JP2015085226A - Composition for production of supported catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for production of a supported catalyst having high stability to ammonia water added as a stabilizer or a pH buffer in preparation of a supported catalyst, and having high stability during a storage period.SOLUTION: A composition used for production of a supported catalyst comprises a reaction product obtained by reacting a platinum compound with an ethanolamine compound in an amount 2.5 to 5.0 times of the platinum molar quantity in an aqueous solution at 70 to 95°C, where the thermal decomposition temperature is 220°C or more. The platinum compound is hexahydroxo platinic acid. The ethanolamine compound is monoethanolamine. The composition for production of a supported catalyst is produced by mixing the platinum compound and the ethanolamine compound in an amount 2.5 to 5.0 times of the platinum molar quantity in an aqueous solution at room temperature, followed by reaction at 70 to 95°C for 2 hours or more.

Description

  The present invention relates to a composition for producing a supported catalyst for use in an exhaust gas purification catalyst or an exhaust gas sensor.

  In the prior art, the stability of the composition for producing a supported catalyst with respect to aqueous ammonia was not satisfactory. When ammonia water was added to the composition for producing a supported catalyst at the time of preparing the supported catalyst, a precipitate was precipitated, and thus a step for removing the precipitate was necessary. Further, since platinum is contained in the precipitate, in order to carry a predetermined amount of catalyst, it is necessary to adjust the concentration and the like, and the working efficiency is remarkably lowered.

JP2000-279811 JP2001-046880

  The present invention provides a composition for producing a supported catalyst that has high stability with respect to aqueous ammonia added as a stabilizer or pH buffer during preparation of the supported catalyst, and that has high stability over the storage period. The purpose is to provide.

  According to the present invention, in a composition used for the production of a supported catalyst, a platinum compound and an ethanolamine compound in an amount of 2.5 to 5.0 times the molar amount of platinum are mixed in an aqueous solution at room temperature, and then reacted at 70 to 95 ° C. And a composition for producing a supported catalyst, characterized in that the thermal decomposition temperature of the obtained reaction product is 220 ° C. or higher.

  According to the present invention, there is provided a composition for producing a supported catalyst, which has a high stability with respect to aqueous ammonia of the composition for producing a supported catalyst and has a high stability with respect to the storage period.

  By having high stability with respect to the ammonia water, the precipitation removal step at the time of manufacturing the supported catalyst which has been conventionally carried out becomes unnecessary, and a predetermined amount of catalyst can be obtained without adjusting the concentration etc. which has been carried out conventionally. Since it can be carried, work efficiency is greatly improved.

  The reason for having high stability with respect to aqueous ammonia is that a polymer is formed in the composition for producing a supported catalyst obtained by reacting a platinum compound and an ethanolamine compound at 70 to 95 ° C. It is presumed that the reaction prevents the formation of a precipitate when ammonia water is added.

  Specific examples of the platinum compound used in the present invention include hexahydroxoplatinic acid, chloroplatinic acid, dinitrodiammineplatinum and the like, preferably hexahydroxoplatinic acid.

The concentration of the platinum compound is 10 to 200 g · dm ⁻³ , preferably 130 to 180 g · dm ⁻³ .
When the amount is less than 10 g · dm ^{−3, the} amount of catalyst that can be supported at one time decreases, and in order to obtain a predetermined amount of supported catalyst, it is necessary to repeat the supporting step, resulting in a reduction in working efficiency. On the other hand, when it exceeds 200 g · dm ⁻³ , there arises a problem that it becomes difficult to make a platinum compound into solution, or the stability of the liquid is lowered and precipitates are easily generated.

  Specific examples of the ethanolamine compound used in the present invention include monoethanolamine, diethanolamine, triethanolamine and the like, and monoethanolamine is preferred.

The amount of monoethanolamine input is 2.5 to 5.0 times the amount of platinum molar amount, preferably 3.0 to 4.0 times the amount of platinum molar.
When the amount is less than 2.5 times, the stability of the solution is lowered, precipitation is likely to occur, and a composition for producing a supported catalyst having a high thermal decomposition temperature of 220 ° C. or higher with high stability against ammonia water cannot be obtained. On the other hand, when the amount exceeds 5.0 times, the reduction reaction proceeds and a reduced product is deposited in the solution.

