JP3520367B2 - Method for producing platinum nitroammine complex - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for a fuel cell, an exhaust gas from an automobile or various plant factories, and an exhaust gas from a combustion device such as a heating facility in a building or a general household. The present invention relates to a method for producing a platinum nitroammine complex which is useful for producing a catalyst or the like for detoxification treatment of gas and the like. 2. Description of the Related Art Platinum sulfite complex salts, for example, are used as platinum compounds for the production of catalysts for fuel cells and platinum catalysts for detoxification of gases emitted from automobiles and various plants. (U.S. Pat. No. 4,044,44)
Nos. 193, 3,922,512 and 3,99
2,331). However, the platinum sulfite complex salt has disadvantages that not only the production process is complicated and costly, but also the deterioration of the catalytic ability is accelerated because it contains sulfur which is a catalyst poison. Japanese Patent Application Laid-Open Nos. 54-92588 and 63-40135 disclose that a gas diffusion electrode for a fuel cell is produced by using a solution of chloroplatinic acid in a lower alcohol. However, chloroplatinic acid has a problem in that it contains chlorine, which is a catalyst poison, and has a drawback that it is aggregated during the reduction treatment. Further, JP-A-60-212235, JP-B-61-33620, and JP-A-2-745.
No. 30 and JP-A-6-178936 propose the use of dinitrodiammine platinum for the production of gas diffusion electrodes for fuel cells. This compound is impregnated into a carrier in the form of an aqueous nitric acid solution, and then calcined in the air to precipitate platinum, which is used as a platinum-supported catalyst.
Since a high temperature is required for calcination reduction, there is a problem that it cannot be used for a carrier having low heat resistance such as a carbon sheet which has been made water-repellent with a fluororesin. Further, Japanese Patent Application Laid-Open No. 4-298238 discloses that a carbon powder is added to a nitric acid solution of dinitrodiammineplatinum, mixed, and an aqueous solution of L-ascorbic acid or alcohol is added thereto to reduce at a temperature of 50 to 70 ° C. After doing
A method for forming a gas diffusion electrode for a fuel cell by forming the obtained platinum-supporting carbon powder into a sheet is disclosed. However, this method not only requires a long time for reduction, but also has a problem in wettability of the carbon powder due to the reaction in an aqueous medium. As other platinum complexes, acetylacetonatoplatinum, diammineethylene nitrateplatinum nitrate, diamminglycinatoplatinic acid, and the like are known. However, all of these are complicated and expensive, so that they are not practical. It is scarce. It is an object of the present invention to provide a platinum-free catalyst which does not contain chlorine or sulfur which is a catalyst poison, is easy to produce, and can deposit platinum in the form of finely dispersed particles on a catalyst carrier. An object of the present invention is to provide a method for producing a compound. [0008] The present invention relates to dissolving and reacting a divalent dinitrodiammineplatinum salt in nitric acid to form a tetravalent platinum complex, and after drying to dryness, reacting with an alcohol. Characteristic Formula [Pt (NH ₃ ) _x (NO ₂ ) _y L] Az (I) In the formula, L represents an alkoxy group, an alkanoyl group or an alkanoyloxy group, and A represents H, NO ₂ or NO ₃ , X is 0, 1 or 2, y is 1, 2 or 3, provided that the sum of x and y varies from 3 to 5 depending on the charge of the central platinum, and z varies depending on the charge of the central metal ( y-1) to (y-3), which provide a method for producing a platinum nitroammine complex represented by the formula: In the above formula (I), examples of the alkoxyl group include methoxy, ethoxy, propoxy, isopropoxy, and butoxy, and examples of the alkanoyl group include formyl and acetyl. Furthermore, examples of the alkanoyloxy group include formyloxy and acetyloxy groups. Thus, specific examples of the platinum nitroammine complex represented by the above formula (I) include the following when ethanol is used as the alcohol in the production. Pt (IV) (NH ₃ ) ₂ (NO ₂ ) ₃ (OC ₂ H ₅ ) Pt (IV) (NO ₂ ) ₃ (OC ₂ H ₅ ) Pt (IV) (NH ₃ ) ₂ (NO ₂ ) ₂ (OC ₂ H ₅ ) (NO
