CS245773B2 - Fluidizable solid cracking catalyst suitable for cracking hydrocarbon feeds containing organic sulfur compounds - Google Patents

Abstract

A fluidizable solid cracking catalyst suitable for cracking hydrocarbon feeds containing organic sulfur compounds in a fluidized bed consists of 30% by weight of a matrix consisting of at least two materials from the group consisting of silicon dioxide, aluminum oxide, thorium dioxide and boron oxide, preferably from 10 to 65% by weight of aluminum oxide and from 35 to 90% by weight of silicon dioxide, calculated on the weight of the matrix, and a crystalline aluminosilicate zeolite in an amount from 0.5 to 50% by weight, based on the weight of the matrix and the zeolite, and a particulate solid, different from the matrix and the zeolite, consisting of at least one sodium compound and at least one inorganic oxide from the group consisting of silicon dioxide and aluminum oxide, wherein the amount of sodium, calculated as metallic sodium, is up to 10% by weight, based on the catalyst as a whole, wherein the solid, different from the matrix and zeolite, is free of crystalline aluminosilicate zeolite.

Description

The invention relates to a catalyst for catalytic cracking and in particular for cyclic catalytic cracking in a fluidized phase. The catalyst is particularly suitable for sulfur-containing hydrocarbon mixtures and leads to a significant reduction in the circulation of carbon oxides and sulfur oxides in the waste gases from the regeneration plant.

The cracking catalyst, which is relatively rapidly deactivated during the cracking of hydrocarbons in the reaction zone by carbonaceous deposits, usually referred to as coke, is continuously discharged from the reaction zone. The spent catalyst is passed from the reaction zone to a stripping zone where the carbonaceous deposits are washed and separated from the catalyst, and the catalyst is then passed to a regeneration zone where the catalyst activity is restored by removing the remaining carbon deposits by burning the coke in a gas stream containing oxygen to produce carbon monoxide and carbon dioxide. The hot, regenerated catalyst is then continuously fed back into the reactor and the entire cycle is repeated.

When crude oil containing sulfur in the form of organic compounds is processed in a stirred catalyst cracking plant, the coke deposited on the catalyst contains sulfur. During the regeneration of catalyst particles deactivated by coke, the coke is burned on the catalyst surface and at the same time the sulfur is converted to sulfur dioxide together with a small proportion of sulfur trioxide and this mixture enters the gas discharged from the regeneration zone. When cracking a crude oil feed using the cracking catalyst according to the invention, the desired reduction in the release of sulfur oxides into the atmosphere is achieved, while the efficiency of the catalyst, its stability and resistance to abrasion under normal cracking conditions in existing or even new cracking plants are not changed.

Although the use of metals in cracking catalysts is generally avoided and it is considered problematic to crack a metal-containing feedstock in the presence of cracking catalysts, South African Patent No. 7924/72 and its corresponding U.S. Patent No. 3,909,392 disclose the possibility of using combustion catalysts or promoters together with cracking catalysts within the regeneration zone in the presence of a metal rod, grid, mesh or screen in the combustion zone, as well as metal compounds which can be set in motion, in particular powdered transition metal oxides such as iron oxide, manganese dioxide and rare earth oxides, which are added to the catalyst feed or their action is limited to the regeneration device. Belgian Patent No. 826,266 describes a process similar to the above-mentioned US Patent, in which a cracking catalyst is used, physically associated with a catalyst accelerating the oxidation of carbon monoxide, and is a metal with an atomic number of at least 20, and suitable oxidation promoters include metals from groups IB, IIB, and III to VIII of the Periodic Table of the Elements, and in particular platinum, palladium, rhodium, molybdenum, tungsten, copper, chromium, nickel, manganese, cobalt, vanadium, iron, cerium, ytterbium and uranium. US Patent No. 3,808,121 describes the regeneration of a cracking catalyst in the presence of a catalyst oxidizing carbon monoxide, the catalyst being used in a regeneration zone.

Belgian patent specification No. 7,412,423 describes a cracking catalyst containing not more than 100 parts per million (ppm), calculated as metal and calculated as total catalyst, of at least one metal compound from the fifth and sixth periods of Group VIII of the Periodic Table of the Elements, and rhenium and its compounds, and this catalyst is supposed to lead to a particularly significant reduction in the carbon monoxide content of the flue gases after catalysis on the cracking catalyst. The said patent specification also includes a molecular sieve type catalyst which is prepared in the form of a sodium salt, exposed to the action of ammonium ions in an ion exchange and then impregnated with metals from the group of rare earth elements.

Regarding the release of sulfur oxides into the atmosphere, various methods of treating waste gases have already been described, such as washing or scrubbing, chemical absorption, neutralization and chemical reactions, but all of these processes, designed to remove sulfur oxides, require bulky and expensive additional equipment, thereby increasing both investment and operating costs.

