JP5378659B2 - Precious metal loading method - Google Patents

Description

The present invention relates to a noble metal-supported how to support a noble metal to the substrate in the preparation of the catalyst.

  As an exhaust gas purifying catalyst, an inorganic oxide is provided with a plurality of holes having an opening at at least one end, the hole communicating with the other end, and a surface of the hole formed in the base And a catalyst component such as a noble metal supported on the coat layer.

Conventionally, when manufacturing the above-described exhaust gas purifying catalyst, a noble metal is supported on the coat layer by immersing a base material (support) having the coat layer in a tank of the noble metal solution (Patent Document 1). reference).
JP-A-9-141092

  However, according to the above-mentioned method of immersing the base material, the amount of the noble metal to be supported is determined by the concentration of the noble metal solution, the immersion time, etc. Since the amount of the noble metal supported on the coating layer changes, there is a problem that it is difficult to support the target amount of the noble metal, and the variation in the amount of the noble metal supported by the base material becomes large.

The present invention has been made in view of such problems, we propose a noble metal-supported how to reduce variations of the support amount of precious metal to the substrate.

The noble metal supporting method according to claim 1, which is made to solve the above-described problem, includes a plurality of holes having openings at at least one end A, and the holes communicate with the other end B. a noble metal-supported method of supporting the noble metal, the saw including a noble metal and a thickening agent, a viscosity at a shear rate of 4 sec ^-1 is a predetermined amount supplied noble metal solution is 1000~7000mPa · s to the end a, the It is a noble metal carrying method characterized by having a first extension step of drawing the noble metal solution supplied to the end A from the end B to extend the noble metal solution to the surface of the hole.

  According to such a noble metal supporting method, the noble metal solution containing the noble metal supplied to the end portion A of the base material is sucked into the end portion B, so that the noble metal solution is extended on the surface of the hole. When the noble metal solution remains, it is discharged from the end B. Therefore, the amount of noble metal supported on the base material after the first extension step described above is the amount obtained by subtracting the amount of noble metal discharged at the end B from the amount of noble metal supplied to the end A (if not discharged, Amount supplied to the end A).

  Therefore, in such a noble metal loading method, the amount of noble metal supported on the base material can be easily adjusted without being affected by the adsorption rate in the coating layer on the surface of the hole, so that noble metal loading between lots is possible. Variation in the amount can be reduced.

Moreover, since it is difficult to be influenced by the adsorption rate, it is possible to reduce variation in the amount of the noble metal supported between a plurality of holes in the same substrate. Therefore, since the supplied noble metal is distributed almost uniformly in each hole, even when it is desired to carry a predetermined amount or more of noble metal in all the holes, it is not necessary to supply the noble metal solution to the end A excessively. The amount of discharge from the end B does not increase.
Also, according to such a noble metal loading method, after the noble metal solution supplied at the end A and the end B is sucked, the noble metal solution extended on the surface of the hole of the base material flows and drips because the viscosity is too low. It is possible to prevent the falling precious metal solution from being accumulated on the surface of the hole and closing the hole. Furthermore, since the viscosity of the noble metal solution is high, the dispersion of the noble metal contained in the noble metal solution is improved, and the movement of the noble metal in the pores after extending to the base material is suppressed. Variations within the substrate can also be reduced.

  In the first extending step, the timing for sucking the noble metal solution supplied to the end A to the end B is not particularly limited. For example, suction may be performed at the same time when the noble metal solution is supplied to the end A, or suction may be performed after a predetermined amount of the noble metal solution is supplied to the end A.

  In addition, the base material here should just be used as a base material of a catalyst. For example, a honeycomb-shaped monolith substrate made of a heat-resistant material such as ceramics and having a plurality of axially formed through-holes, or both ends in the axial direction of the substrate from each end to the other end A plurality of holes extending toward the part, and a filter base material in which the holes communicate with each other through the pores formed on the side walls of the holes, or a flat plate and corrugated plate having a thickness of several tens of μm using a heat-resistant alloy The metal base material etc. which are formed by laminating | stacking alternately and winding are considered.

  The noble metal solution referred to here includes a solution in which a noble metal is dissolved in a solvent by forming a complex, or a solution in which fine particles of a noble metal or a noble metal compound are mixed in a solvent.

