Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
L~
CRACKING CATALYST RESTORATION ~ITH ALUMINUM COMPOUNDS
Backgrcund of the Invention
The present invention relates to catalysts. In another aspect,
the present invention relates to hydrocarbon cracking catalysts. In still
another aspect, the invention relates to restoring the activity of hydrocarbon
cracking catalysts. In yet another aspect, the invention relates to cracking
a hydrocarbon feedstock.
Contaminants, for example, nickel; vanadium, and iron are folmd
in significant concentrations in hydrocarbon feedstock.s such as, for
example, heavy oil fractions and in lower quality crude oils. These
contaminants have a poisoning effect on the catalysts employed to convert
these oils into gasoline and other valuable petroleum products, making
processing of these oils economically unattractive. Unfortunately,-because
of limited supplies of oils containing low levels of contaminants, it is
necessary to employ metals contaminated oils in hydrocarbon processes, such
as ca~alytic cracking processes.
The contaminants found in feedstocks to cracki~g processes become
deposited on the cracking catalyst. The deposition on the catalyst of, for
example, nickel, vanadium and iron, causes a decrease in the activity of
the cracking catalyst to convert the hydrocarbon feedstock into cracked
products, including gasoline. The selectivity of the cracking catalyst for
cracking the fPedstock into gasoline as manifested by the portion of
crack~d products comprising gasoline is also decreased. The production of
undesirable productsJ for example, hydrogen and methane, which must be
compressedl necessitating additional equipmPnt; and coke, which is deposited
on the ca~alyst and must be burned off, requiring addi~ional equipment and
"off time," during which the catalyst is not employed for cracking, is
significantly increased.
~ L9
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..,
Because of these problems, the industry often replaces cracking
catalysts contaminated by more than about 3,000 parts per million (ppm) o~
vanadium equivalents and iron. As used herein, the term vanadi~lm equivalents
is the measure of the combined parts by weight of vanadium and four times
the nickel per million parts by weight of cracking catalyst including the
weight of nickel, vanadium and iron on the cracking catalyst. There is
thus a need for a cracking process suitable for use with contaminated
feedstocks and contaminated cracking catalysts. There is also a need for a
cracking catalyst which is only minimally adversely affected by deposits
thereon of contaminants selected from nickel, vanadium and iron. There is
also a need for a process of treating a contaminated cracking catalyst to
. increase its activity for conversion of the feedstock and selectivity for
producing gasoline and to decrease the catalyst selec*ivity for undesirable
products, for example, hydrogen and coke~
Objects of the Invention
It is thus an object of the present invention to provide a method
for restoring the activity of a contaminated cracking catalyst.
It is a further object of this invention to provide a restored
cracking catalyst wherein contaminants such as nickel, vanadium and iron on
; 20 cracking catalyst are passivated.
It is another object of this invention to provide a process for
cracking hydrocarbons wherein the deleterious effects caused by metals on
the cracking catalyst are at least mitigated.
These and other objects of the present invention will be more
fully explained in the following detailed disclosure of the invention and
the appended claims.
Summary of the Invention
In accordance with the present invention, a catalyst composition
comprises a cracking catalyst and a treating agent selected -from aluminum
and aluminum compounds.
Further, according to the invention, a contaminated cracking
catalyst is improved by contacting the cracking catalyst wi-th aluminum or a
compound thereof.
Still further in accordance with the invention, a hydrocarbon
feedstock is catalytically cracked employing the above described catalyst
composition.
~ l6~ V~
.
Still further, according to the invention, at least one metal
selected from nickel, vanadium and iron in contact with a cracking catalyst
is passivated by contacting the crackin~ catalyst with a trsating agent
selected from aluminum and aluminum compounds.
Still further, according to the invention, a used cracking
catalyst contaminated by at least 3000 ppm vanadium equivalents, is at
least partially restored by contact with a treating agent selected from
aluminum and aluminum compounds.
