JP2014511258A - Catalyst for self-heating propane dehydrogenation, obtained by spray flame synthesis - Google Patents

Abstract

A process for producing catalyst particles comprising platinum, tin, and one or more other elements selected from lanthanum and cesium on a support comprising zirconium dioxide and optionally silicon oxide,
(I) preparing a precursor compound of platinum, tin, and one or more other elements selected from lanthanum and cesium, and a precursor compound of zirconium dioxide;
(Ii) converting the solution into an aerosol;
(Iii) supplying the aerosol to a directly or indirectly heated pyrolysis zone;
(Iv) performing pyrolysis, and (v) separating particles produced from the pyrolysis gas,
Manufacturing method.

Description

  The present invention relates to a catalyst particle, a production method thereof, and a method of using the catalyst particle as a dehydrogenation catalyst.

  It is known to produce dehydrogenation catalysts by impregnation or spray drying. In these methods, a catalytically active metal is applied on an oxide support or silicate support by an impregnation method, or the catalyst is produced by spray drying a coprecipitated oxide precursor.

Patent Document 1 (DE-A196 54 391) describes that a substantially monoclinic ZrO ₂ is impregnated with a solution of Pt (NO ₃ ) ₂ and Sn (OAc) ₂ , or the first in ZrO ₂ A method for producing a dehydrogenation catalyst by impregnating a solution of Pt (NO ₃ ) ₂ and then impregnating a _second solution of La (NO ₃ ) ₃ is described. The impregnated support is dried and then calcined. The catalyst thus obtained is used as a dehydrogenation catalyst for dehydrogenating propane to propene.

  A known method for producing metal catalysts by spray flame pyrolysis is described in “Applied Catalysis A: General 370 1-6, 2009” by Pisduangnawakij et al. In this document, a solution containing a precursor compound of platinum and tin and a precursor compound of aluminum oxide as a carrier in xylene is converted into an aerosol, which is decomposed in a pyrolysis reactor. The treatment is performed in an inert carrier gas at a temperature higher than the temperature, and then the generated metal fine particles are separated from the carrier gas.

  Known synthesis methods of noble metal powder catalysts by wet chemical formulations are time consuming and expensive.

  Therefore, the process for producing the dehydrogenation catalyst still needs to be improved in terms of time and cost.

DE-A 196 54 391

Applied Catalysis A: General 370 1-6, 2009

  The problem to be solved by the present invention is to provide a method for producing a dehydrogenation catalyst with reduced cost and time. Here, the obtained dehydrogenation catalyst should be equivalent in terms of activity and selectivity compared to conventional catalysts by impregnation or spray drying.

The above problem is a method for producing catalyst particles comprising platinum, tin, and one or more other elements selected from lanthanum and cesium on a support containing zirconium dioxide,
(I) preparing a solution containing a precursor containing platinum, tin, and one or more other elements selected from lanthanum and cesium, and a precursor compound of zirconium dioxide;
(Ii) converting the solution into an aerosol;
(Iii) supplying the aerosol to a directly or indirectly heated pyrolysis zone;
(Iv) performing pyrolysis, and (v) separating particles produced from the pyrolysis gas,
This is solved by a manufacturing method including:

  The metal compound and the precursor compound that generates an oxide are supplied to the thermal decomposition region as an aerosol. The aerosol supplied to the pyrolysis zone is preferably obtained by spraying a single solution containing all metal compounds and precursor compounds that form oxides. In this way, the composition of the generated particles is always uniform and constant. In preparing the solution to be converted to an aerosol, the individual components are uniformly dissolved alongside each other until the precursors and noble metal compounds that form the oxides contained in the solution reach spraying of the solution. Selected as Moreover, you may make it use several types of solutions as what contains the precursor which produces | generates an oxide, and on the other hand, what contains an active or promoting metal compound. The solution may be a polar solvent and a nonpolar solvent, or a mixture thereof.

  In the thermal decomposition region, the decomposition of the noble metal compound into the noble metal and the decomposition and / or oxidation of the oxide precursor are performed while forming an oxide. In addition, some noble metals are vaporized and then re-deposited in the cooling region on the already produced carrier particles. Thermal decomposition generally results in a change in the specific surface area of the spherical particles.

