U.S. patent application number 17/069544 was filed with the patent office on 2021-05-13 for systems and methods for synthesis of zsm-22 zeolite.
This patent application is currently assigned to Saudi Arabian Oil Company. The applicant listed for this patent is King Fahd University of Petroleum and Minerals, Saudi Arabian Oil Company. Invention is credited to Emad Naji Al-Shafei, Ki-Hyouk Choi, Anas Karrar Jamil, Oki Muraza, Zain Hassan Yamani.
Application Number | 20210139336 17/069544 |
Document ID | / |
Family ID | 1000005164262 |
Filed Date | 2021-05-13 |
United States Patent
Application |
20210139336 |
Kind Code |
A1 |
Al-Shafei; Emad Naji ; et
al. |
May 13, 2021 |
SYSTEMS AND METHODS FOR SYNTHESIS OF ZSM-22 ZEOLITE
Abstract
Systems and methods for production of consistently-sized ZSM-22
zeolite catalyst crystals, a method including preparing an
aluminate solution; preparing a silica solution; mixing the
aluminate solution and the silica solution to form a
zeolite-forming solution; heating the zeolite solution with
microwave irradiation in a first, a second, a third, and a fourth
distinct isothermal stage to produce the consistently-sized ZSM-22
zeolite catalyst crystals within a pre-selected crystal size range
using a non-ionic surfactant.
Inventors: |
Al-Shafei; Emad Naji;
(Dhahran, SA) ; Muraza; Oki; (Dhahran, SA)
; Jamil; Anas Karrar; (Dhahran, SA) ; Choi;
Ki-Hyouk; (Dhahran, SA) ; Yamani; Zain Hassan;
(Dhahran, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company
King Fahd University of Petroleum and Minerals |
Dhahran
Dhahran |
|
SA
SA |
|
|
Assignee: |
Saudi Arabian Oil Company
Dhahran
SA
King Fahd University of Petroleum and Minerals
Dhahran
SA
|
Family ID: |
1000005164262 |
Appl. No.: |
17/069544 |
Filed: |
October 13, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16682515 |
Nov 13, 2019 |
10843930 |
|
|
17069544 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01B 39/04 20130101;
B01J 19/126 20130101; C01P 2004/64 20130101; C01B 39/46 20130101;
B01J 29/7042 20130101; C01P 2004/12 20130101; C01B 39/48 20130101;
C01P 2004/62 20130101 |
International
Class: |
C01B 39/04 20060101
C01B039/04; B01J 19/12 20060101 B01J019/12; B01J 29/70 20060101
B01J029/70; C01B 39/46 20060101 C01B039/46; C01B 39/48 20060101
C01B039/48 |
Claims
1. A system for producing consistently-sized ZSM-22 zeolite
catalyst crystals, the system comprising: an aluminate solution
mixing chamber; a silica solution mixing chamber; and a
microwave-application mixing unit, the microwave-application mixing
unit in fluid communication with both the aluminate solution mixing
chamber and the silica solution mixing chamber, wherein the
microwave-application mixing unit mixes and heats a zeolite-forming
solution from the aluminate solution mixing chamber and the silica
solution mixing chamber with microwave irradiation in a first, a
second, a third, and a fourth distinct isothermal stage to produce
the consistently-sized ZSM-22 zeolite catalyst crystals within a
pre-selected nano-scale crystal size range using a non-ionic
surfactant.
2. The system according to claim 1, wherein the aluminate solution
mixing chamber prepares an aluminate solution for the
zeolite-forming solution and the silica solution mixing chamber
prepares a silica solution for the zeolite-forming solution.
3. The system according to claim 1, where the system comprises
controllable stirring means in the aluminate solution mixing
chamber, the silica solution mixing chamber, and the
microwave-application mixing unit.
4. The system according to claim 1, where a majority of the
consistently-sized ZSM-22 zeolite catalyst crystals within the
pre-selected nano-scale crystal size range exhibit lengths varying
from about 50 nm to about 600 nm, and widths ranging from about 55
nm to about 75 nm.
5. The system according to claim 2, where the system is operable to
control a ratio of silicon to aluminum to produce the
consistently-sized ZSM-22 zeolite catalyst crystals within the
pre-selected crystal size range.
6. The system according to claim 1, where in the first isothermal
stage microwave irradiation is applied to heat the zeolite-forming
solution to between about 35.degree. C. and about 65.degree. C. for
between about 3 minutes and about 7 minutes, with stirring applied
at a speed between about 200 rpm and about 300 rpm.
7. The system according to claim 6, where in the second isothermal
stage microwave irradiation is applied to heat the zeolite-forming
solution to between about 90.degree. C. and about 120.degree. C.
for between about 5 and about 15 minutes, with stirring applied at
a speed between about 200 rpm and about 300 rpm.
8. The system according to claim 7, where the non-ionic surfactant
is added after the second isothermal stage.
9. The system according to claim 8, where in the third isothermal
stage microwave irradiation is applied to heat the zeolite-forming
solution to between about 35.degree. C. and about 65.degree. C. for
between about 60 and about 80 hours, with stirring applied at a
speed between about 350 rpm and about 450 rpm.
10. The system according to claim 9, where in the fourth isothermal
stage microwave irradiation is applied to heat the zeolite-forming
solution to between about 155.degree. C. and about 205.degree. C.
for between about 8 and about 16 hours.
Description
RELATED APPLICATIONS
[0001] This application is a divisional application of and claims
priority to and the benefit of U.S. Non-Provisional Patent
Application No. 16/682,515, filed Nov. 13, 2019, the entire
disclosure of which is incorporated herein by reference in its
entirety.
BACKGROUND
Field
[0002] The present disclosure relates to systems and methods for
producing consistently-sized ZSM-22 zeolite catalyst crystals.
Specifically, the disclosure presents systems and methods that
apply microwave heating to a zeolite solution comprising non-ionic
surfactant for producing consistently-sized nano-scale ZSM-22
zeolite catalyst crystals.
Description of the Related Art
[0003] Hydrocarbon conversion reactions for petrochemical processes
largely utilize zeolite-type materials for catalysts. Zeolites have
been the subject of continuous developments and modifications for
many years. The zeolites of Beta-type (BEA), Y-type, and ZSM-5-type
structure are important as catalytic materials for chemical
industry applications. ZSM-22 zeolite is identified as a
one-dimensional-pore zeolite, and was discovered by Mobil Oil
Corporation in the early 1980's. ZSM-22 is known as an
orthorhombic, high-silica zeolite of a TON framework topology.
[0004] Zeolites are used in automotive emissions control,
industrial off-gas purification, volatile organic carbon (VOC)
reduction, and nitrogen oxides (NOx) reduction technologies. As
process catalysts, they are used for fuel upgrading, production of
petrochemical intermediates, and processing chemicals. BEA
zeolites, for example, are also useful for adsorption purposes,
such as odor removal and active carbon replacement. Growing demand
for new catalytic chemical processing has led to a rise in the need
for more reactive and selective catalysts. Nanotechnology for the
production of catalytic material is essential to overcoming
catalytic reaction limitations by allowing for greater dispersion
of reactive catalysts, which leads to higher turnover of
hydrocarbon conversion.
[0005] The TON zeolite framework consists of 5-, 6- and 10-membered
rings. The TON zeolite framework group includes ZSM-22, Theta-1,
Nu-10, KZ-2, and ISI-1 zeolites. The pore structure of the TON
framework is known to be linear, one-dimensional, with 10-membered
ring pore openings and effective pore sizes of about 0.45 nm by
0.55 nm.
[0006] Pores of ZSM-22 are smaller than the pores of ZSM-5, and are
classified as a medium-pore on the zeolite size scale. ZSM-22
zeolite crystals synthesized by conventional hydrothermal synthesis
include crystals that are needle-like with a crystal size in the
range of about 1.mu.m to 20 .mu.m. Conventional hydrothermal
synthesis of ZSM-22 zeolite is known.
[0007] ZSM-22 zeolite has been shown to be a weak catalyst or
catalyst support when applied as a steam cracker catalyst, and when
applied in various reactions such as hydroisomerization,
hydrocarbon upgrading, naphtha cracking, methanol conversion to
gasoline, methanol conversion to propylene, butane conversion to
olefins, and hexane conversion to olefins.
[0008] Micro-sized ZSM-22 zeolite is catalytically deactivated
rapidly due to exhibiting pore sizes that can be easily blocked by
coke from hydrocarbon conversion reactions. Prior art systems and
processes for producing ZSM-22 zeolite catalyst crystals are
insufficient for producing consistently-sized crystals without
impurities and without agglomeration, particularly in the nano-size
scale.
SUMMARY
[0009] Applicant has recognized a need for systems and methods
which apply microwave heating to a zeolite solution comprising
non-ionic surfactant for producing consistently-sized ZSM-22
zeolite catalyst crystals, particularly in the nano-scale less than
1 .mu.m. Prior art technical problems include agglomeration during
zeolite production and catalyst deactivation when used in
hydrocarbon conversion reactions with steam.
[0010] Embodiments of systems and methods disclosed here allow for
several size ranges of nano-scale ZSM-22 zeolite crystals to be
consistently produced without agglomeration and without impurities.
There is presently no suitable industrial process to make
nano-scale ZSM-22. Here, ZSM-22 zeolite crystals of three unique
size ranges are produced with lengths varying from about 50 nm to
about 600 nm, and with widths ranging from about 55 nm to about 75
nm. In some embodiments of the process, one or more non-ionic
surfactant and microwave heating is applied in four isothermal
steps. Nonionic surfactants suitable in embodiments here include
those nonionic surfactants based on polyoxyethylene. Systems and
methods can be scaled to an industrial scale to manufacture nano
zeolites for oil upgrading and hydrocarbon conversion reactions. By
reducing crystals size, catalytic activity of the ZSM-22 crystals
is surprisingly and unexpectedly enhanced.
[0011] In ZSM-22 zeolite crystals produced here, it is believed,
without being bound by any theory or practice, that by increasing
mesoporous pore-mouth openings to access larger hydrocarbon
molecules, better catalytic activity is obtained because reaction
diffusional length is shortened. Shortened diffusional length
assists hydrocarbon molecules in contacting acidic sites of nano
ZSM-22 for primary cracking reactions of hydrocarbons and reduces
possible agglomeration of hydrocarbons and coking rates on the
ZSM-22.
[0012] The nano-crystals of ZSM-22 zeolite framework start forming
in a process of nucleation followed by crystallization. Systems and
methods disclosed here produce nano-scale ZSM-22 crystals at
smaller sizes without agglomeration, and produce uniform crystals
both in terms of length and width. Crystal growth is uniquely
controlled during manufacturing processes of the nano-scale ZSM-22
zeolite crystals.
[0013] Specifically controlled surfactant concentration of one or
more nonionic surfactant in the processes reduces agglomeration of
nano-scale ZSM-22 zeolite crystals during production.
[0014] Thus, disclosed here is a method for producing
consistently-sized ZSM-22 zeolite catalyst crystals, the method
including preparing an aluminate solution; preparing a silica
solution; mixing the aluminate solution and the silica solution to
form a zeolite-forming solution; heating the zeolite-forming
solution with microwave irradiation in a first, a second, a third,
and a fourth distinct isothermal stage to produce the
consistently-sized ZSM-22 zeolite catalyst crystals within a
pre-selected nano-scale crystal size range using a non-ionic
surfactant.
[0015] In some embodiments, the step of preparing the aluminate
solution comprises mixing deionized water, a hydroxide-containing
compound, and an aluminum-containing compound. In other
embodiments, the hydroxide-containing compound comprises at least
one compound selected from the group consisting of: NaOH, CsOH,
LiOH, Ca(OH).sub.2, and KOH, and the aluminum-containing compound
comprises at least one compound selected from the group consisting
of: of aluminum sulfate octadecahydrate, aluminum oxide, aluminum
hydroxide, and aluminum metal. Still in other embodiments, the step
of preparing an aluminate solution comprises mixing an organic
template with the aluminate solution. In certain other embodiments,
the organic template comprises at least one compound selected from
the group consisting of: 1,6-diaminohexane, N-ethylpyridine,
1,4-diaminohexane, and diethylamine. Still in other embodiments,
the step of preparing the silica solution comprises mixing a silica
colloidal solution and water.
[0016] Still in yet other embodiments, the silica colloidal
solution is about 40 wt. % silica in water. In certain embodiments,
the step of mixing the aluminate solution and the silica solution
to form the zeolite-forming solution comprises controlling a ratio
of silicon to aluminum to produce the consistently-sized ZSM-22
zeolite catalyst crystals within a pre-selected crystal size range
using the non-ionic surfactant. In certain embodiments, in the
first isothermal stage microwave irradiation is applied to heat the
zeolite solution to between about 35.degree. C. and about
65.degree. C. for between about 3 minutes and about 7 minutes, with
stirring applied at a speed between about 200 rpm and about 300
rpm. In some embodiments, in the second isothermal stage microwave
irradiation is applied to heat the zeolite solution to between
about 90.degree. C. and about 120.degree. C. for between about 5
and about 15 minutes, with stirring applied at a speed between
about 200 rpm and about 300 rpm. In certain embodiments, the
non-ionic surfactant is added after the second isothermal stage.
Still in yet other embodiments, the non-ionic surfactant includes a
polyoxyethylene-based compound selected from the group consisting
of: polyoxyethylene (2) stearly ether, polyoxyethylene (2) olleyl
ether, polyoxyethylene (2) cetyl ether, sorbitan monopalmirate,
sorbitan monolaurate, polyoxyethylene sorbitan monostearate,
polyoxyethylene lauryl ether, polyoxyethylene sorbitan monooleate,
polyoxyethylene (4,5) p-tert-octylphenol, polyoxyethylene sorbitan
trioleate, polyoxyethylene sorbitan tristearate, polyoxyethylene
(6) tridecyl ether, polyoxyethylene (10) stearyl ether,
polyoxyethylene (10) oleyl ether, polyoxyethylene (7-8)
p-tert-octylphenol, polyoxyethylene (10) cetyl ether,
polyoxyethylene alkyl aryl ether, polyoxyethylene (9)
p-tert-octylphenol, polyoxyethylene sorbitan monolaurate,
polyoxyethylene (9-10) nonyl ohenol, polyoxyethylene (9-10)
p-tert-octyl phenol, polyoxyethylene esters of mixed fatty acids,
polyoxyethylene (12) tridecyl ether, polyoxyethylene (12-13)
p-tert-octylphenol, polyoxyethylene sorbitan monostearate,
polyoxyethylene (17) cetyl-stearyl alcohl, polyoxyethylene (20)
stearyl ether, polyoxyethylene (20) oleyl ether, polyoxyethylene
(15) tridecyl ether, polyoxyethylene sorbitan monopalmitate,
polyoxyethylene (20) cetyl ether, polyoxyethylene (16)
p-tert-octylphenol, polyoxyethylene sorbitan monolaurate,
polyoxyethylenelauryl ether, and combinations of the same.
[0017] In other embodiments of the method, the third isothermal
stage microwave irradiation is applied to heat the zeolite solution
to between about 35.degree. C. and about 65.degree. C. for between
about 60 and about 80 hours, with stirring applied at a speed
between about 350 rpm and about 450 rpm. Still in other
embodiments, in the fourth isothermal stage microwave irradiation
is applied to heat the zeolite solution to between about
155.degree. C. and about 205.degree. C. for between about 8 and
about 16 hours. In certain embodiments, the method includes the
steps of neutralizing pH of the produced consistently-sized ZSM-22
zeolite catalyst crystals, water washing the produced
consistently-sized ZSM-22 zeolite catalyst crystals, drying the
produced consistently-sized ZSM-22 zeolite catalyst crystals, and
calcining the produced consistently-sized ZSM-22 zeolite catalyst
crystals.
[0018] Still in other embodiments, the step of calcining is carried
out under static atmospheric air at a temperature of between about
500.degree. C. and about 550.degree. C. for between about 6 and
about 12 hours. In certain embodiments, the method includes the
step of applying the produced consistently-sized ZSM-22 zeolite
catalyst crystals in a hydrocarbon conversion process.
[0019] Additionally disclosed here is a system for carrying out the
various methods disclosed, the system including an aluminate
solution mixing chamber; a silica solution mixing chamber; and a
microwave-application mixing unit, the microwave-application mixing
unit in fluid communication with both the aluminate solution mixing
chamber and the silica solution mixing chamber. In some
embodiments, the system comprises controllable stirring means in
the aluminate solution mixing chamber, the silica solution mixing
chamber, and the microwave-application mixing unit. In other
embodiments, the microwave-application mixing unit is configured to
carry out heating the zeolite solution with microwave irradiation
in the first, the second, the third, and the fourth distinct
isothermal stages to produce the consistently-sized ZSM-22 zeolite
catalyst crystals within a pre-selected crystal size range. In
embodiments of the systems and methods disclosed, a majority of the
consistently-sized ZSM-22 zeolite catalyst crystals within the
pre-selected nano-scale crystal size range exhibit lengths varying
from about 50 nm to about 600 nm, and widths ranging from about 55
nm to about 75 nm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] These and other features, aspects, and advantages of the
present disclosure will become better understood with regard to the
following descriptions, claims, and accompanying drawings. It is to
be noted, however, that the drawings illustrate only several
embodiments of the disclosure and are therefore not to be
considered limiting of the disclosure's scope as it can admit to
other equally effective embodiments.
[0021] FIG. 1 is a schematic diagram for a system and process to
produce consistently-sized ZSM-22 catalyst crystals without
agglomeration or impurities using microwave heating and non-ionic
surfactant.
[0022] FIG. 2 shows a scanning electron microscope (SEM) image for
crystals of nano-sized ZSM-22 zeolite produced at a surfactant to
aluminum oxide molar ratio of 2.5.
[0023] FIG. 3 shows a SEM image for crystals of nano-sized ZSM-22
zeolite produced at a surfactant to aluminum oxide molar ratio of
5.0.
[0024] FIG. 4 shows a SEM image for crystals of nano-sized ZSM-22
zeolite produced at a surfactant to aluminum oxide molar ratio of
7.5.
[0025] FIG. 5 shows X-ray diffraction (XRD) patterns confirming
ZSM-22 structured zeolite was produced.
DETAILED DESCRIPTION
[0026] So that the manner in which the features and advantages of
the embodiments of systems and methods that apply microwave heating
to a zeolite solution comprising non-ionic surfactant for producing
consistently-sized ZSM-22 zeolite catalyst crystals, as well as
others, which will become apparent, may be understood in more
detail, a more particular description of the embodiments of the
present disclosure briefly summarized previously may be had by
reference to the embodiments thereof, which are illustrated in the
appended drawings, and which form a part of this specification. It
is to be noted, however, that the drawings illustrate only various
embodiments of the disclosure and are therefore not to be
considered limiting of the present disclosure's scope, as it may
include other effective embodiments as well.
[0027] Referring first to FIG. 1, a schematic diagram is shown for
a system and process to produce consistently-sized nano-scale
ZSM-22 catalyst crystals without agglomeration or impurities using
microwave heating and non-ionic surfactant. FIG. 1 is described
with respect to an example process for production of ZSM-22 zeolite
crystals. Surfactant-microwave application system 100 includes an
aluminate solution mixer unit 200 and a separate silicate solution
mixer unit 300. System 100 also includes surfactant-microwave
mixing unit 400, which is fluidly coupled to both aluminate
solution mixer unit 200 and silicate solution mixer unit 300.
Surfactant-microwave mixing unit 400 carries out controlled
hydrothermal treatment for nucleation growth and crystallization of
ZMS-22 nano-crystals.
[0028] In one example embodiment, a process operates as follows. In
aluminate solution mixer unit 200, 88.4 kg of deionized water and
3.8 kg of potassium hydroxide (KOH) (purity: 99%) are introduced
via line 210 and stirred at about between 270 rpm and about 330
rpm, preferably about 300 rpm, via stirring rod 220 at a
temperature between about 15.degree. C. and about 35.degree. C. for
between about 25 minutes and about 35 minutes, preferably about 30
minutes. Other suitable hydroxide-containing alkali and alkaline
earth compounds can be used alternatively to or in addition to KOH,
including, but not limited to, NaOH, CsOH, LiOH, or
Ca(OH).sub.2.
[0029] Next, 1.8 kg of aluminum sulfate octadecahydrate (formula:
Al.sub.2(SO.sub.4).sub.3.18H.sub.2O) is introduced via line 210 to
aluminate solution mixer unit 200 and mixed with the solution for
between about 25 minutes and about 35 minutes, preferably about 30
minutes, with stirring via stirring rod 220 at between about 270
rpm and about 330 rpm, preferably about 300 rpm, at a temperature
between about 15.degree. C. and about 35.degree. C. Other
aluminum-containing compounds can be used in addition to or
alternative to aluminum sulfate octadecahydrate including, but not
limited to, aluminum oxide (Al.sub.2O.sub.3), aluminum hydroxide
(Al(OH).sub.3), and aluminum metal (Al).
[0030] Next, 8.2 kg of 1,6-diaminohexane (DAH) (purity: 99.5%) is
added to aluminate solution mixer unit 200 as an organic template
via line 210 and stirred by stirring rod 220 at between about 270
rpm and about 330 rpm, preferably about 300 rpm, for between about
25 minutes and about 35 minutes, preferably about 30 minutes. In
some embodiments, heating is not applied in aluminate solution
mixer unit 200, and temperature is in the range of about 15.degree.
C. to about 35.degree. C. Finally, the solution in aluminate
solution mixer unit 200 is evacuated via outlet 230 to be
introduced to surfactant-microwave mixing unit 400 via inlet 405.
Other suitable organic templates can be used in addition to or
alternative to DAH, including, but not limited to, N-ethylpyridine,
1,4-diaminohexane, or diethylamine.
[0031] Separately in silicate solution mixer unit 300, 36 kg of
silica colloidal solution (40 wt. % in water) and 62 kg of water
are introduced to the compartment via line 310. Stirring is applied
via stirring rod 320 for between about 25 minutes and about 35
minutes, preferably about 30 minutes at a speed of between 270 rpm
and about 330 rpm, preferably about 300 rpm. In some embodiments,
heating is not applied in silicate solution mixer unit 300, and
temperature is in the range of about 18.degree. C. to about
35.degree. C. The solution is evacuated via outlet 330 and sent to
surfactant-microwave mixing unit 400 via inlet 410.
[0032] Surfactant-microwave mixing unit 400 operates after the
separate solutions of aluminate and silica are introduced to the
unit via inlets 405 and 410. In one embodiment, four separate
stages of isothermal heating are carried out with electrical heater
440 producing microwave irradiation 450 to synthesize the
nano-sized ZSM-22. In a first isothermal stage, electrical heater
440 operates to heat the solution mixture in surfactant-microwave
mixing unit 400 to between about 35.degree. C. and about 65.degree.
C., or to between about 45.degree. C. and about 55.degree. C., for
between about 3 minutes and about 7 minutes, preferably about 5
minutes. Mixing via stirring rod 420 is applied when microwave
application begins via electrical heater 440 at a speed between
about 200 rpm and about 300 rpm, preferably about 250 rpm.
[0033] In a second isothermal stage, a selected quantity of
non-ionic surfactant is added via line 430. First, electrical
heater 440 is set at a temperature of between about 90.degree. C.
and about 120.degree. C., or between about 100.degree. C. and about
110.degree. C., and stirring is applied via stirring rod 420 at
between about 200 rpm and about 300 rpm, preferably about 250 rpm,
for between about 5 and about 15 minutes. Then, the selected weight
of nonionic surfactant, for example a nonionic surfactant including
poly-oxyethylene groups, is added to surfactant-microwave mixing
unit 400 via line 430. In one embodiment, if
polyoxyethylene(10)oleyl ether (molecular weight 709 g/mole) is
used as surfactant, suitable surfactant to aluminium oxide molar
ratios are from about 0.1:1 to 10:1, or from about 1:1 to about
7.5:1, or about 2.5:1, 5:1, or 7.5:1, for example.
[0034] Optional nonionic surfactants based on polyoxyethylene
surfactants include, but are not limited to, any one of or any
combination of: polyoxyethylene (2) stearly ether, polyoxyethylene
(2) olleyl ether, polyoxyethylene (2) cetyl ether, sorbitan
monopalmirate, sorbitan monolaurate, polyoxyethylene sorbitan
monostearate, polyoxyethylene lauryl ether, polyoxyethylene
sorbitan monooleate, polyoxyethylene (4,5) p-tert-octylphenol,
polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan
tristearate, polyoxyethylene (6) tridecyl ether, polyoxyethylene
(10) stearyl ether, polyoxyethylene (10) oleyl ether,
polyoxyethylene (7-8) p-tert-octylphenol, polyoxyethylene (10)
cetyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene (9)
p-tert-octylphenol, polyoxyethylene sorbitan monolaurate,
polyoxyethylene (9-10) nonyl ohenol, polyoxyethylene (9-10)
p-tert-octyl phenol, polyoxyethylene esters of mixed fatty acids,
polyoxyethylene (12) tridecyl ether, polyoxyethylene (12-13)
p-tert-octylphenol, polyoxyethylene sorbitan monostearate,
polyoxyethylene (17) cetyl-stearyl alcohl, polyoxyethylene (20)
stearyl ether, polyoxyethylene (20) oleyl ether, polyoxyethylene
(15) tridecyl ether, polyoxyethylene sorbitan monopalmitate,
polyoxyethylene (20) cetyl ether, polyoxyethylene (16)
p-tert-octylphenol, polyoxyethylene sorbitan monolaurate, and
polyoxyethylenelauryl ether.
[0035] The use of nonionic surfactants has several advantages
versus long chain alcohols as there are no electronic charge groups
or limited charge in the nonionic molecules. The utilization of
surfactant helps control the sizes of nano-scale crystals of ZSM-22
without negatively affecting the zeolite framework and
crystallinity. Systems and processes adapt the use of one or more
nonionic surfactant to ZSM-22 zeolite crystal production under
controlled microwave irradiation in order to meet the crystallinity
of the ZSM-22 framework and synthesize different size scales of
nano-sized of ZSM-22.
[0036] The weight of nonionic surfactant is adjusted, in part,
according to the weight of aluminum oxide applied in the process.
The molar ratio of the nonionic surfactant to aluminum oxide can
vary from about 0.05:1 to 30:1.
[0037] For nano-scale ZSM-22 crystal size of length of about 80-95
nm by a width of about 55-65 nm, the surfactant to aluminum oxide
molar ratio is between about 2.4 and about 2.6, preferably about
2.5 (See FIG. 2). For ZSM-22 crystal size of length of about
125-140 nm by a width of about 55-65 nm, the surfactant to aluminum
oxide molar ratio is between about 4.9 and about 5.1, preferably
about 5 (See FIG. 3). For nano-scale ZSM-22 crystal size of length
of about 280-300 nm by a width of about 65-75 nm, the surfactant to
aluminum oxide molar ratio is between about 7.4 and about 7.6,
preferably about 7.5 (See FIG. 4).
[0038] In a third isothermal stage, zeolite aging is applied and
electrical heater 440 is set such that the temperature of
surfactant-microwave mixing unit 400 is between about 35.degree. C.
and about 65.degree. C., or is between about 45.degree. C. and
about 55.degree. C., and stirring is applied via stirring rod 420
at a speed of between about 350 rpm and about 450 rpm, preferably
400 rpm, for about 60 to about 80 hours, preferably about 72
hours.
[0039] In a fourth isothermal stage, zeolite crystallization is
carried out, and microwave irradiation is applied to
surfactant-microwave mixing unit 400 for heating, and the
temperature increases to between about 155.degree. C. and about
205.degree. C., or between about 165.degree. C. and about
195.degree. C., or between about 170.degree. C. and about
190.degree. C., and stirring is applied via stirring rod 420 at a
speed of between about 350 rpm and about 450 rpm, preferably 400
rpm, for between about 8 and about 16 hours, or between about 10
hours and about 14 hours.
[0040] At the end of crystallization of nano-sized ZSM-22, the
fourth isothermal stage, surfactant-microwave mixing unit 400 is
cooled down to between about 18.degree. C. and about 40.degree. C.
Zeolite solution is evacuated via line 460 for further treatment in
a separate container (not pictured). In the separate container, the
acidity of the solution is adjusted to between about pH 6.5 and
about pH 7.5, preferably about pH 7 (neutralized), by addition of
HCl in water solution (concentration of about 0.1 mol/L), with the
volume to be added from about 5 mL to about 200 mL, depending on
the scale of the system and process.
[0041] After pH neutralization, a centrifuge is applied to collect
the powder comprising nano-sized ZSM-22 zeolite crystals. The
centrifuge is run at a speed between about 2000 rpm and about 4000
rpm and a temperature between about 18.degree. C. and about
40.degree. C. Next, distilled water washing is carried out 2-3
times to wash the zeolite powder, and the washed zeolite powder is
retrieved via filtration. Drying is applied to nano-sized ZSM-22
zeolite powder at a temperature of between about 90.degree. C. and
about 100.degree. C. for between about 12 and about 24 hours.
Calcination of dried nano-sized ZSM-22 zeolite is carried out under
static atmospheric air and at a temperature of between about
500.degree. C. and about 550.degree. C., preferably 525.degree. C.
for between about 6 and about 12 hours. The oven ramping rate can
be set at between about 1 and about 3.degree. C./min.
[0042] In some embodiments, the resulting zeolite has a framework
crystal of nano-size ZSM-22 zeolite, and this is shown in FIG. 5.
FIG. 5 shows X-ray diffraction (XRD) patterns of ZSM-22 zeolite.
ZSM-22 is characterized via the 2-theta angle peaks at
20.4.degree., 24.4.degree., 24.6.degree., and 25.8.degree..
[0043] Thus, the surfactant-microwave system and process of FIG. 1
synthesizes nano-sized ZSM-22 zeolite with pre-selected recipes and
process steps, which control sizes of nano-scale crystals produced
in order to use ZSM-22 as catalyst. The ZSM-22 zeolite crystals
produced can be used as material for catalyst support, and can be
used for gas adsorption and catalyst applications in chemical and
hydrocarbon conversion reactions, including those involving steam
cracking.
[0044] FIG. 2 shows a scanning electron microscope (SEM) image for
crystals of nano-sized ZSM-22 zeolite produced at a surfactant to
aluminum oxide molar ratio of 2.5. The ratio of surfactant to
aluminum oxide can vary for example between about 2.4 and about
2.6. In FIG. 2, the length of the zeolite crystals is between about
80 nm and about 95 nm, and the width is between about 55 nm and
about 65 nm. In various embodiments a wide molar ratio range of
Si:Al can be used, varying between about 10 and about 200.
[0045] FIG. 3 shows a SEM image for crystals of nano-sized ZSM-22
zeolite produced at a surfactant to aluminum oxide molar ratio of
5.0. The ratio of surfactant to aluminum oxide can vary for example
between about 4.9 and about 5.1. In FIG. 3, the length of the
zeolite crystals is between about 125 nm and about 140 nm, and the
width is between about 55 nm and about 65 nm.
[0046] FIG. 4 shows a SEM image for crystals of nano-sized ZSM-22
zeolite produced at a surfactant to alumina oxide molar ratio of
7.5. The ratio of surfactant to aluminum oxide can vary for example
between about 7.4 and about 7.6. In FIG. 4, the length of the
zeolite crystals is between about 280 nm and about 320 nm, and the
width is between about 65 nm and about 75 nm.
[0047] The term "about" when used with respect to a value or range
refers to values including plus and minus 5% of the given value or
range.
[0048] The singular forms "a," "an," and "the" include plural
referents, unless the context clearly dictates otherwise.
[0049] In the drawings and specification, there have been disclosed
embodiments of systems and methods which apply microwave heating to
a zeolite solution comprising non-ionic surfactant for producing
consistently-sized ZSM-22 zeolite catalyst crystals, and although
specific terms are employed, the terms are used in a descriptive
sense only and not for purposes of limitation. The embodiments of
the present disclosure have been described in considerable detail
with specific reference to these illustrated embodiments. It will
be apparent, however, that various modifications and changes can be
made within the spirit and scope of the disclosure as described in
the foregoing specification, and such modifications and changes are
to be considered equivalents and part of this disclosure.
* * * * *