U.S. Patent No. 3,699,037 describes the addition of at least a stoichiometric amount of a calcium or magnesium compound, based on the amount of sulfur deposited on the catalyst, to a cracking cycle. This added material is intended to react with sulfur oxides to form substances which are then removed in a very fine state from the cracking cycle as fly ash material from the waste gas from the regeneration unit. However, the continuous addition of the above substances significantly increases operating costs. Similarly, U.S. Patent Nos. 3,030,300 and 3,030,314 describe a catalytic cracking process in which at least one compound of boron, alkali metals and alkaline earth metals is continuously added to a flexible bed cracking cycle. Such catalyst particles, having increased strength and abrasion resistance, contain silicon or silica with a microporous catalytically activated core, which is provided with a protective coating of glass consisting of silicon dioxide and at least one compound of boron, alkali metals or alkaline earth metals.

US Patent No. 3,835,031 describes a cyclic catalytic cracking process in liquid or fluid phase.

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243773 with reduced leakage of sulfur oxides in waste gases from a regeneration device. A catalyst is used, which is a molecular sieve with a matrix, optionally with a carrier, of silica and alumina, wherein the molecular sieve is impregnated with at least one oxide of group IIA. U.S. Patent Nos. 3,388,077, 3,409,390 and 3,849,343 relate to methods for treating waste gases containing carbon monoxide and sulfur oxides. The waste gases are passed through a catalytic system comprising a porous refractory material as a carrier, a catalytically active metal component, for example a metal from the platinum group of elements and a component from the alkaline earth metal group from the group of calcium, strontium and barium.

A new catalyst has now been found for this purpose. The subject of the invention is therefore a solid cracking catalyst suitable for cracking hydrocarbon feeds containing organic sulfur compounds in a fluidized bed, which is characterized in that it consists of at least 30% by weight of a matrix consisting of at least two materials from the group consisting of silicon dioxide, aluminum oxide, thorium dioxide and boron oxide, preferably from 10 to 65% by weight of aluminum oxide and from 35 to 90% by weight of silicon dioxide, calculated on the weight of the matrix, and a crystalline aluminosilicate zeolite in an amount of 0.5 to 50% by weight. based on the weight of the matrix n zeolite, and from a particulate solid, distinct from the matrix and from the zeolite, formed from at least one sodium compound and at least one inorganic oxide from the group comprising silicon dioxide and aluminum oxide, wherein the amount of sodium, calculated as metallic sodium, is up to 10% by weight, based on the catalyst as a whole, and the solid, distinct from the matrix and from the zeolite, is free of aluminosilicate zeolite

The hydrocarbon feedstock when using the catalyst according to the invention may contain 0.2 to 6% by weight of sulfur in the form of organic compounds, 0.5 to 5% by weight of sulfur and especially 1 to 4% by weight of sulfur, always in the form of organic compounds. When using the cracking catalyst according to the invention, a reduction in the escape of sulfur oxides in the waste gases from the regeneration zone is achieved during catalytic cracking in a fluidized bed. In some cases, complete combustion of carbon monoxide occurs in the regeneration zone and heat absorption on solid particles, which are returned to the reaction and expulsion zones.

The sodium compound can be incorporated into the crystalline aluminosilicate zeolite (i.e., molecular sieve) as well as into the matrix. Such incorporation can be done either during the catalytic cracking cycle, in the cracking zone, in the stripping zone, in the regeneration zone, or outside of these processes or zones.

When using the catalyst of the invention in the form of solid particles, the sulfur oxides react with the sodium reactant to form a sodium-sulfur compound.

The matrix of the cracking catalyst according to the invention is a combination of at least two materials from the group comprising silicon dioxide, aluminum oxide, thorium dioxide and boron oxide, preferably containing 10 to 65% and in particular 25 to 60% of aluminum oxide and 35 to 90% and in particular 35 to 70% of silicon dioxide, and crystalline aluminum silicate, preferably 0.5 to 50% and in particular 5 to 50% of crystalline aluminum silicate, whereby the percentages in this case are still meant by weight unless otherwise stated.

The sulfur oxides in the regeneration zone are likely to be absorbed by the sodium component of the catalyst. It is preferred to introduce the sodium component into the catalytic cracking cycle in the form of the oxide. The sodium component of the catalyst is activated to absorb the sulfur oxides in the regeneration zone. This activation is likely based on at least partial conversion of the sodium component to the oxide. The activation is essentially independent of the manner in which the sodium metal is bound at the time of introduction into the cycle.

