FI61513C - FOER REQUIREMENTS FOR THE REGENERATION OF CATALYTIC CONVERTERS AND CATALYTIC FLUID SYSTEMS - Google Patents

Description

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Patent · och registerstyrelsen Amttkan utlajd octi uti.tkriftan pubiiurad 30. OU. 82 (32) (33) (31) Requested for stueiksui — Bsjlrt prtorttat OU.08.75 USA (US) 601851 (71) UOP Inc., Ten UOP Plaza, Algonquin & Mt. Prospect Roads, Des Plaines,

Illinois 600l6, USA (72) David Bruce Bartholic, Edison, New Jersey, Algie James Conner, Downers Grove, Illinois, USA (7I +) Berggren Oy Ab (5I +) Process for the regeneration of a coke-contaminated catalytic fluidized cracking catalyst - FÖrfarande för regeneration of a catalytic catalyst from a catalytic fluidized bed cracking

The field covered by this invention is hydrocarbon processing. More specifically, the invention relates to a regeneration process for the oxidative removal of coke from a PCC catalyst and the catalytic conversion of CO to CCl.

A regeneration technique in which the spent catalyst to be fluidized is regenerated in a regeneration zone covers a wide range of chemical fields. Patents that have sought to solve problems with .

In particular, current refinery practice has been to use conventional regeneration zones to prevent substantially complete conversion of CO to CC 2 in any regeneration zone, and especially in the dilute phase catalyst zone, where little catalyst is present to absorb reaction heat and may result in cyclone or other thermal separation. Substantially 2 * 1513 complete CO conversion in conventional regeneration zones was prevented quite simply by limiting the amount of fresh regeneration gas introduced into the regeneration zone. When oxygen is not present enough to maintain the reaction of CO to CO2, afterburning simply cannot occur regardless of the temperatures in the regeneration zone. Likewise, the temperatures in the regeneration zone were generally limited to less than about 677 ° C by appropriately selecting the operating conditions of the hydrocarbon reaction zone or the fresh feed or reflux streams. At these temperatures, the reaction rate of CO oxidation decreased significantly, so that if disturbances occurred, a larger excess of fresh regeneration gas would be needed to change the CO than would be required at temperatures above about 677 ° C. The resulting combustion gas, which contained several volume percent CO, was either discharged directly into the atmosphere or used as fuel in a CO boiler located downstream of the regeneration zone.

It is common practice for those skilled in the art of PCC processes to initially adjust the flow of fresh regeneration gas to the regeneration zone manually in an amount sufficient to produce partially used regeneration gas, but insufficient to maintain substantially complete CO conversion while limiting the regeneration night. This required flow rate usually corresponded to about 3.63-5.44 kg air / 0.454 kg coke. Once reasonable steady state control was achieved, the fresh regeneration gas flow rate was typically adjusted to respond directly to a small temperature difference between the flue gas outlet temperature (or dilute phase release temperature) and the dense bed temperature to maintain this suitable fresh regeneration gas flow rate regeneration zone. As the temperature difference increased above some predetermined temperature difference, indicating that more CO conversion occurred in the dilute phase, the amount of fresh regeneration gas was reduced to substantially prevent complete conversion of CO to CO2. Examples of this control method are Pohlenz's U.S. Patents 3,161,583 and 3,206,393. · Although such a method produces a small amount of O 2 in the combustion gas, usually between 0.1 and 1% by volume, it prevents substantially complete conversion of CO 2 to CO 2: in the regeneration zone.

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Until the advent of zeolite-containing catalysts, there was little economic incentive for the substantially complete conversion of CO to CC 2 in the regeneration zone. Combustion heat, which. could have been removed was simply not necessary in the process; there was generally no feed preheating for the hydrocarbon reaction zone and the higher coke yield obtained with amorphous catalysts in the hydrocarbon conversion zone was usually sufficient for combustion in the regeneration zone to provide the heat required to balance the entire process at lower feedstock temperatures such as feed preheating. However, the use of zeolite-containing FCC catalysts with lower coke-forming tendencies and the use of a higher temperature in the hydrocarbon conversion zone often made it necessary to supply additional heat to the FCC process. Typically, the additional heat was generated by burning external fuel, such as burner oil in the regeneration zone, or preheated with an FCC hydrocarbon feed in external preheaters. Thus, heat was typically first added and later removed from the FCC process by two external devices, a feed preheater and a CO boiler, both of which represent a substantial capital investment.

