above embodiments, the oxime is selected from
cyclohexanone oxime, cyclooctanone oxime, and cyclododecanone
oxime.
[0023] In one more particular embodiment of any of the above
embodiments, the reaction is performed in the vapor phase. In
another more particular embodiment of any of the above embodiments,
the reaction is performed in the liquid phase.
[0024] In another embodiment, a hierarchical porous catalyst is
provided. The catalyst includes an aluminophosphate framework with
the an IZA framework code selected from the group consisting of
AFI, CHA, and FAU; a plurality of interconnected micropores, each
micropore having a pore diameter from 3 to 10 .ANG.; and a
plurality of mesopores interconnected with the micropores, each
mesopores having a pore diameter from 15 .ANG. to 50 .ANG..
[0025] In a more particular embodiment, the catalyst is a
hierarchical porous aluminophosphate catalyst isomorphously
substituted with one or two metals selected from the group
consisting of: cobalt, silicon, and titanium.
[0026] In a more particular embodiment of any of the above
embodiments, the catalyst is a hierarchical porous
silicoaluminophosphate catalyst selected from the group consisting
of: HP SAPO-5, HP SAPO-34, and HP SAPO-37.
[0027] In a more particular embodiment of any of the above
embodiments, the catalyst is a hierarchical porous aluminophosphate
catalyst isomorphously substituted with one or two metals selected
from the group consisting of: cobalt and titanium.
[0028] In a more particular embodiment of any of the above
embodiments, the catalyst is selected from the group consisting of
HP Co AlPO-5, HP Ti AlPO-5, and HP Co Ti AlPO-5.
[0029] In a more particular embodiment of any of the above
embodiments the catalyst comprises a silicon-containing
aluminophosphate framework with the IZA framework code AFI; a
plurality of interconnected micropores, each micropore having a
pore diameter from 7 to 8 .ANG.; and a plurality of mesopores
interconnected with the micropores, each mesopore having a pore
diameter from 15 .ANG. to 50 .ANG..
[0030] In a more particular embodiment of any of the above
embodiments, the catalyst comprises a silicon-containing
aluminophosphate framework with the IZA framework code CHA; a
plurality of interconnected micropores, each micropore having a
pore diameter from 3 to 4 .ANG.; and a plurality of mesopores
interconnected with the micropores, each mesopores having a pore
diameter from 15 .ANG. to 50 .ANG.. In another more particular
embodiment, the catalyst comprises a aluminophosphate framework
with the IZA framework code CHA isomorphously substituted with one
or two metals selected from the group consisting of cobalt and
titanium; a plurality of interconnected micropores, each micropore
having a pore diameter from 3 to 4 .ANG.; and a plurality of
mesopores interconnected with the micropores, each mesopores having
a pore diameter from 15 .ANG. to 50 .ANG..
[0031] In another more particular embodiment of any of the above
embodiments, the catalyst comprises a silicon-containing
aluminophosphate framework with the IZA framework code FAU; a
plurality of interconnected micropores, each micropore having a
pore diameter from 7 to 8 .ANG.; and a plurality of mesopores
interconnected with the micropores, each mesopore having a pore
diameter from 15 .ANG. to 50 .ANG..
[0032] In a more particular embodiment of any of the above
embodiments, the catalyst is phase pure. In another more particular
embodiment of any of the above embodiments, the catalyst comprises
a plurality of weak Bronsted acid active sites. In still another
particular embodiment of any of the above embodiments, the catalyst
does not include any Lewis acid sites.
[0033] In one exemplary embodiment, a method of producing a
hierarchical porous aluminophosphate catalyst is provided. The
method includes combining a organosilane surfactant, a structure
directing agent, and metal precursors to form a mixture, and adding
a silicon source to the mixture. The method further includes
crystalizing the resulting material to form a catalyst. In a more
particular embodiment of any of the above embodiments, the method
further comprising crystalizing the catalyst at a temperature of
about 200.degree. C. for about 24 hours.
[0034] In a more particular embodiment of any of the above
embodiments, the organosilane surfactant is
dimethyloctadecyl[(3-(trimethoxysilyl)propyl] ammonium chloride. In
a more particular embodiment of any of the above embodiments, the
structure directing agent is triethylamine and triethylammonium
hydroxide. In a more particular embodiment of any of the above
embodiments, the metal precursor is aluminum isopropoxide. In a
more particular embodiment of any of the above embodiments, the
silicon source is silica. In a more particular embodiment, the
hierarchical porous aluminophosphate catalyst is a catalyst
according to any of the above embodiments.
[0035] The above mentioned and other features of the invention, and
the manner of attaining them, will become more apparent and the
invention itself will be better understood by reference to the
following description of embodiments of the invention taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1A illustrates the reaction from cyclohexanone oxime to
.epsilon.-caprolactam.
[0037] FIG. 1B illustrates the reaction from cyclododecanone oxime
to .omega.-laurolactam.
[0038] FIG. 1C illustrates the reaction from cyclooctanone oxime to
caprylolactam.
[0039] FIG. 1D illustrates the potential steps of a reaction
corresponding to a Beckmann rearrangement reaction from
cyclohexanone oxime to .epsilon.-caprolactam.
[0040] FIG. 2 illustrates active sites and pore diameters of an
exemplary zeolite, an exemplary mesoporous silica, and exemplary
SAPO material, and an exemplary hierarchical SAPO material.
[0041] FIG. 3 illustrates Type I, Type II, and Type III isomorphous
substitutions in an AlPO material.
[0042] FIG. 4A illustrates a pore diameter of an exemplary
microporous SAPO-5 material.
[0043] FIG. 4B illustrates a pore diameter of an exemplary
microporous SAPO-34 material.
[0044] FIG. 4C illustrates a pore diameter of an exemplary
microporous SAPO-37 material.
[0045] FIG. 5 illustrates possible micropore and mesopore active
sites in an exemplary hierarchical SAPO material.
[0046] FIG. 6 illustrates an exemplary soft-templating technique
for forming a hierarchical AlPO material.
[0047] FIG. 7A is related to Example 4, and illustrates the X-ray
diffraction spectra for SAPO-5 and HP SAPO-5.
[0048] FIG. 7B is related to Example 4, and illustrates the X-ray
diffraction spectra for SAPO-34 and HP SAPO-34.
[0049] FIG. 7C is related to Example 4, and illustrates the X-ray
diffraction spectra for SAPO-37 and HP SAPO-37.
[0050] FIG. 8A is related to Example 4, and provides the CellRef
refinement values for the SAPO-5 material.
[0051] FIG. 8B is related to Example 4, and provides the CellRef
refinement values for the HP SAPO-5 material.
[0052] FIG. 9A is related to Example 4, and provides the CellRef
refinement values for the SAPO-34 material.
[0053] FIG. 9B is related to Example 4, and provides the CellRef
refinement values for the HP SAPO-34 material.
[0054] FIG. 10A is related to Example 4, and illustrates the BET
adsorption and BJH adsorption pore volume curves for SAPO-5 and HP
SAPO-5.
[0055] FIG. 10B is related to Example 4, and illustrates the BET
adsorption and BJH adsorption pore volume curves for SAPO-34 and HP
SAPO-34.
[0056] FIG. 10C is related to Example 4, and illustrates the BET
adsorption and BJH adsorption pore volume curves for SAPO-37 and HP
SAPO-37.
[0057] FIG. 11A is related to Example 4 and illustrates an SEM
image of SAPO-5.
[0058] FIG. 11B is related to Example 4 and illustrates an SEM
image of HP SAPO-5.
[0059] FIG. 11C is related to Example 4 and illustrates an SEM
image of SAPO-34.
[0060] FIG. 11D is related to Example 4 and illustrates an SEM
image of HP SAPO-34.
[0061] FIGS. 12A and 12B are related to Example 4 and illustrate
SEM images of HP SAPO-34.
[0062] FIG. 13 is related to Example 4 and illustrates an SEM image
and EDS data of HP SAPO-34.
[0063] FIG. 14 is related to Example 4 and illustrates an SEM image
and EDS data of HP SAPO-5.
[0064] FIGS. 15 and 16 are related to Example 4 and illustrate a
TEM image and elemental analysis of HP SAPO-5.
[0065] FIGS. 17-19 are related to Example 4 and illustrate a TEM
image and elemental analysis of HP SAPO-34.
[0066] FIGS. 20A-20I are related to Example 5 and illustrate the
conversion, selectivity, and yield of SAPO-5, HP SAPO-5, SAPO-34,
HP SAPO-34, H-ZSM-5, and MCM-41 for the gas-phase Beckmann
rearrangement of cyclohexanone oxime.
[0067] FIGS. 21A-21I are related to Example 5 and illustrate the
conversion, selectivity, and yield of SAPO-5, HP SAPO-5, SAPO-34,
HP SAPO-34, H-ZSM-5, and MCM-41 for the gas-phase Beckmann
rearrangement of cyclooctanone oxime.
[0068] FIGS. 22A-22C are related to Example 5 and illustrate the
conversion and selectivity for the gas-phase Beckmann rearrangement
of cyclohexanone oxime with HP SAPO-5 at various temperatures.
[0069] FIGS. 23A-23C are related to Example 5 and illustrate the
conversion and selectivity for the gas-phase Beckmann rearrangement
of cyclohexanone oxime with HP SAPO-34 at various temperatures.
[0070] FIGS. 24A-24C are related to Example 5 and illustrate the
conversion and selectivity for the gas-phase Beckmann rearrangement
of cyclohexanone oxime with HP SAPO-5 at various WHSV.
[0071] FIGS. 25A-25C are related to Example 5 and illustrate the
conversion and selectivity for the gas-phase Beckmann rearrangement
of cyclohexanone oxime with HP SAPO-34 at WHSV.
[0072] FIG. 26 is related to Example 6 and illustrates the
conversion of cyclododecanone oxime with different catalysts.
[0073] FIG. 27A is related to Example 6 and illustrates the
conversion of cyclododecanone oxime in the liquid phase with HP
SAPO-5 with different quantities of catalyst.
[0074] FIG. 27B is related to Example 6 and illustrates the
conversion of cyclododecanone oxime in the liquid phase with HP
SAPO-34 with different quantities of catalyst.
[0075] FIG. 27C is related to Example 6 and illustrates the
conversion of cyclododecanone oxime in the liquid phase with HP
SAPO-37 with different quantities of catalyst.
[0076] FIGS. 28A-28C are related to Example 6 and illustrate the
conversion of HP SAPO-34, HP SAPO-5, and HP SAPO-37, respectively,
using a liquid recycle set-up.
[0077] FIGS. 29A-29E are related to Example 7 and illustrate NMR
spectra for SAPO-5 and HP SAPO-5.
[0078] FIGS. 30A-30E are related to Example 7 and illustrate NMR
spectra for SAPO-34 and HP SAPO-34.
[0079] FIGS. 31A-31C are related to Example 7 and illustrate NMR
spectra for HP SAPO-37.
[0080] FIG. 32A is related to Example 7 and illustrates the FT-IR
spectra of SAPO-5 and HP SAPO-5.
[0081] FIG. 32B is related to Example 7 and illustrates the FT-IR
spectra of SAPO-34 and HP SAPO-34.
[0082] FIG. 32C is related to Example 7 and illustrates a
comparison of the FT-IR spectra of HP SAPO-5 and HP SAPO-34.
[0083] FIG. 33A is related to Example 7 and illustrates the
TPD-NP.sub.3 results of SAPO-5 and HP SAPO-5.
[0084] FIG. 33B is related to Example 7 and illustrates the
TPD-NP.sub.3 results of SAPO-34 and HP SAPO-34.
[0085] FIG. 33C is related to Example 7 and illustrates the
TPD-NP.sub.3 results of SAPO-37 and HP SAPO-37.
[0086] FIG. 34A is related to Example 7 and illustrates the CO
adsorption results of HP SAPO-5.
[0087] FIG. 34B is related to Example 7 and illustrates the CO
adsorption results of HP SAPO-34.
[0088] FIG. 35A is related to Example 7 and illustrates the
collidine adsorption results of HP SAPO-5.
[0089] FIG. 35B is related to Example 7 and compares the
distribution of acid sites in the SAPO-5 and HP SAPO-5
materials.
[0090] FIG. 36A is related to Example 7 and illustrates the
collidine adsorption results of HP SAPO-34.
[0091] FIG. 36B is related to Example 7 and compares the
distribution of acid sites as determined by collidine adsorption in
the SAPO-34 and HP SAPO-34 materials.
[0092] FIG. 37 is related to Example 8 and illustrates the powder
X-ray diffraction spectra for HP Co AlPO-5, HP Ti AlPO-5, and HP Co
Ti AlPO-5.
[0093] FIG. 38A is related to Example 8 and illustrates an SEM
image of HP Co AlPO-5.