  By the way, the noble metal supporting method described in claim 1 may be a method as described in claim 2. After the method of claim 1, a predetermined amount of a noble metal solution containing a noble metal and a thickener is supplied to the end B, and the noble metal solution supplied to the end B is sucked from the end A. And a noble metal supporting method having a second extension step of extending the noble metal solution on the surface of the hole.

  According to such a noble metal loading method, after a predetermined amount of the noble metal solution is extended from the end A to the surface of the hole of the base material in the first extension step, the noble metal solution is also applied from the end B in the second extension step. It can be extended to the surface of the hole. In addition, the noble metal solution can be extended and overlapped on the portion where the noble metal solution is extended in the first extension step, in the second extension step.

  Further, in the noble metal loading method according to claim 2, the noble metal solutions supplied to the end A and the end B may be noble metal solutions each containing the same noble metal, but as in claim 3, The noble metal solution extended on the surface of the hole in the first extension step and the noble metal solution extended on the surface of the hole in the second extension step contain different noble metals, respectively. Also good.

  According to such a noble metal supporting method, different noble metal solutions can be extended from the respective end portions to the surface of the hole of the base material, so that different noble metals are supported on the end A side and the end B side. Can do. Further, the length and length of the noble metal solution extending from each end of the hole of the substrate can be adjusted by adjusting the concentration and amount of the noble metal and the thickener in the noble metal solution supplied to each end. Therefore, it is possible to adjust the length in which the noble metal is supported from each end. Further, different noble metal solutions can be extended in the second extension step on the portion where the noble metal solution has been extended in the first extension step.

By the way, in the above-mentioned noble metal supporting method according to claims 1 to 3, a noble metal solution having a viscosity of 100 to 300 mPa · s at a shear rate of 380 sec ⁻¹ as described in claim 4 is used. May be.

  According to such a noble metal loading method, when the noble metal solution supplied at the end A and the end B is sucked, the viscosity is too low, so that a lot of the noble metal solution is discharged by suction, Appropriate suction can be performed without causing problems such as the precious metal solution not being sufficiently extended on the surface of the pores of the substrate because it is too high.

Moreover, in the noble metal carrying | support method of Claim 1 to Claim 4 mentioned above, as described in Claim 5 , pH of the said noble metal solution is good also as 2-10.
According to such a noble metal loading method, even if the viscosity of the noble metal solution is adjusted and left to stand for a long time, the change in viscosity is small, so that it is possible to carry out an appropriate noble metal loading operation even immediately after the noble metal solution is prepared. .

By the way, in the noble metal supporting method according to any one of claims 1 to 5 , the noble metal contained in the noble metal solution is any one or more of platinum, palladium, and rhodium as described in claim 6. You may make it be.

According to such a noble metal supporting method, one or more of platinum, palladium, and rhodium can be supported on the base material .

Embodiments of the present invention will be described using examples.
[Example 1]
(Precious metal carrier)
A noble metal carrying device 1 according to the first embodiment will be described with reference to FIG.

  The noble metal support device 1 includes a holding member 30 that holds a predetermined amount of the noble metal complex solution 10 at one end 24 of the honeycomb-shaped monolith substrate 20, and the noble metal complex solution 10 at the other end of the monolith substrate 20. A suction member 40 that sucks from the portion 26 and a supply member 50 that supplies a predetermined amount of the noble metal complex solution 10 to the end portion 24.

  The monolith substrate 20 includes a plurality of cells in which through holes 22 are formed from the end 24 toward the end 26. In the first embodiment, the length of the through hole 22 (the length from the end 24 to the end 26) is 155 mm.

The holding member 30 covers the end 24 of the monolith substrate 20 and holds the noble metal complex solution 10 supplied from the supply member 50 on the end 24.
The suction member 40 includes a base material receiving portion 44 having an internal space 42, a decompression device (not shown) connected to the internal space 42 via a pipe 46, and a valve 48 that opens and closes the pipe 46. The base material receiving portion 44 has an opening into which the monolith base material 20 can be inserted. When the monolith substrate 20 is inserted into the opening, the monolith substrate 20 comes into close contact with the substrate receiving portion 44 and the side surface of the monolith substrate 20 so that the end portion 26 reaches the internal space 42.

