GB2140791A

GB2140791A - Sulfur oxide gettering agent composition

Info

Publication number: GB2140791A
Application number: GB08414412A
Authority: GB
Inventors: Leo A Rheaume; Ronald Eric Ritter
Original assignee: WR Grace and Co
Current assignee: WR Grace and Co
Priority date: 1981-03-13
Filing date: 1984-06-06
Publication date: 1984-12-05
Also published as: NL8200987A; FR2501531B1; FR2501531A1; DE3208931A1; IT8220091A0; BE892458A; AU554468B2; GB2094657A; AU8122182A; GB2094657B; JPS57162645A; DE3208931C2; MX157849A; CA1182805A; IT1152770B; LU84006A1; GB2140791B; GB8414412D0

Abstract

The invention provides new sulphur oxide gettering agent compositions which comprise alumina and lanthanum oxide distributed essentially as a mono-layer on the surface of said alumina.

Description

1 GB 2 140 791 A 1

SPECIFICATION

Sulfur oxide gettering agent compositions The present invention relates to sulfur oxide absorbing /gettering agent compositions which may 5 be used to control sulfur oxide emissions.

More specifically, the invention contemplates the preparation and use of highly efficient SOx control agents which may be used to control SO. emissions from a variety of processes.

Cracking catalysts which are used to crack hydrocarbon feedstocks become relatively inactive due to the deposition of carbonaceous deposits on the catalyst. These carbonaceous deposits are 10 commonly called coke. When the feedstocks contain organic sulfur compounds, the coke on the catalyst contains sulfur. After the cracking step, the catalyst passes to a stripping zone where steam is used to remove strippable hydrocarbons from the catalyst. The catalyst then goes to the regenerator, where the-catalyst is regenerated by burning the coke in an oxygen-containing gas.

This converts the carbon and hydrogen in the coke to carbon monoxide, carbon dioxide and 15 water. The sulfur in the coke is converted to oxides of sulfur, S02 and S031 i.e. SO Generally, the greater the amount of sulfur in the feedstock, the greater the amount of sulfur in the coke. Likewise, the greater the amount of sulfur in the coke, the greater the amount of sulfur oxides in the flue gas exitirig from the regenerator. In general, the amount Of S02 and S031 i.e. SO., in the flue gas amounts to about 250 to 2,500 parts per million by volume. 20 The prior art has suggested various methods for removing or preventing the liberation of SO,, to the atmosphere during oxidative combustion of sulfur containing fuels/residues. Typically, fluid catalytic cracking (FCC) combustion units have been equipped with conventional scrubbers in which the SO., components are removed from flue gas by absorption /reaction with gettering agents (sometimes referred to as "SO,, acceptors") such as calcium oxide. In some instances, 25 hydrocarbon feedstocks are pretreated (hydrotreated) to remove sulfur. It has also been claimed that sulfur oxide emissions from FCC units may be controlled by use of a cracking catalyst in combination with a sulfur absorber or gettering agent. It has also been claimed that these sulfur gettering agents are more effective when used in the presence of oxidation catalysts.

Oxidation catalysts are currently being used in FCC units to oxidize CO to C02 in the catalyst 30 bed during the coke-burning step in the regenerator. The oxidation of CO to C02 in the catalyst bed yields many benefits. One benefit is the reduction of CO emissions. Another is the avoidance of "after-burning", i.e., the oxidation of CO to C02 outside the catalyst bed, which results in a loss of heat energy and causes damage to the cyclones and flue gas exit lines. The major benefit in using oxidation catalysts to oxidize CO to C02 in the catalyst regenerator bed derives from the heat released when the CO is oxidized to C02. This heat raises the catalyst bed temperature and thereby increases the coke-burning rate. This gives a lower residual carbon level on regenerated catalyst (CRC). This, in turn, makes the regenerated catalyst more active for the cracking step. This increases the amount of useful products produced in the FCC unit.

In view of the fact that CO oxidation catalysts are currently being used in many FCC units for 40 economic reasons, SO, gettering agents for use in FCC units must be compatible and effective in the presence of oxidation catalysts.. Furthermore, SO. gettering agents for use in FCC units must be effective under the actual conditions seen in FCC units, such as temperatures of 800-1000'F (427-538C) and catalyst residence times of 3 to 15 seconds in the reducing atmosphere of the reactor, temperatures of 800-1 000F (427-538C) in the stream atmos- 45 phere of the stripper, temperatures of 1100-1400'F (593-760C) and catalyst residence times of 5 to 15 minutes in the oxidizing atmosphere of the regenerator. Additionally, SO,, gettering agents for use in FCC units must be effective in the presence of the materials present in FCC units, such as cracking catalysts of various compositions, oil feedstocks of various compositions and their cracked products, and, as stated earlier, oxidation catalysts to oxidize CO to C02' The following U.S. patents disclose the use of cracking catalysts which contain various sulfur and carbon monoxide emission control agents.