[0094] FIG. 38B is related to Example 8 and illustrates an SEM
image of HP Ti AlPO-5.
[0095] FIG. 38C is related to Example 8 and illustrates an SEM
image of HP Co Ti AlPO-5.
[0096] FIG. 39A is related to Example 8 and illustrates the
nitrogen adsorption isotherm for HP Co AlPO-5, HP Ti AlPO-5, and HP
Co Ti AlPO-5.
[0097] FIG. 39B is related to Example 8 and illustrates the BJH
pore distribution curves for HP Co AlPO-5, HP Ti AlPO-5, and HP Co
Ti AlPO-5.
[0098] FIG. 40A is related to Example 8 and illustrates the
.sup.29Si MAS NMR of HP Co AlPO-5.
[0099] FIG. 40B is related to Example 8 and illustrates the
.sup.29Si MAS NMR of HP Ti AlPO-5.
[0100] FIG. 40C is related to Example 8 and illustrates the
.sup.29Si MAS NMR of HP Co Ti AlPO-5.
[0101] FIG. 41 is related to Example 8 and illustrates the DR
UV/vis spectra of the HP Co AlPO-5, HP Ti AlPO-5, and HP Co Ti
AlPO-5.
[0102] FIG. 42 is related to Example 8 and illustrates the FTIR
spectra of the OH-stretching region for HP Co AlPO-5, HP Ti AlPO-5,
and HP Co Ti AlPO-5.
[0103] FIG. 43A is related to Example 8 and illustrates the FTIR
spectra of CO adsorbed at 80 k on calcined HP Co AlPO-5.
[0104] FIG. 43B is related to Example 8 and illustrates the FTIR
spectra of CO adsorbed at 80 k on calcined HP Ti AlPO-5.
[0105] FIG. 43C is related to Example 8 illustrates the FTIR
spectra of CO adsorbed at 80 k on calcined HP Co Ti AlPO-5.
[0106] FIG. 44A is related to Example 8 and illustrates the FTIR
spectra of 0.02 cc of CO adsorbed at 80K on calcined HP Co AlPO-5,
calcined HP Ti AlPO-5 and calcined HP Co Ti AlPO-5.
[0107] FIG. 44B is related to Example 8 and illustrates the FTIR
spectra of 0.08 cc of CO adsorbed at 80K on calcined HP Co AlPO-5,
calcined HP Ti AlPO-5 and calcined HP Co Ti AlPO-5.
[0108] FIG. 44C is related to Example 8 and illustrates the FTIR
spectra of 0.16 cc of CO adsorbed at 80K on calcined HP Co AlPO-5,
calcined HP Ti AlPO-5 and calcined HP Co Ti AlPO-5.
[0109] FIG. 45 is related to Example 8 and illustrates the TPD
nitrogen adsorption results for HP Co AlPO-5, HP Ti AlPO-5, and HP
Co Ti AlPO-5.
[0110] FIG. 46 is related to Example 8 and illustrates a summary of
an FTIR collidine probe for HP Co AlPO-5, HP Ti AlPO-5, and HP Co
Ti AlPO-5.
[0111] FIG. 47A is related to Example 9 and illustrates the percent
conversion, percent selectivity, and percent yield for the liquid
phase Beckmann rearrangement of cyclohexanone oxime to
.epsilon.-caprolactam for various catalysts.
[0112] FIG. 47B is related to Example 9 and illustrates the percent
conversion, percent selectivity, and percent yield for the liquid
phase Beckmann rearrangement of cyclcododecanone oxime to
laurolactam for various catalysts.
DETAILED DESCRIPTION
[0113] The present disclosure is directed to a method to form
lactams from cyclic oxime compounds. Exemplary reactions are shown
in FIG. 1. As illustrated in FIG. 1A, cyclohexanone oxime is
reacted to form .epsilon.-caprolactam, which in turn can be
polymerized to form nylon-6. As illustrated in FIG. 1B,
cyclododecanone oxime is reacted to form .omega.-laurolactam, which
in turn can be polymerized to form nylon-12. As illustrated in FIG.
1C, cyclooctanone oxime is reacted to form caprylolactam, which in
turn can be polymerized to form nylon-8. In one exemplary
embodiment, a cyclic oxime having from as little as 5, 6, 8, as
great as 10, 12, 18, or greater carbon atoms is reacted to form the
corresponding oxime.
[0114] The present method is also useful to perform other Beckmann
rearrangement reactions.
[0115] Oximes are converted to lactams, such as in the examples
illustrated in FIGS. 1A-1C, through contact with the catalysts. The
present disclosure is believed to be generally applicable to any
oxime generated from a variety of aldehydes and ketones. Exemplary
oximes include, but are not limited, to cyclohexanone oxime,
cyclododecanone oxime, 4-hydroxy acetophenone oxime and oximes
formed from acetophenone, butryaldehyde, cyclopentanone,
cycloheptanone, cyclooctanone, benzaldehyde.
[0116] In some exemplary embodiments, the reaction is performed in
the absence of a solvent. In some exemplary embodiments, the
reaction is performed in the presence of a solvent. In reactions
performed in the absence of a solvent, the product is used to
absorb the exothermic heat produced by the reaction. In these
embodiments, a large ratio of lactam to oxime is maintained in the
reaction area to absorb the energy produced by the reaction.
[0117] Exemplary solvents include organic nitriles of the
formula:
R.sup.1--CN
[0118] Wherein R.sup.1 represents C.sub.1-C.sub.8-alkyl,
C.sub.1-C.sub.8-alkenyl, C.sub.1-C.sub.8-alkynyl,
C.sub.3-C.sub.8-cycloalkyl; C.sub.3-C.sub.8-aralkyl including a
C.sub.6 aromatic ring. Exemplary nitriles include acetonitrile,
benzonitrile and mixtures of any of the foregoing.
[0119] Other exemplary solvents include aromatic compounds of the
formula:
R.sup.2-Ar
[0120] Wherein Ar is an aromatic ring and R.sup.2 represents H,
CH.sub.3, F, Cl, or Br. The aromatic ring may be substituted with
one or more R.sup.2 groups. Exemplary aromatic solvents include
benzene, toluene, xylene, and chlorobenzene.
[0121] Still other exemplary solvents include water and alcohols of
the formula:
R.sup.3--OH
[0122] Wherein R.sup.3 represents hydrogen, C.sub.1-C.sub.8-alkyl,
C.sub.1-C.sub.8-alkenyl, C.sub.1-C.sub.8-alkynyl,
C.sub.3-C.sub.8-cycloalkyl; C.sub.3-C.sub.8-arylalkyl. Exemplary
alcohols include alcohols of 8 or fewer carbon atoms such as
methanol, ethanol, n-propanol, iso-propanol, n-butanol,
sec-butanol, iso-butanol, tert-butanol, n-amyl alcohol, n-hexanol,
phenol, and mixtures of any of the foregoing.
[0123] In exemplary embodiments, the solvent is rigorously dried
prior to contact with the catalyst. As used herein, rigorously
dried is understood to mean dried to a level of 100 ppm water or
less. Exemplary methods of drying include adsorption of water using
molecular sieves, such as Activated 4A molecular sieves. As used
herein, a reaction performed in the absence of water means a
reaction in which water comprises less than 0.01 wt % of the weight
of the reactants.
[0124] The reaction is performed as a liquid phase reaction or a
gas phase reaction. As used herein, a liquid phase reaction in a
reaction in which substantially all of the oxime is in the liquid
phase when reacted to form the lactam. As used herein, a gas phase
reaction in a reaction in which substantially all of the oxime and
solvent is in the gas or vapor phase when reacted to form the
lactam.
[0125] When performed as a gas phase reaction, the reaction is
typically performed at a temperature below 350.degree. C. In a more
particular embodiment, the reaction is performed at a temperature
from about 130.degree. C. to about 300.degree. C. In still other
embodiments, the reaction may be performed at a temperature as low
as about 90.degree. C., 100.degree. C., 110.degree. C.,
120.degree., 130.degree., 135.degree. C., or as high as about
140.degree. C., 150.degree. C., 170.degree. C., 180.degree. C.,
190.degree. C., 200.degree. C., 210.degree. C., 220.degree. C.,
230.degree. C., 240.degree. C. 250.degree. C., 275.degree. C.,
290.degree. C., 300.degree. C., 325.degree. C., 350.degree. C., or
within any range defined between any pair of the foregoing values,
such as 90.degree. C. to 350.degree. C., 100.degree. C. to
325.degree. C., or 130.degree. C. to 300.degree. C.
[0126] When performed as a gas phase reaction, the reaction is
typically performed at a pressure from about 0.1 bar to about 1
bar. In some embodiments, a relatively low pressure may be used to
provide a high boiling point component in the gas phase without
decomposing the component. More particularly, in exemplary
embodiments of the reaction performed as a gas phase reaction, the
pressure may be as low as 0.005 bar, 0.01 bar, 0.02 bar, 0.05 bar,
0.1 bar, as high as 0.5 bar, 1 bar, 10 bar, or higher, or within a
range defined between any pair of the foregoing values, such as
0.005 bar to 10 bar, 0.05 bar to 1 bar, or 0.1 bar to 1 bar.
[0127] When performed as a liquid phase reaction, the reaction is
typically performed at a temperature beneath 250.degree. C. In a
more particular embodiment, the reaction is performed at a
temperature from about 100.degree. C. to about 170.degree. C. In
still other embodiments, the reaction may be performed at a
temperature as low as about 90.degree. C., 100.degree. C.,
110.degree. C., 120.degree., 130.degree., or as high as about
140.degree. C., 150.degree. C., 170.degree. C., 180.degree. C.,
190.degree. C., 200.degree. C., 210.degree. C., 220.degree. C.,
230.degree. C., 240.degree. C. 250.degree. C., or within any range
defined between any pair of the foregoing values, such as
90.degree. C. to 250.degree. C., 100.degree. C. to 220.degree. C.,
or 100.degree. C. to 170.degree. C.
[0128] When performed as a liquid phase reaction, the reaction is
typically performed at a pressure from about 1 bar to about 5 bar.
More particularly, in some exemplary embodiments, the pressure may
be as low as 0.5 bar, 1 bar, as high as 1 bar, 2 bar, 5 bar, 10
bar, 15 bar, 20 bar, 25 bar, 30 bar, 35 bar, or within any range
defined between any pair of the foregoing values, such as 0.5 bar
to 35 bar, 0.5 bar to 10 bar, or 1 bar to 5 bar. In some exemplary
embodiments of the reaction performed as a liquid phase reaction,
the solvent is typically a gas at the reaction temperature, but is
maintained in the liquid phase by performing the reaction at an
elevated pressure.
[0129] When performed as a liquid phase reaction, the reaction is
typically performed at a temperature and pressure below the
critical point of the solvent, where the pressure may be as low as
1 bar, as high as 2 bar, 5 bar, 10 bar, 15 bar, 20 bar, 25 bar, 30
bar, 35 bar, or within any range defined between any pair of the
foregoing values, such as 1 bar to 35 bar, 1 bar to 10 bar, or 1
bar to 5 bar.
[0130] The efficiency of the reaction may be expressed in terms of
conversion of oxime, selectivity of the desired product, or yield.
Conversion is a measure of the amount of oxime reactant that is
consumed by the reaction. Higher conversions are more desirable.
The conversion is calculated as:
Conversion ( % ) = 100 % .times. ( 1 - moles of oxime remaining
moles of oxime supplied ) ##EQU00001##
[0131] Selectivity is a measure of the amount of the desired
product that is produced relative to all reaction products. Higher
selectivity is more desirable. Lower selectivity indicates a higher
percentage of reactant being used to form products other than the
desired lactam. The selectivity is calculated as:
Selectivity ( % ) = 100 % .times. moles of desired lactam produced
moles of oxime supplied - moles of oxime remaining ##EQU00002##
[0132] Yield is a measurement that combines selectivity and
conversion. Yield indicates how much of the incoming oxime is
reacted to form the desired lactam. The yield is calculated as:
Yield (%)=Selectivity (%).times.Conversion (%)/100%
[0133] The methods according to the present disclosure result in
high conversion and selectivity of the desired lactam.
[0134] In typical embodiments, the conversion is 50% or higher. In
a more particular embodiment, the conversion is from about 50% to
about 100%. For example, the conversion may be as low as about 50%,
60%, 70%, 75%, or as high as about 80%, 85%, 90%, 95%, 97.5%, 99%,
99.5%, approaching 100%, or 100%, or may be within any range
defined between any pair of the foregoing values, such as 50% to
100%, 75% to 99.5%, or 80% to 99%.
