FI62553B - CYCLIC REGENERATION CATALYTIC CRACKING PROCESS - Google Patents

Description

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Patent * och ragistaretyralaan '' Antokin uttagd edi ικι. · Μ * μ pubtmrad 30.09.82 (32) (33) (31) Pyn1 · »/ • Tuoikuui —pHontut 19.02.76 OU.O5.76 USA (US) 659308, 683115 (71) Mobil Oil Corporation, 150 East U2nd Street, New York, NY 10017, USA (72) Edward Joseph Demmel, Gloucester, NJ, Albert B. Schwartz, Philadelphia, Pennsylvania, USA (7U) Berggren Oy Ab (5U) Rotary, regenerative, catalytic cracking process - Qrklisk, regenererande, This invention relates to the catalytic cracking of hydrocarbons without the addition of hydrogen. In particular, it relates to a process for controlling the combustion of carbon monoxide in a regenerator of a catalytic cracker by adding very small amounts of an oxidation catalyst such as platinum to the cracking catalyst. In one embodiment, the side stream of the cracking catalyst is contacted with a solution of the metal compound, thereby controlling the combustion of carbon monoxide in the regenerator of the catalytic cracker.

A typical example of an industrially implemented mobile bed hydrocarbon catalytic cracker is known as thermofor catalytic cracking (TCC). In this process, the catalyst is in the form of spheres or balls with an average particle size of about 0.4-6 mm, preferably about 3 mm. The active hot catalyst spheres pass downwards in parallel with the hydrocarbon feedstock through the cracking reaction zone. In this zone, the hydrocarbon feed is endothermically cracked to lower molecular weight hydrocarbons while coke is deposited on the surface of the catalyst. At the lower end of the reaction zone, the hydrocarbon products are separated from the coking catalyst and recovered. The coking catalyst is then directed downstream to a regeneration zone to which air is fed such that some of the air travels upstream of the coking catalyst and some of the air travels downstream in parallel with the partially regenerated catalyst. Two carbon dioxide-containing fuel gases are obtained. The regenerated catalyst is separated from the flue gas and then pneumatically or mechanically lifted back to the top of the reaction zone.

Fluidized catalytic cracking of hydrocarbon oils is the main refining process. Installed plants are usually designed to handle about 800-2200 m / day of fresh feed. Most of the facilities are quite large and capable of handling at least n.

3 6500 m / day. The catalyst section of the plant consists of a cracking section in which the heavy hydrocarbon feed is cracked in contact with the fluidized cracking catalyst, and a regenerator section in which the fluidized catalyst coking in the cracking operation is regenerated by combustion with air. All plants use a large circulating amount of cracking catalyst4, which is continuously recycled between the cracking and regenerator parts. The size of this circulating warehouse is between 50 and 600 tons in most existing plants.

Although the designs and structures of the various plants vary, Figures 1 and 2 illustrate the essential parts of the assembly, in particular the catalyst flow, which figures show the conventional catalyst compartment of a liquid catalytic cracking plant.

Figure 1 and its sectional view shown in Figure 2 illustrate the catalyst section of a commercial liquid catalytic cracking unit. Referring now to Figure 1, a hydrocarbon feed 2, such as boiling gas oil boiling between about 315-538 ° C, is passed after preheating to the bottom of the riser 4 for mixing with a hot regenerated catalyst fed through a downcomer 6 equipped with a flow control valve 8. Hydrogen catalyst suspension are at a temperature of at least about 510 ° C, but usually at a temperature of at least 538 ° C, is thus formed in the lower part of the riser 4 to flow upwards through it under hydrocarbon conversion conditions. The suspension initially formed in the riser can be retained during the flow through the riser for a residence time of the hydrocarbons ranging from 1 to 10 seconds.

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The hydrocarbon vapor catalyst suspension formed in the riser reactor is passed upwardly through the riser 4 under hydrocarbon conversion conditions of at least 482 ° C and most commonly at least 538 ° C before being discharged into one or more cyclone separation zones 14 there may be a plurality of such cyclone separator combinations comprising first and second cyclone separator devices attached or spaced apart from the riser discharge end to separate the catalyst particles from the hydrocarbon vapors. The separated hydrocarbon vapors are passed from the separator 14 to the dome chamber 16 for removal therefrom through a pipe 18. These hydrocarbon vapors, together with the gaseous material separated by stripping the gas as defined below, are passed through line 18 to a fractionator, not shown. The catalyst separated from the hydrocarbon vapors in the cyclone separator is passed by means of immersion branches represented by the immersion branch 20 to a dense fluidized bed 22 of the separated catalyst held around the top of the riser conversion zone 4. The catalyst layer 22 is considered to be a downwardly moving fluidized bed of catalyst relative to the upstream gaseous material. The catalyst moves downward immediately through the Strip break zone 24 below it and countercurrent to the rising strip gas which is fed to its lower part through the pipe 26. Spacers 28 are located in the stripping zone to improve the stripping operation.

The catalyst is maintained in the stripping zone 24 for a sufficient time to effect high temperature desorption of the deposited compounds in the feed, which are then passed upstream by the stripping gases. The stripping gas with its desorbed hydrocarbons passes through one or more cyclone separation devices 32, in which the entrained catalyst fines are separated and returned to the catalyst bed 22 by means of an immersion branch 34. The hydrocarbon conversion zone comprising the riser 4 may terminate in the upper expanded portion of the catalyst collection tank with well-known bird cage removal devices, or an open "T" connection may be attached to the riser discharge end not directly connected to the catalyst cyclone separator. The cyclone separator may be spaced apart from the riser discharge end so that the first catalyst separation is accomplished by changing the velocity and direction of the discharged suspension so that less stressed vapors from the catalyst fines can then pass through one or more cyclone separators 4,62553. In all of these arrangements, gaseous materials containing Strip flue gas hydrocarbon vapors and desorbed sulfur compounds are passed from a cyclone separation device represented by separator 32 to a dome chamber 16 for removal with hydrocarbon products from a cracking operation through line 18. The gaseous material consisting of hydrocarbon vapors is passed through line 18 to a product fractionation step, not shown. The hot stripped catalyst is removed from the bottom of the stripping zone through line 36 to be transferred to a catalyst fluidization bed which is regenerated in the catalyst regeneration zone. The coking catalyst pipe 36 is provided with a flow control valve 38.

