JPH0214103B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention The present invention relates to the art of catalyst regeneration. More particularly, the present invention relates to a method for burning off nitrogen-containing coke from a coke-containing granular catalyst while avoiding contamination of the catalyst by flue gases produced during coke combustion.

In catalytic cracking systems, the catalyst is used in a moving or fluidized bed.

Unlike hydrocracking processes, where molecular hydrogen is added during the cracking step, catalytic cracking processes operate without an external supply of molecular hydrogen.

In catalytic cracking, a stock of particulate catalyst is continuously circulated between a cracking reactor and a catalyst regenerator.

In the fluid catalytic cracking (FCC) system, the hydrocarbon feed is carried out in a hydrocarbon cracking zone or reactor with a granular catalyst at about 425°C to 600°C.
Contact is typically made at a temperature of 460°C to 560°C. The reaction of the hydrocarbons at elevated operating temperatures results in the deposition of carbonaceous coke on the catalyst particles. The fluid product resulting from the reaction is separated from the spent catalyst rendered inactive by coke and removed from the reactor.

The coked catalyst particles are typically stripped of volatiles by steam and enter a catalyst regeneration zone.
During catalyst regeneration, the spent catalyst is contacted with a predetermined amount of molecular oxygen.

The desired portion of coke is burned off from the catalyst, restoring the catalyst activity and at the same time the catalyst is
Heat to ~815°C, typically 590°C to 730°C.

The flue gas produced by combustion of coke in the catalyst regenerator may be treated for particulate removal or carbon monoxide conversion, after which the flue gas is discharged to the atmosphere in the normal manner. Ru.

Most FCC devices currently use zeolite-containing catalysts that have very high activity and selectivity. Since zeolite-type catalysts exhibit particularly high activity and selectivity when the concentration of coke on the catalyst after regeneration is relatively low, it is generally desirable to regenerate zeolite-containing catalysts to the lowest possible level of residual carbon. It is also usually desirable to burn off the carbon monoxide as completely as possible to conserve heat in the catalyst regenerator.

Heat conservation is particularly important when the concentration of coke on the spent catalyst is relatively low as a result of the high selectivity of the catalyst.

Among the methods proposed for combusting carbon monoxide in such a way as to reduce the amount of carbon on the regenerated catalyst and to provide heat during the process, active
One method uses combustion-promoting metals to combust carbon monoxide in a dense phase bed in a catalyst regenerator. The metal is used either as an integral component of the cracking catalyst particles or as a component of a separate particulate additive, in which the metal is associated with a support separate from the catalyst component.

Various methods have been proposed for using metals to promote carbon monoxide combustion in cracking systems.

No. 2,647,860 proposes adding 0.1 to 1% by weight of chromium oxide to the cracking catalyst to promote the combustion of carbon monoxide to carbon dioxide and prevent afterburning.

No. 3,808,121 proposes introducing relatively coarse particles containing metals into a cracking catalyst regenerator to promote carbon monoxide combustion.
A circulating particulate solids content containing relatively small catalyst particles is circulated between the cracking reactor and the catalyst regenerator, but the combustion promoting particles remain in the regenerator due to their particle shape. .

Pro-oxidant metals such as cobalt, copper, nickel, manganese, copper chromite impregnated with inorganic oxides such as alumina are disclosed.

Belgian Patent Publication No. 820181 proposes the use of catalyst particles containing platinum, palladium, iridium, rhodium, osmium, ruthenium or rhenium to accelerate the oxidation of carbon monoxide in a catalyst regenerator. Trace amounts to 100ppm
Amounts of metal between 1 and 2 are added during catalyst preparation or during the cracking process in the same way that compounds of combustion promoting metals are added to the hydrocarbon feed.

The publication states that the addition of promoter metals to the cracking system reduces product selectivity during the cracking process by significantly increasing coke and hydrogen production.

Catalyst particles containing combustion-promoting metals can be used alone or circulated in a physical mixture with catalyst particles that do not contain combustion-promoting metals. U.S. Pat.
Discloses use at concentrations of 0.01-50pm.