[0135] In typical embodiments, the selectivity is 50% or higher. In
a more particular embodiment, the selectivity is as low as about
50%, 55%, 60%, 65%, or as high as about 70%, 75%, 80%, 85%, 90%,
95%, 97.5%, 99%, 99.5%, approaching 100%, or may be within any
range defined between any pair of the foregoing values, such as 50%
to 100%, 75% to 99.5%, or 80% to 99%.
[0136] In typical embodiments, the yield is 30% or higher. In a
more particular embodiment, the yield is as low as about 30%, 35%,
40%, 45%, 50%, 55%, 60%, 65%, or as high as about 70%, 75%, 80%,
85%, 90%, 95%, 97.5%, 99%, 99.5%, approaching 100%, or may be
within any range defined between any pair of the foregoing values,
such as 50% to 100%, 75% to 99.5%, or 80% to 99%.
[0137] The methods according to the present disclosure include an
oxime reactant undergoing a Beckmann rearrangement reaction in the
presence of a catalyst. Referring to FIG. 2, exemplary catalysts
include natural and synthetic materials, including molecular
sieves, microporous materials, such as zeolites 102,
aluminophosphate (AlPO) materials (not shown), and
silicoaluminophosphate (SAPO) materials 104, and mesoporous
materials, such as mesoporous silica 106. As illustrated in FIG. 2,
the microporous materials, such as zeolite 102 and SAPO 104,
illustratively includes one or more micropores 110, and the
mesoporous material, such as mesoporous silica 106, illustratively
includes one or more mesopores 112. As shown in FIG. 2, the
micropores 110 and mesopores 112 may include a plurality of active
sites 114, such as a hydrogen atom or hydroxyl group.
[0138] Aluminophosphates (AlPO) catalysts are microporous materials
known to be useful as catalysts. AlPO catalysts include repeating
AlO.sub.4 and PO.sub.4 tetrahedra. It is possible to modify the
catalytic properties of a given AlPO catalyst through, for example,
the choice of topology, isomorphous substitution, deposition,
grafting, and the like. As shown in FIG. 3, the aluminum and/or
phosphorous atoms in the lattice may be isomorphously substituted.
An isomorphous substitution of an aluminum atom with a (+2) or (+3)
metal is illustrated as a Type I substitution, an isomorphous
substitution of a phosphorous atom with a (+4) or (+5) metal is
illustrated as a Type II substitution, and isomorphous
substitutions of both an aluminum and a phosphorous atom with (+4)
metal is illustrated as a Type III substitution. Exemplary metals
that may be isomorphously substituted to form a Type I substitution
include cobalt, copper, nickel, and zinc. Exemplary metals that may
be isomorphously substituted to form a Type II substitution include
titanium, vanadium, silicon, germanium, and tin.
[0139] One class of AlPO catalysts known to be useful as catalysts
is the silicon-containing silicoaluminophosphate (SAPO) catalysts.
Exemplary methods of preparing certain SAPO catalysts, are provided
in U.S. Pat. No. 4,440,871 to Lok, et al., U.S. Pat. No. 8,772,476
to Levy, et al., N. Jappar, Y. Tanaka, S. Nakata, and T. Tatsumi,
"Synthesis and Characterization of a New Titanium
Silicoaluminophosphate: TAPSO-37," Microporous and Mesoporous
Materials, Vol. 23, Issues 3-4, August 1998, pp. 169-178, J.
Paterson, et al., "Engineering Active Sites for Enhancing Synergy
in Heterogeneous Catalytic Oxidations, "Chemical Communications,
47, p. 517-519, 2011, and M. E. Potter, et al., "Role of Isolated
Acid Sites and Influence of Pore Diameter in the Low-Temperature
Dehydration of Ethanol," ACS Catal., 4(11), pp. 4161-4169, the
disclosures of each are hereby incorporated by reference.
[0140] The weight percentage of silicon in the formed catalyst can
also be determined. An exemplary method for determining the weight
percentage of silicon is by inductively coupled plasma. Typically,
silicon comprises from about 1 wt. % to about 10 wt. % of the total
weight of the catalyst. In still other embodiment, silicon
comprises a weight percentage of the total weight of the catalyst
up from as little as 1 wt. %, 1.5 wt. %, 2 wt. %, 2.5 wt. % to as
much as 6 wt. %, 7 wt. %, 8 wt. %, 9 wt. %, 10 wt. %, or within any
range defined between any pair of the foregoing values.
[0141] One exemplary microporous SAPO catalyst, SAPO-5, is
illustrated in FIG. 4A. SAPO-5 is a silicon-containing
aluminophosphate or silicoaluminophosphate catalyst with the
International Zeolite Association (IZA) framework code AFI as
described in the Atlas of Zeolite Framework Types, 6.sup.th ed.,
Baerlocher, et al., Elsevier, Amsterdam (2007), the disclosure of
which is hereby incorporated by reference in its entirety. The
SAPO-5 catalyst comprises a plurality of micropores 110 having a
pore aperture of 7.3 .ANG.. The catalyst comprises a plurality of
silicon atoms 116 isomorphously substituted for phosphorous in the
framework, leading to the formation of active sites 114.
[0142] One exemplary microporous SAPO catalyst, SAPO-34, is
illustrated in FIG. 4B. SAPO-34 is a silicon-containing
aluminophosphate or silicoaluminophosphate catalyst with the
International Zeolite Association (IZA) framework code CHA. The
SAPO-34 catalyst comprises a plurality of micropores 110 having a
pore aperture of 3.8 .ANG.. The catalyst comprises a plurality of
silicon atoms 116 isomorphously substituted for phosphorous in the
framework leading to the formation of active sites 114.
[0143] One exemplary microporous SAPO catalyst, SAPO-37, is
illustrated in FIG. 4C. SAPO-34 is a silicon-containing
aluminophosphate or silicoaluminophosphate catalyst with the
International Zeolite Association (IZA) framework code FAUFAU as
described in the Atlas of Zeolite Framework Types, 6th ed.,
Christian Baerlocher, Lynne B. McCusker and David H. Olson,
Elsevier, Amsterdam (2007), the disclosure of which is hereby
incorporated by reference in its entirety. The SAPO-37 catalyst
comprises sodalite cages linked together through 6,6 (double-6)
secondary building units. Twelve of these sodalite cages are then
used to create a super-cage structure of which the pore-aperture
110 is 7.4 .ANG. and the internal diameter of the super-cage is in
the region of 12-14 .ANG.. The catalyst comprises a plurality of
silicon atoms 116 isomorphously substituted for phosphorous in the
framework, leading to the formation of active sites 114.
[0144] Other exemplary microporous catalysts include AlPO-11 (IZA
framework code AEL), AlPO-18 (IZA framework code AEI), AlPO-31(IZA
framework code ATO), AlPO-37 (IZA framework code FAU), AlPO-41 (IZA
framework code AFO), AlPO-44 (IZA framework code CHA), and
corresponding monometallic and bimetallic structures, wherein the
metal is selected from Mn, Fe, Cu, Mg, Cr, Co, Cu, Zn, Si, Ti, V,
and Sn. In one more particular embodiment, the catalyst is a SAPO
catalyst, such as SAPO-5, SAPO-11, SAPO-18, SAPO-31, SAPO-34,
SAPO-37, SAPO-41, or SAPO-44.
[0145] In one embodiment, the AlPO catalyst or SAPO catalyst is a
hierarchical porous (HP) catalyst. HP AlPO catalysts or HP SAPO
catalysts include pores on more than one length scale, such as the
illustrated hierarchical SAPO catalyst 108 illustrated in FIG. 2.
In a more particular embodiment, the HP AlPO catalyst or HP SAPO
catalyst includes bimodal pore distribution, such a first porous
framework 110 comprising a plurality of micropores and a second
porous framework 112 comprising a plurality of mesopores. In one
exemplary embodiment, the hierarchical catalyst includes a
plurality of micropores as little as 3 .ANG., 4 .ANG., 5 .ANG., 6
.ANG., as great as 7 .ANG., 8 .ANG., 9 .ANG., 10 .ANG., or within
any range defined between any two of the foregoing values, such as
3 .ANG. to 10 .ANG., 3 .ANG. to 6 .ANG., 3 .ANG. to 4 .ANG., 7
.ANG. to 10 .ANG., or 7 .ANG. to 8 .ANG.. In one exemplary
embodiment, the hierarchical catalyst includes a plurality of
mesopores as little as 15 .ANG., 20 .ANG., 25 .ANG., 30 .ANG., as
great as 35 .ANG., 40 .ANG., 45 .ANG., 50 .ANG., or within any
range defined between any two of the foregoing values, such as 15
.ANG. to 50 .ANG., 20 .ANG. to 40 .ANG., or 15 .ANG. to 40
.ANG..
[0146] The micropore framework 110 and mesopore framework 112 are
interconnected. Both the microporous framework 110 and mesoporous
framework 112 may include active sites 114, such as hydrogen atoms
or hydroxyl groups. Without wishing to be held to any particular
theory, it is believed that the micropores possess active sites for
catalyzing the Beckmann rearrangement reaction, while the mesopores
aid in diffusion of molecules into and out of the active sites.
[0147] Exemplary hierarchical AlPOs include HP Mn AlPO-5, reported
by Zhou, et al., "Synthesis of hierarchical MeAPO-5 molecular
sieves--Catalysts for the oxidation of hydrocarbons with efficient
mass transport," Microporous and Mesoporous Materials, Vol 161, pp.
76-83, 2012, and HP SiAlPO-5, reported by Danilina, et al,
"Influence of synthesis parameters on the catalytic activity of
hierarchical SAPO-5 in space-demanding alkylation reactions,"
Catalysis Today, Vol. 168(1), pp. 80-85, 2011.
[0148] Referring next to FIG. 5, an exemplary hierarchical SAPO
catalyst 108 is illustrated. As shown in FIG. 5, the exemplary
hierarchical SAPO catalyst includes both a plurality of micropores
110 and one or more mesopores 112. The micropores illustrated in
FIG. 5 are formed by the crystal lattice of the repeating AlO.sub.4
and PO.sub.4 tetrahedra, which may be isomorphously substituted
with a silicon atom 116. As illustrated in FIG. 5, the SAPO
catalyst may include Type II substitutions in the micropores,
providing an available proton extending from the lattice into the
micropore as a potential Bronsted acid active site 114. As further
illustrated in FIG. 5, the SAPO may also include Type II
substitutions in the much larger mesopores, providing both protons
and/or hydroxyl groups extending from the lattice to serve as a
potential Bronsted acid active site 114. Without wishing to be held
to any particular theory, it is believed that the presence of
silanols may provide desirable properties in the catalyst, such as
additional hydrophilicity, additional acid sites, the potential to
functionalize other active sites, a change in surface area,
improved acid site density, and improved acid site strength.
[0149] As shown in FIG. 5, the micropore framework 110 and mesopore
framework 112 are interconnected. Without wishing to be held to any
particular theory, it is believed that the micropores 110 possess
active sites for catalyzing the Beckmann rearrangement reaction,
while the mesopores 112 aid in diffusion of molecules into and out
of the active sites. The micropores 110 have the same pore aperture
as the microporous SAPO catalyst on which the hierarchical catalyst
is based. In contrast, the mesopore 112 in the hierarchical SAPO
catalyst 108 illustrated in FIG. 5 has a pore diameter larger than
pore aperture of the surrounding micropores 110.
[0150] In one exemplary embodiment, the hierarchical catalyst
includes a plurality of micropores having a total volume as little
as 0.05 cm.sup.3/g, 0.07 cm.sup.3/g, 0.10 cm.sup.3/g, 0.12
cm.sup.3/g, as great as 0.14 cm.sup.3/g, 0.19 cm.sup.3/g, 0.20
cm.sup.3/g, or within any range defined between any two of the
foregoing values, such as 0.05 cm.sup.3/g to 0.20 cm.sup.3/g or
0.10 cm.sup.3/g to 0.14 cm.sup.3/g, and a plurality of mesopores
having a total volume as little as 0.08 cm.sup.3/g, 0.10
cm.sup.3/g, 0.11 cm.sup.3/g, as great as 0.12 cm.sup.3/g, 0.15
cm.sup.3/g, 0.17 cm.sup.3/g, 0.20 cm.sup.3/g, or within any range
defined between any two of the foregoing values, such as 0.08
cm.sup.3/g to 20 cm.sup.3/g or 0.10 cm.sup.3/g to 0.15 cm.sup.3/g.