  The temperature in the pyrolysis region is usually sufficient to produce an oxide between 500-2000 ° C. and exceeds the decomposition temperature of the noble metal compound.

  The pyrolysis reactor may be indirectly heated from the outside using, for example, an electric furnace. Due to the external to internal temperature gradient required in indirect heating, the furnace should be much hotter than the temperature required for pyrolysis. Indirect heating requires a thermally stable furnace material and expensive reactor configuration, but the total amount of gas required is smaller than in a flame furnace.

In a preferred embodiment, the pyrolysis zone is heated by a flame (flame spray pyrolysis). The pyrolysis region includes an ignition device. Hydrogen, methane and ethylene are preferably used, but ordinary flammable gases are used for direct heating. The ratio of the amount of combustible gas to the total amount of gas can be adjusted, and the temperature of the pyrolysis region can be adjusted as necessary. In order to achieve as high a temperature as possible while keeping the total amount of gas low, pure water oxygen can be supplied to the pyrolysis region instead of air as a combustion O ₂ source of combustible gas. Also. The total amount of gas includes a carrier gas for aerosol and a solvent component evaporated from the aerosol. The aerosol supplied to the pyrolysis zone is preferably supplied directly to the flame. Generally the air is preferred as a carrier gas for the aerosol, nitrogen, CO 2, _{O 2,} or hydrogen, methane, ethylene, it is also possible to use a combustible gas propane or butane.

  In another embodiment of the method according to the invention, the pyrolysis zone is heated by discharge plasma or induction plasma. In this embodiment, the catalytically active noble metal particles are applied to the surface of the carrier particles and firmly fixed thereto.

  A flame spray pyrolysis apparatus generally includes a storage container for the liquid to be sprayed, a supply tube for carrier gas, combustible gas, and oxygen-containing gas, a central aerosol nozzle, and an annular burner disposed around it, and A gas phase solid phase separator having a filter element, a solid discharge device, and an outlet for exhaust gas is included. The particles are cooled using a quench gas such as nitrogen or air.

  The pyrolysis zone preferably has so-called pre-drying means for pre-drying the aerosol before it is introduced into the pyrolysis reactor. The pre-drying means is, for example, a heat flow tube that is arranged around the thermal decomposition region.

  If pre-drying is not performed, there is a risk of producing a product with a relatively broad particle size distribution, but it is more preferred that the particles are excessively fine. The temperature of the predrying depends on the nature of the dissolved precursor and its content. The temperature of the preliminary drying is usually higher than the boiling point of the solvent and is 250 ° C. or lower. When water is used as the solvent, the temperature in the preliminary drying is preferably 120 to 250 ° C, more preferably 150 to 200 ° C. The pre-dried aerosol is fed to the pyrolysis reactor via a line and then introduced into the reactor via an outlet nozzle.

  In order to adjust the temperature state, the combustion space (preferably tubular) is insulated.

  A pyrolysis gas is obtained as a pyrolysis product. The pyrolysis gas includes spherical particles having a specific surface area that changes. The size distribution of the resulting pigment particles is substantially directly derived from the aerosol droplet distribution supplied to the pyrolysis zone and the concentration of the solution used.

  Prior to separating the particles from the pyrolysis gas, the pyrolysis gas is cooled to prevent the particles from being sintered together. Therefore, the pyrolysis region preferably has a cooling region adjacent to the combustion space of the pyrolysis reactor. Depending on the filter element used, it is generally required to cool the pyrolysis gas and catalyst particles contained therein to a temperature of 100-500 ° C. It is preferred to cool to about 100-150 ° C. After the pyrolysis gas exits the pyrolysis zone, a pyrolysis gas containing catalyst particles and partially cooled is introduced into an apparatus (having a filter element) for separating the particles from the pyrolysis gas. For cooling, the quench gas is supplied with, for example, nitrogen, air or air containing water.

