EP1343584A2 - Regeneration of a dehydrogenation catalyst - Google Patents

Abstract

The invention relates to a method for the regeneration of a dehydrogenation catalyst, comprising the steps (a)-(f): (a) flushing with inert gas at a pressure of 0.5 to 2.0 bar and a gas loading of 1 000 to 50 000 h<-1>; (b) passage of an oxygen-containing gas mixture, containing an inert gas, at a pressure of 2 to 20 bar and a gas loading of 1,000 to 50,000 h<-1>, over a period of 0.25 to 24 h with sequential or continuous increase of the oxygen concentration from an initial value of 0.01 to 1 vol. % O2 to a final value of 10 to 25 vol. % O2; (c) optional passage of an oxygen-containing gas mixture, containing an inert gas, at a pressure of 0.5 to 20 bar and a gas loading of 10 to 500h<-1> over a period of 0.25 to 100 h with an oxygen concentration of 10 to 25 vol. % O2; (d) optional repeated rapid cyclical pressure changes of a factor of 2 to 20, within the range 0.5 to 20 bar; (e) flushing with an inert gas; (f) activation of the catalyst with hydrogen, whereby at least one of steps (c) or (d) is carried out and the whole regeneration process occurs at a temperature of between 300 and 800 DEG C.

Description

 Regeneration of a dehydrogenation catalyst

The invention relates to a process for the regeneration of dehydrogenation catalysts which are used in heterogeneously catalyzed dehydrogenation of dehydratable C ₂ -C ₃₀ hydrocarbons.

Dehydrated hydrocarbons are required as starting materials for numerous industrial processes in large quantities. For example, dehydrated hydrocarbons are used in the manufacture of detergents, anti-knock petrol and pharmaceutical products. Numerous plastics are also produced by polymerizing olefms.

For example, acrylonitrile, acrylic acid or C -oxoalcohols are produced from propylene. Propylene is currently mainly produced by steam cracking or by catalytic cracking of suitable hydrocarbons or hydrocarbon mixtures such as Νaphtha.

No. 4,788,371 describes a process for the water vapor dehydrogenation of dehydratable hydrocarbons in the gas phase in connection with an oxidative reheating of the intermediate products, the same catalyst being used for the selective oxidation of hydrogen and the water vapor dehydrogenation. Hydrogen can be supplied as a co-feed. The catalyst used contains a Group VIII noble metal, an alkali metal and another Group B, Ga, In, Ge, Sn, and Pb metal on an inorganic oxide support such as alumina. The procedure can be carried out in one or more stages in a fixed or moving bed.

WO 94/29021 describes a catalyst which contains a carrier consisting essentially of a mixed oxide of magnesium and aluminum Mg (Al) O and a noble metal from group VIII, preferably platinum, a metal from group IV A, preferably tin, and optionally an alkali metal, preferably cesium. The Catalyst is used in the dehydrogenation of hydrocarbons, it being possible to work in the presence of oxygen.

No. 5,733,518 describes a process for the selective oxidation of hydrogen with oxygen in the presence of hydrocarbons such as n-butane on a catalyst comprising a phosphate of germanium, tin, lead, arsenic, antimony or bismuth, preferably tin. The combustion of the hydrogen generates the heat of reaction necessary for the endothermic dehydrogenation in at least one reaction zone.

EP-A 0 838 534 describes a catalyst for the water-vapor-free dehydrogenation of alkanes, in particular isobutane, in the presence of oxygen. The catalyst used comprises a platinum group metal which is applied to a support made of tin oxide / zirconium oxide with at least 10% tin. The oxygen content in the feed stream of the dehydrogenation is adjusted so that the amount of heat generated by the combustion of hydrogen with oxygen is equal to the amount of heat required for the dehydrogenation.

WO 96/33151 describes a process for the dehydrogenation of a C ₂ -C ₅ alkane in the absence of oxygen on a dehydrogenation catalyst comprising Cr, Mo, Ga, Zn or a Group VIII metal with simultaneous oxidation of hydrogen formed on a reducible metal oxide such as the oxides of Bi, In, Sb, Zn, Tl, Pb or Te. The dehydration must be interrupted regularly to reoxidize the reduced oxide with an oxygen source. No. 5,430,209 describes a corresponding method in which the dehydrogenation step and the oxidation step take place in succession and the associated catalysts are spatially separated from one another. Oxides of Bi, Sb and Te and their mixed oxides are used as catalysts for the selective hydrogen oxidation.

