EP1654339A1

EP1654339A1 - NOx REMOVAL COMPOSITION

Info

Publication number: EP1654339A1
Application number: EP04743401A
Authority: EP
Inventors: Robert Burch; Adrian St Clair Brown; James R. Nee; Robert H. Harding
Original assignee: Grace GmbH
Current assignee: Grace GmbH
Priority date: 2003-07-16
Filing date: 2004-07-15
Publication date: 2006-05-10
Also published as: RU2352609C2; GB0316659D0; RU2006104699A; GEP20084438B; WO2005007779A1

Abstract

A composition suitable for use in a fluidised catalytic cracking process comprising an acidic oxide support and a transition metal of Group VIII of the Periodic Table or a salt thereof.

Description

NOx REMOVAL COMPOSITION

Field of the Invention

The present invention relates to a composition suitable for reducing NO_x emissions during catalyst regeneration in a fluid catalytic cracking process.

Background of the Invention

Public policy and cost/benefit pressures have created an increasing desire to reduce the amount of polluting gases released by industrial processes. As a result there has been a drive to find ways of decreasing pollution by modifying industrial processes.

In the petroleum refining industry, fluid catalytic cracking (FCC) of hydrocarbons is a commonly used petroleum refining method. In a FCC process, catalyst particles (inventory) are repeatedly circulated between a catalytic cracking zone and a catalyst regeneration zone. In regeneration, coke deposits (from the cracking reaction) on the catalyst particles are removed at elevated temperatures by oxidation. The removal of coke deposits restores the activity of the catalyst particles to the point where they can be reused in the cracking reaction.

While FCC processes are efficient from the point of catalyst use, the regeneration step typically results in the evolution of undesirable gases such as SO_x, CO and NO_x.

Various attempts have been made to limit the amounts of these gases created during the FCC regeneration step or otherwise to deal with the gases after their formation. Most typically, additives have been used either as an integral part of the FCC catalyst particles themselves or as separate admixture particles in the FCC inventory in attempts to deal with these problematic gases. For example, US5627123A, US5324416A, US5002742 and US4918036A concern the use of magnesium aluminate spinel additives to prevent or minimise emission of SO_x from the regenerator. Various noble metal catalysts have been used to minimise the emission of CO from the regenerator, as illustrated in US05110780B1 and US05164072B1. Unfortunately, the additives used to control CO emissions typically cause a dramatic increase (e.g. 30%) in the amount of NO_x evolution from the regenerator. Some of the spinel-based (SO_x) additives act to lessen the amount of NO_x emission, but with limited success.

Catalysts comprising transition metals and oxidic supports have been developed to reduce emissions such as NO_xfor other fields of use, such as automotive exhausts (Tauster SJ, Murrell LU, Catal 197641(1) 192-5) as well as for use in FCC processes. US6129834, US6143167, US6280607 and US6379536 provide ^" compositions suitable for use in FCC processes which are capable of providing NO_x control (sold under the commercial name of DENOχ™). These compositions comprise an acidic oxide support, an alkali metal and/or alkaline earth metal or mixtures thereof, a transition metal oxide having oxygen storage capability and a transition metal selected from Groups lb and/or lib of the Periodic Table. US6165933 and US6358881 concern compositions capable of promoting CO combustion while avoiding mass NO_x formation comprising an acidic oxide support, an alkali metal and/or alkaline earth metal or mixtures thereof, a transition metal oxide having oxygen storage capability and palladium (commercially available as XNOχ™). Whilst use of these compositions does result in decreased NO_x emissions, there still remains a need for more effective NO_x control additives suitable for use in the FCC processes.

Summary of the Invention The present invention provides compositions suitable for use in FCC processes that are capable of providing superior NO_x control performance compared to the above mentioned DENOχ and XNOχ technology.

In one aspect, the invention provides compositions for reducing NO_x emissions in FCC processes, the compositions comprising: (i) an acidic oxide support; and (ii) a transition metal of Group VIII of the Periodic Table or a salt thereof, and catalysts comprising said compositions. In another aspect, the invention encompasses processes using the NO_x reduction compositions of the invention either as an integral part of the FCC catalyst particles themselves or as separate admixture particles in the FCC catalyst inventory.

Thus the present invention provides a composition suitable for use in a fluidised catalytic cracking process comprising: (i) an acidic oxide support; and

(ii) 0.0001 to 10 parts by weight (measured as a metal) of a transition metal of Group VIII of the Periodic Table or a salt thereof per 100 parts by weight of the acidic oxide support.

The invention also provides a fluid cracking catalyst which comprises: a) a component suitable for cracking the feedstock hydrocarbons; and b) a composition comprising: (i) an acidic oxide support; and (ii) 0.0001 to 10 parts by weight (measured as a metal) of a transition metal of Group VIII of the Periodic Table or a salt thereof per 100 parts by weight of the acidic oxide support.