Suitable precursor compounds of zirconium dioxide include alcoholates such as zirconium (IV) ethanolate, zirconium (IV) n-propanolate, zirconium (IV) isopropanolate, zirconium (IV) n-butanolate, and zirconium (IV). tert-Butanolate. In a preferred embodiment in the process of the invention, zirconium (IV) methanolate, preferably as a solution in n-propanol, is used as the ZrO ₂ precursor compound.

  Other suitable zirconium dioxide precursor compounds are carboxylates such as zirconium acetate, zirconium propionate, zirconium oxalate, zirconium octoate, zirconium 2-ethylhexanoate, zirconium acetate, zirconium 2-ethylhexanoate, And neodecanoate zirconium stearate.

In one embodiment, the precursor compound further comprises a silicon dioxide precursor compound. A possible precursor of silicon dioxide is the reaction product of SiCl ₄ with an organosilane and a lower alcohol or carboxylic acid. Moreover, it is also possible to use the condensate of the silanol which has the said organosilane and / or Si-O-Si unit. Siloxane is preferably used. Furthermore, it is possible to use SiO ₂ . In a preferred embodiment of the method of the present invention, the precursor compound comprises hexamethyldisiloxane as a precursor compound that produces silica.

  As a support, in addition to zirconium dioxide and optionally present silicon dioxide, the catalyst particles according to the invention contain one or more other elements selected from platinum, tin and lanthanum and cesium.

  In one preferable embodiment of the present invention, the amount of Pt is 0.05 to 1% by mass, and the amount of Sn is 0.05 to 2% by mass.

  Preferred precursor compounds for lanthanum and cesium are carboxylate and nitrate, respectively, corresponding to the above-mentioned carboxylates associated with, for example, zirconium. In one preferred embodiment of the method according to the invention, the precursor compound comprises lanthanum (III) 2-acetylacetonate and / or cesium acetate.

  Furthermore, in a preferred embodiment of the process according to the invention, the precursor compound comprises lanthanum (III) 2-ethylhexanoate.

  Preferred precursor compounds for tin are, for example, carboxylates and nitrates corresponding to the above-mentioned carboxylates related to zirconium. In a further preferred embodiment of the method according to the invention, the precursor compound comprises tin 2-ethylhexanoate.

  Preferred compounds for the precursor for platinum are carboxylates and nitrates, for example carboxylates and nitrates corresponding to the above-mentioned carboxylates related to zirconium, and ammonium platinate. In a preferred embodiment of the method according to the invention, the precursor compound comprises platinum acetylacetonate.

  Both polar and non-polar solvent mixtures can be used to make the solution required for aerosol production.

Preferred polar solvents are water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, tert-butanol, n-propanone, n-butanone, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, C ₁ -C ₈ carboxylic acids, ethyl acetate, and mixtures thereof.

  In one preferred embodiment of the method according to the invention, one or more precursor compounds, preferably all precursor compounds, are dissolved in a mixture of acetic acid, ethanol and water. This mixture preferably comprises 30-75% by weight acetic acid, 30-75% by weight ethanol, and 0-20% by weight water. In particular, zirconium (IV) acetylacetonate platinum, hexamethyldisiloxane tin 2-ethylhexanoate, platinum acetylacetonate, lanthanum acetylacetonate (II), and cesium acetate are dissolved in a mixture of acetic acid, ethanol, and water. .

  Preferred nonpolar solvents are toluene, xylene, n-heptane, n-pentane, octane, isooctane, cyclohexane, methyl, ethyl or butyl acetate, or mixtures thereof. Also suitable are hydrocarbons having 5 to 15 carbon atoms or mixtures thereof. Xylene is particularly preferred.

  In particular, Zr (IV) propylate, 2-ethylhexanoic acid hexamethyldisiloxane tin, platinum acetylacetonate, and lanthanum acetylacetonate (III) are dissolved in xylene.

The present invention also relates to a support and catalyst particles obtained by the method according to the present invention. These preferably have a specific surface area of 20 to 70 m ² / g.

In a preferred embodiment, the catalyst particles have the following composition ratio: 30 to 99.5% by weight of ZrO ₂ and 0.5 to 25% by weight of SiO ₂ as support, and 0. It is 1-1 mass% Pt, 0.1-10 mass% Sn, La, and / or Cs. Note that at least Sn and at least La or Cs are included.

