CA1072070A - Passivating metals on cracking catalysts with antimony compounds - Google Patents

Abstract

PASSIVATING METALS ON CRACKING CATALYSTS WITH ANTIMONY CATALYSTS
Abstract of the Disclosure Metals on a cracking catalyst are passivated by contacting the catalyst with at least one compound selected from the group of compounds having the general formula

Description

7Z~7~ :

This invention relates to the art of catalytic cracking of hydrocarbons.
More specifically, the invention relates to the regeneration of used cracking catalysts. Particularly, the invention rela~es to the passi-vation of metals on cracking ca~alysts.
Background of the InvPnt on Eydrocarbon feedstock containing higher molecular weight hydro-carbons is cracked by contacting it under elevated temperatures with a cracking catalyst whereby light distillates are produced. However, the 10 cracking catalyst gradually deteriorates during this process. One source for this deterioration is the deposition of metals, such as nickel, vanadium -; . ~:, , and iron, on the catalyst which increase the production of hydrogen, dry gas and coke. At the same time the converslon of the hydrocarbons into gasoline is reduced.
The Invention It is one object o~ this invention to provide a new catalytic cracking process.
Another object of this invention is to provide a process for regeneration of the used cracking catalyst.
A further object of this invention is to provide a process for the passivation of metals deposited on the cracking catalyst.
Further objects, embodiments, advantages and features of this inven-tion will be apparent from the following detaiIed description of the invention -~
and the appended claims.
In accordance with this invention, I have now found that contami-nating metals deposited on cracking catalysts and deactivating said cracking catalysts can be passivated by contacting said cracking catalyst with at least one antimony compound having the general formula -~
'' ' -

- 2 -, ~

~7Z~7~ ~

.
. _ . . .

0~'' ~
~P - S Sb R~ i3 wherein the R groups which can be the same or dlfferent are hydrocarbyl radicals each containing from 1 to about 18 carbon atoms, the overall number of carbon atoms per molac~le being 6 to about 90 and depositing said antimony compound on said catalyst su~h as to passivate said contaminating ~;~
metals. The an~imony compounds are known ~hemical compounds. ~nong these anti~ony compounds the preferred ones are those wherein the R groups are alkyl radicals having 2 to about 10 carbon atoms per radical, the n-propyl and the octyl radicals being presently preferred, substituted or unsubstituted C5 or C6 cycloalkyl radicals and substituted or unsubsti~uted phenyl radicals.
Examples for these radicals R are ethyl, n-propyl, i~opropyl, n-, iso-~ sec-and tert-butyl, amyl, n-hexyl, isohexyl, 2-ethylhexyl, n-heptyl, n-octyl, iso-octyl, tert-octyl, dodecyl, octyldecyl, cyclopentyl, methyl cyclopentyl, cyclohexyl, methylcyclohexyl, ethyl cyclohexyl, phenyl9 tolyl, cresyl, ethyl phenyl, butylphenyl, amylphenyl, octylphenyl, vinylphenyl and the like.
Since the antimony compound useful in accordance with this invention for passivating the metals on the cracking catalyst can also be a mixture of -different antimony compounds of the general formula given above, the treating agent can also be defined by the range of weight percentage of antimony. The preferred anti~ony co~position thus cal~ be defined ~o be within the range of aoout 6 to about 21 weight percent antimony.
The phosphorodithioate compounds can be prepared by reacting an alcohol, such as phenol, with phosphorus pentasulfide to produce the ~ `
dihydrocarbylphosphorodithioic acid. To produce the metal salts, the acid can be neutralized with antimony trioxide and the antimony derivatives are recovered from the mi~ture. Alternately, the dihydrocarbylphosphorodithioic acid can be reacted with ammonia to form the ammoni~lm salt whieh is reacted with antimony trichloride to form the antimony salt. The antimony compounds `

- 3 -`:
~q~O .

