Methods of manufacture of rhenium oxide-coated gamma-alumina-based catalysts and uses thereof

Abstract

Provided here are rhenium oxide-coated γ-alumina-based catalysts and methods of preparing the rhenium oxide-coated γ-alumina-based catalysts for use in the conversion of butenes in an operational metathesis reactor.

Description

METHODS OF MANUFACTURE OF RHENIUM OXIDE-COATED GAMMA-ALUMINA-BASED CATALYSTS AND USES THEREOFCross-Reference to Related Applications

[0001] This application claims priority to and the benefit of European Application No. EP23216352.7, filed on December 13, 2023. The contents of the referenced application are incorporated into the present application by reference.Technical Field

[0002] The disclosure relates to rhenium oxide-coated y-alumina-based catalysts, methods of their preparation, and methods for their use in metathesis reactors.Background

[0003] The demand for propene is growing. Out of various on-purpose propene production routes, such as propane dehydrogenation, metathesis, olefin cracking, methanol to olefins, and high severity fluid catalytic cracking, olefin metathesis provides an opportunity to achieve olefin interconversion of excess ethene or butenes into required propene. However, current commercial metathesis processing of excess ethene and butenes into propene expends high value ethene.Summary

[0004] Applicant has identified a necessity for the development of highly selective and stable catalyst for metathesis reactions of butenes to propene and other olefins. Provided here are compositions and methods to address these shortcomings of the art and provide other additional or alternative advantages. Examples of methods for preparation of rhenium oxide-coated y-alumina (Re2O? / y-A12O3)-based catalysts and methods for use of these resulting compositions in metathesis reactions are provided here. In certain examples, these methods for metathesis reactions of butenes exclude additional consumption of ethene.

[0005] Examples include methods of preparing a rhenium oxide-coated y-alumina-based catalyst. One such method includes the steps of calcining a y-alumina-based support to form a calcined y-alumina-based support at a temperature ranging from about 450 degrees Celsius (°C) toabout 550 °C and treating the calcined y-alumina-based support with an aqueous rhenium- containing mixture in a rotating drum impregnation unit to form a rhenium-coated y-alumina-based support. In certain examples, the aqueous rhenium-containing mixture is one or more of NF ReC or Al(ReO4)3 or HReCh solution. In certain examples, the impregnation unit is rotated at a speed ranging from about 15 revolutions per minute (rpm) to about 35 rpm to form a rhenium-coated y- alumina- based support. The method also includes the steps of aging the rhenium-coated y-alumina- based support to form a rhenium oxide-coated y-alumina-based catalyst containing a rhenium oxide coating ranging from about 150 micrometers (pm) to about 250 pm in thickness, drying the rhenium-coated y-alumina-based catalyst immediately after aging, and calcining the rhenium- coated y-alumina-based catalyst at a temperature ranging from about 450°C to about 550 °C to form rhenium oxide-coated y-alumina (Re2O7 / y-AhO3) catalyst. In certain examples, the step of aging the rhenium-coated y-alumina-based support is conducted for a time less than 5 minutes thereby to form a rhenium-coated y-alumina-based catalyst. In certain examples, the step of drying the rhenium- coated y-alumina-based catalyst immediately after aging at a temperature ranges from about 140 °C to about 160 °C.

[0006] The particle size of the y-alumina-based support can range from about 1.2 millimeters (mm) to about 3 mm. For example, the diameter of a spherical or a cylindrical y-alumina-based support can range from about 1.2 mm to about 3 mm. In certain examples, the y-alumina-based support has a pore volume ranging from about 0.5 milliliter per gram (ml / g) to about 0.65 ml / g. In certain examples, the y-alumina-based support has a pore diameter ranging from about 75 Angstroms (A) to about 110 A. In certain examples, the y-alumina-based support has a total acidity ranging from about 0.58 millimole per gram (mmolNH3 / g) to about 0.62 mmolNH3 / g. In certain examples, the rhenium oxide-coated y-alumina-based catalyst can contain rhenium oxide in an amount ranging from about 4.8 weight percent (wt. %) to about 5.6 wt. %. The rhenium oxi decoated y-alumina-based catalyst can have a surface area ranging from about 200 square meters per gram (m2 / g) to about 270 m2 / g. The rhenium oxide-coated y-alumina-based catalyst can be spherical in shape or an extrudate. An extrudate can be cylindrical or lobed or of other shapes. In certain examples, the rhenium particles of the coating have a particle size ranging from about 0.3 nanometer (nm) to about 1.5 nm.

[0007] Examples include methods of preparing an activated rhenium oxide-coated y-alumina- based catalyst. One such method includes the steps of treating the rhenium oxide-coated y-alumina- based catalyst under air at a temperature from about 500 °C to about 550 °C to produce an activated rhenium oxide-coated y-alumina-based catalyst, purging nitrogen into the activated rhenium oxi decoated y-alumina-based catalyst to displace the air, and cooling the activated rhenium oxide-coated y-alumina-based catalyst to a temperature of about 50 °C. In certain examples, the step of treating the rhenium oxide-coated y-alumina-based catalyst under air is conducted for about 4 hours to about 24 hours to produce an activated rhenium oxide-coated y-alumina-based catalyst. In certain examples, the step of treating the rhenium oxide-coated y-alumina-based catalyst under air is conducted for about 6 hours.

