EP4680387A1

EP4680387A1 - Making catalysts for oxidative dehydrogenation

Info

Publication number: EP4680387A1
Application number: EP24712315.1A
Authority: EP
Inventors: Jared Taylor
Original assignee: Nova Chemicals International SA
Current assignee: Nova Chemicals International SA
Priority date: 2023-03-13
Filing date: 2024-03-12
Publication date: 2026-01-21
Also published as: JP2026509878A; KR20250155018A; CN120826276A; WO2024189533A1; MX2025010610A

Abstract

Methods for preparing a catalyst are provided. An exemplary method includes forming a slurry including metal oxides, a reducing agent, and water; and heating the slurry to form the catalyst. The metal oxides include an oxide of molybdenum; an oxide of vanadium; an oxide of tellurium or an oxide of antimony, or both; and an oxide of tantalum 5 or an oxide of niobium, or both. 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.

Description

MAKING CATALYSTS FOR OXIDATIVE DEHYDROGENATION TECHNICAL FIELD The present disclosure relates generally to 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); tellurium (Te) or antimony (Sb), or both; tantalum (Ta) or niobium (Nb), or both; and oxygen (O). BACKGROUND ART 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. 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. ODH suffers from lower conversion rates when compared to steam cracking, a fact that when combined with lower selectivity may have prevented ODH from achieving widespread commercial implementation. Additionally, synthetic procedures for catalysts used in ODH require a significant amount of water, which may lead to the formation of a large amount of heavy metal contaminated waste. There is a need for improved methods of preparing catalysts having high selectivity, activity, and longevity for ODH reactions. SUMMARY OF INVENTION Provided herein is a method for preparing a catalyst. The method includes forming a slurry comprising metal oxides, a reducing agent, and water; and heating the slurry to form the catalyst. The metal oxides include an oxide of molybdenum; an oxide of vanadium; an oxide of tellurium or an oxide of antimony, or both; and an oxide of tantalum or an oxide of niobium, or both. 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. In some embodiments, 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. In some embodiments, the slurry has a ratio of water to metal oxides between 0.2 mL water per gram of metal oxides and 0.6 mL water per gram of metal oxides. In some embodiments, the slurry has a ratio of water to metal oxides between 0.3 mL water per gram of metal oxides and 0.5 mL water per gram of metal oxides. In some embodiments, the oxide of molybdenum is MoO₃. In some embodiments, the oxide of vanadium is V2O5. In some embodiments, the oxide of tellurium, when present, is TeO2 and the oxide of antimony, when present, is Sb2O5. In some embodiments, the oxide of tantalum, when present, is Ta2O5 ^xH2O, and the oxide of niobium, when present, is Nb₂O₅ ^xH₂O. In some embodiments, the method further includes grinding, wet milling, dry milling, or crushing the metal oxides. In some embodiments, the method further includes grinding, wet milling, dry milling, or crushing the metal oxides and the reducing agent. In some embodiments, the reducing agent includes an alcohol, a carboxylic acid, or an ester. In some embodiments, the reducing agent is oxalic acid or ethanol. In some embodiments, the reducing agent is oxalic acid. In some embodiments, the slurry includes no more than one reducing agent. 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. In some embodiments, the method further includes washing the catalyst with water. 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. In some embodiments, a ratio of the water in the slurry to amount of calcined catalyst formed is less than 1 mL water per gram of calcined catalyst. In some embodiments, the catalyst comprises a formula selected from MoaVbTecTadOx, MoaVbSbcTadOx, MoaVbTecNbdOx, and MoaVbSbcNbdOx; wherein a is 1.0; b is 0.01 to 0.4; c is 0.01 to 0.2; d is 0.01 to 0.10; and x is the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, and d are determined based on the amount of each metal oxide added to the slurry. In some embodiments, the values of a, b, c, and d are also determined by elemental analysis. In some embodiments, b is 0.2 to 0.4; c is 0.03 to 0.07; and d is 0.01 to 0.06. In some embodiments, the catalyst has a formula selected from Mo₁V_0.31Te_0.05Ta_0.05O_x, Mo₁V_0.31Sb_0.05Ta_0.05O_x, Mo₁V_0.31Te_0.05Nb_0.05O_x, and Mo1V0.31Sb0.05Nb0.05Ox. In some embodiments, the catalyst has a formula selected from Mo1V0.32Te0.05Ta0.02Ox, Mo1V0.32Sb0.05Ta0.02Ox, Mo1V0.31Te0.04Nb0.02Ox, Mo1V0.30Sb0.05Nb0.02Ox, Mo1V0.34Te0.05Ta0.02, Mo1V0.34Te0.06Ta0.02, Mo1V0.34Sb0.06Ta0.02, Mo₁V_0.34Te_0.05Nb_0.01, Mo₁V_0.32Sb_0.06Nb_0.02, Mo₁V_0.34Te_0.05Ta_0.02, and Mo₁V_0.34Sb_0.05Ta_0.03, wherein each formula is determined by energy-dispersive X-ray spectroscopy (EDX). In some embodiments, the metal oxides have a particle size distribution in the range of from 0.5 µm to 250 µm. 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. 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 10 mL water per gram of catalyst. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a PXRD pattern of example 2E. Figure 2 is a PXRD pattern of example 3E. Figure 3 is a PXRD pattern of example 4E. Figure 4 is an overlay of PXRD patterns of examples 5E-7E. Figure 5 is an overlay of PXRD patterns of examples 8E-10E. Figure 6 is a PXRD pattern of example 12E. Figure 7 is a PXRD pattern of example 12E-Pelleted. Figure 8 shows scanning electron microscopy (SEM) images of example 3E. Figure 9 shows SEM images of example 4E. Figure 10 shows SEM images of example 5E. Figure 11 shows SEM images of example 6E. Figure 12 shows SEM images of example 7E. Figure 13 shows SEM images of example 9E. Figure 14 shows SEM images of example 11E. Figure 15 is a plot of ethane conversion for calcined catalyst examples 3E and 8E-10E. Figure 16 is a plot of the selectivity of ethylene and acetic acid combined formation for calcined catalyst examples 3E and 8E-10E. Figure 17 is a plot of ethane conversion for calcined catalyst examples 5E and 11E. Figure 18 is a plot of the selectivity of ethylene and acetic acid combined formation for calcined catalyst examples 5E and 11E. DESCRIPTION OF EMBODIMENTS 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 to limit the claims. 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. In the method, catalyst precursor powders are mixed, for example, by being ground together, and then used in a hydrothermal synthesis process to form the catalyst. Previous procedures used a significant amount of water in the hydrothermal synthesis process. However, use of a large amount of water in the synthesis can lead to the formation of a large amount of heavy metal contaminated waste. In addition to a simpler procedure, in embodiments of the catalyst synthesis described herein, lower amounts of water are used, significantly reducing the amount of heavy metal contaminated waste produced during synthesis. For example, the method provided herein can use approximately 30 times less water for the synthesis of the catalyst and approximately four times less water for washing compared to other procedures to form the catalyst using metal oxide precursors. Further, the methods provided herein do not require complex mixing or milling steps that have been reported in previous synthetic procedures for related MoVNbTe oxides. The methods provided herein offer significant cost savings and simplification over previously reported synthetic procedures. Provided herein is a method for preparing a catalyst including forming a slurry including metal oxides, a reducing agent, and water; and heating the slurry to form the catalyst. The metal oxides include an oxide of molybdenum; an oxide of vanadium; an oxide of tellurium or an oxide of antimony, or both; and an oxide of tantalum or an oxide of niobium, or both. In some embodiments, the oxide of molybdenum is MoO3. In some embodiments, the oxide of vanadium is V₂O₅. In some embodiments, the oxide of tellurium is TeO2. In some embodiments, the oxide of antimony is Sb2O5. In some embodiments, the oxide of tantalum is Ta₂O₅ ^xH₂O. In some embodiments, the oxide of niobium is Nb2O5 ^xH2O. As used herein, the term “catalyst” generally refers to the active catalyst 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. As used herein, the term “catalyst material” refers to a material that includes an active 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. The method for preparing a catalyst disclosed herein includes forming a slurry including metal oxides, a reducing agent, and 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), or a colloidal solution. A ratio of 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. 