In one exemplary embodiment, the hierarchical catalyst has more
surface area and/or pore volume than the corresponding microporous
material
[0151] In one exemplary embodiment, the hierarchical catalyst is an
AlPO selected from HP AlPO-5, HP AlPO-11, HP AlPO-18, HP AlPO-31,
HP AlPO-34, HP AlPO-37, HP AlPO-41, HP AlPO-44, and monometallic
and bimetallic structures thereof, wherein the metal is selected
from Mn, Fe, Cu, Mg, Cr, Co, Cu, Zn, Si, Ti, V, and Sn. In one
exemplary embodiment, the metal is cobalt. In a more particular
embodiment, the hierarchical catalyst is a hierarchical porous (HP)
cobalt AlPO catalyst, such as HP Co AlPO-5. In one exemplary
embodiment, the metal is titanium. In a more particular embodiment,
the hierarchical catalyst is a hierarchical porous titanium AlPO
catalyst, such as HP Ti AlPO-5. In one exemplary embodiment, the
hierarchical catalyst is bimetallic, wherein the metals are cobalt
and titanium. In a more particular embodiment, the hierarchical
catalyst is a hierarchical porous bimetallic cobalt and titanium
AlPO catalyst selected from the group consisting of HP Co Ti
AlPO-5, HP Co Ti AlPO-11, HP Co Ti AlPO-18, HP Co Ti AlPO-31, HP Co
Ti AlPO-34, HP Co Ti AlPO-37, HP Co Ti AlPO-41, HP Co Ti AlPO-44.
In a more particular embodiment, the hierarchical catalyst is a
hierarchical porous bimetallic cobalt and titanium AlPO catalyst,
such as HP Co Ti AlPO-5.
[0152] In one exemplary embodiment, the hierarchical catalyst is a
hierarchical porous (HP) SAPO catalyst, such as HP SAPO-5, HP
SAPO-11, HP SAPO-18, HP SAPO-31, HP SAPO-34, HP SAPO-37, HP
SAPO-41, and HP SAPO-44.
[0153] In one exemplary embodiment, the hierarchical SAPO catalyst
is selected from a hierarchical SAPO-5 catalyst, a hierarchical
SAPO-34 catalyst, and a hierarchical SAPO-37 catalyst. In one
exemplary embodiment, the hierarchical SAPO catalyst is selected
from a hierarchical SAPO-5 catalyst and a hierarchical SAPO-34
catalyst. In one exemplary embodiment, the hierarchical SAPO
catalyst is a hierarchical SAPO-5 catalyst. In one exemplary
embodiment, the hierarchical SAPO catalyst is a hierarchical
SAPO-34 catalyst. In one exemplary embodiment, the hierarchical
SAPO catalyst is a hierarchical SAPO-37 catalyst.
[0154] In one embodiment, hierarchical catalysts, such as
hierarchical AlPO and SAPO catalysts, may be formed using a
soft-templating technique, as illustrated in FIG. 6. As illustrated
in FIG. 6, an organosilane surfactant 120, such as
dimethyloctadecyl[(3-(trimethoxysilyl)propyl] ammonium chloride
(DMOD), was used in combination with a structure directing agent
(SDA) 122 and metal precursors 124. Exemplary structure directing
agents 122 include triethylamine and triethylammonium hydroxide.
Exemplary metal precursors include aluminum isopropoxide. DMOD is
an illustrative surfactant 120 containing an 18 carbon chain and a
silicon-containing head. Without wishing to be held to any
particular theory, it is believed that the silica portion of the
surfactant is incorporated into the SAPO framework, and upon
calcination of the organic hydrophobic tail additional silanol
sites may be formed. These additional sites may also provide active
sites for the Beckmann rearrangement.
[0155] Referring to FIG. 6, in an exemplary embodiment, a silicon
source, such as silica, is added dropwise, to a mixture of
surfactant 120, SDA 122, and metal precursor 124 and stirred. The
resulting material is crystalized to form the hierarchical porous
SAPO material 108, including both a plurality of micropores 110
from the SAPO crystalline structure, and a plurality of mesopores
112 from the surfactant.
[0156] In one exemplary embodiment, the surfactant includes a
carbon chain of as little as 5 carbons, 8 carbons, 10 carbons, 15
carbons, as great as 18 carbons, 20 carbons, 25 carbons, 30
carbons, or greater, or within any range defined between any two of
the foregoing values, such as 5 to 30 carbons, 8 to 25 carbons, or
15-20 carbons. In one exemplary embodiment, the surfactant includes
a silicon-containing head group. In another exemplary embodiment,
the surfactant includes a polar head group containing at least one
of carbon, nitrogen, silicon, and phosphorous.
[0157] In one embodiment, the hierarchical catalyst is formed from
a ratio of aluminum:phosphorous:SDA:water:silica:surfactant of
about 1 Al:1 P:1 SDA:65 H.sub.2O:0.15 Si:0.05 surfactant. In one
embodiment, the hierarchical catalyst is formed from a ratio of
aluminum:phosphorous:SDA:water:silica:surfactant of about 1 Al:1
P:0.8 SDA:50 H.sub.2O:0.15 Si:0.05 surfactant. Exemplary SDAs
include triethylamine and triethylamine hydroxide. Exemplary
surfactants include DMOD.
[0158] In one embodiment, the hierarchical catalyst is crystallized
at a temperature of about 200.degree. C. for about 24 hours.
[0159] In one embodiment, the hierarchical catalyst is phase pure.
In some embodiments, the hierarchical catalyst is a SAPO material
that contains amorphous silicon in an amount as little as 1 wt. %,
0.5 wt. %, 0.1 wt. %, 0.05 wt. %, 0.01 wt. %, 0 wt. %, or within
any range defined between any two of the foregoing values.
[0160] In one embodiment, hierarchical catalysts, such as
hierarchical AlPO and SAPO catalysts, may be formed by post
synthetic demetallation of a microporous framework. Exemplary
reactants for demetallation of a zeolite microporous framework
include basic reagents, such as sodium hydroxide, and acidic
reagents, such as hydrochloric acid. In one exemplary embodiment, a
microporous catalyst is added to a base, such as sodium hydroxide,
tetrapropylammonium hydroxide with tetrapropylammonium bromide, or
to an acid, such as hydrochloric acid. In one embodiment, the
microporous catalyst is added to the base or acid in the presence
of a surfactant. In one embodiment, the microporous catalyst is
added to the base or acid without a surfactant. The material is
partially digested, such as at a temperature between 298K and 373K
for about 30 minutes. Following treatment, the partially digested
material is calcined under air, such as at a temperature of about
550.degree. C. for 16 hours, to form the mesoporous material.
[0161] In one embodiment, adsorption testing of the hierarchical
porous material produces a Type IV isotherm with hysteresis,
indicative of polymolecular adsorption of a porous adsorbent.
[0162] In one embodiment, the hierarchical porous materials have
unit cells consistent with the unit cell of the corresponding
microporous materials.
[0163] In one embodiment, the hierarchical porous materials have
weak, isolated Bronsted acid sites. In one embodiment, the
hierarchical porous materials do not have Lewis acidity.
[0164] In one embodiment, the hierarchical porous materials have
isolated, tetrahedral silicon sites. In some embodiments, these
sites may be similar to isolated, tetrahedral silicon sites of the
corresponding microporous material. In some embodiments, the
hierarchical porous materials include silanol active sites.
Example 1
Synthesis of a Microporous SAPO-5 (SAPO-5), a Hierarchically Porous
SAPO-5 (HP SAPO-5)
[0165] The synthetic protocol for the isomorphous substitution of
Si into the hierarchically porous AFI framework is described below.
An equivalent method was deployed for the synthesis of the
microporous analogue without the inclusion of the surfactant
dimethyloctadecyl[(3-(trimethoxysilyl)propyl] ammonium chloride
(DMOD).
[0166] Aluminum isopropoxide (6.807 g, Aldrich) was added to a
Teflon beaker with phosphoric acid (2.28 ml, 85% in H.sub.2O,
Aldrich) and water (10 ml) and vigorously stirred for 1.5 hours
until a homogeneous solution was formed. DMOD (1.2 ml, 72% in
H.sub.2O, Aldrich) was added drop wise, followed immediately by
addition of triethylamine (3.7 ml, Aldrich) drop wise and then
water (20 ml). The resulting thicker solution was stirred for one
hour. Silica sol (0.771 ml, 40% in water, Aldrich) was added drop
wise and the gel was stirred for a further 1.5 hours to obtain a
white gel with the composition: 1 Al:1 P:0.8 TEA:50 H.sub.2O:0.15
Si 0.05 DMOD.
[0167] The gel was divided between three 23 ml Teflon-lined
stainless-steel autoclaves which were transferred to a pre heated
fan assisted oven (WF-30 Lenton) at 200.degree. C. for 24
hours.
[0168] The white solid product from each autoclave was collected
via filtration and washed with 500 ml of deionized water. The
product was left to dry at 80.degree. C. overnight. The
as-synthesized catalyst was calcined in a tube furnace under a flow
of air at 550.degree. C. for 16 hours to produce a white solid.
Example 2
Synthesis of a Microporous SAPO-34 (SAPO-34) and a Hierarchically
Porous SAPO-34 (HP SAPO-34)
[0169] The synthetic protocol for the isomorphous substitution of
Si into the hierarchically porous CHA framework is described below.
An equivalent method was deployed for the synthesis of the
microporous analogue without the inclusion of the surfactant
dimethyloctadecyl[(3-(trimethoxysilyl)propyl]ammonium chloride
(DMOD).
[0170] Aluminium isopropoxide (4.5450 g, Aldrich) was added to a
Teflon beaker with tetraethylammonium hydroxide (TeaOH) (9.14 ml,
35% in H.sub.2O, Aldrich) and stirred for one hour. Fumed silica
(0.2 g) was added slowly and stirred for ten minutes. DMOD (0.8 ml,
72% in water, Aldrich) was added drop wise and the white opaque gel
stirred for one hour. Deionized water (14 ml) was added drop wise
followed directly by phosphoric acid (1.5 ml, 85% in H2O, Aldrich).
The gel was stirred vigorously for two hours to produce a white gel
with the composition: 1 Al:1 P:1 TeaOH:65 H.sub.2O:0.15 Si:0.05
DMOD.
[0171] The contents of the gel were divided between two 23 ml
Teflon-lined stainless-steel autoclaves which were transferred to a
pre heated fan assisted oven (WF-30 Lenton) at 200.degree. C. for
24 hours.
[0172] The white solid product from each autoclave was collected
via filtration and washed with 500 ml of deionized water. The
product was left to dry at 80.degree. C. overnight. The
as-synthesized catalyst was calcined in a tube furnace under a flow
of air at 550.degree. C. for 16 hours to produce a white solid.
Example 3
Synthesis of a Microporous SAPO-37 (SAPO-34) and a Hierarchically
Porous SAPO-37 (HP SAPO-37)
[0173] The synthetic protocol for the isomorphous substitution of
Si into the hierarchically porous FAU framework is described below.
An equivalent method was deployed for the synthesis of the
microporous analogue without the inclusion of the surfactant
dimethyloctadecyl[(3-(trimethoxysilyl)propyl]ammonium chloride
(DMOD).
[0174] Boehmite (5.5844 g) was added slowly to a solution of
phosphoric acid (85 wt. %, 9.251 g) and deionized water (10 g) in a
Teflon beaker. The thick white mixture was stirred magnetically for
7 hours and labelled solution A.
[0175] Solution B was prepared by adding DMOD (72 wt. %, 2 ml) drop
wise to a solution of tetra propyl ammonium hydroxide, TPAOH (40
wt. %, 38.689 g) and tetra methyl ammonium hydroxide. TMAOH (0.365
g), followed by fumed silica (1 g). Solution B was stirred for 2
hours.
[0176] Once both solution A and B were homogenized solution B was
added drop wise to solution A to create a very thick mixture. This
was stirred for 68 hours. Then transferred to autoclaves and
crystallized at 200.degree. C. for 24 hours.
[0177] The resulting white solid was filtered with 1 liter of
deionized water and left to dry in an oven (80.degree. C.)
overnight. The catalyst was then calcined at 550.degree. C. for 16
hours under air to yield a white solid.
Example 4
Characterization of Catalysts
Powder X-Ray Diffraction
[0178] Powder X-Ray diffraction (pXRD) patterns were obtained using
a Bruker D2 diffractometer using Cu K al radiation where
.lamda.=1.54056. Low angle X-ray diffraction patterns were obtained
using a Bruker C2 GADDS diffractometer. The hierarchical catalysts
were confirmed to retain their parent unit cells via pXRD (FIGS.
7A-7C). The corresponding lattice parents were similar to the
microporous analogues (see, e.g. FIGS. 8A, 8B, 9A and 9B) and
confirmed that the hierarchical catalysts were phase pure and
retained their crystallinity.
