CH628825A5 - Process for regenerating catalysts contaminated with coke with simultaneous carefully controlled combustion of carbon monoxide - Google Patents

Description

The invention relates to a method for regenerating coke-contaminated catalysts with simultaneously carefully controlled combustion of carbon monoxide.

Regeneration methods in which a catalyst contaminated with coke is regenerated in a regeneration zone represent a wide range of chemical or hydrocarbon processing technology. Regeneration methods for regenerating coke-contaminated, fluidizable cracking catalysts in the regeneration zone of a catalytic fluid or fluidized bed cracking process (hereinafter) are particularly widespread mostly referred to as fluidized bed cracking for simplification). Up until a few years ago, the state of the art had primarily dealt with removing the largest possible amount of coke from the used catalysts and at the same time preventing excessive temperatures, such as result from the conversion of carbon monoxide to carbon dioxide within certain ranges of the Regeneration zone result, especially in the area where the catalyst is in the dilute phase, thus little catalyst is present to absorb the heat of reaction and accordingly heat damage to cyclones or other separation devices can occur. Essentially complete carbon monoxide conversion was prevented in conventional regeneration zones simply by restricting the amount of fresh regeneration gas flowing into the regeneration zone. Without the presence of enough oxygen to maintain the oxidation of carbon monoxide to carbon dioxide, afterburning cannot occur, of course, no matter what the temperatures in the regeneration zone are. Furthermore, the temperatures in the regeneration zone have generally been limited to less than about 675 ° C by appropriate selection of the operating conditions in the hydrocarbon reaction zone or the fresh feed streams or the recycle streams or by a combination of these measures to thereby reduce the amount of coke on the catalyst used and thus limit the amount of combustible material burned in the regeneration zone. The exhaust gas generated, which contained several percent by volume of carbon monoxide, was either blown off directly into the atmosphere or used as fuel in a CO boiler downstream of the regeneration zone.

The usual method of starting a fluidized bed catalytic cracking process, as is known to those skilled in the fluidized bed catalytic cracking process, has been to initially manually control the flow of fresh regeneration gas to the regeneration zone in an amount sufficient to maintain one in the we5

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considerable complete carbon monoxide conversion is not sufficient, and at the same time to limit the regeneration zone temperatures to a maximum value of about 675 ° C. After reaching and settling a usable steady state of the fluidized catalytic cracking process, the flow rate of the fresh regeneration gas was then typically regulated by instrument control in direct response to a small temperature difference between the exhaust gas outlet temperature (or the temperature in the thin phase separation space) and the temperature of the dense bed automatically maintain this correct flow rate of fresh regeneration gas and preclude essentially complete conversion of CO to C02 anywhere within the regeneration zone. As the temperature difference increased beyond a predetermined temperature difference, indicating that more conversion of CO takes place in the dilute phase, the amount of fresh regeneration gas was reduced to prevent essentially complete conversion of CO to CO 2. This control method is e.g. in U.S. Patent Nos. 3,161,583 and 3,206,393. This method results in a small amount of oxygen in the exhaust gas, generally in the range of 0.1 to 1 percent by volume 02, but it makes an essentially complete conversion of CO to CO 2 within the regeneration zone impossible.

Until the introduction of zeolite-containing catalysts, there was only a relatively small economic incentive for an essentially complete conversion of CO to CO 2 within the regeneration zone. However, the use of zeolite-containing fluidized bed cracking catalysts, which are more thermally stable and have less tendency to form coke, and the use of higher temperatures in the hydrocarbon conversion zone have often made necessary or desirable additional heat input into the catalytic fluidized bed cracking process. Typically, additional heat was obtained by burning an externally supplied fuel, e.g. B. of auxiliary fuel oil, in the regeneration zone or by using or increasing the size of a feed preheating in outer feed preheaters. Normally, therefore, heat was introduced into the catalytic fluidized bed process on the one hand and then removed from it later on, on the other, by means of two external devices or system parts, a feed preheater and a CO boiler, both of which entail considerable investment and operating costs. Catalyst regeneration processes described in the more recent art have recognized the benefits of essentially completely converting CO to CO 2 and recovering at least a portion of the heat of combustion of the carbon monoxide, both within the regeneration zone. Examples of such regeneration processes are US Pat. Nos. 3,844,973 and 3,909,392. The advantages of such working methods are now recognized; such regeneration processes allow feed preheating to be reduced or eliminated, carbon monoxide pollution to be eliminated without the need for external CO boilers, and, when used in conjunction with modern design hydrocarbon reaction zones, improved yields of more valuable products.

Regeneration processes using CO conversion promoters or catalysts have already been reported; for example, such promoters or catalysts have been used in conventional methods for regenerating fluidizable, coke-contaminated cracking catalysts. For example, at

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the fluidized bed catalytic cracking process described in U.S. Patent No. 2,436,927 (1948) employs a physical mixture of separate particles of a cracking catalyst and separate particles of a carrier-containing CO oxidation catalyst in a dense phase area of a regeneration zone to effect CO conversion in the dense phase promote and thereby prevent «post-combustion» in the dilute phase area of the regeneration zone. In the process described in U.S. Patent 3,364,136 (1968), a mixture of a cracking catalyst and a shape-selective crystalline aluminosilicate that contains an oxidation catalyst within its inner pore structure is used to control the CO 2 / CO ratio in the regeneration zone without being affected the reaction taking place in the hydrocarbon reaction zone. The process described in U.S. Patent No. 3,808,121 uses two separate catalysts of different particle size and composition, a cracking catalyst and a CO oxidation catalyst, preferably carried in a matrix material such as alumina balls and monoliths. Furthermore, the carrier-containing CO oxidation catalyst is kept within the regeneration zone and does not flow out of this zone to the hydrocarbon reaction zone, as the cracking catalyst does. Coke and carbon monoxide are subjected to oxidation in the regeneration zone in order to make the CO content in the exhaust gas as low as possible.

Previous regeneration processes have thus used CO oxidation promoters in one of two ways: (1) on separate particles of a matrix or support, the particles being mixed with the fluidized bed cracking catalyst, and (2) as part or component of the fluidized bed cracking catalyst itself Mixtures of cracking catalyst and carrier-containing CO oxidation promoter tend to be non-uniform, which can lead to a CO concentration in the exhaust gas above the permitted emission restrictions. The use of a cracking catalyst containing any predetermined concentration of a CO oxidation promoter as a component generally makes it difficult to provide the optimal concentration of oxidation promoter in any particular regeneration zone that is suitable for the operating characteristics of that particular regeneration zone or to make a particular change a dependent process changeable are required.

By the method of the invention, a CO oxidation promoter is fed to the regeneration zone independently of the cracking catalyst, coke is oxidized from the spent catalyst to produce regenerated catalyst and substantially simultaneously carbon monoxide is converted to carbon dioxide in the presence of the promoter and the regenerated catalyst within the regeneration zone . In this way, a carbon monoxide oxidation promoter, particularly when in a liquid, can be easily and precisely introduced into the regeneration zone in amounts to control the CO concentration in the exhaust gas, to control a temperature within the regeneration zone or to control the amount of residual carbon be introduced on the regenerated catalyst. Accordingly, the introduction of a CO oxidation promoter according to the process of the invention is usually easier, better and more economical than either the use of separate particles of a carrier-containing CO oxidation promoter together with a cracking catalyst or the use of a cracking catalyst which is a CO conversion promoter during catalyst production3

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ganges has been added. In addition, the method of the invention gives operating personnel, for example, an operating condition as a process variable, which was previously essentially a fixed operating condition. Accordingly, the implementation of the operation using the method of the invention is, for example, of increased operational flexibility and adaptability. The method of the invention is normally applicable to any existing or newly installed fluidized bed cracking process.