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. 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 mL water per gram of catalyst and 5 mL water per gram of catalyst, such as between 0.1 mL water per gram of catalyst and 4 mL water per gram of catalyst, between 0.1 mL water per gram of catalyst and 3 mL water per gram of catalyst, between 0.1 mL water per gram of catalyst and 2 mL water per gram of catalyst, between 0.1 mL water per gram of catalyst and 1 mL water per gram of catalyst, or between 0.1 mL water per gram of catalyst and 0.5 mL water per gram of 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. 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 and 0.5 mL water per gram of catalyst. 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, 0.2 mL water per gram of catalyst, 0.3 mL water per gram of catalyst, 0.4 mL water per gram of catalyst, 0.5 mL water per gram of catalyst, 0.6 mL water per gram of catalyst, 0.7 mL water per gram of catalyst, 0.8 mL water per gram of catalyst, 0.9 mL water per gram of catalyst, 1 mL water per gram of catalyst, 2 mL water per gram of catalyst, 3 mL water per gram of catalyst, 4 mL water per gram of catalyst, or 5 mL water per gram of catalyst. 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. 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; an oxide of tellurium or an oxide of antimony, or both; and an oxide of tantalum or an oxide of niobium, or both. In embodiments where the reducing agent is a metal oxide, the total mass of metal oxides used in the slurry does not include the mass of the metal oxide being used as the reducing agent. In some embodiments, the slurry has a ratio of water to metal oxides between 0.2 mL water per gram of metal oxides and 0.6 mL water per gram of metal oxides, such as between 0.3 mL water per gram of metal oxides and 0.5 mL water per gram of metal oxides, or between 0.3 mL water per gram of metal oxides and 0.4 mL water per gram of metal oxides, or between 0.4 mL water per gram of metal oxides and 0.45 mL water per gram of metal oxides. In some embodiments, the slurry has a ratio of water to metal oxides between 0.40 mL water per gram of metal oxides and 0.43 mL water per gram of metal oxides. In some embodiments, the slurry has a ratio of water to metal oxides of 0.1 mL water per gram of metal oxides, 0.2 mL water per gram of metal oxides, 0.3 mL water per gram of metal oxides, 0.4 mL water per gram of metal oxides, 0.5 mL water per gram of metal oxides, 0.6 mL water per gram of metal oxides, 0.7 mL water per gram of metal oxides, 0.8 mL water per gram of metal oxides, 0.9 mL water per gram of metal oxides, 1 mL water per gram of metal oxides, 2 mL water per gram of metal oxides, 3 mL water per gram of metal oxides, 4 mL water per gram of metal oxides, or 5 mL water per gram of metal oxides. In some embodiments, the slurry has a ratio of water to metal oxides of 0.30 mL water per gram of metal oxides, 0.31 mL water per gram of metal oxides, 0.32 mL water per gram of metal oxides, 0.33 mL water per gram of metal oxides, 0.34 mL water per gram of metal oxides, 0.35 mL water per gram of metal oxides, 0.36 mL water per gram of metal oxides, 0.37 mL water per gram of metal oxides, 0.38 mL water per gram of metal oxides, 0.39 mL water per gram of metal oxides, 0.40 mL water per gram of metal oxides, 0.41 mL water per gram of metal oxides, 0.42 mL water per gram of metal oxides, 0.43 mL water per gram of metal oxides, 0.44 mL water per gram of metal oxides, or 0.45 mL water per gram of metal oxides. 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, the slurry has a ratio of reducing agent used in the slurry to metal oxides used in the slurry is between 0.01 g of reducing agent and 1.0 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 be the mass of one reducing agent, the mass of no more than one reducing agent, or the combined mass of two or more reducing agents. The term “metal oxides used 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; an oxide of tellurium or an oxide of antimony, or both; and an oxide of tantalum or an oxide of niobium, or both. In embodiments where the reducing agent is a metal oxide, the total mass of metal oxides used in the slurry does not include the mass of the metal oxide being used as the reducing agent. In some embodiments, the ratio of reducing agent used in the slurry to metal oxides used in the slurry is between 0.1 g of reducing agent 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 and 0.25 g of reducing agent per gram of metal oxides. In a non-limiting example, the reducing agent is oxalic acid, the amount of oxalic acid used in the slurry is between 0.15 g and 0.25 g, and the amount of metal oxides used in the slurry is between 6 g and 8 g. In another non-limiting example, the amount of oxalic acid used in the slurry is between 3.5 g and 7 g and the amount of metal oxides used in the slurry are between 20 g and 35 g. Any suitable reducing agent may be included in the slurry. 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 in the slurry. Suitable reducing agents to facilitate the reaction include reducing agents that are prone to decomposition or oxidation during the reaction process. In some embodiments, the reducing agent includes an alcohol, a carboxylic acid, an ester, or a metal oxide. In some embodiments, the reducing agent includes an alcohol, a carboxylic acid, or an ester. Suitable examples of alcohol reducing agents include but are not limited to ethanol, methanol, reducing sugars, and polyols such as glycol and glycerol. Suitable examples of carboxylic acid reducing agents include but are not limited to oxalic acid, formic acid, acetic acid, and citric acid. Suitable examples of ester reducing agents include but are not limited to ethyl acetate, dimethyl carbonate, dimethyl oxalate, and diethyl oxalate. Suitable metal oxides include vanadium (IV) oxide. In some embodiments, the reducing agent is oxalic acid or ethanol. In some embodiments, the reducing agent is oxalic acid. In some embodiments, the reducing agent is ethanol. The slurry can include one reducing agent, or two or more reducing agents. In some embodiments, the slurry includes one or more reducing agent. In some embodiments, the slurry includes no more than one reducing agent. 