Oxidative dehydrogenation of ethane to ethylene and preparation of multimetallic mixed oxide catalyst for such process

Abstract

Oxidative dehydrogenation of light paraffins, such as ethane at moderate temperatures (<500 C.) to produce ethylene without the formation of side products such as acetic acid and/or other oxygenated hydrocarbons is achieved using tellurium-free, multimetallic catalysts possessing orthorhombic M1 phase and other crystalline structures that have an important role for obtaining high performance catalysts for the oxidative dehydrogenation of ethane to ethylene. Such catalysts are prepared using thermal and hydrothermal methods.

Claims

1. A process for the formation of a multimetallic mixed oxide having the formula
MoV.sub.hSb.sub.iO.sub.x wherein h and i, respectively, are each between 0.001 and 4.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of elements present in the multimetallic mixed oxide, said multimetallic mixed oxide solid catalyst having an orthorhombic M1 crystalline phase, a pseudo-hexagonal M2 crystalline phase and an orthorhombic MoO.sub.3 crystalline phase, and (Mo.sub.4.65V.sub.0.35)O.sub.14, wherein said method for forming said multimetallic mixed oxide comprises, forming a tellurium-free aqueous solution of metallic precursors consisting of molybdenum, vanadium and antimony and a structure-directing compound selected from the group consisting of primary amines, secondary amines, tertiary amines, ammonia, tetra-methyl ammonium and hydrazine, and subjecting said tellurium-free mixture to a hydrothermal treatment at a temperature of 100 to 200 C. for 6 to 150 hours to form a solid, washing said solid to obtain a MoVSb solid, and drying said MoVSb solid, and thermally activating said dried solid by a first thermal treatment at a temperature of 150 to 350 C. under an oxidizing, reducing, or inert atmosphere for 1 to 5 hours, and a second thermal treatment at a temperature of 150 to 700 C. under an oxidizing or inert atmosphere for 1 to 5 hours to form the multimetallic mixed oxide, wherein wherein said Multimetallic mixed oxide has said orthorhombic M1 crystalline phase with XRD diffraction peaks 2 at 6.60.4, 7.70.4, 9.00.4, 22.20.4, 180.4, 36.120.4, 45.090.4, and 49.920.4, the pseudo-hexagonal M2 crystalline phase, and the orthorhombic MoO.sub.3 crystalline phase, and (Mo.sub.4.65 V.sub.0.35)O.sub.14 tetragonal crystal structure.

2. The process of claim 1, wherein structure-directing compound is selected from the group consisting of methylamine, dimethyl amine, tri-methyl amine, diethyl amine, or mixtures thereof.

3. The process of claim 1, wherein said first hydrothermal treatment is at a temperature between 150-180 C. for 12-48 hours.

4. The method of claim 1, wherein said M2 pseudo-hexagonal crystalline phase has cell parameters a=12.6294 ; b=7.29156 ; c=4.02010 ; z=4, and XRD diffraction peaks at 2 equal to 22.30.4, 28.180.4, 36.120.4, 45.090.4, 49.920.4.

5. The method of claim 4, wherein said MoO3 orthorhombic crystalline phase has cell parameters: a=3.963 ; b=13856 ; c=3.697 ; z=4, whose main diffraction peaks appear at 2 equal to 12.770.4, 23.330.4, 25.690.4, 25.870.4, 27.330.4, 33.750.4.

6. The method of claim 5, wherein said (Mo.sub.4.65V.sub.0.35)O.sub.14 tetragonal crystal structure has cell parameters: a=22,839 ; b=22,839 ; c=3.990 , and XRD main diffraction peaks at 2 equal to 7.740.4, 8.660.4, 12.260.4, 16.460.4.22.250.4, 23.340.4, 23.690.4.

7. The method of claim 1, wherein said thermal activating step includes said first thermal treatment in an oxidizing atmosphere, and said second thermal treatment in an inert atmosphere.

8. A process of producing a multimetallic mixed oxide having the formula
MoV.sub.hSb.sub.iO.sub.x wherein h and i, respectively, are each between 0.001 and 4.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of elements present in the multimetallic mixed oxide, wherein said method comprises, forming a tellurium-free aqueous solution of metallic precursors consisting of molybdenum, vanadium and antimony and a structure-directing compound selected from the group consisting of primary amines, secondary amines, tertiary amines, ammonia, tetra-methyl ammonium and hydrazine, and subjecting said tellurium-free mixture to a hydrothermal treatment at a temperature of 100-200 C. for 6-150 hours to form a solid, washing and drying said solid, and thermally activating said dried solid by a first thermal treatment at a temperature of 150 to 350 C. in an oxidizing atmosphere, followed by a second thermal treatment at a temperature of 150 to 700 C. in a nitrogen atmosphere to form the multimetallic mixed oxide having an orthorhombic M1 crystalline phase, a pseudo-hexagonal M2 crystalline phase, an MoO.sub.3 crystalline phase, and a (Mo.sub.4.65 V.sub.0.35)O.sub.14 crystalline phase.

9. The method of claim 8, wherein said M1 crystalline phase has XRD diffraction peaks 2 at 6.60.4, 7.70.4, 9.00.4, 22.20.4, 180.4, 36.120.4, 45.090.4, and 49.920.4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 are XRD spectra of catalyst prepared according to Example 8. (A) Solid dried at 100 C., and (B) Solid thermally-treated under nitrogen atmosphere at 600 C. Symbol [*] denotes phase M1 and [+] phase M2;

(2) FIG. 2 is an XRD spectrum of catalyst prepared in accordance to Example 18 after thermal treatment under air atmosphere at 280 C. followed by thermal treatment under nitrogen flow at 600 C. Symbol [*] denotes phase M1, [+] phase M2, [] (MoV.sub.x).sub.5-xO.sub.14 and [] MoO.sub.3;

(3) FIG. 3 is an XRD spectrum of catalyst prepared in accordance to Example 19 after thermal treatment under air atmosphere at 280 C. followed by thermal treatment under nitrogen flow at 600 C. Symbol [*] denotes phase M1, [+] phase M2, [] (MoV.sub.x).sub.5-xO.sub.14 and [] MoO.sub.3;

(4) FIG. 4 is an XRD spectrum of catalyst prepared in accordance to Example 20 after thermal treatment under air atmosphere at 280 C. followed by thermal treatment under nitrogen flow at 600 C. Symbol [*] denotes phase M1, [+] phase M2, and [] (MoV.sub.x).sub.5-xO.sub.14;

(5) FIG. 5 is an XRD spectrum of catalyst prepared in accordance to Example 21 after thermal treatment under air atmosphere at 300 C. followed by thermal treatment under nitrogen flow at 600 C. Symbol [*] denotes phase M1, [+] phase M2, and [] (MoV.sub.x).sub.5-xO.sub.14;

(6) FIG. 6 is an XRD spectrum of catalyst prepared in accordance to Example 22 after a thermal treatment at 625 C. under nitrogen flow. Symbol [*] denotes phase M1, [+] phase M2, and [] (MoV.sub.x).sub.5-xO.sub.14;

(7) FIG. 7 are XRD spectra of catalyst prepared in accordance to Example 23. (A) Solid dried at 100 C., (B) Solid thermally-treated at 200 C. under air atmosphere followed by thermal treatment at 600 C. under nitrogen flow, and (C) Solid thermally-treated in air atmosphere at 250 C. followed by thermal treatment at 600 C. under nitrogen flow. Symbol [*] denotes phase M1, [+] phase M2, and [] MoO.sub.3;

(8) FIG. 8 are XRD spectra of catalyst prepared in accordance to Example 24. (A) Solid dried at 100 C., (B) catalyst after a thermal treatment at 200 C. under air atmosphere followed by a second thermal treatment at 600 C. Symbol [*] denotes phase M1, and [+] phase M2;

(9) FIG. 9 are XRD spectra of catalyst prepared in accordance to Example 25. (A) Solid after drying at 100 C., (B) catalyst after a thermal treatment at 200 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow, (C) catalyst thermally-treated at 250 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow, and (D) Catalyst thermally-treated at 280 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow. Symbol [*] denotes phase M1, [+] phase M2, and [] MoO.sub.3;