[0179] As shown in FIG. 7A-7C, the phase purity and crystallinity
of all materials were confirmed via powder X-ray diffraction. All
signals can be attributed to the corresponding AFI, CHA, or FAU
structure according to the IZA database. The CellRef refinement
values for the calcined AFI and CHA catalysts are presented as
FIGS. 8 and 9. The results were consistent with the expected AFI
framework for SAPO-5 and HP SAPO-5, and the expected CHA framework
for SAPO-34 and HP SAPO-34.
[0180] Low angle XRD measurements of the hierarchical samples,
shown in the inserts of FIGS. 7A and 7B, revealed a peak at low
angles, which was absent in the microporous samples. This peak
indicates the presence of mesopores in the hierarchical
samples.
BET Surface Area
[0181] Nitrogen adsorption desorption experiments were performed
using a Gemini 2575 Brunauer-Emmett-Teller (BET) Apparatus with
nitrogen as the adsorption gas at 77K.
[0182] BET measurements for each catalyst are presented in Table 1.
As shown in Table 1, the hierarchical catalysts had higher overall
surface area (S.sub.BET), higher micropore volume (V.sub.micro),
and higher mesopores volume (V.sub.meso) than the corresponding
microporous materials.
TABLE-US-00001 TABLE 1 BET properties. Sample S.sub.BET
(m.sup.2g.sup.-1) V.sub.micro (cm.sup.3g.sup.-1) V.sub.meso
(cm.sup.3g.sup.-1) SAPO-5 137 0.06 0.04 HP SAPO-5 237 0.07 0.11
SAPO-34 407 0.14 0.09 HP SAPO-34 566 0.19 0.17 SAPO-37 623.6 0.26
0.11 HP SAPO-37 482.2 0.11 0.27
[0183] The N.sub.2 adsorption desorption isotherms of HP SAPO-5, HP
SAPO-34, and SAPO-37, shown in FIGS. 10A-10C, are typical of a type
IV isotherm with a hysteresis. The exhibited type IV isotherms with
hysteresis for the hierarchical porous materials are consistent
with the presence of mesopores in the corresponding hierarchical
frameworks.
[0184] The BJH adsorption pore volume curves provided as inserts in
FIGS. 10A-10C further confirm the presence of mesopores having a
diameter between about 20 .ANG. and about 60 .ANG. in the
hierarchical systems, as well as the absence of such mesopores in
the microporous materials.
[0185] The hierarchical catalysts exhibited type IV isotherms
(FIGS. 10A-10C) with hysteresis, which is consistent with the
presence of mesopores. The surface areas and mesopore volumes were
also higher in the hierarchical catalysts compared to the
microporous analogues, consistent with incorporation of mesopores
into the hierarchical frameworks (Table 1). The BJH adsorption pore
distribution curves further support the presence of mesopores in
the hierarchical systems and the absence of such mesopores in the
microporous catalysts (FIGS. 10A-10C).
Scanning Electron Microscopy and Transmission Electron Microscopy
Images
[0186] The hierarchical materials porosity was further evaluated
via scanning electron microscopy (SEM) (FIGS. 11-14). FIG. 11A
illustrates the elongated hexagonal crystals of microporous SAPO-5.
FIG. 11B illustrates the crystals of the hierarchical porous HP
SAPO-5. FIG. 11C illustrates cubic crystals of microporous SAPO-34.
FIG. 11D illustrates the crystals of the hierarchical porous HP
SAPO-34. The hierarchical porous material images in FIGS. 11B and
11D depict larger particles than the corresponding microporous
materials in FIGS. 11A and 11C. The hierarchical materials appear
to include aggregates of smaller crystals.
[0187] As shown in FIGS. 12A and 12B, the HP SAPO-34 is composed of
blocky, well-dispersed crystals, as well as larger agglomerations
of possible intergrown and less-dispersed crystals.
[0188] The SEM images indicated the samples have a fairly uniform
composition throughout the sample. As shown in the SEM image and
corresponding energy dispersive (EDS) data of FIG. 13, the
composition of the HP SAPO-34 is fairly uniform. As shown in the
SEM image and corresponding energy dispersive (EDS) data of FIG.
14, the composition of the HP SAPO-5 is fairly uniform.
[0189] The hierarchical materials porosity was further evaluated
via transmission electron microscopy (TEM) (FIGS. 15-19). The TEM
images indicated the samples having a fairly uniform composition
throughout the sample, and revealed fine mesoporosity in both the
crystalline HP SAPOs (see FIGS. 17-19).
[0190] As shown in the TEM image an elemental analysis of FIG. 15,
the HP SAPO-5 material had regions of mesoporosity in the faulted
region 130. The elemental analysis of the ratio of Al:Si:P, was as
expected for a SAPO material.
[0191] The lattice crystal structure of each of the HP SAPO-5 and
HP SAPO-34 was confirmed. As shown in FIG. 16, the diffraction
pattern of the selected portion of the HP SAPO-5 material was
confirmed to be AFI. The elemental analysis in FIG. 15 is
consistent with the expected Al:P:Si ratio for a SAPO material.
[0192] From the TEM and diffraction patterns of HP SAPO-34 it was
possible to elucidate the rod like and elongated shapes of the
mesopores and their positioning perpendicular and parallel to the
rhombohedral basis vectors. It was clear that these mesopores were
well connected within the microporous network. (FIGS. 17, 18). As
shown in FIG. 17, the diffraction pattern of the selected portion
of the HP SAPO-5 material was confirmed to be AFI. The elemental
analysis in FIG. 17 is consistent with the expected Al:P:Si ratio
for a SAPO material. The two reflections (101) (RHS ref1) and
(-1,1,1) (RHS ref 2) are equivalent to (100) and (101), the pores
therefore appear to have rod-like morphology, elongated parallel to
one or another to the rhombohedral basis vectors. As shown in FIG.
18, which includes a TEM image and diffraction pattern of HP
SAPO-34 from the same location, the indexing indicates that the
pores are elongated perpendicular to the (101) plane. This is
equivalent to the (100) of the rhombohedral type unit cell.
[0193] The TEM image and EDS of the HP SAPO-34 in FIG. 19 further
show the presence of some secondary porosity 132.
Example 5
Vapor Beckmann Rearrangement of Cyclohexanone Oxime and
Cyclooctanone Oxime
[0194] The catalytic performance of the hierarchical HP SAPO-5 and
HP SAPO-34 samples was compared to that of the microporous SAPO-5
and SAPO-34 samples. A vapor Beckmann rearrangement of
cyclohexanone oxime (see FIG. 1A) was performed for each pair of
hierarchical and microporous catalysts.
[0195] A cylindrical quartz fixed bed reactor (4 mm in diameter)
with a quartz frit was packed with 0.5 cm layer of glass beads (1
mm), a 4 cm layer of pelletized catalyst (0.2 g), and a further 20
cm of glass beads (1 mm) were placed inside the heater unit of the
reactor assembly. The sample was then pre-treated at 673K under a
50 ml/min flow of helium gas for one hour. The temperature was then
lowered to 598K and the flow of helium was reduced to 33.3 ml/hour.
A liquid feed of 100 g/litre of cyclohexanone oxime in ethanol was
fed into the reactor to maintain a WHSV of 0.79 hr.sup.-1 that was
controlled by an electronic syringe pump. A sample was taken after
every hour when steady state was achieved. Samples were analyzed
using a PerkinElmer Glarus 480 gas chromatogram with FID and using
an Elite 5 column, the peak areas were calibrated using
pre-determined response factors with mesitylene as an internal
standard.
[0196] The feed solution for assessing the carbon balance using
mesitylene as the internal standard was composed of: Mesitylene:
0.444 g; Cyclohexanone oxime: 4.10 g; EtOH: 36.000 g
[0197] Performing an identical procedure to one described above the
following GC data was obtained at 598K, WHSV of 0.79 hr.sup.-1 with
HP SAPO-5 and by using the response factors it was possible to
calculate the number of moles from the peak areas.
[0198] FIG. 20A shows the conversion of the microporous SAPO-5 and
of the hierarchical HP SAPO-5, and FIG. 20B shows the selectivity
for .epsilon.-caprolactam of the reaction. FIG. 20C shows the
corresponding yield for the reactions.
[0199] FIG. 20D shows the conversion of the microporous SAPO-34 and
of the hierarchical HP SAPO-34, and FIG. 20E shows the selectivity
for .epsilon.-caprolactam of the reaction. FIG. 20F shows the
corresponding yield for the reactions.
[0200] As shown in FIGS. 20A-20F, the hierarchical catalysts
provided superior performance compared to the microporous
catalysts. The hierarchical catalysts were able to maintain both a
constant conversion (FIGS. 20A, 20D), and relatively constant
selectivity (FIGS. 20B, 20E), while the corresponding microporous
catalysts appeared to deactivate. For example the HP SAPO-5 retains
a >97% conversion whereas SAPO-5's activity started at 71% and
dramatically dropped to just 33% over 7 hours.
[0201] The performance of the industrial microporous catalyst
H--ZSM-5 and the mesoporous MCM-41 catalysts was also investigated.
The conversion of H-ZSM-5 and MCM-41 is shown in FIG. 20G, and the
selectivities for .epsilon.-caprolactam are shown in FIG. 20H. FIG.
20I shows the corresponding yield for the reactions.
[0202] The microporous H-ZSM-5 catalyst, similar to the microporous
SAPO-5 and SAPO-34, appeared to quickly deactivate. The mesoporous
catalyst MCM-41 was quickly deactivated and exhibited much lower
initial conversion and selectivity than the hierarchical
catalysts.
[0203] The hierarchical materials generally provided high
conversion and selectivity, as well as generally improved longevity
compared to the remaining materials. Without wishing to be bound by
any particular theory, it is believed that the microporous
framework of the hierarchical catalysts provided active sites for
the Beckmann rearrangement reaction, and that the connected
mesopores provided enhanced diffusion of the cyclic oximes and/or
lactams to and from the active sties.
[0204] An identical protocol was followed for the vapor phase
Beckmann rearrangement of the more sterically demanding
cyclooctanone oxime to form the corresponding caprylolactam (see
FIG. 1C).
[0205] FIG. 21A shows the conversion of the microporous SAPO-5 and
of the hierarchical HP SAPO-5, and FIG. 21B shows the selectivity
for the desired lactam. FIG. 21C shows the corresponding yield for
the reactions.
[0206] FIG. 21D shows the conversion of the microporous SAPO-34 and
of the hierarchical HP SAPO-34, and FIG. 21E shows the selectivity
for the desired lactam. FIG. 21F shows the corresponding yield for
the reactions.
[0207] FIG. 21G shows the selectivity of the microporous H-ZSM-5
and the mesoporous MCM-41, and FIG. 21H shows the selectivity for
the desired lactam. FIG. 20I shows the corresponding yield for the
reactions.
[0208] For the cyclooctanone oxime reaction, both hierarchical
catalysts provided relatively good selectivity.
[0209] With respect to SAPO-5 and HP SAPO-5, the selectivity was
seen to increase over time. Without wishing to be held to any
particular theory, this may suggest that that some of the original
strong acid sites become blocked during the course of the reaction,
leaving the desired weaker active sites to participate in the
reaction more often, which in turn results in higher selectivity to
the lactam. It is also possible that the acid sites are modified or
modulated over the course of the reaction, thereby becoming more
amenable/conducive to the desired selectivity over time. With
respect to SAPO-34 and HP SAPO-34, the selectivity to the lactam
remains fairly consistent during the course of the reaction.
[0210] As with the cyclohexanone oxime reaction, the hierarchical
catalysts retained their high activities with cyclooctanone oxime
over 7 hours, whereas the activities of the microporous catalysts
were reduced significantly. In particular, the HP SAPO-34 is just
as active in the rearrangement of cyclohexanone oxime as the
rearrangement of cyclooctanone oxime, but the activity of the
comparative microporous SAPO-34 in the rearrangement of
cyclooctanone oxime is much lower, similar to H-ZSM-5.
[0211] Without wishing to be held to any particular theory, it is
believed that this could be due to the reaction occurring in the
pore mouth of the catalyst, which would be inaccessible to the
larger cyclooctanone oxime. Hence by including mesopores into the
catalyst it is possible to increase the accessibility of the active
sites towards the bulky substrates resulting in higher conversions
than the microporous analogues. Alternatively, or in addition to
the above, the improvements seen in the hierarchical catalyst could
be ascribed to the presence of the additional silanol sites, as
these sites appear to be the common feature in both hierarchical
catalysts. These silanols may attenuate the hydrophobic properties
of the catalyst and this might result in the catalyst having
protection against deactivation.
[0212] As shown in FIGS. 20 and 21, the hierarchical catalysts
provided similar active sites compared to their microporous
analogues, while retaining high conversion levels over the course
of the observed reaction time.
[0213] The effect on the reaction of temperature was investigated.
