CA1095882A - Regeneration method for gravity-flowing deactivated catalyst particles - Google Patents

Abstract

ABSTRACT

A continuous method for regenerating deactivated catalyst particles in a regeneration zone through which the particles are downwardly movable by way of gravity-flow.
Particles are initially introduced into an upper carbon-burn-ing/halogenation zone wherein they are contacted, in a first section, with a first air stream and a first mixture of steam and a halogen, or halogen-containing compound. Partially regenerated/reconditioned particles are then contacted, in a lower second section, with a second air stream and a second mix-ture of steam and halogen. From this two-sectioned, carbon-burning/halogenation zone, the catalyst particles flow via gravity into a drying zone wherein they are contacted by a substantially dry air stream.

Description

lO9S88Z

REGENERATION METHOD FOR GRAVITY-FLOWING
DEACTIVATED CATALYST PARTICLES

* * SPECIFICATION * *

A principal object of our invention is to provide an improved method for continuously regenerating deactivated hydrocarbon conversion catalyst particles. A corollary objective involves a method for regenerating deactivated catalyst particles, comprising a Group VIII noble metal component and a halogen component in combination with a refractory inorganic oxide, in a regeneration zone through which said catalyst particles are movable via gravity-flow.
Another object of our invention is to afford a more economical technique for regenerating catalyst particles which have been deactivated by deposition of carbonaceous matter thereon and loss of halogen therefrom.
Therefore, in one embodiment, our invention is directed toward a method for continuously regenerating hydrocarbon conversion catalyst particles comprising a Group VIII metai component and a halogen component in oombination with a refractory inorganic oxide carrier material, and which have become deactivated (1) by deposi-tion of carbonaceous matter thereon and, (2) through loss of halogen therefrom, in a regeneration zone through which said catalyst particles are downwardly movable via yravity-flow, which regeneration method comprises the inter-related steps of: (a~ introducing (i) deactivated cata-lyst particles, (ii) a first air stream from an external ~4~

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source and, (iii) a first mixture of steam and a halogen, or halogen-containing compound, into a first carbon-burning/halogenation section; (b) maintaining said catalyst particles within said first section for a time sufficient to (i~ remove the greater portion of said carbonaceous matter therefrom and, (ii) increase the halogen content thereof; (c) introducing (i) the catalyst particles from said first section, via gravity-flow, (ii) a second air stream from an external source and, (iii) a second mixture of steam and a halogen, or a halogen-containing oompound, into a second carbon-burning/halogenation section; (d)main-taining said catalyst particles within said second section for a time sufficient to (i) remove substantially all of the remaining carbonaceous material therefrom and, (ii) further increase the halogen content thereof; (e) intro-ducing (i) the catalyst particles from said second section, via gravity-flow, and, (ii) a substantially dry third air stream fro~l an external source into a lower drying section, and maintaining said catalyst particles therein for a time sufficient to remove substantially all the water therefrom;
and, (f) withdrawing substantially water-free, regenerated catalyst particles from said regeneration zone.
Preferably, the temperature in the first and second carbon-burning/halogenation sections is maintained in the range of 399C. to about 566C. Generally, the temperature in the lower drying section will be from 443C. to 538C.
In another embodiment, the excess air and the combus-tion products resulting from the burning of carbon, are 1095E~Z

withdrawn from the carbon-burning/halogenation zone, cooled and at least in part recycled to both the first and second carbon-burning sections.

