Methods of preparing catalysts for oxidative dehydrogenation

Abstract

Methods for preparing catalysts for oxidative dehydrogenation (ODH) of alkanes such as ethane are provided An exemplary method includes providing a first mixture including metal oxides; a reducing agent; and one or more of a bismuth compound, an antimony compound, and a tellurium compound; and heating the first mixture to form the catalyst. The first mixture is essentially free of water. The metal oxides include an oxide of molybdenum and an oxide of vanadium. The bismuth compound includes bismuth oxide, bismuth hydroxide, or a bismuth carbonate. The antimony compound includes an oxide of antimony, antimony acetate, or antimony ethoxide. The tellurium compound includes tellurium dioxide.

Description

[0001] METHODS OF PREPARING CATALYSTS FOR OXIDATIVE DEHYDROGENATION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to methods for preparing catalysts and catalyst materials for oxidative dehydrogenation (ODH) of alkanes such as ethane. More specifically, the catalysts prepared by the methods disclosed herein contain molybdenum (Mo); vanadium (V); one or more of bismuth (Bi), antimony (Sb), and tellurium (Te); oxygen (O); and, optionally, tantalum (Ta), Niobium (Nb), or both.

[0004] BACKGROUND ART

[0005] Olefins like ethylene, propylene, and butylene are basic building blocks for a variety of commercially valuable polymers. Since naturally occurring sources of olefins do not exist in commercial quantities, polymer producers rely on methods for converting the more abundant lower alkanes into olefins. One such method for commercial scale producers is steam cracking, a highly endothermic process where steam-diluted hydrocarbons are subjected very briefly to a temperature of at least 600°C. The fuel demand to produce the required temperatures and the need for equipment that can withstand that temperature add significantly to the overall cost. In addition, the high temperature promotes the formation of coke, which accumulates within the system, resulting in the need for costly periodic reactor shutdowns for maintenance and coke removal.

[0006] Selective oxidation processes, such as oxidative dehydrogenation (ODH), are an alternative to steam cracking that are exothermic and produce little or no coke. In ODH, a lower alkane, such as ethane, is mixed with oxygen in the presence of a catalyst and optionally an inert diluent, such as carbon dioxide or nitrogen or steam, which may be performed at temperatures as low as 300°C, to produce the corresponding alkene. Various other oxidation products may be produced in this process, including carbon dioxide and acetic acid, among others.

[0007] There is a need for improved methods of preparing catalysts having high selectivity, activity, and longevity for ODH reactions.

[0008] SUMMARY OF INVENTION

[0009] The disclosure provides a method for preparing a catalyst. The method includes providing a first mixture including metal oxides; a reducing agent; and one or more of a bismuth compound, an antimony compound, and a tellurium compound; wherein the first mixture is essentially free of water; and heating the first mixture in the presence of steam to form the catalyst. The metal oxides include an oxide of molybdenum and an oxide of vanadium. The bismuth compound includes bismuth oxide, bismuth hydroxide, or a bismuth carbonate. The antimony compound includes an oxide of antimony, antimony acetate, or antimony ethoxide. The tellurium compound includes tellurium dioxide.

[0010] In some embodiments, the first mixture is a dry powder obtained by: combining the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound to provide a mixture of combined powders; and heating the mixture of combined powders.

[0011] In some embodiments, the first mixture is a dry gel obtained by forming a slurry comprising: the metal oxides, the reducing agent, the one or more of the bismuth compound, the antimony compound, and the tellurium compound, and water; and heating the slurry to remove the water.

[0012] In some embodiments, the steam is saturated steam.

[0013] In some embodiments, the metal oxides further include an oxide of tantalum or an oxide of niobium, or both.

[0014] In some embodiments, the reducing agent is an inorganic reducing agent. In some embodiments, the inorganic reducing agent includes one or both of molybdenum dioxide (MOO2) and vanadium dioxide (VO2). In some embodiments, the reducing agent is MoO2.

[0015] In some embodiments, the reducing agent is oxalic acid.

[0016] In some embodiments, the oxide of molybdenum is MoOs.

[0017] In some embodiments, the oxide of vanadium is V2O5. In some embodiments, the oxide of vanadium is VO2.

[0018] In some embodiments, the first mixture includes the bismuth compound, and the bismuth compound includes bismuth hydroxide.

[0019] In some embodiments, the method further includes adding an inert carrier material to the first mixture. In some embodiments, the inert carrier material is added in an amount of 1 wt.% to 90 wt.% with respect to the weight of the metal oxides in the first mixture. In some embodiments, the inert carrier material includes a-alumina.

[0020] In some embodiments, the method further includes grinding, dry milling, or crushing the metal oxides and the reducing agent of the first mixture.

[0021] In some embodiments, the method further includes grinding, dry milling, or crushing the metal oxides the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound of the first mixture. In some embodiments, the method further includes grinding, wet milling, dry milling, or crushing the metal oxides, the reducing agent, the one or more of the bismuth compound, the antimony compound, and the tellurium compound, and the inert carrier material of the first mixture.

[0022] In some embodiments, the catalyst includes the formula MoaVbBicOx, wherein: a is 1.0; b is about 0.01 to about 0.5; c is about 0.005 to about 0.2; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; and wherein a, b, and c are based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

[0023] In some embodiments, the catalyst includes the formula: MoaVbBic(M2)dOx wherein: M2 is Ta or Nb, or a mixture thereof; a is 1.0; b is 0.01 to 0.5; c is 0.005 to 0.2; d is 0.005 to 0.1; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, and d are determined based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

[0024] The disclosure also provides a catalyst prepared by a method disclosed herein. In some embodiments, the catalyst is for use in oxidative dehydrogenation of ethane.

[0025] BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a PXRD pattern of El-DG.

[0027] Figure 2 is a PXRD pattern of El-P.

[0028] Figure 3 is a PXRD pattern of E2-DG1.

[0029] Figure 4 is a PXRD pattern of E2-DG2.

[0030] Figure 5 is a PXRD pattern of E2-DP.

[0031] Figure 6 is a PXRD pattern of E2-P.

[0032] Figure 7 is a PXRD pattern of E3-DG1.

[0033] Figure 8 is a PXRD pattern of E3-DG2.

[0034] Figure 9 is a PXRD pattern of E3-DP.

[0035] Figure 10 is a PXRD pattern of E4-P1.

[0036] Figure 11 is a PXRD pattern of E4-P2.

[0037] Figure 12 is a PXRD pattern of E4-P3.

[0038] Figure 13 is a PXRD pattern of E5-DG.

[0039] Figure 14 is a PXRD pattern of E5-DP.

[0040] Figure 15 is a PXRD pattern of E6-DG.

[0041] Figure 16 is a PXRD pattern of E6-P.

[0042] Figure 17 is a PXRD pattern of E7-DG. Figure 18 is a PXRD patern of E7-DP.

[0043] Figure 19 is a PXRD patern of E7-P.

[0044] DESCRIPTION OF EMBODIMENTS

[0045] Reference will now be made in detail to certain embodiments of the disclosed subject mater, examples of which are illustrated in part in the accompanying figures. While the disclosed subject mater will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject mater is not intended to be limiting.

