[0001] The present invention relates to catalytic cracking catalysts, and more specifically
to cracking catalyst compositions which are particularly effective for the cracking
of residual type hydrocarbon feedstocks.
[0002] In recent years, the refining industry has been required to process ever increasing
quantities of residual type feedstocks. These heavy feedstocks are frequently contaminated
with substantial quantities of metals such as vanadium, nickel, iron and copper which
adversely affect cracking catalyst used in refinery operations.
[0003] Zeolite containing cracking catalysts in particular are susceptable to deactivation
(poisoning by vanadium) and in addition the catalytic selectivity of the catalyst
is adversely affected by the presence of iron, copper and nickel.
[0004] U.S. 3,835,031 and U.S. 4,240,899 describe cracking catalysts which are impregnated
with Group IIA metals for the purpose of reducing sulfur oxide emissions during regeneration
of the catalyst.
[0005] U.S. 3,409,541 describes catalytic cracking processes wherein deactivation of the
catalyst by contaminating metals is decreased by adding to the catalytic inventory
a finely divided alkaline earth or boron type compound which reacts with the metal
contaminants to form an inert product that may be removed from the catalytic reaction
system.
[0006] U.S. 3, 699,037 discloses a catalytic cracking process wherein a finely divided additive
such as calcium and magnesium hydroxides, carbonates, oxides, dolomite and/or limestone
is added to the catalyst inventory to sorb SOx components present in the regenerator
flue gas.
[0007] U.S. 4,198,320 describes catalytic cracking catalysts which contain colloidal silica
and/or alumina additives that are added for the purpose of preventing the deactivation
of the catalyst when used to process metals containing feedstocks.
[0008] U.S. 4,222,896 describes a metals tolerant zeolite cracking catalyst which contain
a magnesia-alumina-aluminum phosphate matrix.
[0009] U.S. 4,283,309 and 4,292,169 describe hydrocarbon conversion catalysts which contain
a metals-absorbing matrix that includes a porous inorganic oxide such as alumina,
titania, silica, circonia, magnesia and mixtures thereof.
[0010] U.S. 4,465,779 discloses cracking catalyst compositions which comprise a high activity
catalytic cracking catalyst and as a separate and distinct entity a magnesium compound
or magnesium compond in combination with a heat stable compound.
[0011] U.S. 4,432,890 and 4,469,588 disclose catalytic cracking catalyst compositions which
are used to crack hydrocarbon oild feedstocks that contain significant quantities
of vanadium which comprise a zeolite and an amorphous invert solid matrix containing
a metal additive such as magnesium which may be introduced into the catalyst during
manufacture or during use in the conversion of hydrocarbons.
[0012] PCT WO 82/00105 discloses cracking catalysts that are resistant to metals poisoning
which comprise two particulate size fractions, and an SO
x absorbing additive such as aluminum oxide, calcium oxide and/or magnesium oxide.
[0013] While the prior art suggests several catalytic systems and compositions which are
effective in controlling the adverse poisoning effects of metals contained in residual
type feedstocks or limiting SO
x emissions during regeneration of the catalyst, many of the systems require the use
of expensive additives and/or processing systems and are not particularly cost effective
when operated on a commercial scale.
[0014] It is therefore an object of the present invention to provide improved catalytic
cracking catalysts which are capable of cracking hydrocarbon feedstocks that contain
substantial quantities of metals and sulfur
[0015] It is another object to provide fluid cracking catalysts (FCC) which are resistant
to metals poisoning and which may be recharged and used in large quantities at reasonable
cost.
[0016] It is a further object to provide a catalytic cracking process which is capable of
handling large quantities of metals, vanadium in particular, without substantial loss
of activity or product yield.
[0017] These and still further objects of the present invention will become readily apparent
to one skilled in the art from the following detailed description and specific examples.
[0018] Broadly, the invention contemplates catalytic cracking catalysts which include a
basic alkaline earth metal component in amounts ranging from about 5 to 80 weight
percent expressed as the oxides, wherein the catalyst is capable of maintaining a
high degree of activity when associated with substantial quantities of deactivating
metals such as vanadium deposited on the catalyst.