In heterogeneously catalyzed dehydrogenation of hydrocarbons, small amounts of high-boiling, high molecular weight organic compounds or carbon are generally formed over time, which deposit on the catalyst surface and in the pores and deactivate the catalyst over time. Some of this must be regenerated under drastic conditions and using corrosive gases such as chlorine. In some cases, the catalysts can no longer be completely regenerated and therefore have only a short service life. The used dehydrogenation catalysts are usually regenerated by purging with inert gas, passing through an oxygen-containing gas mixture, purging with inert gas and subsequent activation with hydrogen, working at atmospheric pressure. In the process according to US Pat. No. 5,087,792, the catalyst is regenerated by flushing with inert gas, passing through an oxygen-containing gas mixture, flushing with inert gas and then passing through an HCl / oxygen mixture to redisperse the active metal (palladium) on the support.

The object of the invention is to provide an effective process for the regeneration of used dehydrogenation catalysts.

The task is solved by a method for the regeneration of a dehydrogenation catalyst with the steps (a) - (f):

(a) purging with inert gas at a pressure of 0.5 to 2.0 bar and a gas load of 1000 to 50,000 h ^"1 ;

(b) Passing through an oxygen-containing gas mixture containing an inert gas at a pressure of 2 to 20 bar and a gas load of 1000 to 50,000 h ^"1 over a period of 0.25 to 24 h with a gradual or continuous increase in

Oxygen concentration from an initial value of 0.01 to 1% by volume of O ₂ to a final value of 10 to 25% by volume of O ₂ ;

(c) optionally passing an oxygen-containing gas mixture containing an inert gas at a pressure of 0.5 to 20 bar and a gas load of 10 to 500 h ^"1 over a period of 0.25 to 100 h, the oxygen concentration being 10 to 25 vol. -% is O ₂ ;

(d) optionally repeated rapid opposite pressure changes by a factor of 2 to 20 within the range of 0.5 to 20 bar;

(e) purging with an inert gas or water vapor;

(f) activation of the catalyst with hydrogen; wherein at least one of steps (c) or (d) is carried out and the entire regeneration process is carried out at a temperature of 300 to 800 ° C.

The dehydrogenation catalyst is preferably installed in a dehydrogenation reactor. However, it can also be regenerated in a separate regeneration reactor.

In step (a), the purging is preferably carried out with inert gas until the purging gas essentially contains no traces of dehydrogenation product, for example propene, and hydrogen, that is to say such traces can no longer be detected using the usual analytical methods, for example gas chromatography. In general, purging over a period of 0.1 to 24 h is required at a pressure of 0.5 to 2.0 bar and a gas load of 1000 to 50 000 h ^-1 . The pressure is preferably 1 to 1.5 bar, the gas load preferably 2000 to 20,000 h ^"1 . The duration of the rinsing step is preferably 0.1 to 6 hours. Nitrogen is generally used as the inert gas. The purge gas can also contain water vapor in amounts of, for example, 10 to 90% by volume.

In step (b), an oxygen-containing gas mixture is passed through the catalyst bed in order to burn off the surface coke deposits on the catalyst particles. Diluted air is preferably used as the oxygen-containing gas mixture, which in addition to an inert gas can also contain water vapor, for example in amounts of 10 to 90% by volume. The oxygen content is gradually increased, generally from an initial concentration of 0.01 to 1% by volume, for example 0.1% by volume, to a final concentration of 10 to 25% by volume. If the oxygen-containing gas contains no water vapor and air is used, the final concentration is generally approx. 21 Nol .-%. Oxygen. It is essential that work is carried out at a pressure significantly above the pressure which prevails during the dehydrogenation. The pressure is preferably 3 to 7 bar, for example 4 to 6 bar. The treatment time is preferably 0.5 to 12 h, for example 1 to 9 h. In general, a high gas load is used. This is preferably 2,000 to 20,000 h ^"1 .