[0046] Selective oxidation (SO) is generally used in oxidative dehydrogenation (ODH) reactions to form alpha-olefins from corresponding alkanes, such as to form ethylene from ethane, in the presence of a catalyst. WO 2024 / 4189533 discloses a method for preparing a catalyst suitable for oxidative dehydrogenation that includes forming a slurry of metal oxides, a reducing agent and water. Provided in the present disclosure is an improved synthetic method for a catalyst for use in the ODH process. In the methods disclosed herein, the catalyst precursor materials are combined, for example, by being ground together as powders, dry powders, or dry gels, to provide a first mixture that is essentially free of water. The first mixture is then used in a hydrothermal synthesis process to form the catalyst.

[0047] The methods disclosed herein can utilize powder conversion, dry powder conversion, or dry gel conversion methods, which involve contacting amorphous or crystalline gel or powder with water vapor (steam) in a hydrothermal reaction to form new crystalline material(s). Without being bound by any particular theory, during this steam- assisted crystallization, a controlled steam atmosphere drives the formation of a new crystal phase(s) from crystalline and / or amorphous starting solid material(s). In some embodiments, the methods disclosed herein may provide at least one of high product yield and low-to-zero waste. A further advantage of these methods can include a reduced number of process steps for the synthesis of ODH catalysts as compared to other synthetic methods. In some embodiments, over 90%, or over 95% by weight of the reagents (e.g., metal oxides, metal hydroxides, etc.) are incorporated into the synthesized catalysts.

[0048] In some embodiments, the methods disclosed herein provide catalyst materials by incorporating inert carrier materials into the first reaction mixture. Advantages of these methods include eliminating a separate blending step in catalyst material preparation, which can reduce costs.

[0049] In some embodiments, the synthesized catalysts are active in the conversion of ethane to ethylene without requiring any washing procedure. In some embodiments of the methods disclosed herein, a colorless filtrate has been observed when washing the catalyst after synthesis, which indicates that a washing step may not be required.

[0050] As used herein, the term “oxidative dehydrogenation” or “ODH” refers to processes that couple the endothermic dehydrogenation of an alkane (CnH2n+2) with the strongly exothermic oxidation of hydrogen as is further described herein to form, amongst other things, alpha-olefins. In some embodiments, the alkane is one or more of ethane, propane, butane, pentane, hexane, octane, decane, and dodecane. In some embodiments, the alkane is ethane or propane. In some embodiments, the alkane is ethane. For catalyst testing herein, the ODH reactions herein are assumed to be referring to the ODH of ethane.

[0051] As used herein, the term “catalyst” generally refers to the active portion of a catalyst material that can promote oxidative dehydrogenation, such as the oxidative dehydrogenation of ethane to ethylene. The catalyst may be processed in further steps to form a catalyst material. The catalyst material may also be processed in further steps to form a final catalyst material.

[0052] As used herein, the term “catalyst material” refers to a material that includes an active catalyst that can promote the oxidative dehydrogenation of ethane to ethylene. The catalyst material may be substantially made up of the catalyst. The catalyst material may be a catalyst on a support or a catalyst formulated with a carrier. The catalyst material can be a plurality of particles or a formed catalyst material. Non-limiting examples of formed catalyst materials include extruded catalyst materials, 3D-printed catalyst materials, spheronized catalyst materials, pressed catalyst materials, and cast catalyst materials. Nonlimiting examples of pressed and cast catalyst materials include pellets, such as tablets, ovals, and spherical particles.

[0053] In the methods of the present disclosure, the method for preparing a catalyst includes providing a first mixture including metal oxides, a reducing agent, and one or more of a bismuth compound, an antimony compound, and a tellurium compound. The first mixture is heated in the presence of steam to form the catalyst. The first mixture is essentially free of water. For example, the first mixture is a powder or a dry gel. As used herein, the expression “essentially free of water” may refer to at least 95%, at least 98%, at least 99%, at least 99.9%, or at least 99.99% free of water. In some embodiments, the first mixture is essentially free of a liquid.

[0054] In some embodiments, the first mixture is a powder that is optionally heated to remove any residual water to provide a “dry powder”. In some embodiments, the first mixture is a powder obtained by combining the metal oxides, the reducing agent, and one or more of the bismuth compound, the antimony compound, and the tellurium compound. In some embodiments, the first mixture is a dry powder obtained by combining the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound to provide a mixture of combined powders; and heating the mixture of combined powders.

[0055] In some embodiments, the first mixture is a dry gel. As used herein, the term “dry gel” refers to a gel that is essentially free of water. In some embodiments, the first mixture is a dry gel obtained by forming a slurry including the metal oxides; the reducing agent; the one or more of the bismuth compound, the antimony compound, and the tellurium compound; and water; and heating the slurry to remove the water. As used herein, the term “slurry” refers to a mixture of solids in a liquid, and includes a suspension, a paste (that is, the mixture is viscous such that it cannot freely move), a free-flowing viscous solution, or a colloidal solution. In some embodiments, the slurry is a free-flowing viscous solution. In some embodiments the slurry includes 1 g to 8 g of powder (i.e., the metal oxides; the reducing agent; the one or more of the bismuth compound, the antimony compound, and the tellurium compound powders) per 1 g of water. In some embodiments, the slurry includes 3 g to 6.5 g of powder per 1 g of water. To obtain the dry gel, water is removed from the slurry.

[0056] As used herein, “water” may refer to deionized water, distilled water, and the like. In some embodiments, the water is distilled, deionized water. In some embodiments, the water may include higher levels of contaminants without harming the catalyst.

[0057] The metal oxides in the first mixture include an oxide of molybdenum and an oxide of vanadium. In some embodiments, the oxide of molybdenum is MoOs. In some embodiments, the oxide of vanadium is V2O5. In some embodiments, the oxide of vanadium is VO2.

[0058] In some embodiments, the metal oxides further includes an oxide of tantalum, an oxide of niobium, or both. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of tantalum. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of niobium. In some embodiments, the oxide of tantalum, when present, is Ta2C>5 xhbO, and the oxide of niobium, when present, is Nb2O5 XH2O.

[0059] In some embodiments, the first mixture includes an oxide of tantalum. In some embodiments, the reducing agent is oxalic acid, and the first mixture includes an oxide of tantalum. In other embodiments, the first mixture is essentially free of a tantalum compound. For example, the first mixture includes less than 10 ppm, less than 5 ppm, less than 2 ppm, or less than 1 ppm tantalum. In some embodiments, the first mixture is essentially free of a niobium compound. For example, the first mixture includes less than 10 ppm, less than 5 ppm, less than 2 ppm, or less than 1 ppm niobium.

[0060] In some embodiments, the first mixture includes the bismuth compound, wherein the bismuth compound includes bismuth oxide, bismuth hydroxide, or a bismuth carbonate. In some embodiments, the bismuth compound is bismuth oxide. In some embodiments, the bismuth compound is bismuth hydroxide. In some embodiments, the bismuth compound is bismuth carbonate. As used herein, the term “bismuth carbonate” includes basic carbonates of bismuth and oxide-carbonates (subcarbonates) of bismuth. Examples of a bismuth carbonate include bismuth carbonate basic or bismuth subcarbonate ((BiO^CCh).