3,542,670 3,699,037 3,835,031 4,071,436 4,115,249 4,115,250 4,115,251 4,137,151 4,151,119 4,152,298 4,153,534 4,153,535 4,166,787 2 GB2140791A 2 4,182,693 4,187,199 4,200,520 4,206,039 4,206,085 4,221,677 4,238,317 As shown in the above noted references, organic sulfur present during regeneration of the cracking catalyst is ultimately oxidized to sulfur trioxide (S03) which reacts with a gettering agent to form a stable sulfate which is retained in the catalyst inventory of the FCC unit.

Regenerated catalyst containing the sulfate compound is recycled to the cracking zone where the catalyst is mixed with oil and steam dispersant to effect the cracking reaction and conversion of the oil to useful products (gasoline, light olefins, etc.).

When the sulfate-containing catalyst is exposed to the reducing and hydrolyzing conditions present during the cracking step and the subsequent hydrolyzing conditions present in the steam 15 stripper, the sulfate is reduced and hydrolyzed to form hydrogen sulfide (H,S) and restore or regenerate the gettering agent. The hydrogen sulfide is recovered as a component of the cracked product stream. The gettering agent is re-cycled to the regenerator to repeat the process. Through use of catalysts containing appropriate gettering agents, it is disclosed that the amount of sulfur oxides emitted from the regenerator may be significantly reduced.

However, it has been found that attempts to produce SO,,-control cracking catalysts which can consistently achieve significant sulfur oxide emission reduction over long periods of time have in general been unsuccessful.

Accordingly, it is an object of the present invention to provide a sulfur oxide gettering agent which is capable of removing sulfur oxides over a long period of time when subjected to multiple gettering /regeneration cycles. These gettering agents may be used in cracking catalyst compositions which effectively and economically reduces the emission of sulfur oxides from FCC units.

It is a further object to provide a SO., control additive which may be added to the catalyst inventory of an FCC unit in amounts necessary to reduce sulfur oxide regenerator stack gas 30 emissions to an acceptable level.

It is still a further object to provide highly effective sulfur oxide gettering agents which may be advantageously combined with conventional cracking catalyst compositions or used to control SO., emissions from a variety of processes.

These and still further objects will become apparent to one skilled in the art from the following 35 detailed description, specific examples and drawing wherein the Figure is a graphical representation of data which illustrates SO., Index vs. La203 content of SO. gettering agents of the present invention.

Broadly, our invention contemplates an improved SO., gettering agent which comprises an alumina (A'203) substrate coated with lanthanum oxide (La203) in amounts which provide approximately a theoretical mono-layer of La203 molecules on the surface of the alumina substrate. These gettering agents may be effectively combined with or included in particulate catalyst compositions used for the catalytic cracking of hydrocarbons, or alternatively the gettering agents may be used in any combustion process which generates SO,, components that are to be selectively removed from the combustion products..

More specifically, we have found that a particularly effective SO. absorber/gettering agent suitable for use with catalytic cracking catayst may be obtained by combining the soluble lanthanum salt solution with a porous alumina substrate in amounts which will distribute upon the surface of the alumina substrate a layer of lanthanum oxide approximately one molecule in thickness.

In practice, we find that the desired result is achieved with about 5 to 50 percent by weight La203 combined with an alumina substrate which has a surface area of from about 45 to 450 M2/g; preferably, about 12 to 30 percent by weight La203 combined with an alumina substrate which has a surface area of about 110 to 270 M2/g; and more preferably about 20 percent by weight La203 combined with an alumina substrate which has a surface area of about 180 M2/g.

Suitable alumina substrates are available from many commercial sources, and comprise the alumina hydrates, such as alpha alumina monohydrate, alpha alumina trihydrate, beta alumina monohydrate and beta alumina trihydrate. Also considered most suitable are the calcined versions of the above alumina hydrates. These include gamma alumina, chi alumina, eta alumina, kappa alumina, delta alumina, theta alumina, alpha alumina and mixtures thereof. 60 The lanthanum oxide component which is distended upon the alumina surface may be obtained as a commercially available lanthanum salt such as lanthanum nitrate or chloride or sulfate, or alternatively, a mixed rare earth salt which contains other rare earth elements such as Nd, Ce, Pr and Sm may be utilized. The rare earth component of a typical commercially available mixed rare earth salt solution which includes lanthanum has the following approximate 65 3 GB 2 140 791A 3 composition, expressed as oxides: 60% La203, 20% Nd2031 14% Ce02, 5% Pr601, and 1 % SM2031 It should be understood that in the event a mixed rare earth salt source is utilized the quantity of mixed rare earth salts used should be sufficient to provide the desired level of La203 on the alumina substrate.

