Catalyst for dehydrogenation of paraffins

Abstract

Methods of making and using alkane dehydrogenation catalysts are provided. A method of making a catalyst for alkane dehydrogenation can include mixing a plurality of aluminum hydroxide, chromium (III) oxide, and alkali metal oxide sources with an aqueous metal-free acid solution to form a moldable mixture. The plurality of aluminum hydroxides may contain from about 60% to about 99% by weight of crystalline aluminum trihydroxide and from about 1% to about 40% by weight of crystalline oxidized aluminum hydroxide or colloidal aluminum hydroxide, or a combination thereof. The method may also include extruding the moldable mixture to form an extrudate and drying and calcining the extrudate to produce the alkane dehydrogenation catalyst.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 476,643, filed on December 22, 2022, the entire contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention generally relates to methods for making and using alkane dehydrogenation catalysts. More particularly, the present invention relates to methods for using and making chromium oxide-aluminum oxide dehydrogenation catalysts without using water-soluble chromium-containing materials for the dehydrogenation of paraffins, among other embodiments. Background Art

[0004] Alkane dehydrogenation is a well-established process for producing a variety of useful hydrocarbon products such as isobutylene for conversion to MTBE, as well as isooctane and alkylates to supplement and enrich gasoline. There are several catalytic processes currently available for the catalytic dehydrogenation of light alkanes, including Süd-Chemie Methods, UOP Method, Phillips' Star TM The catalysts used in these methods are made from two different groups of materials. The Snamprogetti-Yarsintee process and the Snamprogetti-Yarsintee process utilize chromium oxide-aluminum oxide catalysts. In contrast, the catalysts used in the UOP and Phillips processes include supported precious metal platinum as the catalyst.

[0005] Chromium oxide-aluminum oxide dehydrogenation catalyst technology has been used for decades. The stability of the dehydrogenation catalyst plays an important role in the overall efficiency of the dehydrogenation process. Due to the extreme temperature ranges in which the catalytic dehydrogenation process is carried out, the life expectancy of the catalyst is often limited. Therefore, improving the stability of the catalyst translates into a longer catalyst life, thereby allowing better catalyst utilization and ultimately leading to less catalyst consumption during the dehydrogenation process. One of the important requirements in the production of granulated / extruded catalysts for use in fixed-bed catalytic operations is that the catalyst has sufficient strength to support its own weight and process-stream oscillations and similar disturbances commonly encountered in fixed-bed processes. Failure to meet these requirements is a frequent source of difficulty. In addition, the gradual loss of mechanical strength during use is often necessary to discard a catalyst that would otherwise continue to be completely satisfactory.

[0006] There are many different types of alumina that can be used as dehydrogenation catalyst supports. However, medium to high surface area gamma alumina is always the preferred choice of support for catalysts such as those disclosed in, for example, U.S. Patent Nos. 2,956,030, 2,945,823, and 2,374,404. Chromium (III) oxide supported on η-alumina has been reported to be highly stable compared to chromium oxide supported on gamma-alumina (PHYSICAL REVIEW B 2003, 67, 115414; Adv. Mater. 2007, 19, 2129-2133; Energy Technol. 10.1002 / ente.201800736).