[0008] Examples include a rhenium oxide-coated y-alumina-based catalyst. The rhenium oxide-coated y-alumina-based catalyst can be spherical or an extrudate. One such rhenium oxidecoated y-alumina-based catalyst has y-alumina-based spherical particles of a size ranging from about 1.2 mm to about 3 mm and a rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. Other examples include y-alumina-based extrudate particles of a size ranging from 1.2 mm to about 3 mm in diameter and from about 4 mm to about 8 mm in length, with the rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. In certain examples, the rhenium oxide-coated y-alumina-based catalyst contains rhenium oxide in an amount ranging from about 4.8 wt. % to about 5.6 wt. %. The rhenium oxide-coated y-alumina- based catalyst can facilitate conversion of one or more of: (trans / cis (t / c)) but-2-ene with but-1- ene to propene and (t / c) pent-2-ene, but-l-ene with but-l-ene to ethene and (t / c) hex-3-ene, ethene with (t / c) but-2-ene to propene and propene, but-l-ene with (t / c) pent-2-ene to propene and (t / c) hex-3-ene, and (t / c) pent-2-ene and (t / c) pent-2-ene to (t / c) but-2-ene and (t / c) hex-3-ene in an operational metathesis reactor. In certain examples, the rhenium oxide-coated y-alumina-based catalyst can be functional for at least 300 days in the operational metathesis reactor. In certain examples, the catalyst is regenerated for greater than 50 times in the operational metathesis reactor. Based on regeneration times, the catalyst can be functional for about 1000 days or longer.Brief Description of the Drawings

[0009] Examples will be readily understood by the following detailed description inconjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements or procedures in a method. Examples are illustrated by way of example and not by way of limitation in the accompanying drawings. The present disclosure can be better understood by referring to the following figures. These drawings illustrate the principles of the disclosure and no limitation of the scope of the disclosure is thereby intended.

[0010] FIG. 1 is a diagrammatic representation of a method of preparing a rhenium oxidecoated y-alumina-based catalyst, according to an example.

[0011] FIGs. 2A-2C are photographs of three random samples of rhenium oxide-coated y- alumina-based support, subjected to Scanning Electron Microscopy / Energy Dispersive Spectroscopy (SEM / EDS) analysis to evaluate the rhenium coating thickness. FIG. 2D is a graphical representation of the rhenium content in spherical y-alumina-based support as measured against the diameter of the spherical y-alumina-based support, according to an example.

[0012] FIG. 3 is a diagrammatic representation of a method of preparing an activated rhenium oxide-coated y-alumina-based catalyst, according to an example.

[0013] FIG. 4 is a graphical representation of rhenium oxide-coated y-alumina-based catalyst for the metathesis of butene as a function of time on stream with varying WHSV, according to an example.

[0014] FIG. 5 is a graphical representation of the conversion of but-l-ene using the rhenium oxide-coated y-alumina-based catalyst and rhenium dispersed through the catalyst (also known as the thru-thru catalyst), according to an example.

[0015] FIG. 6 is a graphical representation of the conversion of but-l-ene using the rhenium oxide-coated y-alumina-based catalyst and the resulting selectivity’s at various ratios, according to an example.Detailed Description

[0016] The present disclosure describes various examples related to rhenium oxide-coated y- alumina-based catalyst compositions and methods for of use in metathesis reactions. Certain examples include metathesis reactions of butenes to propene and internal olefins.

[0017] Methods of preparation of these rhenium oxide-coated y-alumina-based catalysts include the steps of calcining a y-alumina support to form a calcined y-alumina-based support at a temperature ranging from about 450 °C to about 550 °C, treating the calcined y-alumina-based support with an aqueous rhenium solution in an impregnation unit, and aging the rhenium-coated y-alumina-based support to form a rhenium-coated y-alumina-based support. In certain examples, the rotating drum impregnation unit is operated at a speed ranging from about 15 rpm to about 35 rpm to form a rhenium- coated y-alumina-based support. The method also include the step of aging the rhenium-coated y-alumina-based support for a time less than 5 minutes. In certain examples, the rhenium-coated y-alumina-based catalyst contains a rhenium coating ranging from about 150 pm to about 250 pm in thickness. The method also includes the steps of drying the rhenium- coated y-alumina-based catalyst immediately, and calcining the rhenium-coated y-alumina-based catalyst at a temperature ranging from about 450°C to about 550 °C to form rhenium oxide-coated y- alumina catalyst. The step of drying the catalyst after aging may be conducted at a temperature ranging from about 140 °C to about 160 °C. In the example, the particle size of the y-alumina- based support ranging from about 1.2 mm to about 3 mm.