[0019] More specifically, it has been found that particulate basic alkaline earth metal
compositions are useful which have an intra-particle pore structure characterized
by a pore volume of at least 0.1 cm
3/g in pores having a diameter of about 200 to 10,000 A
° (1 wm=10A), and an average pore diameter (APD) of greater than about 400 A
° when determined in the pore size range of about 200 to 10,000 A
° diameter using the relationship:
wherein PV = pore volume in cm
3/g in pores ranging from 200-10,000 A
° diameter and SA = surface area in m
2/g in pores ranging from 200-10,000 A
° diameter, as determined by mercury porosimetry.
[0020] The alkaline earth metal compound used in the practice of the invention is selected
from group IIA of the periodic Table with calcium and magnesium being preferred and
magnesium the most preferred. In a particularly preferred embodiment of the invention
the basic alkaline earth metal component comprises MgO or magnesia-silica gels and
a significant pore volume in pores greater than about 400 A° at process temperatures
of 760
°C (1400°F) or so.
[0021] In a particularly preferred embodiment a magnesium oxide containing component such
as a magnesia-silica gel (MgO.Si0
2) is prepared in a particulate form wherein the particle has a substantial pore volume
in pores having a diameter of greater than about 400°A. The resulting MgO.Si0
2 composition is included in a FCC catalyst composition either as an integral component
of the FCC catalyst particle or more preferably as a separate particulate additive
in amounts ranging from about 2.5 to 40 by weight of the composition.
[0022] The preferred MgO.SiO
2 gel has the overall weight composition of 30-80% MgO, and a pore volume in pores
greater than about 400°A diameter of at least 0.1 cm3/g and preferably from about
0.2 to 1.0 cm
3/g. Where the MgO.Si0
2 gel is added to a FCC catalyst as a separate particulate additive, the particle size
and density of the additive is preferably similar to that of the FCC catalyst, i.e.
particle size range of about 40 to 80 micrometers and an average bulk density of 0.5
to 1.0 g/cm
3.
[0023] A preferred MgO.Si0
2 gel is prepared by reacting aqueous sodium silicate and magnesium chloride solutions
at a temperature of about 15 to 50°C to form a precipitate gel which is recovered
by filtration, reslurried in water and spray dried at a temperature of about 330 to
500
°C. Furthermore, particulate MgO can be added to the MgO.Si0
2 gel to give composition of 30-80% MgO to the final product.
[0024] As indicated above, the MgO containing catalyst component must have the optimized
pore structure described above in order to be effective for vanadium scavenging. This
is due to the fact that partial molar volume of magnesium vanadate is greater than
magnesium oxide. It is believed that the vanadium poisoning of cracking catalysts
is caused by the poison precursor HsV04 which is formed in the regeneration step from
the reaction of V
20
5 and steam (for vapor pressure data see L.N. Yannopoulos, J. Phys. Chem. 72, 3293
(1968). Hs V0
4 is isoelectronic with H
3P0
4 and is most probably a strong acid. HsV0
4 therefore destroys the zeolite crystallanity and activity by acid hydrolysis of the
SiO
2-Al
2O
3 framework of the zeolite. As H
3V0
4 reacts with MgO and forms (MgO)
2V
2O
5 on the surface of pore, the surface of the pore will swell due to larger molar volume
of (MgO)
2V
2O
5. If the pore is too small, blocking will occur readily and thereby inhibit the further
reaction with H
3V0
4. We have experimentally determined that the average pore diameter must be greater
than 400°A or so to be effective. This effect has been extensively studied with similar
reaction:
CaO + SO3→CaSO4
(see S.K. Bhatia and D. D. Perlmutter AIChE J. 27, 266 and 29, 79).
[0025] As indicated above, MgO is the preferred oxide over the other alkaline earths when
used in conjunction with FCC catalysts. This is due to the presence of sulfur oxides
in the flue gases of the regenerator, which can compete with H
3V0
4 forming alkaline earth S0
4's as shown by a consideration of the equilibrium constants for the reactions of MgS0
4 and CaS0
4 with vanadic acid. Assuming a worst case test in which all of the SO
x is assumed to be S0
3 at a typical level of 2000 ppm in the regenerator, 20% H
2, 1.07 ppm H
3V0
4 and a temperature of 970°K (1285
°F) a calculated equilibrium constant (assuming unit activity for the condensed phases)
from the regenerator conditions above can be compared to the equilibrium constant
for the two reactions from thermochemical data as follows:
[0026] For the case of calcium the calculated equilibrium from regenerator conditions is
much greater than the equilibrium constant for the reaction. By the Le Chatlier's
principle the reaction will favor the left hand side of reaction with calcium. The
opposite is true for the case with MgO. If calcium is used CaS0
4 will be preferentially formed over the vanadate, the opposite is true for magnesium.