One problem that arises with some cracking operations that use combustion-promoting metals is that full carbon monoxide-burning regeneration results in undesirable nitrogen oxides (NO _x ) in the flue gas produced by combustion of the coke. An outbreak is something that happens.

The present invention provides complete coke removal and complete carbon monoxide combustion within the catalyst regeneration system, yet substantially reduces the concentration of nitrogen oxides present in the flue gas produced by coke combustion. The aim is to provide a catalyst regeneration system.

Representative of the catalyst regeneration patents published to date are: U.S. Pat. No. 3,909,392, which describes a device for promoting the combustion of carbon monoxide by thermal means. . Catalysts are used in heat sinks for increased heat generation. British Patent Publication No. 2001545 describes a two-stage method for catalyst regeneration, in which partial regeneration is carried out in the first stage and more complete regeneration is carried out in the second stage using another regeneration gas. There is.

US Pat. No. 3,767,566 describes a two-stage regeneration process in which partial regeneration is performed in an entrained catalyst bed, followed by more complete regeneration in a dense fluidized catalyst bed.

A slightly similar regeneration method is patented in the U.S. Patent No.
No. 3,902,990, which describes a method that uses several steps for regeneration using dilute and dense phase catalyst beds and multiple streams of regeneration gas.

U.S. Pat. No. 3,926,843 describes a multi-stage regeneration scheme that implements lean-phase, dense-phase coke combustion.

British Patent Publication No. 1499682 discloses the use of combustion promoting metals to promote carbon monoxide combustion.

Although each of the patents cited above can achieve essentially complete removal of coke from the catalyst,
There is no way to obtain a flue gas with low concentrations of both carbon monoxide and nitrogen oxide.

SUMMARY OF THE INVENTION The authors convert nitrogen-containing coke to coke-containing coke by lowering an inactivated catalyst with substantially no return mixing and passing oxygen-containing regeneration gas countercurrently upward through a regenerator. It has been discovered that it is possible to burn off the catalyst and obtain a flue gas that does not contain both carbon monoxide and NO _x produced during coke combustion. The nitrogen oxides produced in the lower complete combustion section of the regenerator react in a substantially oxygen-free atmosphere in the middle section of the regenerator to elemental nitrogen, which is then produced in the regeneration gas. The carbon monoxide is combusted in the upper section of the regenerator with additional free oxygen in the presence of a coke-free catalyst.

DESCRIPTION OF THE DRAWINGS The drawing is a schematic representation of one preferred embodiment of the invention.

To explain the drawings, there is a recycling container 1.

The spent catalyst containing coke is introduced through conduit 3 into the intermediate level of the vessel at a rate regulated by valve 5.

A regeneration gas stream containing free oxygen is introduced into the vessel through conduit 7 and distributor 9.

The spent catalyst that enters the vessel generally descends and flows countercurrently to the regeneration gas that ascends through the vessel. The catalyst is retained on the gas distribution grid 11 at the lower end of the vessel.

Substantially coke-free catalyst is removed from the regenerator through conduit 13 over grid 11 and into storage tank 15.
go inside.

A small coke-free catalyst portion in reservoir 15 is retained in a gas stream, such as steam, introduced through conduit 17.

The coke-free catalyst moves upward in the entrained gas through conduit 19 and enters the upper section of vessel 1. Most of the coke-free catalyst is returned by conduit 21 to its role as catalyst or other desired use.

Catalyst regeneration, which essentially takes place in a plug-type downward flow, is facilitated in vessel 1 and the overall back-mixing is carried out by perforated plates 23, 25, 27 and 29 contained within the regeneration vessel. suppressed.