The invention is therefore based on the object of an improved method for regenerating a catalyst contaminated with coke with simultaneous carefully controlled combustion of carbon monoxide in a regeneration zone and an operating procedure which makes a controlled amount of exothermic reaction heat available for the operation of the regeneration zone and the amount of carbon monoxide reduced in the exhaust gas to create, which does not have the above-mentioned and similar shortcomings of known methods of operation and is simple, reliable and economical to perform. In connection with this, the invention aims at a catalytic cracking process, in which coke-contaminated cracking catalyst and oxygen-containing regeneration gas are fed to a regeneration zone kept under coke oxidation conditions for the production of a regenerated catalyst and a CO and CO 2 -containing exhaust gas, the specification of a procedure for the utilization of the on site and place incineration of CO to COz for controlling the operation of the regeneration zone. In connection with this, the invention also aims in connection with a catalytic cracking process in which cracking catalyst contaminated with coke and regeneration gas containing oxygen are fed to a regeneration zone maintained under coke oxidation conditions for producing a regenerated catalyst and a waste gas containing CO and CO 2, the indication (1) of a procedure for Controlling the CO concentration in the exhaust gas within a predetermined CO concentration range, (2) an operation for controlling a regeneration zone temperature within a predetermined temperature range and (3) an operation for controlling the concentration of residual carbon on the regenerated catalyst within a predetermined residual carbon concentration range .

The process according to the invention for the regeneration of catalysts contaminated with coke with simultaneous carefully controlled combustion of carbon monoxide is characterized in that

(a) introduces catalyst contaminated with coke into a regeneration zone,

(b) introduces a carbon monoxide oxidation promoter into the regeneration zone, regardless of the coke-contaminated catalyst, in an amount selected to promote the combustion of carbon monoxide to carbon dioxide,

(c) introduces oxygen-containing regeneration gas into the regeneration zone in an amount selected to burn coke from said coke-contaminated catalyst and present sufficient excess oxygen to achieve the desired level of carbon monoxide combustion,

(d) a first portion of the oxygen-containing regeneration gas with the coke-contaminated catalyst in the regeneration zone under such chosen oxidation conditions for the removal of coke from the coke-contaminated catalyst and for the production of an exhaust gas which contains a major amount of carbon monoxide and a small amount Contains carbon dioxide, relative to the total amount of carbon oxides, and then

(e) contacting the resulting exhaust gas and the remaining portion of the oxygen-containing regeneration gas with the carbon monoxide oxidation promoter in the regeneration zone under the carbon monoxide combustion conditions, thereby making a controlled amount of exothermic heat of reaction available for operation of the regeneration zone while maintaining the amount of carbon monoxide in the Exhaust gas lowers.

In connection with this, according to another preferred embodiment of the invention, in a process for the catalytic cracking of a hydrocarbon feed stream, in which cracked catalyst and oxygen-containing regeneration gas contaminated with coke are passed into a regeneration zone maintained under coke oxidation conditions, in the coke to produce a regenerated catalyst and a carbon monoxide and Exhaust gas containing carbon dioxide is oxidized, a method of utilizing the on-site combustion of carbon monoxide to carbon dioxide for controlling the operation of the regeneration zone, which is characterized in that (a) the regeneration zone is independent of the catalyst contaminated with coke Carbon monoxide oxidation promoter in an amount selected to initiate and maintain carbon monoxide combustion in the regeneration zone in the presence of the regenerated catalyst and (b) thereafter adjusts the amount of oxygen-containing regeneration gas directed to the regeneration zone to a value stoichiometrically sufficient to burn off the coke from the catalyst and convert at least a portion of the carbon monoxide to carbon dioxide, and thereby (1) a controlled amount of exothermic Exposes heat of reaction to the operation of the regeneration zone and (2) reduces the amount of carbon monoxide in the exhaust gas.

Further aspects and preferred measures of the invention relate, for example, to expedient embodiments with regard to carbon monoxide conversion promoters, amounts to be added of a carbon monoxide conversion promoter, procedures for introducing a carbon monoxide conversion promoter into the regeneration zone, and the operating conditions; Further details can be found in the further explanation of the invention below.

First, for the sake of clarity and better understanding of the method of the invention, various terms used herein are defined.

The term "hydrocarbon reaction zone" denotes the part of a fluidized catalytic cracking plant in which a hydrocarbon feed stream is brought into contact with regenerated catalyst under cracking conditions to produce a mixture of fluidized catalytic cracking product components, coke-contaminated (or spent) catalyst and, if necessary, unreacted feed. Typical fluid catalytic cracking product components obtained after separation in facilities located downstream of the hydrocarbon reaction zone are C2 fuel gas, C3 and C4 fractions, a gasoline fraction, light cycle oil and clarified sludge oil. After product components have been separated off, at least part of the spent catalyst is passed to the regeneration zone. The terms “catalyst contaminated with coke” or “spent catalyst” are interchangeable

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and refer to catalyst withdrawn from a hydrocarbon conversion zone due to reduced activity due to coke deposits. Used catalyst flowing into the regeneration zone can contain a few tenths up to about 5 percent by weight of coke; normally the spent catalyst in fluidized bed catalytic cracking operations contains about 0.5 to about 1.5 weight percent coke.

The term “regeneration zone” denotes the part of the catalytic fluidized bed cracking system into which an oxygen-containing regeneration gas and at least part of the spent catalyst are introduced and in which at least a part of the coke from the spent catalyst is oxidized to produce regenerated catalyst and a CO 2 and CO containing exhaust gas is removed. “Regenerated catalyst” is a catalyst from which at least part of the coke has been removed by oxidation. Regenerated catalyst, as produced using the process of the invention, generally contains less than about 0.3 weight percent coke, and more preferably about 0.01 to about 0.15 weight percent coke. The term "regeneration gas" as used here is to be understood in the general sense to mean any gas which is to be brought into contact with the catalyst or which has been in contact with the catalyst in the regeneration zone. The term “oxygen-containing regeneration gas” denotes a regeneration gas that contains free or unbound oxygen, eg. B. air or oxygen-enriched air or oxygen deficient air, and which flows into the regeneration zone to allow coke to burn off from the spent catalyst and convert CO. The term “exhaust gas” denotes regeneration gas which has been in contact with catalyst within the regeneration zone and flows out of the regeneration zone. The exhaust gas generally contains nitrogen, free oxygen, carbon monoxide, carbon dioxide and water. Because CO and CO 2 concentrations are used to carry out routine calculations for the fluidized bed catalytic cracking process and because the CO is a potential fuel that can be burned within the regeneration zone or in an external CO boiler or optionally both ways, and so on Most of the time there are restrictions regarding air pollution due to the emission of CO, the exhaust gas is normally characterized by the concentration of CO and C02 or by the molar ratio of C02 / C0. Depending on the operating conditions used in the regeneration zone, in particular the amount of the oxygen-containing regeneration gas fed into the regeneration zone, the concentrations of CO in this exhaust gas can vary over a wide range from a few hundred parts per million or even up to about 15 percent by volume or vary even further and the concentration of CO 2 can range from about 5 volume percent to about 20 volume percent. When the regeneration zone is operated under conditions to largely prevent controlled oxidation of carbon monoxide within the regeneration zone, the concentrations of CO and CO 2 are approximately the same, both within the range of about 7 to about 15 volume percent, and the CO 2 / CO molar ratio is then in the range of about 0.8 to about 1.5. If the regeneration zone is operated under conditions to achieve partial oxidation of CO, the concentration of CO will be lower than that of CO 2 and in particular the CO 2 / CO molar ratio will normally be about 1.5 to about 100. When the regeneration zone is operated under conditions to achieve substantially complete combustion of CO within the regeneration zone, the CO concentration is typically less than about 1000 parts per million, preferably less than 500 parts per million, and the CO 2 / CO molar ratio is greater than about 100.

The terms "dense phase" and "dilute phase" are common terms in the field of catalytic fluidized bed cracking for the general identification of catalyst densities in different parts of the regeneration zone or the hydrocarbon reaction zone. The limit density is not clearly defined. In the present documents, the expression “dense phase” is intended to denote areas within the regeneration zone where the catalyst density is greater than approximately 80 kg / m3; the term "dilute phase" denotes areas where the catalyst density is less than about 80 kg / m3. Usually the density of the dense phase area is in the range of about 80 to 560 kg / m3 or above and the density of the dilute phase area is well below 80 kg / m3 and in the range of about 1.6 to about 80 kg / m3. Catalyst densities in regeneration zones are usually determined by measuring pressure or column differences (head differences) along pressure sensors installed in the vessels and arranged at known distances from one another.