are then recovered from the reaction mixtures.
The quantity of the antimony compound employed in accordance with this invention can be varied in reasonable ranges. The range for the quan-tity of the antimony compound employed is related to the quantity of cracking ~~
catalyst to be treated. This range can vary considerably. It is, however, presently preferred to use the antimony compound in a quantity of less than about 1.5 weight percent based on the weight of the cracking catalyst, and ;
generally in the range from about 0.1 to about 1.3 wt %.
The cracking catalyst can be contacted wi~h the antimony compound ~ ~
in various ways. One way is to impregnate the cracking catalyst with a solu- -tlon of the antimony compound in a solvent such as cyclohexane. In another :
embodiment the antimony compound is metered ~o the feed oil of the catalytic ~ `-~ .
cracker upstream of the feed pump. This procedure effects thorough dilution and mixing of the feed oll with the antimony compound and avoids laydowns of -~
this antimony compound on, e.g., the heat exchanger walls.
The antimony compound, if added to the hydrocarbon feedstock, is added in a quantity in the range of about 0.1 to 15,000 ppm of feedstock ~;
although higher levels can be employed for rapid deposition. The quantity of antimony compounds actually employed depends upon the amount of antlmony -~
compound desired to be deposited on the cracking catalyst and the rate of catalyst withdrawal and addition. Once the desired level of the antimony ' compound on the cracking catalyst has been reached, only a small quantity of the antimony compound is continued to be metered to the feedstock so that the ~ ~;
desired level of this compound on the catalyst a~ equilibrium conditions is maintained.
In accordance with a further aspect of this invention, I have dis-covered that a cracking process wherein a hydrocarbon feedstock is introduced into a cracking zone and contacted with cracking catalyst under cracking conditions, wherein the cracked feedstock is removed from said cracking zone for further processing, wherein sald cracking catalyst is regenerated by

- 4 -~072~
.:
contacting said cracking catalyst with an antimony compound for passivating metals deposited on said cracking catalyst and by heating said cracking catalyst having deposited thereon said antimony compound in the presence of free oxygen-containing gas can be improved in its efficiency by using as an antimony compound a compound having the general formula R S
- S Sb ~O i3 wherein the R groups which can be the same or different are hydrocarbyl radicals containing from 1 to about 18 carbon atoms per radical, the total ~ ~ ;
number of carbon atoms per antimony compound molecule being from 6 to about ~ ~
90. , ~:
In accordance with one embodiment of this cracking process, the cracking catalyst ls circulated from the cracking zone to the regeneration zone and back and the antimony compound is metered into the hydrocarbon feedstock upstream of a feed pump feeding the feedstock into the cracking ~one.
After feeding a sufficient quantity of antimony compound to the feedstock so -~
that the desired level of an~imony compound on the cracking catalyst is ~ ;~
reached, the quantity of antimony compound metered into the feedstock is controlled such as to maintain the desired level of antimony compound on the catalyst. Thus, constant cracking and regeneration conditions can be maintained and the efficiency of the cracking process can be i~proved.
The feedstocks used for the cracking process are conventional hydrocarbon feedstocks, namely, petroleum, fuel oil, shale oil, gas oil, topped crudes, etc. The cracking step of the catalytic cracking process is carried out at elevated temperatures o~ about 800 to about 1200F and at pressures in the range from atmospheric pressure up to several hundred atmospheres.
The catalyst used for the cracking step is a conventional cracking catalyst. Partlcularly suitable are active clay catalysts having deposited ~ -7Z070 ~