The invention is intended to effect the regeneration of deactivated hydrocarbon conversion catalyst particles comprising a Group VIII noble metal component and halogen oDmponent combined with a refractory inorganic oxide. In accordance with the Periodic Table of the Elements, E.H.
Sargent & Co., 1964, the term "Group VIII noble metal component" is intended to include ruthenium, rhodium, palladium, osmium, iridium, platinum, and mixtures thereof.
Furthermore, our regeneration method is applicable to the recently-developed bi-, tri- and tetra-metallic catalysts in which metallic components other than those of the Group VIII noble metals are incorporated therewith. Such other metallic components include technetium, rhenium, gallium, vanadium, cobalt, nickel, gold, germanium, tin, lead, bismuth, etc~ Generally, the quantity of the Group VIII
noble metal components within the final catalytic compos-ite is small compared to the quantities of the other com-ponents combined therewith, and will be present in an amount of about 0.01% to about 2.0% by weight of the final catalytic composite, calculated on an elemental basis. Similarly, with respect to the multi-metallic catalysts, the other metallic components, herein above set forth will be present in an amount in the range of about 0.01% to about 5.0%, again calculated on an elemen-tal basis.
~nother ingredient of the type of catalytic compos-ites regenerated by the present method is a halogen com-ponent. Although the precise form of the chemistry of the association of this component with the other components of the catalyst is not known with accuracy, it is customary in the art to refer thereto as combined halogen. This may be either fluorine, chlorine, iodine, bromine, or mixtures thereof, with fluorine and particularly chlorine being preferred. The halogen component will be present within the catal~st in an amount within the range of about 0.1%
to about 5.0%, and generally from about 0.5% to about 1.5 by ~leight, ¢alculated on an elemental basis. One or more of the foregoing metallic components and the halogen com-ponent is combined with a suitable refractory inorganic oxide carrier material. With respect to the latter, many compositions have been employed, including alumina, silica, zirconia, hafnia, boria, thoria, mixtures thereof, etc.;
however, with respect to the catalytic reforming of hydro-carbons, alumina in and of itself, is generally preferred.
The foregoing is presented to describe the general type of hydrocarbon conversior. catalyst particles to which the regeneration method of the present invention is particularly directed. It is understood that the precise chemical and/or physical make-up of the catalytic compos-ite is not essential to the present invention, nor is the particular technique selected for the manufacture of the catalyst particles. In short, our invention is concerned solely with a method for continuously regenerating deac-tivated hydrocarbon conversion catalyst particles compris-ing a Group VIII noble metal component and a halogen com-.~

1~9588~ 1 ponent in combination with a refractory inorganic oxide.Further, our method is intended for utilization in those hydrocarbon conversion systems wherein catalyst particles are regenerated in a regeneration zone through which they are movable via gravity-flow.
The principal cause of observed deactivation or instability of catalytic composites employed in hydro-carbon conversion processes is associated with the forma-tion of coke or carbonaceous matter on the interstitial surface of the catalyst. The conditions utilized in these hydrocarbon conversion processes, to effect the desired reactions, typically result in the formation of black carbonaceous matter (often referred to as coke) which deposits on the surface of the catalyst and grad-ually reduces its activity by shielding the active sitesfrom the reactants. With many hydrocarbon conversion catalysts, removal of the carbonaceous matter by burning in air, via one or more suitable techniques, generally suffices to reactivate the catalyst to an acceptable degree. However, when considering dual-function cata-lysts, or those containing a Group VIII noble metal com-ponent and a halogen component, carbon removal in an of itself does not result in an acceptable reactivated cata-lyst~ These catalysts, and their capability to function as intended, are acutely sensitive to the loss of the com-bined halogen both during the processing of the selected hydrocarbon stream and the carbon-burning technique, Therefore, any successful regeneration procedure must recognize the attendant difficulty of restoring a uniorm distribution of the halogen component within the catalyst particles. Furthermore, a comparison of fresh catalyst with deactivated catalyst indicates a substantial change in the character of the Group VIII noble metal component associated therewith. Generally, such a comparison indi-cates that the noble metal component, for example platinum, is no longer thoroughly and uniformly dispersed throughout the catalyst particles, but has been caused to agglomerate.
These difficulties become more pronounced in regeneration techniques involving the bi-, tri-, and tetra-metallic catalytic composites.
A regeneration technique for gravity-flowing catalyst particles is disclosed in United States Patent No.
3,652,231. The regeneration zone is shown as having an upper carbon-burning section, an intermediate halogenation section and a lower drying section. Catalyst particles are introduced initially into the top of the regeneration zone, pass downwardly through the carbon-burning section into the halogenation section and finally into the lower drying section. The air required for reconditioning is intro-duced into the lower drying section and passes upwardly therefrom into the halogenation section, and therethrough into the carbon-burning section. Halogen and steam are introduced into the intermediate halogenation section, and any excess is recycled in admixture with fresh steam and halogen. Furthermore, combustion vapors from the carbon-burning section are introduced into a caustic scrubbing facility, and thereafter recycled to the carbon-burning section. Another three-stage regeneration technique is that set forth in United States Patent No. 3,981,824.
Our catalyst regeneration technique is intended to improve significantly both of the above-described tech-niques. To reiterate briefly, the regeneration technique is accomplished in two discreeet zones, as contrasted to the three zones of the prior art.
Our technique differs from the foregoing three-zone regeneration method in several important aspects which lead to significant advantages and/or benefits. Initially, there exists a simplification of the regeneration tower design relative to the internal hardware. Total residence time of the catalyst particles, within the regeneration tower is reduced; thus, changes in regeneration are more quickly obeserved at the various sample points and espe-cially in the reactor section itself. Start-up procedures become much more simplified; the time required for the start-up procedure is reduced from about twenty-four hours to about sixteen hours, ~nd this greatly lessens the risk of catalyst damage. Simultaneous carbon-burning and halo-genation reduces the likelihood of noble metal agglomera-tion; thus, the metallic components retain their active, dispersed state. When accomplished in two carbon-burning~
halogenation sections, the second section serves as a quasi halogen-adjustment section, while simultaneously removing : 25 the remaining carbonaceous material. Also, the length of time required for catalyst regeneration/reconditioning is lessened by approximately one-third; this will afford an increase in total spent catalyst through-put, for a given size regeneration tower, or a corresponding increase in ,,, ,~

