DE19600741A1 - Catalyst for catalytic oxidative dehydrogenation of alkyl aromatic(s) and paraffin(s) - Google Patents

Abstract

Catalyst comprises of least one side of Bi, Ce, Co, Cr, Cu, Fe, In, Mn, Mo, Nb, Ni, Sb, Sn and V which can assume a number of oxidn. stoles with a metal or noble material selected from Ag, Au, Co, Cu, Ir, N, Os, Al, Pt, Re, Rh and Ru applied as a sol to the catalyst. The catalyst may opt. have a carrier selected from clays, PILC, zeolites, aluminium phosphate, silicon carbide or nitride, boron nitride, carbides and oxides of Al, Ba, Co, Mg, Th, Ti, Si, Zn and Zr. Also claimed is the prepn. of an olefinic unsatd. cpd. by catalytic oxidative dehydrogenation of organic cpd. using the catalyst, which is regenerated after use.

Description

The invention relates to a catalyst and a process for Production of olefinically unsaturated compounds by kata lytic oxidation, namely oxidative dehydration by acid mass transfer from a previously oxidized catalyst acting oxygen transmitter in the absence of molecular Oxygen. The invention preferably relates to the catalytic oxidative dehydrogenation of alkyl aromatics and paraffins to the corresponding alkenyl aromatics and olefins, especially the Dehydrogenation of ethylbenzene to styrene.

Styrene and divinylbenzene are important monomers for technical Plastics and are used in large quantities.

Styrene is predominantly produced by non-oxidative dehydrogenation Ethylbenzene produced on modified iron oxide catalysts, whereby one mole of hydrogen is produced per mole of styrene. More disadvantageous wise, this implementation is an equal weight reaction that occurs at temperatures of typically 600 to 700 ° C and with a turnover of approx. 60% for a styrene Selectivity is about 90%, with increasing sales and increasing concentration of the target product the back reaction uses and limits sales.

Through oxidative dehydration, in which the coal water to be reacted molecular oxygen, d. H. usually air implemented an almost quantitative turnover can be achieved because water is formed. This implementation is already underway at a lower temperature than the non-oxidative dehydrogenation.

A disadvantage of the oxidative dehydrogenation with molecular acid is the total oxidation occurring as a side reaction, whereby So carbon dioxide and other water occur in the product stream. This phenomenon is often referred to as "gasification".

It has therefore been proposed instead of molecular Oxygen acts as a catalyst, that is, reaction-directing the oxygen consisting of a reducible metal oxide insert transmitter. The oxygen is exhausted gradually wear and must be regenerated in a second step which will restore the initial activity. These is a common procedure in classic process engineering  referred to as a regenerative process. In the regeneration phase z. B. coke deposits are burned off. The Regeneration is highly exothermic, so that the waste heat released e.g. B. can be used for the production of steam.

By decoupling the reduction and oxidation step the selectivity can be increased significantly.

Technically, there are two types of decoupling, namely the spatial and temporal separation of the two steps.

In the spatial separation of the two steps, a Moving bed or a circulating fluidized bed being used the catalyst particles from the dehydrogenation zone after separation of the reaction products, to a separate regeneration reactor are promoted in which the reoxidation takes place. The rain The catalyst is returned to the dehydrogenation zone. On such a process can be continuous, i. H. set up cyclically will. The catalyst is subject to high mechanical stresses exposed and must therefore have sufficient hardness. A time separation can be arranged with a fixed Realize oxygen carriers by periodically between the Useful reaction and, possibly after a flushing phase with inert gas, the Regeneration is switched.

The regenerative principle using a reducible and regenerable catalyst was first used for the oxidation or Ammonia oxidation of propene to acrolein and acrylic acid or acrylic nitrile (GB 885 422; GB 999 629; K. Aykan, J. Catal. 12 (1968) 281-190), with arsenate and molybdate catalysts were used. The use of the process in the oxidative Dehydrogenation of aliphatic alkanes to mono- and diolefins with ferrite catalysts (e.g. US 3 440 299, DE 21 18 344, DE 17 93 499) is also known, as is the use for the oxidative coupling of methane to higher hydrocarbons, different classes of catalyst are used (e.g. US 4,795,849, DE 35 86 769 with Mn / Mg / Si oxides; US 4,568,789 with Ru oxide; EP 254 423 with Mn / B oxides on MgO; GB 2 156 842 with Mn₃O₄ spinels). Dehydrodimerization, too from toluene to stilbene in the absence of free oxygen reducing catalysts such as Bi / In / Ag oxides (EP 30 837) is known.  