(10) FIG. 10 are XRD spectra of catalyst prepared in accordance to Example 27. (A) Solid after drying at 100 C., (B) catalyst after a thermal treatment at 200 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow, (C) catalyst thermally-treated at 250 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow. Symbol [*] denotes phase M1, and [+] phase M2, and [] MoO.sub.3;

(11) FIG. 11 are Scanning Electron Microscopy images of the catalyst prepared according to Example 8, after drying at 100 C. This morphology is representative of solids prepared by the hydrothermal method here described;

(12) FIG. 12 are Scanning Electron Microscopy images of the catalyst prepared according to Example 23. (Column A) Images of the solid dried at 100 C., and (Column B) images of the catalyst subjected to a thermal treatment at 250 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow;

(13) FIG. 13 are Scanning Electron Microscopy images of a catalyst prepared according to Example 28. (Column A) Images of the solid dried at 100 C. and (Column B) images of the catalyst subjected to a thermal treatment at 250 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow;

(14) FIG. 14 are Scanning Electron Microscopy images, with elemental chemical analysis within the selected zones (bottom part), by Electron Dispersive Spectroscopy technique. (Column A) catalyst of Example 23 and (Column B) catalyst of Example 28. Both catalysts included in this figure were subjected to thermal treatment at 250 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow;

(15) FIG. 15 are (Column A) High Resolution of Transmission Electronic Microscopy images and of the crystals present in the catalyst prepared in accordance to Example 23. (Column B) are Selected Area Electron Nano-Diffraction Patterns (SAENDP) corresponding to the white encircled area marked over a selected crystal of the column A. These images, are in agreement with the XRD patterns shown in the FIG. 7, thus, confirming the presence of the several crystalline phases. (A) Image corresponds to a crystal of M1 phase, which confirmed by its electrons nano-diffraction pattern (right side), (B) Image corresponds to a crystal of M2 phase, which confirmed by its electrons nano-diffraction pattern (right side), and (C) Image corresponds to a crystal of MoO.sub.3 phase, which confirmed by its electrons nano-diffraction pattern (right side). Such catalyst has been treated thermally at 250 C. under air atmosphere followed by a second thermal treatment at 600 C. under nitrogen flow;

(16) FIG. 16 are Scanning Electron Microscopy images with elemental chemical analysis (right side) within the selected zones by Electron Dispersive Spectroscopy technique of the catalyst prepared in accordance with Example 29. The catalyst was subjected to thermal treatment at 600 C. under nitrogen flow;

(17) FIG. 17 are XRD spectra of catalysts prepared in accordance with: (A) Example 10, (B) Example 11, (C) Example 12, (D) Example 13 and (E) Example 14. Symbol [*] denotes phase M1, [+] phase M2, and [] MoO.sub.3; and

(18) FIG. 18 are chromatographic signals obtained during catalytic testing of catalysts prepared in accordance with example 21, indicating absence of oxygenated hydrocarbons during oxidative dehydrogenation of ethane to ethylene.

DETAILED DESCRIPTION OF THE INVENTION

(19) Catalysts of the present invention may be represented by the general formula MoVSbA, wherein A is one of the following elements: Nb, W, Ga, Bi, Sn, Ti, Fe, Co, Cu, Ni, Cr, Zr, rare earth metals, alkaline metals or alkaline rate earth metals or a mixture of thereof. According to another embodiment, the catalyst may be represented by the formula MoVSb.

(20) The present invention involves the oxidative dehydrogenation of light paraffins to produce olefins, more specifically, a procedure to perform the oxidative dehydrogenation of ethane to ethylene by means of a process wherein ethane is contacted with oxygen or with an oxygen containing stream, and/or with another oxidant agent, over a catalyst composed of mixed multimetallic oxides. The catalyst is a tellurium-free solid, containing Mo, V and Sb, and may include optionally an A metal, the latter one selected from the following list: Nb, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Cu, Ni, Cr, Zr, rare earth metals or rare earth alkaline metals or mixtures of thereof. The catalyst, in the thermally-treated form, is represented by the general formula MoVSbAO corresponding to a solid in which metallic elements are in combination with oxygen to produce a mixture of metallic oxides, with variable oxidation states.

(21) In a preferred embodiment of the invention, molybdenum, vanadium and antimony are present in the form of a thermally-treated mixed oxide in the catalyst formulation having the formula
MoV.sub.hSb.sub.iO.sub.x(II)

(22) wherein h and i, respectively, are each between 0.001 and 4.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of the other elements present in the multimetallic mixed oxide.

(23) In this embodiment, the catalyst is prepared by a process, which comprises, forming a tellurium-free mixture of molybdenum, vanadium and antimony metallic precursors in solution with a structure-directing compound selected from the group consisting of primary amines, secondary amines, tertiary amines, ammonia, tetra-methyl ammonium and hydrazine, and subjecting said tellurium-free mixture to hydrothermal conditions to form a solid. The resulting solid is washed and dried, and thereafter thermally activating to form a catalyst having one or more crystalline phases in addition to the M1 crystalline phase, such as the M2 and/or MoO.sub.3 crystalline phases. It is especially preferred that the only metals in the catalyst in admixture with the structure-directing compound are the MoVSb base metals without any additional or promoter metal. Likewise, after activation and formation of the M1 crystalline phase, no further or post treatment is required to provide a highly active and selective catalyst.

(24) The preferred structure-directing compound is methylamine, dimethyl amine, tri-methyl amine, diethyl amine, or mixtures thereof. The hydrothermal treatment is conducted at a temperature between 100-200 C. for 6-150 hours and the resulting solids are washed and dried at 80-120 C. prior to activation. Preferably, the hydrothermal treatment is at a temperature between 150-180 C. for 12-48 hours. Activation involves a first thermal treatment at a temperature in the range of from about 150 to about 350 C., preferably 160 to about 300 C., under oxidant and/or reducing and/or inert atmosphere for 1 to 5 hours; and a second thermal treatment at temperatures ranging from about 150 to about 700 C., preferably, 550 to 650 under an oxidant or inert atmosphere for 1 to 5 hours.

(25) In another preferred embodiment, the catalyst has the empirical formula:
MoV.sub.hSb.sub.iA.sub.jO.sub.x(III)

(26) wherein A represents Nb, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, rare earth metals or rare earth alkaline metals or mixtures of thereof, h and i, respectively, are each between 0.001 and 4.0, 0.0001j2.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of the other elements present in the multimetallic mixed oxide, said catalyst having an M1 crystalline phase, and one or more additional crystalline phases, said process comprising, forming a tellurium-free mixture of molybdenum, vanadium and antimony metallic precursors and thermally treating said tellurium-free mixture of mixture to form an MoVSb solid, doping said MoVSb solid with a doping metal cation represented by said A, and thermally activating the A metal cation-doped MoVSb solid to form a catalyst having one or more crystalline phases in addition to the M1 crystalline phase. The preferred doping metal cation is Nb, W, Sn, Cu or K. The MoVSb solid is heated a temperature in the range of from about 150 to about 700 C. prior to doping said MoVSb solid and then activating said metal cation-doped MoVSb solid at a temperature in the range of from about 150 to about 700 C. under an oxidizing or inert atmosphere for about 1 to 5 hours. Since x depends on the oxidation state of Mo, V, Sb and A elements, the amount of oxygen in the catalyst represented by x does not only depends on the chemical composition, but mainly on the activation process employed, since the proper combination of oxidant and/or reducing agents allows to tune the oxidation state of the metallic atoms, so generating highly active and selective catalysts.

(27) An especially preferred embodiment of the invention involves formation of a multimetallic mixed oxide having the formula
MoV.sub.hSb.sub.iA.sub.jO.sub.x

(28) wherein A represents Nb, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, rare earth metals or rare earth alkaline metals or mixtures of thereof, h and i, respectively, are each between 0.001 and 4.0, 0.0001j2.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of the other elements present in the multimetallic mixed oxide, said catalyst having an M1 crystalline phase, and one or more additional crystalline phases, said process comprising the steps, (a) forming a tellurium-free mixture of metallic cations, said metallic cations consisting of molybdenum, vanadium and antimony cations, (b) thermally treating the tellurium-free mixture to form an MoVSb solid, (c) calcining the tellurium-free MoVSb solid at a temperature in the range of from about 150 to about 700 C., in an inert atmosphere, for about 1 to about 5 hours; (d) doping the MoVSb solid by adding a metal cation represented by A, such as Nb, W, Sn, Cu or K, and (e) calcining the A metal cation-doped MoVSb solid 150 to about 600 C., in an inert atmosphere, preferably under nitrogen, for about 1 to about 5 hours to form a catalyst having one or more crystalline phases in addition to the M1 crystalline phase,

(29) Each of the steps (a) through (e) are conducted in the absence of added oxygen and added H.sub.2O.sub.2. The expression absence of added oxygen means no air or gas containing oxygen is introduced in any process step through the second calcining step. Likewise, the expression absence of added H.sub.2O.sub.2, means that no H.sub.2O.sub.2 is introduced in any process step. In this preferred embodiment of the invention, no metal cation other than a Mo, V or Sb cation is present during formation of the catalyst until the A metal cation, such as Nb, is added.

