IE43944B1 - Catalyst regeneration by coke oxidation in a dense phase bed and catalysed carbon monoxide conversion in a dilute phase transport riser - Google Patents

Description

Patent Specification No. 37635 describes and claims a process for regenerating coke-contaminated particle-form spent catalyst, particularly spent fluid catalytic cracking (FCC) catalyst, withdrawn from a hydrocarbon conversion zone, which process comprises the steps of: (a) introducing said spent catalyst and an oxygen-containing regeneration gas into a first dense bed of fluidised particles and therein partially regenerating said catalyst by combustion of said coke and producing partially spent regeneration gas containing CO; (b) passing resulting partially regenerated catalyst and partially spent regeneration gas directly from said dense bed upwardly in dilute phase into and through a dilute phase transport riser and therein effecting further combustion of coke from said partially regenerated catalyst, and also therein oxidising at least-a portion of said CO to CO^ in said dilute phase transport riser; (c) separating resulting regenerated catalyst from regeneration gas; (d) recovering said regenerated catalyst as a second dense bed of particles; and (e) withdrawing regenerated catalyst from said second dense bed for return to said conversion zone.

The present application is directed to an embodiment of the above-described process wherein the catalyst contains catalytically effective amounts of a CO conversion promoter.

Such a process in which the CO conversion promoter is a noble metal oxide is disclosed and claimed in Patent Specification No. 43943 and, for this reason, the use of such a CO conversion promoter is disclosed herein.

Thus, according to the present invention there is provided a process for regenerating coke-contaminated particle form spent catalyst withdrawn from a hydrocarbon conversion zone and containing a catalytically effective amount of a CO conversion promoter other than a noble metal oxide, which process comprises, the steps of:(a) introducing said spent catalyst and an oxygen-containing regeneration gas into a first dense bed of fluidized particles and therein partially regenerating said catalyst by combustion of said coke and producing partially spent regeneration gas containing CO; (b) passing resulting partially regenerated catalyst and partially spent regeneration gas directly from said dense bed upwardly in dilute phase into and through a dilute phase transport riser and therein effecting further combustion of coke from said partially regenerated catalyst and also therein oxidising at least a portion of said CO to COj in said dilute phase transport riser; (c) separating resulting regenerated catalyst from regeneration gas; (d) recovering said regenerated catalyst as a second dense bed of particles; and (e) withdrawing regenerated catalyst from said second 439 44 dense bed for return to said conversion zone.

The spent catalyst is preferably spent fluid cracking (FCC) catalyst, the hydrocarbon conversion zone being a fluidised catalytic cracking zone.

The CO conversion promoter may comprise one or more nonnoble metal oxides. The preferred non-noble metal oxides are vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, and rare earth metal oxides.

The catalytically effective amount of the CO conversion promoter is preferably from 0.01 to 20 wt.% of the total catalyst for the non-noble metal oxides.

It is also preferred that essentially complete conversion of Co to C02 should take place in the dilute phase transport riser. The term essentially complete shall be taken to mean that the CO concentration in the spent regeneration gas has been reduced to less than 1000 ppm., and preferably to less than 500 ppm.

All the preferred features which are mentioned in the dependent claims 3 to 17, 20 and 21 of Patent Specification Mo. 37635 are also preferred features in the process of the present invention. The present invention can also be carried out in the apparatus illustrated in Figures 1 to 3 of the drawing accompanying that patent application.

The use of the promoter permits either the same rate of CO conversion to occur at a temperature as much as 55°C (or more) lower than that required with no CO conversion promoter, or a faster rate of CO conversion to occur at a particular temperature than that which would occur at the same temperature without the use of a co conversion promoter. It is this latter advantage which is of particular commercial importance. Without a CO conversion promoter, uneven dispersion of fresh regeneration gas within the dense-phase catalyst bed often requires higher regeneration zone temperatures or higher fresh regeneration gas rates than desired to maintain a sufficiently fast rate of CO conversion so that essentially complete conversion of CO takes place within the regeneration zone. Increasing the regeneration zone temperature may require that torch oil be burned in the regeneration zone or may require that increased amounts of slurry oil be recycled back to the hydrocarbon reaction zone so that the spent catalyst will contain more coke which can be burned in the regeneration zone to increase the temperature. Increased fresh regeneration gas rates, besides using blower capacity, often overloaded cyclone separation devices and produced higher amounts of fluid gas particulate emissions (catalyst) than allowed by air pollution regulations. The use of the co conversion promoter permits the elimination of torch oil or increased slurry oil recycle rates and a reduction in the amount of excess fresh regeneration gas and thus gives back to the refiner more FCC process flexibility.