Detailed Description of the Invention
It has been discovered that the adverse effects of nickel,
vanadium and iron on a cracking catalyst can be at least mitigated by
contacting the cracking catalyst with a treating agent selected from aluminum
and aluminum compounds. The treating agent can be selected from most any
source of alu~inum such as elemental aluminum, inorganic aluminum compounds,
and organic aluminum compounds. Suitable inorganic aluminum compounds
include salts, for example, aluminum nitrate, aluminum sulfate, or alums
that have the empirical formula AlM(S04)2, where M is NH 4 or a member of
Group IA of the periodic table, as found at page 83 of the Handbook of
~hemistry and Physics, 54th edition (1973-74), published by the Chemical
Rubber Company Press, Cleveland Ohio. Less preferred are halogen-
containing aluminum salts, for example, AlX3 or Al(X03)3, where X is selected
from the group Cl, Br and I, because of the corrosive effect of these
halogens on process equipment. Suitable or~anic compounds can be represented
generally by the formula AlR3 wherein R is an organic moiety. Included
within this group are the salts of carboxylic acids, (R'C00)3Al whsrein R'
is hydrogen or a hydrocarbyl radical having from 1 to about 20 carbon
atoms. Examples of suitable carboxyl compounds include aluminum acetAte,
aluminum propionate, aluminum butyrate, aluminum decanoate, sluminum stearate,
and the like. Polyfunctional carboxylates, such as aluminum citrate, can
also be utilized. Other suitable organic compounds are for example, aluminum
tris(hydrocarbyl oxide)s--Al(OR")3--wherein R" preferably contains one to
about 20 carbon atoms and can be an alkyl, alkenyl, cycloalkyl, or aryl
radical, or a combination of radicals such as alkylaryl, arylalkyl, alkyl-
cycloalkyl, and the like. Examples of suitable oxyhydrocarbyl compounds
ars aluminum isopropoxide, aluminum tert-butoxide, aluminum phenoxide9
aluminum decyloxide, and the like. Other suitable or~anic compounds are
for example, aluminum alkyls--AlR"'3--where R"' can be an alkyl group
containing 1-20 carbon atoms~ preferably one to five carbon atoms. Examples
of suitable hydrocarbyl compounds are trie*hylaluminum, tributylaluminum,
diethylpentylaluminum, and the like. It is recognized that these compounds
are pyrophoric and must be treated accordingly. R', R", and R"' can be
substituted with, for example, halogen, sulfur, phosphorus or nitrogen. Of
course, mixtures of any of the above compounds may be utilized. The aluminum-
containing *reating agent of this invention can also be utilized in combina-
tion with other passivating agents, for example, passivating agents contain-
ing elements selected from Groups IVA, VA and VIA of the Periodic Table.
It is most preferable in accordance with the present invention tocontact the cracking catalyst with at least one promotin~ agent selected
from sulfur compounds and phosphorus compounds in addition to the at least
one aluminum compound. The source of phosphorus employed in thls aspect of
invention can vary widely and can be any phosphorus composition which will
enhance the passivation qualities of aluminum, or the promotion quality of
sulfur for enhancing the passivating qualities of aluminum. Exemplary
inorganic sources of phosphorus usefully employed in accordance with the
invention include the white, red, violet and yellow forms of elemental
phosphorus. Phosphorus halides for example phosphorus fluoride, phosphorus
chloride, phosphorus bromide, phosphorus iodide and heterohalides such as
phosphorus dibromotrichloride can also be usefully employed. Nitrogen
containing inorganic phosphorus compounds such as phosphorus dichloronitride
and phosphorus cyanide can also be used as the phosphorus source. Phosphine
is also suit~ble for use. Exemplary of suitable phosphorus oxides which
can be used in accordance with the invention are phosphorus trioxide,
, phosphorus tetraoxide, phosphorus pentaoxide, and phosphorus sesquioxide.
Oxygen containing phosphorus compounds for example phosphorus oxychloride,
phosphorus oxybromide, phosphorus oxybromide dichloride, phosphorus oxy-
fluoride, and phosphorus oxynitride can also be used in accordance with the
invention. Phosphorus selenides and phosphorus tellurides can also be used
in accordance with the invention. Exemplary of this class of compounds are
phosphorus triselenide and phosphorus pentaselenide. Exemplary of suitable
phosphorus acids which can be used in accordance with the invention are
hypophosphorous acid, metaphosphoric acid, orthophosphoric acid, and pyro~
phosphoric acid. The source of sulfur employed in this aspect of invention
` - ~
also can vary widely and can be any sulfur composition which will enhance
the passivation qualities of aluminum or the promotion quality of phosphorus
for enhancing the passivation qualities of aluminum Exemplary inorganic
sources for sulfur include the alpha, beta and gamma forms of elemental
sulfur. Sulfur halides such as sulfur monofluoride, sulfur tetrafluoride,
disulfur decafluoride, sulfur monochloride, sulfur dichloride, sulfur
tetrachloride, sulfur monobromide and sulfur iodide can also be used.