The amount of lanthanurn oxide utilized in the preparation of the novel SO. gettering agent is 5 preferably that quantity which will provide a mono-layer of lanthanum oxide molecules over the surface of the alumina substrate. In the event the quantity of lanthanum oxide, as specified above, is substantially exceeded, i.e., multi-layer or bulk lanthanum oxide is formed, and.the effectiveness of the SO, gettering agent is adversely affected. On the other hand, if insufficient lanthanurn oxide is used, the effectiveness of the gettering agent is less than it could be.

While the precise mechanism is not fully understood, it is believed that the active specie is a La203 molecule fixed on the alumina surface in some sort of a surface complex of La203 and A1203. This surface La203 on A1203 complex is very reactive in combining with sulfur oxides to form a thermally stable solid sulfate or sulfate-type compound. Furthermore, this thermally stable solid sulfate or sulfate-type compound can be easily reduced- hydrolyzed to produce 15 volatile hydrogen sulfide and restore or regenerate the original surface La203 on A1203 complex. The hydrogen sulfide can be recovered as a component of the product stream. The restored or regenerated gettering agent can be recycled to repeat the absorption and regeneration steps.

To prepare our novel SO., gett6ring agent, the alumina substrate is uniformly and thoroughly admixed with a quantity of larithanum salt solution which will provide the desired uniform dispersion of lanthanurn oxide on the surface. Typically, the soluble lanthanurn salt, preferably lanthanurn nitrate, is dissolved in water to provide a desired volume of solution which has the desired concentration of the lanthanurn salt. The alumina substrate is then impregnated, as uniformly as possible, with the lanthanum salt solution to give the desired amount of lanthanurn on the alumina. The impregnated alumina is then calcined at a temperature sufficient to decompose the lanthanurn salt and fix the resulting lanthanum oxide uniformly onto the alumina surface. While it is contemplated that calcination temperatures of up to about 1500F may be used, calcination temperatures on the order of 1 000F have been found to be satisfactory.

In one preferred embodiment of the invention, the alumina substrate to be impregnated is in the form of microspheroidal particles, with about 90% of the particles having diameters in the 30 to 149 micron fluidizable size range. The gettering agent prepared using these microspheroi dal particles may be advantageously physically mixed with FCC catalysts in amounts ranging from about 0.5 to 60 percent by weight of the overall composition.

In another preferred embodiment of the invention, the alumina substrate to be impregnated is in the form of particles which have an average particle size of less than 20 microns in diameter, 35 and preferably less than 10 microns in diameter. The finished gettering agent prepared using these fine particles may be incorporated in a cracking catalyst composition during the formation of the catalyst particles.

Typically, the lanthanurn impregnated alumina is added to an aqueous slurry of catalyst components prior to forming, i.e. Spray drying in the case of FCC catalysts.

In another embodiment of the invention, the alumina substrate to be impregnated is in the form of particles one millimeter or greater in diameter. The finished gettering agent prepared using these particles can be used in either a fixed-bed or moving-bed configuration to reduce SO, emissions from a variety of processes.

Therefore, it is seen that the present gettering agent may be used as a separate additive which is added to the catalyst as a separate particulate component, or the gettering agent may be combined with the catalyst during its preparation to obtain catalyst particles which contain the gettering agent as an integral component. Additionally, the gettering agent may be used by itself to reduce SO, emissions from a variety of processes.

Cracking catalysts which may be advantageously combined with the SO. gettering agent of 50 the present invention are commercially available compositions and typically comprise crystalline zeolites admixed with inorganic oxide binders and clay. Typically, these catalysts comprise from about 5 to 50 percent by weight crystalline aluminosilicate zeolite in combination with a silica, silica-alumina, or alumina hydrogel or Sol binder and optionally from about 10 to 80 percent by weight clay. Zeolites typically used in the preparation of cracking catalysts are stabilized type Y 55 zeolites the preparation of which is disclosed in U.S. 3,293,192, 3,375,065, 3,402,996, 3,449,070 and 3,595, 611. Preparation of catalyst compositions which may be used in the practice of our invention are typically disclosed in U.S. patents 3,957, 689, 3,867,308, 3,912,611 and Canadian 967,136.

In a preferred practice of the invention, the cracking catalyst gettering composition will be used in combination with a noble metal oxidation catalyst such as platinum and/or palladium.

In another preferred practice of the invention, the SO,, gettering agent is combined with a cracking catalyst which comprises an alumina Sol, i.e. aluminum chlorhydroxide solution, bound zeolite/clay composition is disclosed in Canadian Patent 967,136 admixed with a particulate platinum containing oxidation catalyst to obtain a composition which comprises 0.5 to 60 65 4 GB2140791A 4 percent by weight gettering agent, 40 to 99 percent by weight cracking catalyst, and 1 to 5 parts per million platinum.

