EP4637996A1 - Chromium oxide containing catalysts for paraffin dehydrogenation and methods of making and using thereof - Google Patents

Abstract

Methods of preparing and using alkane dehydrogenation catalysts are provided. The method for making an alkane dehydrogenation catalyst may include mixing one or more aluminum hydroxides, a water insoluble chromium (III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. The moldable mixture may be extruded to form exudates. The exudates may be dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.

Description

CHROMIUM OXIDE CONTAINING CATALYSTS FOR PARAFFIN

DEHYDROGENATION AND METHODS OF MAKING AND USING THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to Indian Patent Application No. 202241074398, filed December 22, 2022, the entire contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

[0002] The present disclosure generally relates to methods for preparing and using an alkane dehydrogenation catalyst. More specifically, the present disclosure relates to, among other embodiments, methods for the use and preparation of chromia-alumina dehydrogenation catalysts for the dehydrogenation of paraffins.

BACKGROUND

[0003] Alkane dehydrogenation is a recognized process for the production of a variety of useful hydrocarbon products, such as isobutylene for conversion to MTBE, as well as isooctane and alkylates to supplement and enrich gasolines. There are several current catalytic processes useful for the catalytic dehydrogenation of light alkanes, including the Sud-Chemie CATOFIN® process, UOP's Oleflex® process, Phillips' Star™ process and the Snamprogetti- Yarsintee process. The catalysts that are used in these processes are manufactured from two different groups of materials. The Sud-Chemie CATOFIN® process and the Snamprogetti- Yarsintee process utilize chromia-alumina catalysts. In contrast, the catalysts for the UOP and Phillips processes comprise supported precious metal platinum as catalysts.

[0004] Chromia-alumina dehydrogenation catalyst technology has been in use for many decades. Current chromia-alumina dehydrogenation catalysts are produced by the impregnation of an aluminum carrier with a high-concentration chromic acid solution, which contains primarily hexavalent chromium (chromium(VI)), which is toxic and carcinogenic, and therefore highly undesirable for use on an industrial scale. Methods of catalyst preparation using chromium(VI) oxide are disclosed, for example, in GB Patent No. 942944, U.S. Patent No. 7,279,611, U.S. Patent No. 8,835,347, U.S. Patent No. 9,254,476, U.S. Patent Publication No. 2005/0075243, and U.S. Patent Publication No. 2021/0387167. Each of these methods suffer from the use of environmentally unfriendly chromium(VI) materials.

[0005] One method of overcoming the use of hexavalent chromium in catalyst preparation involves impregnating an aluminum carrier with a water soluble chromium(III) salt, such as an aqueous solution of chromium nitrate. This method requires multiple impregnation steps to arrive at a desirable chromium oxide content. Each impregnation step requires intermediate drying and calcination, and so such a multi-impregnation method is time- and labor-intensive, and cost prohibitive relative to conventional preparation procedures involving chromium(VI)- containing materials.

[0006] Attempts to overcome the use of hexavalent chromium have been described. For example, Chinese Patent 101940922B discloses making a C^Ch/alumina carrier and then immersing the carrier with additional chromium nitrate and potassium nitrate. U.S. Patent No. 10,646,853 to Fridman also discloses making a C^Ch/alumina carrier and then impregnating the carrier with an aqueous solution containing chromium nitrate, sodium hydroxide, magnesium nitrate, and zirconium carbonate. These methods suffer from the fact that catalyst preparation involves an impregnation process followed by drying and calcination steps. Such methods suffer from being time and labor intensive, in addition to having increased costs.

[0007] Chinese Patent No. 102794167A describes another attempt to produce a chromium based dehydrogenation catalyst that includes extruding an acidic solution of chromium(III) oxide powder, activated alumina powder, calcium nitrate and potassium nitrate, followed by drying and calcining. The dried extrudates are then baked at 540 °C for 4 hours with nitrogen gas to obtain the catalyst. A catalyst formed with this process is expected to show alumina in gamma alumina form which strongly affects catalyst stability.

[0008] Accordingly, the Applicant has recognized that there exists a need for a simple, cost effective method for making a chromia-alumina dehydrogenation catalyst having good catalyst performance without the impregnation step.