[0007] Current chromium oxide-alumina dehydrogenation catalysts are produced by impregnating an aluminum support with a highly concentrated chromic acid solution, which primarily contains hexavalent chromium (chromium (VI)), which is toxic and carcinogenic, and is therefore highly undesirable for use on an industrial scale. Attempts to overcome the use of hexavalent chromium are described. For example, Chinese Patent No. 101940922B discloses preparing a Cr2O3 / alumina support and then impregnating the support with additional chromium nitrate and potassium nitrate. Fridman's U.S. Patent No. 10646853 also discloses preparing a Cr2O3 / alumina support and then impregnating the support with an aqueous solution containing chromium nitrate, sodium hydroxide, magnesium nitrate and zirconium carbonate. These methods suffer from the fact that the catalyst preparation includes an impregnation process, followed by drying and calcination steps, which is time-consuming and labor-intensive, as well as costly. Chinese Patent No. 102794167A describes an attempt to produce a chromium-based dehydrogenation catalyst comprising extruding an acidic solution of chromium (III) oxide powder, activated alumina powder, calcium nitrate and potassium nitrate, followed by drying and calcination. The dried extrudates were then calcined at 540°C using nitrogen for 4 hours to obtain the catalyst. The catalyst formed by this method is expected to exhibit aluminum oxide in the form of gamma alumina, which significantly impacts catalyst stability. Furthermore, catalyst preparation methods involving impregnation of aluminum supports with chromium(III) salts require multiple impregnation steps to achieve the desired chromium content. Each impregnation step requires intermediate drying and calcination, and thus such multiple impregnation methods are time-consuming, labor-intensive, and costly relative to conventional preparation procedures involving chromium(VI)-containing materials.

[0008] Therefore, the inventors recognized that there is a need for a simple, cost-effective method for preparing chromia-alumina dehydrogenation catalysts without the use of chromium (VI)-containing materials and which exhibit good activity, improved stability and suitable mechanical strength for the dehydrogenation of lower paraffins. Summary of the Invention

[0009] To address deficiencies in the art, applicants have developed methods for preparing and using alkane dehydrogenation catalysts. Among other embodiments, applicants have discovered a cost-effective method for preparing chromium oxide-alumina dehydrogenation catalysts without using a water-soluble chromium-containing source. The presently disclosed dehydrogenation catalysts have good activity and improved stability and mechanical strength. In some embodiments of the presently disclosed methods for preparing the dehydrogenation catalysts, impregnation of the aluminum support with a chromium (III) salt may not be required or may not be included. In some embodiments, the presently disclosed methods for preparing the dehydrogenation catalysts do not include an impregnation step. Among other uses, the presently disclosed chromium oxide-alumina dehydrogenation catalysts can be used for the dehydrogenation of paraffins.

[0010] According to one aspect of the present disclosure, a method for preparing an alkane dehydrogenation catalyst is provided. In some embodiments, the method may include mixing a plurality of aluminum hydroxides, a water-insoluble chromium (III) oxide source, and an alkali metal oxide source with a metal-free aqueous acid solution to form a moldable mixture. The plurality of aluminum hydroxides may contain about 60 weight percent (wt%) to about 99 weight percent of crystalline aluminum trihydroxide and about 1 weight percent to about 40 weight percent of crystalline aluminum oxide-hydroxide or colloidal aluminum hydroxide, or a combination thereof, or preferably about 60 weight percent to about 97 weight percent of crystalline aluminum trihydroxide and about 3 weight percent to about 40 weight percent of crystalline aluminum oxide-hydroxide or colloidal aluminum hydroxide, or a combination thereof; and more preferably about 90 weight percent to about 99 weight percent of crystalline aluminum trihydroxide and about 1 weight percent to about 10 weight percent of crystalline aluminum oxide-hydroxide or colloidal aluminum hydroxide, or a combination thereof. In some embodiments, the plurality of aluminum hydroxides may contain from about 90% to about 99% by weight of crystalline aluminum trihydroxide and from about 1% to about 10% by weight of crystalline aluminum oxyhydroxide or a combination of colloidal aluminum hydroxides. The method may further include extruding the moldable mixture to form an extrudate and drying and calcining the extrudate to produce the alkane dehydrogenation catalyst.

[0011] According to another aspect of the present disclosure, a method for dehydrogenating alkanes is provided. In some embodiments, the method may include loading a reactor with a dehydrogenation catalyst produced by mixing a plurality of aluminum hydroxides, a water-insoluble chromium (III) oxide source, and an alkali metal oxide source with a metal-free aqueous acid solution to form a moldable mixture. The plurality of aluminum hydroxides may contain about 60% to about 97% by weight of crystalline aluminum trihydroxide and about 3% to about 40% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide. In some embodiments, the plurality of aluminum hydroxides may contain about 90% to about 97% by weight of crystalline aluminum trihydroxide and about 3% to about 10% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide.