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. The method disclosed herein can further include a process for controlled size modification of the metal oxides. For example, grinding, wet milling, dry milling, or crushing the metal oxides. The controlled size modification process may reduce the size of the metal oxides, which can improve their reactivity, or may allow for agglomeration of the metal oxides, 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). In some embodiments, the metal oxides have a particle size of less than 1 mm, such as less than 60 mesh (less than 250 µm). For example, the metal oxides may have a particle size in the range of from 0.5 µm to 250 µm, or from 1 µm to 200 µm, or from 1 µm to 150 µm, or from 1 µm to 100 µm, or from 1 µm to 50 µm, or from 10 µm to 200 µm, or from 10 µm to 150 µm, or from 10 µm to 100 µm, or from 10 µm to 50 µm, or from 50 µm to 200 µm, or from 50 µm to 150 µm, or from 50 µm to 100 µm. In some embodiments, the method further includes a process for controlled size modification of the metal oxides and the reducing agent. For example, grinding, wet milling, dry milling, or crushing the metal oxides and the reducing agent. In some embodiments, the slurry is essentially free of a strong acid. The skilled person will understand 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. In some embodiments, the slurry comprises a tellurium compound. 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. 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. 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 (PFTE) high-pressure tank. In some embodiments, the hydrothermal synthesis vessel is an autoclave. 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 of between 15°C to 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. 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. 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 some embodiments, the method further comprises washing the catalyst with water. For example, the catalyst may be washed with water until the filtrate is colorless. In some embodiments, the method further comprises 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 room temperature for a suitable time or in an oven overnight at, for example, a temperature of 90°C. 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 can be 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. In some embodiments, the ratio of the water in the slurry to amount of calcined catalyst is between 0.1 mL water per gram of calcined catalyst and 10 mL water per gram of calcined catalyst, such as between 0.1 mL water per gram of calcined catalyst and 5 mL water per gram of calcined catalyst, between 0.1 mL water per gram of calcined catalyst and 4 mL water per gram of calcined catalyst, between 0.1 mL water per gram of calcined catalyst and 3 mL water per gram of calcined catalyst, between 0.1 mL water per gram of calcined catalyst and 2 mL water per gram of calcined catalyst, or between 0.1 mL water per gram of calcined catalyst and 1 mL water per gram of calcined catalyst. The phrase “amount of calcined catalyst” as used herein refers to the mass of the catalyst after all the catalyst obtained from catalyst synthesis has undergone calcination, such as the calcination described herein. In a non-limiting example, the ratio of the water in the slurry to amount of calcined catalyst may be between 0.3 mL water per gram of calcined catalyst and 0.8 mL water per gram of calcined catalyst, between 0.4 mL water per gram of calcined catalyst and 0.6 mL water per gram of calcined catalyst, or 0.5 mL water per gram of calcined catalyst. In some embodiments, the ratio of water in the slurry to amount of calcined catalyst is 0.1 mL water per gram of calcined catalyst, 0.2 mL water per gram of calcined catalyst 0.3 mL water per gram of calcined catalyst, 0.4 mL water per gram of calcined catalyst, 0.5 mL water per gram of calcined catalyst, 0.6 mL water per gram of calcined catalyst, 0.7 mL water per gram of calcined catalyst, 0.8 mL water per gram of calcined catalyst, 0.9 mL water per gram of calcined catalyst, 1 mL water per gram of calcined catalyst, 2 mL water per gram of calcined catalyst, 3 mL water per gram of calcined catalyst, 4 mL water per gram of calcined catalyst, or 5 mL water per gram of calcined catalyst. In some embodiments, the ratio of water in the slurry to amount of calcined catalyst formed is 0.45 mL water per gram of calcined catalyst, 0.46 mL water per gram of calcined catalyst, 0.47 mL water per gram of calcined catalyst, 0.48 mL water per gram of calcined catalyst, 0.49 mL water per gram of calcined catalyst, 0.50 mL water per gram of calcined catalyst, 0.51 mL water per gram of calcined catalyst, 0.52 mL water per gram of calcined catalyst, 0.53 mL water per gram of calcined catalyst, 0.54 mL water per gram of calcined catalyst, 0.55 mL water per gram of calcined catalyst, 0.56 mL water per gram of calcined catalyst, or 0.57 mL water per gram of calcined catalyst, 0.58 mL water per gram of calcined catalyst, 0.59 mL water per gram of calcined catalyst, 0.60 mL water per gram of calcined catalyst, 0.61 mL water per gram of calcined catalyst, 0.62 mL water per gram of calcined catalyst, or 0.63 mL water per gram of calcined catalyst, 0.64 mL water per gram of calcined catalyst, or 0.65 mL water per gram of calcined catalyst. In some embodiments, a ratio of a total amount of water used to prepare the catalyst is between 0.1 mL water per gram of catalyst and 60 mL 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 mL water per gram of catalyst and 25 mL 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 mL water per gram of catalyst and 20 mL water per gram of catalyst, 0.5 mL water per gram of catalyst and 15 mL water per gram of catalyst, 1 mL water per gram of catalyst and 10 mL water per gram of catalyst, 5 mL water per gram of catalyst and 10 mL water per gram of catalyst, between 0.1 mL water per gram of catalyst and 5 mL water per gram of catalyst, or between 0.1 mL water per gram of catalyst and 1 mL 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 mL water per gram of catalyst and 10 mL water per gram of catalyst. In some embodiments, the methods disclosed herein may further comprise combining the calcined catalyst with one or more of a solid support, carrier, binder, and lubricant to provide a catalyst material. In some embodiments, the catalyst material is prepared from 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 catalyst support or carrier is at least one of precipitated synthetic silica, fumed synthetic silica, silica-alumina, α-alumina, and anatase titania. In some embodiments, the catalyst support or carrier is precipitated synthetic silica. In some embodiments, the catalyst support or carrier is α-alumina. In some embodiments, binder is used to aid in forming the catalyst material. In some embodiments, catalyst material formation includes 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. In some embodiments, the step of preparing a catalyst material 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 between 50°C and100°C. In some embodiments, the method includes forming the catalyst material into a formed catalyst material such as, for example, a pelleted catalyst material. The catalysts prepared from the methods disclosed herein include molybdenum (Mo); vanadium (V); tellurium (Te) or antimony (Sb), or both; tantalum (Ta) or niobium (Nb), or both; and oxygen (O). In some embodiments, the catalyst has a formula selected from MoaVbTecTadOx, MoaVbSbcTadOx, MoaVbTecNbdOx, and MoaVbSbcNbdOx. The values of a, b, c, and d may refer to the values based on the amount (molar equivalents) of each metal oxide added to the slurry, or may refer to 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). The catalyst formula with respect to the ratios of values a, b, c, and d may be selected in order to affect the activity, selectivity, purity, and stability of the catalyst. In some embodiments, the value of d is minimized to lower costs while maintaining good catalyst performance. In some embodiments, a is 1.0. In some embodiments, b is 0.01 to 0.4. In some embodiments, b is 0.2 to 0.4. In some embodiments, b is 0.01 to 0.3. In some embodiments, b is 0.1 to 0.3. In some embodiments, b is 0.30 to 0.35. In some embodiments, b is 