Note: Descriptions are shown in the official language in which they were submitted.
WO 951~9~06 2 1 7 9 3 8 0 PCr/lJsg~/oo~z7
A C~T YTIC rR7 . ~ PROCE88
This invention relates to a process for the
catalytic cracking of hydrocarbon oils.
Catalytic cracking of hydrocarbon oils utilizing
5 crystalline zeolites is a known process, practiced
for example, in fluid-bed catalytic cracking (FCC)
units, moving bed or thermofor catalytic cracking
~TCC) reactors, and f ixed-bed crackers .
Crystalline zeolites, particularly large pore
10 zeolites having a pore size in excess of 7 Angstom,
and especially zeolite Y, have been found to be
particularly effective for the catalytic cracking of
a gas oil to produce motor fuels, and have been
described and claimed in many patents, including U . S .
Patents 3,140,249; 3,140,251; 3,140,252; 3,140,253;
and 3,271,418. It is also known in the prior art to
incoL~Jr clte the large pore crystalline zeolite into a
matrix for catalytic cracking, and such disclosure
appears in one or more of the above-identified U.S.
2 0 patents .
It is also known that; ~vt:d results can be
obtained in the catalytic cracking of gas oils if a
crystalline zeolite having a pore size of less than 7
Angstrom units is included with the large pore
25 crystalline zeolite with or without a matrix. A
disclosure of this type is found in U. S . Patent
3,769,202. Although the incorporation of a
crystalline zeolite having a pore size of less than 7
Angstrom units into a catalyst composite comprising a
30 large-pore size crystalline zeolite has been very
effective with r~spect to raising the octane number
of the gasoline product, nevertheless it has done so
at the expense of the overall yield of g~col ;n~.
T .,v~:d results in catalytic cracking with
35 respect to both octane number and overall yield were
WO 95/l 91,(\fi PCT/uss~l~P~7
21 79380 -2-
achieved in U . S . Patent 3, 758, 4 03, in which the
cracking catalyst comprised a large-pore size
crystalline zeolite (pore size greater than 7
Angstrom units) in admixture with a 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.
The use of ZSM-5 zeolite in conjunction with a
zeolite cracking catalyst of the X or Y faujasite
variety is described in U.S. Patents 3,894,931;
3,894,933; and 3,894,934. The former two patents
disclose the use of a ZSM-5 zeolite in amounts of
about 5-10 wt. %; the latter patent discloses the
weight ratio of ZSM-5 zeolite to large-pore size
crystalline zeolite within the range of 1:10 to 3:1.
The addition of a separate additive or composite
catalyst comprising ZSM-5 has been found to be
tUL~L- ly efficient as an octane and total yield
improver, when used in very small amounts, in
conjunction with a conventional cracking catalyst.
Thus, in U.S. Patent 4,309,279, it was found that
only 0.1 to 0.5 wt.9~ of a ZSM-5 catalyst, added to a
conventional cracking catalyst under conventional
cracking operations, could increase octane by about
1-3 RON + O (Research Octane Number Without Lead).
U.S. Patent 4,309,280 also teaches ZSM-5 and
other zeolites in conjunction with a conventional
cracking catalyst.
U.S. Patent 4,740,292 discloses catalytic
cracking with a mixture of zeolite Beta and a
faujasite zeolite.
U.S. Patents 4,309,279; 4,309,280; and 4,521,298
disclose catalytic cracking processes characterized
by the addition of very small amounts of additive
promoter comprising a class of zeolites having a
WO 95/I9.t06 2 1 7 9 3 8 0 PCTIUS9 1/0~27
--3--
Constraint Index of about l to 12 to cracking
catalysts .
U.S. Patent 4,416,765 discloses catalytic
cracking using a catalyst comprising an amorphous
cracking catalyst and a minor amount of a class of
crystalline zeolites characterized by a silica to
alumina ratio greater than about 12 and a Constraint
Index of 1 to 12.
In accordance with the present invention, there
has now been discovered an improved process for
upgrading the total yield and octane number of
gasoline boiling range product, while also increasing
the yields of C3, C4 and C5 olefins and isobutane.
This desirable result is obtained by the use of a
catalyst composition comprising ZSM-12 and one or
more large-pore crystalline zeolites having a
Constraint Index less than about 1.
