Chromium alumina catalyst for dehydrogenation of paraffins

Abstract

Methods of making and using alkane dehydrogenation catalysts are provided. A method for preparing an alkane dehydrogenation catalyst can include providing an alumina support derived from a plurality of aluminum hydroxides, contacting the alumina support with a water-soluble chromium source and a metal oxide source to provide an impregnated alumina support, and drying and calcining the impregnated alumina support to produce an alkane dehydrogenation catalyst. The catalyst may contain about 60 wt% to about 95 wt% alumina, about 5 wt% to about 40 wt% trivalent chromium oxide, and about 0.1 wt% to about 5 wt% alkali metal oxide.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority and filing date of European Patent Application No. 63476644, filed on December 22, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to methods for making and using alkane dehydrogenation catalysts. More particularly, among other embodiments, the present disclosure relates to methods for making and using chromium oxide-alumina dehydrogenation catalysts for the dehydrogenation of paraffins. 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 UOP-Phillips process utilize chromium oxide-aluminum oxide catalysts. In contrast, the catalysts of 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 a common situation that necessitates the discarding of a catalyst that would otherwise continue to be completely satisfactory. Therefore, the applicant recognized the need for a simple, cost-effective method for preparing a chromium oxide-aluminum oxide dehydrogenation catalyst that exhibits good activity, improved stability, and suitable mechanical strength for paraffin dehydrogenation. Summary of the Invention

[0006] To address the deficiencies in the art, applicants have developed methods for preparing and using alkane dehydrogenation catalysts. Embodiments of the methods for preparing alkane dehydrogenation catalysts include the steps of providing a transition alumina support derived from a plurality of aluminum hydroxides containing from about 85 weight percent (wt%) to about 99 weight percent crystalline aluminum trihydroxide and from about 1 weight percent to about 15 weight percent crystalline aluminum oxide-hydroxide or colloidal aluminum hydroxide, or a combination thereof. The method also includes the steps of contacting the alumina support with a water-soluble chromium (III) oxide source and an alkali metal oxide source to provide an impregnated alumina support and drying and calcining the impregnated alumina support to produce an alkane dehydrogenation catalyst containing from about 60 weight percent to about 95 weight percent aluminum oxide, from about 5 weight percent to about 40 weight percent chromium (III) oxide, and from about 0.1 weight percent to about 5 weight percent alkali metal oxide. In some embodiments, the transition alumina support is substantially η-alumina. The impregnated alumina support is calcined at a temperature in the range of about 700 degrees Celsius (°C) to 800°C.

[0007] The alkane dehydrogenation catalyst may contain 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. The crystalline aluminum trihydroxide may contain one or more of bayerite and neoalumina trihydrate. The crystalline aluminum oxide hydrate may contain boehmite. The colloidal aluminum hydroxide may contain one or more of amorphous aluminum hydroxide and pseudoboehmite.

[0008] Embodiments disclosed herein also include methods of using the alkane dehydrogenation catalysts. One such method for dehydrogenating alkanes comprises the steps of loading a reactor with a dehydrogenation catalyst prepared as disclosed herein and supplying a feed containing alkanes through the reactor at a temperature sufficient to dehydrogenate the alkanes and produce alkenes. In some embodiments, the temperature sufficient to dehydrogenate the alkanes ranges from 400° C. to 800° C.

[0009] 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

[0010]

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

[0011] 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.

[0012] 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.

[0013] 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%.

[0014] 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."

[0015] 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.

[0016] 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.

[0017] Embodiments of a method for preparing an alkane dehydrogenation catalyst include the steps of providing a transition alumina support derived from a plurality of aluminum hydroxides containing from about 85% to about 99% by weight of crystalline aluminum trihydroxide and from about 1% to about 15% by weight of crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof. The method further includes the steps of contacting the alumina support with a water-soluble source of chromium (III) oxide and an alkali metal oxide source to provide an impregnated alumina support, and drying and calcining the impregnated alumina support to produce an alkane dehydrogenation catalyst containing from about 60% to about 95% by weight of aluminum oxide, from about 5% to about 40% by weight of chromium (III) oxide, and from about 0.1% to about 5% by weight of alkali metal oxide. The impregnated alumina support is calcined at a temperature in the range of about 700° C. to 800° C. Some embodiments of the alkane dehydrogenation catalyst contain from about 60% to about 90% by weight of aluminum oxide, from about 10% to about 40% by weight of chromium (III) oxide, and from about 0.1% to about 5% by weight of alkali metal oxide. These weight percentages are calculated on a calcined basis.

