CA1255646A - Cracking catalyst/sulfur oxide gettering agent compositions - Google Patents
Cracking catalyst/sulfur oxide gettering agent compositionsInfo
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- CA1255646A CA1255646A CA000485047A CA485047A CA1255646A CA 1255646 A CA1255646 A CA 1255646A CA 000485047 A CA000485047 A CA 000485047A CA 485047 A CA485047 A CA 485047A CA 1255646 A CA1255646 A CA 1255646A
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- sulfur
- gettering agent
- catalyst
- mgso4
- catalyst composition
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Abstract
Abstract of the Invention Sulfur oxide gettering agents which comprise a metal sulfate, such as magnesium sulfate, are described. These gettering agents are used to reduce sulfur oxide emissions from a variety of processes and units, including fluid catalytic cracking (FCC) units.
Description
The present invention relates to catalysts which are used to catalytically crack hydrocarbons and to sulfur oxide absorbing/gettering agen'c compositions which may ~e used to control sulfur oxide emissions.
More specifically, the invention contemplates the preparation and use of catalytic cracking catalysts which are capable of reducing the amount of sulfur oxides (SOx~ emitted to the atmosphere during regeneration of the catalyst, and to highly efficient Sx control agents which may be used to control Sx 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 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 water. The sulfur in the coke is converted to oxides of sulfur, SO2 and SO3, i.e. sOx.
Generally, the greater the amount of sulfur in the feedstock, the greater the amount of sulfur in the coke. Likewise, the greater the amount o~ sulfur in the coke, the greater the amount of sul~ur oxides in the flue gas exiting from the regenerator. In general, the amount of SO2 and SO3, i.e. SOx, in the flue gas amounts to about 250 to 2,500 parts per million by volume.
The prior art has suggested various methods for ~emovin~ o~ preventing the libe~ation o~ Sx to the atmosphere during oxidative combustion of sulfur containing fuels/residues. Typically, FCC/combustion units have been equipped with conventional scrubbers in which the Sx components are removed from flue gas by absorption/reaction with gettering agents (sometimes referred to as ~Sx acceptorsa) such as magnesium and/or calcium oxide. In some instances, 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 CO2 in the catalyst bed during the coke-burning step in the regenerator. The oxidation of CO to CO2 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 CO2 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 CO2 in the catalyst regenerator bed derives from the heat released when the CO is oxidized to CO2~ This heat raises the catalyst bed temperature and thereby increases the coke-burning rate. This gives a lo~er residual carbon level on regenerated catal~st (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 economic reasons, ~x gettering agents for use in FCC units must be compatible and effective in the presence of oxidation catalysts. Furthermore, Sx gettering agents for use in FCC units must be effective under the actual conditions seen in FCC units, such as ~emperatures of 800-1050F and catalyst residence times of 3 to 15 seconds in the reducing atmosphere of the reactor, temperatures of 800-1050F in the steam atmosphere of the stripper, temperatures of 1150-1550F
and catalyst residence times of 5 to 15 minutes in the oxidizing atmosphere of the regenerator. Additionally, Sx 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 CO2.
The following patents disclose the use of cracking catalysts which contain various sulfur and carbon monoxide emission control ayents.
U.S. 3,542,670 3,699,037 3,~35,031 4,071,436 4,115,249 4,115,250 4,115,251 4,137,151 4,146,463 4,151,119 ~6 4,152,298 4,153,535 4,166,787 4,182,693 4,187,199 4,200,520 4,206,039 4,20~,085 4,221,~77 4,238,317 4,240,899 4,267,072 4,300,997 4,325,811 4,369,108 4,369,130 4,376,103 4,376,696 Canadian 1,110,5~7 As shown in the above noted references, organic sulfur present during regeneration of the cracking catalyst is ultimately oxidized to sulfur trioxide ~SO3) 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, 33 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 stripper, the sulfate is reduced and hydrolyzed to form hydrogen sulfide (H2S) and restore or regenerate the gettering agent.
The hydrogen sulfide is recovered as a component of the cracked product stream, The gettering agent is recycled 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.
Howeverl it has been found that attempts to produce sox-control cracking catalysts which can consistently achieve significant sulfur oxide emission reduction at reasonable cost over long periods of time have in general been unsuccessful.
Accordingly, it is an object of the present invention to provide cracking catalyst compositions which effectively and economically reduces the emission of sulfur oxides from FCC units.
It is another object to provide sulfur oxide gettering agents which are capable of removing sulfur oxides over a long period of time when subjected to multiple gettering/regeneration cycles.
It is a further object to provide Sx control additives which may be added to the catalyst inventory of an FCC unit in amounts necessary to reduce sulfur oxide regenerator stack gas 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 Sx emissions from a variety of processes.
These and still further objects will become apparent to one skilled in the art from the following Z5564~
detailed description and specific examples.
The invention~ provides in a method for controlling Sx emissions which comprises:
(a) including in an oxidation reaction zone a sulfur oxide gettering agent which will combine with sulfur oxides in Eaid zone;
(b) regenerating the sulfur-containing gettering agent obtained in step (a) by reduction and/or hydrolysis in the presence of a reducing gas and/or steam; and (c) recycling the restored or regenerated sulfur oxide gettering agent to the reaction zone; the improvement comprising adding magnesium sulfate as said sulfur oxide gettering agent.
Broadly, our invention contemplates catalytic cracking catalyst compositions which include metal sulfates, such as magnesium sulfate, as Sx gettering agents. Furthermore, ourinvention contemplates an improved Sx gettering agent which preferably aomprises a particulate magnesium sulfate, or magnesium sulfate combined with an appropriate binder or support such as alumina. These gettering agents may be effectively combined with, or included in, particulate catalyst compositions used for the aatalytic cracking of hydrocarbons, or alternatively the gettering agents may be used in any combustion process which generates SOx componentes that are tobe selectively removed from the combustion products.
More specifically, we have found that a particularly effective Sx absorber/gettering agent composition suitable for use with catalytic cracking catalyst may be obtained by preparing a metal sulfate, which is stable at temperatures of up to about 1550F, such as magnesium sulfate, in suitable particulate form such as by combining a magnesium sulfate solution with a porous particulate alumina substrate.
In one preferred practice of the invention, sulfates of Group IIA metals, and in particular MgSO4, CaSO4 and BaSO~, are prepared in appropriate particulate form such as by crushing or grinding solid metal sulfate and separating particles of desired size which comprise essentially pure metal sulfate.
In another preferred praatice of the invention we find that the desixed result is achieved by combining about 1 to 60 percent by weight MgS04 with an alumina -8a-:.
substrate which has a surface area of from about 45 to 450 m2/g.
In still another preferred embodiment finely divided MgS04 is combined with suitable binders and/or supports such as alumina sol, silica sol, silica-alumina sol, alumina gel, silica gel, silica-alumina gel, and clays in natural or chemically and/or thermally modified form and formed into particles of desired shape and sizeO
Alumina substrates are preferred and are available from many commercial sources, and comprise the alumina h~drates, such as alpha alumina monohydrate, alpha ~lumina trihydrate, beta alumina monohydrate and beta alumina trihydrate. Also considered most suitable are the calcined versions o~ the above alumina hydrates.
These include gamma alumina, chi alumina, eta alumina, kappa alumina, delta alumina, theta alumina, alpha alumina and mixtures thereof.
We have found that MgS04 is particularly very effective in reducing SX emissions from cat-crackiny units. The MgS04 can be used by itself, or it can be supported on a carrier. Any carrier can be used.
And that carrier can be loaded with as much MgS04 as it will take. An example of such a carrier is aluminum oxide. The MgS04 can also be intimately mixed with another material or materials to form discreet particles. An example ls a spray-dried product of MgS04 and A1203.
The active material is the MgS0~. The use of a carrier for the MgS04 merely facilitates the use of the MgS04 for reducing SX emissions. MgS04 by itself, or in combination with a carrier, can be used directly as an additive, i.e., physically mixed with the cracking catalyst. It can also be incorporated on 3æ~
or within the cracking catalyst particle. MgSO~ when used by itself, can be added as MgS04.7H20, the usual commercial form of MgS040 We have also found that MgS04 by itself~ and combinations of MgS04 and A1203, are superior to MgO and combinations of MgO
and A1203, in reducing Sx emissions. We have tested samples of MgO obtained from different sources, and nor.e .s as good as MgS04.
A possible explanation for the superiority of stable metal sulfates is that, in a cat-cracking unit, some of the original sulfur is removed from the surface of the metal sulfate. This leaves sites expressly tailored to accept Sx molecules. This can be seen as a memory effect. These sites will accept (capture) Sx molecules in the regenerator of the cat-cracking unit, and release them, as H2S, in the reactor-stripper of the unit. After releasing the Sx molecules, as H2S, the sites are now free to again accept (capture) Sx molecules in the regenerator and release them in the reactor-stripper.
These sites will then continue to repeat the cycle, i.e., accept ~capture) Sx molecules in the regenerator, and release them, as H2S, in the reactor-stripper.
