Cracking catalyst poisons passivated with tin compounds plus both sulfur and phosphorus

Deposits on a cracking catalyst are passivated by contacting the cracking catalyst with tin and at least one of phosphorus or sulfur.

BACKGROUND OF THE INVENTION 
This invention relates to the art of the catalytic cracking of 
hydrocarbons. In another aspect, the invention relates to reducing the 
detrimental effects of contaminating deposits on a cracking catalyst. In 
still another aspect, the invention relates to the passivation of metals 
on cracking catalysts. 
In most conventional catalytic cracking processes in which hydrocarbon 
feedstocks are cracked to produce light distillates a gradual 
deterioration of the catalyst occurs. Some of this deterioration is 
attributable to the deposition on the catalyst of contaminants contained 
within the feedstock. The deposition of these contaminants, which include 
nickel, vanadium and iron, tends to adversely affect the cracking process 
by decreasing conversion of the feedstock to cracked products, decreasing 
production of gasoline and increasing yields of hydrogen and coke. 
It is known in the art that the adverse effects of catalyst contamination 
can be partially offset by treating the cracking catalyst with passivating 
agents, for example, antimony and its compounds. Treatment of the cracking 
catalyst with antimony is extremely desirable in that all four indicia of 
catalyst deterioration due to deposits of contaminants are improved. 
Conversion and selectivity to gasoline increase, while hydrogen and coke 
production decrease. Other passivating agents do not result in improvement 
in all four indications of undesirable cracking behavior due to deposits 
of contaminants on the catalyst. In fact, some passivating agents actually 
worsen one or more of the indicators of undesirable cracking behavior, for 
example, by decreasing conversion, but are still termed a passivating 
agent because they improve another of the indicators, for example, by 
reducing the production of hydrogen. 
Cracking catalysts which are resistant to acquiring undesirable cracking 
behavior when contaminants are deposited thereon from the feedstock are 
very desirable in that they make possible the economic conversion of poor 
quality feedstocks to gasoline and other light hydrocarbons. Because poor 
quality feedstocks are in relative abundance, there is a need for new and 
improved passivating agents which impart more desirable cracking 
characteristics to contaminated cracking catalysts. There is also a need 
for passivating agents which impart to cracking catalysts resistance to 
becoming adversely affected by contamination from the feedstock. Because 
of environmental laws which might restrict the use of certain passivating 
agents, it is also extremely desirable to provide alternative passivating 
agents so that contaminated oils can continue to be economically cracked. 
OBJECTS OF THE INVENTION 
It is thus an object of this invention to counteract the effects of metals 
deposition on a cracking catalyst. 
It is another object of this invention to at least partially reactivate a 
cracking catalyst which has been partially deactivated by deposits of 
contaminants thereon. 
It is a further object of this invention to provide an improved process 
which is particularly useful for cracking hydrocarbon feedstocks 
containing contaminating metals. 
These and other objects of the present invention will be more fully 
explained in the following detailed description of the invention and the 
appended claims. 
SUMMARY OF THE INVENTION 
According to one embodiment of the invention, a cracking catalyst is 
contacted with a tin source and at least one of a phosphorus source and a 
sulfur source. When used for the catalytic cracking of hydrocarbons, the 
contacted cracking catalyst exhibits improved resistance to the adverse 
effects caused by contaminants becoming deposited thereon from the 
feedstock. When the catalyst has deposits of contaminants thereon at the 
time of contact in accordance with the invention, its activity and 
selectivity are improved and its value for catalytic cracking immediately 
enhanced. Even cracking catalysts exhibiting such poor cracking behavior 
due to deposits thereon of contaminants that their continued use for 
cracking would be economically unjustifiable can be contacted in 
accordance with the invention and frequently economically employed for the 
cracking of hydrocarbon feedstock, especially for the cracking of heavy 
oils and the like. 
DETAILED DESCRIPTION OF THE INVENTION 
It has been found that tin in combination with phosphorus and/or sulfur is 
especially useful for passivating contaminants on a cracking catalyst. 
Such a combined treatment increases dramatically the selectivity of the 
cracking catalyst for production of a gasoline fraction. It was further 
found that treatment of a cracking catalyst having metals deposited 
thereon from the hydrocarbon feedstock with tin alone decreased catalyst 
activity, although this decrease in catalyst activity could be offset by 
employing antimony in combination with tin. It has now been found, 
surprisingly, that treatment of the cracking catalyst with sulfur and/or 
phosphorus in addition to treatment with tin can actually increase 
catalyst activity, increase dramatically the selectivity of the cracking 
catalyst for the production of gasoline range products, in addition to 
decreasing hydrogen and coke production, even in the absence of antimony. 
The tin source of this invention is any tin composition which can be 
contacted with the cracking catalyst to increase the concentration of tin 
on the catalyst. The valence state of the tin in the composition contacted 
with cracking catalyst is unimportant. Thus, stannous or stannic 
compounds, alone or in conjunction, can be employed in the process of the 
present invention. Elemental tin, inorganic tin compounds and organic tin 
compounds as well as mixtures thereof are suitable sources of tin. 
Examples of inorganic tin sources which can be employed include the 
elemental forms of tin: gray tin, white tin and brittle tin. Tin (II) 
and/or tin (IV) oxides and the hydrates of such compounds are also 
exemplary tin sources. Tin (II) or tin (IV) halides for example stannous 
fluoride, stannic fluoride, stannous chloride, stannic chloride, stannous 
bromide, stannic bromide, stannous iodide, stannic iodide, and tin 
heterohalides, for example stannic bromotrichloride as well as the 
hydrates of such compounds can be employed as the tin source. Stannic 
hydride can be used as a source of tin. Tin nitrates which can be used in 
accordance with the invention include stannous nitrate and stannic 
nitrate. Tin selenides and tin tellurides can also be employed as the tin 
source. 
The source of phosphorus employed in this invention can vary widely and can 
be any phosphorus composition which will enhance the passivation qualities 
of tin, or the promotion quality of sulfur for enhancing the passivating 
qualities of tin. 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 suitable for use. Exemplary of 
suitable phosphorus oxides which can be used in accordance with the 
invention are phosphorus trioxide, phosporus tetraoxide, phosphorus 
pentaoxide, and phosphorus sesquioxide. Oxygen containing phosphorus 
compounds for example phosphorus oxychloride, phosphorus oxybromide, 
phosphorus oxybromide dichloride, phosphorus oxyfluoride, 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 
hypophosphorus acid, metaphosphorus acid, orthophosphorus acid, and 
pyrophosphorus acid. 
The source of sulfur employed in this invention also can vary widely and 
can be any sulfur composition which will enhance the passivation qualities 
of tin or the promotion quality of phosphorus for enhancing the 
passivation qualities of tin. 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 compounds, for example, tetrasulfur dinitride, 
tetrasulfur tetranitride, and trithiazylchloride can also be used in 
accordance with the invention. Oxides of sulfur, for example sulfur 
dioxide, sulfur heptoxide, sulfur monoxide, sulfur sequioxide, 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 fluoride and pyrosulfuryl chloride are also suitable for 
use. 
Of course, single compositions containing more than one of tin, phosphorus 
or sulfur can be employed as a combined source. Thus, suitable treating 
agents include inorganic compounds containing tin and phosphorus. Tin (II) 
metaphosphate, tin (II) orthophosphate, tin (II) monohydrogen 
orthophosphate, tin (II) dihydrogen orthophosphate, and tin (II) 
pyrophosphate are suitably employed. The tin phosphides are also suitable 
sources of tin and phosphorus. For example, tin monophosphide, tin 
triphosphide, and tetratintriphosphide can be used in accordance with the 
invention. 
Likewise, inorganic compositions which contain tin and sulfur can be 
usefully employed as treating agents in accordance with the present 
invention as a combined tin-sulfur course. Exemplary of these compositions 
are tin (II) sulfate, tin (IV) sulfate, tin (II) sulfide, and tin (IV) 
sulfide. 
Similarly, treating agents comprising both phosphorus and sulfur include 
phosphorus oxysulfide, tetraphosphorus heptasulfide, 
phosphoruspentasulfide, and tetraphosphorus trisulfide. 