Finally, the principle for dehydration, dehydro Cyclization and dehydroaromatization of paraffin hydrocarbons substances used for gasoline refinement (US 4,396,537 with Co / P- Oxide catalysts).

EP 397 637 and 403 462 disclose the principle of the process the oxidative dehydrogenation of paraffin hydrocarbons and To use alkyl aromatics. After that, reducible metal oxides used, selected from the group V, Cr, Mn, Fe, Co, Pb, Bi, Mo, U and Sn, applied to supports made of clays, zeolites and Oxides of Ti, Zr, Zn, Th, Mg, Ca, Ba, Si, Al.

Although a high yield can be achieved with these catalysts should, it occurs in the initial phase of dehydration when the Hydrocarbon with the freshly regenerated and therefore special active catalyst comes into contact, to a very strong Gasification (total combustion). Except for the loss of raw materials significantly more oxygen is consumed than for the mere dehydration, so that the oxygen carrier turns out prematurely exhausted and the cycle time is shortened unnecessarily.

The transient dehydrogenation of ethylbenzene succeeds US 4,067,924 with Mg Chromite catalysts. The transient oxidative dehydrogenation of ethylbenzene and butene with Bi-Cr-Vana data is described in US 3,842,132.

A process in which a dehydrogenation catalyst (V, Cr, Mo / Al₂O₃) and a redox-active YBCO perovskite as a hydrogen acceptor in Are connected in series is described in EP 558 148. After one Proposed in WO 94/05608 is a dehydrogenation catalyst and a zeolite coated with a porous membrane as hydrogen Absorber connected in series. The series connection from one Dehydrogenation catalyst (Al-Mg-O, Al-Cr-O) and a reducible Oxidation catalyst (bi-vanadate) can be found as a suggestion in US 3,488,402.

In EP 556 489 propane and / or isobutane become unsteady with oxidatively dehydrated a catalyst made from alkali-doped V- Oxide is on a support and contain Pd and / or Pt and Ce can.

Au / Ce oxide contacts for transient oxidative dehydrogenation of alkanes and alcohols are used in EP 543535.  

The invention relates to a new redox-active noble metal-containing catalyst and its production based on a precious metal sol and the use of the catalyst for transient oxidative dehydrogenation reactions.

The use of precious metal sols as unsupported catalysts has been known for a long time. As from W. Hückel, with catalysis colloidal metals, Leipzig, 1927, were colloidal Metals especially for the catalytic hydrogenation of multiple bindings used.

From a more recent document, JP 03/215 607 is the manufacture of an organometallic sol by decomposing an organometallic Complex in an organic solvent and its use known as a catalyst. The use of precious metal brines Carriers, preferably ceramic materials, as catalysts also known. For example, according to JP 03/086 240 Production of a rhodium or platinum organometallic sol and its Application described on a ceramic support. These Catalysts are for the removal of hydrocarbons, CO and NOx in exhaust gases. In JP 63/058 621 the manufacturer a hydrogenation catalyst from a polymeric anion exchange shear and a rhodium sol.

Oxidation and dehydration have high reaction temperatures due to increased by-product formation, often selectivities loss of crime.

The invention is therefore based on the object of being a highly active Catalyst for oxidation and dehydrogenation reactions to fin the one that allows a significantly lower reaction temperature, than previously possible, whereby the special task had to be solved, to find such a catalyst of at least the same height Generate sales as before and by reducing totaloxi dation and crack product formation due to the lower turnover bring about an improvement in selectivity should. Lower reactor temperatures also save energy costs and advantageously lead to lower material stress chung.

It has now been found that noble metal-containing redox catalysts from at least one precious metal that is in the form of a sol on the Carrier is applied and at least one redox-active metal oxide much higher activity than the previously known nobles have metal-free redox catalysts and already at relative  low temperature, high turnover and high selectivity chen.

It is believed - which does not limit the scope of the invention is that the precious metal as a highly active dehydrogenation center and The redox system acts as a hydrogen scavenger because it is hydrogen is a better reducing agent than ethylbenzene and also at low levels Temperatures is still capable of implementation.