By the process of our invention, coke from a spent fluidizable cracking catalyst containing catalytically effective amounts of a CO conversion promoter is oxidized and substantially complete catalyzed conversion of CO to CO 2 is initiated and controlled in the dense phase catalyst bed in the regeneration zone. The recovery of the heat of reaction from CO combustion in at least a partially dense phase catalyst bed allows either lower feed preheating requirements or higher hydrocarbon reaction zone temperatures without additional feed preheating while eliminating the air pollution problem without the need for an external CO boiler. More specifically, the use of a catalytic fluidized cracking catalyst in our process containing catalytically effective amounts of CO conversion agents allows either the same CO conversion rate to occur up to 55 ° C or more below that required without a CO conversion agent, or a faster C0 conversion rate to occur. at a certain temperature than would occur at the same temperature without the use of a CO conversion promoter. It is this latter advantage that is of particular commercial importance.

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Without a CO conversion promoter, the uneven distribution of fresh regeneration gas in the dense phase catalyst bed often requires higher regeneration zone temperatures or higher fresh regeneration gas rates than is desirable to maintain a sufficiently high CO conversion rate so that substantially complete CO conversion occurs. To raise the temperature in the regeneration zone, the burner oil was burned in the regeneration zone or larger amounts of slurry oil were recycled back to the hydrocarbon reaction zone so that the spent catalyst contained more coke that could be burned in the regeneration zone to raise the temperature. Increased fresh regeneration gas rates, in addition to fan capacity utilization, often overloaded cyclone separators and produced higher amounts of particulate emissions (catalyst) from the combustion gas than allowed by air pollution regulations. The use of a CO conversion promoter makes it possible to eliminate burner oil or increased recycled sludge oil rates and reduce the amount of excessive fresh regeneration gas and give the refinery back more FCC process flexibility.

Although the use of temperatures above about 677 ° C in regeneration zones has been widely taught in the art in the past (see, e.g., U.S. Patents 3,751,359, 3,757,777, 3,563,911, and 3,769,203) and also discloses extensive control of air flow rates relative to flue gas. oxygen (see, e.g., U.S. Patents 2,4 ± 4,002 and 2,466,041), the process of our invention is clearly distinguishable therefrom in that it requires and does not substantially avoid complete conversion of CO to CO 2 in the regeneration zone. In addition, our process states that the oxidation of C0 is not achieved by the high temperature factor alone, i. at temperatures above about 677 ° C; in fact, the process of our invention requires, as a distinct step, the introduction of sufficient fresh regeneration gas into a dense bed to allow for substantially complete conversion of CO2 to CO2. If not enough O 2 is present, temperatures above about 677 ° C do not initiate or maintain afterburning.

A temperature of about 677 ° C is initially required to provide a sufficiently high reaction rate once the CO conversion has been initiated to ensure that it is substantially complete in the dense bed of the regeneration zone.

Prior art information relating to the use of CO conversion agents in regeneration zones is U.S. Patent 3,88,121. In the process of that invention, the oxidation of coke and CO is accomplished using two separate catalysts of different particle size and composition: a hydrocarbon conversion catalyst; CO oxidation catalyst. Moreover, the CO oxidation catalyst is kept in a regeneration zone of the conventional type and does not leave this zone to the hydrocarbon reaction zone as the catalyst used in the process of our invention does.

Accordingly, it is a broad object of the process of this invention to provide a process for oxidizing coke from a spent fluidized catalyst containing catalytically effective amounts of CO conversion aids and substantially complete catalytic conversion of CO to produce a regenerated catalyst and spent regeneration gas such that at least some of the heat of CO conversion is recovered in the regeneration zone. It is a further object of our invention to provide a lowering of the minimum temperature required for substantially complete CO conversion and to provide an increase in the rate of CO conversion by using a CO conversion promoter and not by using high regeneration zone temperatures or high fresh regeneration gas rates. Furthermore, the purpose of our method is to provide that sufficient fresh regeneration gas is available to ensure substantially complete combustion of CO 2 to CO 2 despite variations that may occur in the amount of coke on the surface of the spent catalyst entering the regeneration zone.

Briefly, in one embodiment, our invention is a process for regenerating a coke-contaminated catalytic liquid cracking catalyst containing effective amounts of a CO conversion promoter from a catalytic process and converting carbon monoxide from at a first flow rate sufficient to oxidize the coke to produce a partially used regeneration gas; b. oxidizing the coke under first oxidation conditions, including a first temperature of the catalyst bed between 399 and 677 ° C, to produce a regenerated catalyst and a partially used CO-containing regeneration gas; c. raising the temperature of the catalyst bed from the first temperature to a second temperature between 677-760 ° C; d. introducing fresh regeneration gas into the catalyst bed at a second flow rate stoichiometrically sufficient to oxidize CO to substantially complete CO 2; e. oxidizing CO to produce spent regeneration gas in a catalyst bed maintained under other oxidation conditions, including the presence of a CO conversion enhancer; f. analyzing the regeneration gas used to obtain a measured free oxygen concentration and comparing the measured free oxygen concentration to a predetermined free oxygen concentration; and g. the fresh regeneration gas is then adjusted to a third flow rate to keep the measured free oxygen concentration equal to the predetermined free oxygen concentration, which ensures substantially complete conversion of CO to CCl. The characteristic features of the invention are given mainly in claim 1.