Preferably, the tin source and the at least one phosphorus source or sulfur 
source contain no nickel, no vanadium and no iron. Of the inorganic 
sources, those containing halogens are less preferred, because of their 
corrosive effect on process equipment. The presently preferred combination 
of inorganic sources are stannous oxide and phosphorus pentasulfide. 
Of course, organic treating agents can be employed as the source for tin 
and at least one of phosphorus and sulfur. Generally, the organic treating 
agents contain from about one to about 48 carbon atoms for reasons of 
economics and availability, although organic compounds having a greater 
number of carbon atoms are also applicable. Thus, organic polymers can be 
employed. In addition to carbon and hydrogen, the organic moiety can also 
contain elements for example tin, phosphorus, sulfur, oxygen, nitrogen and 
halogen. 
Examples of organic sources of tin include tin carboxylates, tin 
carbonates, hydrocarbyl tin compounds, and hydrocarbyl tin oxides. Thus, 
stannous formate, stannous acetate, stannous butyrate, stannous octoate, 
stannous decanoate, stannous oxylate, stannous benzoate, stannous 
cyclohexanecarboxylate, stannous propylcarbonate, tetrabutyltin, 
tetraoctyltin, tetradodecyltin, tetraphenyl tin, dipropyltin oxide, 
dibutyltin oxide, dioctyltin oxide, diphenyl tin oxide, stannous diethyl 
carbamate, tri-n-propyltin chloride and dibutyltin dibromide are suitably 
employed as treating agents in accordance with the present invention. 
Examples of organic phosphorus sources include hydrocarbylphosphines, 
hydrocarbylphosphine oxides, hydrocarbylphosphites and 
hydrocarbylphosphates. Exemplary compounds include tri-n-butylphosphine, 
triphenylphosphine, tri-n-butylphosphine oxide, triphenylphosphine oxide, 
trioctylphosphite and triphenylphosphite. 
Examples of organic sulfur sources include mercaptans, thioethers, 
disulfides, polysulfides, thioacids, heterocyclic 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, dibenzothiophene, and carbon 
disulfide. 
Of course, compositions containing both tin and phosphorus can be employed 
as treating agents. Exemplary of these compounds are the tin-hydrocarbyl 
phosphites and tin-hydrocarbyl phosphates, for example stannous 
diphenylphosphite and stannous dipropylphosphate. In the preferred organic 
tin-phosphorus combined sources, at least one phosphorus atom is located 
gamma or closer to the tin. Phrased another way, the phosphorus is alpha, 
beta or gamma to the tin. In this embodiment, there are no more than two 
intervening atoms between the tin and at least one of the phosphorus 
atoms. Of course, more than one phosphorus atom can have this relationship 
with the tin. 
Likewise, compositions containing tin and sulfur can be employed as a 
treating agent. Representative of these tin and sulfur treating agents are 
tin thiocarboxylates, hydrocarbyl tin mercaptoalkanoates, tin 
thiocarbonates, hydrocarbyltin hydrocarbyl mercaptides, and tin 
thiocarbamates. Examples include stannousthioacetate, stannous 
dithioacetate, dibutyltin bis(isooctyl mercaptoacetate), dipropyltin 
bis(butyl mercaptoacetate), stannous O-ethyl dithiocarbonate, dibutyltin 
bis(dodecyl mercaptide), stannous thiophenoxide, stannous benzene 
sulfonate, stannous p-toluene sulfonate, stannous propylthiocarbamate and 
stannous diethyl dithiocarbamate. Preferably, at least one sulfur atom in 
these compositions is located gamma or closer to the tin atom. In this 
embodiment, there are no more than two intervening atoms intermediate the 
tin and at least one of the sulfur atoms. At least one sulfur atom is 
alpha, beta or gamma to the tin. The compositions can contain more than 
one sulfur atom which bears this relationship to the tin. 
The preferred compositions employed in this invention contain a tin source, 
a phosphorus source, and a sulfur source. Although any compositions 
containing tin, phoshorus and sulfur can be employed, it is more 
preferable that the composition have at least one phosphorus atom and at 
least one sulfur atom located at the gamm position or closer to the tin. 
Phrased another way, these compositions have at least one sulfur atom 
which is alpha, beta or gamma to tin, and at least one phosphorus atom 
which is alpha, beta or gamma from tin. More preferably, the sulfur and 
phosphorus bear this relationship to the same tin atom. Of these, the tin 
salts of dihydrocarbyl thiophosphoric acids are particularly preferred, 
because they have been tested with good results. These treating agents are 
conveniently represented by the formula 
##STR1## 
wherein the R groups can be the same or different and each comprise 
hydrocarbyl radicals having from 1 to about 24 carbon atoms, wherein the X 
groups are selected from the group consisting of oxygen and sulfur, and at 
least one of the X groups is sulfur, and where n is 2 or 4. The overall 
number of carbon atoms per molecule can range from 4 to about 200. The 
most preferred tin compounds of this class are those of the above formula 
wherein the R groups are alkyl radicals having from about 2 to about 10 
carbon atoms per radical, for example, n-propyl, because it has been 
tested with good results. The R groups can also comprise substituted or 
unsubstituted C.sub.5 or C.sub.6 cycloalkyl radicals and substituted or 
unsubstituted phenyl radicals. Examples of suitable R radicals are ethyl, 
n-propyl, isopropyl, n-, iso-, sec- and tert-butyl, amyl, n-hexyl, 
isohexyl, sec-hexyl, n-heptyl, n-octyl, isooctyl, tert-octyl, dodecyl, 
octyldecyl, cyclopentyl, methylcyclopentyl, cyclohexyl, methylcyclohexyl, 
ethylcyclohexyl, phenyltoluyl, cresol, ethylphenyl, butylphenyl, 
amylphenyl, octylphenyl, vinylphenyl, and the like. Preferably, the 
hydrocarbyl radicals are bonded to phosphorus through an oxygen atom, 
because such compounds can be prepared by reacting an alcohol, such as 
n-propanol, with phosphorus pentasulfide to produce a 
O,O-dihydrocarbyl-phosporodithioic acid and reacting this acid or a salt 
thereof with a suitable tin compound to produce the tin salt. These 
compounds are conveniently represented by the formula 
##STR2## 
wherein R and n are as defined before. 
These treating agents are most preferred because they are very effective 
passivating agents, are simple and inexpensive to prepare, and, because of 
their oil solubility, are well adapted to dissolve in hydrocarbon 
feedstock and meter continuously into a cyclic cracking process. Examples 
of the most preferred treating agents are: stannous O,O-diethyl 
dithiophosphate; stannic O,O-diethyl dithiophosphate; stannous 
O,O-di-n-propyl dithiophosphate; stannic O,O-di-n-propyl dithiophosphate; 
stannous O,O-diisopropyl dithiophosphate; stannic O,O-diisopropyl 
dithiophosphate; stannous O,O-di-n-butyl dithiophosphate; stannic 
O,O-di-n-butyl dithiophosphate; stannous diisobutyl dithiophosphate; 
stannic O,O-diisobutyl dithiophosphate; stannous O,O-di-sec-butyl 
dithiophosphate; stannic O,O-di-sec-butyl dithiophosphate; stannous 
O,O-di-tert-butyl dithiophosphate; stannic O,O-di-tert-butyl 
dithiophosphate; stannous O,O-diamyl dithiophosphate; stannic O,O-diamyl 
dithiophosphate; stannous O,O-di-n-hexyl dithiophosphate; stannic 
O,O-di-n-hexyl dithiophosphate; stannous O,O-di-sec-hexyl dithiophosphate; 
stannic O,O-di-sec-hexyl dithiophosphate; stannous O,O-di-n-heptyl 
dithiophosphate; stannic O,O-di-n-heptyl dithiophosphate; stannous 
O,O-di-n-octyl dithiophosphate; stannic O,O-di-n-octyl dithiophosphate; 
stannous O,O-diisooctyl dithiophosphate; stannic O,O-diisooctyl 
dithiophosphate; stannous di-tert-octyl dithiophosphate; stannic 
O,O-di-tert-octyl dithiophosphate; stannous O,O-didodecyl dithiophosphate; 
stannic O,O-didodecyl dithiophosphate; stannous O,O-dioctyldecyl 
dithiophosphate; stannic O,O-dioctyldecyl dithiophosphate; stannous 
O,O-dicyclopentyl dithiophosphate; stannic O,O-dicyclopentyl 
dithiophosphate; stannous O,O-dimethylcyclopentyl dithiophosphate; stannic 
O,O-dimethylcyclopentyl dithiophosphate; stannous O,O-dicyclohexyl 
dithiophosphate; stannic O,O-dicyclohexyl dithiophosphate; stannous 
O,O-dimethylcyclohexyl dithiophosphate; stannic O,O-dimethylcyclohexyl 
dithiophosphate; stannous O,O-diethylcyclohexyl dithiophosphate; stannic 
O,O-diethylcyclohexyl dithiophosphate; stannous O,O-diphenyltoluyl 
dithiophosphate; stannic O,O-diphenyltoluyl dithiophosphate; stannous 
O,O-dicresol dithiophosphate; stannic O,O-dicresol dithiophosphate; 
stannous O,O-diethylphenyl dithiophosphate; stannic O,O-diethylphenyl 
dithiophosphate; stannous O,O-dibutylphenyl dithiophosphate; stannic 
O,O-dibutylphenyl dithiophosphate; stannous O,O-diamylphenyl 
dithiophosphate; stannic O,O-diamylphenyl dithiophosphate; stannous 
O,O-dioctylphenyl dithiophosphate; stannic O,O-dioctylphenyl 
dithiophosphate; stannous O,O-divinylphenyl dithiophosphate; and stannic 
O,O-divinylphenyl dithiophosphate. 
