CA1117511A

CA1117511A - Cracking catalyst composition

Info

Publication number: CA1117511A
Application number: CA000304886A
Authority: CA
Inventors: Edwin W. Albers; James J. Blazek, Sr.; John S. Magee, Jr.; Ronald E. Ritter
Original assignee: WR Grace and Co
Current assignee: WR Grace and Co
Priority date: 1977-11-02
Filing date: 1978-06-06
Publication date: 1982-02-02
Also published as: AU522835B2; JPS5472790A; GB2007107B; DE2847005A1; AU4109578A; NL7810826A; JPS6240060B2; FR2407745B1; GB2007107A; FR2407745A1

Abstract

CRACKING CATALYST COMPOSITION

Abstract of the Disclosure An improved catalytic cracking catalyst composition which contains a rare earth exchanged crystalline aluminosilicate zeolite, clay, alumina, an inorganic oxide sol binder or typical alumina-silica type binder and combinations thereof and a minor quantity of platinum and/or palladium. A catalyst is particularly effective for the catalytic cracking of hydrocarbon feedstocks which contain high levels of sulfur and/or heavy metals.

Description

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The presen-t inventlon relates to catalytic compositiolls which are used to crack high molecular wei~lt hydrocarbons into products of lower molecular weight, and more specifically, to a catalyst composition which will economically conver-t sulfur and/or heavy metal containing feedstocks lncluding residual petroleum fractions into products such as yasoline and hea-ting oil.
In recent years the petroleum refining industry has placed considerable emphasis on the cracking of high molecular weight feedstocks to optimize the production of gasoline and heaking oil products.
In order to meet -the demand for these products, increasing amounts of feedstocks which contain relatively high levels of sulfur and/or heavy metals have been subject to catalytic cracking processes.
It is generally known that cracking catalysts tend to lose desirable activity and selectivity characteristics when contaminated with heavy metals such as nickel and vanadium. Furthermore it is observed that the catalytic cracking of high sulfur - feedstocks results in the emission of ecologically unacceptable amounts of sulfur oxides ~ ). It is also noted that recent environment regulations have limited the quantities of carbon monoxide which may be placed into the atmosphere by way of catalytic cracker regenerator stack gas emissions.
It has been previously sugyested that the Sx emissions from catalyst crackers may be reduced through

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modificatiorl of tlle catalyst in a manner which retains the sulfur within the product feed strearn of -the unit.
U.S. 3,~35,031 -to Be:rtolacini describes a magnesium/calcium containing catalyst which retains sulfur during regeneration in a catalytic cracking unit.
South African Patent 74/4642 to Schwartz describes a catalytic cracking catalyst composition which contains minor quantities of noble metals such as platinum and palladium that serve to oxidize carbon ~lonoxide to carbon dioxide during catalyst regeneration in a catalytic cracker.
U.S. 3,944,482 to Mitchell cliscloses the prepara-tion of catalyst compositions which possess preferred pore volume characteristics which enable the catalysts to withstand the deactivating effects of relatively large quantities of heavy metals such as mickel and vanadium.
U.S. 3,501,264 to Pilato et al discloses that alkalized alumina (Na2A12O4) is an effective adsorbent for sulfur dioxide which may be used to remove sulfur compounds from flue gases.
It is also noted that commercial ca-talytic cracking catalysts are available which possess characteristics which enable hydrocarbon processers to control carbon monoxide emisslons and to handle residual oil feedstocks in~a relatively economical manner. ~Iowever, to date a comrnercial catalyst is not available to the industry which controls Sx and carbon monoxide emissions and in addition is capable of with-standing the deactivating effects of heavy metal containing feedstocks.

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It is therefore an object of -the present invention to provide an improved catalytic crackiny catalyst composition which will reduce the CO and Sx emissions from catalytic crackiny un:its.
It is further objec-t to provide a catalyst which will economically and efficiently catalytically crack residual oil feedstocks which contain high levels of heavy me~als such as nickel and vanadium.
It is still another object to provide a catalytic cracking catalyst composition whlch may be used to process a variety of sulfur and/ox heavy metal contain-, ing feedstocks to produce high yields of yasoline fractions while controlling or reducing ecologically unacceptable CO and Sx emissions.
Broadly, our present invention comtemplates a cataly~ic cracking composition which comprises a rare earth exchanged crystalline aluminosilicate zeolite, clay, and alumina bound into a composite with an inorganic oxide sol and/or silica-alumina hydrogel blnder and contai.ning from about 0.1 to 20 parts per million pla-tinum and/or palladium.
More specifically, we have found that a highly active catalytic cracking catalyst which is capable of effectively cracking.sulfur and/or rnetal containing hydrocarbon feedstocks and in addition controlling the amount of.CO and Sx emissions from a commercial cat cracker may be prepared by,combining the following cornponents l. Fro~ about 12 to 60~ by weight of a rare,earth 30 . exchanged crystalline'aluminosilicate zeolite preferably Type Y zeolite.

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2. ~'rom about 0 to 75~ by weiyht clay.

3. From about 5 to ~0% by weiyht alumina.

4. From abou-t 15 to 40~ by weight of an inoryanic oxide binder.

5. From abou-t 0.1 to ~0 par-ts per million of a noble metal, preferably platinum and/or palladiurn.
The above noted components may be cornbined to form a finely divided particu:Late catalyst composition by the follow-ing typical preparation method:
1. An acidic inorganic oxide sol binder is prepared by mixing a sodium silicate solution with an inorganic acid such as sulfuric and/or an acid salt solution such as aluminum sulfate solution to produce.a sol haviny a pH of from about 2.9 to 4Ø
2. The clay and alumina is adde.d to the sol or to the sol forming components.
-3. The zeolite component is slurried with water with pH adjustment of from 3.5-4.5 if required.-4. The sol/clay/alumina mixture and the zeolite slurry is combined to form a spray.drier feed having a pH of from about ~.9 to 4Ø
5. The spray drier feed mixturs is then spray dried - to form a particulate catalyst which is washed and/or ion exchanged to remove soluble salts such as sodium and sulfate, and exchangcd with rare earth ions if the zeol.Lte was not previously rare earth exchanged.
The spray dried composition which has been washed to remove so.luble salts may then be impregnated with a solution of platinum and/or palladium salts to impart the desired -concentratioll of noble metaL. It is also cont~mplated that the platinum incJredient may be added in the ~orm of a separate platillum impregnated additive such as platinum impregnated mullite, alumina or silica~alumina microspheres having a particle size and density similar to that of the zeolite containing catalyst.
The rare earth exchanyed zeolite used in the practice of the present lnvention is preferably a rare earth exchanged Type Y zeolite. The rare earth exchanged Type Y zeolite may comprise a calcined rare ear-th exchanged zeolite such as the so-called CREX and CREY zeolites disclosed in U. S. Patent 3,402,996 to McDaniel. It is also contemplated that thermally stabilized zeolites such as Z-14-US as disclosed in U. S.
3,293,192 to Maher may be utilized when exchanged in the rare earth form, i.e., Z-14-US RE. Furthermore, it is contemplated that the Z-14 US zeolite in combination with a calcined rare earth exchanged zeolite 'CREY), i.e., Z-14-US/CREY, may be utilized and/or combinations of CREY and Na~, wherein the NaY is subsequently exchanged via an exchange of the spray 20 dried catalyst. Also-the partially rare earth exchanged calcined Type Y zeolite disclosed in U. S. Patent 3,507,043 (PCY`? or the rare earth hydrogen exchanged zeolite (REHY) disclosed in U. S. Patent 3,676,368 may be utilized.
In general the type of rare earth exchanged zeolite utilized in the preparation of the catalyst will be determined by the selectivity characteristics which are desired in the final catalysts, For example, where it is desired to produce high yields of C3 and C4 olefins which tend to increase the octane rating of the gasoline fractions produced it is generally found -that Z-14-US RE, Z-14-US in combination 75~

with C~EY, or PCY ~eolite is pre:Eerred. Furthermore, where it is contemplated ~hat -the ca-talyst is to be u-tilized to process heavy resl~ual oll feedstocks which contain substantial quantities of heavy metals such as nickel and vanadium, i-t is generally preferred to use a rare earth exchanged zeolite Type Y zeolite (REY) which contains from abou.t 11 -to 22% by weight rare earth ions. Furthermore, where it is desired to obtain a particularly high degree of Sx control in the regenerator stack gas emissions of the catalytic cracker and residual cracking capabilities it is generally preferred to utilize a zeolite such as CREY.
The clay component of the catalyst may comprise raw kaolin clay or a thermally modified or acid treated clay such as meta]caolin, as well as other clays such as chlori.te.
The.alumina ingredient of the presently contemplated catalyst is preferably added to the catalyst in the form of free alumina hydrate which is commercially available from many sources. The free alumina hydrate is generally re-ferred to as d -trihydrate. It is also contemplated that the alumina may be added in the form of a silica alumina hydrogel which contains 12 to 80% by weight.alumina. It is contemplated that the presence of alumina in these catalysts in conjunction with the sieve content, rare earth and sodium level, along with a - noble metal, performs as an Sx adsorber and converter during thermal/oxidative regeneration of the catalyst and retains the sulfur compounds as sulfur oxides during the regeneration part of the catalytic cracking cycle. '~he regenerated catalyst is recycled and returned to the cracking zone wherein the sulfur compounds are reduced to hydrogen sulfide which is collected i- the product stFeam from the catalyst cracker and 7S~

subse~uently separated by fractionation and/or adsorbing means.
The inorganic sol binder which may be used to prepare the present catalysk is generally described as an acid sol binder ~1hich is prepared in accordance with the procedures set forth in U. S. 3,867,308 to Elliott and 3,957,689 to Ostermaier. The Elliott and Os-termaier patents also clearly set forth general procedures wh.i.ch may be used to prepare the catalyst of the present invention.
The catalyst contemplated herein will contain minor 1~ quantities,that is from about 0.1 to 20 parts per million, of a noble metal such as platlnum and/or palladium. It is ~ound that the presence of this minor quantity of noble metal serves to oxidize carbon monoxide to carbon dioxide in the regenerator section of the catalytic cracker. Furthermore, i-t is found that the presence of the platinum and palladium is critical in the control oE the Sx emissions which evolve through the stack gas of the regenerator section of the catalytic cracker.
It is found that when the sulfur containing components which are carried from the cracking zone of the unit to the regenerator unit by way of sulfur rich carbon formed on the spent catalyst the presence of platinum in the regenerator section promotes the oxidation of the sulfur compounds to S03 which combines with the alumina and other metal oxides present, such as rare earth and sodlum oxide, to ~orm a stable form of sulfur which is not removed from the regenera-tor along with the stack gases. The S0~ containing regenerated ca-talyst is then returned to the reducing zone, i.e., hydrogen atmosphere of the cracking zone, and the S04 is reduced and hydrolyzed , to hydrogen sulfide which remains in the product stream of the catalytic cracker.

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In yeneral, the noble metal-component is preferably added by way oE impreynatiny the spray dried and washed catalyst composi-tion with a dilute solution of the platinum and/or pallaclium salt such as Pt(NH3)4(NO3)2 and Pd(~H3)~(NO3)2 Typically the impreyna-tion procedure is conducted by spraying the catalyst composi-tion with a solution of the desired metal salt.
The ca-talyst of the present invention possesses a high degree o~ activity for the cracking.of hydrocarbons.
Furthermore, the catalysts can be designed to be part.icularly selective for the production of gasoline fractions of increased octane by means of selecting the desired zeolite promoter. Furthermore, as discussed above, the catalysts are resistant to poisoniny by heavy metal, nickel and vanadia components which are present in residual oil .fractions. Also the catalysts may be used to effectively control the SOx and fuel emissions from commercial catalytic crackiny units.
~he catalysts of our invention yenerally possess a .
surface area of from about 100 to 550 m2/g and a pore volume of from about 0.1 to 0.5 Having described the basic aspects of our invention the following examples are given to illustrate specific examples thereof:
Exam~le ~
A silica sol bound catalyst was prepared following a.procedure similar.to those set forth in U. S. Patent 3,957,689 to Ostermaier and Elliott. A buffered silica hy.drosol binder was prepared as follows:

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~ n acid alum solution was prepared by addiny 8.03 liters of an A12SO~ solution containing 84 gr of A12O3/liter to 12.78 liters of a :L~Be solution of sulfuric acid. In -~he resulting solution 40 percent of the hydrogen ion equivalents are present as aluminum Al The acid alum solution was pumped to a high speed mixer at a rate of 555 cc per minute where it was mixed with an 18Be sodium silica-te solution having an SiO2/Na2O ratio of 3.25. The silicate solution had been fed to the mixer at the rate of 1.5 liter per minute. Tne resulting hydrosol had a pH between 2.5 and 3.0 and had an excess of 20 percent of the acid-aluminum sulfate necessary to neutralize the Na2O presen-t in the silicate.
To prepare 10,000 g of finished catalyst (dry basis) 3500 grams of alpha-alumina trihydrate was added to 30,000 g silica-alumina sol. After mixing was complete 3500 g of CREY zeolite in 10 1 of deionized water (pH adjusted to 4.0 with dilute sulfuric acid) was added with good agitation to the sol plus Al2O3 slurry.
After 5-10 minutes of vigorous agitation the result-ing slurry was spray dried in a typical pilot plant typespray drier (6 ft. diameter Bowen-2 fluid nozzle drier).
The spray dried material was ~,~ashed with ammonium sulfate to remove Na2O, water washed to remove excess sulfate, and dried; the final composition consisting of 35% CREY, 30% SiO2 and 35~ A1203 as ~trihydrate.
Prior to testing for residual cracking and Sx reduction capability, a requisite amount of the dried catalyst was impregnated with a dilute solution of Pt(NH3)4(NO3)2 to yield a platinum content on the finished catalyst of 3 ppm. The impregnated material was compared .

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with commercial cJradc catalysts .Eor i-ts metal tolerance using microactivity -testinc3 procedu.re wherein ~he catalysts were combined with various amounts of deactivatiny metals which comprised a mixture oE 2 Moles V per mole Ni. The activity of the catalysts was determined using the procedure of Ciape:tta & EIenderson, Oil & Gas Jour., Oct. 16, 1967, pp. 88 -to 93. The metal tolerance data for this example are sun~arized in Table I, which clearly shows the dramatic improvement over the standard catalyst.
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~xample IL
A catalyst was prepared uslny the procedure of Example I. ~lowever, the zeoli~e was NaY and the spray dried catalyst ~as excllanged with a rare earth chloride solution to a level of 7.5% by weight RE2O3 after ammonium sulfate washing. Af-ter the rare earth exchange the catalyst was Eurther washed with water (to remove excess chloride) and dried.
Example III
A catalyst was prepared by combining silica hydrosol binder, alpha-alumina trihydrate with a silica-alumina gel which contains 80% A12O3 material. The final composition of the finished catalyst was as follows:
25% A12O3 (~ -trihydrate), 27% (80% A12O3, 20% SiO2 gel), 25% NaY and 23% SiO2 (as binder).
The composition was spray dried, washed with ammonium sulfate, exchanged with rare earth chloride to a level of 4.5% by weight RE2O3 and impregnated with 3 ppm platinum.
Example IV
A catalyst was prepared by the procedure of Example I, however, the zeolite input consisted of 17% NaY and 12% ~-14-US sieves (~.SO Patent 3,293,192 to Maher and McDaniel) with 25% A12O3 as ~-trihydrate, 16% kaolin clay and 30% SiO2 as binder.
After spray drying, the catalyst was washed with ammonium sulfate, exchanged with rare earth chloride solution to a level of 4.3~ by weight RE2O3 and , impregnated with 3 ppm platinum.

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xar~ple v ~ catalyst was prepared by ~he procedure set forth in ~xample I, however, the ~eolite input consisted of 25~ NaY, 25% A12O3 as trihydrate, 27~ kaolin clay and 23~ SiO2 as binder.
As in ExaMple IV above, the catalyst slurry was spray dried, followed by washing with ammonium sulfate, exchanged with rare earth chloride solution to a level of 4.5% by weight RE2O3 and irnpregnated with 3 ppm platinum.
Example VI
To illustrate the ability of a catalyst of the present inventions to adsorb and fix sulfur oxides at high temperatures, a sample of the catalyst of Example V was compared to a sample of a commercial catalyst (CBZ-l) which comprised rare earths exchanged type Y zeolite in a silica-alumina/clay matrix. The catalyst samples were exposed to a stream of gas which contained 2000 ppm SO2, 4% 2 and -the balance N2 at a tempera-ture of 1150F for 12 minutes. The catalyst samples were then analyzed for increase in sulfate (S0 content. The results are summarized in Table II below.
Table II

Catalyst SO Content (wt %) .. . ~
BeEore Test Af-ter Test of Invention ~Example V) 0.3 0.5 Of Prior Art (CBZ~ 0 1~0 ~7,~

From the above results i~ is observed that the catalyst of the present inventions have the ability to adsorb SO2 at el.evated ternperatures in th.e presence of 2 and N2 whereas the conventional CBZ-l cakalyst does not. In light of this data it is believed khat our novel catalysts have the ability to adsorb sulfur oxides in the regeneration section of a comrnercial fluid catalytic cracking unit. I-t is also believed -that the adsorbed oxides wo~ld be reduced to H2S during the catalytic cracking cycle, and that the ~12S could be readily recovered from the cracked hydrocarbon gas stream. Therefore, it is concluded that the catalysts of the present invention will have the ability to reduce the ernmissions of sulfur oxides into the atmosphere.

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Claims

WHAT IS CLAIMED IS:

1. A catalytic cracking catalyst which comprises:
(a) from about 12 to 60% by weight of Group II to VIII metal exchanged Type Y zeolite;
(b) from about 5 to 60% by weight alpha-alumina trihydrate;
(c) from about 15 to 40% by weight of an inorganic oxide binder;
(d) from about 0.1 to 20 ppm of a noble metal selected from the group consisting of platinum, palladium and mixtures thereof; and (e) from about 0 to balance percent by weight clay;
said zeolite, clay, alumina and binder being composited into catalyst particles.

2. The catalysts of Claim 1 wherein said zeolite is selected from the group consisting of REY, PCY, CaREY, REHY, CREY and mixtures thereof.

3. The catalyst of Claim 1 wherein said inorganic binder is selected from the group consisting of silica, alumina, and alumina-silica sols.

4. The catalyst of Claim 3 wherein said binder is present in amounts of from about 15 to 40% by weight of said catalyst.

5. The catalyst of Claim 1 which contains from about 2 to 10 parts per million noble metal.

6. The catalyst of Claim 1 wherein said noble metal is impregnated upon said catalyst particles.

7. The catalyst of Claim 1 wherein said noble metal is impregnated upon a particulate inorganic oxide support which is mixed with said catalyst.

8. The catalyst of Claim 1 wherein said zeolite is REY which contains from about 11 to 22% by weight rare earth ions.

9 . The catalyst of Claim 1 wherein the Na2O content thereof is less than 2% by weight.