[0018] The transition alumina support is derived from a variety of aluminum hydroxides and contains about 85% to about 99% by weight of crystalline aluminum trihydroxide and about 1% to about 15% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide or a combination thereof. The crystalline aluminum trihydroxide may contain one or more of bayerite and neoalumina. The crystalline aluminum oxide hydrate may contain boehmite. The colloidal aluminum hydroxide may contain one or more of amorphous aluminum hydroxide and pseudoboehmite. "Transition alumina" is one or more aluminas other than α-alumina that can be at least partially converted to α-alumina upon heat treatment at 900°C or greater. Transition aluminas include, but are not limited to, γ-alumina, δ-alumina, η-alumina, κ-alumina, χ-alumina, ρ-alumina, and θ-alumina. In some embodiments, the transition alumina support is substantially η-alumina. An alumina support containing substantially eta-alumina refers to an alumina support containing from about 75 wt% to about 99 wt% eta-alumina and all ranges and values ​​therebetween, for example, from about 78 wt% to about 93 wt%, from about 80 wt% to about 90 wt%, about 83 wt%, about 85 wt%, or about 87 wt%.

[0019] Various aluminum hydroxides may contain from about 87% to about 99% by weight of crystalline aluminum trihydroxide. Various aluminum hydroxides may contain from about 90% to about 99% by weight of crystalline aluminum trihydroxide. Various aluminum hydroxides may contain from about 85% to about 97% by weight of crystalline aluminum trihydroxide. Various aluminum hydroxides may contain from about 87% to about 97% by weight of crystalline aluminum trihydroxide. Various aluminum hydroxides may contain from about 89% to about 97% by weight of crystalline aluminum trihydroxide. Various aluminum hydroxides may contain from about 85% to about 95% by weight of crystalline aluminum trihydroxide. Various aluminum hydroxides may contain from about 85% to about 92% by weight of crystalline aluminum trihydroxide. In some embodiments, the crystalline aluminum trihydroxide contains bayerite, neoalumina, or both. Calcination of the crystalline bayerite results in the destruction of the original highly crystalline framework and evolution through the alumina phases η and θ before reaching alpha alumina.

[0020] The various aluminum hydroxides may contain from about 1% to about 15% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 3% to about 15% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 5% to about 15% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 7% to about 15% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 9% to about 15% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 1% to about 13% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 1% to about 11% by weight of crystalline aluminum oxide hydrate or colloidal aluminum hydroxide, or a combination thereof. The various aluminum hydroxides may contain from about 3% to about 13% by weight of crystalline aluminum hydroxide or colloidal aluminum hydroxide, or a combination thereof. In some embodiments, the crystalline aluminum hydroxide contains boehmite. In some embodiments, the colloidal aluminum hydroxide contains amorphous aluminum hydroxide, pseudo-boehmite, or both. Calcination of boehmite, pseudo-boehmite, and amorphous aluminum hydroxide results in the formation of gamma-alumina, delta-alumina, and theta-alumina before reaching alpha-alumina.

[0021] In embodiments, the alumina support used in catalyst preparation contains eta-alumina. In other embodiments, the alumina support contains 95% by weight eta-alumina and 5% by weight gamma-alumina. In other embodiments, the alumina support contains 90% by weight eta-alumina and 10% by weight gamma-alumina. Some embodiments of the alumina support contain 85% by weight eta-alumina and 15% by weight gamma-alumina.

[0022] In some embodiments, the catalyst is in the form of extrudates having a diameter in the range of 2 to 5 mm, and all ranges and values ​​therebetween, including the ranges of 2 to 3 mm, 2 to 4 mm, 2.5 to 4 mm, 2.5 to 4.5 mm, and 3 to 4 mm. In some embodiments, a plurality of aluminum hydroxides are mixed with nitric acid and then formed into cylindrical extrudates (approximately 3.5 mm diameter) using an extruder. The extrudates are dried and calcined and cooled to room temperature without external cooling.

