WO2022144711A1

WO2022144711A1 - Open cell foam materials for selectivity enhancement in alkane dehydrogenation

Info

Publication number: WO2022144711A1
Application number: PCT/IB2021/062225
Authority: WO
Inventors: T. Alexander NIJHUIS; Aaron VANDEPUTTE
Original assignee: Sabic Global Technologies B.V.
Priority date: 2020-12-29
Filing date: 2021-12-22
Publication date: 2022-07-07

Abstract

Disclosed is a catalyst bed for a fixed bed reactor. The catalyst bed contains a first alkane dehydrogenation catalyst layer having a height (h1), optionally a second alkane dehydrogenation catalyst layer having a height (h2), at least one open-cell porous foam layer having a height (h3), a first surface, and an opposing second surface, wherein at least a portion of the first surface is in contact with at least a portion of the first alkane dehydrogenation catalyst layer, and wherein at least a portion of the second surface is in contact with at least a portion of the second alkane dehydrogenation catalyst layer, with at least a portion of a support structure of the fixed bed reactor, or with at least a portion of an inert layer, wherein h1 and h3 form at least a portion of the height of catalyst bed (H).

Description

OPEN CELL FOAM MATERIALS FOR SELECTIVITY ENHANCEMENT IN ALKANE DEHYDROGENATION

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Application No. 20217606.1, filed December 29, 2020, the contents of which is incorporated into the present application by reference in its entirety.

FIELD OF INVENTION

[0002] The invention generally concerns catalyst beds that can be used in chemical reactions such as dehydrogenation reactions to produce olefins.

BACKGROUND OF THE INVENTION

[0003] Light olefins such as propylene and iso-butylene are important chemicals with multiple industrial uses. For example, propylene can be used to make polypropylene, which is used in a variety of products. Propylene can also be used as an intermediate for preparing various chemicals, such as acetone, isopropylbenzene, isopropanol, isopropyl halides, propylene oxide, acrylonitrile, and cumene. Iso-butylene can be used for preparing gasoline additives, such as methyl tert-butyl ether (MTBE), and ethyl tert-butyl ether (ETBE).

[0004] Propylene and iso-butylene can be produced by dehydrogenation of propane and iso-butane, respectively. A commonly used industrial process for dehydrogenation of propane and iso-butane is the CATOFIN process. In the CATOFIN process, propane or iso-butane is dehydrogenated using a fixed bed reactor containing a chromia catalyst. Problems with traditional CATOFIN reactors include thermal cracking within the headspace, e.g. space above the catalyst bed, of the reactor. Thermal cracking can reduce selectivity of the dehydrogenation process. Attempts have been made to reduce the headspace of the reactor by raising the catalyst bed. Traditional methods of raising the catalyst bed include increasing catalyst bed height through addition of catalyst and/or inert material to the bed. However, the weight of the additional material can result in a higher load on the support structure of the catalyst bed. Further, raising the catalyst bed through the addition of excess catalyst and/or inert material can increase the pressure drop in the reactor, which can result in lower conversion and/or selectivity. Moreover, with use, small particle deposition and catalyst agglomeration can occur on the catalyst bed. Small particle deposition and catalyst agglomeration can restrict gas or feed flow through the catalyst bed. It can also create dead zones, e.g., zones with reduced gas flow in the bed. The catalyst bed above and below such dead zones can also have relatively restricted gas flow and cannot be used efficiently. Restricted gas flow can also result in pressure maldistribution and drop in the reactor. Referring to FIG. 1 A, a traditional CATOFIN reactor, with dead zones A, in the catalyst bed B, is shown. As can be seen from FIG. 1 A, the regions C above and below the dead zones A can have restricted gas flow. Attempts have been made to increase gas flow to the catalyst particles in the catalyst bed.

[0005] For example, DE102009011375A1 use a porous holding device positioned on the top of the catalyst bed to retain catalyst particles in the direction of gas flow. In particular, the holding device is designed to prevent the catalyst particles from entering the head space by placing the holding device on top of the catalyst bed such that a top surface of the holding device is in contact with the head space and a bottom surface of the holding device is in contact with the catalyst bed. This holding device, however, does not provide a solution to the problems associated with thermal cracking and pressure drop, as the feed stream must first travel through the holding device before reaching the catalyst bed, and thermal cracking may occur in the holding device.

BRIEF SUMMARY OF THE INVENTION

[0006] A solution to at least some of the problems discussed above has been discovered. In one aspect, the solution can include providing a catalyst bed containing at least one open-cell porous foam layer positioned within the catalyst bed and/or positioned below the catalyst bed. It is believed that insertion of open-cell foam layer(s) within or below the catalyst bed can increase the height of the catalyst bed and thereby reduce head space over the catalyst bed. Reducing the head space in such a manner can increase the selectivity of the chemical process (e.g., increase olefin production from dehydrogenation of alkanes, preferably increase C2-C5 olefin production, or more preferably, C3-C4 olefin production). By way of example, the volume of the head space can be reduced such that a feed stream (e.g., an alkane feed stream, preferably a C3 to C4 containing feed stream) has a shorter path to the catalyst bed. Still further, foams have relatively low density, thus the foam layer(s) can increase the height of the bed without substantially increasing the weight of the bed. As illustrated in a non-limiting manner in the Example, iso-butane dehydrogenation using a catalyst bed containing a foam layer can result in increased selectivity when compared to a similar catalyst bed without the foam layer. Further, insertion of open-cell foam layer(s) also permits open paths of gas flow, and thus reduces pressure drop and dead zone formation in the bed. Open-cell foam layer(s) allow gas-redistribution in the catalyst bed, making zones above and below the dead zones (if formed) more accessible to gas flow. As illustrated in a non-limiting manner in FIG. IB, use of foam layer(s) can make zones above and below any formed dead zones A more accessible to gas flow. Referring to FIG. IB, gas can flow more freely through the open-cell foam layers DI and D2, thus zones above and below the dead zones A become more accessible to gas flow and can therefore reduce the negative effects of the dead zones on the reaction process (e.g., dehydrogenation reaction).

