CALCINATION PROCESS;

CALCINED CATALYST; ODH METHOD

TECHNICAL FIELD

The present disclosure relates to a controlled calcination process to produce an enhanced catalyst for the oxidative dehydrogenation for paraffins to olefins, particularly lower paraffins such as C2-4 paraffins to the corresponding olefins.

Mixed metal oxide catalsyts for the dehydrogenation of paraffins have been known since the mid to late 1960’s. The catalyst activity and selectivity depend more on the content of amorphous phase (sometimes referred to as the M2 phase) versus crystalline phase(s) (sometimes referred to as M1 phase) of the catalyst.

BACKGROUND ART

Over about the past 10 years there has been increasing interest in the mixed oxide catalyst comprising Mo, V, Nb and one or more of Te and Sb optionally together with one or more of Pd, Sb Ba, Al, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr,

Zr, and Ca.

Lapsed U.S. Patent 7,319,179 in the name of Lopez Nieto et al., assigned to Consejo Superior De Investigaciones Cientificas, and Universidad Politecnica De Valencia discloses an oxidative dehydrogenation catalyst comprising Mo, Te, V, Nb and at least a fifth element A which is selected from the group consisting of Cu, Ta, Sn, Se, W, Ti, Fe, Co, Ni, Cr, Zr, Sb, Bi, an alkali metal, an alkaline-earth metal and a rare earth. The catalyst is prepared by a two-step process in which the first step comprises forming a solution of ammonium heptamolybdate tetrahydrate telluric acid are dissolved in water at 80°C adjusting the pH to 7.5 and evaporating the water and drying the resulting product. In the second step the product from step 1 is further mixed with an aqueous solution of vanadyl sulphate and niobium (V) oxalate and the mixture is stirred and transferred to a steel autoclave kept at

175°C, static, for 2 days. The content of the autoclave is filtered, it is washed with distilled water and dried at 80°C. The solid obtained is calcined at 450°C for 2 h in a current of nitrogen in order to obtain the catalyst. The XRD of the catalyst is figure 1 of the reference. The reference does not teach a heat up or cool down rate for the calcination step nor does it teach covering the catalyst precursor with a non- woven fabric having a melting temperature greater than the calcination

temperature.

Lapsed United States Patent 7,319,179 further teaches the following: The calcination stage can be carried out by causing a flow of inert gas to pass (with spatial velocities between 1 and 400 h ^-1 ) or statically. The temperature lies between 250 and 1000°C and more preferably between 550 and 800°C. The calcination time is not a determining factor, though between 0.5 hours and 20 hours is preferred. The speed of heating is not a determining factor, though between 0.1 °C./minute and 10°C./minute is preferred. The catalyst can also be initially calcined in an oxidizing atmosphere up to a temperature of 200-350°C., and more preferably between 250 and 290°C, and later be subjected to a calcination in an inert atmosphere. The reference fails to teach the porous cover of the present invention. It also fails to discuss the content of the amorphous phase in the catalyst.

The present invention seeks to provide a method to calcine a mixed oxide oxidative dehydrogenation catalyst. According to the present invention, amorphous content remains high, typically greater than 40 wt. %, preferably above 50 wt. %.

SUMMARY OF INVENTION

The present invention provides a method to calcine a catalyst precursor of the formula MoiVo.i-iNbo.i-iTeo.oi-o.2Xo-20d where X is selected from Pd, Sb Ba, Al, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, Ca and oxides and mixtures thereof, and d is a number to satisfy the valence of the catalyst while maintaining an amorphous content of not less than 40 wt. % comprising:

Calcining the catalyst precursor in an inert container with flow passage there through, comprising heating the catalyst precursor at a rate from 0.5 to 10°C per minute from room temperature to a temperature from 370°C to 540°C under a stream of pre heated gas selected from steam and inert gas and mixtures thereof at a rate of flow comparable to a flow rate of not less 150 seem through a 2.54 cm diameter tube, with a length of 152 cm at a pressure of greater than or equal to 1 psig having a temperature of at least 100°C in some embodiments from 300°C to 540°C and holding the catalyst precursor at that temperature for at least 2 hours and cooling the catalyst precursor to room temperature said catalyst precursor being fully or partially enclosed by a porous material having a melting temperature greater than 600°C.