[0012] The method for dehydrogenating an alkane may further include extruding the moldable mixture to form an extrudate and drying and calcining the extrudate to produce an alkane dehydrogenation catalyst. The method may further include supplying a feed containing the alkane through a reactor at a temperature sufficient to dehydrogenate the alkane. In some embodiments, the method may further include separating the dehydrogenation product from the unreacted alkane.

[0013] Still other aspects and advantages of these exemplary embodiments and other embodiments are discussed in detail herein. Furthermore, it is understood that the foregoing information and the following detailed description provide only illustrative examples of various aspects and embodiments and are intended to provide an overview or framework for understanding the attributes and characteristics of the claimed aspects and embodiments. Therefore, these and other objectives, along with the advantages and features of the present disclosure, will become apparent by reference to the following description. Furthermore, it is understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations. DETAILED DESCRIPTION

[0014]

[0014] This disclosure describes various embodiments related to methods for making and using alkane dehydrogenation catalysts. Additional embodiments may be described and disclosed.

[0015] In the following description, numerous details are set forth to provide a thorough understanding of the various embodiments. In other instances, well-known methods, devices, and systems may not be described in particular detail to avoid unnecessarily obscuring the various embodiments. Additionally, the description of various embodiments may omit features or details so as not to obscure the various embodiments.

[0016] The description may use the phrases "in some embodiments," "in various embodiments," "in one embodiment," or "in multiple 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 the embodiments of the present disclosure are synonymous.

[0017] The term "about" is defined as approximately as understood by one of ordinary skill in the art. In one non-limiting embodiment, the term is defined as within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0018] The use of the word "a" or "an" when used with any of the terms "comprising," "including," "containing," or "having" in the claims or the specification can mean "one," but it also means "one or more," "at least one," and "one or more than one."

[0019] The terms "wt %," "volume %," or "mole %" refer to the weight, volume, or mole percentage, respectively, of a component based on the total weight, volume, or moles of the material in which the component is included. In a non-limiting example, 10 grams of a component is 10% by weight of the component in 100 grams of material.

[0020] 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. The term "substantially free" of component X refers to a composition that contains no more than 1% by weight of component X in the composition.

[0021] Disclosed herein are methods for preparing and using alkane dehydrogenation catalysts. The dehydrogenation catalysts prepared according to the presently disclosed methods have good activity and improved stability and mechanical strength. The presently disclosed methods provide a cost-effective method for preparing chromium oxide-alumina dehydrogenation catalysts without using a chromium (VI) source. The presently disclosed methods provide a cost-effective method for preparing chromium oxide-alumina dehydrogenation catalysts without using a source containing water-soluble chromium. In some embodiments, the presently disclosed methods for preparing the dehydrogenation catalysts do not require or include impregnation of the aluminum support with a chromium (III) salt. In some embodiments, the presently disclosed methods for preparing the dehydrogenation catalysts do not include an impregnation step. Among other uses, the presently disclosed chromium oxide-alumina dehydrogenation catalysts can be used for the dehydrogenation of paraffins to produce olefins. Examples of paraffins include propane, isobutane, n-butane, and isopentane.

[0022] According to one aspect of the present disclosure, a method for preparing an alkane dehydrogenation catalyst is provided. In some embodiments, the method may include mixing a variety of aluminum hydroxides, water-insoluble chromium oxide (III) source and an alkali metal oxide source with a metal-free acid aqueous solution to form a moldable mixture. The alkali metal oxide source may contain sodium oxide, lithium oxide, potassium oxide or a cesium oxide source. Each component may be mixed to provide a moldable mixture by various methods (both manual and mechanical). For example, in some embodiments, the moldable mixture may be mixed by a batch mixer. After the raw materials for catalyst preparation can be fully mixed in a high shear mixer, the metal-free acid aqueous solution may be mixed until a fairly hard mass / granular object is obtained. This mass / granular object may be extruded and / or formed into any suitable shape, including cylinder, cube, star, trilobate, quadrilobate, pellets, pills or spheres. In one embodiment, mixing is performed in a high intensity environment, such as provided by a B&P Littleford mixer available from B&P Littleford, 1000 Hess Avenue, Saginaw, MI 48601.

