Patent Application
20070060780
The present invention is related to the catalytic production of light olefins.
In recent years, there has been a tendency to utilize the fluid catalytic cracking process, not as a gasoline producer, but as a process to make light olefins for use as petrochemical materials or as building blocks for gasoline blending components, such as MTBE and alkylate.
The traditional method for the production of light olefins, such as ethylene, propylene, and butylene, from petroleum hydrocarbon is tubular furnace pyrolysis or pyrolysis over heat carrier or by catalytic conversion of lower aliphatic alcohol. More recently, the fluid catalytic cracking process employing small pore zeolite additives from the pentasil family is being used for the same at modern refinery. The small pore zeolite additives can be prepared as described in several patents (e.g. U.S. Pat. No. 5,472,594, or WO98/41595).
Further descriptions of the production of light olefins by cracking processes are given in U.S. Pat. No. 3,541,179 and JP No. 60-222 428.
The small pore zeolite additives are applied at the refinery by blending with the FCC host catalyst typically at 1-5 wt-% concentration. The obtained light olefin increase depends on the effectiveness of the additive, on the base catalyst formulation, feed type, and FCC process conditions, such as residence time and temperature. However, if the refiner targets a light olefin concentration, which is higher than that obtained at 1-5 wt-% intake of the small pore zeolite additive, usually the overall performance will start to deteriorate. This is because of a dilution of the host catalyst and increase in the bottoms conversion and saturation of the light olefins yield.
In one embodiment, the present invention is a catalyst composition comprising a pentasil type of zeolite, one or more solid acidic promoters, and an additional material selected from the group consisting of anionic clay, smectite clay, and thermally or chemically modified clay (including kaolins and flash calcined gibbsite) and, optionally, a filler and/or binder.
In a second embodiment, the present invention is a method of making the above catalyst composition, wherein an aqueous slurry comprising the pentasil-type zeolite, solid acidic cracking promoter and the additional material is prepared and dried.
In a third embodiment, the present invention is a process for producing olefins having up to about 6 carbon atoms per molecule, comprising contacting a petroleum feedstock at fluid catalytic cracking conditions with the above catalyst composition.
Other embodiments of the invention relate to details concerning catalyst composition, making the catalyst composition and use of the composition in making olefins.
The present invention describes FCC catalyst and catalyst/additive systems, which can be used to produce higher concentrations of olefins, particularly propylene, than obtained with the conventional additive systems as described above, and at the same time achieving high bottoms conversion. The systems are designed to function also in the processing of heavier feeds, which are especially sensitive to the dilution effects when using the conventional catalyst/additive systems at higher additive concentrations. The systems of this invention do not suffer from the dilution of the active ingredients and deterioration of the overall performance.
Particular achievements of the invention are: 1) Effective ex-situ stabilization and/or modification of the small pore zeolite(s) in an additive/host and in catalyst particle system, in the presence of other active catalyst ingredients; 2) Design of the additive/host and one particle catalyst system, which are highly active in upgrading the bottoms in gasoline and gas. The upgraded gasoline components are olefinic in nature. The active ingredients of the catalyst composition are selected in such a way that occurrence of hydrogen transfer and aromatization reactions, which are detrimental to the production of light olefins, are minimized; and 3) The additive/host or the one particle system, as prepared according to this patent, exhibits high bottoms conversion, in particular when very high quantities of the small pore zeolite are used in the blend.
The present invention describes catalyst compositions which exhibit improved activities and selectivities, as compared to the catalysts described in the prior art, for producing higher yields of light olefins, LCO, and gasoline, with minimum activities for hydrogen transfer reactions.
This invention involves the use of certain modified forms of pentasil-type zeolites (metalloaluminosilicates) components together with one or more acidic cracking promoter components and an additional material selected from the group consisting of anionic clay, smectite clay, and thermally or chemically modified clay (including kaolins and flash calcined gibbsite) with the option of including binders, fillers, extenders, etc., incorporated in a catalytic particle.