, . ~
thereon small quantities of rare earth metals, such as cerium and lanthanum.
The invention will be more fully understood from the following examples which constitute preferred embodiments of this invention which are, ` ;
however, not intended to limit the scope ~hereof. ;
~xample I ~ ;
A sample of used ac~ive clay catalyst containing deposited con-taminating metals were dried in a fluid bed at 900F. The catalyst was the commercially available F-1000 catalyst o~ the Filtrol Corporation which had , .
been used in a commercial cracking unit. This unwsed catalyst as received from the manufacturer contained about 0.4 weight percent of cerium and about 1.4 weight percent of lanthanum calculated as the metal as well as smaller amounts of other metal compounds. The weight percentages calculated as weight percent metal of these other metal components were as follows: 0.01 weight percent nickel, 0.03 weight percent vanadium, 0.36 weight percent iro~, 0.16 weight percent calcium, 0.27 weight percent sodium, 0.25 weight percent potassium and less than 0.01 weight percent lithium. The used ~`
catalyst, in contrast, calculated on the same basis as before contained 0.38 -~
weight percent nickel, 0.60 weight percent vanadium, 0.90 weight percent iron~ 0.28 weight percent calcium, 0.41 weight percent sodium, 0.27 weight percent potassiu~ and less than 0.01 weight percent lithium. The metals which were passivated by the practice of this invention are nickel, vanadium and iron. The unused catalysts had a pore volume of about 0.4 cc/g and a surface area of about 200 square meters/gram. The used catalyst had about the same pore volume and a surface area of about 72 square meters per gram.
The dried catalyst was divided into ten portions. In the first series of runs, five of these portions were used. With the e~ception of ~ ~
one portion which serves as a reference, all of the other our portions -were impregnated at ambient temperature with solutions of an antimony 0,0-dlhydrocarbylphosphorodithioate in dry cyclohexane in varying concentrations.

The anti~ony compound was used in solution in a neutral hydrocarbon oil;
TrQ cl~rnc.r k . ~:
- 6 - ;

:

~7~ 7~

lnQrk said solution commercially available under the trade ~e Vanlube 622. -This solution contained 10.9 weight percent antimony, 9.05 weight percent phosphorus, 19.4 weight percent sulfur and less than 100 ppm halogens. This cor~esponds to an antimony compound of the general formula cited above wherein ~
the hydrocarbyl groups are substantially propyl radicals. After drying the ~;
impregnated catalyst under a heat lamp and then heatlng the catalyst to 900~F
in a bed fluidized with nitrogen, the impregnated samples contained the quantities of antimony compound shown in ~he following table. The catalyst samples were all preaged by processing them through ten cracking-regeneration cycles ln a laboratory-size confined fluid bed reactor system in which the -catalyst was fluidized with nitrogen, the feed being a topped crude oil feed ;
from Borger, Texas. One cycle normally consisted of nominal 30 second oil feed time during cracking after which the hydrocarbons were stripped from the system with nitrogen for about 3 to 5 minutes. The reactor was then removed from the sand bath heater and purged with nitrogen as it cooled to room temperature in about 10 minutes. The reactor and its contents were then weighed to determine the weig~t of any cok~ deposited on the catalyst during the ru~. The reactor was then replaced in the sand bath, and while `
it was heated to regeneration temperature, air was passed through it. The overall regeneration time was about 60 minutes. The reactor was then cooled to reaction temperature and purged with nitrogen. Then another cracking-regeneration cycle was started.
Each of these preaged catalyst portions was then evaluated in the fluid bed reactor using the topped crude oil from Borger, Texas as a feed-stock at a reactor temperature of about 950F for 30 seconds. The catalyst was regenerated at 1200F in the manner described before in connection with the preaging. The crude oil used had an API gravity rating at 60F of 21.4, a pour point of 63F and a viscosity of 32.1 SUS at 210F.
The clay catalyst impregnated with the antimony compound had a pore volume of 0.29 cc/gram and a surface area of 74.3 square meters/gram.

,~;

72~7(~ ~:
, . ` : , The catalyst contained metal oxides in a quantity calculated as metal of 0.38 we~ght percent nickel, 0.90 weight percent iron and 0.60 weight percent vanadium. ~;