[0007] One aspect of the present invention is directed to a catalyst bed for a fixed bed reactor. The catalyst bed can contain at least one open-cell porous foam layer positioned within the catalyst bed. In some aspects, the catalyst bed can have a height (H) and can contain i) a first alkane dehydrogenation catalyst layer having a height (hl), ii) optionally a second alkane dehydrogenation catalyst layer having a height (h2), and iii) an open-cell porous foam layer having a height (h3), a first surface, and an opposing second surface, wherein at least a portion of the first surface is in contact with at least a portion of the first alkane dehydrogenation catalyst layer, wherein at least a portion of the second surface is in contact with at least a portion of the second alkane dehydrogenation catalyst layer, or in contact with at least a portion of a support structure of the fixed bed reactor, or in contact with at least a portion of an inert layer, and wherein hl and h3 form at least a portion of H. In some aspects, at least a portion of the second surface is in contact with at least a portion of the second alkane dehydrogenation catalyst layer or in contact with at least a portion of a support structure of the fixed bed reactor

[0008] In some aspects, the first alkane dehydrogenation catalyst layer can be positioned on top of the open-cell porous foam layer, the first surface can be a top surface of the open-cell porous foam layer, the at least a portion of the first surface can be in contact with at least a portion of a bottom surface of the first alkane dehydrogenation catalyst layer, the second surface can be a bottom surface of the open-cell porous foam layer, and at least a portion of the second surface can be in contact with at least a portion of a top surface of the support structure.

[0009] In some aspects, the second alkane dehydrogenation catalyst layer can be positioned below the open-cell porous foam layer, the second surface can be a bottom surface of the open-cell porous foam layer, and the at least a portion of the second surface can be in contact with at least a portion of a top surface of the second alkane dehydrogenation catalyst layer, and hl, h2 and h3 can form at least a portion of H. In some particular aspects, the opencell porous foam layer can be positioned below the first alkane dehydrogenation catalyst layer; the second alkane dehydrogenation catalyst layer can be positioned below the open-cell porous foam layer; the support structure can be positioned below the second alkane dehydrogenation catalyst layer; the first surface can be a top surface of the open-cell porous foam layer and can be in contact with at least a portion of a bottom surface of the first alkane dehydrogenation catalyst layer; and the second surface can be a bottom surface of the open-cell porous foam layer and can be in contact with at least a portion of a top surface of the second alkane dehydrogenation catalyst layer.

[0010] In certain aspects, the catalyst bed can further contain one or more additional layers, such as one or more additional alkane dehydrogenation catalyst layer(s), ii) one or more additional open-cell porous foam layer(s), and/or iii) one or more inert layers. The additional layers can be positioned anywhere within the catalyst bed. In some aspects, the additional layers can be positioned i) on top of the first alkane dehydrogenation catalyst layer, and/or iii) above the support structure.

[0011] In some aspects, the catalyst bed can contain a second open-cell porous foam layer. The second open-cell porous foam layer can have a height (h4), a third surface, and an opposing fourth surface. At least a portion of the third surface can be in contact with at least a second portion of the second alkane dehydrogenation catalyst layer, and hl, h2, h3, and h4 can form at least a portion of H. In some aspects, the second alkane dehydrogenation catalyst layer can be positioned on above of the second open-cell porous foam layer, the third surface can be a top surface of the second open-cell porous foam layer, and the third surface can be in contact with at least a portion of a bottom surface of the second alkane dehydrogenation catalyst layer. In some particular aspects, the open-cell porous foam layer, (e.g. forming a first open-cell porous foam layer) can be positioned below the first alkane dehydrogenation catalyst layer, the second alkane dehydrogenation catalyst layer can be positioned below the open-cell porous foam layer, the second open-cell porous foam layer can be positioned below the second alkane dehydrogenation catalyst layer, and the support structure can be positioned below the second open-cell porous foam layer.

[0012] In some aspects, the catalyst bed can contain a third alkane dehydrogenation catalyst layer, positioned below the second open-cell porous foam layer and above the support structure. The third alkane dehydrogenation catalyst layer can have a height (h5), and hl, h2, h3, h4, and h5 form at least a portion of H. The fourth surface can be a bottom surface of the second open-cell porous foam layer, and can be in contact with at least a portion of a top surface of the third alkane dehydrogenation catalyst layer. In some particular aspects, the open-cell porous foam layer, (e.g. forming a first open-cell porous foam layer) can be positioned below the first alkane dehydrogenation catalyst layer, the second alkane dehydrogenation catalyst layer can be positioned below the open-cell porous foam layer, the second open-cell porous foam layer can be positioned below the second alkane dehydrogenation catalyst layer, the third alkane dehydrogenation catalyst layer can be positioned below the second open-cell porous foam layer, and the support structure can be positioned below the third alkane dehydrogenation catalyst layer.

[0013] In certain aspects, the catalyst bed can contain a top open-cell foam layer, positioned above the first alkane dehydrogenation catalyst layer. The top open-cell foam layer can partially fill up (e.g., 10, 20, 30, 40, 50, 60, 70, or up to 80 vol. %, or any range in between), or essentially fill up (e.g. 80 vol. % or above, 90 vol. % or above), or fill up the head space above the first alkane dehydrogenation catalyst layer. In certain aspect, the catalyst bed can contain a top inert layer positioned above the first alkane dehydrogenation catalyst layer. In certain aspects, the catalyst bed can contain a bottom inert layer positioned above the support structure. In certain aspects, the bottom inert layer positioned above the support structure and below of any alkane dehydrogenation catalyst layer present in the bed. In certain aspects, the bottom inert layer positioned above the support structure and below of any alkane dehydrogenation catalyst layer and open-cell foam layer present in the bed. In certain aspects, the bottom inert layer positioned above the support structure and below of any alkane dehydrogenation catalyst layer, but on top of the bottommost open-cell foam layer present in the bed. In certain aspects, the catalyst bed can optionally contain one or more intermediate inert layer(s) positioned between layers (e.g. between alkane dehydrogenation catalyst layer and open-cell foam layers) of the catalyst bed.

[0014] In certain aspects, the catalyst bed can contain one or more layers containing a heat generating material, such as a heat generating material described herein. The layer(s) containing the heat generating material can independently optionally contain an inert material, such as an inert material described herein, and/or an alkane dehydrogenation catalyst, such as an alkane dehydrogenation catalyst described herein. [0015] The alkane dehydrogenation catalyst layers, e.g., first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, or more, can contain an alkane dehydrogenation catalyst. The alkane dehydrogenation catalyst can be any suitable catalyst used for alkane dehydrogenation. In some aspects, the alkane dehydrogenation catalyst can be a catalyst used for dehydrogenation of light alkanes, such as propane and/or iso-butane. In some aspects, the alkane dehydrogenation catalyst layers can contain a catalyst used for CATOFIN process. In certain aspects, the alkane dehydrogenation catalyst layers can contain a chromium based dehydrogenation catalyst. In some aspects, a chromium based dehydrogenation catalyst can contain chromia (chromium (III) oxide) supported on a support. In some aspects, the alkane dehydrogenation catalyst layers can contain chromia supported on alumina. In some aspects, the alkane dehydrogenation catalyst layers can contain chromia supported on alpha alumina. In some aspects, the alkane dehydrogenation catalyst layers independently can optionally contain a heat generating material. The heat generating material can include but is not limited to a metal selected from the group copper, chromium, molybdenum, vanadium, cerium, yttrium, scandium, tungsten, manganese, iron, cobalt, nickel, silver, bismuth and combinations thereof. Heat generating material used can be in supported and/or unsupported form. In some aspects, the heat generating metal can be supported on a carrier selected from the group aluminum oxides, aluminum hydroxides, aluminum trihydroxide, boehmite, pseudoboehmite, gibbsite, bayerite, transition aluminas, alpha-alumina, gamma-alumina, silica/alumina, silica, silicates, aluminates, calcium aluminate, barium hexaluminate, calcined hydrotalcites, zeolites, zinc oxide, chromium oxides, magnesium oxides and combinations thereof. Heat generating material used in different alkane dehydrogenation catalyst layers can be same and/or different. In some particular aspects, the heat generating material can be copper supported on alpha alumina. In some aspects, the alkane dehydrogenation catalyst layers independently can optionally contain an inert material. In some aspects, the inert material can be silica and/or alumina.