SUMMARY

[0009] To address shortcomings in the art, the Applicant has developed methods for the preparation and use of alkane dehydrogenation catalyst. In addition to other embodiments, the Applicant has discovered cost-effective methods for making chromia-alumina dehydrogenation catalysts without the use of water soluble chromium(VI) containing sources. In certain embodiments, the presently disclosed dehydrogenation catalysts have good activity as well as improved stability and mechanical strength. Additionally, the presently disclosed method of preparing a dehydrogenation catalyst does not require or include impregnation of an aluminum carrier, such as a chromium(III) oxide containing alumina, with a chromium(III) salt. In certain embodiments, the presently disclosed method of preparing a dehydrogenation catalyst excludes an impregnation step. The presently disclosed chromia-alumina dehydrogenation catalysts are useful, among other uses, for the dehydrogenation of lower paraffin.

[0010] According to one aspect of the present disclosure, a method for making an alkane dehydrogenation catalyst is provided. In certain embodiments, the method may include mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. The method may further include extruding the moldable mixture to form extrudates. The method may further include drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing from about 60 weight percent (wt.%) to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of tri valent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.

[0011] According to one aspect of the present disclosure, a method for making an alkane dehydrogenation catalyst is provided. In certain embodiments, the method may include mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, a magnesium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. The method may further include extruding the moldable mixture to form extrudates. The method may further include drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, from about 0.1 wt.% to about 5 wt.% of magnesium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.

[0012] According to another aspect of the present disclosure, a method for dehydrogenation of an alkane is provided. In certain embodiments, the method may include loading a reactor with a dehydrogenation catalyst. The dehydrogenation catalyst may be produced by mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. The moldable mixture may be extruded to form extrudates. The extrudates may be dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide. The method may further include supplying a feed containing alkanes through the reactor at a temperature sufficient to dehydrogenate the alkanes.

[0013] According to another aspect of the present disclosure, a method for dehydrogenation of an alkane is provided. In certain embodiments, the method may include loading a reactor with a dehydrogenation catalyst. The dehydrogenation catalyst may be produced by mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, a magnesium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. The moldable mixture may be extruded to form extrudates. The extrudates may be dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, from about 0.1 wt.% to about 5 wt.% of magnesium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide. The method may further include supplying a feed containing alkanes through the reactor at a temperature sufficient to dehydrogenate the alkanes.

[0014] Still other aspects and advantages of these exemplary embodiments and other embodiments, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Accordingly, these and other objects, along with advantages and features of the present disclosure, will become apparent through reference to the following description. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.

DETAILED DESCRIPTION

[0015] The present disclosure describes various embodiments related to methods for preparing and using an alkane dehydrogenation catalyst. Further embodiments may be described and disclosed.

[0016] In the following description, numerous details are set forth to provide a thorough understanding of the various embodiments. In other instances, well-known processes, devices, and systems may not have been described in particular detail to not unnecessarily obscure the various embodiments. Additionally, illustrations of the various embodiments may omit certain features or details to not obscure the various embodiments. [0017] The description may use the phrases “in some embodiments,” “in various embodiments,” “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.

[0018] The term “about” is defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0019] The use of the words “a” or “an” when used with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0020] The terms “wt.%”, “vol.%”, or “mol.%” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component.

[0021] The words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0022] Disclosed here are methods for preparing and using an alkane dehydrogenation catalyst. In certain embodiments, the dehydrogenation catalysts prepared according to the presently disclosed methods have good activity as well as improved stability and mechanical strength. The presently disclosed methods provide cost-effective methods for making chromia- alumina dehydrogenation catalysts without the use of water soluble chromium(VI) containing sources. In certain embodiments water soluble chromium(VI) containing sources comprise chromium(VI) oxide. Importantly, the presently disclosed method of preparing a dehydrogenation catalyst does not require or include impregnation of an aluminum carrier, such as chromium(III) oxide containing alumina, with a chromium(III) salt. In certain embodiments the chromium(III) salt comprises chromium nitrate. In certain embodiments, the presently disclosed method of preparing a dehydrogenation catalyst excludes an impregnation step. The presently disclosed chromia-alumina dehydrogenation catalysts are useful, among other uses, for the dehydrogenation of lower paraffin. [0023] According to one aspect of the present disclosure, a method for making an alkane dehydrogenation catalyst is provided. In certain embodiments, the method may include mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. The alkali metal oxide sources can contain a sodium oxide source, a lithium oxide source, a cesium oxide source, or a potassium oxide source. The method may further include extruding the moldable mixture to form extrudates. The method may further include drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.