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eoke-burning capacity.
In accordance with our inventive concept, substan-tially dry air is introduced to the lower drying zone and undried air to the upper carbon-burning/halogenation zone.
With respect to the latter, the air is admixed with the steam/halogen mixture and recycled flue gas, and intro-dueed therewith into this dual-function zone. The com-bined carbon-burning/halogenation zone is divided into two sections, into both of whieh the mixture of flue gas, steam, halogen and air is introduced. The mole ratio of air introduced into both carbon-burning sections, to that introduced into the drying zone is at least 1.0:1.0, and generally in the range of about 1.0:1.0 to about 9.0:1Ø
Preferably, the quantity (or proportion) of air intro-duced into the drying zone will be the minimum sufficientto accomplish the necessary drying. Furthermore, the flue gas from the carbon-burning/halogenation sections is recycled thereto without any intermediate treatment, excepting the cooling thereof. The relative rates of the dry air and flue gas recycle are maintained to control the oxygen concentration at a level in the range of about 0.2~ to 2.0%, on a molal basis, and preferably from about 0.5~ to about 1.5%.
The upper section of the regeneration tower essen-tially serves two principal functionsi first, the cokeand/or carbonaceous material must be removed from the catalyst particles and, secondly, the halogen content must be increased while simultaneously properly dispers-ing the metallic components. One consequence of split lO9S88Z
air flow -- i.e. introducing from about 10.0% to about 50.0~ of the required air into the lower drying zone --is to maintain the necessary partial pressure of halogen in the upper combined carbon-burning/halogenation zone with less overall fresh halogen addition. Furthermore, combining the halogenation and carbon-burning functions alleviates noble metal agglomeration normally occurring when the carbonaceous material is removed from the cata-lyst particles. Assuming a fresh catalyst halogen content of about 1.0% by weight (as combined halide), which is reduced to a level of about 0.75~ when the catalyst is deactivated, the concentration will be about 1.1% by weight following halogenation and carbon burning, and about 1.0% by weight following the drying step.
In further describing our invention, reference will be made to the accompanying diagrammatic sketch. This is presented for the sole purpose of illustration, and not with the intent of limiting our invention beyond the scope and spirit of the appended claims. Miscellaneous appurtenances, not required for a clear understanding, have been eliminated.
With specific reference now to the drawing, there is illustrated a regenerating tower 1, having an upper, first carbon-burning/halogenation section 2, a lower, second carbon-burning/halogenation section 3 and a lower drying zone 4. Although the various structural elements may take any suitable tubular form, sound engineering princi-ples and techniques dictate that the same be substantially circular in cross-section. Catalyst particles which have been withdrawn from the lower terminus of a reaction zone, through which they are movable via gravity-flow, are transported to regenerating tower 1 by way of lift line 9 and are introduced thereby into disengaging hopper 10.
Catalyst particles are disengaged from dust-like catalyst fines which are removed from the regeneration facility ~y way of conduit 11, and transported thereby to a dust collector. Separated catalyst particles flow downwardly through a plurality of inlet conduits 12, generally number-ing from about four to sixteen, and into annular-form space 8. The latter is formed by a perforated centerpipe 7 and an outer catalyst-retaining screen 6, through which the reconditioning vapors pass.
The catalyst particles, at a temperature of about 99C., initially traverse carbon-burning/halogenation section 2 which functions in the temperature range of 443C. to 532C. Catalyst-burning/halogenation section 2 is that portion of the regenerating tower which extends from the top plate to a horizontally-disposed baffle 5.
The second carbon-burning/halogenation section 3, also functioning at 443C. to 532C., is that portion of regeneration tower 1 below horizontal baffle 5 and the terminal end of perforated centerpipe 7. Substantially carbon-free catalyst particles flow via gravity into lower drying zone 4 which is maintained at an elevated temperature of 443C. to 538C.; that is, substantially dry air, introduced into the frusto-conical section by way of line 25, is at a temperature of about 538C., 1~:)9588Z