[0061] In some embodiments, the first mixture includes the antimony compound, wherein the antimony compound includes an oxide of antimony, antimony acetate, or antimony ethoxide. In some embodiments, the antimony compound is an oxide of antimony. In some embodiments, the antimony compound is antimony acetate. In some embodiments, the antimony compound is antimony ethoxide.

[0062] In some embodiments, the first mixture includes the tellurium compound, wherein the tellurium compound includes tellurium dioxide (TeCh). In other embodiments, the first mixture is essentially free of a tellurium compound. For example, the first mixture includes less than 10 ppm, less than 5 ppm, less than 2 ppm, or less than 1 ppm tellurium.

[0063] The first mixture includes a reducing agent. As used herein, the term “reducing agent” refers to a chemical substance that is capable of reducing an oxidation state of one or more of the metals of the metal oxides, the bismuth compound, the antimony compound, and the tellurium compound in the first mixture.

[0064] In some embodiments, the reducing agent is an organic reducing agent. In some embodiments, the organic reducing agent includes an alcohol, a carboxylic acid, or an ester. In some embodiments of the method, the reducing agent is oxalic acid.

[0065] In some embodiments, the reducing agent is an inorganic reducing agent. In some embodiments, the reducing agent is a metal oxide. In some embodiments, the reducing agent includes one or both of molybdenum (IV) oxide (also referred to as molybdenum dioxide, MoO2) and vanadium (IV) oxide (also referred to as vanadium dioxide, VO2). In some embodiments, the first mixture is essentially free of an alcohol, a carboxylic acid, an ester, or a combination thereof (i.e., the reducing agent is not an alcohol, a carboxylic acid, or an ester). In some embodiments, the first mixture is essentially free of oxalic acid (i.e., the reducing agent is not oxalic acid). In some embodiments, the reducing agent is MoO2.

[0066] In some embodiments, a ratio of reducing agent used in the first mixture to metal oxides used in the first mixture is between 0.05 g of reducing agent per gram of metal oxides and 1 g of reducing agent per gram of metal oxides. The skilled person will be familiar with choosing an appropriate amount of reducing agent.

[0067] The method includes heating the first mixture in the presence of steam to form the catalyst. In some embodiments, the steam is saturated steam. As used herein, the term “saturated steam” refers to steam when the liquid and gaseous phases of water are in equilibrium at a given temperature and pressure; that is, steam that exists at the same temperature and pressure as the water from which it is formed.

[0068] Any suitable reaction vessel may be used to heat the first mixture. In some embodiments, the first mixture is heated in a hydrothermal synthesis vessel. As used herein, the term “hydrothermal synthesis vessel” refers to a reaction vessel suitable for carrying out a reaction at elevated temperature and pressure, including but not limited to an autoclave, a digestion tank, a pressure vessel, a hydrothermal synthesis reactor, or a polytetrafluoroethylene (PTFE) high-pressure tank. In some embodiments, the hydrothermal synthesis vessel is an autoclave. The reaction vessel may include water to maintain a humid atmosphere (i.e., provide steam) in the reaction vessel.

[0069] In some embodiments, the first mixture is heated to a temperature of between about 100°C to about 250°C. In some embodiments, the first mixture is heated to a temperature of between about 150°C to about 200°C. In some embodiments, the first mixture is heated for about 12 hours to about 100 hours, or about 48 hours to about 72 hours. In some embodiments, the first mixture is heated for at least about 48 hours. In some embodiments, the first mixture is heated for at least about 72 hours. In some embodiments, the first mixture is heated for at least about 96 hours.

[0070] In some embodiments, the method further includes adding an inert carrier material to the first mixture. In some embodiments, the inert carrier material includes precipitated synthetic silica, fumed synthetic silica, silica-alumina, alumina (e.g., a-alumina, y-alumina), titania, silicon carbide, MgAl spinel, an aluminate compound, an aluminosilicate compound, a zeolite, zirconia, doped zirconia, boron nitride, cerium oxide, doped cerium oxide, a perovskite, steel, or any combination thereof. In some embodiments, the inert carrier material includes a-alumina, silica, clay, or any combination thereof. In some embodiments, the inert carrier material includes a-alumina. In some embodiments, the inert carrier material is added to the first mixture in an amount of 1 wt.% to 90 wt.% with respect to the weight of the metal oxides in the first mixture. In some embodiments, the inert carrier material is added in an amount of 10 wt.% to 70 wt.% with respect to the weight of the metal oxides in the first mixture. In some embodiments, the inert carrier material is added in an amount of 25 wt.% to 60 wt.% with respect to the weight of the metal oxides in the first mixture. In some embodiments, the first mixture includes about 1 wt.% to about 80 wt.%, about 10 wt.% to about 70 wt.%, or about 20 wt.% to about 60 wt.% of the inert carrier material.

[0071] The method disclosed herein can further include a process for controlled size modification of at least one of the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound. For example, grinding, dry milling, or crushing. The controlled size modification process may reduce the size of the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound, which can improve reactivity, or may allow for agglomeration, which can allow for the creation of a powder or granule with low dusting properties and improve the powder’s loading into equipment (for example, improved powder flowability or granulating).

[0072] In some embodiments, the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound each have a particle size of less than 1 mm, such as less than 250 pm. For example, the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound each may have a particle size in the range of from 0.5 pm to 250 pm, or from 1 pm to 200 pm, or from 1 pm to 150 pm, or from 1 pm to 100 pm, or from 1 pm to 50 pm, or from 10 pm to 200 pm, or from 10 pm to 150 pm, or from 10 pm to 100 pm, or from 10 pm to 50 pm, or from 50 pm to 200 pm, or from 50 pm to 150 pm, or from 50 pm to 100 pm.

[0073] In some embodiments, the method further includes grinding, dry milling, or crushing the metal oxides and the reducing agent of the first mixture. In some embodiments, the method further includes grinding, dry milling, or crushing the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound of the first mixture. In some embodiments, the method further includes grinding, dry milling, or crushing the metal oxides, the reducing agent, the one or more of the bismuth compound, the antimony compound, and the tellurium compound, and the inert carrier material of the first mixture. In some embodiments, the method further includes washing the catalyst with water. For example, in some embodiments, the catalyst is washed with water until the filtrate is colorless. In some embodiments, the filtrate is colorless on the first wash. In some embodiments, the method does not include washing the catalyst with water.

[0074] In some embodiments, the method can further include calcining the catalyst to form a calcined catalyst. The skilled person will be familiar with suitable methods for calcining the catalyst. In some embodiments, the catalyst is calcined by placing the catalyst in a furnace under an oxygen-free environment; ramping a temperature of the furnace from ambient to a temperature between 500°C and 620°C over a ramping time between 2 hours and 10 hours; and holding the temperature of the furnace at a holding temperature between 500°C and 620°C for a holding time between 1 hour and 10 hours. For example, the catalyst is calcined by placing the catalyst in a furnace; ramping a temperature of the furnace from ambient to a temperature of 600°C over a ramping time of 6 hours; and holding the temperature of the furnace at a holding temperature of 600°C for a holding time of 2 hours.