Accordingly, the present invention resides in a
catalytic cracking process which comprises contacting
a hydrocarbon feed in the absence of added 11YdLU~
with a cracking catalyst comprising a zeolite having
the structure of ZSM-12 and a large-pore, crystalline
zeolite having a Constraint Index less than 1, the
weight ratio of the zeolite having the structure of
ZSN-12 to the large-pore crystalline zeolite
component being in the range 1:10 to 10 :1.
The process enables heavy feedstocks, such as
gas oils boiling above 215C (420-F), to be converted
to gasoline range pIvdu~L~ boiling below 215-C
(420-F) and distillates in the 215 to 343-C (420 to
650 F range) . Use of the catalyst composition of
this invention results in; ~JVC:d cracking activity
over the base REY catalyst, increased octane numbers
of the product gasoline and increased gasoline plus
WO 95/l9~OG PCTIUS9~/OO~t7
2~ 79380
alkylate yield relative to the base REY catalyst
alone .
The present hydrocarbon conver6ion process is an
~,ved catalytic cracking process which involves
5 converting a hydrocarbon feed over a cracking
cataly6t. The catalyst used in the process comprises
a zeolite having the structure of ZSM-12 and a large-
pore, crystalline zeolite having a Constraint Index
less than 1, such as REY, USY and REUSY.
ZSM-12 i5 described in U.S. Patent No.
3,832,449, which is incorporated herein by reference.
The weight ratio of the zeolite having the structure
of ZSr~1-12 to the large-pore, crystalline zeolite
having a Constraint Index less than 1 is in the range
1:10 to 10:1, preferably in the range 1:10 to 3:1 and
most prefably in the range 1:10 to 10:7.
As stated previously, another _ ^~t of the
catalyst mixture of the invention is a large-pore,
crystalline zeolite having a Constraint Index less
20 than 1. The method by which Constraint Index is
det-nm1 ned is described fully in U. 5 . Patent No .
4,016,218. Constraint Index (CI) for some typical
zeolites including some which are suitable as
catalyst . ~s in the catalytic cracking process
25 of this invention are as follows:
W095119~06 2 1 7q380 PCTIUS9110PJ27
--5--
CI (at test t~ ^rature)
ZSM-4 0.5 (316-C)
ZSM-5 6-8.3 (371-C-316-C)
5 ZSM-ll 5-8.7 (371~C-316-C)
ZSM-12 2.3 (316-C)
ZSM-20 0.5 (371-C)
ZSM-22 7.3 (427-C)
ZSM-23 9.1 (427-C)
ZSM-34 50 (371-C)
ZSM-35 4.5 (454-C)
ZSM-48 3 . 5 (538 C)
ZSM--50 2.1 (427-C)
MCM--22 1.5 (454-C)
TMA Offretite 3.7 (316-C)
TEA Mordenite 0.4 (316-C)
Clinoptilolite 3. 4 (510 C)
Mordenite 0.5 (316-C)
REY 0.4 (316-C)
Dealll~;ni 70~ y 0.5 (510-C)
Erion ite 3 8 ( 316 C )
Zeolite Beta 0.6-2.0 (316-C-399-C)
The large-pore, crystalline zeolites having a CI
le6s than about 1 which are useful in the process of
25 this invention are well known in the art and have a
pore size sufficiently large to admit the vast
majority of, ~^,nonts normally found in the
feedstock. The zeolites are generally stated to have
a pore size in excess of 7 Any-LL~ and are
30 represented by zeolites having the structure of,
e.g., ZSM-4, ZSM-20, Mordenite, Zeolite Beta,
Dealuminized Y, ~EY, USY and REUSY. A crystalline
silicate zeolite well known in the art and useful in
the present invention is faujasite. The ZSM-20
35 zeolite resembles faujasite in certain aspects of
wo 95ll9~oG PCTIUS94/~0~27
2 1 79380 -6- --
structure but has a notably higher silica/alumina
ratio than faujasite, as does Dealuminized Y.
ZSM-4 is described in U.S. Patent 3,642,434.
ZSM-20 is described in U.S. Patent 3,972,983.
Mordenite is described in U.S. Patent 4,503,023.
Dealuminized Y zeolite is described in U.S.
Patent 3, 442, 795 .
Zeolite Beta is described in U . S . Patent
3,308,069 and RE 28,341.
Zeolites of particular use include REY, USY, and
REUSY .
REY is described in U.S. Patents 3,595,611 and
3,607,043.
