Tantalum-containing mixed metal oxide catalysts for ethane oxidative dehydrogenation

Abstract

Catalysts useful for the oxidative dehydrogenation of ethane are provided that comprise molybdenum, vanadium, tellurium, tantalum, and oxygen, prepared using a staged hydrothermal synthesis procedure. The catalysts comprise an amorphous content of 30 to 50 wt% and can be combined with a support / carrier material to form a catalyst material. The catalysts and catalyst materials exhibit high selectivity to ethylene at higher temperatures, show little to no decrease in conversion and selectivity over time, and appear to be insensitive to low residual oxygen concentrations.

Description

[0001] CLAIM OF PRIORITY

[0002] This application claims priority to U.S. Provisional Application 63 / 145,943, filed February 4, 2021, the entirety of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates generally to catalysts and systems for oxidative dehydrogenation (ODH). More specifically, the catalyst contains molybdenum (Mo), vanadium (V), tellurium (Te), tantalum (Ta), and oxygen (O). BACKGROUND

[0004] Olefins such as ethylene, propylene, and butylene are the 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 processes to convert more abundant lower alkanes to olefins. The process of choice for current commercial scale producers is steam cracking, a highly endothermic process in which steam-diluted alkanes are subjected to temperatures of at least 800 °C for very short periods of time. The fuel requirements to generate the required temperatures and the need for equipment that can withstand the temperatures significantly increase the overall cost. In addition, the high temperatures promote the formation of coke, which accumulates within the system, resulting in the need for expensive periodic reactor shutdowns for maintenance and coke removal.

[0005] The selective oxidation process, such as oxidative dehydrogenation (ODH), is an alternative to steam cracking that is exothermic and produces little or no coke. In ODH, lower alkanes such as ethane are mixed with oxygen at temperatures as low as 300 °C in the presence of a catalyst and optional inert diluents such as carbon dioxide, methane, nitrogen, or steam to produce the corresponding olefin. Various other oxidation products can be produced in the process, including carbon dioxide and acetic acid. In comparison to steam cracking, ODH has a lower conversion rate, which, when combined with lower selectivity and the risk of thermal explosion due to mixing of hydrocarbons with oxygen, can prevent ODH from achieving widespread commercial implementation.

[0006] There is a need for a catalyst for ethane ODH processes with high ethylene selectivity. It has been observed that MoVNbTeO x The catalyst exhibits permanent activity and selectivity loss over time at elevated ODH temperatures. The robustness of the catalyst to lean oxygen ODH conditions was also tested, and it has been found that while the catalyst activity will fully recover after an air regeneration cycle, the selectivity will only partially recover, dropping to less than 90% at 25% conversion. It has been shown that running the reactor at low space velocities at low temperatures of 350 °C causes less loss of catalyst selectivity compared to subjecting the catalyst to temperatures higher than 360 °C. Therefore, the application of MoVNbTeOx The catalyst will need to be installed in a lower temperature and GHSV to operate to maintain high catalyst performance. These process limitations require larger reactor volume size (higher CAPEX), narrower temperature operating window, and more difficult final reactor operation. SUMMARY

[0007] The present disclosure relates to a mixed metal oxide catalyst comprising Mo, V, Te, and Ta for ethane oxidative dehydrogenation that provides high conversion and selectivity. The catalyst has the following formula:

[0008] Mo a V b Te c Ta d O x

[0009] wherein:

[0010] a is 1.0;

[0011] b is about 0.35 to about 1.0;

[0012] c is about 0.1 to about 1.0;

[0013] d is about 0.06 to about 1.0; and

[0014] x is a number that at least satisfies the valence of the catalyst; and

[0015] wherein the amorphous content of the catalyst is about 30 wt% to about 50 wt%.

[0016] As described herein, using a staged hydrothermal synthesis, preparing and mixing an aqueous precursor salt solution, hydrothermal baking the final solution, and calcining the prepared catalyst shows high selectivity to ethylene at higher temperatures.

[0017] Further, when used in an ethane oxidative dehydrogenation process, the Mo a V b Te c Ta d O x catalyst shows little to no decline in conversion and selectivity over time and is not sensitive to low oxygen concentrations.

[0018] Also described herein is a process for ethane oxidative dehydrogenation, wherein a Mo a V b Te c Ta d O x catalyst is contacted with ethane in the presence of oxygen in a reactor to produce an effluent comprising ethylene. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A cross-sectional schematic of a microreactor unit (MRU) apparatus is shown.

[0020] Figure 2 A plot showing conversion and selectivity of catalyst 1.1 as a function of time at an initial operating temperature of 440 °C, followed by an increase in operating temperature to 448 °C after ~ 15 hours to provide 50% conversion is shown.

[0021] Figure 3 A plot showing conversion and selectivity of catalyst 1.6 as a function of time at an operating temperature of 442 °C, which was maintained for the duration is shown.

[0022] Figure 4 A plot showing conversion and selectivity of catalyst 1.6 as a function of time starting at an operating temperature of 470 °C, providing a residual oxygen content of 0.27 mol% is shown. The operating temperature was decreased to 455 °C after ~ 87 hours to provide 50% conversion.

[0023] Figure 5 A plot showing conversion and selectivity of catalyst material 1.1 as a function of time while maintaining the operating temperature at 455 °C to provide 50% conversion (including catalyst 1.6 for comparison) is shown.

[0024] Figure 6 A plot showing conversion and selectivity of catalyst material 1.2 as a function of time while maintaining the operating temperature at 450 °C to provide 50% conversion (including catalyst 1.6 for comparison) is shown.

[0025] Figure 7 Scanning electron microscope (SEM) images of catalysts 1.1-1.6 and 2.1 at 10,000x magnification are shown.

[0026] Figure 8 SEM images of fresh and used catalyst materials 1.1, 1.4, and 1.5, and fresh catalyst materials 1.2 and 1.3 at 10,000x magnification are shown.

[0027] Figure 9 X-ray diffraction (XRD) spectra of catalysts 1.1, 1.3-1.6, and 2.1 are shown.

[0028] Figure 10 XRD spectra of catalyst materials 1.1-1.4, and 1.6 are shown.

[0029] Figure 11 Fourier transform infrared spectroscopy (FTIR) spectra of catalysts 1.1-1.6, and 2.1 are shown.

[0030] Description of the embodiments

[0031] Selective oxidation (SO) is commonly used for ODH reactions to form ethylene or other a-olefins from ethane. Embodiments described herein provide catalyst systems for selective oxidation reactions.

[0032] Provided herein are MoVTeTaO x catalysts with high ethylene selectivity. In some embodiments, the catalysts exhibit favorable process performance characteristics. In some embodiments, the MoVTeTaO x catalysts exhibit improved properties compared to MoVTeNbO x catalysts. In some embodiments, the MoVTeTaO x catalysts are stable at operation above 400°C, maintaining high activity and selectivity. In some embodiments, the catalysts maintain high activity and selectivity after a slight initial loss of activity. In some embodiments, the slight initial loss of activity is attributed to catalyst equilibration. The enhanced stability is beneficial as it provides the option to operate at higher reactor temperatures than previously considered.

[0033] In some embodiments, the MoVTeTaO x catalysts exhibit high resistance to low residual oxygen conditions while producing high conversion and selectivity. This is beneficial as it should allow for higher conversion, in turn allowing for higher ethylene yield, without negative impact on catalyst life. Lower residual oxygen in the resulting gaseous product stream can also be associated with reduced oxygen separation requirements downstream of the ODH process.

[0034] In some embodiments, the MoVTeTaO x The use of the catalysts results in low acetic acid production, which allows for high ethylene selectivity. High ethylene selectivity means reduced CAPEX & OPEX for acetic acid purification, which is part of downstream processing in an ODH plant. It also means that sales of acetic acid product should be easier to manage, as demand for acetic acid in North America is very small (34 kTA).

[0035] Therefore, this document provides an ODH catalyst that exhibits improved properties compared to other tantalum-containing ODH catalysts disclosed in the prior art. For example, the catalyst of this disclosure can operate at much higher temperatures (resulting in higher conversions) without compromising selectivity; the catalyst of this disclosure is not deactivated by low oxygen concentrations (it almost depletes O2 in the product stream); the catalyst of this disclosure produces low levels of acetic acid; the catalyst of this disclosure is prepared using a staged hydrothermal synthesis, the opposite of a “single-pot” synthesis; the catalyst of this disclosure contains a much higher M1 phase compared to previously disclosed tantalum-containing catalysts; and the catalyst of this disclosure has a unique X-ray diffraction (XRD) profile.

[0036] This article presents an oxidative dehydrogenation catalyst material comprising molybdenum (Mo), vanadium (V), tellurium (Te), tantalum (Ta), and oxygen (O). This catalyst is formulated as MoVTeTaO. x In some embodiments, the catalyst has the formula Mo. a V b Te c Ta d O x Where a is 1.0; b is from about 0.35 to about 1.0; c is from about 0.1 to about 1.0; d is from about 0.06 to about 1.0; and x is a value that at least satisfies the valence of the catalyst. In some embodiments, the catalyst has the formula Mo1V 0.35-1.0 Te 0.1-1.0 Ta 0.06-1.0 In some embodiments, the catalyst has the formula Mo1V 0.39-0.49 Te 0.12-0.17 Ta 0.06-0.15 In some embodiments, the catalyst has the formula Mo1V 0.49 Te 0.15 Ta 0.07 In some embodiments, the amorphous content of the catalyst is from about 30% to about 50% by weight.

[0037] In some implementations, a is 1.0.