(30) In an additional preferred embodiment, A correspond to Nb, W, Ga, Bi, Sn, Ti, Fe, Co, Cu, Ni, Cr, Zr, rare earth metals, alkaline metals, or alkaline rare earth metals, or mixtures thereof.

(31) In another preferred embodiment, A represents Nb, W, Sn, Cu, K or mixtures thereof.

(32) In a preferred embodiment, the as-prepared multimetallic mixed oxides and/or the activated ones, thermally-treated, containing Mo, V and Sb in the form of at least one mixed oxide in the catalyst formulation.

(33) After thermal treatment performed to activate solids, the thermally treated solid exhibits an X-ray pattern with several diffraction lines. The most important diffraction lines present in the activated solid must be located at 2 equal to 6.60.4, 7.70.4, 9.00.4, 22.20.4, 26.70.4, 26.80.4, 27.10.4; which corresponds to the orthorhombic bronze-like structure, denominated as M1 crystalline phase (ICSD 55097). This phase has been recurrently claimed as the most active for oxidative dehydrogenation of ethane to ethylene. Thus, many efforts have been driven to produce solids with sole M1 phase. However, the activated solids prepared according to the methods presented in this invention, often show XRD patterns with additional diffraction lines, denoting the presence of other metallic oxides, which are also part of the composition of the multimetallic catalytic system. It is worth noticing that those activated solids are remarkably more active and selective in the oxidative dehydrogenation of ethane to ethylene, even compared with those exhibiting the sole M1 phase. As seen in the XRD patterns shown in FIGS. 2 to 7, 9, 10 and 17, and microscopy images reported in FIGS. 14 to 16, where the presence of crystalline structures in addition to the M1 phase are detected. The resultant solid is highly active and selective catalysts for the oxidative dehydrogenation of ethane to ethylene.

(34) The catalyst may be supported over a solid, such as, silica, silica gel, amorphous silica, zirconium oxide, silicon carbide, alumina, titanium oxide, cordierite, kaolin, aluminum-silicates or a mixture thereof, the FIG. 16 is presented as illustration. The amount of the selected support ranges from 20 to 70 wt. % of the total catalyst weight. Likewise, the catalyst can be a multimetallic mixed oxide in self-supported form, and/or in strong interaction with the crystalline phase obtained and/or segregated from the metallic elements initially present in the solid precursor, as it is confirmed in FIGS. 10C and 14. In this respect, the segregated metallic oxide allows the formation of crystals of a nanometric size of the M1 active phase of the multimetallic oxide, increasing in this way the number of active sites in the catalyst. In a preferred form, it is desirable that the segregated phase be the crystalline phase of the molybdenum oxide (MoO.sub.3) and/or M2 phase, which facilitate the dispersion of nanometric crystals of the multimetallic mixed oxide, mostly M1 phase.

(35) Preparation Methods of Multimetallic Mixed Oxides

(36) The multimetallic mixed oxides catalyst can be prepared by conventional methods from solutions containing compounds of the various elements, from solutions of the same pure elements, or from the mixture of both, by adjusting the desired atomic ratios. The above mentioned solutions are preferably watery solutions.

(37) The procedure to prepare the multimetallic mixed oxides catalyst comprises at least the following stages: 1.A first stage in which the different metallic precursors are mixed and the pH of the solutions can be adjusted. 2.The second step involves the set-up of the preparation conditions of the metallic precursor mixture of the previous step to produce a solid either by hydrothermal or heat treatment process. 3.The third stage involves the drying the solid obtained in the second step. 4.The fourth stage involves the thermal treatment procedure of the dried solid, in order to get an activated solid, which can be used as catalyst for the oxidative dehydrogenation of ethane to ethylene.

(38) In the first stage, the metallic precursors may be: pure metallic elements, metallic salts, metallic oxides, metallic hydroxides, metallic alkoxides, mineral acids, and/or mixtures thereof. The pH of the mixture of multimetallic mixed oxides of the first stage may be adjusted with organic or inorganic bases or mineral acids, such as, ammonia, H.sub.2SO.sub.4, HNO.sub.3, HCl or mixture of thereof.

(39) According to one preparation procedure, after the second stage the mixture is subject to hydrothermal treatment, as second step, and kept between 100-200 C. for 12-150 hours. After the second stage the mixture is heat treated at a temperature ranging from 50-100 C. Then the mixture is subjected to evaporation process to remove water.

(40) In the doping preparation procedure, in which doping elements are incorporated into the multimetallic mixed oxides of the first stage, such incorporated elements include Nb, Cu, W, Bi, Sn, Ti, Fe, Co, Ni, Cr, Ga, Zr, rare earth elements, alkali metal or alkaline earth metal, as salts, oxides, hydroxides, or alkoxides, pure or as mixtures of thereof. Next, the mixture is heat treated at a temperature ranging from 50-100 C. and subjected to evaporation process to remove water.

(41) The multimetallic mixed oxide mixture, prepared in the second stage either by hydrothermal or heat treatments, is washed or dried at 80-120 C., as a third step.

(42) The dried solids, obtained in the third step, are activated by thermal treatments at temperatures ranging from 150-350 C. under oxidant and/or reducing and/or inert atmosphere for 1 to 5 hours; and then thermally treated at temperatures ranging from 150 to 700 C. under an oxidant and/or inert flow, preferably nitrogen, for 1 to 5 hours.

(43) The washed and dried solids prepared in the second stage either by hydrothermal or heat treatments are thermally treated at temperature ranging from 150 to 700 C. Then doping solutions containing elements, such as, Nb, Cu, W, Bi, Sn, Ti, Fe, Co, Ni, Cr, Ga, Zr, rare earth elements, alkali metal or alkaline earth metal, as salts, oxides, hydroxides, or alkoxides, pure or as mixtures of thereof; are mixed with the thermally treated solid. The promoted materials obtained in this way are dried at 80-120 C. Dried solids are activated by thermal treatments at temperatures ranging from 150-350 C., preferably 160-300 C., under oxidant and/or reducing and/or inert atmosphere for 1 to 5 hours; and then thermally treated at temperatures ranging from 150 to 700 C., preferably 550 to 650 C. under an oxidant and/or inert flow, preferably nitrogen, for 1 to 5 hours.

(44) According to the process for preparing the catalyst of the present invention in which a structure-directing compound is added into the multimetallic mixed oxide mixture prepared in the first step, such organic species are used as a template, or structure directing agent or as a modifier of the oxidation state of metallic elements forming the solid. When such organic compound is added into the multimetallic mixed oxide mixture, the mixture is subjected to either hydrothermal or heat treatment, as second step, at a temperature between 100-200 C., preferably between 150-180 C. for 12-48 hours. As third step, the produced solid is washed and dried at 80-120 C. The organic structure-directing compound may be primary amines, secondary amines, tertiary amines, ammonia, tetra-methyl ammonium or hydrazine. Preferably, methylamine, dimethyl amine, tri-methyl amine, diethyl amine, or mixtures thereof are utilized. The quantity of amine that is incorporated into the multimetallic mixed oxide mixture depends upon the amount of Mo that the catalyst will contain. The atomic ratio of nitrogen (in the amine) to Mo in the multimetallic mixed oxide mixture lies in the 0.0001-5.0 range.

(45) If hydrazine is added to the multimetallic mixed oxide mixture, as the structure-directing compound, it should be used in a molar ratio of N.sub.2H.sub.4/Mo within the range 0.001 to 2.0, preferably from 0.01 and 1.0.

