HK1098982A - Nox reduction composition for use in fcc processes - Google Patents

Description

NO for FCC processesxReduction composition

Background

One major industrial problem involves developing effective methods to reduce the concentration of gaseous pollutants, such as carbon monoxide, sulfur oxides, and nitrogen oxides, in waste gas streams resulting from the treatment and combustion of sulfur, carbon, and nitrogen-containing fuels. It is environmentally undesirable to vent these waste gas streams to the atmosphere at concentrations at which carbon monoxide, sulfur oxides and nitrogen oxides are often present in conventional operation. Regeneration of cracking catalysts that have been deactivated by coke deposition in the catalytic cracking of sulfur and nitrogen containing hydrocarbon feedstocks is a typical example of a process that may produce an exhaust gas stream containing relatively high levels of carbon monoxide, sulfur oxides, and nitrogen oxides.

Catalytic cracking of heavy petroleum fractions is one of the major refining operations employed in the conversion of crude petroleum to useful products such as fuels for internal combustion engines. In the fluid catalytic cracking process, high molecular weight liquid and gaseous hydrocarbons are contacted with finely divided hot solid catalyst particles in a fluidized bed reactor or in an elongated riser reactor and maintained in a fluidized or dispersed state at elevated temperatures for a period of time to crack to the desired degree to lower molecular weight hydrocarbons of the type typically found in motor gasoline and distillate fuels.

In the catalytic cracking of hydrocarbons, certain nonvolatile carbonaceous materials or coke are deposited onto catalyst particles. Coke comprises highly condensed aromatic hydrocarbons and typically contains from about 4 to about 10 weight percent hydrogen. When the hydrocarbon feedstock contains organic sulfur and nitrogen compounds, the coke also contains sulfur and nitrogen. When coke builds up on the cracking catalyst, both the cracking activity of the catalyst and the selectivity for producing a gasoline blendstock are reduced.

Catalyst that has become substantially deactivated by coke deposition is continuously released from the reaction zone. The catalyst is passed to a stripping zone where volatile deposits are carried away by an inert gas at elevated temperatures. The catalyst particles are then substantially restored to their original capacity by sufficient removal of coke deposits in a suitable regeneration process. The regenerated catalyst is then continuously returned to the reaction zone, thereby repeating the cycle.

Catalyst regeneration is accomplished by burning off coke deposits from the catalyst surface with an oxygen-containing gas, such as air. The combustion of these coke deposits can be viewed simply as the oxidation of carbon and the products are carbon monoxide and carbon dioxide.

When sulfur and nitrogen containing feedstocks are used in catalytic cracking processes, the coke deposited on the catalyst contains sulfur and nitrogen. During regeneration of coked deactivated catalyst, burning of the coke off the catalyst surface can subsequently result in the conversion of sulfur to sulfur oxides and the conversion of nitrogen to nitrogen oxides.

The conditions experienced by the catalyst in a Fluid Catalytic Cracking (FCC) unit are very severe. The catalyst is continuously circulated between the reducing atmosphere on the reactor side and the oxidizing atmosphere on the regenerator side. The temperature between these two zones is different so the catalyst will experience a thermal shock. And the regenerator contains about 15-25% steam. All of these factors result in a significant decrease in catalyst activity, requiring continuous addition of fresh catalyst to maintain cracking activity.

Various approaches have been utilized to reduce or treat the formation of harmful gases after their formation. Most typically, additives have been used as an integral part of the FCC catalyst particles or as separate particles mixed with the FCC catalyst.

The additives that have achieved the most widespread acceptance to date for reducing the release of sulphur oxides in FCC units (FCCU) are based on magnesia/magnesium aluminate/ceria technology. Pt-loaded clays or aluminas are most commonly used as additives for reducing carbon monoxide emissions. Unfortunately, additives used to control CO release often result in regeneratorsNO of_xThe release increased dramatically (e.g., > 300%).

Various schemes have been utilized to treat the nitrogen oxide gas in the FCCU. For example, US 5,037,538 describes the removal of NO by adding to an FCC regenerator_xCatalyst to reduce Nitrogen Oxide (NO) in FCC regenerator_x) Release of NO therein_xThe catalyst remains isolated within the FCC regenerator.

US 5,085,762 describes the reduction of harmful nitric oxide emissions with the off-gas of a fluidized catalytic cracking unit regenerator by incorporating into the cracking catalyst recycle stream individual additive particles containing a copper-loaded zeolite material having the characteristic structure of a defined X-ray diffraction pattern.