[0016] The open-cell foam layer(s) can contain open cell foam. The open-cell foam layers can independently contain i) monolithic blocks or plates of open- cell foam, and/or ii) open-cell foam particles (e.g., lumps) arranged to form the foam layer. In some aspects, the open-cell foam particles can have a size of 5 mm to 50 mm. In certain aspects, the foam particles can be cylindrical or substantially cylindrical in shape, and can have a diameter of 5 mm to 50 mm. Foam particles having other shape (e.g. spherical, ovoid, blocks, plates etc.) and/or size can also be used. [0017] A non-limiting example of an open cell foam is shown in FIG. 2. As can be seen in FIG. 2, open-cell foams can contain open cells that can allow fluids to substantially freely pass through the foam. In some aspects, the open-cell foam layer(s) independently can contain a material selected from the group consisting of open cell metallic foams, ceramic foams, silicon carbide foams, or alumina foams, or any combinations thereof. In some aspects, the open-cell foam layer(s) independently can have a voidage of 50 to 99 %. In some aspects, the open-cell foam layer(s) independently can have a 5 to 50 pores per linear inch (PPI). In some aspects, the open-cell foam layer(s) independently can have a surface area of 500 m²/m³ to 4500 m²/m³. In some aspects, the open-cell foam layer(s) independently can have a density of 100 kg/m³ to 600 kg/m³. In some aspects, the open-cell foam layer(s) independently can have a height of, e.g. h3, h4 can independently, be 1 cm to 25 cm, preferably 5 cm to 10 cm. In some aspects, the top open-cell foam layer can have a height of 1 cm to 400 cm, or 3 cm to 200 cm. In some aspects, at least one material specification of the open-cell foam layer material, e.g., metallic foam, ceramic foam, silicon carbide foam, alumina foam, or combination thereof, can vary throughout the material. In some aspects, the at least one material specification that can vary throughout the material is selected from voidage, pores per linear inch, surface area, and density. In some aspects, the open-cell foam layer material comprises metallic foam, and the density of the metallic foam is variable throughout the metallic foam. In some aspects, the open-cell foam layer(s) comprises a combination of materials selected from the group consisting of metallic foam, ceramic foam, silicon carbide foam, and alumina foam. When the open-cell foam layer(s) comprises a combination of materials, at least one material specification selected from voidage, pores per linear inch, surface, and density is variable throughout each foam material within the combination of foam materials. In some aspects, the open-foam cell layer(s) comprises a combination of metallic foam and ceramic foam, where at least one of voidage, pores per linear inch, surface area, and density is variable throughout the metallic foam material, and where at least one of voidage, pores per linear inch, surface, and density is variable throughout the ceramic foam material. In some aspects, the foam material may comprise at least two or more foam materials of the same chemical composition, but having different physical parameters, e.g. the foam may comprise two or more ceramic foams of the same chemical composition, but each of the two or more foam materials having at least one differing physical parameter such as differing pores per linear inch, surface area, and/or densities. Heights of the different foam layer(s) can be same and/or different. The height of the catalyst bed can be increased based on the total height of the foam layer(s) included in the bed. The open-cell foam layer(s) independently can have any one of, any combination of, or all of the open-cell foam layer property described herein.

[0018] The inert layer(s), e.g. top, intermediate, and/or bottom inert layer, can contain an inert material. In certain aspects, the inert layer(s) independently can contain alumina and/or silica. In some aspects, the inert layer(s) independently can contain alumina and/or silica balls. The alumina and/or silica balls of the inert layer(s) e.g. independently can have an average diameter of 1 mm to 50 mm, or 5 mm to 25 mm. In some aspects, the inert layer(s), independently can optionally contain an heat generating material, such as a heat generating material described herein. In some aspects, the inert layer(s), independently can optionally contain an alkane dehydrogenation catalyst, such as an alkane dehydrogenation catalyst described herein.

[0019] The support structure of the fixed bed reactor can be configured to retain/support/hold the catalyst bed and the layers, e.g. alkane dehydrogenation catalyst layer(s), open-cell foam layer(s), inert layer(s), of the catalyst bed. The support structure can have a structure and composition of a support structure known in the art, e.g. support structure of the catalyst bed of a CATOFIN reactor. In some aspects, the support structure can contain refractory bricks and/or tiles.

[0020] In some aspects, the catalyst bed can have a height of 0.5 m to 10 m. The catalyst bed can be positioned inside the fixed bed reactor.

[0021] Certain aspects are directed to the fixed bed reactor. The fixed bed reactor can contain a catalyst bed described herein. The fixed bed reactor can contain the support structure positioned below the catalyst bed. The support structured can be configured to retain the catalyst bed and layers of the catalyst bed. The fixed bed reactor can contain an inlet for a feed stream, an outlet for a product stream, and a head space positioned above the catalyst bed. In certain aspects, the reactor can contain a top open-cell porous foam layer having a height wherein the top open-cell porous foam layer is positioned on the top surface of the catalyst bed, and wherein the top open-cell porous foam layer encompasses at least 50 %, 60 %, 70 %, 80 %, 90 %, or 100 % of the volume of the head space. The reactor can have any suitable shape or size. In some aspects, the reactor can be substantially cylindrical in shape. In some aspects, the substantially cylindrical shaped reactor can be placed on its side, and can have a length of 5 m to 40 m, such as 8 m to 25 m, a width of 1 m to 12 m such as 2 m to 10 m, and/or a height of 1 m to 12 m, such as 2 m to 10 m. The width and height of the reactor can be same or different. In some aspects, the reactor can be substantially cylindrical in shape, and width and height of the reactor can be same or substantially same (e.g. within ± 5 %). In some aspects, the reactor can have an elongated shape along its width or height, and width and height of the reactor can be different. In some aspects, The inner volume of the reactor can be 100 m³ to 5000 m³.