[0018] In some embodiments, the impregnation unit is a rotating drum impregnator. The y- alumina-based support is placed in the drum and the drum is rotated at about 15 rpm to 35 rpm. An aqueous rhenium solution is sprayed on to y-alumina-based support using a spray gun into the rotating drum. In some examples, the rhenium containing impregnating solution is one or more of a NH4ReO4 or Al(ReO4)3 or HReCh solution. The rhenium containing impregnating solution can have a pH of 1.5. The aqueous rhenium containing solution can be present in an amount that corresponds to the pore volume of the y-alumina support. In certain examples, the calcined y- alumina spheres are sprayed with the aqueous rhenium containing solution at 2 barg of pressure and at rate of 31.5 milliliters per minute (ml / min) over the course of 12 minutes for 700 grams of the rhenium oxide-coated y-alumina-based support.

[0019] Example of the rhenium oxide-coated y-alumina-based catalysts include spherical particles or extrudate particles. The spherical rhenium oxide-coated y-alumina-based catalysts include y-alumina-based spherical particles of a size ranging from about 1.2 mm to about 3 mm and a rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. The extrudate rhenium oxide-coated y-alumina-based catalysts include y-alumina-based extrudate particles of a size ranging from 1.2 mm to about 1.6 mm in diameter and from about 4 mm to about 8 mm in length and the rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness.

[0020] Examples of uses of the foregoing catalysts include the metathesis of butenes to propene and internal olefins. Methods of use of these catalysts in the metathesis reaction involve treating and purging of the rhenium oxide-coated y-alumina-based catalysts prior to introduction of the butenes at the reaction temperature. Certain examples include treating the rhenium oxide-coated y-alumina-based catalyst under air at a temperature from about 500 °C to about 550 °C for about 6 hours to produce an activated rhenium oxide-coated y-alumina-based catalyst and purging nitrogen into the activated rhenium oxide-coated y-alumina-based catalyst to displace the air and cooling the activated rhenium oxide-coated y-alumina-based catalyst. Certain examples include activating the rhenium oxide-coated y-alumina-based catalyst under air for about 6 hours. Certain examples include cooling the activated rhenium oxide-coated y-alumina-based catalyst to a temperature of about 50 °C. These catalysts exhibit high selectivity to the foregoing propene and internal olefins production.

[0021] In the following description, reference is made to the accompanying drawings that form a part of this disclosure and numerous details are set forth in order to provide a thorough understanding of the various examples. In other instances, well-known processes, devices, and systems may not been described in particular detail in order not to unnecessarily obscure the various examples. Additionally, illustrations of the various examples may omit certain features or details in order to not obscure the various examples. The drawings may provide an illustration of some of the various examples in which the subject matter of the present disclosure may be practiced. Other examples may be utilized, and logical changes may be made without departing from the scope of this disclosure.

[0022] The description may use the phrases “in some examples,” “in various examples,” “in an example,” or “in examples,” which may each refer to one or more of the same or different examples. 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.

[0023] The term “about” refers to a range of values including the specified value, which a person of ordinary skill in the art would consider reasonably similar to the specified value. In examples, “about” refers to values within a standard deviation using measurements generally acceptable in the art. In one non-limiting example, when the term “about” is used with a particular value, then “about” refers to a range extending to ±10% of the specified value, alternatively ±5% of the specified value, or alternatively ±1% of the specified value, or alternatively ±0.5% of the specified value. In examples, “about” refers to the specified value.

[0024] FIG. 1 is a diagrammatic representation of a method 100 method of preparing a rhenium oxide-coated y-alumina-based catalyst, according to an example. The method 100 includes a step 102 of calcining a y-alumina-based support to form a calcined y-alumina-based support at a temperature ranging from about 450 °C to about 550 °C. In certain examples, the particle size of the y-alumina-based support ranges from about 1.2 mm to about 3 mm for a spherical particle. The particle size can also range from 1.2 mm to about 2.6 mm in diameter. The particle size of for an extrudate y-alumina-based support ranges from about 4 mm to about 8 mm in length. In certain examples, the y-alumina-based support has a pore volume ranging from about 0.5 ml / g to about 0.65 ml / g, a pore diameter ranging from about 75 A to about 110 A, and a total acidity ranging from about 0.58 mmolNH3 / g to about 0.62 mmolNH3 / g. One method for determining acidity is temperature-programmed desorption (TPD) of ammonia. Determination of acidity is based on the number of moles of ammonia adsorbed on the surface of the catalyst. Ammonia base adsorption may occur at Bronsted acid sites and Lewis acid sites on the surface of the catalyst.