0.30 to 0.32. In some embodiments, b is 0.31. In some embodiments, c is 0.01 to 0.2. In some embodiments, c is 0.01 to 0.1. In some embodiments, c is 0.01 to 0.09. In some embodiments, c is 0.01 to 0.07. In some embodiments, c is 0.03 to 0.07. In some embodiments, c is 0.04 to 0.05. In some embodiments, c is 0.05. In some embodiments, d is 0.01 to 0.10. In some embodiments, d is 0.01 to 0.06. In some embodiments, d is 0.01 to 0.05. In some embodiments, d is 0.02 to 0.05. In some embodiments, d is 0.03 to 0.05. In some embodiments, d is 0.05. In each catalyst formulation according to the present disclosure, oxygen is present in sufficient amounts to render the catalyst electrically neutral. The skilled person will appreciate that oxygen-containing species may also be adsorbed or trapped by the catalyst. In some embodiments, the catalyst prepared by the methods disclosed herein has a formula Mo_aV_bTe_cTa_dO_x, wherein the values of a, b, c, and d are as described herein. In some embodiments, the catalyst prepared by the methods disclosed herein has a formula Mo_aV_bSb_cTa_dO_x, wherein the values of a, b, c, and d are as described herein. In some embodiments, the catalyst prepared by the methods disclosed herein has a formula Mo_aV_bTe_cNb_dO_x, wherein the values of a, b, c, and d are as described herein. In some embodiments, the catalyst prepared by the methods disclosed herein has a formula Mo_aV_bSb_cNb_dO_x, wherein the values of a, b, c, and d are as described herein. In some embodiments, the values of a, b, c, and d are determined by elemental analysis, such as EDX. In some embodiments, b is 0.31 to 0.34, c is 0.05 to 0.06, and d is 0.01 to 0.03, wherein the values of a, b, c, and d are determined by EDX. In some embodiments, the catalyst prepared by the methods disclosed herein has a formula selected from Mo₁V_0.32Te_0.05Ta_0.02O_x, Mo₁V_0.32Sb_0.05Ta_0.02O_x, Mo₁V_0.31Te_0.04Nb_0.02O_x, Mo1V0.30Sb0.05Nb0.02Ox, Mo1V0.34Te0.05Ta0.02, Mo1V0.34Te0.06Ta0.02, Mo1V0.34Sb0.06Ta0.02, Mo₁V_0.34Te_0.05Nb_0.01, Mo₁V_0.32Sb_0.06Nb_0.02, Mo₁V_0.34Te_0.05Ta_0.02, and Mo₁V_0.34Sb_0.05Ta_0.03, wherein each formula is determined by energy-dispersive X-ray spectroscopy (EDX). In some embodiments, the catalyst prepared by the method disclosed herein has a formula selected from Mo1V0.34Te0.05Ta0.02, Mo1V0.34Te0.06Ta0.02, Mo1V0.34Sb0.06Ta0.02, Mo₁V_0.34Te_0.05Nb_0.01, Mo₁V_0.32Sb_0.06Nb_0.02, and Mo₁V_0.34Sb_0.05Ta_0.03, wherein each formula is determined by EDX. In some embodiments, the catalyst prepared by the methods disclosed herein has the formula Mo1V0.32Ta0.02Te0.05, wherein the formula is determined by EDX. In some embodiments, the catalyst prepared by the methods disclosed herein has the formula Mo1V0.32Ta0.02Sb0.05, wherein the formula is determined by EDX. In some embodiments, the catalyst prepared by the methods disclosed herein has the formula Mo₁V_0.31Nb_0.02Te_0.04, wherein the formula is determined by EDX. In some embodiments, the catalyst has the formula Mo1V0.30Nb0.02Sb0.05, wherein the formula is determined by EDX. In some embodiments, the values of a, b, c, and d are determined based on the amount of each metal oxide added to the slurry. In some embodiments, the catalyst prepared by the methods disclosed herein has a formula selected from Mo₁V_0.31Te_0.5Ta_0.5O_x, Mo1V0.31Sb0.5Ta0.5Ox, Mo1V0.31Te0.5Nb0.5Ox, and Mo1V0.31Sb0.5Nb0.5Ox, wherein each formula is determined based on the amount of each metal oxide added to the slurry. In some embodiments, the catalyst prepared by the methods disclosed herein has the formula Mo₁V_0.31Te_0.05Ta_0.05O_x, wherein the formula is determined based on the amount of each metal oxide added to the slurry. In some embodiments, the catalyst prepared by the methods disclosed herein has the formula Mo₁V_0.31Ta_0.05Sb_0.05O_x, wherein the formula is determined based on the amount of each metal oxide added to the slurry. In some embodiments, the catalyst prepared by the methods disclosed herein has the formula Mo₁V_0.31Nb_0.05Te_0.05O_x, wherein the formula is determined based on the amount of each metal oxide added to the slurry. In some embodiments, the catalyst prepared by the methods disclosed herein has the formula Mo1V0.31Nb0.05Sb0.05Ox, wherein the formula is determined based on the amount of each metal oxide added to the slurry. In some embodiments of the methods disclosed herein, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of tellurium, and an oxide of tantalum. In some embodiments, the metal oxides include MoO3, V2O5, TeO2, and Ta2O5 ^xH2O. In some embodiments, the slurry includes MoO3, V2O5, TeO2, and Ta₂O₅ ^xH₂O in a mass ratio of MoO₃:V₂O₅:TeO₂:Ta₂O₅ ^xH₂O of 1g MoO₃ : 0.1 to 0.3 g V2O5 : 0.01 g to 0.10 g TeO2 : 0.01 g to 0.10 g Ta2O5 ^xH2O. This mass ratio can be used at any suitable reaction scale. For example, the slurry may include from 4 to 6 g MoO₃, from 0.5 g to 1.5 g V2O5, from 0.1 g to 0.5 g TeO2, and from 0.2 g to 0.6 g Ta2O5 ^xH2O. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of antimony, and an oxide of tantalum. In some embodiments, the metal oxides include MoO₃, V₂O_5, Sb₂O₅, and Ta₂O₅ ^xH₂O. In some embodiments, the slurry includes MoO3, V2O5, Sb2O5, and Ta2O5 ^xH2O in a mass ratio of MoO3:V2O5: Sb₂O₅:Ta₂O₅ ^xH₂O of 1g MoO₃ : 0.1 to 0.3 g V₂O₅ : 0.01 g to 0.10 g Sb₂O₅ : 0.01 g to 0.10 g Ta2O5 ^xH2O. This mass ratio can be used at any suitable reaction scale. For example, the slurry may include from 4 to 6 g MoO₃, from 0.5 g to 1.5 g V₂O₅, from 0.1 g to 0.5 g Sb₂O₅, and from 0.2 g to 0.6 g Ta2O5 ^xH2O. In another non-limiting example, the slurry includes from 15 to 17 g MoO₃, from 2 g to 4 g V₂O₅, from 0.5 g to 1.5 g Sb₂O₅, and from 1 g to 3 g Ta2O5 ^xH2O. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of tellurium, and an oxide of niobium. In some embodiments, the metal oxides include MoO3, V2O5, TeO2, and Nb2O5 ^xH2O. In some embodiments, the slurry includes MoO₃, V₂O₅, TeO_2, and Nb₂O₅ ^xH₂O in a mass ratio of MoO3:V2O5:TeO2:Nb2O5 ^xH2O of 1g MoO3 : 0.1 to 0.3 g V2O5 : 0.01 g to 0.10 g TeO2 : 0.01 g to 0.10 g Ta₂O₅ ^xH₂O. This mass ratio can be used at any suitable reaction scale. For example, the slurry may include from 4 to 6 g MoO3, from 0.5 g to 1.5 g V2O5, from 0.1 g to 0.5 g TeO₂, and from 0.1 g to 0.4 g Nb₂O₅ ^xH₂O. In another non-limiting example, the slurry includes from 26 to 28 g MoO3, from 4 g to 6 g V2O5, from 1 g to 3 g TeO2, and from 1 g to 3 g Nb₂O₅ ^xH₂O. In some embodiments, the metal oxides include an oxide of molybdenum, an oxide of vanadium, an oxide of antimony, and an oxide of niobium. In some embodiments, the metal oxides include MoO3, V2O5, Sb2O5, and Nb2O5 ^xH2O. In some embodiments, the slurry includes MoO₃, V₂O₅, Sb₂O₅, and Nb₂O₅ ^xH₂O in a mass ratio of MoO₃:V₂O₅: Sb2O5:Nb2O5 ^xH2O of 1g MoO3 : 0.1 to 0.3 g V2O5 : 0.01 g to 0.10 g Sb2O5 : 0.01 g to 0.10 g Nb₂O₅ ^xH₂O. This mass ratio can be used at any suitable reaction scale. For example, the slurry may include from 4 to 6 g MoO3, from 0.5 g to 1.5 g V2O5, from 0.1 g to 0.5 g Sb2O5, and from 0.1 g to 0.4 g Nb₂O₅ ^xH₂O. The catalysts prepared by the methods disclosed herein may be suitable as catalysts in oxidative dehydrogenation reactions. As used herein, the term “oxidative dehydrogenation” or “ODH” refers to processes that couple the endothermic dehydrogenation of an alkane (C_nH_2n+2) with the strongly exothermic oxidation of hydrogen as is further described herein to form, amongst other things, alpha-olefins. In some embodiments, alkane refers to one or more of ethane, propane, butane, pentane, hexane, octane, decane, and dodecane. In particular embodiments, alkane refers to ethane and propane and, in some embodiments, ethane. For testing catalysts, the ODH reactions herein are assumed to be referring to the ODH of ethane. Conversion of the ethane feed gas to products by the ODH process is calculated as a volume flow rate change of ethane in the product compared to feed ethane volume flow rate using the following formula: 2^{∗ ^^ா ^ ^^ ^ ^^ ^ 2 ∗ ^^} ^{^^ ൌ} _^ ^{௧^௬^^^^ ^ைଶ ^ை ^^^௧^^ ^^^ௗ} 2_{∗ ^ 2 ∗ ^ ^ ^ 2 ∗ ^^ ^} ^{∗ 100% ^^ ^^.1} 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: 2^{∗ ^^} ^{^^ ா௧^௬^^^^} ா_௧^௬^^^^ ^{ൌ ^ ∗ 100% Eq.2} In 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. 