The catalyst to oil weight ratio in these five runs was adjusted ~o result in a conversion of 70 volume percent. The resul~s of the cracking ;i operation with the catalyst portions containing ~he different quantities of antimony compounds are shown in the following Table I:
TABLE I `
::, YIELDS
Sb Added, (1) Catalyst Coke, SCF H2 Gasoline, Wt. % Oil we. ~ of ~eed Bbl. Conv. Vol._% of Feed 0 5.2 13.0 700 56.0 0.1 5.7 12.2 ~80 56.0 0.25 6.2 11.6 355 56.7 0.5 6.5 11.4 310 58.7 ~ -~
1.0 6.7 1~.8 300 60.3 (1) The weight percentage is based on the weigh~ of the cracking catalyst. i The results shown in the table indicate that the production of hydrogen and ~ ~;
coke is decreased and the yield of gasoline is increased as the concentra-20 tion of the antimony compound is increased. `
With the second series of five portions of catalyst, the impreg-nation, pretreatment, aging and processing as described above was exactly repeated. For this series, however, the catalyst to oil ratio was adjusted in the actual tast runs so that the conversion rate was 75 volu~e percent for ;
all the catalyst portions. The results of this series of runs is shown in the following Table I~:

i ~''`
' ~Z~P7(~

TABL~ II
75% Conversion YI~LDS ;~
Sb Added, (1) Catalyst Coke, SCF H2 Gasoline _Wt. % _ Oil Wt. % of Feed Bbl. Conv. Vol. % of Feed ~;

0 7.~ 16.4 800 54.8 0.1 7.3 13.9 500 57.0 .25 7.2 13.2 ~00 5g.3 .
0.5 7.2 12.7 340 61.6 1.0 7.5 11.6 315 63.0 (1) The weight percentage is based on the weight of the cracking catalyst.
The results shown in this table again indicate the reduction ln hydrogen and coke production with increased antimony compound concentration and the increase in the gasoline production. A comparison with the results shown in Table I indicates that the catalyst activity is somewhat lower at 75 volume percent than at 70 volume percent oE conversion. However, the -same beneficial results as far as the yields are concerned are achieved. ~ ;
Exam~le II
To compare the antimony O,O-dialkylphosphorodithioate compound used in accordance with this invention with known additives, 18 portions of used catalyst were treated, impregnated and preaged as described in Example `~
I. Six of these portions were impregnated wi~h varying quantities of the antimony O,O-diaIkylphosphGrodithioate c~mpound used in Example I. Six portions of the catalyst were impregnated with triphenyl antimony. The last six portions of the catalyst finally were impregnated with tributylphosphine.
All the additives were used as solutions in dry cyclohexane. The quantities of the additives were adjusted such that the weight percentage of antimony for the irs~ two series and the we~ght percentage of phosphorus for the third series of portions was as indicated in the following Table III. With these catalyst samples, Kansas City gas oil was cracked having an API gravity of 30.2 at 60F, a pour point of 100F and a viscosity of 39 SUS at 210F. The cracking was carried out in a laboratory size fixed bed reactor system at _ g ~

~ 7Z~7~ ~

900F. The oil to catalyst ratio was adjusted to a 75 volume percent con~
version rate.
The selectivity to gasoline, the coke content and the hydrogen production were measured. All re~ul~s were compared relative to the results obtained with a catalyst containing no treating agent which were arbitrarily given a rati~g of l.00. The selectivity to gasoline is defined as the volume of liquid products boiling below 400F divided by the volume of oil converted times 100. The oil converted is the volume of feed minus ~he volume of recovered liquid boiling above 400F. 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 selec-tivity 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 results of these various runs are shown in the following Table III:

:
~ 2~70 :~ ~

.,:` ., ~ ~ ~ o~ ~ ~ ~ .. . .
~, ,.. ..
O O O O O O J~ ~ ~ '' i . . `
~ ,d S-l ~
Fq ~ ~ t o ~ ",,, ` .
--~ ~ I~ ~ ~ ~ U) ~ ~ $ ` ' ` ' P~- o ~ d ~ ;
,~ C~ o~
U~
. o~ ~ o oo ~9 ~ r~ /~1 ,. ..
- S~

o o~ 1~ 1~ ~ ~I a~
c~ ..... ~ h O O
. ,~o a~
d ~ -O N 1~ ~ ~1 0 0 ~j d . o~ Co Co CO oo ~ ~ ~ , . ~ 000000 ~ g .~ 4~
H i u) C~
~ ~0 ~
~1 ~, . .. o oo o o o ~ '~ `
: ~
~ ~
I C~ "
" I ~3 : ~ P

P 'I O O O O O ~ ~
~rl O O O O O O O ~
~$o : ` 0~0^)~
~ ooooo~1 ~:4rl~rl i~:`'I
C) ,1 00 ~0 ~3~ ~ o ~ O ~ S~
o o o o o ~
~ 01 . ,.~ . . .
E~ . , ` '' ., .