[0025] The method includes the step 104 of treating the calcined y-alumina-based support with an aqueous rhenium-containing mixture in a rotating drum impregnation unit to form a rhenium-coated y-alumina-based support. In certain examples, the calcined y-alumina-based support can be treated by drop by drop addition of the aqueous rhenium- containing mixture to the surface of the calcined y-alumina-based support. In certain examples, the aqueous rhenium-containing mixture is one or more of an aqueous solution containing NEhReC or Al(ReO4)3 or HReO-i. In certain examples, the rhenium particles forming the coating have a particle size ranging from about 0.3 nm to about 1.5 nm. In the example, the rate at which the aqueous rhenium-containing mixture is added can contribute to the uniform formation of egg-shell kind of structure of the rhenium coating. If the rate of addition of rhenium particles is too low on the calcined y-alumina-based support, the rhenium coating can be greater than 400 mm in depth and may lead to an uneven distribution of rhenium which may cause non-reproducible catalyst with different kind of rhenium distribution. Too fast of addition of the rhenium particles on the calcined y-alumina-based support can also lead to an uneven distribution of rhenium which may cause non-reproducible catalyst with different kind of rhenium distribution.

[0026] In certain examples, the method further includes the step 106 of aging the rhenium- coated y-alumina-based support to form a rhenium oxide-coated y-alumina-based catalyst containing a rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. FIGs. 2A-2C are photographs of three random samples of rhenium oxide-coated y-alumina-based support, subjected to SEM / EDS analysis to evaluate the rhenium oxide coating thickness. Images show that the rhenium oxide-coated y-alumina-based particles have an average 200 pm thickness. FIG. 2D is a graphical representation of the rhenium oxide content in spherical y-alumina-based support as measured against the diameter of the spherical y-alumina-based support. There is no significant change. A dip in the graph means that there is no rhenium coating. Pl, P2, P3 are representative Re20? / Alumina particles that were analyzed for Re2O? coating on alumina, whether it is similar on all particles or not.

[0027] In certain examples, the rhenium-coated y-alumina-based catalyst is aged for a time less than 6 minutes. Increasing the aging time beyond 6 minutes after spraying the rhenium solution can lead to slow dispersion of rhenium particles on the calcined y-alumina-based support. This can also lead to an increased thickness of rhenium coating of >400 pm. More diffusion of rhenium particles into y-alumina can lead to the decrease in the rhenium oxide-coated y-alumina-basedcatalyst stability. Where the aging time is less than 6 minutes, the size of the rhenium particles can increase to greater than 1.5 nm due to rhenium agglomeration. Increased particle size because of agglomeration leads to reduction in catalyst stability. In these instances, the catalyst deactivates faster. The number of rhenium active sites reduces on alumina surface which are required for catalytic activity.

[0028] Stability of the rhenium oxide-coated y-alumina-based catalyst can depend on the coating thickness and rhenium particle size (>1.5 nm). When the rhenium oxide-coated y-alumina- based catalyst have a coating thickness greater than 250 pm, it can lead to unavailability or low availability of all of the rhenium particles for a metathesis reaction. Such catalysts may deactivate fast and be a low stability catalyst. With regards to rhenium oxide-coated y-alumina-based catalyst having a thickness of less than 150 pm and the rhenium particle size being less than 1.5 nm, such as due to fast drying practices, the availability of rhenium particles on the surface can be low. As such, it is recognized herein that the rhenium oxide-coated y-alumina-based catalyst is provided with desirably high rhenium particle availability, high stability, and low catalyst deactivation when produced with a coating thickness ranging from about 150 pm to about 250 pm.

[0029] The method includes the step 108 of drying the rhenium- coated y-alumina-based catalyst immediately after aging at a temperature ranging from about 140 °C to about 160 °C. In certain examples, the rhenium-coated y-alumina-based catalyst is dried for about 5 hours to about 24 hours. The method further includes the step 110 of calcining the rhenium-coated y-alumina- based catalyst at a temperature ranging from about 450°C to about 550 °C to form rhenium oxidecoated y-alumina catalyst. In certain examples, the rhenium oxide-coated y-alumina-based catalyst is spherical or an extrudate. In certain examples, the rhenium oxide-coated y-alumina-based catalyst contains rhenium oxide in an amount from about 4.8 wt. % to about 5.6 wt. %. In other examples, the rhenium oxide-coated y-alumina-based catalyst has a surface area ranging from about 200 m2 / g to about 270 m2 / g.

[0030] FIG. 3 is a diagrammatic representation of a method 300 of preparing an activated rhenium oxide-coated y-alumina-based catalyst, according to an example. The method 300 includes a step 302 of treating the rhenium oxide-coated y-alumina-based catalyst under air at atemperature from about 500 °C to about 550 °C for about 6 hours to produce an activated rhenium oxide-coated y-alumina-based catalyst. The method further includes the step 304 of purging nitrogen into the activated rhenium oxide-coated y-alumina-based catalyst to displace the air and cooling the activated rhenium oxide-coated y-alumina-based catalyst to a temperature of about 50 °C.

[0031] Examples of a rhenium oxide-coated y-alumina-based catalyst include y-alumina-based spherical particles of a size ranging from about 1.2 mm to about 3 mm and a rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness or y-alumina-based extrudate particles of a size ranging from 1.2 mm to about 1.6 mm in diameter and from about 4 mm to about 8 mm in length and the rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. The rhenium oxide-coated y-alumina-based catalyst may be a spherical or an extrudate. In certain examples, the rhenium oxide-coated y-alumina-based catalyst contains rhenium oxide in an amount ranging from about 4.8 wt. % to about 5.6 wt. %.

[0032] In certain examples, the rhenium oxide-coated y-alumina-based catalyst facilitates conversion of one or more of: (trans / cis (t / c)) but-2-ene with but-l-ene to propene and (t / c) pent- 2-ene, but-l-ene with but-l-ene to ethene and (t / c) hex-3-ene, ethene with (t / c) but-2-ene to propene and propene, but-l-ene with (t / c) pent-2-ene to propene and (t / c) hex-3 -ene, and (t / c) pent- 2-ene and (t / c) pent-2-ene to (t / c) but-2-ene and (t / c) hex-3-ene in an operational metathesis reactor. The rhenium oxide-coated y-alumina-based catalyst may have a lifetime of at least 300 days in the operational metathesis reactor.EXAMPLES

[0033] Various examples provided herein illustrate selected aspects of the various examples of rhenium oxide-coated y-alumina-based catalyst, methods of manufacture of these catalysts, and methods of use of these catalysts in metathesis reactions.Example 1

[0034] Rhenium oxide-coated y-alumina-based catalyst in the form of spherical pellets and extrudates were prepared. Commercially available y-AhCh spheres with the following propertieswere procured: an average particle size of 1.2 mm to 3 mm, a surface area of 200 m2 / g to 225 m2 / g, a pore volume of 0.5 ml / g to 0.65 ml / g, a bulk density of 0.65 g / ml to 0.7 g / ml, a particle crush strength of 8 dekanewton (daN) to 12 daN and a loss on ignition of less than 5 wt. % to be used as a support. The catalyst were prepared by calcination of commercially available y-AhCh support. The calcined y-AhCh spheres were introduced into a rotatable impregnation drum. The drum was revolved at 25 revolutions per minute and sprayed with a rhenium-containing impregnating solution, a rhenium oxide (HReO-i) solution having pH of 1.5. The HReCh solution is present in an amount that corresponds to the pore volume of the y-alumina support. The calcined y-AhCh spheres were sprayed with the HReCh solution at 2 barg of pressure and at rate of 31.5 milliliters per minute (ml / min) over the course of 12 minutes for 700 grams of the rhenium-coated y-alumina- based support. The rhenium oxide acts on the rhenium-coated y-alumina-based support for an additional 1 to 5 minutes after impregnation through an aging process to obtain a 200 pm rhenium oxide coating depth. The rhenium-coated y-alumina-based catalyst is immediately dried after the aging process at 160 °C for from 16 to 24 hours. The rhenium-coated y-alumina-based catalyst is then calcinated at 550 °C under air for 6 hours to form rhenium oxide-coated y-alumina catalyst. The final calculated composition of the catalyst is 5.4 wt. % Re2O7 / y-AhO3. This process was robust, repeatable, and scalable to prepare larger than lab scale amounts of catalyst. The catalyst was stable in gas phase and liquid phase operations at reaction conditions of weight hourly space velocity (WHSV) ranging from about 0.6 / hr to 10 / hr, 50 °C at a pressure from about 0 barg to about 30 barg using feedstock of but-l-ene and but-2-enes at ratios ranging from 18:82 to 70:30. The synthesized catalyst properties are provided in Table 1.Table 1Example 2

[0035] Rhenium oxide-coated y-alumina-based catalyst in the form of spherical pellets and extrudates were prepared containing 5.5 wt. % Re2O7 / y-AhO3. 662 grams of commercially available y-AhCh spheres with the following properties were procured: an average particle size of 1.2 mm to 3 mm, a surface area of 205 m2 / g, a pore volume of 0.5 ml / g, a pore diameter of 80 A, and a particle crush strength of 7.56 daN to function as a support. The catalyst was prepared by calcination of commercially available y-AhCh support. The calcined y-AhCh support was then prepared for incipient wetness impregnation of the support with an aqueous solution prepared by dissolving 58.1 grams of commercial perrhenic acid solution with a 50% purity in 368 mL of deionized (DI) water. The impregnation was conducted by introducing the above calcined support into a rotatable impregnation drum, which is revolved at 25 revolutions per minute and sprayed with a perrhenic acid solution containing impregnating solution. The amount of perrhenic acid solution corresponded to the pore volume of the y-AhCh support. The perrhenic acid solution containing impregnating solution is sprayed with a pressure of 2 barg and at a rate of 31.5 (milliliters) mL per minute over the course of 12 minutes for 700 grams of the final calcined catalyst. Aging is completed after the impregnation step by allowing the impregnation solution to act on the support for a further 1 minute to 5 minutes to achieve a rhenium oxide coating on the surface of the calcined y-alumina support, with 200 mm depth. The rhenium-coated y-alumina- based support was then immediately dried at 160 °C for about 16 hours to about 24 hours. The dried rhenium- coated y-alumina-based support was then calcined at 550 °C for 6 hours to form rhenium oxide-coated y-alumina catalyst. After calcination, the catalyst was cooled in the presence of air and the catalyst was stored in an airtight container used for metathesis of but-2-enes and but- 1-ene to propene. The final calculated composition of the rhenium oxide-coated y-alumina-based support was 5.4 wt. % Re2O7 / AhO3.Example 3

