EP3576873A1

EP3576873A1 - Synthesis of a movnbte catalyst having a reduced niobium and tellurium content and higher activity for the oxidative dehydrogenation of ethane

Info

Publication number: EP3576873A1
Application number: EP18725739.9A
Authority: EP
Inventors: Gerhard Mestl; Klaus Wanninger; Daniel Melzer; Maria Cruz SANCHEZ-SANCHEZ; Julia Tseglakova; Johannes Lercher
Original assignee: Clariant Produkte Deutschland GmbH
Current assignee: Clariant Produkte Deutschland GmbH
Priority date: 2017-01-31
Filing date: 2018-01-26
Publication date: 2019-12-11
Also published as: KR20190112791A; DE102017000862A1; US11097254B2; KR102316006B1; WO2018141652A1; JP6876813B2; JP2020507451A; CN110494221B; US20200061583A1; CN110494221A

Abstract

The invention relates to a mixed oxide material comprising the elements molybdenum, vanadium, niobium and tellurium, which mixed oxide material has diffraction reflections h, i, k and l in XRD analysis in the presence of Cu-Kα radiation, said diffraction reflexes having their vertices approximately at the diffraction angles (2⋅) 26.2° ± 0.5° (h), 27.0° ± 0.5° (i), 7.8° ± 0.5° (k) and 28.0° ± 0.5° (l), characterized in that: Mo₁V_aNb_bTe_cO_n (I). a = 0.2 to 0.35, b = greater than 0 to 0.08, c = greater than 0 to 0.08, and n = is a number that is determined by the valency and frequency of the elements in (I) that are different from oxygen.

Description

The invention relates to a novel mixed oxide material containing molybdenum, vanadium, tellurium and niobium, and to the use of the molybdenum mixed oxide material as a catalyst for the oxidative dehydrogenation of ethane. The invention relates to a MoVNbTe catalyst having reduced content of niobium and tellurium and higher activity for the oxidative dehydrogenation of ethane to ethene or the oxidation of propane to acrylic acid and a process for producing the mixed oxide material.

MoVNbTe mixed oxides for the oxidation of propane to acrylic acid, for the ammoxidation of propane to acrylonitrile or for the oxidative dehydrogenation of ethane to ethene are state of the art. More than 200 patents and numerous scientific publications treat catalysts based on MoVNbTe mixed oxides. The promotion of these mixed oxides with other metals of the periodic table is known. The highest acrylic acid yields described above are 60% and that of ethene is about 80%. The MoVNbTe base system based on four elements for a catalyst was proposed by Mitsubishi for the ammoxidation of propane to acrylonitrile (1989, EP 318295 Al) and the oxidation to acrylic acid (1994, EP 608838 A2). JP H07-053414 (Mitsubishi) discloses a catalytic process for the production of ethylene by the oxidative hydrogenation of ethane at low temperature, with a high yield and with a high selectivity. This method of producing ethylene by contacting ethane with a molecular oxygen-containing gas in the presence of a catalyst composition at elevated temperature comprises the catalyst composition Contains mixed metal oxide, which contains as essential components molybdenum, vanadium, tellurium and oxygen and which shows a powder X-ray diffractogram having substantially the following relative peak intensities: 2Θ (+ - 0.4 °), rel. Int: 22.1 ° (100), 28.2 ° (400-3), 36.2 ° (80-3), 45.1 ° (40-3), 50 ° (50-3).

MoVNbTe catalysts consist mainly of two orthorhombic phases called "Ml" and "M2" (T. Ushikubo, K. Oshima, A. Kayou, M. Hatano, Studies in Surface Science and Catalysis 112, (1997), 473). The Ml phase seems to play the essential role in the selective oxidation reactions.

According to P. De Santo et al. , Z. Kristallogr. 219 (2004) 152, the main phases M1 and M2 in MoVNbTe mixed oxides for the selective oxidation can be described, for example, with the following structural formulas:

Ml: MoiVo, i5Teo, i2Nbo, 128O3, 7 or M07, sVi, ₂ Teo, 937 bi028, 9

M2: * MoiVo, 32Teo, 42 bo, os04,6 or M04, 31V1, ₃ eTei, siNbo, 33O19, si

The two main phases can also occur with a slightly different stoichiometry. Thus, both vanadium and molybdenum in the center of an octahedron of oxygen atoms and therefore partially interchangeable in the structure, so that the same structure, for example, the Ml phase, even with a higher vanadium content is possible. A detailed investigation of these relationships can be found in P. Botella et al. , Solid State Science 7 (2005) 507-519. Specifically, the M2 phase is not active for the oxidative dehydrogenation of ethane. (See JS Valente et al., ACS Catal. 4 (2014), 1292-1301 specifically P.1293). For the oxidative dehydrogenation of ethane, therefore, a catalyst which consists of the purest possible Ml phase is desired. It is therefore trying to make these crystal phases also clean and separated. EP 529853 A2 discloses a catalyst suitable for the preparation of a nitrile from an alkane, the catalyst having the empirical formula MoVbTe _c XxOn wherein X is at least one of Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B and Ce, b is 0.01 to 1.0, c is 0.01 to 1.0; x is 0.01 to 1.0; and n is a number satisfying the total metal elements and the catalyst has X-ray diffraction peaks at the following 2Θ angles in its X-ray diffraction pattern: diffraction angle at 2Θ (22.1 ° +/- 0 , 3 °, 28.2 ° +/- 0.3 °, 36.2 ° +/- 0.3 °, 45.2 ° +/- 0.3 °, 50.0 ° +/- 0.3 °).