[0023] The calcined alumina extrudate is subjected to an incipient wetness impregnation technique with an impregnation solution containing a water-soluble chromium (III) oxide source and an alkali metal oxide source. In some embodiments, the alkali metal oxide source contains an alkali metal hydroxide, an alkali metal chromate, an alkali metal dichromate, or a combination thereof. The alkali metal may be sodium, lithium, or potassium. For example, the calcined alumina extrudate is subjected to an incipient wetness impregnation technique with an impregnation solution containing a chromium oxide source and sodium dichromate dihydrate. In some embodiments, the impregnated alumina support is calcined at a temperature in the range of about 500° C. to 800° C. In some embodiments, the impregnated alumina support is calcined at a temperature in the range of about 500° C. to 700° C. In some embodiments, the impregnated alumina support is calcined at a temperature in the range of about 550° C. to 650° C. Embodiments of the catalyst include a catalyst having the following composition: 24.24 wt% Cr2O3, 0.53 wt% Na2O, 1.02 wt% La2O3, and 74.21 wt% Al2O3.

[0024] Embodiments disclosed herein also include methods for using alkane dehydrogenation catalysts. One such method for alkane dehydrogenation comprises the steps of loading a reactor with a dehydrogenation catalyst prepared as disclosed herein and supplying a feed containing an alkane through the reactor at a temperature sufficient to dehydrogenate the alkane and produce olefins. In some embodiments, the temperature range sufficient to dehydrogenate the alkane is 400°C-800°C, and all ranges and values ​​therebetween, including ranges such as 400°C to 780°C, 420°C to 780°C, 440°C to 760°C, 450°C to 750°C, 500°C to 700°C, and 600°C to 800°C. Reaction conditions may also include a reaction pressure of 0.2 bar to 1 bar, and all ranges and values ​​therebetween, including 0.3 bar, 0.4 bar, 0.5 bar, 0.6 bar, 0.7 bar, 0.8 bar, and 0.9 bar. Reaction conditions may also include a gas hourly space velocity of 300 hr -1 Up to 800 hours -1 , and all ranges and values ​​between the upper and lower limits of this range. The dehydrogenation catalyst prepared according to the presently disclosed method has good activity as well as improved stability and mechanical strength.

[0025] The feed containing alkanes can include C2 to C20 linear alkanes, isoalkanes and cycloalkanes, which are basically saturated compounds containing hydrogen and carbon. The feed encompasses a series of cyclic and linear alkanes, such as ethane, propane, normal butane, isobutane, n-pentane, isopentane, normal hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, normal heptane, 2-methylhexane, 2,2,3-trimethylbutane, cyclopentane, cyclohexane, methylcyclopentane, ethylcyclopentane, n-propylcyclopentane and 1,3-dimethylcyclohexane. For example, propane can be used as the feed containing alkanes, and it can be dehydrogenated to produce propylene, and isobutane can be used as the feed containing alkanes, and it can be dehydrogenated to produce isobutene. In some aspects, substantially all hydrocarbons in the feed containing alkanes can be single alkanes, such as pure propane or pure butane.

[0026] In some embodiments, the temperature range sufficient to dehydrogenate the alkanes is 400° C. to 800° C., and all ranges and values ​​therebetween, including ranges such as 400° C. to 780° C., 420° C. to 780° C., 440° C. to 760° C., 450° C. to 750° C., 500° C. to 700° C., and 600° C. to 800° C. The reaction conditions may also include a reaction pressure of 0.2 bar to 1 bar, and all ranges and values ​​therebetween, including 0.3 bar, 0.4 bar, 0.5 bar, 0.6 bar, 0.7 bar, 0.8 bar, and 0.9 bar. The reaction conditions may also include a gas hourly space velocity of 300 hr -1 Up to 800 hours -1 , and all ranges and values ​​between the upper and lower limits of the range.

