Note: Descriptions are shown in the official language in which they were submitted.
12~360~
Field of The Invention
Catalysts used in cracking hydrocarbons can
become contaminated and poisoned by accumulation in the
catalyst of metals such as nickel, vanadium, iron, copper
and cobalt which are present in the hydrocarbon feedstocks.
The detrimental effects of those metals can be mitigated
and reversed by use of certain organo-antimony compounds
as catalyst passivators. Among those organo-antimony
compounds are antimony tricarboxylates. The present
~Z136~9
invention is an improved method of preparing antimony
tricarboxylates in exceedingly high yields.
Background of The Invention
Certain antimony compounds are known to be used
to treat those cracking catalysts conventionally employed
in the catalystic cracking of hydrocarbons for the
production of gasoline, motor fuel, blending components
and light distillates. These conventional cracking
catalysts generally contain silica, or silica-alumina.
Such materials are frequently associated with zeolitic
materials. These zeolitic materials can be naturally
occurring, or they can be produced by conventional ion
exchange methods such as to provide metallic ions which
improve the activity of the catalyst.
While the presence of certain metals can be
beneficial, the presence of others in the catalyst is
detrimental. It is well known that varying amounts of
metals such as nickel, vanadium and iron cause deterioration
of the cracking catalyst during the cracking process. In
fact, some oils contain these metals in such a high
concentration that they cannot be economically cracked
into gasoline and other fuels. The metals accumulate on
the cracking catalyst and cause increased hydrogen
production and coke laydown on the cracking catalyst,
thereby adversely affecting the yield of desired products.
It has heretofore been proposed that those
deleterious metals can be passivated by treating the
contaminated catalyst with compounds containing antimony,
tin, indium or bismuth (see U.S. Patent No. 4,257,919).
lZ~360~
Antimony compounds are particularly useful as passivating
agents and use of a wide variety of both organic and
inorganic antimony compounds has been proposed for that
purpose (see U.S. Patent Nos. 4,111,845 and 4,153,536~.
Among the organic antimony compounds proposed are antimony
tricarboxylates such as antimony tridodecanoate and
antimony trioctadecanoate.
Prior art processes for antimony tricarboxylate
preparation involve a direct reaction between antimony
oxide and a carboxylic acid anhydride. Nerdel et al
(J.Chem.Ber., 90, 59~ (1957)) teach that antimony triacetate
or antimony tribenzoate can be prepared by reacting
antimony oxide with acetic anhydride or benzoic anhydride,
respectively.
Ventura et al (U.S. Pat. 3,803,193) disclose
reacting antimony tricarboxylates with alcohols to produce
antimony trialkoxides. Ventura indicates that the
tricarboxylate can be prepared by reacting antimony oxide
with an organic acid anhydride directly or in some
instances with an acid directly. The acid by-product of
the tricarboxylate-alcohol reaction is taught to be
neutralized with ammonia and removed as ammonium acetate
solid.
The direct production of antimony tricarboxylates
by the prior art methods of direct reaction between
antimony oxide and the desired acid anhydride is not
satisfactory for producing higher tricarboxylates because
the higher anhydrides are not readily available and are
synthetically prepared only with great difficulty.
--3--
lZ13609
Accordingly, it is an object of the present invention to
provide a process for preparation of higher tricarboxylates
of antimony which uses readily available reactants and
affords high yields of the desired tricarboxylates. It
is another object of the invention to provide a synthetic
method of preparation wherein the antimony tricarboxylate
produced is substantially free of deleterious impurities
without extensive purification and has a high level of
thermal stability. These and other objects, aspects and
advantages of the present invention will become apparent
to those skilled in the art from the following description
of the invention.
Summary of The Invention
This invention relates to a highly effective
and efficient method of preparing higher antimony
tricarboxylates in high yields comprising the steps of
reacting antimony oxide with an anhydride of a lower
organic acid, reacting the product from a) with at least
one higher carboxylic acid at an elevated temperature
sufficient to vaporize and remove volatile material,
while optionally simultaneously passing a stream of an
inert gas through the reaction mixture, and recovering
the antimony tricarboxylate of said higher carboxylic
acid.