The term "post-combustion" is generally understood in the art to mean the unintended, uncontrolled oxidation of CO to C02 in the dilute phase area of the regeneration zone or the exhaust pipe, where little catalyst is available to act as a heat absorption material. Since the heat of reaction of the CO-oxy-dation is very strongly exothermic, it is about 2420 Kcal / kg of oxidized CO (4350 BTU / lb), afterburning can accordingly lead to severe damage to the catalyst separation devices arranged in the diluted phase. In general, afterburning is shown by a rapid rise in temperature and occurs during periods of unsteady operating state or “fluctuations” or “disruptions” in the course of the process. Accordingly, it is usually of short duration until a steady operating state is brought about again.

In contrast to post-combustion, the terms “controlled conversion of CO” or “controlled oxidation of CO” are intended, controlled and maintained oxidation of CO in the presence of sufficient catalyst to absorb at least part of the heat of reaction, so that thereby at least part of the Heat of reaction gained and damage to equipment in the regeneration zone is excluded. Depending on the operating conditions used, the controlled oxidation of CO can be partially completed or essentially complete. “Partially completed” is intended to mean that the CO concentration in the exhaust gas has been reduced to such an extent that the CO 2 / CO molar ratio of the gas is in the range from approximately 1.5 to 100. “Essentially complete” conversion of CO is said to mean that the CO concentration of the gas has been reduced to such an extent that the CO 2 / CO molar ratio is greater than about 100. Typically, the substantially complete CO conversion results in CO concentrations of less than about 1000 parts per million, and preferably less than about 500 parts per million.

The terms “CO conversion promoter” or “CO oxidation promoter” or simply “promoter” are intended to identify a substance that catalyzes the oxidation of CO to C02. With a CO conversion promoter, the kinetic rate constant for the oxidation of CO to CO 2 can usually be 2 to 5 times

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or even a lot more. A faster CO conversion rate can thus be achieved under conversion conditions in the presence of a CO conversion promoter than is the case under the same conversion conditions without the promoter. Conversely, the same CO conversion rate can be achieved with less severe conversion conditions, e.g. in terms of temperature than can be achieved without the CO conversion promoter.

The amount of CO conversion promoter introduced into a regeneration zone can be expressed as the amount required to bring about a desired change in a variable or it can be expressed in terms of the circulating catalyst inventory or catalyst circulation rate or replenishment rate for fresh cracking catalyst or, if appropriate, in relation to a unit quantity of the feed. In the present specification, the amount of promoter is usually expressed as the amount required to bring about a desired change in a variable such as temperature, CO concentration or residual carbon content, or is expressed as parts by weight per million of the circulating Catalyst inventory. The term "circulating catalyst stock" denotes the amount of cracking catalyst in the fluidized bed catalytic cracking process that can be circulated from the regeneration zone to the hydrocarbon reaction zone and back again. It differs from the total cracking catalyst inventory, since there is usually a certain proportion of the total catalyst inventory that is not available for circulation, e.g. B. the proportion of the total stock that is typically located in the cone section of the regeneration zone under the pipe grid.

Taking these definitions into account, today's typical modes of operation of fluidized bed catalytic cracking are considered with particular attention to the operation of the regeneration zone. Modern operations of catalytic fluidized bed cracking have achieved a considerable reduction in coke yield through the widespread use of crystalline aluminosilicate cracking catalysts and through the use of short hydrocarbon-catalyst contact times, for example through cracked tube cracking. While this usually resulted in higher yields of more valuable gaseous and liquid products, it also reduced the amount of solid combustible substance available for combustion in the regeneration zone to meet the heat balance requirements of the process. More recent prior art processes have recognized, for example, that by burning CO generated by the oxidation of coke within the regeneration zone and extracting at least a portion of the exothermic heat of reaction, a sufficient amount of heat for the heat balance requirements is brought about by a wide range of operating conditions and feedstocks become available. Such CO combustion has, for example, also made possible further reductions in coke yields and increases in yields of gaseous and liquid products, as well as a reduction or omission of feed preheating, and at the same time without the need to arrange an external CO boiler for air pollution problems due to CO release into the atmosphere eliminated. Typical modern regeneration zones have a single cylindrical vessel, which has a dilute phase in the upper section of the vessel in which cyclone separators are located and a dense phase in the lower section of the

Contains vessel. Spent catalyst usually enters the side or bottom of the vessel and fresh regeneration gas is added to the bottom of the vessel and distributed through the pipe grid or an array of perforated plates within the dense phase. Coke is oxidized to produce regenerated catalyst and CO and CO 2 -containing exhaust gas, and CO can be further oxidized in the presence of a sufficient amount of catalyst to obtain at least part of the heat of combustion. Exhaust gas containing entrained catalyst usually flows upward out of the dense phase into the dilute phase, where cyclone separators separate entrained catalyst and return to the dense phase and carry the separated exhaust gas out of the regeneration zone. Limiting or limiting considerations for operating the regeneration zone typically include the performance of the air blower, limits on the load capacity of the cyclone separator (s), restrictions on the emission of CO and entrained particles by the exhaust gas, and restrictions on the container temperatures. During operation of the regeneration zone, operating personnel usually have to primarily observe and closely monitor the extent of catalyst regeneration, the regeneration zone temperatures and the concentration of CO and entrained particles in the exhaust gas. It is generally typical refinery practice to periodically take samples of the regenerated catalyst and analyze them for known carbon content for their residual carbon content, as a measure of the extent of catalyst regeneration and an indication of the cracking activity of the regenerated catalyst. Regeneration zone temperatures are routinely measured and recorded, typically using thermocouples, to track changes in operations and to ensure that the metallurgical restrictions on the regeneration vessel are not exceeded. Furthermore, it is usually typical practice to take samples of the exhaust gas periodically or continuously and to analyze them for their concentrations of CO, 02, C02 and particulate constituents. The gas analyzes can be carried out by any known method, e.g. Orsat analysis, gas chromatographic methods and mass spectrometric methods. Particulate matter can be determined by opacity measurements or other known analytical methods. Gas analysis results can be used to calculate, through carbon-nitrogen-oxygen balance, such data as coke composition, coke burn rate, need for oxygen-containing regeneration gas, heat of combustion of the coke, and amount of CO that are in an external CO boiler or in the regeneration zone of the fluidized catalytic cracking process or can be burned in both if necessary. Before the exhaust gas can be blown off directly into the atmosphere, the operating personnel must also know the concentrations of CO and particulate matter in the exhaust gas in order to determine whether the exhaust gas complies with the local air pollution restrictions with regard to CO emissions. The concentration of 02 in the exhaust gas is normally important to ensure that the amount of oxygen-containing regeneration gas supplied to the regeneration zone is sufficient to maintain the desired extent of CO combustion, be it a partially completed or essentially complete CO combustion, but not on the other hand is supplied in such a large excess that there is an unnecessary load on the blower capacity for the oxygen-containing regeneration gas.