JP H07-232071 discloses a catalytic process for producing a nitrile, at a relatively low temperature and in a high yield, by using an alkane as a raw material and a specific catalyst. The main component of the catalyst is a mixed metal oxide of molybdenum, vanadium, tellurium, oxygen and X (X is one or more elements selected from the group of niobium, tantalum, etc.), wherein the ratio of the main components, ie excluding oxygen, is expressed Formulas I to IV: I) 0.25 <rMo <0.98, II) 0.003 <rV <0.50, III) 0.003 <rTe <0.50, IV) 0 <rX <0.5, (rMo , rV, rTe and rX are respectively the molar parts of molybdenum, vanadium, tellurium and X) and in the XRD, XRD bands of this mixed oxide at the different 29 angles 9.0 ° ± 0.3 °, 22.1 ° ± 0.3 °, 27.3 ° ± 0.3 °, 29.2 ° ± 0.3 ° and 35.4 ° ± 0.3 °. Thus, a nitrile can be prepared by adding an alkane without the presence of a halogenated substance, eg with water, etc., in the reaction system, at a low temperature with a high yield.

Other successful attempts to produce a pure Ml phase are based on dissolving the M2 phase out of the phase mixture. These experiments are e.g. in EP 1301457 A2, EP 1558569 A1 or WO 2009106474 A2.

A.C. Sanfiz et al. , Top. Catal. 50 (2008) 19-32 describe hydrothermal syntheses of MoVNbTe oxide. These syntheses are based exclusively on soluble compounds. As a soluble compound of tellurium usually telluric acid Te (OH) 6 is used. In the most common oxide tellurium compound TeÜ2, tellurium has the oxidation state +4. Unfortunately, tellurium dioxide (TeÜ2) is poorly soluble in water. In telluric acid, however, tellurium has the oxidation state +6. Tellurium must therefore be highly oxidized in the production of telluric acid. The common synthesis is carried out by oxidation of tellurium oxide with hydrogen peroxide, which entails safety problems on a large scale, because hydrogen peroxide can disproportionate in self-decomposition to water and oxygen. Therefore, telluric acid is difficult to produce in large quantities.

The Nb component used in the synthesis of MoVNbTe mixed oxides is usually ammonium niobium oxalate. By contrast, niobium oxide is sparingly soluble and is therefore only suitable to a limited extent as starting compound.

Watanabe (Applied Catal. A General, 194-195 (2000) 479-485) describes inter alia the hydrothermal synthesis from the less soluble precursors M0O3, V2O5 and TeÜ2. The Hydrothermal synthesis provides a precursor to an ammoxidation catalyst which has twice the activity after calcination compared to a catalyst prepared by the known dry method. The mixed oxides produced by the solid-state reaction show rather low activity. It has been suggested that the higher activity of the catalyst prepared by the hydrothermal synthesis has to do mainly with the higher surface area. D. Vitry et al. Applied Catalysis A: General 251 (2003) 411-424 reports a mixed oxide of stoichiometry MoiVo, 25 bo, uTeo, nO _x . In recent studies on the ethidic oxidative deoxidation (ODH), stoichiometric MoiVo, 3 bo, ioTeo, ioO _x catalysts were used. D. Melzer et al. Angew. Chem. Int. Ed. 55 (2016) 8873-8877) see "supplemental material" Sample B) reports a mixed oxide with a high content of the Ml phase and an analyzed stoichiometry of

MOlV ₀ , 27Nb0,10Te ₀ , 08Ox.

One way to reduce costs is to reduce the amount of niobium and tellurium needed. Another is to use cheaper starting materials.