[0022] In one aspect, a method for dehydrogenating an alkane using a catalyst bed described herein, is described. The method can include contacting the alkane with the catalyst bed under conditions sufficient to dehydrogenate at least a portion of the alkane. The alkane can be dehydrogenated to form an olefin. In certain aspects, the alkane can be propane and/or iso-butane and the olefin can be propene and/or iso-butene respectively. In certain particular aspects, the alkane can be propane and the olefin can be propene. In certain particular aspects, the alkane can be iso-butane and the olefin can be iso-butene. In certain aspects, the alkane dehydrogenation condition can include a temperature of 400 to 800 °C, a pressure of 0.2 to 2.5 bara, and/or weight hourly space velocity (WHSV) of 0.2 to 5 kg feed / kg catalyst / h. In some aspects, a feed stream containing the alkane can be contacted with the catalyst bed during dehydrogenation of the alkane. In some aspects, the feed stream can contain at least 80 wt. % of alkane. In some aspects, the feed stream can contain at least 80 wt. %, of propane or isobutane. In some particular aspects, the feed stream can contain 80 wt. % to 99.9 wt. % of isobutane, optionally minor amounts of propane, and optionally minor amounts of n-butane. In some particular aspects, the feed stream can contain 80 wt. % to 99.9 wt. % of propane, and optionally minor amounts of methane, ethane and/or butanes.

[0023] The following includes definitions of various terms and phrases used throughout this specification.

[0024] The terms “about” or “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

[0025] The terms “wt.%”, “vol.%” or “mol.%” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.

[0026] The term “substantially” and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0027] The terms “inhibiting” or “reducing” or “preventing” or “avoiding” or any variation of these terms, when used in the claims and/or the specification, include any measurable decrease or complete inhibition to achieve a desired result.

[0028] The term “effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0029] The use of the words “a” or “an” when used in conjunction with the term “comprising,” “including,” “containing,” or “having” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0030] The phrase “and/or” can include “and” or “or.” To illustrate, A, B, and/or C can include: A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0031] 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.

[0032] The process of the present invention can “comprise,” “consist essentially of,” or “consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification. With respect to the phrase “consisting essentially of,” and in one aspect of the present invention, a basic and novel characteristic of the invention can include positioning an open-celled foam layer within a catalyst bed and/or at the bottom of the catalyst bed so as to reduce thermal cracking and/or pressure drop occurrences within a reactor such as dehydrogenation reactor. [0033] The term “primarily,” as that term is used in the specification and/or claims, means greater than any of 50 wt.%, 50 mol.%, and 50 vol.%. For example, “primarily” may include 50.1 wt.% to 100 wt.% and all values and ranges there between, 50.1 mol.% to 100 mol.% and all values and ranges there between, or 50.1 vol.% to 100 vol.% and all values and ranges there between.

[0034] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0036] FIGS. 1A and IB: 1A) A traditional CATOFIN reactor and catalyst bed, and IB) a reactor and catalyst bed according to an example of the present invention.

[0037] FIG. 2: An open-cell foam.

[0038] FIGS. 3A-3E: A reactor and catalyst bed according to certain embodiments of the present invention. Side cross-sectional view of the reactor according to a first (3 A), second (3C), third (3D), fourth (3E), and fifth (3F) embodiment of the present invention. A top exploded view of the catalyst bed of the first embodiment (3B).

DETAILED DESCRIPTION OF THE INVENTION

[0039] A solution to at least some of the problems associated with catalyst beds used for alkane dehydrogenation process has been discovered. In one aspect, the solution can include providing a catalyst bed containing at least one open-cell foam layer positioned within the bed and/or at the bottom of the bed. The open-cell foam layer(s) can increase height of the catalyst bed and decrease head space over the bed without substantially increasing the weight of the bed. Further, the open-cell foam layer(s) can increase gas flow and gas distribution in the catalyst bed, decreasing pressure drop during operations. As illustrated in a non-limiting manner in the Example, iso-butane dehydrogenation using a catalyst bed containing a foam layer can result in increased selectivity compared to a similar catalyst bed without a foam layer.

[0040] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Catalyst bed and reactor containing the catalyst bed

[0041] Referring to FIGS. 3A-F, schematic of catalyst beds 100 according to certain embodiments are described. The catalyst bed 100 can be positioned inside a reactor 10. The arrow LR shows the length of the reactor along the central axis of the reactor, and is oriented parallel to the longitudinal axis of the reactor 10. The arrow W shows the width of the reactor at around the geometric center of the reactor and is oriented parallel to a transverse axis of the reactor 10. The arrow HR shows the height of the reactor at around the geometric center of the reactor and is oriented perpendicular to the arrow LR and W. FIGS. 3 A, C, D, and E show side cross-sectional views of the reactor according to different embodiments, where the crosssection taken along a plane perpendicular to the transverse axis ( e.g. shown by the arrow W). FIG. 3B shows a top exploded view of the catalyst bed of FIG. 3 A. In FIG. 3B, the layers of the catalyst bed are shown separated for illustration purpose only.

[0042] Referring to FIG. 3 A, in certain embodiments, the catalyst bed 100 can contain a first alkane dehydrogenation catalyst layer 102, a first open-cell foam layer 104, and a second alkane dehydrogenation catalyst layer 106. A support structure 18 can be positioned below the bed 100. The first open-cell foam layer 104 can be positioned below the first alkane dehydrogenation catalyst layer 102. The second alkane dehydrogenation catalyst layer 106 can be positioned below the first open-cell foam layer 104. The support structure 18 can be positioned below the second alkane dehydrogenation catalyst layer 106. Referring to FIG. 3B, an exploded view of the catalyst bed 100, exploded along the height of the catalyst bed is shown. In one aspect of the present invention, the foam layer 104 can be positioned within the catalyst material, thereby creating the first 102 and second 106 catalyst layers. In one aspect, the second catalyst layer 106 can be positioned, the foam layer 104 can be positioned on top of the second catalyst layer, and the first catalyst layer 102 can be positioned on the foam layer 104.

[0043] Referring to FIG. 3B, the layer 102 can have a top 102a and a bottom 102b surface. The layer 104 can have a top 104a and a bottom 104b surface. The layer 106 can have a top 106a and a bottom 106b surface. At least a portion of the top surface 104a of the first open-cell foam layer 104 can be in contact with at least a portion of the bottom surface 102b of the first alkane dehydrogenation catalyst layer 102. At least a portion of the bottom surface 104b of the first open-cell foam layer 104 can be in contact with at least a portion of a top surface 106a of the second alkane dehydrogenation catalyst layer 106.