A feature of the method of the invention in all 6

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In one embodiment, a CO oxidation promoter is introduced into the regeneration zone independently of the cracking catalyst. Useful carbon monoxide oxidation promoters include, for example, metals from groups Ib, IIb, Via, Vlla and VIII of the Periodic Table of the Elements and compounds thereof. Chromium, nickel, iron, molybdenum, cobalt, copper, zinc, manganese and vanadium and compounds thereof may be mentioned as representative examples. Preferred CO oxidation promoters are the noble metals and compounds thereof, since it has been found that only very small amounts of these promoters are required to achieve the desired results. The term “precious metals” is understood to mean the metals gold, silver, platinum, palladium, iridium, rhodium, ruthenium and osmium in the usual way. The promoter can be added to the regeneration zone in the form of a solid, e.g. B. as powder, chips, pellets or agglomerates, but the promoter is preferably introduced for reasons of simplicity of handling and control in a liquid. The liquid containing the promoter can be added continuously or intermittently by means of known media flow and control devices. For example, the liquid containing the promoter can be squeezed out of a cylinder or a pressure bottle, which is connected by means of pipe connections to an auxiliary fuel oil nozzle or to a probe guided through a pressure sensor, the inflow being controlled by a valve located in the connecting line. The liquid can also be pumped from a container into the nozzle or probe in a quantity / time controlled by a small displacement pump. The CO conversion promoter can be distributed in the liquid in the form of a colloidal dispersion or suspension, or it can be soluble in the liquid. Particularly preferred oxidation promoters are noble metals or compounds thereof, which are soluble or dispersible in water or a liquid hydrocarbon. Suitable water-soluble metal compounds include the metal halides, preferably chlorides, nitrates, amine halides, oxides, sulfates, phosphates and other water-soluble inorganic salts. Examples of suitable water-soluble compounds are chloroplatinic acid, palladium acid, palladium chloride, ruthenium tetrachloride, rhodium trichloride, rhodium nitrate and osmium trichloride. Alternatively, a liquid hydrocarbon containing an oil-soluble or oil-dispersible CO oxidation promoter can be fed to the regeneration zone. Suitable liquid hydrocarbons include the hydrocarbons normally liquid at atmospheric temperatures and pressures, e.g. Heavy petrol and light circulating oil. Oil-soluble or oil-dispersible compounds include, in particular, metal diketonates, carbonyls, metallocenes, olefin complexes, acetylene complexes, alkyl or arylphosphine complexes and carboxylates. Platinum acetylacetonate, palladium acetate, palladium naphthenate, triiodiridium (III) tricarbonyl and (jt, cyclopentadienyl) - (ethylene) rhodium (I) may be mentioned as specific examples of such compounds. Of the noble metals and their compounds, platinum and palladium and compounds thereof are preferred, especially water-soluble compounds, since they are usually more accessible than compounds which are soluble or oil-dispersible in oil. Chloroplatinic acid and palladium acid are particularly preferred water-soluble platinum or palladium compounds.

In order to ensure a broader usability in technical applications, solutions of a CO oxidation promoter with a freezing point of 0 ° C are often used

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or below preferred, so that they are still liquid even at the colder temperatures that can occur at the location of a system. Solutions with freezing points of around -34 ° C or below are particularly cheap, so that they are still liquid even at the coldest temperatures that can occur at the location of a system. Solvents that give solutions with chloroplatinic acid or chloropalladic acid that have freezing points of 0 ° C (32 ° F) or below are, for example, alcohols from the group of saturated aliphatic alcohols with 2 to about 8 carbon atoms per molecule and freezing points of 0 ° C or underneath. Examples of such alcohols, together with their freezing points, are: methanol (-98.7 ° C), ethanol (-112 ° C), 1-propanol (-127 ° C), 2-propanol (-85.8 ° C), 1-butanol (-89.2 ° C), 2-butanol (-89 ° C), 2,3-dimethyl-2-butanol (-14 ° C), 2-methyl-2-butanol ( -14 ° C), 2-methyl-2-butanol (-11.9 ° C),

1-pentanol (-78.5 ° C), 1-hexanol (-51.6 ° C), 2-ethyl

1-hexanol (-70 ° C), 1-heptanol (-34.6 ° C), 4-heptanol (-41.5 ° C) and 1-octanol (-16.4 ° C).

As already mentioned, solutions of a CO oxidation promoter which have freezing points of approximately -34 ° C (-30 ° F) or even below are particularly suitable, so that they are still liquid even at the coldest temperatures that may occur at the location of a system . Accordingly, particularly preferred solvents are the solvents which, with chloroplatinic acid or chloropalladic acid, give solutions with the desired freezing points of -34 ° C. or below. Suitable solvents are also alcohols from the group of saturated aliphatic alcohols with 2 to about 8 carbon atoms per molecule and freezing points of -34 ° C. or below. Examples of this are listed in the above list, with the exception of 2,3-dimethyl-2-butanol, 2-methyl-2-butanol and 1-octanol, since these three alcohols have no freezing points of -34 ° C. or below.

In addition to a freezing point of -34 ° C or below, the solutions of the preferred CO oxidation promoters chloroplatinic acid and chloropalladic acid should generally also be chemically stable, so that no chemical change - indicated by the appearance of another liquid phase or a solid phase - during eligible storage periods. In order to be on the safe side with regard to the possibly unfavorable storage conditions, such solutions should, for example, be chemically stable for a period of 30 days at a temperature of 63 ° C (145 ° F). For example, some of the aforementioned saturated aliphatic alcohols that give solutions that meet the preferred freezing point of -34 ° C did not give solutions that were chemically stable at 63 ° C for 30 days. Methanol, 2-propanol,

For example, 2-butanol and 2-methyl-2-propanol did not give solutions that were chemically stable at 63 ° C for 30 days. Furthermore, some common freezing point depressants for water, such as ethylene or propylene glycol, meet the desired freezing point requirement, but usually do not meet the desired chemical stability requirements. Solvents that gave solutions that did not meet either the -34 ° C freezing point requirement or the chemical stability requirement did not show any noticeable chemical change after 30 days at 63 ° C were generally alcohols from the group of saturated aliphatic primary alcohols with 2 to about 8 Carbon atoms per molecule and freezing points of -34ÙC or below. These solvents are therefore the preferred solvents for the preparation of the solutions

1-Butanol and 2-ethyl-l-hexanol are particularly preferred

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the. In general, with the exception of methanol, it was found that the chemical resistance of the solutions was best when the solvent was a saturated aliphatic primary alcohol and worse when the solvent was formed from a saturated aliphatic secondary or tertiary alcohol. These saturated aliphatic primary alcohols having 2 to about B carbon atoms per molecule and freezing points of -34 ° C. or below are preferably used in the pure, undiluted state with chloroplatinic or chloropalladic acid. Preferred concentrations of chloroplatinic or chloropalladic acid in the solution are concentrations corresponding to about 0.01 to about 10 percent by weight of Pt or Pd, with concentrations of about 0.01 to 5 percent by weight of Pt or Pd being particularly preferred.

In order to best ensure optimal use of the required very small amounts of the promoter, the addition of the promoter is limited to the regeneration zone in the method of the invention. By feeding the promoter directly into the regeneration zone, where the CO oxidation to be catalyzed takes place, there is usually a practically immediate response, so that a controlled amount of exothermic reaction heat is made available for the operation of the regeneration zone and the concentration of carbon monoxide in the exhaust gas is reduced becomes. The CO conversion promoter can be introduced into the dense phase or into the dilute phase of the regeneration zone. Although the promoter can be introduced at multiple delivery sites, it has been found that satisfactory results can be obtained using only a single delivery site. The typical regeneration zone vessels have a number of pressure sensors and auxiliary fuel oil nozzles, one or more of which can serve as supply points; accordingly, only a very slight modification of the vessel itself is required before the method of the invention can be used.

In one embodiment, the invention provides, for example, a procedure for regenerating coke-contaminated catalyst with carefully controlled combustion of carbon monoxide. In this embodiment of the process, the catalyst contaminated with coke is usually introduced into the regeneration zone and the CO oxidation promoter is introduced into the regeneration zone in an amount which is tailored to the desired promotion of the combustion of CO to CO 2, independently of the coke contaminated catalyst. The amount of promoter added generally corresponds to about 0.1 to about 25 parts by weight per million of the circulating catalyst inventory based on elemental metal, and is preferably in the range of about 0.1 to about 15 parts by weight per million of the circulating catalyst inventory. Regeneration gas containing oxygen is then typically introduced into the regeneration zone in an amount sufficient to provide excess oxygen to achieve the desired level of CO combustion. In particular, this amount of oxygen-containing regeneration gas corresponds to approximately 10 to approximately 17 kg of air per kg of coke entering the regeneration zone per unit of time, depending on whether the CO combustion is to be partially completed or essentially complete. It has been found that it is important to first introduce the promoter into the regeneration zone and then the regeneration gas containing oxygen so that a smooth, controlled catalytic conversion of CO can be initiated from the beginning and the possibility of post-combustion is suppressed as much as possible. If this amount of oxygen-containing regeneration gas is first introduced into the regeneration zone and the promoter is then added, there is usually a risk that afterburning will be initiated instead of the desired controlled conversion of CO in the presence of the promoter and regenerated catalyst. A first part of the oxygen-containing regeneration process is then reacted with the coke-contaminated catalyst in the regeneration zone under oxidation conditions which are chosen to remove coke from the catalyst and to produce an exhaust gas containing CO and which are sufficient to cause combustion of CO to CO 2 in the presence of the oxidation promoter . The oxidation conditions, in addition to the presence of the regeneration gas containing oxygen, preferably include temperatures within the range of about 590 to about 790 ° C and pressure within the range of about atmospheric to about 4.5 atm (50 psig). Under such conditions, coke oxidation occurs essentially spontaneously.

