Note: Descriptions are shown in the official language in which they were submitted.
. r ;t
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CATALYST SYSTEM AND PROCESS FOR CATALYTIC CRACKING
Many refineries devote extraordinary amounts of energy
and operating expense to convert most of a whole crude oil
feed into high octane gasoline. The crude is fractionated
to produce a virgin naphtha fraction which is usually
reformed, and a gas oil and/or vacuum gas oil fraction
which is catalytically cracked to produce naphtha, and
light olefins. The naphtha is added to the refiner's
gasoline blending pool, while the light olefins are
converted, usually by HF or sulfuric acid alkylation, into
gasoline boiling range material which is then added to the
gasoline blending pool.
Fluid catalytic cracking (FCC) is a preferred refining
process for converting higher boiling petroleum fractions
into lower boiling products, especially gasoline. In FCC,
a solid cracking catalyst promotes hydrocarbon cracking
reactions. The catalyst is in a finely divided form,
typically with particles of 20-100 um, with an average of
about 60-75 ~Cm. The catalyst acts like a fluid (hence the
designation FCC), and circulates in a closed cycle between
a cracking zone and a separate regeneration zone. Fresh
feed contacts hot catalyst from the regenerator at the base
of a riser reactor. The cracked products are discharged
from the riser cracking reactor to pass through a main
column which produces several liquid streams and a vapor
stream containing large amounts of light olefins. The
vapor stream is compressed in a wet gas compressor and
charged to the unsaturated gas plant for product
purification.
A further description of the catalytic cracking
process may be found in the monograph, "Fluid Catalytic
Cracking With Zeolite Catalysts," P. B. Venuto and E. T.
Habib, Marcel Dekker, New York, 1978.
An earlier process, moving bed cracking or Thermofor
Catalytic Cracking (TCC), is still used in some refineries.
The catalyst is in the form of small beads, which pass as a
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moving bed through a reactor and regenerator. The feed and
product properties can be the same, but TCC units usually °
can crack only distilled feeds, whereas FCC can process
feeds containing some residual materials. . '
While FCC is already an efficient process for
converting heavy feed to lighter products, substantial
modifications to FCC catalysts and hardware are likely to
be required as a result of the 1990 Clean Air Act
Amendments (CAAA). In particular, it is expected that
there will be an increased demand for C3 and C4 olefins for
alkylation and C4 and C5 olefins for methyltertbutyl and
ethyltertbutyl ethers (MTBE and ETBE) to meet reduced
gasoline aromatic and increased gasoline oxygenate
requirements. One of the anticipated difficulties will be
maintaining gasoline octane while complying with clean air
provisions.
There are a number of widely recognized methods to
increase light olefin make. For example, one widely
accepted method is to substitute an ultrastable Y zeolite
for a rare earth exchanged Y zeolite in the base cracking
catalyst. Another is to increase the riser top
temperature. A third method is to use a secondary or
'quench' stream at some point along the length of the
riser. Yet another method is to use a shape-selective
zeolite, such as ZSM-5, in combination with the main
zeolite Y based cracking catalyst.
There are problems associated with each method of
increasing yield of light olefins. Substituting a rare
earth-free ultrastable Y zeolite for a rare earth exchanged
Y produces a less stable and less active cracking catalyst.
Higher riser top temperatures produce more undesirable
light products such as methane and ethane and also produce
more dienes in the gasoline which lead to gum formation and
fouling. Introduction of a quench stream can reduce the
fresh feed rate on a unit close to its hydraulic limit.
The addition of shape-selective zeolites such as ZSM-5, can
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greatly increase light olefin yields, but adds to the cost
to the operation and, if used at high concentrations, may
dilute the 'base' zeolite Y cracking catalyst.
In many refineries addition of the shape-selective
zeolite is preferred because it can be carried out with low
levels of the shape-selective zeolite and requires no
expenditures for new capital or equipment modification. In
fact, this would probably be more widely used if the
beneficial effects of the ZSM-5 could be obtained with even
less ZSM-5.
The use of ZSM-5 in combination with a zeolite Y based
catalyst is described in U.S. Patents 3,758,403; 3,769,202;
3,781,226; 3,894,931; 3894,933; 3,894,934; 3,926,782;
4,100,262; 4,309,280; 4,309,279; 4,375,458.
