JP4284740B2 - Method for preparing palladium-antimony alloy catalyst - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a method for preparing an alloy catalyst containing palladium and antimony as main components. A palladium-antimony alloy catalyst is used when an olefin or aromatic compound is reacted with carboxylic acid and molecular oxygen to produce a carboxylic acid ester.
[0002]
[Prior art]
Various methods are known for preparing catalysts containing palladium and antimony as main components.
[0003]
For example, Japanese Patent Application Laid-Open No. 50-108232 discloses a method in which palladium chloride and antimony chloride are impregnated and dried as raw materials and then reduced with a hydrazine aqueous solution at 40 ° C. to obtain a catalyst. A method of obtaining a catalyst by supporting an antimony compound on a carrier and then calcining it is disclosed in Japanese Patent Application Laid-Open No. 51-8188, in which an antimony component is supported on a carrier and then 500 to 900 in the presence of molecular oxygen. A method characterized by firing in the temperature range of ° C. is disclosed. In these preparation methods, when a catalyst is prepared at an economically advantageous palladium loading of about 1% on the premise of industrial implementation, palladium and antimony are highly dispersed and supported on a carrier having a large surface area. Each component hardly interacts and alloying does not proceed sufficiently. Therefore, in order to obtain an alloy catalyst, (1) a method in which antimony that is not alloyed in anticipation is prepared in advance in excess of the stoichiometric composition, and (2) a melting point (630.8) to increase the mobility of antimony. A method of heating to higher than or equal to (° C.) is required. However, when antimony is made in excess of the stoichiometric composition, antimony that does not form an alloy remains in the catalyst, thereby reducing catalyst stability or causing side reactions, leading to a reduction in selectivity. Further, when heating at a high temperature, the activity decreases due to the aggregation of the alloy particles and the physical strength of the carrier decreases.
[0004]
On the other hand, several methods for preparing alloy catalysts are also known.
[0005]
For example, Japanese Patent Publication No. 8-2556874 discloses a method in which an organic amine salt of a second metal is supported on a support on which a first metal is supported, reduced, and then heated to be alloyed. In this method, since alloying is performed at a high temperature of 700 ° C. or higher, special heating equipment and a great deal of energy are required, which is not industrially preferable from the viewpoint of catalyst production cost. In addition, when this method is applied to a palladium-antimony catalyst, toxic stibine SbH ₃ is generated during the hydrogen reduction process, and a special stibine treatment facility is required for industrial implementation. It becomes a problem from both sides of economy.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for quantitatively preparing a high-purity palladium-antimony alloy catalyst safely and economically at a low temperature of 200 ° C. or lower.
[0007]
[Means for Solving the Problems]
As a result of diligent research to solve the above problems, the present inventors selectively reduced and alloyed the antimony compound dissolved in the solution on the palladium surface, thereby producing a high-purity palladium- It has been found that an antimony alloy catalyst can be prepared, and the present invention has been completed.
[0008]
That is, the present invention is characterized in that, in preparing an alloy catalyst of palladium and antimony, a catalyst precursor containing palladium or palladium and antimony is brought into contact with an antimony compound dissolved in a liquid phase in the presence of a reducing agent. The present invention relates to a method for preparing a palladium-antimony alloy catalyst.
[0009]
Hereinafter, the present invention will be described in detail.
[0010]
The catalyst precursor containing palladium or palladium and antimony used in the present invention can be prepared by a known method. To exemplify the simplest preparation method, palladium or a compound of palladium and antimony is dissolved in an appropriate solvent, mixed with a carrier, and if necessary, allowed to stand for a predetermined time, and then dried. Furthermore, a catalyst precursor is obtained by baking in an atmosphere containing oxygen or oxygen. In addition, you may implement a reduction process by a well-known method after baking.