At substantially the same time, the exhaust gas and a second portion of the oxygen-containing regeneration gas are brought into contact with the CO oxidation promoter under the previously specified oxidation conditions, whereby a controlled amount of exothermic reaction heat is made available for the operation of the regeneration zone and the amount of CO in the exhaust gas is reduced.

The amount of the oxidation promoter introduced into the regeneration zone can be selected in accordance with the achievement of certain desired results, e.g. a desired concentration of CO in the exhaust gas or a desired degree of catalyst regeneration or a desired temperature of the regenerated catalyst or a desired regeneration zone temperature. When adding the required amount of the CO oxidation promoter to achieve such a result, the promoter is usually gradually added in small increments and the dependent variable in question - be it the CO concentration or residual carbon content on the regenerated catalyst or a temperature - is measured and compared to the desired result to determine if an additional portion of the CO oxidation promoter is needed. If, after introducing a small proportion of the promoter into the regeneration zone, the measured concentration of CO in the exhaust gas or the concentration of residual carbon on the regenerated catalyst or the temperature of the regenerated catalyst or the regeneration zone temperature in question is not yet within the respectively predetermined range, a second proportion becomes of the promoter, ie a further increment of the promoter, and if necessary, further increments are added until the measured variable falls within the predetermined range. The addition of the promoter in several small increments, each over a relatively short period of time, for example from a few minutes to a few hours, allows the operating personnel to control and monitor the operation of the regeneration zone more closely in order to achieve the desired result. When the promoter is added in several increments, the total amount of the promoter is normally within the ranges given above. If the variable to be controlled is a dilute temperature, e.g. an exhaust gas temperature, the CO oxidation promoter can be introduced together with a diluent gas to enable the temperature to be controlled below a predetermined value. Oxygen-containing regeneration gas is normally used as the dilution gas. As soon as the

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measured variable is within or below the predetermined range for that variable, the promoter is normally added continuously or intermittently to the extent necessary to keep the measured variable within the predetermined range. The amounts of promoter required to keep a variable within a predetermined range can vary somewhat from plant to plant and are best determined by observation and experience in the operation of the plant in question, however, the amount of promoter has been shown to be that is required on a daily average basis to maintain a variable within a predetermined range, equivalent to about 0.005 to about 10 parts by weight per million of the circulating catalyst inventory based on elemental metal.

Further embodiments of the process are, for example, special independent control methods for use after the initial start-up of the catalytic fluidized bed cracking process and after a usable stationary mode of operation of the process has been achieved. Specifically, in one embodiment, the invention provides a method for catalytically cracking a hydrocarbon feed stream in which coke-contaminated catalyst and oxygen-containing regeneration gas are passed into a regeneration zone maintained under oxidation conditions and coke is oxidized to produce regenerated catalyst and a gas containing CO 2 and CO , for example an operation for controlling the CO concentration in the exhaust gas within a predetermined CO concentration range. In another embodiment, in such a method, the invention generally provides an operation for controlling a regeneration zone temperature within a predetermined range. In yet another embodiment, in such a method, the invention usually provides an operation for controlling the concentration of residual carbon on the regenerated catalyst within a predetermined range. Such control methods can be used independently by the operating personnel. For example, in one case, management may be primarily interested in keeping the CO concentration in the exhaust gas within a predetermined range, and if the temperatures to be expected do not pose any problems with metallurgical considerations of the regeneration zone, they will be the regeneration zone temperatures and the like Allow for the extent of regeneration that occurs when controlling the CO concentration. In another case, management may be primarily concerned with regeneration zone temperatures, for example, with regard to metallurgical restrictions. According to one embodiment of the invention, it can then maintain a regeneration zone temperature within a predetermined range and it will accept the CO concentration of the exhaust gas and the degree of regeneration that result from this control method. In each of these control methods, the CO oxidation promoter is generally first introduced into the regeneration zone and then oxygen-containing regeneration gas is fed to the regeneration zone in an amount which is stoichiometrically sufficient to convert at least part of the carbon monoxide to carbon dioxide. As already mentioned, the order of supply is generally important in order to avoid the risk of post-combustion. At least a portion of the carbon monoxide is then preferably converted under conversion conditions including the presence of the CO oxidation promoter and regenerated catalyst to produce exhaust gas containing CO 2 and CO. The conversion conditions preferably include a temperature within the range of about 590 to about 790 ° C and a pressure within the range of about atmospheric to about 4.5 atm (50 psig). Depending on the control method used, the exhaust gas is then usually analyzed to determine the actual CO concentration and the latter is compared with the CO concentration range to be observed, or a regeneration zone temperature is measured and compared with the specified regeneration zone temperature range, or regenerated catalyst is used to determine the analyzed actual residual carbon concentration and compared the latter with the residual carbon concentration range to be observed. Thereafter the promoter is normally fed to the regeneration zone in such amounts that either the CO concentration or a regeneration zone temperature or the residual carbon concentration are kept within their predetermined ranges. The amount of promoter initially fed to the regeneration zone is preferably added in small increments, as previously explained, until the desired result is achieved. The sum of these increments corresponds, for example, to about 0.1 to about 25 parts by weight per million of the circulating catalyst inventory, based on elemental metal, and is preferably in the range from about 0.1 to about 15 parts by weight per million of the circulating catalyst inventory. The amount of promoter required on average daily to maintain a measured variable within a given range normally corresponds to about 0.005 to about 10 parts by weight per million of the circulating catalyst inventory, calculated as elemental metal.

The type of cracking catalyst used in fluidized bed catalytic cracking processes using the process of the invention is generally not of critical importance, rather any type of conventional cracking catalyst can be used or provided for use in the fluidized bed catalytic cracking process, both the amorphous and crystalline Aluminosilicate catalysts and mixtures of the two types. Of the two general types of cracking catalysts, the catalysts comprising crystalline aluminosilicates are preferred because of the reduced yields of coke and the increased yields of gaseous and liquid products that they produce compared to amorphous catalysts. Since carbon monoxide as fuel is oxidized in addition to the coke within the regeneration zone when using the method of the invention and at least part of the heat of the CO combustion is obtained within the regeneration zone,

the cracking section of the fluidized catalytic cracking process can now be as selective for more valuable products as the operating conditions of the hydrocarbon conversion zone and the cracking catalyst allow. The operating conditions of the hydrocarbon conversion zone are accordingly selected according to maximum yields of gaseous and liquid products and normally include a temperature within the range of about 420 to 600 ° C, a pressure within the range of about atmospheric to about 4.5 atm (50 psig ), a catalyst / oil ratio of from about 3 to about 20 and a hydrocarbon residence time in contact with the catalyst from about 1 to about 30 and preferably from about 1 to about 10 seconds. The feedstock used in fluid catalytic cracking processes using the process of the invention

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Lines need not be different from the feedstocks used in operations without using the method of the invention, and can include any conventional hydrocarbon feedstocks, e.g. B. heavy gasoline, gas oils, light and heavy distillates, residual oils and the like.

The method of the invention can be further illustrated below with the aid of examples and comparative experiments, but it is not restricted to the specified special promoters, concentrations of promoters, operating conditions or methods of introduction into the regeneration zone.

example 1

This example describes investigations carried out in a semi-industrial test facility on the processes in the regeneration zone of a catalytic fluidized bed cracking plant, the investigations being carried out to determine the effectiveness of adding a liquid which contains low concentrations of certain promoters to the regeneration zone of the catalytic fluidized bed cracking plant in order to reduce the concentration of CO in the exhaust gas. The investigations were carried out using a vertical tubular vessel, the upper end of which was provided with a porous stainless steel filter, in order to thereby hold the catalyst sample introduced into the vessel during the sequence of operational measures, and the lower end of which was an inlet device for the fluidizing medium, nitrogen or air, and an introducer for the liquid containing the promoter. Means were also provided to heat the vessel to a constant temperature, and a chromatographic device was used to sample and analyze the exhaust gas from the vessel for CO, C02 and 02.5, so that the instantaneous composition of the gas was used to determine the reduction in the CO concentration could be determined.