Of these compounds, stannous O,O-di-n-propyl phosphorodithioate and stannic 
O,O-di-n-propylphosphorodithioate are most preferred, because they have 
been tested with good results and are relatively stable. 
The tin/phosphorus and tin/sulfur ratios in these compositions can be 
varied by utilizing stannic or stannous salts of the dihydrocarbyl 
thiophosphoric acids. For example, tin (IV) O,O-di-n-propyl 
phosphorodithioates can be prepared by reacting a suitable stannic 
compound, for example, stannic chloride, and the O,O-di-n-propyl 
dithiophosphoric acid or, more preferably, a suitable salt thereof, for 
example potassium dipropyl dithiophosphate, in a suitable solvent, for 
example, tetrahydrofuran. Tin (II) O,O-di-n-propyl phosphorodithioates can 
be prepared by a double decomposition reaction between a tin (II) 
carboxylate, for example, tin (II) octanoate and the thiophosphoric acid, 
for example, with O,O-di-n-propylphosphorodithioic acid dissolved in 
cyclohexane. The tin salt thus produced can be used effectively to treat 
metals contaminated fluid catalytic cracking catalysts without removing 
the free carboxylic acid that it contains. 
Compositions represented by the above formula can thus have a wide range of 
tin/phosphorus ratios, tin/sulfur ratios, and phosphorus/sulfur ratios. 
Treatment of cracking catalysts with tin and at least one of phosphorus 
and sulfur in accordance with this invention effectively reduces the 
detrimental effects of metals contamination on the cracking catalyst to 
the cracking process especially that of decreased catalyst selectivity for 
gasoline. 
In accordance with this invention, a cracking catalyst is contacted with a 
passivating amount of a tin source and a promoting amount of at least one 
of a phosphorus source and a sulfur source. By passivating amount of tin 
source is meant an amount of the tin source sufficient to provide at least 
one improvement selected from the group consisting of an increase in 
catalyst activity, an increase in the selectivity of the catalyst for 
gasoline-range products, a reduction in the production of coke, and a 
reduction in the production of hydrogen. By a promoting amount of at least 
one of the sulfur source and phosphorus source is meant an amount of such 
source which provides an enhancement in said at least one improvement 
and/or provides at least one additional improvement, the enhancement or 
additional improvement being of a magnitude which is greater than the 
improvement which would result from contacting the cracking catalyst with 
at least one of the sulfur source or phosphorus source in a like amount 
without contacting the cracking catalyst with the passivating amount of 
the tin source. Preferably, the cracking catalyst is contacted with a 
sufficient amount of at least one of the phosphorus source or sulfur 
source in addition to the tin source to provide an increase in the 
selectivity of the cracking catalyst for cracking the feedstock to 
gasoline range products. 
Generally, the cracking catalyst is contacted with a sufficient amount of 
tin to impart to the cracking catalyst a tin concentration of between 
about 0.0001 through 4 percent by weight tin based on the weight of the 
tin-treated cracking catalyst. More often, the cracking catalyst is 
contacted with a sufficient amount of tin to impart thereto from about 
0.001 to about 2 weight percent tin based on the weight of the tin-treated 
cracking catalyst. A tin concentration on the cracking catalyst of from 
about 0.005 to 1 percent by weight tin based on the weight of the 
tin-treated cracking catalyst is a more preferred amount of tin for 
reasons of economy, with a tin concentration of from 0.01 to 0.15 weight 
percent based on weight of tin-treated cracking catalyst being the most 
preferred because it closely encompasses tin concentrations which have 
been tested with good results. In addition to the above-described amounts 
of tin, the cracking catalyst is contacted with a sufficient amount of at 
least one of phosphorus or sulfur to promote the passivating effects of 
the tin. When employing sulfur as the promoting agent, it is desirable to 
contact the cracking catalyst with from about one-half to about 8 parts by 
weight sulfur from the sulfur source for each part by weight of tin which 
has been contacted with the cracking catalyst from the tin source. When 
employing phosphorus as the promoting agent, it is desirable to contact 
the cracking catalyst with from about one-quarter to about 1 part by 
weight phosphorus from the phosphorus source for each part by weight tin 
with which the cracking catalyst has been contacted. These ratios are not 
exact, being based on the approximation that phosphorus or sulfur has 
about one-quarter of the atomic weight of tin. Preferably, the cracking 
catalyst is contacted with the tin source and at least one of the 
promoting sources simultaneously, by employing a composition and/or 
mixture which contains tin and at least one of sulfur and phosphorus. More 
preferably, the cracking catalyst is contacted with a composition which 
contains tin and at least one of phosphorus and sulfur. In this 
embodiment, the phosphorus and/or sulfur are located at positions gamma or 
closer, for example, alpha, beta or gamma, to the tin atom. Most 
preferably, the composition contains both phosphorus and sulfur both 
located gamma or closer to the tin atom. Normally, these compositions will 
contain one part by weight or less of phosphorus and from about 1 to about 
4 parts by weight sulfur for each part by weight tin. 
Treatment of the cracking catalyst with tin and at least one promoting 
source selected from sulfur-containing compositions and 
phosphorus-containing compositions is effective to reduce the detrimental 
effects of metals contamination on a cracking catalyst. The treated 
composition can be employed directly for catalytic cracking without first 
subjecting it to a heat treatment. Treatment of the cracking catalyst in 
accordance with this invention is also effective to reduce the 
susceptibility of new cracking catalyst to becoming adversely affected by 
deposits of contaminants from the feedstock. 
When employing the present invention to reactivate used cracking catalysts, 
it is desirable to maintain a ratio of tin to contaminants on the 
catalysts from about 0.2 to 100 to about 200:100, expressed as the weight 
ratio of elemental tin to the combined weights of vanadium and four times 
the weight of nickel on the catalyst. The combined weights of vanadium and 
four times the weight of nickel on the cracking catalyst is commonly 
referred to as the vanadium equivalent and as used herein, is expressed in 
parts vanadium and 4 times nickel combined per million parts weight 
cracking catalyst including vanadium and nickel (ppm). A preferred ratio 
of tin to vanadium equivalents on the cracking catalyst is from about 
0.5:100 to about 50:100, because ratios within such a range have been 
tested with good results. 