Nitrogen containing sulfur compounds3 for example, tetrasulfur dinitride,
tetrasulfur tetranitride, and trithiazylchloride can also be used albeit
with extreme caution, in accordance with the invention. Oxides of sulfur,
for example sulfur dioxide, sulfur heptoxide, sulfur monoxide, sulfur
sesquioxide, sulfur tetraoxide, sulfur trioxide, trisulfur dinitrogen
dioxide, sulfur monooxytetrachloride, and sulfur trioxytetrachloride are
also suitable for use. The sulfur source can also be selected from sulfuric
acids, for example, permonosulfuric acid, per(di)sulfuric acid and pyrosulfuric
acid. Sulfurous acid is also suitable for use. Sulfuryl chlorides, for
example sulfuryl chloride fluoridà and pyrosulfuryl chloride are also
suitable for use.
Of course, single compositions containing more than one of
aluminum, phosphorus or sulfur can be employed as a combined source. Thus,
suitable treating agents include inorganic compounds containing aluminum
and phosphorus, for example, aluminum metaphosphate and aluminum ortho-
phosphate. Likewise, inorganic compositions which contain aluminum and
sulfur can be usefully employed as treating agents in accordance with the
present invention, for example, aluminum sulfide and aluminum sulfate.
Similarly, promoting agents comprising both phosphorus and sulfur can be
employed in addition to aluminum, for example, phosphorus oxysulfide,
tetraphosphorus heptasulfide, phosphoruspentasulfide, and tetraphosphorus
trisulfide.
Examples of organic phosphorus containing promoting agents
include hydrocarbylphosphines, hydrocarbylphosphine oxides, hydro-
carbylphosphites and hydrocarbylphosphates. Exemplary compounds include
tri-n-butylphosphine, triphenylphosphine, tri-n-butylphosphine oxide,
triphenylphosphine oxide, trioctylphosphite and triphenylphosphite.
Examples of organic sulfur containing promoting agents include
mercaptans, thioethers, disulfides, polysulfides, thioacids, heterocyclic
9~
sulfur compounds, and polynuclear compounds, to name but a few. Exemplary
compounds include tertiary octyl mercaptan, n-butyl sulfide, tertiary amyl
disulfide, tertiary butyl polysulfide, dithioacetic acid, thiophene,
methyl thiophene, butylthiophene, benzothiophene, diben~othiophene, and
S carbon disulfide.
The additional contacting of the cracking catalyst with promoting
agent is most conveniently accomplished by contacting the cracking catalyst
with aluminum compounds which additionally contain phosphorus and/or sulfur.
Exemplary of these compounds are the aluminum-hydrocarbyl phosphites,
aluminum-hydrocarbyl phosphates, flluminum thiocarboxylates, hydrocarbyl
aluminum mercaptoalkanoates, aluminum thiocarbonates, hydrocarbylaluminum
hydrocarbyl mercaptides, and aluminum thiocarbamates.