[0038] In some embodiments, b is from about 0.35 to about 1.0. In some embodiments, b is from about 0.35 to about 0.75. In some embodiments, b is from about 0.39 to about 0.49. In some embodiments, b is from about 0.45 to about 0.7. In some embodiments, b is about 0.49.

[0039] In some embodiments, c is from about 0.1 to about 1.0. In some embodiments, c is from about 0.1 to about 0.2. In some embodiments, c is from about 0.12 to about 0.17. In some embodiments, c is from about 0.14 to about 0.18. In some embodiments, c is about 0.15.

[0040] In some embodiments, d is about 0.06 to about 1.0. In some embodiments, d is about 0.06 to about 0.15. In some embodiments, d is about 0.06 to about 0.15. In some embodiments, d is about 0.06 to about 0.10. In some embodiments, d is about 0.07.

[0041] In some embodiments, x is at least the number of oxygen atoms required to satisfy the valence of the catalyst.

[0042] In some embodiments, the amorphous content of the catalyst is about 30 wt% to about 50 wt%. In some embodiments, the amorphous content of the catalyst is about 30 wt% to about 40 wt%. In some embodiments, the amorphous content of the catalyst is about 33 wt% to about 36 wt%. In some embodiments, the amorphous content of the catalyst is about 34 wt% to about 35 wt%.

[0043] MoVTeTaO x catalyst. The first step includes preparing an aqueous solution of catalyst precursor salts of each of the elements molybdenum, vanadium, tellurium, and tantalum. The molybdenum and tellurium components can be prepared as a combined aqueous preparation to which a vanadium aqueous preparation can be added. A tantalum aqueous preparation can then be added to form the final aqueous composition. The second step includes hydrothermally baking the final aqueous composition to form a slurry, which can be filtered and rinsed to isolate the solid catalyst. The final step includes calcining the solid catalyst. The described staged hydrothermal process is different from known "single-pot" synthesis procedures in which all components are added simultaneously to a single pot to form the product in situ.

[0044] The MoVTeTaO x catalyst exhibits a pattern of peaks when analyzed using X-ray diffraction (XRD). In some embodiments, the XRD pattern includes peaks at 2 theta values of 7.9 ± 0.2, 9.0 ± 0.2, 22.2 ± 0.2, 23.0 ± 0.2, 25.0 ± 0.2, 26.7 ± 0.2, and 28.3 ± 0.2.

[0045] Also provided herein are catalyst materials comprising a catalyst, such as a catalyst of the present disclosure, and a catalyst support or carrier. Some supports are particularly suitable for use with catalysts because they are chemically compatible and do not have a significant impact on ethylene selectivity. Other supports can be less compatible, meaning that they can cause a significant reduction in catalyst performance, such as a reduction in ethylene selectivity. Thus, not any support can be selected; the support should be selected in a judicious manner based on short-term and long-term catalyst performance testing. In some embodiments, the focus is on long-term testing showing that selectivity does not lose with time on stream (e.g., > 48 hours TOS). In some embodiments, the catalyst support or carrier is selected from the group consisting of precipitated synthetic silica, fumed synthetic silica, silica-alumina, alpha-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 fumed silica.

[0046] Also provided herein are methods for ethane oxidative dehydrogenation, the method comprising contacting a gaseous feed comprising ethane and oxygen with a catalyst in a reactor to produce an effluent comprising ethylene, wherein the catalyst has the following formula:

[0047] Mo a V b Te c Ta d O x

[0048] wherein:

[0049] a is 1.0;

[0050] b is about 0.35 to about 1.0;

[0051] c is about 0.1 to about 1.0;

[0052] d is about 0.06 to about 1.0; and

[0053] x is a number at least to satisfy the valence of the catalyst; and

[0054] wherein the amorphous content of the catalyst is about 30 wt% to about 50 wt%.

[0055] Suitable reactors for use with the catalysts and methods described herein include fixed bed reactors in which the catalyst is immobilized in a catalyst bed. Also particularly suitable for use with the catalysts and methods described herein are shell-and-tube reactors, including but not limited to shell-and-tube reactors with molten salt cooling capabilities.

[0056] The ability of a catalyst to convert ethane to ethylene in an ethane ODH process can be evaluated by determination of conversion and selectivity. Conversion is described in terms of the temperature at which a particular mole percent of ethane is converted to ethylene and related byproducts. Selectivity is described in terms of the percentage of converted ethane that is converted to ethylene (or a particular byproduct). Conversion generally increases with increasing temperature. Unfortunately, for some ODH catalysts, higher temperatures are associated with lower ethylene selectivity, and in some cases, if the temperature is high enough, the conversion actually decreases, and the catalyst can even become irreversibly deactivated. Commercial success can depend on the use of a catalyst that operates at higher temperatures while maintaining an ethylene selectivity greater than 90%. It would be extremely beneficial to maximize conversion while maintaining selectivity.

[0057] In some embodiments, the catalyst exhibits a conversion of 50 mole percent and an ethylene selectivity of 90% or greater at a temperature of about 350 °C to about 475 °C when used in an oxidative dehydrogenation process of ethane. In some embodiments, the catalyst exhibits a conversion of 50 mole percent and an ethylene selectivity of 90% or greater at a temperature of 390 °C to 450 °C when used in an oxidative dehydrogenation process of ethane. In some embodiments, the catalyst exhibits a conversion of 50 mole percent and an ethylene selectivity of 90% or greater at a temperature of 400 °C to 450 °C when used in an oxidative dehydrogenation process of ethane.

[0058] In some embodiments, the catalyst exhibits a conversion of 35 mole percent and an ethylene selectivity of 90% or greater at a temperature of at least 400 °C when used in an oxidative dehydrogenation process of ethane.

[0059] Further, it is known that the activity of ODH catalysts decreases over time, with the most significant decrease occurring soon after initial use, when the catalyst is still fresh. Catalysts that maintain activity and selectivity over time can prove to be commercially beneficial, as the catalyst lasts longer before needing to be replaced. In some embodiments, the activity or selectivity of the catalyst does not significantly decrease for at least 110 hours after initial activation. In some embodiments, the catalyst exhibits a conversion of 50 mole percent of ethane and an ethylene selectivity of 90% or greater at a temperature of 400 °C or greater for at least 110 hours when used in an oxidative dehydrogenation process of ethane. In some embodiments, the catalyst exhibits a conversion of 50 mole percent of ethane and an ethylene selectivity of 90% or greater at a temperature of 350 °C to 475 °C for 110 hours when used in an oxidative dehydrogenation process of ethane. In some embodiments, the catalyst exhibits a conversion of 50 mole percent of ethane and an ethylene selectivity of 90% or greater at a temperature of 400 °C to 450 °C for 110 hours when used in an oxidative dehydrogenation process of ethane.

[0060] Definitions

[0061] As used herein, the term "catalyst material" refers to a material comprising a combination of an active catalyst that can promote the oxidative dehydrogenation of ethane to ethylene and a support / carrier material. The catalyst material can be a plurality of particulate or shaped catalyst materials. Non-limiting examples of shaped catalyst materials include extruded catalyst materials, pressed catalyst materials, and cast catalyst materials. Non-limiting examples of pressed and cast catalyst materials include pellets - such as tablets, ellipsoids, and spherical particles.

[0062] As used herein, the term "catalyst" generally refers to the active catalyst portion of a catalyst material. The catalyst is typically processed in further steps to form the catalyst material. The catalyst material can also be processed in further steps to form the final catalyst material.

[0063] As used herein, the term "oxidative dehydrogenation" or "ODH" refers to a process that couples the endothermic dehydration of an alkane with the strong exothermic oxidation of hydrogen, as further described herein.

[0064] As used in the present disclosure, the phrase "35% conversion temperature" refers to the temperature at which 35 mole percent of ethane in a gas stream is converted to products other than ethane and is determined using a microreactor unit (MRU) and the test conditions described below. The conversion of the feed gas to ethane is calculated using the following equation as a change in mass flow rate of ethane in the products compared to the mass flow rate of the feed ethane:

[0065]

[0066] where C is the mole percent of the feed gas that has been converted from ethane to another product (i.e., ethane conversion), and X is the molar concentration of the corresponding product in the gaseous effluent exiting the reactor. The ethane conversion is then plotted as a function of temperature to obtain a linear algebraic equation. The linear equation for ethane conversion is solved to determine the temperature at which the ethane conversion is 35% (i.e., the 35% conversion temperature). The "50% conversion temperature" refers to the temperature at which 50 mole percent of ethane in a gas stream is converted to products other than ethane and can be determined using the same linear equation.

[0067] As used in the present disclosure, the phrase "selectivity to ethylene" refers to the mole percent of ethane that is converted or reacted to form ethylene. The selectivity to ethylene of an oxidative dehydrogenation catalyst can be determined using an MRU and the test conditions described below. The selectivity to ethylene of an oxidative dehydrogenation catalyst can be determined using the following equation:

[0068]

[0069] where S C2H4is the selectivity to ethylene, X is the molar concentration of the corresponding compound in the gaseous effluent leaving the reactor. It is noted that the selectivity to ethylene is determined at the indicated conversion temperature, i.e. at the 35% conversion temperature or at the 50% conversion temperature. Thus, after determining the 35% conversion temperature, X C2H4 , X CO2 and X CO the corresponding values at the 35% conversion temperature are used to solve the selectivity equation above.

[0070] Oxidative dehydrogenation of ethane can also result in the production of various other byproducts, including maleic acid, propionic acid, ethanol, acetaldehyde, and their derivatives (e.g. maleic anhydride from the hydrolysis of maleic acid). The amount of these byproducts is negligible, forming less than 0.1 mole% of the products, and thus are not included in the calculation of conversion and selectivity.