A variety of methods can be used to contact the cracking catalyst with the 
tin source and the at least one promoting source selected from phosphorus 
and sulfur. When contacting the cracking catalyst with solid compositions, 
the composition in finely divided form can be mixed with the cracking 
catalyst in an ordinary manner such as by rolling, shaking, stirring or 
the like. Alternatively, these sources can be dissolved or dispersed in a 
suitable liquid, for example, water, hydrocarbon or aqueous acid, 
depending in part upon the particular composition being employed, and the 
resulting solution or dispersant can be used to impregnate the cracking 
catalyst, followed by volatilization of the liquid, or the source can be 
precipitated onto the catalyst from a solution of the source followed by 
solvent removal, or, the source can be sprayed onto the catalyst. The 
order in which the tin source and the promoting source are contacted with 
the cracking catalyst is not critical. For convenience, however, it is 
preferred that the contacting be effected simultaneously. When employing 
an oil-soluble source, the preferable method for contacting the tin source 
and the promoting source with the cracking catalyst is to dissolve or 
disperse the selected sources in the hydrocarbon feedstock to be used in 
the cracking process. In this case, the hydrocarbon feedstock and the tin 
source and promoting source contact the cracking catalyst about the same 
time. Additionally, if desired, the cracking catalyst can be exposed to 
the source in vapor form to deposit the source on the catalyst. Of course, 
combinations of the various methods can be employed to achieve 
modification of the cracking catalyst with the tin source and the 
promoting source. 
The tin source and promoting source can be contacted with used cracking 
catalyst, unused cracking catalyst, or mixture thereof in accordance with 
the present invention and prior to, and/or during the use of the catalyst. 
Treatment of used cracking catalyst with the tin source and promoting 
source increases catalyst selectivity for gasoline production, decreases 
the production of hydrogen and the production of coke often without 
harming catalyst activity. Treatment of new cracking catalysts with the 
tin source and promoting source aids in maintaining high catalyst 
selectivity for gasoline production and low hydrogen and coke production. 
The term "cracking catalyst" as used herein refers to either new or used 
cracking catalyst materials which are useful for cracking hydrocarbons in 
the absence of added hydrogen. 
Cracking catalysts suitable for treatment in accordance with this invention 
can be any of those cracking catalysts employed in the catalytic cracking 
of hydrocarbons boiling above 400.degree. F. (204.degree. C.) in the 
absence of added hydrogen for the production of gasoline, motor fuel 
blending components and light distillates. Because of the high activity 
and selectivity of zeolite containing cracking catalysts, zeolite 
containing cracking catalysts are preferred. The zeolitic materials can be 
naturally occurring or snythetic. Generally they will have been at least 
partially ion exchanged with ammonium or rare earth cations. 
Zeolite-modified silica-alumina catalysts are particularly well suited for 
treatment in accordance with this invention, especially such catalysts 
comprising from 1 to about 50 percent by weight of zeolitic materials. 
Examples of cracking catalysts useful in the present invention include, 
for example, hydrocarbon cracking catalysts obtained by admixing 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. The 
catalytic cracking materials can vary in pore volume and surface area. 
Generally, the unused cracking catalyst will have a pore volume in the 
range of from about 0.1 to about 1 ml/gm. The surface area of this unused 
catalytic cracking material generally will be in the range of from about 
50 to about 500 m.sup.2 /gm. The unused catalytic cracking material 
employed will generally be in particulate form having a particle size 
principally within the range of from about 10 to about 200 micrometers. 
Feedstocks amenable to conversion by the treated cracking catalyst of this 
invention are generally oils having an initial boiling point have 
204.degree. C. This includes gas oils, fuel oils, topped crude, shale oil, 
waste polymers in solvent and oils from coal and/or tar sands. The 
feedstocks can and usually do contain significant concentrations of at 
least one metal selected from the group of nickel, vanadium and iron. The 
presence of such metals normally adversely affects catalyst selectivity 
and activity. Since these metals become concentrated in the least volatile 
fractions of oil suitable for use as feedstock, cracking the heavy oil 
fractions is probably the most important application for the treated 
cracking catalyst of this invention. Such feedstocks can contain, for 
example, nickel concentrations of about 100 parts per million, vanadium 
concentrations of about 500 parts per million, and iron concentrations of 
about 500 parts per million. Because nickel has a stronger affect on the 
activity and selectivity of the cracking catalyst than vanadium and/or 
iron, it is convenient to refer to the total contaminants in the feedstock 
in terms of parts per million by weight of total effective metals, as used 
herein the term "total effective metals" means the sum of vanadium, iron 
and four times the weight of nickel in one million parts by weight of 
feedstock (ppm). 
Most known commercial heavy oil cracking processes are capable of cracking 
heavy oils having a metals content of up to about 100 ppm of total 
effective metals as defined above. Economically marginal results are 
obtained with oils having 50 to 100 parts per million of total effective 
metals. In accordance with this invention, heavy oils with a total metals 
content of about 50 to 100 ppm and even those of about 100 to 200 ppm and 
above of total metals can be cracked in a cracking process by utilizing 
the treated cracking catalyst defined above to yield gasoline and other 
fuels and fuel blending components. Thus, heavy oils with total metals 
content from about 100 to 300 ppm that could not be directly used for fuel 
production in most known processes and in particular for gasoline or 
higher boiling hydrocarbon fuels production, in accordance with this 
invention can be cracked to yield gasoline and higher boiling hydrocarbon 
fuels such as kerosene, diesel fuel and burning oils. 
It is preferable to meter the tin source and at least one promoting source 
into the catalytic cracker along with feedstock at at least a rate which 
is related to the amounts of contaminants in the feedstock as set forth 
below. 
______________________________________ 
Total Effective Metals 
Tin Concentration 
in Feedstock (ppm).sup.1 
in Feedstock (ppm) 
______________________________________ 
&lt;1-40 0.005-20 
40-100 0.2-50 
100-200 0.5-100 
200-300 1.0-200 
300-800 2.0-500 
______________________________________ 
.sup.1 Fe(ppm) + V(ppm) + 4 Ni(ppm) by weight. 
Of course, higher rates can be used if desired, for example, when it is 
desired to increase the concentration of tin on the cracking catalyst. 
A preferred embodiment of the cracking process of the present invention 
utilizes cyclic flow of catalyst from a cracking zone to a regeneration 
zone. In this process, the hydrocarbon feedstock is contacted with a 
fluidized cracking catalyst in a cracking zone under cracking conditions 
in the absence of added hydrogen; a cracked product is obtained and 
recovered; the cracking catalyst is passed from the cracking zone into a 
regeneration zone; and in the regeneration zone the cracking catalyst is 
regenerated by being contacted with a free oxygen-containing gas, 
preferably air. The coke that has built up during the cracking process is 
thereby at least partially burned off the catalyst. The regenerated 
cracking catalyst is reintroduced into the cracking zone usually after 
being supplemented with a make-up catalyst. 
Such cyclic catalytic cracking processes are well known to those skilled in 
the art. Generally, the cracking reaction takes place in the presence of 
fluidized cracking catalyst at catalytic cracking temperatures, for 
example, temperatures beteeen about 900.degree. and 1100.degree. F. 
(482.degree. to 593.degree. C.) usually between 940.degree. and 
1020.degree. F. (504.degree. to 549.degree. C.) at catalytic cracking 
pressures, for example, pressures between about 5 and 50 psig (138-448 
kPa) usually 15 to 35 psig (207-345 kPa). Usually, the cracking catalyst 
employed contains zeolitic materials. The catalyst-to-feedstock contact 
time is generally between about 1 and 4 seconds, and is conducted with 
catalyst-to-feedstock weight ratios of between about 4:1 and 15:1. 
Regeneration is carried out under catalyst regeneration conditions, for 
example, in the presence of oxygen containing gas at temperatures between 
800.degree. and 1600.degree. F. (427.degree. to 871.degree. C.), usually 
from about 1150.degree. to 1350.degree. F. (621.degree. to 732.degree. 
C.) for a period of time ranging from about 3 to 30 minutes and sufficient 
to reduce the concentration of coke on the catalyst to less than 0.3 
weight percent, preferably less than 0.1 weight percent. 