Other objects and embodiments of the present invention include details of catalysts, operating features, and operating conditions, all of which are disclosed below in the following description of all of these various aspects of our invention.

Having thus described the invention in short general terms, reference will now be made to the drawing to provide a better understanding of the present invention. It is to be understood that the drawing is presented only in such detail as is necessary for an understanding of the invention and that minor aspects are omitted for simplicity and do not limit the scope and spirit of our invention.

The accompanying drawing schematically shows a side view of a regeneration zone suitable for carrying out the method of our invention. Spent catalyst, typically containing about 0.5-1.5% by weight? coke, passes from the hydrocarbon reaction zone (not shown) to the regeneration zone 1 via line 9. The catalyst is kept in the regeneration zone 1 in a dense layer 3- The freshly regenerated catalyst is removed from the dense layer 3 and the regeneration zone 1 via a pipe * 1 and returned to the hydrocarbon reaction zone. A control valve 5 in the pipe k, typically a sliding valve, is used to control the amount of regenerated catalyst leaving the regeneration zone 1 and passing into the hydrocarbon reaction zone.

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The pipe 14 may join the pipe 9 for the purpose of admitting one of several special liquids. The liquid may be a stripping medium, such as water vapor, which causes adsorbed and cracked hydrocarbons to be removed from the spent catalyst before the catalyst is introduced into regeneration zone 1. The liquid may be an aeration medium such as air or water vapor to keep the spent catalyst · The liquid may also be a hydrocarbon liquid or gas added to the regeneration zone as an external auxiliary fuel for the purpose of raising the temperature in the regeneration zone.

Fresh regeneration gas is fed through a pipe 6 to a sealed layer 3. · Fresh regeneration gas passes through a distributor 8, which allows the gas to be more easily distributed in a sealed layer 3. Typically, the distributor may be a metal plate with holes or slits. In the presence of sufficient fresh regeneration gas and at a dense bed temperature of at least about 677 ° C, oxidation of the coke and substantially complete post-combustion of CO to CO2 occur in the dense bed to produce regenerated catalyst and spent regeneration gas.

The spent regeneration gas, together with the entrained regenerated catalyst, migrates out of the dense layer 3 and into the dilute phase region 2 located above and in contact with the dense layer 3. The separation device 12, which is typically a cyclone separation device, is located in the dilute phase region 2 and is used to achieve a substantial separation of the spent regeneration gas and the entrained catalyst. Although only one such cyclone is shown in the drawing, it can be assumed that several cyclones arranged for parallel or series flow of gas catalyst could thus be placed in the dilute phase 2. As shown in this drawing, spent regeneration gas exits zone 1 through line 10 while substantially all cyclone the incoming catalyst is recovered via an immersion arm 13 which leads the catalyst downwards towards the dense layer 3 or to this layer itself. The spent regeneration gas travels out of the regeneration zone 1 through the pipe 10 at a rate controlled by the valve 11. The valve 11 in the pipe 10 can be used to maintain a certain 8. 6 '513 pressure in the regeneration zone or, preferably, is used to maintain a certain pressure difference between the regeneration zone and the hydrocarbon reaction zone.

The tube 15 connected to the tube 10 leads the sample from the spent regeneration gas to the analyzer 16. The analyzer 16 is any measuring device known in the art by which the concentration of free oxygen in the used regeneration gas can be measured.

The control device 7 is connected to a fresh regeneration gas supply pipe 6 and regulates the speed of the regeneration gas introduced into the regeneration zone 1 based on the measured free oxygen concentration determined by the device 16. In particular through. The control device 19 has a setpoint input signal corresponding to a predetermined concentration of free oxygen represented by line 20 and can receive an output signal from the analyzer corresponding to the amount of free oxygen passing through the tube 10. The control device compares this amount of free oxygen with the setpoint or the desired free oxygen concentration and via the device 18 it can lead the control device outlet signal to the control device 7 to change the regeneration gas flow to the regeneration zone depending on the measured free oxygen concentration deviation from the desired pre-determined oxygen

The control device 7 can be any device capable of controlling the amount of gas flow through the pipe. More specifically, the control device may include a compressor which supplies fresh regeneration gas through the pipe 6 at the desired speed. The operation of the compressor can be varied to change the flow rate of fresh regeneration gas passing through line 6 depending on the concentration of free oxygen in the spent regeneration gas passing through line 10. Other control devices are valves that control the flow of regeneration gas through the pipe, or combinations of flow control loops comprising a nozzle connected to pressure regulators and control valves in a manner that allows control of regeneration gas passing through pipe 6 to regeneration zone 1.