The antimony higher carboxylates can be
advantageously used as a cracking catalyst component and
results in an unexpected efficiency in laydown efficiency
in cracking.
12136()9
Detailed Description
According to the present invention, higher
antimony tricarboxylates are produced from higher carboxylic
acids by
a) reacting antimony oxide with an anhydride
of a lower organic acid according to the following
equation:
Sb203+3Rl-0-Rl ------> 2Sb(ORl)3
b) reacting the product from a~ with at least
one higher carboxylic acid at temperatures sufficiently
high to vaporize and expel volatile by products of the
reaction according to the equation
Sb(oRl)3+3R2coo~ Sb(0CR2)3+3Rl OH
c) while the reaction proceeds, optionally
passing a stream of inert gas through the reaction mixture,
and d) recovering the antimony tricarboxylate
of said higher carboxylic acid.
The anhydrides of lower organic acids employed
in step a) are those anhydrides which are commercially
available or readily prepared~ Thus Rl in the equation
of step a) has up to five carbon atoms. Preferably Rl is
alkanoyl of up to five carbon atoms and the lower organic
acid anhydrides include acetic anhydride, propionic
anhydride, butyric anhydride and pentanoic anhydride.
Acetic anhydride is the especially preferred anhydride of
a lower organic acid.
"'': ' `
~ `"" '' ~
lZ~3609
The reaction of step a) can be conducted either
with a solvent or without a solvent. When conducted with
a solvent, the solvent must be inert to both reactants
and the reaction product. A suitable solvent is a
hydrocarbon having a boiling point of at least 120C and
includes xylene, toluene, cumene, kerosene, and so forth.
Although an elevated temperature is used to
increase reaction speed, the temperature of the step a)
reaction is not critical. A suitable temperature range
is from 100 to 140C. A temperature of about 120C
results in a reaction time of about 3 to 4 hours between
antimony oxide and acetic anhydride.
The reaction product from step a) is reacted
with one or more higher carboxylic acids. Higher carboxylic
acids are those acids which have at least six carbon
atoms. There is no criticality on the upper limit for
the number of carbon atoms and is dictated only by
practicality. Preferably, R2 in the equation of step b)
is alkyl having from five to about 24 carbon atoms. More
preferably, R2 is straight chain or branched chain alkyl
having seven to eleven carbon atoms.
As illustrated above by the equation of the
step (b) reaction, the reaction by-product of step (b) is
the lower organic acid which corresponds to the lower
acid anhydride employed in step (a). Thus when acetic
anhydride is a reactant in step (a), acetic acid would be
the by-product in step (b). In conducting step (b), a
technical yrade neodecanoic acid (an isomer mixture) is
an especially suitable higher carboxylic acid. Such
lZ~3609
technical grade neodecanoic acid is mixed with the product
of step (a) and the temperature of the mixture is increased
until the by-product lower organic acid is evolved as a
vapor. When acetic anhydride is a reactant in step (a),
evolution of acetic acid vapor is observed in step tb) at
a temperature of about 150C. The temperature is
continually increased until the reaction is substantially
complete and the upper temperature can be about 300C.
When the reaction for step (b) is substantially complete,
it is advantageous to reduce the pressure of the reaction
in order to produce as complete removal as possible of by-
product lower organic acid and the attendant completeness
of reaction. Of course, it is possible to conduct the
entirity of reaction step (b) under a sub-atmospheric
pressure. The degree of pressure reduction is not
particularly critical and its choice depends in part on
the physical properties (e.g., boiling point) of the
particular by-product species being removed. Thus a
convenient pressure reduction can be easily determined by
those having ordinary skill in the art.