In this embodiment of the invention, the tin source and one or both of the 
phosphorus source and the sulfur source are metered continuously into the 
cracking unit for contact with the cracking catalyst. The tin source and 
at least one of the phosphorus source and sulfur source need not be 
introduced into the unit at the same point. For example, at least one of 
the phosphorus source and sulfur source could be introduced into the 
cracking zone and the tin source could be introduced into the regeneration 
zone; or at least one promoter could be introduced into the unit at 
completion of regeneration into the regeneration zone, and the tin source 
introduced into the cracking zone. It is preferred to introduce the tin 
source and at least one promoter source into the cracking unit so that the 
tin and at least one promoter contact the cracking catalyst at about the 
same time. This is conveniently accomplished by mixing or dissolving the 
tin source and at least one promoter source into the feedstock, as 
previously described. When employing oil-soluble sources, the tin and at 
least one of phosphorus and sulfur can be diluted with a neutral 
hydrocarbon oil and metered into the feedstock.

The invention will be still more fully understood from the following 
examples, which are intended to illustrate preferred embodiments of the 
invention but not limit the scope thereof. 
EXAMPLE 1 
Synthesis of Stannic O,O-Dihydrocarbylphosphorodithioates 
The subject compound is prepared by a double decomposition (or metathesis) 
reaction between a stannic salt and dihydrocarbylphosphorodithioic acid 
or, preferably, a salt of the acid with an element from Group Ia or IIa of 
the periodic table of the elements, such as lithium, sodium, potassium, 
magnesium, and calcium. In the anion of the phosphorus compound 
[(RO).sub.2 PS.sub.2 ].sup.- R is a hydrocarbyl radical that contains from 
one to about 24 carbon atoms and can be an alkyl, cycloalkyl, alkenyl, 
cycloalkenyl, or aryl radical or a combination of these radicals such as 
alkaryl, aralkyl, etc. Examples of suitable hydrocarbyl radicals are 
methyl, normal and isopropyl, normal and branched hexyl, decyl, and 
octadecyl, cyclohexyl, cyclohexenyl, phenyl, xylyl, 1- and 2-anthracyl, 
and the like. 
Suitable stannic salts for the double decomposition reaction are, in 
general, those that are soluble in the solvent selected for the reaction 
medium. Examples are the stannic halides, particularly the chlorides, 
bromides, and iodides, and stannic sulfate. 
Solvents suitable to effect the synthesis of tin 
dihydrocarbylphosphorodithioate are those in which the reactants and the 
tin produce are soluble to at least a limited extent. Examples are water 
and polar organic compounds such as methanol and ethanol, tetrahydrofuran, 
acetone, and the like, and mixtures thereof. Reaction conditions for the 
synthesis are not critical. Temperature for the reaction can range 
generally from 0.degree. C. to 75.degree. C.; for convenience of operation 
ambient temperatures are preferred. The reaction appears to resemble ionic 
reactions in its speed. Consequently extended reaction times are not 
required although a time of 2-3 hours can be used at the lower limits of 
the cited temperature range. At about 25.degree. C. and above the reaction 
can be considered to be complete when the reactants have been combined but 
additional time can be used to permit phase separation of the products, 
e.g., oils from aqueous solution or inorganic salts from organic solvents. 
The order in which reactants are combined is not critical, i.e., the tin 
salt can be added to the phosphorus-containing reactant or vice versa. 
And, since the reaction is not equilibrium limited the preferred ratio for 
combining reactants is the stoichiometric. (This does not imply 
quantitative yields because nonproductive reactions can occur, e.g., the 
tin compound with the solvent). Although the quantity of solvent in which 
the reaction occurs is not critical, it will conveniently be at least 
about one liter per gram-mole of total reactants. Preferably there will be 
sufficient solvent to dissolve completely the reactants. 
For many purposes, including the preparation of a passivating agent for 
metals-contaminated cracking catalyst, it is required to separate the 
desired product from the by-product of the double decomposition reaction. 
When water is the solvent this can be done conveniently by separating the 
product which appears as an insoluble oil. When any of the organic 
solvents cited above are used, the resulting inorganic salt is 
precipitated and can be separated by filtration, centrifugation, etc. 
The following illustrates the synthesis of tin (IV) 
di-n-propylphosphorodithioate: 
To a solution of 3.51 g (grams) (10 mmol) of SnCl.sub.4.5H.sub.2 O in about 
50 mL (milliters) of tetrahydrofuran (THF) was added dropwise a solution 
of 10.10 g (40 mmol) of potassium di-n-propylphosphorodithioate in about 
50 mL of THF. The solution immediately became bright yellow and potassium 
chloride precipitated. The mixture was warmed to 65.degree. C. for 30 
minutes, cooled to room temperature, and filtered to remove the potassium 
chloride. THF was removed from the filtrate with a rotary evaporator and 
the residue was treated with about 50 mL of n-hexane; this solution was 
again filtered to remove unconverted reactants and finally n-hexane was 
removed from the product with a rotary evaporator. Yield of product was 
7.15 g, which was 74% of the calculated theoretical yield. Elemental 
analyses on the product, calculated as C.sub.24 H.sub.56 O.sub.8 P.sub.4 
S.sub.8 Sn, were: calculated 29.66% C, 5.81% H, 12.75% P, and 12.21% Sn; 
found 29.00% C, 5.63% H, 12.2% P, and 11.7% Sn. 
EXAMPLE II 
Synthesis of Stannous Bis(di-n-propylphosphorodithioate) 
A solution of 25 g. (0.048 moles) of stannous octanoate (Catalyst T-9 from 
M & T Chemicals Inc., Rahway, N.J.) in about 25 mL of cyclohexane was 
treated dropwise, at about 25.degree. C., with 20.76 g. (0.097 moles) of 
(C.sub.3 H.sub.7 O).sub.2 PS.sub.2 H, with constant stirring. The solution 
became orange-brown immediately and was deep mahogany when addition was 
complete. After standing for three days the solvent was removed from the 
preparation with a rotary evaporator, leaving a viscous liquid product. 
Upon chemical analysis it was found to contain 16.3 weight percent tin. 
EXAMPLE III 
Two commercial fluid cracking catalysts comprising amorphous silica-alumina 
and rare earth cation-exchanged zeolite, were used in a commercial fluid 
catalytic cracker until they had attained equilibrium with respect to 
metals accumulation (catalyst was being removed from the process systems 
at a constant rate) and were characterized by the following properties: 
TABLE I 
______________________________________ 
CATALYST I 
______________________________________ 
Surface area, m.sup.2 /g (square meters per gram) 
74.3 
Pore Volume, mL/g (milliliters per gram) 
0.29 
Composition, wt. % 
Aluminum 21.7 
Silicon 24.6 
Sodium 0.39 
Cerium 0.40 
Carbon 0.06 
Nickel 0.38 
Vanadium 0.60 
Iron 0.90 
______________________________________ 
Catalyst I contained 21,200 ppm vanadium equivalents. 
TABLE II 
______________________________________ 
CATALYSTS II 
Surface area, m.sup.2 /g 
89.2 
Pore Volume, mL/g 0.30 
Composition, wt. % 
Aluminum 19.7 
Silicon 26.5 
Sodium 0.49 
Cerium 0.60 
Carbon 0.17 
Nickel 0.038 
Vanadium 0.11 
Iron 0.62 
______________________________________ 
Catalyst II contained about 2620 ppm vanadium equivalents. 
A topped crude oil from Borger, Tex. is characterized by the following 
properties: 
TABLE III 
______________________________________ 
Feed I 
______________________________________ 
API gravity at 60.degree. F. 
21.3 
Carbon residue, Conradson 
5.33 wt. % 
Elemental analysis 
Sulfur 1.9 wt. % 
Nitrogen 0.28 wt. % 
Sodium 0.5 ppm 
Nickel 5.24 ppm 
Vanadium 14.2 ppm 
Iron 7.4 ppm 
______________________________________ 
A gas oil from Sweeny, Tex. is characterized by the following properties: 
TABLE IV 
______________________________________ 
Feed II 
______________________________________ 
API gravity at 60.degree. F. 