This type of catalyst regeneration operation is referred to as vortex-type catalyst regeneration because the catalyst bed tends to rotate or rotate in a circumference about the vertical axis of the vessel and this movement is facilitated by tangential feeding of spent catalyst to the circulating catalyst bed. Thus, the catalyst fed tangentially at elevated temperature is further mixed with the hot regenerated catalyst or regenerated catalyst at elevated temperature and moved in a circular or vortex pattern about the vertical axis of the regenerator while also moving downward to the next to the grille. In this catalyst regeneration environment, it has been found that regeneration gases containing combustion gas products from the combustion of carbonaceous material tend to move generally vertically upward through a generally horizontally moving rotating catalyst to cyclone separators located above the catalyst bed in a particular segment. As shown in Figure 2, the catalyst fed tangentially to the regenerator via line 36 causes the catalyst to rotate clockwise in this particular embodiment. As the catalyst bed continues to rotate, some catalyst particles pass downward from the top of the mass of regenerated catalyst particles in the regeneration gas through it to a catalyst outlet passage in a block of vessels 40 adjacent to the catalyst feed block. In the regeneration zone 42, which contains the mass of circulating suspended catalyst particles 44 in the upstream oxygen-containing regeneration gas fed to its lower part by the pipe divider 46, the density of the mass of suspended catalyst particles in the given block space can be varied in any given block space. Generally speaking, the circulating suspended mass 44 of catalyst particles, which undergoes regeneration with oxygen-containing gas to remove carbonaceous precipitates by combustion, remains a suspended mass of rotating catalyst particles having a density varying in the direction of the catalyst flow. Under carefully selected relatively low regeneration gas velocity conditions, a rather striking boundary line can be made to occur between the dense fluidized bed of suspended catalyst particles and the more dispersed suspended catalyst phase (dilute phase) above it. However, as the regeneration gas velocity conditions are increased, there are fewer boundaries and the suspended catalyst passes through catalyst particle density ranges, 3 which are generally less than about 0.5 g / cm 3. A lower catalyst layer density of at least the order of 0.3 g / cm is recommended.

A truncated regeneration gas distribution grid 50 located in the lower part of the cross-sectional area of the regeneration vessel 42 is provided as shown in Figure 1 and is adapted to control the flow of regeneration gas to any given vertical segment of the catalyst bed above it. In this arrangement, it has been found that even when a generally horizontally circulating catalyst mass is used, the regeneration gas flows generally vertically upward through the catalyst particle mass so that the regeneration gas fed to the catalyst bed through any given grate block or portion can be controlled by grate openings and openings. Thus, after the oxygen-containing combustion gases have been in contact with the catalyst in the regeneration zone, they are separated from the entrained catalyst particles by cyclone devices provided and placed vertically apart thereon. The cyclone combinations schematically shown in Figure 1 are intended to be similar to those shown in Figure 2. The catalyst particles separated from the fuel gases passing through the cyclones are returned to the catalyst mass below by means of several catalyst immersion branches.

As mentioned above, the regenerated catalyst removed through the channel 40 is conveyed through the downcomer 6 to the hydrocarbon conversion riser 4.

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The regenerator system shown in Figures 1 and 2 is usually designed to produce a flue gas that contains a significant concentration of carbon monoxide along with carbon dioxide. In fact, the typical CCl / CO ratio is about 1.2.

As mentioned above, there has been a recent significant increase in the desire to reduce carbon monoxide emissions from the regenerator of a reflective, non-hydrogenating catalytic cracking process. Previously proposed solutions to increase the regenerator temperature sufficiently to thermally burn CO or to add chromium or iron to the cracking catalyst to support catalytic CO combustion have not resulted in a sufficient reduction in CO emissions or, when this reduction has approached adequacy, has occurred in the cracking process. at the expense of a large handicap-side operations and tuotejakaantuman. In addition to the fact that the increased formation of coke on the cracking side pushes this fully reflective system into thermal imbalance, the increased formation of light gas puts an unreasonable strain on the capacity of the compressor and the entire gas plant, i. a separation procedure in which the gaseous C 2 part of the product is redissolved in its component parts.

It is therefore an important object of the present invention to provide a new means of reducing carbon monoxide emissions from a reflective, non-hydrogenating catalytic cracking process.

Another object of the present invention is to provide a novel catalyst for such a process.

Another object of the present invention is to provide an improved process for the fluidized catalytic cracking of gas oils without the addition of hydrogen.

According to the present invention, there is provided a known circulating, regenerative, catalytic cracking process in which a catalyst, after contact with a feed in a reactor under cracking conditions without added hydrogen, passes through an external circuit containing a regenerator which returns 0.01-50 ppm, which process is characterized in that a platinum group metal or rhenium is applied to the catalyst as it passes through said circuit.

It will be seen from Figure 1 that the term "catalyst circulating storage" referred to herein includes a catalyst in a vertical tube 4, a sealed layer 22, a sealed layer in a stripper 24 and a sealed layer in a regenerator 44, and a catalyst material and catalyst material in tubes 36 and 6, which is suspended in the dilute phase and in the cyclones of the reactor section and the regenerator section. This circulating storage is very hot everywhere, substantially above about 315 ° C, as the regenerator operates at a temperature above about 538 ° C and the reactor above 427 ° C.

In actual operation, because the catalytic activity of the circulating stock of the catalyst tends to decrease with age, fresh replenishment catalyst, which usually rises to about 1-2% of the circulating stock, is added daily to maintain optimum catalyst activity with approximately the same amount of daily removal and losses. . This catalyst supplement is usually added through a funnel and tube (not shown) to the regenerator.