The regeneration gas in the lower section of the vessel adjacent to grid 11 and plate 23 has a high concentration of free oxygen.

in this part of the vessel in a highly oxidizing atmosphere, preferably in the presence of a metallic combustion promoter;
Nitrogen oxides are produced in the regeneration gas due to the high temperatures generated by the combustion of coke and carbon monoxide. In the upper levels of vessel 1, in the intermediate section of the catalyst bed, generally near plate 25, the free oxygen in the regeneration gas has been substantially all consumed by combustion of coke and carbon monoxide.
The regeneration gas in the intermediate section is a substantially oxygen-free atmosphere, typically with fairly high concentrations of carbon monoxide and carbon dioxide.

The carbon concentration of the spent catalyst and partially regenerated catalyst that comes into contact with the regeneration gas in this intermediate section is quite high.

Nitrogen oxide in the regeneration gas reacts in an oxygen-free atmosphere to produce free nitrogen (molecular nitrogen).

Generally, free oxygen is added to the regeneration gas stream in the upper section of the vessel above plate 27, for example through conduit 31 and distributor 33. The carbon monoxide present in the regeneration gas is combusted with additional free oxygen in contact with a substantially coke-free catalyst in the upper section of the regeneration vessel.

Coke-free catalysts are advantageous because of the heat drop of the thermal energy generated by the combustion of additional free oxygen and carbon monoxide.

The resulting flue gas free of carbon monoxide and nitrogen oxide is passed through a cyclone separator 35.
and the entrained catalyst is separated from the flue gas and returned to the coke-free catalyst bed. The top of the coke-free catalyst bed is indicated by line 37.

The contaminant-free flue gas is discharged through conduit 39 at the top of the vessel.

For ease of explanation, various conventional elements of the above-described reproduction design have been omitted from the drawings and description.

The operation and operation of controls, valves and pumps, and other such elements will be apparent to those skilled in the art.

DETAILED DESCRIPTION OF THE INVENTION Oxidizing atmosphere as used herein
The term "oxidizing atmosphere" means an atmosphere containing at least 1.0 volume percent molecular oxygen and 0.1 volume percent carbon monoxide.

As used herein, the term "Substantially Coke-free Catalyst" refers to a catalyst containing less than 0.2% carbon by weight.

The catalysts most suitable for regeneration by the process of the invention are those in the form of particulate solids. Preferably,
The catalyst to be regenerated is in a form suitable for catalytic use in an entrained or fluidized bed.

With respect to catalytic conversion systems currently in commercial use, the present invention is particularly advantageous for the regeneration of FCC catalysts, but the present invention is not limited to the regeneration of FCC catalysts, and is not limited to the regeneration of FCC catalysts containing any coke. It can be used to burn off coke from granular catalysts.

Regeneration according to the invention includes any vertically extending vessel capable of containing regeneration gas and catalyst particles at the temperatures and pressures used for this operation;
Or it can be done in a chamber.

A variety of suitable containers will be apparent to those skilled in the art from the description herein. The vessel used is preferably capable of preventing gases and catalyst particles from bypassing each other, substantially inhibiting back-mixing of catalyst particles in fluidized bed operation, and ensuring that the catalyst stream does not flow within the vessel in fluidized bed operation. It is a container whose internal construction is such that it flows downwardly in essentially a plug-type flow.

Such interiors include perforated plates, buttfuls,
It may also be a fixed internal shape, such as a rod or the like, or a filling.

When the catalyst is regenerated in a moving bed operation rather than in a fluidized bed, internals are usually not effective since backmixing of the catalyst is not a problem.

The regeneration gas or gas mixture used must have an appropriate free oxygen (molecular oxygen) content.
Generally, the use of air is not essential, although air is quite suitable for supplying free oxygen.

For example, pure oxygen or oxygenated air can also be used if desired.

Common gases used in commercial FCC operations such as free nitrogen (molecular nitrogen), carbon dioxide, steam and the like are suitable as flowing and entraining gases.

Generally, the regeneration conditions used in the present process include a combination of temperature and pressure sufficient to cause coke combustion, carbon monoxide combustion, and nitrogen oxide reactions to occur in the manner described below. Temperatures between 540°C and 815°C are usually suitable. Temperatures between 590°C and 730°C are preferred. The flow of regeneration gas and entrained gas and catalyst particles is maintained at a rate that creates a fluidized bed of catalyst in the regeneration zone, although a moving bed of catalyst can be used if desired.

