Catalyst for dehydrogenation of paraffins

Abstract

Methods of making and using alkane dehydrogenation catalysts to dehydrogenate alkanes are provided. A method for dehydrogenation of alkanes can 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 non-metallic acidic aqueous solution to form a moldable mixture. The moldable mixture may be extruded to form an extrudate. The extrudate may be dried and calcined to produce an alkane dehydrogenation catalyst containing about 60 wt% to about 90 wt% alumina, about 10 wt% to about 40 wt% trivalent chromium oxide, and about 0.1 wt% to about 5 wt% alkali metal oxide. The method may also include supplying a feed containing alkanes through the reactor at a pressure less than 1 atm to dehydrogenate the alkanes.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 476,641, filed on December 22, 2022, the entire contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure generally relates to methods for dehydrogenating alkanes and methods for preparing and using alkane dehydrogenation catalysts. More particularly, the present disclosure relates to methods for using and preparing chromium oxide-aluminum oxide dehydrogenation catalysts without the use of water-soluble chromium-containing materials for dehydrogenating alkanes, 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] Chromia-alumina dehydrogenation catalyst technology has been used for decades. The stability of the dehydrogenation catalyst plays a significant role in the overall efficiency of the dehydrogenation process. Due to the extreme temperature ranges in which catalytic dehydrogenation processes are conducted, the catalyst's life expectancy is often limited. Therefore, improving catalyst stability translates into a longer catalyst life, allowing for better catalyst utilization and ultimately leading to less catalyst consumption during the dehydrogenation process.

[0006] Chromia-alumina dehydrogenation catalysts are typically 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. In addition, catalyst preparation processes involving impregnation of an aluminum support with a chromium (III) salt require multiple impregnation steps to achieve the desired chromium content. Each impregnation step requires intermediate drying and calcination, and such multiple impregnation processes are therefore time-consuming, labor-intensive, and costly relative to conventional preparation procedures involving chromium (VI)-containing materials. Applicants have therefore recognized a need for a simple, cost-effective process for preparing chromia-alumina dehydrogenation catalysts that do not use chromium (VI)-containing materials and that exhibit good activity, improved stability, and are useful for the dehydrogenation of lower paraffins. Summary of the Invention

[0007] To address deficiencies in the art, applicants have developed methods for dehydrogenating alkanes and 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. Among other uses, the presently disclosed chromium oxide-alumina dehydrogenation catalysts can be used for the dehydrogenation of lower paraffins. Additionally, it has been unexpectedly discovered that supplying an alkane-containing feed through a reactor at a pressure less than 1 atmosphere to dehydrogenate the alkanes results in higher alkane dehydrogenation rates when using catalysts prepared according to the presently disclosed methods.

[0008] According to one 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 can be prepared by mixing a variety of aluminum hydroxides, a water-insoluble chromium oxide (III) source, and an alkali metal oxide source with a non-metallic acidic aqueous solution to form a moldable mixture. The moldable mixture can then be extruded to form an extrudate. The extrudate can then be dried and calcined to produce an alkane dehydrogenation catalyst containing about 60 weight percent (wt%)-about 90 weight % aluminum oxide, about 10 weight %-about 40 weight % trivalent chromium oxide, and about 0.1 weight %-about 5 weight % alkali metal oxide. The method for dehydrogenating alkanes may also include supplying a feed containing alkanes through a reactor under a pressure less than 1 atmosphere to dehydrogenate the alkanes.

[0009] According to another aspect of the present disclosure, a method for dehydrogenating alkanes is provided. The method may include loading a reactor with a dehydrogenation catalyst. Dehydrogenation catalysts can be produced by mixing a plurality of aluminum hydroxides, a water-insoluble chromium oxide (III) source, and an alkali metal oxide source with a non-metallic acidic aqueous solution to form a moldable mixture. The plurality of aluminum hydroxides may contain crystallized aluminum trihydroxide (aluminum trihydroxide) of about 90 wt % to about 97 wt % and crystallized aluminum oxide hydrate (aluminum oxide-hydroxide) or colloidal aluminum hydroxide or a combination thereof of about 3 wt % to about 10 wt %. In other embodiments, the plurality of aluminum hydroxides may contain crystallized aluminum trihydroxide of about 60 wt % to about 97 wt % and crystallized aluminum oxide hydrate or colloidal aluminum hydroxide or a combination thereof of about 3 wt % to about 40 wt %. The moldable mixture may then be extruded to form an extrudate. The extrudates can then be dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60% to about 90% by weight alumina, from about 10% to about 40% by weight trivalent chromium oxide, and from about 0.1% to about 5% by weight alkali metal oxide. The method for dehydrogenating an alkane can also include supplying a feed containing an alkane through a reactor at a pressure of less than 1 atmosphere to dehydrogenate the alkane.