[0024] According to another aspect of the present disclosure, a method for making an alkane dehydrogenation catalyst is provided. In certain embodiments, the method may include mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, a magnesium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. The alkali metal oxide sources can contain a sodium oxide source, a lithium oxide source, a cesium oxide source, or a potassium oxide source. The method may further include extruding the moldable mixture to form extrudates. The method may further include drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, from about 0.1 wt.% to about 5 wt.% of magnesium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.

[0025] In certain embodiments, the aqueous metal free acid solution and/or the method for preparing a dehydrogenation catalyst excludes metal containing acids, such as chromic acid. In some instances, the plurality of aluminum hydroxides may include crystalline aluminum trihydroxide containing one or more of bay erite and nordstrandite. In certain embodiments, the plurality of aluminum hydroxides may include crystalline aluminum oxide-hydroxide containing boehmite. In certain embodiments, the gelatinous aluminum hydroxides is selected from one or more of amorphous aluminum hydroxide and pseudoboehmite. In certain embodiments, a single aluminum hydroxide may be used in place of the plurality of aluminum hydroxides, preferably bayerite.

[0026] In certain embodiments of the method for making an alkane dehydrogenation catalyst, the extrudates may be calcined at a temperature ranging from about 700 degrees Celsius (°C) to about 1000 °C. In certain embodiments, the extrudates are not subject to any subsequent impregnation with a water soluble chromium(III) oxide source. In certain embodiments “a water soluble chromium(III) oxide source” is any water soluble chromium compound which on calcination transforms to chromium(III) oxide. Further, a water soluble chromium(III) oxide source may comprise chromium(VI) oxide and chromium(III) nitrate. In at least some embodiments, the temperature sufficient to dehydrogenate alkanes using the dehydrogenation catalyst ranges from about 400 °C to about 800 °C.

[0027] The moldable mixture can include other materials such as binders, cements, pore formers, texturizers, extrusion aids, lubricants, surfactants, and any other materials to aid with mixing or molding, or to provide a desired structure to the as-calcined material. For example, in certain embodiments, the moldable mixture may include a pore forming organic compound, such as a polymer. In such instances, the pore forming organic compound does not dissolve into the water of the moldable mixture, and thus remains as discrete small regions of organic matter within the material when formed. During the calcination, the pore forming organic compound is burned away, which forms a gas that increases the porosity of the calcined material. The pore forming organic polymer can be, for example, a polyolefin such as polyethylene, or a cellulose derivative such as methocel. The pore forming organic compound can be provided in the moldable mixture in any desirable amount, for example, in an amount within the range of about 0.1 wt.% to about 5 wt.% on a dry basis. In certain embodiments, the pore forming organic compound is present in the moldable mixture in an amount within the range of about 0.2 wt.% to about 5 wt.%, or about 0.5 wt.% to about 5 wt.%, or about 0.1 wt.% to about 3 wt.%, or about 0.2 wt.% to about 3 wt.%, or about 0.5 wt.% to about 3 wt.%, or about 0.1 wt.% to about 2 wt.%, or about 0.2 wt.% to about 2 wt.%, or about 0.5 wt.% to about 2 wt.%.

[0028] The moldable mixture may include an aqueous non-metal acid. The non-metal acid herein refers to an acid in which the molecular structure of the acid does not involve a metal atom. In certain embodiments of the process as otherwise described herein, the non-metal acid may be nitric acid. In other embodiments of the process, the non-metal acid may be an organic acid, such as formic acid or acetic acid. In still other embodiments, the non-metal acid may be a combination of nitric acid and an organic acid such as formic acid or acetic acid. The use of an organic acid can be beneficial in that it can reduce the nitrogen oxides concentration during heat treatment. However, it can also make the peptization of aluminum hydroxide less efficient. The person of ordinary skill in the art may determine the appropriate amounts and types of acids to use to provide a desired moldable material. [0029] The various components can be mixed by a variety of methods, both manual and mechanical, to provide the moldable mixture. For example, in certain embodiments, the moldable mixture may be mixed by a batch mixer. The raw materials used for the catalyst preparation can be mixed well in a high shear mixer followed by mixing with a metal free aqueous acid solution until a rather stiff dough/granules are obtained. This dough/granules can be extruded and/or formed into any suitable shape including cylinders, cubes, stars, tri-lobes, quadra-lobes, pellets, pills, or spheres by suitable mechanical means. In one embodiment, mixing is conducted in a high intensity environment