As shown in FIG. 22A, a weight hourly space velocity (WHSV) of 0.79
hr.sup.-1 cyclohexanone oxime were provided to a reactor containing
0.2 g of catalyst as a 10 wt. % solution of the oxime in ethanol.
The reaction was run at 300.degree. C., 325.degree. C., 350.degree.
C., and 400.degree. C. The conversion and selectivity of the
reaction for .epsilon.-caprolactam as a function of time is shown
in FIGS. 22B and 22C.
[0214] As shown in FIG. 23A, a similar experiment was conducted
using HP SAPO-34 as the catalyst. The reaction was run at
300.degree. C., 325.degree. C., 350.degree. C., and 400.degree. C.
The conversion and selectivity of the reaction for
.epsilon.-caprolactam as a function of time is shown in FIGS. 23B
and 23C.
[0215] As shown in FIGS. 22A-22C and 23A-23C, both HP SAPO-5 and HP
SAPO-34 are stable in the vapor phase Beckmann rearrangement of
cylcohexanone oxime over a range of temperatures. High
selectivities and conversions are retained over the reaction time
and structural integrity of the catalyst was also maintained.
[0216] The effect on the reaction of oxime concentration was
investigated. As shown in FIG. 24A, cyclohexanone oxime was
provided to a reactor containing 0.2 g of catalyst as a 10 wt. %
solution of the oxime in ethanol. The reaction was run at
325.degree. C.
[0217] The flow rate of cyclohexanone oxime was varied between 0.8
hr.sup.-1 and 1.6 hr.sup.-1. The conversion and selectivity of the
reaction for .epsilon.-caprolactam as a function of time is shown
in FIGS. 24B and 24C.
[0218] As shown in FIG. 23A, a similar experiment was conducted
using HP SAPO-34 as the catalyst. The reaction was run at 0.8
hr.sup.-1, and 1.6 hr.sup.-1 cyclohexanone oxime. The conversion
and selectivity of the reaction for .epsilon.-caprolactam as a
function of time is shown in FIGS. 25B and 25C.
[0219] As shown in FIGS. 24 and 25, HP SAPO-5 and HP SAPO-34
maintain high conversion and selectivity over a range of WHSV
values, further supporting the stability and versatility of the
catalysts.
Example 6
Liquid Beckmann Rearrangement of Cyclohexanone Oxime and
Cyclooctanone Oxime
[0220] Cyclohexanone oxime (0.1 g), internal standard anhydrous
chlorobenzene (0.1 g) and freshly calcined catalyst (0.1 g) were
added to anhydrous benzonitrile (20 ml) in a 3-necked batch reactor
flask at 130.degree. C. under reflux and nitrogen. The resulting
suspension was stirred magnetically at the reaction temperature.
Over the course of the reaction aliquots of the reaction mixture
were taken and analyzed via GC.
[0221] The conversions of the HP SAPO-5, HP SAPO-34 and HP SAPO-37
catalysts in the liquid phase rearrangement of cyclododecanone
oxime to laurolactam as a function of time are provided in FIG. 26.
The reaction was run at 130.degree. C. under nitrogen with PhCN (20
ml) as the solvent. 0.1 g of the catalyst was provided to the
reactor along with 0.1 g of the oxime, and allowed to reflux for 7
hours.
[0222] As shown in FIG. 26, comparative performance of the
microporous and hierarchical catalysts in the liquid-phase Beckmann
rearrangement of cyclododecanone oxime, with the hierarchical
analogues displaying enhanced rates at lower contact times. In
addition, the smaller pore (3.8 .ANG.) microporous SAPO-34 has a
much inferior performance (mass-transfer and diffusion limitations)
compared with its hierarchical analogue, thereby highlighting the
catalytic potential of the latter with bulkier substrate molecules.
HP SAPO-5, HP SAPO-34 and HP SAPO-37 are all active in the liquid
phase Beckmann rearrangement of cycloddodecanone oxime to
laurolactam. They each reach 100% conversion with 100% selectivity
by 5 hours. All the HP SAPOs are more active than their microporous
analogues, illustrating the benefits of having more accessible
active sites within a hierarchically porous framework.
[0223] The effect on the reaction of cyclododecanone oxime of the
amount of catalyst was investigated. As shown in FIGS. 27A-27C, the
amount of catalyst was varied from 0.02 g catalyst per 0.1 g oxime
to 0.1 g catalyst per 0.1 g oxime. FIG. 27A illustrates the results
for HP SAPO-5. FIG. 27B illustrates the results for HP SAPO-34.
FIG. 27C illustrates the results for HP SAPO-37.
[0224] The effect on the reaction of cyclododecanone oxime
catalyzed with HP SAPO-34 of the temperature was investigated. The
results are provided in Table 2.
TABLE-US-00002 TABLE 2 Conversion, selectivity, and yield of
cyclododecanone oxime at various temperatures Temperature Time
Conversion Selectivity Yield (.degree. C.) (minutes) (mol %) (mol
%) (mol %) 110 60 26.3 100 26.3 110 120 44.2 100 44.2 110 180 56.4
100 56.4 110 240 67.8 100 67.8 110 300 74.0 100 74.0 110 360 78.6
100 78.6 110 420 83.0 100 83.0 130 60 58.6 100 58.6 130 120 86.9
100 86.9 130 180 94.4 100 94.4 130 240 97.7 100 97.7 130 300 98.8
100 98.8 130 360 100 100 100 130 420 100 100 100 150 60 82.1 100
82.1 150 120 94.9 100 94.9 150 180 98.4 100 98.4 150 240 100 100
100 150 300 100 100 100 150 360 100 100 100 150 420 100 100 100
[0225] As shown in Table 2, HP SAPO-34 has been tested over a range
of reaction temperatures including 110.degree. C., 130.degree. C.
and 150.degree. C. The rate of reaction improved significantly as a
function of increasing temperature. Under all the conditions the
catalyst reaches maximum conversion with 100% selectivity to the
desired lactam.
[0226] Referring next to FIGS. 28A-28C, a recycle experiment was
conducted for each catalyst for the Beckmann rearrangement of
cyclododecanone oxime. Cyclohexanone oxime, internal standard
anhydrous chlorobenzene, and freshly calcined recovered catalyst
were added to anhydrous benzonitrile in a 3-necked batch reactor,
with a 1:1:1:30.6 weight ratio respectively, at 130.degree. C.
under reflux and nitrogen. The resulting suspension was stirred
magnetically at the reaction temperature. Over the course of the
reaction aliquots of the reaction mixture were taken and analyzed
via GC. Conversion was determined after 7 hours. FIG. 28A
illustrates the change in percent conversion for each recycle using
the HP SAPO-34 catalyst. FIG. 28B illustrates the change in percent
conversion for each recycle using the HP SAPO-5 catalyst. FIG. 28C
illustrates the change in percent conversion for each recycle using
the HP SAPO-34 catalyst.
[0227] As illustrated in FIGS. 28A-28C, HP SAPO-5, HP SAPO-34 and
HP SAPO-37 all retain structural integrity and demonstrated
sustained catalytic performance (near 100% conversion) after the
recycle tests.
Example 7
Characterization of Catalysts Acidic Properties
[0228] From Example 4, it was observed that the hierarchical
catalysts exhibited improved longevity in the reactions. This
suggests minimal coking is occurring in these systems. Coking can
occur if acid sites are too strong and therefore, do not permit the
desorption of the product, or it can occur if diffusion is hindered
therefore preventing the egress of products. Without wishing to be
bound by any particular theory, it is believed that the
hierarchical catalysts acidity is attenuated by the presence of
mesopores and that the mesopores are aiding the mass transport of
substrates and products.
[0229] Therefore to further establish the origin of these
improvements, the structural properties (N.sub.2 adsorption
desorption isotherms and electron microscopy) and acidic properties
(NMR, TPD-NH.sub.3 FT-IR using CO and collidine as a probe
molecule) of the catalysts were further investigated.
Solid State NMR
[0230] FIG. 29A illustrates the .sup.27Al MAS NMR spectra of
SAPO-5. FIG. 29B illustrates the .sup.27Al MAS NMR spectra of HP
SAPO-5. FIG. 30A illustrates the .sup.27Al MAS NMR spectra of
SAPO-34. FIG. 30B illustrates the .sup.27Al MAS NMR spectra of HP
SAPO-34.
[0231] FIG. 29C illustrates the .sup.31P MAS NMR spectra of SAPO-5.
FIG. 29D illustrates the .sup.31P MAS NMR spectra of HP SAPO-5.
FIG. 30C illustrates the .sup.31P MAS NMR spectra of SAPO-34. FIG.
30D illustrates the .sup.31P MAS NMR spectra of HP SAPO-34.
[0232] The .sup.27Al and .sup.31P MAS NMR support the formation of
a fully condensed crystalline AlPO framework. The .sup.27Al MAS/NMR
has a strong signal at around -35 to -37 ppm indicating the
presence of tetrahedral aluminium. Although there are weaker
signals at around -16 and 8 ppm indicating the presence of hydrated
aluminium centres which are octahedral and five coordinate
respectively.
[0233] FIG. 29E illustrates the .sup.29Si MAS NMR spectra of SAPO-5
and HP SAPO-5. The spectra may suggest that the presence of the
surfactant encourages the formation of silicon islands and results
in silica nests, which are absent in the microporous system.
[0234] FIG. 30E illustrates the .sup.29Si MAS NMR spectra of
SAPO-34 and HP SAPO-34. The Si NMR supports the formation of
isolated silicon sites which are comparable to the microporous
analogue.
[0235] FIG. 31A illustrates the .sup.27Al MAS NMR spectra of HP
SAPO-37. FIG. 31B illustrates the .sup.31P MAS NMR spectra of
SAPO-37. FIG. 31C illustrates the .sup.29Si MAS NMR spectra of
SAPO-37.
FT-IR, NH.sub.3, CO and Collidine Probes
[0236] To further investigate the acidic properties of the
resulting hierarchical catalysts FT-IR with probe molecules (CO and
collidine) was used. FT-IR permitted direct observation of the
hydroxyl region of the hierarchical SAPOs.
[0237] The FT-IR spectra of SAPO-5 and HP SAPO-5 are presented in
FIG. 32A, and the FT-IR spectra of SAPO-34 and HP SAPO-34 are
presented in FIG. 32B. Both catalysts had bands attributable to
POH/AlOH (3678 cm.sup.-1) defect sites and bands (3628-3600
cm.sup.-1) arising from the substitution of silicon into the
framework (Si--OH--Al). There was also an additional band at 3746
cm.sup.-1 that were assigned to defect Si--OH groups which were
marginal in the FT-IR of the microporous catalysts indicating that
these silanol sites were formed via the calcination of the
surfactant.
[0238] A comparison of the FT-IR spectra for HP SAPO-5 and HP
SAPO-34 is presented in FIG. 32C. As shown in FIG. 32C, the
hierarchical porous materials share a common Si--OH peak
(.about.3750 cm.sup.-1) that is significantly greater than in the
spectra of the corresponding microporous SAPO-5 and SAPO-34 (see
FIGS. 32A and 32B).
[0239] The quantity and strength of acid sites was investigated
using a programmed temperature desorption of ammonia (TPD) for
SAPO-5 and HP SAPO-5, the results of which are presented in FIG.
33A, for SAPO-34 and HP SAPO-34, the results of which are presented
in FIG. 33B, and for SAPO-37 and HP SAPO-37, the results of which
are presented in FIG. 33C.
[0240] All TPD measurements were performed on a custom built system
using TCD detectors to monitor ammonia concentration. Samples were
pre-treated by heating at 10.degree. C./min to 550.degree. C. in a
20% O.sub.2/Helium mixture for 2 hours. The samples were exposed to
ammonia and allowed to equilibrate at 150.degree. C. for 8 hours.
Desorption was performed in flowing at 10.degree. C./min to
600.degree. C. and held for 40 minutes at 600.degree. C.
[0241] The results indicated similar acid strength between SAPO-5
and HP SAPO-5 (see FIG. 33A), between SAPO-34 and HP SAPO-34 (see
FIG. 33B), and between SAPO-37 and HP SAPO-37 (see FIG. 33C).
Without wishing to be held to any particular theory, it is believed
that the slight additional feature in FIG. 33B at 250-300.degree.
C. may be attributable to the weakly acidic silanol sites and
further allude to the presence of the SiOH sites in the
hierarchical catalysts.
[0242] While the FT-IR spectra provided information about the types
of hydroxyl groups present, it did not discriminate regarding the
strength and type of acid sites present in the hierarchically
porous materials. The acid strength of these materials is believed
to be related to the ensuing catalytic properties of the materials.
Without wishing to be held to any particular theory, the Beckmann
rearrangement with solid acid catalysts is believed to rely on a
subtle balance of acidity within the active site; it needs to be
strong enough to permit the reaction to perform but weak enough to
enable the basic lactam to desorb before over reacting, coke
formation and deactivation.