At high temperature, the reverse would happen in principle take place, d. H. the precious metal would convert styrene to ethylbenzene hydrogenate so that the styrene yield with noble metal doping should even sink.

The immediate subject of the invention is a precious metal Redox catalyst of the aforementioned type and its use, d. H. a process for the oxidative dehydrogenation of hydrocarbons fen.

The catalyst according to the invention consists of at least one Oxide selected from the group of oxides of multiple oxidations step accepting elements Bi, Ce, Co, Cr, Cu, Fe, In, Mn, Mo, Nb, Ni, Sb, Sn and V and can be strapless or on a carrier ger be applied. Suitable carriers can e.g. B. Tone, PILC, Zeolites, aluminum phosphate, silicon carbide or nitride, boron nitride, carbon in any form and metal oxides selected from the group Al, Ba, Ca, Mg, Th, Ti, Si, Zn or Zr, as well such as their mixtures and reaction products. The catalyst can further promoters, in particular (earth) alkali and / or rare Earths included. According to the invention, the catalyst also contains at least one different from the above elements Metal or precious metal, selected from the elements Ag, Au, Co, Cu, Ir, Ni, Os, Pd, Pt, Re, Rh, and Ru, the catalyst being the Has properties that it receives when the metal or precious metal on the strapless or attached to a carrier Oxide catalyst has been applied as a sol.

A suitable catalyst preferably contains up to 30% by weight (Alkali, alkaline earth, rare earth) oxide, 90 to 99.9% by weight reducible metal oxide, and 0.1 to 10% by weight (noble) metal, where the existing carrier is not included.

The oxidative dehydrogenation to be operated with the catalyst can be carried out at a temperature of 200 to 700, preferably 300 to 500 ° C. and at pressures of 100 mbar to 10 bar, preferably 500 mbar to 2 bar, at a space velocity (liquid hourly space velocity; LHSV) from 0.01 to 20 h ^-1 , preferably 0.1 to 5 h ^-1 . In addition to the hydrocarbon to be oxidized / dehydrogenated, diluents such as CO₂, N₂, noble gases or steam can be present in the feed. The regeneration of the reduced catalyst is carried out at temperatures in the range from 100 to 800, preferably 250 to 600 ° C. with a free oxidizing agent, preferably with N 2 O or an oxygen-containing gas including pure oxygen. Here too, diluents can be contained in the reactor inflow. Are also suitable z. B. air or lean air. The regeneration can be operated at reduced pressure, atmospheric or superatmospheric pressure. Here, too, pressures in the range from 500 mbar to 10 bar are preferred.

The catalysts of the invention are either thereby put that all ingredients mixed in the usual way and then be heated high enough to be an active one to obtain uniform catalyst. This is analogous to that The procedure described in detail below is used. The Precious metal sol is used during the manufacture of the catalyst admitted. In this case, the active component lies on everyone Case homogeneously distributed over the catalyst strand.

Dry mixing, slurrying, impregnation, Precipitation, co-precipitation, spray drying and then calcination, d. H. Heating to a temperature of 300 to 1000 ° C, which is uniform or can be done in stages. The raw needed fabrics can e.g. B. as oxides, hydroxides, carbonates, acetates, Ni occur or generally water-soluble salts of the respective metal atoms with inorganic or organic anions are present. Also Transition metal complexes can be used. The calcination then takes place at temperatures at which the respective raw materials form the catalyst, d. H. be installed in these, whereby They usually go straight to the active phase, usually Oxides or oxide mixtures or mixed oxides are converted. Of the The condition of the precious metal or metals used is not special known and can both the elementary state and a chemi be connected with the other components. Typical cal Filming temperatures are in the range from 300 to 1000 ° C., preferably 400 to 800 ° C.

When used rare earth metal to support the effect should not be, especially when using lanthanum the oxide, La₂O₃ can be assumed, since then the effect is only slight is. Instead, La oxide carbonate, La (OH) ₃, La₃ (CO₃) ₂ or organic lanthanum compounds, such as La acetate, La formate or La oxalate can be used, which in the calcination to a lead finely divided and surface-rich active La phase.  

A preferred calcining temperature for the decomposition of La (Ac) ₃ for active La phase is, for example, 600 ° C to 800 ° C.

However, the catalyst is preferred in a two-stage Ver drive manufactured, with the first without precious metal such as prepared above, already redox-active kata subsequently by spraying or soaking a precious metal Sol is applied.