It is well known that improved light olefins (C3 - C4)
and improved gasoline octane will be obtained in the
catalytic cracking of gas oils if a crystalline zeolite
having a pore size of less than 0.7 nm (7 Angstrom units),
e.g. ZSM-5, is admixed with a crystalline zeolite having a
pore size greater than 0.7 nm (7 Angstrom units), either
with or without a matrix. A disclosure of this type can be
found in U.S. Pat. No. 3,769,202. Although the
incorporation of a crystalline zeolite having a pore size
of less than 0.7 nm (7 Angstrom units) into a catalyst
comprising a larger pore size crystalline zeolite (pore
size greater than 0.7 nm (7 Angstrom units)) has indeed
been very effective with respect to the raising of octane
number, it did so at the expense of the yield of gasoline.
Improved octane number with some loss in gasoline
yield was shown in U.S. Pat. No. 3,758,403. In said patent,
the cracking catalyst was comprised of a large pore size
crystalline zeolite (pore size greater than 0.7 nm (7
Angstrom units)) in admixture with ZSM-5 zeolite, wherein
the ratio of ZSM-5 zeolite to large pore size crystalline
zeolite was in the range of 1:10 to 3:1.
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The use of ZSM-5 zeolite in conjunction with a zeolite
cracking catalyst of the X or Y variety is described in
U.S. 3,894,9311 3,894,933; 3,894,934 and 4,521,298. The
first two patents disclose the use of ZSM-5 zeolite in
amounts up to and about 5 to l0 wt.%: the third patent
discloses the weight ratio of ZSM-5 zeolite to large pore
size crystalline zeolite in the range of 1:10 to 3:1. The
fourth utilizes a catalyst inventory wherein the zeolite is
unbound.
Combinations of zeolite Y and other zeolites and
molecular sieves including crystalline silicoalumino-
phosphates (SAPOs) have also shown potential for increasing
light olefins and octane at the expense of gasoline yield.
Most of the evaluations were undertaken with the assumption
that small changes in the diameter or shape of the pore
might produce significant changes in selectivity. To date,
the commercial application of crystalline materials other
than ZSM-5 as octane cracking catalysts appears to be
limited. The scientific and patent literature includes
references to the evaluation of at least four other shape
selective aluminosilicate zeolites as FCC additives. These
are: offretite (US 4,992,400), ZSM-23, ZSM-35 (4,016,245)
and ZSM-57 (US 5,098,555) Non-zeolitic molecular sieve
patents teach the use of SAPO-5 (US 4,791,083; EP 0 202 304
B1), SAPO-11 (US 4,791,083) and SAPO-37 (US 4,842,714;
4,681,864) in FCC applications.
There are also references to the use of zeolite beta
in combination with zeolite Y catalysts as a means for
improving gasoline octane and producing light olefins.
Thus, for example, Chen et al., in US 4,740,292 and in US
4,911,823, describe the use of REY + zeolite beta as an effective
means to improve the octane of gasoline while increasing the yield
of C3/C4 olefins.
While all=of the above approaches were effective at
increasing olefin yields in FCC, none provided a complete
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solution to the problem of making more light olefins, while
maintaining gasoline yields and gasoline octane. We knew
that cracking refineries of the future would need more
olefins.
We found that the combination of a ZSM-5 type zeolite
(e.g., ZSM-5, ZSM-11) and zeolite beta, optionally with a
zeolite Y containing catalyst, is unexpectedly effective in
increasing gasoline octane while at the same time producing
substantial amounts of light olefins.
Zeolite beta, and shape selective zeolites such as
ZSM-5 can be said to operate synergistically in catalytic
cracking, in that the combination of the two zeolites is
more effective than either of the individual components
when measured on a constant zeolite basis.
Accordingly, the present invention provides a process
for catalytic cracking, in either a moving of fluidized bed
(FCC), of a normally liquid hydrocarbon feed containing
hydrocarbons boiling above 343°C (650°F) comprising
cracking the liquid feed in a cracking reactor at cracking
conditions by contact with a source of regenerated
equilibrium catalyst comprising catalytically effective
amounts of: zeolite beta and a shape selective zeolite
having a Constraint Index (CI) of 3-12; and a faujasite cracking
catalyst and wherein the weight ratio R, defined as (wt ~ CI 3-12
zeolite) / (wt ~ CI 3-12 zeolite + wt ~ zeolite beta), on a pure
crystal basis and exclusive of matrix or other catalytic components
which may be present, ranges from 0.01 to 0.95.
