JPS6054099B2 - Preparation method of platinum catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing and activating a noble metal catalyst that completely oxidizes and decomposes odor-bearing compounds in exhaust gas for purification of exhaust gas from industrial plants, automobiles, etc., particularly for deodorization. It is something.

Examples of odorous compounds include oxygen-containing compounds, nitrogen-containing compounds, sulfur-containing compounds, etc., and specific examples thereof include alcohols, aldehydes, ketones, amines, and mercaptans. Noble metal catalysts, such as platinum, rhodium, palladium, or other metals or salts supported on silica, alumina, or other inorganic inert carriers, are generally used as typical catalysts for completely oxidizing harmful components in automobile exhaust gas. Are known. These catalysts are required to exhibit activity quickly and to be able to exhibit the desired activity even at relatively low temperatures, and as with normal solid catalysts, there are various factors such as the catalytic active components to be used and the type of support. In addition to research on catalyst preparation methods, especially activation methods are important sections WW: 11-call
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Since chloroplatinic acid is used as a platinum compound as a town charge, very insufficient results have been obtained regarding the low-temperature activity of the catalyst. Platinum catalysts using chloroplatinic acid as a starting material are activated by either reduction calcination with hydrogen or air calcination, but a method in which water vapor is allowed to coexist has been proposed as an improved method. For example, the special public
-1067, a method of firing at 250 to 595°C in air containing about 1.5% by weight of water, and JP-A-49-12
9692, heated to 500 to 9°C with a reducing gas such as hydrogen and carbon monoxide, an inert gas such as nitrogen, helium, and argon, and an oxidizing gas such as air, in the coexistence of 3% or more water vapor by volume. There are known methods for doing so.

The present inventors discovered that the activity of the catalyst could be improved by 100% steam treatment at 500°C by comparing untreated platinum catalysts with single treatments of hydrogen, oxygen, and steam, which led to the present invention. Reached. The present inventor used n-butane, which is generally used in this type of test and is difficult to undergo an oxidative decomposition reaction, as a standard substance for the catalyst performance evaluation test.

That is, by oxidizing n-butane contained in air at a concentration of 100 pμm, the temperature of steam treatment (in this case, hydrogen reduction was performed after 2 hours) and the temperature required for 50% oxidation, that is,
7T5. As a result of investigating the relationship between oxidation activity and
The activity peaked at 550°C, and as the temperature was raised above this level, the activity actually decreased. The highest activity was at 550°C, T5O
% was 196°C. (See Table 1) Incidentally, T.
O% is 286℃, low temperature long time treatment (170℃, 4 hours)
The catalyst after subsequent hydrogen reduction had T5O%=21rc. The inventor presumed that the chlorine ions remaining in the platinum catalyst affected the activity, and confirmed the correspondence between the activity and the chlorine ion removal rate in the above experiment (see Table 1). ]1 30 cc of catalyst containing 0.2% platinum on alumina carrier was used.

Hydrogen reduction after treatment for 2 hours with 2100% steam and SV: 1000.

The trichloride ion removal rate (%) was determined based on the calculated value of chloroplatinic acid.

Although the catalyst used in the above experiment contained 0.2% platinum, it was produced in a factory rather than in a laboratory. The prototype catalyst was treated with hot water to remove % of chlorine ions)
The n-butane oxidation activity was 2 degrees Celsius;
When steam-treated for 3 hours, the temperature increased to 248°C.

In contrast, dinitrodiamine platinum, which does not contain chloride ions, was prepared as a raw material. ``When we attempted similar experiments with catalysts, we found that they were completely ineffective.In the case of dinitrodiamine, the platinum penetrates into the carrier, so there is no dispersion effect.