When the valve 48 is opened in this state, the internal space 42 is depressurized, whereby the noble metal complex solution 10 held on the end 24 is sucked from the through hole 22 toward the end 26. In the present embodiment, the inside of the through hole 22 is sucked at a linear velocity of 10 to 50 m / s. In addition, in this noble metal carrying | support apparatus 1, even if each edge part 24 and 26 is replaced, it can operate similarly.
(Preparation of noble metal complex solution)
The noble metal complex solution 10 described above is obtained by adding a thickener to an aqueous solution of a platinum complex shown below.

Platinum (Pt) complex aqueous solution: Pt equivalent to 1 g Thickener: HEC (hydroxyl ethyl cellulose) 1 wt%
The viscosity of the noble metal complex solution 10 having the above composition is 100 mPa · s at a shear rate of 380 sec ⁻¹ (hereinafter “high shear rate” refers to this value), and a shear rate of 4 sec ⁻¹ (hereinafter “low shear rate” is This value is 1000 mPa · s). These viscosities were measured using a viscometer TVE-30H (manufactured by Toki Sangyo Co., Ltd.).

The thickener may be a water-soluble polymer such as carboxymethylcellulose, methylcellulose, polyvinyl alcohol, etc., instead of HEC.
(Precious metal loading method)
In Example 1, first, the monolith substrate 20 was set so that one end portion 24 of the monolith substrate 20 was covered with the holding member 30 and the other end portion 26 was inserted into the substrate receiving portion 44.

Next, a predetermined amount (corresponding to Pt 1 g) of the noble metal complex solution 10 was supplied from the supply member 50, and held on one end 24 of the monolith substrate 20 by the holding member 30.
Next, the valve 48 was opened to decompress the internal space 42, and the noble metal complex solution 10 held on the end 24 was sucked into the through hole 22. The noble metal complex solution 10 spread from the end 24 to the end 26 in the through hole 22 by suction, and a part of the noble metal complex solution 10 was discharged from the end 26.
(result)
Pt could be supported over the entire through-hole 22 (155 mm) of the cell. Moreover, Pt discharged without being supported by suction was less than 0.5% of the supply amount (less than 0.005 g of Pt).
[Example 2]
(Precious metal carrier)
In Example 2, the same noble metal supporting device 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
The noble metal complex solution 10 in Example 2 is basically the same as that in Example 1, but the amount of HEC added is 1.5 wt%. The viscosity of the noble metal complex solution 10 was 200 mPa · s at a high shear rate and 3000 mPa · s at a low shear rate.
(Precious metal loading method)
In Example 2, Pt was supported on each of the 20 monolith substrates 20 using the same noble metal loading method as in Example 1, and the variation in the amount supported between the monolith substrates 20 was examined.

In all the monolith substrates 20, the noble metal complex solution 10 spread from the end 24 to the end 26 in the through hole 22 by suction, and a part of the noble metal complex solution 10 was discharged from the end 26.
(result)
In all the monolith substrates 20, Pt could be supported over the entire through-hole 22 of the cell (155 mm). Moreover, Pt discharged without being supported by suction was less than 0.5% of the supply amount (less than 0.005 g of Pt).

Further, the value 4σ indicating the degree of variation in the amount of Pt supported in the 20 monolith substrates 20 was 2%. Here, σ is a standard deviation.
[Example 3]
(Precious metal carrier)
In Example 3, the same noble metal supporting apparatus 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
The noble metal complex solution 10 in Example 3 is basically the same as that in Example 1, but the amount of HEC added is 2 wt%. The viscosity of the noble metal complex solution 10 was 300 mPa · s at a high shear rate and 7000 mPa · s at a low shear rate.
(Precious metal loading method)
In the present Example 3, the noble metal supporting operation with respect to the monolith substrate 20 was performed using the same noble metal supporting method as in Example 1. The noble metal complex solution 10 spread from the end 24 to the end 26 in the through hole 22 by suction, and a part of the noble metal complex solution 10 was discharged from the end 26.
(result)
Pt could be supported over the entire through-hole 22 (155 mm) of the cell. Moreover, Pt discharged without being supported by suction was less than 0.5% of the supply amount (less than 0.005 g of Pt).
[Example 4]
(Precious metal carrier)
In Example 4, the same noble metal supporting device 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
In this Example 4, the same noble metal complex solution 10 as in Example 1 was used.
(Precious metal loading method)
In Example 4, first, the monolith substrate 20 was set so that one end portion 24 of the monolith substrate 20 was covered with the holding member 30 and the other end portion 26 was inserted into the substrate receiving portion 44.