(46) In the first mixing stage, the metallic precursors are molybdenum, vanadium and antimony, which can be added as pure metallic elements, or metallic salts, or metallic oxides, or metallic hydroxides, or metallic alkoxides or mineral acids or as mixtures of them. Hence, sulfates, oxalates, halides or nitrates can be used as metallic salts, preferably halides and sulfates. The term metallic precursor is intended to include any such form of molybdenum, vanadium and antimony.

(47) Molybdenum may be added in the mixing stage preferably in the form of ammonium molybdate, molybdic acid, ammonium hepta-molybdate or molybdenum oxide. Vanadium can be incorporated during the mixing stage as well, preferably in the form of ammonia vanadate, vanadyl sulfate, vanadium oxide, vanadyl oxalate or vanadyl chloride. Antimonium, in turn, can be also added during the mixing stage preferably as antimonium oxide, antimonium sulfate, antimonium oxalate, antimonium chloride, antimonium bromide, antimonium iodide, antimonium fluoride or metallic antimonium. In the said compounds, antimonium can be in the form of Sb(III), Sb(V) or Sb(0), preferably as compound of Sb(III).

(48) The doping elements Nb, Cu, W, Bi, Sn, Ti, Fe, Co, Ni, Cr, Ga, Zr, rare earth metals, alkali metal or alkaline rare earths metals, can be added in the form of oxides, hydroxides or alkoxides, pure or as a part of a mixture of two or more elements. As a metals source, metallic sulfates, oxalates, halides or nitrates can be utilized, more preferably halides and sulfates.

(49) Hydrazine, in turn, can be also added during the mixing stage or once all the different metallic compounds have been already incorporated.

(50) The mixing stage can be followed by a holding period in a reactor either in static mode or under stirring. The period of time, statics or under stifling, can be conducted at atmospheric pressure or under pressure. After concluding the mixing stage, the formation of the solid precursor of the multimetallic mixed oxide catalyst is conducted either by hydrothermal or heat thermal process.

(51) The third stage, for the heat thermal process, can be performed by means of conventional methods, that is evaporation in an oven, or vacuum drying, or spray drying, and/or mixture of thereof.

(52) In the particular case of preparing said materials through a hydrothermal procedure, the temperature and time of reaction synthesis have an important influence on the physicochemical properties of the solid. Hence, the temperature of synthesis is ranging from 100 to 200 C. and, preferably between 150 and 180 C. The time of synthesis lies, preferably, within the 6-150 hours range, and more specifically, from 12 to 48 hours.

(53) In an alternative preparation of the procedure disclosed in the present invention, wherein into the mixture of multimetallic mixed oxides of molybdenum, vanadium and antimony are incorporated as metallic oxides on a support, such as, silica, silica gel, amorphous silica, zirconium oxide, silicon carbide, alumina, titanium oxide, cordierite, kaolin, alumino-silicates or a mixture thereof.

(54) In an alternative preparation of the procedure disclosed in the present invention, wherein the amount of metallic oxides used as support, such as, silica, silica gel, amorphous silica, zirconium oxide, silicon carbide, alumina, titanium oxide, cordierite, kaolin, alumino-silicates, or a mixture thereof, may range from 20 to 70 wt. %.

(55) In an alternative preparation of the procedure disclosed in the present invention, wherein an oxidant agent, such as H.sub.2O.sub.2, is added to the mixture of multimetallic mixed oxides of molybdenum, vanadium and antimony and the support selected, in order to adjust the oxidation state of cations. The final mixture is heat treated at a temperature ranging from 50-100 C., preferably between 70-90 C., and then it is subjected to evaporation process to remove water. As final step, the produced solid is washed and dried at 80-120 C.

(56) Activation Process of Multimetallic Mixed Oxides

(57) The activation process for the dried multimetallic mixed oxides is performed by thermal treatments at temperatures ranging from 150-350 C., preferably from 160-300 C. under oxidant and/or reducing and/or inert atmosphere for 1 to 5 hours, preferably 2 hours; and then thermally treated at temperatures ranging from 150 to 700 C., preferably from 550-650 C. under an oxidant and/or inert flow, preferably nitrogen, for 1 to 5 hours, preferably 2 hours.

(58) In the activation process of the dried solids obtained in the third stage, the oxidizing agents may be oxygen, air, CO.sub.2, nitrous oxide, ozone or mixtures thereof, more preferably oxygen and air.

(59) Alternatively, the activation of the dried solids obtained in the third stage may be conducted with inert agents including nitrogen, argon, helium, krypton, neon, xenon or mixtures thereof, more preferably nitrogen.

(60) Likewise, the activation process of the dried solids obtained in the third stage may be conducted with reducing agents including hydrogen, CO, alcohols, H.sub.2O.sub.2, light hydrocarbons such as methane, or mixtures thereof.

(61) Once available in the thermally-treated form, the catalyst prepared in accordance to the procedure described in the present invention is suitable to be used for the oxidative dehydrogenation of ethane to produce ethylene.

(62) Application of Activated Multimetallic Mixed Oxides as Catalysts for Oxidative Dehydrogenation of Ethane to Ethylene

(63) The oxidative dehydrogenation of ethane to produce ethylene involves contacting ethane or ethane mixed with other light hydrocarbons, with an oxidant agent and/or an inert agent, using as catalyst the activated multimetallic mixed oxide solid. The feedstock for conversion of ethane, or ethane mixed with other light hydrocarbons, to ethylene; preferably utilize light hydrocarbons restricted to C.sub.1 to C.sub.4 in which their content is lower than 15 volume % with respect to ethane. Conversion of ethane, or ethane mixed with other light hydrocarbons, to ethylene, utilizes an oxidizing agent which may be oxygen, air, CO.sub.2, nitrous oxide, ozone or mixtures thereof, more preferably oxygen and air. Ethane, or ethane mixed with other light hydrocarbons, may include an inert agent, which can be nitrogen, argon, helium, krypton, neon, xenon or mixtures of thereof, more preferably nitrogen. When the oxidative dehydrogenation of ethane to ethylene is conducted in the gas phase, it is carried out in the presence of water vapor. The water content can vary from 0.0001 to 80 mole %, more preferably between 20 and 60 mole %. The catalyst of the present invention exhibits high ethane conversion of and high ethylene selectivity of higher than 92%, at moderate reaction temperatures <500 C., and atmospheric pressure, without the formation of acetic acid and/or other oxygenated hydrocarbons. The conversion of ethane, or ethane mixed with other light hydrocarbons, to ethylene, may be performed in fixed-bed multi-tubular or fluidized-bed reactors at atmospheric pressure (between about 0.77 and 1 atmosphere) or under pressure as is conventional at a reaction temperature of from about 250 to 550 C., preferably between 300 and 480 C., and more preferably within the range 350-450 C. A space-time corresponding to the ratio of the catalyst mass to the inlet molar flow rate of ethane (W/F.sub.ethane) was spanned in the range 10 and 800 g.sub.cat h (mol).sup.1, preferably within the 20-600 g.sub.cat h (mol).sup.1 range, and more preferably between 30 and 350 g.sub.cat h (mol).sup.1 may be utilized. The catalysts of the present invention provide high ethane conversion, ethylene selectivity and ethylene yield. For example, MoV.sub.hSb.sub.iA.sub.jO.sub.x catalysts display an ethane conversion higher than 86 mole % and the ethylene selectivity can be higher than 95 mole %, at reaction temperatures varied from 250 to 550 C., and at atmospheric pressure; wherein the space-time corresponding to the ratio of the catalyst mass to the inlet molar flow rate of ethane (W/F.sub.ethane) was spanned in the range 10 and 800 g.sub.cat h (mol).sup.1. The use of activated MoV.sub.hSb.sub.i catalyst can provide an ethylene selectivity higher than 92%, ethane conversion is higher than 86% with the reaction temperatures ranges from 420 to 540 C., under an operating pressure comprised between 0.8 to 1 atm. The (W/F.sub.ethane) was spanned in the 80 to 160 g.sub.cat h (mol).sup.1 range.

(64) An activated MoV.sub.hSb.sub.i catalyst, prepared according to the claims 1 to 6 wherein the ethylene yield is higher than 70% at reaction temperatures ranging from 420 to 540 C., under an operating pressure comprised between 0.8 to 1 atm. and the W/F.sub.ethane spanned in the 80 to 160 g.sub.cat h (mol).sup.1 range.