Fluidized bed operation is carried out in a conventional manner by maintaining the surface regeneration gas velocity appropriate to the size and density of the catalyst particles undergoing regeneration and by maintaining catalyst introduction and removal at appropriate levels. be able to.

Downward movement of the flowing catalyst within the vessel can be accomplished by simply removing the catalyst from the bottom of the bed.

Operating pressure is usually not particularly important.

1 to 20 atmospheres (absolute) is generally quite suitable.
A pressure of 1 to 5 atmospheres is preferred.

The use of carbon monoxide combustion promoting metals to promote the combustion of carbon monoxide in the regeneration gas is preferred in the practice of the present invention. Metals and metal compounds can be used, such as many transition metals, which have previously been proposed for use as carbon monoxide combustion promoters. Platinum, palladium, iridium, rhodium, ruthenium,
Metals and metal compounds selected from osmium, manganese, copper, and chromium.

The combustion promoting metal is used in a concentration sufficient to promote combustion of carbon monoxide to the desired degree. The use of platinum in various forms as a metal for promoting the combustion of carbon monoxide in commercial FCC operations is well known.

The combustion-promoting metal may be included as a total component of the catalyst particles, as a major fraction, or as a minor fraction, or as a separate component mixed with the catalyst stock in essentially physical admixture with the catalyst particles. , may be included as substantially catalytically inactive particles. A preferred metal used in the separate CO-flame promoter is platinum.

Oxidized sulfur present in the regeneration gas as a result of combustion of sulfur-containing coke can advantageously be removed from the gas by using a solid reactant, or acceptor, as a component of the particulate solids in the regeneration zone.
Oxidized sulfur in the regeneration gas reacts with reactants or receptors or is adsorbed to produce sulfur-containing solids in the regenerator.

By such a method, the content of sulfur oxides in the flue gas leaving the regenerator is significantly reduced. A preferred solid reactant for use in this method is alumina.

Alumina reacts with sulfur oxide to produce sulfur-containing solids.

The alumina used must have a surface area of at least 50 m ² /g. Alpha alumina is not suitable.

Alumina may be included as a component of the catalyst particles or as a separate particle present in the regenerator as a physical mixture with the catalyst particles. If separate alumina-containing particles are mixed with the catalyst, it is preferred that a sufficient amount of alumina be mixed with the catalyst to provide a significant amount of sulfur oxide removal from the regeneration gas.

Good results are usually obtained by adding 0.1 to 25% by weight of alumina.

If alumina is present as all or part of a component of the catalyst itself, the catalyst particles preferably contain at least 50% by weight of alumina in the catalyst, based on the weight excluding zeolite;
Particularly preferred is at least 60% by weight.

For those skilled in the art, the amount of coke contained in the spent catalyst will depend on the composition of the hydrocarbon feed to be converted using the catalyst, and the boiling point range, as well as the nitrogen and sulfur impurities in the coke. It should be widely recognized that the composition of the catalyst itself will vary widely depending on factors such as the composition of the catalyst itself and the type of catalytic reaction mode in which it is used (e.g. moving bed, fluidized bed, entrained bed). be.

The advantages of burning coke according to the invention are obtained for catalysts containing coke that vary over a very wide range, and also for catalysts containing coke that contain a wide range of nitrogen content.

According to the invention, the spent catalyst is introduced at the intermediate level of the vertically extending regeneration zone. The vessel, or chamber, used as the regeneration zone has three sections and a solids residence time sufficient to allow essentially complete combustion of the coke in the catalyst by the time the lower end of the regeneration zone is reached. There must be sufficient vertical height to allow for removal. The spent catalyst is introduced into the regeneration vessel at a sufficient distance from the bottom of the regeneration zone so that essentially all the coke is burned off from the catalyst particles as the catalyst descends from the spent catalyst inlet to the lower end of the regeneration zone. be done.