The platinum group metal may be a component of all catalyst particles or only some of the catalyst particles. Given its concentration throughout the system, it must be present in a quantity large enough to be able to effect the reaction of carbon monoxide with oxygen to carbon dioxide, provided that the conditions in the regenerator are otherwise sufficient to maintain this combustion; e.g., high enough temperature and enough air. However, it may not be present in such a large amount, it is essential that the process krakkauspuolen adversely affect the performance. This latter, upper limit of the platinum group metal content is to some extent a reflection of the design capacity of the cracking system, including ancillary equipment and downstream product dissolution equipment, relative to the actual functional production volume. The upper level of the platinum group metal content shall be less than that which would cause this design capacity to be exceeded.

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Further, as a matter of practice, each of the seven metals in the platinum group defined herein has a different degree of efficiency for their intended use in this system. Therefore, the numerical upper and lower limits for metal amounts are group-wide. They may not be applicable as a suitable range for any species of this metal genus. Thus, for example, a suitable upper limit for the amount of metal in the entire platinum group metal family is about 100 ppm, based on the natural catalyst mixture. While it is clear that this is a suitable upper limit for this genus, it is also clear that this numerical value may be quite high for certain species of the genus, especially platinum and iridium, in which case the recommended upper limit might be better set to about 10 ppm calculated in the same way.

It is also clear that although a lower numerical limit may be applied to the amount of "platinum group metal" used in this catalyst, this value must also be considered. genus and must be carefully reconsidered for each private species. So n.

A lower limit of 0.1 ppm for a platinum group metal is considered suitable for the use of some metals, such as platinum, but this value may be less than a suitable minimum for the use of other metals, such as rhenium.

However, in any case, the most appropriate measure of the amount of metal in any given platinum group is relative solely to how it functions in reflective, endothermic, non-hydrogenating catalytic cracking. It should be sufficient to maintain as much carbon monoxide combustion as desired, taking into account the internal limitations of any given operating system, such as temperature limitations based on the metallurgy of the equipment and / or the tendencies of the respective feed or feed slate to form coke.

In this context, it is important to note that in some cases it may be desirable to oxidize substantially all of the carbon burned in the regenerator to carbon dioxide. In other cases, it may be desirable to cause only a portion of the carbon to oxidize to carbon dioxide and to allow some substantial amount to oxidize only partially to carbon monoxide. The use of the catalyst in question now allows the refiner to select the exact amount of heat generated in the regenerator as a function of efficient carbon monoxide combustion. It allows him to raise the temperature of the regenerator by burning some of the carbon monoxide in it 9 62553 (reducing the residual coke with the regenerated catalyst and increasing the activity of the regenerated catalyst) and burning the rest outside the regenerator, for example in a steam-generating CO boiler.

Because the amount of platinum group metal used is so very small, it is very difficult to analyze the form of the metal in the catalyst in operation, especially after it has been running for some time and has undergone many cracking and regeneration cycles.

The platinum group metal is attached to the cracking component while the latter is in the cracking / regeneration system. In a preferred embodiment of the invention, the spent catalyst is periodically removed from the moving catalyst mass and replaced with a new catalyst in a manner known per se, and the metal is added to the catalyst from time to time to keep the metal concentration substantially constant. The metal can also be added to the endothermic cracking / regeneration system as an emulsion, suspension or solution, for example in an oil feed. Metal, i.e. pt,

Pd, Ru, Ir, Os, Rh or Re can be in any of a large number of metallic or non-metallic forms, collectively described herein as "dispersible." Decomposable metal compounds include, for example: suspensions of colloidal platinum; dispersions of platinum on an inorganic substrate such as alumina, this substrate having a substantially smaller particle size, i. less than about half the average particle size of a catalyst such as colloidal alumina; suspensions of the aforesaid dispersions in a liquid carrier such as fuel oil, air or water; emulsions of aqueous solutions of platinum compounds; and vapors of volatile metal compounds in a suitable carrier such as an inert gas. Thus, the term "dispersible" as used herein broadly encompasses all forms of metal suitable for incorporation into a cracking component. In general, a decomposable metal compound, in contact with a cracking component in a cracking / regeneration system, undergoes a change such that a close, irreversible combination is formed with the cracking component, i. the dispersible metal compound loses its identity and cannot be easily recovered as such by conventional physical means of separation.

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Decomposable metal compounds are mentioned above; as an example, alternatively, the metal oil-soluble or oil-dispersible compound may be added to a suitable amount of a hydrocarbon feedstock, such as a gas oil feedstock, for incorporation into a catalyst. Such compounds include metal diketonates, carbonyls, metallocenes, olefin complexes having 2 to 20 carbons, acetylene complexes, alkyl or arylphosphine complexes, and carboxylates having 1 to 20 carbons. Typical examples of these are platinum acetylacetonate, tris (acetylacetonate) rhodium (III), triiodouridium (III) tricarbonyl, H-cyclopentadienylrhemium (I) tricarbonyl, rutenosene, u-cyclopentadienyl osmium (I) -dicarbide (I) -dicarbide -lene) palladium (II) dimer, (H-cyclopentadienyl) (ethylene) -rhodium (I), diphenylacetylene bis (triphenylphosphino) platinum (O), bromomethylbis (triethylphosphino) palladium (II), tetrakis (triphenylphosphino) palladium O), chlorocarbonylbis (triphenylphosphino) iridium (I), palladium acetate and palladium naphthenate.

The metal can also be added to the catalyst by mixing the combination of metal and refractory support with the catalyst. The support is preferably an inorganic oxide such as alumina, silica-alumina or clay. Even more preferably, the support is granular and has substantially the same dimensions as the catalyst.

Feedstocks that can be cracked using the catalysts of this invention include all conventional hydrocarbon feedstocks such as fuel oils, gas oil, light and heavy distillates, residual oils, and the like.

Referring now to Figure 1, which is intended to illustrate an FCC unit, a dispersible metal compound may be fed suspended to an air supply 46 to a regenerator; or with steam fed to the reactor stripping compartment at 26; or directly to the spent catalyst transfer tube 36; or in the downcomer 6 of the regenerated catalyst; or a dense fluidized bed 22; or to the top of the vertical tube conversion zone 4; or a cyclone separator 32; or immersion branch 34; or catalyst 62553 to layer 44; or suspended catalyst particles 48; or separation devices, such as immersion arms 60, 62, 64, and 66 contained in the jacket 42. Direct injection into the sealed bed of regenerator 44 is the preferred method of supply.