[0075] As used herein, an “oxygen-free environment” refers to an environment having a molecular oxygen content below 10 ppm. For example, the furnace may be under an inert atmosphere, such as a purified nitrogen atmosphere or a purified argon atmosphere, or the furnace may be under a CO2 and / or steam atmosphere.

[0076] In some embodiments, the catalyst prepared from the methods disclosed herein has the formula MoaVb(Mi)cOx. In each of these formulations, Mi is one or more of Bi, Sb, and Te.

[0077] In each of these formulations, a is 1.0, and x refers to at least the number of oxygen atoms necessary to render the catalyst electrically neutral. In some embodiments, x is the number of oxygen atoms necessary to render the catalyst electrically neutral. In some embodiments, x is greater than the number of oxygen atoms necessary to render the catalyst electrically neutral, for example, wherein the catalyst includes adsorbed or trapped oxygencontaining species.

[0078] The values of a, b, and c may refer to the values based on the molar amount of each starting material used to form the catalyst. The values of a, b, and c may refer to the values measured by elemental analysis, for example by inductively coupled plasma mass spectroscopy (ICP-MS), neutron activation analysis (NAA), X-ray fluorescence (XRF), ion chromatography mass spectrometry (IC-MS), proton induced X-ray emission (PIXE), or energy-dispersive X-ray spectroscopy (EDX). In some embodiments, the values of a, b, and c are the values measured by EDX. In some embodiments, b is about 0.01 to about 0.5. In some embodiments, b is about 0.2 to about 0.4. In some embodiments, b is about 0.25 to about 0.35. In some embodiments, b is about 0.3.

[0079] In some embodiments, c is about 0.005 to about 0.2. In some embodiments, c is about 0.01 to about 0.1. In some embodiments, c is about 0.01 to about 0.07. In some embodiments, c is about 0.04 to about 0.07. In some embodiments, c is about 0.05. In some embodiments, c is about 0.06.

[0080] In some embodiments, Mi includes two of bismuth, antimony, and tellurium and the catalyst is represented by formula MoaVb(MiA)ci(MiB) c2Ox. In each of these formulations, MIA and MIB are each independently bismuth, antimony, or tellurium, wherein MIA and MIB are different. In some embodiments, the sum of cl and c2 is about 0.01 to about 0.2. In some embodiments, the sum of cl and c2 is about 0.005 to about 0.2. In some embodiments, the sum of cl and c2 is about 0.01 to about 0.1. In some embodiments, the sum of cl and c2 is about 0.01 to about 0.07. In some embodiments, the sum of cl and c2 is about 0.04 to about 0.07. In some embodiments, the sum of cl and c2 is about 0.05.

[0081] In some embodiments, the catalyst further includes tantalum, niobium, or both. In these embodiments, the catalyst has formula MoaVb(Mi)c(M2)dOx wherein M2 is tantalum, niobium, or both. In some embodiments, d is about 0.005 to about 0.1. In some embodiments, the catalyst does not include tantalum or niobium and d is 0. In some embodiments, the catalyst has a formula selected from MoaVbBicTaaOx, and MoaVbBicNbdOx.

[0082] The formula with respect to the ratios of values a, b, c, and d can be selected to affect the activity, selectivity, purity, and stability of the catalyst. In some embodiments, the values of a, b, c, and d are determined based on the amount of each starting material used to form the catalyst. For example, the values of a, b, c, and d are determined based on the amount (molar equivalents) of each Mo, V, Mi, and M2 (when present) compound used in a hydrothermal synthesis reaction to prepare the catalyst. In some embodiments, the values of a, b, c, and d are determined or are further determined by elemental analysis, for example, EDX, ICP-MS, or both. In some embodiments, the values of a, b, c, and d are determined by EDX to match the values of a, b, c, and d determined based on the amount of each starting material within about 0.05, about 0.04, about 0.02, or about 0.01.

[0083] In some embodiments, the catalyst includes the formula MoaVbBicOx, wherein: a is 1.0; b is about 0.01 to about 0.5; c is about 0.005 to about 0.2; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; and wherein a, b, and c are based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

[0084] In some embodiments, the catalyst includes the formula Mo1V0.20-0.40Bi0.01-0.07Ox. In some embodiments, the catalyst includes the formula Mo1V0.30-0.35Bi0.04-0.05Ox.

[0085] In some embodiments, the catalyst comprises the formula:

[0086] MOaVbBlc(M2)dOx wherein:

[0087] M2 is Ta or Nb, or a mixture thereof; a is 1.0; b is 0.01 to 0.5; c is 0.005 to 0.2; d is 0.005 to 0.1; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, and d are determined based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

[0088] In some embodiments, the catalyst includes the formula Mo1V0.20-0.40Bi0.01-0.07Ta0.03- o.osOx or Mo1V0.20-0.40Bi0.01-0.07Nb0.03-0.05Ox.

[0089] In some embodiments, the catalyst is uncalcined. In some embodiments, the catalyst is prepared by a method that does not include thermal treatment at 500°C or greater.

[0090] In some embodiments, the catalyst does not include detectable amounts of niobium (Nb) and tantalum (Ta) when measured using energy-dispersive X-ray spectroscopy (EDX). In some embodiments, the catalyst includes less than about 0.2 wt.%, less than about 0.15 wt.%, less than about 0.1 wt.%, or less than about 0.01 wt.% of Nb and Ta.

[0091] The catalysts prepared by a method disclosed herein are for use in oxidative dehydrogenation of ethane.

[0092] Other than in the operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be understood as modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties, which the present disclosure desires to obtain. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0093] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0094] In addition, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” or “from 1 to 10” is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10; that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. Because the disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless expressly indicated otherwise, the various numerical ranges specified in this application are approximations.

[0095] EXAMPLES

[0096] Equipment and Chemicals

[0097] The molybdenum(VI) oxide (MoCh), molybdenum(IV) oxide (MoCh), vanadium oxide (V2O5), bismuth hydroxide (Bi(OH)3) and oxalic acid dihydrate were purchased from Sigma- Aldrich. The tantalum pentoxide hydrate (Ta2O5 xFLO) was purchased from BassTech International. All water used was distilled deionized water.

[0098] All catalyst were synthesized in a 300 mb Parr autoclave equipped with a borosilicate glass liner. Power X-ray diffraction (PXRD) experiments were performed using a PANalytical Empyrean powder X-ray diffractometer equipped with a monochromatized Cu Ka X-ray source. Data was acquired between 3 - 80° 20 at a scan rate of l° / min. Data was analyzed using PANalytical HighScore software Version 4.8.

[0099] Example 1. Oxalic Acid-Free Preparation of MoVBiTaOx Catalyst Samples from Dry Gel (El-DG) and Powder (El-P)

[0100] The sample was prepared with solid reagents listed in Table 1. The solid reagents were added to a blender and blended and pulverized for 1 minute (15 s x 4) to obtain a powder El-P. TABLE 1

[0101] Into a 40 mL glass vial was placed 7.51 g of the El-P powder with 1.24 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel El-DG.

[0102] The vial of El-DG and a vial containing 6.0281 g of El-P were both placed uncovered in a steel autoclave, and about 7 mL water was fdled around the vial to help with heat transfer and provide the source of steam. The autoclave was then sealed and placed in a pre-heated oven at 180° and held for 72 hours, then turned off to cool back to ambient temperature. The resulting samples were a purple-grey hard solids, and were scraped from the vials, weighed, and dried in an oven at 90°C overnight.