  Furthermore, the present invention relates to the use of catalyst particles as a hydrogenation catalyst or dehydrogenation catalyst. For example, alkanes such as butane and propane, and ethylbenzene are preferably dehydrogenated.

  It is particularly preferred to use the catalyst according to the invention for the dehydrogenation of propane to propene.

The invention is illustrated in more detail by the following examples.

Chemical substance used Zirconium acetylacetonate: Zr (acac) ₂ (98%)
Zirconium (IV) propoxide: Zr (OPr) ₄ (70% in 1-propanol)
Hexamethyldisiloxane (/ HMDSO) (98%)
Tin (II) 2-ethylhexanoate (about 95%)
Platinum (II) acetylacetonate (98%)
Lanthanum 2-ethylhexanoate (III) (10% w / v)
Lanthanum acetylacetonate (III) (99.99%)
Cesium acetate (99.99%)
Mixture of acetic acid (100%), ethanol (96%) and water (deionized) Xylene (BASF, isomer mixture)
The preparation solvent of the precursor compound solution is a mass ratio of HoAc: EtOH: / H ₂ O = 4.6: 4.6: 1. A fresh mixture of acetic acid ethanol was prepared. Precursor compounds for Sn, Cs, La, Si, Pt, and Zr were dissolved in this mixture.

  Table 1 shows the compositions of the polar solutions of the precursor compounds in Examples 1, 2, 3, 9 and 10.

Table 1: Composition of polar mixture precursor compound solution (EtO / H: / HoAc: / H ₂ O)

  In order to prepare a solution of the precursor compound of Example 4, the following materials were dissolved in xylene. The composition is shown in Table 2.

  Table 2: Composition of precursor compound solution of non-polar mixture (xylene)

  When preparing solutions of the precursor compounds of Examples 5, 6, and 8, an additional 2.14 g of cesium acetate was used as well.

(Examples 1 to 10)
Preparation of catalyst particles by flame spray pyrolysis A solution containing the precursor compound was fed through a two-component nozzle using a piston pump to atomize the corresponding amount of air. In order to reach the corresponding temperature, a support flame provided from an ethylene air mixture through an annular burner placed around the nozzle was used. The pressure drop was kept constant at 1.1 bar.

The flame synthesis conditions are shown in Table 3.
Table 3: Experimental parameters related to the production of flame spray pyrolysis catalysts

Solution without cesium precursor compound ** Only Si and Zr precursors exist
¹ GLMR = mass ratio of gas to liquid.

A baghouse filter was used for particle separation. These filters can be cleaned by applying 5 bar surge pressure of nitrogen to the filter bag. Particle characteristics were performed by X-ray diffraction (XRD) and BET measurements, and elemental analysis was performed as well. The crystallite size of the catalyst particles produced using the solutions of precursor compounds 3 and 4 is listed in Table 4.
Table 4: X-ray powder diffraction method for characterization of zirconia

Particles having a specific surface area of 36 to 70 m ² / g were produced by synthesis of a catalyst using the above-described solution containing the precursor compound under the above-described set conditions (see Table 5).

  In further experiments, BET surface area was investigated as a function of combustion chamber temperature. This study includes a comparison of solutions containing precursor compounds in terms of their solvents (acetic acid and xylene). In the case of the acetic acid mixture, no apparent tendency was observed.

  The xylene mixture shows an increase in BET specific surface area with increasing temperature, which achieves a shorter residence time and limits particle growth.

(Examples 11 to 17)
Catalyst Measurement Propane dehydrogenation was performed at about 600 ° C. (20 ml catalyst volume flow, see Table 5 for mass). : Total gas amount of 21 Nl / h (20 Nl / h propane, 1 Nl / h nitrogen as internal standard), 5 g / h water was used. The regeneration was carried out at 400 ° C. as follows: 21 Nl / h N ₂ +4 Nl / h air in 2 hours; 25 Nl / h air in 2 hours; 25 Nl / h hydrogen in 1 hour.
The reference catalyst support obtained by hydrothermal synthesis (ZrO ₂ ) using subsequent spray drying is composed of 95% ZrO ₂ and 5% SiO ₂ . The active / promoting metal is 0.5% Pt, 1% Sn, 3% La, 0.5% Cs, and 0.2% K, which is subjected to chemical wet impregnation according to EP1074301. (Example 4).