In still another preferred practice of the invention, the SO, gettering agent is combined with a zeolite cracking catalyst which possesses an essentially silica-free matrix. These catalysts are obtained by using the procedure set forth in Canadian 967,136 by mixing together the following materials: 5 to 50 weight percent zeolite, 10 to 80 weight percent alumina hydrate (dry basis), and 5 to 40 weight percent aluminum chlorhydroxide sol (A'20,), and water. The mixture was spray- dried to obtain a finely divided catalyst composite and then calcined at a temperature of about 1 000'F (538C). The SO,, gettering agent may be included as a component in the spray dried slurry in lieu of some of the alumina hydrate or the SO., gettering 10 agent may be physically blended with the catalyst in the amount of about 0.5 to 60 weight percent.

As indicated above, the gettering agent may be utilized in the form of a separate particulate additive which is physically blended with a particulate catalyst or the gettering agent may be incorporated in the catalyst particle by admixing the additive with the catalyst components prior to forming of the catalyst. In addition it is contemplated that the gettering agent may be utilized in any combustion /reaction process where it is desirable to collect or remove sulfur oxides from a product gas stream. Typically, the SO,, gettering agent may be used in a fluidized coal combustion process to remove SQ, formed during burning of the coal. The SO. gettering agent may then be removed from -the combustion/ reaction zone periodically or continuously to restore 20 or regenerate the gettering agent by subjecting it to reduction- hydrolysis in the presence of hydrogen or carbon monoxide-hydrogen reducing gas mixtures (i.e. syn-gas) and H20. Using this technique, the SO,, component of the combustion products is selectively removed as a stable sulfate, and the sulfate is subsequently reduced-hydrolyzed to liberate H2S and restore or regenerate the gettering agent. The H2S may be recovered using conventional adsorbing 25 techniques.

Having described the basic aspects of our invention, the following examples are given to illustrate specific embodiments thereof.

EXAMPLE 1

A solution of lanthanum nitrate was prepared by dissolving 79.7 9 of lanthanum nitrate, La(N01.6 HO, in a sufficient amount of water to give 100 mi of solution. 10 mi of this solution contains 3.0 9 of lanthanum expressed as lanthanum oxide, La203.

EXAMPLE 2

36.8 g (27 g dry basis) of a commercial alpha alumina monohydrate having an average particle size (APS) of 67 microns with 96 weight percent of the particles in the 20 to 149 micron size range were impregnated with 10 ml of solution described in Example 1. The impregnated alumina was heated to 1 000F (538C) and held at 1 000F for 30 minutes. The resultant La,03/A'203 sample contained 10 weight percent La201, EXAMPLE 3

Alpha alumina monohydrate of the type described in Example 2 was calcined in air for one hour at 900 F (482'C). 27 g of this calcined alumina was impregnated with 10 ml of solution described in Example 1. The impregnated sample was heated to 1000F (538C) and held at I 000'F (538C) for 30 minutes. The resultant La203 sample contained 10 weight percent lanthanum oxide La203.

EXAMPLE 4

The procedure of Example 3 was repeated except that the alumina hydrate was calcined for 50 one hour at 1250'F (677'C) prior to impregnation with lanthanum nitrate solution.

EXAMPLE 5

The procedure of Example 3 was repeated, except that the alumina hydrate was calcined for 55 one hour at 1650'F (899'C) prior to impregnation with lanthanum nitrate solution.

EXAMPLE 6

The procedure of Example 3 was repeated, except that the alumina hydrate was calcined for one hour at 1850'F (1010'C) prior to impregnation with lanthanum nitrate solution.

EXAMPLE 7

The procedure of Example 3 was repeated, except that the alumina hydrate was calcined at 1 950'F (1 OWC) prior to impregnation with lanthanum nitrate solution.

EXAMPLE 8 i GB 2 140 791 A 5 Alumina hydrate of the type described in Example 2 was calcined in air for one hour at 1250F (677C). 5 mi of the solution described in Example 1 was mixed with 5 mi of water to yield 10 mi of solution having a lanthanum concentration of 1.50 g of lanthanum expressed as La203. 28.5 of the calcined alumina were impregnated with the 10 mi of solution. The impregnated sample was heated to 1 000F (538'C) and held at 1 000F (538C) for 30 minutes. The resultant La203/A1203 sample contained 5 weight percent La203.