WO 2005120702 A1 describes a process for the hydrothermal preparation of multimetal compositions consisting of Mo and V, essentially with the exclusive use of starting materials from the group of oxides, oxide hydrates, oxyacids and hydroxides for the elemental constituents of the oxide multimetal masses, wherein a Subset of the constituent elements contained in the starting materials has an oxidation number below the maximum oxidation number. WO 2013021034 A1 relates to a catalyst material for the oxidation and / or oxidative dehydrogenation of

Hydrocarbons, in particular for the selective oxidation of propane to acrylic acid, comprising a) molybdenum (Mo), b) vanadium (V), c) niobium (Nb), d) tellurium (Te), e) manganese (Mn) and cobalt in the the molar ratio of at least one element selected from manganese and cobalt to molybdenum in the range 0.01 to 0.2, more preferably 0.02 to 0.15 and most preferably from 0.03: 1 to 0.1: 1 lies. Further, a catalyst for the oxidation and / or oxidative dehydrogenation of

Hydrocarbons, a use of the catalyst material or the catalyst, a method for producing a catalyst material for the oxidation and / or oxidative dehydrogenation of hydrocarbons and a method for the selective oxidation of propane to acrylic acid specified.

WO 2008068332 A1 relates to novel mesoporous Mischmetalloxid- catalysts and a process for their preparation and their use as a catalyst for the oxidation of hydrocarbons or partially oxidized hydrocarbons. In particular, the disclosure relates to mesoporous mixed oxide catalysts containing at least two, preferably at least three different metal species, at least one of which belongs to the group of transition metals, to a process for the preparation of such a catalyst comprising a "neutral templating" preparation step. Route and one

Calcining step in a substantially oxygen-free atmosphere at a temperature between 300 to 700 ° C, the use of such catalysts as oxidation catalysts for the production of oxidized hydrocarbons and in particular for the selective oxidation or ammoxidation of propane to acrylic acid and acrylonitrile. A preferred catalyst comprises the elements Mo, V, Te and Nb.

The synthesis of the Ml phase described in the prior art has in common that after the reaction of the starting materials, the Ml phase only in the context of a

High temperature treatment, typically above 500 ° C under inert gas, forms. In the context of the present invention, a synthesis method for the preparation of a high-purity Ml phase was found, which dispenses with the final high-temperature treatment.

The object of the present invention is to provide a new simplified and efficient synthetic route for the preparation of a mixed oxide material containing molybdenum, vanadium, tellurium and niobium ("MoVTeNb mixed oxide"), which is present in high phase purity as Ml phase.

This object is achieved by a method for

Preparation of a mixed oxide material containing molybdenum, vanadium, tellurium and niobium comprising the steps of: a) preparing a mixture of starting compounds, the molybdenum, vanadium, niobium and a tellurium

containing starting compound in which tellurium in the oxidation state +4 is present, and oxalic acid and at least one further oxo ligand, b) hydrothermal treatment of the mixture of

Starting compounds at a temperature of 100 to 300 ° C to obtain a product suspension, c) separating and drying the mixed oxide material, which in the suspension resulting from step b) is containing.

The mixture of starting compounds is preferably in the form of an aqueous suspension and is subsequently treated hydrothermally. The term "hydrothermal" refers primarily to reaction conditions for the preparation of a

Catalyst material in the presence of water and at elevated temperature and / or elevated pressure, for example in an autoclave. The pressure may be in the range from 5 to 30 bar, preferably from 10 to 27 bar. Exemplary pressure ranges are 11 to 20 bar.

The hydrothermal treatment (step b)) gives a product suspension which contains the MoVNbTe mixed oxide as a solid. In the process according to the invention, the separation of the solid of the suspension in step c), which is the MoVNbTe mixed oxide according to the invention, in one or more steps, the filtration, e.g. filtering off the mother liquor. The drying can be carried out in one step or in two steps in flowing or static air. In this case, the first drying step is preferably at 60 ° C to 150 ° C (more preferably at 80 ° C to 120 ° C), a second drying step can be carried out at 200 ° C to 400 ° C. Additionally, step c) of the process of the invention may include one or more of washing, calcining (thermal treatment), and / or milling. The calcination can be carried out at 200 to 500 ° C, preferably 250 ° C to 350 ° C in air.

After drying the filtrate in step c), optionally, the dried mixture, for example, in a flowing or static inert gas atmosphere at about 500 to 700 ° C for activated for at least 1 hour (step d)). In particular, nitrogen, helium or argon is suitable as the inert gas. It is preferred if the activation takes place in the range of 550 to 650 ° C. For example, activation may be at about 600 ° C for about 2 hours.

It is crucial here that in the process according to the invention the activation after the hydrothermal synthesis, in contrast to the known syntheses is not required. Furthermore, it is crucial that in this synthesis the desired stoichiometry of V (up to 0.3 relative to Mo), niobium and tellurium can be predicted in the synthesis. There remain only extremely low concentrations of the ions in the mother liquor of the crystallization. The metals are incorporated in exactly the desired stoichiometry in the MoVNbTe mixed oxide.