Compounds which contain phosphorus and/or sulfur located at the
gamma position or closer to an aluminum atom appear particularly efficient
for reducing the detrimental effects of contaminating deposits on a cracking
catalyst. Aluminum thiophosphates, particularly aluminum dihydrocarbyl
thiophosphates because of their oil solubility and because they have been
tested with good results, are the preferred treating agents of the present
invention. These compounds are conveniently represented by the formula
~ ~ Xl ~
P - X - Al
, . X ~
_ _ 3
~ 25 wherein R is hydrocarbyl and due to availability normally has
I from 1 to about 20 carbon atoms and X is selected from the group conslsting
of oxygen and sulfur and at least one X is sulfur. Compositions represented
by the formul~
Ir S
P - Sl Al
R 3
wherein R is as defined before are particularly preferred because of ease
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of synthesis and because they have been tested with good results. In both
represented formulas, R can be alkyl, alkenyl, cycloalkyl, aryl and combina-
tions thereof, for example, aralkyl, in nature. Examples of suitable
aluminum containing treating agents containing both phosphorus and sulfur
promoting agents include aluminum tris(dipropyl phosphate), aluminum tris(0,0-
dipropyl phosphorothioate), aluminum tris(0,0-dipropylphosphorodithioate,
aluminum tris(O,S-dipropyl phosphorothioate), aluminum tris(S,S-
dipropylphosphorodithioate), aluminum tris(O,S-dipropylphosphorodithioate~,
aluminum tris (S,S-dipropylphosphorotrithioate), and aluminum tris (S,S-
dipropylphosphorotetrathioate). In addition, the propyl groups in thepreceding examples can be replaced with, for example, methyl, butyl,
octyl, ethyl, cyclohexyl, phenyl, hexenyl radicals and the like. An
example is aluminum (0-methyl S-phenyl phosphorodithioate). Aluminum
tris(di-n-propylphosphorodithioate) is the treating agent presently preferred
because it has been tested with good results.
Generally, the amount of aluminum containing treating agent
contacted with the cracking catalyst is a "passivating amount." By passivating
amount is meant an amount of treating agent which is sufficient to mitigate
at least one of the deleterious effects caused by deposition on the cracking
catalyst of at least one contaminant selected from the group of nickel,
vanadium and iron, such as, for example, decreased catalyst activity for
feedstock conversion, decreased catalyst selectivity for gasoline production,
increased hydrogen production and increased co~e production.
Although not intending to be bound to any particular thaory of
operation, it is believed that the decomposition products o~ the aluminum
containing treating agent react with the contaminan~s present on the
cracking catalyst in such a way as to decrease the activity of the contaminants
for detrimentally affecting the cracking process It is therefore believed
that an effect of the contact between the cracking catalyst and a passivating
amount of aluminum containing treating agent is an increase in the aluminum
concentration of the cracking catalyst However, for many applications,
the increased aluminum concentration in the cracking catalyst may be too
small to measure as most commercial cracking catalysts contain substantial
amounts of aluminum.
Generally, a sufficient amount of the aluminum-containing treating
agent is contacted with the cracking catalyst to impart to the cracking
~ C~
catalyst a concentration of added aluminum of between about 1 and about
100,000 parts per million (0.0001 to 10 percent) by weight of cracking
catalyst after treatment. Where an alumina-containing cracking catalyst is
treated, the added aluminum will be manifested as an increased aluminum
concentration in the cracking catalyst. It is preferred to contact the
cracking catalyst with a sufficient amount of aluminum-containing treating
agent to impart to the cracking catalyst a concentration of added aluminum
of between about 200 and about 20,000 parts per million by weight of cracking
catalyst after treatment, because treated cracking catalysts having concentra~
tions of added aluminum within this range have been tested with good
results.
Generally, the amount of aluminum added to the cracking catalyst
should be an amount sufficient to impart to the cracking catalyst a ratio
of weight of added aluminum to vanadium equivalents on the cracking catalyst
of between about 1:1000 to about 10,000:1,000. More preferably, the added
aluminum is in an amount sufficient to impart to the cracking catalyst a
ratio of weight of added aluminum to vanadium equivalents on the cracking
catalyst of between S:1000 to 5,000:1000. Most preferably, the added
aluminum is in an amount sufficient to impart to the cracking catalyst a
ratio of weight of added aluminum to vanadium equivalents of be$ween about
50:1000 to about 500:1000, because treated cracking catalysts having weight
added aluminum:vanadium equivalents ratios within this range have been
tested with good results.
The present invention has particular utility for improving the
cracking characteristics of cracking catalysts having deposited thereon
3,000 ppm and greater of vanadium equivalents. Untreated cracking
catalysts have usually developed undesirable cracking behavior at a
contamination level of 3,000 vanadium equivalents. Treatment of the
cracking catalyst in accordance with the present invention is effective
to mitigate the undesirable cracking behavior of cracking catalysts
having deposited thereon 3,000 ppm vanadium equivalents, lO,000 ppm
vanadium equlvalents and even 20,000-50,000 vanadium equivalents and
beyond of contaminants.