[0023] In another embodiment, mixing is performed using an Eirich intensive mixer (e.g., provided by Maschinenfabrik GustavEirich GmbH & Co KG, Hardheim, Germany). Mixing is performed for a time sufficient to produce a homogeneous mixture. In other embodiments, other batch or continuous methods may be used to produce the moldable mixture. The components may be added sequentially or together in any convenient order, as will be apparent to one of ordinary skill in the art.

[0024] The various aluminum hydroxides may contain from about 60% to about 97% by weight of crystalline aluminum trihydroxide and from about 3% to about 40% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. In some embodiments, the various aluminum hydroxides may contain from about 90% to about 97% by weight of crystalline aluminum trihydroxide and from about 3% to about 10% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 91% to about 96% by weight of crystalline aluminum trihydroxide and from about 4% to about 9% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 92% to about 96% by weight of crystalline aluminum trihydroxide and from about 4% to about 8% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 93% to about 97% by weight of crystalline aluminum trihydroxide and from about 3% to about 6% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain about 95% by weight of crystalline aluminum trihydroxide and about 5% by weight of crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof. The use of various aluminum hydroxides is expected to increase crush strength without affecting catalyst performance until a specific combination of aluminum hydroxides is reached. The method may also include extruding the moldable mixture to form an extrudate and drying and calcining the extrudate to produce an alkane dehydrogenation catalyst. In some embodiments of the method for preparing an alkane dehydrogenation catalyst, the extrudate 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.

[0025] In some embodiments of the method of preparing an alkane dehydrogenation catalyst, the extrudates may be calcined at a temperature in the range of about 700° C. to about 1000° C. In some embodiments, the presently described alkane dehydrogenation catalysts may take the form of extrudates having a diameter of about 1 to about 4 mm, or about 2 to about 3.5 mm, and a length of about 2 to about 10 mm, or about 3 to about 9 mm.

[0026] In some embodiments, the alkane dehydrogenation catalyst produced by the method may contain about 60% to about 90% by weight of aluminum oxide, about 10% to about 40% by weight of water-insoluble chromium (III) oxide, and about 0.1% to about 5% by weight of alkali metal oxide. In some embodiments, the metal-free aqueous acid solution includes an acid such as nitric acid. The moldable mixture includes an aqueous non-metallic acid. In this article, a non-metallic acid refers to an acid that does not include a metal atom in its molecular structure. In some embodiments of the method, as described herein, the non-metallic acid may be nitric acid. In other embodiments of the method, as described herein, the non-metallic acid may be an organic acid such as formic acid or acetic acid. In yet other embodiments of the method, the non-metallic acid may be a combination of nitric acid and an organic acid (such as formic acid or acetic acid). In some embodiments, the use of an organic acid may be advantageous because it can reduce the concentration of nitrogen oxides during heat treatment. However, it may also make the peptization of aluminum hydroxide less efficient. One of ordinary skill in the art will determine the appropriate amount and type of acid used to provide the desired moldable material.

[0027] In some embodiments, the crystalline aluminum trihydroxide may be selected from one or more of bayerite and neoalumina trihydrate. The crystalline aluminum oxide hydrate may be, at least in some cases, boehmite. In some embodiments, the colloidal aluminum hydroxide may be selected from one or more of amorphous aluminum hydroxide or pseudoboehmite. In some embodiments, the water-insoluble chromium (III) oxide source used to prepare the alkane dehydrogenation catalyst may be substantially free of hexavalent chromium oxide.