₃ ) Pt (II) (NH ₃ ) (NO ₂ ) (OC ₂ H ₅ ) [Pt (II) (NH ₃ ) (NO ₂ ) ₂ (OC ₂ H ₅ )] H [Pt (II) (NO ₂ ) ₃ (OC ₂ H ₅ )] H ₂ Pt (IV) (NH ₃ ) ₂ (NO ₂ ) ₃ (COCH ₃ ) Pt (II) (NH ₃ ) ₂ (NO ₂ ) (COCH ₃ ) [Pt (II _{) (NH 3) (NO 2} ) 2 (COCH 3)] H Pt (IV) (NH 3) 2 (NO 2) 3 (OCOCH 3) Pt (II) (NH 3) 2 (NO 2) (OCOCH 3 ) [Pt (II) (NH ₃ ) (NO ₂ ) ₂ (OCOCH ₃ )]
H etc. In the complex of the formula (I), the charge of the central platinum can be tetravalent or divalent, or it can take a trivalent value in the case of its reaction intermediate. The structure of the complex varies depending on its production conditions, for example, the reaction temperature, the reaction time, and the molar ratio of the raw materials. The platinum nitroammine complex represented by the formula (I) of the present invention is prepared by, for example, dissolving a divalent dinitrodiammine platinum salt in nitric acid and reacting to form a tetravalent platinum complex. After that, it can be produced by reacting with alcohol. The divalent dinitrodiammine platinum salt used as a starting material here is a compound known per se. For example, platinum is dissolved in aqua regia and then denitrated to form an aqueous solution of chloroplatinic acid. And boiled to obtain a platinum nitrite solution. Then, ammonia water is added to the solution to cause a reaction, and the product can be produced. The divalent dinitrodiammine platinum salt is a planar four-coordinate complex, and waits for two forms, a cis-form and a trans-form. In producing the platinum nitroammine complex of the present invention, either form of the complex is used. Or a mixture thereof, and any commercially available product can be used. The divalent dinitrodiammine platinum salt thus obtained is an aqueous nitric acid solution, usually having a concentration of 200 to 70%.
By dissolving in a 0 g / l nitric acid aqueous solution at 60 to 112 ° C and maintaining for about 3 to 16 hours, a tetravalent platinum complex, for example, trinitrodiammine platinum salt can be produced. More specifically, 350 to 60 in terms of platinum.
0 g / l of dinitrodiammine platinum salt with a nitric acid concentration of 45
A tetravalent platinum complex can be obtained by dissolving in a 0 to 700 g / l nitric acid aqueous solution and maintaining the solution at a normal pressure under boiling conditions of 107 ° C. or higher for 3 to 6 hours. The formation of this tetravalent platinum complex can be confirmed by comparing with the absorbance of chloroplatinic acid hexahydrate corresponding to the JIS special grade reagent according to the method described in JIS-K8153, and the amount of the formation is usually , An absorbance of chloroplatinic acid hexahydrate of 100
The relative absorbance is about 92 to 94%. The resulting tetravalent platinum complex solution is preferably dried and then reacted with an alcohol. The dryness of the reaction solution containing the tetravalent platinum complex is, for example, about 50 to about 200.
C., preferably under a reduced pressure in a hot plate heated to a temperature of about 80 to about 160.degree. C. or a rotary evaporator. 4 obtained in this way
The crystals of the divalent platinum complex are reacted with the alcohol. Examples of the alcohol include lower alcohols such as methanol, ethanol, propanol, isopropanol, and butanol, and among them, ethanol is preferable. The reaction between the tetravalent platinum complex and the alcohol is as follows:
It can be carried out by mixing both and maintaining the temperature at about 20 to about 50 ° C. The amount of the alcohol used at this time is not strictly limited, but is usually 0.5 to 20 times, preferably 2 to 15 times the weight of platinum in the tetravalent platinum complex. Is appropriate. In this reaction, the platinum ions in the tetravalent platinum complex are reduced by the alcohol, and at the same time, the alcohol is at least partially converted to an aldehyde and / or carboxylic acid depending on the reaction conditions, which are It is introduced into the complex as an alkoxy group, an alkanoyl group, or an alkanoyloxy group. Thus, an alcohol solution containing the platinum nitroammine complex represented by the formula (I) as a dissolved species can be obtained. This solution is prepared, for example, using a rotary evaporator at about 25 to 80 ° C., preferably about 35 ° C.