In contrast to the prior art, this invention does not depend on the use of traditional Rare Earth Y (REY, REHY, REUSY, REMgY) used in commercial FCC products. Use of these zeolites decreases olefin yields because of the high hydrogen transfer reaction activities.
Catalyst Composition of the Invention
As stated above, the catalyst composition of the invention comprises a pentasil-type of zeolite, one or more solid acidic cracking promoters and an additional material selected from the group consisting of anionic clay, smectite clay, and thermally or chemically modified clay (including kaolins and flash calcined gibbsite) and, optionally, a filler and/or binder. The pentasil-type of zeolite may comprise: 1) zeolite selected from the group consisting of ITQ-type zeolite, beta zeolite and silicalite; 2) ZSM-type zeolite; 3) pentasil zeolite doped with a compound comprising a metal ion selected from the group consisting of ions of alkaline earth metals, transition metals, rare earth metals, phosphorous, boron, aluminum, noble metals and combinations thereof; or 4) crystals having metals in tetrahedral coordination in the crystals selected from the group consisting of Al, As, B, Be, Co, Cr, Fe, Ga, Hf. In, Mg, Mn, Ni, P, Si, Ti, V, Zn, Zr and mixtures thereof.
The solid acidic cracking promoter in the catalyst composition of the invention may be selected from the group consisting of alumina modified by incorporation of acid centers thereon or therein, acidic silica-alumina co-gels, acidic natural or synthetic clays, acidic titania, acidic zirconia, acidic titania-alumina, acidic zeolite materials and co-gels of titania, alumina, zirconia, phosphates, borates, aluminophosphates, tungstates, molybdates and mixtures thereof. The acid centers may be selected from the group consisting of halides, sulfates, nitrates, titanates, zirconates, phosphates, borates, silicates and mixtures thereof. The solid acidic cracking promoter may comprise acidic silica-alumina, titania-alumina, titania/zirconia, alumina/zirconia or aluminum phosphate co-gels modified by the incorporation therein of metal ions or compounds selected from the group consisting of alkaline earth metals, transition metals, rare earth metals and mixtures thereof. The acidic silica-alumina co-gels may have been subjected to hydrothermal treatment.
The acidic natural or synthetic clays may have been modified by calcining, steaming, dealumination, desilification, ion exchange, pillaring exfoliation or combinations thereof.
The acidic titania, acidic zirconia, or both may be doped with sulfates, vanadates, phosphates, tungstates, borates, iron, rare earth metals or mixtures thereof.
The acidic zeolite materials may be selected from the group consisting of mordenite, zeolite Beta, NaY zeolite and USY zeolite that is dealuminated or ion exchanged with transition metals or both. The preferred transition metal is vanadium.
In the catalyst composition of the invention, the solid acidic cracking promoter may comprise a co-gel of alumina-aluminum-phosphate or aluminum phosphate that has been doped with an acidic compound.
The catalyst composition of the invention may comprise one or more additional materials selected from the group consisting of particle binders, diluents, fillers and extenders. The pentasil-type zeolite is a pentasil type of zeolite may comprise from about 5.0 wt % to about 80 wt % of the composition. The composition may comprise particles having average lengths along their major axis of from about 30 microns to about 150 microns. The weight ratio of said pentasil-type zeolite to solid acidic cracking promoter in the catalyst composition of the invention may be from about 0.03 to about 9.0.
The solid acidic cracking promoter in the composition may comprise from about 5.0 wt % to about 80 wt % of the composition.
The catalyst composition of the invention may comprise particles having average lengths along their major axis of from about 20 microns to about 200 microns.