[0028] According to another aspect of the present disclosure, a method for dehydrogenating alkanes is provided. In some embodiments, the method may include loading a reactor with a dehydrogenation catalyst, the dehydrogenation catalyst being produced by mixing a plurality of aluminum hydroxides, a chromium (III) oxide source, and an alkali metal oxide source with a metal-free aqueous acid solution to form a moldable mixture. The plurality of aluminum hydroxides may contain about 60% by weight to about 97% by weight of crystalline aluminum trihydroxide and about 3% by weight to about 40% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide or a combination thereof. In some embodiments, the plurality of aluminum hydroxides may contain about 90% by weight to about 97% by weight of crystalline aluminum trihydroxide and about 3% by weight to about 10% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide or a combination thereof.

[0029] The dehydrogenation method for alkanes may also include extruding a moldable mixture to form an extrudate and drying and calcining the extrudate to produce an alkane dehydrogenation catalyst. The method may also include supplying a feed containing alkanes through a reactor at a temperature sufficient to dehydrogenate the alkanes. In some embodiments, the method may also include separating the dehydrogenation product from the unreacted alkanes. In some embodiments, the alkane dehydrogenation catalyst used in the method contains about 60% by weight to about 95% by weight of aluminum oxide, about 4% by weight to about 39% by weight of chromium (III) oxide, and about 0.1% by weight to about 5% by weight of alkali metal oxide. In some embodiments, the alkane dehydrogenation catalyst used in the method contains about 60% by weight to about 90% by weight of aluminum oxide, about 10% by weight to about 40% by weight of chromium (III) oxide, and about 0.1% by weight to about 5% by weight of alkali metal oxide. In some cases, crystalline aluminum trihydrate may be selected from one or more of bayerite and new aluminum trihydrate. Crystallized aluminum oxide hydrate may be boehmite in at least some cases. In some embodiments, the colloidal aluminum hydroxide may be selected from one or more of amorphous aluminum hydroxide or pseudo-boehmite. In some embodiments of the alkane dehydrogenation method, the extrudate may be calcined at a temperature in the range of about 700° C. to about 1000° C. In at least some embodiments of the method, the temperature sufficient to dehydrogenate the alkane may be in the range of about 400° C. to 800° C.

[0030] Example

[0031] Catalyst preparation

[0032] Example 1 (Comparative Example Prepared Without Pseudoboehmite)

[0033] By mixing bayerite (2323.6 g, Versal B, UOP), chromium (III) oxide (388.8 g, )、Basic zirconium (IV) carbonate (ZrO) 2 (OH) 2 CO 3 (17.0 g, ) (which were dry mixed for 10 minutes in an Eirich mixer (EL-5 ProfiPlus)) to prepare the catalyst of this example. 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 resulting blend was aged at 25° C. for 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder. The cylindrical extrudates were dried at 70° C. and then at 120° C. for 12 hours, calcined at 850° C. in air in a muffle furnace for 2 hours, cooled to room temperature and used for catalyst testing. The composition of the resulting catalyst was 20 wt % Cr2O3, 0.60 wt % Na2O, 1.0 wt % MgO, 0.7 wt % ZrO2 and 77.70 wt % Al2O3.

[0034] Example 2 ( The present invention having pseudo-boehmite )

[0035] Bayerite (2101.0 g, Versal B, UOP), pseudoboehmite (219.9 g, Versal 250, UOP), chromium (III) oxide (390.6 g, )、Zirconium (IV) basic carbonate (17.1 g, ) for 10 minutes to prepare the catalyst of this example. An aqueous solution of nitric acid (320 ml of 25 wt% nitric acid mixed with 30 ml of water) containing dissolved sodium nitrate (32.1 g) and magnesium nitrate hexahydrate (124.2 g) was added to a mixer and mixed for about 10 minutes. The resulting blend was aged at 25°C for 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder, dried at 70°C followed by 120°C for 12 hours, calcined in a muffle furnace at 850°C in air for 2 hours, cooled to room temperature and used for catalyst testing. The composition of the resulting catalyst of this example was 20 wt% Cr2O3, 0.60 wt% Na2O, 1.0 wt% MgO, 0.7 wt% ZrO2 and 77.70 wt% Al2O3.