The control device 19 is any device capable of generating an output signal corresponding to the deviation of the input signal input thereto from the desired setpoint which the control device attempts to maintain. In normal operation, the input signal fed to the control device via line 17 is read by the control device. The possible deviation of this signal from the setpoint input signal represented by line 20, which deviation is programmed in the control device 19, is determined. The output signal passes through the device 18 to the control device according to the deviation of the input value going to the control device.

The structural materials of the regeneration zone may be metals or other state-resistant materials capable of withstanding the relatively high temperatures and consumption conditions in fluidized regeneration processes.

At the beginning of the course of the invention, the definitions of the various expressions used herein are helpful in understanding the method of our invention.

The phrase "afterburning," as generally understood by those skilled in the art, refers to the incomplete oxidation of C0 in the regeneration zone or flue gas pipe. In general, afterburning is characterized by a rapid rise in temperature and occurs during periods of changing operations or "shaking" of the process. Its duration is therefore short until unchanged functions are restored.

In contrast to post-combustion, the phrase "substantially complete C0 conversion" refers to the intentional, permanent, controlled, and substantially complete combustion of C0 to CO2 in the regeneration zone, and more specifically in the dense bed of catalyst maintained in the regeneration zone. "Substantially complete" means that the concentration of CO in the regeneration gas used (defined below) is reduced to less than about 1000 ppm, and preferably less than 500 ppm.

The term "spent catalyst" as used in this specification means a catalyst that has been removed from the hydrocarbon conversion zone due to reduced activity caused by coke deposits. The spent catalyst entering the dense phase catalyst bed may contain any amount of coke from a few tenths of a percent to about 5 weight percent, but typically the catalyst used in FCC processes contains about 0.5 to 1.5 weight percent coke.

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The term "regenerated catalyst" as used in this specification means a catalyst from which at least a portion of the coke has been removed. The regenerated catalyst produced by our process generally contains less than about 0.5 weight percent coke and more typically contains about 0.01 to 0.15 weight percent coke.

The term "regeneration gas" as used in this specification means, in a general sense, any gas that is intended to come into contact with a catalyst or that has been in contact with a catalyst in a regeneration zone. In particular, the term "fresh regeneration gas" includes free oxygen-containing gases such as air or oxygen-enriched or oxygen-free air entering the dense phase layer of the regeneration zone, allowing oxidation of the coke from the spent catalyst and substantially complete CO conversion. Usually the fresh regeneration gas is air. Free oxygen refers to unbound oxygen in the regeneration gas.

The phrase "partially spent regeneration gas" refers to a regeneration gas that has been in contact with the catalyst in a dense phase bed and that contains a reduced amount of free oxygen compared to fresh regeneration gas. The partially used regeneration gas generally contains several percent by volume of nitrogen, free oxygen, carbon monoxide, carbon dioxide, and water. More specifically, the partially used regeneration gas generally contains n.

7-1 ^ 1 by volume # of both carbon monoxide and carbon dioxide.

The phrase "spent regeneration gas" means a regeneration gas that contains a reduced CO concentration compared to a partially used regeneration gas. Preferably, the regeneration gas used contains less than about 1000 ppm CO 2 and even more typically and preferably less than about 500 ppm CO. Free oxygen, carbon dioxide, nitrogen and water are also present in the regeneration gas used. The free oxygen concentration of the regeneration gas used is generally greater than 0.1% by volume of the regeneration gas used.

The terms "dense phase" and "dilute phase" are terms commonly used in the FCC art to generally characterize catalyst densities in various parts of the regeneration zone. Although the cut-off density is somewhat difficult to determine when the term "dense phase" is used herein, it refers to areas in the regeneration zone 11,61513 where the catalyst density is greater than about 240 kg / m 2, and when "dilute phase" is used herein, it refers to areas where the density of the catalyst is less than about 240 kg / m 2. Usually the dense phase density is between about 320-640 kg / ir? or more and the dilute phase density is much less than 240 kg / m 2 and between about 1.6-80 kg / m 2. Catalyst densities in FCC vessels are generally measured by measuring pressure or fluid pressure differences across manometers installed in the vessels and at known distances from each other.

