Making catalysts for oxidative dehydrogenation

Abstract

Methods for preparing catalysts for oxidative dehydrogenation (ODH) of alkanes such as ethane are provided. An exemplary method includes forming a slurry including metal oxides; one or more of a bismuth compound, an antimony compound, and a tellurium compound; a reducing agent; and water; and heating the slurry 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, an antimony acetate, or an antimony ethoxide. The tellurium compound includes tellurium dioxide. The reducing agent includes molybdenum dioxide and may further include vanadium dioxide. The methods use all inorganic reagents, with no build up COx pressure observed during the hydrothermal synthesis.

Description

[0001] MAKING CATALYSTS FOR OXIDATIVE DEHYDROGENATION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to preparing catalysts 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. The method of choice for today's 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 temperature 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, 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] The synthesis of active ODH catalysts typically requires the use of chelating carboxylic acids, such as oxalic acid, in a dilute aqueous solvent and heated in a sealed autoclave. These conditions, along with the presence of oxidants in the form of high valent metals (e.g., molybdenum(VI)), may cause decomposition of the carboxylic acid to form COx, which may create excessive pressure in the sealed vessel and possible formation of carbon monoxide. There is a need for improved methods of preparing catalysts having high selectivity, activity, and longevity for ODH reactions. SUMMARY OF INVENTION

[0008] Provided herein is a method for preparing a catalyst. The method includes forming a slurry comprising: metal oxides; one or more of a bismuth compound, an antimony compound, and a tellurium compound; a reducing agent; and water; and heating the slurry 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, an antimony acetate, or an antimony ethoxide. The tellurium compound includes tellurium dioxide.

[0009] In some embodiments, the metal oxides further comprise an oxide of tantalum, or an oxide of niobium, or both.

[0010] In some embodiments, the reducing agent further includes vanadium dioxide.

[0011] In some embodiments, a ratio of the water in the slurry to amount of catalyst formed is between 0. 1 m water per gram of catalyst and 10 m water per gram of catalyst. In some embodiments, the ratio of the water in the slurry to amount of catalyst formed is between 0.2 mb water per gram of catalyst and 1 mb water per gram of catalyst.

[0012] In some embodiments, the slurry has a ratio of water to metal oxides between 0.3 mb water per gram of metal oxides and 0.8 mb water per gram of metal oxides.

[0013] In some embodiments, the oxide of molybdenum is MoOs.

[0014] In some embodiments, the oxide of vanadium is V2O5.

[0015] In some embodiments the oxide of vanadium is VO2.

[0016] In some embodiments, the bismuth compound comprises bismuth hydroxide.

[0017] In some embodiments, the antimony compound is an oxide of antimony.

[0018] In some embodiments, the oxide of tantalum, when present, is Ta2C>5 xbhO, and the oxide of niobium, when present, is Nb2C>5 xbhO.

[0019] In some embodiments, the reducing agent is MoO2.

[0020] In some embodiments, the method further includes grinding, wet milling, dry milling, or crushing the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound. In some embodiments, the method further includes grinding, wet milling, dry milling, or crushing the reducing agent.

[0021] In some embodiments, the method includes heating the slurry by ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours. In some embodiments, the method includes heating the slurry by ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 120 hours.

[0022] In some embodiments, the method further includes washing the catalyst with water.

[0023] In some embodiments, the method further includes calcining the catalyst to form a calcined catalyst. In some embodiments, the method includes calcining the catalyst 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.

[0024] 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 in the range of from 0.5 pm to 250 pm.

[0025] In some embodiments, a ratio of a total amount of water used to prepare the catalyst is between 0.2 mL water per gram of catalyst and 25 mL water per gram of catalyst.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a powder X-ray diffraction (PXRD) pattern of Comparative Catalyst A.

[0028] Figure 2 is a PXRD pattern of Comparative Catalyst B.

[0029] Figure 3 is a PXRD pattern of Catalyst Example A.

[0030] Figure 4 is a PXRD pattern of Catalyst Example B.

[0031] Figure 5 is a PXRD pattern of Catalyst Example C.

[0032] Figure 6 is a PXRD pattern of Catalyst Example D.

[0033] Figure 7 is a PXRD pattern of Catalyst Example E.

[0034] Figure 8 is a PXRD pattern of Catalyst Example F.

[0035] Figure 9 is a PXRD pattern of Catalyst Example G.

[0036] DESCRIPTION OF EMBODIMENTS

[0037] Reference will now be made in detail to certain embodiments of the disclosed subject matter, examples of which are illustrated in part in the accompanying figures. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended be limiting.

[0038] 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. Provided in this disclosure is a synthesis method for a catalyst, for example, for use in the ODH process. The synthesis method disclosed herein advantageously uses all inorganic reagents and has been found to provide an Ml phase ODH catalyst by complete substitution of the commonly used reducing agent oxalic acid with molybdenum (IV) oxide, or a combination of molybdenum (IV) oxide and vanadium (IV) oxide. The catalyst precursor powders are mixed, for example by being ground together, and then used in a hydrothermal synthesis process to form the catalyst. By eliminating oxalic acid from the hydrothermal synthesis and using all inorganic reagents, COx is no longer formed at high temperature in the reaction vessel, which can prevent excessive pressure build-up and carbon monoxide formation. Further, a colorless filtrate has been observed when washing the catalyst after synthesis, which contrasts with the deep blue / green color when oxalic acid is used and indicates that a washing step may not be required. Moreover, molybdenum(IV) oxide can partially replace molybdenum(VI) oxide in the synthesis, and the vanadium(IV) oxide can partially to fully replace vanadium(V) oxide in the synthesis.

[0039] 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.

[0040] As used herein, the term “catalyst material” refers to a material that includes a catalyst that can promote oxidative dehydrogenation of ethane to ethylene. The catalyst material may include a carrier and / or support. The catalyst material may be substantially comprised of the catalyst. 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. Non-limiting examples of pressed and cast catalyst materials include pellets such as tablets, ovals, and spherical particles. Binder may be used to aid in forming the catalyst material. Catalyst material formation may also include optional workup steps such as: debinding, calcining / sintering, and / or activating / pre- treatment. Workup steps may be introduced to prepare the catalyst material to be loaded into a reactor and produce an expected productivity and mitigate any unexpected thermal runaways during startup.

[0041] The method for preparing a catalyst disclosed herein includes forming a slurry including metal oxides; one or more of a bismuth compound, an antimony compound, and a tellurium compound; a reducing agent; and water; and heating the slurry to form the catalyst. The metal oxides include an oxide of molybdenum and an oxide of vanadium. The reducing agent includes molybdenum (IV) oxide, also referred to as molybdenum dioxide (MOO2). In some embodiments, the reducing agent further includes vanadium (IV) oxide, also referred to as vanadium dioxide (VO2).