In the conversion, long-term stability and selectivity for propene production were investigated in the catalytic test. The results are shown in Table 5. Activity and selection are related to optimal operating conditions.
Table 5: Catalyst results obtained from flame synthesis catalyst particles during dehydrogenation of autothermal propane

  FIG. 1 shows the activity and selectivity of a flame synthesis catalyst (Δ Example 13, □ Example 17) and a reference catalyst (−) in the dehydrogenation of autothermal propane to propene. In the case of the catalyst (□), only the support was produced by thermal decomposition, and then chemical wet impregnation was performed on the support as a reference catalyst. Time was plotted on the horizontal axis in units of time (/ h) and conversion (40-50%) and selectivity (> 80%) were plotted on the vertical axis.

  Three catalysts were found to have considerable performance. The reference catalyst had a low initial selectivity. However, after several weeks of the test cycle, it became equivalent to the catalyst according to the present invention. Thus, the flame synthesis catalyst behaved like a time-lapsed catalyst produced by a conventional wet chemical process.

Claims (19)

A method for producing catalyst particles comprising platinum, tin, and one or more other elements selected from lanthanum and cesium on a support comprising zirconium dioxide and optionally silicon oxide,
(I) preparing a solution containing a precursor containing platinum, tin, and one or more other elements selected from lanthanum and cesium, and a precursor compound of zirconium dioxide;
(Ii) converting the solution into an aerosol;
(Iii) supplying the aerosol to a directly or indirectly heated pyrolysis zone;
(Iv) performing pyrolysis, and (v) separating particles produced from the pyrolysis gas,
Manufacturing method.   Furthermore, the manufacturing method of Claim 1 in which a precursor compound contains the precursor compound of a silicon dioxide.   The manufacturing method according to claim 1 or 2, wherein the pyrolysis region is heated by a flame.   The production method according to claim 1, wherein the produced catalyst particles contain 0.05 to 1 mass% and 0.05 to 2 mass% of Sn.   The manufacturing method of any one of Claims 1-4 in which a precursor compound contains zirconium acetylacetonate (IV).   The production method according to any one of claims 1 to 5, wherein the precursor compound contains lanthanum (III) acetylacetonate and / or cesium acetate.   The manufacturing method of any one of Claims 1-6 in which a precursor compound contains hexamethyldisiloxane.   The manufacturing method of any one of Claims 1-7 in which a precursor compound contains 2-ethyl hexanoic acid tin.   The manufacturing method of any one of Claims 1-4 in which a precursor compound contains platinum acetylacetonate.   The manufacturing method of any one of Claims 1-4 in which a precursor compound contains a zirconium (IV) propoxylate.   The manufacturing method of any one of Claims 1-4 in which a precursor compound contains 2-ethyl hexanoic acid lanthanum (III).   The manufacturing method according to any one of claims 1 to 9, wherein one or more precursor compounds are dissolved in a mixture of acetic acid, ethanol, and water.   The production method according to any one of claims 7 to 11, wherein one or more precursor compounds are dissolved in xylene.   The manufacturing method of any one of Claims 1-13 which perform a thermal decomposition at 900-1500 degreeC.   The catalyst particle obtained by the manufacturing method of any one of Claims 1-14. The catalyst particles according to claim 15, having a specific surface area of 36 to 70 m ² / g. Relative to the weight of the carrier, _ZrO 2 of 30 to 99.5% by weight as a carrier, 0.5 to 25 mass% of SiO _2, and 0.1 to 1 wt% of Pt, 0.1 to 10 wt% Sn, La, and / or Cs
The catalyst particle according to claim 15 or 16, comprising at least Sn, and at least La or Cs.   A method for using the catalyst particles according to any one of claims 15 to 17 as a dehydrogenation catalyst.   The method according to claim 18, wherein the catalyst particles are used for the dehydrogenation of propane to propene or the dehydrogenation of butane to butene.

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