JPS6329587B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a catalyst carrier having high strength and excellent attrition resistance. It is already known that a catalyst in which a catalyst component such as platinum is supported on a catalyst carrier such as alumina is used for purifying exhaust gas from automobiles. This catalyst not only functions as a catalyst, but also has to operate in a steady state for at least a certain period of time after the engine starts, and must also withstand vibrations during driving. Warm-up properties and abrasion resistance are required, and these requirements are usually achieved by a catalyst carrier. Alumina catalyst carriers are most commonly used as they have excellent catalytic properties, and the conventional manufacturing method is to partially dehydrate aluminum hydroxide obtained by the Bayer process, crush it, and granulate it. It was common practice to cure the material under saturated steam pressure, dry it, and fire it. However, in the alumina catalyst carrier obtained by the above method, it is necessary to increase the density in order to ensure strength above a certain level, which has the disadvantage that the weight of the catalyst increases.
There was also the problem that as the density increased, the warm-up performance of the catalyst bed deteriorated significantly. As a method to solve the above-mentioned drawbacks, the present inventors previously proposed a method in which the strength of the carrier is improved by curing the granulated material in an aqueous solution of caustic alkali or an aqueous solution of sodium aluminate. . However, although this method improves the strength, it does not result in a significant improvement in wear resistance. The present invention solves the above-mentioned drawbacks and provides a method for producing a catalyst carrier having high specific strength and excellent wear resistance. The present invention partially dehydrates aluminum hydroxide,
This compound may be used as it is or pulverized, mixed with appropriate additives if necessary, granulated, and then calcined. The granulated product is cured in an aqueous sodium aluminate solution, then dried and calcined. The present invention relates to a method for producing a catalyst carrier characterized by the following. In the present invention, suitable additives include, for example, organic compounds such as cellulose, CeO ₂ , MgO,
Fe ₂ O ₃ , MnO ₂ , Mn ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ , CuO,
Examples include various oxides such as CoO, Co ₂ O ₃ and NiO. In addition, the baking temperature is not particularly limited, but is 150℃.
The above is preferred, and especially when an organic additive is mixed, it is desirable to sinter at a temperature higher than the decomposition temperature of the organic additive. The catalyst carrier produced in the present invention is used as a catalyst by supporting noble metals such as platinum, palladium, and rhodium, as well as catalytic metals such as iron, copper, and nickel. The following examples illustrate the invention in more detail. Example 1 Aluminum hydroxide produced by the Bayer process and having an average particle size of 40 μm was partially dehydrated and then ground to an average particle size of 12 μm to produce alumina granules with a particle size of 2.8 to 4.0 mmφ using a dish granulator. The alumina granules were calcined at various temperatures from 80 to 500° C. for 5 hours, and then cured in a 10% NaAlO ₂ aqueous solution. This curing is carried out for 10
I spent time. Each cured alumina granule is
By washing with water to remove adhering or solid-dissolved Na ⁺ , the amount of Na in the carrier was reduced to 0.3% or less as Na ₂ O. Thereafter, the alumina granules were dried at 150°C for 3 hours and fired at 800°C for 3 hours to activate them again. The activated alumina granules obtained as described above were examined for crushing strength, bulk density, and attrition resistance using the methods described below. 1. Method for Measuring Compressive Strength The strength of the activated alumina granules was measured using a Kiya hardness tester, and the average value of 20 grains was taken as the crushing strength. 2. Bulk Density Measuring Method Approximately 40 c.c. of activated alumina granules were filled into a 100 c.c. graduated cylinder, and the bulk density was calculated from the volume and weight. 3. Measuring method of attrition rate The attrition rate was measured using the attrition tester shown in FIG. First, the activated alumina granules tested
After baking cc at 550℃ for about 1 hour, measure the weight.
The weight at this time was defined as _W1 . Next, this sample was prepared with a maximum diameter of 130 mm, a minimum diameter of 20 mm, and a cone height of 230 mm.
The activated alumina granules in the attrition tube 3 are placed in the attrition tube 3 of the attrition tester shown in FIG. Atraction exercise was performed for 5 minutes. Note that the air blown into the attrition cylinder 3 is discharged to the outside of the system from the upper metal mesh cap 2. Thereafter, the activated alumina granules were taken out from the attrition cylinder 3 and fired at 550° C. for 1 hour, and their weight was measured. Using this weight as W ₂ , the attrition rate was calculated using the following formula. Attrition rate (%) = W ₁ - W ₂ /W ₁ × 100 As a comparative example, the granulated alumina granules were calcined and then cured in water (Comparative Example 1) instead of in an aqueous NaAlO ₂ solution. and 〓In NaAlO ₂ aqueous solution without baking (Comparative Example 2)
Alternatively, the characteristics of the alumina granules cured in water (Comparative Example 3) were also measured in the same manner. FIG. 2 is a graph showing the relationship between the calcination temperature and attrition rate of alumina granules before curing.
Open circles indicate Comparative Example 2, and open triangles indicate Comparative Example 3. Figure 3 is a graph showing the relationship between calcination temperature and crushing strength of alumina granules before curing.
Figure 4 is a graph showing the relationship between the sintering temperature and bulk density of alumina granules before curing.
Lines and B lines, white circles, and white triangles indicate the same things as in FIG. 2. As is clear from these figures, according to the present invention, the strength and attrition resistance of the alumina granules are significantly improved, and the bulk density increases only slightly. Example 2 Aluminum hydroxide with an average particle size of 40μ produced by the Bayer method was partially dehydrated and then ground to an average particle size of 12μ. Next, 75% by weight of this alumina powder and 25% by weight of crystalline cellulose were mixed, and this powder was granulated into alumina granules having a particle size of 2.8 to 4.0 mmφ using a dish granulator. A test similar to that in Example 1 was conducted using the above alumina granules. In addition, as Comparative Examples 4, 5, and 6, the above alumina granules were used as Comparative Examples 1, 5, and 6, respectively.
The test was conducted in the same manner as in 2 and 3. The results are shown in Figures 5, 6, and 7. Line A in each figure shows the one according to the present invention (Example 2), and line B, white circles, and white triangles show Comparative Examples 4, 5, and 6, respectively. Example 3 Aluminum hydroxide with an average particle size of 40 μm produced by the Bayer method was partially dehydrated and then ground to an average particle size of 12 μm. Next, 72% by weight of this alumina powder, 20% by weight of crystalline cellulose, and 8% by weight of cerium oxide (CeO ₂ ) with an average particle size of 1μ are mixed, and this powder is pulverized using a dish-type granulator with a particle size of 2.8 to 4.0 mmφ. It was granulated into alumina granules. After baking the above granules at 400℃ for 10 hours, 10%
Carrier A (Example 3) was cured in NaAlO ₂ aqueous solution; Carrier B was cured in water after baking in the same manner; Carrier C was cured in water without baking; Carrier D (Comparative Example 7) was obtained by curing in a 10% NaAlO ₂ aqueous solution without
And so. The curing conditions were all 160°C for 5 hours. Further, the carrier properties of each carrier after curing were investigated in the same manner as in Example 1. The results are shown in Table 1.