The starting compounds are the molybdenum, vanadium, tellurium and niobium containing reactants of the hydrothermal synthesis (precursor compounds). These each contain one or more of the elements molybdenum, vanadium, tellurium or niobium. The molybdenum-containing starting compound may be e.g. an ammonium heptamolybdate or molybdenum trioxide, the vanadium-containing starting compound may be e.g. one

Ammonium metavanadate, vanadyl sulfate or vanadium pentoxide, the niobium-containing starting compound may be, for example, ammonium niobium oxalate or niobium oxalate or niobium oxide. The tellurium-containing starting compound according to the invention is one in which tellurium is present in the +4 oxidation state, ie as the tellurium (IV) cation, as in tellurium dioxide or a compound of the formula M _x ^{n +} TeC> 3 (where n = 1 or 2 and x = 2 / n), where M is an alkali or alkaline earth metal, for example Na2TeC> 3. More preferably, the tellurium-containing starting compound is tellurium dioxide, which may be in any Hydration degree may be present.

An advantage of the preparation process according to the invention is that a synthesis of the Ml phase from the insoluble and inexpensive oxides, e.g. M0O3, V2O5, 2Üs and TeÜ2 be used as starting compounds. Other oxo ligands (i.e., besides oxalic acid) have been found to be particularly useful are dicarboxylic acids and diols, as well as organic compounds having two adjacent carbon atoms each having a hydroxy group. Particularly preferred as another oxo ligand is the use of a mixture of citric acid and glycol.

The oxalic acid should preferably be in a mixture of the starting compounds in a Mo / oxalic acid ratio of 1: 0.01 to 1: 1, preferably 1: 0.08 to 1: 0.4, more preferably 1: 0.15 to 1: 0 , 25 present.

The at least one further oxo ligand, or all further oxo ligands together, should preferably be more preferred in a mixture of the starting compounds in a Mo / oxo ligand ratio of 1: 0.01 to 1: 1, preferably 1: 0.025 to 1: 0.2 1: 0.05 to 1: 0.1.

Surprisingly, this synthesis provides the Ml phase already after the hydrothermal synthesis and the drying, without the need for a high-temperature treatment at a temperature above 400 ° C. Surprisingly, when using this method, the amount of tellurium and niobium used can be significantly reduced and yet the catalytically active Ml phase forms in high phase purity. It has been found that when M0O3, V2O5, b2Üs and TeÜ2 are used with citric acid, glycol and oxalic acid, the hydrothermal crystallization to the Ml phase succeeds without subsequent calcination. Preferably, no ammonium ions are present during the synthesis. The invention

Manufacturing process allows the synthesis of a MoVTeNb mixed oxide material containing the elements Mo, V, Te and Nb (MoVTeNb mixed oxide) having the Ml phase with only minor amounts of niobium and / or tellurium. It is therefore an object of the present invention to find a MoVTeNb mixed oxide with Ml phase and the lowest possible amount of niobium and tellurium, which can be used as catalyst material and has the highest possible activity for the oxidation of alkanes. This object is achieved by a mixed oxide material comprising the elements molybdenum, vanadium, niobium and tellurium, which has in the XRD diffraction reflections h, i, k and 1, whose vertices approximately at the diffraction angles (2 x) 26.2 ° ± 0.5 ° (h), 27.0 ° ± 0.5 ° (i), 7.8 ° ± 0.5 ° (k) and 28.0 ° ± 0.5 ° (1), characterized in that has the following stoichiometry:

M _Ol V _a Nb _b Te _c 0 _n (I) a = 0.2 to 0.35,

b = greater than 0 to 0.08, preferably greater than 0.01 to 0.08 c = greater than 0 to 0.08, preferably greater than 0.01 to 0.08 n = a number determined by the valence and frequency of oxygen different elements in (I) is determined. Here, b is preferably between 0.001 to 0.8, or between 0.01 and 0.5 and c is preferably between 0.001 to 0.8 or between 0.01 and 0.5.

The mixed oxide material according to the invention can be used as a catalyst or as a catalyst material for the oxidation and / or oxidative dehydrogenation of hydrocarbons, in particular for the selective oxidation of ethane to ethylene.

The catalyst material prepared by the process of the present invention can be used in a variety of ways in a commercial catalyst. For example, For example, it can be processed by tabletting into catalyst tablets which can then be filled into a reactor.

The catalyst material may also be processed into an extrudate (tablets, shaped bodies, honeycomb bodies and the like) together with a suitable binder. Any binder known to those skilled in the art and appearing suitable may be used as the binder. Preferred binders include pseudoboehmite and silicate binders such as colloidal silica or silica sol. The catalyst material can also be processed into a washcoat together with other components, preferably with a binder, more preferably with an organic binder, for example an organic adhesive, polymers, resins or waxes, which can be applied to a metallic or ceramic support. If necessary, additional impregnation steps or calcination steps can take place.

The MoVNbTe mixed oxide according to the invention is used in the examples as a catalyst material and therefore partially referred to in the experimental information as a catalyst. FIG. 1: X-ray diffractogram of the catalyst from Example 1.

FIG. 2: X-ray diffractogram of the catalyst from Example 2.

FIG. 3: X-ray diffractogram of the catalyst from Comparative Example 1.