~1 , ' , ~`,:' 972~7~0 ~ ~

From the results of this ~able, it can be seen that the treating agent of the present invention provides the best overall results of the tested additives. The high selectivity for the formation of gasoline and the lowest amount of hydrogen produced is achieved by ~he additive of this invention whereas the coke formation is intermediate between the coke forma~
tions of the other two additives.
Example III .
The following example was carried out in order to determine whether a mixture of the known treating agents triphenyl antimony and tri-n-butyl phosphine would give results superior to each one of tha individual treating -~
agents alone. Therefore, triphenyl antim~ny and tri-n-butyl phosphine were l -dissolved in dry cyclohexane and the mixture was used to impregnate dry used cracking catalysts of the type and in the manner described in Example I. The catalyst samples preaged as described using ten cracking-regeneration cycles with the topped crude oil feed from Borger, Texas. Each treated catalyst was then used to crack Kansas City gas oil at 900F and an oil feed ~ime of about 30 seconds as described. The ratio of catalyst to oil was varied to vary the conversion. Three catalyst samples were prepared, the first of `~
which contained 0.25 weight percant phosphorus and 0.75 weight percent antimony, the second c-ontained 0.5 weight percent of phosphorus and 0.5 weight percent of antimony and the third contained 0.75 weigh-t percent of phosphorus and 0.25 weight percent of antimony.
At 75 volume percent conversion rate, the hydrogen produced with the coimpregnated catalysts was 25 to 40 percen~ less than the hydrogen produced with the untreated catalyst. The quantity of hydrogen produced was essentially equal to the amount of hydrogen produced with a catalyst ~reated with an equal amount of antimony derived from the trip`henylantimony alone, ~ -i.e. without any trl-n-butyl phosphina. Also the quantity of coke produced and the selectivity to gasoline were the same in those runs containing the same quantity of antimony regardless of whether or not any tri-n-butyl .:~

phosphine was present.
The~e results -lndicate that the treating of the catalyst with the ~ixture of antimony compound and the phosphorus compound did not improve the operation over a process using a catalyst treated with triphenyl-antimony alone. E~amples I and II, on the other hand, show that the treatment of catalyst with the antimony compounds of the instant invention provides con-siderably better cracking results than were obtained with a catalyst treated only with the triphenyl antimony compound.
Example IV -A cracking catalyst that is commercially available under the trade-mark Filtrol 900 was employed in this example. This catalyst was a clay-based catalyst. The used catalyst contained about 0.6 weight percent cerium, 0.4 weight percent lanthanum and 0.33 weight percent nickel7 0.56 weight percent vanadium and 0.89 weight percent iron. The catalyst was used in a pilot plant size transfer line cracking reactor to crack Kansas City gas oil.
To this gas oil feed the same antimony compound as employed in Example I was added in a quantity of about 10.8 weight percent based on the gas oil feed for a time sufficiently long to deposit 0.37 or, respectively, 0.67 weight percent of antimony on the catalys~. Thus two samples of treated catalyst were obtained, one contaîning 0.37 weight percent of antimony and the second containing 0.67 weight percent of antimony. The thus-treated catalysts were recovered from the reactor and evaluated in a laboratory siVe fixed bed reactor at 900F for cracking Kansas City gas oil for about 30 seconds and in a fluid bed reactor for cracking Borger topped crude oil at 950~F for about 30 seconds. The aging and the test runs were carried out in the same was as described in connection with Example I. Ths surface area of the untreated catalyst was 67.4 square meters/gram and the pore volume of the catalys~ was :: .
0.31 cc/gram. The treated catalyst containing 0.67 weight percent of antimony had a surface area of 57.5 square meters/gram and a pore volume of 0.26 cc/gram.
The results obtained with the catalyst samples are contained in the following -~Z~70 tables. `