[0042] 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), or a colloidal solution. As used herein, the term “reducing agent” refers to a chemical substance that can reduce an oxidation state of one or more of the metals of the metal oxides, or the bismuth compound, or the antimony compound, or the tellurium compound in the slurry. The reducing agents used in the method disclosed herein are inorganic reducing agents. Inorganic reducing agents do not contain carbon atoms.

[0043] In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and further include an oxide of tantalum or 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 molybdenum is MoOs. In some embodiments, the oxide of vanadium is V2O5. In some embodiments, the oxide of vanadium is VO2. In some embodiments, the oxide of tantalum, when present, is Ta2Ch xEEO, and the oxide of niobium, when present, is Nb2O5 XH2O.

[0044] The bismuth compound used in forming the slurry can include bismuth oxide, bismuth hydroxide, or a 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). In some embodiments, the bismuth compound is bismuth hydroxide. The antimony compound can include an oxide of antimony, an antimony acetate, or an antimony ethoxide. In some embodiments, the antimony compound is an oxide of antimony. The tellurium compound includes tellurium dioxide (TeCh).

[0045] The slurry can include one reducing agent, one or more reducing agents, or two or more reducing agents. In some embodiments, the slurry includes two reducing agents, including MoO2. In some embodiments, the slurry includes no more than one reducing agent. Some embodiments of the method disclosed herein can provide the advantage of a simplified procedure having a single reducing agent compared to previously reported methods that utilize more than one reducing agent. In some embodiments, the reducing agent is molybdenum dioxide. In some embodiments, the reducing agent includes molybdenum dioxide and vanadium dioxide. The amount of reducing agent used in the slurry may be chosen based in part on the nature of the reducing agent being used. In some embodiments, a ratio of reducing agent used in the slurry to metal oxides used in the slurry 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 phrase “reducing agent” in the expression “a ratio of reducing agent used in the slurry to the amount of metal oxides used in the slurry” as used herein refers to the total mass of reducing agent used in the slurry, which may be the mass of MoO2, or the combined mass of MoO2 and VO2. The phrase “metal oxides in the slurry” in the expression “a ratio of reducing agent used in the slurry to metal oxides used in the slurry” as used herein refers to the total mass of metal oxides used in the slurry, which includes an oxide of molybdenum; an oxide of vanadium; and, in some embodiments, one or both of an oxide of tantalum or an oxide of niobium, but excludes the metal oxide(s) being used as a reducing agent.

[0046] For example, a slurry comprising 0.9858 g of MoO2 as the reducing agent, 4.0203 g of MoOs, and 1.0051 g V2O5, would have 5.0254 g total metal oxides and a ratio of total reducing agent used in the slurry to total metal oxides used in the slurry of 0.2.

[0047] In some embodiments, the ratio of reducing agent used in the slurry to metal oxides in the slurry is between 0. 1 g of reducing agent per gram of total metal oxides and 0.5 g of reducing agent per gram of metal oxides. In some embodiments, the ratio of reducing agent used in the slurry to metal oxides used in the slurry is between 0. 15 g of reducing agent per gram of metal oxides and 0.25 g of reducing agent per gram of metal oxides.

[0048] In some embodiments, a ratio of water in the slurry to amount of catalyst formed is between 0.1 mb water per gram of catalyst and 10 mb water per gram of catalyst. As used herein, the phrase “water in the slurry” refers to the amount of water used to form the slurry for the hydrothermal synthesis reaction and does not include water that is not consumed or contaminated during the reaction or water that is used after the reaction. For example, “water in the slurry” does not include water present in the hydrothermal synthesis vessel for heat transfer and / or to maintain a humid atmosphere, or water that is used to wash the catalyst.

[0049] As used herein, “water” may refer to deionized water, distilled water, and the like. In some embodiments, the water is distilled water. In some embodiments, the water is distilled, deionized water. In some embodiments, the water may include higher levels of contaminants without harming the catalyst. In some embodiments, the ratio of water in the slurry to amount of catalyst formed is between 0.1 mb water per gram of catalyst and 5 mL water per gram of catalyst formed, such as between 0.1 mL water per gram of catalyst formed and 4 mL water per gram of catalyst formed, between 0. 1 mL water per gram of catalyst formed and 3 mL water per gram of catalyst formed, between 0. 1 mL water per gram of catalyst formed and 2 mL water per gram of catalyst formed, between 0. 1 mL water per gram of catalyst formed and 1 mL water per gram of catalyst formed, or between 0.1 mL water per gram of catalyst formed and 0.5 mL water per gram of catalyst formed. As used herein, “catalyst formed” refers to the total amount of catalyst solid obtained from the catalyst synthesis after drying the catalyst. In some embodiments, the ratio of water in the slurry to amount of catalyst formed is between 0.2 mL water per gram of catalyst and 1 mL water per gram of catalyst formed. In some embodiments, the ratio of water in the slurry to amount of catalyst formed is between 0.3 mL water per gram of catalyst to 0.5 mL water per gram of catalyst formed.

[0050] In some embodiments, the ratio of water in the slurry to the amount of catalyst formed is 0.1 mL water per gram of catalyst formed, 0.2 mL water per gram of catalyst formed, 0.3 mL water per gram of catalyst formed, 0.4 mL water per gram of catalyst formed, 0.5 mL water per gram of catalyst formed, 0.6 mL water per gram of catalyst formed, 0.7 mL water per gram of catalyst formed, 0.8 mL water per gram of catalyst formed, 0.9 mL water per gram of catalyst formed, 1 mL water per gram of catalyst formed, 2 mL water per gram of catalyst formed, 3 mL water per gram of catalyst formed, 4 mL water per gram of catalyst formed, or 5 mL water per gram of catalyst formed.

[0051] In some embodiments, an optimal ratio of water in the slurry to amount of catalyst formed minimizes the amount of water used in the slurry, and therefore minimizes the amount of wastewater produced, while maintaining saturated vapor pressure in the hydrothermal synthesis reaction.

[0052] In some embodiments, the slurry has a ratio of water to metal oxides between 0. 1 mL water per gram of metal oxides and 10 mL water per gram of metal oxides, such as between 0.1 mL water per gram of metal oxides and 5 mL water per gram of metal oxides, between 0.1 mL water per gram of metal oxides and 4 mL water per gram of metal oxides, between 0.1 mL water per gram of metal oxides and 3 mL water per gram of metal oxides, between 0.1 mL water per gram of metal oxides and 2 mL water per gram of metal oxides, or between 0.1 mL water per gram of metal oxides and 1 mL water per gram of metal oxides. The phrase “ratio of water to metal oxides” as used herein refers to the ratio of water used in the slurry to the total mass of metal oxides used in the slurry, which includes an oxide of molybdenum; an oxide of vanadium; MoO2; in some embodiments, one or both of an oxide of tantalum and an oxide of niobium; and, in some embodiments, VO2. For example, a slurry comprising 2.2 mb of water, 4.0203 g of MoOs, 1.0051 g V2O5, and 0.9858 g MoO2 would comprise 6.0112 g of total metal oxides and provide a ratio of water to metal oxides of 0.37.