In a further embodiment the inert container is made from high temperature glass (e.g. Pyrex), quartz, ceramics (Beryllium Oxide, alumina) or steel. In a further embodiment the inert container has a heat conductivity greater than 0.34W nr ¹ -K.

In a further embodiment the flow rate of inert gas and mixtures thereof is greater than 150 seem.

In a further embodiment the pressure of inert gas greater than 1 psig.

In a further embodiment the heat up rate is 0.9 to 2.0 C per min.

In a further embodiment wherein the catalyst precursor is held at a temperature from 2 - 24 hours.

In a further embodiment the catalyst is held at a temperature from 400°C to

525°C.

In a further embodiment the stream of inert gas and mixtures thereof comprises nitrogen.

In a further embodiment the porous material is selected from glass and mineral fiber.

In a further embodiment optionally charcoal or activated carbon is on the outer surface of the porous material in an amount up to 0.5 g per 1 g of catalyst precursor is present on the upper surface of the material.

In a further embodiment X is one or more metals and oxides thereof selected from Pd, Sb, Ba, Al, Cu, Ti, Fe, Ca, Zr and mixtures thereof.

In a further embodiment the molar ratio of said one or more metals and oxides selected from Pd, Sb, Ba, Al, Cu, Ti, Fe, Ca, Zr and mixtures thereof to Mo is from 0.001 - 0.3, preferably from 0.05 - 0.15.

In a further embodiment X is selected from the group consisting of one or more metals and oxides thereof are selected from Pd, Sb, Ba, Al, Cu and mixtures thereof.

In a further embodiment in the catalyst precursor X is absent.

In a further embodiment the catalyst precursor has the formula:

Moi .oVo.10-049T eo.o6-o.17N bo.13-0.190d

In a further embodiment the calcined catalyst has the formula:

Mo1V0.40-0.45Te0.10-0.i6Nb0.13-0.i6Od

In a further embodiment the calcined catalyst has the formula:

MoV0.40-0.45Te0.10-0.i6Nb0.13-0.i6Od

having an amorphous content of not less than 40 wt.%. In a further embodiment the calcined catalyst according has a crystalite size calculated according to the Scherrer equation of 45 to 55 nm.

In a further embodiment the calcined catalyst has a crystalite size calculated according to the Scherrer equation of 50 to 52 nm.

In a further embodiment the calcined catalyst is bound, agglomerated, filled, promoted, impregnated, supported with from 5 - 90, weight % of a material other than active phase.

A further embodiment provides a method for the oxidative dehydrogenation of a mixed feed comprising one or more C2-4 paraffins and oxygen in a volume ratio from 70:30 to 95:5 and optionally one or more C3-6 alkanes or alkenes and oxygenated species including CO and CO2 at a temperature from 320°C up to 385°C, a gas hourly space velocity of not less than 100 hr ¹ , and a pressure from 0.8 to 7 atmospheres comprising passing said mixture over the above catalyst (s).

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a diagram of the location of the samples of catalyst precursor in the quartz tube reactor showing the heating zones and the flow of nitrogen over the catalyst precursor.

Figure 2 is an XRD of an uncalcined (low calcined) catalyst of boat 4 with an underlying base line for the calcined sample.

Figure 3 is a plot of the conversions and selectivity of the catalyst for ethane to ethylene at various temperatures over a long term run of about 650 hours.

Figure 4 is plot of the pore size distribution of the catalysts of the present invention.

DESCRIPTION OF EMBODIMENTS

Numbers Ranges

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

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention 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.

Also, 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.

All compositional ranges expressed herein are limited in total to and do not exceed 100 percent (volume percent or weight percent) in practice. Where multiple components can be present in a composition, the sum of the maximum amounts of each component can exceed 100 percent, with the understanding that, and as those skilled in the art readily understand, that the amounts of the components actually used will conform to the maximum of 100 percent.

In the specification the phrase the temperature at which there is 25% conversion of ethane to ethylene is determined by plotting a graph of conversion to ethylene against temperature typically with data points below and above 25% conversion or the data is fit to an equation and the temperature at which there is a 25% conversion of ethane to ethylene is determined. In some instances in the examples the data had to be extrapolated to determine the temperature at which 25% conversion occurred.