while catalyst particles emanating from the regenerating tower, via outlet port 13 and line 14, are at a temper-ature of about 443C. Dried, reconditioned catalyst parti-cles are subjected to hydrogen reduction either in a separate vessel prior to being transported to the reactionzone, or in a vessel which is an integral part of the reaction zone.
At least a portion of the effluent vapors, flue gas, emanating from the carbon-burning/halogenation sections of the regeneration tower 1, are recycled thereto. Through this technique, the oxygen concentration within tnis upper zone is regulated and maintained in the preferred range of about 0.5% to about 1.5%. Furthermore, dilution of the halogen-steam atmosphere within the carbon-burning/halo-genation sections is effected by the vapors emanating fromthe drying section. This relatively severe oxidizing atmosphere facilitates the redistribution of the no~le metal component.
The remainder of the drawing will be described in conjunction with a commercially-scaled regeneration designed to process about 227 kg/hr. of deactivated cata-lyst particles containing about 0.75% by weight of combined chloride and about 5.2% by weight of carbona-ceous matter (co~e). About 11.55 moles/hr. of air, from a suitable external source, are introduced by way of line 20. Approximately 50.0% is diverted through line 21 into dryer 22, through line 23 and an electric heater 24. The temperature thereof is increased to about 538C., and the heated air is introduced into drying zone 4 via line 25.