[0053] In some embodiments, the slurry has a ratio of water to metal oxides between 0. 1 mb water per gram of metal oxides and 0.7 mb water per gram of metal oxides, such as between 0.3 mb water per gram of metal oxides and 0.7 mb water per gram of metal oxides, or between 0.3 mb water per gram of metal oxides and 0.6 mb water per gram of metal oxides.

[0054] In some embodiments, the slurry has a ratio of water to metal oxides of 0.1 mb water per gram of metal oxides, 0.2 mb water per gram of metal oxides, 0.3 mb water per gram of metal oxides, 0.4 mb water per gram of metal oxides, 0.5 mb water per gram of metal oxides, 0.6 mb water per gram of metal oxides, 0.7 mb water per gram of metal oxides, 0.8 mb water per gram of metal oxides, 0.9 mb water per gram of metal oxides, 1 mb water per gram of metal oxides, 2 mb water per gram of metal oxides, 3 mb water per gram of metal oxides, 4 mb water per gram of metal oxides, or 5 mb water per gram of metal oxides.

[0055] The method disclosed herein can further include a process for controlled size modification of the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound. For example, grinding, wet milling, dry milling, or crushing the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound. 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).

[0056] 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 firoml 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.

[0057] In some embodiments, the method further includes a process for controlled size modification of the reducing agent. For example, grinding, wet milling, dry milling, or crushing the reducing agent.

[0058] In some embodiments, the slurry is essentially free of a tellurium compound. The term “essentially free” as used herein means less than 10 ppm, less than 5 ppm, less than 2 ppm, or less than 1 ppm.

[0059] In the methods disclosed herein, the slurry is essentially free of a strong acid. The skilled person will appreciate that a strong acid is an acid that is completely or nearly completely ionized in a solution. For example, in some embodiments, the slurry is essentially free of nitric acid.

[0060] In some embodiments, the slurry is essentially free of oxalic acid. That is, oxalic acid is not added to the slurry and the method is performed without oxalic acid.

[0061] In some embodiments, 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; and the reducing agent includes molybdenum dioxide (MoCh). In some embodiments, the metal oxides include an oxide of molybdenum and an oxide of vanadium; the bismuth compound is bismuth hydroxide; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum and an oxide of vanadium; the antimony compound includes an oxide of antimony, an antimony acetate, or an antimony ethoxide; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum and an oxide of vanadium; the tellurium compound includes tellurium dioxide; and the reducing agent includes molybdenum dioxide.

[0062] In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of tantalum or an oxide of niobium, or both; the bismuth compound includes bismuth oxide, bismuth hydroxide, or a bismuth carbonate; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of tantalum; the bismuth compound includes bismuth oxide, bismuth hydroxide, or a bismuth carbonate; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of niobium; the bismuth compound includes bismuth oxide, bismuth hydroxide, or a bismuth carbonate; and the reducing agent includes molybdenum dioxide.

[0063] In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of tantalum or an oxide of niobium, or both; the bismuth compound is bismuth hydroxide; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of tantalum; the bismuth compound is bismuth hydroxide; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of niobium; the bismuth compound is bismuth hydroxide; and the reducing agent includes molybdenum dioxide.

[0064] In some embodiments, the oxide of molybdenum is MoOs, the oxide of vanadium is V2O5, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide. In some embodiments, the oxide of molybdenum is MoOs, the oxide of vanadium is V2O5, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide and vanadium dioxide.

[0065] In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is VO2, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide and vanadium dioxide. In such embodiments where the VO2 acts as both the source of vanadium for the catalyst and as a reducing agent.

[0066] In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is V2O5, the oxide of is Ta2C>5 XH2O, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide. In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is VO2, the oxide of tantalum is Ta2C>5 XH2O, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide. In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is VO2, the oxide of tantalum is Ta2C>5 XH2O, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide and vanadium dioxide.

[0067] In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is V2O5, the oxide of niobium is Nb20s XH2O, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide. In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is VO2, the oxide of niobium is Nb20s XH2O, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide. In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is VO2, the oxide of niobium is Nb20s XH2O, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide and vanadium dioxide.

[0068] In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of tantalum or an oxide of niobium, or both; the antimony compound includes an oxide of antimony, an antimony acetate, or an antimony ethoxide; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of tantalum; the antimony compound includes an oxide of antimony, an antimony acetate, or an antimony ethoxide; and the reducing agent includes molybdenum dioxide. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of niobium; the antimony compound includes an oxide of antimony, an antimony acetate, or an antimony ethoxide; and the reducing agent includes molybdenum dioxide.

[0069] In some embodiments, the oxide of molybdenum is MoOs, the oxide of vanadium is V2O5, the oxide of is Ta2C>5 XH2O, the antimony compound is an oxide of antimony, and the reducing agent includes molybdenum dioxide. In some embodiments, the oxide of molybdenum is MoOs, the oxide of vanadium is VO2, the oxide of tantalum is Ta2C>5 XH2O, the antimony compound is an oxide of antimony, and the reducing agent includes molybdenum dioxide.

[0070] In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is V2O5, the oxide of niobium is Nb2C>5 XH2O, the bismuth compound is bismuth hydroxide, and the reducing agent includes molybdenum dioxide. In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is VO2, the oxide of niobium is Nb20s XH2O, the antimony compound is an oxide of antimony, and the reducing agent includes molybdenum dioxide.

[0071] In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of tantalum or an oxide of niobium, or both; and the tellurium compound includes tellurium dioxide (TeCh). In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of tantalum; and the tellurium compound includes tellurium dioxide. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, and an oxide of niobium; and the tellurium compound includes tellurium dioxide.

[0072] In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is V2O5, the oxide of is Ta2Ch xhbO, and the tellurium compound is TeCh. In some embodiments, the oxide of molybdenum is MoOs, the oxide of vanadium is VO2, the oxide of tantalum is Ta2C>5 xFFO, and the tellurium compound is TeCh.

[0073] In some embodiments, the oxide of molybdenum is MoOs, the oxide of vanadium is V2O5, the oxide of niobium is Nb2Ch xFbO, and the tellurium compound is TeCh. In some embodiments, the oxide of molybdenum is MoO3, the oxide of vanadium is VO2, the oxide of tantalum is Ta2Ch xFbO, and the tellurium compound is TeCh.

[0074] In the methods disclosed herein, the catalyst is formed in a hydrothermal synthesis reaction by heating the slurry. Any suitable reaction vessel may be used for the hydrothermal synthesis reaction. In some embodiments, the slurry is heated in a hydrothermal synthesis vessel. In some embodiments, the slurry is formed in a hydrothermal synthesis vessel and subsequently heated in the hydrothermal synthesis vessel. In some embodiments, the slurry is transferred to a hydrothermal synthesis vessel after the slurry is formed and then heated in the hydrothermal synthesis vessel.

[0075] 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.