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, described later herein) 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. 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. 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” 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. 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. EXAMPLES Preparation of Comparative Sample 1C Synthesis of ammonium molybdate tellurate hydrate Ammonium molybdate tellurate hydrate ((NH4)6Mo6TeO24 ^7H2O), was first prepared. Ammonium molybdate hydrate ((NH₄)₆Mo₇O₂₄ ^4H₂O; 530 g) was added to 2400 mL of distilled water at 80°C while stirring to get a solution of pH 5.22. Separately, telluric acid (Te(OH)₆; 115 g) was dissolved in 800 mL of distilled water at 60°C. The telluric acid solution was then added to the molybdate solution dropwise with an addition funnel at 63°C over 10 minutes to produce a solution of pH 2.4. Ammonium hydroxide (28 wt.% in water) was then added in small portions until the pH of the solution reached 7.5 (235 mL was used). The solution was left to stir at temperature in open air until the water had evaporated, leaving a colorless solid, which was subsequently dried in an oven overnight at 90°C. A final mass of 517 g of crystalline solid was obtained. Synthesis of Comparative Sample 1C To prepare the comparative sample 1C, ammonium molybdate tellurate hydrate (59.1633 g) was dissolved in 750 mL of distilled water pre-heated to 60°C while stirring. Separately, vanadyl sulfate hydrate (VOSO4 ^3.46H2O; 39.4405 g) was dissolved in 240 mL of distilled water pre-heated to 60°C while stirring. The vanadyl sulfate solution was then added to the molybdate solution dropwise at 60°C while stirring over 12 minutes to produce a black solution. To the black molybdate solution at 60°C, 117.6 mL of a solution of tantalum oxalate (0.400 mol/L Ta⁵⁺) pre-heated to 60°C was added dropwise over 11 minutes to produce an olive-green slurry after 1 hour of stirring at 60°C. The resulting solution was cloudy with a fine precipitate. This mixture was then added to a glass lined steel autoclave at 60°C, then sealed, purged with nitrogen ten times, then left under 20 psi nitrogen. The autoclave was then heated to 166°C for 48 hours. After cooling to room temperature, the reactor was vented, then the solution was vacuum filtered and washed with distilled water to obtain a purple-black solid. The solid was subsequently dried in an oven at 90°C for overnight to obtain 60.30 g of dry powdered solid. A portion of this solid was then calcined in a furnace under nitrogen flow with 6 hours heating to 600°C, held at 600°C for 2 hours, then the furnace was turned off and the sample cooled back to ambient conditions over approximately 6 hours. A 9.3% mass loss was observed from calcination. Total water used for synthesis (not including wash solvent) was 1500.7 mL to obtain 54.45 g of calcined catalyst, or 27.6 mL water per gram of catalyst. This includes the water required to prepare the initial ammonium molybdate tellurate hydrate sample as well. Preparation of Examples 2E-4E Reagents Molybdenum(VI) oxide (MoO₃), vanadium(V) oxide (V₂O₅), tellurium dioxide (TeO2), oxalic acid dihydrate, polyethylene glycol 1000, MOWIOL^® 8-88, and poly(acrylic acid) were purchased from Sigma Aldrich. The tantalum pentoxide hydrate (Ta₂O₅ ^xH₂O) was purchased from BassTech International. The x in Ta2O5 ^xH2O was 2.57 as measured by thermogravimetric analysis. The niobium pentoxide hydrate (Nb₂O₅ ^xH₂O) was purchased from Companhia Brasileira de Metalurgia e Mineração. The x in Nb2O5 ^xH2O was 4.57 as measured by thermogravimetric analysis. Alpha alumina was purchased from Fisher Scientific Canada. All reagents were used as is without any further purification. Water was distilled, deionized water. Preparation of Catalysts Three separate examples, examples 2E, 3E and 4E, were prepared with solid reagents listed in Table 1. For each example, the solid reagents were mixed and lightly ground using a mortar and pestle, mainly to pulverize the larger oxalic acid dihydrate crystals to better disperse with the other solids. The solid mixtures were then transferred into individual 8 mL glass vials, after which 2 mL 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 1 mL of water was then used to rinse sample stuck to the stir rod back into the vial. Table 1. Amounts of Reagents Used to Prepare Slurry for Examples 2E-4E. 2E 3E 4E MoO₃ 5.3894 g 5.3707 g 5.4070 g V2O5 1.0339 g 1.0310 g 1.0535 g TeO2 0.3017 g 0.3033 g 0.3014 g Ta2O5 ^xH2O 0.4197 g 0.4192 g 0.4313 g Oxalic acid dihydrate 1.0134 g 1.3167 g 1.7023 g Distilled water 3 mL 3 mL 3 mL The vials were then placed together in a glass lined steel autoclave, along with a blank reference vial filled with water, and water was filled around the vials to the level of the solids to help with heat transfer and to maintain a humid atmosphere in the vessel. The autoclave was a 300 mL PARR reactor, available from Parr Instrument Company of Moline, IL, USA (Head of assembly serial number: 453HC T31609190224820B; Body of assembly serial number: 452HC T31609190224820A). The autoclave was 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 to 4 hours. After the reaction, the samples were deep purple hard solid samples that had increased in volume by approximately 1.5x. The samples were scraped from the vials onto filter paper in a vacuum filtration set-up and were washed with approximately 50 mL of distilled water, with the filtrate being a clear faintly blue color for sample 2E and a deep blue for samples 3E and 4E. The sample was washed until the filtrate from the sample was colorless, then were left to dry on the filter paper to obtain shiny purple-black powdered solid. The solids were then calcined in a tubular autoclave under N2 flow (linear velocity at standard temperature and pressure (STP) of 3.9 cm/min, 0.25 ppm (vol.) of residual oxygen) for 12 hours at 60°C, after which they were 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. After calcination, the samples were all deep purple-black powders. The mass of the solid samples before and after calcining is shown in Table 2. Table 2. Mass of Examples Before and After Reaction Steps. 2E 3E 4E Total mass of oxides prior to heating 7.1447 g 7.1242 g 7.1932 g Mass after drying on filter paper 6.5546 g 8.0241 g 7.8111 g Mass after calcination 5.7883 g 5.9457 g 5.9703 For example 3E, the total water used for synthesis, not including wash solvent, was 3 mL to obtain 5.9457 g of calcined catalyst, or 0.505 mL water per gram of calcined catalyst, which represents a 54.6x decrease in solvent needed versus the comparative sample 1C. Preparation of Examples 5E-7E Three separate examples, examples 5E, 6E and 7E, were prepared with the reagents listed in Table 3. For example 5E, the procedure for example 4E was repeated with a molar equivalent of Sb₂O₅ (based on moles of Sb) replacing the TeO₂ in the reaction. For example 6E, the procedure for example 4E was repeated with a molar equivalent of Nb2O5 ^xH2O replacing the Ta₂O₅ ^xH₂O in the reaction. For example 7E, the procedure for example 4E was repeated with a molar equivalent of Sb2O5 (based on moles of Sb) replacing the TeO2 in the reaction, and a molar equivalent of Nb2O5 ^xH2O replacing the Ta2O5 ^xH2O in the reaction. Table 3 also includes the mass of each sample after the drying step and after the calcining step.