In another embodiment, the present invention
provides a process for the fluidized catalytic cracking
(FCC) of a normally liquid hydrocarbon feed containing
hydrocarbons boiling above 343°C (650°F) comprising
cracking the liquid feed in an FCC cracking reactor at FCC
cracking conditions by contact with regenerated equilibrium
catalyst comprising, on a matrix free basis 40 to 90 wt %
zeolite Y having a silica:alumina ratio above 5:1 and
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containing 0.2 to 5.0 wt % rare earths; 5 to 50 wt %
zeolite beta; and 1/2 to 25 wt % ZSM-5.
In another embodiment, the present invention provides
a catalyst composition for fluidized catalytic cracking
comprising particles having an average particle size within
the range of 50 to 100 um and comprising zeolite Y, zeolite beta and
ZSM-5, and wherein the ratio R defined as ZSM-5 (ZSM-5 + zeolite beta),
on a matrix free basis ranges from 0.01 to 0.95, and wherein the
zeolites are essentially free of added hydrogenation/dehydrogenation
components.
Figure 1 (Prior Art) shows a Conventional FCC unit
with a riser reactor.
Figure lA shows the effect of ZSM-5 and beta, on a %
I5 additive basis, on the research octane of FCC gasoline.
Figure 2 shows the effect of ZSM-5 and beta, on a %
additive basis, on the motor octane of FCC gasoline.
Figure 3 shows the effect of ZSM-5 and beta, on a %
additive basis, on propylene yields from an FCC unit.
Figure 4 shows the effect of ZSM-5 and beta, on a %
additive basis, on isobutane yields from an FCC unit.
Figure 5 shows the effect of ZSM-5 and beta, on a %
additive basis, on butene yields from an FCC unit.
Figure 6 shows the effect of ZSM-5 and beta, on a pure
zeolite basis, on the research octane of FCC gasoline.
Figure 7 shows the effect of ZSM-5 and beta, on a pure
zeolite basis, on the motor octane of FCC gasoline.
Figure 8 shows the effect of ZSM-5 and beta, on a,pure
zeolite basis, on propylene yields from an FCC unit.
Figure 9 shows the effect of ZSM-5 and beta, on a pure
zeolite basis, on isobutane yields from an FCC unit.
Figure 10 shows the effect of ZSM-5 and beta, on a
pure zeolite basis, on butene yields from an FCC unit.
Figure 11 shows the effect of ZSM-5 and beta on motor
octane at different conversions in the FCC unit.
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WO 95!02653 PCT/US94107865
Figure 1 (Prior Art) is a simplified schematic view of
an FCC unit of the prior art, similar to the Kellogg Ultra
Orthoflow converter Model F shown as Fig. 17 of Fluid
Catalytic Cracking Report, in the January 8,.1990 edition
of Oil & Gas Journal.
A heavy feed such as a gas oil, vacuum gas oil is
added to riser reactor 6 via feed injection nozzles 2. The
cracking reaction is completed in the riser reactor, which
takes a 90° turn at the top of the reactor at elbow 10.
Spent catalyst and cracked products discharged from the
riser reactor pass through riser cyclones 12 which
efficiently separate most of the spent catalyst from
cracked product. Cracked product is discharged into
disengager 14, and eventually is removed via upper cyclones
16 and conduit 18 to the fractionator.
Spent catalyst is discharged down from a dipleg of
riser cyclones 12 into catalyst stripper 8, where one, or
preferably 2 or more, stages of steam stripping occur, with
stripping steam admitted via lines 19 and 21. The stripped
hydrocarbons, and stripping steam, pass into disengager 14
and are removed with cracked products after passage through
upper cyclones 16.
Stripped catalyst is discharged down via spent
catalyst standpipe 26 into catalyst regenerator 24. The
flow of catalyst is controlled with spent catalyst plug
valve 36.
This stripper design is efficient due to its generous
size. Most riser reactor FCC's have strippers disposed as
annular beds about the riser reactor, and do not provide
., 30 this much cross sectional area for catalyst flow.
Catalyst is regenerated in regenerator 24 with air,
added via air lines and air grid distributor not shown.
Cat cooler 28 permits heat removal from the regenerator.
Regenerated catalyst is withdrawn via regenerated catalyst
plug valve assembly 30 and discharged via lateral 32 into
the base of the riser reactor 6 to contact and crack fresh
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feed injected via injectorsl2, as previously discussed.