[Table] Example 4 Aluminum hydroxide having an average particle size of 1 μm produced by the Bayer method was partially dehydrated. This alumina powder 75
% by weight and 25% by weight of crystalline cellulose were mixed, and this powder was granulated into granules having a particle size of 2.8 to 4.0 mmφ using a dish granulator. After baking the above granules at 400℃ for 10 hours,
% NaAlO ₂ aqueous solution (Example 4), Carrier F was cured in water after being baked in the same way, Carrier G was cured in water without baking, and Carrier G was cured in water without baking. Carrier H (Comparative Example 8) was obtained by curing in a 5% NaAlO ₂ aqueous solution without
And so. The curing conditions were all 160°C for 10 hours. Further, the carrier properties of each carrier after curing were investigated in the same manner as in Example 1. The results are shown in Table 2.

[Table] Example 5 After partially dehydrating aluminum hydroxide with an average particle size of 40μ manufactured by the Bayer method, it was crushed to obtain an average particle size of 40 μm.
It was made into 12μ alumina powder. This powder and magnesium oxide (MgO) were mixed at a ratio of Al ₂ O ₃ :MgO = 1:1 (mole ratio), and the particle size was 2.8 using a dish granulator.
Granules with a diameter of ~4.0 mm were produced. 15% after baking the above granules at 500℃ for 5 hours
Carrier K (Example 5) was cured in NaAlO ₂ aqueous solution, Carrier L was cured in water after baking, Carrier M was cured without baking, and Carrier M was cured in water without baking. Carrier N (Comparative Example 9) was prepared by curing it in a 15% NaAlO ₂ aqueous solution.
The curing conditions were all 120°C for 20 hours. Further, the carrier properties of each carrier after curing were investigated in the same manner as in Example 1. The results are shown in Table 3.

[Table] As described above, according to the present invention, it is possible to produce a catalyst carrier which has greater strength and excellent wear resistance than catalyst carriers produced by conventional production processes. Therefore, if they have the same strength and wear resistance,
Since the density can be lower than that of conventional catalyst carriers, it is very advantageous in terms of weight reduction and warm-up performance, and the present invention has extremely great value. The reason why the relationship between the calcination temperature and the crushing strength of the carrier before curing is different between Example 1 and Example 2 is because cellulose is present in the carrier in Example 2, and when the calcination temperature is low, This is probably because cellulose remains in the carrier, reducing the curing effect.
On the other hand, at high temperatures, the cellulose in the carrier is burned and removed during sintering, which seems to increase the curing effect. Further, although only the case where cellulose is used as the organic additive is shown, it goes without saying that organic additives other than cellulose can be used.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway view of the attrition rate tester, and Figures 2, 3, and 4 show the calcination temperature of the catalyst carriers obtained in Example 1 and Comparative Examples 1, 2, and 3, respectively. Graphs showing the relationship between attrition rate, crushing strength, and bulk density, Figures 5, 6, and 7 show the attrition versus calcination temperature of the catalyst carriers obtained in Example 2 and Comparative Examples 4, 5, and 6, respectively. 2 is a graph showing the relationship between modulus, crushing strength, and bulk density. In the figure, 1...nozzle, 2...wire mesh cap, 3...attrition cylinder, 4...granular material.

Claims (1)

[Claims] 1. A catalyst characterized in that aluminum hydroxide is partially dehydrated, the compound is left as is or pulverized, granulated and calcined, the granulated product is cured in an aqueous sodium aluminate solution, and then dried and calcined. Method for manufacturing carrier.