[0027] Some embodiments of the alkane dehydrogenation catalysts are based on transition alumina supports derived from substantially all eta-alumina. These catalysts have a surface area of ​​about 88.8 m2 / g (m 2 / g) and a crush strength of about 1.77 decaNewtons / millimeter (daN / mm). Some embodiments of the alkane dehydrogenation catalyst are based on a transition alumina support derived from about 95% by weight eta-alumina and about 5% by weight gamma-alumina. The surface area of ​​these catalysts is about 94.9 m 2 / g and a crush strength of about 1.95 daN / mm. Some embodiments of the alkane dehydrogenation catalyst are based on a transition alumina support derived from about 90 wt% η-alumina and 10 wt% γ-alumina. The surface area of ​​these catalysts is about 92.9 m 2 / g and a crush strength of about 2.45 daN / mm. Some embodiments of the alkane dehydrogenation catalyst are based on a transition alumina support derived from about 85 wt% η-alumina and 15 wt% γ-alumina. The surface area of ​​these catalysts is about 97 m 2 / g and a crush strength of about 2.74 daN / mm. As discussed in detail in Example 8 and Table 1, similar isobutane conversion and isobutylene yields were observed for catalysts prepared using an alumina support containing up to 15 wt% γ-alumina. Catalysts with an alumina support containing 20 wt% γ-alumina exhibited lower isobutylene yields and lower catalyst stability.

[0028] Example

[0029] Specific examples of some embodiments are included here for illustrative purposes only and are not intended to limit any aspect of the claimed embodiments.

[0030] Example 1

[0031] The alumina support with η-alumina for catalyst preparation was prepared as follows: approximately 3125 g of bayerite (Pural BT, SASOL) was mixed in an Eirich mixer (EL-5 ProfiPlus) for 10 minutes. An aqueous solution of nitric acid (520 ml, 15 wt%) was added to the mixer and mixed for approximately 9 minutes. The resulting blend was aged at approximately 25°C for approximately 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder. The extrudates were dried at 70°C and then at 120°C for approximately 12 hours, calcined in air at 600°C in a muffle furnace for 2 hours, and cooled to room temperature without external cooling.

[0032] Approximately 73 grams of calcined alumina extrudates were impregnated using the incipient wetness technique. The calcined alumina extrudates were contacted with an aqueous solution containing 29.7 grams of chromium (VI) oxide, 1 gram of lanthanum oxide, and 2.5 grams of sodium dichromate dihydrate. The wet extrudates were aged in a closed container at approximately 25°C for approximately 12 hours. The sample was then dried at 120°C for approximately 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 resulting catalyst had a composition of 24.24% by weight CrO, 0.53% by weight NaO, 1.02% by weight LaO, and 74.21% by weight AlO.

[0033] Example 2

[0034] An alumina support having 95% by weight of η-alumina and 5% by weight of γ-alumina for catalyst preparation was prepared as follows: 2969 grams of bayerite (Pural BT, SASOL) and 139 grams of pseudoboehmite (PBAM-05, Chika Pvt. Ltd.) were mixed in an Eirich mixer (EL-5 Profi Plus) for 10 minutes. An aqueous solution of nitric acid (520 ml, 15% by weight) was added to the mixer and mixed for approximately 8.5 minutes. The resulting blend was aged at approximately 25°C for approximately 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder. These extrudates were dried at 70°C and then at 120°C for approximately 12 hours. These extrudates were calcined in air in a muffle furnace at 600°C for 2 hours and cooled to room temperature without external cooling.

[0035] Approximately 73 grams of calcined alumina extrudates were impregnated using the incipient wetness technique. The calcined alumina extrudates were contacted with an aqueous solution containing 29.7 grams of chromium (VI) oxide, 1 gram of lanthanum oxide, and 2.5 grams of sodium dichromate dihydrate. The wet extrudates were aged in a closed container at approximately 25°C for approximately 12 hours. The sample was then dried at 120°C for approximately 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 resulting catalyst had a composition of 24.24% by weight CrO, 0.53% by weight NaO, 1.02% by weight LaO, and 74.21% by weight AlO.