In the embodiment of the invention wherein phosphorus and/or
sulfur-containing promoting agents are contacted with the cracking
catalyst in addition to aluminum~ the amount of aluminum contacted with
the cracking catalyst can be within the ranges as defined above. The
amount of sulfur and/or phosphorus contacted with the cracking catalyst
in addition to the aluminum can be selected over a broad range. Generally,
a promoting amount of sulfur and/or phosphorus is contacted with the
cracking catalyst. For example, aluminum and phosphorus can be contacted
S with the cracking catalyst at any suitable weight ratio such as a weight
ratio of aluminum to phosphorus of between about 5:1 to about 1:5, with
a weight ratio of between about 1:2 to about 1:4 being preferred because
cracking catalysts treated with ratios within this range have been
tested with good results. A suitable weight ratio of aluminum to
sulfur with which the cracking catalyst can be contacted can be selected
from a relatively broad range, such as for example within the range of
from about l:l to about 1:20, with a range from about 1:4 to about 1:10
being preferred. Cracking catalysts contacted with compositions having
aluminum:sulfur weight ratios within this latter range have been tested
lS with good results. The above weight ratios are suitable when employing
either or both phosphorus and sulfur with aluminum.
Any suitable method can be used to contact the treating agent
comprising a source of aluminum and optionally at least one of a source
of phosphorus and sulfur with the catalyst. It can be mixed with the
; 20 catalyst as a finely divided solid and dispersed by rolling, shaking,
stirring, etc. Or, it can be dissolved in a suitable solvent, aqueous
or organic, and the resulting solution used to impregnate the cracking
catalyst--followed by drying to remove the solvent. Or, it can be
sprayed on the catalyst, such as by being dissolved or suspended in the
feedstock to a catalytic cracking unit.
The time required to effect a contact between the treating
agent and cracking catalyst is not particularly important. Generally,
for a batch treatment outside of a catalytic cracker such time period
can range from 0 to 30 minutes. Likewise, the temperature at which thc
contact is effected can be selected from a wide range of values, depending,
for example, on wh~ther the treating agent is contacted with the cracking
catalyst as a vapor or as in solution with a relatively low boiling
solvent.
The cracking catalysts which can be advantageously treated in
accordance with the above-described process are generally any of those
cracking catalysts employed for the catalytic cracking of hydrocarbons
boiling above 400F (204C) in the absence of added hydrogen which have
become partially deactivat~d by deposits of contaminating metals thereon.
Treatment of such contaminated cracking catalysts in the above-described
manner produces the modified cracking catalyst of the present invention.
These cracking catalysts generally contain silica or silica alumina and
are frequently and preferably associated with zeolitic materials.
Generally, from 1 to 60 percent, usually from about 30 to about 40% by
weight of the catalyst will comprise zeolitic materials. The zeolitic
materials can be naturally occurring or synthetic, and such materials
can be produced by ion exchange methods and provided with metallic ions
w~ich improve the activity of the catalyst. Zeolite-modified silica
alumina catalysts are particularly applicable to this invention because
of their high activity and selectivity. Examples of metals contaminated
cracking catalysts into or onto which a source of alumi.num and optionally
a source of at least one of phosphorus and sulfur can be incorporated
include hydrocarbon cracking catalysts obtained by admi~ing an inorganic
oxide gel with an aluminosilicate, and aluminosilicate compositions
which are strongly acidic as the result of treatment with a fluid medium
containing at least one rare earth metal cation and a hydrogen ion, or
ion capable of conversion to a hydrogen ion.
It is inherent in this invention that the treated cracking
catalyst will be subjected to elevated temperatures. When utilized in a
continuous cracking process, the treated cracking catalyst can be subjected
to temperatures between 800 F (427C) and 1200F (649C) in the cracking
zone and temperatures between 1000F (538C) and 1500F (816C) in the
regeneration zone. Generally free oxygen containing gas is present in
the regeneration zone. The contacting of the treating agent with the
cracking catalyst can occur in the cracking zone~ in the regeneration
zone, or in the catalyst stream between the two zones.