U.S. Pat. No.5,002,654 describes the NO reduction using a zinc base_xCatalytic reduction of NO_xA method for regenerating a cracking catalyst while minimizing the release of the cracking catalyst.

US 5,021,146 describes the NO removal in the use of group IIIb groups_xAdditive to make NO_xA method for regenerating a cracking catalyst while minimizing the release of the cracking catalyst.

US 5,364,517 describes the use of spinel/perovskite additives to reduce NO in FCC regenerator off-gas_xAnd (4) content.

US 5,750,020 and US 5,591,418 describe a process for removing sulfur oxides or nitrogen oxides from a gas mixture of an FCC process using a collapse composition (collapsedcomposition) consisting essentially of crystallites which are each of the formula:

M_2m ²⁺Al_2-pM_p ³⁺T_rO_7+r-s

wherein M is²⁺Is a divalent metal, M³⁺Is a trivalent metal and T is vanadium, tungsten or molybdenum.

US 6,165,933 describes a composition comprising components comprising (i) an acidic oxide support, (ii) an alkali and/or alkaline earth metal or mixtures thereof, (iii) a transition metal oxide having oxygen storage capacity and (iv) palladium, in the presence of NO_xWhile forming a minimum, it promotes CO combustion in the FCC process.

US 6,129,834 and US 6,143,167 describe compositions comprising a component comprising (i) an acidic oxide support, (ii) an alkali and/or alkaline earth metal or mixtures thereof, (iii) a transition metal oxide having oxygen storage capability, and (iv) a transition metal selected from group Ib and/or group lib of the periodic table, which controls NO in an FCC process_xThe performance of (c).

Co-pending, commonly assigned U.S. patent application No.10/001,485, publication No. US20030098259, describes a composition comprising components comprising (i) an acidic oxide support, (ii) ceria, (iii) at least one oxide of a lanthanide series element other than ceria, and (iv) a transition metal oxide selected from group Ib or IIb, e.g., Cu and Ag, which controls NO in an FCC process_xThe performance of (c).

All additives added to the FCC unit must have sufficient hydrothermal stability to withstand the harsh environment of the FCCU. NO with improved hydrothermal stability for use in FCC_xThere remains a need for additives.

Disclosure of Invention

The present invention provides novel compositions suitable for use in FCC processes which provide improved NO_xAnd controlling the performance.

In one aspect, the present invention provides methods for reducing NO in FCC processes_xA delivery composition comprising a mixed oxide of cerium and zirconium and optionally at least one oxide of a rare earth element other than cerium. The composition may also comprise at least one oxide of a transition metal selected from groups Ib and IIb of the periodic Table. The mixed oxide is preferably spray dried into microspheres suitable for use in an FCC process and impregnated with a transition metal oxide as a salt of the selected metal either before or after microsphere formation.

In another aspect, the invention includes an FCC process using the NO of the invention_xThe reduction composition is provided as an integral part of the FCC catalyst particles or as separate particles mixed with the FCC catalyst.

These and other aspects of the invention are described in detail below.

Detailed Description

The present invention relates to this finding: certain classes of compositions are useful for reducing NO in FCC processes_xThe gas release is very efficient. Moreover, such compositions unexpectedly have better hydrothermal stability than existing compositions.

NO of the invention_xThe reducing composition is characterized by comprising a mixed oxide of cerium and zirconium and optionally an oxide of a rare earth element other than cerium. Preferred oxides of rare earth elements other than cerium are oxides of La, Nd and Pr. In addition, at least one transition metal oxide selected from metals of groups Ib and IIb of the periodic Table or a mixture thereof may be included in the composition of the present invention. The mixed oxide should contain at least 20 wt.% cerium and at least 15 wt.% zirconium. The NO is_xThe abating additive composition comprises at least 20 wt%, typically at least 60 wt% ceria-zirconia and up to about 20 wt% of an oxide of a non-cerium rare earth element. The NO is_xThe reducing additive composition generally comprises at least 40 wt%, generally at least 55 wt% of (i), (ii) and (iii).