[0076] The slurry can be heated by ramping a temperature of the slurry and subsequently holding a temperature of the slurry. The ramping of the temperature can be used to avoid surface boiling of the slurry. The expression “ramping a temperature”, as used herein, refers to changing from an initial temperature to a final temperature over a time. For example, the temperature of the slurry may be ramped from an initial temperature of room temperature to a final temperature greater than room temperature over the course of a specified number of hours. The final temperature may be the holding temperature. The term “room temperature” as used herein refers to a temperature between 15°C and 28°C. The term “holding temperature,” as used herein, refers to the temperature at which the reaction vessel is held, which can be measured by the ambient temperature of the oven the reaction vessel was placed in.

[0077] In some embodiments of the method disclosed herein, the slurry is heated by ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours. In some embodiments, the slurry is heated by ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 120 hours. In some embodiments, the slurry is heated by ramping a temperature from ambient to a temperature between 150°C and 200°C over a ramping time between 2 hours and 24 hours; and holding the temperature at a holding temperature between 150°C and 200°C for a holding time between 24 hours and 60 hours.

[0078] In a non-limiting example, the slurry is heated by ramping a temperature from ambient to 180°C over 12 hours; and holding the temperature at 180°C for a holding time of 48 hours. In another non-limiting example, the slurry is heated by ramping a temperature from ambient to 180°C over 24 hours; and holding the temperature at 180°C for a holding time of 60 hours. In another non-limiting example, the slurry is heated by ramping a temperature from ambient to 180°C over 2 hours; and holding the temperature at 180°C for a holding time of 48 hours. In another non-limiting example, the slurry is heated by ramping a temperature from ambient to 180°C over 24 hours; and holding the temperature at 180°C for a holding time of 156 hours.

[0079] In some embodiments, the method disclosed herein may further include washing the catalyst with water. For example, the catalyst may be washed with water until the fdtrate is colorless. In some embodiments, the catalyst fdtrate is colorless after a first water wash.

[0080] In some embodiments, the method further includes a step of drying the catalyst, for example, at temperatures below 100°C. The drying can be done by any suitable method including, for example, at ambient temperature for a suitable time or in an oven overnight at, for example, a temperature of 90°C. The drying may be performed independent of a washing step. That is, the drying step may be performed in the absence of a washing step, before a washing step, or after a washing step.

[0081] 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. 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.

[0082] In some embodiments, a ratio of a total amount of water used to prepare the catalyst is between 0. 1 mb water per gram of catalyst and 60 mb water per gram of catalyst. In some embodiments, a ratio of a total amount of water used to prepare the catalyst is between 0.1 mb water per gram of catalyst and 25 mb water per gram of catalyst. As used herein, a “total amount of water used to prepare the catalyst” includes the water in the slurry, as well as any water used in any other steps, such as the optional step of washing the catalyst with water, and / or any water used to transfer materials between reaction vessels. In some embodiments, a ratio of a total amount of water used to prepare the catalyst is between 0.1 mb water per gram of catalyst and 20 mb water per gram of catalyst, 0.5 mb water per gram of catalyst and 15 mb water per gram of catalyst, 1 mb water per gram of catalyst and 10 mb water per gram of catalyst, 5 mb water per gram of catalyst and 10 mb water per gram of catalyst, between 0.1 mb water per gram of catalyst and 5 mb water per gram of catalyst, or between 0. 1 mb water per gram of catalyst and 1 mb water per gram of catalyst. In some embodiments, a ratio of a total amount of water used to prepare the catalyst is between 0.2 mb water per gram of catalyst and 10 mb water per gram of catalyst.

[0083] In some embodiments, the method includes forming a slurry including an oxide of molybdenum, an oxide of vanadium, one or more of bismuth oxide, bismuth hydroxide, or a bismuth carbonate, and molybdenum dioxide; and heating the slurry by ramping a temperature from ambient to a temperature between 100°C and 200°C, over a ramping time between 2 hours and 48 hours, and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours to from the catalyst. In these embodiments, the ratio of the water in the slurry to amount of catalyst formed may be between 0.2 mb water per gram of catalyst and 1 mb water per gram of catalyst formed.

[0084] In some embodiments, the method includes forming a slurry including an oxide of molybdenum, an oxide of vanadium, bismuth hydroxide, and molybdenum dioxide; and heating the slurry by ramping a temperature from ambient to a temperature between 100°C and 200°C, over a ramping time between 2 hours and 48 hours, and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours to from the catalyst. In these embodiments, the ratio of the water in the slurry to amount of catalyst formed may be between 0.2 mL water per gram of catalyst and 1 mL water per gram of catalyst formed.

[0085] In some embodiments, the method includes forming a slurry including MoOs, V2O5, bismuth hydroxide, and MO2; and heating the slurry by ramping a temperature from ambient to a temperature between 100°C and 200°C, over a ramping time between 2 hours and 48 hours, and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours to from the catalyst. In these embodiments, the ratio of the water in the slurry to amount of catalyst formed may be between 0.2 mL water per gram of catalyst and 1 mL water per gram of catalyst.

[0086] In some embodiments, the method includes forming a slurry including MoOs, V2O5, bismuth hydroxide, MO2 and VO2; and heating the slurry by ramping a temperature from ambient to a temperature between 100°C and 200°C, over a ramping time between 2 hours and 48 hours, and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours to from the catalyst. In these embodiments, the ratio of the water in the slurry to amount of catalyst formed may be between 0.2 mL water per gram of catalyst and 1 mL water per gram of catalyst formed.

[0087] The catalysts prepared by the methods disclosed herein include molybdenum (Mo); vanadium (V); one or more of bismuth (Bi), antimony (Sb), or tellurium (Te); and oxygen (O). In some embodiments, the catalyst prepared by the method disclosed herein has the formula MoaVbMcOx, wherein M is one or more of Bi, Sb, and Te; 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; wherein a, b, and c are determined by one or both of the amount of each starting material used to form the catalyst and elemental analysis. In some embodiments, the catalyst prepared by the methods disclosed herein has a formula MoaVbBicOx, wherein a, b, c, and x are as described above. In some embodiments, the catalysts prepared by the methods disclosed herein include the formula Mo1V0.20-0.40Bi0.01-0.07Ox or Mo1V0.30-0.35Bi0.04-0.05Ox.

[0088] In some embodiments, the catalysts prepared by the methods disclosed herein further include tantalum (Ta), or niobium (Nb), or both. In some embodiments, the catalysts prepared by the method herein include the formula MoaVbBicMdOx, wherein M 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. In some embodiments, the catalyst has a formula selected from MoaVbBicTaaOx, and MoaVbBicNbdOx. In some embodiments, the catalyst has a formula of Mo1V0.20-0.40Bi0.01-0.07Ta0.03-0.05Ox or Mo1V0.20-0.40Bi0.01- 0.07Nb0.03-0.05Ox.