Sodium must be present in the regeneration zone in an amount sufficient to absorb the sulfur oxides formed by the combustion of the carbon and sulfur-containing deposits on the catalyst. Of the sulfur oxides formed, at least 50% and preferably over 80% is absorbed by the sodium in the regeneration zone. Therefore, the sulfur oxide concentration in the waste gases from the regeneration zone is then lower than 600 to 1000 ppm and sometimes lower than 400 ppmv.

The approximate amount of sodium, based on the catalyst as a whole, is up to 10%, for example 0.6 to 3%, in particular 0.8 to 2% and most particularly 0.85 to 1.5%. The sodium component is not distributed evenly on the matrix and on the molecular sieve.

The deactivated catalyst, freed from the expeller portions in the stripping zone, is regenerated in the regeneration zone at temperatures at which solid sodium and sulfur compounds are formed from sodium and sulfur oxides. The regeneration temperatures are approximately 566 to 788 °C and especially 638 to 732 °C. The hydrocarbon feed is cracked at reaction temperatures of 454 to 649 °C and especially 466 to 649 °C, at which the sodium and sulfur compound reacts to form sodium sulfide. The expeller deposits from the deactivated cracking catalyst are removed by the action of a gas containing steam at temperatures at which the sodium sulfide reacts with water to form hydrogen sulfide gas. The expeller temperatures are generally 554 to 649 °C and especially 466 to 538 degrees Celsius. The weight ratio of steam to cracking catalyst in the stripping zone is approximately 0.0005 to 0.025 and preferably 0.0015 to 0.0125. The waste gases from the reaction zone preferably contain at least 0.1% by volume and especially at least 0.5% oxygen to achieve the desired reduction in the harmful gases in the discharged waste gases.

The metal reagent may be added to the molecular sieve or to the matrix. When incorporated into the catalytic cracking cycle, the sodium reagent is added to the fluid cracking cycle as an oil- or water-soluble or dispersible sodium compound in the form of a solid, liquid or gas and may be introduced into the other catalyst components in situ.

The sodium component of the catalyst is essentially inert with respect to the cracking reaction or has very little effect on the catalytic conversion reaction under the conditions used. In order to reduce the sulfur content of the waste gases from the regeneration zone, the solid particles absorb sulfur oxides in the regeneration zone. The molecular sieve type catalyst component often serves as such to absorb sulfur oxides. The sodium reagent reacts with the absorbed sulfur oxides to form a sodium-sulfur-containing compound, especially to form sodium sulfate. Provided that such a sodium-sulfur-containing compound is solid under the operating conditions in the reagent zone, it is transferred on the surface of the solid particles to the regeneration zone and to the stripping zone, where it is reduced and separated as a sulfur-containing gas, especially hydrogen sulfide.

The catalysts of the invention are in the form of particles with an average particle size of at most about 20 to 150 microns, so that they are suitable for being spun. Such catalysts can be prepared using any suitable method, such as milling, gel coprecipitation or the like, provided that the finished catalyst is in a suitable physical form for being spun.

Suitable molecular sieves include both natural and synthetic materials of the nature of aluminum silicates, such as faujasite, chabasite, aluminum silicates of the "X" and "Y" types and ultra-stable, large-pore crystalline aluminum silicates, or materials containing them. When mixed with, for example, silica and alumina, the molecular sieve content in freshly prepared particles is 0.5 to 50%, preferably 5 to 50%. Crystalline aluminum silicates are usually available in the sodium form or are prepared in such form. The sodium component is then reduced as much as possible, usually to below about 0.3% by weight, by ion exchange with hydrogen ions or their precursors, such as ammonium ions or polyvalent metal ions such as calcium, strontium, barium and rare earth metals, as found in nature and as mixtures thereof. The pore structure of the crystalline materials used should be preserved under the high temperature conditions of catalyst preparation, hydrocarbon processing and catalyst regeneration. Crystalline aluminum silicates are often characterized by a uniform pore structure with a mean diameter of 0.6 to 2.0 mm and preferably a mean diameter of 1.0 to 1.5 millimeters.

In catalytic cracking, a certain amount of non-volatile hydrocarbons or coke is deposited on the catalyst particles. As mentioned above, coke is understood to mean highly condensed aromatic hydrocarbons, usually containing a small amount of hydrogen, for example 4 to 10 %. If the hydrocarbon feed contains sulfur in the form of organic compounds, the sulfur is also contained in the coke. As the amount of hydrocarbon deposits on the catalyst increases, the activity of the catalyst in catalytic cracking decreases and the selectivity of the catalyst in the production of gasoline fractions also decreases. The catalyst particles can be regenerated again by removing the main part of the coke from them by a suitable regeneration process.