Mixed oxides of cerium and zirconium and other optional rare earth oxides have found wide use in automotive exhaust applications. Examples are described in commonly assigned U.S. patent nos. 4,624,940 and 5,057,483 and U.S. patent application publication No. 2003/0100447. U.S. patent No.5,057,483 describes that the co-formed rare earth oxide-zirconia composition can be made by any suitable technique, such as co-precipitation, co-gelation, and the like. One suitable technique is listed in the articles Luccii, E., Mariani, S. and Sbaazero, O., "Preparation of zirconium Ceium carbide in Water with Urea", Int.J. of materials and Product Technology, 4, 167-. As disclosed in this article starting on page 169, a proportion ofDiluted distilled water solution (0.1M) of zirconium oxychloride and cerium nitrate, with ammonium nitrate added as a buffer to control pH, to form ZrO as a final product₂-10mol％CeO₂. Under continuous stirring for 2 hours, the solution boils; and at any stage the pH is kept at no more than 6.5, achieving complete precipitation.

Other techniques for preparing mixed oxide formulations of ceria-zirconia and optionally other rare earth oxides are described in U.S. patent nos. 6,528,029, 6,133,194 and 6,576,207, the contents of which are incorporated herein by reference.

Any other suitable technique for preparing the co-formed rare earth oxide-zirconia may be employed so long as the resulting product comprises the rare earth oxide completely dispersed in and/or in solid solution with the zirconia in the final product. Thus, for the above-described co-precipitation methods, the zirconium salt and the cerium salt (or other rare earth metal salts) may include chlorides, sulfates, nitrates, acetates, and the like. The co-precipitate may be spray dried to remove moisture after washing, and then calcined in air at about 500 ℃ to form a co-formed rare earth oxide-zirconia mixed oxide composition.

The group Ib and/or IIb transition metal may be any metal or combination of metals selected from these groups of the periodic table. Preferably, the transition metal is selected from Cu, Ag, Zn or mixtures thereof. The transition metal is preferably present in an amount of at least about 100 parts by weight (measured as metal oxide) per million parts of NO_xAn additive reduction agent, more preferably at least about 0.1 to about 5 parts by weight per million parts by weight NO_xAnd reducing the additive.

When the mixed oxide is used as a single particle in NO_xWhen reduced in composition, the oxide can be formed into microspheres useful in FCC processes by conventional methods. Thus, the compositions of the invention may be combined with fillers (e.g., kaolin, clay, silica-alumina, silica and/or alumina particles) and/or binders (e.g., silica sol, alumina sol, silica alumina sol, etc.), preferably by spray drying, and, if desired, subsequent calcination to form a suitable binderThe particles used in the FCC process. Preferably, any added binder or filler does not significantly adversely affect NO_xReducing the performance of the components. The size of the additive particles is preferably suitable for circulation with the catalyst inventory in the FCC process. The microspheres comprising the mixed oxide composition are typically 20-200 microns and can be effectively used in an FCC process. The additive particles preferably have attrition characteristics so that they can withstand the harsh environment of the FCCU. Microsphere sizes of 50-100 microns may be more typical in FCC applications.

When NO is present_xWhen the composition is used as an additive particle (rather than as an integral part of an FCC catalyst particle), NO is reduced_xThe amount of the reducing component in the additive particles is preferably at least 30 wt%, more preferably at least 55 wt%. It is desirable to make NO_xThe amount of active ingredient in the additive granules is reduced to a maximum. However, small amounts of fillers and/or binders are generally required to form the mixed oxide composition into microspheres. NO formed by cerium oxide_xThe amount in the reducing composition may vary considerably. Preferably, NO_xThe reducing composition comprises at least about 0.5 parts by weight of ceria per 100 parts by weight of the final formed additive, more preferably at least 1 to about 20 parts by weight of ceria per 100 parts by weight of the final additive composition.

As mentioned earlier, NO according to the invention_xThe reduction composition may itself be an integral part of the FCC catalyst particles. Such catalyst particles typically comprise a zeolite cracking catalyst, such as synthetic faujasite, including zeolite Y or X, or other known zeolite cracking catalysts, such as those of the ZSM-5 series. In this case, any conventional FCC catalyst particle component can be used with the NO of the present invention_xThe combination of the compositions is reduced. NO of the invention if it is an integral part of FCC catalyst particles_xThe reduction composition is preferably at least about 0.02 wt%, more preferably from about 0.1 to 10 wt% of the FCC catalyst particles. NO can be converted by any known technique_xThe reduction composition is incorporated directly into FCC catalyst particles. Examples of suitable techniques for this purpose are disclosed in U.S. Pat. Nos. 3,957,689, No.4,499,197, No.4,542,188 and No.4,458,623, the disclosures of which are incorporated herein by reference.