[0103] Example 2, Preparation of MoVBiTaOx Catalyst Samples from Dry Gels (E2-DG1, E2- DG2) and Powders (E2-P, E2-DP)

[0104] The samples were prepared with solid reagents listed in Table 2. The solid reagents were added to a blender and blended and pulverized for 1 minute (15 s x 4) to obtain a powder E2-P.

[0105] TABLE 2

[0106] Into a 40 mL glass vial was placed 8.0217 g of the E2-P powder with 2.6455 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel E2-DG1. Into a 40 mL glass vial was placed 8.0769 g of the E2-P powder with 1.2865 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel E2-DG2.

[0107] Into a 40 mL glass vial was placed 8.0860 g of the E2-P powder with no water. The vial was put in an oven at 100°C for 3 h to remove any residual water to obtain a dry powder E2 -DP.

[0108] The vials of E2-DG1, E2-DG2, E2-DP, and a vial containing 6.0109 g of E2-P were placed uncovered in a steel autoclave, and about 4.5 mL water was filled around the vial to help with heat transfer and provide the source of steam. The autoclave was then sealed and placed in a pre-heated oven at 180° and held for 96 hours, then turned off to cool back to ambient temperature. The resulting catalyst samples were purple-grey hard solids and were scraped from the vials, weighed, and dried in an oven at 90°C overnight.

[0109] Example 3, Preparation of MoVBiTaOx Catalyst Samples from Dry Gels (E3-DG1, E3- DG2) and Powder (E3-DP)

[0110] The samples were prepared with solid reagents listed in Table 3. The solid reagents were added to a blender and blended and pulverized for 1 minute (15 s x 4) to obtain a homogenous powder E3-P.

[0111] TABLE 3

[0112] Into a 40 mL glass vial was placed 13.44 g of the E3-P powder with 4.3755 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel E3-DG1.

[0113] Into a 40 mL glass vial was placed 13.74 g of the E3-P powder with 2.275 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel E3-DG2. Into a 40 mL glass vial was placed 13.38 g of the E3-P powder with no water. The vial was put in an oven at 100°C for 3 h to remove any residual water to obtain a dry powder E3 -DP.

[0114] The vials of E3-DG1, E3-DG2, and E3-DP were placed uncovered in a steel autoclave, and about 6.55 mL water was fdled around the vial to help with heat transfer and provide the source of steam. The autoclave was then sealed and placed in a pre-heated oven at 180° and held for 48 hours, then turned off to cool back to ambient temperature. The resulting catalyst samples were a deep purple-grey color. The catalyst samples prepared from E3-DG1 and E3-DG2 were hard solids, and the catalyst sample prepared from E3-DP was a wet solid (a very viscous slurry). All samples were dried in an oven at 90°C overnight.

[0115] Example 4, Preparation of MoVBiTaOx and MoVBiOx Catalyst Samples from Powders (E4-P1, E4-P2, E4-P3)

[0116] The samples were prepared with solid reagents listed in Table 4. The solid reagents were added to a blender and blended and pulverized for 1 minute (15 s x 4) to obtain a powder.

[0117] TABLE 4

[0118] Into 40 mL glass vials were placed 13.2357 g of sample E4-P1, 11.6064 g of sample E4-P2, and 13.5954 g of the sample E4-P3. These were placed in a steel autoclave with about 62 g of water to help with heat transfer and provide the source of steam. The autoclave was then sealed and placed in a pre-heated oven at 180° and held for 48 hours, then turned off to cool back to ambient temperature. The catalyst sample prepared from E4- PI was a hard solid and the catalyst samples prepared from E4-P2 and E4-P3 were viscous slurries. The catalyst samples prepared from E4-P1, E4-P2, and E4-P3 were dried in an oven at 90°C overnight. Example 5, Oxalic Acid-Free Preparation of MoVBiOx Catalyst Samples from Dry Gel (E5- DG) and Powder (E5-DP),

[0119] The samples were prepared with solid reagents listed in Table 5. The solid reagents were added to a blender and blended and pulverized for 1 minute (15 s x 4) to obtain a powder E5-P.

[0120] TABLE 5

[0121] Into a 40 mL glass vial was placed 4.1098 g of the E5-P powder with 4.92 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel E5-DG.

[0122] Into a 40 mL glass vial was placed 4.2058 g of the E5-P powder with no water. The vial was put in an oven at 100°C for 3 h to remove any residual water to obtain a dry powder E5 -DP.

[0123] The vials of E5-DG and E5-DP were placed uncovered in a steel autoclave, and approximately 20 mL water was fdled around the vial to help with heat transfer and provide the source of steam. The autoclave was then sealed and placed in a pre-heated oven at 180° and held for 48 hours, then turned off to cool back to ambient temperature. The resulting solids were a fully purple -grey hard solid and was scraped from the bottle, weighed, and dried in an oven at 90°C overnight. The catalyst sample prepared from E5-DG was a deep purple -grey hard solid and the catalyst sample prepared from E5-DP was a light purple solid.

[0124] Example 6, Oxalic Acid-Free Preparation of MoVBiOx Catalyst Samples from Dry Gel (E6- DG) and Powder (E6-P)

[0125] The sample was prepared with solid reagents listed in Table 6. The solid reagents were added to a blender and blended and pulverized for 1 minute (15 s x 4) to obtain a powder E6-P. TABLE 6

[0126] Into a 40 mL glass vial was placed 6.94 g of the E6-P powder with 2.23 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel E6-DG.

[0127] The vial of E6-DG and a vial containing 5.9207 g of E6-P were placed uncovered in a steel autoclave, and about 7 mL water was fdled around the vial to help with heat transfer and provide the source of steam. The autoclave was then sealed and placed in a pre-heated oven at 180° and held for 48 hours, then turned off to cool back to ambient temperature. The catalyst materials prepared from E6-DG and E6-P were fully purple-grey hard solids and were scraped from the bottle, weighed, and dried in an oven at 90°C overnight. Example 7, Oxalic Acid-Free Preparation of MoVBiOx Catalyst Material Samples from Dry Gels (E7-DG, E7-DP) and Powder (E7-P) including Inert Carrier Material (a-AbQ?)

[0128] The samples were prepared with solid reagents listed in Table 7. The solid reagents, except a-AhOs, were added to a blender and blended and pulverized for 1 minute (15 s x 4) to obtain a powder. Then a-AbO? was added and blended for an additional minute to obtain powder E7-P.

[0129] TABLE 7

[0130] Into a 40 mL glass vial was placed 6.04 g of the E7-P powder with 3.5 g of distilled water to form a slurry. The vial was put in an oven at 100°C for 3 h to evaporate the water to obtain a dry gel E7-DG. Into a 40 mL glass vial was placed 6.34 g of the powder with no water. The vial was put in an oven at 100°C for 3 h to remove any residual water to obtain a dry powder E7-DP.