The reaction temperature is 70 to 95 ° C, preferably 80 to 90 ° C, more preferably 85 to 90 ° C.
When the temperature is lower than 70 ° C., the stability of the solution decreases, precipitates are easily generated, and a composition for producing a supported catalyst having a high thermal decomposition temperature of 220 ° C. or higher with respect to aqueous ammonia cannot be obtained. On the other hand, when the temperature exceeds 95 ° C., the reduction reaction proceeds and a reduced product is deposited in the solution.

  The reaction time is not particularly limited as long as the platinum compound reacts with the ethanolamine compound and the thermal decomposition temperature is changed to a state of 220 ° C. or higher, but is preferably 2 hours or longer, more preferably the reaction surface and 2 to 4 hours is appropriate from the viewpoint of workability.

The supported catalyst can be produced, for example, as follows using the present invention.
First, aqueous ammonia is added as a stabilizer to the composition for producing a supported catalyst of the present invention. Next, this solution is mixed with a carrier such as alumina powder to prepare a slurry. The slurry is dried and calcined to obtain a supported catalyst.

(Example 1)
To 1 mol of hexahydroxoplatinic acid, 3-fold equivalent of monoethanolamine was added at room temperature and stirred at 90 ° C. for 3 hours to obtain a reaction product, a composition for producing a supported catalyst.

(Examples 2 to 3, Comparative Examples 1 to 5)
In the same manner as in Example 1, compositions for producing supported catalysts in Examples 2-3 and Comparative Examples 1-5 in Table 1 were obtained with the compositions and conditions described in Table 1.

  [1] Thermal decomposition temperature [2] Stability with respect to storage period [3] Stability with respect to aqueous ammonia was confirmed for the obtained composition for producing supported catalyst. The confirmed results are shown in Table 1.

  The above tests [1], [2], and [3] were performed by the following methods.

(Measurement of thermal decomposition temperature)
The thermal decomposition temperature of the platinum compound in the supported catalyst production composition was measured by a differential thermal analyzer. The temperature was raised to 400 ° C., and the temperature at the top of the exothermic peak of the DTA curve was defined as the thermal decomposition temperature. The results are shown in Table 1.

(Evaluation of stability against storage period)
The stability of the platinum compound in the composition for producing a supported catalyst of each example and comparative example was evaluated. Each supported catalyst production composition was allowed to stand at 30 ° C. for 1 month. Thereafter, it was visually confirmed whether precipitation occurred. The results are shown in Table 1.

(Stability test against ammonia water)
Using the supported catalyst production compositions of each Example and Comparative Example, a stability test against ammonia water was performed. 0.2 cm ³ of 28% aqueous ammonia was added to 5 cm ^{3 of} each supported catalyst production composition, stirred for 30 minutes, and allowed to stand at room temperature for 20 hours. The precipitate deposited in the solution was filtered off, and the platinum content contained in the precipitate was measured with an ICP emission spectrometer. The platinum deposition rate was calculated by the following formula (1). The results are shown in Table 1.

Formula (1)
Platinum precipitation rate (%) = {Platinum amount in precipitate (g) / Platinum amount in noble metal compound solution (g)} × 100

Claims (3)

  A composition used for the production of a supported catalyst, which consists of a reaction product obtained by reacting a platinum compound and an ethanolamine compound in an amount of 2.5 to 5.0 times the molar amount of platinum in an aqueous solution at 70 to 95 ° C. A composition for producing a supported catalyst, wherein the temperature is 220 ° C or higher.   The composition for producing a supported catalyst according to claim 1, wherein the platinum compound is hexahydroxoplatinic acid and the ethanolamine compound is monoethanolamine.   A process for producing a composition for producing a supported catalyst, comprising mixing a platinum compound and an ethanolamine compound in an amount of 2.5 to 5.0 times the molar amount of platinum in an aqueous solution at room temperature and then reacting at 70 to 95 ° C for 2 hours or more.