[0044] Referring to FIG. 3C, in some embodiments, the catalyst bed 100 can have a top open-cell foam layer 110, a first alkane dehydrogenation catalyst layer 102, a first open-cell foam layer 104, and a second alkane dehydrogenation catalyst layer 106. A support structure 18 can be positioned below the bed 100. The top open-cell foam layer 110 can be positioned above the first alkane dehydrogenation catalyst layer 102. The first open-cell foam layer 104 can be positioned below the first alkane dehydrogenation catalyst layer 102. The second alkane dehydrogenation catalyst layer 106 can be positioned below the first open-cell foam layer 104. The support structure 18 can be positioned below the second alkane dehydrogenation catalyst layer 106. The top open-cell foam layer 110 can partially fill up (e.g., 10, 20, 30, 40, 50, 60, 70, or up to 80 vol. %, or any range in between), or essentially fill up (e.g. 80 vol. % or above, 90 vol. % or above), or fill up the head space 11 over the dehydrogenation catalyst layer 102. Although layer 110 is shown to fill up the entire head space 11 above the layer 102, an opencell foam layer partially filling up the head space above 102 can readily be made, for instance, by reducing the height of the layer 102.

[0045] Referring to FIG. 3D, in some embodiments, the catalyst bed 100 can contain a top inert layer 112, a first alkane dehydrogenation catalyst layer 102, a first open-cell foam layer 104, and a second alkane dehydrogenation catalyst layer 106, a second open cell foam layer 114, a third alkane dehydrogenation catalyst layer 116, and a bottom inert layer 118. A support structure 18 can be positioned below the bed 100. The top inert layer 112 can be positioned on top of the alkane dehydrogenation catalyst layer 102. The first open-cell foam layer 104 can be positioned below the first alkane dehydrogenation catalyst layer 102. The second alkane dehydrogenation catalyst layer 106 can be positioned below the first open-cell foam layer 104. The second open-cell foam layer 114 can be positioned below the second alkane dehydrogenation catalyst layer 106. The third alkane dehydrogenation catalyst layer 116 can be positioned below the second open-cell foam layer 114. The bottom inert layer 118 can be positioned below the third alkane dehydrogenation catalyst layer 116. The support structure 18 can be positioned below the bottom inert layer 118. At least a portion of the top surface 114a of the second open-cell foam layer 114 can contact at least a portion of the bottom surface 106b of the second alkane dehydrogenation catalyst layer 106. At least a portion of the bottom surface 114b of the second open-cell foam layer 114 can contact at least a portion of the top surface 116a of the third alkane dehydrogenation catalyst layer 116. In some aspects, the catalyst bed can contain a top open-cell foam layer positioned over the top inert layer 112. The top open-cell foam layer can partially fill up, or essentially fill up (e.g. 80 vol. % or above 90 vol. % or above), or fill up the head space over the top inert layer 112 (not shown).

[0046] Referring to FIG. 3E, in some embodiments, the catalyst bed 100 can contain a top inert layer 112, a first alkane dehydrogenation catalyst layer 102, a first open-cell foam layer 104, and a second alkane dehydrogenation catalyst layer 106, a third alkane dehydrogenation catalyst layer 116, a second open cell foam layer 114, and a bottom inert layer 118. A support structure 18 can be positioned below the bed 100. The top inert layer 112 can be positioned on top of the alkane dehydrogenation catalyst layer 102. The first open-cell foam layer 104 can be positioned below the first alkane dehydrogenation catalyst layer 102. The second alkane dehydrogenation catalyst layer 106 can be positioned below the first open-cell foam layer 104. The third alkane dehydrogenation catalyst layer 116 can be positioned below the second alkane dehydrogenation catalyst layer 106. The second open-cell foam layer 114 can be positioned below the third alkane dehydrogenation catalyst layer 116. The bottom inert layer 118 can be positioned below the second open-cell foam layer 114. The support structure 18 can be positioned below the bottom inert layer 118. At least a portion of the top surface 114a of the second open-cell foam layer 114 can contact at least a portion of the bottom surface 116b of the second alkane dehydrogenation catalyst layer 116. At least a portion of the bottom surface 114b of the second open-cell foam layer 114 can contact at least a portion of the top surface 118a of the bottom inert layer 118. In some aspects, the catalyst bed can contain a top open-cell foam layer positioned over the top inert layer 112. The top open-cell foam layer can partially fill up, or essentially fill up (e.g. 80 vol. % or above 90 vol. % or above), or fill up the head space over the top inert layer 112 (not shown). [0047] Referring to FIG. 3F, in some embodiments, the catalyst bed 100 can contain a first alkane dehydrogenation catalyst layer 102, and a first open-cell foam layer 104. A support structure 18 can be positioned below the bed 100. The first open-cell foam layer 104 can be positioned below the first alkane dehydrogenation catalyst layer 102. The support structure 18 can be positioned below first open-cell foam layer 104. In certain aspects, for the catalyst bed can contain a bottom inert layer can be positioned below the layer 104 and above the support structure 18 (not shown).

[0048] In certain aspects, the catalyst bed, e.g. catalyst bed of FIG. 3 A, C, D, E, and F can further contain one or more additional layers, such as i) one or more additional alkane dehydrogenation catalyst layer(s), ii) one or more additional open-cell porous foam layer(s), and/or iii) one or more inert layers. The additional layers can be positioned anywhere within the catalyst bed. In some aspects, the additional layers can be positioned i) on top of the first alkane dehydrogenation catalyst layer 102, and/or ii) above the support structure 18.

[0049] The layers 102, 104, 106, 110, 112, 114, 116 and/or 118 independently can extend between the opposing walls of the reactor along the width and length of the reactor 10. The width and length of the layers 102, 104, 106, 110, 112, 114, 116 and/or 118 independently can depend on the width and length of the reactor 10 at the position of the respective layers. In some aspects, the length of the layers 102, 104, 106, 110, 112, 114, 116 and/or 118 independently can be similar or substantially similar (e.g. within 1%, 5%, or 10 %) of the length of the reactor 10 at the position of the respective layers. In some aspects, the width of the layers 102, 104, 106, 110, 112, 114, 116 and/or 118 independently can be similar or substantially similar (e.g. within 1%, 5%, or 10 %) of the width of the reactor 10 at the position of the respective layers. The length of the layers 102, 104, 106, 110, 112, 114, 116 and/or 118 independently can be same or different. The width of the layers 102, 104, 106, 110, 112, 114, 116 and/or 118 independently can be same or different. The first alkane dehydrogenation catalyst layer 102 can have a height hl, the second alkane dehydrogenation catalyst layer 106 can have a height h2, the first open-cell foam layer 104 can have a height h3, the second opencell foam layer 114 can have a height h4, the third alkane dehydrogenation catalyst layer 116 can have a height h5, the top open-cell foam layer 110 can have height IIFT, the top inert layer 112 can have a height hrr, and the bottom inert layer 118 can have a height hiB. The height of the layers 102, 104, 106, 110, 112, 114, 116 and/or 118, e.g. hl, h3, h2, IIFT, h i, h4, h5, and/or hBi can be independently be same or different. The layers 100, 102, 104, 106, 110, 112, 114, 116 and/or 118, can independently have a uniform or non-uniform height, and hl, h3, h2, IIFT, h i, h4, h5, and/or hm can be the average height of the layers. The height H of the catalyst bed 100 can depend on the height of the layers in the bed. In some aspects, the height H can be a sum of the heights of the layers in the bed. In some aspects, the H can be sum of hl, h2, and h3, (e.g. FIG. 3A and 3B). In some aspects, the H can be sum of IIFT, hl, h2, and h3 (e.g. FIG. 3C). In some aspects, the H can be sum of hrr, hl, h2, h3, h4, h5, and hiB (e.g. FIG. 3D). The length, height and width of the layers 102, 104, 106, 110, 112, 114, 116 and 118 can be measured along the direction of the length, height and width of the reactor 10, respectively.

[0050] The alkane dehydrogenation catalyst layers, (e.g. layers 102, 106, 116) can contain an alkane dehydrogenation catalyst. Alkane dehydrogenation catalyst in different alkane dehydrogenation catalyst layers can be same or different. The alkane dehydrogenation catalyst can be any suitable catalyst used for alkane dehydrogenation. In some aspects, the alkane dehydrogenation catalyst can be a catalyst used for dehydrogenation of light alkanes, such as propane and/or iso-butane. In some aspects, the alkane dehydrogenation catalyst layers can contain a catalyst used for CATOFIN process. In certain aspects, the alkane dehydrogenation catalyst layers can contain a chromium based dehydrogenation catalyst. In some aspects, a chromium based dehydrogenation catalyst can contain chromia (chromium (III) oxide) supported on a support. In some aspects, the alkane dehydrogenation catalyst layers can contain chromia supported on alumina. In some aspects, the alkane dehydrogenation catalyst layers can contain chromia supported on alpha alumina. In some aspects, the alkane dehydrogenation catalyst layers independently can optionally contain a heat generating material. The heat generating material can include but is not limited to a metal selected from the group copper, chromium, molybdenum, vanadium, cerium, yttrium, scandium, tungsten, manganese, iron, cobalt, nickel, silver, bismuth and combinations thereof. The heat generating material can be in supported or unsupported form. In some aspects, the heat generating material can be supported on a carrier selected from the group aluminum oxides, aluminum hydroxides, aluminum trihydroxide, boehmite, pseudoboehmite, gibbsite, bayerite, transition aluminas, alpha-alumina, gamma-alumina, silica/alumina, silica, silicates, aluminates, calcium aluminate, barium hexaluminate, calcined hydrotalcites, zeolites, zinc oxide, chromium oxides, magnesium oxides and combinations thereof. Heat generating material used in different alkane dehydrogenation catalyst layers can be same and/or different. In some particular aspects, the heat generating material can be copper supported on alpha alumina. Support for chromia and the heat generating material metal can be same or different. In some aspects, the alkane dehydrogenation catalyst layers independently can optionally contain an inert material. In some aspects, the inert material can be silica and/or alumina.

[0051] The alkane dehydrogenation catalyst layers, (e.g., 102, 106, 116,) independently can have a height of, e.g. hl, h2, h5 can independently, be 1 cm to 400 cm, or at least any one of, at most any one of, equal to any one of, or between any two of 1, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, and 400 cm. Heights of the different alkane dehydrogenation catalyst layer(s) can be same and/or different.

[0052] The open-cell foam layer(s), (e.g. 104, 110, 114) can contain open cell foam. The open-cell foam layers can independently contain i) monolithic blocks and/or plates of open- cell foam, and/or ii) open-cell foam particles (e.g., lumps) arranged to form the foam layer. In some aspects, the open-cell foam particles can have a size of 5 mm to 50 mm, or at least any one of, at most any one of, equal to any one of, or between any two of 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, and 50 mm. In certain aspects, the foam particles can be cylindrical or substantially cylindrical in shape, and can have a diameter of 5 mm to 50 mm. Foam particles having other shapes (e.g. irregular, sheet, plate, spherical, pyramidal, cubic, block, ovoid, etc.) and/or size can also be used. In some aspects, the foam layer(s) can independently contain blocks and/or plates of open- cell foams having a size smaller than the height, width and/or length of the foam layer, and the blocks and/or plates can be arranged to form the foam the layer. In some aspects, the opencell foam layer(s) independently can contain a material selected from the group consisting of open cell metallic foams, ceramic foams, silicon carbide foams, or alumina foams, or any combinations thereof. In some aspects, the open-cell foam layer(s) independently can have a voidage of 50 to 99 %, or at least any one of, equal to any one of, or between any two of 50, 55, 60, 65, 70, 75, 80, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, and 99 %. In some aspects, the open-cell foam layer(s) independently can have 5 to 50 pores per linear inch, or at least any one of, equal to any one of, or between any two of 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 pores per linear inch. In some aspects, the open-cell foam layer(s) independently can have a surface area of 500 m²/m³ to 4500 m²/m³ or at least any one of, equal to any one of, or between any two of 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 and 5000 m²/m³. In some aspects, the open-cell foam layer(s) independently can have a density of 100 kg/m³ to 600 kg/m³, or at least any one of, at most any one of, equal to any one of, or between any two of 100, 150, 200, 250, 300, 350, 400, 450, 500, 550 and 600 kg/m³. In some aspects, the open-cell foam layers 104 and/or 114 can independently have a height of, e.g. h3 and h4 can independently be 1 cm to 25 cm, or at least any one of, at most any one of, equal to any one of, or between any two of 1, 2, 4, 6, 8, 10, 11, 12, 14, 16, 18, 20, 22, 24, and 25 cm. In some aspects, the top open-cell foam layer can have a height (EFT) of 1 cm to 400 cm, or at least any one of, at most any one of, equal to any one of, or between any two of 1, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, and 400 cm. At least one material specification of the open-cell foam layer material, e.g., metallic foam, ceramic foam, silicon carbide foam, alumina foam, or combination thereof, can vary throughout the material. The variable material specification can be selected from voidage, pores per linear inch, surface area, and density. The open-cell foam layer(s) can include a combination of materials selected from the group consisting of metallic foam, ceramic foam, silicon carbide foam, and alumina foam. When the open-cell foam layer(s) comprises a combination of materials, a specification of each material can vary throughout that material. Examples of variable specifications include voidage, pores per linear inch, surface, and density. In some aspects, the at least one open-cell foam layer includes at least two materials of the same chemical composition, wherein each of the at least two materials of the same chemical composition possess different voidages, pores per linear square inch, surface areas or densities. The open-cell foam layer(s) independently can have any one of, any combination of, or all of the open-cell foam layer properties mentioned herein.