Table 3. Amounts of Reagents Used to Prepare Slurry for Examples 5E-7E and Mass of Samples After Reaction Steps. 5E 6E 7E MoO3 (g) 5.393 5.3770 5.3755 V₂O₅ (g) 1.0461 1.0510 1.0403 TeO2 (g) - 0.3015 - Nb2O5 ^xH2O (x = 4.6) (g) - 0.2554 0.2589 Ta₂O₅ ^xH₂O (x = 2.6) (g) 0.4241 - - Sb2O5 (g) 0.3051 - 0.3057 Oxalic acid dihydrate (g) 1.7 1.7 1.7 Distilled water 3 mL 3 mL 3 mL Mass after drying (g) 5.5375 5.1615 6.1465 Mass after calcination (g) 5.2517 4.8556 5.7577 Preparation of Examples 8E-10E The procedure for examples 2E-4E was repeated with modified heating conditions. For each sample 8E-10E, the autoclave was sealed and placed in an oven to heat from room temperature to 180°C over 2 hours, held at 180°C for 48 hours, then turned off to passively cool. The amounts of reagents for example 8E were the same as for example 2E. The amounts of reagents for example 9E were the same as for example 3E. The amounts of reagents for sample 10E were the same as for example 4E. Preparation of Example 11E The procedure for example 5E was repeated with scaled up amounts of reagents as shown in Table 4. Table 4. Amounts of Reagents Used to Prepare Slurry for Example 11E and Mass of Samples After Reaction Steps. 11E MoO3 (g) 16.1783 V₂O₅ (g) 3.0850 Ta2O5 ^xH2O (x = 2.6) (g) 1.2516 Sb₂O₅ (g) 0.9087 Oxalic acid dehydrate (g) 3.9 Distilled water (mL) 6.5 Mass after drying (g) 19.8417 A modified heating profile was used. The autoclave was sealed and placed in an oven to heat from room temperature to 180°C over 24 hours, held at 180°C for 60 hours, then turned off to cool back to ambient temperature passively. A portion of the sample was calcined (8.0872 g before calcination, 7.5789 g after calcination). Preparation of Example 12E Example 12E was synthesized following a similar procedure described for samples 2E-4E, with amounts of reagents used listed in the Table 5. Table 5. Amounts of Reagents Used to Prepare Slurry for Example 12E and Mass of Samples After Reaction Steps. MoO3 (g) 27.0689 V2O5 (g) 5.1234 Nb₂O₅ ^xH₂O (x = 4.6) (g) 1.3117 TeO2 (g) 1.5534 Oxalic acid dehydrate (g) 6.4894 Distilled water (mL) 12 Mass after drying (g) 32.2259 All solid components were added to a blender and mixed for 1 minute pulses three times to pulverize and blend the solids. The solid mixture was then transferred to a 40 mL vial. Water was added and the mixture was stirred to form an orange slurry. The vial was then placed into a 2 L steel autoclave with water filled around the outside of the vial to improve heat transfer and maintain 100% relative humidity inside the vessel. The autoclave was sealed and placed in an oven to heat from room temperature to 180°C over 12 hours. The temperature was then held at 180°C for 48 hours, after which heating was stopped and the vessel was cooled to room temperature passively over approximately 6 hours. After cooling, the autoclave was vented and the vial was removed. The orange slurry became a deep purple solid over the course of the reaction. The solid was pulverized and transferred onto a vacuum filtration setup, then was washed with water until the filtrate ran clear and colorless. The deep purple solid was then placed in an oven to dry overnight at 90°C. After drying, 32.2259 g of purple solid was obtained. The solid sample was then calcined under N₂ flow (3.9 cm/min linear velocity at STP) in a tubular quartz furnace. The solid was heated to 600°C at a rate of 1.6°C/min. The temperature was held at 600°C for 2 hours, after which heating was stopped and the solid was cooled passively to room temperature under N2 flow for approximately 12 hours. After calcination, a 2.45% mass loss was observed. The PXRD pattern for the sample after calcination is shown in Figure 6. Preparation of Pelleted Catalyst Example 12E-Pelleted A portion of the calcined sample of 12E was used to prepare pelleted catalyst with inert carrier. Catalyst Sample 12E (10.0050 g), alpha alumina (10.0207 g), polyethylene glycol 1000 (0.3986 g), MOWIOL 8-88 (0.6095 g), and poly(acrylic acid) (0.0230 g) were added to a 1 L beaker with 100 mL of water. The mixture was heated to 90°C using an oil bath and was stirred with an overhead stirrer. Heating continued until most of the water had evaporated, leaving a thick purple paste. The beaker was then transferred to an oven at 90°C to dry completely overnight, leaving a hard purple solid. The solid was pulverized using a mortar and pestle, and sieved to obtain granules between 180 – 500 µm in diameter. The granules were fed into an autopress (Dott Bonapace CPR-6) and pressed into cylindrical pellets with approximate dimensions of 3 mm diameter and 5 mm length. The pellets were sintered in a tubular quartz furnace by first heating under dry air flow (1.8 cm/min linear velocity at STP) to 400°C at 1.0°C/min, the temperature was held at 400°C for 1 hour, then the temperature was cooled to room temperature passively over approximately 8 hours. The flow in the quartz furnace was then switched to nitrogen (3.9 cm/min linear velocity at STP), and after sufficient time was given to completely purge the air out of the furnace, the sample was heated from room temperature to 600°C at 1.6°C/min, held at 600°C for 2 hours, then allowed to passively cool to room temperature over approximately 12 hours. A mass loss of 5.24% was observed after the sintering process. The PXRD pattern of sample 12E-Pelleted is shown in Figure 7. Instruments and Measurements Elemental Analysis Catalyst metal compositions were determined by energy dispersive X-ray spectroscopy (EDX) for calcined samples 3E-7E, 9E, and 11E. EDX was conducted using a JEOL JED-2300 DRY SDD EDX detector. The EDX scan was conducted on the largest rectangular area that was covered by the sample (approximately 2.8 mm x 2.1 mm, typically at ~50x magnification but this can vary depending on sample size and coverage). The data analysis software was AnalysisStation provided by JEOL. The scan was conducted at 25kV accelerating voltage. The catalyst formulas determined by EDX are shown in Table 6 below. Table 6 Calcined Sample Catalyst Formula 3E Mo₁V_0.34Te_0.05Ta_0.02 4E Mo1V0.34Te0.06Ta0.02 5E Mo₁V_0.34Sb_0.06Ta_0.02 6E Mo1V0.34Te0.05Nb0.01 7E Mo1V0.32Sb0.06Nb0.02 9E Mo₁V_0.34Te_0.05Ta_0.02 11E Mo1V0.34Sb0.05Ta0.03 Powder X-ray Diffraction (PXRD) Power X-ray diffraction (PXRD) experiments were performed using a PANalytical Empyrean powder X-ray diffractometer equipped with a monochromated Cu Kα X-ray source. Data was acquired between 3 – 80° 2θ at a scan rate of 1°/min. Data was analyzed using PANalytical HighScore software Version 4.8. Powder X-ray diffraction (PXRD) analysis was conducted on the samples 2E-4E following calcination (Figures 2-4, respectively). By PXRD, all three samples were characterized as a doped molybdenum vanadium oxide phase known in academic literature as M1. Sample 2E was characterized with a minor impurity of MoO₃ (shown with arrows in Figure 1), while samples 3E (Figure 2) and 4E (Figure 3) are purely M1 phase. This analysis shows that the synthetic procedure produces a high crystalline purity of the catalytically active M1 phase. Figure 4 shows an overlay of the PXRD patterns for examples 5E-7E. The PXRD characterization of sample 5E shows that the TeO2 in this synthesis can be substituted with a molar equivalent of Sb₂O₅ (based on moles of Sb) while still producing highly pure M1 phase and active catalyst. The PXRD characterization of sample 6E shows that the Ta₂O₅ ^xH₂O in this reaction can be substituted with approximately a molar equivalent of Nb2O5 ^xH2O while still producing highly pure M1 phase. The PXRD characterization of sample 7E shows that both TeO₂ and Ta₂O₅ ^xH₂O can be substituted while still producing highly pure M1 phase. Figure 5 is an overlay of the PXRD patterns of samples 8E-10E, showing that shorter ramping/heating times also produce the M1 phase. Scanning Electron Microscopy Scanning Electron Microscopy (SEM) images were collected using a JEOL - JSM300 LV scanning electron microscope. Figures 8 to 14 show SEM images of samples 3E-7E, 9E, and 11E. Catalyst Testing 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 SWAGELOK^® 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 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. The samples were pressed into pellets using a steel die and hydraulic press, then the pellet was pulverized and particle sizes of 425 – 710 µm were sieved out for loading into the MRU. Approximately 2 g of sample was placed in the reactor. For 12E-pelleted, the pelleted samples were pulverized with a mortar and pestle and granules of 425 – 710 µm were sieved out for loading into the MRU. To achieve a loading of approximately 2 g of catalyst phase, approximately 4 g of the pulverized sample were 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. 