Next, a predetermined amount (equivalent to 0.5 g Pt) of the noble metal complex solution 10 was supplied from the supply member 50, and was held on one end 24 of the monolith substrate 20 by the holding member 30.
Next, the valve 48 was opened to decompress the internal space 42, and the noble metal complex solution 10 was sucked into the through hole 22. The noble metal complex solution 10 spread from the end 24 in the through hole 22 to a position of 78 ± 12 mm by suction. There was no noble metal complex solution 10 discharged from the end portion 26.

Next, the monolith base material 20 was removed and, contrary to what was described above, one end portion 24 was inserted into the base material receiving portion 44 and the other end portion 26 was set so that the holding member 30 was covered. .
Next, a predetermined amount (equivalent to 0.5 g Pt) of the noble metal complex solution 10 was supplied from the supply member 50, and was held on the other end portion 26 of the monolith substrate 20 by the holding member 30.

Next, the valve 48 was opened to decompress the internal space 42, and the noble metal complex solution 10 was sucked into the through hole 22. The noble metal complex solution 10 spread from the end portion 26 in the through hole 22 to a position of 78 ± 12 mm by suction. There was no noble metal complex solution 10 discharged from the end 24.
(result)
Pt could be carried from the end 24 in the cell through-hole 22 to a position of 78 ± 12 mm, and Pt could be carried from the end 26 to a position of 78 ± 12 mm. That is, Pt could be carried over the entire through-hole 22 of the cell (155 mm). Moreover, there was no Pt discharged without being supported on the monolith substrate 20 by suction.
[Example 5]
(Precious metal carrier)
In Example 5, the same noble metal supporting device 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
In Example 5, the same noble metal complex solution 10 as in Example 2 was used.
(Precious metal loading method)
In the present Example 5, a noble metal supporting operation on the monolith substrate 20 was performed using the same noble metal supporting method as in Example 4. At that time, the noble metal complex solution 10 held in the end portion 24 spread from the end portion 24 in the through hole 22 to a position of 78 ± 12 mm by suction. Further, the noble metal complex solution 10 held at the end portion 26 spread from the end portion 26 to a position of 78 ± 12 mm by suction. There was no noble metal complex solution 10 discharged from the end 24 or the end 26.
(result)
Pt could be carried from the end 24 in the cell through-hole 22 to a position of 78 ± 12 mm, and Pt could be carried from the end 26 to a position of 78 ± 12 mm. That is, Pt could be carried over the entire through-hole 22 of the cell (155 mm). Moreover, there was no Pt discharged without being supported on the monolith substrate 20 by suction.
[Example 6]
(Precious metal carrier)
In Example 6, the same noble metal supporting device 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
The noble metal complex solution 10 in Example 6 is basically the same as that in Example 2, but the viscosity of the noble metal complex solution 10 is increased by increasing the Pt concentration in the noble metal complex solution 20 by 20%. The speed was adjusted to 300 mPa · s, and the low shear rate was adjusted to 7000 mPa · s.
(Precious metal loading method)
In Example 6, the same noble metal loading method as in Example 1 was used to carry the noble metal loading operation on the monolith substrate 20. Note that the amount of the noble metal complex solution 10 to be supplied was reduced by the amount of Pt concentration in the noble metal complex solution 10 being high, and the total amount of Pt to be supplied was set to 1 g as in Example 1. The noble metal complex solution 10 spread from the end 24 in the through hole 22 to a position of 20 ± 3 mm by suction. There was no noble metal complex solution 10 discharged from the end portion 26.
(result)
Pt could be supported from the end 24 in the through hole 22 of the cell to a position of 20 ± 3 mm. Moreover, there was no Pt discharged without being supported on the monolith substrate 20 by suction.
[Example 7]
(Precious metal carrier)
In Example 7, the same noble metal supporting apparatus 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
The noble metal complex solution 10 in Example 7 is basically the same as that in Example 2, but the viscosity of the noble metal complex solution 10 is increased by reducing the Pt concentration in the noble metal complex solution 20 by 20%. The speed was adjusted to 100 mPa · s, and the low shear rate was adjusted to 1000 mPa · s.
(Precious metal loading method)
In Example 7, the same noble metal supporting method as that in Example 1 was used to carry the noble metal on the monolith substrate 20. Note that the amount of noble metal complex solution 10 to be supplied was increased by the amount of Pt concentration in the noble metal complex solution 10 being low, and the total amount of Pt to be supplied was set to 1 g as in Example 1. The noble metal complex solution 10 spread from the end 24 in the through hole 22 to a position of 100 ± 15 mm by suction. There was no noble metal complex solution 10 discharged from the end portion 26.
(result)
Pt could be supported from the end 24 in the through-hole 22 of the cell to a position of 100 ± 15 mm. Moreover, there was no Pt discharged without being supported on the monolith substrate 20 by suction.
[Example 8]
(Precious metal carrier)
In the present Example 8, the same noble metal supporting apparatus 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
In Example 8, noble metal complex solutions 10A and 10B having the following composition were prepared.
(Noble metal complex solution 10A)
Palladium (Pd) complex aqueous solution: Pd equivalent to 0.5 g Thickener: HEC 1 wt%
The viscosity of the noble metal complex solution 10A having the above composition was 100 mPa · s at a high shear rate and 1000 mPa · s at a low shear rate.
(Precious metal complex solution 10B)
Aqueous solution of Pt and rhodium (Rh) complex: Pt · Rh total equivalent to 0.5g Thickener: HEC 1wt%
The viscosity of the noble metal complex solution 10A having the above composition was 100 mPa · s at a high shear rate and 1000 mPa · s at a low shear rate.
(Precious metal loading method)
In Example 8, first, the monolith substrate 20 was set so that one end portion 24 of the monolith substrate 20 was covered with the holding member 30 and the other end portion 26 was inserted into the substrate receiving portion 44.