[0053] The inert layer(s) 112 and 118, can contain an inert material. In certain aspects, the inert layer(s) independently can contain alumina and/or silica. In some aspects, the inert layer(s) independently can contain alumina and/or silica spheres or balls. The alumina and/or silica balls of the inert layer(s), independently can have an average diameter of 1 mm to 50 mm, or 10 mm to 40 mm. In some aspects, the inert layers, can independently have a height of, e.g. hi and hiB can independently be 1 cm to 25 cm, or at least any one of, at most any one of, equal to any one of, or between any two of 1, 2, 4, 6, 8, 10, 11, 12, 14, 16, 18, 20, 22, 24, and 25 cm. In certain aspect, the bottom inert layer 118, can contain a first bottom inert layer containing silica and/or alumina balls having an average diameter of 1 mm to 12 mm, and a second bottom inert layer containing silica and/or alumina balls having an average diameter of 15 mm to 40 mm. The height of the first bottom inert layer can be 1 cm to 15 cm. The height of the second bottom inert layer can be 1 cm to 15 cm. In some aspects, the first bottom inert layer can positioned on top of the second bottom inert layer.

[0054] In some aspects, the catalyst bed 100 can have a height of 0.5 m to 10 m, or at least any one of, at most any one of, equal to any one of, or between any two of 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 m.

[0055] The support structure 18 can be configured to retain/support/hold the catalyst bed and the layers, e.g. alkane dehydrogenation catalyst layer(s), open-cell foam layer(s), inert layer(s) of the catalyst bed. The support structure can have a structure and composition of a support structure known in the art, e.g. support structure of the catalyst bed of a CATOFIN reactor. In some aspects, the support structure can contain refractory bricks and/or tiles.

[0056] The reactor 10 can have any suitable shape or size. In some aspects, the reactor 10 can have shape and size of a reactor used for CATOFIN process. In some aspects, the reactor 10 can be substantially cylindrical in shape, although reactors having other shapes can readily be used. In some aspects, the substantially cylindrical shaped reactor 10 can be placed on its side, e.g. the longitudinal axis of the reactor can be parallel or substantially parallel to horizontal axis, although reactors having other orientation can readily be used. The reactor 10 can have an inlet 12 and two outlets 14 and 16. A reaction feed, e.g. reaction feed for an alkane dehydrogenation process, such as CATOFIN process, can enter the reactor through the inlet 12. A reaction product produced in the reactor 10, e.g. by dehydrogenation of alkane in the reactor, can exit the reactor through the outlets 14 and/or 16. The outlets 14 and/or 16 can also be an air outlet. In some aspects, 14 can be a product/hydrocarbon outlet and 16 can an air outlet. In some aspects, i) length (LR) of the reactor 10 can be 5 m to 40 m, or at least any one of, at most any one of, equal to any one of, or between any two of 5, 10, 15, 20, 25, 30, 35, and 40 m, ii) width (W) of the reactor 10 can be 1 m to 12 m, or at least any one of, at most any one of, equal to any one of, or between any two of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 m, and/or iii) height (HR) of the reactor 10 can be 1 m to 12 m, or at least any one of, at most any one of, equal to any one of, or between any two of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 m. The width (W) and height (HR) of the reactor can be same or different. The inner volume of the reactor 10 can be 100 m³ to 5000 m³, or at least any one of, at most any one of, equal to any one of, or between any two of 100, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, and 5000 m³. B. Method of using the catalyst bed

[0057] In one aspect, a method for dehydrogenating an alkane using the catalyst bed 100 is described. The method can include contacting the alkane (e.g., C2, C3, C4, or C5) or a mixture comprising alkanes (e.g., comprising any one, any two of, any three of, or all four of C2, C3, C4, and/or C5 alkanes) with a catalyst bed 100 under conditions sufficient to dehydrogenate at least a portion of the alkane. In certain aspects, the alkane can be fed to the reactor 10 through the inlet 12, and in the reactor 10 the alkane feed can be contacted with the catalyst bed 100. The alkane can be dehydrogenated to form an olefin. In certain aspects, the alkane can be a C2 to C5 olefin, with C3 (e.g., propane) and/or C4 (e.g., butane or iso-butane) being preferred, and the olefin can be a C2 to C5 olefin, with C3 (e.g., propene) and/or C4 (e.g., butene or iso-butene) being preferred. In certain particular aspects, the alkane can be propane and the olefin can be propene. In certain particular aspects, the alkane can be iso-butane and the olefin can be iso-butene. In certain aspects, the alkane dehydrogenation condition in the reactor 10 can include i) a temperature of 400 to 800 °C, or at least any one of, at most any one of, equal to any one of, or between any two of 400, 450, 500, 550, 600, 650, 700, 750, and 400 °C, ii) a pressure of 0.2 to 2.5 bara, or at least any one of, at most any one of, equal to any one of, or between any two of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, and 2.5 bara, and/or iii) a weight hourly space velocity (WHSV) of 0.2 to 5 kg feed / kg catalyst / h, or at least any one of, at most any one of, equal to any one of, or between any two of 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 and 5 kg feed / kg catalyst / h. In some aspects, pressure at different positions of the reactor during the dehydrogenation process can vary. In some aspects, a top portion of the reactor can have a pressure higher than the pressure in a bottom portion of the reactor. In some aspects, a feed stream containing the alkane can be contacted with the catalyst bed 100 during dehydrogenation of the alkane. In some aspects, the feed stream can contain at least 80 wt. % to 99.9 wt. % or at least any one of, equal to any one of, or between any two of 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, and 99.9 wt. % of alkane, such as propane or iso-butane. In some particular aspects, the feed stream can contain 80 wt. % to 99.9 wt. % of iso-butane, optionally minor amounts of propane, and optionally minor amounts of n-butane. In some particular aspects, the feed stream can contain 80 wt. % to 99.9 wt. % of propane, and optionally minor amounts of methane, ethane and/or butanes. [0058] Although embodiments of the present invention have been described with reference to blocks of FIGS. 1A-3E should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIGS. 1A-3E Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIGS. 1A-3E.

[0059] The systems and processes described herein can also include various equipment that is not shown and is known to one of skill in the art of chemical processing. For example, some controllers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and the like may not be shown.

[0060] As part of the disclosure of the present invention, specific examples are included below. The examples are for illustrative purposes only and are not intended to limit the invention. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results.