Although the present invention is not limited to any particular preparation method, NO of the present invention_xThe reduction composition is preferably prepared by the following steps:

(I) (a) spray-drying a slurry comprising a mixed oxide comprising ceria, optionally kaolin as filler and silica, alumina or silica-alumina sol as binder, and a nitrate of a group Ib or lib element;

(b) calcining the spray-dried microspheres.

(II) (a) spray-drying a slurry comprising a mixed oxide comprising ceria, optionally kaolin as filler and a silica sol, aluminium sol or silica-alumina sol as binder;

(b) calcining the spray-dried microspheres;

(c) impregnating the spray dried microspheres with a nitrate of a group Ib or IIb element;

(d) the impregnated and spray dried microspheres are calcined.

(III) (a) spray-drying a slurry comprising a cracking catalyst comprising a mixed oxide of ceria, for example zeolite Y, optionally kaolin as filler and a silica, alumina or silica alumina sol as binder;

(b) adding a nitrate of a group Ib or IIb element to the slurry of (a);

(c) the impregnated and spray dried microspheres are calcined.

It is apparent that other alternative preparation methods known or suggested to those skilled in the art may be used to form the NO of the present invention_xThe composition is reduced.

The compositions of the present invention can be used in any conventional FCC process. Typical FCC processes are catalyzed at a reaction temperature of 450-650 ℃ and a temperature of 600-850 DEG CAt the regeneration temperature of the agent. The compositions of the present invention may be used in any typical FCC processing of hydrocarbon feedstocks. Preferably, the compositions of the present invention can be used in FCC processes that include cracking hydrocarbon feedstocks that contain nitrogen above average, particularly those residual feedstocks or feedstocks having a nitrogen content of at least 0.1 wt%. According to the particular FCC process, NO of the present invention_xThe amount of the reducing component may vary. Preferably, NO_xThe amount of the reducing component (in the recycle stream) is from about 0.1 wt% to about 15 wt% based on the weight of the FCC catalyst in the recycle catalyst stream. The presence of the composition of the invention during the catalyst regeneration step of the FCC process significantly reduces the NO released during the regeneration process_xAmount, and at the same time hydrothermal stability is improved.

The following examples are intended to illustrate the invention and should not be construed as strictly limiting the invention to the embodiments shown.

Example 1

20% ceria-80% zirconia

A mixed oxide consisting of 20% ceria and 80% zirconia was granulated and pulverized and sieved to a size where all particles could pass through 40 mesh and could not pass through 170 mesh.

Example 2

20% ceria-80% zirconia

An aqueous slurry consisting of 60 wt% of a commercial mixed oxide as in example 1, containing 20% ceria-80% zirconia mixed oxide was mixed with 20% kaolin filler and 20% alumina sol binder and spray dried to microspheres. The microspheres were calcined at 1200 f 1200 ℉ for 2 hours. The final additive composition contained 12 wt% ceria.

Example 3

A slurry consisting of 60 wt% of the commercial mixed oxide used in examples 1 and 2, 2 wt% copper oxide (based on salt) was mixed with 18% kaolin filler and 20% alumina sol binder and spray dried to microspheres. The microspheres were calcined at 1200 f 1200 ℉ for 2 hours. The final additive composition comprised 12 wt% ceria and 2 wt% copper oxide.

Example 4

20％CeO₂/6％La₂O₃/6％Nd₂O₃68% zirconium oxide

Will consist of 20 wt% CeO₂、6wt％La₂O₃、6wt％Nd₂O₃And 68 wt% zirconia, and pulverizing and sieving to a size such that all particles can pass through 40 mesh and cannot pass through 170 mesh.

Example 5

29.5％CeO₂/0.9％La₂O₃/8％Nd₂O₃/8％Pr₆O₁₁53.6% zirconium oxide

Will consist of 29.5 wt% ceria, 0.9% La₂O₃、8％Nd₂O₃、8％Pr₆O₁₁And the balance zirconia, and pulverizing and sieving to a size such that all particles can pass through 40 mesh and cannot pass through 170 mesh.

Example 6

70％CeO₂/15％La₂O₃15% zirconium oxide

Will consist of 70 wt% ceria, 15% La₂O₃And the balance zirconia, and pulverizing and sieving to a size such that all particles can pass through 40 mesh and cannot pass through 170 mesh.