[0011]
In preparing the catalyst precursor in the present invention, there are no particular limitations on the raw materials of palladium and antimony used. Specifically, as the raw material of palladium, ammonium hexachloropalladate, potassium hexachloropalladate, sodium hexachloropalladate, ammonium tetrachloropalladate, potassium tetrachloropalladate, sodium tetrachloropalladate, potassium tetrabromopalladate Palladium oxide, palladium chloride, palladium bromide, palladium iodide, palladium nitrate, palladium sulfate, palladium acetate, potassium dinitrosulfite palladium acid, chlorocarbonyl palladium, dinitrodiammine palladium, tetraammine palladium chloride, tetraammine palladium nitrate, cis- Dichlorodiamine palladium, trans-dichlorodiamine palladium, dichloro (ethyl Diamine) palladium, potassium tetracyanopalladate, and the like. Antimony materials include antimony metal, antimony fluoride, antimony chloride, antimony bromide, antimony iodide, antimony acetate, antimony methoxide, antimony ethoxide. And antimony isopropoxide, antimony butoxide, antimony ethylene glycoloxide, antimony potassium tartrate, antimony tartrate, antimony oxide, antimony sulfide, triphenyl antimony and the like. In consideration of industrial catalyst preparation, water is suitable as a solvent, and water-soluble raw materials are preferable.
[0012]
In the present invention, the composition ratio of antimony to palladium in the catalyst precursor is preferably less than the stoichiometric composition of the target alloy. This is because if the composition of antimony exceeds the stoichiometric composition of the target alloy, the alloy catalyst prepared by the alloying process becomes a mixture with another non-targeted alloy or non-alloyed antimony. For example, in order to prepare an alloy catalyst of Pd ₈ Sb ₃ , the atomic ratio of palladium / antimony in the catalyst precursor is preferably 8/0 or more and less than 8/3.
[0013]
In the preparation of the catalyst precursor of the present invention, it is preferable to support it on a carrier in order to use expensive palladium sufficiently efficiently. As the carrier, an oxide carrier such as activated carbon, silica, alumina, titania, zirconia, or a composite oxide thereof is used, and silica is particularly preferable. There is no restriction | limiting in particular in a silica, What was prepared by what raw material and manufacturing method can be used. If the physical properties are strong, it is preferable that the BET specific surface area is 10 m ² / g or more and the pore volume is 0.2 cc / g or more.
[0014]
There is no particular limitation on the method for supporting palladium or a raw material salt of palladium and antimony on a carrier, and it can be supported by a known method. For example, it can be prepared by a precipitation method, an ion exchange method, an impregnation method, a deposition method, or a kneading method.
[0015]
When preparing a catalyst precursor containing palladium and antimony by the impregnation method, the palladium raw material and the antimony raw material may be impregnated and supported at the same time, and after impregnating and supporting one of them, the remaining raw materials are impregnated and supported. It doesn't matter. The amount of palladium and antimony supported in the catalyst precursor is not particularly limited, but is 0.1 to 20% by weight, preferably 0.3 to 10% by weight, based on the support.
[0016]
There is no restriction | limiting in particular in the shape of a catalyst precursor, According to the format of the catalytic reaction to be used, a powdered thing or a molded article can be used. For a fixed bed, a tablet tableting product, a spherical or rod-like extrusion molding, and the like are preferably used for a suspension bed. If the particle size of the catalyst precursor is too large in the fixed bed, there will be fewer effective parts, and conversely if it is too small, the pressure loss inside the reactor will increase. Those having a size of 8 mm are effective. When used in a liquid phase suspension bed, a size of 20 to 500 μm is effective for natural sedimentation separation and a size of 0.1 to 20 μm is effective for filter separation because of the ease of catalyst separation.
[0017]
Next, a method for obtaining an alloy catalyst from palladium or a catalyst precursor containing palladium and antimony will be described. By contacting the above-mentioned catalyst precursor with an antimony compound dissolved in the liquid phase in the presence of a reducing agent, the antimony is selectively reduced and alloyed on the palladium surface to obtain the alloy catalyst of the present invention. be able to. The details of alloying are unknown, but in the absence of palladium, the antimony compound is not reduced by the reducing agent, so the antimony compound is reduced by the dissociatively adsorbed hydrogen produced on the palladium by the palladium and the reducing agent. And can be estimated to be further alloyed.