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. The flow rate of the gas feed was adjusted to a target of 150 sccm (weight hour space velocity (WHSV) = 3.57 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. 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. 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 (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: 2^{∗ ^^ா௧^௬^^^^ ^ ^^ ^ ^^ ^ 2 ∗ ^^} ^{^^ ൌ} _^ ^{^ைଶ ^ை ^^^௧^^ ^^^ௗ} 2_{∗ ^^ ^ 2 ∗ ^ ^ ^ 2 ∗ ^} ^{∗ 100% ^^ ^^.1} 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. 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 (S_Ethylene) was determined using the following equation: 2^{∗ ^^} ^{^^ ா௧^௬^^^^} ா_௧^௬^^^^ ^{ൌ ^} ^_{^ ^} ^{∗ 100% Eq.2} 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. Therefore, selectivity is reported as combined ethylene and acetic acid selectivity. Summary of Catalyst Performance The results on the comparative sample 1C, and examples 3E, and 5E-11E are summarized in Table 7. Table 7 Catalyst Flow Ethane Combined Temperature Mass (g) (sccm) Conversion Ethylene and (°C) (%) Acetic Acid Selectivity (%) 1C 1.9996 152 26.1 94.1 400 3E 2.0146 153 57.2 86.8 390^a 5E 2.0668 157 46.9 87.9 400 6E 2.0155 152 50.2 86.3 375^a 7E 2.0153 153 46.1 83.6 390 8E 2.0239 154 40.1 87.4 400 9E 2.0345 155 44.5 86.9 400 10E 2.0045 155 44.1 82.3 400 11E 2.0063 153 35.9 95.4 390 ^aDue to high activity, samples 3E and 6E could not be heated to 400°C under these conditions without fully depleting the oxygen in the reaction. As one can see, samples 3E, 5E, and 8E-10E, as compared to sample 1C, demonstrate higher activity and a higher ethane conversion, and a slightly lower combined ethylene and acetic acid selectivity (Table 7). Sample 11E demonstrated improved activity and selectivity at lower temperature compared to Sample 1C. Further, at an approximately equivalent ethane conversion % to sample 1C, Sample 11E showed 96.6% combined ethylene and acetic acid selectivity at 370°C (at 25.4% ethane conversion). Accordingly, the synthesis method disclosed herein using significantly lower amounts of water can produce high quality, active catalysts. Figure 15 is a plot of the conversion of ethane for comparative catalyst 1C, and calcined samples 3E and 8E-10E. Figure 16 is a plot of the selectivity of combined ethylene and acetic acid formation for comparative catalyst 1C, and calcined samples 3E and 8E- 10E. Figure 17 is a plot of the conversion of ethane for comparative catalyst 1C, and calcined samples 5E and 11E. Figure 18 is a plot of the selectivity of combined ethylene and acetic acid formation for comparative catalyst 1C, and calcined samples 5E and 11E. As shown in Figures 15 and 17, samples 3E, 5E, 8E-10E, and 11E showed higher ethane conversion (%) at lower temperatures than comparative sample 1C. Catalyst performance of example 12E-pelleted is shown in Table 8. This data shows that formulated catalyst produced from the method disclosed herein is extremely active for ethane ODH with high selectivity to value added products (ethylene and acetic acid), even at high ethane conversion. Table 8 Catalyst Flow Ethane Combined Temperature Mass (g)^a (sccm) Conversion Ethylene and (°C) (%) Acetic Acid Selectivity (%) 12E-Pelleted 4.0056 152 40.3 96.0 350 12E-Pelleted 4.0056 152 55.7 94.0 370 12E-Pelleted 4.0056 152 62.8 92.9 380 12E-Pelleted 4.0056 457 49.1 93.7 407 ^aTotal catalyst pellet mass in the reactor was 4.0056. Pellets were 50 wt.% catalyst phase and 50 wt.% inert carrier material. Non-limiting embodiments of the present disclosure include the following: Embodiment A. A method for preparing a catalyst comprising: forming a slurry comprising metal oxides, a reducing agent, and water; and heating the slurry to form the catalyst; wherein the metal oxides comprise: an oxide of molybdenum; an oxide of vanadium; an oxide of tellurium or an oxide of antimony, or both; and an oxide of tantalum or an oxide of niobium, or both; and 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. Embodiment B. The method according to Embodiment A, 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. Embodiment C. The method according to Embodiment A or B, wherein the slurry has a ratio of water to metal oxides between 0.2 mL water per gram of metal oxides and 0.6 mL water per gram of metal oxides. Embodiment D. The method according to Embodiment A or B, wherein the slurry has a ratio of water to metal oxides between 0.3 mL water per gram of metal oxides and 0.5 mL water per gram of metal oxides. Embodiment E. The method according to Embodiment A, B, C, or D, wherein the oxide of molybdenum is MoO3. Embodiment F. The method according to Embodiment A, B, C, D, or E, wherein the oxide of vanadium is V2O5. Embodiment G. The method according to Embodiment A, B, C, D, E or F, wherein the oxide of tellurium, when present, is TeO2 and the oxide of antimony, when present, is Sb₂O₅. Embodiment H. The method according to Embodiment A, B, C, D, E, F, or G, wherein the oxide of tantalum, when present, is Ta₂O₅ ^xH₂O, and the oxide of niobium, when present, is Nb2O5 ^xH2O. Embodiment I. The method according Embodiment A, B, C, D, E, F, G, or H, further comprising grinding, wet milling, dry milling, or crushing the metal oxides. Embodiment J. The method according to Embodiment A, B, C, D, E, F, G, H, or I, further comprising grinding, wet milling, dry milling, or crushing the metal oxides and the reducing agent. Embodiment K. The method according to Embodiment A, B, C, D, E, F, G, H, I, or J, wherein the reducing agent comprises an alcohol, a carboxylic acid, or an ester. Embodiment L. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, or K, wherein the reducing agent is oxalic acid or ethanol. 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 oxalic acid. Embodiment N. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, or M, wherein the slurry comprises no more than one reducing agent. Embodiment O. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, or N 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. Embodiment P. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, N, or O, further comprising washing the catalyst with water. 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 calcining the catalyst to form a calcined catalyst. Embodiment R. The method according to Embodiment Q, 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. Embodiment S. The method according to Embodiment Q, or R, wherein a ratio of the water in the slurry to amount of calcined catalyst formed is less than 1 mL water per gram of calcined catalyst. Embodiment T. The method according to Embodiment A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, or S, wherein the catalyst comprises a formula selected from MoaVbTecTadOx, MoaVbSbcTadOx, MoaVbTecNbdOx, and MoaVbSbcNbdOx; wherein: a is 1.0; b is 0.01 to 0.4; c is 0.01 to 0.2; d is 0.01 to 0.10; and x is the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, and d are determined based on the amount of each metal oxide added to the slurry. Embodiment U. The method according to Embodiment T, wherein the values of a, b, c, and d are also determined by elemental analysis. Embodiment V. The method according to Embodiment T, or U, wherein: b is 0.2 to 0.4; c is 0.03 to 0.07; and d is 0.01 to 0.06. Embodiment W. The method according to Embodiment T, U, or V, wherein the catalyst has a formula selected from Mo₁V_0.31Te_0.05Ta_0.05O_x, Mo₁V_0.31Sb_0.05Ta_0.05O_x, Mo1V0.31Te0.05Nb0.05Ox, and Mo1V0.31Sb0.05Nb0.05Ox. Embodiment X. The method according to Embodiment T or U, wherein the catalyst has a formula selected from Mo1V0.32Te0.05Ta0.02Ox, Mo1V0.32Sb0.05Ta0.02Ox, Mo1V0.31Te0.04Nb0.02Ox, Mo1V0.30Sb0.05Nb0.02Ox, Mo1V0.34Te0.05Ta0.02, Mo1V0.34Te0.06Ta0.02, Mo1V0.34Sb0.06Ta0.02, Mo1V0.34Te0.05Nb0.01, Mo1V0.32Sb0.06Nb0.02, and Mo1V0.34Sb0.05Ta0.03, wherein each formula is determined by energy-dispersive x-ray spectroscopy (EDX). Embodiment Y. 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, or X, wherein the metal oxides have a particle size distribution in the range of from 0.5 µm to 250 µm. 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 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. 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 mL water per gram of catalyst and 10 mL water per gram of catalyst. Other implementations are also within the scope of the following claims.