The fact that MgS04 is more effective than MgO
means that the sites formed on the surface of the MgS04 differ from the sites present on MgO.
An additional novel feature of this invention is that all sulfate compounds, stable at regenerator 30 temperatures of 1150-1550F, would appear to be effective in some degree in reducing Sx emissions, However, we have found that M~S04 is far more effective than closely related compounds such as CaS04 and BaS04 which never-the-less may be used separately or combined with MgSO4 if desired. This also applies to all combinations of stable metal sulfate compounds with any other material or materials.
Although intended for use in FCC units, the materials of this invention can be used to reduce Sx emissions from any operation. An example would be the reduction of Sx emissions from the flue gas of coal-burning units. In this case, the materials, after capturing SOx, would be rejuvenated by introducing a reducing gas or a reducing gas and steam. The H2S
produced would be absorbed using conventional techniques.
As indicated above, we have found that MgSO4 with carriers are very effective in reducing Sx emissions from cat-cracker regenerators. This is not limited to MgSO4 but would apply to all stable sulfate compounds and to all combinations of sulfate compounds with MgSO~. The amount of sulfate compound which could be used to reduce Sx emissions from an FCC unit could 20 range from 0.001% to 50% by weight of the unit cracking catalyst inventory.
To prepare our novel Sx gettering agent, a solid form of the stable metal sulfate may be crushed, sized and dried to obtain a particulate composition which comprises essentially 100 percent metal sulfate.
Alternatively, an alumina substrate is admixed with a ~uantity of metal sulfate salt solution which will provide the desired amount of sulfate on the surface.
Typically, MgSO4.7H2O is dissolved in water to provide a desired volume of solution which has the desired concentration of the salt. The alumina substrate is then impregnated with the salt solution to give the desired amount of MgSO4 on the alumina. The impregnated alumina is then dried at a temperature of 250F to 1250F. While it is contemplated that calcination temperatures of up to about 1500F may be used, calcination temperatures on the order of 1000F
have been found to be satisfactory or calcination may be omitted.
In one preferred embodiment of the invention, the alumina substrate to be impregnated is in the form of microspheroidal particles, with about 90 percent of the particles having diameters in the 20 to 149 micron fluidizable size range. The gettering agent prepared using these microspheroidal 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 impreganted is in the form of particles which have an average particle size of less than 20 microns in diameter, 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.
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 Sx 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 incorporated in the catalyst particle during its preparation. Additionally, the gettering agent may be used by itself to reduce Sx emissions from a variety of processes.
Cracking catalysts which may be advantageously combined with the Sx gettering agent of the present inventlon are commercially available compositions and typically comprise crystalline zeolites admixed with inorganic ~xide 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 optiGnally from about 10 ~o 80 percent by weight clay. zeolites typically used in the preparation of cracking catalysts are stabilized type Y
zeolites, i.e. Ultrastable (US) and calcined rare earth exchanged zeolite (CREY), 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 Sx gettering agent is combined with a cracking catalyst which comprises an alumina sol, i.e. aluminum chlorhydroxide solution, bound zeolite/clay composition as disclosed in Canadian Patent 967,136 admixed with a particulate platinum containing oxidation catalyst to obtain a composition which comprises 0.5 to 60 percent by weight gettering agent, 40 to 99 percent by weight cracking catalyst, and 1 to 5 parts per million platinum.
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In still another preferred practice of the invention, the Sx 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 al~min~ hydrate (dry basis~, and 5 to 40 weight percent aluminum chlorhydroxide sol (A12O3), and water.
The mixture was spray-dried to obtain a finely divided catalyst composite and then calcined at a temperature of about 1000Fo The Sx gettering agent may be included as a component in the spray dried slurry in lieu of some of the alumina hydrate or the Sx gettering agent may be physically blended with the catalyst in the amount of about 0.1 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 qettering 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 Sx gettering agent may be used in a fluidized coal combùsLL~l~ process to remove Sx formed during burning of the coal. The Sx gettering agent may then be removed from the combustion/reaction zone peri^d -~'ly or continuously to restore 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 H2O. Using this techni~ue, the Sx 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 techni~ues.
To determine the Sx sorbtion/desorbtion effectiveness of the FCC compositions of the present invention, the compositions were steam-deactivated at 1350~F, 100% steam, 15 psig, for 8 hours. After steam deactivation, the blends were tested in the Sx Index Test described as follows.
In a lab-scale test unit, a low sulfur gas oil was cracked over the catalyst or catalyst mixture at a temperature of 980F. The catalyst or catalyst mixture was then steam-stripped at 980F. Regeneration of the catalyst or catalyst mixture, i.e., the coke-burning regenerator step, was carried out with air at temperatures ranging from 1250F to 1450F. The air used for the coke-burning step contained 2000 ppm SO2. This is equivalent to the amount of SO2 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 H2S, the Sx captured in the regenerator. The regeneration and the cracking and steam-stripping steps were repeated. During this second cycle, a portion of the catalyst or catalyst mixture ~as removed after the regeneration step, and another portion of the catalyst or catalyst mixture was removed after the cracking and steam-stripping steps.
An Sx Index which gives a measure of the Sx captured in the regenerator and released in the reactor and stripper was defined as / t. % sulfur \ ~t. ~ sulfur 5 I content of the~ content of the I catalyst or ~ catalyst or Sx Index = catalyst _ catalyst mixture x 1000 mixture after after the cracking the re- and steam-_ ~step. j ~tripping steps.
The Sx Index Test measures the ability of a catalyst or catalyst mixture to reduce Sx emissions from a cat-cracker regenerator. The result is expressed as an Sx Index, with a range of 0 to 115.
An Sx Index of 0 means that the sample does not reduce Sx emissions. An Sx index of 115 means essentially 100% reduction of Sx emissions.
Generally, Sx indices of 91 to 115 are expressed as ~above 90~. Specifically, the Sx Index measures the amount of Sx captured in a catalytic cracking regenerator and released in the reactor and stripper.
Having described the basic aspects of our invention, the ~ollowing examples are given to illustrate specific embodiments thereof.
Example 1 A commercial alpha-alumina monohydrate, which has a particle size in the fluidizable range, was screened to obtain the 38-180 micron size (diameter) fractionO
This fraction amounted to 85 percent of the total sample. The 38-180 micron particle size fraction was calcined, in air, for 15 minutes at 900F and for 1 hour at 1250F.
Exam~le 2 Reagent grade magnesium sulfate heptahydrate, MgSO4.7H2O, was calcined in air for 30 minutes at 1250F. The calcined material was crushed to give particles in the 45 to 250 micron range. The composition of the final product was 100% MgSO4. The product is referred to as an additive.
Example 3 27.0 g of the calcined alumina (A12O3) of Example 1 was impregnated with 12 ml of an aqueous solution of MgSO4.7H2O which contained 3.0 g of MgSO4. The impregnated A12O3 was then calcined for 30 minutes at 1250F. The composition of the resultant ~MgSO4 on A12O3~ product was 10%
MgSO4-90~ A1~03. This product will be referred to as an additive comprising 10~ MgSO4 on A12O3.
Example 4 22.5 g of the calcined A12O3 of Example 1 was given a double impregnation. The first impregnation was with 11 ml of an aqueous solution of MgSO~.7H2O
which contained 3O75 g of MgSO4. After this first impregnation, the sample was dried for 1 hour at 250F
in a forced-draft oven. After cooling to room temperature, the sample was given a second impregnation with 11 ml of an aqueous solution of Mg504.7H2O
which contained 3~75 g of MgSO4. Following the second impregnation, the sample was dried for 1 hour at 250F in a forced-draft oven. The composition of the resultant ~MgSO4 on A12O3~ product was 25%
MgSO4-75% A12O3. This product will be referred to as an additive comprising 25% MgSO4 on A12O3.
Example 5 The procedure of Example 4 was repeated except that, after each impregnation, the sample was dried for 1 hour at ~00F in a forced-draft oven.
Example 6 The procedure of Example 4 was repeated except that, after each impregnation, the sample was dried for 1 hour at 575F in a forced-draft oven.
Example 7 The procedure of Example 4 was repeated except that, after each impregnationl the sample was calcined in air for 30 minutes at 1000F.
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Example 8 The procedure of Example 4 was repeated except that, after each impregnation, the sample was calcined in air for 30 minutes at 1100F.
Example 9 The procedure of Example 4 was repeated except that, after each impregnation, the sample was calcined in air for 30 minutes at 1250F.