As a redox-active catalyst z. B. the in the not vorver public DE patent application P 44 23 975.0 described Kata lysator can be used. A procedure is also recommended ren, in which the precious metal sol by kneading with the rest Raw components of the catalyst are mixed and then the catalyst sator is shaped and processed as usual.

A noble metal sol can start from a noble metal salt the reduction of which are produced in aqueous solution. It can z. B. aqueous solutions of chlorides, acetates or nitrates of Precious metal are used, but there are also other noble metal salts possible, a restriction on the anion does not exist. Organic ver bonds such as ethanol, methanol, carboxylic acids and their alkali salts and inorganic compounds such as hydroxylamine or NaBH₄ to serve. The particle size of the metal particles in the sol generally depends on on the strength of the reducing agent used and on the used metal salt. Generally one observes with stronger reducing agents the formation of smaller metal particles. The brine can be added by adding organic Polymers such as polyamines, polyvinyl pyrrolidone or polyacrylates stabilize. The precious metal brine can also be applied to others in usually found in the relevant literature be put. Bonnemann et al. (Angew. Chemie, 103 (1991) 1344) describe, for example, the production of stable metal salt by reducing metal salts with tetraoctylammonium-bo ranate (C₈H₁₇) ₄N [BEtH₃]. The catalysts produced in this way have the advantage that the precious metal in highly dispersed form lies. Because the precious metal component in the sol is already reduced Form is present, an additional reduction step can be carried out to be waived. Because this reduction step is often at high Temperature must be carried out, it can be agglomerated tion of the precious metal come, which is associated with loss of activity is.  

The catalysts of the invention have a noble content metal from 0.001 to 5% by weight; the noble is advantageous metal content 0.005 to 2, in particular 0.1 to 1 wt .-%.

Catalyst preparation

According to a proposal that has not been published beforehand, a Based on K / La / Bi / TiO₂ built catalyst, which is active and selective in itself and at a temperature un above 500 ° C allows a maximum styrene yield of over 90% light, but its activity at temperatures below 450 ° C decreases rapidly (hereinafter referred to as "comparative catalyst" net).

First stage: 107.35 g of lanthanum acetate (La content 41.75% by weight) and 297.5 g of TiO₂ type DT-51 (Rhône-Poulenc) are dry mixes. Then with 3 wt .-% extrusion aid and 159 ml of water are added and the mixture is compacted in a kneader for two and a half hours. It is dried at 120 ° C for two hours and at five hours Calcined at 600 ° C. The material obtained is in the analytical mill crushed.

Second stage: 312 g of the mass of the first stage are added 138.22 g of basic bi-carbonate (Bi content 81% by weight) and 91.55 g K₂CO₃ mixed dry for one hour, with 3 wt .-% extrusion tools and water and two and a half hours in the kneader condensed. The plasticine becomes 3 mm full strands in the extruder deformed. It is dried at 120 ° C for two hours and two hours calcined at 500 ° C.

The catalyst contains 12.5% K₂O, 25% Bi₂O₃, 9.4% La₂O₃ and 53.1% TiO₂.

The cutting hardness of the strands is 7 N / strand, the BET surface surface 16 m² / g.

The strands are broken for the reactor tests in the pulse reactor and sieved a grain size fraction of 50 to 100 microns.

The result given below for comparison with this Ka talysator is not a comparison with the state of the art, but rather should clarify the effect of the addition of precious metal. The Designations STV. . are arbitrary laboratory names gene.

Example 1 (STV 33; 0.1% Pd) 1. Preparation of a palladium sol

5.482 g of an 11% palladium nitrate solution are mixed in one Mixture of 700 ml dist. Dissolved water and 300 ml of ethanol and with 5 g of polyvinylpyrrolidone added. The solution will first be a stirred for half an hour at room temperature and then four Heated at reflux for hours. After cooling, a stabi is obtained les sol.

2. Preparation of the catalyst according to the invention

12.0 g of the catalyst prepared for comparison (see above) presented in a heatable pelletizing plate. 20 ml of Sols are diluted to 200ml and applied through a two-fluid nozzle sprayed the catalyst. The pelletizing plate is used during the Spraying process heated by a hot air stream. After completion The spraying process turns the catalyst at 120 ° C for sixteen hours dried.