Each run was carried out on a 500 gram sample of spent zeolite-containing cracking catalyst containing about 0.9 percent by weight coke. The coke had been deposited on the catalyst by enforcing gas oil feed through the cleanly regenerated catalyst in a semi-experimental scale hydrocarbon reaction zone operated under standard operating conditions with a predetermined sequence of work.

In experiment 1, no liquid containing a promoter was introduced into the vessel during the work sequence; the test was carried out to obtain a basis of comparison for further tests in which the procedure according to the invention was used. A 500 g sample of the spent catalyst was placed in the vessel and fluidized with nitrogen; the latter entered the bottom of the vessel. At the same time, the device was heated to a temperature of 593 ° C. At a fixed point in time, the nitrogen was replaced by air, which initiated the oxidation of the coke. The exhaust gas from the vessel had the CO concentrations given in Table I below, determined by the chromatographic device at various times after the introduction of air:

Table I

Regeneration zone of the test facility, test 1 No CO oxidation promoter

CO concentrations in the exhaust gas

Time CO in dry C02 / C0-

Minutes of exhaust gas,% ratio

1 2.4 3.09

2 3.5 3.00

3 5.0 2.86

4 6.0 2.58

5 5.7 2.96

As can be seen from the values, the C02 / C0 ratio remained in the fairly narrow range of about 2.5 to about 3.0 during the experiment.

Experiment 2 was carried out in the same manner as Experiment 1, except that 15 seconds after switching the fluidizing nitrogen to the supply of air and while an increase in the CO concentration was observed, 30 ml of diluted chloroplatinic acid solution (H2PtCl6) were injected into the vessel. The solution was prepared by diluting chloroplatinic acid containing about 28.6 weight percent Pt with distilled water to form diluted chloroplatinic acid containing 0.1 mg Pt / ml. This amount of chloroplatinic acid corresponds to approximately 6.0 parts by weight per million of the catalyst sample, calculated as metallic platinum. The instantaneous values of the chromatography device indicated that the CO concentration was now decreasing. In the course of the experiment, the exhaust gas had the following compositions:

Tables

Regeneration zone of the test facility, test 2

Diluted chloroplatinic acid, 0.1 mg Pt / ml CO concentrations in the exhaust gas

Time CO in dry C02 / C0-

Minutes of exhaust gas,% ratio

1 1.7 9.3

60 2 <0.1> 100

3 <0.1> 100

The carbon monoxide concentrations are much lower and the C02 / C0 ratios are much higher than the corresponding values in test 1 for the same time periods. To see how quickly platinum works to reduce CO levels

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giert, the regenerated catalyst from experiment 2 was used for further circuits in an experimental hydrocarbon reaction zone and then in the regeneration zone without the addition of a promoter. After the first three further cycles through the hydrocarbon reaction zone and the regeneration zone, substantially no CO formation was observed in the coke combustion, but a small amount of CO was present in the exhaust gas at the start of the fourth cycle, but this amount was considerably less than the amount at Experiment 1, in which no promoter was used.

The same procedure was used with a new 500 g catalyst sample for Experiment 3, with which

Exception that a more dilute solution was used and the liquid containing the promoter was fed into the vessel immediately before the fluidizing nitrogen was switched to air. In this experiment, 25 ml of the more dilute chloroplatinic acid, equivalent to about 0.5 part by weight per million of the catalyst, based on metallic platinum, was introduced into the vessel. The solution was prepared by diluting a portion of the solution used for Experiment 2, which contained 0.1 mg Pt / ml, with distilled water to form a dilute chloroplatinic acid solution containing 0.01 mg Pt / ml . The CO concentrations in the exhaust gas were as follows:

Table III

Regeneration zone of the test facility, test 3

Diluted chloroplatinic acid, 0.01 mg Pt / ml CO concentrations in the exhaust gas

Time, CO in dry C02 / C0-

Minutes of exhaust gas,% ratio

1 0.6 20.8

2 <0.1> 100

3 <0.1> 100

Although the reduced amount of promoter used in this experiment appeared to give results comparable to the results obtained in experiment 2 with a higher promoter concentration, the regenerated catalyst apparently lost much of its promoter activity quite quickly, since in subsequent cycles the Presence of some CO was detected during the regeneration stage. After three cycles, the catalyst appeared to generate about two thirds as much CO as was generated in Experiment 1 without the addition of a promoter.

In Experiment 4, 25 ml of a solution of chloropalladic acid in water containing 0.1 mg Pd / ml, corresponding to about 5 parts by weight per million of the catalyst sample, calculated as Pd metal, was placed in the vessel 15 seconds after the switchover from that fluidizing nitrogen is injected onto air, thereby initiating combustion. Within two minutes, the CO concentration in the exhaust gas dropped to less than 0.2 percent by volume.

Example 2

This example describes the behavior of the regeneration zone of a large scale catalytic fluidized bed cracking process shortly after the introduction of small amounts of a liquid containing a CO oxidation promoter by the process of the invention, with no other operational changes being made.

The catalytic fluidized bed cracking plant used for the investigation processed about 124m3 / hour 60 (18,670 barrels / day) of a mixture of vacuum and kerkergas oils and had a circulating catalyst inventory of about 54,500 kg (60 tons) of zeolite-containing catalyst. The plant was brought into a steady operating condition under typical operating conditions, 65 without efforts to partially or substantially completely reduce the CO concentration in the exhaust gas, and without the presence of any

CO conversion promoter in the regeneration zone.

A number of relevant operating conditions of the process, prior to supplying a promoter to the regeneration zone, are summarized in Table IV below.

Then 2 liters of a solution of chloroplatinic acid in water were pressed from a cylinder into the regeneration zone within a period of 2-3 minutes, specifically through a nozzle located in the regeneration zone for density determination. The diluted chloroplatinic acid solution was prepared by diluting 61.4 g of a concentrated chloroplatinic acid solution containing 28.637 wt% Pt to 2 liters by volume using distilled water. The introduction of this amount of solution into the regeneration zone means a promoter feed corresponding to approximately 0.32 parts by weight per million circulating catalyst inventory, based on metallic platinum. The regeneration zone responded almost immediately to this encore; the CO concentration in the exhaust gas decreased to about half the CO concentration before the solution was introduced and the temperature of the dense phase of the regeneration zone rose by approximately 25 ° C. above the temperature before the solution was introduced. No other operational changes to the process were made. A summary of the operating conditions after this first addition of solution can also be found in Table IV.

Several hours later, a smaller amount of solution containing the promoter corresponding to about 0.13 parts by weight per million of the circulating catalyst inventory based on metallic Pt was introduced into the regeneration zone in the same manner as the first addition. Except for the addition of the promoter, no other operational changes to the process were made. A summary of the operating conditions shortly after this second addition is also found in Table IV below.

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Table IV

Response of the regeneration zone of a large-scale catalytic fluidized bed cracking plant to the addition of a promoter

Selected operating conditions

Start without After adding After adding

Promoter addition 0.32 weight 0.13 weight

share-per-million share-per-million

Temperatures, ° C regeneration zone, dense phase regeneration zone, dilute phase regeneration zone, exhaust gas hydrocarbon reaction zone combined feed exhaust gas composition, vol .-%

CO

co2

02

C02 / C0 ratio of residual carbon on the regenerated catalyst,% by weight

Fresh feed supply, m3 / h return material admixture, m3 / h air supply, m3 / second

655 681 713

661 687 717

667 678 703

510 511 511

328 328 329

10.5 5.9 1.4

10.8 12.8 17.1

0.0 0.0 0.0

1.03 2.17 12.2

0.30 0.16 0.06

124 124 124

11 11 11

15 15 15

As can be seen from the values in Table IV, the CO concentration in the exhaust gas rose from 10.5 volume percent before the addition of promoter solution to 5.9 volume percent after the addition of the first amount of solution (0.32 parts by weight per million Pt). and 1.4 volume percent after the addition of the second amount of solution (0.13 parts by weight per million Pt). The residual carbon on the regenerated catalyst decreased from 0.30 weight percent to 0.16 weight percent after the addition of the first solution and then to 0.06 weight percent after the addition of the second solution, while the temperature in the dense phase of the regeneration zone rose from 655 681 ° C and then to 713 ° C after the addition of the specified amounts of solution. Other regeneration zone temperatures also increased, but not as much as the dense phase temperature.