Example 10 19.5 g of the calcined A12o3 of Example 1 was given a triple impregnation. The first impregnation was with 10 ml of an aqueous solution of MgSO4.7H2O
which contained 3.50 g of MgSO4. After this first impregnation, the sample was calcined in air for 30 minutes at 1250F. After cooling to room temperature, the sample was given a second impregnation and calcination similar to the first one. Again, a~ter cooling to room temperature, the sample was given a third impregnation and calcination similar to the first one. The composition of the resultant "~gSO4 on A12O3" product was 35% MgSO4-65~ A12O3. This product was called an additive. It will be referred to g 4 2 3-Example 11 An aqueous solution was prepared ~hich contained MgSO4 and aluminum chlorhydroxide, the latter component having the approximate formula A12(OH)5Cl. The concentrations of the two components were set to give a MgSO4 to A12O3 ratio of 1 to 19. This solution was spray-dried to give a solid microspheroidal product. This spray-dried product was calcined in air for 1 hour at 1250F. The composition of the final product was essentially 5%
MgSO~-95% A12O3 This product will be referred to as an additive comprising 5% MgSO4-95% A12o3.
Example 12 An aqueous solution was prepared which contained MgSC4 and aluminum chlorohydroxide~ the latter component having the approximate formula A12(OH!5Cl. The concentrations of the two components were set to give a MgSO4 to A12O3 ratio of 1 to 9. This solution was spray-dried to give a solid microspheroidal product. This spray-dried product was calcined in air for 1 hour at 1250F. The composition of the final product was essentially 10%
MgSO4-90% A12O3. This product will be referred to as an additive comprising 10% MgSO4-90% A12O3.
Example 13 29.25 g of the calcined A12O3 of Example 1 was given a double impregnation. The first impregnation was with 10 ml of an aqueous solution of Mg(NO3)2.6H2O which contained 0.75 9 of magnesium, expressed as MgO. After this first impregnation, the sample was calcined for 30 minutes at 1000F. After cooling to room temperature, the sample was given a second impregnation with 10 ml of an aqueous solution of Mg(NO3)2~6H2O which contained 0.75 y o~ magnesium, expressed as MgO. Following the second impregnation the sample was calcined in air for 30 minutes at 1000F. The composition of the resultant 30 ~MgC on A12O3a product was 4.9~ MgO-95.1%
A1~03. This product will be referred to as an additive comprising 4.9% MgO, ex nitrate, on A12O3.
Exam~le 14 L
27.0 g of the calcined Al2O3 of Example l was given a triple impregnation. The first impregnation was with ll ml of an aqueous solution of Mg(NO3)2.6H2O which contained 1.0 g of magnesium, expressed as MgO. After this first impregnation, the sample was calcined in air for 30 minutes at 1000F.
After cooling to room temperature, the sample was given a second impregnation with ll ml of an aqueous solution of Mg(NO3)2.6H2O which contained 1.0 g of magnesium, expressed as MgOO After this second impregnation, the sample was calcined in air for 30 minutes at 10D0F. After cooling to room temperature, the sample was given a third impregnation with ll ml of an aqueous solution of Mg(NO3)2.6H2O which contained 1.0 g of magnesium, expressed as MgO. After this third impregnation, the sample was calcined in air for 30 minutes at 1000F. The composition of the resultant ~MgO on Al2O3~ was 10~ MgO-90~
A12O3. This product will be referred to as an additive comprising MgO, ex nitrate, on Al2O3.
Example 15 27.0 g of the calcined Al2O3 of Example 1 was given a double impregnation. The first impregnation was with 13 ml of an aqueous solution of MgCl2.6H2O
which contained 1.5 g of magnesium, e~pressed as MgO.
After this first impregnation, the sample was calcined for 30 minutes at 1250F. After cooling to room temperature, the sample was given a second impregnation with 13 ml of an aqueous solution MgCl2.6H2O which contained 1.5 g of magnesium, expressed as MgO. After this second impregnation, the sample was calcined for 3a minutes at 1250F. The composition of the resultant "MgO on A12O3~ prodùct was 10% MgO 90% A12O3.
This product will be referred to as an additive comprising 10~ MgO, ex chloride, on A12O3.
Example 16 24.0 g of the calcined A12O3 of Example 1 was given a triple impregnation. The first impregnation was wlth 11 ml of an aqueous solution of MgC12.6H2O
which contained 2.0 g of magnesium, expressed as MgO.
The impregnated sample was calcined for 30 minutes at 1250F. After cooling to room temperature, the sample was given a second impregnation and calcination similar to the first onè~ After cooling to room temperature, the sample was given a third impregnation and calcination similar to the first one. The composition of the resultant ~MgO on A12O3~ product was 20%
MgO-80~ A12O3. This product will be referred to as an additive comprising 20% MgO, ex chloride, on A12O3.
A commercial product called Magchem 40 was obtained which comprised a high purity technical grade of magnesium oxide processed from magnesium-rich brine.
Its typical composition is given as 98.0% MgO, 0.8%
CaO, 0.30% SiO2, 0.20% Fe2O3, 0.35% other oxides, 0.40% Cl. For purpose of the present examples, this material will be referred to as an additive comprising Magchem 40, 98~ MgO.
Example 18 A sample of reagent geade CaSO4.2H2O, was heat-treated for 1 hour at 1500F. It lost 21.53~ of its weight. The 21.53% weight loss means that 1.274 g of CaSO4.2H2O are equivalent to 1.000 g of CaSO4. CaSO4.2H2O was used as an additive, expressed as CaSO4. It will be referred to as 100%
CaSO4.2H2o as CaSO4.
5Example 18-2 A sample of reagent grade BaSO4 was used as an additive. It will be referred to as 100% BaSO4.
Exam~le 19 DA-250, a commercial cracking catalyst, was blended with CP-3 Combustion PromoterTM (both manufactured by the Davison Chemical Division of W. R. Grace & Co.), to give the blend composition listed as Item A in Table I.
The calcined A12O3 of Example 1 and the additives of Examples 2 through 4, and 9 through 18-2, were separately blended with DA-250 and CP-3 to give the blend compositions listed as Items B through R in Table I, and as Items A through D in Table I~.
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Example 20 The blends listed in Tables I and II were steam-deactivated at 13~0F, 100% steam, 15 psig, for 8 hours.
After steam deactivation, the blends were tested in the Sx Index Test, at a regenerator temperature of 1250F, to determine the Sx Index of each blend.
~ x Indices for the blends listed in Tables I
and II are also included in Tables I and II~
Item A of Table I shows that a blend, without an additive, has an SO~ Index of 10. Item C of Table I
shows that a blend containing 1.25% of the Additive of Example 2 (100% MgSO4) has an Sx Index of 49.
Item C-2 of Table I shows that a blend containing 2% of the Additive of Example 2 (100% MgSO4) has an Sx Index of greater than 90. This shows that MgSO4 is effective in reducing Sx emissions. It also shows that increasing the concentration of MgSO4 in the blend increases the Sx Index and hence the ability to reduce Sx emissions.
Tl~ ~ of Table I shows that a blend containing 5%
of th~ ~Aitive of Example 9 (25% MgSO4 on A12O3) has an Sx Index of 48. When compared to Item C of Table I, this shows that MgSO4 on A12O3 is also effective in reduciny Sx emissions. In this comparison, the amount of MgSO4 in the blends is the same in bvth cases, namely, 1.25% MgSO4.
Item B to Table I shows that a blend containing 10%
A12~3 o~ Example 1 (100% A12O3) has an Sx Index of 18. Item G of Table I shows that a blend containing 10% of the Additive of Example 3 (10%
MgSO4 ~n ~i2O3) has a Davison Sx Index o~ 58.
This shows that the presence of MgSO4 on the A12O3 gives an additive that is more effective, in reducing Sx emissions, than A1203 without the added MgS04.
Item E of Table I shows that a blend containing 5%
of the Additive of Example 9 (25% MgS04 on A1203) has an Sx Index of 48. Item F of Table I shows that a blend containing 5~ of the Additive of Example 10 (35% MgS04 on A1203) has a Index of 70. This shows that increasing the ~oncentration of MgS04 on the A1203 from 25~ MgS04 to 35% MgS04 increases the Sx Index and hence the ability to reduce Sx emissions.
Item G of Table I shows that a blend containing 10%
of the Additive of Example 3 (10% MgS04 on A1203) has an Sx Index of 58. Item H of Table I shows that a blend containing 10% of the Additive of Example 9 (~5% MgS04 on A1203) has an Sx Index of greater than 90. This shows that increasing the concentration of MgS04 on the A1203 from 10%
MgS04 to 25% MgS04 increases the Sx Index and hence the ability to reduce Sx emissions.
In concert, Items D through I of Table I, show that increasing the MgS04 concentration on the A1203 from 10% MgS04 to 35% MgS04 increases the Sx Index and hence the ability to reduce Sx emissions.
Item E of Table I shows that 5% of the Additive of Example 9 (25% MgS04 on A1203) has an Sx Index of 4~. Item H of Table I shows that 10% of the Additive of Example 9 (25% MgS04 on A1203) has a Sx Index of greater than 90. This shows that increasing the concentration of the Additive in the blend increases the Sx Index and hence the ability to reduce Sx emissions.
~ tem K of Table I shows that a blend containing 10%
of the Additive of Example 12 (10~ MgSO4-90%
A12O3) has an Sx Index of 58. This additive was prepared by spray drying an aqueous solution of MgSO4 and aluminum chlorhydroxide, followed by a calcination. I~ has the same Sx Index as the Additive of Example 3 (10% MgSO4 on A12O3) (Item G cf ~able I)~ which was prepared by impreg~ation of A12O3 with MgSO4, followed by a calcination.