[0027] The fluid catalytic cracking catalysts which are combined with the basic alkaline
earth metal component, are conventional and well known to those skilled in the art.
Typically, the catalysts comprise amorphous inorganic oxide gels such as silica-alumina
hydrogels, and/or a crystalline zeolite dispersed in an inorganic oxide matrix.
[0028] Preferred zeolites are synthetic faujasite (type Y zeolite) and/or shape selective
zeolites such as ZSM-5. Type Y zeolites which are exchanged with hydrogen and/or rare
earth metals such as HY and REY, and those which have been subjected to thermal treatments
such as calcined, rare-earth exchanged Y (CREY) and/or Z14US are particularly suited
for inclusion in fluid cracking catalyst compositions. Catalytically active zeolite
components are typically described in U.S. patents 3,293,192 and RE 28,629.
[0029] In addition to an active zeolite component, the catalysts contain an inorganic oxide
matrix. The inorganic oxide matrix is typically a silica-alumina hydrogel, which may
be combined with substantial quantities of clay such as kaolin. In addition, it is
contemplated in catalyst matrix systems which comprise silica, alumina, silica-alumina
sols and gels may be utilized in the practice of the present invention. Methods for
producing suitable catalyst compositions are described in U.S. 3,974,099, 3,957,689,
4,226,743, 3,867,308, 4,247,420, and US-A 4 499 197 (U.S. Serial No. 361,426 filed
March 24, 1982).
[0030] The basic alkaline earth metal component may be added to the catalyst composition
in the form of a finely divided particulate solid or the component may be added in
the form of a salt which is subsequently converted to a solid oxide. Magnesium and
calcium oxides, hydroxides, carbonates or sulfates are particularly suited forms of
the basic alkaline earth metal components which are added to the catalyst either during
or after manufacture. In one preferred embodiment, the basic alkaline earth containing
component is physically admixed with the particulate catalyst. In another preferred
embodiment, the alkaline earth metal component is included in the catalyst composition
(matrix) during manufacture. In order to obtain the maximum degree of metals tolerance
while avoiding undue deactivation of a zeolite component which may be present in the
catalyst, the alkaline earth metal component is added to the zeolite containing catalyst
in a form that does not ion exchange with the zeolite component.
[0031] In a typical FCC catalyst preparation procedure in which the component is added to
the catalyst composition, a finely divided alkaline earth metal component is blended
with an aqueous slurry which contains silica-alumina hydrogel, optimally a zeolite,
and clay to obtain a pumpable slurry which is then spray dried to obtain microspheroidal
particles of catalyst having a particle size ranging from about 20 to 100 micrometers.
The spray dried catalyst, which typically contains from about 0 to 35 percent by weight
zeolite, 25 to 70 percent by weight clay, and 10 to 50 percent by weight matrix binder,
such as silica, alumina, silica-alumina hydrogel or sol, and from 5 to 80 percent
by weight alkaline earth metal component, is washed and ion exchanged to remove soluble
impurities such as sodium and sulfates. After drying to about 10-30 percent total
volatiles the catalyst is ready to be used in conventional catalytic cracking processes.
Typical FCC processes involve contact of the catalyst with a hydrocarbon feedstock
which may contain significant quantities, i.e. from 1 to 200 ppm of vanadium and other
metals such as nickel, iron and copper at temperatures on the order of 482 to 538
°C (900 to 1000
°F) to obtain cracked products of lower molecular weight such as gasoline and light
cycle oil.
[0032] It is found that during the catalytic cracking process, the catalysts contemplated
in tt
fe present invention can sorb in excess of 0.1 percent and up to 10 percent by weight
of metals, particularly vanadium, while maintaining an acceptable level of activity
and product selectivity. Typical "conventional" catalysts, which do not contain the
alkaline earth metal component contemplated herein, lose substantial activity when
the metals content (vanadium in particular) exceeds about 0.1 weight percent.