The Modified Forms of Pentasil-Type Zeolite
For clarity and simplicity, and to distinguish from the ZSMs known in the art, the modified pentasil zeolites, prepared according to this invention are identified as MPZ-(ZSMs). For example, some of thel types of pentasil zeolites used in the invention involve, but are not limited to, ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, zeolite beta, zeolite boron beta, which are described in U.S. Pat. Nos. 3,308,069; 3,702,886; 3,709,979; 3,832,449; 4,016,245; 4,788,169; 3,941,871; 5,013,537; 4,851,602; 4,564,511; 5,137,706; 4,962,266; 4,329,328; 5,354,719; 5,365,002; 5,064,793; 5,409,685; 5,466,432; 4,968,650; 5,158,757; 5,273,737; 4,935,561; 4,299,808; 4,405,502; 4,363,718; 4,732,747; 4,828,812; 5,466,835; 5,374,747; 5,354,875; incorporated herein by reference. Metals in tetrahedra coordination in the zeolite crystals include: AL, AS, B, Be, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, P, Si, Ti, V, Zn, Zr.
Modified forms of pentasil-type zeolites (here and after referred to as MPZs) such as ZSMs, Beta and so on, briefly involve doping said zeolites with metal ions such as, but not limited to alkaline earth, transition metals, rare earth metals, phosphorous, boron, aluminum. The MPZ zeolites can be mixed with regular pentasil zeolites (i.e., ZSM, Beta, etc.) or with ion exchanged forms of pentasil zeolites, known to present state of the art such as pentasil zeolites exchanged with transition metals.
The pentasil zeolite may be doped with a compound comprising a metal ion selected from the group consisting of ions of alkaline earth metals, transition metals, rare earth metals, phosphorous, boron, aluminum, noble metals and combinations thereof. The pentasil-type zeolite may be doped by any of the following methods: 1) ion exchange with the metal ion; 2) use of doped seeds; 3) use of doped reactants; 4) use of seeds comprising X- or Y-type zeolites that have never been ion exchanged with the metal ion; or 5) incorporating salts comprising the metal ion in a reaction mixture comprising the precursor of the pentasil-type zeolite.
Making the Catalyst of the Invention
In making the catalyst composition of the invention an aqueous slurry comprising a pentasil-type zeolite and solid acidic cracking promoter is prepared and dried. Separate aqueous slurries of the pentasil-type zeolite and solid acidic cracking promoter may be prepared, mixed together and dried. The aqueous slurry may be spray dried to obtain catalyst particles having average lengths along their major axis of from about 40 microns to about 100 microns.
The catalyst composition of the invention may comprise one or more additional materials selected from the group consisting of particle binders, diluents, fillers and extenders. This may be made by modifying pentasil-type zeolite by ion exchange with ions selected from the group consisting of ions of alkaline earth metals, transition metals, rare earth metals, phosphorous, boron, aluminum, noble metals and combinations thereof, preparing an aqueous slurry of acidic cracking promoter and other catalyst ingredients other than the modified pentasil-type zeolite, adding the modified pentasil-type zeolite to the slurry and shaping the slurry, the addition of the modified pentasil-type zeolite being carried out as a final step immediately prior to shaping. The addition of the modified pentasil-type zeolite may be carried out by mixing with the aqueous slurry until the slurry is substantially homogeneous. Shaping may be carried out by spray drying.
During the mixing of the catalyst compounds and the preparation of the catalyst slurry, there is an opportunity for cations to be leached from the zeolite. One method of limiting this process is to add the zeolite after the rest of the catalyst slurry has been prepared and mixed, and most preferably, shortly before the shape forming process, e.g., spray drying. Alternatively, NH4OH may be added to the slurry prior to the addition of the modified pentasil-type zeolite to raise the pH of the slurry. A pH buffer may also be added to the slurry prior to the addition of the modified pentasil-type zeolite. The buffer may be selected from the group consisting of aluminum chlorohydrol, phosphate sol or gel, anionic clay, smectite and thermally or chemically modified clay (including kaolins and flash calcined gibbsite). These pH buffers will be incorporated into the catalyst composition. Finally, all of these measure may be taken to limit the cations from being leached from the zeolite.
An aqueous slurry may be prepared comprising solid acidic cracking promoter, other materials and precursors of the pentasil-type zeolite comprising silica, alumina and seeds containing one or more metals from the group consisting of rare earth metals, alkaline earth metals and transition group metals, forming the aqueous slurry into shaped bodies and crystallizing the pentasil-type zeolite in situ in the shaped body.