The rate of coke oxidation is not per se affected by employing a spent fluid catalytic cracking or other catalyst containing a CO conversion promoter, but the rate of CO conversion is increased. With a CO conversion promoter, the kinetic rate constant for CO conversion to C02 may be increased typically from 2 to 5 times or more. Thus, a faster rate of co conversion can be obtained in the presence of a CO conversion promoter at a given regeneration zone temperature than can be obtained without the promoter. Conversely, the same rate of CO conversion can be obtained at a lower regeneration zone - 6 -temperature than' that required without a CO conversion promoter.

The catalysts used in the process of the invention are especially those which are in a physical form capable of fluidisation in an FCC process and which possess hydrocarbon cracking activity, as well as containing catalytically effective amounts of a CO conversion promoter.

The CO conversion promoter can be incorporated as a component Of the cracking catalyst into any of the well-known amorphous FCC catalysts comprising silica and/or alumina or into any of the molecular sieve — containing FCC catalysts by methods known to the catalyst manufacturing art such as co-preeipitating or cogelling therewith or by impregnating with an aqueous solution of a thermally decomposable salt and heating to dry and decompose the salt. Suitable molecular sieves include both naturally occurring and synthetic aluminosilicate materials known to the art such as faujasite, mordenite, chabazite, zeolite X and zeolite Y to name a few. in addition to permitting lower temperatures the use of a catalyst containing a CO conversion promoter in other FCC process units has permitted a reduction in the fresh regeneration gas (air) rate needed for a particular feed rate to achieve a desired CO concentration in the flue gas. In an FCC process unit, being operated near the design limits of cyclone separators such a reduction nay in turn reduce particulate emissions from the unit. Where cyclone separation efficiency is not a problem, other units may be able to increase the fresh feed rate at a fresh regeneration gas rate no higher than that previously used with a lower fresh feed rate but without a catalyst containing a CO conversion promoter.

Claims (9)

1. CLAIMS:1. A process for regenerating coke-contaminated particle-form spent catalyst withdrawn from a hydrocarbon conversion zone and containing a catalytically effective amount of a CO conversion promoter, which process comprises the steps of: (a) introducing said spent catalyst and an oxygencontaining regeneration gas into a first dense bed of fluidised particles and therein partially regenerating said catalyst by combustion of said coke and producing partially spent regeneration gas containing CO; (b) passing resulting partially regenerated catalyst and partially spent regeneration gas directly from said dense bed upwardly in dilute phase into and through a dilute phase transport riser and therein effecting further combustion of coke from said partially regenerated catalyst and also therein oxidising at least a portion of said CO to C0 2 in said dilute phase transport riser; (c) separating resulting regenerated catalyst from regeneration gas; (d) recovering said regenerated catalyst as a second dense bed of particles; and (e) withdrawing regenerated catalyst from said second dense bed for return to said conversion zone.

2. The process of claim 1 wherein said CO conversion promoter comprises one or more non-noble metal oxides.

3. The process of claim 2 wherein said CO conversion promoter is selected from vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, and rare earth metal oxides. - 8

4. The process of claim 2 or 3 wherein said catalytically effective amount is from 0.01 to 20 wt.% of said catalyst.

5. The process of any of claims 1 to 4 wherein essentially all of the CO is oxidised to C0 2 in said dilute phase transport riser.

6. The process of any of claims 1 to 5, wherein said particle-form spent catalyst is spent fluid catalytic cracking catalyst withdrawn from a fluidised catalytic cracking zone.

7. A process for regenerating coke-contaminated ι particle-form spent catalyst as claimed in claim 1 ahd carried out substantially as hereinbefore specifically described.

8. A particle-form catalyst which has been regenerated by a process as claimed in any of claims 1 to 7.

9. A fluidised catalyst cracking process in which a hydrocarbon charge is cracked at cracking conditions in contact with a fluid catalytic cracking catalyst containing a catalytically effective amount of a CO conversion promoter and, when the catalyst becomes coke-contaminated, the spent • catalyst is withdrawn from the cracking operation, regenerated by the process of any of claims 1 to 7 and reused in the cracking.