[0033] Having described the basic aspects of the present invention, the following examples
are given to illustrate the specific embodiments thereof.
Example 1
[0034] This example shows the preparation and use of large and small pore MgO based vanadium
scavenging additives. A magnesia-silica gel was prepared by mixing a 3.62% Si0
2 and 10.87% NaOH aqueous solution with 13.28% MgCI
2 aqueous solution at equal flow rates through a mix pump to form a MgO.Si0
2 gel with composition 60 wt.% MgO 40 wt.% Si0
2. The temperature of the reaction mixture was 30°C for example A to make smaller pore
diameters, and 20
°C for example B for larger pore diameters. The resultant gel in both cases was filtered,
reslurried in water to -10% solids and spray dried at 330
°C. The spray dried material was washed with 70
°C H
20 to remove NaCI. Both preps were calcined for 2 hours at 538
°C.
[0035] Two catalyst samples were prepared by blending 20 % by weight of additive A or B
with 80 % by weight of a commercial FCC catalyst (Super D). The so obtained catalyst
samples were impregnated to a level of 0.67 wt % vanadium, using a solution which
contained vanadyl oxylate dissolved in water. The samples were then pre-heated at
482°C (900°F) for 1 hour and then 2 hours at 760°C (1400°F). The catalyst samples
were then subjected to a hydrothermal deactivation treatment which involved contacting
the catalyst with 100 % steam at a pressure of 0.2 MPa (2 atm) at 732
°C (1350
°F) for 8 hours.
[0036] The catalysts of this Example (as well as the catalysts evaluated in Example 2) were
then tested for catalytic cracking activity using the microactivity test described
in ASTM D-3907. The microactivity (MA) of the catalyst samples is expressed in terms
of volume percent (vol%) of feedstock converted. The results are summarized in Table
I set forth below.
[0037] Analytical data in Table I shows the two Samples have similar properties except that
the metals tolerance of an 80% commercial FCC catalyst (Super D) 20% additive (either
A or B) was dramatically improved for example B. This example clearly demonstrates
the importance of the larger pore volume and APD for vanadium scavenging effectiveness.
Example 2
[0038] This example again shows the use of high pore volume and low pore volume MgO. Catalyst
A is a blend of 80% Super D, 20% commercially available high pore volume MgO (from
Martin Marietta grade Mag-Chem-30). Catalyst B is a blend of 80% Super D, 20% commercially
available low pore volume MgO (from Martin Marietta grade Mag-Chem 10). Both catalysts
are impregnated by the procedure in Example 1. Table II shows the microactivity results.
1. A catalytic cracking catalyst composition which comprises:
(a) a cracking catalyst component, and
(b) from about 5 to 80 percent by weight expressed as the oxides of a basic alkaline
earth metal component wherein said component is characterized by a pore volume of
at least 0.1 cm3/g and an average pore diameter greater than about 40 µm (400 A°)
in pores having diameter of 20-1,000 µm (200-10,000 A°).
2. The composition of claim 1 which contains greater than 0.1 percent by weight vanadium
deposited on the catalyst during use in a catalytic cracking process.
3. The composition of claim 2 which contains from about 0.1 to about 10 percent by
weight vanadium.
4. The composition of claim 1 wherein the catalyst component comprises synthetic faujasite
dispersed in an inorganic oxide matrix.
5. The composition of claim 4 wherein said inorganic oxide matrix comprises silica-alumina
gel and clay.
6. The composition of claim 1 wherein said basic alkaline earth metal compound is
selected from the group consisting of calcium and/or magnesium oxides, carbonates,
acid salts and mixtures thereof.
7. The composition of claim 1 wherein said basic alkaline earth metal component comprises
a magnesia-silica gel having the weight composition 30 to 80 % MgO.
8. The composition of claim 1 wherein said basic alkaline earth metal compound is
dispersed in said matrix as a separate oxide phase.
9. The composition of claim 1 wherein said basic alkaline earth metal component is
physically mixed as a separate particulate additive.