This shows that a spray-dried solid product of MgSO4 and A12O3 has the same effectiveness as MgSO4 on A12O3.
Item J of Table I shows that a blend containing 10%
of the Additive of Example 11 (5% MgSO4-95~
15 A12O3) has an Sx Index of 38. This compares with an Sx Index of 58 for a blend containing 10% of the Additive of Example 12 (10% MgSO4-90% A12O3) (Item K of Table I). This shows that increasing the concentration of MgSO4, in a spray-dried solid product of MgSO4 and A12O3, increases the Sx Index, and hence the ability to reduce Sx emissions.
Item L of Table I shows that a blend containing 10%
of the Additive of Example 13 (4.9% MgO, ex-nitrate, on A12O3) has an Sx Index of 26. This compares with an Sx Index of 38 for a blend containing 10% of the Additive of Example II (5% MgSO~-95% A12O3) (Item J of Table I). This shows that MgSO4, in a spray-dried solid product of MgSO4 and A12O3, is more effective than MgO on A12O3, in reducing Sx emissions.
ltem M of Table I shows that a blend containing 10%
of the Additive of Example 14 (10~ MgO, ex-nitrate on A12O3) has an Sx Index of 36~ Item N of Table I
shows that a blend containing 10% of the Additive of Example 15 (10% MgO, ex-chloride, on Al2O3) has an Sx Index of 37. This shows that MgO's, from two different sources, on A12O3, have similar Sx Indices. These indices compare with an Sx Index of 58 for a blend containing 10% of the Additive of Example 3 (10% MgSO4 on A12O3) (Item G of Table I). They also compare with a Sx Index of 58 for a blend containing 10% of the Additive of Example 12 (10%
MgSO4-90% A12O3) (Item K of Table I). These comparisons show that combina~ions of MgSO4 and A12O3 are more effective than combinations of MgO
and A12O3 in reducing Sx emissions.
Item O of Table I shows that a blend containing 10%
of the Additive of Example 16 (20% MgO, ex-chloride, on A12O3) has an Sx Index of 29. Compared to Items M and N of Table I, this shows that an increase in the concentration of MgO, from 10% to 20~, causes a decrease in the Sx Index. This contrasts with MgSO~, where an increase in MgS04 concentration from 10~ to 25% and 35%, caused an increase in the Sx Index (Items D through I of Table I).
Item P of Table I shows that a blend containing 10%
of the Additive of Example 17 (Magchem 40, 98% MgO) has an Sx Index of zero. This compares with an Sx Index of 49 for a blend containing 1.25% of the Additive of Example 2 (100% MgSO4) (Item C of Table I). This shows that pure MgSO4 is effective in reducing Sx emissions, while pure MgO is not effective.
In this example (Example 20), we have compared MgSo4 with MgO on a same percentage basis, e.g., 10 MgSO4 on A12O3 was compared with 10% MgO on A12O3. It should be pointed out the MgSO4 contains less magnesiurn than MgO. For example, 10%
MgSO4 is equivalent to 3.3% MgO, when expressed as MgO. Therefore, in all comparisons, the superiority of MgSo4 would have been even greater if the comparisons had been made on an equivalent magnesium basis.
Item A of Table II shows that a blend containing 5%
of the Additive of Example 4 (25~ MgSO4 on Al2O3), which was prepared by drying at 250F after each of the two impregnations, has an Sx Index of 49. Item B of Table II shows that a blend containing 10 5% of the ~dditive of Example 9 (25% MgSO4 on A12O3), which was prepared by calcination at 1250F
after each of the two impregnations, has an Sx Index of 48. This shows that the effectiveness of the Additive is independent of the drying/calcination temperature used after each of the two impregnations.
Similarly, items C and D of Table II show the same thing for additive concentrations of 10% in the blend.
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Example 21 A blend composition similar to Item H of Table I, namely 10% Additive of Example 9 (25~ MgSO4 on A12O3), 89.63% DA-250 and 0.37~ CP-3, was steam deactivated at 1350F, 100% steam, 15 psig, for 8 hours. This steam-deactivated blend had an SO~ Index of greater than 90. This blend was charged to a cyclic flxed ~luid-bed pilot cracking unit. In this unit, the blend was aged by subjecting it to 20 cycles of gas oil cracking followed by steam-stripping and then regeneration of the cracking catalyst by burning-off the coke deposit with air. The pilot unit aging conditions were:
Reactor Temp. = 950F
Regenerator Temp. = 1250F
Gas Oil Feed ~= Sohio Heavy Gas Oil WHSV = 40 C/O = 2.5 Af~Pr 20 cycles of aging, the blend was discharged from the Pilot unit and tested for Sx capability in our laboratory Sx test. The discharged, aged blend gave an Sx Index of greater than 90, the same as was obtained for the blend before aging. This shows that the Ad~itive of Example 9 (25% ~gSO4 on A12O3) is stable to repeated cracking-regeneration cycles.
~5~
Example 22 The three blends listed in Table III were steam-deactivated at 1500F, lO0~ steam, 0 psig, for 5 hours in a fluid bed. The cracking activities of the three steam-deactivated blends were determined in the standard Micro-Activity Test. The results, given in Table III, show that the presence of 10% of the Additive of Example 4 (25% MgSO4 on Al2O3) (dried at 250F), and 10% of the Additive of Example 9 (25%
MgS04 on A12O3) (calcined at 1250~F), do not affect the activity of the cracking catalyst for cracking gas oil. These additives also do not affect the gas and coke selectivities as shown by the Gas and Carbon Factors in Table III.
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~rt tn 7¢ tn ta ta ros~ o tn o Example 23 Item A of Table I shows that a blend, which does not contain any additive, has an Sx Index of 10.
Item Q of Table I shows that a blend which contains 2%
o~ the Additive of Example 18 (100~ CaSO~-2H2O as CaSO4) has an Sx Index of 17. This shows that CaSO4 is effective in reducing Sx emissions.
Example 24 Item A of Table I shows that a blend, which does not contain any additive, has an Sx Index of 10.
Item R of Table I shows that a blend which contains 2%
of the Additive of Example 18-2 (100% BaSO4) has an Sx Index of 17. This shows that BaSO4 is effective in reducing Sx emissions.
ExamPle 25 Item H of Table I shows that a blend containing 10%
of the additive of Example 9 (25% MgSO4 on A12O3) has an Sx Index of greater than 90. The actual Sx Index, in this case, was 112. This was at a regenerator temperature of 1250F.
Sx Indices for this blend were also determined at regenerator temperatures of 1350F and 1450F. The results, given in Table IV, show that the Sx Index decreases with increasing regenerator temperature.
~5~6~
TABLE IV
Re~enerator Temperature (F)SOx Index The above examples clearly indicate that effective, economical Sx control agents may be obtained using the teaching of our invention.
More specifically, the invention contemplates the preparation and use of catalytic cracking catalysts which are capable of reducing the amount of sulfur oxides (SOx~ emitted to the atmosphere during regeneration of the catalyst, and to highly efficient Sx control agents which may be used to control Sx 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 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 water. The sulfur in the coke is converted to oxides of sulfur, SO2 and SO3, i.e. sOx.
Generally, the greater the amount of sulfur in the feedstock, the greater the amount of sulfur in the coke. Likewise, the greater the amount o~ sulfur in the coke, the greater the amount of sul~ur oxides in the flue gas exiting from the regenerator. In general, the amount of SO2 and SO3, i.e. SOx, in the flue gas amounts to about 250 to 2,500 parts per million by volume.
The prior art has suggested various methods for ~emovin~ o~ preventing the libe~ation o~ Sx to the atmosphere during oxidative combustion of sulfur containing fuels/residues. Typically, FCC/combustion units have been equipped with conventional scrubbers in which the Sx components are removed from flue gas by absorption/reaction with gettering agents (sometimes referred to as ~Sx acceptorsa) such as magnesium and/or calcium oxide. In some instances, 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 CO2 in the catalyst bed during the coke-burning step in the regenerator. The oxidation of CO to CO2 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 CO2 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 CO2 in the catalyst regenerator bed derives from the heat released when the CO is oxidized to CO2~ This heat raises the catalyst bed temperature and thereby increases the coke-burning rate. This gives a lo~er residual carbon level on regenerated catal~st (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 economic reasons, ~x gettering agents for use in FCC units must be compatible and effective in the presence of oxidation catalysts. Furthermore, Sx gettering agents for use in FCC units must be effective under the actual conditions seen in FCC units, such as ~emperatures of 800-1050F and catalyst residence times of 3 to 15 seconds in the reducing atmosphere of the reactor, temperatures of 800-1050F in the steam atmosphere of the stripper, temperatures of 1150-1550F
and catalyst residence times of 5 to 15 minutes in the oxidizing atmosphere of the regenerator. Additionally, Sx 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 CO2.