EXAMPLE 9 Alumina hydrate of the type described in Example 2 was calcined in air for one hour at 1250'F (677C). 24 g of this calcined alumina was impregnated with 10 ml of solution described in Example 1. The impregnated sample was heated to 1000F (538C) and held at 1 000F (538C) for 30 minutes. After being allowed to cool to room temperature, the impregnated and calcined sample was given a second impregnation with 10 ml of solution described in Example 1. After this second impregnation, the sample was heated to 1 000'F (538C) and held at 1000F (538'C) for 30 minutes. The resultant La203/AI203 sample 15 contained 20 weight percent La2031 EXAMPLE 10

A solution of lanthanum nitratewas prepared by dissolving 99.8g of La(N01. 61-120 in water to give 100 mi of solution. 8 mi of solution contains 3.0 g of lanthanum expressed as La203. 20 EXAMPLE 11

Alumina hydrate was calcined in air for one hour at 1250'F (677C) as in Example 9. 21 g of this calcined alumina were impregnated with 8 ml of solution described in Example 10. The impregnated sample was heated to 1000F (538'C) and held at 1000F (538C) for 30 25 minutes. After being allowed to cool to room temperature, the impregnated and calcined sample was given a second impregnation with 8 ml of solution described in Example 10. After this second impregnation, the sample was heated to 1 000F (538'C) and held at 1 000F (538C) for 30 minutes. After being allowed to cool to room temperature, this doubly impregnated and calcined sample was given a third impregnation with 8 ml of solution described in Example 10. 30 After this third impregnation, the sample was heated to 1 000'F (538 Q and held at 1 000'F for minutes. The resultant La2o3/A'203 sample contained 30 weight percent La203.

EXAMPLE 12

The procedure of Example 11 was repeated, except that 18.0 g of calcined alumina was 35 used, and after the third impregnation and calcination, the sample was given a fourth impregnation and calcination at 1000F (538C). The resultant La20a3/A'203 sample contained 40 weight percent La203.

EXAMPLE 13

A solution of mixed rare-earth nitrates was prepared by mixing 153.1 g of a commercial mixed rare-earth nitrate solution with water to give 100 mi. 8 mi of the solution contained 3.0 9 of mixed rare-earths expressed as the oxides. The rare earth component of this solution, expressed by weight as oxides, has the following composition: 60% La203, 20% Nd203, 14% Ce02, 5% Pr601, and 1 % Sm203.

EXAMPLE 14

The procedure of Example 9 was repeated, except that the impregnations were carried out with 8 mi of the solution described in Example 13. The resultant sample contained 20 weight percent mixed rare-earth oxides. Sixty percent of these rare-earth oxides were lanthanum oxide, 50 so the resultant sample contained 12 weight percent La203.

EXAMPLE 15

The procedure of Example 11 was repeated, except that the impregnations were carried out with 8 mi of solution described in Example 13. The resultant sample contained 30 weight 55 percent mixed rare-earth oxides of which 60% were lanthanum oxide. The resultant sample contained 18 weight percent La203.

EXAMPLE 16

A solution of mixed rare-earth nitrates was prepared by mixing 152.8 g of a commercial 60 mixed rare-earth nitrate solution with water to give 100 mi. 10 mi of solution contains 3.7 5g of mixed rare-earth expressed as the oxides. The rare earth component of this solution, expressed as oxides, has the following composition: 60% La203, 20% Nd203, 14% Ce02, 5% Pr601, and 1 % SM203 6 GB 2 140791A 6 EXAMPLE 17

The procedure of Example 9 was repeated, except that the impregnations were carried out with 10 mi of solution described in Example 16. The resultant sample contained 25 weight percent mixed rare-earth oxides. Sixty percent of these rare-earth oxides were lanthanum oxide, so the resultant sample contained 15 weight percent La203.

EXAMPLE 18

Fine-size alpha alumina monohydrate was calcined in air for 1 hour at 1250 (677C). This calcined alumina had an average particle size of 15 to 20 microns. 2000 g (dry basis) of this calcined alumina was mixed with a solution which contained 592 g of La(N03)3.6H20 dissolved 10 in 1400 ml of water in a mechanical mixer. The solution was added at a rate 100 ml per minute to this alumina. The impregnated alumina was removed from the mixer, heated to 1000'F (538C) and held at 1000F (538C) for 30 minutes. The sample contained 10 weight percent La20, and had an average particle size of less than 10 microns.

EXAMPLE 19

Alpha alumina monohydrate was calcined in air for 1 hour at 125017 (677C) to obtain a product having an average size of 15 to 20 microns in diameter. 2000 g (dry basis) of this calcined alumina was mixed with a solution of 670 g of La (N0366H20 dissolved in 1400 ml of water in a mixer. The solution was added at a rate of 100 ml per minute. The impregnated alumina was removed from the mixer, heated to 1000'F (538'C) and held at 1000F (538C) for 30 minutes. This impregnated and calcined alumina was returned to the mixer and given a second impregnation with 670 g of La(N03)3.6H20 in 1200 ml of water which was added at -a rate of 100 ml per minute. The impregnated material was heated to 1 000F (538'C) and held at 1 000'F (538 Q for 30 minutes. The finished material contained 20 weight percent La203 25 and had an average particle size of less than 10 microns.