Next, a predetermined amount (corresponding to 0.5 g of Pd) of the noble metal complex solution 10A was supplied from the supply member 50 and held on one end 24 of the monolith substrate 20 by the holding member 30.
Next, the valve 48 was opened to decompress the internal space 42, and the noble metal complex solution 10 </ b> A was sucked into the through hole 22. The noble metal complex solution 10A spread from the end 24 in the through hole 22 to a position of 78 ± 12 mm by suction. There was no noble metal complex solution 10A discharged from the end portion 26.

Next, the monolith base material 20 was removed and, contrary to what was described above, one end portion 24 was inserted into the base material receiving portion 44 and the other end portion 26 was set so that the holding member 30 was covered. .
Next, a predetermined amount (corresponding to a total of 0.5 g of Pt · Rh) of the noble metal complex solution 10 </ b> B was supplied from the supply member 50, and held by the other end portion 26 of the monolith substrate 20 by the holding member 30.

Next, the valve 48 was opened to decompress the internal space 42, and the noble metal complex solution 10 </ b> B was sucked into the through hole 22. The noble metal complex solution 10B spread from the end 26 in the through hole 22 to a position of 78 ± 12 mm by suction. There was no noble metal complex solution 10 </ b> B discharged from the end 24.
(result)
Pd could be carried from the end 24 in the cell through-hole 22 to a position of 78 ± 12 mm, and Pt and Rh could be carried from the end 26 to a position of 78 ± 12 mm. Further, no noble metal was discharged without being supported on the monolith substrate 20 by suction.
[Example 9]
(Precious metal carrier)
In Example 9, the same noble metal supporting device 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
In Example 9, the same noble metal complex solutions 10A and 10B as in Example 8 were used, but the amount of HEC added was 2 wt%. The viscosities of the noble metal complex solutions 10A and 10B were 300 mPa · s at a high shear rate and 7000 mPa · s at a low shear rate.
(Precious metal loading method)
In Example 9, a noble metal loading operation was performed on the monolith substrate 20 using the same noble metal loading method as in Example 8. At that time, the noble metal complex solution 10A held at the end 24 spread from the end 24 in the through hole 22 to a position of 78 ± 12 mm by suction. Moreover, the noble metal complex solution 10B held at the end portion 26 spread from the end portion 26 in the through hole 22 to a position of 78 ± 12 mm by suction. None of the noble metal complex solutions 10 </ b> A and 10 </ b> B was discharged from the end 24 or the end 26.
(result)
Pd could be carried from the end 24 in the cell through-hole 22 to a position of 78 ± 12 mm, and Pt and Rh could be carried from the end 26 to a position of 78 ± 12 mm. Further, no noble metal was discharged without being supported on the monolith substrate 20 by suction.
[Example 10]
In Example 10, first, seven noble metal complex solutions 10 similar to those in Example 2 were prepared. Then, the pH of the noble metal complex solution 10 is adjusted to 1, 2, 4, 6, 8, 10, 11 and left for 24 hours to examine changes in the respective viscosities, and the same noble metal supporting apparatus as in Example 1. No. 1 and the noble metal loading method were used to carry the noble metal loading operation.
(result)