[0089] In some embodiments, the methods for preparing a catalyst disclosed herein may further include combining the catalyst with one or more of a solid support, carrier, binder, and lubricant, such as the solid supports, carriers, binders, and lubricants disclosed elsewhere herein, to provide a catalyst material. In some embodiments, the catalyst material is prepared by a method that includes preparing an aqueous mixture that includes (i) a catalyst disclosed herein; (ii) a solid support or carrier, and (iii) a lubricant and / or a binder. In some embodiments, the method can further include removing a substantial amount of the water (for example, from 50 wt. % to 99 wt. %) from the aqueous mixture, such as, for example, by heating the mixture at a temperature from 50°C to 100°C. In some embodiments, the method includes forming the catalyst material into a formed catalyst materials such as, for example, a pelleted catalyst material.

[0090] The catalysts disclosed herein may be suitable as catalysts in oxidative dehydrogenation reactions. As used herein, the term “oxidative dehydrogenation” or “ODH” refers to a process that couples 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. Fortesting catalysts, the ODH reactions herein are assumed to be referring to the ODH of ethane.

[0091] In some embodiments, the catalyst has a 45% ethane conversion temperature from 300°C to 420°C. In some embodiments, the catalyst has a 45% ethane conversion temperature from 300°C to 400°C. In some embodiments, the catalyst has a 45% ethane conversion temperature from 325°C to 390°C. In some embodiments, the catalyst has a 45% ethane conversion temperature from 340°C to 390°C. In some embodiments, the catalyst has a 45% ethane conversion temperature from 350°C to 400°C. In some embodiments, the catalyst has a 45% ethane conversion temperature from 350°C to 380°C. In some embodiments, the catalyst has a 45% ethane conversion temperature from 360°C to 375°C. As used herein, the phrase “45% ethane conversion temperature” refers to the temperature at which 45% of ethane in a gas stream is converted to a product other than ethane at a given fixed feed composition, weight hourly space velocity, and reactor inlet pressure. The 45% ethane conversion temperature of an oxidative dehydrogenation catalyst can be determined using a microreactor unit (MRU).

[0092] In a microreactor unit, the 45% ethane conversion temperature of a catalyst can be determined by passing a feed gas over a catalyst bed in a reactor tube. The MRU reactor tube has an outer diameter of 0.5 inches and an internal diameter of 0.4 inches and length of 15 inches. For example, the reactor tube can be stainless-steel SWAGEUOK® Tubing with a wall thickness of 0.049 inches. The feed gas can include ethane and oxygen having a molar ratio of 70:30 to 90: 10. For example, the feed gas can include ethane and oxygen having a molar ratio of 82: 18. Alternatively, the feed gas can include ethane, oxygen, and nitrogen. The molar ratio of ethane to oxygen to nitrogen can be 18:8:74 to 54: 18:28. For example, the molar ratio of ethane to oxygen to nitrogen can be 20: 10:70. The flow rate of the feed gas can be 70 standard cubic centimeters per minute (seem) to 80 seem. For example, the flow rate of the feed gas can be 75 seem (e.g., 74.6 seem). The catalyst bed consists of the oxidative dehydrogenation catalyst and a filler, such as quartz sand, 1:0.5 to 1 :3 volume ratio, with the total weight for the oxidative dehydrogenation catalyst being 1.96 to 2.00 g. Any remaining space in the reactor tube (e.g., below or above the catalyst bed) is packed with an additional filler, such as quartz sand. The 45% ethane conversion temperature is determined at a weight hourly space velocity (WHSV) of 3.57 h-1, with the WHSV based on the weight of catalyst in the sample, and a gas hourly space velocity (GHSV) of 2,000 to 5,000 h-1. As used herein, the expression “weight hourly space velocity” refers to the weight flow of the total feed gas divided by the weight of the catalyst. Typically, the inlet pressure is in the range of 1 pound per square inch gauge (psig) to 2.5 psig and the outlet pressure is in the range of 0 psig to 0.5 psig. The gas feed exiting the catalyst bed is analyzed by gas chromatography to determine the percentage of various hydrocarbons (e.g., ethane and ethylene) and, optionally, other gases such as O2, CO2, and CO.

[0093] Conversion of the ethane feed gas to products by the ODH process can be calculated as a volume flow rate change of ethane in the product compared to feed ethane volume flow rate using the following formula:

[0094] In Equation 1, C is the percent (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. Furthermore, the gas exiting the reactor can be analyzed by gas chromatography to determine catalyst or catalyst material selectivity to ethylene (that is, the percentage on a molar basis of ethane that forms ethylene). Selectivity to ethylene can be determined using the following equation:

[0095] In 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. As used herein, the phrase “selectivity to ethylene” refers to the percentage on a molar basis of converted or reacted ethane that forms ethylene.

[0096] 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.

[0097] 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.

[0098] In addition, any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” or “between 1 and 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.

[0099] In this document, the terms “a”, “an”, or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B”. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation.

[0100] EXAMPLES

[0101] Reagents

[0102] Molybdenum(VI) oxide (MoOs), vanadium(V) oxide (V2O5), bismuth hydroxide (Bi(0H)3) and oxalic acid dihydrate were purchased from Fisher Scientific Canada. Tantalum pentoxide hydrate (Ta2Os XH2O) was purchased from BassTech International. The x in Ta2Os xELO was 2.57 as measured by thermogravimetric analysis. Molybdenum(IV) oxide (MOO2), tellurium dioxide (TeCh), and vanadium(IV) oxide (VO2) were purchased from Sigma-Aldrich Canada. All reagents were used as is without any further purification. All water used was distilled deionized water.

[0103] Preparation of Comparative Catalyst A

[0104] Comparative Catalyst A was prepared with the reagents listed in Table 1.

[0105] Table 1. Amounts of Reagents used for Comparative Catalyst A,

[0106] The solid reagents listed in Table 1 were mixed and lightly ground using a mortar and pestle, to pulverize the larger oxalic acid dihydrate crystals to better disperse with the other solids. The solid mixtures were then transferred into an 8 mb glass vial, after which 2 mb of the distilled water solvent was added. The sample was stirred lightly with a glass stir rod to form a thick orange slurry and another 0.7 mb of water was then used to rinse sample stuck to the stir rod back into the vial. The vial was then placed in a glass lined steel autoclave, water was filled around the vial to the level of the slurry to help with heat transfer and to maintain a humid atmosphere at 100% relative humidity in the vessel. 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 over 3 - 4 hours.

[0107] After reaction, the sample was a hard, deep purple solid and had increased in volume by about 1.5x. The sample was scraped from the vial onto filter paper in a vacuum filtration set-up and was washed with approximately 50 mb of distilled water, with the filtrate a deep blue color. The sample was washed until the filtrate from the sample was colorless, then left to dry on the filter paper to obtain shiny purple-black powdered solid. The solid was then calcined in a tubular autoclave under N2 flow for 12 hours at 60°C, after which it was heated to 600°C over 6 hours, held at 600°C for 2 hours, then the furnace was turned off and the samples cooled back to ambient conditions over approximately 12 hours to provide Comparative Catalyst A.