[0036] Crushing strength measurement results

[0037] The catalyst extrudate crushing strength was measured using the Vinci Technologies VERSATILE CATALYST CRUSHINGSTRENGTH TESTER (VCS) using the ASTM D6175 method. A sample of 50 to 100 g was heated at 400 ± 15°C for 3 h. After heating, the test sample was cooled in a desiccator to prevent absorption of moisture before testing. Only the number of extrudates that could be tested within a 10-minute period was removed from the desiccator. The length of the extrudate was measured to the nearest tenth of a millimeter and recorded. Tweezers, pliers, or other suitable devices or procedures were used to prevent moisture from being transferred from the operator's hands to the extrudate being tested. The measured extrudate with a length-to-diameter ratio greater than or equal to one, preferably an extrudate with a length in the range of 6 to 8 mm and a diameter in the range of 2.9 to 3.3 mm, was placed between the anvils of the compression tester. The extrudate was placed flat on the face of the anvil and radially crushed by applying a gradually increasing force at a uniform rate in the range of 1 to 5 lbf / s (4.4 to 22 N / s) until the extrudate broke or collapsed. The anvil was then separated and any residue removed with a soft brush. Care was taken to ensure that the face of the anvil was free of particles adhering to the surface. Each extrudate was subjected to a gradually increasing load until the breaking point (maximum load value 100 daN). The compressive strength over the length ratio is reported in daN / mm. The results are shown in Table 1.

[0038] The results provided in Table 1 illustrate that the catalyst prepared according to the presently disclosed method (Example 2) is characterized by a higher crush strength than the catalyst prepared by the comparative method (Example 1).

[0039] Table 1: Crushing strength measurement results

[0040]

[0041] Catalyst activity test

[0042] The catalysts of Examples 1 and 2 were tested for isobutane dehydrogenation activity using a fixed bed reactor. The catalyst loading and reactor details were as follows: catalyst weight 70 g, catalyst particle size about 3 mm diameter, catalyst diluent quartz (ring) size 2.2 x 2 mm, catalyst diluent weight ratio 1:3, reactor inner diameter 41 mm, reactor outer diameter 45 mm. Catalyst extrudates (7 batches of 10 g) and inert quartz diluent (7 batches of 30 g) were loaded into the reactor in layers. The above-mentioned quartz rings were loaded above the catalyst bed. Nitrogen purge was used between the dehydrogenation, catalyst regeneration / oxidation and reduction steps with hydrogen. The isobutane flow in the dehydrogenation step corresponded to 600 ml h -1 g -1The reactor was operated at atmospheric pressure using isobutane (99.9% by volume) diluted with nitrogen. The reaction pressure during dehydrogenation was 0.33 atmospheres of isobutane and 0.67 atmospheres of nitrogen. The reactor outlet gas was analyzed by an 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 product 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) oxidizing / regenerating the catalyst with air for 10 minutes with a starting temperature of 650°C. 2) purging the catalyst bed with nitrogen at 650°C for 3 minutes. 3) reducing the catalyst with hydrogen at a starting temperature of 650°C for 3 minutes. 4) cooling the catalyst bed under nitrogen from 650°C to 585°C and maintaining it at 585°C for 15 minutes. 5) dehydrogenating the catalyst with isobutane at a starting temperature of 585°C for 10 minutes. The reactor outlet gas composition was analyzed using gas chromatography at the 9th minute from the start of the isobutane feed. Because the fresh catalyst activity changed during the initial cycle, the catalyst was balanced under the cyclic oxidation (air, 2 minutes)-purge (nitrogen, 4 minutes)-reduction (hydrogen, 2 minutes) conditions to achieve stable catalyst performance. The balance of the fresh catalyst was carried out at 650°C for 100 cycles. Steps 1 to 5 were then repeated for 30 cycles and the catalyst performance results after catalyst stabilization are provided in Table 2 (21-30 cycle average). The results shown in Table 2 illustrate that the catalyst prepared according to the method of the present invention (Example 2) is characterized by similar performance compared to the catalyst prepared by the comparative method of Example 1.