[0071] Except in the Examples, or where otherwise explicitly indicated, all numbers or expressions referring to ingredients, reaction conditions and the like used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless otherwise indicated, the numerical parameters set forth in the following specification and attached claims are approximations. At the very least, each numerical parameter should at least be construed in light of the number of significant digits it contains and by applying ordinary rounding techniques. Each numerical parameter should at least be construed in light of the number of significant digits it contains and by applying ordinary rounding techniques.

[0072] 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 value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0073] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed Examples

[0074] Catalysts comprising Mo, V, Te, and Ta were prepared using a staged hydrothermal procedure as described below and characterized for activity (conversion and selectivity), composition (FTIR, XRD, SEM, PSD), and durability (TOS, low oxygen conditions). Selected catalysts were further combined with selected support materials to form catalyst materials and further characterized.

[0075] The general synthesis procedure includes three general steps. The first step is to prepare an aqueous solution of catalyst precursor salts of each of the elements molybdenum, vanadium, tellurium, and tantalum. The molybdenum and tellurium components are prepared as combined aqueous preparations to which the vanadium aqueous preparation is added. The tantalum aqueous preparation is then added to form the final aqueous composition. The second step includes hydrothermal baking of the final aqueous composition to form a slurry, which is filtered and rinsed to isolate the solid catalyst. The final step includes calcination of the solid catalyst. The synthesis procedure for Catalyst 1.1, which includes the steps described below, is used as the base procedure for all examples. Modifications to the procedure for additional examples are noted.

[0076] Aqueous preparation

[0077] Tantalum oxalate was prepared from tantalum ethoxide by the general description provided in the literature by Grasselli et al. (2006). Topics in Catalysis 38. 7-16. An aqueous oxalic acid solution was prepared by dissolving 12.7259 g of anhydrous oxalic acid (C2O4H2) in 118 mL of distilled water with a 65 °C water bath and stirring at 250-450 rpm (enough to create a small vortex) to give a clear colorless solution. The aqueous oxalic acid solution was added to 19.10 g of Ta(OEt) 5(1) at once, which immediately gave a white suspension that was stirred at 65 °C for 2 days to form a 0.4 mol Ta / L H x [Ta(C2O4)3] (aq) aqueous solution that was clear and colorless.

[0078] 463.89 g of ammonium heptamolybdate tetrahydrate (NH4)6Mo7O 24 ·4H2O (s) was dissolved in 3500 mL of distilled water to form a clear colorless solution that was then stirred at 80 °C. 100.55 g of telluric acid (OH) 6(s) was added to the warm aqueous (NH4)6Mo7O 24 solution in one portion to form a hazy solution. The pH of the hazy solution was adjusted to 7.5 by slow addition of 191 mL of aqueous NH4OH (28 wt% aqueous NH3solution) to form a clear colorless solution. The pH of the solution was monitored by a temperature-compensated pH meter. The solution was stirred open to the atmosphere at 80 °C for about 48 hours to evaporate all of the water to isolate a clean colorless solid. The colorless solid obtained was ground and dried overnight to give a white powder of (NH4)6Mo6TeO 24 ·7H2O (s)To 750 mL of distilled water, 59.16 g of the above solution was dissolved at 60 °C with stirring to give a clear colorless solution.

[0079] To 240 mL of distilled water, 39.44 g of vanadium sulfate (VOSO4-3.36 H2O) was dissolved with stirring at 60 °C to give a clear blue solution. The warm VOSO4solution was added dropwise to the warm (NH4)6Mo6TeO24solution in the aqueous (NH4)2C2O4solution over approximately 11 minutes to give a black solution. Immediately after the black MoVTe solution was formed, the entire solution of 24 H2O2was added dropwise to the black MoVTe solution to give a dark green solution. x [Ta(C2O4)3] (aq) The dark green solution was stirred at 60 °C for 1 hour in air during which time a fine precipitate formed.

[0080] Hydrothermal baking

[0081] The 60 °C dark green slurry was poured into the glass liner of a 2000 mL PARR autoclave equipped with an overhead stirrer reactor top and transferred into the autoclave. The autoclave was closed, the atmosphere inside the autoclave was evacuated (vacuumed) and filled with nitrogen (12 psig from the bulk nitrogen line) 10 times. The autoclave was sealed under 12 psig bulk nitrogen and placed into a heating mantle for hydrothermal baking. The heating mantle and autoclave were well insulated and heated at an external temperature of 175 °C for 48 hours, the hydrothermal reaction was run in static mode. The external set point temperature was measured by a thermocouple located on the wall of the reactor below the heating mantle. The temperature of the solution, as measured via a wetted thermocouple through a Hastelloy thermowell, was recorded as 166 °C. The heating time from room temperature to the internal temperature of 164 °C was ~4.5 hours.

[0082] The reactor pressure and volume were maintained with the apparatus described in US Patent 10,589,258 (B2) (assignee NOVA Chemicals International S.A). This apparatus was connected to the top of the reactor but was a shell and tube heat exchanger (condenser) with cooling water circulating on the outside tubes at ~25 °C (controlled through a closed system, cooling bath) and the inside tubes connected to the reactor (process) to allow excess gas pressure to be vented through a back pressure regulator. The back pressure regulator set point was set to 140 psig and this pressure was recorded on the second day of the reaction. The pressure set point of 140 psig was determined by reference to the steam table pressure of water heated at 175 °C and a pressure slightly higher than indicated on the steam table was chosen to ensure the liquid reached temperature (i.e. elevated boiling point). Some pressure release was observed through a glass water bubbler connected to the outlet side (outlet) of the back pressure regulator. Slow bubbling (venting of excess C02(g) pressure from oxalic acid decomposition) was observed only on the second day of the 48 hour reaction.

[0083] After 48 hours, the reactor was allowed to cool to room temperature and the excess carbon dioxide (from oxalic acid decomposition) and nitrogen gas pressure was vented into the fume hood. Vigorous bubbling of carbon dioxide was produced when the purple slurry was disturbed. The purple solid was filtered through a Buchner funnel with 3 layers of qualitative filter paper to separate the blue liquor from the dark purple (almost black) solid. The solid was rinsed with about five 400 mL portions of distilled water until the filtrate no longer had any visible blue color after passing through the solid. The solid was then dried in an oven at 90 °C overnight and then pulverized into small particles using a mortar / pestle.

[0084] Calcination

[0085] A portion of the pulverized recovered product was loaded into a quartz boat and this boat was placed into a quartz tube for calcination. The quartz tube was purged with bulk nitrogen (<10 ppm oxygen) at a flow rate of 30 seem and the outlet side of the tube was vented through a silicone oil bubbler to help maintain the tube under an anaerobic atmosphere. The tube atmosphere was purged with bulk nitrogen (<10 ppm oxygen) for 6 hours and then the inlet bulk nitrogen was redirected through an oxygen trap (LabClear OxiClear TM Gas Purifier) to purge the tube with purified nitrogen (<1 ppm oxygen) for an additional 12 hours. The calcination was performed under a flow of 30 seem of purified nitrogen with the following heating conditions: RT (~20 °C) to 600 °C (1.6 °C / minute) in 6.25 hours, hold at 600 °C for 2 hours, and natural cool down.

[0086] Additional catalyst examples were prepared by varying the amount of starting material and making the following modifications to the general procedure:

[0087] Catalyst 1.2: The amount of tantalum ethoxide was increased to 23.1 g and during the hydrothermal bake, the external temperature control was set to 185 °C and the slurry was stirred at 150 rpm.

[0088] Catalyst 1.3: The slurry was stirred at 20 rpm during the hydrothermal bake.

[0089] Catalyst 1.4: The tantalum oxalate was a commercial source rather than prepared by digesting tantalum ethoxide with oxalic acid.

[0090] Catalyst 1.5: The tantalum oxalate was a commercial source and its amount was reduced by a factor of 1.94 compared to Catalyst 1.1.

[0091] Catalyst 1.6: The same procedure as Catalyst 1.5 was followed.

[0092] Catalyst 1.7: (NH4)6Mo6TeO 24 ·7H2O (s) was generated in situ in aqueous solution rather than isolated as a solid using a two-step pH adjustment, first with NH4OH (aq) to pH ~ 7.5 and then with H2SO4 (aq) to pH ~ 5.

[0093] Catalyst 1.8: Followed the same procedure as Catalysts 1.5 and 1.6 but (NH4)6Mo6TeO 24 ·7H2O (s) was prepared in situ using a single pH adjustment to ~ 5.0 with NH4OH (aq).

[0094] Catalyst 1.9: Followed the same procedure as Catalyst 1.1 but scaled up by a factor of ~ 5.

[0095] Comparative Example Catalyst 2.1 was prepared by the procedure outlined in US20100222623 for Example 1. Specifically, 20.9995 g (NH4)6Mo7O 24 ·4H2O (s) was dissolved in 150 mL distilled water with stirring at 80 °C. 7.64 g Te(OH) 6(s) was dissolved in 85 mL distilled water. The Te(OH)6(aq) solution was added to the (NH4)6Mo7O 24(aq)In solution, a clear colorless solution was obtained and stirred at 80 °C for 15 minutes. To the MoTe solution at 80 °C, 4.5940 g of NH4VO3(s) was added in one portion to immediately produce a bright orange solution which was stirred at 80 °C for 5 minutes during which time some trace solid precipitate formed. The stirred orange mixture was then allowed to cool to room temperature over 45 minutes. To the orange mixture at room temperature, 11.742 mmol of a clear colorless aqueous tantalum oxalate solution was added dropwise over 20 minutes to give a clear orange solution. The aqueous tantalum oxalate solution used was prepared in the same manner as described in Example 1, for example from an aqueous oxalic acid solution digested with tantalum pentoxide precipitated from Ta(OEt)5 5(1) at 50 °C.