The high temperature used to drive the reaction
of step (b) to completeness also serves to eliminate
excess and unreacted neodecanoic acid which is also
vaporized. At the completion of the reaction of step
(b), the product remaining in the reactor is antimony
tricarboxylate of mixed neodecanoate isomer ligands
essentially free of deleterious impurities which can be
used as a hydrocarbon cracking catalyst passivator without
1213609
further purification. The recovery of the product
therefore involves merely removing said antimony
tricarboxylate from the reactor after completion of step
(b).
Neodecanoic acid is a ten-carbon acid having a
substantial number of theoretical position isomers and
said acid is generically represented as follows:
R
R' - C - COO~
R''
wherein the sum of the carbon atoms of R, R' and R'' is
eight alkyl carbon atoms. Although many isomers of
neodecanoic are possible, one antimony tricarboxylate
preferred for the present invention is produced from a
technical grade neodecanoic acid produced by Exxon
Chemical Company and which is a highly branched multi-
isomer mixture with a typical hydrocarbon odor and a
melting point of less than -40C.
Another preferred higher carboxylic acid
reactant for step (b) is a mixture of 2-ethyl hexanoic
acid and neodecanoic acid. The molar ratio of 2-ethyl
hexanoic acid to neodecanoic acid is about 2:1 so that
the resulting antimony tricarboxylate has two ligands of
2-ethylhexanate and one of neodecanoate.
~ f course, other higher carboxylic acids as
previously defined as well as mixtures thereof prepared
by steps (a) through (c) described above are suitable.
~2~3609
The yield of the desired antimony tricarboxylate
of higher carboxylic acids can be dramatically increased
by passing an inert gas through the reaction mixture
while the prod~uct of step a) is reacted with a higher
carboxylic acid. One method of passing the inert gas
through the reaction mixture is to bubble the gas through
the reaction mixture by use of a subsurface sparge.
Other means for passing the gas through the mixture will
be readily apparent to those skilled in the art and any
means for gas-liquid contact is suitable.
The inert gas useful in increasing the yield of
antimony tricarboxylates according to this invention is
any gas which will not react with a component of the
reaction mixture of step b) and which will not leave a
possibly deleterious residual substance in the antimony
tricarboxylate product. Suitable inert gases include
nitrogen, argon, helium, and neon. Nitrogen is preferred.
The flow rate of the inert gas is not critical
and its magnitude is limited by practical considerations.
For example, the volatile by-product of step b) is
generally removed by distillation, e.e., the vapors are
condensed and removed. An excessive inert gas flow rate
would promote overloading the distillation condenser and
thereby impede by-product removal as condensate. Also,
an excessive flow rate might cause excessive frothing of
the reaction mixture which would not be desired. A
suitable inert gas flow rate can easily be determined by
those skilled in the art by balancing the gas flow rate
against the physical effects to be avoided as a result of
~2136~9
excessive flow. In general gas flow rates of about
1 cu. ft./min. to about 20 cu. ft./min. are expected to be
effective. of course, reactor size and volume of the
reaction mixture would also be factors to be considered
in determining an appropriate gas flow rate.
In conducting the reaction of step b), the
higher carboxylic acid is mixed with the product of step
a) and the temperature of the mixture is increased until
the by-product lower organic acid is evolved as a vapor.
When acetic anhydride is a reactant in step a), evolution
of acetic acid vapor is observed in step b) at a temperature
of above about 150C. The temperature is continually
increased until the reaction is substantially complete
and the upper temperature can be about 300C. ~hen the
reaction of step b) is substantially complete, it is
advantageous to reduce the pressure of the reaction in
order to produce as complete removal as possible of by-
product lower organic acid and the attendant completeness
of reaction. Of course, it is possible to conduct the
entirety of reaction step b) under a sub-atmospheric
pressure along with an inert gas passing through the
mixture. The degree of pressure reduction is not
particularly critical and its choice depends in part on
the physical properties (e.g., boiling point) of the
particular by-product species being removed. Thus a
convenient pressure reduction can be easily determined by
those having ordinary skill in the art.