The Acidic Cracking Promotor Components
Referred to hereinafter as ACPs, these are solid acidic materials which provide an additional higher acidic function to the catalytic cracking particle which supplements the function of the pentasil zeolite component and synergistically through the cracking process produce higher yields of light olefins (i.e., ethylene, propylene, butylene, and pentenes).
There is a large number of solid acids known in the state of the art, of which a few are described below to illustrate the scope of this invention; however, this invention is not thereby limited.
Some of the ACPs involve solid acids, solid super acids, acidic zeolites such as hydrogen modernite, dealuminated Y zeolites such as DAYs, high SAR USY dealuminated zeolites used in hydrocracking, aluminum exchanged zeolites, LZ-210, USY aluminum exchanged, transition metal ion exchanged Y, USY, DAY zeolites, alumina containing acidic ions, silica-alumina exchanged with acidic ions, titania-alumina containing acidic ions, titania-zirconia containing acidic ions, alumina-zirconia containing acidic ions, alumina-aluminum phosphates also doped with acidic ions. Modified clays, such as acid leached bentonites, as such and ion exchanged with acidic ions such as Ce, Zn, Fe, and so on, including pillared synthetic and natural clays.
ACPs also include doped alumina with acidic promoters such as, for example, boehmite doped with phosphate ions, sulphate ions, Rare Earth and transition metal ions, and so on.
The pentasil-type zeolite of the catalyst composition as claimed above may be prepared in any manner as described above.
Use of the Catalyst of the Invention
The refinery process in which use of the catalyst of the invention in contemplated may be any fluid catalytic cracking process designed to produce light olefins, having up to about 6 carbon atoms per molecule, such as FCC or DCC. The process involves contacting a petroleum feedstock with the catalyst composition of the invention at fluid catalytic cracking conditions, typically comprising a temperature from about 450-780° C., residence time from about 0.01 to 20 seconds, with and without added steam, and a catalyst-to-oil ratio from 1 to 100. The catalyst composition may comprise about 5.0 to about 80 wt % of a mixture of the catalyst composition of the invention and a second fluidized catalytic cracking catalyst composition.
The pentasil zeolites used in the following examples were synthesized and modified with various metals and phosphorous as described above.
Commercially available ZSM-5 additive (65 wt. % pseudo boehmite alumina and 35 wt % ZSM-5 zeolite) was calcined and blended with a base catalyst of a formulation 34 wt % Y zeolite (Re/Y)=2, 13 wt % (pseudoboehmite) alumina, 12 wt % binder, and clay to balance. The amount of additive in the blend was 10 wt %. Absent from the blend was a solid acidic cracking promoter.
ZSM-5 was mixed with H3PO4 solution at pH <3, dried, and calcined at 600° C. for 1 hr. The resulting zeolite (15 wt % P2O5) was milled and embedded into a slurry of a peptized (pseudoboehmite) alumina and clay. The slurry was mixed with high shear, dried, and calcined. The final composition was 15 wt % ZSM-5, 65 wt % Al2O3, and 10 wt % clay. Also absent from this blend was a solid acidic cracking promoter.
Example 1 was repeated, but instead of 65 wt % of (pseudoboehmite), alumina in the additive, an acidic cracking promoter of 15 wt % deeply stabilized, low sodium USY and 15 wt % modified (pseudoboehmite) alumina was employed. The modified (pseudoboehmite) alumina was prepared by adding 975 g phosphoric acid and 5823 g ReCI3 (Rare Earth) solution to a heel of H-water. Under stirring, 13700 g Natal (25 wt-% Al2O3) and 10172 g sulphuric acid was added at a fixed pH of 9.5 into the mixture. The slurry was aged at 100° C. for 24 h, filtrated, washed, dried, and calcined.
A summary of catalyst properties and performance for the above Examples is given in the following Table.
Small scale fluidized bed reactor at 540° C.. Feed was a long residue with a CCR of 3.2
As is clear from the Table, use of the composition of the invention results in a marked increase in the yield of olefins as compared to use of a conventional composition.
