JPS6021774B2 - Method for manufacturing oxidation catalyst - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing an oxidation catalyst.

Because platinum or palladium has high oxidation activity,
Oxidation catalysts based on them are manufactured.

However, since these active materials are expensive, a method of supporting the active metal on a carrier is mainly used. Methods for producing catalysts using such mortar include the immersion method and the coating method.

The impregnating method is a method in which a carrier is immersed in an active metal solution, and the coating method is a method in which an active metal solution is dropped onto a heated carrier to coat it, thereby causing each carrier to support an active metal. After drying, the carrier impregnated or coated with the active metal component is calcined at around 500°C under air circulation or reduced with hydrogen at around 500°C to obtain a catalyst. If the carrier is not porous, fine particles of porous alumina, silica, silica/alumina, etc. are attached to the carrier to form a porous part on the outer surface, and the active metal is damaged on the carrier. It is designed to last. In the production method of such a catalyst, the preparation of the carrier and the characteristics of supporting the active metal component in the carrier have a remarkable influence on the oxidation activity, and various ideas have been made in this regard, but in any case Also, complex preparation conditions are required.

An object of the present invention is to provide a method for producing an oxidation catalyst that uses a noble metal substance as an active ingredient and has excellent low-temperature activity and durable activity.

The method for producing an oxidation catalyst according to the present invention includes a honeycomb carrier made of cordierite or mullite, a Q-alumina pellet carrier, etc., on which porous refractory fine particles such as alumina, silica, magnesia, zirconia, and chromia are attached;
Alternatively, an oxidation catalyst is produced by supporting an active noble metal substance on a carrier to which these fine particles are not attached.

Here, as the active noble metal, those mainly composed of platinum or palladium, and those to which other metals are added as co-catalysts are used. In the above method for producing an oxidation catalyst, the drying step after impregnating or coating the carrier with the active noble metal component is important in determining the catalyst activity. In order to effectively utilize the active noble metal component, it is important to uniformly support the active noble metal on the carrier.
It is conceivable that if they are uniformly dispersed and supported, the activity will be improved compared to when they are supported in agglomerated form even if the amount of metal supported is the same. Therefore, the inventors investigated various conditions for the drying process and found that these conditions had a particularly large effect on the uniform dispersion lamp, and at the same time influenced the initial activity and durable activity of the catalyst. Now adjusting the catalyst,
Regarding the uniform support of active metals, it is necessary to consider both 1. Uniformity on the outer surface of the catalyst carrier. 2. Uniformity taking into account the inside of the catalyst carrier. In some cases, uniformity on the surface can be easily ensured.

However, when considering the inside of the carrier, the conventional method results in non-uniform distribution. That is, the active metal may collect on the outer surface or, in some cases, in the center of the catalyst support. Here, the uniformity of dispersion of the active ingredient within the pores of the carrier is affected by the drying process of the catalyst after impregnation. That is, when a slight temperature difference occurs in the carrier due to heating during drying, the noble metal diffuses toward the higher temperature, that is, the higher evaporation rate, and coagulates in that region. As a result, an uneven distribution will be exhibited. Further, possible causes of deterioration of catalyst activity include 1) half-melted aggregation of the active substance under the reaction conditions, and 2) damage caused by constituent components and products in the reactants.

It is necessary to support the noble metal as uniformly as possible on the carrier. 1. In order to prevent the molten agglomeration of the catalyst, generally the metal present on the outer surface of the catalyst sequentially causes agglomeration by being subjected to thermal history.

In this case, the higher the concentration of the active metal present on the outer surface and the worse the uniform dispersion, the more remarkable the deterioration of the catalyst activity. In order to maintain catalytic activity at a certain level for a long time, that is, to create a long-life catalyst, it is necessary to
It is important to uniformly support the active metal from the outer surface to the inside of the carrier. This is because when the activity of the active metal on the outer surface deteriorates during use of the catalyst, the active metal inside which still has sufficient active metals diffuses from the inside to the outer surface of the catalyst. For this reason, how the active metal can be carried into the interior of the catalyst body greatly influences the durability of the catalyst activity. In the present invention, in order to solve this problem, a hydrophilic low-boiling organic compound is added to the active metal solution in advance to speed up the drying of the active metal solution in the drying process, thereby uniformly distributing the active noble metal into the carrier. Dispersion can be achieved. Examples of organic compounds include methanol, lso-pro/gnol, ethanol, acetone, tetrahydrofuran, triethylamine, and allylamine. The amount of these organic compounds added is 5 to 5 mol% of the active metal solution. The amount added was 50 (vol.
%) or higher, the drying speed will slow down, but the evaporation of the organic compound into the air and the uniform loading of the active noble metal on the carrier will be improved, but on the other hand, the amount supported will be small and the activity will be reduced, and conversely, it will be better to have no additives. This is problematic because it is lower than in the case of . According to the method of the present invention, it is possible to prepare a catalyst in which active metals are uniformly dispersed, and the effect is exhibited in improving initial activity and, in particular, improving durable activity.

The present invention will be explained in detail below using Examples and Comparative Examples.