Our process focuses primarily on the process of oxidizing coke from spent catalytic cracking catalyst containing catalytically effective amounts of a CO conversion promoter and initiating and controlling substantially complete conversion of CO to CO2 in the regeneration zone in the presence of an accelerator in a regeneration zone.

In the process of our invention, the oxidation of coke and the substantially complete catalyzed conversion of CO to CO 2 are initiated and occur in a dense catalyst bed in the regeneration zone and at least a portion of the heat of combustion of CO is recovered by the regenerated catalyst for use in the FCC process. The regenerated catalyst passing into the hydrocarbon reaction zone is therefore at a higher temperature than the regenerated catalyst prepared in the C0 non-combustion regeneration zone, thus allowing the preheating of the external feed to be reduced or eliminated. In addition, the CO conversion is adjusted to ensure substantially complete elimination of atmospheric CO pollution without the need for an external CO boiler. Besides, the method of our invention can be composed into existing regeneration units without extensive modifications or repair of the old one.

In addition, part of our process is that the substantially complete conversion of CO to CO 2 is catalyzed by catalytically effective amounts of a CO conversion promoter that passes as part of the fluidized bed catalyst throughout the FCC process. The oxidation rate of coke is not affected by the use of a catalytic fluidized bed catalyst containing a CO conversion promoter or by the conversion of hydrocarbons in the hydrocarbon conversion zone, but the rate of CO conversion increases. Using a CO conversion promoter, the kinetic rate constant of the reaction CO + 1/2 O 2 * CO 2 can typically be increased 2-5 times or more. Thus, a higher CO conversion rate can be achieved in the presence of a CO conversion promoting agent at a certain regeneration zone temperature and oxygen concentration than can be achieved without an accelerator. Since complete distribution of the fresh regeneration gas and without ideal mixing in the catalyst of the dense phase bed is never achieved, it has often happened that the reaction rate of CO oxidation has to be increased to ensure that substantially complete CO conversion takes place in the dense bed. The reaction rate has been increased by raising the temperature of the regeneration zone or by increasing the oxygen concentration of the fresh regeneration gas. Temperatures in the regeneration zone were raised by methods such as burning burner oil in regeneration zones, increasing the amount of sludge oil recycle to the hydrocarbon conversion zone to form more combustible coke, preheating Such methods generally increase the operating costs of the FCC process and take away some of the flexibility of the FCC process. The use of an FCC catalyst containing catalytically effective amounts of a CO conversion agent allows the combustion of oil and the recycling of sludge oil to be reduced. regeneration zone.

Catalysts suitable for use in the process of our invention may include any catalyst known in the catalytic fluidized bed that contains catalytically effective amounts of a CO conversion promoter. These amounts can range from a few parts per million by weight to about $ 20 by weight or more based on the weight of the FCC catalyst. Preferably, these amounts range from about 100 ppm by weight to about 10% by weight of the FCC catalyst.

Suitable CO conversion promoters generally consist of one or more oxides selected from transition metals and rare earth metals. Particularly suitable CO conversion promoters consist of one or more oxides selected from the group consisting of vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, palladium oxide, platinum oxide and rare earth oxides. CO conversion promoters can be incorporated into amorphous FCC catalysts consisting of silica and / or alumina, or any zeolite-containing FCC catalysts by any suitable method known in the art of catalyst preparation, such as co-precipitation or co-gelation or absorption. Suitable zeolites include both naturally occurring and synthetic crystalline aluminosilicate materials known in the art, such as faujasite, mordenite, cabazite, type X and type Y zeolites, and so-called "ultrastable" crystalline aluminosilicate materials.

In order to initiate and maintain a substantially complete combustion of CO in the solid layer of the regeneration zone, two requirements must be met: the temperature of the dense layer must be high enough to cause a sufficiently rapid CO oxidation reaction and the amount of fresh regeneration gas must be at least stoichiometrically sufficient for substantially complete oxidation of CO .

The reaction rate of the CO oxidation must be high enough to allow substantially complete combustion of the CO with a reasonable gas residence time in the dense bed of the regeneration zone.

If the reaction rate is too low, it is possible that all of the combustion of CO has not been completed during the time that the partially used regeneration gas is in a dense bed with sufficient catalyst density to absorb the heat of reaction. In this situation, the C0 conversion can take place in the dilute phase region of the regeneration zone or in the flue gas pipe outside the regeneration zone where it is not desirable. The temperature above a minimum in the presence or absence of a CO conversion promoter is therefore important to ensure a suitable reaction rate.

An appropriate amount of fresh regeneration gas is important because without the presence of sufficient oxygen to maintain the oxidation reaction of CO to CO2, the reaction does not occur at any temperature in the regeneration zone. In addition, it is important that a slight excess of fresh regeneration gas is present stoichiometrically to the required amount to ensure substantially complete conversion of CO.