[0131] Vials containing E7-DG, E7-DP, and 6.2080 g E7-P were placed were placed uncovered in a steel autoclave, and about 30 g of water was fdled around the vial to help with heat transfer and provide the source of steam. The autoclave was then sealed and placed in a pre-heated oven at 180° and held for 48 hours, then turned off to cool back to ambient temperature. The samples prepared from E7-DG, E7-DP, and E7-P were easily recovered from the vials (no hard solid). All samples were dried in an oven at 90°C overnight.

[0132] Comparative Example 1. Preparation of Comparative Catalyst Sample Cl

[0133] Comparative Catalyst Sample Cl was prepared with the solid reagents listed in Table 8, below. The solid reagents were added to a blender and mixed for 1 minute to blend and pulverize. The solid mixture was then transferred a 40 mL glass bottle, after which distilled water solvent was used to rinse the grinder and transfer the residual solids to the bottle. The sample was stirred with a PTFE stir bar, yielding an orange slurry. The vial was then placed in a glass-lined steel autoclave, and water was filled around the vial to the level of the slurry to aid heat transfer and to maintain a humid atmosphere in the vessel (~20 mL of water). The autoclave was then sealed and placed in an oven to heat from room temperature to 180°C over 12 hours, held at 180°C for 48 hours, then turned off to cool back to ambient temperature over 3 - 4 hours.

[0134] After reaction, the sample was a purple-grey hard solid. The sample was scraped from the bottle onto filter paper in a vacuum filtration setup and was washed with distilled water (-300 mL) in portions, to yield a deep blue filtrate. The sample was washed until the filtrate from the sample was nearly colorless, then was dried in an oven at 90°C overnight to yield 26.8753 g of Catalyst Sample A, a purple-grey powdered solid.

[0135] TABLE 8 Powder X-rav Diffraction (PXRD)

[0136] Power X-ray diffraction (PXRD) experiments were performed using a PANalytical Empyrean powder x-ray diffractometer equipped with a monochromated Cu Ka x-ray source. Data was acquired between 3 - 80° 20 at a scan rate of l° / min. Data was analyzed using PANalytical HighScore software Version 4.8.

[0137] Figures 1 and 2 show PXRD patterns of catalyst samples prepared in Example 1, El- DG (Figure 1) and El-P (Figure 2).

[0138] Figures 2-6 show PXRD patterns of catalyst samples prepared in Example 2, E2- DG1 (Figure 3), E2-DG2 (Figure 4), E2-DP (Figure 5), and E2-P (Figure 6).

[0139] Figures 7-9 show PXRD patterns of catalyst samples prepared in Example 3, E3- DG1 (Figure 7), E3-DG2 (Figure 8), and E2-DP (Figure 9).

[0140] Figures 10-12 show PXRD patterns of catalyst samples prepared in Example 4, E4- P1 (Figure 10), E4-P2 (Figure 11), and E4-P3 (Figure 12).

[0141] Figures 13 and 14 show PXRD patterns of catalyst samples prepared in Example 5, E5-DG (Figure 13) and E5-DP (Figure 14).

[0142] Figures 15 and 16 show PXRD patterns of catalyst samples prepared in Example 6, E6-DG (Figure 15) and E6-P (Figure 16).

[0143] Figures 17-19 show PXRD patterns of catalyst samples prepared in Example 7, E7- DG (Figure 17), E7-DP (Figure 18), and E7-P (Figure 19).

[0144] The amount of Ml phase in the catalyst sample can be determined from the PXRD pattern. A summary of the Ml phase characterization from the PXRD patterns is shown in Table 9. Ml / MoOs ratios are based on relative peak intensity at 22° and 13° 20, respectively.

[0145] TABLE 9

[0146] *50% less water was used in DG2 preparation compared to DG1. See Examples 2 and 3.

[0147] In general, lower Ml phase yields were observed with oxalic acid as the reducing agent, less water in gel led to a decrease in Ml phase with oxalic acid as reducing agent, and higher yields of the Ml phase were observed for Ta-free catalysts using MoO2 as reducing agent. Catalyst Testing

[0148] The catalysts described herein were tested for their ability to catalyze the oxidative dehydrogenation (ODH) of ethane using a microreactor unit (MRU). The MRU has a reactor tube made from stainless-steel SWAGEUOK® Tubing, which had an outer diameter of 0.5 inches (1.27 cm), an internal diameter of about 0.4 inches (1.02 cm), and a length of about 13.4-15 inches (34.0 - 38.1 cm). Experimental temperatures of the MRU are measured using a 6-point WIKA Instruments Ltd. K-type thermocouple, which had an outer diameter of 0. 125 inches (0.318 cm) and was inserted through the reactor. The 6-point thermocouple is used to measure and control the temperature within the catalyst bed. A room temperature stainless steel condenser is located after the reactor to collect water / acetic acid condensates. The gas product flow was allowed to either vent or was directed to an Agilent 8890 “hot gas” Gas Chromatograph (HGGC) during times when product gas analysis was required.

[0149] The samples were pressed into pellets using a steel die and hydraulic press, then the pellet was pulverized and particle sizes of 425 - 710 pm were sieved out for loading into the MRU. Approximately 2 g of sample was placed in the reactor. Once the catalyst bed was loaded into the reactor and connected to the MRU equipment, the testing was conducted as described herein.

[0150] The catalyst bed was loaded in the middle zone of the reactor and the remaining volume of the reactor was packed with quartz sand to produce the catalyst bed volume of 6 mL to ensure the catalyst volume was sufficient to cover the thermocouple area between points 2 and 5. The reactor loading was then secured with glass wool on both the top and the bottom of the reactor. Quartz sand was added to produce the catalyst bed volume of 6 mL to ensure the catalyst volume was sufficient to cover the thermocouple area.

[0151] The flow rate of the gas feed was adjusted to a target of 150 seem (weight hour space velocity (WHSV) = 3.57 h'1). The expression “weight hourly space velocity” here refers to the weight flow of the total feed gas divided by the weight of the catalyst. The target gas feed composition was 20 mol% ethane, 10 mol% oxygen and 70 mol% nitrogen for all testing. Gas composition was determined by gas chromatography (GC) using an Agilent 6890N Gas Chromatograph, and analyzed using Chrom Perfect - Analysis, Version 6.1.10 for data evaluation. Samples were left on stream at temperature between 380 and 420°C until data appeared to equilibrate, which was approximately 5 days.

[0152] The mol. % ethane conversion temperature was determined at the WHSV of 3.57 h" \ and a gas hourly space velocity (GHSV) in the range of 2000 to 5000 h'1. GHSV (gas hourly space velocity) is defined as volumetric flow of the reactor feed gas divided by the volume of the catalyst bed. As used herein, the term “volume of the catalyst bed” refers to the volume occupied by catalyst particles, optional diluent particles, and any void spaces within the catalyst bed. For GHSV values of catalyst materials, the catalyst bed is treated as catalyst only (not including support) where an assumption is made that the total volume of the catalyst material measured when multiplied by the wt.% of catalyst is the volume of the catalyst. The GHSV can be calculated based off the measured volume of the pressed particles (before mixing with quartz sand) and varies depending on each catalyst or catalyst material bulk density. For catalyst materials discussed herein, the GHSV reported is for the catalyst only, where an assumption was made that the total volume of the catalyst material measured when multiplied by the wt.% of catalyst is the volume of the catalyst.