[0108] Preparation of Comparative Catalyst B

[0109] Comparative Catalyst B was prepared with the reagents listed in Table 2.

[0110] Table 2, Amounts of Reagents used for Comparative Catalyst B,

[0111] The solid reagents listed in Table 2 were added to a blender and mixed for 1 minute to blend and pulverize. The solid mixture was then transferred to a 40 mb glass bottle, after which the distilled water was used to rinse the grinder and transfer the residual solids to the bottle. The sample was stirred with a PTFE stir bar to form an orange slurry. The vial was then placed in a steel autoclave, and water was filled around the vial to the level of the slurry to help with heat transfer and to maintain a humid atmosphere in the vessel (~20 mb 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 over 3 - 4 hours. After reaction, the sample was a purple-grey hard solid. The sample was scraped from the bottle onto filter paper in a vacuum filtration set-up and was washed with distilled water (-300 mL) in portions, with the filtrate being initially a deep blue color. The sample was washed until the filtrate from the sample was nearly colorless, then was then dried in an oven at 90°C overnight to obtain 26.8753 g of purple-grey powdered solid Comparative Catalyst B. This sample was not treated further before catalytic testing. Preparation of Catalysts Examples Catalyst Example A

[0112] Catalyst Example A was prepared following the same procedure as for Comparative catalyst A, excluding the calcination step at 600°C. The solids listed in Table 3 were used for synthesis.

[0113] Table 3 , Amounts of Reagents used for Hydrothermal Synthesis of Catalyst Example A

[0114] In this example, VO2 was used in an amount to both replace the molar equivalent of V2O5 used in Comparative Catalyst A and act as a reducing agent.

[0115] Catalyst Examples B to F

[0116] Catalyst Examples B to F were prepared following the same procedure as for Comparative Catalyst A, excluding the calcination step at 600°C. The solids listed in Table 4 were used for synthesis. For these examples, a colorless filtrate was observed during the washing step.

[0117] Table 4, Amounts of Reagents used for Hydrothermal Synthesis of Catalyst Examples B to F, Catalyst Example G

[0118] The solids listed in Table 5 were added to a blender and mixed three times in 30 second pulses, knocking the solids down in the blender between each pulse. The blended solids were then transferred to a 40 m disposable glass hypo vial, then the water was added, and the mixture was stirred to form a thick grey slurry. The hypo vial was then placed in a 2 L steel Parr autoclave and 150 m of water was added around the vial to act as a heat transfer medium and to maintain 100% relative humidity in the vessel. The autoclave was then sealed and placed in a programmable oven to heat from room temperature to 180°C over 12 hours, held at 180°C for 48 hours, then heating was stopped, and the oven was cooled passively back to room temperature. After cooling, the vial was removed from the autoclave and a purple solid had formed. The vial was placed open inside an oven at 90°C for 18 hours to dry. Obtained 27.0313 g of fine purple solid after drying. Table 5 , Amounts of Reagents used for Hydrothermal Synthesis of Catalyst Example G.

[0119] Powder X-ray Diffraction (PXRD)

[0120] 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. As shown in Figures 1 through 9, all samples were characterized as Ml phase with varying degrees of molybdenum (VI) oxide impurity. As shown in Figure 3, the PXRD of the product where VO2 was used as the reducing agent and the vanadium oxide (that is, replacing V2O5 used in Comparative Catalyst A), demonstrates formation of the Ml phase but also unreacted MoOs. Without being bound by any particular theory, it is believed that VO2 may not have sufficient reducing power alone to act as both the reducing agent and vanadium oxide source when a molar equivalent is used. Figures 4 through 8, showing the PXRD patterns of example catalyst prepared using MoO2 as the reducing agent, indicate that increased amounts of MoO2 reducing agent results in an unidentified peak in the PXRD at 25.98° 20. Without being bound by any particular theory, it is believed that the strength of the molybdenum (IV) oxide reducing agent may preclude it from being used as both a reducing agent and the molybdenum oxide source for the exemplified catalysts.

[0121] Catalyst Testing

[0122] 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 0.4 inches (1.02 cm), and a length of 13.4- 15 inches (34.0 - 38.1 cm). Experimental temperatures of the MRU were 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 was used to measure and control the temperature within the catalyst bed.

[0123] 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 tubular reactor Approximately 2 g of sample was placed in the reactor.

[0124] 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 mb 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 the top and bottom. Quartz sand was added to produce the catalyst bed volume of 6 mb to ensure the catalyst volume was sufficient to cover the thermocouple area.

[0125] The flow rate of the gas feed was adjusted to a target of 150 seem (weight hour space velocity (WHSV) = 3.57 h'1) and a target pressure of 22 psig. 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.

[0126] The mol. % ethane conversion temperature was determined at the WHSV of 3.57 h’1, and a gas hourly space velocity (GHSV) in the range of 2000 to 5000 h’1. 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 I 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:

[0127] In Eq. 1, X is the molar concentration of the corresponding compound in the gaseous effluent exiting the reactor at corresponding temperature.

[0128] 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:

[0129] 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.

[0130] In order to close the mass balance for ODH experiments based on GC analysis of non-condensable products, it was assumed that all non-condensable gaseous products behave as ideal gases. The ideal gas equation of state is accurate in prediction of gas mixture behavior at operating pressure close to 1 atm absolute. For the ODH experiments, the product gas samples were collected and injected into a gas chromatograph (GC) at operating pressure close to 1 atm absolute. Therefore, the ideal gas behavior assumption is expected to generate accurate prediction of the gas mixture behavior. The bulk chemical reactions shown in Table 6 were assumed in order to calculate the amounts of condensable products. The reactions in Table 6 were used for stoichiometrically balanced mass balance calculations and not to represent the actual chemical reactions occurring in the ODH reaction.

[0131] Table 6, Bulk Chemical Reactions Assumed for Mass Balance Methodology.

[0132] “ As a result, the corresponding amount of water per mole of produced acetic acid and ethylene will be reduced. For example, 1 mole of acetic acid and 4 moles of ethylene would give 5 moles of water, when produced by reacting ethane and oxygen, but the same amount of both compounds would result in 2 moles of water for the same compounds to be produced by reaction of ethane and CO2. This results in 3 moles less water produced to make these compounds for each 2 moles of CO2 being consumed. These will be subtracted in the mass balance.

[0133] Based on reactions shown in Table 6, the following method was programmed and used in MS Excel. A GRG Nonlinear solving method was used with the objective of setting the absolute deviation of estimated and measured oxygen from the reactor to zero by modifying the acetic acid output in the solver.