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It is generally believed that the operation of the FCC regeneration zone is substantially adiabatic. While it is true that some heat is lost to the environment, this amount is a small fraction of the total heat released. Since the operation of the regeneration zone is substantially adiabatic, the temperature of the regeneration zone is a direct function of the amount of fuel burned in the regeneration zone. As the total amount of fuel increases, the temperature in the regeneration zone increases. Until the intentional conversion of CO to CCl is initiated in the regeneration zone, the fuel is primarily coke on the surface of the spent catalyst, but may also contain any adsorbed or porous hydrocarbons passing into the regeneration zone with the catalyst used in the regeneration zone, or any regenerating zone. . In fact, during the first start of the FCC process, the fuel is primarily burner oil until sufficient coke has accumulated on the catalyst surface. Once the intentional conversion of CO to CCl is initiated, CO forms a significant portion of the total fuel burned in the regeneration zone.

Thus, by adjusting either the amount of fuel introduced into the regeneration zone or the fresh regeneration gas that would allow the combustion of the fuel, the temperature of the regeneration zone can be adjusted to any temperature between about 399-760 ° C. The amount of coke can typically be controlled by varying the operating conditions of the hydrocarbon reaction zone, such as temperature, or by varying the composition of the material fed to this reaction zone. In particular, more coke is formed when the conditions in the hydrocarbon reaction zone become more severe or when the feedstock becomes heavier, i. as the Conradson carbon content increases.

It has been common practice to limit the temperatures of conventional (CO-free) regeneration zones to about 677 ° C. In FCC processes using amorphous catalysts, this was generally done by limiting the temperature of the hydrocarbon reaction zone to some maximum or by limiting the amount of coke-producing slurry oil returned to the hydrocarbon reaction zone to some maximum. These maximum levels are determined for each feedstock primarily based on user experience gained from FCC processes. In FCC processes using zeolite-containing catalysts that formed less coke, it often became necessary to burn the burner oil to maintain the temperature of the regeneration zone 61513 at about 677 ° C. A temperature close to 677 ° C was desirable to produce the hottest regenerated catalyst possible, but the temperature was limited to a maximum of about 677 ° both because of possible metallurgical limitations and because the afterburning reaction rate, if any during process failures, was relatively low.

The catalyst used in the process of our invention, which contains catalytically effective amounts of a CO conversion promoter, and fresh regeneration gas are first introduced into a dense bed in the regeneration zone. More specifically, fresh regeneration gas is initially introduced into the dense bed at a first flow rate sufficient to oxidize the coke to produce partially used regeneration gas. More specifically, this first flow rate is preferably in the range of about 8-12 g of air per gram of coke entering the regeneration zone. The coke is then oxidized under the first oxidation conditions to produce a regenerated catalyst and partially spent regeneration gas.

The first oxidation conditions comprise a dense bed temperature of about 399-677 ° C, not because of any metallurgical limitation, but because the rate of the afterburning reaction, if it occurred during the irregular start conditions, is relatively low. During the start, the burner oil is burned in the regeneration zone until sufficient coke has been deposited on the catalyst in the hydrocarbon reaction zone. The burner oil is then gradually reduced or removed as the amount of coke in the spent catalyst increases and the temperature of the solid bed is limited to about 677 ° C by the methods described above. Other first oxidation conditions are approx.

An operating pressure of 1-4.4 atm with a recommended range of about 2-3.7 atm. In addition, the velocities of the fresh regeneration gas along the surface are limited to the transport rate, i.e. the rate at which the catalyst would pass away from the dense bed upward to the dilute phase region. The gas velocities along the surface are therefore preferably less than about 1 m / s with the usual range being 0.5-0.8 m / s.

After the coke has been oxidized to produce regenerated catalyst and partially spent regeneration gas, the temperature of the dense bed is raised to a second temperature between about 677-760 ° C so that when CO oxidation is allowed to occur, its rate is high enough to ensure substantially complete CO to CC ^ in a dense layer. The temperature can be raised by any of several methods or combinations thereof. The severity of the operating conditions in the hydrocarbon reaction zone can be increased, thus producing more coke on the surface of the spent catalyst; the amount of slurry oil returned to the hydrocarbon reaction zone can be increased to produce more coke for the spent catalyst; the burner oil may be added again or increased in the regeneration zone; the stripping of spent catalyst can be reduced, allowing a greater amount of combustible material to pass with the spent catalyst into the regeneration zone; or heavier feedstocks may be used.