[0243] Characterization of the strength of the acid sites was
investigated using probe molecules such as CO and
2,4,6-trimethylpyridine (collidine) with the FT-IR to indirectly
study the acidity of the material. The absence of absorption
.gtoreq.2190 cm.sup.-1 in FIGS. 34A and 34B indicates that no Lewis
acidity was observed in either the HP SAPO-5 or the HP SAPO-34
materials, and that only Bronsted acid sites were present.
Evaluation of the band shift of the Bronsted acid sites between 260
and 286 cm.sup.-1 upon interaction with CO revealed that both
samples primarily consisted of moderate strength Bronsted acid
sites. By integrating the area of the Bronsted acid peaks it was
possible to ascertain that the HP SAPO-34 has more total Bronsted
acidity, as well as some stronger acid sites (larger peak shift)
compared the HP SAPO-5 sample. These results were similar to the
ammonia temperature programmed desorption results shown in FIGS.
33A and B, and the FT-IR collidine data shown in FIGS. 35A and 35B.
The strength of acidity of the hierarchical catalysts was similar
to the acid strength of microporous catalysts, indicating that the
hierarchical porous material has similar active sites to those of
the corresponding microporous materials.
[0244] FT-IR with CO demonstrated that in both HP SAPO-5 (see FIG.
34A) and HP SAPO-34 (see FIG. 34B) no Lewis acidity was observed,
characterized by an absence of absorption .gtoreq.2190 cm.sup.-1.
Instead only Bronsted acid sites were present. Evaluation of the
band shift of the Bronsted acid sites between 260-286 cm.sup.-1
upon interaction with CO (Table 2) revealed that both samples
primarily consisted of moderate strength Bronsted acid sites. Table
3 provides the position of maxima of OH Bronsted sites and their
shifts (.DELTA.v.sub.OH) upon CO Adsorption at 80K on HP SAPO-34,
HP SAPO-5 and their microporous analogues.
TABLE-US-00003 TABLE 3 Position of Maxima of OH Bronsted sites
v.sub.OH v.sub.OH . . . CO .DELTA.v.sub.OH Catalysts (cm.sup.-1)
(cm.sup.-1) (cm.sup.-1) SAPO-5 OHA 3638 3368 270 HP SAPO-5 OHA 3637
3369 268 SAPO-34 OHA 3633 3347 286 OHB 3610 3281 329 HP SAPO-34 OHA
3633 3347 286 OHB 3612 3281 331
[0245] By integrating the area of the Bronsted acid peaks it was
possible to ascertain that the HP SAPO-34 has more total Bronsted
acidity, as well as some stronger acid sites (larger peak shift)
compared the HP SAPO-5 sample. This trend was in good agreement
with the ammonia temperature programme desorption results (FIGS.
33A and 33B). The results in Table 3 further indicated that the
hierarchical catalysts have active sites that are similar to those
in the corresponding microporous catalysts.
[0246] In order to further explore the acid sites within the
hierarchical SAPOs, collidine was used as a probe with FT-IR.
Collidine was chosen for three key reasons: i) It is a sterically
demanding probe and therefore provides insight into the
accessibility of the acidic sites, ii) It can assess the strength
of interaction between the OH . . . N, by quantifying the bands at
1652 cm.sup.-1 and 1637 cm.sup.-1, hence allude to the strength of
interaction between the substrates in the Beckmann rearrangement
and finally iii) It is stable at high temperatures and therefore
the strength of interaction can be screened over temperatures
typical of the reaction conditions.
[0247] FIG. 35A illustrates the results of the collidine adsorption
on HP SAPO-5. The collidine interacts with all of the OH group
types after 150.degree. C. desorption. Essentially all the
collidine is desorbed by 450.degree. C. FIG. 35B illustrates the
distribution of weak, medium, and strong acid sites in the SAPO-5
and HP SAPO-5 catalysts. As shown in FIG. 35B, the HP SAPO-5
catalyst generally contains a greater number of weak, medium, and
total acid sites than the SAPO-5 catalyst. In the case of the HP
SAPO-5 the collidine is able to interact with all the OH group
types (Si--OH, P--OH, Si--OH--Al and the H-bonded) after
150.degree. C. desorption and their accessibility is greatly
enhanced in comparison to the microporous analog SAPO-5.
[0248] FIG. 36A illustrates the results of the collidine adsorption
on HP SAPO-34. The collidine interacts primarily with the Si--OH
and P--OH groups after 150.degree. C. desorption. FIG. 36B
illustrates the distribution of weak, medium, and strong acid sites
in the SAPO-34 and HP SAPO-34 catalysts. As shown in FIG. 36B, the
HP SAPO-34 catalyst has a similar distribution of acid sites
compared to the SAPO-5 catalyst. As shown in FIG. 36A, similar to
the microporous structure only a small fraction of the bridging OH
groups are accessible to collidine as there is very minimal
attenuation of the bridging hydroxy groups.
[0249] The differences between the accessibility of the two
hierarchical catalysts active sites could be explained by their
very different microporous structures (see FIGS. 4A and 4B). SAPO-5
has much larger pores, 7.3 .ANG., than SAPO-34, 3.8 .ANG.. As the
hierarchical materials are largely microporous, it is likely that
not all the mesopores are accessible owing to them being surrounded
by the microporous system, and therefore the FT-IR-collidine may
not truly represent all the types of acid sites that are present.
In both cases all the collidine is desorbed by 450.degree. C.
Similar to the FT-IR-CO results, the collidine adsorption indicates
that the collidine largely adsorbs onto moderate to weak acid
sites.
[0250] The hierarchical catalysts, such as HP SAPO-5 and HP
SAPO-34, had comparable acidity to their corresponding microporous
analogues, but provided improvements in one or more of lifetime,
activity and substrate versatility in the Beckmann rearrangement,
whilst not compromising selectivity. Without wishing to be held to
any particular theory, it is believed that the inclusion of the
mesopores has resulted in increased access of the substrates to the
active sites, as well as the formation of additional active sites
(silanols) that may participate in the reaction.
Example 8
Synthesis and Characterization of Additional Hierarchical Porous
AlPO Catalysts
[0251] Aluminum isopropoxide (6.807 g, Aldrich) was added to a
Teflon beaker with phosphoric acid (2.28 ml, 85% in H2O, Aldrich)
and water (10 ml) and vigorously stirred for 1.5 hours until a
homogeneous solution was formed.
dimethyloctadecyl[(3-(trimethoxysilyl)propyl]ammonium chloride
(DMOD) (1.2 ml, 72% in H.sub.2O, Aldrich) was added drop wise,
followed immediately by the addition of triethylamine (3.7 ml,
Aldrich) drop wise and then water (20 ml). The resulting thicker
solution was stirred for one hour. The metal precursors as shown in
Table 4 were added drop wise and the gel was stirred for a further
1.5 hours.
[0252] A microporous analog was formed using the same method, but
without the inclusion of the DMOD.
TABLE-US-00004 TABLE 4 Gel composition Catalyst Gel Composition
(wt. %) HP Co AlPO-5 1 Al: 1.3 P: 0.8 SDA: 0.1 DMOD: 50 H.sub.2O:
0.03 Co HP Ti AlPO-5 1 Al: 1.3 P: 0.8 SDA: 0.1 DMOD: 50 H.sub.2O:
0.03 Ti HP Co Ti 1 Al: 1.3 P: 0.8 SDA: 0.1 DMOD: 50 H.sub.2O: 0.03
Co: 0.03 Ti AlPO-5
[0253] The contents of the gel were divided between three 23 ml
Teflon-lined stainless-steel autoclaves that were transferred to a
pre heated fan assisted oven (WF-30 Lenton) at 200.degree. C. for
24 hours. The solid product from each autoclave was collected via
filtration and washed with 500 ml of deionized water. The product
was left to dry at 80.degree. C. overnight. The as-synthesized
catalyst was calcined in a tube furnace under a flow of air at
550.degree. C. for 16 hours to produce a white solid.
[0254] The effect of different metal combinations within the
multi-metallic hierarchically porous (HP) catalysts was
investigated using an array of spectroscopic techniques. All the
multi-metallic HP catalysts were synthesized using the same
soft-templating technique, which employed the organosilane
surfactant, dimethyloctadecyl[(3-(trimethyoxysilyl)propyl]ammonium
chloride (DMOD) to direct the formation of the mesopores and
triethylamine to direct the formation of the micropores. DMOD was
chosen as an appropriate surfactant owing to its silicon containing
hydrophilic head and the high propensity for Si--O--Si and
Si--O--Al bonds to form, therefore promoting the formation of
mesopores throughout the AlPO framework. In order to assess the
impact of different metal combinations on the intrinsic nature of
the active site identical synthesis procedure was used for the
catalysts. The catalysts will contain silicon in the framework too
due to the nature of the synthesis.
[0255] As shown in the powder X-ray diffraction patterns
illustrated in FIG. 37, the various metal combinations, cobalt,
titanium as well as cobalt and titanium, within the HP AlPO-5
framework did not result in any structural or phase imperfects and
the intended crystalline AFI framework was yielded.
[0256] FIG. 38A is an SEM image of HP Co AlPO-5, FIG. 38B is an SEM
image of HP Ti AlPO-5, and FIG. 38C is an SEM image of HP Co Ti
AlPO-5. As shown in FIGS. 38A-38C, scanning electron microscopy
revealed the expected spherical AlPO-5 particles I the region of
5-30 microns further substantiating the successful synthesis of the
AlPO-5 framework.
[0257] BET measurements were performed to assess the efficacy of
our design strategy in the generation of hierarchically porous
catalysts. FIG. 39A illustrates the nitrogen adsorption isotherm
for each catalyst. FIG. 39B illustrates the BJH pore distribution
curves for each catalyst. All the hierarchically porous samples
exhibited a type IV isotherm, indicating the presence of mesopores
within the catalyst.
TABLE-US-00005 TABLE 5 BET measurements for microporous and HP
M.sup.IIM.sup.III AlPO-5 catalysts Mesopore and Micropore Mesopore
BET Surface External Surface volume volume Catalyst Area
(m.sup.2/g) area (m2/g) (cm.sup.3/g) (cm.sup.3/g) Co AlPO-5 192.2
30.3 0.08 0.11 Ti AlPO-5 200.7 22.7 0.09 0.05 Co Ti AlPO-5 165.6
43.7 0.06 0.08 HP Co AlPO-5 306.2 111.8 0.08 0.30 HP Ti AlPO-5
312.2 106.3 0.09 0.23 HP Co Ti AlPO-5 288.8 115.56 0.07 0.35
[0258] The BJH adsorption pore distribution curves further
demonstrated that all the HP catalysts contained mesopores that are
approximately 40 .ANG. in diameter. As shown in Table 5, all the HP
catalysts had larger total surface areas and mesopore volumes than
their microporous analogues, whilst still retaining similar
microporous surface areas and micropore volumes. The BET data
strongly indicates the successful incorporation of mesopores into
the hierarchically porous frameworks.
[0259] In order to investigate the local coordination geometry of
the AI(III), P(V) and Si(IV) sites MAS NMR was deployed. FIG. 40A
illustrates the .sup.29Si MAS NMR of HP Co AlPO-5. FIG. 40B
illustrates the .sup.29Si MAS NMR of HP Ti AlPO-5. FIG. 40C
illustrates the .sup.29Si MAS NMR of HP Co Ti AlPO-5. The .sup.29Si
MAS NMR of the three hierarchically porous catalysts further
confirmed the incorporation of the silicon into the framework due
to the utilization of the organosilane in the synthesis procedure.
The signals in the .sup.29Si MAS NMR is broad for all three of the
HP catalysts, which indicates that there is an element of silicon
zoning, which would be expected due nature of the synthesis.
Although the main peak observed for the HP catalysts was at about
-90 ppm, this is often assigned to isolated acidic Si(OAl).sub.4
sites which are isolated sites formed via type II substitution.
This is actually unusual for Si AlPO-5 frameworks; typically one
would expect a much broader signal with a lower ppm near to -100
ppm..sup.7 Therefore this is very interesting catalytically and
synthetically as the HP catalysts represent a way as to generate
isolated silicon sites within an AFI aluminophosphates framework
that are otherwise difficult to form.