[0036] The rhenium oxide-coated y-alumina-based support, prepared as described in Example 2, was evaluated to determine the activity of the catalyst. The rhenium oxide-coated y-alumina- based support was accurately weighted and loaded into the reactor. The plug flow conditions were maintained. The thermowell was placed at the top, middle, and bottom of the catalyst bed. A 13X molecular sieve was loaded above the catalyst bed to absorb moisture from feedstock prior to contacting the catalyst bed. At below the catalyst bed, inert alpha alumina was loaded. After loading of the catalyst, the catalyst was activated for the metathesis of but-2-enes with but-l-ene. Activation of the catalyst was performed under air at 550 °C for 6 hours, and then purging was conducted using air with nitrogen. The catalyst was then cooled to 50 °C under nitrogen. Once a reaction temperature of 50 °C was reached, a feed containing n-butane 1.14%, trans but-2-ene 54.6%, cis but-2-ene 23%, but-l-ene 21% was supplied to the reactor. N-butane was used as an internal standard. The feed was supplied to maintain a weight hourly space velocity (WHSV) of 5 / hr. The reactor outlet gases were analyzed by online gas chromatography (GC) (Agilent 6890) equipped with a flame ionization detector for hydrocarbon analysis and thermal conductivity detector for ideal gases. The reactor and products molar flowrates were calculated using internal standard n-butane based on its molar flow rate as well as GC areas.

[0037] FIG. 4 is a graphical representation of rhenium oxide-coated y-alumina-based catalyst for the metathesis of butene as a function of time on stream (TOS) with varying WHSV. The rhenium oxide-coated y-alumina-based catalyst of Example 2 was deactivated within 200 hours of TOS, with an WHSV: 5 / hr compared to 830 hours of TOS, with an WHSV: 0.6 / hr. With a decreasing WHSV, less feed is processed and the catalyst stability is thereby increased.

[0038] FIG. 5 is a graphical representation of but-l-ene conversion comparison of rhenium oxide-coated y-alumina-based catalyst and thru-thru catalyst for butene metathesis reaction as a function of time on stream (TOS). The conversion with respect to but-l-ene using rhenium oxi decoated y-alumina-based catalyst was initially 90% and dropped over the course of 5 days to 85%. The cycle time during this process was 5 days. In addition, the propene selectivity was 50% over the entire cycle time. When the cycle was completed, the catalyst was regenerated by calcination under air at 550 °C followed by cooling under nitrogen to 50 °C. At the beginning of the second cycle, the conversion with respect to but-l-ene was again 90%, equal to the activity level of thefresh catalyst at the beginning of the first cycle. Propene selectivity was also 50%, similar to the first cycle over the entire second cycle. Multiple reaction and regeneration cycles (for example over fifty times) were conducted when the initial activity no longer reached the level of at least 99% of the initial activity of the fresh catalyst. In certain examples, the catalyst life at reaction conditions can be more than 300 days. In certain examples, the catalyst life at reaction conditions can be one or more years. In certain examples, the catalyst life at reaction conditions can be longer than three years. This time period is dependent on the WHSV ranging from 0.6 / hr to 10 / hr.Example 4

[0039] Sample catalysts in the form of spherical pellets with rhenium dispersed throughout the pellets were prepared, also known as thru-thru catalyst. 662 grams of y-AhCh spheres with the following properties were procured: 205 m2 / g, pore volume of 0.5 ml / g, pore diameter 80 A, crushing strength of 7.56 daN to function as a support. The catalyst was prepared by calcination of commercially available y-AhCh support in an air stream rotatory furnace at 550 °C for 5 hours. The calcined y-AhCh support was then prepared for incipient wetness impregnation of the support with an aqueous solution prepared by dissolving 58.1 grams of commercial perrhenic acid solution with a 50% purity in 736 mb of DI water and made into a clear solution. The impregnation was conducted by introducing above calcined support into a perrhenic acid solution-containing beaker under constant stirring for 1 hour. Aging is completed after the impregnation step by allowing the impregnation solution to act on the support for further 24 hours. The thru-thru catalyst was then immediately dried at 160 °C for about 16 hours to about 24 hours. The dried rhenium- coated y- alumina-based support was then calcined at 550 °C for 6 hours to form rhenium oxide. After calcination, the catalyst was cooled in the presence of air and the catalyst was stored in an airtight container used for metathesis of but-2-enes and but-l-ene to propene. The final calculated composition of the rhenium oxide-coated y-alumina-based catalyst was 5.3 wt. % Re2O7 / AhO3.Example 5