The viscosity after leaving the noble metal complex solution 10 at each pH for 24 hours is shown in FIG. FIG. 2 (a) shows the viscosity at a high shear rate, and FIG. 2 (b) shows the viscosity at a low shear rate.

  In the noble metal complex solution 10 having a pH of 1, the viscosity at a high shear rate was 60 mPa · s, and the viscosity at a low shear rate was 800 mPa · s. When the monolith substrate 20 was loaded with Pt, 50% Pt (equivalent to 0.5 g Pt) was discharged without being loaded.

  Further, in the noble metal complex solution 10 having a pH of 11, the viscosity at a high shear rate was 70 mPa · s, and the viscosity at a low shear rate was 850 mPa · s. Then, when an operation for supporting Pt on the monolith substrate 20 was performed, 40% of Pt (equivalent to 0.4 g of Pt) was discharged without being supported.

Further, in the noble metal complex solution 10 prepared at other pH values, the same results as in Example 1 were obtained.
[Reference Example 1]
(Precious metal carrier)
In this reference example 1, the same noble metal supporting apparatus 1 as that of the example 1 was used.
(Preparation of noble metal complex solution)
The noble metal complex solution 10 in Reference Example 1 is basically the same as in Example 1, but the amount of HEC added is 0.5 wt%. The viscosity of the noble metal complex solution 10 was 50 mPa · s at a high shear rate and 600 mPa · s at a low shear rate.
(Precious metal loading method)
In the present Reference Example 1, a noble metal support operation was performed on the monolith substrate 20 using the same noble metal support method as in Example 1. The noble metal complex solution 10 spread from the end 24 to the end 26 in the through hole 22 by suction, and a part of the noble metal complex solution 10 was discharged from the end 26.
(result)
Pt could be supported over the entire through-hole 22 (155 mm) of the cell. However, about 70% of Pt (equivalent to 0.7 g of Pt) was discharged without being supported by suction.
[Reference Example 2]
(Precious metal carrier)
In the present Reference Example 2, the same noble metal supporting device 1 as that in Example 1 was used.
(Preparation of noble metal complex solution)
The noble metal complex solution 10 in Reference Example 2 is basically the same as that in Example 1, but the amount of HEC added is 2.5 wt%. The viscosity of the noble metal complex solution 10 was 450 mPa · s at a high shear rate and 10,000 mPa · s at a low shear rate.
(Precious metal loading method)
In the present Reference Example 2, a noble metal support operation on the monolith substrate 20 was performed using the same noble metal support method as in Example 1. The noble metal complex solution 10 spread from the end 24 in the through hole 22 to a position of 130 ± 20 mm by suction. There was no noble metal complex solution 10 discharged.
(result)
Although Pt could be supported from the end 24 in the cell through hole 22 to a position of 130 ± 20 mm, Pt could not be supported throughout the through hole 22. Moreover, there was no Pt discharged without being supported on the monolith substrate 20 by suction.
[Comparative example]
In this comparative example, 20 monolith substrates 20 were immersed in a tank of a noble metal complex solution containing Pt to support Pt, and the variation in the supported amount between the monolith substrates 20 was examined.
(result)
The value 4σ indicating the degree of variation in the amount of Pt supported on the 20 monolith substrates 20 was 8%.
[effect]
Table 1 shows a list of results of Examples 1 to 9, Reference Examples 1 and 2, and Comparative Example.

