JPH0341517B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is suitable for use with sulfur-containing hydrocarbon feedstocks and is characterized by a significant reduction in sulfur oxide emissions to the regenerator stack gas.
process). Prior art: During the cracking of hydrocarbons in the reaction zone, typically “coke”
The cracking catalyst, which has become relatively inactive due to the deposition of carbonaceous deposits called coke, is continuously withdrawn from this reaction zone. From the reaction zone this spent catalyst is passed to a stripping zone where the strippable carbonaceous deposits, i.e. hydrocarbons, are stripped from the catalyst and the catalyst is then passed to a regeneration zone where carbon monoxide and dioxide are removed. The activity of the catalyst is restored by removing non-stripping carbonaceous deposits by burning the coke in an oxygen-containing gas to form carbon. The hot regenerated catalyst is then continuously returned to the reactor for repeating the cycle. In catalytic cracking, problems arise from the incomplete combustion of carbon monoxide to carbon dioxide in the regeneration zone, leaving significant amounts of carbon monoxide in the regeneration zone flue gas. Besides the undesirability of carbon monoxide emissions into the atmosphere,
The carbon monoxide and residual oxygen in the regeneration zone flue gas have a tendency to react, causing combustion in the plant's ducts and flues and damaging this structure due to excessive temperatures. Furthermore, when a high sulfur feedstock, ie, a petroleum hydrocarbon fraction containing organic sulfur compounds, is charged to a fluid catalytic cracker, the coke deposited on the catalyst contains sulfur. During coking and regeneration of deactivated catalysts, coke is burned from the catalyst surface,
In this combustion process, the sulfur present is then converted to sulfur dioxide along with a small portion of sulfur trioxide and is thus included in the regeneration zone flue gas effluent stream. When cracking high sulfur feedstocks, sulfur oxide emissions are often in the range of about 1200 ppm. It is expected that pollution control standards have been established for carbon monoxide and particulates, and will soon be considered for other emissions such as sulfur oxides, especially sulfur dioxide. As a result, much attention has been focused on reducing the levels of various combustion products and particulate emissions from regeneration zone effluents connected to petroleum crackers. Methods to reduce this emission need to be effective without reducing the activity and selectivity of the cracking catalyst. Similarly, the chosen method must not replace one form of undesirable emissions with another problem, such as particulate emissions or increased operating costs. With these considerations in mind, a highly desirable approach to the reduction of sulfur oxide emissions from petroleum crackers is to increase catalytic activity under conventional cracking conditions in either existing or new crackers.
The present invention consists in using a decomposition catalyst modified to minimize sulfur oxide emissions while maintaining stability and wear resistance. Metals are generally avoided in cracking catalysts, and decomposition of metal-containing feedstocks in the presence of cracking catalysts seems questionable, but South African Patent No. 7924/72 and later patents are discussed in detail below. Corresponding U.S. Pat. No. 3,909,392 (1975) discloses the use of a combustion catalyst in conjunction with a cracking catalyst or promoter in the regeneration zone, which includes metal rods, mesh or screens and flowable metal compounds, especially Contains powdered oxides of transition metals, such as ferric oxide, manganese dioxide, and rare earth oxides, which are added to the catalyst charge or confined within the regenerator vessel. Belgian patent no. 826,266 (1975) discloses a method very similar to that of U.S. patent no. catalytic cracking catalysts and as useful oxidation promoters metals from Groups B, B, and Groups to Groups of the Periodic Table, especially platinum, palladium,
Mention is made of rhodium, molybdenum, tungsten, copper, chromium, nickel, manganese, cobalt, vanadium, iron, cerium, yttrium, and uranium. Additionally, US Pat. No. 3,808,121 discloses regeneration of a cracking catalyst in the presence of a carbon monoxide oxidation catalyst retained in a regeneration zone. Dutch patent application No. 7412423 discloses that at least one metal component selected from the group consisting of metals from the 5th and 6th periods of groups of the periodic table, rhenium and compounds thereof, on the basis of a gold catalyst, It has been disclosed that cracking catalysts containing up to 100 ppm, calculated as metals, show a particularly striking reduction in carbon monoxide content in the flue gas from catalytic cracking catalysts. This patent also discloses a molecular sieve-type cracking catalyst that is prepared in the sodium form, ion-exchanged with ammonium ions, and then impregnated with rare earth metals. Regarding sulfur oxide emissions, various methods have been devised to treat the flue gas, such as washing or scrubbing, chemical absorption, neutralization and chemical reactions or transformations, but all for the removal of sulfur oxides. The method requires extensive and expensive auxiliary equipment, thus increasing operating costs and capital. The approach described in US Pat. No. 3,699,037 contemplates the addition of at least stoichiometric amounts of calcium or magnesium compounds to the cracking catalyst for sulfur deposition on the catalyst. This additive material has a tendency to react with the sulfur oxides and is then, in a finely divided state, discharged from the cracking cycle as particulates into the regeneration zone flue gas stream.
The continuous addition of this material clearly increases operating costs. Similarly, U.S. Pat. microstructure with an adhesive protective coating of silica and a glaze consisting of one or more compounds of boron, alkali metals, and alkaline earth metals. A catalytic cracking process is disclosed that includes providing catalyst particles comprised of siliceous catalyst particles having a porous, catalytically active core. U.S. Pat. No. 3,835,031 (1974) discloses a circulating flow catalytic cracking process that provides reduced emissions of sulfur oxides to the regenerator stack gas. The process operates with a catalyst containing molecular sieves in a silica-alumina matrix and impregnated with one or more Group A metal oxides. U.S. Pat. Nos. 3,388,077 (1968); 3,409,390 (1968); and 3,849,343 (1974) disclose methods for converting toxic waste gas streams containing carbon monoxide and sulfur oxides, which comprising contacting the stream with a porous refractory carrier material, a catalytically active metal component, such as a catalytic complex of a platinum group metal and an alkaline earth metal component selected from the group consisting of calcium, barium and strontium. . Thus, the method of the invention is not described in any way. The present invention relates to a recirculating flow catalytic cracking process that provides reduced emissions of sulfur oxides to the regeneration zone flue gas. In some embodiments, the present invention also provides substantially complete combustion of carbon monoxide in the regeneration zone and the removal of heat generated during this combustion by solid particles that are recycled to the reaction zone and stripping zone prior to return to the regeneration zone. Provides absorption. The solid particles include a molecular sieve type cracking catalyst and a metal reactant, and may also include an amorphous cracking catalyst and a solid that is substantially inert to hydrocarbon cracking. The metal reactant can be incorporated into a molecular sieve-type decomposition catalyst, an amorphous decomposition catalyst, or a substantially inert solid. This formulation can be done either before or after the particular material is introduced into the cracking process cycle. Conditions are used in this cracking process cycle such that stable metal- and sulfur-containing compounds are formed into solid particles in the regeneration zone and sulfur-containing gases are withdrawn from the stripping zone. In the development of catalysts for the reduction of sulfur oxide emissions in the flue gas from the regeneration zone of fluidized cracking operations, it is important to note that not only do these catalysts initially demonstrate the ability to perform a specific function, but also that they remain stable over a long period of time. It is important to have a performance that works satisfactorily for a long time. Therefore, in the development of this catalyst, attention must be paid to the activity and stability characteristics of the catalyst. In this context, activity is a measure of the ability of a catalyst to reduce the emission of sulfur oxides into the regenerated flue gas at a specified stringency level, where stringency level depends on the conditions used, i.e. temperature, pressure, contact time, etc. means. Catalyst stability is a measure of a catalyst's ability to retain its active properties over a specified period of time. Stability indicates the rate of change of activity parameters over time, with a lower rate indicating a more stable catalyst. This stability must be such that the active properties can be maintained for a long period of time. An effective agent for reduced sulfur oxide emissions, the present invention involves introducing a metal reactant into the cracking process cycle, and rather than incorporating it into a molecular sieve cracking catalyst during the preparation of the cracking catalyst. These characteristics are more easily obtained by in-situ incorporation of the into solid particles. In contrast to complexing this with a molecular sieve-type cracking catalyst during cracking catalyst production, the introduction of metal reactants into the cracking process produces a greater reduction in sulfur oxide emissions of the regenerated flue gas. It has been found. Adding a metal reactant to the cracking process cycle can also alter the rate and/or amount of this metal reactant introduced into the cracking cycle, thereby overcoming the potential deleterious effects of the metal reactant on the cracking reaction. It is useful that a significant degree of adjustment is maintained. This metal reactant, previously combined with the cracking process cycle, is also lost as particulates during wear of the cracking catalyst. The addition of metal reactants to the cracking process cycle and their incorporation into the solid particles in situ allows the desired amount of metal reactants to be retained on the external surface or accessible portion of the cracking catalyst. The present invention comprises homogeneous or heterogeneous, renewable, flowable solid particles comprising a molecular sieve type decomposition catalyst comprising a metal reactant and a decomposition catalyst matrix containing a crystalline aluminosilicate distributed through the matrix, under flow conditions. An improved circulating flow catalytic cracking process in which an organic sulfur-containing hydrocarbon feedstock is subjected to cracking in a reaction zone in which the cracking catalyst is concomitantly inactivated by a sulfur-containing carbonaceous deposit. Fluid solid particles are cracked from the cracked hydrocarbon reaction zone effluent and passed to a stripping zone where strippable carbonaceous deposits are removed from the deactivated cracking catalyst by contact with stripping gas. Stripped. The fluidized solid particles are then separated from the gaseous stripping zone effluent and sent to a regeneration zone where they are contacted with an oxygen-containing gas stream to remove unstripped, sulfur from the stripped and deactivated cracking catalyst. The decomposition catalyst, which has been stripped and deactivated by burning the containing carbonaceous deposits, is regenerated to high activity, thereby forming carbon monoxide, carbon dioxide and sulfur oxides, which are combined with the metal reactants. The solid particles react to form metal- and sulfur-containing compounds. The fluidized solid particles containing regenerated cracking catalyst are separated from the regeneration zone effluent flue gas and recycled to the regeneration zone. This improvement includes introducing a metal-containing material with a metal reactant into the cracking process cycle and incorporating the metal reactant into solid particles within the cracking process cycle; using a stripping gas containing steam; By; solid particles of metal and sulfur