[0153] The gaseous product exiting the catalyst bed was directed to vent during runs. When the gaseous product was to be analyzed, it was momentarily redirected to a gas chromatography unit to determine the percent of ethane, ethylene, O2, CO2, CO, and, optionally, acetic acid. The gas exiting the reactor was analyzed by gas chromatography. Conversion (C) of the ethane feed gas was calculated as a volume flow rate change of ethane in the product compared to feed ethane mass flow rate using the following formula: In Eq. 1, C is the molar percent of ethane feed gas that has been converted from ethane to another product (that is, ethane conversion) and X is the molar concentration of the corresponding compound in the gaseous effluent exiting the reactor at corresponding temperature. Acetic acid molar concentration was assumed to be 0 mol. %, since it could not be measured at the time.

[0154] The gas exiting the reactor was analyzed by GC to determine catalyst or catalyst material selectivity to ethylene (i.e., the percentage on a molar basis of ethane that forms ethylene). Selectivity to ethylene (SEthyiene) was determined using the following equation:

[0155] In the above equation 2, SEthyiene is the selectivity to ethylene and X is the molar concentration of the corresponding compound in the gaseous effluent exiting the reactor at corresponding temperature. Acetic acid molar concentration was assumed to be 0 mol. %, since it could not be measured at the time.

[0156] Summary of Catalyst Performance

[0157] Prior to catalyst testing, catalyst samples were pretreated at 450°C under N2 flow at 153 seem and 23 psig on MRU1 for 6 hours. Results on catalyst performance were collected on MRU 1 under conditions of 20 / 10 / 70 ethane / oxygen / nitrogen at 23 psig and 153 seem flow rate. See Table 10.

[0158] Positive control catalyst sample Cl is an MoVBiOx catalyst synthesized using a slurry with oxalic acid as a reducing agent and was washed with water after synthesis. This sample was treated under the same nitrogen flow conditions at 450°C for 2 hours prior to testing.

[0159] Data from positive control, samples prepared from E5-DG, and E7-DG is after 250 hours on stream. Data from the sample prepared from E6-DG is after 24 hours on stream.

[0160] TABLE 10 This data shows that the catalyst samples prepared from E5-DG, E6-DG, and E7-DG have nearly equivalent performance to the positive control catalyst C 1 without the need for oxalic acid or a washing procedure in the synthesis. Further, the data shows that catalyst prepared using dry gel conversion methods have nearly equivalent performance to catalysts prepared from slurries.

[0161] Impact of H2O and / or CO2 Diluent on Catalyst Activity

[0162] A fixed bed reactor unit (FBRU) was used to investigate the impact of various diluent in the feed (H2O and CO2) on the performance of a catalyst having the formula MoV0.33Ta0.03Bi0.05Ox.

[0163] The FBRU was setup with a stainless-steel tube (SA213 316SS) reactor having a total length of 63.20” and 1” outer diameter with 0.083” wall thickness. A section of this reactor tube is housed inside another stainless-steel pipe (SA312 316 / 316LSS) with a total length of 60” and an outer diameter of 1.50” to form a shell and tube heat exchanger. The reactor was the tube side while the outer larger pipe (the “jacket”) was the shell side of the heat exchanger setup. The space between the reactor and jacket carried the molten salt heat transfer fluid for heating / cooling the reactor.

[0164] The reactor was loaded with catalyst to a specified height in the mid-section (bed height of 49.50”), with the top and bottom ends loaded with alumina beads to ensure that the catalyst bed was within the heat-exchange section of the reactor. The reactor setup was insulated and a 7-point thermocouple was placed in the center of the reactor side for temperature control and monitoring. The 7-point thermocouple was positioned in the reactor to have points 1 / 7 measure the feed inlet / product outlet temperatures in the inert zones of the catalyst bed, while the other 5 points were positioned within the active zone of the catalyst bed.

[0165] To heat / cool the reactor, a molten salt unit (MSU) with separate electric heaters and a circulating pump was used to circulate molten salt through the heat-exchange section of the reactor setup. The transfer lines for the molten salt were heat-traced and insulated to ensure that the salt remained in its molten state while being circulated.

[0166] Five comparative trials were carried out on the FBRU. All runs were conducted at the same GHSV (2600 h'1), reactor inlet pressure (50 psig), and Ch / ethane reactants feed composition. In these runs, the composition of the feed diluent was fixed at ~ 74 ± 0.3 vol. %. The diluent feed varied between varying amounts of H2O and CO2 (see Table 11; values in mol. %). The catalyst activity for each of the experiment is reported in Table 12 (conversion in mol. %; product selectivity in C-atom mol. %). In all the runs, the ethane conversion was kept constant at 50 ± 3 %. Gas and liquid product streams were analyzed by gas chromatography.

[0167] TABLE 11 TABLE 12

[0168] In this example, feed reactant conversion was calculated as follows: where compound (i) refers to either ethane or oxygen; and X is the molar flow rate of the compound, either in the feed or product, as indicated by the prefix.

[0169] In this example, product selectivity was calculated as follows: where compound (i) refers to ethylene, acetic acid, carbon monoxide, or carbon dioxide; X is the molar flow rate of the compound, either in the feed or product; N<com ound i) is the ratio of the number of carbon atoms in compound (i) to the number of carbon atoms in ethane; and the result is expressed in carbon atom percentage (C-atom %).

[0170] The yield of a given compound was calculated by multiplying the ethane conversion by the selectivity of the given compound The highest ethylene yield was observed when lowest H2O feed composition and highest CO2 feed composition was used, whereas the highest acetic acid yield was observed at highest H2O feed composition and lowest CO2 feed composition. The CO selectivity remained unchanged independent from composition of H2O and CO2 in the feed. Surprisingly, it was observed that at the highest H2O feed composition and lowest CO2 feed composition, the selectivity to CO2 became negative. This implies that part of the CO2 has been consumed in the reactor.

[0171] Non-limiting embodiments of the present disclosure include the following: Embodiment A. A method for preparing a catalyst comprising: providing a first mixture comprising: metal oxides comprising an oxide of molybdenum and an oxide of vanadium; a reducing agent; and one or more of a bismuth compound, an antimony compound, and a tellurium compound; wherein the bismuth compound comprises bismuth oxide, bismuth hydroxide, or a bismuth carbonate; the antimony compound comprises an oxide of antimony, antimony acetate, or antimony ethoxide; and the tellurium compound comprises tellurium dioxide; wherein the first mixture is essentially free of water; and heating the first mixture in the presence of steam to form the catalyst.

[0172] Embodiment B. The method according to Embodiment A, wherein the first mixture is a powder obtained by combining the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound.

[0173] Embodiment C. The method according to Embodiment A, wherein the first mixture is a dry powder obtained by: combining the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound to provide a mixture of combined powders; and heating the mixture of combined powders.

[0174] Embodiment D. The method according to Embodiment A, wherein the first mixture is a dry gel obtained by: forming a slurry comprising: the metal oxides, the reducing agent, the one or more of the bismuth compound, the antimony compound, and the tellurium compound, and water; and heating the slurry to remove the water.

[0175] Embodiment E. The method according to Embodiment A, B, C, or D, wherein the steam is saturated steam.