In the specification the phrase selectivity at 25% conversion is determined by plotting the selectivity as function of temperature or fit to an equation. Then having calculated the temperature at which 25% conversion occurs one can determine either from the graph or from the equation the selectivity at that temperature. The ratio of amorphous component to crystalline component may be determined by obtaining an XRD for the calcined catalyst. Within 24 hours of obtaining the sample XRD you run a standard (100% crystalline material such as Corundum on the XRD instrument to determine the K factor for the instrument. Then knowing the K factor you determine the percentage of crystalline phase per i

unit mass of sample and the difference is the weight of the amorphous content per unit mass of sample. Such as disclosed in: O. Connor and Raven (1988), Powder Diffraction, 3(1), 2-6; http://www.icdd.com/ppxrd/12/presentations/P30-Arnt-Kern- ppxrd-12.pdf.

A typical procedure is as follows:

1. The sample is finely ground to reduce particle size to less than 250 microns and obtain a uniform mixture.

2. The ground sample is loaded onto an XRD sample holder preferably having an EDS stub for XRD and EDS analysis.

3. Acquire the XRD spectrum and where applicable perform EDS analysis using a scanning electron microscope (SEM).

5. Combine Highscore Plus, EDS and Rietveld Refinement to perform qualitative and quantitative analysis.

4. Amorphous analysis- Run standard using exactly same holder and same program as we did with the sample. Standard must be run with 24hrs after the sample was run.

7. Using external standard method to determine the amorphous content.

8. With an external standard method we are determining an instrument intensity constant often called K-factor (sometimes called G-factor as well). Our instrument and software already have program set up for this method.

9. Generate report.

In this specification non-antagonistic binder means a binder other than Nb205 which when incorporated into the agglomerated catalyst has less than a 5% antagonistic effect on the agglomerated catalysts. Some non-antagonistic binders include oxides of aluminum, titanium and zirconium. Silica oxides have an antagonistic effect on the agglomerated catalysts and the catalyst active sites.

The Catalyst Precursor

The catalyst precursor may be prepared using a hydrothermal process including following steps: i) forming an aqueous solution of ammonium heptamolybdate

(tetra hydrate) and telluric acid in a molar ratio of Mo:Te 1 : 0.14 to 0.20, in some instances from 1 :0.17, at a temperature from 30°C to 85°C and adjusting the pH of the solution to 6.5 to 8.5, preferably from 7 to 8, most preferably from 7.3 to 7.7 preferably with a nitrogen-containing base to form soluble salts of the metals;

ii) stirring the pH adjusted solution for a time of not less than 15 minutes, in some instances from not less than 2 hours, in some instances not more than 4 hours;

iii) adjust the pH of the resulting solution to from 4.5 to 5.5, preferably from 4.8 to 5.2, desirable from 5.0 to 5.2 with an acid, preferably sulfuric acid (0.01 - 18 M, typically 2 - 18 M) and stir the resulting solution at a temperature of 80°C until it is homogeneous in some instances with a stirring time up to 30 minutes. In some circumstances, to maintain 80°C temperature, a cooling device needs to be used to maintain temperature at 80°C;

iv) preparing a aqueous solution of vanadyl sulphate at a temperature from room temperature to 80°C (preferably 50°C to 70°C, most preferably 55°C to 65°C);

v) mixing the solutions from steps i) and iv) together to provide a molar ratio of V:Mo from 1.00 - 1.67 to 1 in some cases from 1.45 - 1.55 to 1.00;

vi) preparing a solution of H2C20 ₄ and Nb20sxH20 in a molar ratio from 5.0 to 6:0, in some instances 5.0-5.3:1 ;

vii) slowly (dropwise) adding the solution from step vi) to the solution of step vi) to provide molar ratio of Nb: Mo from 5.56 - 7.14:1 in some instances from 6.20 - 6.40 to form a slurry (typically the addition is at temperatures between 20°C and 80°C; preferably 20°C to 30°C); and

vii) heating the resulting slurry in an autoclave under an inert gas, air, carbon dioxide, carbon monoxide and mixtures there-of at a pressure of not less than 1 psig and at a temperature from 140°C to 190°C for not less than 6 hours, typically not less than 6 hours.

The temperature for the hydrothermal treatment may range from 140°C - 180°C, in some embodiments from145°C to 175°C.