(65) The use of activated MoV.sub.hSb.sub.iA.sub.j catalysts can provide ethylene selectivity higher than 92%, ethane conversion higher than 84% and the reaction temperatures ranges from 420 to 450 C., under an operating pressure comprised between 0.8 to 1 atm, with a W/F.sub.ethane of 160 g.sub.cat h (mol).sup.1. Likewise, such catalyst can provide an ethylene yield higher than 71%, at reaction temperatures ranging from 420 to 450 C., under an operating pressure comprised between 0.8 to 1 atm. The W/F.sub.ethane was 160 g.sub.cat h (mol).sup.1.

(66) The use of activated MoV.sub.hSb.sub.i catalyst provides ethylene selectivity higher than 93%, ethane conversion is higher than 75% at reaction temperatures from 390 to 470 C., under an operating pressure comprised between 0.8 to 1 atm. The W/F.sub.ethane was spanned in the 80 to 160 g.sub.cat h (mol).sup.1 range. Likewise, such catalyst can provide ethylene yield higher than 62%, at reaction temperatures ranging from 390 to 470 C., under an operating pressure comprised between 0.8 to 1 atm. The W/F.sub.ethane was spanned in the 80 to 160 g.sub.cat h (mol).sup.1 range.

(67) The use of activated MoV.sub.hSb.sub.iA.sub.j catalyst supported over a metal oxide results in ethylene selectivity higher than 95% and ethane conversion higher than 71% using reaction temperatures from 430 to 460 C., under an operating pressure comprised between 0.8 to 1 atm. The W/F.sub.ethane is in the 170 to 320 g.sub.cat h (mol).sup.1 range. An activated MoV.sub.hSb.sub.iA.sub.j catalyst supported over a metal oxide can provide an ethylene yield higher than 63%, at reaction temperatures ranging from 430 to 460 C., under an operating pressure comprised between 0.8 to 1 atm. The W/F.sub.ethane was in the 170 to 320 g.sub.cat h (mol).sup.1 range. Thus, the catalysts of the present invention provide an ethane conversion higher than 86 mole % and the ethylene selectivity can be higher than 95 mole %, at moderate reaction temperatures <500 C., and at atmospheric pressure as indicated by the following Examples.

EXAMPLES

(68) Once the basic aspects related to the present invention have been described a series of examples are offered to illustrate specific embodiments; notwithstanding, the invention should not be considered to be limited to said. Room temperature is defined herein after as temperature ranging from 10 and 40 C. The results of the catalytic tests, associated to examples here presented, were obtained at atmospheric pressure, which is here defined as a pressure ranging between 0.77 and 1 atmosphere.

Examples 1 to 14 are Related to Catalyst Prepared by Means of the So-Called Hydrothermal Method

Example 1

(69) 11.7 grams of tetra-hydrated ammonium hepta-molybdate and 2.7 grams of antimonium sulfate are dissolved in 85 grams of distilled water at 80 C. In parallel, a solution is prepared with 4.0 grams of vanadyl sulfate in 17 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is coded as Catalyst 1, with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15. In a further stage, it is catalytically tested in quartz made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 2

(70) 10.7 grams of tetra-hydrated ammonium hepta-molybdate and 3.3 grams of antimonium bromide are dissolved in 78 grams of distilled water at 80 C. In parallel, a solution is prepared with 3.6 grams of vanadyl sulfate in 15 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is denoted as Catalyst 2, with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15. In a further stage, it is catalytically tested in a quartz-made fixed-bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 3

(71) 12.3 grams of tetra-hydrated ammonium hepta-molybdate and 2.4 grams of antimonium chloride are dissolved in 90 grams of distilled water at 80 C. In parallel, a solution is prepared with 4.1 grams of vanadyl sulfate in 17 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is coded as Catalyst 3, with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 4

(72) 9.0 grams of tetra-hydrated ammonium hepta-molybdate and 2.1 grams of antimonium sulfate are dissolved in 79 grams of distilled water at 80 C. and then, this solution is acidified with 4.0 ml of H.sub.2SO.sub.4 1M (pH=2.0). In parallel, another solution is prepared with 3.0 grams of vanadyl sulfate in 13 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stirring. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is denoted as Catalyst 4, with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 5

(73) 18.1 grams of tetra-hydrated ammonium hepta-molybdate and 4.1 grams of antimonium sulfate are dissolved in 132 grams of distilled water at 80 C. and, the resulting solution is acidified with 8.5 ml of H.sub.2SO.sub.4 1M (pH=2.0). In parallel, another solution is prepared with 6.0 grams of vanadyl sulfate in 25 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is coded as Catalyst 5, with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 6

(74) 8.9 grams of tetra-hydrated ammonium hepta-molybdate and 2.7 grams of antimonium bromide are dissolved in 141 grams of distilled water at 80 C. In parallel, a solution is prepared with 3.0 grams of vanadyl sulfate in 13 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is coded as Catalyst 6, with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 7

(75) 17.1 grams of tetra-hydrated ammonium hepta-molybdate and 5.3 grams of antimonium bromide are dissolved in 125 grams of distilled water at 80 C. In parallel, a solution is prepared with 5.7 grams of vanadyl sulfate in 24 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stirring, at 175 C. for 2 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is coded as Catalyst 7, with the atomic ratio Mo.sub.1.0V.sub.1.36Sb.sub.0.15. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 8

(76) 10.8 grams of tetra-hydrated ammonium hepta-molybdate and 3.3 grams of antimonium bromide are dissolved in 79 grams of distilled water at 80 C. In parallel, a solution is prepared with 3.6 grams of vanadyl sulfate in 15 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is coded as Catalyst 8 with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15. The X-ray diffraction spectra of the catalyst, (A) dried at 100 C. and (B) thermally treated at 600 C. under nitrogen flow are shown in FIG. 1. Scanning Electron Microscopy (SEM) images of the catalyst, dried at 100 C., are presented in FIG. 11; it is observed clearly the well ordering of crystallites, which are arranged forming cavities with suitable porosity to enhance the molecular traffic. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 9

(77) 17.5 grams of tetra-hydrated ammonium hepta-molybdate and 5.4 grams of antimonium bromide are dissolved in 127 grams of distilled water at 80 C. In parallel, a solution is prepared with 5.8 grams of vanadyl sulfate in 25 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling and then 0.2 grams of potassium hydrogen carbonate are incorporated into the new solution. The resulting mixture is next transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid resulting from this example is coded as Catalyst 9 with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15K.sub.0.02. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 10

(78) 18.1 grams of tetra-hydrated ammonium hepta-molybdate and 5.5 grams of antimonium bromide are dissolved in 132 grams of distilled water at 80 C. In parallel, a solution is prepared with 6.0 grams of vanadyl sulfate in 25 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. Separately, 0.01 grams of potassium hydrogen carbonate are dissolved in 3.1 grams of water at room temperature to produce a solution that is added to 7.8 g of the solid previously obtained. The suspension resulting from the previous stage is filtered and the solid obtained is washed with distilled water, dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. This thermally-treated sample is designated Catalyst 10 with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15K.sub.0.002. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 11

(79) 18.1 grams of tetra-hydrated ammonium hepta-molybdate and 5.5 grams of antimonium bromide are dissolved in 132 grams of distilled water at 80 C. In parallel, a solution is prepared with 6.0 grams of vanadyl sulfate in 13 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. Separately, 0.02 grams of copper (II) sulfate are dissolved in 3.1 grams of water at room temperature to produce a solution that is added to 7.8 g of the solid previously obtained. The suspension resulting from the previous stage is filtered and the solid obtained is washed with distilled water, dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. This thermally-treated sample is denoted as Catalyst 11 with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15Cu.sub.0.003. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 12

(80) 18.1 grams of tetrahydrated ammonium hepta-molybdate and 5.5 grams of antimonium bromide are dissolved in 132 grams of distilled water at 80 C. In parallel, a solution is prepared with 6.0 grams of vanadyl sulfate in 13 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. Separately, 0.02 grams of niobium oxalate are dissolved in 3.1 grams of water at room temperature to produce a solution that is added to 7.8 g of the solid previously obtained. The suspension resulting from the previous stage is filtered and the solid obtained is washed with distilled water, dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. This thermally-treated sample is designated Catalyst 12 with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15Nb.sub.0.003. In a further stage, it catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 13

