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  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/61—Surface area
  • B01J35/613—10-100 m2/g
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/03—Precipitation; Co-precipitation
  • B01J37/036—Precipitation; Co-precipitation to form a gel or a cogel
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
  • B01J37/349—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of flames, plasmas or lasers
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  • B01J38/00—Regeneration or reactivation of catalysts, in general
  • B01J38/04—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst
  • B01J38/10—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst using elemental hydrogen
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  • B01J38/00—Regeneration or reactivation of catalysts, in general
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  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
  • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
  • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates
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  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/32—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with formation of free hydrogen
  • C07C5/327—Formation of non-aromatic carbon-to-carbon double bonds only
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  • C07C2521/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
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  • C07C2523/04—Alkali metals
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  • C07C2523/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals of the platinum group metals
  • C07C2523/42—Platinum
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  • C07C2523/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals combined with metals, oxides or hydroxides provided for in groups C07C2523/02 - C07C2523/36
  • C07C2523/56—Platinum group metals
  • C07C2523/62—Platinum group metals with gallium, indium, thallium, germanium, tin or lead
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/584—Recycling of catalysts

Definitions

• the invention relates to oxidic catalyst supports and catalyst particles prepared therefrom, to a process for their preparation and to the use of the catalyst particles as dehydrogenation catalyst.
• DE-A 196 54 391 describes the preparation of a dehydrogenation catalyst by impregnation of essentially monoclinic ZrO 2 with a solution of Pt (NO 3 ) 2 and Sn (OAc) 2 or by impregnation of ZrO 2 with a first solution of Pt (NO 3 ) 2 and then a second solution of La (NO 3 ) 3 .
• the impregnated carriers are dried and then calcined.
• the catalysts thus obtained are used as dehydrogenation catalysts, for example for the dehydrogenation of propane to propene.
• the preparation of the catalyst support is usually carried out by the sol-gel method, precipitation of the salts, dewatering of the corresponding acids, dry mixing, slurrying or spray drying.
• a ZrO AI 2 0 3 "Si0 2 mixed oxide can first a water-rich zirconia of the general formula ZrO xH 2 0 containing by precipitation of a suitable zirconium precursor be prepared. Suitable precursors of the zirconium are, for example, Zr (NO 3 ) 4 , ZrOCl 2 , or ZrCl 4 .
• the precipitation itself is carried out by adding a base such as NaOH, KOH, Na 2 C0 3 and NH 3 and is described for example in EP-A 0 849 224.
• the zirconium-containing precursor can be mixed with a precursor containing silicon.
• a precursor containing silicon for example, hydrous sols of Si0 2 such as Ludox TM.
• the mixture of the two components can be carried out, for example, by simple mechanical mixing or by spray-drying in a spray tower.
• a known process for the preparation of metal catalysts by flame spray pyrolysis is described in Pisduangnawakij et al., Applied Catalysis A: General 370 1-6, 2009.
• a solution containing precursor compounds of platinum and tin and of alumina as a carrier in xylene is converted into an aerosol, this treated in an inert carrier gas in a pyrolysis reactor at a temperature above the decomposition temperature of the precursor compounds and then separated the finely divided metal formed from the carrier gas ,
• the object of the present invention is to provide a cost-effective and time-saving process for the preparation of oxidic supports for dehydrogenation catalysts, wherein the resulting dehydrogenation catalysts should be comparable in activity and selectivity with the prior art catalysts prepared exclusively by impregnation or spray drying.
• the object is achieved by a method for producing catalyst carrier particles containing zirconium dioxide and optionally silicon oxide, comprising the steps
• the oxide-forming precursor compounds are fed to the pyrolysis zone as an aerosol. It is expedient to supply to the pyrolysis zone an aerosol which has been obtained by nebulization of only one solution which contains all oxide-forming precursor compounds. In this way, it is ensured in each case that the composition of the particles produced is homogeneous and constant.
• the individual components are therefore preferably selected so that the oxide-forming precursors present in the solution are present in homogeneously dissolved state until the solution has been atomized.
• the solution or solutions may contain both polar and non-polar solvents or solvent mixtures.
• the temperature in the pyrolysis zone is at a sufficient temperature for oxide formation, usually in the range between 500 and 2000 ° C.
• the pyrolysis is carried out at a temperature of 900 to 1500 ° C.
• the pyrolysis reactor can be indirectly heated from the outside, for example by means of an electric furnace. Because of the temperature gradient from outside to inside required for indirect heating, the furnace must be much hotter than the temperature required for pyrolysis. Indirect heating requires a temperature-stable furnace material and a complex reactor design, the required total amount of gas is, on the other hand, lower than in the case of a flame reactor.
• the pyrolysis zone is heated by a flame (flame spray pyrolysis).
• the pyrolysis zone then comprises an ignition device.
• conventional fuel gases can be used, but preferably hydrogen, methane or ethylene are used.
• the temperature can be adjusted in the pyrolysis zone targeted.
• the pyrolysis zone instead of air as a source of 0 2 for the combustion of the fuel gas and pure oxygen can be supplied.
• the total amount of gas also includes the carrier gas for the aerosol and the vaporized solvent of the aerosol.
• the one or more of the pyrolysis zone supplied aerosols are conveniently passed directly into the flame. While air is usually preferred as the carrier gas for the aerosol, it is also possible to use nitrogen, CO 2 , O 2 or a fuel gas, for example hydrogen, methane, ethylene, propane or butane.
• the pyrolysis zone is heated by an electrical plasma or an inductive plasma.
• a flame spray pyrolysis device generally comprises a reservoir for the liquid to be atomized, feed lines for carrier gas, fuel gas and oxygen-containing gas, a central aerosol nozzle and an annular burner arranged around it, a device for gas-solid separation comprising a filter element and a removal device for the solid and an outlet for the exhaust gas.
• the cooling of the particles is carried out by means of a quenching gas, e.g. Nitrogen or air.
• the combustion chamber which is preferably tubular, is thermally insulated.
• a pyrolysis gas containing spherical particles of varying specific surface area is obtained.
• the size distribution of the particles obtained gives inter alia from the droplet size spectrum of the aerosol supplied to the pyrolysis zone and the concentration of the solution or solutions used.
• the pyrolysis gas is cooled sufficiently before deposition of the particles formed from the pyrolysis gas, so that sintering of the particles is excluded.
• the pyrolysis zone preferably comprises a cooling zone which adjoins the combustion chamber of the pyrolysis reactor.
• a cooling of the pyrolysis gas and the catalyst particles contained therein to a temperature of about 100 - 500 ° C is required, depending on the filter element used.
• a cooling to about 100 - 150 ° C instead.
• the pyrolysis gas containing the catalyst particles and partially cooled, after leaving the pyrolysis zone, enters an apparatus for separating the particles from the pyrolysis gas, which comprises a filter element.
• a quenching gas for example nitrogen, air or a water humidified gas is introduced.
• Suitable zirconia-forming precursor compounds are alcoholates, such as zirconium (IV) ethanolate, zirconium (IV) n-propoxide, zirconium (IV) isopropoxide, zirconium (IV) n-butoxide and zirconium (IV) -tert butoxide.
• zirconium (IV) propoxide which is preferably in the form of a solution in n-propanol, is used as the ZrO 2 precursor compound.
• Suitable zirconia-forming precursor compounds are also carboxylates such as zirconium acetate, zirconium propionate, zirconium oxalate, zirconium octoate, zirconium 2-ethylhexanoate, zirconium acetate, zirconium propionate, zirconium oxalate, zirconium octanoate, zirconium 2-ethylhexanoate, zirconium neodecanoate, zirconium stearate and zirconium propionate.
• zirconium (IV) acetylacetonate is used as precursor compound.
• the precursor compounds additionally comprise a silica precursor compound.
• Suitable precursors for silicon dioxide are organosilanes and reaction products of SiCl 4 with lower alcohols or lower carboxylic acids. It is also possible to use condensates of the stated organosilanes or silanols with Si-O-Si members. Preference is given to using siloxanes. The use of Si0 2 is also possible.
• the precursor compounds comprise, as the precursor compound which forms the silica, hexamethyldisiloxane. To prepare the solution or solutions required for aerosol formation, it is possible to use both polar and apolar solvents or solvent mixtures.
• Preferred polar solvents are water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, n-propanone, n-butanone, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, CrC 8 -Carboxylic acids, ethyl acetate and mixtures thereof.
• one or more precursor compounds are dissolved in a mixture of acetic acid, ethanol and water.
• this mixture contains 30 to 75 wt .-% acetic acid, 30 to 75 wt .-% ethanol and 0 to 20 wt .-% water.
• zirconium (IV) acetylacetonate, hexamethyldisiloxane are dissolved in a mixture of acetic acid, ethanol and water.
• Preferred apolar solvents are toluene, xylene, n-heptane, n-pentane, octane, isooctane, cyclohexane, methyl, ethyl or butyl acetate or mixtures thereof. Hydrocarbons or mixtures of hydrocarbons with 5 to 15 carbon atoms are also suitable. Especially preferred is xylene.
• Zr (IV) -ethylhexanoate and hexamethyldisiloxane are dissolved in xylene.
• the catalyst carrier particles obtained by spray pyrolysis preferably have a specific surface area of 36 to 70 m 2 / g.
• the resulting catalyst support particles are then impregnated with one or more solutions containing compounds of platinum, tin and at least one other element selected from lanthanum and cesium.
• the impregnated catalyst support particles are dried and calcined.
• the invention thus also provides a process for the preparation of catalyst particles comprising platinum and tin and at least one further element selected from lanthanum and cesium on a zirconium dioxide-containing support, the process comprising steps (i) to (v) and additionally the steps
• precursor compounds are usually used compounds which can be converted by calcination in the corresponding oxides. Suitable examples are hydroxides, carbonates, oxalates, acetates, chlorides or mixed hydroxycarbonates of the corresponding metals.
• the application of the dehydrogenating component is usually carried out by impregnation. Instead of impregnation, however, the dehydrogenating component can also be carried out by other methods, such as, for example, spraying on the metal salt precursor.
• Platinum is preferably used as H 2 PtCl 6 or Pt (NO 3 ) 2 .
• Suitable solvents are water as well as organic solvents. Particularly suitable are water and lower alcohols such as methanol and ethanol.
• Suitable precursors in the use of noble metals as the dehydrogenating component are also the corresponding noble metal sols, which can be prepared by one of the known methods, for example by reduction of a metal salt in the presence of a stabilizer such as PVP with a reducing agent.
• a stabilizer such as PVP with a reducing agent.
• the manufacturing technique is discussed in detail in the German patent application DE 195 00 366.
• the content of platinum in the catalyst as the dehydrogenating component is from 0.01 to 5% by weight, preferably from 0.05 to 1% by weight, particularly preferably from 0.05 to 0.5% by weight.
• the catalyst contains at least tin in amounts of 0.01 to 10 wt .-%, preferably 0.05 to 2 wt .-%.
• Suitable tin compounds are carboxylates such as tin (II) acetate, tin 2-ethylhexanoate or tin (II) chloride.
• the loading with Pt is 0.05 to 1 wt .-% and the loading with Sn 0.05 to 2 wt .-%.
• the active composition may contain the following further components, wherein at least cesium or lanthanum are contained:
• Cesium and optionally potassium with a content between 0.1 and 10% by weight are included in cesium or Kalimoxidprecursoren using compounds that are can be converted by calcination in the oxides, for example, the hydroxides, carbonates, oxalates, acetates or formates.
• the precursor salts suitable are, for example, lanthanum oxide carbonate, La (OH) 3 , La 2 (CO 3 ) 3, La (NO 3 ) 3, lanthanum formate, lanthanum acetate and lanthanum oxalate.