Flue gas, and some entrained catalyst, are discharged into
a dilute phase region in the upper portion of regenerator
24. Entrained catalyst is separated from flue gas in
multiple stages of cyclones 4, and discharged via outlets 8
into plenum 20 for discharge to the flare via line 22.
Having provided an overview of the process and
apparatus of the invention, more details will now be
provided about the FCC process and the reactor design
(which can be conventional) and the catalyst system of the
present invention.
FEED
Any conventional FCC or moving bed cracking unit feed
can be used. The feeds for FCC may range from the typical,
such as petroleum distillates or residual stocks, either
_ virgin or partially refined, to the atypical, such as coal
oils and shale oils. Moving bed cracking units usually can
not handle feeds containing much resid. The feed
frequently will contain recycled hydrocarbons, such as
light and heavy cycle oils which have already been cracked.
Preferred feeds for both FCC and TCC are relatively
light, clean feeds. The ideal feeds are those which are
completely distillable and have been hydrotreated.
However, the benefits of combining the two zeolites will be
observed with any feed.
i_aEACTOR CONDITIONS
Conventional cracking conditions may be used. In FCC
processing, riser cracking is preferred. Most riser FCC
units operate with catalyst/oil weight ratios of 1:1 to
10:1, and a hydrocarbon residence time of 1 - l0 seconds.
Most operate with reactor outlet temperatures of 510 -
566°C (950 - 1050°F). The reactor outlet temperature is
preferably above 538°C (1000°F), most preferably from 552
to 593°C (1025 to 1100°F), and most preferably about
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580°C (1075 F). Short contact times, 0.1 - 1 seconds, and
temperatures of 538° - 649°C (1000 - 1200°F), may also be
used.
Quench is beneficial but not essential.. Quench will
augment production of gasoline boiling range olefins, which
the catalyst system of the present invention efficiently
converts into lighter olefins.
Conventional all riser cracking FCC's, such as
disclosed in U.S. 4,421,636, may be used.
In moving bed cracking units, such as the one shown in
US 4,980,051, conventional conditions may also be used.
More details about the TCC design and operating conditions
are also reported by Avidan and Shinnar in Development of
Catalytic Cracking Technology. A Lesson in Chemical
Reactor Design, I & EC RESEARCH, 1990, 29. Typical TCC
cracking conditions include a cat:oil weight ratio of 1.5
to 15, and preferably 4 to 10, and a reactor temperature of
450 to 550 C, preferably about 500 to 530 C. The catalyst
formulation for TCC can be identical to that used in FCC
units, but the catalyst will be in the form of 3-5 mm
spheres.
FCC RISER REACTOR OUTLETfCATALYST SEPARATION
It is preferred, but not essential, to separate
rapidly spent catalyst from cracked products discharged
from the reactor. Use of a cyclone separator, or other
inertial separator will help separate coked catalyst from
cracked products.
Closed cyclones, such as those available from the M.
W. Kellogg company, which rapidly remove cracked products
from the reactor vessel are preferred.
CATALYST STRIPPING
Conventional stripping techniques can be used to
remove strippable hydrocarbons from spent catalyst, usually
contact with 1 to 5 wt % steam.
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CATALYST REGENERATION
The process and apparatus of the present invention can
use conventional FCC regenerators. Most use a single
large vessel, with a dense phase, bubbling fluidized bed of
catalyst. High efficiency regenerators, with a fast fluid
bed coke combustor, a dilute phase transport riser above
it, and a second fluidized bed to collect regenerated
catalyst, may be used. More details about several
representative bubbling dense bed regenerators are
presented below.
Swirl regenerators are disclosed in US 4,490,241,
Chou, and US 4,994,424 Leib and Sapre.
A cross-flow regenerator is disclosed in US 4,980,048
Leib and Sapre.
A regenerator associated with a stacked or Orthoflow
type FCC unit is disclosed in US 5,032,252 and US 5,043,055
Owen and Schipper.
TCC regeneration conditions include catalyst air
contact at temperature from 600 to 700 C, with the catalyst
passing as a moving bed through the regenerators, sometimes
called kilns.
samar.vcm wSTFM OF THE INVENTION
The catalyst system of the invention must contain
catalytically effective amounts of both ZSM-5 (or other
zeolite having the appropriate constraint index such as
ZSM-11) and zeolite beta. The weight ratio of the ZSM-5
"type zeolite" (i.e., ZSM-5 or ZSM-11 or combinations of
the two) to the combination of the ZSM-5 and zeolite beta:
R = (ZSM-5/(ZSM-5 + zeolite beta)
must be greater than 0.01 and less than 0.95 and preferably
in the range of 0.02 to 0.50.
R can be approximately determined from the relative
ratios of the XRD peak intensities of the two zeolites in
non-intersecting 2 Theta regions. For ZSM-5 this would be
for the five indexed peaks in the 22.5 - 25.2R region. For
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zeolite beta, this would be for the indexed peaks in the 20
- 24R region. To attain these peak intensities for an FCC
catalyst sample where ZSM-5 and zeolite beta may be in
' small concentration, e.g., in combination with a Y zeolite,
it may be required to use synchrotron radiation as~the X-
ray source.
The catalyst system may, and usually will, contain
large amounts of conventional zeolite Y based cracking
catalyst. When zeolite Y based catalyst is present best
results will be achieved if a low hydrogen transfer
catalyst is used. An example of a low hydrogen transfer
catalyst is USY or USY containing small amounts of rare
earth oxides. Such catalysts are available "off the shelf"
from many FCC catalyst manufacturers.
When the equilibrium catalyst, or "E-Cat" is a mix of
faujasite catalyst and ZSM-5 + beta, the following
additional guidelines can be given regards optimum amounts
of each. Preferably the Y zeolite provides at least 75 %
of the total zeolite content of the E-Cat, on a matrix free
basis. The total (ZSM-5 + beta) zeolite content should
usually be the remainder, i.e., less than 25 wt %.
The zeolite beta component should be present in
excess, i.e., it should be a majority of the non-Y zeolite
present. Preferably the beta content is at least twice
that of the ZSM-5 or other CI 3 - 12 zeolite. More
preferably, the weight ratio of zeolite beta:ZSM-5 is above
5:1, and most preferably above 10:1. We have achieved good
results with ratios of beta:ZSM-5 of around 20:1 to 30:1,
and believe optimum results can be achieved in many
refineries with a beta:CI 3 - 12 zeolite weight ratio of
15:1 to 50:1.
Thus almost an order of magnitude more beta than ZSM-5
may be required for optimum results. The reasons for this
are not entirely understood, as both zeolite beta and ZSM-5
are relatively high silica materials.
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All parts of the catalyst system may be in the same
particle, or in separate particles with about the same
fluidization characteristics, i.e., similar particle size
and density so that essentially the same catalyst system
will be at the base of a riser reactor as at the top.
Conventional additives for CO combustion, metals
passivation, etc., may also be present.
Each part of the catalyst system of the invention is
reviewed in depth hereafter, starting with the preferred,
but optional, zeolite Y based cracking catalyst and
additives.
CONVENTIONAL ZEOLITE Y CATALYST
Much, even most, of the circulating catalyst inventory
may be commercially available zeolite Y based FCC catalyst.
This Y zeolite catalyst usually contains at least 10 wt %
large pore zeolite in a porous refractory matrix such as
silica-alumina, clay, or the like. The zeolite content may
be much higher than this, e.g., 20 wt % or 30 wt % or more.
All zeolite contents discussed herein refer to the
zeolite content of the makeup catalyst, rather than the
zeolite content of the equilibrium catalyst, or E-Cat.
Much crystallinity is lost in the weeks and months that the
catalyst spends in the harsh, steam filled environment of
modern FCC regenerators, so the E-cat has a lower zeolite
content by classical analytic methods than the makeup
catalyst. Most refiners refer to the zeolite content of
their makeup catalyst, and the MAT (Modified Activity Test)
or FAI (Fluidized Activity Index) of their E-Cat and this
specification adopts this naming convention.
3o Conventional zeolites such as hydrogen (HY) and rare
earth exchanged (REY) zeolites, or aluminum deficient forms
of these zeolites such as dealuminized Y (DEAL Y),
ultrastable Y (USY) and ultrahydrophobic Y (UHP Y) may be
used. The modified Y zeolites may be stabilized with Rare
Earths, e.g., 0.1 to 20 wt % RE203.
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LOW HYDROGEN TRANSFER Y ZEOLITE
Preferably the zeolite Y cracking catalyst, if
present, has a low hydrogen transfer activity. Thus use of
TM
a low rare earth, high silica Y zeolite, such as LREUSY
increases production of gasoline boiling range olefins
which increases production of lighter olefins.
To maximize gasoline olefin content the rare earth
content of the USY catalyst should be 0.2 to 10 wt %,
preferably 0.2 to 5.0 wt %, and most preferably 1.0 to 3.0
wt %.
The silica:alumina ratio of the ultrastable Y zeolite
will usually be 5 to 100, preferably 6 to 20, and most
preferably 6 to 15. The unit cell size will typically be
less than 2.46 nm (24.60 Angstrom).
One minor distraction of using LREUSY is that there
will usually be some reduction in gasoline yield, more than
if an equivalent amount of zeoiite beta based cracking
catalyst were used instead of LREUSY based catalyst.
ADDITIVES
The circulating catalyst inventory typically contains
one or more additives, either present as separate additive
particles,. or mixed in with each particle of the cracking
catalyst. Additives can be added to enhance fluidization,
promote CO combustion, or SOx capture, impart metals
resistance, etc. These may be present but are not
essential.
The above materials, the zeolite Y based cracking
catalyst and various additives, are optional. The two
essential catalyst elements will now be reviewed, the ZSM-5
or ZSM-11 zeolite and the zeolite beta zeolite.
CI 3 - 12 COMPONENT
Any crystalline material having a Constraint Index of
3-12 can be used but ZSM-5 is especially preferred.
Details of the Constraint Index test procedures are
WO 95/02653 ' t ,.~ ~ '~, ' p~ PCT/US94/07865
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provided in J. Catalysis 67, 218-222 (1981), U.S. 4,016,218
and in U.S. 4,711,710 (Chen et al).
Preferred shape selective crystalline materials are
exemplified by ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-
48, ZSM-57 and similar materials.
ZSM-5 is described in U.S. 3,702,886, U.S. Reissue
29,948 and in U.S. 4,061,724 (describing a high silica ZSM
5 as '°Sl.llcallte°°) .
ZSM-11 is described in U.S. 3,709,979.
ZSM-12 is described in U.S. 3,832,449.
ZSM-23 is described in U.S. 4,076,842.
ZSM-35 is described in U.S. 4,016,245.
ZSM-48 is described in U.S. 4,350,835.
Zeolites in which some other framework element is
present in partial or total substitution of aluminum can be
advantageous. Elements which can be substituted for part
of all of the framework aluminum are boron, gallium,
zirconium, titanium and trivalent metals which are heavier
than aluminum. Specific examples of such catalysts include
ZSM-5 containing boron, gallium, zirconium and/or titanium.
In lieu of, or in addition to, being incorporated into the
zeolite framework, these and other catalytically active
elements can be deposited upon the zeolite by any suitable
procedure, e.g., impregnation.
Relatively high silica shape selective zeolites may be
used, i.e., with a silica/alumina ratio above 20/1, and
more preferably with a ratio of 70/1, 100/1, 500/1 or even
higher.
Preferably the shape selective zeolite is placed in
the hydrogen form by conventional means, such as exchange
with ammonia and subsequent calcination.
The CI 3 - 12 component, hereafter frequently referred
to by the preferred member of this group, ZSM-5, may be
incorporated as a separate, individual catalyst in its own
matrix system or it may be combined with the zeolite beta
zeolite in the same particle. Alternatively, ZSM-5 may be
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combined into one particle along with both the Y zeolite
and zeolite beta or with either Y or zeolite beta. The
ZSM-5 content in the particle may range from 1 wt % to 80
' wt %. Below 1.0 wt % ZSM-5 in the particle,.the
effectiveness of the zeolite is diminished because of
dilution. Above 80 wt % the structural integrity of the
catalyst particle drops markedly.
ZEOLITE BETA COMPONENT
The zeolite beta component may be incorporated as a
separate, individual catalyst in its own matrix system or
it may be combined with the ZSM-5 zeolite in the same
particle. Alternatively, zeolite beta may be combined into
one particle along with both the Y zeolite and ZSM-5 or
with either Y or zeolite beta. The zeolite beta content in
the particle may range from 1 wt % to 80 wt %. As With
ZSM-5, at levels below 1.0 wt % in the particle, the
effectiveness of the zeolite is diminished because of
dilution. Above 80 wt %~the structural integrity of the
catalyst particle drops markedly. .
2o Different forms of zeolite beta, which have the same
X-ray diffraction pattern, may also be used, e.g., Ga
containing zeolite beta wherein the Ga has been
isomarphously substituted. See for example EP-A-45314B on
Ga Beta.