By regenerating the stripped and deactivated cracking catalyst at a regeneration temperature within a range in which the contained compounds are stable; and producing enough oxygen that the molecular oxygen-containing flue gas is withdrawn from the regeneration zone. By feeding the regeneration zone with a stream of oxygen-containing regeneration gas. Hydrocarbon feedstocks suitable for use in this process contain from about 0.2 to about 6 weight percent sulfur in the form of organic sulfur compounds. Advantageously, the feedstock comprises about 0.5 to about 5% by weight sulfur, more advantageously about 1 to about 4% by weight sulfur, where the sulfur is present in the form of an organic sulfur compound. The cracking catalyst matrix of the molecular sieve cracking catalyst is a combination of at least two materials selected from the group consisting of silica, alumina, thoria and boria, and more preferably silica-alumina. The cracking catalyst matrix preferably has about 10 to about 65 and more preferably about 25 to about 60
weight percent alumina; preferably from about 35 to about 90;
More preferably about 35 to about 70% by weight silica,
and preferably about 0.5 to about 50, more preferably about 5 to about 50% by weight crystalline aluminosilicate, the molecular sieve-type decomposition catalyst preferably contains about 10 to about 99.9975, more preferably about 30% by weight of solid particles. from about 99.99, and most preferably about 90
Forming from about 99.9% by weight. The metal reactant consists of at least one free or combined metal element selected from the group consisting of magnesium, calcium, strontium, and barium. As a result, the metal reactants include magnesium, calcium, strotium, barium,
It can be selected from the group consisting of these compounds and mixtures thereof. More preferably the metal reactant is selected from the group consisting of magnesium and calcium. It is believed that the metal element or oxides or oxides of the metal reactant are primarily responsible for the absorption of sulfur oxide in the regeneration zone.
Consequently, it is advantageous to introduce the metal reactant metal element or elements into the catalytic cracking process cycle in the form of an oxide or oxides. However, in carrying out the method it is sufficient that one or more suitable metal elements are selected as metal reactants and introduced into the process cycle.
The metal element or elements of the metal reactant is activated for absorption of sulfur oxides in the regeneration zone as a result of the process cycle of the present invention. This activation is believed to involve either a partial or substantially complete conversion of the metal or metals of the metal reactant to the corresponding oxide or oxides. This activation is substantially unaffected by the exact manner in which the metal element or elements are chemically combined when initially introduced into the process cycle. This metal reactant is present in the regeneration zone in an average amount sufficient to absorb most of the sulfur oxides produced by combustion of the sulfur-containing carbonaceous deposit. At least about 50%, and beneficially about 80%, of the sulfur oxides produced by this combustion
The above amount is absorbed by the metal reaction zone in the regeneration zone.
As a result, the concentration of sulfur oxides in the regeneration zone effluent gas stream from this new method is approximately 600-
It is kept below 1000 parts per million (ppmv), advantageously below about 600 ppmv, and even more advantageously below about 400 ppmv. The amount of metal reactant used, calculated as metal or metal(s), is preferably about
25 ppm to about 7% by weight, more preferably about 0.01
from about 5% by weight and most preferably from about 0.1 to about 0.5% by weight. A particular individual solid in the solid particles of the method of the invention is a solid particle when this particular individual solid is mixed with other individual solids in the solid particles containing a small amount of metal reactant. The solid particles can contain a greater than average amount of metal reactant such that the solid particles contain the above-mentioned average level of metal reactant. The stripped, deactivated catalyst is regenerated at a regeneration temperature within the range that safe metal- and sulfur-containing compounds are formed in the solid particles from the metal and sulfur oxides in the metal reactants. The regeneration temperature is preferably within the range of about 1050 to 1450㎓,
More preferably, it is within the range of about 1180 to about 1350. The hydrocarbon feedstock is decomposed at a reaction temperature within the range at which the metal- and sulfur-containing compounds in the solid particles react to form sulfides of the metals in the metal reactants. The decomposition reaction temperature is preferably about
Within the range of 850 to about 1200〓, and more preferably within the range of about 870 to about 1100〓. This strippable deposit is stripped from the deactivated decomposition catalyst with a steam-containing gas and at a stripping temperature within a range where the sulfide of the metal in the metal reactant reacts with water to form hydrogen sulfide gas. The stripping temperature is preferably about 850 to about
1200〓, and more preferably within the range of about 870 to about 1000〓. The weight ratio of steam to molecular sieve cracking catalyst to be fed to the stripping zone is preferably within the range of about 0.0005 to about 0.025, and more preferably from about 0.015 to about
It is within the range of 0.0125. The regeneration flue gas preferably contains at least 0.01% by volume and more preferably at least 0.5% by volume of oxygen in order to obtain the desired reduction in toxic gas emissions. In one embodiment of the invention, the material containing the metal as the metal reactant is an oil- or water-soluble or -dispersible compound, and the metal reactant is incorporated into a molecular sieve-type cracking catalyst. In this case,
The metal reactant is incorporated into either a matrix of crystalline aluminosilicate or molecular sieve type decomposition catalyst. In this embodiment of the invention, the solid particles may additionally include at least one component selected from the group consisting of solid and amorphous cracking catalysts that are substantially inert to the hydrocarbon feedstock; and The metal reactant is incorporated into this component. In this embodiment, the compounds introduced into the catalytic cracking process cycle, including the cracking reaction zone, stripping zone and regeneration zone, are preferably metal salts. Examples include metal diketonates and metal carboxylates having 1 to 20 carbon atoms. More preferably the compound is magnesium acetylacetonate. In another embodiment of the invention, the material containing metal as metal reactant is a metal reactant in powder form, such as magnesium oxide. In another specific example,
This material is a composite of metal reactants supported on either an amorphous decomposition catalyst or a solid that is substantially inert to the decomposition reaction. The present invention includes an improved method for the regeneration of cracking catalysts used in fluid catalytic conversion and in which the cracking catalyst is deactivated by the deposition of sulfur-containing coke on the surface of the cracking catalyst. The present invention relates to improved methods for reducing sulfur oxide emissions in cracking catalyst regeneration zone effluent gases, including conversion of sulfur-containing hydrocarbon feedstocks. The solid particles of the process of the present invention, including the molecular sieve type cracking catalyst, are circulated in well-dispersed physical association with one another throughout the cracking process cycle, which includes a cracking zone, a stripping zone, and a regeneration zone. The conditions used affect the reduction of sulfur oxides in the regeneration zone flue gas. The decomposition catalyst and metal reactant of the process of the invention serve separate and essential functions. The cracking catalyst serves to catalyze the cracking reaction, while the metal reactant is virtually inert to the cracking reaction and has little, if any, adverse effect on the catalytic conversion under the conditions used. I don't have it. Regarding the reduction of sulfur oxides in the regeneration zone flue gas, the solid particles absorb sulfur oxides in the regeneration zone. The molecular sieve cracking catalyst itself often serves as an adsorbent for sulfur oxides. The metal reactants react with the adsorbed sulfur oxides to form metal- and sulfur-containing compounds, especially metal sulfates, especially alkaline earth metal sulfates with solid particles. This metal and sulfur
If the contained compound is stable under the operating conditions in the regeneration zone, it takes place at the surface of the solid particles into the reaction zone and stripping zone where it is reduced and separated as a sulfur-containing gas, especially hydrogen sulfide. The activity of reducing sulfur oxide emissions in the regeneration zone flue gas appears to vary depending on the type of metal serving as the metal in the metal reactant. Similarly, many of the specific metals that serve as metals in metal reactants do not necessarily produce equivalent results when compared to other specific metals that can be used as metal reactants or when used under various conditions. . The solid particles of the process of the invention are finely divided and, for example, about
It has an average particle size within the range of 20 to about 150 microns or less. Preferred decomposition catalyst matrices are those containing silica and/or alumina. Other refractory metal oxides can be used, limited only by their ability to be effectively regenerated under the selected conditions. Clay-extended alumina mixtures can also be used. Suitable catalysts also include combinations of silica and alumina mixed with "molecular sieves" known as zeolites or crystalline aluminosilicates.