EXAMPLE 20

The finished SOx agent of Example 18 was incorporated within the particle of an alumina- bound cracking catalyst. The catalyst was prepared by mixing together the following materials: 30 The SO. gettering agent of Example 18, a rare earth ion-exchanged Y-type crystalline aluminosilicate, clay, aluminum chlorhydroxide sol (approximate formula: A12CI (OH)j and water.

The mixture was spray-dried and then calcined for 2 hours at 1000F (538oC). The proportion of starting materials were such that the finished catalyst contained 20 percent of the SO.

gettering agent of Example 18, 12 percent of rare earth ion-exchanged Ytype crystalline 35 aluminosilicate, 54 percent clay and 14 percent alumina. The finished catalyst had an average particle size (APS) of 116 microns with 65 weight percent of the particles in the 20 to 149 micron size range.

EXAMPLE 21

The procedure of Example 20 was repeated except that the SO, gettering agent of Example 19 was used.

In this Example, the finished catalyst had an average particle size (APS) of 77 microns with 87 weight percent of the particles in the 20 to 149 micron size range.

- 45 i EXAMPLE 22

An alumina sol-bound cracking catalyst was prepared by mixing together the following materials: A rare earth ion-exchanged Y-type crystalline aluminosilicate (CREY), clay, aluminum chlorhydroxide sol (approximate formula: AI,CI(OH),) and water. The mixture was spray-dried and then calcined for 2 hours at 1000 F (538'C). The proportion of starting materials were 50 such that the finished catalyst contained 12 percent of a rare earth ion- exchanged Y-type crystalline aluminosilicate, 78 percent clay and 10 percent alumina.

The finished catalyst had an average particle size (APS) of 71 microns with 97 weight percent of the particles in the 20 to 149 microns size range.

29.89 g (dry basis) of this alumina-bound cracking catalyst was thoroughly mixed with 55 0.1110 g (dry basis) of an oxidation catalyst which comprises 810 ppm platinum on a gamma alumina support having a particle size in the fluidizable range.

EXAMPLE 23

26.89 g (dry basis) of the cracking catalyst described in Example 22 was thoroughly mixed 60 with 0. 1110 g (dry basis) of the oxidation catalyst, also described in Example 22. 3.00 g (dry basis) of a commercial alpha alumina monohydrate was added to this mixture and thoroughly mixed.

EXAMPLE 24 - -c Z 7 GB 2 140 79 1A 7 26.89 9 (dry basis) of the cracking catalyst described in Example 22 was thoroughly mixed with 0. 1110 9 (dry basis) of the oxidation catalyst, also described in Example 22. 3.00 9 (dry basis) of the La,03/A1203 composition prepared in Example 2 was added to this mixture and thoroughly mixed. EXAMPLES 25-36 The procedure of Example 24 was repeated except that the

third component to be mixed was the composition prepared in Example 3. Like-wise, the procedure was repeated, except that the third components were, in turn, the compositions prepared in Examples 4, 5, 6, 7, 8, 9, 11, 10 12, 14, 15, 17.

EXAMPLE 37

29.89 9 (dry basis) of the finished caatalyst of Example 20 was thoroughly mixed with 0. 1110 9 (dry basis) of the oxidation catalyst described in Example 22.

EXAMPLE 38

29.89 g (dry basis) of the finished catalyst of Example 21 was thoroughly mixed with 0. 1110 g (dry basis) of the oxidation catalyst described in Example 22.

EXAMPLE 39

A laboratory scale catalytic cracking unit was used to test the catalyst compositions for their ability to reduct SO, (S02 + S03) emissions from the regenerator.

Prior to testing in the lab unit, the catalysts or catalyst mixtures were steam deactivated with percent steam at 15 psig (103 kPa) at 1 350F(732C) for 8 hours. This steam deactivation simulates the deactivation which occurs in a commercial cat-cracking unit. The ability of a catalyst or catalyst mixture to reduce SO. emissions in the lab test unit after this steam deactivation will be a measure of iti ability to reduce SO,, emissions in commercial units. In contrast, the ability of a fresh or undeactivated catalyst or catalyst mixture to reduce SOx emissions in a lab test is inconclusive as far as projecting the ability of the catalyst or catalyst mixture to reduce SO, emissions in commercial units, because the catalyst or catalyst mixture 30 would be deactivated in the commercial unit soon after being charged to the commercial unit and may become ineffective in reducing SO,, emissions.