Low sodium Ultrastable Y molecular sieve (USY)
is described in U.S. Patents 3,293,192 and 3,449,070.
REUSY is described in U.S. Patent 3,957,623.
It may be desirable to incorporate the zeolites
into a material resistant to the temperature and
other conditions employed in the process. Such
matrix materials include synthetic and naturally
occurring substances, such as inorganic materials,
e.g., clay, silica, and metal oxides. The latter may
be either naturally occurring or in the form of
gelatinous precipitates or gels, including mixtures
of silica and metal oxides. Naturally occurring
clays can be composited with the zeolites, including
those of the -- t _illonite and kaolin families.
These clays can be used in the raw state as
originally mined or initially subj ected to
calcination, acid treat, ~, or chemical
modif ication .
The zeolites may be composited with a porous
matrix material, such as alumina, silica-alumina,
silica-magnesia, silica-zirconia, silica-thoria,
silica-beryllia, silica-titania, as well as ternary
WO 95/19 106 2 1 7 9 3 ~ ~ PC'r/US9 1/OO~Z7
--7--
c4mpositions such as silica-alumina-thoria, silica-
alumina-zirconia, silica-alumina-magnesia, and
silica-magnesia-zirconia. The matrix may be in the
form of a cogel or sol. The relative proportions of
zeolite - ~ and inorganic oxide gel matrix on
an anhydrous basis may vary widely with the zeolite
content ranging from 5 to 99, more usually 10 to 65,
wt. % of the dry composite. The matrix itself may
possess catalytic properties, generally of an acidic
nature, and may be impregnated with a combustion
promoter, such as platinum, to enhance a carbon
combustion.
The matrix material may include rho~rhorus that
is derived from a water soluble phosphorus c _u.-d
including phosphoric acid, ammonium dihydrogen
phosphate, ~1;; ;um llydL~ phosphate, ammonium
phosphate, ammonium hypophosrh~te, ammonium
phosphite, ammonium l~y~ l h~ ; te and i l~m
dillydL~ or~hnphnsphite.
The zeolite having the structure of ZSM-12 and
the large-pore, crystalline zeolite having a
Constraint Index less than 1 may be used on separate
catalyst particles , i . e ., a mixture of the catalysts .
The ZSM-12 zeolite and the large-pore, crystalline
zeolite may also be used as a composite, i.e.,
catalyst particles containing both zeolites in the
same particle.
The ZSM-12 and the large-pore, crystalline
zeolite may be combined, blended, dispersed, or
otherwise intimately admixed or composited with a
porous matrix in such proportions that the resulting
product cnnt lin~: 1 to 95 wt%, and preferably 10 to 70
wt. 96 of the total zeolites in the final composite.
In a moving bed process, the use of a composite
..
WO 95/19.S06 2 1 7 9 3 8 0 PCT/I~S9 J100~27
--8--
catalyst may be preferred; but in a fluid process a
mixture is satisfactory.
The feedstock of the present conversion process
comprises a heavy hydrocarbon oil, such as gas oil,
coker tower bottoms fraction reduced crude, vacuum
tower bottoms, tlpAcrhAlted vacuum resids, FCC tower
bottoms, and cycle oils. Oils derived from coal,
shale or tar sands may also be treated in this way.
Oils of this kind generally boil about 650'F t343 C)
although this process is also useful with oils which
have initial boiling points as low as 500-F t260C).
These heavy oils comprises high molecular weight
long-chain paraf f ins, naphthenes and high molecular
weight aromatics with a large proportion of fused
ring aromatics. The heavy hydrocarbon oil feedstock
will normally contain a substantial amount boiling
above 230-C t450F) and will normally have an initial
boiling point of about 550-F t288-C), more usually
about 650F t343-C). Typical boiling ranges will be
650 to 1050-F t343 to 566-C), or 650 to 950-F t343 to
510-C), but oils with a narrower boiling range may,
of course, be p~,cessed, for example, those with a
boiling range of about 650 to 850-F t343 to 454-C).
Heavy gas oils are often of this kind, as are cycle
oils and other nonresidual materials. It is possible
to co-process materials boiling below 500-F (288-C),
but the degree of conversion will be lower for such
- ~ ~s. Feedstocks containing lighter ends of
this kind will normally have an initial boiling point
above about 300-F tl49-C).