[0096] The resulting orange mixture was evaporated by 650 mm Hg vacuum with heating (via a hot water bath) and stirring at 500 rpm. During the removal of water, orange solids were observed roughly halfway through the evaporation. After all visible water was removed, a light orange solid was obtained which was dried in an oven at 120 °C for 4 hours to produce a dark orange solid which was ground via mortar and pestle and weighed as 34.8748 g.

[0097] The 34.8748 g of ground dark orange solid was all loaded into a quartz boat for calcination in a quartz tube reactor furnace. Prior to calcination, the quartz tube containing the solid to be calcined was purged with bulk nitrogen (<10 ppm oxygen) at a flow rate of 30 seem, the outlet side of the tube vented through a silicone oil bubbler to help maintain the tube under an anaerobic atmosphere. The tube atmosphere was purged with bulk nitrogen (<10 ppm oxygen) for 6 hours, then the inlet bulk nitrogen was redirected through an oxygen trap (LabClear OxiClear gas purifier) to purge the tube with purified nitrogen (<1 ppm oxygen) for an additional 12 hours. Calcination was performed under a flow of 30 seem of purified nitrogen, heating conditions as follows: RT to 600 °C in 1 hour (approximately 10 °C / minute), hold at 600 °C for 2 hours, and natural cool down. TM

[0098] After calcination, a black, hard, sintered powder catalyst 2.1 was obtained which weighed 26.8901 g for a weight yield of 77.1%. Note that the outlet of the quartz tube was significantly coated with a grey sublimation deposit, significantly more than observed for any of the examples of the invention.

[0099] Catalyst material

[0100] ​Catalyst materials comprising a catalyst and a support / carrier material were prepared using catalysts 1.1, 1.6, and comparative catalyst 2.1. Activity evaluations and physical characterizations were performed to determine which supports or carriers were suitable or compatible for use in the catalyst materials. Compatibility was determined by catalytic testing of the catalyst materials on an MRU reactor and observing initial (within the first 8 hours of testing) high ethylene selectivity, for example, >89 mole% selectivity to ethylene at about 50 mole% ethane conversion. The catalyst materials were prepared as follows.

[0101] Catalyst material 1.1 was prepared by mixing catalyst 1.6 with synthetic amorphous silica to give a combined weight product of 40 wt% catalyst 1.6 and 60 wt% support. The synthetic amorphous silica applied in this example was obtained from PQ Corporation, product identifier CS6846; PD-10042, classified as precipitated synthetic (precipitated from an alkaline silicate solution) and categorized under CAS No. 112926-00-8. 4.0375 g of catalyst 1.6 and 6.0493 g of the precipitated synthetic silica were suspended together in 35 mL of distilled water to form a slurry, which was heated to 100 °C and stirred by an electric motor-driven overhead Teflon stirrer at 80 rpm. Stirring and heating were continued at 100 °C until sufficient water was evaporated to form a thick paste (consistency of modeling clay), which was then dried overnight in a 90 °C oven. After oven drying, 9.6999 g of the entire remaining material was loaded into a quartz boat, which was inserted into a quartz tube of a split-tube furnace. The tube was sealed and purged overnight with non-purified nitrogen (<10 ppm oxygen concentration) at a flow rate of 14 seem and room temperature. Two hours before starting the furnace heating, the purge was switched to purified nitrogen (e.g., non-purified nitrogen was redirected through an oxygen trap, LabClear OxiClear gas purifier, to produce nitrogen containing <1 ppm oxygen). The purified nitrogen flow rate was reduced to 5 seem, the furnace was heated to 500 °C at a rate of 1.6 °C / min, held at 500 °C for 2 hours, and then cooled (heater turned off). The catalyst was removed and weighed (9.2891 g - 95.8% mass yield). A second calcination was performed to prepare catalyst material 1.1, in which the sample was transferred to a 50 mL beaker and calcined in air at 250 °C for 2 hours, both heating and cooling were performed at a ramp rate of 2 hours. TM Gas Purifier, to produce nitrogen containing <1 ppm oxygen). The purified nitrogen flow rate was reduced to 5 seem, the furnace was heated to 500 °C at a rate of 1.6 °C / min, held at 500 °C for 2 hours, and then cooled (heater turned off). The catalyst was removed and weighed (9.2891 g - 95.8% mass yield). A second calcination was performed to prepare catalyst material 1.1, in which the sample was transferred to a 50 mL beaker and calcined in air at 250 °C for 2 hours, both heating and cooling were performed at a ramp rate of 2 hours.

[0102] Specifically, it was prepared by mixing catalyst 1.6 with synthetic amorphous silica to obtain a combined weight product of 40 wt% catalyst 1.6 and 60 wt% silica. The synthetic amorphous silica applied in this example was obtained from Sigma-Aldrich Corporation, product number S5130, and is classified as fumed synthetic (produced by flame hydrolysis of silicon tetrachloride or similar) and classified as CAS number 112945-52-5. 1.6. 6.0015 g of fumed synthetic silica was mixed with 50 mL of distilled water to form a silica gel, which was transferred to a 50 mL beaker containing 4.0002 g of catalyst 1.6. The contents of the beaker were mixed with a spatula to create a slurry, which was then heated in an oil bath at 100 °C and stirred by an electric motor driven overhead Teflon stirrer at 80 rpm. The beaker was stirred and heated at 100 °C for about 3.5 hours until sufficient water was evaporated to form a thick paste (consistency of modeling clay), then removed from the oil bath. The beaker containing the paste was placed in a 90 °C oven and dried overnight with no agitation. After oven drying, 9.6906 g of material was recovered, which was ground with a mortar and pestle and loaded into a quartz boat, which was inserted into a quartz tube of a split-tube furnace. The tube was sealed and purged with non-purified nitrogen (<10 ppm oxygen concentration) overnight at a flow rate of 14 seem and room temperature. Two hours before starting furnace heating, the purge was switched to purified nitrogen (e.g., non-purified nitrogen was redirected through an oxygen trap, LabClear OxiClear Gas Purifier, to produce nitrogen containing <1 ppm oxygen). The purified nitrogen flow rate was reduced to 5 seem, then the furnace was heated to 500 °C at a rate of 1.6 °C / min, held at 500 °C for 2 hours, then cooled (heater turned off). The catalyst was removed and weighed. The weight of the calcined catalyst material 1.2 was 9.4840 g (96.2% mass yield). A sample (9.3224 g) was transferred to a 50 mL beaker and calcined in air at 250 °C for 2 hours, with both heating and cooling at a ramp rate of 2 hours. After the second calcination, 9.4840 g of catalyst material 1.2 was recovered. TM

[0103] ​Catalyst material 1.3 was prepared by mixing catalyst 1.6 with aluminum silicate to obtain a combined weight product of 40 wt% catalyst 1.6 and 60 wt% aluminum silicate. The aluminum silicate used in this example was obtained from Sigma-Aldrich, product number 343358, and is assigned the product name: Silica-Alumina Catalyst Support, Grade 135. The aluminum silicate is classified as an aluminum salt of silicic acid according to the nomenclature of CAS number 1335-30-4. Catalyst material 1.3 was prepared following the procedure for catalyst material 1.1, starting with 4.0021 g catalyst 1.6 and 5.9995 g Sigma-Aldrich Silica-Alumina Catalyst Support, Grade 135. After calcination under nitrogen at 500 °C, the weight was 9.8475 g (99.9% mass yield). After calcination under air at 250 °C, the mass of recovered catalyst material 1.3 was 9.8451 g (100.01% mass yield).

[0104] Catalyst material 1.4 was prepared by mixing catalyst 1.6 with alpha-alumina to obtain a combined weight product of 40 wt% catalyst composition and 60 wt% support. The alpha-alumina used in this example was obtained from Saint-Gobain, product name: 99. DENSTONE 99 is >99 wt% alumina, CAS number 1344-28-1. Prior to use, the DENSTONE 99 alpha-alumina was ground and passed through a #60 sieve to ensure a particle size < 250 μm. Catalyst material 1.4 was prepared following the procedure described previously for catalyst material 1.1, starting with 4.0013 g catalyst 1.6 and 5.9998 g ground alpha-alumina. After calcination under nitrogen at 500 °C, the weight was 9.9876 g (99.7% mass yield). After calcination under air at 250 °C, the mass of recovered catalyst material 1.4 was 9.8959 g (100.01% mass yield).

[0105] Catalyst material 1.5 was prepared by mixing catalyst 1.6 with anatase titanium dioxide to obtain a combined weight product of 40 wt% catalyst 1 and 60 wt% anatase titanium dioxide. The anatase titanium dioxide used in this example was Sigma Aldrich product number 232033, CAS number 1317-70-0. Catalyst material 1.5 was prepared following the procedure described previously for catalyst material 1.1, starting with 4.0004 g catalyst 1.6 and 5.9999 g anatase titanium dioxide. After calcination under nitrogen at 500 °C, the weight of catalyst material 1.5 was 9.6920 g (99.7% mass yield). After calcination under air at 250 °C, the mass of recovered catalyst material 1.5 was 9.6605 g (99.7% mass yield).

[0106] The following catalyst supports (carriers) were determined to be incompatible with the mixed catalyst and were deemed unsuitable for use in the catalyst material. Incompatibility was determined by catalytic testing of the catalyst material on an MRU reactor and observing a significant loss in ethylene selectivity, for example <90 mole% selectivity to ethylene for about 50 mole% ethane conversion. In some cases, the catalyst composition was also deemed incompatible with the support if the resulting catalyst material was very unactive.