[0260] To elucidate the nature of the cobalt and titanium metallic
sites in the substituted HP AlPO-5 catalysts diffuse reflectance
(DR) UV/vis was employed. FIG. 41 illustrates the DR UV/vis spectra
of the HP Co AlPO-5, HP Ti AlPO-5, and HP Co Ti AlPO-5. Diffuse
reflectance UV Vis measurements enabled the molecular environments
of the substituted cobalt and titanium ions within the AlPO
framework to be investigated. The DR UV/vis of the reduced cobalt
containing HP AlPOs have triplet bands in the visible region
between 500 and 700 nm which can be attributed to the d-d
transitions of Co(II) ions in tetrahedral coordination. The DR
UV-Vis spectrum of reduced HP Co Ti ALPO-5 and HP Ti AlPO-5 show
one strong absorption band in the 200-250 nm range due to
tetrahedral Ti(IV) LMCT transitions with the framework oxygen
ligands. The broad nature of this band indicates that the titanium
isn't purely tetrahedral. Rather, the titanium centres are likely
to be a mix between the tetrahedral and octahedral Ti (IV) sites
this is often commonly seen within titanium substituted AlPOs.
Although it should be noted that the Ti(IV) band in the HP Co Ti
AlPO-5 is sharper than in HP Ti AlPO-5, indicating that the Ti (IV)
ions are more tetrahedral in nature in the cobalt containing
catalyst. This phenomenon can be attributed to `support synergy` in
which a second metal can help direct the titanium into the
framework and has been observed in the microporous analogues
previously.
[0261] The isomorphous substitution of Co(II) via type I
substitution and Ti(IV) via type II substitution will both lead to
an acid site being generated as will the incorporation of the
Si(IV), and the strength, type and quantity of these sites will be
intimately related to the catalysts activity. Therefore FT-IR was
utilised to probe the acidity of the hierarchically porous
frameworks further, as provided in FIG. 42. FIG. 42 illustrates the
FTIR spectra of the OH-stretching region for HP Co AlPO-5, HP Ti
AlPO-5, and HP Co Ti AlPO-5. Direct observation of the O--H
stretching region indicated that the spectra was very similar for
all three of the catalysts. Each contained bands due to Al--OH and
P--OH defects as well as bands owing to silicon incorporation into
the AlPO framework. There was a band at about 3640 cm.sup.-1 in all
three hierarchically porous frameworks that corresponds to Bronsted
acid sites within the catalysts owing to the silicon being
isomorphously substituted into the framework via type 2 or type 3
substitutions or a combination of both. There was also an
additional band at 3750 cm.sup.-1, this is attributed to the
silanol sites in the catalysts which originate from the calcination
of the surfactant in the mesopores. The FTIR data therefore
indicates, as did the .sup.29Si MAS NMR (see FIG. 40A-40C), that
the surfactant has been successfully incorporated into the
frameworks.
[0262] FTIR spectroscopy coupled with the small basic CO probe
molecule enabled the elucidation of the type and strength of acid
sites present in the frameworks, as shown in FIGS. 43A-C. FIG. 43A
illustrates the FTIR spectra of CO adsorbed at 80 k on calcined HP
Co AlPO-5. FIG. 43B illustrates the FTIR spectra of CO adsorbed at
80 k on calcined HP Ti AlPO-5. FIG. 43C illustrates the FTIR
spectra of CO adsorbed at 80 k on calcined HP Co Ti AlPO-5.
Observation of the CO region of the FTIR spectra revealed that the
cobalt containing catalysts (HP Co AlPO-5 and HP Co Ti AlPO-5)
contained Lewis acid sites as well as Bronsted acid sites. The HP
Ti AlPO-5 also had absorbance bands due to CO coordinated with both
Lewis and Bronsted acid sites, although it was observed with much
lower CO adsorption on Lewis acid sites compared to the cobalt
containing samples, hence indicating that the HP Ti AlPO-5 has much
less Lewis acidity than the cobalt containing frameworks.
[0263] FIGS. 44A-44C illustrate the FTIR spectra after the addition
of 0.02 cc, 0.08 cc and 0.16 cc, respectively, of CO adsorbed at
80K on calcined HP Co AlPO-5, HP Ti AlPO-5, and HP Co Ti AlPO-5. As
shown in FIGS. 44A-44C and Table 6, in the OH region CO adsorption
resulted in a shift of the Si--OH, P--OH and Si--OH--Al bands to
lower frequency.
TABLE-US-00006 TABLE 6 BET measurements for microporous and HP
M.sup.IIM.sup.IIIAIPO-5 catalysts Bridging OH CO Area Before After
After (AU) (0.18 cc Catalyst CO CO Shift CO Shift added) HP Co
AIPO-5 3644 3366 278 3236 408 2.082 HP Ti AIPO-5 3641 3366 275
0.586 HP Co Ti AIPO-5 3642 3364 278 3232 410 2.098
[0264] As shown in FIGS. 44A-44C and Table 6, at low CO coverage
all samples showed a shifted Si--OH--Al band around 3365 cm.sup.-1
in the hydroxyl region. This resulted in a band shift between 275
and 278 cm.sup.-1 which is typical for a SAPO catalyst..sup.8 The
two cobalt-containing samples also had an additional band around
3235 cm.sup.-1 with a shift of >400 cm-1 which is attributed to
the CO interacting with stronger Bronsted acid sites. At higher CO
coverage ((0.08 cc), the three catalysts had an additional shifted
OH band around 3470 cm.sup.-1 due to interaction of the CO with the
P--OH defect groups. At even higher CO coverage (0.16 cc) there is
a small amount of attenuation of the Si--OH bands around 3745
cm.sup.-1 for the three samples. The FTIR-CO revealed that the
cobalt containing HP AlPO-5s contained considerable stronger and
more acid sites than the HP Ti AlPO-5.
[0265] FIG. 45 illustrates the TPD nitrogen adsorption results for
HP Co AlPO-5, HP Ti AlPO-5, and HP Co Ti AlPO-5. FIG. 45 further
supports the observation above and indicates that the Cobalt
containing catalysts have essentially identical acid site number
and strength distributions, whereas the HP Ti AlPO-5 catalyst has
significantly lower total acidity and fewer stronger sites. This is
very revealing, as from .sup.29Si NMR the local environmental of
the silicon is essentially the same for the three catalysts (FIGS.
40A-40C) and from BET (FIGS. 39A and 39B) and SEM (FIG. 38A-38C)
the porosity and particle sizes were ascertained to be extremely
similar. Therefore these differences in acid strength and type must
be originating from the dopant metals, hence highlighting the real
possibilities of tuning the active sites for particular
reactions.
[0266] FIG. 46 illustrates the results of a probe with a bulkier
basic probe, collidine. As shown in FIG. 46, the FTIR with a
bulkier basic probe, collidine enabled the accessibility of the
Bronsted acid sites as well as their strength and quantity to be
assessed. Each catalyst was loaded with collidine and then heated
to a certain temperature in order to investigate the strength of
the acid sites. Observation of the hydroxyl region of the FTIR
revealed that the collidine interacted with all the hydroxyl groups
within all the catalysts and this resulted in the formation of a
protonated species that has a N--H stretch around 3300 cm.sup.-1.
As the temperature of the sample with collidine was increased the
collidine desorbed from the sample and very little remained after
450.degree. C. desorption. The behavior of the three HP catalysts
was very similar. The total collidine adsorption is highest on the
cobalt only HP catalyst and it also had the highest number of
strong sites. The strength distribution was very similar for the
two cobalt-containing samples, with a higher proportion of moderate
sites compared to the titanium only sample.
[0267] By employing a range of spectroscopic techniques it was
possible to ascertain the various strengths and type of acid sites
within the HP AlPOs. Given that the samples had analogous porosity
and silicon environments it would be reasonable to assume that the
differences in acidity are due to the cobalt and titanium
isomorphously substituted into the framework. In order to
investigate these catalysts further they were tested in catalytic
reactions.
Example 9
Beckmann Rearrangement of Cyclohexanone Oxime
[0268] The Beckmann rearrangement of cyclohexanone oxime to
.epsilon.-caprolactam was performed in a three necked round bottom
flask under nitrogen. Benzonitrile (20 ml) was added to the flask
with 0.1 g of cyclohexanone oxime, 0.1 g of chlorobenzene (internal
standard) and 0.1 g of catalyst. The reaction was performed at
130.degree. C. and aliquots were taken frequently in order to
monitor the course of the reaction. The solutions were centrifuged
and analyzed by Perkin Elmer Calrus 480 GC using an Elite-5 column
and Flame Ionization Detector. The products were identified and
quantified by using cholorbenzene as an internal standard and
employing the calibration method.
[0269] It was ascertained from the spectroscopic investigations
that all three HP catalysts contained Bronsted acid sites, with the
cobalt containing sites also having some Lewis acidity. Therefore
the industrially significant Beckmann rearrangement was chosen as
the probe reaction to investigate the catalysts active sites
further. This transformation is used to convert cyclic oximes into
the lactam monomeric building blocks for Nylon synthesis. It is
well known that weak Bronsted acid sites are preferred for this
reaction with stronger sites and Lewis acid sites often promoting
the formation of the unwanted ketone. Therefore the nature of the
acid sites within the HP AlPOs should affect their catalytic
activity and selectivity.
[0270] All three of the HP AlPO catalysts were active in the liquid
phase Beckmann rearrangement. FIG. 47A illustrates the percent
conversion, percent selectivity, and percent yield for the liquid
phase Beckmann rearrangement of cyclohexanone oxime to
.epsilon.-caprolactam for various catalysts. The reaction was
performed using 0.1 g cyclohexanone oxime, 0.1 g catalyst, 0.1 g
chlorobenzene (IS), 20 ml anhydrous PhCN, 130.degree. C. under
nitrogen for 7 hours. The HP Ti AlPO-5 was 100% selective towards
the desired product, .epsilon.-caprolactam. Both HP Co AlPO5 and HP
Co Ti AlPO-5 produced cyclohexanone as a by-product. Without
wishing to be held to any particular theory, the formation of
cyclohexanone is thought to be due to Lewis acidity as well as
stronger acid sites being present, which both HP Co AlPO-5 and HP
Co Ti AlPO-5 have (FIGS. 40A-40C). Interestingly though the HP Co
Ti AlPO-5 is more selective than the HP Co AlPO-5 even though both
have near identical acid strength and quantity. The HP Co Ti AlPO-5
also has the highest conversion at 71% and hence the largest yield
of .epsilon.-caprolactam at 39%, with the HP Ti AlPO-5 that has
100% selectivity with a lower yield of 29%. These differences
between the two catalysts could be due to synergy between the Co
and Ti sites. From DR UV/Vis (FIG. 41) it was speculated that the
titanium was more tetrahedral in nature in the bimetallic HP
catalyst. This more tetrahedral nature may be more amenable for the
catalysis and therefore lead to higher conversions and hence higher
yields of .epsilon.-caprolactam.
[0271] As shown in FIG. 47A, the hierarchical porous catalysts
demonstrate high activity and improved selectivies in catalytic
performance.
[0272] Referring next to FIG. 47B, In order to further test the
efficacy of the HP catalysts a larger substrate, cyclcododecanone
oxime (0.9 nm) was utilized in the Beckmann rearrangement to
laurolactam, precursor to industrially significant Nylon 12. The
reaction carried out was the liquid phase Beckmann rearrangement of
cyclododecanone oxime to laurolactam under reaction conditions of
0.1 g cyclohexanone oxime, 0.1 g catalyst, 0.1 g chlorobenzene
(IS), 20 ml anhydrous PhCN, 130.degree. C. under nitrogen, for 2
hours. As shown in FIG. 47B, the hierarchically porous catalysts
were far more active than the microporous catalysts
Cyclcododecanone oxime (0.9 nm) is larger than the micropores of
AlPO-5 (0.7 nm), therefore seeing as the microporous catalysts are
active in this rearrangement it is likely that both external and
internal sites are active for this reaction. The hierarchically
porous catalysts will have both external and internal sites
accessible to the substrate leading to extremely high conversions
after just two hours (92% for HP Ti AlPO-5) whereas in the case of
the microporous analogue only the external sites will be available
and hence a lower conversion is observed (just 24% for Ti AlPO-5).
In this reaction the hierarchically porous catalysts all have very
high conversions 81-92% with 100% selectivity. In order to
elucidate the origin for the high conversions both MCM 41 and HP
AlPO-5 were tested in this reaction. Unlike in the rearrangement of
cyclohexanone oxime, MCM 41 was active in this reaction and was
able to form laurolactam, likewise HP AlPO-5 was also active.
Although they both were not as successful as the multi-metallic HP
AlPO-5, therefore highlighting the importance of the metals within
the framework to subtly tune the intrinsic nature of the active
site for a particular reaction.
[0273] While the present disclosure is primarily directed to
Beckmann rearrangement of cyclohexanone oxime, cyclooctanone oxime,
and cyclododecanone oxime to their corresponding lactams, it should
be understood that the features disclosed herein have application
to the production of other lactams and other monomers.
[0274] While this invention has been described as relative to
exemplary designs, the present invention may be further modified
within the spirit and scope of this disclosure. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains.
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