The following patents disclose the use of cracking catalysts which contain various sulfur and carbon monoxide emission control ayents.
U.S. 3,542,670 3,699,037 3,~35,031 4,071,436 4,115,249 4,115,250 4,115,251 4,137,151 4,146,463 4,151,119 ~6 4,152,298 4,153,535 4,166,787 4,182,693 4,187,199 4,200,520 4,206,039 4,20~,085 4,221,~77 4,238,317 4,240,899 4,267,072 4,300,997 4,325,811 4,369,108 4,369,130 4,376,103 4,376,696 Canadian 1,110,5~7 As shown in the above noted references, organic sulfur present during regeneration of the cracking catalyst is ultimately oxidized to sulfur trioxide ~SO3) 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, 33 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 stripper, the sulfate is reduced and hydrolyzed to form hydrogen sulfide (H2S) and restore or regenerate the gettering agent.
The hydrogen sulfide is recovered as a component of the cracked product stream, The gettering agent is recycled 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.
Howeverl it has been found that attempts to produce sox-control cracking catalysts which can consistently achieve significant sulfur oxide emission reduction at reasonable cost over long periods of time have in general been unsuccessful.
Accordingly, it is an object of the present invention to provide cracking catalyst compositions which effectively and economically reduces the emission of sulfur oxides from FCC units.
It is another object to provide sulfur oxide gettering agents which are capable of removing sulfur oxides over a long period of time when subjected to multiple gettering/regeneration cycles.
It is a further object to provide Sx control additives which may be added to the catalyst inventory of an FCC unit in amounts necessary to reduce sulfur oxide regenerator stack gas 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 Sx emissions from a variety of processes.
These and still further objects will become apparent to one skilled in the art from the following Z5564~
detailed description and specific examples.
The invention~ provides in a method for controlling Sx emissions which comprises:
(a) including in an oxidation reaction zone a sulfur oxide gettering agent which will combine with sulfur oxides in Eaid zone;
(b) regenerating the sulfur-containing gettering agent obtained in step (a) by reduction and/or hydrolysis in the presence of a reducing gas and/or steam; and (c) recycling the restored or regenerated sulfur oxide gettering agent to the reaction zone; the improvement comprising adding magnesium sulfate as said sulfur oxide gettering agent.
Broadly, our invention contemplates catalytic cracking catalyst compositions which include metal sulfates, such as magnesium sulfate, as Sx gettering agents. Furthermore, ourinvention contemplates an improved Sx gettering agent which preferably aomprises a particulate magnesium sulfate, or magnesium sulfate combined with an appropriate binder or support such as alumina. These gettering agents may be effectively combined with, or included in, particulate catalyst compositions used for the aatalytic cracking of hydrocarbons, or alternatively the gettering agents may be used in any combustion process which generates SOx componentes that are tobe selectively removed from the combustion products.
More specifically, we have found that a particularly effective Sx absorber/gettering agent composition suitable for use with catalytic cracking catalyst may be obtained by preparing a metal sulfate, which is stable at temperatures of up to about 1550F, such as magnesium sulfate, in suitable particulate form such as by combining a magnesium sulfate solution with a porous particulate alumina substrate.
In one preferred practice of the invention, sulfates of Group IIA metals, and in particular MgSO4, CaSO4 and BaSO~, are prepared in appropriate particulate form such as by crushing or grinding solid metal sulfate and separating particles of desired size which comprise essentially pure metal sulfate.
In another preferred praatice of the invention we find that the desixed result is achieved by combining about 1 to 60 percent by weight MgS04 with an alumina -8a-:.
substrate which has a surface area of from about 45 to 450 m2/g.
In still another preferred embodiment finely divided MgS04 is combined with suitable binders and/or supports such as alumina sol, silica sol, silica-alumina sol, alumina gel, silica gel, silica-alumina gel, and clays in natural or chemically and/or thermally modified form and formed into particles of desired shape and sizeO
Alumina substrates are preferred and are available from many commercial sources, and comprise the alumina h~drates, such as alpha alumina monohydrate, alpha ~lumina trihydrate, beta alumina monohydrate and beta alumina trihydrate. Also considered most suitable are the calcined versions o~ the above alumina hydrates.
These include gamma alumina, chi alumina, eta alumina, kappa alumina, delta alumina, theta alumina, alpha alumina and mixtures thereof.
We have found that MgS04 is particularly very effective in reducing SX emissions from cat-crackiny units. The MgS04 can be used by itself, or it can be supported on a carrier. Any carrier can be used.
And that carrier can be loaded with as much MgS04 as it will take. An example of such a carrier is aluminum oxide. The MgS04 can also be intimately mixed with another material or materials to form discreet particles. An example ls a spray-dried product of MgS04 and A1203.
The active material is the MgS0~. The use of a carrier for the MgS04 merely facilitates the use of the MgS04 for reducing SX emissions. MgS04 by itself, or in combination with a carrier, can be used directly as an additive, i.e., physically mixed with the cracking catalyst. It can also be incorporated on 3æ~
or within the cracking catalyst particle. MgSO~ when used by itself, can be added as MgS04.7H20, the usual commercial form of MgS040 We have also found that MgS04 by itself~ and combinations of MgS04 and A1203, are superior to MgO and combinations of MgO
and A1203, in reducing Sx emissions. We have tested samples of MgO obtained from different sources, and nor.e .s as good as MgS04.
A possible explanation for the superiority of stable metal sulfates is that, in a cat-cracking unit, some of the original sulfur is removed from the surface of the metal sulfate. This leaves sites expressly tailored to accept Sx molecules. This can be seen as a memory effect. These sites will accept (capture) Sx molecules in the regenerator of the cat-cracking unit, and release them, as H2S, in the reactor-stripper of the unit. After releasing the Sx molecules, as H2S, the sites are now free to again accept (capture) Sx molecules in the regenerator and release them in the reactor-stripper.
These sites will then continue to repeat the cycle, i.e., accept ~capture) Sx molecules in the regenerator, and release them, as H2S, in the reactor-stripper.
The fact that MgS04 is more effective than MgO
means that the sites formed on the surface of the MgS04 differ from the sites present on MgO.
An additional novel feature of this invention is that all sulfate compounds, stable at regenerator 30 temperatures of 1150-1550F, would appear to be effective in some degree in reducing Sx emissions, However, we have found that M~S04 is far more effective than closely related compounds such as CaS04 and BaS04 which never-the-less may be used separately or combined with MgSO4 if desired. This also applies to all combinations of stable metal sulfate compounds with any other material or materials.
Although intended for use in FCC units, the materials of this invention can be used to reduce Sx emissions from any operation. An example would be the reduction of Sx emissions from the flue gas of coal-burning units. In this case, the materials, after capturing SOx, would be rejuvenated by introducing a reducing gas or a reducing gas and steam. The H2S
produced would be absorbed using conventional techniques.
As indicated above, we have found that MgSO4 with carriers are very effective in reducing Sx emissions from cat-cracker regenerators. This is not limited to MgSO4 but would apply to all stable sulfate compounds and to all combinations of sulfate compounds with MgSO~. The amount of sulfate compound which could be used to reduce Sx emissions from an FCC unit could 20 range from 0.001% to 50% by weight of the unit cracking catalyst inventory.
To prepare our novel Sx gettering agent, a solid form of the stable metal sulfate may be crushed, sized and dried to obtain a particulate composition which comprises essentially 100 percent metal sulfate.
Alternatively, an alumina substrate is admixed with a ~uantity of metal sulfate salt solution which will provide the desired amount of sulfate on the surface.
Typically, MgSO4.7H2O is dissolved in water to provide a desired volume of solution which has the desired concentration of the salt. The alumina substrate is then impregnated with the salt solution to give the desired amount of MgSO4 on the alumina. The impregnated alumina is then dried at a temperature of 250F to 1250F. While it is contemplated that calcination temperatures of up to about 1500F may be used, calcination temperatures on the order of 1000F
have been found to be satisfactory or calcination may be omitted.
In one preferred embodiment of the invention, the alumina substrate to be impregnated is in the form of microspheroidal particles, with about 90 percent of the particles having diameters in the 20 to 149 micron fluidizable size range. The gettering agent prepared using these microspheroidal 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 impreganted is in the form of particles which have an average particle size of less than 20 microns in diameter, 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.
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 Sx 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 incorporated in the catalyst particle during its preparation. Additionally, the gettering agent may be used by itself to reduce Sx emissions from a variety of processes.
Cracking catalysts which may be advantageously combined with the Sx gettering agent of the present inventlon are commercially available compositions and typically comprise crystalline zeolites admixed with inorganic ~xide 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 optiGnally from about 10 ~o 80 percent by weight clay. zeolites typically used in the preparation of cracking catalysts are stabilized type Y
zeolites, i.e. Ultrastable (US) and calcined rare earth exchanged zeolite (CREY), 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 Sx gettering agent is combined with a cracking catalyst which comprises an alumina sol, i.e. aluminum chlorhydroxide solution, bound zeolite/clay composition as disclosed in Canadian Patent 967,136 admixed with a particulate platinum containing oxidation catalyst to obtain a composition which comprises 0.5 to 60 percent by weight gettering agent, 40 to 99 percent by weight cracking catalyst, and 1 to 5 parts per million platinum.