The processing is carried out under conditions
similar to those used for conventional catalytic
cracking. Process temperatures of 750 to 1200-F (400
to 650-C) may conveniently be used, although
35 temperatures above 1050 F t565 C) will normally not
..h'O 9S~19-106 2 1 7 9 38 0 PCT/Us9~100~27
g
be employed. Generally, temperatures of 840 to
1050F (450 to 565'C) will be employed. The space
velocity of the feedstock will normally be from 0.1
to 20 LHSV, preferably 0.1 to 10 LHSV.
The conversion may be conducted by contacting
the feedstock with a fixed stationary bed of
catalyst, a fluidized bed, or with a transport bed.
The catalyst may be regenerated by burning in air or
other oxygen-containing ga6.
A pr-~l ;m;nAry hydL~JL- l:ating step to remove the
nitrogen and sulfur and to saturate aromatics to
naphthenes without substantial boiling range
conversion will usually~improve catalyst performance
and permit lower temperatures, higher space
velocities, or combinations of these conditions to be
employed .
The invention will now be more particularly
.1.~5.';h~ with reference to the following examples and
the A~ ying drawings, in which:
Figure lA is a plot illustrating the
relat;nn~h;r of C5+ ~A~:olin~ yield to activity t%
conversion) .
Figure lB is a plot illustrating the
relat;~nchi~ of octane number of C5+ gasoline to
activity (% conversion).
Figure 2A is a plot illustrating the
relati~n~h;~ of total C4's yield to activity (%
conversion) .
Figure 2B is a plot illustrating the
relationship of dry gas (C3-) yield to activity (%
conversion).
Figure 2C is a plot illustrating the
relationship of coke yield to activity (%
conversion) .
Wo 95/l9~0C PCT~S9~/00~27
21 793~ -lo- ~
Figure 3A i8 a plot illustrating the
relationship of % pentenes/pentanes yield to activity
(% conversion).
Figure 3B is a plot illustrating the
5 relation6hip of % butenes/butanes yield to activity
( % conversion) .
Figure 3C is a plot illustrating the
relationship of % propenes/propanes yield to activity
(% conversion).
Figure 4A is a plot illustrating the
relationship of C5+ gasoline + alkylate yield to
activity (% conversion).
Figure 4B is a plot illustrating the
relationship of octane number of C5+ gasoline +
15 alkylate to activity t % conversion) .
Figure 5A is a plot illustrating the
relationship of coke yield to crackability.
Figure 5B is a plot illustrating the
relation~hip of catalyst/oil ratio to crackability.
~S--VPT,~
Catalyst A
A commercially available FCC catalyst which
comprises about 15 wt% REY is used as the base
catalyst. This catalyst is withdrawn from a
25 commercial FCC unit after oxidative regeneration.
The catalyst contains 560 ppm V, 260 ppm Ni and 1. 7
wt% rare earth oxide. The catalyst has a unit cell
size of 24.41 Al~y~r and is henceforth referred to
as Catalyst A.
Cat~lyst B t
A catalyst for use in the present process is
prepared by spray drying an aqueous slurry containing
25 wt . % ZSM-12, synthesized in accordance with U. S .
Patent 3, 832, 449, in a SiO2-A1203 gel/clay matrix.
WO 95/19406 2 1 7 9 3~0 PCT/U594/00~27
The 6pray dried catalyst i5 ~n;~ Yrh;~n~-~tl and
calcined. The calcination is carried out at 1000-F
t540-C) for 2 hours in air followed by steaming the
catalyst for 4 hours at 1200-F (650-C) in a 45%
steam/55% air mixture at 0 psig (100 kPa). One part
by weight ZSM-12 catalyst is then blended with 3
parts by weight REY catalyst (Catalyst A) to provide
a cracking catalyst having 6.25 wt% ZSM-12/11.25 wt%
REY and is henceforth referred to as Catalyst B.
CatalYst C
A catalyst for use in the process of the present
invention is prepared by spray drying an aqueous
slurry containing 40 wt. % ZSN-12, synthes; Psd in
accordance with U.S. Patent 3,832,449, in a SiO2-
A12O3-H3PO4 sol/clay matrix. The spray dried
catalyst is ammonium ~yrh~n~ed and calcined. The
calcination is carried out at 1000-F (540-C) for 2
hours in air. One part by weight ZSM-12 catalyst is
then blended with 3 parts by weight REY catalyst
(Catalyst A) to provide a cracking catalyst having
8 . O wt~ ZSN-12/11. 25 wt% REY and is henceforth
referred to as Catalyst C.