TRI
It may be desirable to incorporate the zeolites (any
of them, ranging from the conventional zeolite Y to zeolite
beta or ZSM-5) into a conventional matrix. Such matrix
materials include synthetic and naturally occurring
substances, such as inorganic materials, e.g., clay,
silica, and metal oxides such as alumina, silica- alumina,
silica-magnesia, etc. The matrix may be in the form of a
cogel or sol.
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The relative proportions of zeolite component and
inorganic oxide gel matrix on an anhydrous basis may vary
widely with the zeolite content ranging from'S to 99, more
usually 10 to 65, wt.% of the dry composite.. The matrix
may have catalytic properties, generally acidic, and may be
impregnated with a combustion promoter, such as platinum.
The matrix material may include phosphorus that is
derived from a water soluble phosphorus compound including
phosphoric acid, ammonium dihydrogen phosphate, diammonium
hydrogen phosphate, ammonium phosphate, ammonium
hypophosphate, ammonium phosphite, ammonium hypophosphite
and ammonium dihydrogen orthophosphite.
The zeolites may be used on separate catalyst
particles or the different zeolites may be present in the
same particle.
The following examples are provided in support of the
invention.
ERAMPLE 1
A zeolite beta fluid catalyst was prepared by spray
drying an aqueous slurry containing 1600 grams of zeolite
beta, 3212 grams of colloidal silica (34% Si02; ex. Nalco ).
144 grams of pseudoboehmite alumina (75% solids: ex.
Condea~)peptized-with 21.6 grams of formic acid (90%) and
756 grams of deionized water, 1988 grams of Thiele RC-32T"
clay slurry (60.37% solids), 472 grams of phosphoric acid
(86.1%), and 3928 grams of deionized water.
The catalyst composition was: 40 wt.% zeolite beta,
27.3 wt.% silica, 2.7 wt.% alumina, and 30.0 wt.% clay.
After spray drying, the catalyst was calcined. The
calcination was carried out at 538°C (1000°F) for 3 hours
in air.
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EXAMPLE 2
The catalyst of Example 1 was steamed for 10 hours,
788°C (1450°F), 45% steam at a pressure of 105 kPa (0
psig) .
EXAMPLE 3
A commercial ZSM-5 FCC additive catalyst containing 15
wt % zeolite was steamed for 10 hours, 788°C (1450°F), 100%
steam at a pressure of 150 kPa (6 psig).
ERAMPLE 4
The zeolite Y catalyst employed in the present study
was an RE-USY FCC catalyst removed from a commercial FCC
unit following oxidative regeneration. The fresh or makeup
catalyst to this unit contained 35 wt % zeolite Y.
EXAMPLE 5
The catalyst of Example 3 was blended with Example 4
to the following additive level:
2 wt.% Example 3
98 wt.% Example 4
The 'value of R, the ratio of ZSM-5 to (ZSM-5 + zeolite
beta) for this example was unity, as no zeolite beta was
present.
ERAMPLE 6
The catalysts of Example 2 and Example 3 were blended
with Example 4 to the following additive level:
WT % ADDITIVE
g Zeolite/100 g Mixture
23 wt.% Example 2 9.2 g beta
2 wt.% Example 3 0.3 g ZSM-5
75 wt.% Example 4 26.3 g Y
The value of R, the ratio of ZSM-5 to (ZSM-5 + zeolite
beta), was 0.032.
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EXAMPLE 7
The catalyst of Example 2 was blended with Example 4 '
to the following additive level:
25 wt.% Example 2
75 wt.% Example 4
The value of R, the ratio of ZSM-5 to (ZSM-5 + zeolite
beta), was zero because no ZSM-5 additive was present.
CA'T'ALYTIC EVALUATION
The catalysts of Examples 4 - 7 were evaluated in a
fixed-fluidized bed (FFB) unit at 516°C (960°F), 1.0 minute
catalyst contact time using a Nigerian Light Vacuum Gas Oil
(NLVGO) with the properties shown in Table 1.
Table 1. Properties of Nigerian Light Vacuum Gas Oil
Pour Point, °C (°F) 38 (100)
1~ K.V. ~ 100°C 10.05
Aniline Point, °C (°F) 86 (187.4)
Gravity, API 21.6
Carbon, wt % 87.56
Hydrogen, wt % 12.0
Sulfur, wt % 0.30
Nitrogen, wt % 0.14
Total 100.0
A range of conversions was scanned by varying the
catalyst/oil ratios. The FFB results (after interpolation
at 70 vol.% conversion) are summarized in Table 2.