~13-~,5~
In still another preferred practice of the invention, the Sx 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 al~min~ hydrate (dry basis~, and 5 to 40 weight percent aluminum chlorhydroxide sol (A12O3), and water.
The mixture was spray-dried to obtain a finely divided catalyst composite and then calcined at a temperature of about 1000Fo The Sx gettering agent may be included as a component in the spray dried slurry in lieu of some of the alumina hydrate or the Sx gettering agent may be physically blended with the catalyst in the amount of about 0.1 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 qettering 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 Sx gettering agent may be used in a fluidized coal combùsLL~l~ process to remove Sx formed during burning of the coal. The Sx gettering agent may then be removed from the combustion/reaction zone peri^d -~'ly or continuously to restore 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 H2O. Using this techni~ue, the Sx 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 techni~ues.
To determine the Sx sorbtion/desorbtion effectiveness of the FCC compositions of the present invention, the compositions were steam-deactivated at 1350~F, 100% steam, 15 psig, for 8 hours. After steam deactivation, the blends were tested in the Sx Index Test described as follows.
In a lab-scale test unit, a low sulfur gas oil was cracked over the catalyst or catalyst mixture at a temperature of 980F. The catalyst or catalyst mixture was then steam-stripped at 980F. Regeneration of the catalyst or catalyst mixture, i.e., the coke-burning regenerator step, was carried out with air at temperatures ranging from 1250F to 1450F. The air used for the coke-burning step contained 2000 ppm SO2. This is equivalent to the amount of SO2 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 H2S, the Sx captured in the regenerator. The regeneration and the cracking and steam-stripping steps were repeated. During this second cycle, a portion of the catalyst or catalyst mixture ~as removed after the regeneration step, and another portion of the catalyst or catalyst mixture was removed after the cracking and steam-stripping steps.
An Sx Index which gives a measure of the Sx captured in the regenerator and released in the reactor and stripper was defined as / t. % sulfur \ ~t. ~ sulfur 5 I content of the~ content of the I catalyst or ~ catalyst or Sx Index = catalyst _ catalyst mixture x 1000 mixture after after the cracking the re- and steam-_ ~step. j ~tripping steps.
The Sx Index Test measures the ability of a catalyst or catalyst mixture to reduce Sx emissions from a cat-cracker regenerator. The result is expressed as an Sx Index, with a range of 0 to 115.
An Sx Index of 0 means that the sample does not reduce Sx emissions. An Sx index of 115 means essentially 100% reduction of Sx emissions.
Generally, Sx indices of 91 to 115 are expressed as ~above 90~. Specifically, the Sx Index measures the amount of Sx captured in a catalytic cracking regenerator and released in the reactor and stripper.
Having described the basic aspects of our invention, the ~ollowing examples are given to illustrate specific embodiments thereof.
Example 1 A commercial alpha-alumina monohydrate, which has a particle size in the fluidizable range, was screened to obtain the 38-180 micron size (diameter) fractionO
This fraction amounted to 85 percent of the total sample. The 38-180 micron particle size fraction was calcined, in air, for 15 minutes at 900F and for 1 hour at 1250F.
Exam~le 2 Reagent grade magnesium sulfate heptahydrate, MgSO4.7H2O, was calcined in air for 30 minutes at 1250F. The calcined material was crushed to give particles in the 45 to 250 micron range. The composition of the final product was 100% MgSO4. The product is referred to as an additive.
Example 3 27.0 g of the calcined alumina (A12O3) of Example 1 was impregnated with 12 ml of an aqueous solution of MgSO4.7H2O which contained 3.0 g of MgSO4. The impregnated A12O3 was then calcined for 30 minutes at 1250F. The composition of the resultant ~MgSO4 on A12O3~ product was 10%
MgSO4-90~ A1~03. This product will be referred to as an additive comprising 10~ MgSO4 on A12O3.
Example 4 22.5 g of the calcined A12O3 of Example 1 was given a double impregnation. The first impregnation was with 11 ml of an aqueous solution of MgSO~.7H2O
which contained 3O75 g of MgSO4. After this first impregnation, the sample was dried for 1 hour at 250F
in a forced-draft oven. After cooling to room temperature, the sample was given a second impregnation with 11 ml of an aqueous solution of Mg504.7H2O
which contained 3~75 g of MgSO4. Following the second impregnation, the sample was dried for 1 hour at 250F in a forced-draft oven. The composition of the resultant ~MgSO4 on A12O3~ product was 25%
MgSO4-75% A12O3. This product will be referred to as an additive comprising 25% MgSO4 on A12O3.
Example 5 The procedure of Example 4 was repeated except that, after each impregnation, the sample was dried for 1 hour at ~00F in a forced-draft oven.
Example 6 The procedure of Example 4 was repeated except that, after each impregnation, the sample was dried for 1 hour at 575F in a forced-draft oven.
Example 7 The procedure of Example 4 was repeated except that, after each impregnationl the sample was calcined in air for 30 minutes at 1000F.
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Example 8 The procedure of Example 4 was repeated except that, after each impregnation, the sample was calcined in air for 30 minutes at 1100F.
Example 9 The procedure of Example 4 was repeated except that, after each impregnation, the sample was calcined in air for 30 minutes at 1250F.
Example 10 19.5 g of the calcined A12o3 of Example 1 was given a triple impregnation. The first impregnation was with 10 ml of an aqueous solution of MgSO4.7H2O
which contained 3.50 g of MgSO4. After this first impregnation, the sample was calcined in air for 30 minutes at 1250F. After cooling to room temperature, the sample was given a second impregnation and calcination similar to the first one. Again, a~ter cooling to room temperature, the sample was given a third impregnation and calcination similar to the first one. The composition of the resultant "~gSO4 on A12O3" product was 35% MgSO4-65~ A12O3. This product was called an additive. It will be referred to g 4 2 3-Example 11 An aqueous solution was prepared ~hich contained MgSO4 and aluminum chlorhydroxide, the latter component having the approximate formula A12(OH)5Cl. The concentrations of the two components were set to give a MgSO4 to A12O3 ratio of 1 to 19. This solution was spray-dried to give a solid microspheroidal product. This spray-dried product was calcined in air for 1 hour at 1250F. The composition of the final product was essentially 5%
MgSO~-95% A12O3 This product will be referred to as an additive comprising 5% MgSO4-95% A12o3.
Example 12 An aqueous solution was prepared which contained MgSC4 and aluminum chlorohydroxide~ the latter component having the approximate formula A12(OH!5Cl. The concentrations of the two components were set to give a MgSO4 to A12O3 ratio of 1 to 9. This solution was spray-dried to give a solid microspheroidal product. This spray-dried product was calcined in air for 1 hour at 1250F. The composition of the final product was essentially 10%
MgSO4-90% A12O3. This product will be referred to as an additive comprising 10% MgSO4-90% A12O3.
Example 13 29.25 g of the calcined A12O3 of Example 1 was given a double impregnation. The first impregnation was with 10 ml of an aqueous solution of Mg(NO3)2.6H2O which contained 0.75 9 of magnesium, expressed as MgO. After this first impregnation, the sample was calcined for 30 minutes at 1000F. After cooling to room temperature, the sample was given a second impregnation with 10 ml of an aqueous solution of Mg(NO3)2~6H2O which contained 0.75 y o~ magnesium, expressed as MgO. Following the second impregnation the sample was calcined in air for 30 minutes at 1000F. The composition of the resultant 30 ~MgC on A12O3a product was 4.9~ MgO-95.1%
A1~03. This product will be referred to as an additive comprising 4.9% MgO, ex nitrate, on A12O3.
Exam~le 14 L
27.0 g of the calcined Al2O3 of Example l was given a triple impregnation. The first impregnation was with ll ml of an aqueous solution of Mg(NO3)2.6H2O which contained 1.0 g of magnesium, expressed as MgO. After this first impregnation, the sample was calcined in air for 30 minutes at 1000F.
After cooling to room temperature, the sample was given a second impregnation with ll ml of an aqueous solution of Mg(NO3)2.6H2O which contained 1.0 g of magnesium, expressed as MgOO After this second impregnation, the sample was calcined in air for 30 minutes at 10D0F. After cooling to room temperature, the sample was given a third impregnation with ll ml of an aqueous solution of Mg(NO3)2.6H2O which contained 1.0 g of magnesium, expressed as MgO. After this third impregnation, the sample was calcined in air for 30 minutes at 1000F. The composition of the resultant ~MgO on Al2O3~ was 10~ MgO-90~
A12O3. This product will be referred to as an additive comprising MgO, ex nitrate, on Al2O3.