The spent catalyst from the oil conversion reactor is stripped of expellers before being introduced into the regeneration device. The stripper, used in conjunction with the moving bed cracker, can operate most effectively at the same temperature as that of the conversion reactor, i.e. at a temperature of about 454 to 649 °C and preferably at a temperature above 466 °C. The stripping gas is preferably steam, but nitrogen containing steam or some other inert gas containing steam, or waste or flue gas, may be used. The stripping gas is preferably used at an overpressure of generally 0.68 to 2.41 MPa, which is suitable for substantially complete removal of expellers from the spent catalyst.

The cracking catalyst of the invention can be used in any process or in any regeneration system after catalytic cracking, but is preferably used in a regeneration system that includes at least one dense bed zone and one dilute phase zone. The spent catalyst particles, after the expelling of the expellables, can be led by a suitable conduit from the expeller to the dense bed section of the regeneration device. The inlet can be made from the bottom or from the side and should be near the upper end of the moving dense bed zone. The inlet can also be directed to the upper end of the regeneration device, where the catalyst is first brought into contact with the substantially spent regeneration gas in a limited dilute phase zone.

Catalyst regeneration is achieved by burning coke on the catalyst surface by the action of a gas containing molecular oxygen, such as air. A number of regeneration processes are operationally carried out, in which a high degree of catalyst activity regeneration is achieved depending on the degree of coke removal. The removal of the last portions of coke is increasingly difficult and in practice the degree of coke removal is chosen to obtain

......

acceptable catalyst activities under economic conditions.

Burning off the coke deposits from the catalyst requires a large volume of oxygen or air. The oxidation of this coke can be viewed in a simplified form as the oxidation of carbon and the process can be expressed by the following equations, which are not intended to be limiting:

aj C-j-02---->COa bj 2 C + O2----► 2 CO2

c) 2 CO 4-O ₂ ----> 2 CO2

Reactions aj and bj occur in both cases under typical catalyst regeneration conditions, where the catalyst temperature is 566 to 788 °C and there are known cases of chemical action of oxygen on solid carbon and vice versa, which occur during catalyst regeneration at the mentioned temperatures. The increase in temperature is reflected in an increased rate of carbon combustion and a more complete removal of carbon or coke from catalyst particles. Since the increased combustion temperature is accompanied by a greater amount of heat generated, the reaction c) can take place in the gas phase in the presence of a sufficient amount of free or molecular oxygen.

The combustion of sulfur contained in coke deposits on the catalyst leads to the formation of sulfur oxides, which can be expressed by the following reactions, which are not intended to be limiting:

d) S(vcoke)+°2---— SO2 ej SO2 + 1/2 O2 SO3

Reactions dj and ej take place under typical conditions for the regeneration of cracking catalysts. While reaction dj takes place rapidly, reaction ej takes place relatively slowly. Reaction ej can, however, be catalyzed by the same catalysts that catalyzed the preceding reaction cj. Molecular sieves absorb sulfur oxides and reaction e) can therefore take place on solid particles of the cracking catalyst. Other proportions of the solid particles can also absorb sulfur oxides. The sulfur trioxide formed can then react with sodium or, in particular, sodium oxide to form solid sodium sulfate. After the solid particles have been separated from the waste gases of the regeneration zone, the sodium sulfate is returned to the reaction zone. This prevents sulfur from escaping in the form of gaseous sulfur oxides in the waste gases from the regeneration zone.

Sodium sulfate is returned to the cracking zone, where it is reduced to sodium sulfide in the reducing environment and eventually to hydrogen sulfide. During stripping with a steam-containing gas, sulfide is converted to hydrogen sulfide in the stripping zone, which enters the stripping zone waste gases.

The sodium reagent is regenerated in this way and is restored for reaction with sulfur oxides in the next regeneration. Hydrogen sulfide can be recovered together with the cracking fractions from the stripping column, separated and converted into elemental sulfur in the usual manner.

These reactions can be expressed by the following equations, which are not intended to be limiting:

regenerator:

NagO + SO2 + 1/2 O2---- NazO + + SO3----> NA2SO4 reactor:

NaaSCU + 4 H2----> NazS +

4- 4 H2O----* NaaO + HaS + 3 H2O ejector device:

NazS HzO----► NaaO + H2S

The high cracking activity typically associated with molecular sieve catalysts is essentially unaffected by the presence of the sodium component, resulting in the expected feed conversion and cracking products in adequate yield, with reduced carbon monoxide and sulfur oxide emissions to the atmosphere.