[0043] Table 2: Catalyst performance results

[0044]

[0045] When a range is disclosed herein, the range from any lower limit can be combined with any upper limit to record an unspecified range, and the range from any lower limit can be combined with any other lower limit to record an unspecified range. In the same manner, the range from any upper limit can be combined with any other upper limit to record an unspecified range. In addition, even if not explicitly stated, the values ​​stated in the range include every value within the range. Therefore, each point or single value can serve as its own lower limit or upper limit, combined with any other point or single value or any other lower limit or upper limit to record an unspecified range.

[0046] In the context of the present invention, at least sixteen embodiments are now described. Embodiment 1 is a method for preparing an alkane dehydrogenation catalyst. The method comprises the steps of: mixing a plurality of aluminum hydroxides, a water-insoluble chromium (III) oxide source, and an alkali metal oxide source with a metal-free aqueous acid solution to form a moldable mixture, the plurality of aluminum hydroxides containing about 60% to about 99% by weight of crystalline aluminum trihydroxide and about 1% to about 40% by weight of crystalline aluminum oxide or colloidal aluminum hydroxide, or a combination thereof; extruding the moldable mixture to form an extrudate; and drying and calcining the extrudate to produce the alkane dehydrogenation catalyst. Embodiment 2 is the method of embodiment 1, wherein the plurality of aluminum hydroxides contains about 90% to about 99% by weight of crystalline aluminum trihydroxide and about 1% to about 10% by weight of crystalline aluminum oxide or colloidal aluminum hydroxide, or a combination thereof. Embodiment 3 is the method of embodiment 1, wherein the crystalline aluminum trihydroxide is one or more of bayerite and neoalumina. Embodiment 4 is the method of embodiment 1, wherein the crystalline aluminum oxide is boehmite. Embodiment 5 is the method of embodiment 1, wherein the colloidal aluminum hydroxide is one or more of amorphous aluminum hydroxide or pseudo-boehmite. Embodiment 6 is the method of embodiment 1, wherein the extrudate is calcined at a temperature in the range of about 700° C. to about 1000° C. Embodiment 7 is the method of embodiment 1, wherein the alkane dehydrogenation catalyst comprises about 60% to about 90% by weight aluminum oxide, about 10% to about 40% by weight chromium(III) oxide, and about 0.1% to about 5% by weight alkali metal oxide.

[0047] Embodiment 8 is a method for dehydrogenating alkanes. The method includes the steps of loading a reactor with an alkane dehydrogenation catalyst produced by: mixing a plurality of aluminum hydroxides, a water-insoluble chromium (III) oxide source, and an alkali metal oxide source with a metal-free aqueous acid solution to form a moldable mixture, the plurality of aluminum hydroxides containing about 60% to about 99% by weight of crystalline aluminum trihydroxide and about 1% to about 40% by weight of crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof; extruding the moldable mixture to form an extrudate; and drying and calcining the extrudate to produce the alkane dehydrogenation catalyst; and supplying a feed containing an alkane through the reactor at a temperature sufficient to dehydrogenate the alkane. Embodiment 9 is the method of embodiment 8, wherein the plurality of aluminum hydroxides contains about 90% to about 99% by weight of crystalline aluminum trihydroxide and about 1% to about 10% by weight of crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof. Embodiment 10 is the method of embodiment 8, wherein the alkane dehydrogenation catalyst comprises about 60% to about 90% by weight of aluminum oxide, about 10% to about 40% by weight of chromium (III) oxide, and about 0.1% to about 5% by weight of an alkali metal oxide. Embodiment 11 is the method of embodiment 8, wherein the crystalline aluminum trihydroxide is one or more of bayerite and neoalumina trihydrate. Embodiment 12 is the method of embodiment 8, wherein the crystalline aluminum oxide trihydroxide is boehmite. Embodiment 13 is the method of embodiment 8, wherein the colloidal aluminum hydroxide is one or more of amorphous aluminum hydroxide or pseudoboehmite. Embodiment 14 is the method of embodiment 8, wherein the extrudate is calcined at a temperature in the range of about 700° C. to 1000° C. Embodiment 15 is the method of embodiment 8, wherein the temperature sufficient to dehydrogenate the alkane is in the range of 400° C. to 800° C. Embodiment 16 is the method of embodiment 8, further comprising separating the dehydrogenation product from the unreacted alkane.