[0040] The catalyst process described in Example 4 was used to evaluate the activity of the catalyst. The prepared thru-thru catalyst spheres were loaded into a tubular fixed bed reactor. The thru-thru catalyst was accurately weighted at 50 g with a 1.5 to 2 mm diameter. The thru-thrucatalyst was then loaded into the tubular fixed bed reactor and the plug flow conditions were maintained. The thermowell was placed at the top, middle, and bottom of the catalyst bed. Above the catalyst bed, 13X molecular sieve was loaded to absorb the moisture from the feedstock prior to the feedstock contacting the catalyst bed. An inert alpha alumina was loaded below the catalyst bed. After loading, the thru-thru catalyst was used for metathesis of but-2-enes with but-l-ene. The spherical catalyst was activated under air at 550 °C for 6 hours then the air was purged with nitrogen and cooled to 50 °C under nitrogen. Once the temperature of the thru-thru catalyst reached 50 °C reaction temperature, a feed containing n-butane 1.14%, trans but-2-ene 54.6%, cis but-2- ene 23%, but-l-ene 21% was fed into the tubular fixed bed reactor. N-butane was used as an internal standard. The feed was fed to maintain the WHSV of 5 / hours at 6 barg pressure. The reactor outlet gases were analyzed by online gas chromatography (Agilent 6890) equipped with a flame ionization detector for hydrocarbon analysis and thermal conductivity detector for ideal gases. The reactor and products molar flowrates was calculated using internal standard n-butane based on its molar flow rate as well as GC areas.

[0041] As shown in FIG. 5, the conversion with respect to but-l-ene was initially 90% and then the conversion dropped over the course of 5 days to 85%. The cycle time for testing was 5 days. Propene selectivity was 50% over the entire cycle time. When the cycle was completed, the catalyst was regenerated by calcination under air at 550 °C followed by cooling under nitrogen to 50 °C. At the beginning of the second cycle, the conversion with respect to but-l-ene was again 90%, the same activity level of the fresh thru-thru catalyst at the beginning of the first cycle. Propene selectivity was 50%, similar to the first cycle over the entire second cycle. Multiple reaction and regeneration cycles was conducted over >60 times. The thru-thru catalyst showed a more rapid conversion decline compared to the rhenium- coated y-alumina-based catalyst. The thru-thru catalyst initial activity on each regeneration cycle, never regained at least 99% of the initial activity stability of the fresh thru-thru catalyst. The thru-thru catalyst life may be at least 240 days or this catalyst life may last for less than 40 reaction-regeneration cycles.

[0042] The rhenium-coated y-alumina-based catalyst, shown as the egg-shell catalyst in FIG. 5, was shown to have at least 60 day longer catalyst life or at least 10 reaction-regeneration cycles more than the thru-thru catalyst. It was also observed that the cycle time increases with a decrease of WHSV and results in an increase in the catalyst lifetime accordingly for both the rhenium-coated y-alumina-based catalyst and the thru-thru catalyst. However, at same WHSV, the thru-thru catalyst deactivates faster than the rhenium-coated y-alumina-based catalyst.Example 6

[0043] The rhenium- coated y-alumina-based catalyst from Example 2 was evaluated by varying the feed composition. The feed composition was changed by varying the but-l-ene to but-2-enes ratio at the metathesis reaction conditions of a temperature 50 °C, a pressure of 6 barg, and a WHSV of 1 / hr. As described in Table 2, three runs were conducted varying the but-l-ene: but-2- enes ratio. Run-1 was conducted with but-l-ene: but-2-enes ratio of 50:50 weight ratio, Run-2 20:80 weight ratio and Run-3 3:97 weight ratio, respectively.

[0044] The total butene conversion was greater in Run-1 and was the least in Run-3. Olefins selectivity included analysis for propene, pentene, hexene, and ethene. FIG. 6 is a graphical representation of the conversion of but-l-ene using the rhenium-coated y-alumina-based catalyst and the resulting selectivity at various ratios. Run-3 had the greatest olefins selectivity of propene with Run-1 with the least olefins selectivity of propene. However, the variation between the three runs was less than the variation between the three runs for pentene. After propene, pentene was the next largest selectivity. Run-3 had the greatest olefins selectivity of propene with Run-1 having the least olefins selectivity of propene. Run-1 had the greatest olefins selectivity of ethene and hexene and Run-3 had the least olefins selectivity of ethene and hexene.Table 2

[0045] Two additional runs were also conducted, as shown in Table 3.Table 3

[0046] When ranges are disclosed herein, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, reference to values stated in ranges includes each and every value within that range, even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0047] Other objects, features and advantages of the disclosure will become apparent from the foregoing drawings, detailed description, and examples. These drawings, detailed description, and examples, while indicating specific examples of the disclosure, are given by way of illustration only and are not meant to be limiting. In further examples, features from specific examples may be combined with features from other examples. For example, features from one example may be combined with features from any of the other examples. In further examples, additional features may be added to the specific examples described herein. It should be understood that although the disclosure contains certain aspects, examples, and optional features, modification, improvement, or variation of such aspects, examples, and optional features can be resorted to by those skilled in the art, and that such modification, improvement, or variation is considered to be within the scope of this disclosure.