FIG. 4: X-ray diffractogram of the catalyst from Comparative Example 2.

FIG. 5: X-ray diffractogram of the catalyst from Example 4.

FIG. 6: STEM image of the catalyst from Example 1, in which the crystal structure of the Ml phase can be seen.

FIG. 7: SEM image of the catalyst from Example 1, in which the needle crystal form of the Ml phase can be seen.

FIG. 8: N 2 pore distribution of the catalyst from Example 1.

FIG. 9: N 2 pore distribution of the catalyst from Example 2.

FIG. 10: N 2 pore distribution of the catalyst from Example 3.

FIG. 11: Comparison of the catalytic activity of

Catalysts of Examples 1 and 2 in the oxidative dehydrogenation of ethane.

Figure 12: Ethane-ODH activity of Example 4 and 5

FIG. 13: X-ray diffractogram of the catalyst from Example 5 It can be clearly seen that the XRD of the catalyst according to the invention in FIG. 2 shows the typical reflections of the Ml phase at (2Θ =) 26.2 ° ± 0.5 ° (h), 27.0 ° ± 0.5 ° (FIG. i), 7.8 ° ± 0.5 ° (k) and 28.0 ° ± 0.5 ° (1) (using Cu-K radiation), although only a Mo / Nb ratio of 1 : 0.05 and a Mo / Te ratio of 0.05. The reflections are slightly wider than in the comparative examples in which a high-temperature treatment has taken place (Figure 3). Fig. 4 shows that in Comparative Examples 1 and 2, without the high-temperature treatment, only the 22.5 ° reflection reflecting the interlayer distance can be clearly identified. Only after the high-temperature treatment (FIG. 3) does this catalyst also show the typical reflexes of the Ml phase.

FIG. 11 shows that the catalyst according to the invention of Example 1 has a higher activity in the oxidative dehydrogenation of ethane than that of the comparative examples.

It can be clearly seen that the uncalcined inventive catalyst of Example 1 is significantly more active with only half as much niobium and tellurium. The calcined catalyst according to the invention with only half as much niobium and tellurium from Example 2 is just as active as the treated at the same high temperature catalyst according to the prior art of Comparative Example 1. However, it is much cheaper, because it is less expensive metals niobium and tellurium needed. Characterization methods:

For determining the parameters of the invention

Catalysts are used the following methods:

1. BET surface area:

The determination is made according to the BET method according to DIN 66131; a publication of the BET method can also be found in J. Am. Chem. Soc. 60, 309 (1938). The measurements were performed on a Sorptomatic 1990 device at 77K. Before the

Measurement, the sample was evacuated for 2 h at 523 K. The linear regression of the isotherms according to the BET method was carried out in a pressure range of p / po = 0.01-0.3 (po = 730 Torr).

2. Chemical analysis (ICP) with Aufschluß method

Used devices:

Microwave Multiwave GO

Reaction vessel PTFE

Plastic tube 50 ml

ICP Spectro Arcos

Used chemicals:

HF 40% pA.

HCl 37% pA.

Sulfuric acid 98% pA.

Sulfuric acid 1: 1 The sample was finely ground in each case before the analysis.

50 mg of sample were weighed into a reaction vessel and redistilled with 2 ml. Water, 2 ml hydrofluoric acid, 2 ml hydrochloric acid staggered and closed. The sample was then exposed to the following microwave program:

Step 1 Hold for 10 min. At 100 ° C, 1 min.

Step 2 Hold for 5 min. At 180 ° C for 20 min.

0.1 ml of scandium standard is placed in a plastic tube and then the digestion solution is transferred,

then it was tempered, filled and shaken. All elements are detected at the ICP Arcos,

The following basic settings were used:

Plasma power: 1400 watts

Cooling gas flow: 14 1 / min

Auxiliary gas flow: 1.4 1 / min

Atomizing gas flow: 0.8 1 / min

The standards are all adjusted with acidity and the

Mass concentration of scandium is 2 mg / l.

Standards:

Mo 300/400/500 mg / l

Nb 100/50/20 mg / l

Te 150/100/50 mg / 1

V 100/50/20 mg / 1

Wavelengths:

Mo 287, 151 nm corr. Sc 424, 683 nm

202, 095 nm corr. Sc 424, 683 nm

204, 664 nm corr. Sc 424, 683 nm

202, 095 nm

Nb 269.706 nm corr. Sc 424, 683 nm

316.240 nm corr. Sc 424, 683 nm

316.340 nm

Te 225, 902 nm corr. Sc 335.373 nm

170, 000 nm corr. Sc 335.373 nm 170,000 nm

V 292.402 nm corr. Sc 424.683 nm

292.402 nm

311.071 nm corr. Sc 424.683 nm

w (E * in percent) = ß (E * value in mg / l) x V (volumetric flask in I) x 100 m (weight in mg)

E * = respective element

3. Powder X-ray diffractometry (XRD)

The X-ray diffractogram was generated by powder X-ray diffractometry (XRD) and evaluation using the Scherrer formula.