The sodium reagent may be used in a very fine form, for example in powder form, separate from the other catalyst components with which it is cycled through the catalytic cracking process. It is generally considered to be advantageous to have a particle size that allows for easy handling in a moving bed catalytic cracking system. It is desirable that the particles of the sodium component are not too small to prevent excessive drift of these particles with the gases escaping from the bed. However, filters, cyclones and the like are also used to prevent drift. The powder should be sufficiently solid to prevent excessive abrasion and disintegration. The median particle size of the powdered sodium reagent is approximately 0.5 to 100 and preferably below 50 microns. Particles with a median size below 1 micrometer, for example 0.01 to 0.5 microns, tend to agglomerate to form larger aggregates, which are preferred. In any case, care must be taken to avoid undesirably affecting the cracking activity and selectivity of the cracking catalyst. If the cracking catalyst is of the type characterized by the presence of exchangeable ion sites, it is advantageous to carry out and complete the ion exchange before adding the sodium reagent.

In all of the above cases, the exact manner in which sodium is bound to the molecular sieve or matrix is not known. The expression "sodium reagent is introduced or processed into the substrate" therefore always refers to sodium as a component in combined or bound form and/or in the elemental state.

The sodium reagent can be incorporated into the substrate by ion exchange, impregnation or other methods, such as contacting the substrate or one of its components with a solution or solutions of sodium compounds or compounds in an appropriate amount to achieve the desired concentration of sodium reagent in the catalyst of the invention.

The sodium reagent can be mixed with the substrate either at any stage of substrate preparation or after substrate preparation. One possibility for incorporating the sodium reagent is ion exchange with the substrate. For example, it is advantageous to ion exchange crystalline aluminum silicate with a solution or solutions of the sodium compound or compounds of the sodium reagent, after which the product is combined with a porous matrix after the ion exchange. Also suitable is ion exchange of solids containing silicon, or silicon oxide or clay-like materials with a solution or solutions of the sodium compound or compounds in the sodium reagent. Metal halides, preferably chlorides, are suitable for this purpose, as are nitrates, amine halides, oxides, sulfates, phosphates and other inorganic sodium salts soluble in water, as well as sodium salts with carboxylic acids with 1 to 5 carbon atoms and with the corresponding alcoholates.

Another method of preparation is to impregnate a suitable carrier with a sodium compound soluble or dispersible in water or an organic solvent. Impregnation can be carried out by any suitable method that does not destroy the structure of the substrate. A carrier that is inert during hydrocarbon cracking, a molecular sieve or a matrix can be impregnated with the sodium reagent.

Impregnation leads to deposition and primary physical bonding to the substrate surface, while ion exchange leads to primary chemical bonding with greater diffusion and thus reduced surface deposition. During impregnation, sodium is deposited and no substantial ion exchange occurs between sodium and the substrate. When impregnating a substrate, the sodium of the sodium reagent may be used in the form of a salt or salts soluble in water or an organic solvent, dissolved in sufficient quantity to provide the substrate with the desired amount of sodium, and the substrate is then contacted with such solutions. The material thus treated is then dried to remove the solvent, while the sodium reagent remains deposited on the substrate.

Water-soluble nitric acid salts are preferably used for impregnation, since the residues after thermal decomposition of nitric acid salts are relatively harmless with respect to the activity of the cracking catalyst in cracking hydrocarbons. Salts of hydrohalic acids or sulfuric acid can also be used for impregnation purposes, but since their thermal decomposition by-products can adversely affect the efficiency of the cracking catalyst, these salts are used when applied to substrates that are essentially inert during cracking and do not adversely affect the cracking of hydrocarbons.

Another option for physically applying a sodium reagent to a substrate, especially a porous substrate such as crystalline aluminum silicates, is to adsorb a degradable compound or compounds of sodium in the liquid state onto the substrate and then thermally or chemically decompose it. The substrate can be activated by heating to remove any water present and to bring the substrate into contact with the degradable sodium compound of the sodium reagent, whereby the sodium compound is adsorbed onto the substrate. The adsorbed compound can then be thermally or chemically converted into an activated form, while the sodium reagent remains uniformly dispersed on the substrate. Thermal reduction can be carried out, for example, in a regeneration device during the regeneration process itself.

Both the impregnation of the substrate and the adsorption onto the substrate can be carried out before the substrate is introduced into the cycle. However, it is preferred to introduce the sodium compound or compounds of the sodium reagent into the cracking cycle and apply them to the substrate in situ. The suitable compound or compounds can be added either in the form of a substance soluble or dispersed in oil or water, or in a solid, liquid or gaseous state at any stage of the cracking cycle, thereby achieving dispersion on the solid particles. For example, the compound or compounds used can be mixed either with the feed or with the swirling gas in the reaction zone, further with the regeneration gas or with water in the reaction zone, or with the stripping gas in the stripping zone, or the compounds can be introduced as a separate stream.