[0107] Catalyst material 2.1 was prepared by mixing catalyst 1.6 with silicon carbide to obtain a combined weight product of 40 wt% catalyst 1.6 and 60 wt% silicon carbide. The silicon carbide applied in this example was obtained from Saint-Gobain, product code: SC55167, 13 wt% Si02and the balance SiC (CAS number 409-21-2). The silicon carbide was ground and passed through a #60 sieve to ensure a particle size <250 pm prior to application. Catalyst material 2.1 was prepared following the procedure described previously for catalyst material 1.1, starting with 4.0017 g catalyst 1.6 and 6.0005 g ground silicon carbide. After a 500 °C nitrogen calcination, the weight was 9.8806 g (99.5% mass yield). After a 250 °C air calcination, the mass of recovered catalyst material 2.1 was 11.9546 g (121.0% mass yield).

[0108] Catalyst material 2.2 was prepared by mixing catalyst 1.6 with colloidal alumina to obtain a combined weight product of 40 wt% catalyst 1.6 and 60 wt% support. The colloidal alumina applied in this example was Alfa Aesar, catalog number 12733, which contains 20 wt% Al203dispersed in water. Catalyst material 2.2 was prepared following the procedure described previously for catalyst material 1.1, starting with 4.0418 g catalyst 1.6 and 30.0648 g 20 wt% Al203.

[0109] Catalyst material 2.3 was prepared by mixing catalyst 1.1 with boehmite hydroxy alumina to obtain a combined weight product of 40 wt% catalyst 1.1 and 60 wt% boehmite alumina. The boehmite hydroxy alumina used in this example was obtained from Honeywell UOP, product name Versal V-250 (catalog number 86251), which is described as a low density pseudo-boehmite alumina (wt% < 95%; CAS number 1344-28-1). For the synthesis, a 50 mL beaker was charged with 4.0263 g of catalyst 1.1 and 6.0622 g of boehmite hydroxy alumina to form a slurry with the addition of sufficient distilled water to create a suspension. The beaker containing the slurry was placed in an oil bath, which was heated to 100 °C and stirred by an electric motor driven overhead Teflon stirrer at 85 rpm. The beaker was stirred and heated at 100 °C until sufficient water was evaporated (about 3 hours) to form a thick paste (consistency of plastic clay), which was then removed from the oil bath. The beaker containing the paste was placed in a 90 °C oven and dried overnight with standing. After oven drying, the recovered material was loaded in a quartz boat, which was inserted into a muffle furnace, and calcined in air by heating to 350 °C over 4 hours, holding the temperature at 350 °C overnight, and then naturally cooling (heater turned off). The recovered solid was used as catalyst material 2.3.

[0110] Catalyst material 2.4 was prepared by mixing catalyst 1.6 with calcium titanate to obtain a combined weight product of 40 wt% catalyst 1.6 and 60 wt% calcium titanate. The calcium titanate used in this example was Goodfellow Corporation product code: CA546, which is classified as 80-100 wt% calcium titanate (CaTi03) and is classified as CAS number 12049-50-2. Catalyst material 2.4 was prepared following the procedure described previously for catalyst material 1.1, starting with 3.9986 g of catalyst 1.6 and 6.0013 g of calcium titanate powder. After 500 °C nitrogen calcination, the weight was 9.7932 g (99.2% mass yield). After 250 °C air calcination, the mass of recovered catalyst material 2.4 was 9.7813 g (100.02% mass yield).

[0111] Catalyst material 2.5 was prepared by mixing catalyst 1.6 with zirconium oxide powder to obtain a combined weight product of 40 wt% catalyst 1.6 and 60 wt% support. The zirconium oxide (IV) used in this example was Sigma Aldrich product number 204994, CAS number 1314-23-4. Following the procedure described above with respect to catalyst material 1.1, catalyst material 2.5 was prepared starting with 4.0001 g of catalyst 1.6 and 6.0015 g of zirconium oxide. After calcination in nitrogen at 500 °C, the weight was 9.6723 g (99.3% mass yield). After calcination in air at 250 °C, the recovered catalyst material 2.5 had a mass of 9.6725 g (101.1% mass yield).

[0112] Catalyst material 2.6 was prepared by mixing catalyst 1.6 with colloidal zirconium oxide to obtain a combined weight product of 40 wt% catalyst 1.6 and 60 wt% colloidal zirconium oxide. The colloidal zirconium oxide used in this example was Alfa Aesar, catalog number 40124, which contains 20 wt% ZrO2 dispersed in water. Catalyst material 2.6 was prepared starting with 4.0371 g of catalyst 1.6 and 30.0044 g of 20 wt% ZrO2 colloidally dispersed in water, following the procedure described above with respect to catalyst material 1.1.

[0113] Performance

[0114] The prepared catalysts and catalyst materials were tested for their physical properties and their ability to convert ethane to ethylene. The performance of the catalysts was evaluated at temperatures of 35% and 50% conversion, and the corresponding selectivity to ethylene. The robustness of the catalysts and catalyst materials was further tested; that is, they were tested to evaluate their effects on conversion and selectivity over longer time periods, as many oxidative dehydrogenation catalysts have shown a decrease in activity, selectivity, or both over time. Finally, the recovery of the catalysts and catalyst materials to low residual oxygen levels and their selectivity to acetic acid were evaluated.

[0115] MRU

[0116] In the microreactor unit (MRU) 100 ( Figure 1 The cross-section shown in the figure demonstrates the ability of the catalysts and catalyst materials described herein to participate in the oxidative dehydrogenation of ethane. The MRU 100 includes a vertically oriented reactor tube 1 made of stainless steel with an outer diameter of 0.5 inches, an inner diameter of 0.4 inches, and a length of 13.4 inches. The tube is formed, surrounded by a two-zone electric heater 2 or tube furnace, and connected to the upper and lower tubes by SWAGELOK connectors 6. A catalyst bed 3 (grey shading) containing catalyst or catalyst material, located at or near the middle (along the length) of the reactor tube, is held in place by packing 4 (hatched shading) comprising glass wool abutting the upper (4a) and lower (4b) boundaries of the catalyst bed. Temperature within the catalyst bed is measured using a 6-point WIKA Instruments Ltd. Type K thermocouple 5 with an outer diameter of 0.125 inches inserted into the centre of the reactor tube 1 and along its length. Temperature input from the thermocouple 5 is used to control the power output of the electric heater 2 to control the temperature within the reactor. The 6 points, represented by the hollow circles, are distributed along the length of the reactor tube 1 with points 3 and 4 located within the catalyst bed 3. A room temperature stainless steel condenser is located downstream of the reactor to collect water / acetic acid condensate. The gaseous product stream is either vented or directed through a sampling loop (not shown) to a gas chromatograph (GC; Agilent 6890N gas chromatograph with ChromPerfect-Analysis, version 6.1.10 used for data evaluation).

[0117] To prepare catalysts and catalyst materials for testing on the MRU, the catalyst or catalyst material is loaded into a 1 inch diameter die, pressed with a compression force of 12 tonnes and held under this pressure for at least 10 seconds. The resulting puck of pressed catalyst or catalyst material is then crushed into small pieces using a mortar and pestle. The crushed catalyst or catalyst material is sieved and the particles with a particle size of 425 pm to 1000 pm are collected and loaded onto the MRU for testing.

[0118] For standard catalyst testing, 2.00 g of sieved catalyst from the crushed pressed catalyst (particle size 425 pm to 1000 pm) is physically mixed with quartz sand such that the mixture results in a total catalyst bed volume of 6 ml. Once the catalyst bed is loaded into the reactor and connected to the MRU apparatus, a pre-mixed feed gas comprising 20 mole% ethane, 10 mole% oxygen and 70 mole% nitrogen (molar ratio of ethane to oxygen is 1 / 0.5) is passed through the reactor tube 1 from the upper tube 8 (direction indicated by the hatched arrow) and the effluent gas exits through the lower tube 9. The pre-mixed feed is prepared using a gas blending apparatus and the calibrated mass flow controllers involved (not shown). An outlet pressure of 20 psig is maintained using a back pressure regulator (not shown). The flow of the pre-mixed feed gas is controlled to 152 standard cubic centimetres (seem) such that a space velocity of 5.46 h -1The gas leaving the reactor was analyzed by GC (Agilent 6890N gas chromatograph using Chrom Perfect-Analysis, version 6.1.10 for data evaluation) to determine the percentage of various hydrocarbons (e.g., ethane and ethylene) and optional other gases such as O2, CO2, and CO and acetylene, the results being used to calculate the conversion and selectivity as defined above. The temperature was monitored in real time at all 6 points, the average of points 3 and 4 (which are within the catalyst bed) providing the temperature used to plot the conversion versus temperature curve.

[0119] Several catalysts were subjected to the modified MRU setup and operating conditions. Specifically, the length of reactor tube 1 was 15 inches, and the catalyst loading included 2.00 to 4.00 g of crushed pressed catalyst in a 6 ml catalyst bed volume. In addition, the pre-mixed feed gas entering reactor tube 1 was 35 mole% ethane, 17.5 mole% oxygen, and 47.5 mole% nitrogen (mole ratio of ethane to oxygen was 1 / 0.5), and the reactor was operated at near ambient reactor outlet pressure, with the internal reactor pressure recording less than 3 psig due to the dP created by the reactor bed loading. The flow of the pre-mixed feed gas was controlled between 76-152 standard cubic centimeters (seem) depending on the weight loading in order to achieve a constant weight hourly space velocity (WHSV) of 2.79 h -1 The resulting modified method is correlated to the higher temperatures used for conversion, which is not surprising given the pressure differential when compared to the standard method described above. The limits on conversion and selectivity described herein are meant to represent the limits determined using the standard method under the conditions of a 15 inch reactor tube with an internal diameter of 0.4 inches, a feed gas comprising 20 mole% ethane, 10 mole% oxygen, and 70 mole% nitrogen, a WHSV of 5.46 h -1 and a pressure of 20 psig.