The high temperature used to drive the reaction
of step b) to completeness also serves to eliminate excess
--10--
~Z13609
and unreacted higher carboxylic acid which is also
vaporized. At the completion of the reaction of step b),
the product remaining in the reactor is antimony
tricarboxylate essentially free of deleterious impurities
and can be used as a hydrocarbon cracking catalyst
passivator without further purification. Recovery of the
product therefore involves merely removing the antimony
tricarboxylate of the higher carboxylic acid from the
reactor after completion of step b).
Hydrocarbon feedstock containing higher
molecular weight hydrocarbons is cracked by contacting
it at an elevated temperature with a cracking catalyst
whereby light distillates such as gasoline are produced.
~owever, the cracking catalyst gradually deteriorates
during this process. One reason for this deterioration
is the deposition of contaminating metals such as nickel,
vanadium, and iron on the catalyst, resulting in increased
production of hydrogen and coke and decreased catalyst
activity for cracking. Furthermore, the conversion of
hydrocarbons into gasoline is reduced by these metals.
In accordance with another embodiment of this
invention, we have discovered that the adverse effects
of nickel, vanadium or iron on cracking catalyst can be
precluded or reduced by using with the cracking catalyst
the antimony higher tricarboxylates prepared as described
above.
3~13609
An improved cracking catalyst may be prepared
by contacting the catalyst with the tricarboxylate of
antimony before, during or after use of the catalyst in
a hydrocarbon cracking process.
The term "cracking catalyst" as used herein
refers either to fresh or used cracking catalyst materials
that are useful for cracking hydrocarbons in the absence
of added hydrogen. The cracking catalyst can be any
conventional cracking catalyst.
Such cracking catalyst materials can be any of
those cracking catalysts conventionally employed in the
catalytic cracking of hydrocarbons boiling above 400F.
(204C.) for the production of gasoline, motor fuel,
blending components and light distillates. These
conventional cracking catalysts generally contain silica
or silica-alumina. Such materials are frequently
associated with zeolitic materials. These zeolitic
materials can be naturally occurring, or they can be
produced by conventional ion exchange methods such as to
2~ provide metallic ions which improve the activity of the
catalyst. Zeolite-modified silica-alumina catalysts are
particularly applicable in this invention. Examples of
cracking catalysts into or onto which the mixed-ligand
tricarboxylate of antimony can be incorporated include
hydrocarbon cracking catalysts obtained by admixing an
inorganic oxide yel with an aluminosilicate and alumino-
silicate compositions which are strongly acidic as a
result of treatment with a fluid medium containing at
~Z~3609
least one rare earth metal cation and a hydrogen ion,
or ion capable of conversion to a hydrogen ion. The
unused catalytic cracking material employed will
generally be in particulate form having a particle size
principally within the range of about 10 to about 200
microns.
The catalytic cracking materials can vary in
pore volume and surface area. Generally, however, the
unused cracking catalyst will have a pore volume in the
range of about 0.1 to about 1 ml/g. The surface area of
this unused catalytic cracking material generally will
be in the range of about 50 to about 500 m2/g.
The modified catalyst of this invention con-
sists essentially of a conventional cracking catalyst
having a modifying or passivating amount of the antimony
higher tricarboxylate prepared as defined herein deposited
on or in such catalyst. Such "modifying amount" is that
amount sufficient to preclude or reduce the adverse
effects of the nickel, iron or vanadium metals. Generally,
the amount of antimony compound added corresponds to the
level of impurity metals in the hydrocarbon feedstock
and a typical "modifying amount" is from about 0.005% to
5~ by weight of catalyst calculated as antimony metal.
The manner in which the conventional cracking
catalyst is contacted with the antimony compound is not
critical. Fresh catalyst can be impregnated with the
antimony compound. Also, the catalyst can be contacted
with the antimony compound during the cracking process
~2~3609
by metering the antimony compound into the hydrocarbon
feedstock being fed to the cracking process.