The invention also gives a method of reducing NO_x emissions during fluid catalytic cracking of a hydrocarbon feedstock into lower molecular weight components, comprising contacting the feedstock with a cracking catalyst at elevated temperature wherein said cracking catalyst comprises:

(a) a component suitable for cracking the feedstock hydrocarbons; and (b) a composition comprising: (i) an acidic oxide support; and (ii) 0.0001 to 10 parts by weight (measured as a metal) of a transition metal of Group VIII of the Periodic Table or a salt thereof per 100 parts by weight of the acidic oxide support.

The above described compositions may further contain a metal oxide having oxygen storage capability. The acidic oxide support may comprise one or more of the following species: alumina and an aluminosilicate.

The Group VIII transition metal is preferably rhodium or iridiu , or a salt thereof.

Detailed Description of the Invention

The inventors have surprisingly found that the compositions of the present invention comprising a Group VIII transition metal or salt thereof on an acidic oxide support, without the presence of CO (oxidation) promoters, show superior NO_x reduction performance over the additives of the prior art.

The composition of the present invention is preferably in particulate form; preferably the particles have a size of from 10 to 500 μm, for example 20 to 200 μm.

The acidic oxide support of the present invention can be crystalline or amorphous and preferably comprises an alumina, [such as γ-alumina, or CPBase-alumina (of GRACE Davison)], or an aluminosilicate, [for example kaolin or a zeolite such as H-ZSM-5]. Alumina supports are preferred, in particular CPBase-alumina. Details regarding the characteristics of CPBase-alumina are given below:

Further, the support should have a surface area sufficient to promote the NO_x reduction process, for example of at least 50 m²/g, for example of from 70 to 200 m²/g.

The transition metal of Group VIII of the periodic table or salt thereof, may be any of iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium or platinum or mixtures thereof. Rhodium and iridium are preferred and iridium is particularly preferred. The transition metal, or salt thereof, is present in an amount of from 0.0001 to 10, for example from 0.0001 to 5, from 0.1 to 0.5, from 0.05 to 0.1 or from 0.01 to •0.1 parts by weight of the transition metal per 100 parts by weight of the acidic oxide support.

The composition may optionally further comprise a metal oxide having oxygen storage capability. The metal oxide may be any non-stoichiometric metal oxide which possess oxygen storage capability. Preferably the metal oxide comprises ceria. The metal oxide is preferably present as a microdispersed phase. The metal oxide is preferably present in an amount of from 2 to 50, for example from 10 to 20, parts by weight of the metal per 100 parts of the acidic oxide support.

The composition of the present invention may contain minor amounts of other materials that do not significantly affect its capability to reduce NO_x. For use in an FCC process, the composition may be combined with fillers (such as clay, silica, alumina or aluminosilicate particles) and/or binders (such as silica sol, alumina sol, aluminosilicate sol).

The present composition may be used either as an integral part of the FCC catalyst particles themselves or as separate admixture particles in the FCC catalyst inventory. WTien the present composition is used as a separate admixture, the additive particles preferably have a size of from 10 to 500 μm, for example 20 to 200 μm and contain the present composition in an amount of from 25 to 100%, for example of at least 50%, preferably of at least 75%, more preferably in an amount of 100%. Alternatively, the present composition may be used as an integral part of the FCC catalyst particles in which case any conventional FCC catalyst components may be mixed with the present composition. In such a case, the present composition is preferably present in an amount of greater than 0.02 wt %, preferably from 0.1 to 15 wt %.

The invention is not limited to any particular process of manufacture, however the present composition is preferably made by the following method: a) impregnate the acidic oxide support particles with a source of a Group VIII transition metal, or salt thereof (for example by wet incipient impregnation methods) to obtain the required metal loading; and b) calcine the impregnated support of step a).

In the case that the composition further comprises metal oxide having oxygen storage capability, step a) is preceded with steps al) and a2):

al) impregnate the acidic oxide with a source of the metal oxide; and a2) calcine the impregnated support of step al).

The sources of Group VIII transition metals [step a)] are preferably solutions of the salts of the transition metals. For example, a suitable source of iridium is an organic solution of Ir ex acac or an aqueous solution of IrCl₃. A suitable source of rhodium is an aqueous solution of RhGl₃. Sources of the metal oxide [step al)] are preferably slurries, sols and/or solutions of the metal oxides themselves or salts of the metal which decompose to form the oxides during step a2). For example, a suitable source of ceria is Ce(NO₃)₃. The impregnated samples are then preferably dried in an oven before being calcined. Drying is carried out for from 1 to 12 hours, typically 10 hours at a temperature of from 80 to 250°C, for example at from about 110 to about 150 °C .