[0018]
As the solvent used in the alloying treatment, water and / or an organic solvent can be selected, but water is preferred industrially. Therefore, as the reducing agent, a general water-soluble reducing agent such as hydrazine, formalin, formic acid or methanol is preferable. The reducing agent is used in an amount of 0.5 to 100 times mol, practically 2 to 50 times mol of palladium present in the catalyst precursor.
[0019]
The antimony compound used in the alloying treatment is not particularly limited as long as it can be dissolved in a solvent in the presence of a reducing agent. In view of practical use, water is preferable as a solvent, and therefore, a water-soluble antimony compound is preferable. Examples of the water-soluble antimony compound include antimonic acid, metaantimonic acid, pyroantimonic acid, condensed antimonic acid and salts thereof, and organic acids such as tartaric acid, succinic acid and glycolic acid or complex compounds thereof. Considering the solubility, antimony tartrate and potassium antimony tartrate are preferable. The amount of the antimony compound used is selected from a range in which the total amount of antimony contained in the catalyst precursor is 0.9 to 1.5 times the stoichiometric composition of the target alloy catalyst. Specifically, for example, in order to obtain a high purity alloy catalyst Pd ₈ Sb ₃ , the palladium / antimony composition ratio contained in the catalyst precursor and the alloying treatment solution is 8 / 2.7 or more, 8 / 4.5 What is necessary is just to dissolve an antimony compound in the treatment solution so as to be in the following range. Further, the concentration of the antimony compound used in the alloying treatment is not particularly limited, but practically, the antimony concentration in the alloying treatment solution is preferably 0.1% by weight or more. The antimony compound may be added before the reduction treatment or may be added during the alloying treatment.
[0020]
The temperature of the alloying treatment is in the range of 50 to 200 ° C, preferably 50 to 150 ° C. This is because it takes a long time to reduce the antimony compound dissolved in the liquid phase when the treatment temperature is less than 50 ° C., and when the temperature exceeds 200 ° C., a large pressure is required to maintain the liquid phase state. This is because it is not suitable. When the treatment temperature is close to the boiling point of the solvent used or when it is desired to suppress the vaporization of the solvent, the treatment can be performed under pressure.
[0021]
The time for the alloying treatment is not generally determined depending on the temperature and type of the treatment, but is usually selected from the range of 0.1 to 100 hours, preferably from the range of 0.5 hours to 24 hours. The alloying operation is carried out in a stirred tank reactor or a fixed bed reactor.
[0022]
By carrying out the above treatment, a high-purity palladium-antimony alloy catalyst can be obtained. As the palladium-antimony alloy, an alloy as shown in the phase diagram of the palladium-antimony binary alloy of FIG. 5 is known, and Pd ₈ Sb ₃ (Powder Diffraction File No. 30-95), Pd ₂₀ Examples thereof include a solid solution in which antimony is solidified in the crystal structure of an intermetallic compound such as Sb ₇ (Powder Diffraction File No. 31-102) and palladium metal (Powder Diffraction File No. 5-681). Whether the alloying has progressed can be easily judged from the powder X-ray diffraction (XRD) pattern. For example, in the case of the above-described intermetallic compound, the 2θ value of the peak characteristic of the intermetallic compound is as follows (the relative intensity is shown in parentheses).
2θ value of Pd ₈ Sb ₃ :
36.1 (16), 39.3 (97), 41.0 (100), 44.7 (16)
2θ value of Pd ₂₀ Sb ₇ :
37.1 (16), 40.2 (87), 40.6 (100), 46.0 (14)
Further, since the lattice constant of the solid solution changes with the crystal structure of the palladium metal as it is, the 2θ value of the peak characteristic of the solid solution is obtained by shifting the 2θ value of the following palladium metal to the lower angle side.