Example 7

20％CeO₂/6％La₂O₃/6％Nd₂O₃68% zirconium oxide

Will consist of 20 wt% ceria, 6% La₂O₃、6％Nd₂O₃The balance ofThe mixed oxide composed of zirconia was granulated and crushed and sieved to a size such that all particles could pass through 40 mesh and could not pass through 170 mesh.

Comparative examples

Example A

100％CeO₂

The ceria was granulated and crushed and sieved to a size where all particles could pass through 40 mesh and could not pass through 170 mesh.

Example B

100% zirconium oxide

The zirconia was granulated and crushed and sieved to a size where all particles passed 40 mesh and failed 170 mesh.

Example 8

As previously mentioned, hydrothermal stability is an important property of FCC catalysts and additives. Different methods are known in the art to accelerate experimental scale hydrothermal deactivation of FCC catalysts and additives. The most common method for laboratory scale hydrothermal deactivation is to distill the catalyst or additive at a temperature of 1300 ℉ -1500 ℉ in the presence of 100% steam for 4-8 hours.

The additives listed in table 1 below were deactivated by steaming at 1500 ℉ for 4 hours at 100% water vapor. The surface areas of the fresh and deactivated additives were measured according to the standard BET method. After reduction with hydrogen at 1000 ℉, the NO uptake (uptake) on the additive was measured at room temperature. Table 1 below shows the surface area and NO uptake data. The remaining surface area is the percentage of surface area remaining after steaming. The remaining NO uptake rate is the percentage of the remaining NO uptake capacity after steaming.

It can be seen that examples 1 and 4-7 within the scope of the present invention have greater residual NO uptake and surface area stability relative to comparative examples a and B. The test results are particularly unexpected as 100% zirconia results in a steamed material with NO uptake capacity.

TABLE 1

	NO uptake x 105mol/g	Surface area, m2/g	Residual surface area,% (after steaming)	Residual NO uptake,% (after steaming)
					Example A	23.3	155	7	13
Example B	0.0	102	12	N.A.
					Example 1	25.1	51.1	56	59
Example 4	29.5	64.2	56	69
					Example 5	26.4	59.7	71	63
Example 6	56.1	90.0	48	57
					Example 7	29.5	83.5	72	69

Claims (10)

1. Method for reducing NO in catalyst regeneration process in fluid catalytic cracking process_xReleased NO elimination_xA composition comprising microspheres having an average size of about 20 to 200 microns and comprising (i) a mixed oxide of cerium and zirconium, (ii) optionally an oxide of a non-cerium lanthanide, and (iii) optionally at least one oxide selected from group Ib and IIb transition metals of the periodic table or mixtures thereof.

2. The composition as claimed in claim 1, wherein the mixed oxide (i) comprises at least 20% by weight of ceria and at least 15% by weight of zirconia.

3. The composition of claim 2, wherein the mixed oxide (i) is present in an amount of at least 70 wt% relative to the total of (i), (ii), and (iii).

4. The composition of claim 1, wherein the at least one transition metal oxide (iii) is copper oxide.

5. Reduction of NO in fluidized catalytic cracking of hydrocarbon feedstocks to lower molecular weight components_xA process for liberation comprising contacting a hydrocarbon feedstock with a cracking catalyst suitable for catalyzing the cracking of hydrocarbons at elevated temperature in the presence of NO_xReducing contact in the presence of the composition, thereby forming a low molecular weight hydrocarbon component; wherein said NO_xThe reduction composition comprises (i) a mixed oxide of cerium and zirconium, (ii) optionally at least one oxide of a non-cerium lanthanide, and (iii) optionally an oxide of a transition metal selected from groups Ib and IIb of the periodic Table, said NO_xReduction of components to substantially reduce NO_xIs present in an amount.

6. The process of claim 5 wherein the cracking catalyst and NO_xThe reduction composition is a separate particle.

7. The process of claim 5 wherein the cracking catalyst and NO_xAbatement composition as cracking catalyst component and NO_xReducing the presence of single particles of the overall combination of components of the composition.

8. The process of claim 5 wherein the mixed oxide (i) comprises at least 20 wt.% ceria and at least 15 wt.% zirconia.

9. The method of claim 5, wherein said NO_xThe reduction composition comprises (iii) copper oxide.

10. The method of claim 5, wherein (ii) comprises an oxide of La, Nd, Pr, or mixtures thereof.