Claims

CLAIMS What is claimed is: 1. A method for preparing a catalyst comprising: forming a slurry comprising metal oxides, a reducing agent, and water; and heating the slurry to form the catalyst; wherein the metal oxides comprise: an oxide of molybdenum; an oxide of vanadium; an oxide of tellurium or an oxide of antimony, or both; and an oxide of tantalum or an oxide of niobium, or both; and 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. 2. The method according to claim 1, 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.

3. The method according to claim 1, wherein the slurry has a ratio of water to metal oxides between 0.2 mL water per gram of metal oxides and 0.6 mL water per gram of metal oxides.

4. The method according to claim 1, wherein the slurry has a ratio of water to metal oxides between 0.3 mL water per gram of metal oxides and 0.5 mL water per gram of metal oxides.

5. The method according to claim 1, wherein the oxide of molybdenum is MoO₃.

6. The method according to claim 1, wherein the oxide of vanadium is V2O5.

7. The method according to claim 1, wherein the oxide of tellurium, when present, is TeO2 and the oxide of antimony, when present, is Sb2O5.

8. The method according to claim 1, wherein the oxide of tantalum, when present, is Ta2O5 ^xH2O, and the oxide of niobium, when present, is Nb2O5 ^xH2O.

9. The method according to claim 1, further comprising grinding, wet milling, dry milling, or crushing the metal oxides.

10. The method according to claim 1, further comprising grinding, wet milling, dry milling, or crushing the metal oxides and the reducing agent.

11. The method according to claim 1, wherein the reducing agent comprises an alcohol, a carboxylic acid, or an ester.

12. The method according to claim 11, wherein the reducing agent is oxalic acid or ethanol.

13. The method according to claim 11, wherein the reducing agent is oxalic acid.

14. The method according to claim 1, wherein the slurry comprises no more than one reducing agent.

15. The method according to claim 1, 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.

16. The method according to claim 1, further comprising washing the catalyst with water.

17. The method according to claim 1, further comprising calcining the catalyst to form a calcined catalyst.

18. The method according to claim 17, 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.

19. The method according to claim 17, wherein a ratio of the water in the slurry to amount of calcined catalyst formed is less than 1 mL water per gram of calcined catalyst.

20. The method according to claim 1, wherein the catalyst comprises a formula selected from MoaVbTecTadOx, MoaVbSbcTadOx, MoaVbTecNbdOx, and MoaVbSbcNbdOx; wherein: a is 1.0; b is 0.01 to 0.4; c is 0.01 to 0.2; d is 0.01 to 0.10; and x is the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, and d are determined based on the amount of each metal oxide added to the slurry

21. The method according to claim 20, wherein the values of a, b, c, and d are also determined by elemental analysis.

22. The method according to claim 20, wherein: b is 0.2 to 0.4; c is 0.03 to 0.07; and d is 0.01 to 0.06.

23. The method according to claim 20, wherein the catalyst has a formula selected from Mo₁V_0.31Te_0.05Ta_0.05O_x, Mo₁V_0.31Sb_0.05Ta_0.05O_x, Mo₁V_0.31Te_0.05Nb_0.05O_x, and Mo1V0.31Sb0.05Nb0.05Ox.

24. The method according to claim 21, wherein the catalyst has a formula selected from Mo1V0.32Te0.05Ta0.02Ox, Mo1V0.32Sb0.05Ta0.02Ox, Mo1V0.31Te0.04Nb0.02Ox, Mo₁V_0.30Sb_0.05Nb_0.02O_x, Mo₁V_0.34Te_0.05Ta_0.02, Mo₁V_0.34Te_0.06Ta_0.02, Mo₁V_0.34Sb_0.06Ta_0.02, Mo1V0.34Te0.05Nb0.01, Mo1V0.32Sb0.06Nb0.02, and Mo1V0.34Sb0.05Ta0.03, wherein each formula is determined by energy-dispersive x-ray spectroscopy (EDX).

25. The method according to claim 1, wherein the metal oxides have a particle size distribution in the range of from 0.5 µm to 250 µm.

26. The method according to claim 1, 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.

27. The method according to claim 1, 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 10 mL water per gram of catalyst.