(81) 18.1 grams of tetra-hydrated ammonium hepta-molybdate and 5.5 grams of antimonium bromide are dissolved in 132 grams of distilled water at 80 C. In parallel, a solution is prepared with 6.0 grams of vanadyl sulfate in 13 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. Separately, 0.03 grams of ammonium meta-tungstate are dissolved in 3.1 grams of water at room temperature to produce a solution that is added to 7.8 g of the solid formerly obtained. The suspension resulting from the previous step is filtered and the solid obtained is washed with distilled water, dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. This thermally-treated sample is designated Catalyst 13 with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15W.sub.0.002. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

Example 14

(82) 18.1 grams of tetra-hydrated ammonium hepta-molybdate and 5.5 grams of antimonium bromide are dissolved in 132 grams of distilled water at 80 C. In parallel, a solution is prepared with 6.0 grams of vanadyl sulfate in 13 grams of distilled water at room temperature. The second solution is added slowly to the first one at room temperature under constant stifling. The resulting mixture is then transferred to a Teflon coated stainless-steel autoclave. Nitrogen is bubbled for 5 minutes in the mixture to remove the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 4 days. Autoclave is subsequently cooled down to room temperature. The content of the autoclave is filtered and, next, the solid fraction is recovered and washed with distilled water. Subsequently, the solid is dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. Separately, 0.03 grams of tin (II) sulfate are dissolved in 3.1 grams of water at room temperature to produce a solution that is added to 7.8 g of the solid formerly obtained. The suspension resulting from the previous step is filtered and the solid obtained is washed with distilled water, dried at 100 C. and then treated thermally at 600 C. for 2 hours under nitrogen flow. This thermally-treated sample is designated Catalyst 14 with the atomic ratio Mo.sub.1.0V.sub.0.36Sb.sub.0.15Sn.sub.0.003. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 1.

(83) As seen in the XRD spectra of FIG. 17, the catalysts of Examples 10-14 possess M1, M2 and MoO.sub.3 crystalline phases.

Examples 15 to 22 Correspond to the Preparation of Catalysts by Means of the Heat Thermal Method

Example 15

(84) 3.6 grams of tetra-hydrated ammonium hepta-molybdate and 0.9 grams of antimonium sulfate are dissolved in 63 grams of distilled water at 80 C. under continuous stirring for around 1 hour. The previous solution is acidified by adding 2.3 ml of HNO.sub.3 1M (pH=2.2) followed by the incorporation of 0.6 grams of ammonium metavanadate. The resulting mixture is stirred for several minutes (solution A). In parallel, 0.5 grams of niobium oxalate are dissolved in 18 grams of distilled water at 80 C. (solution B). Subsequently, solution B is slowly added to solution A at room temperature under continuous stifling. The water constituting the new solution is removed by evaporation under vacuum at 50 C. in a rotavapor. The resulting solid is dried at 100 C., then treated thermally at 280 C. under nitrogen flow and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is referred to as Catalyst 15 with the atomic ratio Mo.sub.1.0V.sub.0.25Sb.sub.0.16Nb.sub.0.06. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

Example 16

(85) 2.5 grams of tetra-hydrated ammonium hepta-molybdate and 0.6 grams of antimonium sulfate are dissolved in 43 grams of distilled water at 80 C. under continuous stirring for around 1 hour. The previous solution is acidified by adding 1.6 ml of HNO.sub.3 1M (pH=2.4) followed by the incorporation of 0.4 grams of ammonium meta-vanadate. The resulting mixture is stirred for several minutes (solution A). In parallel, 0.4 grams of niobium oxalate are dissolved in 12 grams of distilled water at 80 C. (solution B). Subsequently, solution B is slowly added to solution A at room temperature under continuous stifling. The water constituting the new solution is removed by evaporation under vacuum at 50 C. in a rotavapor. The resulting solid is dried at 100 C., then treated thermally at 280 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is designated Catalyst 16 with the atomic ratio Mo.sub.1.0V.sub.0.25Sb.sub.0.16Nb.sub.0.06. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

Example 17

(86) 3.4 grams of tetrahydrated ammonium hepta-molybdate and 0.8 grams of antimonium sulfate are dissolved in 60 grams of distilled water at 80 C. under continuous stirring for around 1 hour. The previous solution is acidified by adding 1.3 ml of H.sub.2SO.sub.4 1M (pH=2.5) followed by the incorporation of 0.6 grams of ammonium meta-vanadate and 4.7 ml of HNO.sub.3 1M (pH=2.4). The resulting mixture is stirred for several minutes (solution A). In parallel, 0.5 grams of niobium oxalate are dissolved in 17 grams of distilled water at 80 C. (solution B). Subsequently, solution B is slowly added to solution A at room temperature under continuous stirring. The water constituting the new solution is removed by evaporation under vacuum at 50 C. in a rotavapor. The resulting solid is dried at 100 C., then treated thermally at 280 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is coded as Catalyst 17 with the atomic ratio Mo.sub.1.0V.sub.0.27Sb.sub.0.16Nb.sub.0.06. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

Example 18

(87) 4.0 grams of tetra-hydrated ammonium hepta-molybdate and 0.9806 grams of antimonium sulfate are dissolved in 70 grams of distilled water at 80 C. under continuous stirring for around 1 hour. This solution is acidified by adding 1.2 ml of H.sub.2SO.sub.4 1M (pH=2.5) followed by the incorporation of 0.6452 grams of ammonium meta-vanadate and 1.2 ml of HCl 1M (pH=2.5). The resulting mixture is stirred for several minutes (solution A). In parallel, 0.4211 grams of niobium oxalate are dissolved in 20 grams of distilled water at 80 C. The previous solution is cold down to room temperature and next 0.7 ml of NH.sub.4OH 1M (pH=2.0) are added (solution B). Subsequently, solution B is slowly added to solution A at room temperature under continuous stirring. The water constituting the new solution is removed by evaporation under vacuum at 50 C. in a rotavapor. The resulting solid is dried at 100 C., then treated thermally at 280 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is coded as Catalyst 18 with the atomic ratio Mo.sub.1.0V.sub.0.24Sb.sub.0.16Nb.sub.0.06. The X-ray diffraction pattern of the catalyst thermally treated at 280 C. under air atmosphere and then thermally treated at 600 C. under nitrogen flow is shown in FIG. 2. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/83. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

Example 19

(88) 8.0 grams of tetra-hydrated ammonium hepta-molybdate and 2.62 grams of antimonium bromide are dissolved in 140 grams of distilled water at 80 C. under continuous stirring for ca. 1 hour. This solution is acidified by adding 1.3 ml of H.sub.2SO.sub.4 1M (pH=2.5) followed by the incorporation of 1.27 grams of ammonium meta-vanadate and 4.7 ml of HNO.sub.3 1M (pH=2.5). The resulting mixture is stirred for several minutes (solution A). In parallel, 0.86 grams of niobium oxalate are dissolved in 40 grams of distilled water at 80 C. (solution B). Later, solution B is slowly added to solution A at room temperature under continuous stirring. The water constituting the new solution is removed by evaporation under vacuum at 50 C. in a rotavapor. The resulting solid is dried at 100 C., and then treated thermally at 280 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is coded as Catalyst 19 with the atomic ratio Mo.sub.1.0V.sub.0.24Sb.sub.0.16Nb.sub.0.06. The X-ray diffraction pattern of the catalyst thermally treated at 280 C. under air atmosphere and then thermally treated at 600 C. under nitrogen flow is shown in FIG. 3. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

Example 20

(89) 7.985 grams of tetra-hydrated ammonium hepta-molybdate and 1.642 grams of antimonium chloride are dissolved in 140 grams of distilled water at 72 C. under continuous stifling for around 1 hour. Then 1.295 grams of ammonium metavanadate are added to the previous solution followed by an acidification with 15.5 ml of HCl 1M (pH=1.5). The resulting mixture is stirred for several minutes (solution A). In parallel, 1.204 grams of niobium oxalate are dissolved in 40 grams of distilled water at 80 C. This solution is cooled down to room temperature and next 2.5 ml of NH4OH 1M (pH=2.0) are added (solution B). Solution B is slowly added to solution A at room temperature under continuous stifling. The water constituting the new solution is removed by evaporation under vacuum at 60 C. in a rotavapor. The resulting solid is dried at 100 C., then treated thermally at 280 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is coded as Catalyst 20 with the atomic ratio Mo.sub.1.0V.sub.0.25Sb.sub.0.16Nb.sub.0.06. The X-ray diffraction pattern of the catalyst thermally treated at 280 C. under air atmosphere and then thermally treated at 600 C. under nitrogen flow is shown in FIG. 4. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