[0134] In step 1, the total molar flow of C2 (ethane) into the reactor is calculated using

[0135] Equation 3 :

[0136] F2Total = 100000*FTotal* (CEthane + 0.5 * CcO2) / 22.4 Eq. 3 wherein F2Totai is the total molar flow of C2 into the reactor, [mmol / min]; Frotai is the total feed flow to reactor (including all diluents), [seem]; CEthane is the molar fraction of ethane in total feed; Cco2 is the molar fraction of CO2 in total feed; and 22.4 is the molar volume at

[0137] STP, [1 / mol],

[0138] In step 2, the molar flow of all reactive compounds in product effluent from the reactor is calculated excluding inert diluents.

[0139] The total molar flow of acetic acid in the product, [mmol / min] (FAAOUI) is estimated by Equation 4:

[0140] FAAOUI = y (first estimate: y = 1 [mmol / min]) Eq. 4

[0141] The total molar flows of C2 in non-condensable compounds in the reactor product is calculated using Equation 5 :

[0142] F2outx=F2Total * (CxoutZ(SCxout)) * ((F2Total - PAAout) / F2Total) Eq. 5 wherein F2outx is the total molar flow of C2 of x, [mmol / min]; Cxout is the molar fraction of x in the reactor product; and x is Ethane, Ethylene, CO2, or CO.

[0143] The total molar flow of O2 from the reactor is calculated using the following algorithm:

[0144] If F20UTC-2 - (100000*FTotai*(0.5*Cco2) / 22.4)) > 0 then use Equation 6:

[0145] Fo2out = (I00000*FTotal*(0.5*Co2) / 22.4)) - 0.5* F2outetha-e - 3.5* F2OUTCO2- 2.5* F2out-0 -

[0146] 1.5* FoutAAout Eq. 6 If F20UTC02 - ( 100000*FTotai* (0.5 * Cco2) / 22.4)) < 0 then use Equation 7:

[0147] F02out = ( 100000*FTotal* (0.5 *Co2) / 22.4)) - 0.5* F2outethane + ABS(3.5 * F2OLTCO ) - 2.5* F2out-0 " 1 .5 * FoutAAout Eq. 7

[0148] The total molar flow of H2O from the reactor is calculated using Equation 8: FffiOoutx = FH2O + F2outetha-e - 3 * F2OUTCO2- 3 *F2out-0 - FAAout Eq. 8

[0149] In step 3, the molar fractions of all reactive compounds in the product effluent from the reactor are calculated on the dry (water free) basis, using FAAOUI from step X04.

[0150] The molar fraction of acetic acid in the product is calculated using Equation 9:

[0151] CAAoutcalc=FAAout / (FAAout + SFxout + Fo2out) Eq. 9

[0152] The molar fraction of C2 in ethane, ethylene, CO2, and CO in the product is calculated using Equation 10:

[0153] Cxoutcalc=F2outx / (FAAout + SFxout + Fo2out) Eq. 10

[0154] The molar fraction of oxygen in the product is calculated using Equation 11 :

[0155] Co2outcalc=Fo2out / (FAAout + SFxout + Fo2out) Eq. 11

[0156] In step 4, the absolute deviation of estimated and measured O2 in the noncondensable product from the reactor is calculated using Equation 12:

[0157] D02 = Co2outcalc - (C02 / (CEthane +CEthylne + 0.5*CcO2 + 0.5Cco+ C02) * -1 - CAAoutcalc))

[0158] Eq. 12

[0159] Step 5 is the decision point, if D02 is less than 10'4, proceed to step 6. If D02 is not less than 10'4, return to step 2 and repeat. On the repeated steps, FAAout = y (wherein y = new estimate [mmol / min]) is changed, and the steps are repeated to determine whether D02 is closer to the target in step 410.

[0160] In step 6, ethane conversion is calculated using Equation 13: and selectivity toward each product is calculated using Equation 14: wherein CxoutCalc=CEthyleneoutCalc, CAAoutCalc, 0.5 * Cc02outCalc Or 0.5 * CcOOutcalc .

[0161] Summary of Catalyst Performance

[0162] Comparative Catalyst A was placed on stream without any pretreatment of the catalyst, as it had already been calcined at 600°C. Comparative Catalyst B, Example Catalyst C and Example Catalyst D were initially placed on stream on the MRU under nitrogen flow (153 seem) at 450°C for 2 hours before cooling and flowing the target feed composition of 20% ethane, 10% oxygen and 70% nitrogen. Data from the samples are listed in Table 7.

[0163] Table 7, Catalyst Performance.

[0164] The data in Table 6 shows that Catalyst Examples C and D, prepared by the method disclosed herein, both are highly active and selective for ethane ODH, similar to ODH catalysts prepared using oxalic acid in the synthetic procedure. Using all inorganic reagents can prevent pressure build-up and carbon monoxide formation during hydrothermal synthesis, while still producing an active ODH catalyst.

[0165] Non-limiting embodiments of the present disclosure include the following:

[0166] Embodiment A. A method for preparing a catalyst comprising: forming a slurry comprising: metal oxides; one or more of a bismuth compound, an antimony compound, and a tellurium compound; a reducing agent; and water; and heating the slurry to form the catalyst; wherein the metal oxides comprise: an oxide of molybdenum; and an oxide of vanadium; wherein the bismuth compound comprises bismuth oxide, bismuth hydroxide, or a bismuth carbonate; wherein the antimony compound comprises an oxide of antimony, an antimony acetate, or an antimony ethoxide; wherein the tellurium compound comprises tellurium dioxide; and wherein the reducing agent comprises molybdenum dioxide.

[0167] Embodiment B. The method according to Embodiment A, wherein the metal oxides further comprise an oxide of tantalum or an oxide of niobium, or both.

[0168] Embodiment C. The method according to Embodiment A or B, wherein the reducing agent further comprises vanadium dioxide. Embodiment D. The method according to Embodiment A, B, or C, wherein a ratio of the water in the slurry to amount of catalyst formed is between 0. 1 mb water per gram of catalyst and 10 mb water per gram of catalyst.

[0169] Embodiment E. The method according to Embodiment A, B, or C, wherein the ratio of the water in the slurry to amount of catalyst formed is between 0.2 mb water per gram of catalyst and 1 mb water per gram of catalyst.

[0170] Embodiment F. The method according to Embodiment A, B, or C, wherein the slurry has a ratio of water to metal oxides between 0.3 mb water per gram of metal oxides and 0.8 mb water per gram of metal oxides.

[0171] Embodiment G. The method according to Embodiment A, B, C, D, E, or F, wherein the oxide of molybdenum is MoOs.

[0172] Embodiment H. The method according to Embodiment A, B, C, D, E, F, or G, wherein the oxide of vanadium is V2O5.

[0173] Embodiment L The method according to Embodiment A, B, C, D, E, F, or G, wherein the oxide of vanadium is VO2.

[0174] Embodiment J. The method according to Embodiment A, B, C, D, E, F, G, H, or I, wherein the bismuth compound comprises the bismuth hydroxide.

[0175] Embodiment K. The method according to Embodiment A, B, C, D, E, F, G, H, or I, wherein the antimony compound is an oxide of antimony.