10. A method for the catalytic cracking of metals containing hydrocarbons wherein
said hydrocarbon is reacted under catalytic cracking conditions with a catalyst, and
deactivating metals including vanadium are deposited on said catalyst, the improvement
comprising:
Conducting the reaction using the catalyst of claim 1..
11. The method of claim 10 wherein said catalyst comprises a crystalline zeolite dispersed
in an inorganic oxide matrix.
12. The method of claim 11 wherein said zeolite is synthetic faujasite.
13. The method of claim 12 wherein said zeolite is calcined rare earth exchanged type
Y zeolite.
14. A composition for scavenging vanadium which comprises a magnesia-silica gel having
the weight composition 30 to 80% MgO and a pore volume of at least 0.1 cm3/g and an average pore diameter greater than about 40 µm (400 A°) diameter in pores ranging from about 20 to 1,000 µm (200 to 10,000 A) in diameter.
15. The composition of claim 14 wherein said composition has a total pore volume of
0.2 to 1.0 cm3/g.
16. The composition of claim 14 wherein the composition is formed into particles having
a size range of 40 to 80 micrometers.
17. The composition of claim 16 wherein the particles have a density of about 0.5
to 1.0 g/cm3.
1. Katalytische Crackkatalysatorzusammensetzung, die umfaßt:
(a) eine Crackkatalysatorkomponente und
(b) etwa 5 bis 80 Gew.% ausgedrückt als Oxide einer basischen Erdalkalimetallkomponente,
wobei diese Komponente gekennzeichnet ist durch ein Porenvolumen von mindestens 0,1
cm3/g und einen durchschnittlichen Porendurchmesser von mehr als etwa 40 µm (400 A) in
Poren mit einem Durchmesser von 20 bis 1000 J.lm (200 bis 10 000 Ä).
2. Zusammensetzung nach Anspruch 1, die während der Verwendung in einem katalytischen
Crackverfahren mehr als 0,1 Gew.% auf dem Katalysator niedergeschlagenes Vanadin enthält.
3. Zusammensetzung nach Anspruch 2, die etwa 0,1 bis etwa 10 Gew.% Vanadin enthält.
4. Zusammensetzung nach Anspruch 1, bei der die Katalysatorkomponente synthetischen
Faujasit verteilt in einer anorganischen Oxidmatrix umfaßt.
5. Zusammensetzung nach Anspruch 4, bei der die anorganische Oxidmatrix Siliciumdioxid-Aluminiumoxid-Gel
und Ton umfaßt.
6. Zusammensetzung nach Anspruch 1, bei der die basische Erdalkalimetallverbindung
ausgewählt ist aus der Gruppe bestehend aus Calcium- und/oder Magnesiumoxiden, -carbonaten,
-säuresalzen und Mischungen derselben.
7. Zusammensetzung nach Anspruch 1, bei der die basische Erdalkalimetallkomponente
ein Magnesiumoxid-Siliciumdioxid-Gel mit 30 bis 80 Gew.% Mg0 umfaßt.
8. Zusammensetzung nach Anspruch 1, bei der die basische Erdalkalimetallverbindung
in der Matrix als separate Oxidphase verteilt ist.
9. Zusammensetzung nach Anspruch 1, bei der die basische Erdalkalimetallkomponente
als ein separates teilchenförmiges Additiv physikalisch zugemischt ist.
10. Verfahren zum katalytischen Cracken von Metalle enthaltenden Kohlenwasserstoffen,
bei dem der Kohlenwasserstoff unter katalytischen Crackbedingungen mit einem Katalysator
umgesetzt wird und desaktivierende Metalle einschließlich Vanadin auf dem Katalysator
niedergeschlagen werden, dadurch gekennzeichnet, daß die Reaktion unter Verwendung
des Katalysators von Anspruch 1 durchgeführt wird.
11. Verfahren nach Anspruch 10, bei dem der Katalysator einen kristallinen Zeolith
verteilt in einer anorganischen Oxidmatrix umfaßt.
12. Verfahren nach Anspruch 11, bei dem der Zeolith synthetischer Faujasit ist.
13. Verfahren nach Anspruch 12, bei dem der Zeolith calcinierter, mit Seltenen Erden
ausgetauschter Zeolith vom Typ Y ist.