Although optional methods for feeding a dispersable metal compound to the fluid catalytic cracking (FCC) unit have been described, fluidized bed systems also provide numerous points for spraying. Also, if the "vortex" regenerator of Figure 1 is replaced with a riser-regenerator described more fully below, the dispersible metal compound may be fed to the riser itself, to the dense bed of regenerated catalyst, or to a tube to return the regenerated catalyst to the spent catalyst, described in Figure 1.

The small amounts of metal compound catalysts used in this invention affect the entire catalytic cracking process to varying degrees and in a different way than previous catalysts used by the oil industry in its attempts to burn CO in the regenerator. They also produce different results compared to non-catalytic C0 combustion. Nickel and vanadium are both known to deposit on the cracking catalyst from the hydrocarbon feed and both are known to be carbon monoxide oxidation catalysts. However, the oil industry considers these materials to be catalyst poisons. To understand this, it must be borne in mind that the purpose of catalytic cracking is to increase the production of petrol and other low-boiling distillate fractions from all crude oil.

When a catalyst component such as nickel or vanadium is considered a poison, even though it has some activity in achieving the desired goal, e.g., in catalyzing the oxidation of CO, this occurs because its overall effect is to reduce gasoline yield from the entire system. In the case of nickel and vanadium, and perhaps to a lesser extent other transition metals such as manganese and / or chromium, there is a significant increase in the amount of coke produced on the cracking side of the reflective catalytic cracking process as defined herein. This increased coke production may result in a higher amount of residual carbon on the surface of the regenerated catalyst despite some increased catalytic combustion of C0. With a higher amount of residual carbon, the total effect of the deposition of these metals is to reduce the catalytic activity and gasoline selectivity of the cracking component. In contrast, the very small amounts of the special catalyst components for CO oxidation of this invention have the overall effect of reducing the equilibrium amounts of coke on the surface of the cracking catalyst. These new catalysts also have the overall effect of increasing gasoline selectivity.

Examination of thermal (non-catalytic) CO oxidation shows that initiating and maintaining non-catalytic CO oxidation requires and produces much higher temperatures than in the presence of a catalyst. It would be shown that exposing a zeolite cracking catalyst to high temperatures such as those found in thermal (non-catalytic) CO combustion may adversely affect it.

Therefore, the overall effect of non-catalytic CO combustion in the regenerator of the reflective, non-hydrogenating cracking system may be a decrease in gasoline production.

In conventional reflective, non-hydrogenating, endothermic catalytic hydrocarbon cracking coupled with rapid catalyst cycle regeneration (coke combustion), the regenerator operates in one of several common ways. FCC types of modes in a regeneraattorikaaviossa, of which Figure 1 is an example, is used to close the catalyst fluidized bed, a chilled Coke krakkausreaktiovyöhykkeestä catalyst is fed and from which the heated regenerated catalyst for transfer into the reaction zone in krakkauspuolen feed point. It is common for the dilute phase temperature in such regenerators to be higher, sometimes as much as 37 ° C or more, than the temperature of the dense bed. The flue gas can be at an even higher temperature.

One significant advantage of using the platinum group metal-modified catalyst of this invention in conjunction with the addition of oxygen to the regeneration zone is that it tends to cause carbon monoxide to return in the dense phase rather than the dilute phase, reducing the temperature difference (ΔΤ) between the two phases. The temperature of the dilute phase can be significantly lowered while the temperature of the dense phase is raised only moderately. This makes it possible to store the additional heat generated in the CO combustion to a greater extent in the catalyst, which is returned to the cracking zone.

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There are new models of FCC units on the market today that operate on conventional catalysts and CO conversion is performed thermally rather than catalytically. However, there are many problems with the actual operation of these units. These problems can be eliminated by using the catalyst of the present invention. Catalysts containing suitably low concentrations, usually well below 10 ppm in total, of one or more metals selected from the group consisting of Pt, Pd, Rh, Ru, Ir, Os and Re, several advantages will be apparent in the operation of these units. ΔΤ values decrease: i.e. the temperature of the dense bed rises and a sharp drop occurs in the temperature of the dilute phase, the cyclone and the exhaust gas. The dense layer then retains more process heat for use in the reactor. At elevated dense bed temperatures, a lower catalyst recycle rate is required to bring the same amount of heat to the reactor. The slowed catalyst circulation results in less grinding and less particulate matter removal with the effluent regeneration gas and may also reduce catalyst replenishment requirements to maintain a given activity. The higher the temperature of the dense bed, the lower the amount of residual carbon returning to the reactor on the surface of the catalyst. It has been found that a lower amount of residual carbon results in a higher activity of the efficient catalyst. The lower rotation speed of the catalyst and the lower amount of residual carbon improve the selectivity, in particular by reducing the coke yield calculated from the feed and increasing the products to be recovered accordingly. When using the catalyst of the present invention, spraying steam to reduce high cyclone temperatures is unnecessary. Injection of fuel oil to raise the temperature of the dense bed to maintain thermal conversion of CO is also unnecessary. Without interfering with the cost of steam and fuel oil, both of these adjustments accelerate catalyst deactivation and make the process more difficult to control. An additional benefit of the reduced catalyst rotation rate is less wear on the internal parts of the system. Although preheating of the feed to the cracking unit can also cause or allow a decrease in catalyst circulation, the efficiency of energy transfer to the reactor in the form of heat is higher when heat is generated directly in the catalyst bed.

In some fluidized bed cracking units as well as in the moving bed units, coke is insufficiently deposited on the catalyst during the cracking cycle to generate enough heat when the coke is burned in the regenerator. In such cases, the temperature in the regenerator is too low to effectively reduce the residual carbon content of 62553 14 to the desired level (e.g., less than 0.2% by weight C). Moreover, new cracking catalysts with higher selectivity, which produce more valuable liquid products at the expense of coke, cannot be used in these units as they would be even more difficult to regenerate. When using the catalyst of this invention, sufficient additional heat is generated by oxidation of carbon monoxide to take advantage of all such improved selectivities.