A further embodiment of the present invention is directed to a
catalytic cracking process wherein a hydrocarbon feedstock is contacted
with the above-described modified cracklng catalyst under cracking
conditions to produce a cracked product. Such cracking operations are
generally carried out at temperatures between 800F (4~7C) and about
1200F (649C) at pressures within the range of subatmospheric to several
hundred atmospheres. A preferred example of this embodiment of the
ll
invention utilizes a cyclic flow of catalyst between a fluidized cracking
zone and a regeneration zone in a cracking reactor. Such a system is
well known to those skilled in the art.
Specific conditions in the cracking zone and the regeneration
zone of a fluid catalytic cracker depend on the feedstock used, the
condition of the catalyst, and the products sought. In general, conditions
in the cracking zone include:
Table I
Temperature: 427-649C (800-1200F)
Contact time: 1-40 seconds
Pressure: lO kiloPascals to 21 megaPascals
(0.1 to 205 atm.)
Catalyst:oil ratio: 3/1 to 30/1, by weight
Conditions in the regeneration zone include:
Table II
Temperature: 538-816C (lO00-1500F)
Contact time: 2-40 minutes
Pressure: 10 kiloPascals to 21 megaPascals
(0.1 to 205 atm.)
Air rate (at 16C, 100-250 ft3/lb coke,
1 atm.): (6.2-15.6 m3/kg coke.)
The feedstocks introduced into the catalytic cracking unit are
generally oils having an initial boiling point of above 204 C. This
includes gas oils, fuel oils, topped crude, shale oil and oils from coal
and/or tar sands.
:
,:
. . ~
- 12
Such feedstocks can and usually do contain a significant
concentration of at least one metal selected from vanadium, iron and
nickel. Because these metals tend to be concentrated in the least
volatile hydrocarbon fractions suitable for use as feedstocks, a process
; 5 for cracking these heavy oil fractions is probably the most important
embodiment of this invention. Currently, the industry obtains only
economically marginal results when cracking feedstocks containing from
about 50 to about 100 parts per million of total effective metals, where
total effective metals is defined herein as the sum of the elemental
10 weights of iron, vanadium and four times the weight of nickel in 1,000,000
parts by weight of feedstock, including the i~on, vanadium and nickel
contained therein. In accordance with the present invention, feedstocks
containing 50-lO0 parts per million of total effective metals, and even
those containing 100-200 parts per million of total effective metals and
beyond can be economically cracked to produce gasoline and other light
distillates. The quantlty of added aluminum required to passivate
vanadium, iron and nickel is related directly to the concentration of
these metals in the feedstock. In a preferred embodiment, the aluminum
containing treating agent is dissolved or suspended in a suitable solvent
and introduced into the catalytic cracking unit along with the hydrocarbon
feedstock. It is advantageous to employ a concentration of aluminum in
the hydrocarbon feedstock in relationship to the contaminating metals
concentration in the feedstock as shown by the following table.
Table III
25 Total Effective MetalsAluminum Concentration
in Feedstock, ppmin Feedstock (ppm~
<40 - 100 1 - lO0
lO0 - 200 10 - 250
200 - 300 25 - 500
300 - 800 50 - ~000
This invention is illustrated by the following example.
Example I
A commercial cracking catalyst that had been used in a commercial
fluid catalytic cracker until it had attained equilibrium composition
; with respect to metals accumulation (catalyst was being removed from the
- 5 process system at a constant rate) was used to demonstrate passivation
with aluminum. The catalyst, being a synthetic zeolite combined with
amorphous silica/alumina (clay), was pradominantly silica and alumina.
Concentrations of other elements together with pertinent physical
properties are shown in Table IV.
Table IV
Surface area, m2 g 1 74.3
Pore volume~ ml g l 0.29
Composition, wt. %
Nickel 0.38
Vanadium 0.-60
Iron 0.90
Cerium 0.40
Sodium 0.39
Carbon 0.06
Z0 A portion of this used, metals-contaminated catalyst was
treated with aluminum as follows. A solution, prepared by dissolving
1.59 gm of aluminum phenoxide in 35 ml of cyclohexane, was stirred into
35 gm of the used catalyst. Solvent was removed by heating, with stirring,
on a hot plate at about 260C. This treatment added 0.40 wt. % aluminum
to the catalyst. The trePted catalyst was then prepared for testing by
14
aging it as follows. The catalyst, in a quartz reactor, was 1uidized
with nitrogen while being heated to 482C, then lt was fluidized with
hydrogen while the temperature was raised frorn 482 to 649C. Maintaining
that temperature, fluidization continued for 5 minutes with nitrogen,
then for 15 minutes with air. The catalyst was then cooled to about
482C, still being fluidized with air. The catalyst was then aged
through 10 cycles, each cycle being conducted in the following manner.