The diffractograms were performed on a PANalytical Empyrean equipped with a Medipix PIXcel 3D detector in Θ-Θ geometry in an angular range of 2Θ = 5 - 70 ⁰

added. The X-ray tube produced Cu-K radiation. The Cu-Kβ radiation was suppressed by using a Ni filter in the incident X-ray beam path, so that only Cu-K radiation having a wavelength of 15.4 nm (E = 8.04778 keV) was diffracted on the sample. The height of the source-side beam path was adjusted by means of an automatic divergent slit (PDS) such that the sample was irradiated over the entire angular range over a length of 12 mm. The width of the detector-side X-ray beam was limited by a fixed aperture to 10 mm. Horizontal divergence was minimized by using a 0.4 rad Soller Slit.

The height of the detector-side beam path was analogous to the source-side beam path by means of automatic anti-scatter slit z (programmable anti-scatter slit - PASS) so adapted to reflect over the entire angular range of a length of 12 mm on the sample

X-ray was detected.

The samples were prepared, depending on the amount present, either on an amorphous silicon platter or tabletted as flat-bed samples.

4. STEM

Scanning transmission electron microscopy was performed on a FEI Titan 80/300 TEM / STEM electron microscope with a

Acceleration voltage of 300 keV performed. Spherical aberration was compensated by illumination correction. All large-angle annulare darkfield (HAADF) images were taken with a convergent half-angle of 17.4 mrad and Annular dark-field detector half-angles of 70-200 mrad

added. The crystal samples were prepared by microtome technique.

5. REM

Scanning electron microscopy was recorded on a JEOL JSM with a secondary electron detector. The

Acceleration voltage was 2.0 kV and the

Emission current 10 μΑ. The working distance was mm.

Examples:

Example 1: MoV ₀ , 3Nbo, osTeo, os

In a 100 mL PTFE beaker, 75 mL bidistilled water were introduced, 175.8 mg monoethylene glycol was added dropwise and then 5397, 5 mg Mo0 ₃ , 1023, 3 mg V ₂ 0 ₅ , 299, 2 mg Te0 ₂ , 274.4 mg Nb ₂ 0 ₅ "x H ₂ O (Nb = 63.45 wt%), 540.3 mg Citric acid and 168.5 mg of oxalic acid slurried. The teflon cup was sealed and placed in a

Conveyed stainless steel autoclave bomb. This was pressure-tight and clamped in a preheated to 190 ° C oven on a horizontal rotating shaft. After 48 hours, the autoclave bomb was removed from the oven and immediately quenched under running water and then cooled in an ice bath for 45 minutes.

The resulting product suspension was filtered through filter paper (pore size 3 pm) and the solid was washed with 200 ml bidistilled water.

The product thus obtained was for 16 hours in one

Drying oven dried at 80 ° C and then ground in a hand mortar. There was achieved a solids yield of 6.8 g, the

Elemental composition of the metals in the product normalized to molybdenum was MoVo, 3oTeo, osNbo, osO _x , this corresponds to a mass-based composition of 53.0 wt% Mo, 8.4 wt% V, 2.9 wt% Te and 2.3 wt% Nb. Scanning transmission electron micrographs of the product are shown in FIGS. 6 and 7.

The BET surface area of the product is 66.4 m ² / g

Product has a pore volume of 0.11 cm ³ / g and a

Pore distribution, the figure 8 is shown.

Example 2:

The catalyst described in Example 1 was subjected to a heat treatment in a tube furnace. To this was added 1 g of the dried solid in Transferred porcelain boats, so that its bottom was covered about 2 mm high with powder. Activation took place for 2 h at 600 ° C, at a heating rate of 10 ° C / min in an N2 flow of 100 mL / min. The elemental composition of

Metals in the product normalized to molybdenum was:

MoV ₀ , 30Te ₀ , 04Nb0,04Ox

The BET surface area of the product was 25.0 m ² / g, the product had a pore volume of 0.04 cm ³ / g and a pore distribution shown in FIG. The XRD of the product is shown in FIG.