[0010] 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

[0011]

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

[0012] In the following description, numerous details are set forth to provide a thorough understanding of the various embodiments. In other cases, well-known methods, devices, and systems may not be described in particular detail to avoid unnecessarily obscuring the various embodiments. In addition, the description of the various embodiments may omit certain features or details so as not to obscure the various embodiments.

[0013] 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.

[0014] 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%.

[0015] The use of the word "a" or "an" in the claims or the specification when used in conjunction with any of the terms "comprising," "including," "containing," or "having" can mean "one," but it also means "one or more," "at least one," and "one or more than one."

[0016] 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.

[0017] 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.

[0018] Disclosed herein are methods for preparing and using alkane dehydrogenation catalysts to dehydrogenate alkanes. Dehydrogenation catalysts prepared according to the presently disclosed methods have good activity and improved stability. The presently disclosed methods provide a cost-effective method for preparing chromium oxide-alumina dehydrogenation catalysts without using a chromium (VI)-containing source. Among other uses, the presently disclosed chromium oxide-alumina dehydrogenation catalysts can be used for the dehydrogenation of lower paraffins. Examples of paraffins include propane, isobutane, n-butane, and isopentane. It has been unexpectedly discovered that supplying a feed containing an alkane through a reactor at a pressure less than 1 atmosphere to dehydrogenate the alkane results in a higher alkane dehydrogenation rate for olefin production when using the catalyst prepared according to the presently disclosed methods. In some embodiments, the operating pressure using the presently disclosed alkane dehydrogenation catalysts can be from about 0.3 atmosphere to about 0.9 atmosphere.

[0019] According to one aspect of the present disclosure, a method for dehydrogenating an alkane is provided. In some embodiments, the method may include loading a reactor with a dehydrogenation catalyst.

[0020] Dehydrogenation catalyst can be prepared by mixing a variety of aluminum hydroxides, water-insoluble chromium oxide (III) source and alkali metal oxide source with non-metallic acidic aqueous solution to form a moldable mixture. Each component can be mixed to provide a moldable mixture by various methods (both manual and mechanical). For example, in some embodiments, the moldable mixture can be mixed by a batch mixer. After the raw materials for catalyst preparation can be fully mixed in a high shear mixer, they are mixed with non-metallic acidic aqueous solution until a fairly hard mass / granular material is obtained. This mass / granular material can be extruded and / or formed into any suitable shape, including cylinder, cube, star, trilobate, quadrilobate, pellets, pills or spheres by suitable mechanical means. In one embodiment, mixing is carried out in a high-intensity environment, for example, it is provided by the B&P Littleford mixer available from B&P Littleford, 1000 Hess Avenue, Saginaw, MI 48601. In another embodiment, mixing is performed using an Eirich intensive mixer (e.g., provided by Maschinenfabrik Gustav Eirich 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.

[0021] 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. In other embodiments, 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. 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 crystalline aluminum trihydroxide and about 5% by weight crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof. The use of various aluminum hydroxides is expected to improve crush strength without affecting catalyst performance until a specific combination of aluminum hydroxides is achieved. The moldable mixture can then be extruded to form an extrudate. The extrudate can then be dried and calcined to produce an alkane dehydrogenation catalyst containing about 60% to about 90% by weight aluminum oxide, about 10% to about 40% by weight trivalent chromium (i.e., chromium (III)) oxide, and about 0.1% to about 5% by weight alkali metal oxide.

[0022] In some embodiments, the plurality of aluminum hydroxides may include crystalline aluminum trihydroxide, crystalline aluminum oxide hydrate, colloidal aluminum hydroxide, and any combination thereof. In some cases, the crystalline aluminum trihydroxide may include one or more of bayerite and neoaluminum trihydrate. In some embodiments, the crystalline aluminum oxide hydrate may include boehmite. In some cases, the colloidal aluminum hydroxide may be one or more of amorphous aluminum hydroxide and pseudoboehmite.

[0023] In some embodiments, the alkali metal oxide source present in the moldable mixture is a sodium oxide source, and the catalyst comprises about 60 wt % to about 90 wt % aluminum oxide, about 10 wt % to about 40 wt % trivalent chromium oxide, and about 0.1 wt % to about 5 wt % sodium oxide. In other embodiments, the moldable mixture further comprises a lithium oxide source and the catalyst comprises about 60 wt % to about 90 wt % aluminum oxide, about 10 wt % to about 40 wt % trivalent chromium oxide, about 0.1 wt % to about 5 wt % sodium oxide, and about 0.1 wt % to 3 wt % lithium oxide (Li O). According to at least one aspect of the present disclosure, in at least some embodiments, it has been found that the catalysts currently disclosed comprising both sodium oxide and lithium oxide can have advantageous properties over catalysts prepared using an impregnation method. In some embodiments, the alkali metal source can be lithium oxide. Non-limiting examples of water-insoluble chromium (III) oxide sources can include chromium (III) oxide, chromium (III) hydroxide, or mixtures thereof.

[0024] Non-metallic acidic aqueous solution herein refers to an aqueous solution containing acid in which the molecular structure of the acid does not include metal atoms. In some embodiments of the method, as described in addition herein, the non-metallic acid can be nitric acid. In other embodiments of the method, as described in addition herein, the non-metallic acid can be an organic acid such as formic acid or acetic acid. In other embodiments of the method, the non-metallic acid can 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 can be advantageous because it can reduce nitrogen oxide concentration during the heat treatment. However, it can also make the peptization of aluminum oxide 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.

[0025] 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. The extrudate may be calcined at a temperature in the range of about 700° C. to 1000° C. in some embodiments of the method.

[0026] According to another aspect of the present disclosure, a method for dehydrogenating alkanes is provided. The method may include loading a reactor with a dehydrogenation catalyst. The dehydrogenation catalyst can be produced by mixing a plurality of aluminum hydroxides, a water-insoluble chromium (III) oxide source, and an alkali metal oxide source with a non-metallic acidic aqueous 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 trihydrate 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 other embodiments, the plurality of aluminum hydroxides may contain about 90% by weight to about 97% by weight of crystalline aluminum trihydrate and about 3% by weight to about 10% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide or a combination thereof. The moldable mixture may then be extruded to form an extrudate. The extrudates can then be dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60% to about 90% by weight of alumina, from about 10% to about 40% by weight of trivalent chromium oxide, and from about 0.1% to about 5% by weight of an alkali metal oxide. The method for dehydrogenating an alkane can also include supplying a feed containing an alkane through a reactor at a pressure of less than 1 atmosphere to dehydrogenate the alkane. In some embodiments, the operating pressure using the presently disclosed alkane dehydrogenation catalyst can be from about 0.3 atmosphere to about 0.9 atmosphere.

[0027] In some embodiments, the plurality of aluminum hydroxides may contain from about 90% to about 97% by weight crystalline aluminum trihydroxide and from about 3% to about 10% by weight crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide or a combination thereof. In some embodiments, the plurality of aluminum hydroxides may contain crystalline aluminum trihydroxide, crystalline aluminum oxyhydroxide, colloidal aluminum hydroxide, and any combination thereof. In some cases, the crystalline aluminum trihydroxide may contain one or more of bayerite and neoaluminum trihydrate. In some embodiments, the crystalline aluminum oxyhydroxide may contain boehmite. In some cases, the colloidal aluminum hydroxide may be one or more of amorphous aluminum hydroxide and pseudoboehmite. The use of multiple aluminum hydroxides is expected to increase crush strength without affecting catalyst performance until a specific combination of aluminum hydroxides is reached.

[0028] In some embodiments, the alkali metal oxide source present in the moldable mixture is a sodium oxide source, and the catalyst comprises from about 60% to about 90% by weight aluminum oxide, from about 10% to about 40% by weight trivalent chromium oxide, and from about 0.1% to about 5% by weight sodium oxide. In other embodiments, the moldable mixture further comprises a lithium oxide source, and the catalyst comprises from about 60% to about 90% by weight aluminum oxide, from about 10% to about 40% by weight trivalent chromium oxide, from about 0.1% to about 5% by weight sodium oxide, and from about 0.1% to 3% by weight lithium oxide (LiO).

[0029] In some embodiments of the method, the extrudate may be calcined at a temperature in the range of about 700°C to 1000°C. The method for dehydrogenating alkanes may also include supplying a feed containing alkanes through a reactor at a pressure of less than 1 atmosphere to dehydrogenate the alkanes. In some embodiments, the operating pressure using the presently disclosed alkane dehydrogenation catalysts may be from about 0.3 atmospheres to about 0.9 atmospheres. In some embodiments, the temperature range sufficient to dehydrogenate alkanes using this method is from 400°C to 800°C. In some embodiments, the method may also include separating the dehydrogenation product from the unreacted alkanes.

[0030] Example

[0031] The examples provided below illustrate selected aspects of various methods of making and using alkane dehydrogenation catalysts useful in the presently disclosed methods of dehydrogenating alkanes.

[0032] Example 1

[0033] An alkane dehydrogenation catalyst having a composition of 20 wt% CrO, 0.43 wt% NaO, 0.25 wt% LiO, and 79.32 wt% AlO was prepared by mixing 2408.6 g of bayerite (Pural BT, SASOL), 412 g of chromium (III) oxide (Sigma-Aldrich), and 128 g of pseudo-boehmite (PBA M 05, Chika Pvt. Ltd.) in an Eirich mixer (EL-5 Profi Plus) for 10 minutes. An aqueous solution of nitric acid (476 ml, 25 wt%) containing 24.3 g of sodium nitrate and 24.3 g of lithium nitrate dissolved therein was added to the mixer and mixed for approximately 10 minutes. The obtained blend was aged at about 25° C. for about 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder, dried at 70° C. and then at 120° C. for about 12 hours, calcined in air at 850° C. in a muffle furnace for 2 hours and cooled to room temperature without external cooling. The surface area of ​​this catalyst was found to be 90.2 m 2 / g. CrO3 calculated from temperature programmed reduction (TPR) experiments was found to be 1.5 wt%.

[0034] Surface area measurements were performed using a Micromeritics Tristar surface area and porosity analyzer. Prior to measurement, the catalyst sample (approximately 200 mg) was evacuated at 300° C. for 2 hours to remove physically adsorbed water and N 2 physical adsorption was performed at −196° C. TPR experiments were performed on an Autochem 2920 (Micromeritics) instrument. Prior to TPR analysis, the catalyst sample (approximately 100 mg) was pretreated by passing pure argon (50 mL / min) for 30 min at 400° C. to remove physically adsorbed water. After pretreatment, the sample was cooled to 50° C. and 10% hydrogen in argon was passed through the sample, and the sample was heated to 600° C. at 10° C. / min while recording data.

[0035] Example 2

[0036] An alkane dehydrogenation catalyst having a composition of 20 wt% CrO, 0.43 wt% NaO, 0.25 wt% LiO, and 79.31 wt% AlO was prepared by mixing 2940.4 g bayerite (Pural BT, SASOL) and 154.8 g pseudoboehmite (PBAM-05, Chika Pvt. Ltd.) in an Eirich mixer (EL-5 Profi Plus) for 10 minutes. An aqueous solution of nitric acid (500 ml, 15 wt%) containing 29.7 g lithium nitrate dissolved therein was added to the mixer and mixed for about 10 minutes. The resulting blend was aged at about 25° C. for about 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder, dried at 70° C. and then at 120° C. for about 12 hours, and calcined in a muffle furnace at 850° C. in air for 2 hours and cooled to room temperature without external cooling. 250 g of the prepared calcined alumina extrudates were impregnated with an aqueous solution containing 62.3 g of chromium (VI) oxide and 5.2 g of sodium dichromate dihydrate to incipient wetness. The wet extrudates were aged in a closed container at about 25° C. for about 12 hours. The sample was then dried at 120° C. for about 6 hours and calcined in air at 750° C. in a muffle furnace for 2 hours and cooled to room temperature without external cooling. The surface area of ​​this catalyst was found to be 76.7 m 2 / g. CrO3 calculated from TPR was found to be 1.8 wt%.

[0037] Surface area measurements were performed using a Micromeritics Tristar surface area and porosity analyzer. Prior to measurement, catalyst samples (approximately 200 mg) were evacuated at 300° C. for 2 h to remove physically adsorbed water and N 2 physical adsorption was performed at −196° C. TPR experiments were performed on an Autochem 2920 (Micromeritics) instrument. Prior to TPR analysis, catalyst samples (approximately 100 mg) were pretreated by passing pure argon (50 mL / min) for 30 min at 400° C. to remove physically adsorbed water. After pretreatment, the sample was cooled to 50° C. and 10% hydrogen in argon was passed through the sample, and the sample was heated to 600° C. at 10° C. / min while recording data.

[0038] Example 3

[0039] The dehydrogenation activity of the catalysts prepared in Examples 1 and 2 was measured in a tubular fixed-bed quartz reactor. The catalyst loading and reactor details were as follows: catalyst weight = 70 g, catalyst particle size = approximately 3 mm diameter extrudates, catalyst diluent quartz (ring) size = 2.2×2 mm, catalyst diluent weight ratio = 1:3, reactor inner diameter = 41 mm, reactor outer diameter = 45 mm. The catalyst and inert quartz were divided into equal parts by weight and then loaded into the reactor in layers. Quartz rings of the above-mentioned dimensions were installed above the catalyst bed. Nitrogen purge was used between the dehydrogenation, catalyst regeneration / oxidation and reduction steps with hydrogen. The total isobutane flow in the dehydrogenation step corresponds to a GHSV of 600 mlh -1 g -1The 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. A Ritter-type wet gas flow meter was used to measure the reactant and product flow rates. The reactor was operated at atmospheric pressure using a pure isobutane feed (99.9% by volume) or isobutane diluted with nitrogen and in a circulation mode with the following steps: 1) oxidizing the catalyst with air for 10 minutes with a starting temperature of 650°C; 2) purging the catalyst with nitrogen at 650°C for 3 minutes; 3) reducing the catalyst with H2 with a starting temperature of 650°C for 3 minutes; 4) cooling from 650°C to 585°C under nitrogen and maintaining the temperature of 585°C for 20 minutes; 5) dehydrogenating isobutane with a starting temperature of 585°C for 10 minutes; 6) analyzing the reactor outlet gas composition by gas chromatography at the 9th minute from the start of the isobutane feed. Steps 1 to 6 were repeated for 350 cycles using pure isobutane feed at a pressure of 1 atmosphere and the reaction was then stopped. Thereafter, the reaction was restarted and steps 1 to 6 were repeated for up to 430 cycles using isobutane diluted with nitrogen with an isobutane pressure of 0.33 atmospheres and a nitrogen pressure of 0.67 atmospheres as feed. Steps 1 to 6 were then repeated for up to 462 cycles using pure isobutane feed at a pressure of 1 atmosphere and the reaction was then stopped. Table 1 provides catalyst performance data after catalyst stabilization. The results from Table 1 illustrate that the catalyst prepared according to the currently disclosed method (Example 1) is characterized in that it has a higher conversion rate than the catalyst prepared by the impregnation method (Example 2). As shown in Table 1, the catalyst prepared according to Example 1 is characterized in that it has better performance across all pressures and better selectivity at less than 1 atmosphere compared to the catalyst prepared by Example 2.

[0040] Table 1

[0041]

[0042] 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, a reference to a value stated in a range includes each and every value within the range. Thus, each point or individual value can serve as its own lower or upper limit, combined with any other point or individual value or any other lower or upper limit to record an unspecified range.

[0043] Other objectives, features and advantages of the disclosure will become apparent from the above-mentioned detailed description and examples. Although the specific embodiments of the disclosure are shown, the detailed description and examples are provided by way of illustration only and are not intended to be restrictive. In other embodiments, features from specific embodiments 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. Although the disclosure contains some aspects, embodiments and optional features, it should be understood that modifications, improvements or variations of such aspects, embodiments and optional features can be carried out by those skilled in the art, and such modifications, improvements or variations are considered to be within the scope of the present disclosure.

Claims

1. A method for dehydrogenating alkanes, comprising: The reactor is loaded with a dehydrogenation catalyst produced by: mixing a plurality of aluminum hydroxides, a source of chromium (III) oxide, and a source of an alkali metal oxide with a non-metallic acidic aqueous solution to form a moldable mixture; extruding the moldable mixture to form an extrudate; and drying and calcining the extrudates to produce a dehydrogenation catalyst comprising about 60% to about 90% by weight alumina, about 10% to about 40% by weight trivalent (chromium (III)) oxide, and about 0.1% to about 5% by weight alkali metal oxide; as well as A feed containing alkanes is supplied through the reactor at a pressure less than 1 atmosphere to dehydrogenate the alkanes to produce olefins.

2. The method according to claim 1, wherein the plurality of aluminum hydroxides contain crystalline aluminum trihydroxide, crystalline aluminum oxyhydroxide, and colloidal aluminum hydroxide, the crystalline aluminum trihydroxide contains one or more of bayerite and neoalumina trihydrate, and the crystalline aluminum oxyhydroxide contains boehmite.

3. The method according to claim 2, wherein the colloidal aluminum hydroxide is one or more of amorphous aluminum hydroxide and pseudo-boehmite.

4. The process of any one of claims 1 to 3, wherein the alkali metal oxide source is a sodium oxide source and the dehydrogenation catalyst comprises from about 60 wt% to about 90 wt% alumina, from about 10 wt% to about 40 wt% trivalent chromium oxide, and from about 0.1 wt% to about 5 wt% sodium oxide.

5. The method of claim 4, wherein the moldable mixture further comprises a source of lithium oxide and the dehydrogenation catalyst comprises about 60 wt % to about 90 wt % aluminum oxide, about 10 wt % to about 40 wt % trivalent chromium oxide, about 0.1 wt % to about 5 wt % sodium oxide, and about 0.1 wt % to 3 wt % lithium oxide.

6. The process according to any one of claims 1 to 5, further comprising separating the olefin from unreacted alkanes.

7. The method of any one of claims 1 to 6, wherein the extrudate is calcined at a temperature in the range of about 700°C to about 1000°C.

8. The process according to any one of claims 1 to 7, wherein the alkane-containing feed is supplied to the reactor at a temperature in the range of about 400°C to about 800°C.

9. A method for dehydrogenating alkanes, the method comprising: The reactor is loaded with a dehydrogenation catalyst produced by: mixing a plurality of aluminum hydroxides containing from about 60% to about 97% by weight crystalline aluminum trihydroxide and from about 3% to about 40% by weight crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof, a source of chromium (III) oxide, and a source of an alkali metal oxide with a non-metallic acidic aqueous solution to form a moldable mixture; extruding the moldable mixture to form an extrudate; and drying and calcining the extrudates to produce a dehydrogenation catalyst comprising about 60% to about 90% by weight alumina, about 10% to about 40% by weight trivalent chromium oxide, and about 0.1% to about 5% by weight alkali metal oxide; as well as A feed containing alkanes is supplied through the reactor at a pressure less than 1 atmosphere to dehydrogenate the alkanes.

10. The method according to claim 9, wherein the crystalline aluminum trihydroxide contains one or more of bayerite and neoalumina trihydrate.

11. The method of claim 9 or claim 10, wherein the crystalline aluminum oxide hydrate comprises boehmite, and the colloidal aluminum hydroxide comprises one or more of amorphous aluminum hydroxide or pseudo-boehmite.

12. The method of any one of claims 9 to 11, wherein the alkali metal oxide source present in the moldable mixture is a sodium oxide source and the catalyst comprises from about 60% to about 90% by weight aluminum oxide, from about 10% to about 40% by weight trivalent chromium oxide, and from about 0.1% to about 5% by weight sodium oxide.

13. The method of claim 12, wherein the moldable mixture further comprises a source of lithium oxide and the catalyst comprises about 60 wt% to about 90 wt% aluminum oxide, about 10 wt% to about 40 wt% trivalent chromium oxide, about 0.1 wt% to about 5 wt% sodium oxide, and about 0.1 wt% to 3 wt% lithium oxide.

14. The method according to any one of claims 9 to 13, further comprising separating the dehydrogenation product from unreacted alkanes.

15. The method of any one of claims 9-14, wherein the extrudates are calcined at a temperature in the range of about 700°C to about 1000°C, and wherein the temperature sufficient to dehydrogenate the alkanes is in the range of about 400°C to about 800°C.

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