[0023]
2d value of Pd:
40.1 (100), 46.6 (42), 68.1 (25), 82.1 (24)
Depending on the preparation conditions, the 2θ value may vary within a range of ± 0.3 and the relative intensity within a range of ± 30%. In the palladium-antimony binary solid solution, the solid solubility limit of antimony in palladium is 16 wt% (14 mol%).
[0024]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, unless it deviates from a claim, it is not limited only to these Examples.
[0025]
Example 1
4.17 wt% palladium nitrate aqueous solution (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) 9.17 g and 26-28% ammonia water (manufactured by Wako Pure Chemical Industries Ltd.) 0.98 g were weighed in a 200 ml round bottom flask, and pure water was added. 43 ml of a homogeneous solution was obtained.
[0026]
Next, 40 g of silica dried at 180 ° C. for 2 hours in a drier (manufactured by Fuji Silysia Co., CARIACT-Q30, BET specific surface area: 100 m ² / g, pore volume: 1.05 cc / g, spherical diameter of 3 mm) In addition, it was impregnated with stirring until the liquid was completely absorbed by the silica.
[0027]
After the impregnation, water was removed at 50 ° C. under reduced pressure using a rotary evaporator.
[0028]
The product thus obtained was put into a tubular heat treatment tube and calcined at 300 ° C. for 5 hours while flowing air at 200 ml / min to obtain catalyst precursor A (Pd loading: 1.0 wt%). It was.
[0029]
The X-ray diffraction (XRD) chart of this catalyst precursor A is shown in FIG.
[0030]
The catalyst precursor A was used for alloying treatment.
[0031]
2.00 g of antimony trioxide (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 98.00 g of a 10% aqueous tartaric acid solution (hereinafter referred to as an antimony tartrate aqueous solution).
[0032]
To a 100 ml round bottom flask was added 0.27 g of hydrazine hydrate (manufactured by Wako Pure Chemical Industries, Ltd.), 1.25 g of an antimony tartrate aqueous solution (containing 2.0 wt% Sb ₂ O ₃ ), and 37.20 g of pure water. Prepared.
[0033]
To this homogeneous solution, 5.03 g of catalyst precursor A was added, heated at 80 ° C. for 8 hours, then washed with water and dried (110 ° C., 3 hours) to prepare an alloy catalyst (feeding: Pd / Sb molar ratio) 8/3).
[0034]
The XRD of this alloy catalyst was measured. The measurement was carried out using M18XHF manufactured by Mac Science Co., Ltd., and measuring the diffraction angle 2θ at 40 kV and 200 mA using CuKα rays in accordance with the usual measurement procedure of powder X-ray diffraction. The XRD peak values are 36.3 (25), 39.4 (92), 41.0 (100), 45.0 (18), and the supported palladium-antimony alloy is an intermetallic compound Pd ₈ Sb ₃ . The structure was shown (FIG. 1). As a result of elemental analysis, the supported amount of palladium was 0.92 wt%, the supported amount of antimony was 0.39 wt%, and the Pd / Sb molar ratio was 2.7 (8/3).
[0035]
Example 2
Except for using 0.27 g of hydrazine hydrate and 1.15 g of an antimony tartrate solution (containing 2.0 wt% Sb ₂ O ₃ ), the same alloying treatment as in Example 1 was applied to 5.03 g of catalyst precursor A. (Feed Pd / Sb molar ratio: 20/7). The measurement result of XRD is shown in FIG. The XRD peak values were 39.9 (68) and 40.7 (100), and the supported palladium-antimony alloy had the structure of the intermetallic compound Pd ₂₀ Sb ₇ . As a result of elemental analysis, the supported amount of palladium was 0.92 wt%, the supported amount of antimony was 0.38 wt%, and the Pd / Sb molar ratio was 2.8 (20/7).