EXAMPLE

Iso-butane dehydrogenation using catalyst bed containing open cell foam layer

[0061] Simulations were carried out for a iso-butane dehydrogenation reaction. Two parallel experiments were run. The reaction conditions were kept similar for both the experiments. For experiment 1 (comparative) a traditional CATOFIN catalyst bed was used. For experiment 2, a catalyst bed according to one example of the present invention was used. Catalyst bed of experiment 2 had a 16 cm open-cell foam layer added at the bottom of the catalyst bed of experiment 1. Catalyst bed of experiment 3 had a 16 cm open-cell foam layer added at the top of the catalyst bed of experiment 1. Use of foam layer reduced the head space and thermal cracking, and increased selectivity of both experiments 2 and 3. Table 1 provides the conversion, selectivity and yield obtained for experiments 1, 2 and 3. As can be seen from Table 1, selectivity increases for both experiments 2 and 3. Table 1

[0062] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

CLAIMS A catalyst bed having a height (H) for a fixed bed reactor, the catalyst bed comprising: a first alkane dehydrogenation catalyst layer having a height (hl); optionally a second alkane dehydrogenation catalyst layer having a height (h2); and at least one open-cell porous foam layer having a height (h3), a first surface, and an opposing second surface, wherein at least a portion of the first surface is in contact with at least a portion of the first alkane dehydrogenation catalyst layer, wherein at least a portion of the second surface is in contact with at least a portion of the second alkane dehydrogenation catalyst layer, in contact with at least a portion of a support structure of the fixed bed reactor, or in contact with at least a portion of an inert layer, and wherein hl and h3 form at least a portion of H. The catalyst bed of claim 1, comprising the second alkane dehydrogenation catalyst layer, wherein the first alkane dehydrogenation catalyst layer is positioned above the at least one open-cell porous foam layer, the first surface is a top surface of the at least one open-cell porous foam layer that is in contact with the first alkane dehydrogenation catalyst layer, the second alkane dehydrogenation catalyst layer is positioned below the at least one open-cell porous foam layer, the second surface is a bottom surface of the least one open-cell porous foam layer that is in contact with the second alkane dehydrogenation catalyst layer. The catalyst bed of claim 1, wherein the first alkane dehydrogenation catalyst layer is positioned above the at least one open-cell porous foam layer, the first surface is a top surface of the at least one open-cell porous foam layer that is in contact with the first alkane dehydrogenation catalyst layer, the support structure is positioned below the at least one open-cell porous foam layer, the second surface is a bottom surface of the least one open-cell porous foam layer that is in contact with the support structure.

23 The catalyst bed of any one of claims 1 to 3, wherein the first and/or second alkane dehydrogenation catalyst layer(s) comprise a chromium based dehydrogenation catalyst. The catalyst bed of any one of claims 1 to 4, wherein the at least one open-cell foam layer is a monolithic layer. The catalyst bed of any one of claims 1 to 4, wherein the at least one open-cell foam layer comprises a plurality of open-cell particles. The catalyst bed of any one of claims 1 to 6, wherein the at least one open-cell foam layer comprises a material selected from the group consisting of metallic foam, a ceramic foam, a silicon carbide foam, or an alumina foam, or any combinations thereof. The catalyst bed of any one of claims 1 to 7, wherein the at least one open-cell foam layer comprises a voidage of 50 to 99 %, a pores per linear inch (PPI) of 5 to 50, a surface area of 500 m²/m³ to 4500 m²/m³, and/or a density of 100 kg/m³ to 600 kg/m³. The catalyst bed of any one of claims 1 to 8, wherein the at least one open-cell foam layer comprises a material selected from the group consisting of metallic foam, a ceramic foam, a silicon carbide foam, or an alumina foam, or any combinations thereof, wherein at least one material specification selected from voidage, pores per linear inch, surface area, and density is variable throughout the material. The catalyst bed of claim 1, wherein the at least one open-cell foam layer comprises a at least two materials of the same chemical composition, wherein each of the at least two materials of the same chemical composition possess different voidages, pores per linear square inch, surface areas or densities. The catalyst bed of any one of claims 1 to 10, wherein the at least one open-cell foam layer comprises a combination of foam materials selected from the group consisting of metallic foam, a ceramic foam, a silicon carbide foam, and an alumina foam. The catalyst bed of claim 11, wherein at least one material specification selected from voidage, pores per linear inch, surface, and density is variable throughout each foam material within the combination of foam materials The catalyst bed of claim 12, wherein the at least one open-cell foam layer comprises a combination of metallic foam and ceramic foam, wherein the metallic foam voidage is variable throughout the metallic foam and wherein the ceramic foam voidage is variable throughout the ceramic foam. The catalyst bed of any one of claims 1 to 13, further comprising an inert layer, wherein the inert layer preferably comprises alumina and/or silica. The catalyst bed of any one of claims 1 to 14, wherein the first and/or second alkane dehydrogenation catalyst layer(s) independently comprise a heat generating material comprising a group 2 to group 14 metal, more preferably copper. The catalyst bed of any one of claims 1 to 15, further comprising at least a second opencell porous foam layer having a height (h4), wherein hl, h2, h3, and h4 form at least a portion of H. The catalyst bed of any one of claims 1 to 16, wherein h3 is 1 cm to 25 cm, preferably 5 cm to 10 cm, and wherein H is 0.5 m to 10 m. A reactor comprising the catalyst bed of any one of claims 1 to 17, the support structure positioned below the catalyst bed and configured to retain the alkane dehydrogenation catalyst layer, an inlet for a feed stream, an outlet for a product stream, and a head space positioned above the catalyst bed. The reactor of claim 18, further comprising a second open-cell porous foam layer having a height (h4), wherein the second open-cell porous foam layer is positioned on the top surface of the catalyst bed, and wherein the second open-cell porous foam layer encompasses at least 50 %, 60 %, 70 %, 80 %, 90 %, or 100 % of the volume of the head space. A method of dehydrogenating an alkane, preferably a C3 to C4 alkane, the method comprising contacting a feed stream comprising a C2 to C5 alkane, preferably a C3 to C4 alkane, with the catalyst bed of any one of claims 1 to 12 to form a products stream comprising an olefin, preferably a C3 to C4 olefin, wherein the reaction conditions preferably comprise a temperature of 400 to 800 °C, a pressure of 0.2 to 2.5 bar absolute, and a weight hour space velocity (WHSV) of 0.2 to 5 kg feed / kg catalyst / h. The catalyst bed of claim 1 , wherein at least a portion of the second surface is in contact with at least a portion of the second alkane dehydrogenation catalyst layer or in contact with at least a portion of a support structure of the fixed bed reactor.

26