In step (c), an oxygen-containing gas mixture which has a high oxygen content is passed through the catalyst bed. Air is preferably used for this purpose. The oxygen-containing gas mixture can contain water vapor, for example in amounts of 10 to 90% by volume. In this step, the pores in the Catalyst particles of deposited coke burned off. This is carried out at low gas loads of generally 10 to 500 h ^"1 , preferably 20 to 100 h ^{" 1} . The pressure is not critical, it can be the same as the pressure in step (b) or lower. In general, it is 0.5 to 20 bar, preferably 1 to 5 bar.

In step (d), the pressure is repeatedly changed in the opposite direction, that is to say the pressure increases and the pressure decreases in short time intervals. In this way, CO ₂ formed in the pores can be effectively removed. Preferably, the pressure is changed 2 to 20 times by a factor of 2 to 5 within the range of 1 to 5 bar. For example, a total of 3 pressure increases and decreases from 1 to 5 and 5 to 1 bar are carried out. The total duration of all pressure increasing and reducing steps is preferably 0.1 to 1 hour. In order for the pressure in the reactor to build up quickly, the gas load should not be chosen too low and is generally 100 to 50,000 h ^"1 , preferably 1000 to 20,000 h ^{" 1} .

Step (c) and step (d) can alternatively be carried out, in any case one of these steps is carried out. Step (d) is carried out in particular if step (c) has been carried out over a short period of time, for example 0.25 to 5 hours. If step (c) is carried out over a longer period of time, for example 20 to 100 h, step (d) can be omitted.

In step (e), flushing is carried out with inert gas such as nitrogen or argon or water vapor, preferably over a period of 1 min to 1 h. This is followed in step (f) by the known activation of the catalyst with hydrogen. It can be carried out with pure hydrogen or with a hydrogen-containing gas which can contain an inert gas and / or water vapor, for example in amounts of 10 to 90% by volume. The activation is preferably carried out at normal pressure over a period of 10 minutes to 2 hours.

In all steps (a) to (f) the temperature is 300 to 800 ° C, preferably 400 to 700 ° C.

Any porous catalysts can be regenerated by the process according to the invention, preferably porous catalysts which contain noble metals on an oxidic support. Examples are the catalyst used in the Linde Statoil process, which contains Pt and Sn on an MgO / Al ₂ O _{3 support} , the catalyst used in the STAR process, the Pt on a Zn / Al or Mg / Al spinel contains, or the catalyst used in the UOP-Oleflex process, which contains Pt on theta-Al ₂ O ₃ .

The dehydrogenation catalysts which can be regenerated according to the invention generally have a support and an active composition. The carrier consists of a heat-resistant oxide or mixed oxide. The dehydrogenation catalyst preferably contains a metal oxide, which is selected from the group consisting of zirconium dioxide, zinc oxide, aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide, lanthanum oxide, cerium oxide and mixtures thereof, as a carrier. Preferred supports are zirconium dioxide and / or silicon dioxide, and mixtures of zirconium dioxide and silicon dioxide are particularly preferred.

The active composition of the dehydrogenation catalyst which can be regenerated according to the invention generally contains one or more elements of subgroup VIII, preferably platinum and / or palladium, particularly preferably platinum. In addition, the dehydrogenation catalyst can have one or more elements of the 1st and / or 2nd main group, preferably potassium and / or cesium. Furthermore, the dehydrogenation catalyst can include one or more elements of III. Subgroup including the lanthanides and actinides contain, preferably lanthanum and / or cerium. Finally, the dehydrogenation catalyst can include one or more elements of III. and / or IV. Main group, preferably one or more elements from the group consisting of boron, gallium, silicon, germanium, tin and lead, particularly preferably tin.

The dehydrogenation catalyst which can be regenerated according to the invention preferably contains at least one element from subgroup VIII, at least one element from main group I and / or II, at least one element from III. and / or IV. main group and at least one element of III. Subgroup including the lanthanides and actinides.

The dehydrogenation catalysts which can be regenerated according to the invention can be produced as follows:

The dehydrogenation catalysts which can be regenerated according to the invention can be based on

Precursors for oxides of zirconium, silicon, aluminum, titanium, magnesium, lanthanum or cerium, which can be converted into the oxides by calcining, can be produced.