25.8 
Carbon residue, Ramsbottom 
0.87 wt. % 
Elemental analysis 
Sulfur 0.40 wt. % 
Nitrogen 0.07 wt. % 
______________________________________ 
A gas oil from Kansas City is characterized by the following properties 
TABLE V 
______________________________________ 
Feed III 
______________________________________ 
API gravity at 60.degree. F. 
30.2 
Carbon residue, Ramsbottom 
0.23 wt. % 
Elemental analysis 
Sulfur 0.2 wt. % 
Nitrogen 0.08 wt. % 
Nickel 0.25 ppm 
Vanadium 9 ppm 
______________________________________ 
EXAMPLE IV 
Catalyst I was employed to crack Feed I in a laboratory-sized fluidized bed 
quartz reactor at 510.degree. C. and atmospheric pressure with about 0.5 
minute cracking periods and about 30 minutes intervening regeneration 
periods at about 649.degree. C. The runs were carried out at a number of 
different catalyst/oil ratios and the data presented in Table VI were from 
regression analysis curves calculated from the observed data points. In 
this and subsequent examples, treatment of experimental data by regression 
analysis is based on not less than five runs; generally the analysis 
utilized at least 10 runs. 
The data are presented to show the cracking behavior of metals contaminated 
fluid catalytic cracking catalyst at varying conversion levels. Conversion 
is increased by increasing the catalyst/oil ratio, for example, by 
reducing the oil feed rate. Note that as conversion increases, the 
selectivity of the cracking catalyst for gasoline production declines, 
even though the yield of gasoline increases. Coke and hydrogen production 
also increase at increasing levels of conversion. 
Catalyst I was also employed to crack Feed II at varying levels of 
conversion. Results from regression analysis of these runs are presented 
in Table VII. 
A comparison of the data set forth in Table VI to that set forth in Table 
VII shows that the activity of the cracking catalyst to crack Feed I is 
greater than its activity to crack Feed II. However, the trends shown by 
Table VII are in the same directions as those in Table VI. As conversion 
levels increase, the selectivity of the cracking catalyst to convert the 
feed to gasoline products decreases and the absolute yield of gasoline, 
coke and hydrogen all increase. 
EXAMPLE V 
Four samples of catalyst I were treated to contain varying concentrations 
of dibutyltin oxide. This was done by combining weighed portions of dry 
catalyst with weighed portions of dibutyltin oxide that had been ground to 
pass a 325 mesh sieve. These components were mixed by shaking, then were 
conditioned in the following manner. The catalyst was placed in a 
laboratory-sized confined fluid bed quartz reactor and heated from room 
temperatures (about 20.degree. C.) to about 482.degree. C. while fluidized 
with nitrogen, then treated from that temperature to about 650.degree. C. 
while fluidized with hydrogen. While maintained at 650.degree. C. the 
catalyst was fluidized for 5 minutes with nitrogen followed by 
fluidization for 15 minutes with air. The catalyst was then aged by being 
subjected to 10 cycles, each cycle consisting of the following treatment. 
The catalyst was cooled from 650.degree. C. for 30 seconds while 
fluidizing with air, then cooled to about 482.degree. C., fluidized with 
nitrogen for one minute, then heated to about 650.degree. C. during two 
minutes while fluidized with hydrogen, then maintained at about 
650.degree. C. for one minute while fluidized with nitrogen, then 
maintained at 650.degree. C. for 10 minutes while fluidized with air, and 
then cooled to about 482.degree. C. during about 0.5 minutes while 
fluidization with air continued. After 10 such cycles the catalyst was 
used in runs conducted as described in Example IV. The tin content of five 
catalysts together with results of runs made to crack Feed II at a 
catalyst/oil ratio of 7.7 are presented in Table VIII. 
Table IX presents results from these catalysts obtained at 64% conversion; 
these were obtained from regression analysis curves derived from a large 
number of runs with these catalysts. 
As is apparent from the Conversion column of Table VIII, impregnation of 
the cracking catalyst with dibutyltin oxide to any of the tin 
concentrations indicated decreased the cracking ability of the cracking 
catalyst. As shown by the Selectivity to Gasoline column of Table IX, 
impregnation of the cracking catalysts with dibutyltin oxide somewhat 
increased the selectivity of the cracking catalyst for gasoline 
production. In particular note that impregnation of the cracking catalyst 
to 0.1 wt. % Sn increased the selectivity of the cracking catalyst for 
gasoline production by only about 1% at constant conversion of 64 vol. %. 
The results are summarized in Tables VIII and IX. 
EXAMPLE VI 
Six samples of catalyst I were treated to contain varying concentrations of 
tributyl phosphine by impregnating weighed portions with a solution of 
tributyl phosphine in dry cyclohexane. After removal of solvent by 
evaporation, the catalysts were used in runs to crack Feed III. These runs 
were made in a fixed bed reactor at 482.degree. C. The catalyst/oil ratio 
was adjusted to obtain 75 volume percent conversion of the feed. 
The selectivity to gasoline, the coke content and the hydrogen production 
were measured. All results were compared relative to the results obtained 
with a catalyst containing no treating agent which were arbitrarily given 
a rating of 1.00. The selectivity to gasoline is defined as the volume of 
liquid products boiling below 400.degree. F. divided by the volume of oil 
converted times 100. The oil converted is the volume of feed minus the 
volume of recovered liquid boiling above 400.degree. F. Thus, for 
instance, if the selectivity to gasoline of the untreated catalyst was 50 
volume percent, the selectivity of a treated catalyst of 1.04 in the 
following table would refer to a selectivity of 52 volume percent of this 
treated catalyst. 
The coke content of the catalyst is measured by weighing the dry catalyst 
after the cracking process. The hydrogen quantity produced is determined 
in standard equipment analyzing the hydrogen content of the gaseous 
products leaving the reactor. 
The phosphorus content of these catalysts and the results of the runs are 
summarized in Table X. 
In particular, note that impregnation of the cracking catalyst to a level 
of 0.1 wt. % P increased the selectivity of the cracking catalyst for 
gasoline production by only about 2% at constant conversion of 75 vol. %. 
EXAMPLE VII 
A sample of catalyst I was treated with P.sub.2 S.sub.5 by combining a 
weighed quantity of the catalyst with a weighed portion of solid P.sub.2 
S.sub.5. These components were mixed by shaking. The resulting mixture was 
conditioned and aged as detailed in Example V, then used in a run to crack 
Feed I as described in Example IV. The phosphorus content of this catalyst 
together with results of runs made with it and with a control are 
presented in Table XI. 
As shown by the decreased catalyst/oil ratio, the addition of P.sub.2 
S.sub.5 increased the activity of the cracking catalyst for cracking the 
hydrocarbon feed. The process increased the selectivity of the cracking 
catalyst for gasoline production by about 3.9% at a conversion level of 
74%. 
EXAMPLE VIII 
A sample of Catalyst I was treated with P.sub.2 S.sub.5 to a phosphorus 
level of 0.1 wt. % P exactly as described in Example VII. The treated 
cracking catalyst, after conditioning and aging, is employed in fluid 
catalytic cracking of Feed II at about 950.degree. F. following the 
procedure described in Example IV. The results are shown in Table XII. 
The above results appear to somewhat contradict those shown by Table XI. In 
the runs set forth in Table XII, it appears that the incorporation of 
P.sub.2 S.sub.5 into the catalyst decreased slightly the activity of the 
cracking catalyst for cracking the hydrocarbon feed, and decreased the 
selectivity of the catalyst for gasoline production at about the same 
conversion level by about 7.0%. 
EXAMPLE IX 
A sample of Catalyst II was impregnated with a cyclohexane solution of 
(C.sub.4 H.sub.9).sub.2 Sn(SCH.sub.2 CO.sub.2 C.sub.8 H.sub.17).sub.2 
(Thermolite 31, commercially available from M & T Chemicals, Inc.) to a 
tin concentration of 0.011 wt. % and employed to crack feed III. After 
removal of solvent the catalyst preparation was conditioned and aged as 
described in Example V. The catalyst, together with an untreated control, 
was used in runs at several catalyst/oil ratios. These are defined and 
results of the runs are summarized in Table XIII. 