• the calcination takes place at temperatures of 400 to 1000 ° C, preferably from 500 to 700 ° C, more preferably at 550 to 650 ° C.
• the present invention also provides the carrier and catalyst particles obtainable by the process according to the invention. These preferably have a specific surface area of 20 to 70 m 2 / g.
• the catalyst supports have the following percentage composition: 30 to 99.5% by weight Zr0 2 , 0.5 to 25% by weight Si0 2 .
• the catalyst particles further contain 0.1 to 1 wt .-% Pt, 0.1 to 10 wt .-% Sn, La and / or Cs, based on the mass of the carrier, wherein at least Sn and at least La or Cs are included.
• the present invention also relates to the use of the catalyst particles as hydrogenation catalysts or dehydrogenation catalysts.
• Alkanes such as butane and propane, but also ethylbenzene are preferably dehydrated.
• catalysts of the invention for the dehydrogenation of propane to propene.
• HMDSO Hexamethyldisiloxane
• the solvent is HoAc: EtOH: H 2 O in the mass ratio 4.6 to 4.6 to 1.
• the acetic acid-ethanol mixture is freshly prepared. This dissolves the precursor compounds for Si and Zr. Alternatively, xylene is used.
• Table 1 Compositions of solutions of precursor compounds for apolar
• the solution containing the precursor compounds was fed by means of a piston pump via a two-fluid nozzle and sprayed with an appropriate amount of air.
• a support flame was partially used from an ethylene-air mixture, which was metered via a ring burner located around the nozzle.
• the pressure drop was kept constant at 1, 1 bar.
• Table 2 summarizes the flame synthesis conditions.
• Xylene 1 310 3500 1200 A baghouse filter was used to separate the particles. To clean these filters, the filter bags were subjected to 5 bar pressure surges of nitrogen.
• the impregnation was carried out according to Example 4 of EP 1 074 301.
• the flame-synthesized Si0 2 / Zr0 2 support of the 1 to 2 mm sieve fraction was poured over a solution of SnCl 2 and H 2 PtCl 6 in ethanol.
• the excess solution was removed on a rotary evaporator, the solid dried and calcined.
• An aqueous solution of CsN0 3 and La (NO 3 ) 3 was added thereto and the supernatant was removed.
• the catalyst was obtained after drying and calcining with a BET surface area of 23 m 2 .
• the reference catalyst according to EP 1 074 301 consists of 95% by weight Zr0 2 , 5% by weight Si0 2 (carrier), 0.5% by weight Pt, 1% by weight Sn, 3% La, 0, 5 wt .-% Cs and 0.2 wt .-% K (active and promoter metals based on the mass of the carrier) prepared according to Example 4 by wet-chemical means.
• the support was prepared by spray-drying the oxide mixture obtained by precipitation by the sol / gel process.
• the propane dehydrogenation was carried out at about 600 ° C. 21 Nl / h of total gas (20 Nl / h of propane, 1 Nl / h of nitrogen as internal standard), 5 g / h of water.
• the regeneration is carried out at 400 ° C: 2 hours 21 Nl / h N 2 + 4 Nl / h air; 2 hours 25 Nl / h air; 1 hour 25 Nl / h of hydrogen.
• FIG. 1 shows for comparison the activities and selectivities of the reference catalyst (-) with support prepared by precipitation and spray-drying and the catalyst according to the invention whose support originates from the flame synthesis ( ⁇ ), the other elements being applied in each case by impregnation.
• the results for a flame-only synthesized catalyst of the same composition (A) are also shown.
• the abscissa shows the time in hours the ordinate shows conversions (40 to 50%) and selectivities (> 80%) for the autothermal dehydrogenation of propane to propene.
• the reference catalyst has lower initial selectivities. However, it is similar to the test cycles of a few weeks.
• the flame-synthesized catalyst and the flame-synthesized carrier after wet-chemical application of the other elements behave like an aged catalyst whose carrier was prepared by spray-drying.

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• 2012
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