[0048] Other objectives, features and advantages of the disclosure will become apparent from the above detailed description. However, it should be understood that although the specific embodiments of the disclosure are shown, the detailed description is provided by way of illustration only and is not intended to be restrictive. In other embodiments, features from a specific embodiment can be combined with features from other embodiments. For example, features from an embodiment can be combined with any features from other embodiments. In other embodiments, additional features can be added to the specific embodiments described herein.

Claims

1. A method for preparing an alkane dehydrogenation catalyst, comprising: mixing a plurality of aluminum hydroxides containing from about 60 weight percent (wt %) to about 99 wt % crystalline aluminum trihydroxide and from about 1 wt % to about 40 wt % crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof, a water-insoluble source of chromium (III) oxide, and a source of an alkali metal oxide with a metal-free aqueous acid solution to form a moldable mixture; extruding the moldable mixture to form an extrudate; and The extrudates are dried and calcined to produce the alkane dehydrogenation catalyst.

2. The method of claim 1 , wherein the plurality of aluminum hydroxides comprises from about 90% to about 99% by weight crystalline aluminum trihydroxide and from about 1% to about 10% by weight crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof.

3. The method according to claim 1, wherein the crystalline aluminum trihydroxide is one or more of bayerite and neoalumina trihydrate.

4. The method of claim 1, wherein the crystalline aluminum oxide hydroxide is boehmite.

5. The method according to claim 1, wherein the colloidal aluminum hydroxide is one or more of amorphous aluminum hydroxide or pseudo-boehmite.

6. The method of claim 1, wherein the extrudate is calcined at a temperature in the range of about 700 degrees Celsius (°C) to about 1000°C.

7. The process of claim 1 , wherein the alkane dehydrogenation catalyst comprises about 60 wt % to about 90 wt % alumina, about 10 wt % to about 40 wt % chromium (III) oxide, and about 0.1 wt % to about 5 wt % alkali metal oxide.

8. A method for dehydrogenating alkanes, comprising: The reactor is loaded with an alkane dehydrogenation catalyst produced by: mixing a plurality of aluminum hydroxides containing from about 60 weight percent (wt %) to about 99 wt % crystalline aluminum trihydroxide and from about 1 wt % to about 40 wt % crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof, a water-insoluble source of chromium (III) oxide, and a source of an alkali metal oxide with a metal-free aqueous acid solution to form a moldable mixture; extruding the moldable mixture to form an extrudate; as well as drying and calcining the extrudates to produce the alkane dehydrogenation catalyst; and supplying a feed containing an alkane through the reactor at a temperature sufficient to dehydrogenate the alkane.

9. The method of claim 8, wherein the plurality of aluminum hydroxides comprises from about 90% to about 99% by weight crystalline aluminum trihydroxide and from about 1% to about 10% by weight crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof.

10. The process of claim 8, wherein the alkane dehydrogenation catalyst comprises about 60 wt% to about 90 wt% alumina, about 10 wt% to about 40 wt% chromium (III) oxide, and about 0.1 wt% to about 5 wt% alkali metal oxide.

11. The method according to claim 8, wherein the crystalline aluminum trihydroxide is one or more of bayerite and neoalumina trihydrate.

12. The method of claim 8, wherein the crystalline aluminum oxyhydroxide is boehmite.

13. The method of claim 8, wherein the colloidal aluminum hydroxide is one or more of amorphous aluminum hydroxide or pseudo-boehmite.

14. The method of claim 8, wherein the extrudate is calcined at a temperature in the range of about 700°C to 1000°C.

15. The method of claim 8, wherein the temperature sufficient to dehydrogenate the alkanes is in the range of 400°C to 800°C.

16. The method of claim 8, further comprising separating the dehydrogenation product from unreacted alkanes.

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