[0036]
Example 3
Alloying treatment was performed in the same manner as in Example 1 except that 4.05 g of formalin was used instead of hydrazine hydrate as the reducing agent and 0.12 g of potassium antimonyl tartrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the antimony source. (Feed Pd / Sb molar ratio: 8/3). The XRD measurement results of this alloy catalyst are shown in FIG. The XRD peak values were 36.1 (20), 39.5 (70), 41.1 (100), and the supported palladium-antimony alloy had a structure of an intermetallic compound Pd ₈ Sb ₃ . As a result of elemental analysis, the palladium loading was 0.91 wt%, the antimony loading was 0.39 wt%, and the Pd / Sb molar ratio was 2.7 (8/3).
[0037]
Example 4
A 8.26 wt% palladium nitrate aqueous solution (Tanaka Kikinzoku Kogyo Co., Ltd.) 4.84 g and 26-28 wt% ammonia water (Wako Pure Chemical Industries Co., Ltd.) 0.98 g were weighed in a 200 ml round bottom flask. 6.68 g of antimony tartrate solution (containing 2.0 wt% Sb ₂ O ₃ ) was added thereto, and pure water was further added to obtain 43 ml of a uniform solution.
[0038]
Thereafter, impregnation, drying, and calcination were performed in the same manner as in Example 1, and catalyst precursor B (Pd loading: 1.0 wt%, Sb loading: 0.3 wt%, Pd / Sb molar ratio: 4) 0.0 (8/2)).
[0039]
An XRD chart of the catalyst precursor B is shown in FIG.
[0040]
The catalyst precursor B was used for alloying treatment.
[0041]
To a 100 ml round bottom flask was added 0.25 g of hydrazine hydrate (manufactured by Wako Pure Chemical Industries, Ltd.), 0.43 g of antimony tartrate aqueous solution (containing 2.0 wt% Sb ₂ O ₃ ), and 37.25 g of pure water. Prepared.
[0042]
To this homogeneous solution, 5.04 g of catalyst precursor B was added, heated at 80 ° C. for 8 hours, washed with water and dried (110 ° C., 3 hours) to prepare an alloy catalyst (final catalyst charge Pd / Sb molar ratio: 8/3).
[0043]
An XRD chart of this alloy catalyst is shown in FIG. The XRD peak values are 36.0 (23), 39.2 (88), 41.0 (100), 44.7 (21), and the supported palladium-antimony alloy is an intermetallic compound Pd ₈ Sb ₃ . The structure was shown. As a result of elemental analysis, the supported amount of palladium was 0.93 wt%, the supported amount of antimony was 0.40 wt%, and the Pd / Sb molar ratio was 2.7 (8/3).
[0044]
Comparative Example 1
In the preparation method of Example 4, the amount of the antimony tartrate solution (containing 2.0 wt% Sb ₂ O ₃ ) was changed to 10.02 g, and the catalyst precursor C (Pd supported amount) having a Pd / Sb molar ratio of 8/3 was used. : 1.0 wt%, Sb loading: 0.4 wt%).
[0045]
10.75 g of the catalyst precursor C was put into a heat treatment tube, and reduction was performed at 400 ° C. for 5 hours while flowing hydrogen at 100 ml / min to prepare a catalyst. From the XRD chart of the obtained catalyst (FIG. 3, peak value 39.8), a solid solution structure in which antimony was partly dissolved in palladium was confirmed, but no intermetallic compound was confirmed. As a result of elemental analysis, the supported amount of palladium was 0.95 wt%, the supported amount of antimony was 0.33 wt%, and the Pd / Sb molar ratio was 3.3. The solid solution limit of antimony in palladium (Pd / Sb molar ratio: 6 1) The presence of antimony above suggests the presence of non-alloyed antimony. In addition, generation of stibine (SbH ₃ , toxic) was confirmed in the hydrogen reduction process, which led to loss of antimony.
[0046]
Comparative Example 2
6.46 g of hydrazine hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and 80.24 g of pure water were added to a 100 ml round bottom flask to prepare a uniform solution.