These can be done, for example, by the sol-gel process, precipitation of the salts, dewatering the corresponding acids, dry mixing, slurries or spray drying. For example, to produce a ZrO ₂ Al ₂ O ₃ SiO ₂ mixed oxide, a water-rich zirconium oxide of the general formula ZrO ₂ xH ₂ O can first be prepared by precipitation of a suitable precursor containing zirconium. Suitable zirconium precursors are, for example, Zr (NO ₃ ), ZrOCl ₂ , or ZrCl ₄ . The precipitation itself is carried out by adding a base such as NaOH, KOH, Na ₂ CO ₃ and NH ₃ and is described, for example, in EP-A 0 849 224.

To produce a ZrO ₂ SiO mixed oxide, the zirconium-containing precursor obtained beforehand can be mixed with a silicon-containing precursor. Well-suited precursors for SiO ₂ are, for example, water-containing brines of SiO ₂ such as Ludox ™. The two components can be mixed, for example, by simple mechanical mixing or by spray drying in a spray tower.

To produce a ZrO ₂ “SiO ₂ ” Al ₂ O ₃ mixed oxide, the SiO ₂ “ZrO ₂ powder mixture obtained as described above can be mixed with an aluminum-containing precursor. This can be done, for example, by simple mechanical mixing in a kneader. The ZrO ₂ “SiO” Al ₂ O ₃ mixed oxide can, however, also be produced in a single step by dry mixing the individual precursors.

A concentrated acid is added to the powder mixture obtained in the kneader and then into a shaped body, e.g. by means of an extruder or an extruder.

In special embodiments, the dehydrogenation catalysts which can be regenerated according to the invention have a defined pore structure. This is specifically influenced by the use of mixed oxides. For example, the use of Al ₂ O ₃ can produce macropores in the structure with a low loss on ignition and a defined grain size composition.

A further possibility for the targeted production of the supports with special pore radius distributions for the dehydrogenation catalysts which can be regenerated according to the invention is the addition of various polymers during production which are partially or completely removed by calcination, pores being formed in defined pore radius regions. The polymers and the oxide precursors can be mixed, for example, by simple mechanical mixing or by spray drying in a spray tower. Carriers with a bimodal pore madiene distribution can be produced using PVP (polyvinylpyrrolidone). If this is added to one or more oxide precursors for oxides of the elements Zr, Ti, Al or Si in one production step, macropores in the range from 200 to 5000 nm are formed after the calcination.

The calcination of the supports for the dehydrogenation catalysts which can be regenerated according to the invention is advantageously carried out after the application of the active components and is carried out at temperatures from 400 to 1000 ° C, preferably from 500 to 700 ° C, particularly preferably at 550 to 650 ° C and in particular at 560 to 620 ° C performed.

The supports of the dehydrogenation catalysts which can be regenerated according to the invention generally have high BET surface areas after the calcination. The BET surface areas are generally larger than 40 m ² / g, preferably larger than 50 m ² / g, particularly preferably larger than 70 m Ig. The pore volume of the dehydrogenation catalysts according to the invention is usually 0.2 to 0.6 ml / g, preferably 0.25 to 0.5 ml / g. The average pore diameter of the dehydrogenation catalysts that can be regenerated according to the invention, which can be determined by mercury porosimetry, is between 3 and 20 nm, preferably between 4 and 15 nm.

A bimodal pore madiene distribution is also characteristic of an embodiment of the dehydrogenation catalysts which can be regenerated according to the invention. The pores are in the range up to 20 nm and between 40 and 5000 nm. Based on the total pore volume of the dehydrogenation catalyst, these pores have a total of at least 70%. The proportion of pores smaller than 20 nm is generally between 20 and 60%, the proportion of pores between 40 and 5000 nm is also generally 20 to 60%.

The dehydrogenation-active component, which is usually a metal from subgroup VIII, is generally applied by impregnation with a suitable metal salt precursor. Instead of impregnation, the dehydrogenation-active component can also be carried out by other methods such as, for example, spraying on the metal salt precursor. Suitable metal salt precursors are, for example, the nitrates, acetates and chlorides of the corresponding metals; complex anions of the metals used are also possible. Platinum is preferably used as H ₂ PtCl ₆ or Pt (NO ₃ ) ₂ . As a solvent for the Metal salt precursors are suitable for water as well as organic solvents. Water and lower alcohols such as methanol and ethanol are particularly suitable.