Example 1 ■ A cordierite honeycomb carrier 200 x 3 sides was immersed in alumina sol (Nissan Chemical Alumina Sol 200) for 1 hour, and then taken out and dried at 120:00 for 2 hours.

Then, the mixture was fired for 2 hours at 500 °C under air circulation to obtain a porous carrier. Next, (1) this carrier is soaked for 1 hour at room temperature in a solution prepared by adding 20% of ethanol to 80% of palladium chloride aqueous solution containing 2% of palladium.
Next, ■ dry this in a hot air dryer, and then dry it in a dryer again.
After drying at 20° C. for 2 hours, the mixture was calcined at 500°C for 2 hours under air circulation to obtain a palladium catalyst. Example 2 (1) Three Q alumina pellets were soaked at room temperature for 1 hour in a solution prepared by adding 10 parts methanol to 90 parts aqueous chloroplatinic acid solution containing 1.5% platinum.

Next, (1) this was dried in a hot air dryer, further dried at 120° C. for 2 hours, and then reduced with hydrogen at 50 pi for 2 hours to obtain a platinum catalyst. Example 1 A carrier prepared in the same manner as in Example 1 was mixed with 100% palladium containing 1.6% palladium.
It was immersed in an aqueous solution of palladium chloride at room temperature for 1 hour.

Thereafter, drying and calcination were performed in the same manner as in Example 1 to obtain a palladium catalyst. Comparative Example 2 Q to 100M chloroplatinic acid aqueous solution containing 1.4% platinum
Soak 3 ribs of alumina pellets ◇ at room temperature for 1 hour.

Thereafter, drying and calcination were performed in the same manner as in Example 2 to obtain a platinum catalyst. The catalysts obtained in Examples and Comparative Examples were filled into a quartz reaction tube with an inner diameter of 2 mm, and an oxidation activity test was carried out.

The reaction gas composition was as shown in Table 1, and the gas hourly space velocity (SV) was 2000 r-1. The reaction temperature was determined by the gas temperature before the inlet of the packed catalyst layer as shown in Table 1.

The activity test results are shown in Table 2. Activity test is 250oo,
At a reaction temperature of 350 qo, the conversion rates of carbon monoxide and propane were calculated from the gas concentrations before and after the reaction. Similarly, the catalysts obtained in Examples and Comparative Examples were heat-treated at 900° C. for 5 hours and tested in the same manner. Table 3 shows the results. Table 2 Activity test results Table 3 Activity test results (after heating at 900°C for 50 hours) Example 3 Active noble metal in the Q alumina catalyst carrier when the mixing ratio of the noble metal solution and methanol shown in Example 2 was changed The state of the carrier was investigated.

As shown in FIG. 1, the distribution of noble metals was examined on the cut surface using an EPMA (Electron Probe X-ray Micro Analyzer). The loading state on the AMB line shown in the figure was investigated, and the results are shown in FIG. Example 4 Palladium loss weight was measured for a palladium-supported catalyst obtained in the same manner as in Example 1 except that the ethanol addition ratio was changed.

The results are shown in FIG. In addition, the oxidation activity of the palladium-supported catalyst was measured, and the results are shown in Table 4.
Table 4 Furthermore, the oxidation activity of the samples heat-treated at 900 am for 5 q hours was measured in the same manner, and the results are shown in Table 15.

Table 5 Example 5 The amount of supported platinum was measured for the platinum supported catalyst obtained in the same manner as in Example 2 except that the methanol addition ratio was varied.

The results are shown in FIG. Further, the oxidation activity of the platinum supported catalyst was measured, and the results are shown in Table 16. Table 6 Furthermore, the oxidation activity of the samples heat-treated at 900° C. for 5 q hours was measured in the same manner, and the results are shown in Table-7.

Table 7 From the above 4 to 7, it can be seen that the active noble metal raccoon mochi catalyst prepared with the addition ratio of the hydrophilic low-boiling organic compound of 5 to 5 mol% has good durability activity.

The oxidation catalyst according to the method of the present invention has a propane acid Q tongue property at 250 qo that is approximately twice as high as that of the conventional catalyst, and there is almost no decrease in activity at 250 qo even after heating at 900° C. for 5 q hours. These are made by immersing a carrier in a solution containing a low-boiling point organic compound in a noble metal solution, and then heating and dispersing the low-boiling point organic compound during drying. Uniform dispersion is achieved by
As a result, good results were obtained in the activity test.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a measurement sample for measuring the palladium-supported state of the palladium-supported catalyst in Example 3, and FIG. 2 shows the measurement results of the palladium-supported state of the catalyst in Example 3. 3 is a graph showing the relationship between the amount of ethanol added and the amount of palladium supported in the palladium-supported catalyst of Example 3, and FIG. 4 is a graph showing the relationship between the amount of methanol added and the amount of platinum supported in the platinum-supported catalyst of Example 6. This is a graph showing. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In an oxidation catalyst in which an active noble metal is supported on a carrier made of cordierite honeycomb, mullite honeycomb, alpha alumina pellets, etc., in order to support the active noble metal, a hydrophilic low-boiling point organic A method for producing an oxidation catalyst, which comprises adding a compound in an amount of 5 to 50 vol%.