Fresh regeneration gas is then added from the first flow rate to a second flow rate that is stoichiometrically sufficient to allow substantially complete oxidation of CO to CCl, thereby producing the spent regeneration gas. This second flow rate is preferably in the range of about 12-16 g of air per gram of coke entering the regeneration zone. The carbon monoxide is then oxidized in a dense bed to produce the regeneration gas used under the second oxidation conditions. With the temperature of the dense bed at a second temperature of about 677 ~ 760 ° C, the substantially complete conversion of CO to CCl occurs substantially immediately in the dense bed as soon as the rate of fresh regeneration gas is increased to the second flow rate. Since the oxidation of CO is exothermic, it is not necessary, once the oxidation of CO has been initiated, to continue the procedures used to raise the temperature of the dense bed to another temperature.

Other oxidation conditions include a temperature of about 677-760 ° C and a subsurface fresh regeneration gas rate that is limited to the transport rate as described above. The operating pressure is approximately 1 - ^, 4 atm with the recommended range being about 2-3.7 atm.

At this stage in the operation of the regeneration zone, it is possible that normal variations in the flow rate of the feedstock, and in particular in the composition, will result in time intervals in which not all of the CO is substantially completely converted to CCl. The flow rate of fresh regeneration gas at this stage of operation is just sufficient for substantially complete oxidation of CO to CO2 without the possibility of overshoot. The CO concentration of the regeneration gas used can increase during these time intervals from the recommended concentration of less than about 500 ppm to several thousand ppm of CO. The process of our invention comprises the steps of preventing this and ensuring substantially complete combustion of CO to CO2 despite these variations.

Typically, the regeneration gas used in our process is analyzed to obtain a free oxygen concentration measured by an analyzer, and this measured concentration is then compared to a predetermined free oxygen concentration. The predetermined free oxygen content of the regeneration gas used represents the amount of free oxygen that exceeds the amount stoichiometrically required for CO oxidation. The rate of fresh regeneration gas is then adjusted to a third flow rate to keep the measured free oxygen concentration equal to the predetermined free oxygen concentration, ensuring substantially complete conversion of CO to CO 2. The third flow rate is therefore higher than the second flow rate. Typically, the third flow rate corresponds to about 13-17 grams of air / g of coke.

The free oxygen content of the regeneration gas used is generally greater than about 0.1% by volume of the stream of regeneration gas used, and more specifically may be about 0.1 to 10% by volume or more of free oxygen. Preferably, the free oxygen content is about 0.2-5 volume - $ of the regeneration gas used, and even more preferably about 1-3 volume - #.

The analyzer used in the regeneration gas used to measure the free oxygen content in the process of this invention may be any device capable of measuring the concentration of O 2 in a gas mixture containing O 2, CO, CO 2, N 2, H 2 and light hydrocarbons in concentrations ranging from parts by volume to many parts by volume. percentages. These devices include, in particular, Orsat, gas chromatograph and mass spectrograph equipment. Flue gas samples may be periodically taken manually from the process and analyzed manually, or taken automatically and analyzed continuously or at programmed intervals by sampling and analysis equipment.

Once the measured free oxygen concentration has been determined and compared to a predetermined free oxygen concentration, the control device is adjusted, if necessary, manually or automatically to deliver more or less fresh regeneration gas to the regeneration zone. Typically, the control device comprises a valve for controlling the flow or a control device capable of controlling the speed or the outlet pressure of the fresh regeneration gas compressor to change the flow rate of the fresh regeneration gas to the regeneration zone. In an automatic system, the analyzer can generate and send to the control device an output signal representing the measured free oxygen concentration. The control device may typically be connected to the analyzer control device or may be connected to one of the structures and may have a variable setpoint representing a predetermined free oxygen concentration. The control device receives the output signal of the analyzer, compares it with the setpoint and, if a difference occurs, leads the signal to the control device to change the rate of fresh regeneration gas to the regeneration zone so that the measured free oxygen concentration in the used regeneration gas corresponds to a predetermined free oxygen concentration. The analyzer, the control device and the control device can all be connected to each other by methods known in the art and can be combined into one control unit.

The following examples are provided to illustrate some features and advantages of the process of our invention and are not intended to unnecessarily reduce the limits defined by the appended claims.

Example I

In this example, coke and CO were oxidized in a regenerator operating at a dense bed temperature of about 732 ° C and a pressure of about 3.7 atm. Approximately 9 ^ 5,000 kg / h. spent catalyst containing about 0.8% by weight of? coke was introduced into the regenerator while maintaining a ratio of about 14.60 g air / g coke without supplying the regenerator.

The air feed rate to the regenerator was adjusted to maintain a predetermined free oxygen concentration in the regeneration gas used between about 1-2 vol. The conversion of CO 2 to CO 2 * was substantially complete and was maintained unchanged and continuously in the dense bed in the regenerator. The gas velocity along the surface was about 0.85 m / s.