[0120] The MRU catalyst test data for catalysts 1.1-1.9 and 2.1 are shown in Table 1 below, where the temperature was incrementally increased to determine catalyst performance. At each temperature interval, GC data of the product gas composition was collected. Linear algebraic expressions were then generated with the raw GC data to arrive at the ethane conversion (35 and 50 mole%) and corresponding ethylene selectivity (mole%) results in the table below.

[0121] The data in Table 1 show that the conversion temperature for most of the catalysts is significantly lower than Comparative Example 2.1, which indicates poor activity because the conversion did not reach 35 mole% or 50 mole% before the reactor temperature reached 500°C. Except for catalysts 1.2 and 1.7, the examples show ethylene selectivity greater than 90% even at the 50 mole% conversion temperature. In addition, the results for catalyst 1.9 show that scaling up the synthesis to provide larger quantities does not have a deleterious effect on performance, and in fact catalyst 1.9 actually shows better performance than catalyst 1.1 with a lower conversion temperature and similar ethylene selectivity. Note that catalysts 1.1 and 1.5 were evaluated using both the standard MRU method and the modified method, which had no effect on selectivity, but the conversion temperature was 14°C to 39°C higher for the modified method. The asterisk indicates a sample that was evaluated using only the modified method.

[0122] Table 1

[0123]

[0124] Catalysts 1.1 and 1.6 were selected for evaluation of suitable supports. Suitable or compatible supports were evaluated by determining the effect of the combination of catalyst and support on selectivity and conversion. The MRU testing of the catalyst materials followed the procedure of the standard test described above. Specifically, 4.00-5.00 g of the pressed catalyst material (particle size 425 μιη to 1000 μιη) was physically mixed with quartz sand such that the mixture resulted in a total catalyst bed volume of 6-8 mL. In cases where the density of the catalyst material was too low and 5 g of the catalyst material reached 6 mL volume, no sand was added. In cases where the density of the catalyst material was too low and 5 g of the catalyst exceeded 6 mL, the catalyst was loaded to the maximum volume of 8 mL and the flow was adjusted to maintain the WHSV specification of 5.47 h -1 . Since all of the catalyst materials were prepared with 40 wt% catalyst, the weight loading of the catalyst in the MRU test apparatus was in the range of 1.60-2.00 g. The flow of the pre-mixed feed gas was controlled between 126-152 standard cubic centimeters (seem) depending on the weight loading in order to achieve a constant weight hourly space velocity (WHSV) of 5.46 h -1 for all of the catalyst material tests.

[0125] It will be apparent to those skilled in the art that the use of variable catalyst amounts and total catalyst bed volumes has no significant effect on the measured conversion and selectivity provided that the measurements are obtained using the same reactor dimensions, feed composition, operating pressure, and WHSV of 5.47 h -1 as described above. The limits of the conversion and selectivity described and claimed herein are measured under the described conditions.

[0126] The data in Table 2, which was collected using the standard catalyst testing described above on the MRU, indicates that support materials comprising precipitated silica, fumed silica, aluminum silicate, alpha-alumina, anatase titania, and zirconium oxide powders provided the best results, maintaining conversion below 431 °C and selectivity above 87%, respectively. In contrast, support materials comprising silicon carbide, colloidal alumina, boehmite aluminum, calcium titanate, and colloidal zirconia appeared incompatible due to a large decrease in selectivity.

[0127] Table 2

[0128]

[0129] Robustness

[0130] Fresh catalysts generally show robust activity that decreases over time. Without wishing to be bound by theory, this effect can be due to elements within the catalyst undergoing sublimation, leading to changes in structure and composition. Catalysts with more stable structure and phase composition can maintain high conversion and selectivity over time, and are therefore more advantageous for use in commercial processes, as they can withstand longer periods before needing to be replaced.

[0131] In the MRU, catalysts and catalyst materials were tested for robustness using the standard test conditions described above for catalyst loading, feed gas composition, pressure, and WHSV. The effluent gas was monitored by gas chromatography (GC) to adjust the temperature to provide a predetermined standard: 50% conversion temperature or residual oxygen level (mole %). The 50% conversion temperature was determined for each tested catalyst material, which was used as an estimate of the temperature required to provide 50% conversion. Inherent variability (~1-3 degrees) meant that conversion at a set temperature did not always drop to 50%. To test the robustness of the catalyst, the temperature was set to provide 50% conversion. If the conversion steadily decreased and reached a plateau, the temperature was adjusted to provide 50% conversion. The run was conducted for up to 48 hours (and up to 144 hours).

[0132] To test the robustness of the catalyst materials, the temperature was set and maintained throughout the run time. The run was conducted for up to 48 hours (and up to 144 hours), but was stopped when the conversion or selectivity dropped to an unacceptable level (e.g. catalyst material 2.1).

[0133] Figure 2The effects of long-term testing of catalyst 1.1 are shown, with results obtained using ~144 hours of time on stream (TOS). Catalyst 1.1 was previously determined to have a 50% conversion temperature of ~443 °C (Table 1). A calibration was then performed using a similar temperature of 440 °C, based on the previous determination. During the calibration (~15 hours), the catalyst showed a slight decrease in conversion (top plot), but no significant change in selectivity (bottom plot). The temperature was then increased (indicated by the arrow) to 448 °C to provide 50% conversion and was held at this for the duration. The catalyst again showed a slight decrease in conversion over time, but stabilized as the curve flattened. The selectivity remained essentially constant at all times. The WHSV was held constant at 5.47 h -1 These results indicate that catalyst 1.1 is stable, and is able to maintain activity and selectivity over time.

[0134] Figure 3 The effects of long-term testing of catalyst 1.6 are shown, with results obtained using ~96 hours of time on stream (TOS), with the temperature held constant at 442 °C. The catalyst showed no significant changes in either conversion (top plot) or selectivity (bottom plot). These results indicate that catalyst 1.6 is stable, and is able to maintain activity and selectivity over time at a temperature of 442 °C.

[0135] Figure 4 The effects of long-term testing of catalyst 1.6 at low residual oxygen are shown, with results obtained using ~120 hours of time on stream (TOS). The starting temperature for the robustness testing of catalyst 1.6 was set at a temperature that provided a residual oxygen content of ~0.27 mole% in the effluent stream (470 °C). The conversion (top plot) slowly decreased over ~87 hours before the temperature was changed to 455 °C (indicated by the arrow) to provide ~50% conversion. The selectivity (bottom plot) remained essentially constant at all times, increasing slightly after the temperature was decreased to 455 °C. The results indicate that catalyst 1.6 is stable, and is able to maintain activity and selectivity over time. In addition, catalyst 1.6 appears to be restorable at low residual oxygen content. This is important, as many known catalysts have been shown to become irreversibly deactivated at low oxygen levels.

[0136] Similar results were observed with catalyst 1.5 (not shown), where the conversion slightly decreased over 120 hours, while the selectivity showed no significant change, plateauing at ~91%. In contrast, catalyst 2.1, which did not undergo robustness testing, did not reach a conversion of 35% even at temperatures above 500 °C (Table 1).

[0137] To show the effect of the combination of catalyst and support on conversion and selectivity, the catalyst material formed from catalyst 1.6 was subjected to robustness testing. Figure 5The results of long-term testing of catalyst material 1.1 are shown, including the results of catalyst 1.6 as a comparison, for a run time (TOS) of ~48 hours. The start temperature for the robustness testing of catalyst material 1.1 was set at a temperature that provided ~50% conversion (residual oxygen content of 2.06 mole %) at 455 °C. The conversion (top graph) remained essentially constant with minimal deviation (±1-2 °C) throughout, similar to catalyst 1.6. The selectivity showed a gradual increase over time, moving from ~88% to ~90%. The results indicate that the precipitated silica is suitable for use as a support, as it shows good conversion and selectivity at temperatures in excess of 400 °C for at least 48 hours.

[0138] Figure 6 The results of long-term testing of catalyst material 1.2 are shown, including the results of catalyst 1.6 as a comparison, for a run time (TOS) of ~48 hours. The start temperature for the robustness testing of catalyst material 1.2 was set at a temperature that provided ~50% conversion (residual oxygen content of 2.40 mole %) at 450 °C. The conversion (top graph) remained essentially constant with minimal deviation (±1-2 °C) throughout, similar to catalyst 1.6. The selectivity showed a gradual increase over time, moving from ~88% to ~90%. The results indicate that the fumed silica is suitable for use as a support.

[0139] The results of catalyst materials 1.3, 1.4, and 1.5 demonstrate similar robustness results, with a slight decrease in conversion over time prior to stabilization. The temperature used was slightly higher, set at 460 °C, which can explain the decrease. Despite the slight decrease, these catalyst materials demonstrated the ability to maintain a relatively high selectivity (~90%) at temperatures in excess of 450 °C. Operation at lower temperatures, such as 430 °C, would likely result in stable conversion and possibly higher selectivity.

[0140] In contrast, catalyst materials 2.1, 2.3, 2.4, and 2.5 showed poor performance, as the conversion decreased significantly or the selectivity decreased to as low as 65% levels during the testing. The overall results of the robustness testing are summarized in Table 3 below.