CatAlvst D
This is a catalyst blend used for comparative
purposes comprising ZSM-5 and Catalyst A to show that
the ZSM-12/large-pore, crystalline zeolite catalysts
of the present invention selectively enhance the
yield of C4 olefins over the ZSM-5/large-pore,
crystalline zeolite catalyst. A ~ ;ially
available ZSM-5 fluid catalyst which comprises about
25 wt. % ZSM-5 in a SiO2-A12O3-clay matrix is calcined
at 1000-F (540-C) for 2 hours in air followed by
steaming the catalyst for 4 hours at 1200-F (650-C)
in a 4596 stean/ 55% air mixture at 0 psig (100 kPa).
One part by weight ZSM-5 catalyst is then blended
Wo 95/19406 PCT/U594Mn427
21 7q380 -12-
with 3 parts by weight REY catalyst (Catalyst A) to
provide a cracking catalyst having 6 . 25 wt . % ZSM-5/
11.25 wt.% REY and is henceforth referred to as
Catalyst D.
Catalysts A, B, C, and D were evaluated in a
fixed-fluidized bed (FFB) unit at a t~ c.Lul~: of
960F (515-C), a 1.0 minute contact time and
a' , ~^r ic plc:S~-ULe: (100 kPa) using a Sour Heavy Gas
oil (SHGO) having the properties as shown in Table 1.
Tabla 1
~rop~rtias of Joliat Sour ~vy GA8 oil
Pour Point, F(-C) 95(35)
Conradson Coke Residue, wt. 9~ 0 . 56
Rinematic Viscosity @ 40C 104.8
15Kinematic Viscosity e lOO-C 7.95
Aniline Point, F(-C) 168.5(76)
Bromine Number 6 . 9
Gravity, API 2 0 .1
Carbon, wt. % 85 .1
20Hydrogen, wt. % 12 .1
Sulfur, wt.% 2.6
Nitrogen, wt. 96 0 . 2
~otal, wt.% 100.0
Basic Nitrogen, ppm 465
25Nickel, ppm 0 . 5
Vanadium, ppm 0 . 3
Iron, ppm 1. 2
Copper, ppm < 0. 1
Sodium, ppm 0 . 8
Wo gs/l9406 2 1 7 q 3 ~3 0 Pcrl[rss4loo~27
--13--
A range of conversions were scanned by varying
the catalyst to oil ratio. The fixed-fluidized bed
results, after interpolation to 65 vol96 conversion,
21re summarized in Tables 2 and 3 below.
!l~ 2
Catalyst Cataly$ Catalyst Catalyst
A B C D
C5+ Gasoline, vol.% 52.4 - 49.9 40.0 37.4
Gasoline + allylate,
10 vol.% 71.2 72.4 74.4 73.8
Alkylate, vol.% 18.8 22.6 34.4 36.5
RON, C5+ Gasoline 90.5 91.4 93.2 93.6
RON, C5+ Gasoline +
Alkylate 91.4 92.2 93.5 93.6
15 Coke, wt.% 6.2 5.3 6.0 5.8
LightFuel Oil wt.% 29.3 29.0 28.3 28.9
Heavy Fuel Oil ~vt.% 7.8 8.3 9.5 8.8
G+D, wt.% 71.9 69.8 60.9 59.7
Total C3, vol.% 7.7 8.9 15.8 18.8
20 Total C4, vol.% 11.7 14.7 19.9 19.4
n-C~;, vol.% 0.4 0.3 o.5 0.3
N-C'4, vol.% 0.8 0.2 0.2 0.1
C, vol.% 1.9 2.9 4.5 4.9
i-~, vol.% 5.3 6.1 5.0 5.0
25 i-C4, vol.% 5.5 7.2 10.4 11.1
Outside i-CA for
Alkylate, vol.% 7.3 8.1 13.2 14.0
Light Gases
Light Gas, wt.% 2.5 2.5 25 3.2
30 C2, wt.% 0.5 0.4 0-5 0-5
C2=, wt.% 0.5 0.3 0.5 0-9
Cl, w~ % 05 0.4 0.5 0.6
H~, wt.% 0.17 0.11 0.13 0.17
H~S, wt.% 0.93 1.26 0.78 0.99
35 H~drogen Factor 146 107 94 95
Wo 95tl940~ PCTrUSs4/00427
21 7~380
Table 3
Catalyst Catalyst Catalyst Catalyst
A B C D
Olefin Yield
5Propylene, vol% 5.8 6.0 11.3 13.9
Butenes, vol.% 5.4 7.5 93 8.2
Pentenes, vol.~fo 4.2 5.3 5.0 3.9
Total, vol.% 15.4 18.8 25.6 26.0
Olefin/Paraffin Selectivity
10 Propylene/Propane 3.1 2.1 25 2.8
Butenes/Butanes 0.9 1.0 0.9 0.7
Pentenes/Pentanes 0.7 0.8 0.9 0.7