This indicates that the effect of steam treatment on a platinum catalyst free of chloride ions is unique to the case where chloroplatinic acid is used as a raw material. Factors that increase the reaction activity of the supported platinum catalyst can be considered to be chemical or physical, and the removal of chlorine ions by steam treatment corresponds to the former. Physically, this is thought to be an increase in the platinum surface area; in fact, observation using an electron microscope at 1x magnification revealed that before steam treatment, the platinum particles had an average size of angstroms, but after steam treatment, they were so fine that they were difficult to distinguish. , it was recognized that the thickness was about 25 angstroms. As described above, the reason why the activity of the platinum catalyst is significantly increased by steam treatment is due to two factors: the removal of chlorine ions from the catalyst surface and the miniaturization of platinum particles. Is the oxidation activity high due to the highly oxidized state Ptδ8-C1δ--AI in which chlorine ions have not been removed? -A
In order to bring about the state of 1, we came up with the idea of adding ions with low electronegativity, ie, alkali metal ions and alkaline earth metal ions, and completed the present invention.

The catalyst was prepared by immersing an alumina support in an aqueous solution containing chloroplatinic acid and various chlorides at a metal atomic ratio of 1:1, drying it at 12CfC for 2 hours, steaming it at 5000C for 4 hours, and further drying it at 200CfC for 4 hours.
C. for 3 hours, and as shown in Table 2, the removal rate of chlorine ions and n-butane oxidation activity by steam treatment were sufficient except for the R-Ca system.
[Note] The chloride ion removal rate (%) was determined based on the calculated values of chloroplatinic acid and chloride. On the other hand, when caustic potassium or potassium chloride was added to the catalyst which had been steam-treated in advance, the oxidation activity was 23CfC1245°C, respectively, which actually decreased the activity.

Example 1 50 cc of an aqueous solution containing chloroplatinic acid containing 0.135y of platinum and 0.05y of potassium chloride was placed in a beaker.
This was pre-dried at 120℃ for 2 hours.
100ml (67y) of spherical activated alumina with a particle size of Hydrogen reduction was performed.

The steam treatment method was performed as follows. A steam treatment tube in a tubular electric furnace was filled with 30 ml of the above untreated catalyst,
After purging the inside of the tube with nitrogen gas in a commercially available cylinder, the temperature was raised.
After the temperature reaches 150-200℃, pure water is started to be injected, and it is vaporized in the preheating section at the entrance of the processing tube to become 100% steam.
It was flowed into the catalyst layer at VlOOOO. 4 when it reaches 500℃
The introduction was continued for a certain period of time, and after cooling, 3 liters of hydrogen reduction was carried out at 200°C.

In the activity test, 30 mt of catalyst was packed in a 20 Tfnφ quartz tube, and the gas in a commercially available 1% n-butane (diluted with nitrogen) cylinder was diluted with air to make 100 ppm n-butane.
Run with O.

After flowing at 400'C for 2 hours, the temperature was lowered, and when a steady state was reached at each temperature, the concentrations at the inlet and outlet were analyzed using a gas chromatograph, and the conversion rates were 30%, 50%, and 70%.
The temperature reached was measured.

Examples 2 to 5 In Example 1, calcium chloride dihydrate 0.12y1 magnesium chloride hexahydrate 0
．． 15y1 Sodium chloride 0.04y1 Barium chloride 2
Exactly the same treatments and tests were carried out except that 0.19y of hydrate was used.

Comparative Example 6 The same treatment and test as in Example 1 were carried out except that potassium chloride was omitted and the steam treatment time was shortened to 2 hours.

Comparative Example 2 A treatment test was carried out in exactly the same manner as in Example 1, except that potassium chloride was omitted, and after catalyst preparation, the product was calcined in air at 500° C. for 2 hours instead of steam treatment.

Comparative Example 3 The same treatment and test as in Example 1 were carried out, except that a platinum catalyst that had been previously subjected to a steam treatment at 500° C. for 4 hours was immersed in an aqueous potassium chloride solution.

Claims (1)

[Claims] 1 Platinum for exhaust gas purification for the purpose of deodorization, characterized in that an alumina carrier is immersed in an aqueous solution of chloroplatinic acid to which a type of alkali metal chloride is added, dried, and then treated with steam that does not contain other gases. Method for producing a containing oxidation catalyst.