Suitable precursors when noble metals are used as the dehydrogenation-active component are also the corresponding noble metal sols, which can be prepared by a known method, for example by reducing a metal salt in the presence of a stabilizer such as PVP with a reducing agent. The manufacturing technology is dealt with in detail in German patent application DE 195 00 366.

The content of a noble metal as a dehydrogenation-active component in the regenerable dehydrogenation catalysts according to the invention is 0 to 5% by weight, preferably 0.05 to 1% by weight, particularly preferably 0.05 to 0.5% by weight.

The further components of the active composition can be applied either during the preparation of the carrier, for example by co-precipitation, or subsequently, for example by impregnating the carrier with suitable precursor compounds. As precursor compounds, use is generally made of compounds which can be converted into the corresponding oxides by calcining. For example, hydroxides, carbonates, oxalates, acetates, chlorides or mixed hydroxycarbonates of the corresponding metals are suitable.

In further embodiments of the catalysts which can be regenerated according to the invention, the active composition contains the following further components:

at least one element from main group I or II, preferably cesium and / or potassium, with a content between 0 and 20% by weight, preferably between 0.1 and 15% by weight, particularly preferably between and 0.2 and 10% by weight;

- at least one element of III. Sub-group including the lanthanides and actinides, preferably lanthanum and / or cerium with a content between 0 and 20

% By weight, preferably between 0.1 and 15% by weight, particularly preferably between and 0.2 and 10% by weight;

- at least one element from III. and IV. main group, preferably tin with a content between 0 and 10 wt .-%. The dehydrogenation catalyst can be fixed in the reactor or used, for example, in the form of a fluidized bed and have a corresponding shape. Forms such as grit, tablets, monoliths, spheres or extrudates (strands, wagon wheels, stars, rings) are suitable, for example.

Paraffins, alkylaromatics, naphthenes or olefins with 2 to 30 C atoms can be used as dehydratable hydrocarbons. The process is particularly suitable for the dehydrogenation of straight or branched chain hydrocarbons with a chain length of 2 to 15 carbon atoms, preferably with 2 to 5 carbon atoms. Examples are ethane, propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tride-can, n-tetradecane, n-pentadecane. A particularly preferred hydrocarbon is propane. In the further description of the invention, this particularly preferred case of propane dehydrogenation is discussed in more detail, but the corresponding features apply analogously to other dehydratable hydrocarbons.

The catalysts which can be regenerated according to the invention are used in all customary reactor types.

The catalysts which can be regenerated according to the invention can be used in a fixed bed tube or tube bundle reactor. In these, the catalyst (dehydrogenation and possibly special oxidation catalyst) is located as a fixed bed in a reaction tube or in a bundle of reaction tubes.

The catalysts which can be regenerated according to the invention can be used in a moving bed reactor. For example, the moving catalyst bed can be accommodated in a radial flow reactor. In this the catalyst moves slowly from top to bottom while the reaction gas mixture flows radially. This procedure is used, for example, in the so-called UOP-Oleflex dehydrogenation process. The dehydrogenation catalyst used there is generally spherical.

The catalysts which can be regenerated according to the invention can also be used in a fluidized bed. Appropriately, two fluidized beds are operated side by side, one of which is usually in the state of regeneration. The catalysts which can be regenerated according to the invention can be used in a tray reactor. This contains one or more successive catalyst beds.

The number of catalyst beds can be 1 to 20, advantageously 2 to 8, in particular 4 to 6. The reaction beds preferably flow radially or axially through the catalyst beds. Such a tray reactor is generally operated with a fixed catalyst bed.

The invention is illustrated by the examples below.

Examples

example 1

catalyst preparation

5000 g of a strand-like ZrO ₂ -SiO ₂ mixed oxide from Norton (diameter of the strands 3 mm, length of the strands 3 mm) are mixed with a solution of 59.96 g SnCl ₂ -2H ₂ O and 39.45 g H ₂ PtCl Pour ₆ -6H ₂ O into 1600 ml of ethanol.

The composition is rotated at room temperature for 2 hours, then dried at 100 ° C. for 15 hours and calcined at 560 ° C. for 3 hours. The catalyst is then poured with a solution of 38.4 g of CsNO ₃ , 67.7 g of KNO ₃ and 491.65 g of La (NO ₃ ) ₃ in 1600 ml of H ₂ O. The catalyst is rotated at room temperature for 2 hours, then dried at 100 ° C. for 15 hours and calcined at 560 ° C. for 3 hours.

The catalyst has a BET surface area of 84 m ² / g. Mercury porosimetry measurements show a pore volume of 0.26 ml / g, a pore area of 71 m ² / g and an average pore radius of 11.2 nm. 70% of the pore volume is accounted for by pores with a diameter of at most 20 nm, approximately 20% of the pore volume is accounted for by pores with a diameter of 40 to 100 nm and about 30% of the pore volume is accounted for by pores with a diameter of more than 40 and less than 5000 nm. Example 2

Regeneration of the catalyst

1000 ml of the catalyst prepared according to Example 1 are diluted with 500 ml of steatite and installed in a tubular reactor with an inner diameter of 40 mm. The catalyst is mixed in succession for 30 minutes at 500 ° C. first with hydrogen, then with lean air (80% nitrogen and 20% air) and then again with hydrogen. The processes are always separated from each other by a 15 minute flush with nitrogen. Subsequently, the catalyst at 625 ° C with 500 NL / h of propane (99.5%) and water vapor in the molar ratio propane / HO of 1: 1. The pressure is 1.5 bar, the catalyst load (GHSV) is 1000 h ^"1. The reaction products are recorded by gas chromatography. After two hours of reaction, 47% of the propane used is converted to propene with a selectivity of 95%. After a reaction time of 12 hours the conversion is 39%) and the selectivity is 95%. The propane supply is switched off and the reactor is flushed with nitrogen and steam (GHSV 2000h ^"1 ). Then at a pressure of 4 bar lean air (98% nitrogen and 2% air) at 500 ° C is passed over the catalyst. The air content is then increased three times (first 96% nitrogen and 4% air, then 92% nitrogen and 8% air, then 83% nitrogen and 17% air). The load is always 2000 h ^"1. Then pure air (GHSV 500 h ^{" 1} ) is passed over the catalyst until the CO ₂ discharge is less than 0.04% by volume. By quickly reducing and rebuilding the reactor pressure three times (4 bar - 1 bar - 4 bar), residual adsorbed CO _{2 is} desorbed from the catalyst. Then, after the reactor has been flushed with nitrogen for 15 minutes, hydrogen is passed over the catalyst for 30 minutes. Propane is again added as a feed. After a dehydration time of 2 hours at 625 ° C, 48% propane conversion with 95% selectivity are achieved. After a dehydration time of 12 h, the conversion is 39% and the selectivity is 95%. Repeating the same regeneration and dehydrogenation sequence leads to 47% propane conversion at 625 ° C. with a propene selectivity of 95% after 2 hours. After a dehydration time of 12 h, the conversion is 39% and the selectivity is 95%. Nergleichsbeispiel

Regeneration of the catalyst

1000 ml of the catalyst prepared according to Example 1 are diluted with 500 ml of steatite and installed in a tubular reactor with an inner diameter of 40 mm. The catalyst is mixed in succession for 30 minutes at 500 ° C. first with hydrogen, then with lean air (80% nitrogen and 20% air) and then again with hydrogen. The processes are always separated from each other by a 15 minute flush with nitrogen. Then the catalyst at 605 ° C with 500 ΝL / h propane (99.5%) and water vapor in the molar ratio propane / H ₂ O of 1: 1 is applied. The pressure is 1.5 bar, the catalyst load (GHSV) is 1000 h ^"1. The reaction products are recorded by gas chromatography. After two hours of dehydrogenation, 45% of the propane used is converted to propene with a selectivity of 96%. After a dehydrogenation time of 12 h the conversion is 35% and the selectivity is 96%. The propane feed and the water feed are switched off and the reactor is flushed with nitrogen (GHSV: 250 h ^"1 ). Lean air (92% nitrogen and 8% air) is then passed over the catalyst at 400 ° C and 1.5 bar (GHSV 250 h ^"1 ). The air content is then increased twice (first 83% nitrogen and 17% air, then 64% nitrogen and 36% »air), then pure air (GHSV 250 h ^{" 1} ) is passed over the catalyst for 3 hours. After the reactor has been flushed with nitrogen for 15 minutes, hydrogen is passed over the catalyst for 30 minutes. Propane and water vapor are added again as feed. After a dehydration time of two hours at 605 ° C., 38% propane conversion with 96% selectivity is achieved. After a dehydration time of 12 h, the conversion is 33% and the selectivity is 96%.