Claims

Claims1. A method of preparing a rhenium oxide-coated y-alumina-based catalyst, the method comprising: calcining a y-alumina-based support with a particle size ranging from about 1.2 millimeters (mm) to about 3 mm to form a calcined y-alumina-based support at a temperature ranging from about 450 degrees Celsius (°C) to about 550 °C; treating the calcined y-alumina-based support with an aqueous rhenium solution in an impregnation unit to form a rhenium-coated y-alumina-based support; aging the rhenium-coated y-alumina-based support to form a rhenium- coated y-alumina- based catalyst containing a rhenium coating ranging from about 150 micrometers (pm) to about 250 pm in thickness; drying the rhenium-coated y-alumina-based catalyst immediately after aging at a temperature ranging from about 140 °C to about 160 °C; and calcining the rhenium-coated y-alumina-based catalyst at a temperature ranging from about 450°C to about 550 °C to form rhenium oxide-coated y-alumina-based catalyst.

2. The method of claim 1, wherein treating the calcined y-alumina-based support with an aqueous rhenium solution is conducted by spraying the aqueous rhenium solution in a rotating drum impregnation unit at a speed ranging from about 15 revolutions per minute (rpm) to about 35 rpm.

3. The method of claim 1, wherein aging the rhenium-coated y-alumina-based support is carried for a time less than 5 minutes.

4. The method of claim 1, wherein the y-alumina-based support has a pore volume ranging from about 0.5 milliliter per gram (ml / g) to about 0.65 ml / g and a pore diameter ranging from about 75 Angstroms (A) to about 110 A.

5. The method of claim 1, wherein the rhenium-coated y-alumina-based catalyst is dried for about 5 hours to about 24 hours.

6. The method of claim 1, wherein the rhenium oxide-coated y-alumina-based catalyst contains rhenium oxide in an amount from about 4.8 weight percent (wt. %) to about 5.6 wt. %.

7. The method of claim 1, wherein the rhenium oxide-coated y-alumina-based catalyst has a surface area ranging from about 200 square meters per gram (m2 / g) to about 270 m2 / g.

8. The method of claim 1, wherein the rhenium particles have a diameter ranging from about 0.3 nanometer (nm) to about 1.5 nm.

9. A method of preparing an activated rhenium oxide-coated y-alumina-based catalyst, the method comprising: treating the rhenium oxide-coated y-alumina-based catalyst of Claim 1 under air at a temperature from about 500 °C to about 550 °C for about 6 hours to produce an activated rhenium oxide-coated y-alumina-based catalyst; and purging nitrogen into the activated rhenium oxide-coated y-alumina-based catalyst to displace the air and cooling the activated rhenium oxide-coated y-alumina-based catalyst to a temperature of about 50 °C.

10. A rhenium oxide-coated y-alumina-based catalyst comprising y-alumina-based spherical particles of a size ranging from about 1.2 mm to about 3 mm and a rhenium coating ranging from about 150 pm to about 250 pm in thickness.

11. The catalyst of claim 10, wherein the rhenium oxide-coated y-alumina-based catalyst contains rhenium oxide in an amount ranging from about 4.8 wt. % to about 5.6 wt. %.

12. The catalyst of claim 10, wherein the rhenium oxide-coated y-alumina-based catalyst facilitates conversion of one or more of (trans / cis (t / c)) but-2-ene with but-l-ene to propene and (t / c) pent-2-ene, but-l-ene with but-l-ene to ethene and (t / c) hex-3-ene, ethene with (t / c) but-2- ene to propene and propene, but-l-ene with (t / c) pent-2-ene to propene and (t / c) hex-3-ene, and(t / c) pent-2-ene and (t / c) pent-2-ene to (t / c) but-2-ene and (t / c) hex-3-ene in an operational metathesis reactor.

13. The catalyst of claim 10, wherein the rhenium oxide-coated y-alumina-based catalyst lasts longer than fifty reaction regeneration cycles.

14. A rhenium oxide-coated y-alumina-based catalyst comprising y-alumina-based extrudate particles of a size ranging from 1.2 mm to about 3 mm in diameter and from about 4 mm to about 12 mm in length and the rhenium coating ranging from about 150 pm to about 250 pm in thickness.

15. The catalyst of claim 14, wherein the rhenium oxide-coated y-alumina-based catalyst contains rhenium in an amount ranging from about 4.8 wt. % to about 5.6 wt. %.

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