Example 3

This example also illustrates the application of the method of the invention in the same large-scale plant used in Example 2 and further demonstrates the advantages thereby achieved. Before the addition of the two promoter solutions was carried out as in Example 2, a fairly complete investigation, hereinafter referred to as Test 1, was carried out for the purpose of comparison with subsequent investigations after the addition of promoter solution to the regeneration zone. Over the course of the day after the addition of the first two promoter solutions, two further promoter solutions containing the promoter corresponding to approximately 0.13 and 0.32 parts by weight-per million, based on the circulating catalyst inventory and calculated as metallic Pt, were found in the im Example 2 was added. This time, however, the air supply to the regeneration zone was increased to ensure that enough oxygen was present for a substantially complete conversion of CO to CO 2. Test 2 then took place during stationary operation, when the CO was essentially completely burned within the regeneration zone in the presence of the mixture of CO conversion promoter and regenerated catalyst

In the regeneration zone, the diluted chloroplatinic acid of the CO oxidation promoter was introduced in an amount corresponding to about 0.9 part by weight per million, based on the circulating catalyst inventory and calculated as metallic platinum. Test 2 was carried out with practically the same feed feed and practically the same pressures in the regeneration zone and in the 35 hydrocarbon reaction zone as Test 1. No measures were taken to bring about the same conversion rate as in Test 1 before the start of Test 2, nor have any efforts been directed to optimizing the flow rate of the air required to achieve substantially complete CO conversion. Relevant results of Test 1 and Test 2 are summarized in Table V.

A comparison of the test results shows a reduction in the CO concentration of the exhaust gas from 9.6 45 percent by volume to <0.1 percent by volume, a reduction in the residual carbon on the regenerated catalyst from 0.28 percent by weight to 0.11 percent by weight, which indicates a better catalyst regeneration , and a general increase in regeneration zone temperatures by about 38 to 44 ° C using the method of the invention. Although the temperatures of the hydrocarbon reaction zone are not quite the same, recovering some of the heat of CO combustion within the regeneration zone in Test 2 has enabled the temperature of the combined feed to be significantly reduced 55. Although the conversion in Test 2 was about 1.7% lower than in Test 1, a comparison of the yields shows that Test 2 achieved a more selective cracking to more valuable products than Test 1. 60 The coke yield in Test 2 was 4.3 percent by weight, compared to 5.4 percent by weight in Test 1, and in spite of the 1.7% lower conversion in Test 2 than in Test 1, the gasoline yield in Test 2 was 57.4 Volume percent almost the same as the 65 Test 1 with 57.6 volume percent. If the same conversion is brought about, a significantly higher gasoline yield is thus achieved using the method of the invention.

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Table V

Comparative studies on catalytic fluidized bed cracking before and after adding a CO conversion promoter

Test 1 2

Before after

Processing conditions hydrocarbon reaction zone

Temperature, ° C 510 505

Combined feed, temp., ° C 328 313 regeneration zone

Dense phase temperature, ° C 656 696

Diluted phase temperature, ° C 661 699

Exhaust gas temperature, ° C 667 710

Carbon on the regenerated catalyst, wt .-% 0.28 0.11 exhaust gas analysis, vol.%

C02 10.5 14.1

CO 9.6 <0.1

02 0.0 3.5

C02 / C0 ratio 1.09> 140 product yields

C2 and lighter components, wt% 2.7 2.4

Propylene, vol.% 8.5 8.2

Propane, vol.% 2.5 2.5

Isobutane, vol.% 6.1 5.5

n-butane, vol.% 1.7 1.6

Butenes, vol.% 9.1 9.2

C5 + gasoline, vol.% 57.6 57.4

Light cycle oil, vol.% 20.1 21.2

Sludge oil, vol.% 3.1 3.8

Coke, wt% 5.4 4.3

Conversion, vol.% 79.7 78.0

Longer operations with the same large-scale technical plant showed that an essentially complete conversion of CO can be maintained if one brings daily amounts of promoter solution into the regeneration zone, the promoter corresponding to about 0.12 parts by weight per million of the circulating catalyst inventory based on metallic platinum.

Platinum analyzes of catalyst samples from this large-scale plant showed that a significant proportion of the promoter remains on the cracking catalyst. For example, at a point in time at which a total amount of chloroplatinic acid solution with a total content of promoter corresponding to 75 g of platinum had been introduced into this industrial plant, a sample of the catalyst in equilibrium was withdrawn from the plant and analyzed for its paltin content. The value obtained from this sample was 1.0 part by weight per million platinum. If the entire 75 g of platinum that had been introduced into the plant were evenly distributed over the 54,500 kg (60 tons) of catalyst stock, this would result in a concentration of 1.4 parts by weight per million Pt on the equilibrium catalyst.

their tap water, dissolved to prepare two solutions, each containing 0.045 weight percent Pt. These two solutions were tested for solubility properties at -29 ° C and for their thermal stability at 22.43 and 63 ° C. The data in Table VI below show that the solutions remained flowable at -29 ° C but did not have the desired chemical stability at 63 ° C for 30 days; a black precipitate formed in about 11 days at 22 ° C and in only 0.7 days at 63 ° C. The black precipitate was separated by centrifugation, washed with water and analyzed for its platinum content. The elemental Pt content of the black precipitate was 94% and chemical electron spectroscopy analysis showed the presence of mainly metallic Pt (Pt °) with about 5% PtO. The platinum recovery from the precipitate, the flask and the clear solution gave a value of 100.3% of the amount originally used. These results show

that the black precipitate consists essentially of metallic platinum and apparently a reduction of the Pt + 4 present in the chloroplatinic acid to Pt ° and an oxidation of the ethylene glycol has taken place. Ethylene glycol oxidation products have not been identified.

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50

Example 4

This example illustrates the point of view of chemical instability of the promoter solution. In particular, it shows studies on the chemical instability of a solution of chloroplatinic acid in a mixture of water and a conventional freezing point depressant for water, namely ethylene glycol. Chloroplatinic acid with a content of 25.46 percent by weight Pt was in a mixture of equal parts by weight of ethylene glycol of technical quality and water, on the one hand distilled water and on the other hand Table VI stability of chloroplatinic acid in a mixture of ethylene glycol and water

Sample Type of day until precipitation occurs

Water -29 C 22 ° C 43 ° C 63 ° C

1 distilled soluble ~ 11 4 0.7

2 line soluble ~ 11 0.7 0.7

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14

This example shows studies of freezing point and chemical stability at temperatures of -36.22 and 63 C for ten solutions of chloroplatinic acid with a concentration corresponding to 0.045 weight percent Pt in various undiluted primary, secondary or tertiary alcohols of reagent quality or mixtures thereof. A temperature of -36 ° C was chosen to account for the coldest temperatures that could occur at the location of a plant; the temperature of 22 C corresponds to medium environmental conditions; the temperature of 63 ° C was chosen to record medium or possibly occurring storage conditions (inside and outside of rooms or containers). The time in days until black precipitation, most likely primarily metallic platinum, was observed for each temperature. The

Example 5

Results are shown in Table VII below.

The chemical stability of chloroplatinic acid is best for saturated aliphatic primary alcohols, with the exception of methyl alcohol, and poorer for saturated aliphatic secondary and tertiary alcohols. In addition to being unsuitable due to poor chemical stability, the solution of chloroplatinic acid in io 2-methyl-2-propanol was solid at -36 ° C. A classification of the chloroplatinic acid solutions in different solvents in the order of decreasing chemical stability at 63 ° C results in: 2-ethyl-l-hexanol (more than 60 days), 1-propanol (more than 58 days), 1-butanol (50 Days), ethanol and 15 1-hexanol (42-44 days), 2-methyl-2-propanol (13 days), 2-propanol and 2-butanol (1-2 days), methanol (0.25 days).

Table VII

Resistance of chloroplatinic acid5 in different solvents at different temperatures

Solution solvent days until precipitation

Art

Melting point, ° C1

Boiling point, ° Cl

Flash point 2, "C1

-36 ° C

22 ° C

63 ° C

1

Methanol

-97

65

12

n.b.4

14

0.25

2nd

Ethanol

-112

78

12

liquid

> 61

44

3rd

1-propanol

-127

98

16-29

liquid

> 61

> 58

4th

2-propanol

-85

83

12-16

n.b.