Example 15 27.0 g of the calcined Al2O3 of Example 1 was given a double impregnation. The first impregnation was with 13 ml of an aqueous solution of MgCl2.6H2O
which contained 1.5 g of magnesium, e~pressed as MgO.
After this first impregnation, the sample was calcined for 30 minutes at 1250F. After cooling to room temperature, the sample was given a second impregnation with 13 ml of an aqueous solution MgCl2.6H2O which contained 1.5 g of magnesium, expressed as MgO. After this second impregnation, the sample was calcined for 3a minutes at 1250F. The composition of the resultant "MgO on A12O3~ prodùct was 10% MgO 90% A12O3.
This product will be referred to as an additive comprising 10~ MgO, ex chloride, on A12O3.
Example 16 24.0 g of the calcined A12O3 of Example 1 was given a triple impregnation. The first impregnation was wlth 11 ml of an aqueous solution of MgC12.6H2O
which contained 2.0 g of magnesium, expressed as MgO.
The impregnated sample was calcined for 30 minutes at 1250F. After cooling to room temperature, the sample was given a second impregnation and calcination similar to the first onè~ After cooling to room temperature, the sample was given a third impregnation and calcination similar to the first one. The composition of the resultant ~MgO on A12O3~ product was 20%
MgO-80~ A12O3. This product will be referred to as an additive comprising 20% MgO, ex chloride, on A12O3.
A commercial product called Magchem 40 was obtained which comprised a high purity technical grade of magnesium oxide processed from magnesium-rich brine.
Its typical composition is given as 98.0% MgO, 0.8%
CaO, 0.30% SiO2, 0.20% Fe2O3, 0.35% other oxides, 0.40% Cl. For purpose of the present examples, this material will be referred to as an additive comprising Magchem 40, 98~ MgO.
Example 18 A sample of reagent geade CaSO4.2H2O, was heat-treated for 1 hour at 1500F. It lost 21.53~ of its weight. The 21.53% weight loss means that 1.274 g of CaSO4.2H2O are equivalent to 1.000 g of CaSO4. CaSO4.2H2O was used as an additive, expressed as CaSO4. It will be referred to as 100%
CaSO4.2H2o as CaSO4.
5Example 18-2 A sample of reagent grade BaSO4 was used as an additive. It will be referred to as 100% BaSO4.
Exam~le 19 DA-250, a commercial cracking catalyst, was blended with CP-3 Combustion PromoterTM (both manufactured by the Davison Chemical Division of W. R. Grace & Co.), to give the blend composition listed as Item A in Table I.
The calcined A12O3 of Example 1 and the additives of Examples 2 through 4, and 9 through 18-2, were separately blended with DA-250 and CP-3 to give the blend compositions listed as Items B through R in Table I, and as Items A through D in Table I~.
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Example 20 The blends listed in Tables I and II were steam-deactivated at 13~0F, 100% steam, 15 psig, for 8 hours.
After steam deactivation, the blends were tested in the Sx Index Test, at a regenerator temperature of 1250F, to determine the Sx Index of each blend.
~ x Indices for the blends listed in Tables I
and II are also included in Tables I and II~
Item A of Table I shows that a blend, without an additive, has an SO~ Index of 10. Item C of Table I
shows that a blend containing 1.25% of the Additive of Example 2 (100% MgSO4) has an Sx Index of 49.
Item C-2 of Table I shows that a blend containing 2% of the Additive of Example 2 (100% MgSO4) has an Sx Index of greater than 90. This shows that MgSO4 is effective in reducing Sx emissions. It also shows that increasing the concentration of MgSO4 in the blend increases the Sx Index and hence the ability to reduce Sx emissions.
Tl~ ~ of Table I shows that a blend containing 5%
of th~ ~Aitive of Example 9 (25% MgSO4 on A12O3) has an Sx Index of 48. When compared to Item C of Table I, this shows that MgSO4 on A12O3 is also effective in reduciny Sx emissions. In this comparison, the amount of MgSO4 in the blends is the same in bvth cases, namely, 1.25% MgSO4.
Item B to Table I shows that a blend containing 10%
A12~3 o~ Example 1 (100% A12O3) has an Sx Index of 18. Item G of Table I shows that a blend containing 10% of the Additive of Example 3 (10%
MgSO4 ~n ~i2O3) has a Davison Sx Index o~ 58.
This shows that the presence of MgSO4 on the A12O3 gives an additive that is more effective, in reducing Sx emissions, than A1203 without the added MgS04.
Item E of Table I shows that a blend containing 5%
of the Additive of Example 9 (25% MgS04 on A1203) has an Sx Index of 48. Item F of Table I shows that a blend containing 5~ of the Additive of Example 10 (35% MgS04 on A1203) has a Index of 70. This shows that increasing the ~oncentration of MgS04 on the A1203 from 25~ MgS04 to 35% MgS04 increases the Sx Index and hence the ability to reduce Sx emissions.
Item G of Table I shows that a blend containing 10%
of the Additive of Example 3 (10% MgS04 on A1203) has an Sx Index of 58. Item H of Table I shows that a blend containing 10% of the Additive of Example 9 (~5% MgS04 on A1203) has an Sx Index of greater than 90. This shows that increasing the concentration of MgS04 on the A1203 from 10%
MgS04 to 25% MgS04 increases the Sx Index and hence the ability to reduce Sx emissions.
In concert, Items D through I of Table I, show that increasing the MgS04 concentration on the A1203 from 10% MgS04 to 35% MgS04 increases the Sx Index and hence the ability to reduce Sx emissions.
Item E of Table I shows that 5% of the Additive of Example 9 (25% MgS04 on A1203) has an Sx Index of 4~. Item H of Table I shows that 10% of the Additive of Example 9 (25% MgS04 on A1203) has a Sx Index of greater than 90. This shows that increasing the concentration of the Additive in the blend increases the Sx Index and hence the ability to reduce Sx emissions.
~ tem K of Table I shows that a blend containing 10%
of the Additive of Example 12 (10~ MgSO4-90%
A12O3) has an Sx Index of 58. This additive was prepared by spray drying an aqueous solution of MgSO4 and aluminum chlorhydroxide, followed by a calcination. I~ has the same Sx Index as the Additive of Example 3 (10% MgSO4 on A12O3) (Item G cf ~able I)~ which was prepared by impreg~ation of A12O3 with MgSO4, followed by a calcination.
This shows that a spray-dried solid product of MgSO4 and A12O3 has the same effectiveness as MgSO4 on A12O3.
Item J of Table I shows that a blend containing 10%
of the Additive of Example 11 (5% MgSO4-95~
15 A12O3) has an Sx Index of 38. This compares with an Sx Index of 58 for a blend containing 10% of the Additive of Example 12 (10% MgSO4-90% A12O3) (Item K of Table I). This shows that increasing the concentration of MgSO4, in a spray-dried solid product of MgSO4 and A12O3, increases the Sx Index, and hence the ability to reduce Sx emissions.
Item L of Table I shows that a blend containing 10%
of the Additive of Example 13 (4.9% MgO, ex-nitrate, on A12O3) has an Sx Index of 26. This compares with an Sx Index of 38 for a blend containing 10% of the Additive of Example II (5% MgSO~-95% A12O3) (Item J of Table I). This shows that MgSO4, in a spray-dried solid product of MgSO4 and A12O3, is more effective than MgO on A12O3, in reducing Sx emissions.
ltem M of Table I shows that a blend containing 10%
of the Additive of Example 14 (10~ MgO, ex-nitrate on A12O3) has an Sx Index of 36~ Item N of Table I
shows that a blend containing 10% of the Additive of Example 15 (10% MgO, ex-chloride, on Al2O3) has an Sx Index of 37. This shows that MgO's, from two different sources, on A12O3, have similar Sx Indices. These indices compare with an Sx Index of 58 for a blend containing 10% of the Additive of Example 3 (10% MgSO4 on A12O3) (Item G of Table I). They also compare with a Sx Index of 58 for a blend containing 10% of the Additive of Example 12 (10%
MgSO4-90% A12O3) (Item K of Table I). These comparisons show that combina~ions of MgSO4 and A12O3 are more effective than combinations of MgO
and A12O3 in reducing Sx emissions.
Item O of Table I shows that a blend containing 10%
of the Additive of Example 16 (20% MgO, ex-chloride, on A12O3) has an Sx Index of 29. Compared to Items M and N of Table I, this shows that an increase in the concentration of MgO, from 10% to 20~, causes a decrease in the Sx Index. This contrasts with MgSO~, where an increase in MgS04 concentration from 10~ to 25% and 35%, caused an increase in the Sx Index (Items D through I of Table I).
Item P of Table I shows that a blend containing 10%
of the Additive of Example 17 (Magchem 40, 98% MgO) has an Sx Index of zero. This compares with an Sx Index of 49 for a blend containing 1.25% of the Additive of Example 2 (100% MgSO4) (Item C of Table I). This shows that pure MgSO4 is effective in reducing Sx emissions, while pure MgO is not effective.