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Because the conversion of CO in the dense bed of the regenerator could be controlled, the reaction temperature could be raised to about 538 ° C without increasing the preheating of the feed, which increased the conversion and the amount of gasoline and lighter compounds produced.

Example II

In this example, a comparison is made between the functions of a commercial FCC unit before and after the initiation and control of substantially complete CO conversion.

Table I

Commercial FCC process before and after CO conversion

Without the con-CO version of CO at the time of the sion

Reactor temperature, ° C 550 530

Regenerator dense phase temperature, ° C 677 732

Regenerator dilute phase temperature, C 699 73 * 4

Supply preheating temperature, ° C 363 260

Conversion L.V. # 79.4 79.1

Coke yield, weight # 5.4 4.6

Gasoline Yield, L.V. # 63.2 65.6 CO in the flue gas, by volume # 10.1 0.0 * CO2 in the flue gas, by volume # 9.7 16.7 02 in the flue gas, by volume # 0.2 2.1%

The actual assay result was 350 ppm

The above results show the benefits of reduced feed preheating, higher conversion, and higher gasoline yield made possible by the process of our invention. Likewise, CO contamination is substantially eliminated without the need for an external CO boiler.

Example III

This example shows a comparison of the functions of a commercial FCC process before and after the use of an FCC catalyst containing a CO conversion enhancer in a regeneration zone where both processes underwent substantially complete conversion of CO to CO2. The results are shown in Table 2.

20. P>, 7 61 51 3

Table 2 FCC Process Before and After CO Conversion Promoter Use

Before after

Reactor Temperature, ° C 535 533

Feed rate, m ^ / h 185 178

Sludge oil recycling, m ^ / h 7.8 5.7

Feed preheating, ° C -

Regenerator Temperatures, ° C 169 185

Cyclones 780 738

Dilute phase 717 703

Dense phase 715 703

Without heater 169 185

Air speed m ^ / min 2040 1810

Surface velocity m / s 1.1 0.9 Analysis of spent regeneration gas CO2, volume # 12.5 16.5 O2, volume # 4.4 1.2 CO, volume ppm <500 <500

The comparison shows a significant decrease in air velocity from 2040 m ^ / min to 1810 m'Vmin made possible by the use of an FCC catalyst containing a CO conversion promoter. This decrease in air velocity reduced the air surface velocity in the Regeneration zone from 1.1 m / s to 0.9 m / s and resulted in less catalyst loss from the regeneration zone. Lower regeneration zone temperatures, reduced slurry oil recycling, and lower O 2 in the regeneration gas used are also reflected in the process using the catalyst containing the CO conversion enhancer.

Claims (10)

A process for regenerating a coke-contaminated catalyst in fluid catalytic cracking, comprising catalytically effective amounts of a CO conversion, accelerating agent and for substantially complete catalytic conversion of carbon monoxide to carbon dioxide, the process comprising a step of catalyst layers in the regeneration zone catalyst and fresh regeneration gas at a first flow rate sufficient for the coke's oxidation to produce a partially spent regeneration gas; B. Oxidizes the coke in first oxidizing conditions associated with a first temperature in the catalyst layer at 399-677 ° C to produce a partially consumed, CO-containing regenerating gas; c. raises the temperature of the catalyst layer from the first temperature to a second temperature between 677 and 760 ° C; d. leads fresh regeneration gas to the catalyst layer at a second flow rate, which is stoichiometric enough for substantially complete oxidation of CO to CO 2; e. oxidizing CO in the catalyst layer to produce a spent regeneration gas, which layer is poured into other oxidizing conditions, which include the presence of the CO conversion accelerating agent; f. analyzes the spent regeneration gas to obtain the measured free oxygen concentration and compares the measured free oxygen concentration with the predetermined free oxygen concentration; and g. then regulates fresh regeneration gas to a third flow rate to pour the measured concentration of free oxygen equal to the predetermined concentration of free oxygen, ensuring a substantially complete conversion of CO to CO 2, characterized by using a catalyst in fluidized cracking, containing a catalytically effective amount of a CO conversion, accelerating agent containing one or more oxides selected from vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, palladium oxide, platinum oxide of rare earth metals. Process according to Claim 1, characterized in that the regeneration zone contains a dense phase catalyst layer and a diluted phase area which lies above the dense phase layer. Process according to claim 1 or 2, characterized in that the first flow rate of fresh regeneration gas corresponds to 8-12 g of air / g of coke. Process according to any of claims 1-3, characterized in that the first flow rate of fresh regeneration gas corresponds to 12-16 g of air / g of coke.