[0030] , such as that supplied by a B&P Littleford Mixer available from B&P Littleford, 1000 Hess Avenue, Saginaw, MI 48601. In another embodiment, mixing is conducted using an Eirich Intensive Mixer, such as that supplied by Maschinenfabrik GustavEirich Gmbh & Co KG, Hardheim, Germany. Mixing is conducted for a time sufficient to result in a uniform mixture. In other embodiments, other batch or continuous processes can be used to create the moldable mixture. Components may be added serially or together in any convenient order, as would be apparent to the person of ordinary skill in the art.

[0031] According to another aspect of the present disclosure, a method for dehydrogenation of an alkane is provided. In certain embodiments, the method may include loading a reactor with a dehydrogenation catalyst. The dehydrogenation catalyst may be produced by mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. In certain embodiments, the method may use only a single aluminum hydroxide to form the moldable mixture. The moldable mixture may be extruded to form extrudates. The extrudates may be dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide. The method may further include supplying a feed containing alkanes through the reactor at a temperature sufficient to dehydrogenate the alkanes.

[0032] According to another aspect of the present disclosure, a method for dehydrogenation of an alkane is provided. In certain embodiments, the method may include loading a reactor with a dehydrogenation catalyst. The dehydrogenation catalyst may be produced by mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, a magnesium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture. In certain embodiments, the method may use only a single aluminum hydroxide to form the moldable mixture. The moldable mixture may be extruded to form extrudates. The extrudates may be dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60 wt.% to about 90 wt.% of alumina, from about 10 wt.% to about 40 wt.% of trivalent chromium oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, from about 0.1 wt.% to about 5 wt.% of magnesium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide. The method may further include supplying a feed containing alkanes through the reactor at a temperature sufficient to dehydrogenate the alkanes.

[0033] In certain embodiments, the method may further include separating a dehydrogenated product from unreacted alkanes. In some instances, the plurality of aluminum hydroxides may include crystalline aluminum trihydroxide containing one or more of bayerite and nordstrandite, preferably bayerite. In certain embodiments, the plurality of aluminum hydroxides comprises boehmite. In certain embodiments, the gelatinous aluminum hydroxide is selected from one or more of amorphous aluminum hydroxide and pseudoboehmite. In certain embodiments, only a single aluminum hydroxide may be used in the method, preferably bayerite. Non-limiting examples of water insoluble chromium(III) oxide sources can include chromium(III) oxide, and chromium(III) hydroxide, or a mixture thereof. In certain embodiments, the amount of crystalline aluminium trihydroxide ranges from about 60 wt.% to about 99 wt.%, and including values between these values, such as from about 60 wt.% to about 97 wt%, from about 62 wt.% to about 95 wt.%, from about 65 wt.% to about 97 wt.%, from about 67 wt.% to about 97 wt.%, from about 70 wt.% to about 97 wt.%, from about 72 wt.% to about 97 wt.%, from about 74 wt.% to about 97 wt.%, from about 75 wt.% to about 97 wt.%, from about 77 wt.% to about 97 wt.%, from about 60 wt.% to about 95 wt.%, from about 60 wt.% to about 93 wt.%, or from about 60 wt.% to about 90 wt.%, or from about 85 to about 97 wt.%, or from about 80 wt.% to about 97 %, or from about 90 to about 97 wt.%. In certain embodiments, the crystalline aluminium trihydroxide contains one or more of bayerite and nordstrandite.