The pressure in the autoclave may range from equal or above the saturated water vapor pressure at the corresponding reaction temperature in some embodiments from 30 to 200 psig (206 kPag to 1375 kPag), in some embodiments from 55 psig (380 kPag) to 170 psig (1170 kPag) above atmospheric pressure.

The gaseous product species is vented from the autoclave (reactor).

Optionally there is a condenser upstream of the autoclave outlet which may be operated at a temperature above 0°C and below reaction temperature.

The pressure inside the autoclave may be maintained above atmospheric using a liquid filled column or bubbler or a pressure regulator valve.

The hydrothermal treatment may be from 6 to 15 hours.

The autoclave (reactor) is allowed to cool to room temperature, typically overnight. The reactor contents are filtered using a Buchner filter and washed with (distilled) water or an aqueous oxalic acid solution and dried in an oven for not less than 6 hours at a temperature from 70°C to 120°C.

In some embodiments the precatalyst is separated from the aqueous phase, typically by filtration or evaporation, and washed with (distilled or deionized) water and dried in an oven for not less than 6 hours at a temperature from 70°C to 120°C. The precatalyst may be dried in an atmosphere substantially one or more inert gases. In some instances optionally, the dried precatalyst may be ground using mechanical means (e.g. a ball or roller mill) or the dried precatalyst could be subject to cryogenic grinding. The dried and ground precatalyst may in some instances be subject to sieving through a small particle size sieve to obtain a fraction having a particle size less than 250 microns, preferably less than 125 microns.

In some embodiments the product from the hydrothermal treatment is treated with from 0.3 - 2.5 ml_ of a 30 wt. % solution of aqueous H2O2 per gram of catalyst precursor.

Generally the catalyst precursor (i.e. prior to calcining) has the formula:

MoiVo.i-i Nbo.i-iTeo.oi-o.2Xo- 20d

where X is selected from Pd, Sb Ba, Al, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, Ca and oxides and mixtures thereof, and d is a number to satisfy the valence of the catalyst precursor. In some embodiments X is selected from from Pd, Sb, Ba, Al, Cu, Ti, Fe, Ca, Zr and mixtures thereof. Preferably X is selected from Pd, Sb, Ba, Al, Cu and mixtures thereof. In the formula for the precursor the molar ratio of said one or more metals and oxides and mixtures thereof to Mo is up to 2, typically if X is present from 0.001 - 0.3, preferably from 0.05 - 0.15. In some embodiments X is absent from the catalyst precursor and it has the formula:

Mo1.0V0.10-0.49Te0.06-0.17Nb0.13-0.19Od where d is a number to satisfy the valence of the catalyst precursor.

The reactor is allowed to cool to room temperature, typically overnight. The reactor contents were filtered using a Buchner filter and washed with (distilled) water or an aqueous oxalic acid solution and dried in an oven for not less than 6 hours at a temperature from 70°C to 120°C. The dried precatalyst is ground, typically to a size less than 250 pm and calcined in an inert atmosphere such as nitrogen for a time from 1 to 20 hours.

The catalyst precursor is calcined in an inert container with a flow passage there through, comprising heating the catalyst precursor at a rate from 0.5 to 10°C per minute in some embodiments from 0.9 to 2 C. per min from room temperature to a temperature from 300°C to 540°C, in some cases from 400°C to 525°C. under a dynamic stream of inert gas such as nitrogen, helium, etc. and mixtures thereof a flow rate of nitrogen comparable to (based upon) a flow of nitrogen through a 1 inch internal diameter tube having a length of 152 cm (59.8 inches) at a flow rate from 200 - 500 seem per 30 - 250 gram of catalyst precursor.

The inert container may have a heat conductivity greater than

0.34 W m ^_1 K ¹ , in some embodiments from 1.2 W m ¹ K ¹ to 50 W-nr ¹ -K ¹ . The container may be made from high temperature glass (e.g. Pyrex), quartz, ceramics (Beryllium Oxide, alumina) or steel, preferably a low carbon steel or a grade of stainless steel.