Therefore, the spent catalyst must be introduced into the regeneration vessel at a sufficient distance from the top of the regeneration zone to create a coke-free catalyst bed in the top section of the regeneration zone.

The part of the catalyst bed at the spent catalyst inlet preferably constitutes 60-95% of the total catalyst bed volume in the regenerator, particularly preferably 80-90% of the total bed volume.

The height of the upper section of the regeneration zone containing the regenerated catalyst bed must be sufficiently high to provide essentially complete combustion of the carbon monoxide in the regeneration gas stream in contact with the coke-free catalyst.

Regeneration gas is introduced from the bottom of the regeneration zone.
According to the present invention, the amount of free oxygen (molecular oxygen) initially introduced into the regeneration gas is determined by (1) converting substantially all of the coke carbon in the spent catalyst introduced into the regeneration zone into carbon monoxide; and (2) less than stoichiometrically to react substantially all of the coke carbon in the spent catalyst introduced into the regeneration zone to carbon dioxide. Limit quantity.

When the amount of free oxygen in the regeneration gas introduced from the lower end of the regeneration vessel is maintained within a reasonable range, the composition of the regeneration gas is such that it contacts an essentially coke-free catalyst in the lower section of the regeneration zone. From a highly oxidizing atmosphere with a high oxygen concentration and a low carbon monoxide concentration, the spent catalyst and partially regenerated catalyst in the intermediate section of the regenerator are generally The atmosphere changes to an oxygen-free atmosphere.

Due to the high oxidizing atmosphere obtained by the high free oxygen concentration and low carbon monoxide concentration in the regeneration gas in the lower section of the regeneration zone, the combustion of nitrogen-containing compounds present in the coke burned in the lower section is reduced to nitrogen. There is a tendency to form oxides, especially when carbon monoxide combustion promoting metals are present.

According to the invention, these nitrogen oxides react to free nitrogen (molecular nitrogen) in the intermediate section of the regeneration zone in the presence of an anoxic atmosphere provided by the absence of free oxygen. Accordingly, the regeneration gas exiting the intermediate section of the regeneration zone typically contains significant amounts of carbon monoxide, but relatively no nitrogen oxides.

At the same time, the catalyst particles reaching the bottom of the regeneration zone are substantially coke-free.

Additional free oxygen is added to the oxygen-free, typically carbon monoxide-containing regeneration gas above the spent catalyst inlet level.

Additional free oxygen can be suitably added by any free oxygen containing gas such as pure oxygen, air or the like.

The amount of additional free oxygen introduced is preferably sufficient to react stoichiometrically to carbon dioxide with at least all the carbon monoxide present in the regeneration gas leaving the intermediate section of the regenerator. .

Particularly preferred is the addition of sufficient free oxygen to provide at least 3% by volume (excess) free oxygen in the regeneration gas in addition to the free oxygen required to stoichiometrically burn out all the carbon monoxide in the regeneration gas. Introduce free oxygen.

Combustion of the added free oxygen and carbon monoxide in the regeneration gas releases a significant amount of thermal energy into the regeneration gas.

It is highly desirable to recover this thermal energy before it is removed from the regenerator. This additional thermal energy is used for subsequent catalytic conversion operations using coke-free regenerated catalyst (e.g.
FCC conversion).

Typically, uncatalyzed carbon monoxide combustion can heat the flue gas to extremely high temperatures due to the low heat capacity of the regeneration gas, so cyclones,
with the risk of thermal damage to equipment in contact with flue gases, such as conduits.

Coke-free catalyst is transferred to the upper section by directing a portion of the regenerated catalyst from the lower end of the regeneration zone to the upper section to recover the heat generated by the combustion of carbon monoxide and cause a heat drop. supply

Since the regenerated catalyst at the lower end of the regenerator is substantially coke-free, in the upper section essentially no more heat or combustion products and especially nitrogen oxides are produced in the regenerated gas.
As a result, the flue gas leaving the regeneration system is free of nitrogen oxides and carbon monoxide.