In this example (Example 20), we have compared MgSo4 with MgO on a same percentage basis, e.g., 10 MgSO4 on A12O3 was compared with 10% MgO on A12O3. It should be pointed out the MgSO4 contains less magnesiurn than MgO. For example, 10%
MgSO4 is equivalent to 3.3% MgO, when expressed as MgO. Therefore, in all comparisons, the superiority of MgSo4 would have been even greater if the comparisons had been made on an equivalent magnesium basis.
Item A of Table II shows that a blend containing 5%
of the Additive of Example 4 (25~ MgSO4 on Al2O3), which was prepared by drying at 250F after each of the two impregnations, has an Sx Index of 49. Item B of Table II shows that a blend containing 10 5% of the ~dditive of Example 9 (25% MgSO4 on A12O3), which was prepared by calcination at 1250F
after each of the two impregnations, has an Sx Index of 48. This shows that the effectiveness of the Additive is independent of the drying/calcination temperature used after each of the two impregnations.
Similarly, items C and D of Table II show the same thing for additive concentrations of 10% in the blend.
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Example 21 A blend composition similar to Item H of Table I, namely 10% Additive of Example 9 (25~ MgSO4 on A12O3), 89.63% DA-250 and 0.37~ CP-3, was steam deactivated at 1350F, 100% steam, 15 psig, for 8 hours. This steam-deactivated blend had an SO~ Index of greater than 90. This blend was charged to a cyclic flxed ~luid-bed pilot cracking unit. In this unit, the blend was aged by subjecting it to 20 cycles of gas oil cracking followed by steam-stripping and then regeneration of the cracking catalyst by burning-off the coke deposit with air. The pilot unit aging conditions were:
Reactor Temp. = 950F
Regenerator Temp. = 1250F
Gas Oil Feed ~= Sohio Heavy Gas Oil WHSV = 40 C/O = 2.5 Af~Pr 20 cycles of aging, the blend was discharged from the Pilot unit and tested for Sx capability in our laboratory Sx test. The discharged, aged blend gave an Sx Index of greater than 90, the same as was obtained for the blend before aging. This shows that the Ad~itive of Example 9 (25% ~gSO4 on A12O3) is stable to repeated cracking-regeneration cycles.
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Example 22 The three blends listed in Table III were steam-deactivated at 1500F, lO0~ steam, 0 psig, for 5 hours in a fluid bed. The cracking activities of the three steam-deactivated blends were determined in the standard Micro-Activity Test. The results, given in Table III, show that the presence of 10% of the Additive of Example 4 (25% MgSO4 on Al2O3) (dried at 250F), and 10% of the Additive of Example 9 (25%
MgS04 on A12O3) (calcined at 1250~F), do not affect the activity of the cracking catalyst for cracking gas oil. These additives also do not affect the gas and coke selectivities as shown by the Gas and Carbon Factors in Table III.
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~rt tn 7¢ tn ta ta ros~ o tn o Example 23 Item A of Table I shows that a blend, which does not contain any additive, has an Sx Index of 10.
Item Q of Table I shows that a blend which contains 2%
o~ the Additive of Example 18 (100~ CaSO~-2H2O as CaSO4) has an Sx Index of 17. This shows that CaSO4 is effective in reducing Sx emissions.
Example 24 Item A of Table I shows that a blend, which does not contain any additive, has an Sx Index of 10.
Item R of Table I shows that a blend which contains 2%
of the Additive of Example 18-2 (100% BaSO4) has an Sx Index of 17. This shows that BaSO4 is effective in reducing Sx emissions.
ExamPle 25 Item H of Table I shows that a blend containing 10%
of the additive of Example 9 (25% MgSO4 on A12O3) has an Sx Index of greater than 90. The actual Sx Index, in this case, was 112. This was at a regenerator temperature of 1250F.
Sx Indices for this blend were also determined at regenerator temperatures of 1350F and 1450F. The results, given in Table IV, show that the Sx Index decreases with increasing regenerator temperature.
~5~6~
TABLE IV
Re~enerator Temperature (F)SOx Index The above examples clearly indicate that effective, economical Sx control agents may be obtained using the teaching of our invention.
Claims (5)
1. In a method for controlling SOx emissions which comprises:
(a) including in an oxidation reaction zone a sulfur oxide gettering agent which will combine with sulfur oxides in said zone;
(b) regenerating the sulfur-containing gettering agent obtained in step (a) by reduction and/or hydrolysis in the presence of a reducing gas and/or steam; and (c) recycling the restored or regenerated sulfur oxide gettering agent to the reaction zone; the improvement comprising adding magnesium sulfate as said sulfur oxide gettering agent.
(a) including in an oxidation reaction zone a sulfur oxide gettering agent which will combine with sulfur oxides in said zone;
(b) regenerating the sulfur-containing gettering agent obtained in step (a) by reduction and/or hydrolysis in the presence of a reducing gas and/or steam; and (c) recycling the restored or regenerated sulfur oxide gettering agent to the reaction zone; the improvement comprising adding magnesium sulfate as said sulfur oxide gettering agent.
2. In a method for controlling SOx emissions during the cracking of hydrocarbon feedstocks which contain organic sulfur compounds comprising:
(a) reacting hydrocarbon feedstocks which contain organic sulfur compounds with a catalyst composition which comprises a catalytic cracking catalyst and a sulfur oxide gettering agent component under catalytic cracking conditions to obtain a cracked product stream and a catalyst composition combined with sulfur-containing coke;
(b) passing the catalyst composition to a steam stripping zone to remove the strippable hydrocarbons from the catalyst composition;
(c) passing the stripped catalyst composition to a regeneration zone wherein the sulfur-containing coke is oxidized to carbon monoxide, carbon dioxide, water, and sulfur oxides, and said sulfur oxides combine with the gettering agent component of said catalyst composition to form a solid compound; and (d) returning the regenerated catalyst composition obtained in step (c) to the reacting step (a) and steam-stripping step (b) wherein the sulfur oxide-containing gettering agent is reduced and hydrolyzed to produce volatile hydrogen sulfide which is recovered as a component of the cracked product stream and to restore or regenerate the gettering agent which is recycled in the process, the improvement comprising including magnesium sulfate as the sulfur oxide gettering agent component of said catalyst composition.
(a) reacting hydrocarbon feedstocks which contain organic sulfur compounds with a catalyst composition which comprises a catalytic cracking catalyst and a sulfur oxide gettering agent component under catalytic cracking conditions to obtain a cracked product stream and a catalyst composition combined with sulfur-containing coke;
(b) passing the catalyst composition to a steam stripping zone to remove the strippable hydrocarbons from the catalyst composition;
(c) passing the stripped catalyst composition to a regeneration zone wherein the sulfur-containing coke is oxidized to carbon monoxide, carbon dioxide, water, and sulfur oxides, and said sulfur oxides combine with the gettering agent component of said catalyst composition to form a solid compound; and (d) returning the regenerated catalyst composition obtained in step (c) to the reacting step (a) and steam-stripping step (b) wherein the sulfur oxide-containing gettering agent is reduced and hydrolyzed to produce volatile hydrogen sulfide which is recovered as a component of the cracked product stream and to restore or regenerate the gettering agent which is recycled in the process, the improvement comprising including magnesium sulfate as the sulfur oxide gettering agent component of said catalyst composition.
3. The method of claim 1 or 2 wherein an oxidation catalyst is combined with said gettering agent.
4. The method of claim 1 or 2 wherein said magnesium sulfate is combined with an alumina support.
5. The method of claim 2 wherein said gettering agent is added as a separate particulate component.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US64121184A | 1984-08-16 | 1984-08-16 | |
| US641,211 | 1991-01-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1255646A true CA1255646A (en) | 1989-06-13 |
Family
ID=24571409
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000485047A Expired CA1255646A (en) | 1984-08-16 | 1985-06-25 | Cracking catalyst/sulfur oxide gettering agent compositions |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS6154234A (en) |
| AU (1) | AU4614685A (en) |
| CA (1) | CA1255646A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0435539A1 (en) * | 1989-12-29 | 1991-07-03 | Chevron U.S.A. Inc. | Cracking catalyst having enhanced vanadium passivation and sulfur tolerance |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1326232C (en) * | 1987-08-13 | 1994-01-18 | Engelhard Corporation | Thermally stabilized catalysts containing alumina and methods of making the same |
| EP2808081A4 (en) | 2012-01-23 | 2015-08-26 | N E Chemcat Corp | Alumina material containing barium sulfate and exhaust gas purifying catalyst using same |
-
1985
- 1985-06-25 CA CA000485047A patent/CA1255646A/en not_active Expired
- 1985-08-12 JP JP60175961A patent/JPS6154234A/en active Pending
- 1985-08-13 AU AU46146/85A patent/AU4614685A/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0435539A1 (en) * | 1989-12-29 | 1991-07-03 | Chevron U.S.A. Inc. | Cracking catalyst having enhanced vanadium passivation and sulfur tolerance |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6154234A (en) | 1986-03-18 |
| AU4614685A (en) | 1986-02-20 |
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