7

1

5

1-butanol

-89

117

373

liquid

> 63

50

6

2-butanol

-89

100

24th

n.b.

56

2nd

7

2-methyl-2-propanol

25th

83

11

Solid

22

13

8th

1-hexanol

-51

157

74

liquid

> 56

42

9

2-ethyl-1-hexanol

-70

184

85

> 60

> 60

> 60

10th

Ethanol +

1-butanol (1: 1)

-

-

-

n.b.

> 48

> 48

1 Literature values for the melting point, the boiling point and the flash point

2 Flash point with closed cup, Cleveland

3 determinations according to Penske-Martens with closed cup

4 n.a. = not determined

5 chloroplatinic acid concentration in each solution corresponding to 0.045 weight percent Pt

Example 6

This example describes investigations in the regeneration zone of a semi-technical test facility which were carried out to determine the effectiveness of a solution containing chloroplatinic acid in 1-butanol for reducing the concentration of CO in the exhaust gas. The investigations were carried out using the in the example

1 explained test device. As in Example 1, precautions were taken to heat the device to a constant temperature, and samples of the exhaust gas were continuously taken from the vessel by means of a chromatographic device and measured for CO, CO 2 and

02 analyzed. A chromatographic trace was recorded for CO, C02 and 02, so that instant analysis was available to identify the combustion of CO during the test. A specific C02 / C0 ratio, hereinafter referred to as the minimum C02 / C0 ratio, was determined from the chromatographic lines for each test by first determining the maximum CO concentration for the test (which is usually within 2 to 3 Minutes after the initiation of combustion occurred), the C02 concentration at the moment of the maximum CO concentration was determined and then the C02 / C0 ratio for the concentrations determined in this way

45 trations was calculated. This ratio is referred to as the C02 / C0 minimum ratio, since it has been observed in many such regeneration tests that if the current C02 / C0 ratios are plotted against the elapsed time, there is a curve for each test that goes through a minimum, and the C02 / C0 ratio at this minimum has a value as calculated according to the method explained above. It has shown,

that this minimum C02 / C0 ratio best characterizes the effectiveness and performance of any CO promoter-55 containing solution for the catalysis of CO combustion.

The tests were carried out on 500 g samples of an equilibrated zeolite fluidized bed cracking catalyst which had previously been brought into a "spent" state by a gas oil feed in a hydrocarbon reaction zone of semi-industrial scale that was operated under standard conditions with a given sequence of work passed through the equilibrium catalyst sample. 65 Each sample of the spent catalyst contained approximately 0.9 weight percent coke.

In test 1, no solution containing a promoter was added. This test was done as a basis

for a comparison with a subsequent test in which a solution containing a promoter was used. A 500 gram sample of the spent catalyst was placed in the vessel and fluidized with nitrogen that entered the bottom of the vessel while the device was heated to a temperature of 593 ° C. At a specified time, the nitrogen was replaced by air, which initiated the oxidation of coke. The exhaust gas from the vessel was analyzed with the chromatographic device for C02, CO and 02 and from the lines for 10 C02 and CO the minimum C02 / C0 ratio was calculated. To determine a measure of the reproducibility of the results obtained by this test method, the test was repeated a total of four times with separate samples of the used catalyst. The C02 / C0-15 minimum ratios ranged from 2.5 to 3.3 as shown in Table VIII below.

Test 2 was carried out in the same manner as Test 1, except that immediately before switching the fluidizing nitrogen to air, a 20 25 g sample of a solution of chloroplatinic acid in 1-butanol

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was injected into the regeneration zone. The concentration of chloroplatinic acid in the sample corresponded to 0.008 wt% Pt and the amount of platinum in the sample was 2 mg Pt, i.e. 4 parts by weight per million based on the 500 g catalyst sample. The C02 / C0 mini-ratio was 52.1. In order to obtain a measure of the speed at which the particle mixture of promoter and regenerated catalyst particles loses its effectiveness in reducing the CO concentration in the exhaust gas, the mixture was operated in further circuits. Specifically, to complete another cycle, the mixture in the semi-industrial scale hydrocarbon reaction zone was brought to the "spent" state in the manner described above, and then the regeneration zone test was repeated, but without adding any further amounts of promoter solution. At the end of the seventh cycle, the C02 / C0 minimum ratio for the particle mixture was 41.5, indicating that the mixture had largely retained its CO combustion activity. Results of tests 1 and 2 are shown in Table VIII.

Table VIII

Regeneration zone investigations in a semi-technical test facility with and without the use of a promoter solution

C02 / C0 minimum cycle ratios: 12 3 4

Testi; no application of promoter solution 3.3 ----- -

2.5 ----- -

3.1 ----- -

3.0 ----- -

Test 2; 25 g solution of chloroplatinic acid in 1-butanol with a content of 0.008 wt .-% Pt 52.1 _____ 41.5

Solutions of chloroplatinic acid in other preferred solutions of chloroplatinic acid in solvents used in this example show behavior similar to that of 40 1-butanol.

s

Claims (10)

628 825 2nd PATENT CLAIMS 1. A method for regenerating coke-contaminated catalysts with simultaneous carefully controlled combustion of carbon monoxide, characterized in that (a) introduces catalyst contaminated with coke into a regeneration zone, (b) introduces a carbon monoxide oxidation promoter into the regeneration zone, regardless of the coke-contaminated catalyst, in an amount selected to promote the combustion of carbon monoxide to carbon dioxide, (c) introduces oxygen-containing regeneration gas into the regeneration zone in an amount selected to burn coke from said coke-contaminated catalyst and present sufficient excess oxygen to achieve the desired level of carbon monoxide combustion, (d) a first portion of the oxygen-containing regeneration gas with the coke-contaminated catalyst in the regeneration zone under such chosen oxidation conditions for the removal of coke from the coke-contaminated catalyst and for the production of an exhaust gas which contains a major amount of carbon monoxide and a small amount Contains carbon dioxide, relative to the total amount of carbon oxides, and then (e) contacting the resulting exhaust gas and the remaining portion of the oxygen-containing regeneration gas with the carbon monoxide oxidation promoter in the regeneration zone under the carbon monoxide combustion conditions, thereby making a controlled amount of exothermic heat of reaction available for operation of the regeneration zone while maintaining the amount of carbon monoxide in the Exhaust gas lowers. 2. The method according to claim 1, characterized in that the carbon monoxide oxidation promoter in step (b) is introduced in the form of a solution in a solvent. 3. The method according to claim 2, characterized in that solvent comprising or consisting of an alcohol from the group of saturated aliphatic primary alcohols having 2 to 8 carbon atoms per molecule and freezing points of 0 ° C or below is used. 4. The method according to any one of claims 1-3, characterized in that the carbon monoxidation promoter in the regeneration zone in step (b) is introduced in such an amount that a sufficient amount of exothermic heat of reaction to the temperature of the regenerated catalyst increasing a predetermined amount is cleared. 5. The method according to any one of claims 1-4, characterized in that one uses a carbon monoxidation promoter from the group of noble metals and their compounds. 6. The method according to claim 5, characterized in that one uses a carbon monoxide oxidation promoter from the group of platinum, palladium and their compounds. 7. The method according to any one of claims 1-6, characterized in that the oxidation promoter of the regeneration zone in step (b) in an amount corresponding to 0.1 to 15 parts by weight per million of the circulating catalyst stock, based on elemental metal, is fed . 8. The method according to any one of claims 1-7, characterized in that the oxygen-containing regeneration gas is supplied in an amount corresponding to 10 to 17 kg of air per kg of coke entering the regeneration zone, per unit of time. 9. The method according to any one of claims 1-8, characterized in that one maintains in the regeneration zone oxidation conditions with a temperature of 590 to 790 ° C and a pressure of atmospheric pressure to 4.5 atm. 10. The method according to any one of claims 1-9, characterized in that the regeneration zone, the carbon monoxidation promoter in an average daily amount corresponding to 0.005 to 10 parts by weight per million of the circulating catalyst inventory, based on elemental metal, is supplied.