Passage of the substantially coke-free catalyst to the top of the regeneration zone ensures that there is sufficient coke-free catalyst in the carbon monoxide combustion zone to absorb essentially all the heat released by the combustion of the carbon monoxide. It is preferable to do this at a speed that can be maintained.

Particularly preferably, the heat drop caused by the coke-free catalyst has the effect of keeping the maximum temperature of the regeneration gas in the upper section below the maximum temperature in the middle section of the regeneration zone plus 27°C. The height of the essentially coke-free catalyst bed maintained in the upper section of the regeneration zone is sufficiently high to bring the carbon monoxide in the regeneration gas into contact with the regeneration catalyst and combust at least a large portion thereof. .

Particularly preferably, the amount of regenerated catalyst introduced into the upper section of the regeneration zone and the height of the bed of regenerated catalyst maintained in the upper section are such that the total amount of regenerated catalyst in the regenerated catalyst during contact of the gas with the regenerated catalyst bed is high enough to cause substantially complete combustion of carbon monoxide.

Preferred Embodiments The invention will be better understood by reference to specific preferred embodiments illustrated in the accompanying drawings.

Practicing a preferred embodiment of the invention regenerates a spent zeolite-type FCC catalyst containing a separate alumina phase comprising at least 50% by weight of the catalyst (based on excluding zeolite). In this method, combustion-promoting metal additives are
It is used in the form of alumina particles containing 0.1% by weight of platinum.

The additive particles are mixed with sufficient catalyst particles to provide 1 ppm (by weight) of platinum in the catalyst and additive mixture.

The spent FCC catalyst that is regenerated typically has a
It contains 2.0% coke, of which typically 0.01-1% nitrogen and 0.25-5.0% sulfur.

It is well known to those skilled in the art that the amount of coke contained in a typical spent FCC catalyst varies considerably depending on the particular feed and catalyst used, and the upper and lower limits of this concentration vary considerably. Dew.

Spent catalyst and combustion promoting additives are introduced through conduit 3 of regeneration vessel 1 at a rate of 2400 tons/hour.

The spent catalyst entering the regeneration vessel mixes with flowing pre-regenerated catalyst that moves generally downwardly from the top of the perforated plate 27.

Air is introduced into the regeneration vessel through distributor 9 at a rate sufficient to provide the desired amount of free oxygen.

Steam is added as necessary to maintain the regeneration gas flow rate and surface velocity at appropriate levels to fluidize the particles in the regeneration vessel.

Back-mixing of the catalyst particles in the fluidized bed is suppressed by the perforated plates 23, 25, 27 and 29, so that the catalyst particles move downward through the regeneration zone in a plug-type flow.

Before the catalyst particles reach the distribution grid 11 at the bottom end of the regeneration vessel, most of the coke has been burned off from the catalyst particles so that the catalyst at the bottom end of the bed contains less than 0.1% by weight of coke. The coke-free regenerated catalyst is removed through conduit 13.

A portion of the regenerated catalyst is passed through conduit 19 to regeneration vessel 1.
is introduced into the upper section at a rate of 600 tons/hour.

The remaining regenerated catalyst is removed from the regeneration system through conduit 21 for catalyst use at a rate of 2400 tons/hour.

The amount of free oxygen contained in the regeneration gas introduced through the distributor 9 is limited so that when it passes the perforated plate 27 the free oxygen in the regeneration gas is below 0-1% by volume. The carbon monoxide concentration is approximately 2% by volume. The maximum temperature of the regeneration gas is plate 27.
It is approximately 650℃ when passing through.

Additional free oxygen in the gas, such as air or a mixture of air and steam, is provided by distributor 33 to essentially completely burn all the carbon monoxide in the initial regeneration gas to carbon dioxide. Free oxygen is supplied and introduced through conduit 39 in a proportion sufficient to result in at least 3% by volume free oxygen remaining in the flue gas exiting the regeneration vessel.