[0176] Embodiment L. The method according to B, C, D, E, F, G, H, I, J, or K, wherein the tantalum oxide, when present, is Ta2C>5 xFEO, and the niobium oxide, when present, is Nb2C>5 xFEO.

[0177] Embodiment M. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, or L, wherein the reducing agent is MoO2.

[0178] Embodiment N. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, or M, further comprising grinding, wet milling, dry milling, or crushing the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound.

[0179] Embodiment O. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, or M, further comprising grinding, wet milling, dry milling, or crushing the reducing agent.

[0180] Embodiment P. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, N, or O, comprising heating the slurry by: ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours.

[0181] Embodiment Q. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, N, or O, comprising heating the slurry by: ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 120 hours.

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

[0183] K, L, M, N, O, P, or Q, further comprising washing the catalyst with water.

[0184] Embodiment S. The method according to Embodiment B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, or R, further comprising calcining the catalyst to form a calcined catalyst.

[0185] Embodiment T. The method according to Embodiment S, comprising calcining the catalyst 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.

[0186] Embodiment U. The method according Embodiment A, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, or R 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; wherein a, b, and c are determined by one or both of the amount of each starting material used to form the catalyst and elemental analysis.

[0187] Embodiment V. The method according to Embodiment U, wherein the catalyst comprises the formula Mo1V0.20-0.40Bi0.01-0.07Ox.

[0188] Embodiment W. The method according to Embodiment U, wherein the catalyst comprises the formula Mo1V0.30-0.35Bi0.04-0.05Ox.

[0189] Embodiment X. The method according to Embodiment B, C, D, E, F, G, H, I, J, K,

[0190] L, M, N, O, P, Q, R, S, or T, wherein the catalyst comprises the formula: MoaVbBicMdOx wherein: M 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. Embodiment Y. The method according to Embodiment X, wherein the catalyst comprises the formula Mo1V0.20-0.40Bi0.01-0.07Ta0.03-0.05Ox or Mo1V0.20-0.40Bi0.01-0.07Nb0.03- o.osOx.

[0191] Embodiment Z. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, or Y, wherein the metal oxides and the bismuth compound each have a particle size in the range of from 0.5 pm to 250 pm.

[0192] Embodiment AA. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X , Y, or Z, wherein a ratio of a total amount of water used to prepare the catalyst is between 0.2 mb water per gram of catalyst and 25 mb water per gram of catalyst.

[0193] Other implementations are also within the scope of the following claims.

[0194] INDUSTRIAL APPLICABILITY

[0195] Methods of making catalysts for the oxidative dehydrogenation of alkanes, such as the oxidative dehydrogenation of ethane to ethylene.

Claims

CLAIMSWhat is claimed is1. A method for preparing a catalyst comprising: forming a slurry comprising: metal oxides; one or more of a bismuth compound, an antimony compound, and a tellurium compound; a reducing agent; and water; and heating the slurry to form the catalyst; wherein the metal oxides comprise: an oxide of molybdenum; and an oxide of vanadium; wherein the bismuth compound comprises bismuth oxide, bismuth hydroxide, or a bismuth carbonate; wherein the antimony compound comprises an oxide of antimony, an antimony acetate, or an antimony ethoxide; wherein the tellurium compound comprises tellurium dioxide; and wherein the reducing agent comprises molybdenum dioxide.

2. The method according to claim 1, wherein the metal oxides further comprise an oxide of tantalum, or an oxide of niobium, or both.

3. The method according to claim 1 or 2, wherein the reducing agent further comprises vanadium dioxide (VO2).

4. The method according to any one of claims 1 to 3, wherein a ratio of the water in the slurry to amount of catalyst formed is between 0. 1 mL water per gram of catalyst and 10 mL water per gram of catalyst.

5. The method according to any one of claims 1 to 3, wherein the ratio of the water in the slurry to amount of catalyst formed is between 0.2 mL water per gram of catalyst and 1 mL water per gram of catalyst.

6. The method according to any one of claims 1 to 3, wherein the slurry has a ratio of water to metal oxides between 0.3 mL water per gram of metal oxides and 0.8 mL water per gram of metal oxides.

7. The method according to any one of claims 1 to 6, wherein the oxide of molybdenum is MoOs .

8. The method according to any one of claims 1 to 7, wherein the oxide of vanadium is V2O5.

9. The method according to any one of claims 1 to 7, wherein the oxide of vanadium is VO2.

10. The method according to any one of claims 1 to 9, wherein the bismuth compound comprises the bismuth hydroxide.

11. The method according to any one of claims 1 to 9, wherein the antimony compound is an oxide of antimony.

12. The method according to any one of claims 2 to 11, wherein the tantalum oxide, when present, is Ta2Os XH2O, and the niobium oxide, when present, is Nb2Os XH2O.

13. The method according to any one of claims 1 to 12, wherein the reducing agent is MoO2.

14. The method according to any one of claims 1 to 14, further comprising grinding, wet milling, dry milling, or crushing the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound.

15. The method according to any one of claims 1 to 13, further comprising grinding, wet milling, dry milling, or crushing the reducing agent.

16. The method according to any one of claims 1 to 15, comprising heating the slurry by: ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 160 hours.

17. The method according to any one of claims 1 to 15, comprising heating the slurry by: ramping a temperature from ambient to a temperature between 100°C and 200°C over a ramping time between 2 hours and 48 hours; and holding the temperature at a holding temperature between 100°C and 200°C for a holding time between 12 hours and 120 hours.

18. The method according to any one of claims 1 to 17, further comprising washing the catalyst with water.

19. The method according to any one of claims 2 to 18, further comprising calcining the catalyst to form a calcined catalyst.

20. The method according to claim 19, comprising calcining the catalyst 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.

21. The method according to any one of claims 1 to 18, 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; wherein a, b, and c are determined by one or both of the amount of each starting material used to form the catalyst and elemental analysis22. The method according to claim 21, wherein the catalyst comprises the formulaMo1V0.20-0.40Bi0.01-0.07Ox.

23. The method according to claim 21, wherein the catalyst comprises the formula Mo1V0.30-0.35Bi0.04-0.05Ox.

24. The method according to any one of claims 2 to 20, wherein the catalyst comprises the formula:MOaVbBlcMdOx wherein:M 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.

25. The method according to claim 24, wherein the catalyst comprises the formula Mo1V0.20-0.40Bi0.01-0.07Ta0.03-0.05Ox or Mo1V0.20-0.40Bi0.01-0.07Nb0.03-0.05Ox.

26. The method according to any one of claims 1 to 25, wherein the metal oxides and the one or more of the bismuth compound, the antimony compound, and the tellurium compound each have a particle size in the range of from 0.5 pm to 250 pm.

27. The method according to any one of claims 1 to 26, wherein a ratio of a total amount of water used to prepare the catalyst is between 0.2 mL water per gram of catalyst and 25 mL water per gram of catalyst.

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