The inert gas (e.g. nitrogen) in the calcination chamber is not static. It is dynamic and flows over the precatalyst. Flow rates are a function of many variables such as the shape of the chamber, the size of the opening and exit ports of the chamber, the pressure drop across the inlets and outlets. One skilled in the art or having access to computational fluid dynamic programs can calculate flow rates. However some starting point for the calculation is required. A starting point is the flow rate for a tubular drying chamber (tube) having a one inch (2.54 cm) internal diameter and a length of 152 cm (59.8 inches) is from 200 - 500 seem per 30 - 250 gram of catalyst precursor. In some instances the flow rate may be equivalent to a flow rate through a 1 inch diameter tubular drying chamber having a length of 152 cm from 250 to 450 seem per 30 - 250 gram of catalyst precursor. However, the flow rate needs to be increased as the chamber volume increases.

The pressure in the interior of the flow chamber should be at least 1 psig (6.9 kPag) in some instances from 1 to 5 psi, in some cases, higher than 5 psi.

The temperature of the gas flowing through the chamber is from 300°C to 540°C (in some cases from 400 to 525°C). The temperature of the inert gas flowing over the catalyst is influenced by the temperature of the calcination and the flow rate.

The catalyst precursor is held at the calcining temperature for at least 2 hours, typically from 2 - 24 hours, and cooled to room temperature.

During the calcining process the catalyst precursor is at least partially enclosed in a breathable or permeable covering. In some embodiments it is preferred that the covering substantially encloses the catalyst precursor (e.g. at least 50% and preferably not less than 75% of the external surface of the catalyst precursor is covered by the breathable or permeable covering). The covering should have a permeability to gas from 5 cubic feet per minute (8.5 cubic meter/h) to 100 cubic feet per minute (170 cubic meter/hour) in some cases from 10 cubic feet per minute to 60 cubic feet per minute according to the measurement method specified by ASTM E2945-14. The permeable covering should have a melting point greater than 600°C. Provided the covering is breathable or permeable it may be a woven or nonwoven material. For example, it could be a plastic or metallic (or a metalized plastic substrate) substrate having a melting point above 600°C.

Permeability could be provided by any mechanical means to permit the passage of gas through the covering such as needle type punching process. The permeable covering could be a non woven selected from polymers having a melting point above 600°C and glass and mineral fiber, desirably glass and mineral fiber (e.g. fiber glass batting). If the covering is a woven fabric, the permeability would be controlled by the tightness of the weaving of the fabric. For example the fabric could have up to 960 of pores per cm ² for multifilament woven fabric.

In some embodiments activated carbon (greater than 90%, preferably greater than 95% purity) may be placed on top of the permeable covering to scavenge oxygen and materials released form the catalyst. The carbon may be used in amounts up to 0.5 g, typically 0.1 to 0.3 g per 1 g of catalyst precursor being calcined. The catalysts prepared in accordance with the present invention have an x- ray diffraction pattern (XRD having) typically associated with a polycrystalline (broad reflection peaks) structure vs. predominantly crystalline material (narrow reflection peaks), which is characteristic of the classical catalyst. It is the common belief in the literature that the active phase is the crystalline MoVNbTeOx phase referred to as M1 (narrow reflection peaks) as opposed to the broad smoother reflection peaks of the present catalyst. The XRD for a typical ODH catalyst has the intense diffraction angles) at 2 F (Cu source) at 22° having a half height peak width from 19° to 21 ° and broad secondary peak at 28° having a half width from 25° to 33°. Generally, the typical ODH catalyst has a crystallite size (T) of about 90 nm. Whereas the Inventive Example has a crystallite size of from 45 nm to 55 nm, typically 48 to 52 nm, in some cases 50± 1 nm. Crystallite size is calculated using the Scherrer equation, where K (dimensionless shape factor) is assumed to be 1 , l is the X-ray wavelength from Copper source and is 1.5406 A, Q is the Bragg angle of 22.29°, and b is the line broadening at half the maximum intensity (FWHM) as determined for the XRD data.

The catalysts in accordance with the present invention demonstrate a higher amorphous component not less than 40 wt. %, in some embodiments not less than 50 wt. %, preferably greater than 60 wt. % desirably greater than 70 wt. %.

The catalysts of the present invention have a smaller pore size than those of the base line (prior art). The catalysts made in accordance with the present process have a majority of pores having a size less than 10 nm. Catalysts prepared without the calcination of the present invention tend to have relatively flat pore size distribution.

In a further embodiment from 10 to 95, preferably from 25 to 80, desirably from 30 to 45, weight % of the catalyst is bound, agglomerated, filled, promoted, impregnated, or supported with from 5 to 90, preferably from 20 to 75, desirably from 55 to 70 weight % of a material (for example, a binder) other than active phase selected from the group consisting of acidic, basic or neutral binder slurries of T1O2, Zr0 ₂ AI2O3, AIO(OH), Nb20s and mixtures thereof provided that Zr02 is not used in combination with an aluminum containing binder.

In a further embodiment there is provided a method for the oxidative dehydrogenation of a mixed feed comprising a C2-4 paraffin (e.g. ethane) and oxygen in a volume ratio from 70:30 to 95:5 and optionally one or more C3-6 alkanes or alkenes and oxygenated species including CO and CO2 at a temperature greater than 320°C up to than 385°C, a gas hourly space velocity of not less than 100 hr ¹ , and a pressure from 0.8 to 7 atmospheres comprising passing said mixture over the above catalyst.

In a further embodiment the ODH process has a selectivity to ethylene of not less than 85%.

In a further embodiment the gas hourly space velocity of the ODH process is not less than 500 hr ¹ desirably not less than 1500 hr ¹ in some embodiments 3000 hr ¹ .

In a further embodiment the temperature of the ODH process is less than 375°C, preferably less than 360°C.

The catalysts prepared using the calcining procedure of the present invention are more robust than comparable catalysts prepared using a conventional calcination method (higher temperatures and no non-woven covering no carbon) and maintains it activity albeit as a slightly lower selectivity than a catalyst calcined in a conventional process. The catalysts may also be regenerated in situ in the oxidative dehydrogenation reactor by passing oxygen, air optionally in combination with one or more inert gasses over the catalyst.

In one embodiment the present invention provides a method to calcine a catalyst precursor of the formula MoiVo.i-iNbo.i-iTeo.oi-o.2Xo-20d where X is selected from Pd, Sb Ba, Al, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, Ca and oxides and mixtures thereof, and d is a number to satisfy the valence of the catalyst while maintaining an amorphous content of not less than 40 wt. % comprising calcining the catalyst precursor in an inert container with flow passage there through, comprising heating the catalyst precursor at a rate from 0.5 to 10°C per minute from room temperature to a temperature from 370°C to 540°C under a stream of pre heated gas selected from steam and inert gas and mixtures thereof at a rate of flow comparable to a flow rate of not less 150 seem through a 2.54 cm diameter tube, with a length of 152 cm at a pressure of greater than or equal to 1 psig having a temperature from 300°C to 540°C and holding the catalyst precursor at that temperature for at least 2 hours and cooling the catalyst precursor to room

temperature said catalyst precursor being fully or partially enclosed by a porous material having a melting temperature greater than 600°C. In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the inert container is made from high temperature glass, quartz, ceramics, or steel.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the inert container has a heat conductivity greater than 0.34W nr ¹ K.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the flow rate of inert gas and mixtures thereof is greater than 150 seem.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the pressure of inert gas greater than 1 psig.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the heat up rate is 0.9 to 2.0°C per min.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the catalyst precursor is held at a temperature from 2 - 24 hours.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the catalyst is held at a temperature from 400°C to 525°C.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the stream of inert gas and mixtures thereof comprises nitrogen.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the porous material is selected from glass and mineral fiber.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein optionally charcoal or activated carbon is on the outer surface of the porous material in an amount up to 0.5 g per 1 g of catalyst precursor is present on the upper surface of the material.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein X is one or more metals and oxides thereof are selected from Pd, Sb, Ba, Al, Cu, Ti, Fe, Ca, Zr and mixtures thereof.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the molar ratio of said one or more metals and oxides selected from Pd, Sb, Ba, Al, Cu, Ti, Fe, Ca, Zr and mixtures thereof to Mo is from 0.001 - 0.3.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein the X is selected from the group consisting of one or more metals and oxides thereof are selected from Pd, Sb, Ba, Al, Cu and mixtures thereof.

In a further embodiment the present invention provides in combination with one or more other embodiments a method wherein jn the catalyst precursor X is absent.