The catalyst at about 482C was fluidized with nitrogen for one minute,
then heated to 510C during two minutes while fluidized with hydrogen,
then maintained at 510C for one minute while fluidized with nitrogen,
then heated to about 649C for 10 minutes while fluidized with air, and
then cooled to about 482C during O.S minutes while fluidized with air.
After 10 such cycles it was cooled to room temperature while being
fluidized with nitrogen.
The used catalyst and the aluminum-treated catalyst were
evaluated in a fluidized bed reactor using topped West Texas crude oil
as feedstock to the cracking step`. The cracking reaction was carried
out at 510C and atmospheric pressure for 0.5 minutes, and the regeneration
step was conducted at about 649C and atmospheric pressure for about 30
minutes using fluidizing air~ the reactor being purged with nitrogen
before and after each cracking step.
Properties of the topped West Texas crude used in the cracking
steps are summarized in Table V.
,
Table V
API gravity at 15.6C 21.4
: . Distillation (by ASTM D 1160-61)
: .
IBP 291C
10% 428
20% 468
30% 498
40% 528
, ..
:- ..
50% 555
Carbon residue~ Ramsbottom 5.5 wt. X
Analysis for some elements
Sulfur . 1.2 wt. %
Vanadium 5.29 ppm
Iron ~9.0 ppm
Nickel 5.24 ppm
Pou~ point (by ASTM D 97-66) 17C
Kinematic viscosity (by ASTM D 445-65)
at 82.2C 56.5 eentistokes
. at 98.9C 32.1 centistokes
,
~J 3~
16
Results of the tests using the two catalys-ts are summarized in
Table VI.
Table VI
Catalyst Used ~sed, ~ 0.40% Al
5 Catalyst:Oil weight ratio7.7 7.2
Conversion, Vol. % of feed 74.9 79.8
.
Gasoline Selectivity,
Vol. % of Conversion 72.9 81.0
Yields
Coke, wt. % of feed 17.6 14.0
SCF H2/bbl feed converted 895 704
Gasoline, Vol.% of feed54.6 64.6
Material balance, wt. % 100.7 99.9
This comparison of the two catalysts shows that the addition
of 0.4 wt. percent alu~ninum, as aluminum phenoxide, to -the metals-
contaminated cracking catalyst increased conversion of the feedstock by
6.6%, at a catalyst/oil ratio about 6% lower than in the control, increased
the selectivity of the catalyst for gasoline production in excess of 6%,
in spite of the higher conversion level, increaszd gasoline yield by
18%, and decreased both the production of coke and the formation of
hydrogen by 21%.
17
EXAMP~E II
A commercial cracking catalyst that had been used in a fluid
catalytic cracker until it had attained equilibrium composltion with
respect to metals accumulation was characterized by the following properties:
TABLE VII
Surface Areaj m2/g 75.9
Pore vol., mL/g 0.36
Composition, wt. %
` Nickel 0.38
Vanadium Q.58
Iron Q.85
Cerium 0.39
Sodium 0.46
.: Carbon O.Q6
15 A portion of the catalys~ characterized above was treated to
contain phosphorus by impregnation with di-n-propylphosphorodithioic
acid (DNPPTA) (C3H70)2PS2H). I'his was done as follows. A solution
containing 4.65 g DNPPTA in dry cyclohexane was used to cover 40 g Qf
catalyst. The mixture was warmed on a hot plate, with stirring, until
2Q the solvent had evaporated. Dry catalyst was placed in a quartz reactor
and aged as described in Example I.
The used catalyst and the DNPPTA-treated catalyst were tested
in a fluidized bed reactor as described in Example I. Results of the
tests were as follows:
TABLE VIII
Additive None 1.? wt.% pl
Catalyst/Oil Ratio 7.4/1 7.5/1 7.4/1
Conversion, Vol. % 82.0 72.7 71.0
Gasoline Selectivity
3Q Vol.% of Conversion 6~.3 67.6 65.2
Yields
Coke, Wt.% 16.Q 14.2 15.