Another type of FCC regeneration system uses a lower dense fluidized bed of catalyst to which cooled, coking catalyst is added from the cracking zone and an upper non-dispersed or dilute phase into which all of the dense phase catalyst is thrown. A portion of the upper dilute phase hot regenerated catalyst may be returned to the lower dense bed to maintain the temperature of the dense bed hot enough to at least initiate coke combustion. In this form, substantially all of the regenerated catalyst returned to the cracking zone is taken from the upper dispersed phase and substantially nothing comes directly from the lower dense layer. The use of a platinum group metal modified cracking catalyst together with a sufficient amount of oxygen to the regenerator to maintain carbon monoxide combustion results in a dense bed temperature rise, a decrease in residual coke on the dense bed catalyst, and

In mobile bed reflective catalytic cracking, exemplified by the TCC process mentioned above, the coking catalyst is transferred from a cracking zone to a regeneration zone, sometimes referred to as an annealing furnace. The annealing furnace itself has an upper zone and a lower zone. Oxygen-containing gas, preferably air, is fed between the zones while coking catalyst is fed from the two zones to the upper one. The air travels countercurrent to the coking catalyst to the upper zone, burning off some coke to form a combustion gas containing carbon oxides, including substantial amounts of carbon monoxide. The partially decoke-free catalyst now travels from the upper zone downstream with a portion of the feed air to the lower zone, where additional coke deposits are burned off and a combustion gas containing carbon oxides is formed. When a platinum group metal catalyst such as that disclosed herein is used and sufficient oxygen is fed to the annealing furnace, small changes in the ratio of carbon dioxide to carbon monoxide are observed in the combustion gas from the upper countercurrent regeneration zone. However, under these same conditions, it is found that the flue gas from the lower, downstream regeneration zone contains substantially no carbon monoxide after it has become substantially completely oxidized to carbon monoxide. The regenerated catalyst leaving the annealing furnace is substantially hotter than without the platinum group metal monodionization in question, and the entire combustion gas, which is a combination of the upper and lower zone combustion gases of the annealing furnace, may contain somewhat less carbon monoxide.

In the process of the invention, the platinum group metal decomposing compound is contacted with the cracking catalyst while being used in the cracking process. For example, in the TCC process, a platinum group metal decomposable compound can be applied directly to a coking cracking catalyst between a cracking reaction zone and a regeneration annealing zone. This type of operation, combined with the supply of a sufficient amount of air, causes at least part of the carbon monoxide generated in the upper countercurrent regeneration zone to burn to carbon dioxide, which at least reduces the carbon monoxide content of the combustion gas from the upper regeneration zone. In this context, it should be understood that there is considerable competition, especially in the upper regeneration zone, between available coke and carbon monoxide for available oxygen. Therefore, in the upper zone, where relatively low temperatures and high coke concentrations prevail, it is difficult to burn CO with very high efficiency.

Another aspect of the present invention that appears to make it possible to increase the usefulness of the cracking catalyst modified herein by the addition of small amounts of platinum group metal, especially in moving bed type cracking, is to recycle a small amount of regenerated catalyst from the annealing furnace outlet to its feed point. Recycling rates can be up to about 10% by weight or perhaps more. It is appropriate to keep this recycling rate to a minimum as it increases the required catalyst stock. However, it is preferred in the sense that it results in a hotter and cleaner regenerated catalyst and a lower amount of carbon monoxide in the combustion gas.

A further aspect of the present invention in the context of a mobile bed, e.g., TCC cracking systems using a platinum group metal modified cracking catalyst, involves a change in the conventional flue gas discharge scheme. In normal operation, the fuel gas from the lower annealing furnace is mixed with the fuel gas from the upper annealing furnace and the mixture is discharged. According to this aspect of the invention, the fuel gas from the upper annealing furnace, which contains substantial amounts of carbon monoxide, is fed to the regeneration zone formed by the lower annealing furnace together with the air supplied to it. This allows the upper flue gas loaded with carbon monoxide to come into contact with the partially and fully regenerated platinum group metal-containing catalyst and excess air, and therefore allows and promotes the combustion of carbon monoxide to carbon dioxide to a greater extent than hitherto possible.

In moving bed catalyst cracking systems, it is conventional to operate the entire cracking cycle and subsequent regeneration as the catalyst flows continuously downward and then lifts the pneumatically or mechanically regenerated catalyst from the regenerator annealing furnace to the top of the cracking reactor. Some refineries use air for pneumatic lifting, some use a combination of steam and combustion gas. By incorporating small amounts of platinum group metal into the cracking catalyst, it is possible to substantially reduce or perhaps even remove carbon monoxide from the flue gas. According to this aspect of the invention, the hot, regenerated catalyst is lifted as slowly as possible with the mixture of fuel gas and air. The platinum group metal with the hot regenerated cracking catalyst catalyzes the combustion of carbon monoxide in the riser. This not only purifies the exhaust gas, but also further heats the regenerated catalyst, allowing it to more efficiently catalyze hydrocarbon cracking reactions.

The oils fed to this process are mainly petroleum distillates, commonly known as gas oils, boiling in the temperature range of about 343-538 ° C and occasionally supplemented by coke oven gas oil.

17 62553 vacuum tower upstream, etc. These oils are generally substantially free of metal impurities.

The feedstock used herein to refer to the entire fresh feed of one or more oils is cracked in the reactor section in a reaction zone maintained at a temperature of about 427-649 ° C, a pressure of about 1-5 atm and a normal oil residence time of n 1-10 seconds with a modern short contact time riser structure. The residence time of the catalyst is about 1-15 seconds.

Because the feedstock contains trace amounts of metal, primarily nickel and vanadium, the circulating storage of the catalyst collects these metals until an equilibrium is reached between the metal removed from storage and the amount fed with the fresh feed with losses. A circulating catalyst stock that has been in use for some time and has reached the normal amount of nickel and vanadium replenishment is commonly referred to as an "equilibrium catalyst." The equilibrium catalyst is usually characterized by a metal content between about 200-600 ppm nickel equivalent metal, defined as ppm nickel equivalent = ppm nickel + 0.25 ppm vanadium.