In a further embodiment the present invention provides in combination with one or more other embodiments a catalyst precursor having the formula:

Moi ,oVo.i 0-049T e0.06-0.17N bo.13-0.190d

In a further embodiment the present invention provides in combination with one or more other embodiments a calcined catalyst of the formula:

M01V0.40-0.45T eo.10-0.16 N bo.13-0.160d

In a further embodiment the present invention provides in combination with one or more other embodiments a calcined catalyst of the formula

MoV0.40-0.45Te0.10-0.i6Nb0.13-0.i6Od

having an amorphous content of not less than 40 wt. %.

In a further embodiment the present invention provides in combination with one or more other embodiments a calcined catalyst having a crystalite size calculated according to the Scherrer equation of 45 to 55 nm.

In a further embodiment the present invention provides in combination with one or more other embodiments a calcined catalyst having a crystalite size calculated according to the Scherrer equation of 50 to 52 nm.

In a further embodiment the present invention provides in combination with one or more other embodiments a calcined catalyst bound, agglomerated, filled, promoted, impregnated, supported with from 5 - 90 weight % of a material other than active phase. In a further embodiment the present invention provides in combination with one or more other embodiments a method for the oxidative dehydrogenation of a mixed feed comprising one or more C2-4 paraffins and oxygen in a volume ratio from 70:30 to 95:5 and optionally one or more C3-6 alkanes or alkenes and oxygenated species including CO and CO2 at a temperature from 320°C up to 385°C, a gas hourly space velocity of not less than 100 hr ¹ , and a pressure from 0.8 to 7 atmospheres comprising passing said mixture over a catalyst as above. EXAMPLES

An oxidative dehydrogenation catalyst was prepared using the following hydrothermal process.

Hydrothermal Synthesis:

• 259.4 g of (NH4)6Mq6Tbq2·7H2q < _S) was dissolved in 600 mL of de-ionized water in a 2 L three neck round bottom flask (RBF), with a stir rate of 750 rpm with the addition of a warm water bath

• 189.11 g of VOS04-3.41 H20 (s) was dissolved in 300 mL of de-ionized water, with the addition of a warm water bath

• 194.35 g of H3[Nb0(C204)3] (soin.) was weighed into a 250 mL beaker and held for later use

• V0S0 ₄ -3.41 H2O (aq) solution was added to the (NH4)6MqqTbq2·7H2q (aq) solution in the 1 L RBF

• Solution turned black

• Solution was left to stir for 30 minutes, after which the solution turned a purple color

• All manipulations were performed in air

• 194.35 g of H3[Nb0(C204)3] (soin.) was added to a 250 mL addition funnel, affixed to the 3 neck RBF

• Solution was added dropwise to the agitating purple slurry (60 minutes for addition time)

• Solution remained as a dark purple slurry

• Solution was transferred to a 1 L glass liner inside a 1 L PARR autoclave

• Autoclave set up was sealed and purged 10 times with repeating N2 (g) evacuation sequences

• Autoclave was connected to the condenser set up • Reaction was left to stir overnight in the autoclave set up at room

temperature

• The following day the PARR autoclave was hated to 175°C, the autoclave reached a temperature of 172°C after 48 hours

• Reaction mixture was left to heat in the autoclave set up overnight at 175°C with the condenser set up

• The following day the temperature was set back to room temperature

• Reaction set up was not cooled by the end of the day and was left to cool over the weekend

• After the reaction was cooled it was depressurized and filtered through 4 X Whatmann 4 filter paper media

• The filter cake was rinsed with approximately 0.5 L of deionized water until the filtrate ran clear

• Filtration time was approximately 2 hours

• Filter dried catalyst was dried in the oven at 90°C overnight

• Dried catalyst was ground and sieved

Calcining Procedure

Catalyst was loaded in four 25 g portions into quartz tube reactor (QRU). The QRU was purged under bulk nitrogen for several hours and then switched to purified nitrogen (bulk nitrogen passed through catalyst beds) for two days to ensure a sufficiently oxygen free environment for calcination. The purified nitrogen flow was 400 seem. The heating program used was: RT to 600°C in 6 hours and held at 600°C for 2 hours, then cooled to room temperature by convective cooling.

Four boats loaded with catalyst were loaded into quartz tube according to the scheme as shown in figure 1.