Olefin Selectivity
15 C~=/Total
(C3 + Cd + C5 ) 0.38 0.32 0.44 0.53
C,~=/rotal
tC~3=+ C4=+ C5=) 0.35 0.40 0.36 0.32
C5=/Total
20 (C3 + C4 + C5 ) 0.27 0.28 0.20 0.15
Figures lA and lB compare the C5 catalytically
cracked gasoline yield and RON as a function of
650-F+(343 C+) conversion. Figures L~ and lB show
the use of ZSM-12 ~L~,~uces a si~nif1~-Ant drop in
gasoline yield and a concomitant increase in RON. The
ZS~-12/REY catalysts (Catalysts B and C) show
~-nhAn~ activity as measured by RON as compared to
the base REY catalyst alone (Catalyst A). The RON
boosts are in the 1-2 range.
Figures 2A, 2B and 2C compare the C4, dry gas
and coke yields as a function of 650-F+(343-C+)
conversion. Figures 2A and 2B show the use of ZSM-
12/REY catalysts (Catalysts B and C) increase the
amount of C4's (butenes + butanes) ~nluced while
increasing dry gas (H2S + H2 + Cl + C2 + C3 ) only
wo 9SII9l0~ 2 1 7 ~ 3 8 0 PcT/uss4mn~27
--15--
marginally. C4's are more desirable than dry gas.
The use of ZSM-12/REY catalysts also re6ult in no
change in coke make.
Figures 3A, 3B and 3C compare the olefin to
5 paraffin ratio for the light gases (C3 through C5) as
a function of 650 F (343-C+) conversion. Figure 3C
shows that the ZSM-12/REY catalysts (Catalyst B and
C) reduce the olefinicity of the C3, -nts while
increasing the olefinicity of the C4 and C5
10 ~ ^-,ts, as shown in Figures 3A and 3B. C4 and C5
olefins are valuable for methyl tert butyl ether
(MTBE) and tertiary amyl methyl ether (TAME)
production which are maj or, ts in u~-yy~ ated
gasol ine .
Figure 3B in conjunction with Table 3 further
shows that ZSM-12/REY catalysts (Catalysts B and C)
are also more selective toward C4 olefins (butenes)
than the ZSM-5/REY catalyst (Catalyst D). Butenes
are the preferred feedstock for alkylation and for
MTBE production.
Figures 4A and 4B compare the C5+ catalytically
cracked ~colin~ + alkylate, which equals the net
gasoline from the process, and RON as a function of
650-F (343 C) conversion. Figure 4A shows that the
ZSM-12/REY catalysts (Catalysts B and C) make more
net ~col in~ than REY (Catalyst A) alone. Figure 4B
shows that the ZSM-12/REY catalysts (Catalysts B and
C) also produce a higher octane gasoline product as
measured by RON.
Figures 5A and 5B compare the coke make and the
res~uired catalyst to oil ratio versus crackability.
Crackability is a kinetic parameter that reflects the
global second order kinetics of the cracking
reaction. Higher crackabilities correspond to higher
wo 95119~06 --16- PCTIUSg~/00~27
21 79380
conversions. Figure 5A shows that at the same
crackability ( - conversion), the addition of the
ZSM-12 (Catalysts B and C) has little effect on coke
make. At equivalent crackabilities higher catalyst
5 to oil ratios ~uLL~o~.d to lower catalyst activity.
Figure 5B shows that the unsteamed ZSM-12 (Catalyst
C) produces a slightly more active catalyst while the
stea~ned ZSM-12 (Catalyst B) is marginally less active
than the base REY (Catalyst A) with which it is
10 co~bined.