[0034] Embodiments also include crystalline aluminium oxide-hydroxide or gelatinous aluminium hydroxide or both ranging from about 1 wt.% to about 40 wt.%, and including values between these values, such as from about 3 wt.% to about 40 wt.%, 5 wt.% to about 40 wt.%, from about 8 wt.% to about 40 wt.%, from about 10 wt.% to about 40 wt.%, from about 15 wt.% to about 40 wt.%, from about 3 wt.% to about 35 wt.%, from about 3 wt.% to about 30 wt.%, from about 5 wt.% to about 30 wt.%, from about 3 wt.% to about 25 wt.%, from about 5 wt.% to about 25 wt.%, or from about 3 wt.% to about 20 wt.%, or from about 3 wt.% to about 15 wt.%, or from about 3 wt.% to about 10 wt.%. The crystalline aluminium oxidehydroxides can contain boehmite. The gelatinous aluminium hydroxides can contain one or more of amorphous aluminium hydroxide and pseudoboehmite. The use of a plurality of aluminum hydroxides is expected to increase crush strength without affecting the catalyst performance up to a particular combination of aluminum hydroxides.

[0035] In certain embodiments of the method for making an alkane dehydrogenation catalyst, the extrudates may be dried to remove water by heating at a temperature of 50 °C to 200 °C, 100 °C to 140 °C, 110 °C to 120 °C, or 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125, °C, 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, or any range or value therebetween. In certain embodiments of the method, the extrudates may be calcined at a temperature ranging from about 700 degrees Celsius (°C) to about 1000 °C. In certain embodiments, the extrudates are not subject to any subsequent impregnation with a water soluble chromium oxide source. In at least some embodiments, the temperature sufficient to dehydrogenate alkanes using the method ranges from about 400 °C to about 800 °C.

[0036] According to another aspect of the present disclosure, an alkane dehydrogenation catalyst composition is provided. In certain embodiments, the alkane dehydrogenation catalyst composition may include from about 60% wt.% to about 90 wt.% of aluminum oxide, from about 10 wt.% to about 40 wt.% of water insoluble chromium(III) oxide, from about 0.1 wt.% to about 5 wt.% of zirconium oxide, from about 0.1 wt.% to about 5 wt.% of magnesium oxide, and from about 0.1 wt.% to about 5 wt.% of an alkali metal oxide. In at least certain embodiments, the catalyst composition is operable to dehydrogenate alkanes at a temperature of from about 400 °C to about 800 °C .

Catalyst Preparation

Example 1 (Invention)

[0037] Bayerite (2323.6 g, Versal B, UOP), chromium (III) oxide (388.8 g, Sigma- Aldrich®), zirconium (IV) basic carbonate (17.0 g, Sigma-Aldrich®) were mixed for 10 minutes in an Eirich mixer (EL-5 Profi Plus). An aqueous solution of nitric acid (320 ml, 25 wt.%) containing dissolved sodium nitrate (32.0 g) and magnesium nitrate hexahydrate (123.7 g) was added to the mixer and mixed for about 10 minutes. The obtained blend was aged at 25 °C for 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot lab extruder, dried at 70 °C followed by 120 °C for 12 hours, calcined at 850°C for 2 hours in air in a muffle furnace, cooled to room temperature and used for catalyst testing.

[0038] The catalyst of Example 1 had a composition of 20 wt.% CnCh, 0.60 wt.% Na2O, 1.0 wt.% MgO, 0.7 wt.% ZrO2 and 77.70 wt.% AI2O3.

Example 2 (Comparison)

[0039] The carrier used for the catalyst preparation was prepared by mixing Bay erite (2524.8 g, Versal B, UOP) and chromium (III) oxide, (360.2, Sigma-Aldrich®) for 10 minutes in an Eirich mixer (EL-5 Profi Plus). An aqueous solution of nitric acid (400 ml, 25 wt.%) was added to the mixer and mixed for about 10 minutes. The obtained blend was aged at 25 °C for 1 hour and formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot lab extruder, dried at 70 °C followed by 120 °C for 12 hours, calcined at 600 °C for 2 hours in air in a muffle furnace, cooled to room temperature and used for catalyst preparation. The catalyst was prepared using this carrier.

[0040] The calcined extrudates (189.51 g) were impregnated with an aqueous solution prepared by dissolving chromium nitrate nonahydrate (31.01 g), sodium nitrate (3.29 g), magnesium nitrate hexahydrate (12.72 g) and zirconium (IV) basic carbonate (1.75 g) in water (38.1 g). The impregnated extrudates were aged 25 °C for 12 hours in a closed container. The sample was dried at 70 °C followed by 120 °C for 12 hours, calcined at 760 oC for 2 hours in air in a muffle furnace, cooled to room temperature and used for catalyst testing.