The activity and stability characteristics can be particularly easily achieved by introducing the sodium reagent into the cracking cycle and applying it to the solid particles in situ, as opposed to mixing it with, or incorporating it into, the other catalyst components during the catalyst preparation. Adding the sodium reagent into the cracking process and incorporating it in situ results in a greater reduction in the amount of sulfur oxides escaping in the waste gases from the regeneration zone than mixing it with the other catalyst components during its preparation. Adding the sodium reagent during the cracking cycle is also advantageous because it achieves a greater effect with respect to the possible detrimental effect of such a sodium reagent on the cracking reaction, since the rate and/or amount of such a sodium reagent introduced into the cracking cycle can be varied. Such a sodium reagent, previously

243773 applied to the molecular sieve and matrix, or introduced into the cracking cycle, can be lost in the form of fine particles for cracking catalyst abrasion. The addition of sodium reagent to the cracking cycle and its incorporation into the solid particles in situ allows the desired amount of sodium reagent to be maintained at accessible locations of the catalyst.

The main advantage of the catalyst according to the invention is that an unusually low carbon monoxide content is achieved in the waste gases from the regeneration device. If the waste gas after regeneration of a cracking device of a catalyst known from the prior art generally contains 6 to 10% carbon monoxide, a similar amount of carbon dioxide and a small amount of oxygen, it is possible to reduce the carbon monoxide content in the waste gas to 0.2% by volume, for example to 500 to 1000 ppmv, when using the catalyst according to the invention. However, a carbon monoxide content of 0 to 500 ppmv is preferably achieved. This makes it possible to discharge the waste gas directly into the atmosphere. If necessary, the remaining carbon monoxide can be burned in the exhaust from the regeneration device. This eliminates the investment costs for installing a carbon monoxide combustion device and the associated equipment for at least partial use of the released energy.

When using the catalyst according to the invention in cyclic cracking, the phenomenon known as afterburning, which is the combustion of carbon monoxide to carbon dioxide according to the above equation c), which is strongly oxothermic, is also eliminated. During catalyst regeneration, this afterburning is extremely undesirable, as it is associated with high temperatures damaging the equipment and possibly the cracking catalyst particles.

When using the catalyst according to the invention, the supply of thermal energy to the cracking process from an external source can be reduced to a minimum, since the heat of the solid particles returned to the reactor is effectively used. When burning coke on catalysts known from the prior art, a heat value of 35,520 kJ/kg of coke is obtained. When using the catalyst according to the invention, this value is at least 37,200 kJ/kg of coke. This higher heat of combustion affects the temperature in the regeneration device, the reduction of the coke content on the regenerated catalyst and allows a reduction in the circulation speed of the solid particles, while achieving improved yields at a given degree of conversion of the hydrocarbon feeds.

In the following examples, parts and percentages are by weight unless otherwise indicated.

Example 1

200 g of calcined, commercially available molecular sieve type cracking catalyst in equilibrium, i.e. consisting of cracking catalyst mass, crystalline aluminosilicate and a matrix containing 5.3% hydrogen, treated by ion exchange with rare earths, obtained from crystalline type "Y" aluminum silicate and a mixture of silica and alumina containing 30% alumina, are impregnated with 3.90 g of a 50% manganese nitrate solution and 210 ml of water. About 80% of the catalyst consists of particles with a size of 20 to 75 microns. The impregnated catalyst particles are dried at 121 °C, calcined for 3 hours at a temperature of 677 °C, after which the catalyst thus prepared contains 0.3% manganese.

Example 2

The procedure of Example 1 is repeated, but a solution of 1.265 grams of uranyl nitrate in 210 ml of water is used for impregnation. The impregnated catalyst is dried at 121°C and calcined for 3 hours at 649°C. It contains 0.3% uranium by weight.

Example 3

The procedure of Example 1 is repeated, but a solution of 2.35 grams of cerium ammonium nitrate in 200 milliliters of water is used for impregnation. The catalyst is dried and calcined as in Example 1 and contains 0.3% cerium.

Example 4

The procedure according to Example 1 is repeated, but a solution of 2.73 g of zinc nitrate hexahydrate in 200 ml of water is used for impregnation. After drying and calcination as in Example 1, the catalyst contains 0.3% zinc.

Example 5

The procedure of Example 1 is repeated, but 4.35 grams of ferric nitrate in 200 ml of water is used as the impregnation solution. After drying and calcination according to Example 1, the catalyst contains 0.3% iron. Example 6

The procedure of Example 1 is repeated, but a solution of 1.1 g of ammonium molybdate in 210 ml of water is used for impregnation. The impregnated catalyst is dried at 121°C and then calcined for 3 hours at 649 ^° C. The finished catalyst contains 0.3% molybdenum.