Suitable cracking catalysts contain a sufficient amount of crystalline aluminosilicate to substantially increase the cracking activity of the catalyst, limited only by its ability to be effectively regenerated under the selected conditions. The crystalline aluminosilicate is usually at least about 2:1, such as about 2 to 12:1, preferably about 4 to about 6:1.
It has a silica to alumina molar ratio of 1. For example, cracking catalysts having a silica base with a predominance of about 35 to about 90 weight percent silica and about 10 to about 65 weight percent alumina are suitable. The catalyst can be prepared by any suitable method, such as milling, cogelation, etc., provided only that the final catalyst is provided in a fluidizable physical form. Suitable "molecular sieves" include aluminosilicate materials of both natural origin and synthetic origin, such as phouzite, chabazite, X-type and Y-type aluminosilicate materials, and ultrastable, large-porous crystalline aluminosilicates. Including materials. When mixed with e.g. silica-alumina to provide a petroleum cracking catalyst, the molecular sieve content of the freshly finished catalyst particles is preferably about
Within the range of 0.5 to about 50% by weight, preferably about 5%
and about 50% by weight. Equilibrium "molecular sieve" cracking catalysts contain as little as about 1% by weight of crystalline material. Crystalline aluminosilicates are usually suitable and made in the sodium form; this sodium component is then combined with hydrogen ions or hydrogen precursor ions such as ammonium ions, or with calcium, strontium, barium and cerium, lanthanium, neodymium. Through polyvalent metal ion exchange, including rare earths such as, and natural rare earths and mixtures thereof, the amount is reduced to as little as possible, generally less than about 0.30% by weight. Crystalline materials that can be used under the high temperature conditions of catalyst production, hydrocarbon processing, and catalyst regeneration can maintain their pore structure. The crystalline aluminosilicate often has a uniform pore structure of excessively small size, with a pore cross-section of about 6 to about 20 Å, preferably about 10 to about
Within the dimensional range of 15 Å. Catalytic cracking of heavy mineral oil components is one of the major refinery operations used to convert crude oil into desirable fuel products such as spark ignition, high octane gasoline fuels used in internal combustion engines. “fluid”
An example of a catalytic conversion process is where a polymeric hydrocarbon liquid or vapor is contacted with hot finely divided solid catalyst particles in either a fluidized bed reactor or an elongated riser reactor and is typically used in motor gasoline or distillate fuels. A fluid catalytic cracking process in which the catalyst-hydrocarbon mixture is held at elevated temperatures in a fluidized or dispersed state for a period sufficient to effect the desired degree of cracking to the low molecular weight hydrocarbons present in the catalyst. Hydrocarbon feeds suitable for the cracking process are e.g.
400 to about 1200〓 generally boils above the gasoline boiling range, and about 850 to about
It normally decomposes at temperatures ranging up to 1200°C. This feed may be derived from a variety of mineral oil fractions boiling above the gasoline range, such as light gas oil, heavy gas oil, wide cut gas oil, vacuum gas oil, kerosene, decant oil, residue fraction, atmospheric distillation residue, and any of these. This includes recycled oils, appropriate fractions derived from shingle oil, tar sands processed synthetic oils, coal liquefied oils, etc. This fraction can be used alone or in any desired combination. Although the process of the present invention can be used in any conventional catalytic cracking system, it is possible to perform at least one hydrocarbon conversion in a dilute phase transfer line or in a riser reactor system that utilizes a highly active catalyst used at relatively high space velocities. It is advantageously carried out in a fluid catalytic cracking system in which a substantial portion of the process is carried out. Preferably cracking occurs essentially exclusively in the riser reactor and the subsequent rich catalyst bed is not used for cracking. In typical cases where riser cracking is used for light oil conversion, the throughput ratio or volume ratio of total feed to fresh feed varies from about 1 to 3. Conversion level is about 40 to approx.
Different at 100% by weight, and beneficially about 60% by weight
For example, it is maintained at about 60 to 90% by weight.
Conversion means a reduction in the weight percentage of hydrocarbons boiling above about 430 ㎓ at atmospheric pressure due to the formation of lighter materials or coke. The weight ratio of total cracking catalyst to oil in the riser reactor varies from about 2 to about 20 because the fluidized dispersion has a density within the range of about 1 to about 20 pounds per cubic foot. Desirably, the catalyst to oil ratio is maintained within the range of about 3 to about 20, preferably 3 to about 7. Flow rates in riser reactors vary from about 10 to about 100 feeds per second. Riser reactors generally have a length to average diameter ratio of about 25. For typical naphtha product production, the bottom mixing temperature in the riser reactor is beneficially between about 1000 and about 1100° for the oil feed and such that the top exit temperature is about 950°.
is maintained. Substantially higher temperatures may be required for cracked residues and synthetic fuels. Under these conditions, only brief contact is established between the catalyst and the oil, including providing for rapid separation of the used catalyst from the spilled oil vapor. Contact times in the riser reactor generally range from about 1 to about 15 seconds, and preferably from about 3 to about 10 seconds. Short contact times are preferred since most of the hydrocarbon cracking occurs during the first increment of contact time, and second undesirable reactions are avoided. This is particularly important if high product yields and selectivities are to be achieved, including less coke production. Short contact times between catalyst particles and oil vapor can be obtained by various means. For example, the catalyst may be injected at one or more locations along the length of the lower or bottom portion of the riser. Similarly, oil feed can be injected at all points along the lower length of the riser reactor, and different injection points can be used for fresh and recycled feed streams. For this purpose, the lower part of the riser reactor comprises up to about 80% of the total riser length, providing a very short effective contact time resulting in optimal conversion of the petroleum feed. When a dense catalyst bed is used, provision is also made for injection of catalyst particles and/or oil feed directly into the zone of the dense bed. While the above conversion conditions are intended for the production of gasoline as a fuel for spark-ignited internal combustion engines, this processing scheme is suitable for the production of gasoline as a fuel for spark-ignited internal combustion engines, while this processing scheme is suitable for the production of gasoline as a fuel for spark-ignited internal combustion engines, while this processing scheme is suitable for the production of gasoline as a fuel for spark-ignited internal combustion engines, while the processing scheme is suitable for the production of gasoline as a fuel for spark-ignited internal combustion engines. Suitable variations can be made to allow maximum production of hydrogen product. In the catalytic process some non-volatile carbonaceous material or "coke" is deposited on the catalyst particles. Coke contains highly concentrated aromatic hydrocarbons that generally contain small amounts of hydrogen, ie, about 4 to about 10% by weight. When the hydrocarbon feedstock contains organic sulfur compounds,
Coke also contains sulfur. As the coke is deposited on the catalyst, the activity of the catalyst for cracking and the selectivity of the catalyst for producing gasoline miscible stock is reduced. By removing most of the coke therefrom by suitable regeneration methods, the catalyst particles recover most of their original performance. The spent catalyst is stripped from the oil conversion reactor before entering the regenerator. The stripping vessel used in the fluidized bed catalytic cracker is suitably about 850
The conversion reactor temperature can be maintained essentially within the range of from about 1200°C to about 1200°C, and is desirably maintained above about 870°C. The preferred stripping gas is steam, but steam-containing nitrogen or other steam-containing inert or flue gases may also be used. The stripping gas is generally introduced at a pressure of at least about 10, and preferably about 35 pounds per parallel inch gauge, suitable for substantially complete removal of volatile compounds from the conversion catalyst used. Although the method of the present invention can be used in any conventional cracking catalyst regeneration system, it is advantageously used in a regeneration system that includes at least one rich bed and at least one lean phase zone. The stripped and used catalyst enters the rich bed of the regeneration vessel via appropriate lines leading from the stripping vessel. Entry can be from the bottom or the sides, preferably from the top of the dense bed fluidized zone. It is also possible to enter from the top of the regeneration zone where the catalyst is first contacted with the substantially spent regeneration gas in a narrow dilute phase zone. Catalyst regeneration is accomplished by burning off coke deposits from the catalyst surface with a molecular oxygen-containing gas such as air. A number of regeneration techniques are practiced commercially, which, depending on the extent of coke removal, result in significant recovery of catalyst activity. As coke is removed from the catalyst gradually, removal of the remaining coke becomes most difficult and in practice intermediate levels of restored catalyst activity are accepted as an economic compromise. Combustion of coke deposits from the catalyst requires large amounts of oxygen or air. Although the disclosed patent is not limited thereto, the oxidation of coke is characterized by a simplified mode of oxidation of carbon and is illustrated by the following chemical formula: (a) C+O ₂ →CO ₂ (b) 2C+O ₂ →2CO (c) 2CO+O ₂ →2CO ₂ Reactions (a) and (b) both occur under typical catalyst regeneration conditions, where the catalyst temperature ranges from about 1050 to about 1450 °C, and at temperatures within this range. This is an example of gas-solid chemical interaction when regenerating a catalyst.
The effect of increasing temperature is reflected in an increased rate of combustion of carbon and a more complete removal of carbon or coke from the catalyst particles. Gas phase reactions (c) occur whenever sufficient free or molecular oxygen is present, since the increased rate of combustion is obtained by increased generation of heat. This latter reaction is initiated and propagated by free radicals and is catalyzed. Combustion of sulfur-containing coke deposits from the catalyst also results in the formation of sulfur oxides; and although the disclosed invention is not limited thereto, this combustion is represented by the following chemical formula: (d) S (in coke) + O ₂ →SO ₂ (e) SO ₂ +1/2O ₂ →SO ₃ Reactions (d) and (e) also occur under typical cracking catalyst generation conditions. Reaction (d) is fast, but reaction (e) is relatively slow. Reaction (e) is catalyzed by a catalyst that catalyzes reaction (c) above. The molecular sieve adsorbs sulfur oxides and therefore reaction (e) takes place over the solid particle decomposition catalyst of the process of the invention. Other components of the solid particles also adsorb sulfur oxides. The sulfur trioxide formed then reacts with a suitable metal, or more particularly an oxide of the metal in the metal reactant, to form a stable metal sulfate in the solid particles. When the solid particles are separated from the regeneration zone flue gas, the metal sulfate in the solid particles is recycled to the reaction zone. Thus, sulfur is no longer emitted as gaseous sulfur oxides into the regeneration zone flue gas. The sulfate remains on the solid particles as it passes into the decomposition reaction zone and is converted in the reducing atmosphere to metal reactant metal sulfide and possibly hydrogen sulfide. Upon stripping with a steam-containing stripping gas in the stripping zone, this sulfur is converted to hydrogen sulfide and exits as the stripping zone effluent. This regenerates the metal reactants and makes them available again for reaction with sulfur oxides in the next pass through the regeneration zone. Hydrogen sulfide is then recovered in the decomposition products from the stripping zone, separated and converted to elemental sulfur in conventional equipment. Although the disclosed invention is not limited to this,
These reactions can be summarized as follows. Regenerator MO + SO ₂ +1/2O ₂ or MO + SO ₃ → MSO ₄ Reactor MSO ₄ +4H ₂ → MS + 4H ₂ O → MO + H ₂ S + 3H ₂ O Stopper MS + H ₂ O → MO + H ₂ S These reactions are carried out using the molecular sieve type decomposition catalyst and the present invention. The method is made possible through the use of both metal reactants. The high cracking activity normally present in molecular sieve catalysts is virtually unaffected by the presence of metal reactants, so the expected conversion of feedstock and cracked product yields are significantly lower than the sulfur oxide emissions. Realized with a decrease. The metal reactant may be in finely divided form, such as a powder, and can be separated from the molecular sieve-type decomposition catalyst or any other support. In this case, the metal reactants are introduced separately into the catalytic cracking process cycle and mixed with the molecular sieve cracking catalyst in situ into the catalytic cracking process cycle, but the molecular sieve cracking catalyst is introduced into the cracking process cycle. It is a powder that is not mixed before being mixed. Generally, the powdered metal reactants are useful because the powders are easy to charge and handle in fluid catalytic cracking process systems. The particle size of the powder should be selected to avoid agglomeration of particles at the flow rate. Preferably, the particles of this powder are not so fine as the entrained particulates that problems such as excessive emissions with the gas from the bed occur; however, most of the entrained particulates are recovered and lost. Filters, cyclones, precipitators, etc. are commonly used in conjunction with fluid catalytic cracking operations to return this to the system to reduce the The powder must be strong enough to avoid excessive wear and deterioration of the sized powder. Often, the average particle size of the powdered metal reactants is about 0.5 or 1 to 100 microns in diameter, preferably about 50 microns or less in diameter. Finely divided particles, i.e., having an average particle size of less than about 1 micron, such as about 0.01 to 0.5 micron, exhibit a tendency to form large-sized agglomerates;
It has been found that this can be advantageously used in the method of the invention. Examples of powdered metal reactants that can be used in the present invention are magnesium oxide, calcium oxide, Dolomy and Trimex® sold by Trimex Corporation and described in US Pat. No. 3,630,696. Alternatively, the metal reactant is formulated outside the cracking process cycle on a suitable support other than a molecular sieve-type cracking catalyst, and this complex is then introduced into the cracking process cycle, where it is incorporated into solid particles. Become a part of. The support may be an amorphous decomposition catalyst or a solid that is substantially inert to the decomposition reaction, and is, for example, refractory in nature. In this case, the supported metal reactant is mixed with the molecular sieve cracking catalyst within the cracking process cycle, but not before the molecular sieve cracking catalyst is introduced into the cracking process cycle. Desirably, the support used is porous and often contains at least about 10, preferably at least about 50 per gram, including the area of the pores on the surface.
With a surface area of square meters. Examples of supports are silica, alumina, silica-alumina, etc. A solution or solution of the compound or compounds of the metal in the metal reactant by ion exchange, impregnation or other means or in the amount necessary to provide the desired concentration of metal reactant within the scope of the present invention. The metal reactant can be incorporated into the substrate by contacting the substrate or a component thereof. The metal reactant may be combined with the substrate at any step during the manufacture of the substrate or after the substrate has been manufactured. One method of formulation is ion exchange to the substrate. Also useful is the ion exchange of a siliceous solid or clay with a solution or solution(s) of a metal element or compound(s) of element(s) or compound(s) of the metal reactant. Compounds useful for this purpose are metal halides, preferably chlorides,
nitrates, amine halides, oxides, sulfates,
Includes phosphates and other water-soluble inorganic salts and also metal carboxylates and alcoholates of 5 to 5 carbon atoms. Alternatively, the metal reactant is incorporated into the catalytic cracking process cycle with the molecular sieve cracking catalyst or parts thereof in the solid particles of the process of the invention, but before the molecular sieve cracking catalyst is introduced into the cracking process cycle. It is not included in In this case, metal reactants are introduced to the cracking catalyst during the cracking process cycle. In this case, care should be taken in the method of introduction so that the cracking activity and selectivity of the cracking catalyst are not adversely affected. In such cases, the exact manner in which the metal reactant metal or metals is incorporated into the molecular sieve-type decomposition catalyst, the amorphous decomposition catalyst, or the substantially inert substrate is known with absolute precision. do not have. This metal is in complex combination with the carrier material and other components of the solid particles of the present invention. Therefore, the use of the terms "metallic reactant" and "formulated" in the substrate implies the metal of this component present within the carrier material in bound and/or elemental form. Impregnation is carried out in a manner that does not destroy the structure of the substrate. The metal reactant is impregnated onto a molecular sieve-type cracking catalyst only within the cracking process cycle or into a support or amorphous cracking catalyst that is inert to hydrocarbon cracking either within or outside the cracking process cycle. Impregnation is different from cation exchange. Impregnation results in greater deposition and primarily physical bonding on the surface of the substrate, while ion exchange primarily results in chemical bonding and greater diffusion and therefore less surface deposition. In impregnation, the metal is deposited and no significant ion exchange occurs between the metal and the substrate. Impregnating the substrate allows the metal or metal(s) in the metal reaction to be water-soluble, organic solvent-soluble, or monochromatic in an amount sufficient to contain the desired amount of metal or metal(s) on the substrate. The dispersible compound or compounds are present in or as such and the substrate is contacted with these. The complex is dried to remove the solvent, leaving the metal reactant deposited on the substrate. Preferably, water-soluble nitrates are used in impregnating the solution since the residue from the pyrolysis of the nitrates is relatively innocuous to the activity of the hydrocarbon cracking catalyst. Nitrate salts of the halogen and the metal to be impregnated can also be used; however, the by-products resulting from the thermal decomposition of this salt are detrimental to the activity of the hydrocarbon cracking catalyst, so they are virtually inert to the cracking catalyst and the hydrocarbon cracking These salts are most often used when depositing metal reactants on substrates that do not significantly adversely affect the reaction. Another method of physically depositing metal reactants onto a substrate, particularly a porous substrate such as a crystalline aluminosilicate, is to deposit a fluid decomposable compound of the metal or metal(s) of the metal reactant onto the substrate. or by adsorption of the compound(s) followed by thermal or chemical decomposition of this compound or compounds. The substrate is activated by heating to remove the adsorbed water and then contacted with the metal reactant metal or fluid decomposable compound or compounds of the metal(s), thereby Adsorb a compound or compounds onto the surface. Examples of such compounds include metal alkyls, volatile metal halides, and the like.
The adsorbed compound or compounds are then thermally or chemically reduced to its active state, thus leaving the active metal reactant homogeneously distributed on the substrate.
Thermal reduction takes place, for example, in the regeneration vessel during the regeneration process. It is also advantageous to introduce the metal reactant metal or compound or compounds of metal(s) into the decomposition process cycle and incorporate this into the substrate in situ. The compound or compounds can be introduced at any stage of the cracking process cycle in either oil- or water-soluble or dispersible form or in the solid-liquid or gaseous state so that a wide distribution of the solid particles is obtained. For example, this compound or compounds
can be mixed with the feedstock or fluidizing gas in the reaction zone, with the regeneration gas, torch oil, or water in the regeneration zone, or with the stripping gas in the stripping zone, or can be introduced as a separate stream. Compounds suitable for in situ formulation include metal salts. Examples include metal diketonates and metal carboxylates having from 1 to 20 carbon atoms. A particular example is magnesium acetylacetonate. A preferred embodiment of the method of the invention is described in U.S. Pat.
Includes operations related to the playback mechanism of No. 3909392. No. 3,909,392, which is incorporated herein by reference in its entirety, the catalyst is deactivated by the deposition of coke on the catalyst surface. The present invention relates to an improved off-the-shelf catalytic process, including an improved process for the regeneration of catalysts used in fluidized catalytic exchange of hydrocarbon feedstocks. This method allows the coke level on the regenerated catalyst to be kept at a very low level, while at the same time maintaining a favorable heat balance in the converter and providing a flue gas stream with a very low carbon monoxide content. . Heat from the combustion of carbon monoxide is absorbed by the regenerated catalyst and provides a portion of the process heat required for the hydrocarbon conversion zone. In one embodiment of the method of this patent, the combustion of carbon monoxide to carbon dioxide is approximately 1200 to 1500%;
Desirably, the reaction is carried out to substantially completion in a regeneration vessel of a second, advantageously relatively lean catalyst regeneration zone at a temperature of about 1250 to 1450°C. The temperature of the second zone is about 50 to about 100 degrees higher than the temperature of the first regeneration zone. Partially regenerated catalyst from the relatively dense first catalyst regeneration zone can be conditioned through the second zone in an amount and at a rate sufficient to absorb substantially all of the heat released by combustion occurring in the second zone. can flow. Although most of the coke is combusted from the catalyst in the first zone, excess coke is combusted from the partially regenerated catalyst while present in the second zone, and the substantially coke-free catalyst remains at a hydrocarbon conversion level. until recovered for recirculation. In a second embodiment of the method of U.S. Pat. No. 3,909,392,
Virtually all of the combustion, including both oxygen and carbon monoxide oxidation of the coke and carbon over the catalyst, occurs in a single, relatively rich phase depending on proper adjustment of regeneration temperature and gas velocity. Occurs within the regeneration zone. Similarly, when the process of the present invention is operated in an embodiment that includes the regeneration mechanism of U.S. Pat. solid particles and provide part of the heat required for the decomposition zone. Advantageously, in this embodiment, the method of the present invention results in the combustion of significant coke and carbon monoxide in the rich phase zone as compared to the lean phase zone when a substantially increased amount of solid particles is present. can be used to disperse the heat generated from it.
As the fraction of combustion that occurs in the dense phase zone increases;
Heat generation in the dilute phase zone is substantially reduced, thus reducing or eliminating the need for rapid rotation of solid particles in the dilute phase zone to absorb the heat generated. This embodiment involves the use of solid particles of the present invention comprising a molecular sieve-type decomposition catalyst and a metal reactant of the present process in a system that substantially supports complete combustion of carbon monoxide. The low catalyst coke level obtained is approx.
Up to 0.2% by weight, preferably up to about 0.05% by weight. This method uses less than about 0.2% by volume, e.g. about 500%
Flue gases can be produced with carbon monoxide contents as low as from 1000 ppm to about 0 to 500 ppm. This method also provides for the recovery of generated heat by direct transfer to the solid particles within the regeneration vessel. In this embodiment, the fluidizing gas in the rich phase of the regenerator has a velocity within the range of, for example, about 0.2 to 4 feet per second, preferably about 0.5 to 3 feet per second. The regeneration gas that serves to fluidize the rich bed contains free or molecular oxygen, and this oxygen is preferably that required for the complete combustion of coke (carbon and hydrogen) to carbon dioxide and steam. A slightly excess amount is charged to the regenerator. The amount of oxygen in excess of that required for complete combustion of coke may vary from about 0.1 to about 25% or more of the stoichiometric oxygen requirement for complete combustion of coke, but advantageously need not be more than about 10%. For example, when air is used as the regeneration gas, a 10% excess of air provides only about 2% by volume of oxygen in the effluent use gas stream. Beneficially, the concentration of molecular or free oxygen and carbon monoxide at any point within the regenerator is kept outside the explosive range under these conditions, preferably the concentration of carbon monoxide eliminates the risk of detonation. Therefore, it is below the explosive range under these conditions. In addition to free or molecular oxygen, the regeneration gas includes inert or dilutive gases such as nitrogen, steam, etc., as well as recycle gas from the regenerator effluent. Frequently, the oxygen concentration of the regeneration gas at the inlet to the regenerator is about 2 to 30% by volume, preferably about 5 to 25% by volume. Since air is conveniently used as the oxygen source, the inert gas may be mostly nitrogen. This inert gas serves to dissipate excess heat from the combustion of coke from the catalyst. The source of the hot, inert gas is the effluent from the regenerator, and a portion of this gas can be recycled to the regenerator and combined with, for example, sufficient entering air or other oxygen-containing gas containing essentially pure oxygen. combined to provide the desired oxygen content. Thus, the recycle gas is used for direct heat exchange to increase the temperature of the regeneration gas, further contributing to the thermal economy of the system. The solid particles within the dilute phase are conveyed in part in multiple stages to a separation zone, usually comprising a cyclone separator, from which the solid particles are returned via a dip-leg directly to the dense bed zone. The used regeneration and combustion gases are then recovered in a plenum and finally discharged for appropriate recovery of the thermal energy contained therein. Methods of recovering heat from flue gases include steam generation, stripping of spent catalyst, indirect heat exchange with various refinery streams, such as feed to a particular conversion process, and the use of various drying or evaporation equipment. Figures 1 and 2 of the accompanying drawings are U.S. Pat.
3909392 is a partially sectional, side view of an apparatus suitable for catalyst regeneration according to an embodiment of the method of the invention, including the regeneration mechanism of No. 3909392; FIG. In fact, this embodiment can be advantageously used in many existing petroleum hydrocarbon cracking units, particularly fluid catalytic cracking units having various spatial arrangements of cracking, stripping and regeneration sections. FIG. 1 shows one embodiment of the invention that uses a bottom charge of stripped and used catalyst fed from a cracking reactor (not shown) to the regenerator. Solid particles containing the used catalyst impregnated with metal reactants enter from the bottom of the regeneration vessel 1 from the reactor through a stripping zone connected to the contact outlet. The solid particles flow upwardly through lines 2 and 3 and are discharged through discharge heads 4 and 5 to the dense phase bed. A dense phase bed is maintained within the lower part 6 of the regenerator vessel and extends upwardly to the phase interface 7. The solid particles in the dense phase bed are fluidized by the flow of combustion air through line 8, valve 9 and line 10 to air ring 11. A substantially balanced airflow pattern through the regeneration zone is achieved by the use of additional air rings (not shown), if desired. Combustion of the coke contained in the catalyst used with air is initiated in the dense phase bed. High temperatures are obtained by temporarily burning torch oil, for example a stream of decanted oil, in the bed. Torch oil is added through line 12 , valve 13 and line 14 terminating in a nozzle located above air ring 11 . The flowing air velocity continuously transports some of the solid particles upward into the dilute phase zone occupying the upper part of the regeneration vessel, ie the part above the phase interface 7. Combustion of the coke continues in the lean phase zone and the primarily used combustion gases along with the entrained solid particles are withdrawn to first stage cyclone separators 20 and 21. Most of the solid particles are separated in the first stage cyclone and discharged downward through diplegs 22 and 23 into the dense phase zone. The gas and remaining solid particles are passed through intermediate stage cyclone lines 24 and 25 to second stage cyclone separators 26 and 27 where substantially all remaining solid particles are separated and passed through diplegs 28 and 29 to a dense phase bed. is sent downward. The substantially used combustion gases are then passed through lines 30 and 31 to the plenum and finally discharged from the regeneration vessel through line 33. This effluent can be suitably heat exchanged for the production of a refinery stream (not shown) or process steam. Solid particles containing regenerated catalyst from the dense bed are withdrawn through standpipes 34 and 35 with collection heads 36 and 37 for return to the cracking reactor. Although the supply of combustion air normally provides an excess of oxygen over that required to effect complete combustion of the coke on the catalyst particles to steam and carbon dioxide,
In one embodiment of the present invention using the regeneration mechanism of US Pat. No. 3,909,392, the combustion of the coke is not completed in the dense bed. In this situation, the combustion gases resulting from the dense bed zone therefore contain significant amounts of carbon monoxide, as well as carbon dioxide and oxygen. The remaining coke and carbon monoxide on the catalyst burns out virtually completely in the lean phase zone with the evolution of much heat. When carbon monoxide burns in the dilute phase, high temperatures are usually present throughout much of the dilute phase zone and particularly at the location approximately indicated by X and are easily visible horizontally through a window (not shown). Can be done. Absorption of heat by masses of solid particles carried upward by the rising combustion gas stream or separated upward from the eductor tube 40 and the solids distributor head 41 where a rain or fountain of solid particles is distributed in the dilute phase zone. The adjustment of the regeneration temperature in the dilute phase zone takes place in part via . line 4
2. Solid particles can be separated by air, steam or other inert gas entering through valve 43 and jet pipe 44 which extends a short distance to the lower end of eductor pipe 40. Excessive temperature levels in the top of the regenerator can be further controlled by sparging steam, for example through lines 45 and 46, valve 47 and line 48 to steam pot 49. The temperature near Plenum is Plenum 3
Line 50 to steam ring 53 surrounding 2, valve 51
and steam supplied through line 52. If desired, extra cooling is provided by water spray (not shown), which is advantageously directed into the area of intermediate stage cyclone lines 24 and 25. This low temperature favors the formation of stable metal- and sulfur-containing compounds in the regeneration zone. FIG. 2 is another embodiment of the present invention using the regeneration scheme of U.S. Pat. No. 3,909,392 for side charging of solid particles containing stripped used catalyst and metal reactants from the cracking reactor to the regenerator. It shows. Solid particles containing the used catalyst impregnated with metal reactants were placed on the side of the regeneration vessel so that they could be charged to the dense phase bed held in the lower part 106 a short distance below the phase interface 107. It flows downwardly through inlet line 102 and into regeneration vessel 101 . Line 108 to air ring 111, valve 109
and fuel air passing through line 110 to fluidize the solid particles. Extra air rings (not shown) can be used as desired to further balance the airflow pattern through the regeneration zone. As shown in Figure 1. Combustion of the coke on the catalyst used begins in the dense phase zone, where high temperatures are obtained by temporary combustion of the torch oil stream in the zone, if desired. This torch oil can be added through line 112, valve 113 and line 114 terminating in the nozzle. Dilute phase zone or phase interface 10 occupying upper portion 115 of the regeneration vessel
The velocity of the flowing air can be adjusted to continuously transport solid particles upwards for the purpose of heat absorption into the upper part of 7. Combustion of coke and carbon monoxide continues in the lean phase zone, and the primarily used combustion gases along with the entrained portion of solid particles are withdrawn to first stage cyclone separators 120 and 121. Most of these solid particles are separated in the first stage cyclone and discharged downward into the dense phase zone through diplegs 122 and 123.
a second stage cyclone separator 126 in which substantially all of the remaining solid particles are separated and sent down through diplegs 128 and 129 to a dense bed;
The gas and remaining solid particles are subsequently sent through intermediate stage cyclone lines 124 and 125 to and 127. The substantially used combustion gases then pass through lines 130 and 131 to plenum 132.
and finally discharged from the regeneration vessel through line 133. Solid particles containing regenerated catalyst are withdrawn from the rich bed through standpipes 134 and 135 with collector heads 136 and 137 for return to the catalytic cracking reactor. As described for the embodiment of FIG. 1, carbon monoxide burns in the lean phase providing a high temperature zone throughout most of the lean phase zone and particularly at the general location indicated by X. Regulation of the regeneration temperature within the dilute phase zone is achieved entirely through the absorption of heat by the mass of solid particles carried upward by the rising combustion gas stream. Steam supplied through line 150, valve 151, and line 152 to a steam ring 153 surrounding plenum 132 can reduce the temperature in the vicinity of the plenum, cyclones, and connecting lines as needed. Water spray means (not shown) can be used as well. Another particularly preferred embodiment of the invention uses the apparatus shown in FIG. 2 with significant changes in operating parameters compared to the previous embodiments. In this embodiment, the gas velocity and solid particle charge are adjusted so that essentially complete fueling of coke and carbon monoxide is completed within the dense phase, and the heat is dispersed through the bed. When the system is operated according to either of the first two aforementioned embodiments, the recovery of the heat released by essentially complete combustion of the coke and carbon monoxide is achieved by absorption in the solid particles of both phases and by concentrated The incorporation of solid particles into the phase also helps ensure maintenance of suitably high temperatures within the dense phase zone. The combined solid particles carry extra heat with them to raise the temperature of the dense phase zone to a temperature that favors the removal of additional increments of coke deposits so that the combustion of the final increments of coke is substantially complete. carry. When the system is operated such that essentially all combustion is completed within the rich catalyst phase, the heat is dispersed through the phase as it is absorbed by the fluidized solid particles and the final increments of coke are combusted. . Thus, in all embodiments, the solid particles containing regenerated catalyst that are sent to the cracking reactor back to the regenerator are preferably from 0.01 to about 0.10% by weight, preferably from 0.01 to 0.05% by weight, and preferably from 0.01 to about 0.10% by weight. It contains about 0.01 to about 0.03 weight percent carbon or coke on the catalyst and can be withdrawn from the regenerator at a temperature useful for use in a cracking reactor. A significant advantage of the present invention is that it provides a regenerated catalyst that generally has enhanced activity and selectivity properties very close to those of the new conversion catalyst, particularly for use in conversions carried out in riser reactors with very short contact times. There is a particular thing. Both the cracking activity of the sieve-containing catalyst and the selectivity for converting hydrocarbon feed to desired products are dramatically affected in favor of increased elimination of residual carbon or coke on the catalyst during regeneration. Low coke levels on the regenerated catalyst are particularly advantageous for fluid cracking catalysts containing catalytically active crystalline aluminosilicates.
Higher yields of the desired product are therefore obtained. In this decomposition method, which uses a lower rich phase zone and an upper dilute phase zone in the regeneration zone, the oxidation of carbon monoxide to carbon dioxide is mostly at least about 60%, and often about 65 to 95% or more. It is carried out in the rich phase of the regenerator until completion. The oxidation of carbon monoxide to dense phase carbon dioxide provides heat from the fluidized catalyst to assist in the combustion of coke deposits. Furthermore, a significant portion of the carbon monoxide is oxidized in the dense phase, and a smaller amount of carbon monoxide is present for combustion in the upper phase of the fluidized catalyst in the regenerator, and therefore in the reactor, waste gas flue. , an unregulated excess of carbon monoxide in the upper part of the regenerator, detrimentally affecting the material used to construct the collector, e.g. cyclone, for particulate matter in the waste gas, and impairing the catalyst activity. "Afterburn" and high temperatures due to combustion are substantially reduced or avoided. Solid particles containing regenerated catalyst particles having a significantly low residual coke content are removed from the dense phase and substantially passed through a standpipe to a cracking reactor for contact with fresh hydrocarbon feed or recycled hydrocarbon fractions and mixtures thereof. Delivered at top concentrated bed temperature. Because the oxidation of carbon monoxide generated from the combustion of coke deposits on the catalyst occurs mostly in the rich phase, and in the preferred embodiment essentially entirely in the rich phase, the regenerated catalyst is can be returned to the cracking reactor at higher temperatures as well as higher activities. One major advantage from the process of the invention concerns the significantly lower carbon monoxide content in the gas stream leaving the regenerator from which it is obtained. Flue gas from conventional regeneration of cracking catalysts typically accounts for about 6 to 10%
For those containing carbon monoxide, similar amounts of carbon dioxide and negligible amounts of oxygen, this new regeneration method reduces the carbon monoxide content of the flue gas to approximately 0.2% by volume or less.
For example, the capacity is maintained at approximately 500 to 1000 ppm (ppmv). Advantageously, this content is even lower, for example in the range of 0 to about 500 ppmv. This low concentration of carbon monoxide in the flue gas allows direct exhaustion of the effluent gas to the atmosphere while meeting ambient air quality standards. If desired, the remaining carbon monoxide can be suitably combusted in the exhaust from the regenerator flue gas stack. This advantage of the present invention provides for the recovery of a portion of the energy produced by the subsequent oxidation of carbon monoxide while meeting existing standards for ambient air quality for carbon monoxide boilers and associated turbine-type equipment or carbon monoxide emissions. The capital investment required to install separate equipment for this purpose can further be eliminated. The method of the invention provides other advantages. This advantage concerns afterburning and heat balance issues. One major problem that often arises and should be avoided in practice, especially in fluidized catalyst regeneration, is for example the Petroleum Processing of Hengstebeck,
McGraw-Hill Books, 1959, pp. 160 and 175, and Oil and Gas Journal, No. 53.
Volume (No. 3) 1955, pages 93-94, a phenomenon known as "afterburn." This term refers to the further combustion of carbon monoxide to carbon dioxide, as is the case with reaction (c) above, which is highly exothermic. Afterburning is strictly avoided in catalyst regeneration methods because it leads to very high temperatures that damage the equipment and cause permanent deactivation of the cracked catalyst particles. Many fluidized catalyst regeneration operations experience afterburning, and a substantial technical community has developed a number of means for adjusting regeneration techniques to avoid afterburning. More recently, increasing regenerator temperatures have been sought for various reasons;
For example, US Patent Nos. 3,161,583 and 3,206,393;
and as described in U.S. Pat. No. 3,513,087,
Precise equipment has been developed for regulating the regenerator temperature at the point of initial afterburning by suitable means for regulating the oxygen supply to the regenerator. Therefore, with regard to afterburn prevention, typical modern practice is that the flue gas from the catalytic regenerator normally contains very small amounts of oxygen and significant amounts of carbon monoxide and carbon dioxide in almost equimolar amounts. do. The further combustion of carbon monoxide to carbon dioxide is a sink of thermal energy as reaction (c) is highly exothermic. Afterburning occurs at temperatures above about 110°C, and per pound of carbon monoxide oxidized
Emits 4350BTU. This typically represents about 1/4 of the total heat production that can be achieved by burning coke. As described, for example, in U.S. Pat. No. 2,753,925, the combustion of carbon monoxide, after separation of the effluent gas from the catalyst, is tunably carried out in a separator zone or in a carbon monoxide boiler, and the thermal energy released is converted into high-pressure steam. Used in various essential oil operations such as generation of oil.
Other uses of this thermal energy are covered by U.S. Patent No.
No. 3012962 and No. 3137133 (turbine drive) and No. 3363993 (preheating of petroleum feedstock). Although this heat recovery method requires separate and delicate equipment, it helps to minimize the emission of carbon monoxide into the atmosphere as a component of the effluent gas, thus helping to avoid potentially severe pollution hazards. . Furthermore, the silica-alumina catalysts conventionally used for many years in various processes for the cracking of petroleum hydrocarbons have been found to have poor performance relative to the level of residual coke on the catalyst unless the coke level is greater than about 0.5% by weight. It's not particularly sensitive. However, silica
The alumina catalyst is further compounded with a crystalline alumino-silicate component and zeolite or "molecular sieve"
It has been largely replaced by a catalyst known as This molecular sieve-containing catalyst is sensitive to residual coke levels and is greatly influenced with respect to catalyst activity and catalyst selectivity for conversion of the feed to the desired product or products. Due to the difficulties encountered with conventional catalyst regeneration techniques for removing the last increments of residual carbon, actual coke levels typically correspond to residual coke content on the regenerated catalyst in the range of about 0.2 to about 0.3% by weight. do. The increased activity and selectivity obtained with molecular sieve cracking catalysts with low coke levels provides an attractive incentive to find means of reducing residual coke levels even further. Coke levels below about 0.05% by weight are highly desirable, but are not usually obtained by commercially viable means. Considerations such as larger regeneration vessels, larger catalyst stocks, and larger heat losses all interfere with reaching this ideal equilibrium catalyst activity level. Many fluid crackers operate on a "heat balance" principle, depending on the combustion of coke to generate the heat required for the process. However, this device has not been able to take full advantage of cracking catalysts, especially zeolite catalysts, which are particularly available in riser reactors where the contact time between catalyst and oil vapor is very short. A type of operation that allows high conversion combined with high selectivity favors a low catalyst-to-oil ratio in the riser reactor;
This leads to less coke being available in the regenerator to generate heat by combustion. Therefore, an external heat source, such as a feed preheating furnace, is often added to increase the temperature of the catalyst, or alternatively, the equipment is operated at the lower temperature of the fresh feed. This undesirable feature is avoided or minimized by the method of the present invention which allows efficient recovery of excess heat by solid particles for transfer to the riser reactor. In conventional operation, the heat of combustion of coke is approximately 12,000 BTU per pound. The method of the present invention can increase the heat available from combustion of course to values of about 17,000 BTU per pound or more. This higher heat of combustion increases the regenerator temperature,
The trend is to reduce the level of coke on the regenerated catalyst and to reduce the circulation rate of solid particles while providing improved yields at a given conversion level. Reference Example 1 Lubricating oil additive containing 9.2% by weight of magnesium distributed as magnesium hydroxide, magnesium carbonate and magnesium polypropylbenzenesulfonate dissolved in 33.1g of catalytic light circulating oil.
10 g of a 6.9 g solution containing 2.5 wt.% molecular sieves and about 0.6 wt.% sodium was withdrawn from a commercial fluidized catalytic cracker and then calcined to 220 g of an equilibrium commercially available cracking catalyst. It was cracked in a bench scale cracker with a fluidized bed. This circulating oil was decomposed at 700°C for 4 minutes. After purging the catalyst bed with nitrogen for 10 minutes at 1250 °C, the catalyst bed was
The decomposition-purge-regeneration cycle was repeated until the magnesium, zinc and phosphorus contents of the catalyst reached levels of 1100, 703 and 59 ppm, respectively. Zinc and phosphorus were naturally present. Reference example 2 The process of reference example 1 was repeated, but with 6.5g of oil.
and 1.6wt% Zn, 1.3wt% P and 4.6wt%
The cracking-purge-regeneration cycle was repeated using a solution containing 3.5 g of the Mg-containing lubricating oil additive until the magnesium, zinc, and phosphorus contents of the catalyst reached 2400, 1200, and 1097 ppm, respectively. Reference Example 3 The process of Reference Example 2 was repeated, except that silica
An equilibrated, commercial cracking catalyst containing 3.3% by weight molecular sieves in an alumina matrix and also drawn from a commercial fluid catalytic cracker and calcined was used and the catalyst magnesium, zinc,
The decomposition-purge-regeneration cycle was repeated until the and phosphorus contents reached 4600, 304, and 1136 ppm, respectively. Reference Example 4-8 A bench scale laboratory regenerator was used to test the performance of a number of impregnated catalysts to provide reduced emissions of sulfur dioxide to the regeneration zone flue gas. Synthetic flue gas consisting of 1500 ppm sulfur dioxide in a mixture of 4% by volume each of oxygen and water vapor in nitrogen,
It was passed through a fixed fluidized bed of metal-impregnated molecular sieve cracking catalyst, which was kept in a glass regenerator surrounded by a furnace to provide the desired regeneration temperature of 1250°C. The temperature of the catalyst was measured with a thermocouple.
A cyclone was used to separate the entrained catalyst from the gas exiting the regenerator and return the catalyst to the catalyst bed. In actual fluid catalytic cracker operation, the time the regenerator is operated under the given set of conditions is about 40 to about 90 minutes to allow sufficient time to establish the oxidation state of the metals on the catalyst. ranged. The sulfur dioxide content of the gas exiting the regenerator was continuously analyzed using an ultraviolet analyzer. The amount of sulfur dioxide removed from the regeneration zone flue gas was measured as the difference between the sulfur dioxide content of the fresh synthesis gas mixture and the gas exiting the regenerator. The volume % of sulfur dioxide removed from the regeneration flue gas is shown in Table 1 as a function of the time elapsed after the start of the experiment. The % volume removed decreased as the catalyst surface became saturated. Reference Example 4 is a comparative test using a flow rate of a synthetic flue gas mixture of 1084 ml per minute and the unimpregnated equilibrium catalyst used in Examples 1 and 2, while Reference Examples 5 and 6 are compared with Reference Examples 1 and 2, respectively. Impregnated catalysts were prepared and flow rates for synthetic flue gas mixtures of 989 and 1014 ml per minute, respectively.

Table: Reference Example 7 was a comparative test using the unimpregnated catalyst used in Reference Example 3 and a flow rate of 891 ml of synthetic flue gas mixture per minute. Reference Example 8 included the impregnated catalyst prepared in Reference Example 3 and a flow rate of 992 ml of synthetic flue gas mixture per minute. The flow rate was measured at 60〓. Reference Example 9-10 In Reference Example 9, the steps of Reference Examples 4-8 were repeated, except that a synthetic flue gas mixture consisting of 4% by volume each of carbon monoxide, oxygen and water vapor in nitrogen was used.
Magnesium oxide with a particle size of 5 microns
Fine and unimpregnated, calcined containing 5.3% by weight hydrogen and rare earth ion exchange, Y-type crystalline aluminosilicate and silica-alumina (which contains 30% by weight alumina instead of impregnated catalyst) The mixture was passed through a fluidized bed of a mixture with a commercially available molecular sieve-type decomposition catalyst at a flow rate of about 1000 ml per minute (measured at 60 ml). This mixture contains 0.3% by weight of magnesium oxide and about 70% of carbon monoxide.
% by volume was converted to carbon dioxide. In reference example 10,
When the unimpregnated catalyst used in Reference Example 9 was used in the absence of magnesium oxide under otherwise identical conditions, approximately 58% by volume of carbon monoxide was converted to carbon dioxide. Reference Example 11 and Example 1 In Reference Example 11, a gas oil feed having a sulfur content of 1.67% by weight was cracked in a commercially available fluidized catalytic cracker having a riser reactor. A commercially available balanced molecular sieve cracking catalyst containing 2.5% by weight molecular sieves and about 0.6% by weight sodium was used.
In Example 1, a second gas oil feed having a sulfur content of 1.68% by weight was cracked in the same commercial equipment using the same regeneration mechanism and the same cracking catalyst, but in addition the catalyst was impregnated with magnesium and zinc. .
Magnesium and zinc were deposited on the catalyst as follows. A small amount of a mixture of magnesium sulfonate and zinc dialkyldithiophosphate is dissolved in the gas oil feedstock prior to introduction into the reaction zone of the catalytic cracker. These compounds thermally decompose within the reaction zone, resulting in the deposition of magnesium and zinc on the catalyst.
After several hours of addition in this manner, levels of 0.3% by weight magnesium and 0.1% by weight zinc were deposited on the cracking catalyst. Catalyst particles deactivated with sulfur-containing carbonaceous deposits were transferred from the reaction zone to a stripping zone of a catalytic cracker, where volatile deposits were removed from the deactivated catalyst by contacting with a stripping gas. . The stripping gas is water vapor. The stripped catalyst particles were transferred from the stripping zone to the regeneration zone of the apparatus, and the sulfur-containing carbonaceous deposits that could not be stripped from the stripped catalyst particles were regenerated by burning with air. Regenerated catalyst particles were recycled to the reaction zone. The operating conditions and composition of the regenerated flue gas are
Shown in the table.

[Table] Reference example 12 Calcium nitrate [Ca(NO ₃ ) ₂ .
Using a solution containing 36.9 g of 4H ₂ O, 0.260 cm ³ /
82.4 g of granular α-alumina with a porosity of 1.5 g was impregnated. Dry the impregnated alumina overnight at 250 °C.
It was then calcined at 1000°C for 3 hours to produce a granular composition containing 7% by weight calcium. Reference example 13 450g of magnesium nitrate [Mg(NO ₃ ) ₂ .
A solution was prepared by dissolving 6H ₂ O] in enough water to give 500 ml of solution. in this solution
Granular fluidizable α passed through a 100 mesh sieve
- 232 g of alumina were added. Next, the excess solution was filtered and the impregnated alumina was dried at 250°C.
Calcined at 1000㎓. A 20 g sample of the obtained solid was taken and the remainder was added to the above solution, the excess solution was removed by filtration, and the solid was dried at 250 ml and calcined at 1000 ml. This procedure was repeated two more times, but before each repetition a 20 g sample was taken and 14.3% by weight
of magnesium. Reference example 14 Using a solution of 0.116 g of barium nitrate [Ba(NO ₃ ) ₂ ] in enough water to make 12 ml of solution,
20 g of granular α-alumina with a specific surface area of 1.4 m ² /g and a porosity of 0.254 cm ³ /g were impregnated. The impregnated alumina was dried overnight at 250° and calcined for 3 hours at 1000° to give a granular composition containing 0.3% barium by weight. Reference Example 15 The ability to absorb sulfur dioxide from a gas stream was measured for various compositions using the following procedure.
A 1.00 g sample of the composition was placed on top of a glass wool stopper in a quartz sample tube having a diameter of 1.3 cm and a length of 41 cm. The sample tube is then placed in a tube furnace and brought to the desired temperature while a purging gas consisting of helium containing approximately 2.6% water vapor by volume is passed downward through the sample bed at a flow rate of 10 cm ³ /min. Heated. After one hour of purge, a synthesis gas consisting of 0.10% by volume sulfur dioxide, 2.9% by volume oxygen, 2.6% by volume water vapor, and the balance helium was passed downward through the sample bed at a rate of 10 cm ³ /min. The gas stream was periodically sampled after passing through the sample bed and the samples were analyzed for sulfur dioxide by gas chromatography. From the analytical values, 29.1% Al ₂ O ₃ , 0.46% Na ₂ O and
Contains 0.11% Fe and Y-zeolite
CBZ-1 Granular Decomposition Catalyst [Davison Chemical
Davison Chemical Divison,
WRGrace & Co.] are listed in Table 3 as Test A. Table 3 shows the results for the mixture of 1% by weight of the particulate additive prepared according to Reference Examples 12 to 13 and the CBZ-1 decomposition catalyst in Test B.
and described as Test C. Finally, Table 3 shows the results for the pure additive prepared according to Reference Example 14.
This is described as Test D. The samples used in Tests A, B, and C were subjected to steam (100% steam at atmospheric pressure) at 1400°C for 5 hours before use.

EXAMPLE 2 A gas oil feed having a sulfur content of 1.67% by weight was cracked in the same commercial equipment as used in Reference Example 11 using the same cracking catalyst and operating conditions. However, a granular fluidizable additive consisting of 15% by weight magnesium supported on an amorphous silica-alumina substrate results in a mixture of the additive and decomposition catalyst in a device containing 0.5% by weight magnesium. was introduced into the circulation process by adding it to the regenerator in an amount sufficient to Small amounts of additives were then added periodically at a rate sufficient to maintain a 0.5% by weight magnesium concentration in the mixture of particulate solids circulating through the process equipment. The particle mixture containing the catalyst rendered inactive by the sulfur-containing carbonaceous deposits is transferred from the reaction zone to the stripping zone of the catalytic cracker, where the volatile deposits are removed from the particle mixture by contacting it with a stripping gas. did. The stripping gas is water vapor. transferring the stripped particles from the stripping zone to the regeneration zone of the device;
Therefore, the decomposition catalyst was regenerated by burning the sulfur-containing carbonaceous deposits that could not be stripped from the stripped particles with air. The particle mixture containing regenerated catalyst particles was recycled to the reaction zone. The operating conditions are shown in Table 2. The effluent gas from the reaction zone was 13 mol% _CO2 , 0.5 mol% CO, and less than 200 ppmv _SO2 . Analysis of the regeneration zone effluent gas showed that the sulfur oxide content was less than 50% of the amount produced in Reference Example 11 without the magnesium-containing additive.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional, side view of an apparatus suitable for catalyst regeneration embodying the method of the present invention, and FIG. 2 is a partially sectional, side view of an apparatus illustrating another embodiment of the method of the present invention. FIG.

Claims (1)

[Claims] 1. () A feedstock containing from about 0.2 to about 6% by weight of sulfur as an organic sulfur compound is subjected to decomposition in a reaction zone having fluidized particles of a molecular sieve-type decomposition catalyst;
() Catalyst particles inactivated by sulfur-containing carbonaceous deposits are separated from the reaction zone effluent and transferred to a stripping zone where the volatile deposits are inactivated by contact with a stripping gas. removing from the catalyst, () separating the stripped catalyst particles from the stripping zone effluent and transferring them to a regeneration zone, and combusting unstrappable sulfur-containing carbonaceous deposits from the stripped catalyst particles with an oxygen-containing gas; as an organic sulfur compound, and () the regenerated catalyst particles are separated from the regeneration zone effluent and recycled to the reaction zone.
In a recirculating fluid catalytic cracking process for hydrocarbon feedstocks containing from 0.2 to about 6 wt. adding particles containing the flowable metal reactant other than the catalyst to form a mixture of particles containing from about 10 to about 99.9975% by weight molecular sieve cracking catalyst;
or () by adding a solution or dispersion of said metal reactant, and said metal reactant is at least one free or compound selected from the group consisting of magnesium, calcium, strontium and barium. and wherein the amount of metal reactant added is sufficient to effect absorption of at least about 50% of the sulfur oxides produced by said combustion of the sulfur-containing carbonaceous deposit in the regeneration zone. (b) decompose said feedstock at a temperature of from about 850 to about 1200°; (c) separated from the reaction zone with a stripping gas containing steam at a temperature of from about 850 to about 1200°; stripping the volatile deposits from the catalyst and metal reactant combination, and the weight ratio of steam to decomposition catalyst is from about 0.0005 to about 0.025; (d) at a temperature of from about 1050 to about 1450°; (e) regenerating at least about 50% of the sulfur oxides produced by said combustion of the sulfur-containing carbonaceous deposit in the regeneration zone;
% of the catalyst and metal reactant combination, (f) transferring the catalyst and metal reactant combination containing the absorbed sulfur oxide from the regeneration zone to the reaction zone, and (g) molecular oxygen. (h) withdrawing from the regeneration zone an effluent gas stream containing sulfur oxides and having a low concentration of sulfur oxides; A method of reducing sulfur oxide emissions in a regeneration zone effluent gas stream consisting of drawing steps. 2. The method of claim 1, wherein the metal reactant comprises at least one free or combined metal element selected from the group consisting of magnesium and calcium. 3. The method of claim 1, wherein the amount of said metal reactant is from about 0.1% to about 0.5% by weight of said mixture of particles, calculated as metal. 4. said flowable particles containing a metal reactant comprising a supported metal reactant, said support selected from the group consisting of an amorphous decomposition catalyst and a solid substantially inert to the decomposition catalyst; The method according to claim 1. 5. The method of claim 4, wherein said support is selected from the group consisting of silica, alumina, thoria and boria. 6. The method of claim 1, wherein the particles of molecular sieve cracking catalyst represent from about 90 to about 99.9% by weight of the mixture of particles. 7 The ratio of steam to said decomposition catalyst is approximately
2. The method of claim 1, wherein 0.0015 to about 0.0125. 8. The method of claim 1, wherein the regeneration zone effluent gas stream contains at least about 0.01% by volume molecular oxygen. 9. The method of claim 1, wherein the regeneration zone effluent gas stream contains less than about 600 ppmv sulfur oxides. 10. The method of claim 1, wherein the feedstock has a sulfur content within the range of about 0.2% to about 6% by weight. 11. The method of claim 1, wherein the flowable particles containing metal reactants are particles of magnesium oxide.