The impregnation of the cracking catalyst with Thermolite 31 to a tin level 
of 0.011 wt. % Sn decreased catalyst activity, increased catalyst 
selectivity for gasoline production, increased coke production and 
appeared to decrease hydrogen production at high conversion levels. At 70% 
conversion, the tin and sulfur treated cracking catalyst increased 
selectivity to gasoline by 4.5%. At 75% conversion, the improvement was 
2.9%. At 80% conversion, the improvement was 1.5%. Comparison of the 
results set forth in Table XIII to those of Table IX shows that the 
tin-sulfur treatment improved catalyst selectivity for gasoline production 
substantially better than treatment with tin alone. In fact, on a weight 
basis of tin added, it would appear that treatment of the catalyst with 
tin and sulfur in combination is at least 10 times more effective for 
improving catalyst selectivity for gasoline production than treatment with 
tin alone. Because a commercial cracking unit often has 200 tons or more 
of circulating catalyst, the greater efficacy of tin and sulfur for 
improving catalyst selectivity for gasoline production can represent a 
substantial economic savings. 
EXAMPLE X 
A sample of Catalyst I was impregnated with stannic di-n-propyl 
phosphorodithioate to a tin concentration of 0.1 wt. % Sn. The weight 
ratio of phosphorus to tin contacted with the cracking catalyst was about 
1:1. The weight ratio of sulfur to tin contacted with the cracking 
catalyst was about 2:1. The weight ratio of phosphorus to sulfur contacted 
with the cracking catalyst was about 1:2. 
The treated cracking catalyst after conditioning and aging as described in 
Example V was employed for the fluid catalytic cracking of Feed II at 
950.degree. F. following the procedure used in Example IV. The results are 
set forth in Table XIV. 
Treatment of the cracking catalyst with tin, phosphorus and sulfur slightly 
improved catalyst activity, decreased hydrogen and coke production, and 
increased catalyst selectivity for gasoline production at a slightly 
higher conversion level by about 11%. This is especially surprising in 
view of the data presented in Tables IX and XIII. Impregnation of the same 
cracking catalyst of this example with the tin compound of Example V to a 
level of 0.1 wt. % Sn improved catalyst selectivity for cracking the same 
feedstock to gasoline by only about 1%. Impregnation of the same cracking 
catalyst of this example with P.sub.2 S.sub.5 of Example VIII to a level 
of 0.1 wt. % P decreased catalyst selectivity for cracking the same 
feedstock gasoline by about 7.0% at a conversion level of 64%. It is 
remarkable that the combined Sn-P-S treatment of this example provided an 
improvement in catalyst selectivity for gasoline production of about 11%. 
EXAMPLE XI 
In Example II of U.S. Pat. No. 4,101,417, a sample of zeolite-containing 
cracking catalyst having 10,350 vanadium equivalents deposited thereon was 
impregnated with hexabutyltin to a level of 0.61 wt. % Sn and another 
sample was impregnated with tin chloride to a tin concentration of 0.61 
wt. % Sn and thereafter contaminated with 10,350 vanadium equivalents. 
Because of the high surface area, it does not appear that the catalyst to 
be treated in that patent was an equilibrium cracking catalyst. The 
hexabutyltin treatment increased conversion by about 7.3% and selectivity 
to gasoline by about 3.8% at the higher conversion level. The tin chloride 
treatment increased conversion by about 13.7% and selectivity to gasoline 
by about 4.1% at the higher conversion level. The weight ratio of tin to 
vanadium equivalents on the cracking catalyst was about 0.6:1. In Example 
X of this application, the weight ratio of tin to vanadium equivalents on 
the cracking catalyst was about 0.047:1. Regarding the apparent 
discrepancy between Example V of the present application and Example II of 
U.S. Pat. No. 4,101,417, it should be noted that the catalyst employed in 
Example V was an equilibrium cracking catalyst with metallic deposits 
accumulated thereon during commercial employment of the cracking catalyst, 
whereas fresh metals were present on the cracking catalyst employed in the 
examples of U.S. Pat. No. 4,101,417. It is believed that the 
susceptibility of metals deposited on the cracking catalyst during the 
cracking of metals laden feedstock to becoming passivated by treating 
agents is different from the susceptibility of metals freshly deposited by 
other means. The discovery that treatment of cracking catalysts containing 
equilibrium deposits of metals with tin and at least one of phosphorus and 
sulfur provided dramatically improved catalyst selectivity for gasoline 
production is especially surprising in view of the rather poor performance 
of tin alone on the same cracking catalyst. 
EXAMPLE XII 
A catalyst containing 0.10 wt. % tin was prepared by impregnating 40 g. of 
catalyst I with 0.325 g. of tin(IV) dipropyl phosphorodithioate in 40 mL 
of cyclohexane. The solvent was removed by evaporation and the dry 
catalyst was placed in a vertical quartz tube reactor in a tube furnace. 
While being fluidized with nitrogen the catalyst was heated to 482.degree. 
C. Nitrogen was replaced with hydrogen and the temperature was raised to 
649.degree. C. Nitrogen replaced hydrogen and the catalyst was fluidized 
for 5 minutes to purge the reactor after which the catalyst was fluidized 
with air for 15 minutes at that temperature. 
A catalyst containing 0.10 wt. % antimony and 0.01 wt. % tin was prepared 
by impregnating 40 g. of Catalyst I with 0.363 g. of antimony (III) 
dipropylphosphorodithioate and 0.033 g. of the tin compound in 40 ml of 
cyclohexane. The solvent was removed by evaporation and the catalyst 
conditioned as described above. 
A catalyst containing 0.10 wt. % of antimony was prepared as described 
immediately above except that the addition of tin was omitted. 
A sample of catalyst I and the three above described modified catalysts 
were employed to crack feedstock II at 510.degree. C. in fluidized bed 
reactors. Atmospheric pressure was used with 0.5 minute cracking periods 
and intervening regeneration periods at 649.degree. C. 
Before being tested, each of the catalysts was aged by fluidization with 
nitrogen at about 482.degree. C. for about one minute, then heated to 
510.degree. C. while fluidized with hydrogen for 2 minutes, then fluidized 
with nitrogen at 510.degree. C. for 1 minute, then fluidized with air at 
about 649.degree. C. for ten minutes, then cooled to about 482.degree. C. 
under air fluidization over about 0.5 minute. After 10 such cycles, the 
catalysts were cooled to room temperature while being fluidized with 
nitrogen. 
Results of the cracking runs are summarized in Table XVI. 
As is apparent from the data presented in Table XVI, treatment of the 
cracking catalyst with tin and antimony di-n-propylphosphorodithioate to 
provide in the catalyst a tin:antimony weight ratio of about 1:10 
synergistically improved at least the cracking activity of the cracking 
catalyst. 
A catalyst containing 0.10 wt. % tin was prepared by dry blending 
dibutyltin oxide (ground until it passed through a 325 mesh screen) with a 
portion of Catalyst I. The blend was wetted with cyclohexane and the 
resulting mixture taken to apparent dryness by heating on a hot plate. The 
catalyst was preconditioned and aged similarly to the method described 
above and employed to fluid catalytically crack feedstock II as described 
above. A series of runs were made at varying catalyst/oil ratios and the 
results shown below in Table XVI are read from a smooth curve fit of the 
data points. 
A catalyst containing 0.10 wt. % antimony and 0.01 wt. % tin was prepared 
by dry blending dibutyltin tin oxide with a portion of catalyst I as 
described above followed by impregnation with a mineral oil solution of 
antimony (III) dipropylphosphorodithioate dissolved in cyclohexane in 
place of the wetting step with cyclohexane as described above. The 
resulting catalyst was then conditioned and aged as described above and 
employed to fluid catalytically crack feedstock II as described above. A 
series of runs were made at varying catalyst/oil ratios and the results 
shown below in Table XVI are read from a smooth curve fit of the data 
points. 
A catalyst containing 0.10 wt. % antimony was prepared as described above 
except that dibutyltin oxide was not first mixed with the catalyst. A 
series of runs were made at varying catalyst/oil ratios and the results 
shown below in Table XVI are read from a smooth curve fit of the data 
points. 