As mentioned, in a preferred embodiment of the invention, a side stream is taken from the circulating storage of the cracking catalyst and impregnated in the contact zone with a solution containing said combustion promoting metal compound dissolved in a solvent boiling above about 60 ° C but below 315 ° C, which the contact causes a metal compound to deposit on the surface of the catalyst. Before or during contact, the side stream is cooled to a temperature below about 315 ° C. The by-product is then returned to the catalyst circulating tank. The side flow can be limited to a single vessel that is closed except for its connection to the catalyst circuit. The vessel may open into the reactor, the coke catalyst line, or the regenerated catalyst downcomer. The by-pass may thus originate from different parts of the catalyst compartment. However, it is recommended to take it from the reactor section or the coke catalyst tube to provide a side stream of coke catalyst. It is also recommended that at least a portion of the contact be made approximately at or above the boiling point of the solvent as described below.

In order to obtain close contact and consequent deposition or impregnation of the combustion promoting metal compound, it is recommended that the catalyst be fluidized in the contact zone during the contact period. Useful solvents include water and liquid organic compounds with the described boiling specifications.

It has been found that according to this embodiment of the invention, the efficiency of the combustion promoting metal to promote the combustion of carbon monoxide is improved and the possible loss of a portion of the promoter metal or partial deposition of this metal on the surface other than the catalyst is avoided. Although the efficiency of a particular metal may depend on the manner in which it is fed to the catalyst, Figure 3 shows the relative efficiency obtained with a series of cracking catalysts containing various combustion-promoting metals deposited in a conventional manner during the preparation of these catalysts. For the purposes of this invention, it is recommended to use platinum.

Metal compounds useful in this invention include metal halides, preferably chlorides, nitrates, amine halides, oxides, sulfates, phosphates, and other water-soluble inorganic salts; also metal carboxylates containing 1 to 5 carbon atoms; or alcoholates. Typical examples are palladium chloride, chloroplatinum acid, tetramine-niplatin (II) dichloride, ruthenium pentaamine chloride, osmium chloride-perrhenium acid, dioxybis (ethylenediamine) rhenium (V) chloride, rhodium chloride yras. Organometallic compounds or organometallic compounds of the described metals can also be used, including metal diketonates, carbonyls, metallocenes, olefin complexes having 2 to 20 carbon atoms, acetylene complexes, and alkyl or arylphosphine complexes having 1 to 20 carbon atoms, and carboxylates. Typical examples of these are platinum acetylacetonate, tris (acetylacetonate) rhodium (III), triiodouridium (III) tricarbonyl, H-cyclopentadienyl rhenium (I) tricarbonyl, rutenosene, H-cyclopentadienyl osmium (I) dicarboxylic acid ethylene) palladium (II) dimer, (f-cyclopentadienyl) (ethylene) rhodium (I), diphenylacetylene bis (triphenylphosphino) platinum (0), bromomethylibis) triethylphosphino) palladium (II), tetrakis (triphenylphosphino) palladium ), chlorocarbonyl (triphenylphosphino) iridium (I), palladium acetate and palladium naphthenate.

It is a special feature of this invention that relatively simple and halo metal compounds such as chloroplatinic acid or tetraamine platinum dichloride can be used.

Solvents useful in the process of this invention include water, polar organic solvents, and liquid hydrocarbons, and generally all organic and inorganic liquids that are solvents for the selected metal compound. Typical examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, tert-butanol, 2-ethylhexanol, octanol, glycerol and ethylene glycol; esters such as ethyl acetate, butyl acetate; amyyliasetaat-phosphate; ethers such as diethylene glycol, diisopropyl ether, di-n-butyl ether, cellosolve, methylcellosolve, butylcellosolve; hydrocarbons such as octane, nonane, decane, dodecane, hexadecane, benzene, toluene, xylene, cumene and mixtures thereof.

Mixtures of solvents can be utilized, as described in more detail below. Such mixtures include, for example, water and ethylene glycol, benzene and cumene, and tertiary butyl alcohol and water. These mixtures are presented for illustrative purposes only and are not to be construed as limiting.

Preferred solvents or mixtures thereof useful in this invention are those that boil above about 60 ° C but below 315 ° C at the contact zone pressure.

For the purposes of this invention, it is believed necessary to cool the hot circulating storage side stream of the cracking catalyst at a temperature substantially above 315 ° C and to cool it below 315 ° C. While not wishing to be bound by any theoretical assumptions, it is believed that the method of the present invention is effective, at least in part, in that it avoids premature decomposition of the combustion-promoting metal compound, i. decomposition of the compound before it has had sufficient opportunity to come into contact with the catalyst and achieve optimum distribution on its surface. Therefore, it will be appreciated that the exact temperature for contacting the flame retardant metal solution and the cracking catalyst side stream to achieve maximum promoter metal efficiency may vary depending on the thermal stability of the metal compound itself and the choice of solvent and in some cases perhaps the nature of the cracking catalyst itself. Unusual efficacy has been observed, for example, as described below, with tetraamine platinum dichloride using water as a solvent at or above about 135 ° C, which is approximately the boiling point of water at a contact zone overpressure of n.

20 62553 210 kPa. It is generally recommended to perform the contacting step under conditions such that at least a portion of the solvent wets the catalyst.

Prior to the contacting step, the side stream of the cracking catalyst may be indirectly cooled by a condenser using air or other heat transfer medium to remove heat through a mechanical barrier, such as a pipe wall. It can also be directly cooled by contact with an inert gas or water that is injected into the stream. Combinations of direct and indirect cooling can also be used.

Those skilled in the art will recognize that at least some direct cooling occurs when the side stream of the cracking catalyst is forced into contact with a solution of the combustion promoting metal compound, this cooling being due to evaporation of the solvent. Thus, a substantial portion, if not all, of the desired cooling can be accomplished simply by diluting the solution of the metal precursor compound with a substantial excess of solvent and injecting relatively larger fractions from the solution into the contact zone.