14. Zusammensetzung zum Abfangen von Vanadin, die ein Magnesiumoxid-Siliciumdioxid-Gel
mit 30 bis 80 Gew.% MgO, einem Porenvolumen von mindestens 0,1 cm3/g und einem durchschnittlichen Porendurchmesser von mehr als etwa 40 µm (400 A) in
Poren mit einem Durchmesser von 20 bis 1000 µm (200 bis 10 000 h) umfaßt.
15. Zusammensetzung nach Anspruch 14, die ein Gesamtporenvolumen von 0,2 bis 1,0 cm3/g aufweist.
16. Zusammensetzung nach Anspruch 14, die zu Teilchen mit einem Größenbereich von
40 bis 80 Mikrometern geformt ist.
17. Zusammensetzung nach Anspruch 16, bei der die Teilchen eine Dichte von etwa 0,5
bis 1,0 g/cm3 besitzen.
1. Composition d'un catalyseur de craquage catalytique qui comprend :
(a) un composant de catalyseur de craquage, et
(b) environ 5 à 80% en poids en exprimant comme oxydes d'un composant basique d'un
métal alcalino-terreux où ledit composant est caractérisé par un volume des pores
d'au moins 0,1 cm3/g et un diamètre moyen des pores plus grand qu'environ 40 J.lm (400 A) en pores ayant
un diamètre de 20-1.000 µm (200-10.000 Â).
2. Composition de la revendication 1 qui contient plus de 0,1% en poids de vanadium
déposé sur le catalyseur pendant l'utilisation dans un procédé de craquage catalytique.
3. Composition de la revendication 2 qui contient environ 0,1 à environ 10% en poids
de vanadium.
4. Composition de la revendication 1 où le composant du catalyseur comprend de la
faujasite synthétique dispersée dans une matrice d'oxyde inorganique.
5. Composition de la revendication 4 où ladite matrice d'oxyde inorganique comprend
un gel d'aluminosilicate et de l'argile.
6. Composition de la revendication 1 où ledit composé basique d'un métal alcalino-terreux
est choisi dans le groupe consistant en oxydes, carbonates, sels d'acide de calcium
et/ou de magnésium et leurs mélanges.
7. Composition de la revendication 1 où ledit composant basique d'un métal alcalino-terreux
comprend un gel de silice-magnésie ayant la composition pondérale de 30 à 80% de MgO.
8. Composition de la revendication 1 où ledit composé basique d'un métal alcalino-terreux
est dispersé dans ladite matrice sous la forme d'une phase d'oxyde séparée.
9. Composition de la revendication 1 où ledit composant basique d'un métal alcalino-terreux
est physiquement mélangé sous la forme d'un additif particulaire séparé.
10. Méthode pour le craquage catalytique de métaux contenant des hydrocarbures où
l'on fait réagir ledit hydrocarbure en conditions de craquage catalytique avec un
catalyseur, et des métaux désacti- vants comprenant du vanadium sont déposés sur ledit
catalyseur, le perfectionnement consistant à :
Entreprendre la réaction en utilisant le catalyseur de la revendication 1.
11. Méthode de la revendication 10 où ledit catalyseur comprend une zéolite cristalline
dispersée dans une matrice d'oxyde inorganique.
12. Méthode de la revendication 11 où ladite zéolite est de la faujasite synthétique.
13. Méthode de la revendication 12 où ladite zéolite est de la zéolite du type Y échangée
en terres rares et calcinée.
14. Composition pour balayer le vanadium qui comprend un gel de magnésie-silice ayant
une composition pondérale de 30 à 80% de MgO et un volume des pores d'au moins 0,1
cm3/g et un diamètre moyen des pores plus grand qu'environ 40 µm (400 A), le diamètre
des pores étant compris entre environ 20 et 1.000 µm (200 à 10.000 Å) de diamètre.
15. Composition de la revendication 14 où ladite composition a un volume total des
pores de 0,2 à 1,0 cm3/g.
16. Composition de la revendication 14 où la composition est formée en particules
ayant une plage de granulométrie de 40 à 80 microns.
17. Composition de la revendication 16 où les particules ont une densité d'environ
0,5 à 1,0 g/cm3.