[0047]
To this homogeneous solution, 21.92 g of the catalyst precursor C of Comparative Example 1 was added, reduced at 20 ° C. for 8 hours, washed with water and dried (110 ° C., 3 hours) to prepare a catalyst.
[0048]
From the XRD chart (FIG. 3, peak value 39.8) of this catalyst, a solid solution structure in which antimony was partly dissolved in palladium was confirmed, but no intermetallic compound was confirmed. As a result of elemental analysis, the supported amount of palladium was 0.92 wt%, the supported amount of antimony was 0.19 wt%, and the Pd / Sb molar ratio was 5.7. On the way, a large amount of Sb elution was confirmed in the washing step, which led to loss of antimony.
[0049]
Comparative Example 3
In the preparation method of Example 4, the amount of the antimony tartrate solution (containing 2.0 wt% Sb ₂ O ₃ ) was changed to 16.03 g, and the catalyst precursor D (Pd supported amount) having a Pd / Sb molar ratio of 5/3 was changed. : 1.0 wt%, Sb loading: 0.7 wt%).
[0050]
Furthermore, 10.32 g of catalyst precursor D was put into a heat treatment tube, and reduction was performed at 400 ° C. for 5 hours while flowing hydrogen at 100 ml / min to prepare a catalyst. On the way, generation of stibine (SbH ₃ , toxic) was confirmed. In the XRD chart (FIG. 4) of the obtained catalyst, only a broad peak was observed, and the crystal structure could not be determined. As a result of elemental analysis, the palladium loading was 0.93 wt%, the antimony loading was 0.51 wt%, and the Pd / Sb molar ratio was 2.1.
[0051]
Comparative Example 4
To a 100 ml round bottom flask, 3.23 g of hydrazine hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and 40.00 g of pure water were added to prepare a uniform solution.
[0052]
To this homogeneous solution, 10.86 g of the catalyst precursor D of Comparative Example 1 was added, reduced at 20 ° C. for 8 hours, washed with water and dried (110 ° C., 3 hours) to prepare a catalyst.
[0053]
From the XRD chart of this catalyst (FIG. 4, peak value 39.4), a solid solution structure in which antimony was partly dissolved in palladium was confirmed. As a result of elemental analysis, the supported amount of palladium was 0.92 wt%, the supported amount of antimony was 0.39 wt%, and the Pd / Sb molar ratio was 2.7 (8/3). On the way, a large amount of Sb elution was confirmed in the washing step, which led to loss of antimony.
[0054]
【The invention's effect】
According to the present invention, a catalyst precursor containing palladium or palladium and antimony is brought into contact with an antimony compound dissolved in a liquid phase in the presence of a reducing agent, so that it is safe and economical at a low temperature of 200 ° C. or lower. In addition, it can be prepared to produce a palladium-antimony alloy catalyst with high stoichiometry.
[Brief description of the drawings]
1 is an XRD chart of catalysts obtained in Examples 1, 2, and 3. FIG.
2 is an XRD chart of the catalyst obtained in Example 4. FIG.
3 is an XRD chart of the catalysts obtained in Comparative Examples 1 and 2. FIG.
4 is an XRD chart of the catalyst obtained in Comparative Examples 3 and 4. FIG.
FIG. 5 is a phase diagram of a binary alloy of palladium and antimony.

Claims (3)

In preparing an alloy catalyst of palladium and antimony, a palladium-antimony alloy characterized by contacting palladium or a catalyst precursor containing palladium and antimony with an antimony compound dissolved in a liquid phase in the presence of a reducing agent. Catalyst preparation method. The palladium-antimony alloy catalyst according to claim 1, wherein the temperature at which the catalyst precursor is brought into contact with the antimony compound dissolved in the liquid phase in the presence of a reducing agent is in the range of 50 to 200 ° C. Preparation method. The method for preparing a palladium-antimony alloy catalyst according to claim 1 or 2, wherein the palladium-antimony alloy is an intermetallic compound Pd ₈ Sb ₃ , Pd ₂₀ Sb ₇ .

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