Example 2 (STV 35; 0.5% Pd)

As in Example 1, but 100 ml of the sol was diluted to 200 ml and then sprayed onto 12.0 g of the comparative catalyst.

Example 3 (STV 34; 1% Pd)

As in Example 1, but 200 ml of the sol was undiluted to 12.0 g of the comparative catalyst sprayed.

Example 4 (STV 59; 0.43% platinum) 1. Production of a platinum sol

7.311 g of Pt (NO₃) ₂ were dissolved in 1000 ml of distilled water. For this purpose, 5.0 g of polyvinylpyrrolidone were added with vigorous stirring given as a stabilizer and 300 ml of ethanol, half an hour stirred at room temperature and then four hours on the back river heated. After cooling, a stable sol (3 g Platinum per l).

First stage: 107.35 g of lanthanum acetate (La content: 41.75% by weight) and 297.5 g of TiO₂ type DT-51 from the manufacturer Rhönen-Poulenc mixed dry for one hour. Then with 3 wt .-% Ver strands and 134 ml of the platinum sol and added in Kneader compacted for two and a half hours. It'll be at two hours  Dried 120 ° C and calcined at 600 ° C for five hours. The The material obtained is crushed in the analytical mill.

Second stage: 312 g of the mass of the first stage are added 138.22 g of basic bi-carbonate (Bi content 81% by weight) and 91.55 g K₂CO₃ mixed dry for one hour, with 3 wt .-% extrusion auxiliaries and 105 ml of platinum sol added and sixteen hours compacted in the kneader. The plasticine is 3 mm in the extruder Full strands deformed. It is dried at 120 ° C for two hours and calcined at 500 ° C for two hours.

The finished catalyst contains 0.43% platinum, the BET surface area is 21 m² / g.

Example 5 (STV 60; 0.43% palladium)

Of the palladium sol described in Example 1 with a Concentrations of 3 g / l were, as described in Example 4, in the first stage used 134 ml of the palladium sol in which second stage 105 ml.

The finished catalyst contains 0.43% palladium, the BET Ober area is 20.87 m² / g.

Example 6 (STV 61; 0.1% platinum)

8.3 ml of the Pt sol of the concentration 3 g / l were ver to 100 ml thins. The diluted sol was as described in Example 1 25 g of the comparative catalyst sprayed. The finished catalyst contains 0.1% platinum.

Example 7 (STV 62; 0.5% platinum)

42 ml of the platinum sol with a concentration of 3 g / l was made up to 100 ml diluted. The diluted sol was as described in Example 1 sprayed onto 25 g of the comparative catalyst. The finished Kataly sator contains 0.5% platinum.

Example 8 (STV 63; 1% platinum)

84 ml of the platinum sol with a concentration of 3 g / l was made up to 100 ml diluted. The diluted sol was as described in Example 1 sprayed onto 25 g of the comparative catalyst. The finished Kataly sator contains 1% platinum.  

Investigation results

The catalytic oxidative dehydrogenation of ethylbenzene to styrene is on a micro scale in a pulse reactor at a temperature from 400 to 500 ° C examined. The catalyst is in one Fixed bed (weight 0.3 to 0.6 g) in the absence of free Pulsed oxygen with ethylbenzene and the Reaction products analytically (on-line GC) for each pulse quanti tativ captured. In the period between two consecutive Pulse (approx. 1.5 min) helium carrier gas flows through the reactor. A single pulse contains 380 µg of ethylbenzene. The speed speed of the carrier gas is 21.5 ml / min. That way the deactivation behavior of the catalyst without dead times Track with high time resolution right from the start.

At the beginning the catalyst is highly active, the reaction rate accordingly, is high. Has high initial activity however, a certain increase in the by-product level (e.g. Gasification to carbon oxides) combined with less calculation Selectivity. In the further course the minor goes product formation and the selectivity then improves steadily to their final value. As the duration of the experiment progresses however, the catalyst becomes as acidic as its lattice substance is consumed, more and more deactivated, so that the Ethylbenzene conversion drops. Depending on the deactivation behavior of the Ka talysators must be regenerated after 90 to 200 pulses. It he shows that the styrene yield as a product of selectivity and sales in general goes through a flat maximum. The in Table 1 obtain the listed measurement results (styrene yield and conversion) to just this maximum value.

After the end of a dehydration phase, an air flow of 25 ml / min switched and the catalyst at about two hours the respective reaction temperature regenerated. After that closes the next cycle. Several cycles are run through. The reoxidation of the deactivated reduced catalysts left the catalytic activity of both the comparative catalyst and also the catalysts of the invention in full again Restore: None of the measured cycles was with the Progressive loss of activity determined. The numerical values given in Table 1 represent the mean values from multiple cycles.

On an industrial scale, the catalyst will not be up to exploit full deactivation, but regeneration initiate as long as sales are still economically acceptable, d. H. about 10 to 20% below the maximum value achieved  is. Then the regeneration time can be much shorter because the catalyst was partially reduced.

Table 1

Results

The test results can be interpreted as follows:

• - Compared to a non-precious metal catalyst, the catalyst of the invention a significantly higher styrene Yield at the same reactor temperature;
• - It is the first time a yield of 90% with almost quantitative v sales reached at a temperature below 450 ° C, d. H. same catalytic performance at significantly lower Temperature.

Claims (14)

1. Carrier-free or on a carrier selected from the group the clays, PILC, zeolites, aluminum phosphate, silicon carbide and nitride, boron nitride and carbon as well as the metal oxides, selected from the group Al, Ba, Ca, Mg, Th, Ti, Si, Zn or Zr applied catalyst from at least one oxide selected from the group of oxides of several oxidation levels accepting elements Bi, Ce, Co, Cr, Cu, Fe, In, Mn, Mo, Nb, Ni, Sb, Sn and V and from at least one of the above the elements of different metal or precious metal chooses from the elements Ag, Au, Co, Cu, Ir, Ni, Os, Pd, Pt, Re, Rh, and Ru as obtained when the metal or Precious metal on the strapless or on a carrier brought oxide catalyst as a sol has been applied. 2. Catalyst according to claim 1, further comprising an alkali tall, alkaline earth metal or rare earth metal, optionally in Form of an oxide or a compound with another Catalyst component. 3. Catalyst according to claim 1, containing 10 to 99.9 wt .-% at least one oxide which assume several oxidation states the elements, 0.1 to 10% by weight of at least one metal or precious metal and up to 30 wt .-% at least one Alkali, alkaline earth or rare earth oxide, each related on the composition in the highest oxidation state, a possibly existing carrier not included is not. 4. Catalyst according to claim 1, containing bismuth oxide on a Titanium dioxide carrier and at least one alkali, alkaline earth or rare earth metal and at least one precious metal selects from the group platinum, palladium, ruthenium or rho dium, the precious metal being applied in the form of a sol or has been introduced into the catalyst. 5. Process for the production of olefinically unsaturated Compounds by catalytic oxidation / oxidative dehydration by oxygen transfer from a previously oxidized oxygen catalyst acting in the absence of molecular oxygen, the catalyst after the Exhaustion is regenerated, characterized in that the Compound to be dehydrogenated with the catalyst according to An saying 1 is implemented.   6. The method according to claim 5, characterized in that a temporal decoupling of the sub-steps of the redox reaction follows, using a catalyst fixed bed a periodic switching of the reactor input current between the reactants and the regeneration gas det. 7. The method according to claim 6, characterized in that between between the dehydrogenation step and the regeneration step Rinsing phase is inserted, in which the fixed bed reactor by one Flushing gas is flowed through. 8. The method according to claim 6, characterized in that a spatial decoupling of the sub-steps of the redox reaction follows in such a way that using a circulating Fluidized bed the catalyst particles cyclically between one Dehydrogenation reactor and a separate regeneration reactor in the Circle. 9. The method according to claim 5, characterized in that the to dehydrating hydrocarbons are alkyl aromatics that too the corresponding alkenyl aromatics are dehydrated. 10. The method according to claim 5, characterized in that ethyl benzene is dehydrated to styrene. 11. The method according to claim 5, characterized in that the to dehydrating hydrocarbons are paraffins that are among the corresponding olefins are dehydrated. 12. The method according to claim 5, characterized in that the reduced catalyst with an oxygen-containing gas or pure oxygen is regenerated. 13. The method according to claim 5, characterized in that the reduced catalyst with N₂O as an oxidizing agent is riert. 14. The method according to claim 5, wherein the oxidative dehydrogenation between 200 and 800 ° C, at 100 mbar to 10 bar and with an LHSV of 0.01 to 20 h ^{-1 is} carried out.