[0141] Table 3

[0142]

[0143] Acetic acid production

[0144] Acetic acid selectivity was determined by running the MRU test for a sufficient length of time to collect aqueous condensate in the condenser downstream of the MRU (e.g., 1-5 days). After collecting the condensate sample, the sample was subjected to liquid phase GC analysis (Agilent 6890N gas chromatograph using Chrom Perfect-Analysis, version 6.1.10 for data evaluation). To perform the liquid GC analysis, 300-450 mg of liquid sample was transferred to a scintillation vial. Then, 25 mg of isopropyl alcohol (IPA) was added as an internal standard. In addition, 18-20 mL of distilled H2O was added to dilute the sample. The prepared sample was then transferred to a GC vial and set in sequence for testing using an auto-sampler. The GC analysis was split-injection with a temperature program and FID detector. In addition, a set of 3 calibration standards was run in duplicate for the relative response factors used to calculate the acetic acid content in the samples.

[0145] The corresponding weight % acetic acid measured by GC analysis in the aqueous condensate product of the MRU long-term robustness test data for catalysts 1.1, 1.5, and 1.6 and catalyst materials 1.1-1.5, 2.3, and 2.5 is shown in Table 4 below. The aqueous condensate samples were collected on the dates indicated, which allowed for collection of a sufficient amount of liquid to be subsequently quantified by GC analysis. Due to the small scale of the MRU apparatus, it was necessary to use GC analysis to measure the acetic acid in the aqueous condensate. On a commercial scale, the amount of aqueous acetic acid would be large enough that a mass balance calculation could be performed on the gaseous product stream to measure the acetic acid content with high accuracy. The use of GC analysis provided an accurate measurement of the acetic acid level (in weight %) of the entire reactor effluent. It should be noted that the selectivity calculation did not include the acetic acid component, which is not part of the gas phase.

[0146] Table 4

[0147]

[0148] The results demonstrate that the acetic acid level did not exceed 3.5 wt% despite showing some day-to-day variability. This is quite low, especially considering that the measurements were made when the conversion level was close to 50%. Many ODH catalysts known in the art have demonstrated acetic acid selectivity of 5-12 wt%.

[0149] Physical characterisation

[0150] The prepared catalysts and catalyst materials were physically characterized to determine the molar ratio of elements present, phase composition (particularly with respect to M1and amorphous phase), and particle size.

[0151] SEM

[0152] Scanning Electron Microscopy (SEM) images were collected using a JSM-IT300LV InTouchScope TM Scanning Electron Microscopy (SEM) images were collected using a JSM-IT300LV InTouchScope Figure 7 SEM images (10,000x magnification) of fresh and used catalyst materials 1.1, 1.4, and 1.5, and fresh catalyst materials 1.2 and 1.3. Figure 8 SEM images (10,000x magnification) of fresh and used catalyst materials 1.1, 1.4, and 1.5, and fresh catalyst materials 1.2 and 1.3.

[0153] SEM-EDS

[0154] Energy Dispersive X-ray Spectroscopy (EDS) was performed using a JEOL JED-2300DRY SDD EDS detector. Samples were sent to SEMx Incorporated for EDS analysis to determine the molar ratios of elements present in the catalyst and catalyst materials. The tested catalyst and catalyst material samples were finely ground to reduce particle size and obtain a uniform mixture. They were then loaded onto the EDS column for analysis by SEM. EDS was used for elemental analysis and surface inspection. EDS is a trace analysis technique that provides semi-quantitative elemental analysis of the surface (e.g., top 1 to 3 microns) of a sample. SEM was used to inspect surface morphology at magnifications of 20-100,000x. The EDS instrument can detect elements with atomic numbers equal to or greater than sodium, but also has light element capability, meaning it can also detect carbon, nitrogen, oxygen, and fluorine. The estimated detectable lower limit for any given element is typically about 0.2-0.5 wt%.

[0155] EDS evaluation of the catalyst and catalyst materials was performed to determine the elemental composition. The EDS elemental mass wt% of the detected elements was used to determine the molar ratios, as shown in Table 5. Catalysts 1.1-1.6 were significantly different from comparative catalyst 2.1. V was significantly higher and Te was significantly lower relative to the molybdenum component. The tantalum levels were generally higher, with the exception of catalysts 1.5 and 1.6.

[0156] Table 5

[0157]

[0158] EDS measurements of the molar ratios of the catalyst materials were also performed, and the results are shown in Table 6. The chemical formula also identifies other elements identified, such as Si, Al, Na, and Mg (which can come from the support material). The trend of some catalysts losing activity or selectivity over time can be due to changes in composition under the conditions of the oxidative dehydrogenation process. After performing the robustness testing, several of the catalyst materials (labeled “used”) were re-evaluated using EDS to determine if there were significant changes in composition. No significant changes were observed for the four elements Mo, V, Te, and Te. The low levels of iron that appeared in the used catalyst materials can be due to leaching of iron from the reactor piping.

[0159] Table 6

[0160] Sample EDS determined catalyst chemical formula (molar ratio) Catalyst material 1.1 Mo1V 0.43 Te 0.15 Ta 0.07 Si 5.14 Al 0.03 ]]> Catalyst material 1.1 (used) Mo1V 0.47 Te 0.16 Ta 0.11 Si 5.79 Al 0.07 Fe 0.01 ]]> Catalyst material 1.2 Mo1V 0.47 Te 0.16 Ta 0.11 Si 2.44 Al 0.03 ]]> Catalyst material 1.3 Mo1V 0.43 Te 0.15 Ta 0.09 Si 1.83 Al 0.15 Fe 0.02 Na 0.02 Mg 0.01 ]]> Catalyst material 1.4 Mo1V 0.50 Te 0.16 Ta 0.11 Si 0.04 Al 2.68 ]]> Catalyst material 1.4 (used) Mo1V 0.50 Te 0.16 Ta 0.11 Si 0.04 Al 2.10 ]]> Catalyst material 1.5 Mo1V 0.54 Te 0.16 Ta 0.10 Si 0.04 Al 0.04 Ti 5.17 ]]> Catalyst material 1.5 (used) Mo1V 0.51 Te 0.17 Ta 0.08 Si 0.03 Al 0.05 Ti 6.85 ]]>

[0161] PSD by SEM

[0162] The samples were sent to SEMx Incorporated for particle size analysis using a scanning electron microscope (SEM) with a model number of JEOL-JSM300 LV. The particles in the sample were observed and counted using the SEM to obtain the particle size distribution (PSD). For the PSD measurement, the SEM instrument takes pictures at different magnifications. 400-800 particles were measured at different magnifications to cover the size range (statistical population). The size was measured by the length in microns on the longest dimension of the particle. The SEM-based PSD is the preferred method for analyzing samples where particles are agglomerated (stuck together) because the analyst can visually see this through the microscope and make intelligent decisions to measure different particles rather than agglomerates. The statistics and analysis are based on the total counts measured by the SEM.

[0163] The results of the particle size distribution for catalysts 1.1-1.6 and 2.1 are shown in Table 7, and the results of the particle size distribution for catalyst materials 1.1 and 1.2 are shown in Table 8.

[0164] Table 7

[0165]

[0166] Table 8

[0167]

[0168] Pore volume, BET surface area analysis, and BJH pore size distribution analysis

[0169] Gas adsorption manometry was used to determine the adsorption isotherm of nitrogen at liquid nitrogen temperature (~77 K). The amount of gas adsorbed was evaluated by measuring the change in pressure of the gas. The isothermal nitrogen adsorption process was measured and surface area and volume were calculated by applying various theories / equations.

[0170] The total pore volume was calculated by the amount of nitrogen absorbed at a relative pressure P / P0 = 0.99.

[0171] Brunauer-Emmett-Teller (BET) analysis was used to quantify the specific surface area (m²) of solid samples. 2 / g). BET assessment was performed via nitrogen multilayer adsorption and measured as a function of relative pressure. Comparisons are difficult because different solids can have significantly different isotherm shapes. Applying BET theory allows for a more quantitative comparison of solid surface areas by determining the so-called monolayer capacity through nitrogen multilayer adsorption experiments. Monolayer capacity is a representation of the total specific surface area and includes both the external surface area and the pore area of ​​the porous solid.

[0172] The Barrett-Joyner-Halenda (BJH) method is used for Kelvin models (cm) with hole filling. 3 The pore size was calculated from the adsorption isotherms collected experimentally (g·A). Pore ​​size distribution. This technique characterizes pore size distribution, independent of the external area caused by sample particle size, and can be applied to both mesopores and small macropores.

[0173] Nitrogen physisorption experiments were performed on a TriStar (Micromeritics Instruments) instrument, with samples undergoing nitrogen adsorption analysis at 77 K. Prior to the adsorption experiment, the samples were placed in a physisorption cell and degassed at 200 °C for 1 hour.

[0174] The surface area and pore volume measurements of catalysts 1.6 and 2.1 are shown in Table 9.

[0175] Table 9

[0176] Sample BET surface area (m 2 / g) Pore volume (cm 3 / g) Catalyst 1.6 4 0.03 Catalyst 2.1 (comparative) 1 0.01

[0177] XRD

[0178] X-ray diffraction (XRD) data were collected using a PANalytical Aeris X-ray diffractometer from SEMx Incorporated. This data was used to determine the phase composition present in the prepared catalyst. The diffractometer consists of three basic components: an X-ray tube, a sample holder, and an X-ray detector. X-rays are emitted through a cathode ray tube (…). X-rays generated in a copper source are directed onto the sample. As the sample and detector rotate, the intensity of the reflected X-rays is recorded to produce a characteristic X-ray spectrum. Constructive interference occurs and an intensity peak (y-axis) appears when the incident X-rays reflected from the sample satisfy the Bragg equation (n l = 2d sin q). The X-ray diffractometer is set up so that the sample rotates in the path of the X-ray beam at an angle q, while the X-ray detector is mounted on an arm to collect the diffracted X-rays and rotates at a 2q angle of ~5° to 70° (x-axis).