Example 7

The procedure of Example 1 is repeated, but a solution of 5.0 g of titanium sulfate in 25 ml of an aqueous 30% hydrogen peroxide solution is used for impregnation, the solution being diluted with water to a volume of 200 ml. The solution is heated until the titanium salt is completely dissolved. The catalyst is dried at a temperature of 121 ^° C and then calcined at a temperature of 049 °C. The finished catalyst contains 0.3% titanium.

Example 8

The procedure of Example 1 is repeated, but a solution of 1.2 g of chromium trioxide in 200 ml of water is used for impregnation. The impregnated catalyst is dried for 3 hours at a temperature of 121 °C, then calcined for another 3 hours at a temperature of Θ49 °C. The finished catalyst contains 0.6% chromium.

Example 9

The procedure of Example 1 is repeated, but 0.2506 g of a 50% manganese nitrate solution in 200 ml of water is used for impregnation. The impregnated catalyst is dried for 3 hours at a temperature of 121 °C and then calcined for 3 hours at a temperature of 649 °C. The finished catalyst contains 0.02% manganese. Example

The procedure of Example 9 is repeated, but 1.253 g of a 50% manganese nitrate solution in 210 ml of water is used for impregnation. The catalyst obtained contains 0.1% manganese.

Example 11

Particulate alpha alumina monohydrate (CA-TAPAL-SB from Conoco Chemical Division of Continental Oll Company), containing by weight 74.2% alumina, 0.008% silica, 0.005% ferric oxide, 0.004% sodium oxide, and less than 0.01% sulfur, having a bulk density of 660 to 740 g/l, 78% of the particles of which have a diameter of less than 90 microns, is dried at 121°C and then calcined at 649 ^° C for 3 hours to obtain particulate gamma alumina. A solution of 56.4 g cadmium nitrate tetrahydrate in 240 ml water is then used to impregnate 184.5 g of particulate gamma alumina. The impregnated alumina is dried at 121°C and then calcined at 649°C for 3 hours to yield a particulate product containing 10% cadmium.

Example 12

The procedure of Example 11 is repeated, except that a solution of 33.2 parts of a 51.8% manganese nitrate solution in 112.8 parts water is used to impregnate 100 parts of particulate gamma alumina. The impregnated alumina is dried and calcined as in Example 11 to give a product containing 5% manganese.

Example 13

The method of Example 11 is repeated, but a solution of ammonium paramolybdate tetrahydrate of the formula {NH4]δMθ7θ24.4 HzQ in 32.5 ml of water is used to impregnate 25.1 g of particulate gamma alumina. The impregnated alumina is dried and calcined as in Example 11 to give a product containing 10% molybdenum.

Example 14

The process of Example 11 is repeated, except that an aqueous solution of 36.1 parts of zinc nitrate hexahydrate is used to impregnate 100 parts of particulate gamma alumina. The impregnated alumina is dried and then calcined at 538°C for 5 hours to give a product containing 9% zinc, calculated as zinc oxide.

Example 15

The method of Example 11 is repeated, except that 47.5 parts of titanium sulfate dissolved in an aqueous solution of hydrogen peroxide are used to impregnate 100 parts of gamma alumina particulates. The impregnated alumina is dried, treated with hydrogen at 690°C and calcined at 538°C for 5 hours to give a particulate product containing 9% titanium, calculated as titanium dioxide. Example 16

A solution of 10.8 g of sodium hydroxide in 100 ml of water is used to impregnate 81.3 g of alpha alumina particulate. The impregnated alumina is dried at 121 degrees Celsius and then calcined at 538 °C for three hours to obtain a particulate product containing 9% sodium, calculated as sodium oxide. One part of the sodium additive is combined with 99 parts of molecular sieve and matrix.

Example 17 g of ammonium cerium nitrate, containing 25.6% cerium, is dissolved in 50 ml of water and the resulting solution is used to impregnate 25.2 grams of silica gel particles. The impregnated silica gel is dried and then calcined at 538°C to obtain a particulate product containing 10% cerium.

Example 18

A solution is prepared by dissolving 29.05 g of lanthanum nitrate hexahydrate, 9.94 g of lead nitrate and 35.80 g of a 50% aqueous solution of manganese nitrate in sufficient water to give a total volume of 200 ml. The solution is then mixed with 60 ml of concentrated ammonium hydroxide solution. It is left to stand overnight at room temperature, the precipitate formed is filtered off, washed with water and dried and calcined at 593 °C. The resulting product in the form of particles contains lanthanum, lead and manganese in an atomic ratio of 7 : 3 : 10.

Example 19

A solution is prepared by dissolving 3.80 g of copper nitrate trihydrate and 6.60 g of chromium nitrate monohydrate in sufficient water to produce 45 ml of solution. This solution is used to impregnate 47.5 gamma alumina in the form of a part to a diameter of 833 to 1397 microns. The impregnated alumina is dried at 121 °C for 3 hours and then calcined at 538 °C for 3 hours to obtain a product in the form of particles containing copper and chromium, namely 2.5% copper oxide and 2.5% chromium oxide. The yellow, calcined product is ground to pass through a sieve with a mesh size of 147 microns.