[0036] Example 3

[0037] An alumina support having 90% by weight of η-alumina and 10% by weight of γ-alumina for catalyst preparation was prepared as follows: 2813 grams of bayerite (Pural BT, SASOL) and 277 grams of pseudoboehmite (PBAM-05, Chika Pvt. Ltd.) were mixed in an Eirich mixer (EL-5 ProfiPlus) for 10 minutes. An aqueous solution of nitric acid (520 ml, 15% by weight) was added to the mixer and mixed for about 8.5 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. These extrudates were dried at 70°C and then at 120°C for about 12 hours. These extrudates were calcined in air in a muffle furnace at 600°C for 2 hours and cooled to room temperature without external cooling.

[0038] Approximately 73 grams of calcined alumina extrudates were impregnated using the incipient wetness technique. The calcined alumina extrudates were contacted with an aqueous solution containing 29.7 grams of chromium (VI) oxide, 1 gram of lanthanum oxide, and 2.5 grams of sodium dichromate dihydrate. The wet extrudates were aged in a closed container at approximately 25°C for approximately 12 hours. The sample was then dried at 120°C for approximately 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 resulting catalyst had a composition of 24.24% by weight CrO, 0.53% by weight NaO, 1.02% by weight LaO, and 74.21% by weight AlO.

[0039] Example 4

[0040] An alumina support having 85% by weight of η-alumina and 15% by weight of γ-alumina for catalyst preparation was prepared as follows: 2656 grams of bayerite (Pural BT, SASOL) and 416 grams of pseudo-boehmite (PBAM-05, Chika Pvt. Ltd.) were mixed in an Eirich mixer (EL-5 ProfiPlus) for 10 minutes. An aqueous solution of nitric acid (520 ml, 15% by weight) was added to the mixer and mixed for approximately 6 minutes. The resulting blend was aged at approximately 25°C for approximately 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder. These extrudates were dried at 70°C and then at 120°C for approximately 12 hours. These extrudates were calcined in air in a muffle furnace at 600°C for 2 hours and cooled to room temperature without external cooling.

[0041] Approximately 73 grams of the prepared calcined alumina extrudates were impregnated with an aqueous solution containing 29.7 grams of chromium (VI) oxide, 1 gram of lanthanum oxide, and 2.5 grams of sodium dichromate dihydrate to achieve incipient wetness. The wet extrudates were aged in a closed container at approximately 25°C for approximately 12 hours. The sample was then dried at 120°C for approximately 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 resulting catalyst had a composition of 24.24% by weight CrO, 0.53% by weight NaO, 1.02% by weight LaO, and 74.21% by weight AlO.

[0042] Example 5

[0043] An alumina support having 80 wt% η-alumina and 20 wt% γ-alumina for catalyst preparation was prepared as follows: 2500 g of bayerite (Pural BT, SASOL) and 554 g of pseudoboehmite (PBAM-05, Chika Pvt. Ltd.) were mixed in an Eirich mixer (EL-5 ProfiPlus) for 10 minutes. An aqueous solution of nitric acid (500 ml, 10 wt% HNO3 + 20 ml water) was added to the mixer and mixed for approximately 12.5 minutes. The resulting blend was aged at approximately 25°C for approximately 1 hour and then formed into cylindrical extrudates (3.5 mm diameter) using an ETP1 Bonnot laboratory extruder. These extrudates were dried at 70°C and then at 120°C for approximately 12 hours. These extrudates were calcined in air in a muffle furnace at 600°C for 2 hours and cooled to room temperature without external cooling.

[0044] Approximately 73 grams of the prepared calcined alumina extrudates were impregnated using the incipient wetness technique. The calcined alumina extrudates were contacted with an aqueous solution containing 29.7 grams of chromium (VI) oxide, 1 gram of lanthanum oxide, and 2.5 grams of sodium dichromate dihydrate. The wet extrudates were aged in a closed container at approximately 25°C for approximately 12 hours. The sample was then dried at 120°C for approximately 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 resulting catalyst had a composition of 24.24% by weight Cr2O3, 0.53% by weight Na2O, 1.02% by weight La2O3, and 74.21% by weight Al2O3.