At a given conversion, zeolite beta combined with ZSM-
5 (Example 6) produces a higher octane gasoline than the
conventional RE-USY (Example 4), the combination of ZSM-
5/RE- USY (Example 5) or the combination of zeolite
beta/RE-USY (Example 7) as measured by Research Octane
Number (RON). Figure 11 also shows that the combination of
ZSM-5 and beta is superior to either ZSM-5 or beta combined
with RE-USY as measured by Motor Octane Number (MON).
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Also, Figures 1 - 10 shop that the ZSM-5 + zeolite
beta combination (Example 6) produces more light olefins
(C3= and C4=) and isobutane yields vs. the conventional RE-
USY or combination of ZSM-5/RE-USY. ,
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Tablet
Example -
Additive Concentration
ZSM-5, wt % - 2 - 2 '
'
Beta, wt % - - 25 23
RE-USY, wt % 100 98 75 75
R ratio ~ 0 1.0 -0- 0.03
Yield Shifts Relative RE-USY
To
Conversion, vol % 70.0 0.0 0.0 0.0
Conversion, wt % 65.9 (0.3) (0.2) (0.3)
C5+ Gasoline, wt % 49.0 (3.3) (4.4) (5.3)
C5+ Gasoline, vol % 54.5 (3.3) (4.2) (5.1)
Light Gas, wt % 1.5 0.6 0.4 (0.2)
Total C3, vol % 7.5 2.5 2.0 4.3
Total C4, vol % 10.7 0.2 3.4 3.4
Coke, wt % 3.6 0.8 0.3 0.2
LFO, wt % 25.5 0.1 (2.2) (1.4)
HFO, wt % 8.6 0.2 2.4 1.8
G+D, wt % 74.6 (3.3) (6.8) (6.8)
Alkylate, vol % 16.0 4.1 8.1 10.6
Gasoline+ Alkylate vol 70.6 0.7 3.8 5.4
%
Outside iC4 for Alky LV % 6.3 2.3 4.6 5.7
n-C5, vol % 0.8 (0.1) (0.4) (0.4)
i-C5, vol % 3.4 0.6 0.8 1.1
vol % 3.2 0.2 2.5 1.9
C5=
, 1.7 (1.2) (0.2) (0.7)
n-C4, vol %
n-C4, wt % 1.1 (0.8) (0.1) (0.4)
i-C4, vol % 4.7 0.5 0.9 1.5
i-C4, wt % 3.1 0.3 0.5 1.0
C4=, vol % 4.3 0.9 2.7 2.6
C4=, wt % 3.1 0.6 1.9 1.8
C3, vol % 2.2 0.9 (0.1) 0.5
C3, wt % 1.3 0.5 (0.1) 0.3
vol % 5.3 1.6 2.1 3.8
C3=
, 3.2 1.0 1.3 2.3
C3=, wt %
C2, wt % 0.2 0.1 0.6 0.1
C2=, wt % 0.6 0.1 (0.1) (0.2)
C1, wt % 0.6 0.1 (0.1) (0.1)
H2, wt % 0.11 0.0 0.0 0.0
H2S, wt % 0.04 0.1 0.0 0.0
Crackability 2.3 0.0 0.0 0.0
Hydrogen Factor 86 (15.0) (26.0)(21.0)
RON, Raw Gasoline 90.8 1.9 1.7 2.7
RON, C5+ Gasoline 90.0 1.4 2.0 2.8
RON, C5+ Gaso. + Alky 90.9 1.2 1.7 2.1
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These examples show the synergism between ZSM-5 and
' zeolite beta in accomplishing the objectives of higher
olefin makes and higher octanes.
The combination of the two zeolites can. be
characterized by a weight ratio,
R = (ZSM-5)/(ZSM-5 + zeolite beta)
wherein the synergistic effects are noted when 0.01 < R <
0.95 and preferably when 0.02 < R < 0.50.
R can be approximately determined from the relative
ratios of the XRD peak intensities of the two zeolites in
non-intersecting 2 Theta regions. For ZSM-5 this would be
for the five indexed peaks in the 22.5 - 25.2R region. For
zeolite beta, this would be for the indexed peaks in the 20
- 24R region. To obtain these peak intensities for an FCC
catalyst sample where ZSM-5 and zeolite beta are in small
concentration, e.g., in combination with a Y zeolite, it
may be necessary to use synchrotron radiation as a source
for the X-rays.