The temperature of the regeneration gas stream (flue gas) above the top of the regenerated catalyst in the upper section of the vessel, indicated by line 37 in the figure, is approximately 670°C. The flue gas stream leaving the regenerated solvent bed and entering cyclone 35 contains less than 0.1% by volume carbon monoxide and less than 200 ppm (by volume) nitrogen oxides.

Preferred embodiments of the invention as hereinbefore described, as well as various modifications and equivalent methods of the invention that fall within the scope of the invention as defined in the claims, will be apparent to those skilled in the art. Will.

[Brief explanation of drawings]

The drawing is a schematic representation of one of the preferred embodiments of the invention. DESCRIPTION OF SYMBOLS 1... Regeneration vessel, 3... Waste catalyst conduit, 5... Valve, 7... Regeneration gas conduit, 9... Regeneration gas distributor, 11... Gas distribution grid, 15... Coke-free catalyst storage container, 17 ...Gas conduit, 19...Catalyst, gas conduit, 21...Regenerated catalyst removal conduit, 2
3, 25, 27, 29...perforated plate, 31...additional oxygen conduit, 33...distributor, 35...flue gas cyclone separator, 37...line indicating the upper part of the coke-free catalyst bed, 39... Flue gas discharge duct.

Claims (1)

Claims: 1. A method for removing nitrogen-containing coke from a coke-containing granular catalyst, comprising: (a) introducing the coke-containing catalyst at an intermediate vertical level of a vertically extending regeneration zone; passes downward through the zone;
and inhibiting backmixing of the catalyst in said zone; (b) introducing regeneration gas containing free oxygen into the lower end of said zone and passing said regeneration gas upwardly through said catalyst to substantially eliminate said regeneration gas from said catalyst; All of the coke is burned off and substantially all of the carbon monoxide produced in the lower section of the regeneration zone is burned off, with at least 1 volume percent free oxygen in the regeneration gas being present in the lower section of the regeneration zone. (c) sufficient free oxygen is included in the regeneration gas in the middle section to contact the catalyst in the lower section to generate nitrogen oxides in the regeneration gas; carbon monoxide and carbon dioxide by substantially completely reacting the free oxygen of coke and carbon monoxide with substantially all of the coke and carbon monoxide in contact with the catalyst in an intermediate section of the regeneration zone. reducing the amount of nitrogen oxide in the regeneration gas in the intermediate section by creating an oxygen-free atmosphere and reacting at least a portion of the nitrogen oxide to generate free nitrogen in the oxygen-free atmosphere; (d) introducing a substantially coke-free catalyst into the upper section of the zone and passing the coke-free catalyst downwardly through the zone; (e) substantially all of the coke-free catalyst contained in the regeneration gas; The method characterized in that carbon monoxide is combusted in the upper section with additional free oxygen in contact with the substantially coke-free catalyst and the regeneration gas is removed from the upper section. 2. In the method according to item 1 above, the coke in the coke-containing catalyst contains a sulfur component, the combustion of the coke produces oxidized sulfur, and the oxidized sulfur reacts with the solid contained in the catalyst particles. said method of reacting with a sulfur-containing solid to produce a sulfur-containing solid in said zone. 3. The method of item 2 above, wherein the solid reactant comprises alumina. 4 said first said substantially coke-free catalyst passes from said lower end of said regeneration zone to said upper section;
The method described in section. 5. The method of paragraph 1 above, with sufficient additional free oxygen in the regeneration gas in the upper part of the intermediate section such that the free oxygen in the regeneration gas discharged from the upper section is at least 3 percent by volume. Said method of adding. 6. The method of item 1 above, wherein a metal combustion promoter is introduced into the regeneration zone along with the coke-containing catalyst. 7. In the method according to item 6 above, the metal combustion promoter is at least one metal selected from platinum, palladium, iridium, osmium, rhodium, ruthenium, copper, chromium, and manganese;
or a metal compound.