The cracXing process of this invention is
basically an improvement of a known cracking process
carried out in the absence of added hydrogen. This
process is improved in accordance with this invention
by the use of a novel metal passivator as defined above.
More specifically, a hydrocarbon feedstock is cracked
into lighter hydrocarbon materials by contacting this
feedstock with an unused catalytic cracking material
and antimony higher tricarboxylate prepared as defined
herein and in the absence of added hydrogen and recover-
ing the cracked materials.
A preferred embodiment of the cracking process
of this invention utilizes a cyclic flow of catalyst
from a cracking zone to a regeneration zone. In this
process, a hydrocarbon feedstock containing contaminating
metals such as nickel, vanadium or iron ~is contacted in
a cracking zone under cracking conditions and in the
absence of added hydrogen with an antimony containing
cracking catalyst as defined above; a cracked product is
obtained and recovered; the cracking catalyst is passed
from the cracking zone into a regeneration zone; in the
regeneration zone the cracking catalyst is regenerated
by contacting the cracking catalyst with a free oxygen-
containing gas, preferably air. The coke that has been
built up during the cracking process is thereby at least
partially burned off the catalyst. The regenerated
12~3G09
cracking catalyst is reintroduced into the cracking
zone.
Also, it is to be understood that the used
cracking catalyst coming from the cracking zone before
it is introduced into the regenerator is stripped of
essentially all entrained liquid or gaseous hydrocarbons.
Similarly, the regenerated catalyst can be stripped of
any entrained oxygen before it reenters the cracking
zone. The stripping is generally done with steam.
The specific conditions in the cracking zone
and in the regeneration zone are not critical and depend
upon several parameters such as the feedstock used, the
catalyst used and the results desired. Those skilled in
the art are thoroughly familiar with those specific
conditions and they can be easily determined for the
given parameters. Preferably and most commonly, the
cracking and regeneration conditions are within the
following ranges:
Cracking Zone
Temperature: 800F to 1200F (427-649C)
Pressure: Subatmospheric to 3,000 psig
Catalyst/Oil Ratio: 3/1 to 30/1, by weight
Regeneration Zone
Temperature: 1,000F to 1800F (538C to 982C)
Pressure: Subatmospheric to 3,000 psig
Air: 100-250ft3/lb coke (6.2-15.6 m3/kg
(60F. 1 atm) coke)
-15-
~213609
The following examples further illustrate
specific embodiments of this invention but are not to
be considered as limiting the invention to the specifics
involved.
Example 1 -
A three neck reaction flask was equipped with a
stirrer, a heating mantle and a reflux condenser attached
to a Dean-Stark trap. The flask was charged wi~h 175
grams of antimony oxide, 212 grams of acetic anhydride
and 125 grams of xylene. With stirring, the reaction
mixture was heated to 120C and maintained at that
temperature for 3 to 4 hours. Then, 663.9 grams of
neodecanoic acid (technical grade) was added and the
reaction mixture heated to 195C. During the heating,
xylene was removed by distillation and at approximately
155C, the evolution of acetic acid was observed and was
removed. Heating continued to 195C and when 195C was
reached, the reaction mixture was cooled and the antimony
trineodecanoate yield was determined to be 72.6%.
The technical grade neodecanoic acid used is a
product of Exxon Chemicals and is a highly branced multi-
isomer mixture combination with a typical hydrocarbon-
type odor and melting point of less than -40C. The
structure of these isomers is generically represented by
R'
R-C-COO~
-16-
~2~3609
The sum of the carbon atoms for R, R' and R" in each
isomer is eight. The Exxon technical grade neodecanoic
acid employed has a typical isomer distribution as
follows:
i) R=CH3~ R'=CH3, R =C6H13----------31~
ii) R<C6H13r ~'=CH3, R">cH3....... ~ 67%
iii) R<C6H13~ R'> CH3, Rn~CH3~ 2%
Therefore, as the term is used herein, neodecanoic acid
and neodecanoate esters include each of the several
isomers of the technical grade material, either alone or
in mixture,
Example 2
The apparatus described in Example 1 was
charged with 175 grams of antimony oxide, 212 grams of
acetic anhydride and 125 grams of xylene. With stirring
the reaction mixture was heated to 120C and maintained
at that temperature for 3 to 4 hours. Then, about 664
grams of neodecanoic acid (technical grade) was added and
the reaction mixture heated to 200C. During the heating
from 120C to 200C, nitrogen was bubbled through the
reaction mixture by use of a subsurface nitrogen sparge.