表１から分かるように、上述した実施例１〜９の貴金属担持方法では、貫通孔２２表面のコート層における吸着速度の影響を受けず、モノリス基材２０に担持される貴金属量を容易に調整することができる。すなわち、上記各実施例においては、排出される貴金属量が非常に少なく、端部２４および端部２６に保持した貴金属はほぼ全量担持されているため、端部２４および端部２６に保持する量を調整することで貴金属の担持量を調整できる。

As can be seen from Table 1, in the above-described noble metal supporting methods of Examples 1 to 9, the amount of noble metal supported on the monolith substrate 20 is easily adjusted without being affected by the adsorption rate in the coating layer on the surface of the through-hole 22. can do. That is, in each of the above embodiments, the amount of noble metal discharged is very small, and almost all of the noble metal held at the end 24 and the end 26 is supported, so the amount held at the end 24 and the end 26. The amount of noble metal supported can be adjusted by adjusting.

  Further, in the noble metal loading method of the second embodiment, since almost the entire amount of the noble metal held at the end portions 24 and 26 is loaded, variation in the amount of noble metal carried on the monolith substrate 20 can be reduced. In Example 2, the value 4σ indicating the degree of variation was 2%. On the other hand, in the comparative example, 4σ showed a large variation of 8%.

  Moreover, according to the noble metal carrying | support method of Example 4, 5, after extending the noble metal complex solution 10 of predetermined amount from the edge part 24 to the through-hole 22 surface, it is extended also from the edge part 26 to the through-hole 22 surface. Can do. Therefore, the noble metal complex solution 10 necessary for supporting the target amount of the noble metal can be held in two locations, the end portion 24 and the end portion 26 in two portions. The amount of the noble metal complex solution 10 can be reduced as compared with the case where the noble metal complex solution 10 is sucked only by one suction step.

  Therefore, since the amount of the noble metal complex solution 10 discharged in the two suction steps can be reduced and the amount of the noble metal discharged can be reduced, the noble metal contained in the noble metal complex solution 10 held in the two holding steps. Therefore, the amount of noble metal supported can be made closer to the target value, and the variation for each monolith substrate 20 can be further reduced. Furthermore, in the noble metal supporting methods of Examples 8 and 9, different noble metals can be supported from the end 24 and the end 26 to the surface of the through hole 22.

  Moreover, the noble metal complex solution hold | maintained in the edge part 24 and the edge part 26 by making the viscosity of the noble metal complex solution 10 in high shear rate into 100-300 mPa * s like the noble metal carrying | support method of Examples 1-9. When sucking 10, the viscosity is too low so that a large amount of the noble metal complex solution 10 is discharged by suction, or the viscosity is too high that the noble metal complex solution 10 does not sufficiently extend to the surface of the through-hole 22. Appropriate suction can be performed without causing problems such as.

  Further, by setting the viscosity of the noble metal complex solution 10 at a low shear rate to 1000 to 7000 mPa · s, the noble metal complex solution 10 held at the end 24 and the end 26 is sucked and then penetrated due to the viscosity being too low. It is possible to prevent the noble metal complex solution 10 extending on the surface of the hole 22 from flowing and dripping, and the flowing noble metal complex solution 10 from being accumulated on the surface of the through hole 22 to block the through hole 22. Further, since the viscosity of the noble metal complex solution 10 is high, the dispersion of the noble metal contained in the noble metal complex solution 10 is improved, and the movement of the noble metal in the through holes 22 after being extended to the monolith substrate 20 is suppressed. Therefore, the dispersion | variation in the monolith base material 20 of the noble metal carrying amount can also be reduced.

  Further, by adjusting the pH of the noble metal complex solution 10 to 2 to 10 as in the noble metal loading method of Example 10, the viscosity change becomes small even after leaving for a long time after adjusting the viscosity, and the noble metal complex solution 10 Even if it is not immediately after preparing a suitable noble metal carrying | support operation | work can be performed.