[0041] The catalyst of Comparison Example 2 had a composition of 20 wt.% C^CE, 0.60 wt.% Na2O, 1.0 wt.% MgO, 0.7 wt.% ZrO2 and 77.70 wt.% AI2O3.

Catalyst Testing

[0042] The catalysts were tested in isobutane dehydrogenation using a fixed bed reactor. Catalyst loading and reactor details were as follows: The catalyst weight was 70 g, catalyst particle size was about 3 mm diameter extrudates, catalyst diluent quartz (ring) size was 2.2 x 2 mm, catalyst diluent weight ratio was 1:3, reactor inner diameter was 41 mm, reactor outer diameter was 45 mm. Catalyst extrudates (10 g of 7 batches) and inert quartz diluent (30 g of 7 batches) were loaded into reactor in a layer manner. Quartz rings having a size mentioned above were loaded above the catalyst bed. A nitrogen purge was employed between the steps of dehydrogenation, catalyst regeneration/oxidation and reduction with hydrogen. The isobutane flow in the dehydrogenation step corresponds to GHSV of 600 ml h^g'¹. The reactor was operated at atmospheric pressure using isobutane (99.9 vol. %) diluted with nitrogen. The reaction pressure during dehydrogenation was 0.33 atmosphere of isobutane and 0.67 atmosphere of nitrogen. The reactor outlet gases were analyzed by online gas chromatograph (Agilent 6890) equipped with a flame ionization detector for hydrocarbon analysis and a thermal conductivity detector for hydrogen analysis. The reactant and products flow rates were measured using a Ritter type wet gas flow meter. The reactor was operated in a cyclic mode with the following steps: 1) Catalyst oxidation/regeneration with air with a start temperature of 650 °C for 10 minutes; 2) Purge the catalyst bed with nitrogen at 650 °C for 3 minutes; 3) Reduce the catalyst with hydrogen with a start temperature of 650 °C for 3 minutes; 4) Catalyst bed cooling under nitrogen from 650 °C to 585 °C and maintaining at 585 °C for 15 minutes; 5) isobutane dehydrogenation with a start temperature of 585 °C for 10 minutes. Reactor outlet gas composition analysis with gas chromatograph at 9th minute from the start of the isobutane feed.

[0043] Because the fresh catalyst activity changes during the initial cycles the catalysts were equilibrated under cyclic oxidation (air, 2 minutes) - purge (nitrogen, 4 minutes) -reduction (hydrogen, 2 minutes) conditions to achieve stable catalyst performance. The equilibration of the fresh catalyst was conducted at 650 oC for 100 cycles.

[0044] Then Steps 1 to 5 repeated for 30 cycles and the catalyst performance results after catalyst stabilization is provided in Table 1 (21-30 cycle average). The results from Table 1 demonstrate that the catalyst prepared according to the presently method of the invention (Example 1) is characterized by better performance in comparison with the catalyst prepared by the impregnation method (Example 2).