[0176] Embodiment F. The method according to Embodiment A, B, C, D, or E, wherein the metal oxides further comprise an oxide of tantalum or an oxide of niobium, or both.

[0177] Embodiment G. The method according to Embodiment A, B, C, D, E, or F, wherein the reducing agent is an inorganic reducing agent.

[0178] Embodiment H. The method according to Embodiment G, wherein the inorganic reducing agent comprises one or both of molybdenum dioxide and vanadium dioxide.

[0179] Embodiment L The method according to Embodiment A, B, C, D, E, or F, wherein the reducing agent is oxalic acid.

[0180] Embodiment J. The method according to Embodiment A, B, C, D, E, F, G, H, or I, wherein the oxide of molybdenum is MoOs .

[0181] Embodiment K. The method according to Embodiment A, B, C, D, E, F, G, H, I, or J, wherein the oxide of vanadium is V2O5.

[0182] Embodiment L. The method according to Embodiment A, B, C, D, E, F, G, H, I, or

[0183] J, wherein the oxide of vanadium is VO2.

[0184] Embodiment M. The method according to Embodiment A, B, C, D, E, F, G, H, I, J,

[0185] K, or L, wherein the first mixture comprises the bismuth compound, and the bismuth compound comprises bismuth hydroxide.

[0186] Embodiment N. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, or M, further comprising adding an inert carrier material to the first mixture.

[0187] Embodiment O. The method according to Embodiment N, wherein the inert carrier material is added in an amount of 1 wt.% to 90 wt.% with respect to the weight of the metal oxides in the first mixture.

[0188] Embodiment P. The method according to Embodiment N or O, wherein the inert carrier material comprises a-alumina.

[0189] Embodiment Q. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, or P, further comprising grinding, dry milling, or crushing the metal oxides and the reducing agent of the first mixture. Embodiment R. The method according to Embodiments A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, or P, further comprising grinding, dry milling, or crushing the metal oxides the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound of the first mixture.

[0190] Embodiment S. The method according to Embodiment N or O, further comprising grinding, wet milling, dry milling, or crushing the metal oxides, the reducing agent, the one or more of the bismuth compound, the antimony compound, and the tellurium compound, and the inert carrier material of the first mixture.

[0191] Embodiment T. The method according to Embodiment A, wherein the catalyst comprises the formula MoaVbBicOx, wherein: a is 1.0; b is about 0.01 to about 0.5; c is about 0.005 to about 0.2; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; and wherein a, b, and c are based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

[0192] Embodiment U. The method according to Embodiment F, wherein the catalyst comprises the formula MoaVbBic(M2)dOx, wherein:

[0193] M2 is Ta or Nb, or a mixture thereof; a is 1.0; b is 0.01 to 0.5; c is 0.005 to 0.2; d is 0.005 to 0.1; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, and d are determined based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

[0194] Embodiment V. A catalyst prepared by the method of Embodiment A, B, C, D, E, F, G, H, I, J, K, L, or M.

[0195] Embodiment W. The catalyst of Embodiment V, for use in oxidative dehydrogenation of ethane. Embodiment X. A catalyst material prepared by the method of Embodiment N or O.

[0196] Other implementations are also within the scope of the following claims.

[0197] INDUSTRIAL APPLICABILITY

[0198] Methods of making catalysts for the oxidative dehydrogenation of alkanes, such as the oxidative dehydrogenation of ethane to ethylene.

Claims

CLAIMS1. A method for preparing a catalyst comprising: providing a first mixture comprising: metal oxides comprising an oxide of molybdenum and an oxide of vanadium; a reducing agent; and one or more of a bismuth compound, an antimony compound, and a tellurium compound; wherein the bismuth compound comprises bismuth oxide, bismuth hydroxide, or a bismuth carbonate; the antimony compound comprises an oxide of antimony, antimony acetate, or antimony ethoxide; and the tellurium compound comprises tellurium dioxide; wherein the first mixture is essentially free of water; and heating the first mixture in the presence of steam to form the catalyst.

2. The method according to claim 1, wherein the first mixture is a powder obtained by combining the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound.

3. The method according to claim 1, wherein the first mixture is a dry powder obtained by: combining the metal oxides, the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound to provide a mixture of combined powders; and heating the mixture of combined powders.

4. The method according to claim 1, wherein the first mixture is a dry gel obtained by: forming a slurry comprising: the metal oxides, the reducing agent, the one or more of the bismuth compound, the antimony compound, and the tellurium compound, and water; and heating the slurry to remove the water.

5. The method according to any one of claims 1 to 4, wherein the steam is saturated steam.

6. The method according to any one of claims 1 to 5, wherein the metal oxides further comprise an oxide of tantalum or an oxide of niobium, or both.

7. The method according to any one of claims 1 to 6, wherein the reducing agent is an inorganic reducing agent.

8. The method according to claim 7, wherein the inorganic reducing agent comprises one or both of molybdenum dioxide and vanadium dioxide.

9. The method according to any one of claims 1 to 6, wherein the reducing agent is oxalic acid.

10. The method according to any one of claims 1 to 9, wherein the oxide of molybdenum is MoOs .

11. The method according to any one of claims 1 to 10, wherein the oxide of vanadium is V2O5.

12. The method according to any one of claims 1 to 10, wherein the oxide of vanadium is VO2.

13. The method according to any one of claims 1 to 12, wherein the first mixture comprises the bismuth compound, and the bismuth compound comprises bismuth hydroxide.

14. The method according to any one of claims 1 to 13, further comprising adding an inert carrier material to the first mixture.

15. The method according to claim 14, wherein the inert carrier material is added in an amount of 1 wt.% to 90 wt.% with respect to the weight of the metal oxides in the first mixture.

16. The method according to claim 14 or 15, wherein the inert carrier material comprises a-alumina.

17. The method according to any one of claims 1 to 16, further comprising grinding, dry milling, or crushing the metal oxides and the reducing agent of the first mixture.

18. The method according to any one of claims 1 to 16, further comprising grinding, dry milling, or crushing the metal oxides the reducing agent, and the one or more of the bismuth compound, the antimony compound, and the tellurium compound of the first mixture.

19. The method according to claim 14 or 15, further comprising grinding, wet milling, dry milling, or crushing the metal oxides, the reducing agent, the one or more of the bismuth compound, the antimony compound, and the tellurium compound, and the inert carrier material of the first mixture.

20. The method according to claim 1, wherein the catalyst comprises the formula MOaVbBlcOx, wherein: a is 1.0; b is about 0.01 to about 0.5; c is about 0.005 to about 0.2; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; and wherein a, b, and c are based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

21. The method according to claim 6, wherein the catalyst comprises the formula: MOaVbBlc(M2)dOx, wherein:M2 is Ta or Nb, or a mixture thereof; a is 1.0; b is 0.01 to 0.5; c is 0.005 to 0.2; d is 0.005 to 0.1; and x is at least the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, and d are determined based on one or both of the amount of each starting material used to form the catalyst and elemental analysis.

22. A catalyst prepared by the method according to any one of claims 1 to 13.

23. The catalyst of claim 22, for use in oxidative dehydrogenation of ethane.

24. A catalyst material prepared by the method according to claim 14 or 15.

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