The heating zone where the 4 ^th boat was located was not heated. The estimated temperature for calcination in boat 4 was from 400 to 525°C. The first two boats were calcined via the usual calcination procedure at 600°C. Boat #3 and #4 were covered with ceramic membrane material (glass wool), which resulted in lower flow of nitrogen above (over) the catalyst precursor. Additionally, activated carbon was placed on the top of the ceramic membrane material over boat 4 to scavenge any oxygen released from the surface of non-calcined catalyst. Figure 2 is and X ray diffraction pattern (XRD) for the uncalcined catalyst sample. The figures also contains a baseline of an XRD of a typical calcined catalyst. In figure 2 the relatively sharper peak to the left side of the XRD is the M1 phase. The larger broader peek to the right is the M2 phase. The sample of low or partially calcined catalyst from boat 4 has a broader M2 peek than that of a calcined catalyst.

The catalyst produced from boat 4 was tested in a lab scale

dehydrogenation reactor (Micro reactor unit - MRU) and the results are compared to a conventional calcination process. The results are set forth in Table 1.

TABLE 1

Activity and Selectivity Comparison Between Baseline Example and Inventive Example at 25% Conversion

The catalyst calcined in accordance with the procedures of the current application were tested in a long term oxidative dehydrogenation reactor together with two baseline samples (a conventionally calcined catalyst and an un-calcined catalyst). The results are set forth in Table 2 below.

TABLE 2

Summary of Performance Comparisons Between Inventive Example

and Conventionally Calcined Catalyst and Un-Calcined Catalyst

The un-calcined catalyst had good conversion - 25% conversion at 340°C which is very completive with the conversion for the sample in accordance with the present disclosure (Low calcined catalyst). However the catalyst died after about 8 hours testing.

The testing shows the catalyst calcined in accordance with the present application has a better stability than the baseline catalyst and is fully regeneratable with oxygen.

A sample of catalyst obtained from boat 4 was in a micro reactor unit (MRC) ethane oxidative dehydrogenation unit in a longer term run with several in situ air regenerations of the catalyst. The results are shown in figure 3. In figure 3, the upper line is the selectivity to ethylene at 25% conversion and the lower line is conversion at the temperature specified in the sections of the graph. At 300°C the conversion is slightly below 25%. At 320°C the conversion is slightly below 25%. The temperature of the reactor was increase to 375°C so that there was no residual oxygen the product stream leaving the reactor. At 375°C the conversions is around 28%. For part of the experiment dimethyl disulphide (DMDS) was injected with the feed. And the temperature was reduced to 356°C and the conversion dropped slightly. Throughout the run the selectivity was in the 88 to 90% range.

The number following the temperature is hourly space velocity of the feed gas (ethylene and oxygen). The vertical darker bars show air regeneration.

The catalyst showed excellent stability/ robustness even on regeneration and in the presence of DMDS.

The pore size of the base line catalyst and the catalyst of the present disclosure before and after testing in an ethylene dehydrogenation unit were measured using BET. The results are shown in figure 4. The results show the catalyst according to the present disclosure has majority of small pores less than 10 nm. After testing the volume of pores less than 10 nm has decreased but is still larger than the base line catalyst. In use the pore size of the base line catalyst is further reduced.

The following table show the reaction conditions and results for the trial.

TABLE 3

Long Term Oxidative Dehydrogenation of Ethane on Microreactor Unit (MRU)

Using Inventive Catalyst

Testing was carried out over 30 days under various conditions (no residual oxygen or exposure to sulfur-containing environments) to demonstrate robustness of catalyst. Standard conversion conditions were established at start of run to create a reference point, i.e. at 3000 h ¹ flow, what temperature is needed to achieve 25% conversion. After catalyst was exposed to unfavorable conditions, the reference conditions were revisited to see what temperature was needed to achieve 25% conversion. Re-establishing the reference conditions provided a means of evaluating how the catalyst was responding to testing. An increase in 25% conversion temperature is acceptable as long as the temperature stays the same/below the threshold value (conversion temperature of standard catalyst) and has selectivity that is better than a standard catalyst run over similar long-term and oxygen-deprived conditions.

INDUSTRIAL APPLIBABILITY

The present disclosure provides a method to produce a mixed metal oxide of

MoVTeNb having an improved conversion of ethane to ethylene in an oxidative dehydrogenation process.