Comparative Example 1: (M0V0, 3 bo, i Te o, 1 of soluble

precursors)

In an autoclave (40 L) 3.3 L dist. Submitted H ₂ O and heated to 80 ° C with stirring. Meanwhile, 725.58 g of ammonium heptamolybdate tetrahydrate (from HC Starck) was added.

put in and dissolved (AHM solution). In three 5 L

Beakers were each 1.65 L dist. H ₂ O with stirring on a magnetic stirrer with temperature control also heated to 80 ° C. 405.10 g of vanadyl sulfate hydrate (of GfE, V content: 21.2%), 185.59 g of ammonium niobium oxalate (HC Starck, Nb content: 20.6%) and 94.14 g of telluric acid were then added to each beaker and dissolved (V solution, Nb solution and Te solution). Then the V solution, the Te solution and finally the Nb solution was pumped into the AHM solution by means of a peristaltic pump (pumping time: V solution: 4.5 min at 190 rpm,

Hose diameter: 8x5 mm, Nb solution: 6 min with 130 rpm hose diameter: 8x5 mm). The resulting suspension was stirred for 1 0 min at 8 0 ° C. The speed of the stirrer at the

Precipitation was 90 rpm. Subsequently, it was overlaid with nitrogen by pressurizing to about 6 bar in the autoclave with nitrogen and the drain valve was opened so far that the autoclave was flowed through under pressure of 2 (5 min). In the end, the pressure was over

Bleed valve, up to 1 bar residual pressure again

drained. The hydrothermal synthesis was carried out in the 4 0 L autoclave at 175 ° C for 2 0 h. with an anchor stirrer (heating time: 3 h) at a stirrer speed of 90 rpm.

After the synthesis was filtered off with the aid of a vacuum pump with Blauband filter and the filter cake with 5 L dist. Washed H2O.

Drying was carried out at 8 0 ° C in a drying oven for 3 days and then was ground in a hammer mill. The resulting solids yield was 0, 8 kg, the product was calcined at 2 8 0 ° C for 4 h in air, (heating rate

5 ° C / min air: 1 L / min).

The activation was carried out in a retort in an N 2 gas atmosphere in the oven at 60 ° C. for 2 h (heating rate 5 ° C./min 2: 0.5 L / min). After this treatment, the BET surface area was 13 m ² / g. The result was a catalyst with stoichiometry

M01V0, 3Nbo, io Te o, ιοθχ, corresponding to a weight proportion of the metals in the total weight of the catalyst of Mo = 4 9 wt .-%; V = 7, 9 wt .-%; Te = 6, 5 wt .-%; Nb = 4, 9 wt .-%.

The mother liquor after filtration still contained 0.23% by weight of vanadium and 0.1% by weight of molybdenum. Comparative Example 2:

The catalyst of Comparative Example 1 was used directly after calcination at 280 ° C for 4 hours. The

Calcination at 600 ° C under nitrogen for 2 h was not performed.

Example 3:

The catalytic activity in the oxidative dehydrogenation of ethane of the catalysts of Example 1 and the

Comparative Examples 1 and 2 were tested in a tube reactor at atmospheric pressure in the temperature range 330 ° C to 420 ° C. For this purpose, 25 mg each (Example 1 and

Comparative Example 1) or 200 mg (Comparative Example 2) catalyst (particle size 150-212 pm) with silicon carbide (particle size 150 to 212 pm) in a mass ratio of 1: 5 diluted. Below and above the catalyst bed, a layer of 250 mg of silicon carbide of the same particle size was filled in and the ends of the tubular reactor were closed by quartz wool grafting.

The reactor was purged with inert gas prior to the start of the experiment and then heated to 330 ° C. under a helium flow of 50 sccm. After the desired temperature was reached and stable for one hour, was switched to the reaction gas mixture.

The input gas composition was Cz ^ He / Oz ^ / H = 9.1 / 9.1 / 81.8 (v / v) at a total volumetric flow of 50 sccm.

The analysis of the product gas stream was in a

Gas chromatograph equipped with Haysep N and Haysep Q columns, one molecular sieve column 5A and one

Thermal conductivity detector determined. The ethylene formation rates below those described above

Conditions are shown in FIG. In the measurement of Comparative Example 1, 200 mg of catalyst was used instead of 25 mg, because the catalyst of the invention was so much more active that the activity would not have been measurable with the same mass flow controllers and the same amount of catalyst. However, the representation in FIG. 11 is normalized to the space velocity so that the values are comparable. Example 4: MoV ₀ , 3oNb ₀ , 03 e ₀ , 03

75 mL bidistilled water were initially taken in a 100 mL PTFE beaker, 180.3 mg monoethylene glycol were added dropwise and then 5399.9 mg MoO ₃ , 1024.0 mg V ₂ O ₅ , 180.2 mg TeO ₂ , 166, 8 mg Nb ₂ O ₅ "x H ₂ O (Nb = 63.45 wt.%), 542.4 mg citric acid and 101.3 mg oxalic acid slurried. The teflon cup was sealed and placed in a

The product thus obtained was for 16 hours in one

Drying oven dried at 80 ° C and then ground in a hand mortar. Example 5: MoV ₀ , 3oNbo, oeTeo, 03

In a 100 mL PTFE beaker 75 mL bidistilled water were introduced, 182.3 mg monoethylene glycol was added dropwise and then with 5406.7 mg M0O3, 1023.1 mg V2O5, 177.7 mg Te0 ₂ , 329, 9 mg Nb ₂ 0 ₅ "xH ₂ 0 (Nb = 63, 45 wt .-%), 543, 4 mg of citric acid and 204.5 mg of oxalic acid slurried. The teflon cup was sealed and placed in a

Conveyed stainless steel autoclave bomb. This was pressure-tight and clamped in a preheated to 190 ° C oven on a horizontally rotating shaft. After 48 hours, the autoclave bomb was removed from the oven and immediately quenched under running water and then cooled in an ice bath for 45 minutes.