Table 1: Catalyst performance results

[0045] In the context of the present invention, twenty embodiments are now described. Embodiment 1 is a method for making an alkane dehydrogenation catalyst. The method includes the steps of mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture; extruding the moldable mixture to form extrudates; and drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing about 60% wt.% to about 90 wt.% of alumina, about 10 wt.% to about 40 wt.% of trivalent chromium oxide, about 0.1 wt.% to about 5 wt.% of zirconium oxide, and about 0.1 wt.% to about 5 wt.% of an alkali metal oxide. Embodiment 2 is the method of embodiment 1, wherein only one aluminum hydroxide is present. Embodiment 3 is the method of embodiment 1, wherein the one aluminum hydroxide is bay erite. Embodiment 4 is the method of embodiment 1, wherein the one or more aluminum hydroxides comprises at least one gelatinous aluminum hydroxide comprises at least one member selected from the group consisting of an amorphous aluminum hydroxide and pseudoboehmite. Embodiment 5 is the method of embodiment 1-4, wherein the extrudates are calcined at a temperature ranging from about 700 degrees °C to about 1000 °C. Embodiment 6 is the method of any one of embodiments 1-4, wherein the extrudates are not subject to any subsequent impregnation with a water soluble chromium(III) oxide source. Embodiment 7 is the method of any one of embodiment 1, wherein the moldable mixture is formed by mixing the one or more aluminum hydroxides, the water insoluble chromium(III) oxide source, the zirconium oxide source, the magnesium oxide source, and the alkali metal oxide source with an aqueous metal free acidic solution until a uniform mixture is formed. Embodiment 8 is the method of any one of embodiments 1-4, wherein the alkane dehydrogenation catalyst further contains about 0.1 wt.% to about 5 wt.% of magnesium oxide. Embodiment 9 is the method of embodiment 2, wherein the one aluminum hydroxide is bay erite. Embodiment 10 is the method of embodiment 1, wherein the one or more aluminum hydroxides contain from about 60 wt.% to about 99 wt.% of crystalline aluminum trihydroxide and from about 1 wt.% to about 40 wt.% of crystalline aluminum oxide-hydroxide or gelatinous aluminum hydroxide or a combination thereof, and preferably from about 60 wt.% to about 97 wt.% of crystalline aluminum trihydroxide and from about 3 wt.% to about 40 wt.% of crystalline aluminum oxi de-hydroxide or gelatinous aluminum hydroxide or a combination thereof. Embodiment 11 is the method of embodiment 1, wherein the one or more aluminum hydroxides comprises crystalline aluminum trihydroxide containing one or more of bay erite and nordstrandite and the crystalline aluminum oxide-hydroxide contains boehmite.

[0046] Embodiment 12 is a method for dehydrogenation of an alkane. The method includes the steps of loading a reactor with a dehydrogenation catalyst produced by: mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture; extruding the moldable mixture to form extrudates; drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing about 60 wt.% to about 90 wt.% of alumina, about 10 wt.% to about 40 wt.% of trivalent chromium oxide, about 0.1 wt.% to about 5 wt.% of zirconium oxide, and about 0.1 wt.% to about 5 wt.% of an alkali metal oxide; and supplying a feed containing alkanes through the reactor at a temperature sufficient to dehydrogenate the alkanes. Embodiment 13 is the method of embodiment 12, wherein only one aluminum hydroxide is present. Embodiment 14 is the method of embodiment 13, wherein the one aluminum hydroxide is bay erite. Embodiment 15 is the method of embodiment 12, further comprising separating a dehydrogenated product from unreacted alkanes. Embodiment 16 is the method of any one of embodiments 12 to 15, wherein the extrudates are not subject to any subsequent impregnation with a water soluble chromium(III) oxide source. Embodiment 17 is the method of any one of embodiments 12 to 16, wherein the extrudates are calcined at a temperature ranging from about 700 °C to about 1000 °C. Embodiment 18 is the method of any one of embodiments 12 to 15, wherein the temperature sufficient to dehydrogenate alkanes ranges from about 400 °C to about 800 °C . Embodiment 19 is the method of embodiment 12, wherein the crystalline aluminum trihydroxide is one or more of bayerite or nordstrandite, the crystalline aluminum oxidehydroxide is boehmite, and the gelatinous aluminum hydroxide is one or more of amorphous aluminum hydroxide or pseudoboehmite. Embodiment 20 is the method of embodiment 12, wherein the moldable mixture is formed by mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, a magnesium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution until a uniform mixture is formed; and the alkane dehydrogenation catalyst contains about 60 wt.% to about 90 wt.% of alumina, about 10 wt.% to about 40 wt.% of trivalent chromium oxide, about 0.1 wt.% to about 5 wt.% of zirconium oxide, about 0.1 wt.% to about 5 wt.% of magnesium oxide, and about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.

[0047] When ranges are disclosed herein, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited. lin the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, reference to values stated in ranges includes each and every value within that range, even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0048] Other objects, features and advantages of the disclosure will become apparent from the foregoing detailed description and examples. It should be understood, however, that the detailed description and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

Claims

Claims We Claim:

1. A method for making an alkane dehydrogenation catalyst, the method comprising: mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture; extruding the moldable mixture to form extrudates; and drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing about 60 weight percent (wt.%) to about 90 wt.% of alumina, about 10 wt.% to about 40 wt.% of trivalent chromium oxide, about 0.1 wt.% to about 5 wt.% of zirconium oxide, and about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.