While the reaction mixture was heated from 120C to
200C, xylene was removed by distillation and evolution
of acetic acid was observed at about 155C and was
removed. When the temperature of 200C was reached, the
reaction mixture was cooled and the antimony trineo-
decanoate yield was determined to be 90%.
-17-
B,l`
3~iO9
Example ~
The procedure of Example 2 was repeated with
the exception that the reac~ion mixture was heated to
225C after adding the neodecanoic acid reactant. After
reaching 225C, the reaction mixture was cooled and the
antimony trineodecanoate yield was determined to be
94.2%.
Example 4
A Midwestern United States refinery typically
uses thirty gallons per day of a commercial antimony
F.C.C. catalyst aide with a hydrocarbon feed rate to the
unit of 20,000 barrels per day. The catalyst aide was a
colloidal dispersion of Sb20s in a hydrocarbon carrier.
The refiner was charging 30-35 tons of fresh catalyst
per day while maintaining a constant catalyst inventory
of approximately 300 tons of catalyst and targeting for
a hydrogen to methane molar ratio (H2:CH4) of 1Ø
The concentration of nickel on the catalyst was deter-
mined to typically be 2000-3500 ppm. Typical analyses
for antimony present on the catalyst and the determi-
nation of the H2:CH4 ratio are shown below:
Antimony Antimony
Charged Found on Lay-Down H2:
(llbs. per catalyst Efficiency CH4
day) (ppm) (%) Ratio
69 500 47 >1.0
Example 5
The antimony tricarboxylate product of Example
2 was subjected to field evaluation in a typical
Midwestern United States refinery as in Example 4. The
~2~3609
initial charge of 30 gallons per day of antimony
tricarb~xylate replaced the catalyst aide of Example 4.
Analyses for antimony present on the catalyst and the
determination for the H2:CH4 ratio were run after
fourteen days. Additional data was collected after
approximately two months time wherein the feed-rate of
chemical had been lowered to 25 gallons per day. Those
results are shown below:
Sb Sb
Charged Found on Lay- Lay
10Time (llbs. Catalystdown H2:CH4
(days) per day (ppm)Efficiency (%) Ratio
14 59 '79086 0.9-1.0
16 49 70092 1.0
As seen by this example, the feed-rate of the
antimony catalyst aide can be expected to decrease 28.57%
with a lay-down efficiency increase of approximately 2-
fold while maintaining the H2:CH4 ratio in the desired
range as compared with the aide of Example 2.
Example 6
The Midwest refinery of this example was
charging 15,000 barrels per day of hydrocarbon feedstock
to the F.C.C. unit while maintaining a constant catalyst
inventory and fresh catalyst make-up. A commercial
catalyst aide, Sb2P~ was in use which contained 11 to
12% antimony, a density of 10 lbs. per gallon and at a
feed-rate of 5 gallons per day. The catalyst regenera-
tion unit has a maximum operating temperature of 1400F.
The measure of performance of the catalyst aide was
based upon regenerator temperature, antimony found on
-19-
~213609
the catalyst and the hydrogen to methane molar ratios.
Typical results are presented below for both the
commercial catalyst side and the antimony tricarboxylate
from Example 2:
Antimony Regene-
lbs. Found On ration H2:
Catalyst Sb Fed Catalyst Temp. CH4
Aide per day (ppm) (~F) Ratio
Commercial 11.5 400 1370 >1.0
Product Ex. 2 9.89 1100 1350 0.8-0.9
Product Ex. 2 7.91 800 1350 1.0
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