By concentrating to dryness under reduced pressure at a temperature of ~ 60 ° C,
The platinum nitroammine complex of the formula (I) can be obtained in powder form. The platinum nitroammine complex of the present invention can be advantageously used in the production of a platinum-supported catalyst. For example, after dissolving the complex of the present invention in an alcohol at room temperature or under heating up to about 80 ° C. and adjusting the platinum concentration to a predetermined value, the solution is transferred to a metal carrier (eg, iron-nickel system, iron-chromium-nickel). System, iron-chromium system, etc.), ceramic carrier (for example, alumina, silica, alumina-silica,
Coating or dipping on a carrier material such as cordierite, zirconia, or the like, or a carbon carrier (for example, a porous carbon carrier composed of a carbon powder and a fluororesin as a binder), and then adsorbing it. By reducing at a temperature of about 100 to about 200 ° C, a platinum-supported catalyst can be obtained. Since the platinum compound provided by the present invention does not contain chlorine or sulfur, which is a catalyst poison, not only can a platinum-supported catalyst with little deterioration of catalytic ability be produced, but also the platinum compound of the present invention can be used. If used, the catalyst can be applied to the catalyst carrier in the form of an alcohol solution without using an aqueous medium, so that a catalyst in which platinum particles are finely and uniformly dispersed on the carrier can be produced. The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. Example 1 100 g of dinitrodiammine platinum salt in terms of platinum was added to 200 ml of a solution having a nitric acid concentration of 500 g / l, mixed, stirred and dispersed, and dinitrodiammineplatinum was dissolved at the boiling temperature. Hold for 4 hours. Next, it was evaporated to dryness on a hot plate having a surface temperature of 100 ° C. to obtain a yellow-brown powder. This powder was gradually added to 200 g of absolute ethanol, dissolved while cooling, and kept at 40 ° C. for 3 hours.
Using a rotary evaporator, 80 g of the solution,
Evaporation to dryness at a temperature of 50 ° C. and under reduced pressure gave a platinum compound powder. With respect to the platinum compound powder obtained above,
Functional group analysis by FT-IR, composition by elemental analysis, and analysis by ¹ H-NMR were performed. The results were as follows. [0024] In the infrared absorption measurement by FT-IR, as shown in FIG. 1, a nitro group (NO ₂ ^-) based on 5
78,1384Cm ^-1, and nitrate ions (NO ₃ ^-)
1474cm ^-1 based on the peak, such 838,1020,1329Cm ^-1 attributed to ammine group (NH ₃₎ is observed. Also, as a peak due to the ethoxy group, 1
Absorption is observed around 000-1200 cm ^-1, which corresponds to the OH stretching vibration seen in alcohol.
Since no broad absorption was observed at around 0 to 1400 cm ^-1, it was found that there was almost no residual alcohol and that an ethoxy group capable of coordinating with platinum was present. Therefore, it can be seen that each functional group of nitro, ammine and ethoxy is coordinated to platinum. Next, FIG. 2 shows the result of ¹ H-NMR measurement. CH ₃ and CH ₂ belonging to an ethyl group or an ammine group
And NH ₃ shifts were confirmed, and it was found that an ethoxy group and an ammine group were present. Also, at this time, the ratio of the ammine group to the ethoxy group was found to be 2: 1 from the ratio of the peak intensities. Table 1 below shows the results of the elemental analysis. Here, the theoretical value is a value when the platinum complex is represented by the following formula: Pt (NH ₃ ) ₂ (NO ₂ ) ₂ (OC ₂ H ₅ ) (NO ₃ ). [Table 1] The measured value of the resulting platinum complex, platinum, is smaller than the theoretical value, while the measured values of oxygen and hydrogen are higher than the theoretical value. However, in any case, the ratio of carbon and nitrogen to platinum is found to be appropriate. Accordingly, it can be seen that carbon and nitrogen atoms are present at least in the functional group coordinated to platinum. The platinum compound powder obtained from the above analysis results was mainly composed of a platinum nitroamine ethoxy complex represented by Pt (NH ₃ ) ₂ (NO ₂ ) ₂ (OC ₂ H ₅ ) (NO ₃ ). Then, the ethanol solution of the platinum complex prepared in this example was left in a dark place at room temperature for 7 days.
The alcohol solvent was distilled off, and identification was performed by gas chromatography mass spectrometry. As shown in FIG. 3, satellite peaks having mass numbers of 73 and 103 were observed.
This corresponds to the satellite peak of diethyl acetal CH ₃ CH (OC ₂ H ₅ ) ₂ , and is considered to be the result of the oxidation of ethanol in the presence of a tetravalent platinum complex and the progress of the reaction through the formation of aldehyde. Can be In other words, it can be seen that the reduction of platinum from tetravalent to divalent with the oxidation of the alcohol can occur in the alcohol solvent.
Therefore, it was found that a divalent platinum alcohol complex was also present in the crystal. This was also confirmed by the shift of the 4f electron peak of platinum by X-ray photoelectron spectroscopy. Example 2 50 g of dinitrodiammine platinum salt in terms of platinum was added to 100 ml of a solution having a nitric acid concentration of 500 g / l, mixed, stirred and dispersed, and then dinitrodiammineplatinum was dissolved at a boiling temperature. Hold for hours. Next, the surface temperature 1
Evaporate to dryness on a hot plate at 00 ° C. to obtain a yellow-brown powder. This powder is converted to methyl alcohol 10 for precision analysis.