2. The method of claim 1, wherein only one aluminum hydroxide is present.

3. The method of claim 1, wherein the one aluminum hydroxide is bayerite.

4. The method of claim 1, wherein the one or more aluminum hydroxides comprises at least one gelatinous aluminum hydroxide comprising at least one member selected from the group consisting of an amorphous aluminum hydroxide and pseudoboehmite.

5. The method of any one of claims 1-4, wherein the extrudates are calcined at a temperature ranging from about 700 °C to about 1000 °C.

6. The method of any one of claims 1-4, wherein the extrudates are not subject to any subsequent impregnation with a water soluble chromium(III) oxide source.

7. The method of claim 1, wherein the moldable mixture is formed by mixing the one or more aluminum hydroxides, the water insoluble chromium(III) oxide source, the zirconium oxide source, the magnesium oxide source, and the alkali metal oxide source with the aqueous metal free acidic solution until a uniform mixture is formed.

8. The method of any one of claims 1-4, wherein the alkane dehydrogenation catalyst further contains about 0.1 wt.% to about 5 wt.% of magnesium oxide.

9. The method of claim 2, wherein the one aluminum hydroxide is bayerite.

10. The method of claim 1, wherein the one or more aluminum hydroxides contain from about 60 wt.% to about 99 wt.% of crystalline aluminum trihydroxide and from about 1 wt.% to about 40 wt.% of crystalline aluminum oxide-hydroxide or gelatinous aluminum hydroxide or a combination thereof, and preferably from about 60 wt.% to about 97 wt.% of crystalline aluminum trihydroxide and from about 3 wt.% to about 40 wt.% of crystalline aluminum oxide-hydroxide or gelatinous aluminum hydroxide or a combination thereof.

11. The method of claim 1, wherein the one or more aluminum hydroxides comprises crystalline aluminum trihydroxide containing one or more of bay erite and nordstrandite and the crystalline aluminum oxi de -hydroxi de contains boehmite.

12. A method for dehydrogenation of an alkane, the method comprising: loading a reactor with a dehydrogenation catalyst produced by: mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution to form a moldable mixture; extruding the moldable mixture to form extrudates; drying and calcining the extrudates to produce an alkane dehydrogenation catalyst containing about 60 wt.% to about 90 wt.% of alumina, about 10 wt.% to about 40 wt.% of trivalent chromium oxide, about 0.1 wt.% to about 5 wt.% of zirconium oxide, and about 0.1 wt.% to about 5 wt.% of an alkali metal oxide; and supplying a feed containing alkanes through the reactor at a temperature sufficiento dehydrogenate the alkanes.

13. The method of claim 12, wherein only one aluminum hydroxide is present.

14. The method of claim 13, wherein the one aluminum hydroxide is bayerite.

15. The method of claim 12, further comprising separating a dehydrogenated product from unreacted alkanes.

16. The method of any one of claims 12 to 15, wherein the extrudates are not subject to any subsequent impregnation with a water soluble chromium(III) oxide source.

17. The method of any one of claims 12 to 15, wherein the extrudates are calcined at a temperature ranging from about 700 °C to about 1000 °C.

18. The method of any one of claims 12 to 15, wherein the temperature sufficient to dehydrogenate alkanes ranges from about 400 °C to about 800 °C.

19. The method of claim 12, wherein the crystalline aluminum trihydroxide is one or more of bayerite or nordstrandite, the crystalline aluminum oxide-hydroxide is boehmite, and the gelatinous aluminum hydroxide is one or more of amorphous aluminum hydroxide or pseudoboehmite.

20. The method of claim 12, wherein the moldable mixture is formed by mixing one or more aluminum hydroxides, a water insoluble chromium(III) oxide source, a zirconium oxide source, a magnesium oxide source, and an alkali metal oxide source with an aqueous metal free acidic solution until a uniform mixture is formed; and the alkane dehydrogenation catalyst contains about 60 wt.% to about 90 wt.% of alumina, about 10 wt.% to about 40 wt.% of trivalent chromium oxide, about 0.1 wt.% to about 5 wt.% of zirconium oxide, about 0.1 wt.% to about 5 wt.% of magnesium oxide, and about 0.1 wt.% to about 5 wt.% of an alkali metal oxide.