Calcination step b) is preferably carried out in air at from 350 to 750 °C, for example at around 600, 650 or 700 °C for between 2 to 10 hours, for example for 3, 6 or 9 hours. Calcination step a2) is carried out in air at from 450 to 550 °C, for example at 500 ^°C, for between 2 to 4 hours, for example for 3 hours. The composition particles produced by the above method may be used directly or may subsequently be mixed with binders and/or fillers by any conventional technique and used as separate admixture particles in the FCC catalyst inventory. Alternatively, the composition particles may be incorporated into the FCC catalyst particles by any known technique to form an integral part of the FCC catalyst particles.

The compositions of the present invention may be used in any conventional FCC process for processing of any typical hydrocarbon feedstock. FCC processes are typically carried out at temperatures of from 450 to 600 °C and catalyst regeneration temperatures of from 600 to 850 °C. The present composition is preferably present in an amount of from 0.1 to 15 wt% based on the weight of the FCC catalyst present in the inventory.

The compositions of the present invention may used alongside other emission reducing additives, such as additives to reduce NO_x, CO or SO_x emissions, for example DENOχ, XNOχ. Such additives may be present as separate additives, be present within the particles of the present composition or be present within the FCC catalyst particulate (which optionally comprises the present composition).

Examples The following acidic oxide supports were manufactured as detailed in Table 1.

Table 1 Examples of the present composition are given in Table 2.

Table 2 Compositions of the present invention (present in the inventory at a concentration of 0.5 wt %) were tested in CPERI FCC pilot plant using an equilibrium FCC catalyst. This plant features a circulating riser operating with a conversion of 72-77 %wt, a catalyst/oil (C/O) ratio of 10-16, a riser temperature of 537-548 °C, a regenerator temperature of from 693-704 °C and a catalyst inventory of 3500-4000g. Emissions were compared to those produced when a standard CO (combustion) promoter is used - in this case CP-3™ (of Grace Davison). The results are shown in Table 3.

*negative sign indicates a decrease in emissions compared to the base.

Table 3

Claims

1. A composition suitable for use in a fluidised catalytic cracking process comprising: (i) an acidic oxide support; and (ii) 0.0001 to 10 parts by weight (measured as a metal) of a transition metal of Group VIII of the Periodic Table, or a salt thereof, per 100 parts by weight of the acidic oxide support.

2. Composition according to claim 1 wherein the acidic oxide support comprises one or more of the following species: i) an alumina; and ii) an aluminosilicate.

3. Composition according to claim 1 or 2 wherein the acidic oxide support comprises alumina.

4. Composition according to any one of the previous claims wherein the Group VIII transition metal is iridium or rhodium, or a salt thereof.

5. Composition according to any one of the previous claims wherein the transition metal of Group VIII of the Periodic Table or a salt thereof is present in an amount of from 0.01 to 0.1 % by weight.

6. Composition according to any one of the previous claims, which further comprises a metal oxide having oxygen storage capability.

7. Composition according to claim 6 wherein the metal oxide is ceria.

8. Composition according to anyone of the previous claims wherein said composition is in particulate form, the particles of the particulate composition having a size of from 10 to 500 μm.

9. A fluid cracking catalyst, which comprises: a) a component suitable for cracking the feedstock hydrocarbons; and b) a composition as defined in any one of claims 1 to 8.

10. Catalyst according to claim 9 wherein said catalyst comprises an admixture of particles of component a) and particles of component b).

11. Catalyst according to claim 9 wherein said catalyst is in particulate form and the particles of the catalyst comprise integral particles which contain both components a) and b).

12. Catalyst according to any one of claims 9 to 11 wherein catalyst comprises component b) in an amount of from 0.1 to 15 % by weight.

13. Catalyst according to any one of claims 9 to 12 wherein the catalyst further comprises: c) one or more emission reducing additives.

14. Catalyst according to claim 13 wherein the one or more emission reducing additives of component c) reduce NO_x, CO and/or SO_x emissions.

15. Catalyst according to claim 13 or 14 wherein the catalyst is in particulate form and component c) is present: - in an admixture of particles of components a), b) and c); - as an integral part of the particles which contain either component a) or b); or - in integral particles which contain components a), b) and c).

16. Method of reducing NO_x emissions during fluid catalytic cracking of a hydrocarbon feedstock into lower molecular weight components, comprising contacting the feedstock with a cracking catalyst as defined in any one of claims 9 to 15 at elevated temperature.

7. A composition according to any of claims 1 to 8 for use as an integral part of a catalyst for a fluidised catalytic cracking process or as separate admixture particles in a fluidised catalytic cracking process.