Example 21

(90) 7.985 grams of tetra-hydrated ammonium hepta-molybdate and 1.642 grams of antimonium chloride are dissolved in 140 grams of distilled water at 70 C. under continuous stifling for around 1 hour. Then 1.295 grams of ammonium meta-vanadate are added to the previous solution followed by an acidification with 8.5 ml of HCl 1M (pH=1.8). The resulting mixture is stirred for several minutes (solution A). In parallel, 1.204 grams of niobium oxalate are dissolved in 40 grams of distilled water at 80 C. (solution B, pH=1.7). Later, solution B is slowly added to solution A at room temperature under continuous stifling. The water constituting the new solution is removed by evaporation under vacuum at 60 C. in a rotavapor. The resulting solid is dried at 100 C., then treated thermally at 300 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is coded as Catalyst 21 with the atomic ratio Mo.sub.1.0V.sub.0.25Sb.sub.0.16Nb.sub.0.06. The X-ray diffraction pattern of the catalyst thermally treated at 300 C. under air atmosphere and then thermally treated at 600 C. under nitrogen flow is shown in FIG. 5. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

Example 22

(91) 7.0 grams of tetra-hydrated ammonium hepta-molybdate are dissolved in 40 grams of distilled water at room temperature under continuous stifling and then 0.99 grams of antimonium trioxide and 0.80 grams of 50 wt. % solution of hydrogen peroxide are added. The resulting mixture is maintained under stifling at 80 C. for 1 hour until complete dissolution of the antimonium trioxide to produce solution A. In parallel, 1.4 grams of ammonium meta-vanadate are dissolved in 40 grams of distilled water at 80 C. (solution B). Also in parallel, 1.28 grams of niobium oxalate are dissolved in 20 grams of distilled water at 80 C. producing solution B. Later solution C is added to the solution produced after blending solution A and solution B to yield a new solution. Next, 0.136 grams of monohydrated hydrazine are added to this new solution at 80 C. stirring for 20 minutes. 2.55 ml of H.sub.2SO.sub.4 10 wt. % (pH=4.7) are incorporated to mixture of the previous stage. The water that is part of this final mixture is vaporized by heating it at 200 C. The remaining solid is finally treated thermally at 625 C. for 2 hours under nitrogen flow. The thermally-treated solid is coded as Catalyst 22 with the atomic ratio Mo.sub.1.0V.sub.0.30Sb.sub.0.17Nb.sub.0.07. The X-ray diffraction pattern of the catalyst thermally treated at 625 C. under nitrogen flow is shown in FIG. 6. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 2.

(92) The examples described from here on correspond to the preparation of the catalyst through the hydrothermal method involving the incorporation of amines in the synthesis.

Example 23

(93) 6.9 grams of molybdic acid, 2.27 grams of methylamine hydrochloride (CH.sub.3NH.sub.2HCl) along with 1.58 g of antimonium sulfate are dissolved in 85 grams of distilled water at 80 C. In parallel, a second solution containing 2.29 g of vanadyl sulfate in 17 grams of water at room temperature is prepared. The second solution is slowly added to the first one at room temperature under stirring. The resulting mixture is further stirred for 30 minutes and, later, transferred into a Teflon coated stainless-steel autoclave. The mixture is bubbled with nitrogen for 5 minutes in order to displace out the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature, its content is filtered. The solid fraction is recovered and then subjected to washing with distilled water. The solid is later dried at 100 C., then treated thermally at 250 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The thermally-treated sample is designated Catalyst 23 with the atomic ratio Mo.sub.1.0V.sub.0.38Sb.sub.0.16. The X-ray diffraction patterns of the catalysts, (A) dried at 100 C., (B) thermally treated under air atmosphere at 200 C. and then thermally treated at 600 C. under nitrogen flow and (C) thermally treated under air atmosphere at 250 C. and then thermally treated at 600 C. under nitrogen flow, are shown in FIG. 7. Representative Scanning Electron Microscopy images of the catalyst, (Column A) dried at 100 C. and (Column B) thermally treated under air atmosphere at 250 C. and then thermally treated at 600 C. under nitrogen flow, are shown in FIG. 12. In FIG. 14, column A, in addition to Scanning Electron Microscopy images of the catalyst, is shown the elemental chemical analysis, of the selected zones, by Electron Dispersive Spectroscopy (EDS) technique (bottom part), of the catalyst thermally treated under air atmosphere at 250 C. and then thermally treated at 600 C. under nitrogen flow. Representative High-Resolution Transmission Electron Microscopy images of the catalyst are shown in FIG. 15, (A) crystal of M1 phase, and its corresponding electron nano-diffraction (END) pattern (right side), (B) crystal of M1 phase, and its corresponding END pattern (right side), and (C) crystal of MoO.sub.3 phase, and its corresponding END pattern (right side). In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 3.

Example 24

(94) 6.9 grams of molybdic acid, 2.73 grams of dimethylamine hydrochloride (CH.sub.3NH CH.sub.3HCl) along with 1.58 g of antimonium sulfate are dissolved in 85 grams of distilled water at 80 C. In parallel, a second solution containing 2.29 g of vanadyl sulfate in 17 grams of water at room temperature is prepared. The second solution is slowly added to the first one at room temperature under stirring. The resulting mixture is further stirred for 30 minutes and, later, transferred into a Teflon coated stainless-steel autoclave. The mixture is bubbled with nitrogen for 5 minutes in order to displace out the air contained inside the autoclave. Then, the autoclave is maintained, without stirring, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature, its content is filtered. The solid fraction is recovered and then subjected to washing with distilled water. The solid is later dried at 100 C., then treated thermally at 200 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The thermally-treated sample is designated Catalyst 24 with the atomic ratio Mo.sub.1.0V.sub.0.38Sb.sub.0.16. The X-ray diffraction patterns of the catalyst, (A) dried at 100 C., (B) thermally treated under air atmosphere at 200 C. and then thermally treated at 600 C. under nitrogen flow are shown in FIG. 8. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 3.

Example 25

(95) 6.9 grams of molybdic acid, 2.73 grams of ethylamine hydrochloride (CH.sub.3CH.sub.2NH HCl) and 1.58 g of antimonium sulfate are dissolved in 85 grams of distilled water at 80 C. In parallel, a second solution containing 2.29 g of vanadyl sulfate in 17 grams of water at room temperature is prepared. The second solution is slowly added to the first one at room temperature under stirring. The resulting mixture is further stirred for 30 minutes and, later, transferred into a Teflon coated stainless-steel autoclave. The mixture is bubbled with nitrogen for 5 minutes in order to displace out the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature, its content is filtered. The solid fraction is recovered and then subjected to washing with distilled water. The solid is later dried at 100 C., then treated thermally at 250 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The thermally-treated sample is designated Catalyst 25 with the atomic ratio Mo.sub.1.0V.sub.0.38Sb.sub.0.16. The X-ray diffraction patterns of the catalyst, (A) dried at 100 C., (B) thermally treated under air atmosphere at 200 C. and then thermally treated at 600 C. under nitrogen flow, (C) thermally treated under air atmosphere at 250 C. and then thermally treated at 600 C. under nitrogen flow and (D) thermally treated under air atmosphere at 280 C. and then thermally treated at 600 C. under nitrogen flow are shown in FIG. 9. In a further stage, is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 3.

Example 26

(96) 6.9 grams of molybdic acid, 2.73 grams of ethylamine hydrochloride (CH.sub.3CH.sub.2NH HCl) along with 1.58 g of antimonium sulfate are dissolved in 85 grams of distilled water at 80 C. In parallel, a second solution containing 2.29 g of vanadyl sulfate in 17 grams of water at room temperature is prepared. The second solution is slowly added to the first one at room temperature under stirring. The resulting mixture is further stirred for 30 minutes and, later, transferred into a Teflon coated stainless-steel autoclave. The mixture is bubbled with nitrogen for 5 minutes in order to displace out the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature, its content is filtered. The solid fraction is recovered and then subjected to washing with distilled water. The solid is later dried at 100 C., then treated thermally at 200 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The thermally-treated sample is designated Catalyst 26 with the atomic ratio Mo.sub.1.0V.sub.0.38Sb.sub.0.16. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 3.