A slurry was prepared in water containing 40% of MPZ-(ZSM-S) (rare earth-doped and phosphated), 20% by weight of catapal alumina peptised with nitric acid, 8% sodium free silica sol and 32% by weight kaolin clay. Slurry was homogenized using a high shear mixer and spray dried to form microspheres which were used in conjunction with a regular FCC product in a FCCU as an additive which enhanced the olefin yield.
Example 4 was repeated except that one quarter of the weight of the kaolin clay (8% by weight) was replaced with a dealuminated (DAY) USY zeolite of SAR of about 12. The rest of the composition and processing was the same. Microspheres thus prepared were used as FCC product which was tested in FCC pilot plant that showed increased yield of propylene and butylene.
Example 4 was repeated except that the 20% peptised catapal and 8% silica sol were replaced with 16% by weight aluminum chlorohydral and 12% by weight of sodium-free silica sol. The rest of the composition was the same. FCC pilot plant that showed increased yield of propylene and butylene.
Example 4 was repeated except that catapal alumina and silica sol were replaced with 12% by weight of aluminum chlorohydrol and the weight of kaolin clay increased to 48%. FCC pilot plant that showed increased yield of propylene and butylene.
Example 4 was repeated except that the 20% by weight of peptised catapal and 8% silica sol were replaced with a silica alumina cogel which was washed with ammonium hydroxide and which contained about 17% by weight of Al2O3 and 83% SiO2 based on dry weights. FCC pilot plant that showed increased yield of propylene and butylene.
A magnesium doped MPZ-(ZSM-S) was mixed with an aluminum exchanged USY zeolite in slurry which contained aluminum phosphate and kaolin and slurry milled before spray dried. The components, based on dry weights, were present in portions of 40% magnesium doped MPZ-(ZSM-S) zeolite, 25% aluminum exchanged USY zeolite, 20% aluminum phosphate gel and 15% kaolin. Slurry was milled extensively in a colloidal mill and subsequently spray dried. FCC pilot plant that showed increased yield of propylene and butylene.
Example 4 was repeated except that the peptised catapal alumina was replaced with aluminum chlorohydrol and mixed with the sodium-free silica sol in equal proportions (based on Al2O3 and SiO2) by weight, of which mixture 28% by weight was used in the slurry containing the doped MPZ (ZSM-S) and kaolin which was homogenized by milling and spray dried. FCC pilot plant that showed increased yield of propylene and butylene.
An MPZ (ZSM-S) doped with copper metal ions was mixed with an MPZ (ZSM-5) doped with rare earth metal ions in portions by weight of ⅓ and ⅔ respectively based on dry weights. A portion of this mixture, in a slurry, was added to another slurry containing aluminum phosphate gel doped with 12% lanthanum and milled. The final slurry contained about 54% by dry weight of both the ZSM-5 zeolites, 20% of the lanthanum containing aluminum phosphate and 26% kaolin. FCC pilot plant that showed increased yield of propylene and butylene.
A solid precursor to sodium Y zeolite synthesis was prepared by treating metakaolin in sodium hydroxide and sodium silicate, which has basic exchange capacity and substantial surface area, but is amorphous to XRD, was ion exchanged after washing with rare earth metal ions. About 43% of this material was added to slurry which contained 38% MPZ (ZSM-5) doped with rare earth ions and stabilized with phosphate, 10% of USY zeolite and 9% aluminum chorohydrol. Final slurry was milled and then spray dried. FCC pilot plant that showed increased yield of propylene and butylene.
While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions, methods and/or processes and in the steps or in the sequence of steps of the methods described herein without departing from the concept and scope of the invention. More specifically, it will be apparent that certain agents which are both chemically and physiologically related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention.
This application is a continuation-in-part of U.S. patent application Ser. No. 10/650,313, filed Aug. 28, 2003, which claims priority from U.S. Patent Application No. 60/407,223, filed Aug. 29, 2002.
| Number | Date | Country | |
|---|---|---|---|
| 60407223 | Aug 2002 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10650313 | Aug 2003 | US |
| Child | 11472155 | Jun 2006 | US |