In the lab unit, a low sulfur gas oil was cracked over the catalyst or catalyst mixture at a temperature of 980F. (527C). Regeneration of the catalyst or catalyst mixture, i.e., the coke- burning step, was carried out with air at 1 250F, (677'C). The air used for coke-burning step 35 contained 2000 PPM S02. This is equivalent to the amount Of S02 which would be formed in the regenerator if a high sulfur gas oil had been used for the cracking step.

The regenerated catalyst or catalyst mixture was then subjected to the cracking and steam stripping steps to release, as H2S1 the SO,, captured in the regenerator.

The regeneration and the cracking and steam-stripping steps were repeated. During this 40 second cycle, a portion of the catalyst or catalyst mixture was removed after the regeneration step, and another portion of the catalyst or catalyst mixture was removed after the cracking and steam-stripping steps.

An SO, Index which gives a measure of the SO. captured in the regenerator and released in the reactor and stripper was defined as SOX Index - w t. I sulfur wtA sulfur w content of the content of t catalyst or catalyst mixture after the re generation (w c c c m t 9 tep.

catalvst or catalyst mixture after the cracking and steam- strippinq steps I 1000 A sample calculation for the catalyst mixture described in Example 31 and listed in Table 1 is 60 given below.

SO, Index = [(0. 167)-(0.097)]1000 = 70 It should be noted that the SQ, Index is a measure of the amount of SO. 'captured in the regenerator and released in the reactor and stripper. A catalyst or catalyst mixture which 65 8 GB2140791A 8 captures SO. in the regenerator, but does not release it in the reactor and stripper would have an SQ, Index of zero. Such a catalyst or catalyst mixture would soon become saturated, likely after one or two cycles, and lose its effectiveness for reduction of SO. emissions.

For long-term effectiveness, a catalyst or catalyst mixture must not only capture SO, in the regenerator but be able to release it in the reactor and stripper, and thereby restore its ability to 5 repeat the process.

The greater the Davison SO., Index, the greater the long-term effectiveness of the catalyst or catalyst mixture in reducing SO. emissions from the regenerator. As stated above, a Davison SO.

Index of zero means that the catalyst is not effective, long-term, for the reduction of SO.

emissions from the regenerator. At the other extreme, a Davison SO. Index of 100 means 10 essentially 100 percent effectiveness, long-term, in the reduction of SO. emissions from the regenerator.

The catalyst mixtures described in Examples 22, 23, 26, 31, 32, 33, 34 and 35 were tested for their ability to reduce SO. emissions according to the procedure described above. The SO, Indices are given in Table 1. A graphical representation of the data in Table I (except for the catalyst mixture described in Example 22) is set forth in the Figure wherein SO., index is plotted against percent La203 content of the SO,, gettering agent in the mixture. The curve plotted in the Figure indicates the maximum SOx index is obtained when the SO, gettering agent contains about 20 percent La203. More broadly, the data in Table I shows that the maximum in the SO, index is obtained at La203 concentrations on A1203 greater than 12 percent and less than 30 percent (Examples 32 and 34).

Table 1

Catalyst Mixture 25 Described in Example S0x Index 22 10 23 18 26 42 30 34 58 70 31 69 32 56 33 44 35 EXAMPLE 40

The catalyst mixtures described in Examples 37 and 38 were tested for their ability to reduce SQ, emissions according to the procedure described in Example 39. The SO, Indices obtained 40 are given in Table 11.

Table 11

Catalyst Mixture Described in Example S0x Index 37 38 46 58 EXAMPLE 41

The catalyst mixtures in Examples 24, 25, 26, 27, 28 and 29 were tested for their ability to reduce SO. emissions according to the procedure described in Example 39. The Davison SOx 55 indices obtained are given in Table 111.

The data in Table I I I show the effect of calcination of the alumina hydrate prior to impregnation with a solution of La(NO3)3.6H20, In Example 24, the alumina hydrate was not calcined prior to impregnation. In Examples 25, 26, 27, 28 and 29 the alumina hydrate was calcined at temperatures ranging from 900F to 1950F. (482 to 1066C.) t c i - 1 9 GB2140791A 9 TABLE III Effect of Calcination -of Alumina Prior to Impregnation Catalyst Mixture Described in Example S0x Index 24 32 25 35 10 26 42 27 35 28 29 29 36 15 EXAMPLE 42

The cracking catalyst used in this example is a commercially available cracking catalyst containing 17 weight percent of 6 rate earth ionexchanged Y-type crystalline aluminosilicate (REY), 63 weight percent clay and 20 weight percent silica-alumina sol binder.

29.89 g (dry basis) of this cracking catalyst was throughly mixed with 0. 1110 g (dry basis) of an oxidation catalyst which comprises 810 ppm platinum impregnated on a gamma alumina support having a particle size in the fluidizable range.