[0045] Example 6

[0046] The alumina support with pure gamma-alumina for catalyst preparation was prepared as follows: 2000 g of pseudo-boehmite (PBAM-05, Chika Pvt. Ltd.) was mixed in an Eirich mixer (EL-5 ProfiPlus) for 10 minutes. An aqueous solution of nitric acid (1290 ml, 1.5 wt %) was added to the mixer and mixed for about 18 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. The catalyst extrudates were dried at 70° C. and then at 120° C. for about 12 hours and calcined at 600° C. in air in a muffle furnace for 2 hours and cooled to room temperature without external cooling.

[0047] Approximately 73 grams of calcined alumina extrudates were impregnated using the incipient wetness technique. The calcined alumina extrudates were contacted with an aqueous solution containing 29.7 grams of chromium (VI) oxide, 1 gram of lanthanum oxide, and 2.5 grams of sodium dichromate dihydrate. The wet extrudates were aged in a closed container at approximately 25°C for approximately 12 hours. The sample was then dried at 120°C for approximately 6 hours and calcined in air at 750°C in a muffle furnace for 2 hours and cooled to room temperature without external cooling.

[0048] The composition of the resulting catalyst was 24.24 wt% Cr2O3, 0.53 wt% Na2O, 1.02 wt% La2O3 and 74.21 wt% Al2O3.

[0049] Example 7 - Catalyst Testing

[0050] The dehydrogenation activity of the prepared catalyst was measured in a tubular fixed-bed quartz reactor at atmospheric pressure. The catalyst loading and reactor details were as follows: catalyst weight = 8.5 g, catalyst particle size = 3-3.2 mm, inert quartz weight = 8.5 g, inert quartz flakes = 0.4-0.5 mm, reactor ID = 16 mm, reactor OD = 19 mm. The catalyst and inert quartz were divided into equal parts by weight and then loaded into the reactor by mixing the catalyst and inerts. Isobutane (99.9% by volume) was used as feed. Quartz flakes with a size of 1-1.4 mm were loaded on the catalyst bed. Nitrogen purging was used between the dehydrogenation, catalyst regeneration / oxidation and reduction steps with hydrogen. The total feed flow in the dehydrogenation step corresponded to 600 mlh -1 g -1 The gas hourly space velocity (GHSV) of 100 ℃ was measured. 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. A Ritter-type wet gas flow meter was used to measure the reactant and product flow rates. The reactor was operated at atmospheric pressure and in a cycle mode with the following steps: 1) the catalyst was oxidized with air for 20 minutes with a starting temperature of 650°C; 2) the catalyst was purged with nitrogen at 650°C for 3 minutes; 3) the catalyst was reduced with H2 for 6 minutes with a starting temperature of 650°C; 4) the catalyst was cooled from 650°C to 585°C under nitrogen and maintained at 585°C for 30 minutes; 5) isobutane was dehydrogenated for 21 minutes with a starting temperature of 585°C; 6) the reactor outlet gas composition was analyzed by gas chromatography (GC) at the 20th minute from the start of the isobutane feed. Steps 1 to 6 were repeated 20 times. The catalyst performance data after catalyst stabilization are given in Table 1 (average of 10 cycles).

[0051] Example 8 - Catalyst Stability Evaluation

[0052] Catalyst stability was evaluated by artificial accelerated aging in a cycle mode. The cycle consisted of H2-N2-isobutane-N2-air flow phases of varying duration. Aging was performed at 820°C for 72 hours. Catalyst stability evaluation parameters included a catalyst weight of 8.5 g, a 400 ml h -1 g -1 The isobutane was supplied at a GHSV of 2 and the air to isobutane volume ratio was 2. The catalyst was oxidized under air for 15 minutes and then purged with nitrogen for 3 minutes. The catalyst was then reduced with H2 for 6 minutes and then purged with nitrogen for 3 minutes. The catalyst was then subjected to a flow of isobutane for 3 minutes and then purged with nitrogen for 3 minutes. After aging, the performance of the catalyst was evaluated in the recycle mode described above. The products from the dehydrogenation of isobutane were analyzed by gas chromatography.

[0053] The surface area and crush strength of the catalysts were analyzed. The results showed that catalysts prepared using alumina supports containing η-alumina and γ-alumina exhibited similar surface areas. The catalyst prepared using η-alumina exhibited a lower surface area, while the catalyst prepared using γ-alumina exhibited a higher surface area. The catalyst prepared using η-alumina as a support exhibited a lower crush strength, and the crush strength increased as the γ-alumina content in the support used in the catalyst preparation increased.

[0054] The results from Table 1 show similar isobutylene yields for catalysts prepared using an alumina support containing up to 15 wt% gamma-alumina. The catalyst having an alumina support with 20 wt% gamma-alumina showed lower isobutylene yields and lower catalyst stability.

[0055] Table 1

[0056]

[0057]

[0058] 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.

[0059] Other objectives, features and advantages of the disclosure will become apparent from the above detailed description and examples. However, it should be understood that 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 the 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.

Claims

1. A method for preparing an alkane dehydrogenation catalyst, comprising: Providing a transition alumina support derived from a plurality of aluminum hydroxides containing from about 85 weight percent (wt%) to about 99 wt% crystalline aluminum trihydroxide and from about 1 wt% to about 15 wt% crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof; contacting the alumina support with a water-soluble source of chromium (III) oxide and a source of an alkali metal oxide to provide an impregnated alumina support; and The impregnated alumina support is dried and calcined to produce an alkane dehydrogenation catalyst containing from about 60 wt% to about 95 wt% alumina, from about 5 wt% to about 40 wt% chromium (III) oxide, and from about 0.1 wt% to about 5 wt% alkali metal oxide.

2. The method of claim 1 , wherein the transition alumina support is substantially η-alumina.

3. The process of claim 1 or claim 2, wherein the alkane dehydrogenation catalyst comprises from about 60 wt% to about 90 wt% alumina, from about 10 wt% to about 40 wt% chromium (III) oxide, and from about 0.1 wt% to about 5 wt% alkali metal oxide.

4. The method according to any one of claims 1 to 3, wherein the crystalline aluminum trihydroxide contains one or more of bayerite and neoalumina trihydrate.

5. The method according to any one of claims 1 to 4, wherein the crystalline aluminum oxide hydroxide contains boehmite.

6. The method according to any one of claims 1 to 5, wherein the colloidal aluminum hydroxide comprises one or more of amorphous aluminum hydroxide and pseudo-boehmite.

7. The method of any one of claims 1 to 6, wherein the impregnated alumina support is calcined at a temperature in the range of about 700 degrees Celsius (°C) to 800°C.

8. A method for dehydrogenating alkanes, comprising: The reactor was loaded with the dehydrogenation catalyst produced by: Providing a transition alumina support derived from a plurality of aluminum hydroxides containing from about 85 weight percent (wt%) to about 99 wt% crystalline aluminum trihydroxide and from about 1 wt% to about 15 wt% crystalline aluminum oxyhydroxide or colloidal aluminum hydroxide, or a combination thereof; contacting the alumina support with a water-soluble source of chromium (III) oxide and a source of an alkali metal oxide to provide an impregnated alumina support; and drying and calcining the impregnated alumina support to produce an alkane dehydrogenation catalyst comprising from about 60 weight percent to about 95 weight percent alumina, from about 5 weight percent to about 40 weight percent chromium (III) oxide, and from about 0.1 weight percent to about 5 weight percent alkali metal oxide; and A feed containing alkanes is supplied through the reactor at a temperature sufficient to dehydrogenate the alkanes and produce alkenes.

9. The method of claim 8, wherein the transition alumina support is substantially eta-alumina.

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

11. The method according to claim 8 or 9, wherein the crystalline aluminum oxide hydroxide contains boehmite.

12. The method according to one of claims 8 to 10, wherein the colloidal aluminum hydroxide comprises one or more of amorphous aluminum hydroxide or pseudo-boehmite.

13. The method of one of claims 8 to 11, wherein the impregnated alumina support is calcined at a temperature in the range of about 700°C to 800°C.

14. The process according to one of claims 8 to 12, wherein the temperature sufficient to dehydrogenate the alkane is in the range of 400°C to 800°C.

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