Mixtures of solvents of different volatilities can be advantageously used, such as a smaller amount of glycerol with the main fraction of water. In such a case, water acts as a co-solvent and coolant, while less volatile glycerol ensures that the metal promoter compound retains its integrity without dispersing until adequate contact with the catalyst is achieved. The cooling efficiency due to solvent volatility can be improved by using a solvent that decomposes endothermically upon contact with the hot cracking catalyst. Examples are alcohols, such as tertiary butyl alcohol, which dehydrates to isobutylene and water, or isopropyl alcohol, which forms propylene and water. Such endothermically decomposable solvents may be used alone or in admixture with other solvents.

Mixtures of solvents boiling above about 60 ° C but below 315 ° C are suitable. Mixtures are generally characterized by a boiling range, and it is to be understood that when the term "boiling range" is used herein, it is meant to include both the range of temperatures suitable for mixtures when used and the boiling point indicated by a single temperature of 62553 for a private solvent when used. , in which at least 95% of the solvent, i.e. essentially all of the solvent is distilled off. In addition, when reference is made herein to boiling or boiling range without mentioning the prevailing pressure, it is to be understood that the overpressure prevailing in the contact zone, which is usually about 70-350 kPa, must be used.

Although the by-product of the catalyst can be removed from anywhere in the hot, circulating storage of the cracking catalyst, it proves advantageous to use the by-product of the coking catalyst for the purposes of this invention. Therefore, it is recommended to remove the side stream from the reactor or coking catalyst tube. When the removal takes place from the reactor, it is recommended to remove the catalyst from the stripping zone in order to avoid possible difficulties due to the presence of volatile hydrocarbons on the surface of the catalyst, i. the coking catalyst should be substantially free of gas oil or its conversion products when in contact with a solution of the combustion promoting metal.

The removed by-pass is passed to a contact zone where it is brought into contact with the solution. The solution may be delivered by a syringe nozzle or other suitable device that promotes close contact. It is desirable to keep the catalyst in a fluidized state in the contact zone which promotes a uniform temperature and good distribution of the metal compound to the catalyst. Evaporation of the solvent promotes fluidization. After impregnation, the side stream is recycled and allowed to mix with the hot, circulating reservoir of catalyst. As the compound returns to high temperatures, it is believed to decompose to provide the active form of the metal combustion promoter. Due to the very small amounts of metal present, it is not possible to accurately determine the nature of the metal in its active form, i. whether it is present as an elemental metal, sulfide, oxide, or some other form.

The combustion-promoting metal provided in the catalyst reservoir by the process of this invention may be a component of all or only some of the catalyst particles. As for its concentration in the whole system, it must be present in a quantity large enough to be able to effect the reaction of carbon monoxide with oxygen into carbon dioxide, provided that the conditions in the regenerator are otherwise sufficient to maintain this combustion; e.g., high enough temperature and enough air. However, it may not be present in such a large amount that it affects adversely the process krakkauspuolen essential activities. This latter upper limit of the metal diluent concentration is to some extent a reflection of the calculated capacity of the cracking system, including auxiliaries and downstream product separators, compared to the actual actual production volume. The upper limit of the metal content of the platinum group must be lower than that which would cause this computational capacity to be exceeded.

The concentration of the combustion promoting metal may be, for example, 0.01 to 50 ppm and preferably 0.5 to 10 ppm.

Figures 4 and 5 show two side current and contact zone arrangements as examples of the system of the present invention. In both figures, the catalyst compartment shown in Figure 1 is illustrated by a simple line drawing; characters not otherwise identified in the following paragraphs are reproduced in Figure 1 and have the same components as in this figure.

In the side flow and contact arrangements shown in Figure 4, the coking catalyst passes from the coking catalyst tube 36 to a tube 70 provided with a control valve 71. The control valve operates to control the flow rate of the flow. The material passing through the valve is passed through a pipe 72 through a heat exchanger 73 which cools the side stream. The cooled catalyst passes through line 74 to vessel 75.

The vessel 75 is provided with a nozzle, spray head or other discharge device 78 which acts to discharge a solution of a combustion promoting metal compound which is fed to the discharge device via a pipe 77. The tube 79 passes into the vessel 75 and also communicates with the discharge device 78. This tube, which may be separate from or connected to the tube 77, acts to conduct compressed air, steam, nitrogen, volatile solvent or other inert dispersant to the vessel 75 to hold the catalyst in the fluidized state in the contact zone 75. The contacted catalyst is passed through line 80 to the regenerator and is thus returned to circulating storage.

Although the representation of Figure 4 shows a side stream to be taken from the tube 36 leaving the stripping zone 24 shown in Figure 1, it may equally be taken from the reactor vessel 81 directly or from the regenerator or regenerated catalyst tube 6 or any suitable location for the hot catalyst storage. Although the side stream in Figure 4 is shown to be returned to the circulating reservoir through line 80, which returns current to the regenerator, it could just as well be returned to any suitable location in the catalyst compartment, such as the regenerated catalyst line 6.

It should be noted that the vessel 75 is suitably provided with a temperature measuring device, such as a thermocouple device 76. Figure 5 shows another arrangement of the system of the present invention. In this arrangement, the vessel 90 connected to the tube 91 is attached to the stripping zone of the reactor vessel 81 so that the contents of the stripping zone and the vessel 90 are in free communication through the tube 91. Tubes 77 and 79 and the discharge device 78 refer to the same components as shown in Figure 4. Tubes 77 and 79 lead to a vessel 90 and a discharge device 78 is located in said vessel. In this system, the fluidized catalyst passes from the stripping zone 24 to the vessel 90, is contacted with a solution of the combustion promoting metal compound, and is returned to the stripping zone along the same tube. It will be appreciated that the attachment 91 may be made elsewhere than shown, such as to a regenerator.

However, it is recommended that the attachment be at locations that provide a connection between the contents of vessel 90 and the fluidized bed of hot, coking catalyst.

Although the present invention has been described with reference to a vortex generator such as that shown in Figure 1, it is equally applicable to a system using other regenerator models, such as a riser-regenerator designed for complete combustion of carbon monoxide. By the process of this invention, a solution of a combustion-promoting metal compound can be applied to a fresh catalyst or an equilibrium catalyst. Moreover, it can be used as the only method for providing said combustion-promoting metal to said catalyst, or it can be used in connection with a supplementary catalyst containing a combustion-promoting metal deposited on its surface during its preparation. The method of the present invention can be used to control the combustion of carbon monoxide in a regenerator, which control is performed by a suitable switching device which controls the side flow rate or the pumping rate or concentration of the combustion metal compound solution, for example according to the combustion gas composition.