In addition, according to the above-described noble metal supporting method, one or more of platinum, palladium, and rhodium can be supported on the monolith substrate 20.
[Modification]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various forms can be taken as long as they belong to the technical scope of the present invention.

  For example, in Examples 8 and 9 described above, a method was used in which the noble metal complex solutions 10A and 10B each contain the same amount of noble metal (both 0.5 g) and each have the same viscosity. However, the amount of the noble metal contained in these noble metal complex solutions 10A and 10B may not be the same, and the respective viscosities may be different. By doing so, the noble metal complex solution 10 </ b> A from each end of the through hole 22 according to the concentration and viscosity of the noble metal of the noble metal complex solution 10 </ b> A, 10 </ b> B and the amount of the solution held at the end 24 and the end 26. , 10B can be adjusted.

Alternatively, the noble metal complex solution 10B may be extended so as to overlap the portion of the through hole 22 where the noble metal complex solution 10A has already extended.
Moreover, in each said Example, after supplying and hold | maintaining the noble metal complex solution 10 to the edge part (edge part 24 or edge part 26) of the monolith base material 20, the method of performing attraction | suction was illustrated. However, the timing for sucking the noble metal complex solution 10 supplied to the end is not particularly limited. For example, suction may be performed simultaneously when the noble metal complex solution 10 is supplied to the end portion.

  Further, in each of the above-described embodiments, the substrate using the honeycomb-shaped monolith substrate 20 is exemplified as the substrate for supporting the noble metal. However, the base material is not limited to the above base material as long as it can support a noble metal and can be used as a base material for the catalyst. For example, a filter base in which a plurality of holes extending from each end toward the other end are formed at both ends in the axial direction of the base material, and each hole communicates through the pore formed in the side wall of each hole. You may use the metal base material etc. which are formed by alternately laminating | stacking a material, a flat plate and corrugated board using a heat-resistant alloy, and several tens of micrometers.

  Moreover, in each said Example, the method of using the noble metal complex solution 10 in which the complex of platinum, palladium, and rhodium dissolved was illustrated as a noble metal solution for making the monolith base material 20 carry | support a noble metal. However, the noble metal solution is not limited to one in which the noble metal is dissolved in the solvent as long as the noble metal can be supported on the substrate. For example, the noble metal may be supported using a mixture of noble metal or noble metal compound fine particles mixed with a solvent.

Side view showing a noble metal carrying device of the present invention Diagram showing the relationship between pH and viscosity

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Noble metal carrying | support apparatus 10, 10A, 10B ... Noble metal complex solution, 20 ... Monolith base material, 22 ... Through-hole, 24, 26 ... End part, 30 ... Holding member, 40 ... Suction member, 42 ... Internal space, 44 ... base material receiving part, 46 ... piping, 48 ... valve, 50 ... supply member.

Claims (6)

A plurality of holes having openings at at least one end A, wherein the holes support a noble metal on a base material communicating with the other end B,
A predetermined amount of a noble metal solution containing the noble metal and a thickener and having a viscosity at a shear rate of 4 sec ⁻¹ of 1000 to 7000 mPa · s is supplied to the end A, and the noble metal solution supplied to the end A is A noble metal loading method comprising: a first extension step of drawing the noble metal solution on the surface of the hole by suction from the end B. A predetermined amount of a noble metal solution containing a noble metal and a thickener is supplied to the end portion B, and the noble metal solution supplied to the end portion B is sucked from the end portion A, whereby the noble metal solution is applied to the surface of the hole. The precious metal carrying method according to claim 1, further comprising a second extending step of extending the material. The noble metal solution extended on the surface of the hole in the first extension step and the noble metal solution extended on the surface of the hole in the second extension step each contain different noble metals. The noble metal loading method according to claim 2. The noble metal supporting method according to any one of claims 1 to 3, wherein the noble metal solution has a viscosity of 100 to 300 mPa · s at a shear rate of 380 sec- ¹ . The noble metal loading method according to any one of claims 1 to 4, wherein the noble metal solution has a pH of 2 to 10. The noble metal loading method according to any one of claims 1 to 5, wherein the noble metal is one or more of platinum, palladium, and rhodium.

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