EXAMPLE 43

26.89 g (dry basis) of the cracking catalyst described in Example 42 was thoroughly mixed with 0. 1110 g (dry basis) of the oxidation catalyst, also described in Example 42. 3.00 g (dry basis) of a commercial alpha alumina monohydrate was added to this mixture and thoroughly mixed.

EXAMPLE 44

26.89 9 (dry basis) of the cracking catalyst described in Example 42 was thoroughly mixed with 0. 1110 g (dry basis) of the oxidation catalyst, also described in Example 42. 3.00 g (dry basis) of the La203/A1203 composition prepared in Example 9 was added to this mixture and thoroughly mixed.

EXAMPLE 45

The catalyst mixtures described in Examples 42, 43 and 44 were tested for their ability to reduce SO, emissions according to the procedure described in Example 39. The SO. Indices 40 obtained are given in Table IV.

The results show that the silica-alumina sol cracking catalyst gave an SO. Index of zero (Example 42). Use of alumina as an SO,, gettering agent gave an SO,, Index of 5 (Example 43). Use of a La203/A'203 SO,, gettering agent of this invention gave an SO. Index of 50 (Example 44), which represents a considerable improvement over the use of alumina.

TABLE IV

Catalyst Mixture Described in Example S0x Index 42 43 44 0 5 50 EXAMPLE 46

27.00 g (dry basis) of the cracking catalyst described in Example 22 was thoroughly mixed with 3.00 g (dry basis) of the La203/A1203 composition prepared in Example 9. This catalyst mixture was tested for its ability to reduce S0x emissions according to the procedure described in Example 39. The S0x index obtained had a value of 48. This compares with an S0x index of 60 69 obtained for the catalyst mixture described in Example 31 which contains an oxidation catalyst. This shows that the SQ, gettering agent of this invention works without the presence of an oxidation catalyst. It also shows that the presence of an oxidation catalyst increases the ability of the gettering agent to reduce SO, emissions.

GB 2 140 791 A 10

Claims

1. A sulfur oxide gettering agent composition which comprises alumina, and lanthanum oxide distributed essentially as a mono-layer on the surface of said alumina.

2. A sulfur oxide gettering agent composition which comprises from about 5 to 50 percent by weight lanthanum oxide uniformly distributed on the surface of an alumina having a surface 5 area of at least 45 M2/g.

3. The dettering agent of claim 2 wherein said lanthanum oxide is distributed on the surface of said alumina as a mono-layer.

4. The gettering agent of any of claims 1 to 3 wherein said alumina has a surface area of about 110to 270 M2 /g and contains about 12 to 30 percent by weight lanthanum oxide. 10

5. The gettering agent of any of claims 1 to 4 wherein the lanthanum oxide is included in a mixture of rare-earth metal oxides.

6. The composition of any of claims 1 to 5 formed into microspheroidal particles and having about 90% of the particles in the 20 to 105 micron range in diameter.

7. The composition of any of claims 1 to 5 formed into particles and having about 90% of 15 the particles in the 0.5 to 20 micron range in diameter.

8. The composition of any of claims 1 to 5 formed into particles greater than one-millimeter in diameter.

9. The composition of any of claims 1 to 8 wherein the said composition includes an oxidation catalyst.

10. The composition of claim 9 wherein the said composition includes a noble metal oxidation catalyst.

11. The composition of claim 10 wherein the said oxidation catalyst is included in amounts of from about 0. 1 to 1000 parts per million by weight of the said composition.

12. The composition of claim 10 or 11 wherein the said oxidation catalyst is selected from 25 platinum, palladium and mixtures thereof.

13. The composition of claim 12 wherein said oxidation catalyst is added to said compo sition as platinum and/or palladium impregnated on a particulate inorganic oxide.

14. The composition of claim 12 wherein the said lanthanum oxide is distributed on the surface of said alumina in combination with an oxidation catalyst selected from platinum, 30 palladium and mixtures thereof.

15. The composition of claim 1 substantially as described in any one of Examples 2 to 12, 14, 15 and 17 to 19.

16. A method for controlling SO,, emissions which comprises:

(a) including in a reaction zone a gettering agent as claimed in any of claims 1 to 15 to combine with sulfur oxides in said zone; and (b) restoring or regenerating the sulfur containing gettering agent obtained in step (a).

17. The method of claim 16 wherein an oxidation catalyst is present in said zone.

18. The method of claim 16 or 17 wherein said gettering agent is restored or regenerated by reduction and/or hydrolysis in the presence of a reducing gas and/or steam.

19. The method of any of claims 16 to 18 wherein the restored or regenerated gettering agent is recycled to the reaction zone.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935, 1984, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from,,jhich copies may be obtained.

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