The following examples illustrate certain aspects of this invention and are not to be construed as limiting it. All parts and percentages given are by weight unless otherwise indicated.

Example 1 In this and the following examples, a continuous FCC test plant was used. The pilot plant consisted of a regenerator, a riser reactor corresponding to Figure 1 number 4 in communication with the stripping zone corresponding to Figure 1 number 24, and tubes corresponding to Figures 1 numbers 6 and 36. The equilibrium catalyst was removed from a commercial catalytic cracker and used in the examples described hereinabove. The catalyst was a typical rare earth-exchanged faujaite-type commercial material in which faujasite was dispersed in a silica-alumina matrix. Its composition was found to be 61.3% SiO 2, 35.9% Al 2 O 3, 2.77% Re 2 <3> 0.51% Na, 3.59 ppm nickel and 404 ppm vanadium.

For the purposes of this example, a tubular container, as illustrated in Figure 5, was attached and in communication with the sealed layer in the regenerator. The volume of the tube was 25 cm 2.

The vessel was equipped with a nitrogen supply to keep the catalyst fluidized in the tube.

Before starting the contacting and impregnation of the catalyst with the combustion promoting metal compound, the pilot plant unit was charged with a stock of 3500 g of the catalyst described above and a medium volume of 62553 crude gas oil from crude oil and the operating conditions were adjusted as follows:

Reactor temperature, ° C 538

Stripper temperature, ° C 538

Regenerator temperature, ° C 676

Catalyst residence time in the riser, p 7.0 Oil residence time in the riser, s 4.5

Weight ratio of catalyst to oil 6.0

A solution of 6 mg of metallic platinum as tetramine platinum dichloride in 250 ml of water was charged to a feed burette. The solution was pumped as a syringe into the tube described above containing the fluidized catalyst, and the pumping rate was adjusted to give a contact zone temperature of about 177 ° C as expressed by surface temperature measurement. Prior to feeding the solution, the temperature of the contact zone was measured to be about 482 ° C. The adjusted pumping rate was 66 ml / h and was stopped after 231 ml of solution was pumped into the contact zone. Catalyst samples were removed from the stripper every half hour and the catalytic efficiency was evaluated in the combustion of carbon monoxide.

The results are summarized in Table 1.

Table 1 Sample No. Saturation time ppm C0_ / C0 ratio

Pt 1 0 minutes 0 2.7 2 30 "0.22 4.7 3 60 0.44 3.7 4 90" 0.66 3.9 5 120 "0.88 3.6 6 150" 1.10 4 , 7

Example 2

The procedure of Example 1 was repeated with a fresh feed of equilibrium catalyst except that heavy vacuum gas oil from Sour West Texas crude oil was used instead of broad distillate gas oil. In this experiment, 6 mg of platinum as tetraminoplatinum dichloride was dissolved in 180 ml of water. The solution was pumped at a rate of 119 ml / h for one hour, at which time the temperature in the contact zone was approximately room temperature. The catalyst sample removed from the stripper at one 62553 for 26 hours showed no increased activity in promoting CO combustion. Impregnation was continued for another hour by pumping 78 ml of the described solution, which at the end of the period has a contact zone temperature of about 177 ° C. The catalyst sample removed after two hours of impregnation gave a CO 2 / CO ratio of 6.3 compared to 2.7 with catalyst before impregnation. The calculated promoter metal content of the sample was 1.9 ppm.

Example 3 A tubular vessel used for contacting purposes for the purposes of this invention was attached to the stripping zone of a pilot plant. Untreated equilibrium catalyst was charged to the system and adjusted as described in Example 1, but using the heavy vacuum gas oil used in Example 2.

A solution of 2 mg of platinum in 250 ml of water was pumped at a rate of 90 ml / h into contact with the catalyst until 135 ml of solution was consumed. The temperature in the contact zone initially varied from about 204 ° C, dropping to 104 ° C, at which point the run was stopped and the catalyst sample was taken. The sample was calculated to contain 0.31 ppm platinum and gave a CO 2 / CO2 ratio of 410.

Example 4

Example 3 was repeated with a fresh charge of equilibrium catalyst, but the contact solution flow rate and nitrogen flow rate were adjusted to keep the contact zone temperature between about 204-315 ° C. A sample of the final catalyst, calculated to contain 0.29 ppm platinum, gave complete combustion of carbon monoxide, i. infinitely high CO2 / CO2 ratio.

Claims (10)

A cyclic, regenerative, catalytic cracking process of the known kind, in which the catalyst, after being in contact with a charge in a reactor under cracking conditions without the addition of hydrogen, passes through an external circuit comprising a regenerator and which returns the catalyst in regenerated state to the reactor. tower, wherein the moving mass of the catalyst contains a metal from the platinum group or rhenium at a content of up to 0.01-50 ppm of the catalyst, characterized in that the metal from the platinum group or rhenium is applied to the catalyst during its passage through the catalyst. said circuit outside the reactor. Process according to Claim 1, characterized in that the metal from the platinum group or rhenium is applied to the catalyst in the form of a compound which is disintegrated under the conditions under which the catalyst is subjected during the process. Process according to claim 1, characterized in that the metal from the platinum group or rhenium is applied to the catalyst in the form of a colloidal suspension in a suitable medium or a dispersion on a refractory oxide carrier of colloidal particle size. Process according to claim 1 or 2, characterized in that the metal from the platinum group or rhenium is applied to the catalyst in the form of an emulsion of a compound of the metal in a liquid or in the form of either of this compound in a gaseous carrier material. Process according to any of the preceding claims, characterized in that spent catalyst is periodically removed from said moving mass and replaced with fresh catalyst in a known manner and that the metal from the platinum group or rhenium is applied to the catalyst from time to time. keep the said concentration substantially unchanged. Process according to any of the preceding claims, characterized in that the metal from the platinum group or rhenium is applied to the catalyst as it is in a side stream.