The product thus obtained was dried for 16 hours in a drying oven at 80 ° C and then ground in a hand mortar.

Example 6:

The catalytic activity in the oxidative dehydrogenation of ethane of the catalysts of Examples 4 and 5 was investigated in a tubular reactor at atmospheric pressure in the temperature range 330-420 ° C. For each 50 mg of catalyst

(Particle size 150-212 pm) diluted with silicon carbide (particle size 150-212 pm) in a mass ratio of 1: 5. Below and above the catalyst bed was a layer of 250 mg of silicon carbide of the same particle size filled and sealed the ends of the tubular reactor by Quarzwollepfropfen.

The reactor was purged with inert gas prior to the start of the experiment and then heated to 330 ° C under helium flow of 50 sccm. After the desired temperature was reached and stable for one hour, was switched to the reaction gas mixture.

The input gas composition was C2H6 / 02 / He = 9.1 / 9.1 / 81, (v / v) at a total volumetric flow of 50 sccm.

The analysis of the product gas stream was in a

Thermal conductivity detector determined.

The ethylene formation rates below those described above

Conditions are shown in FIG.

Table 1:

Table 1 shows the stoichiometries, and the BET surfaces of the catalysts according to the invention

Comparative Examples.

Claims

Claims:

Mixed oxide material comprising the elements molybdenum,

Vanadium, niobium and tellurium, which in XRD, using the Cu-K radiation, has diffraction reflectances h, i, k and 1 whose vertices are approximately at the diffraction angles (2 x) 26.2 ° ± 0.5 ° (h ), 27.0 ° ± 0.5 ° (i), 7.8 ° ± 0.5 ° (k) and 28.0 ° ± 0.5 ° (1), characterized in that it has the following stoichiometry :

M _Ol V _a Nb _b Te _c 0 _n (I) a = 0.2 to 0.35,

b = greater than 0 to 0.08,

c = greater than 0 to 0.08,

n = a number determined by the valency and frequency of the elements other than oxygen in (I).

Mixed oxide material according to claim 1, characterized in that it has a BET surface area greater than 15 m ² / g.

A method for producing a mixed oxide material according to claim 1 or 2, comprising the steps:

a) preparing a mixture of

Starting compounds containing molybdenum, vanadium, niobium and a tellurium-containing starting compound in which tellurium is present in the oxidation state +4, and oxalic acid and at least one further oxo ligand,

b) hydrothermal treatment of the mixture

Starting compounds at a temperature of

100 ° C to 300 ° C to a product suspension receive,

c) separating and drying the mixed oxide material which is contained in the suspension resulting from step b).

4. The method according to claim 3, characterized in that the tellurium-containing starting compound is tellurium dioxide or a compound of the formula M _x ^{n +} TeC> 3 with n = 1 or 2 and x = 2 / n, where M is an alkali or alkaline earth metal.

A method according to claim 3 or 4, characterized in that the mixture of starting compounds is present as an aqueous suspension.

A method according to claim 3 to 5, characterized in that the mixture of starting compounds a

Dicarboxylic acid, a diol or other compound having two hydroxy groups in adjacent position as another oxo ligand.

7. The method according to any one of claims 3 to 6, characterized

in that the mixture of starting compounds contains molybdenum trioxide.

8. The method according to any one of claims 3 to 7, characterized

characterized in that the mixture of starting compounds contains vanadium pentoxide.

9. The method according to any one of claims 3 to 8, characterized

in that the mixture of starting compounds contains citric acid as further oxo ligand.

10. The method according to any one of claims 3 to 9, characterized in that the mixture of starting compounds citric acid and glycol contains as further oxo ligands. 11. The method according to any one of claims 3 to 10, characterized in that the drying in step c) is carried out at 50 ° C to 400 ° C.

12. The method according to any one of claims 3 to 11, characterized in that the drying in step c) in two

Steps, first at 50 ° C to 150 ° C and then at 350 ° C to 400 ° C is performed.

13. The method according to any one of claims 3 to 12, characterized in that there is one more to the drying

Activation at 500 ° C to 650 ° C under inert gas

connects.

14. Use of a mixed oxide material according to claim 1 or 2 for the oxidative dehydrogenation of ethane to ethene.

15. Use of a mixed oxide material according to claim 1 or 2 for the oxidation of propane to acrylic acid. 16. Use of a mixed oxide material according to claim 1 or 2 for the ammoxidation of propane with ammonia

Acrylonitrile.