Comparison of the runs in Tables XV and XVI employing antimony and tin in 
combination yields no clue as to the surprising effectiveness of the 
particular tin compound tested by itself in Table XV. 
TABLE VI 
______________________________________ 
Con- 
ver- Selectivity 
sion to Yields Catalyst/ 
Vol. Gasoline Gasoline Coke H.sub.2 (SCF/ 
Oil 
% (% vol) (vol. %) (wt. %) 
bbl conv.) 
Ratio 
______________________________________ 
70 77.5 54.2 13.8 797 5.3 
71 77.2 54.8 14.1 805 5.7 
72 77.0 55.4 14.4 817 6.0 
73 76.8 56.0 14.6 825 6.3 
74 76.5 56.6 14.9 836 6.6 
75 76.2 57.1 15.2 848 6.9 
76 75.9 57.6 15.4 857 7.2 
77 75.5 58.1 15.7 867 7.5 
78 75.0 58.5 15.9 876 7.8 
79 74.0 58.9 16.3 888 8.3 
80 73.8 59.0 16.6 898 8.7 
______________________________________ 
TABLE VII 
______________________________________ 
Con- 
ver- Selectivity 
sion to Yields Catalyst/ 
Vol. Gasoline Gasoline Coke H.sub.2 (SCF/ 
Oil 
% (% vol) (vol. %) (wt. %) 
bbl conv.) 
Ratio 
______________________________________ 
60 86.5 51.9 5.8 621 5.7 
61 85.9 52.4 6.1 624 6.2 
62 85.2 52.8 6.6 627 6.6 
63 84.4 53.2 7.0 629 7.1 
64 83.8 53.6 7.6 630 7.5 
65 82.9 53.9 8.0 632 8.0 
66 82.3 54.3 8.4 634 8.4 
67 81.6 54.7 8.9 635 8.9 
68 81.1 55.1 9.3 636 9.3 
69 80.3 55.4 9.7 638 9.8 
70 79.7 55.8 10.3 639 10.3 
______________________________________ 
TABLE VIII 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive.sup.1 
Ratio (vol. %) 
Gasoline (vol. %) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None 7.7 64 83.3 53.3 640 8.0 
2 0.01 
wt. % Sn 
7.7 62 85.0 52.7 638 7.8 
3 0.1 
wt. % Sn 
7.7 61.4 88.1 54.1 578 7.2 
4 0.5 
wt. % Sn 
7.7 62 88.1 54.6 480 6.6 
5 1.0 
wt. % Sn 
7.7 60.1 89.7 53.9 530 6.6 
__________________________________________________________________________ 
.sup.1 dibutyltin oxide; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 25.8.degree. API 
TABLE IX 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive.sup.1 
Ratio (vol. %) 
Gasoline (vol. %) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None 7.8 64 83.1 53.2 640 8.2 
2 0.01 
wt. % Sn 
8.8 64 83.3 53.3 640 8.2 
3 0.1 
wt. % Sn 
8.8 64 83.9 53.7 615 7.8 
4 0.5 
wt. % Sn 
8.9 64 84.7 54.2 560 7.3 
5 1.0 
wt. % Sn 
8.9 64 85.2 54.5 500 7.0 
__________________________________________________________________________ 
.sup.1 dibutyltin oxide; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 25.8.degree. API 
TABLE X 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive 
Ratio (vol. %) 
Gasoline (vol.%) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None -- 1.00 -- 1.00 1.00 
2 0.1 wt.% P 
-- 75 1.02 -- 0.91 1.00 
3 0.2 wt.% P 
-- 75 1.04 -- 0.86 0.98 
4 0.3 wt.% P 
-- 75 1.05 -- 0.82 0.97 
5 0.4 wt.% P 
-- 75 1.04 -- 0.79 0.97 
6 0.5 wt.% P 
-- 75 1.04 -- 0.78 0.96 
7 1.0 wt.% P 
-- 75 1.01 -- 0.74 0.92 
__________________________________________________________________________ 
.sup.1 tributyl phosphine; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 30.2.degree. API 
TABLE XI 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive.sup.1 
Ratio (vol. %) 
Gasoline (vol.%) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None 6.5 74 67.3 49.8 840 16.4 
2 0.085 wt. % P 
6.15 74 69.9 51.7 740 14.3 
__________________________________________________________________________ 
.sup.1 P.sub.2 S.sub.5 ; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 21.3.degree. API 
TABLE XII 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive.sup.1 
Ratio (vol. %) 
Gasoline (vol.%) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None 7.8 64 83.1 53.2 640 8.2 
2 0.1 wt.% P 
7.8 62.1 76.7 47.7 432 7.9 
3 0.1 wt.% P 
7.6 65.0 77.9 50.6 453 7.8 
4 average 0.1 P 
7.7 63.55 77.3 49.15 442.5 7.85 
__________________________________________________________________________ 
.sup.1 P.sub.2 S.sub.5 ; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 25.8.degree. API 
TABLE XIII 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive.sup.1 
Ratio (vol. %) 
Gasoline (vol.%) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None 4.6 70 84.6 59.2 165 6.4 
2 0.011 wt. % Sn 
5.4 70 88.4 61.9 171 7.9 
3 None 5.8 75 84.0 63.0 187 7.5 
4 0.011 wt. % Sn 
6.4 75 86.4 64.8 180 8.9 
5 None 7.2 80 82.6 66.1 209 8.7 
6 0.011 wt. % Sn 
7.4 80 83.8 67.0 188 9.9 
__________________________________________________________________________ 
.sup.1 (C.sub.4 H.sub.9).sub.2 Sn(SCH.sub.2 CO.sub.2 C.sub.8 
H.sub.17).sub.2 ; 
.sup.2 2,620 vanadium equivalents; 
.sup.3 30.2.degree. API 
TABLE XIV 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive.sup.1 
Ratio (vol. %) 
Gasoline (vol.%) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None 7.7 64.5 80.2 51.7 635 8.7 
2 0.1 wt. % Sn 
7.7 64.8 89.4 57.9 488 7.4 
3 0.1 wt. % Sn 
7.7 64.5 88.7 57.2 515 7.9 
4 average 0.1 wt.% Sn 
7.7 64.65 
89.0 57.55 501.5 7.65 
__________________________________________________________________________ 
.sup.1 stannic din-propyl phosphorodithioate; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 25.8.degree. API. 
TABLE XV 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
conversion 
Selectivity to 
Yields 
No. 
Additive.sup.1 
Ratio (vol. %) 
Gasoline (vol.%) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
coke (wt. 
__________________________________________________________________________ 
%) 
1 None 7.7 64.5 80.2 51.7 635 8.7 
2 0.1 wt. % Sn 
7.7 64.7 89.0 57.6 502 7.7 
3 0.01 Sn + 0.1 Sb 
7.7 70.9 87.6 62.1 375 6.9 
4 0.1 wt. % Sb 
7.7 64.8 84.9 55.0 410 6.0 
__________________________________________________________________________ 
.sup.1 stannic din-propylphosphorodithioate antimony 
din-phosphorodithioate; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 25.8.degree. API 
TABLE XVI 
__________________________________________________________________________ 
Run Cat.sup.2 /Oil.sup.3 
Conversion 
Selectivity to 
Yields 
No. 
Additive Ratio (vol. %) 
Gasoline (vol.%) 
Gasoline (vol. %) 
H.sub.2 (SCF/bbl 
Coke (wt. 
__________________________________________________________________________ 
%) 
1 None 7.7 64 83.4 53.3 640 8.0 
2 0.1 wt. % Sn 
7.7 61.4 88.6 54.1 578 7.2 
3 0.01 Sn + 0.1 Sb 
7.7 69.8 87.6 61.1 385 6.6 
4 0.1 wt. % Sb 
7.7 64.8 85.0 55.0 410 6.0 
__________________________________________________________________________ 
.sup.1 dibutyltin oxide and/or antimony din-propylphosphorodithioate; 
.sup.2 21,200 vanadium equivalents; 
.sup.3 25.8.degree. API