Table IV

Catalyst Yields Wt. % (1) Catalyst/Oil Conversion Gasoline, Coke, SCF H2/Bbl.
~ntimony Ratio Vol. % Vol. % W~. % Conv. `~

0 (control~ 6.3 73.4 52.4 8.0 477 0.37 7.5 73.4 57.5 6.9 269 0.67 9.4 73.4 5104 7.3 330 (1) The weight percentage is based on the weight of the cracking catalyst.

Table V

Catalyst Wt. %Catalyst/Oil Conversion Gasoline, Coke, SCF H2/~bl. -~
Antimony _ Ratio _ _ Vol. % Vol. % Wt. % Conv.

O (con~rol) 8.2 72.5 68.0 13.8 685 0.678.~ 69.9 63.3 11.0 541 -From the results shown, it can be seen that at the same conversion rate the coke production and the hydrogen production were reduced as compared to ~ ;

the untreated catalyst by the additive of this invention. The gasoline con-~.~., -:
version was comparable in the case of the higher concentration of antimony treating agent. In the case where the catal~st/oil ratio was kept constant, the coke production and the hydrogen production were reduced by the antimony compound. The lower activity of the catalyst with 0.67 weigh~ percent antimony is supposed to reside in the fact that this catalyst had a lower surface area and a smaller pore volume than the control catalyst. `'!'~
Example V

This calculated example is given to show the operation of the invention in plant scale. In a cracking unit containing 200 tons of active clay ca~alyst, 24,300 bbl/day of oil having an API gravity of 20.8 are cracked. In order to build up a level of 0.5 weight percent (based on catalyst) of antimony on the catalyst the antimony compound has to be added in a quantity of 20 ppm of antimony to the feedstock for 17 days or of 30 ppm of antimony to the feedstock for 10 days. In order to keep the ant$mony level at 0.5 weight percent, the rate of addition has to be 10 ppm of antimony in case 8 tons of catalyst per day are withdrawn from the reactor ''; :

~ l~q~,~7~
and replaced by untreated catalyst. In case only 6 tons of catalyst per day are replaced, this addition would be sufficient to keep the antimony level of the system at 0.65 weight percent. In absolute figures this means : -that 2175 pounds oflVanlube 622/lper day have to be added to the feedstock for lO days ~1450 pounds respectively for 17 days) and that 725 pounds of Vanlube per day have to be added to the feedstock ~o maintain the desired level of antimony compound on the catalyst at 0.5 weight percent.
Reasonable variations and modifications which will be apparent to those skilled in the art can be made in thls invention without departing 10 fro~ the splrit and scope the-eof.

: '~
, .

',' '''`
.. : .

- 15 - ;

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for passivating metal on an active clay cracking catalyst which has become contaminated with at least one metal of the group consisting of nickel, vanadium, and iron which comprises contacting said catalyst with at least one antimony compound having the formula wherein the R groups which can be the same or different are hydrocarbyl radicals having from 1 to about 18 carbon atoms per radical, the total num-ber of carbon atoms in the molecule being 6 to about 90, for a time suffi-cient to passivate said metal on said catalyst.

2. A process in accordance with claim 1 wherein the radicals R
are selected from the group consisting of alkyl radicals having 2 to about 10 carbon atoms per radical, substituted or unsubstituted cyclopentyl or cyclohexyl radicals or substituted or unsubstituted phenyl radicals.

3. A process in accordance with claim 1 wherein said antimony compound comprises about 6 to about 21 weight percent of antimony.

4. A process in accordance with claim 1 wherein said antimony compound is used in a quantity of up to about 1.5 weight percent of the catalyst to be treated.

5. A process in accordance with claim 1 wherein an active clay cracking catalyst is contacted with that antimony compound and heat treated therewith in the presence of free oxygen in order to regenerate said catalyst.