Example 20

A solution is prepared by dissolving 0.3116 g of ferric nitrate monohydrate in sufficient water to produce 12 ml of solution. The solution is then used to impregnate 20 g of alpha alumina particles passing through a 147 micron mesh screen and having a surface area of 1.4 ^m2 /g. The impregnated alumina is then dried at 121°C and then calcined at 538°C for 3 hours to give a particulate product containing 0.2% iron.

Example 21

The procedure of Example 20 is repeated, except that 20 g of alpha alumina is impregnated with a solution prepared by dissolving 0.3083 g of nickel nitrate hexahydrate in sufficient water to obtain 12 ml of solution. The impregnated alumina is dried and calcined under the conditions of Example 20 to give a particulate material containing 0.45% nickel by weight.

Example 22

Synthetic flue gas containing 1500 ppmv sulphur dioxide and 4% oxygen by volume in nitrogen is passed through a fixed fluidised bed of catalyst and/or particulate additive in a regenerator at 677 or 788 °C at a rate of 1000 ml/min. A 100 g sample of catalyst and/or additive is used for each test and the sulphur dioxide content of the exhaust gas is measured with an ultraviolet analyser. The additives are steamed for 5 hours at 760 °C (100% steam at atmospheric pressure) before use.

The results for the CBZ-1 cracking catalyst having a composition of 29.1% alumina, 0.46% sodium oxide and 0.11% iron and containing Y-zeolite are given in Table I as Tests A and E. The results for various mixtures of CBZ-1 catalyst with 1 to 5% particulate additive prepared by the method of Examples 11, 12, 14, 15 and 16 are given in Table I as Tests F, G and B to D. The results with the molecular sieve type cracking catalyst containing 2% by weight rare earth oxides and 46% alumina, Filtrol 800, and the results of Filtrol 800 with 0.1% additive prepared by the method of Example 18 are given in Table I as Tests I and J. And the results with the additive prepared by the method of Example 17 are given in Table I as Test H.

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Pilot plant tests of the cyclic fluid catalytic cracking are carried out with a wide boiling range West Texas gas oil containing 1.47% sulfur. Comparative tests are carried out with the CBZ-1 particulate cracking catalyst and also using a mixture of 99 parts of the CBZ-1 catalyst with 1 part of a 5% manganese on alumina additive prepared as in Example 12, but calcined at 538°C. The manganese on alumina additive reduces the sulfur dioxide emission in the regenerator off-gas from 763 to 275 ppmv, a 64% reduction. Comparative values are given in Table II.

Table II

Exam

A B Catalyst: CBZ-1 CBZ-1 -j- 1% additive Cracking conditions reactor temperature, °C 510 510 speed, g/min 9 9 Eviction conditions temperature, °C 495 495 steam, g/h 16 16 nitrogen, m ³ /h 0.031 0.031 Regeneration conditions temperature, °C 649 649 oxygen concentration in the waste gas, volume % 2.0 2.0 sulfur oxide content in the waste gas, ppmv 763 275 Considered sum of sulfur dioxide and sulfur trioxide discharged from the regenerator.

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Claims (5)

A fluidizable solid cracking catalyst suitable for cracking hydrocarbon feeds containing organic sulfur compounds in an animal layer, characterized in that it comprises at least 30% by weight of a matrix consisting of at least two materials selected from the group consisting of silica, alumina, oxide thorium and boron oxide preferably from 10 to 65% by weight of alumina and from 35 to 90% by weight of silica, based on the weight of the matrix, and crystalline aluminosilicate zeolite in an amount of 0.5 to 50% by weight of the matrix and zeolite, and solid particulate matter other than matrix and zeolite, consisting of at least one sodium compound and at least one inorganic oxide selected from silica and alumina, the amount of sodium calculated as sodium metal being I INVENTION up to 10% by weight based on the catalyst as a whole. 2. A fluidizable solid cracking catalyst as claimed in claim 1, containing by weight based on the catalyst as a whole 0.6 to 3% of a sodium compound, calculated as sodium metal. 3. The fluidizable solid cracking catalyst of claim 2 wherein the inorganic oxide comprises alumina. 4. The fluidizable solid cracking catalyst of claim 3 comprising an inorganic oxide of greater than 50% by weight of the particulate solid, different from the matrix and zeolite. 5. The fluidizable solid cracking catalyst of claim 2, wherein the particulate solid, olefin of matrix and zeolite, has a mean particle size of 20 to 150 microns.