SCF H2/B Conv. 720 602 620
Gasoline, Vol.% 56.Q 49.1 47.3
Source of P was (C3H70)~PS2H
,,
', : .
18
As shown by Table VIII, the addition of phosphorus to metals-
contaminated FCC catalyst via impregnation with DNPPTA reduced hydrogen
- yield by about 15% and reduced coke yield by about 6%. However, these
benefits were at the expense of conversion, which fell about 12%, and
gasoline yield, which fell about 14%. The lowered coke and hydrogen
yields are probably at least partially due to the lower level of conversion.
Also as shown by the above table, the selectivity of the cracking catalyst
for gasoline production was lowered, even though the catalyst was employed
to effect a lower level of conversion. This example demonstrates the
advantages obtained by using aluminum in combination with phosphorus and
sulfur.
EXAMPLE III
` Aluminum tris(0,0-di-n-propylphosphorodithioate was prepared
by a double decomposition reaction between aluminum chloride and potassium
0,0-di-n-propylphosphorodithioate. To a solution of 4.02 gm (0.016
moles) AlCl3.6H20 in methanol was added, dropwise, a solution of (C3H70)2PSSK.
Solid potassium chloride precipitated during this addition. Nethanol
solvent was removed by evaporation in a rotary evaporator, then replaced
with diethyl ether, precipitating still more potassium chloride, which
was removed by filtration. Diethyl ether solvent was removed by evaporation,
the last traces requiring warming in a vacuum. Slightly grey crystals
remained. Elemental analysis of them showed ~he following. Calculated:
32.42% C, 6.35% H, 13.93% P, 4.05% Al. Found: 27.86% C, 6.62% H, 9.7%
P, 3.4% Al.
The commercial cracking catalyst of Example I was treated with
the above prepared aluminum tris(0,0-di-n-propylphosphorodithioate) as
follows. A solution, prepared by dissolving 4.32 gm of [(1-
C3H70)2PSS]3Al in 35 ml of methanol, was stirred into 35 gm of the used
catalyst. Solvent was removed by heating, with stirring, on a hot plate
at about 260 C. This treatment added 0.50 wt. % aluminum to the catalyst.
The treated catalyst was then prepared for testing by aging it as in
Example I.
Phe catalyst was employed to crack the feedstock set forth in
Example I under the reactor conditions employed in Example I. The
results obtained were:
19
TABLE IX
Addi.tive None Oi5 Wt.% Al
Catalyst:Oil Weight Ratio 7.7 7.4
Conversion, Vol. % of feed 74.9 78.0
Gasoline Selectivity,
Vol. % of Conversion 73 84
Yields
Coke, Wt. % of Feed 17.6 15.0
SCF H2/bbl Feed Converted 895 543
Gasoline Vol. % of Feed 54.6 65.4
Material Balance, Wt. % 100.7 100.3
Al added via impregnation with Al((C3H70)2PS2)3
As shown by Table IX, ~he addition of Al to the catalyst as
the di-n-propylphosphorodithioate increased conversion by about 4%,
increased gasoline yield by about 20%, decreased coke yield by about
15%, decreased hydrogen selectivity by about 39%, and improved catalyst
selectivity for gasoline production from 73% to 84% despite the higher
conversion level.
As compared to untreated cracking catalysts, the modified
cracking catalysts tested in Examples I, II and III modify the cracking
behavior of the catalyst at a catalyst/oil ratio of 7.4/1 as follows:
TABLE X
1 2 3
Additive, wt. % 0.5 Al 1.7 P 0.5 Al+1.7 P
Percent Change over
Untreated Catalyst
Conversion, (Vol.%~ +6.6 -12` +4
Coke (Wt.%) -21 -6 -15
X2/Bbl Conv. -21 -15 -39
Gasoline, Vol.%+18 -14 +20
via Al(OC6H5~3 impregnation
via ~C3H7)2Ps2H impregnation
3via Al((C3H70)2PS2)3 impregnation
` The high gasoline yields and low selectivity for hydrogen
production exhibi~ed by the catalyst treated with Al((C3H70)2PS2)3
are unexpected in view of the results obtained by treatment of the
15 cracking with Al(OC6H5)3 or (C3H70)2PS2H-