Claims

claims 1. Method for regenerating a dehydrogenation catalyst with steps (a) to (f): (a) purging with inert gas at a pressure of 0.5 to 2.0 bar and a gas load of 1000 to 50,000 h ^"1 ; (b) Passing through an oxygen-containing gas mixture containing an inert gas at a pressure of 2 to 20 bar and a gas load of 1000 to 50,000 h ^"1 over a period of 0.25 to 24 h with a gradual or continuous increase in the oxygen concentration from an initial value of 0.01 to 1% by volume of O to a final value of 10 to 25 % By volume O ₂ ; (c) optionally passing an oxygen-containing gas mixture containing an inert gas at a pressure of 0.5 to 20 bar and a gas load of 10 to 500 h ^"1 over a period of 0.25 to 100 h, the Oxygen concentration is 10 to 25 vol.% O ₂ ; (d) optionally repeated rapid opposite pressure changes by a factor of 2 to 20 within the range of 0.5 to 20 bar; (e) purging with an inert gas; (f) activation of the catalyst with hydrogen; wherein at least one of steps (c) or (d) is carried out and the whole Regeneration process is carried out at a temperature of 300 to 800 ° C. 2. The method of claim 1 with one or more of the following features: - step (a) is carried out over a period of 0.1 to 24 h; in step (a) the purge is continued until the purge gas contains essentially no traces of the dehydrogenation product and hydrogen; in step (a) the gas load is 2000 to 20,000 h ^"1 ; in step (a) the pressure is 1 to 1.5 bar; - in step (b) diluted air is used as the oxygen-containing gas mixture; in step (b) contains the oxygen-containing gas mixture 10 to 90 vol .-% Steam; in step (b) the pressure is 3 to 7 bar; - In step (c) air is used as the oxygen-containing gas mixture, which may optionally contain water vapor; in step (c) the gas load is 20 to 100 h ^"1 ; in step (d) the pressure is changed 2 to 20 times by a factor 2 to 5 within the range of 1 to 5 bar; - step (c) is over a period of 0.25 to 5 h and Step (d) is carried out; Step (c) is carried out over a period of 20 to 100 h and Step (d) is not carried out. 3. The method according to claim 1 or 2, characterized in that the dehydrogenation catalyst to be regenerated is a porous catalyst. 4. The method according to claim 3, characterized in that the dehydrogenation catalyst is a metal oxide selected from the group consisting of zirconium dioxide, aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide, Contains lanthanum oxide and cerium oxide. 5. The method according to claim 4, characterized in that the dehydrogenation catalyst contains zirconium dioxide and / or silicon dioxide. 6. The method according to any one of claims 3 to 5, characterized in that the dehydrogenation catalyst at least one element from subgroup VIII, at least one element from main group I or II, at least one element from III. or IV. main group and at least one element of III. Subgroup, including the lanthanides and actinides, contains. 7. The method according to any one of claims 3 to 6, characterized in that the dehydrogenation catalyst contains platinum and / or palladium. 8. The method according to any one of claims 3 to 7, characterized in that the dehydrogenation catalyst contains cesium and or potassium. 9. The method according to any one of claims 3 to 8, characterized in that the dehydrogenation catalyst contains lanthanum and / or cerium. 10. The method according to any one of claims 3 to 9, characterized in that the dehydrogenation catalyst contains tin. 11. The method according to any one of claims 3 to 10, characterized in that the dehydrogenation catalyst has a bimodal pore radius distribution, 70% to 100% of the pore volume being attributed to pores with a pore diameter of less than 20 nm or between 40 and 5000 nm.