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About 0.24 moles/hr. of water are removed from the cata-lyst particles in the drying zone.
A mixture of steam and halogen, or a halogen-contain-ing compound is introduced by way of line 26, admixed with recycled flue gas from line 18, and the remaining portion of substantially air from line 20. Approximately one-half (1/2) to two-thirds (2/3) of the resul~ing mix-ture is diverted through line 27 and blower 28 into con-duit 29, through which it is introduced into upper carbon-burning/halogenation section 2. This halogen-containing stream is at a temperature of about 443C. The halogen, for example chlorine, may be employed in its elemental state, or as a compound such as hydrogen chloride, ethylene dichloride, propylene dichloride, tertiary butyl chloride, etc. The remaining portion of flue gas, steam, halogen and air mixture continues through conduit 18 and blower 30 into line 31, through which it is introduced into the second carbon-burning/halogenation section 3.
In the present illustration, halogen addition takes the form of a steam/hydrogen chloride mixture entering by way of conduit 26; of the ~.44 moles/hr., about 0.13 moles is hydrogen chloride.
Effluent vapors from upper carbon-burning/halogena-tion section 2, at a temperature of about 498C., are withdrawn through the extension of centerpipe 7 and out-let port 15; these are introduced, by way of line 16, into cooler 17, wherein the temperature is decreased to about 4~9~C. Thus cooled vapors are withdrawn via line 18, and about 400 moles/hr. continue there through. The remaining portion of the cooled flue gas vapors are vented from the system through conduit 19.
The catalyst particles introduced into the regenera-tion zone from disengaging hopper 10, contain about 11.8 kg./hr. of coke and about 0.75% by weight of combined chloride. When these leave the carbon-burning/halogena-tion sections, they are substantially coke-free; the halogen content has been increased to about 1.1% by weight, and the catalyst particles contain about 0.90%
by weight of water. The latter is removed in the drying zone, and the dried catalyst particles are withdrawn from the regeneration zone containing 1.0% by weight of halo-gen. The upper carbon-burning/halogenation sections and the lower drying zone, of the regeneration zone 1, are sized and designed to provide an effective residence time, of the catalyst particles passing ~hrough each section, of from one to about three hours.
The foregoing illustrates the regeneration technique of the present invention wherein the regenerati~ tower consists of two stages as contrasted to the three-stage technique of the prior art. As a principal result, there is afforded an approximate two- to three-fold increase in coke-burning capacity.

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for continuously regenerating hydrocarbon conversion catalyst particles comprising a Group VIII
metal component and a halogen component in combination with a refractory inorganic oxide carrier material, and which have become deactivated (1) by deposition of carbon-aceous matter thereon and, (2) through loss of halogen therefrom, in a regeneration zone through which said cata-lyst particles are downwardly movable via gravity-flow, which regeneration method comprises the inter-related steps of:
(a) introducing (i) deactivated catalyst parti-cles, (ii) a first air stream from an external source and, (iii) a first mixture of steam and a halogen, or halogen-containing compound, into a first carbon-burning/halogena-tion section;
(b) maintaining said catalyst particles within said first section for a time sufficient to (i) remove the greater portion of said carbonaceous matter therefrom and, (ii) increase the halogen content thereof;
(c) introducing (i) the catalyst particles from said first section, via gravity-flow, (ii) a second air stream from an external source and, (iii) a second mix-ture of steam and a halogen, or a halogen-containing com-pound, into a second carbon-burning/halogenation section;
(d) maintaining said catalyst particles within said second section for a time sufficient to (i) remove substantially all of the remaining carbonaceous material therefrom and, (ii) further increase the halogen content thereof;
(e) introducing (i) the catalyst particles from said second section, via gravity-flow, and, (ii) a substantially dry third air stream from an external source into a lower drying section, and maintaining said catalyst particles therein for a time sufficient to remove substan-tially all the water therefrom; and, (f) withdrawing substantially water-free, regen-erated catalyst particles from said regeneration zone.

2. The method of Claim 1 wherein said first and second carbon-burning/halogenation sections are maintained at a temperature in the range of 399°C. to about 566°C.

3. The method of Claims 1 or 2 wherein said lower drying section is maintained at a temperature of 443°C.
to about 538°C.

4. The method of any of Claims 1 to 3 wherein said first air stream is introduced into said first carbon-burning/halogenation section through the same locus through which said first steam/halogen mixture is intro-duced.

5. The method of any of Claims 1 to 4 wherein said second air stream is introduced into said second carbon-burning/halogenation section through the same locus through which said second steam/halogen mixture is intro-duced.

6. The method of any of Claims 1 to 5 wherein the mole ratio of the air in said first and second streams to the air in said third stream is at least 1.0:1Ø

7. The method of any of Claims 1 to 6 wherein excess air and the combustion products resulting from the burning of carbon, are withdrawn from said first carbon-burning section, cooled and at least in part recycled to said first and second carbon-burning sections.

8. The method of Claim 7 wherein said excess air and combustion products are recycled to said carbon-burning/
halogenation sections without intermediate treatment.