[0179] Qualitative XRD analysis and Rietveld refinement were performed using HighScore Plus XRD analysis software. The samples were finely ground to reduce particle size and obtain a homogeneous mixture. They were then loaded onto the XRD sample holder and XRD spectra were acquired. The Rietveld refinement results were combined with the Highscore Plus and EDS results for qualitative and quantitative analysis.

[0180] Amorphous content determination

[0181] The weight percent of amorphous content was determined by an external standard method. An external standard phase was used to determine the instrument intensity constant K factor. Corundum was used as the external standard and measured using the same instrument configuration shortly after the unknown samples were measured. The K factor method is described by O’Connor and Raven: 1988, Powder Diffraction, 3(1), 2-6. For each sample, the weight percent of the crystalline MoTeVTaO orthorhombic phase must be determined in order to assign a weight percent to the amorphous content. The crystallinity (DOC) method is based on an estimate of the total area intensity each component contributes to the overall diffraction pattern in the analysis for determining the amount of amorphous phase. The crystallinity is calculated from the total area under the crystalline and amorphous components defined by:

[0182] DOC = crystalline area crystalline area + amorphous area

[0183] where the weight fraction of amorphous material can be calculated by:

[0184] Wamorphous = 1 - DOC

[0185] Orthorhombic MoTeVTaO x contribute to the relative crystalline area and therefore need to be quantified to determine the amorphous area. To compensate for the fact that different materials and backgrounds can have different effects, the orthorhombic Pba2 MoVTeNbO x phase sample to calibrate some constants needed for the DOC method. MoTeVTaO x orthorhombic Pba2 phase sample has a weight percent based on MoVTeNbO x This phase weight percent was used to calibrate the semi-quantitative determination.

[0186] M1 phase content determination

[0187] Literature crystal structure data of different but crystallographically similar compounds were used to fit MoTeVTaO x Orthorhombic Pba2 phase (also referred to in the literature as Ml phase) because its orthorhombic Pba2 crystal phase is the matching one. See DeSanto. P, Jr & Buttrey, D. & Grasselli, R. & Pyrz, W. & Lugmair, C. & F, Jr & Vogt, Thomas & Toby, Brian. (2006). Topics in Catalysis 38: 31-40 (“DeSanto”).

[0188] Lattice parameters:

[0189] Raw data comparative analysis

[0190] Rietveld refinements for phase identification of catalysts 1.1-1.6 and 2.1 and the relevant wt% of the identified phases are shown in Table 10. The 9-digit code below the phase chemical formula represents the corresponding reference code in PDF-4+ 2020. (TeO) 0.43 ((Mo 4.08 V 0.70 Ta 0.22 )O 14 ) corresponds to the phase identified in DeSanto. The (TeO) 0.43 ((Mo 4.08 V 0.70 Ta 0.22 )O 14 ) representing the Ml phase was not detected in catalyst 1.2 and was significantly lower in catalyst 2.1 synthesized following the method disclosed in US20100222623. Considering the performance results, the results indicate that a significant Ml phase is necessary to achieve high conversion and selectivity even at temperatures higher than 400°C. In addition, the most active catalysts contained at least 26.9 amorphous phase, with most of the examples containing 34.2 to 48.9 amorphous phase.

[0191] Table 10

[0192]

[0193]

[0194] Rietveld refinements for phase identification of catalyst materials 1.1-1.5 and the associated wt% of identified phases are shown in Table 11 below. The 9-digit code below the phase chemical formula represents the corresponding reference code in PDF-4+ 2020. (TeO) 0.43 ((Mo 4.08 V 0.70 Ta 0.22 )O 14 ) corresponds to the phase identified in DeSanto.

[0195] The results show that the suspected M1 phase (TeO) 0.43 ((Mo 4.08 V 0.70 Ta 0.22 )O 14 ) is reduced compared to catalyst 1.6, but is still higher than comparative catalyst 2.1 (see Table 10). This indicates that catalyst materials with at least 2.5 wt% or greater of the M1 phase will provide good conversion and selectivity at temperatures in excess of 400°C. Furthermore, the combination of catalyst supports / carriers listed in Table 2 for catalysts 1.1, 1.2, 1.4 and 1.5 are unlikely to reduce the M1 phase to a level where conversion and selectivity are compromised.

[0196] Table 11

[0197]

[0198]

[0199] Table 12 includes the Rietveld refinements for phase identification and the associated wt% of identified phases for selected catalyst materials before and after MRU testing. The 9-digit code below the phase chemical formula represents the corresponding reference code in PDF-4+ 2020. (TeO) 0.43 ((Mo 4.08 V 0.70 Ta 0.22 )O 14 ) corresponds to the phase identified in DeSanto. These results show that the M1 phase does not change significantly over time, which can explain the robustness exhibited by these catalyst materials.

[0200] Table 12

[0201]

[0202]

[0203] Figure 9XRD spectra of catalysts 1.1, 1.3, 1.4, 1.5, and 1.6, and comparative catalyst 2.1 are shown in FIG. 1. The relative peak intensities and 2 theta angle ranges of the peaks identified in Table 13 for catalysts 1.1, 1.3, 1.4, 1.5, and 1.6 (composites) are shown in Table 14. The peaks correlate to the general pattern determined from the crystal structure. Key peaks include those near 22.2°, 26.7°, and 28.3°, which show a maximum intensity of at least 100%. Other peaks of note include those near 7.8°, 9.0°, 22.9°, and 25.0°. Catalyst 2.1 has some similarities, but is missing peaks near 7.8° and 9.0°. Figure 9

[0204] Table 13

[0205]

[0206]

[0207]

[0208] Figure 10 XRD spectra of catalyst materials 1.1, 1.2, 1.3, 1.4, and 1.5 are shown in FIG. 2. As can be seen from the figure, the characteristic pattern has changed due to the addition of the support material. The key peaks near 22.2°, 26.7°, and 28.3° are still visible, as are the peaks near 7.9° and 9.0°. Comparison of the XRD of fresh and used catalyst materials 1.1, 1.3, and 1.4 shows a slight change in the pattern (data not shown) and the relevant peaks are still present.

[0209] FTIR

[0210] Fourier Transform Infrared Spectroscopy (FTIR) is a technique used to obtain an infrared spectrum (IR) of a solid or liquid sample by shining monochromatic light on the sample and measuring the absorbance over a range of wavelengths. FTIR techniques can be used as a fingerprinting technique, where the IR spectrum of an unknown sample is overlaid with the IR spectrum of a known sample, or it can be used to identify characteristic absorptions that are representative of specific kinds of molecular bonds (e.g., C=0, O-H, N-H, C-H, C-O, S-O, S=0, etc.). Solid samples for FTIR scanning were prepared by the KBr pellet technique. The benchtop instrument was a Bruker Tensor 27 FTIR spectrophotometer, and a laser with a 633 nm operating wavelength was used.

[0211] FTIR spectra of catalysts 1.1-1.6 and 2.1 are shown in FIG. 3. Figure 11

[0212] ​​Industrial applicability

[0213] The present disclosure relates to a catalyst useful for the oxidative dehydrogenation of ethane. The catalyst comprises molybdenum, vanadium, tellurium, and tantalum and shows good conversion and selectivity to ethylene at temperatures exceeding 400°C.

Claims

1. A catalyst having the following formula: For1V 0.39-0.49 The 0.12-0.17 Print 0.06-0.15 Oh x in: x is a value that at least satisfies the catalytic valence; and The amorphous content of the catalyst is 30% to 50% by weight.

2. The catalyst according to claim 1, wherein the amorphous content of the catalyst is 30% to 40% by weight.

3. The catalyst according to claim 1, wherein the amorphous content of the catalyst is from 33% to 36% by weight.

4. A catalyst material comprising the catalyst and catalyst support as described in claim 1.

5. The catalyst material according to claim 4, wherein the catalyst support is selected from precipitated silica, pyrolysis silica, silica-alumina, α-alumina, and anatase titanium dioxide.

6. The catalyst material according to claim 4, wherein the catalyst support is precipitated synthetic silica.

7. A method for the oxidative dehydrogenation of ethane, the method comprising contacting a gaseous feed comprising ethane and oxygen with a catalyst in a reactor to produce an effluent comprising ethylene, wherein the catalyst has the following formula: For1V 0.39-0.49 The 0.12-0.17 Print 0.06-0.15 Oh x in: x is a value that at least satisfies the catalytic valence; and The amorphous content of the catalyst is 30% to 50% by weight.

8. The method according to claim 7, wherein the amorphous content of the catalyst is 30% to 40% by weight.

9. The method according to claim 7, wherein the catalyst has an ethane conversion of 50 mol% and an ethylene selectivity of 90% or higher at a temperature of 350°C to 475°C.

10. The method of claim 7, wherein the catalyst has an ethane conversion of 50 mol% or higher and an ethylene selectivity of 90% or higher at a temperature of 400°C to 450°C.

11. The method of claim 7, wherein the catalyst has an ethane conversion of 50 mol% or higher and an ethylene selectivity of 90% or higher at a temperature of 350°C to 475°C for at least 110 hours.

12. The method of claim 7, wherein the catalyst has an ethane conversion of 50 mol% or higher and an ethylene selectivity of 90% or higher at a temperature of 400°C to 450°C for at least 110 hours.

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