Example 27

(97) 6.9 grams of molybdic acid, 3.18 grams of trimethylamine hydrochloride [(CH.sub.3).sub.3N HCl] along with 1.58 g of antimonium sulfate are dissolved in 85 ml of distilled water at 80 C. In parallel, a second solution containing 2.29 g of vanadyl sulfate in 17 grams of water at room temperature is prepared. The second solution is slowly added to the first one at room temperature under stirring. The resulting mixture is further stirred for 30 minutes and, later, transferred into a Teflon coated stainless-steel autoclave. The mixture is bubbled with nitrogen for 5 minutes in order to displace out the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature, its content is filtered. The solid fraction is recovered and then subjected to washing with distilled water. The solid is later dried at 100 C., then treated thermally at 200 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The thermally-treated sample is designated Catalyst 27 with the atomic ratio Mo.sub.1.0V.sub.0.38Sb.sub.0.16. The X-ray diffraction patterns of the catalyst, (A) dried at 100 C., (B) thermally treated under air atmosphere at 200 C. and then thermally treated at 600 C. under nitrogen flow, (C) thermally treated under air atmosphere at 250 C. and then thermally treated at 600 C. under nitrogen flow are shown in FIG. 10. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 3.

Example 28

(98) 6.9 grams of molybdic acid, 3.18 grams of trimethyl-amine hydrochloride [(CH.sub.3).sub.3N HCl] together with 1.58 g of antimonium sulfate are dissolved in 85 ml of distilled water at 80 C. In parallel, a second solution containing 2.29 g of vanadyl sulfate in 17 grams of water at room temperature is prepared. The second solution is slowly added to the first one at room temperature under stirring. The resulting mixture is further stirred for 30 minutes and, later, transferred into a Teflon coated stainless-steel autoclave. The mixture is bubbled with nitrogen for 5 minutes in order to displace out the air contained inside the autoclave. Then, the autoclave is maintained, without stifling, at 175 C. for 1 day. Autoclave is subsequently cooled down to room temperature, its content is filtered. The solid fraction is recovered and then subjected to washing with distilled water. The solid is later dried at 100 C., then treated thermally at 250 C. under air atmosphere and finally treated thermally at 600 C. for 2 hours under nitrogen flow. The thermally-treated sample is designated Catalyst 28 with the atomic ratio Mo.sub.1.0V.sub.0.38Sb.sub.0.16. Representative Scanning Electron Microscopy images of the catalyst, (Column A) dried at 100 C. and (Column B) thermally treated under air atmosphere at 250 C. and then thermally treated at 600 C. under nitrogen flow, are shown in FIG. 13. In FIG. 14, column B, in addition to Scanning Electron Microscopy images of the catalyst, is shown the elemental chemical analysis, of the selected zones, by Electron Dispersive Spectroscopy technique (bottom part), of the catalyst thermally treated under air atmosphere at 250 C. and then thermally treated at 600 C. under nitrogen flow. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 3.

(99) The following example corresponds to the preparation of supported catalysts by the heat thermal method.

Example 29

(100) 8.0 grams of tetrahydrated ammonium hepta-molybdate, 1.2189 grams of ammonium meta-vanadate and 1.734 grams of antimonium oxide (Sb.sub.2O.sub.3) are dissolved in 32 grams of water at 100 C., the mixture was kept under stirring for 2 hours, after this, the solution was cooled at 50 C. Then, 7.96 grams of Silica gel, with a pore size of 60 and a surface area of 500 m.sup.2/g was added and stirred for 30 min. Finally, 8 grams of diluted H.sub.2O.sub.2 (5 wt. %) was added and stirred for 1 hour (Solution A).

(101) In parallel, a solution is prepared with 1.88 grams of niobium oxalate in 5 grams of water at 60 C. under stirring; the solution was cooled down at room temperature. The later solution is added slowly to the solution A at room temperature under constant stirring. The water constituting the new solution is removed by evaporation. The resulting solid is dried at 100 C., and then treated thermally at 600 C. for 2 hours under nitrogen flow. The solid sample produced in this example is composed by the 40 wt. % of SiO.sub.2 and 60 wt. % of active phase with the atomic ratio Mo.sub.1.0V.sub.0.23Sb.sub.0.26Nb.sub.0.09, sample was labeled as Catalyst 29. In FIG. 16, in addition to Scanning Electron Microscopy images of the catalyst, is shown the elemental chemical analysis, of the selected zones, by Electron Dispersive Spectroscopy technique (right side), of the catalyst thermally treated at 600 C. under nitrogen flow. In a further stage, it is catalytically tested in a quartz-made fixed bed reactor using, as a feed, a gaseous mixture composed of ethane/oxygen/nitrogen with a nominal molar ratio of 9/7/84. The results of the catalytic activity testing with corresponding operating conditions in terms of temperature and space-time are displayed in Table 3.

(102) Tables 1 to 3 show the catalytic performance results of multimetallic mixed oxides, which were prepared by several methodologies and with varied chemical compositions. Only, the most important parameters were included.

(103) TABLE-US-00001 TABLE 1 Catalytic performance with corresponding operating conditions of the ODH-E over catalysts MoV.sub.hSb.sub.iA.sub.j, which were prepared through the hydrothermal method. Tem- pera- W/F.sub.ethane.sup.o Ethane Ethylene Ethylene ture, g.sub.cat conversion, selectivity, yield, Example C. h(mol).sup.1 % mol %. mol % Example 1 540 80 70 70 49 Example 2 440 80 60 91 55 470 80 73 88 64 425 160 72 87 63 440 160 82 83 68 Example 3 450 80 55 90 50 490 80 78 81 63 Example 4 430 160 72 87 63 450 160 81 83 67 Example 5 430 160 78 86 67 Example 6 430 160 81 86 70 Example 7 420 80 52 92 48 440 80 63 90 57 430 160 78 86 67 450 160 86 81 70 Example 8 430 160 77 87 67 450 160 86 83 71 Example 9 430 160 64 91 59 450 160 78 87 68 Example 10 430 160 65 92 60 450 160 76 89 68 Example 11 430 160 55 92 51 450 160 66 89 59 Example 12 430 160 80 88 70 Example 13 430 160 74 90 67 450 160 84 85 71 Example 14 420 160 69 91 63

(104) TABLE-US-00002 TABLE 2 Catalytic performance with corresponding operating conditions of the ODH-E over catalysts MoV.sub.hSb.sub.iA.sub.j, which were prepared through the heat thermal method. Tem- pera- W/F.sub.ethane.sup.o Ethane Ethylene Ethylene ture, g.sub.cat conversion, selectivity, yield, Example C. h(mol).sup.1 % mol %. mol % Example 15 440 160 37 93 34 Example 16 450 160 45 90 41 470 160 57 87 50 Example 17 440 160 47 92 43 Example 18 440 70 29 95 28 Example 19 440 70 23 93 21 Example 20 440 70 30 93 28 Example 21 440 70 33 91 30 440 140 50 89 45 Example 22 440 70 23 90 21 480 70 50 83 42

(105) TABLE-US-00003 TABLE 3 Catalytic performance with corresponding operating conditions of the ODH-E over catalysts MoV.sub.hSb.sub.iA.sub.j which were prepared through the hydrothermal method with the incorporation of amines in the synthesis. Tem- pera- W/F.sub.ethane.sup.o Ethane Ethylene Ethylene ture, g.sub.cat conversion, selectivity, yield, Example C. h(mol).sup.1 % mol %. mol % Example 23 390 80 43 92 40 400 80 55 89 49 430 80 67 85 57 450 80 75 82 62 Example 24 450 80 61 88 54 470 80 71 85 60 Example 25 400 80 43 93 40 430 80 53 91 48 450 80 60 88 53 Example 26 400 160 37 86 32 430 160 51 84 43 450 160 66 79 52 Example 27 400 80 26 78 20 430 80 37 77 29 450 80 51 74 38 Example 28 400 80 49 92 45 430 80 60 89 53 450 80 72 85 61 Example 29 440 320 55 92 51 460 320 71 88 63 430 177 32 95 31 450 177 47 92 43