The solution was gradually added to 0 g, dissolved while cooling, and kept at 40 ° C. for 3 hours. Using a rotary evaporator, 80 g of the solution was evaporated to dryness at a temperature of 50 ° C. and under reduced pressure to obtain a platinum compound powder. About the platinum compound powder obtained above, F
Functional group analysis by T-IR, mass spectrometry and ¹ H-NMR
Structural analysis. As a result, it was found that the powder was substantially composed of a platinum nitroammine methoxide complex represented by the formula Pt (NH ₃ ) ₂ (NO ₂ ) ₂ (OCH ₃ ) (NO ₃ ). FIG. 4 shows the infrared absorption spectrum of this compound. Comparative Example 1 Chloroplatinic acid was diluted with ethanol to a platinum concentration of 1 g / l. REFERENCE EXAMPLE 1 Each of the ethanol solution of the platinum compound prepared in Example 1, the methyl alcohol solution of the platinum compound prepared in Example 2, and the ethanol solution of chloroplatinic acid in Comparative Example 1 were mixed with a platinum concentration of 1.0 g. / L was adjusted with the alcohol used for each reaction. Then, acetylene carbon black was impregnated with each solution so that the amount of supported platinum was 5.5 mg / cm ³ ,
After drying for 5 minutes, in a mixed gas stream consisting of hydrogen: nitrogen = 5: 5,
It was reduced at 160 ° C. to deposit platinum on acetylene carbon black. With respect to the three types of acetylene carbon black on which the platinum thus obtained was deposited, the particle diameter of the supported platinum catalyst was measured from transmission electron microscope images. Table 2 shows the results. [Table 2] As is clear from the results in Table 2, Example 1
It can be seen that the particle size of platinum deposited on the support using the platinum compounds of Examples 1 and 2 is smaller than the particle size of the platinum catalyst produced by the conventional method described in Comparative Example 1. As described above, in the present invention, a nitric acid solution obtained by dissolving a divalent dinitrodiammineplatinum salt in nitric acid to form a tetravalent platinum complex is concentrated to dryness to obtain a powder. By reacting the powder with a lower alcohol to form an alcohol solution of a platinum nitroammine complex compound containing an alkoxyl group and an alkanoyl group or an alkanoyloxy group, chlorine ions or sulfur compounds are present in the catalyst, which has been a conventional drawback as a platinum catalyst. Can be produced. Further, the platinum compound of the present invention is a platinum nitroammine complex compound containing an alkoxyl group and an alkanoyl group or an alkanoyloxy group, which can be used by dissolving it in an alcohol, so that the wettability and permeability to the carrier can be improved. It provides a platinum compound that can support a platinum catalyst that is excellent in dispersibility and that has a small particle size of the platinum catalyst that is reduced and supported, and that can be expected to improve catalyst efficiency when used as a catalyst. can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an infrared absorption spectrum of the platinum ethoxide complex of the present invention obtained in Example 1. FIG. 2 is a ¹ H-NMR spectrum of the platinum ethoxide complex of the present invention obtained in Example 1 in heavy water. FIG. 3 shows a gas chromatography mass spectrometry spectrum of a solution obtained by allowing the ethanol solution of the platinum ethoxide complex of the present invention obtained in Example 1 to stand in a dark place at room temperature for 7 days and distilling the ethanol solvent. is there. 4 is an infrared absorption spectrum of the platinum methoxide complex of the present invention obtained in Example 2. FIG.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Keisuke Oguro, Inventor Keisuke Oguro, 1-38-31 Midorioka, Ikeda-shi, Osaka Prefecture Inside the Osaka Institute of Technology (72) Inventor Masayuki Oguri 2--12-30, Aoyagi, Soka-shi, Saitama No.Ishifuku Metal Industry Co., Ltd., Soka Daiichi Plant (72) Inventor Yuki Sasaki 2-12-30 Aoyagi, Soka City, Saitama Prefecture Ishifuku Metal Industry Co., Ltd., Soka Daiichi Plant (56) References JP 4-298238 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 29/70 C07C 31/28 C07F 15/00 H01M 4/92 B01J 23/42

Claims (1)

(57) [Claim 1] A divalent dinitrodiammine platinum salt is dissolved in nitric acid and reacted to form a tetravalent platinum complex, which is then dried and then reacted with alcohol. in that formula _{[Pt (NH 3) x (} NO 2) y L] Az formula, L is an alkoxy group, an alkanoyl group or an alkanoyloxy group, a represents H, an NO ₂ or NO _3, x is 0 Y is 1, 2 or 3, provided that the sum of x and y varies from 3 to 5 depending on the charge of the central platinum, and z varies depending on the charge of the central metal (y-1). ~ (Y-
3) A method for producing a platinum nitroammine complex represented by the formula: