JPS58199832A - Method for recovering rhodium - Google Patents

Abstract

PURPOSE:To recover efficiently Rh from a used catalyst contg. Rh on an aluminous carrier by adding a compound of an element which forms a compound together with Rh and prevents Rh from being solubilized in alumina to the catalyst, carrying out calcination and reduction, and dissolving and extracting Rh. CONSTITUTION:To a used catalyst contg. Rh on an aluminous carrier is added 0.01-2mol/l of a compound of an element which forms a compound together with Rh and prevents Rh from being solubilized in alumina. The chloride, nitrate, carbonate or acetate of La, Ca, Pb or Na or the oxyacid salt of boron is used as the compound. Calcination is carried out an 600-1,300 deg.C. Rh can be dissolved easily and extracted from the used catalyst, and it is efficiently recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for efficiently recovering rhodium from a spent catalyst.

Platinum group metals In recent years, their use as catalysts in fields such as the chemical industry and the bicycle industry has rapidly increased, rather than as decorations. The catalyst used here becomes a spent catalyst after being used for a certain period of time. For this reason, it is an urgent social need to recover the platinum group metals in this spent catalyst and turn them into resources.

These catalysts use alumina granules or alumina coated as a platinum group metal support (carrier).
Many use a base material.

Although many proposals have been made as methods for recovering platinum group metals in such catalysts, there are only a few methods for recovering rhodium.

Therefore, regarding the recovery method of rhodium (Rh), which is considered to be difficult to recover, it is desired to develop a method to efficiently recover rhodium in the same way as platinum (pt), .9 radium (Pd), etc. .

Conventionally, rhodium and other platinum group metals on an alumina support have been recovered by dissolving and extracting the platinum group metal using a strong acid solution. A large amount of alumina, which is Therefore, it is not easy to dissolve and process the alumina, and if the alumina that is the carrier is not completely dissolved, the dissolved and extracted Rh" will be adsorbed to the undissolved alumina, so a high extraction rate cannot be expected. Therefore, in order to avoid this problem, the catalyst is calcined at a high temperature of 1200 C or higher as a pretreatment for dissolution and extraction, and the alumina is pregelatinized on the carrier, so that the alumina does not dissolve and the platinum is removed. The problem of re-accumulation of group metals does not occur, and platinum group metals can be easily and efficiently recovered.However, by performing this pretreatment, it is possible to recover platinum and However, for rhodium, the recovery rate was 1096
The rate is as low as below.

One of the reasons why rhodium is difficult to dissolve and extract is that rhodium itself is stable against strong acids, but the inventors believe that the main reason is that alumina becomes pregelatinized. When %Rh, 0. is dissolved in α-alumina. This α-At2o
The fact that s and Rb203 are in solid solution indicates that At(OH) and R
When the mixture with h(OH) was calcined in air at a temperature of 1200°C, it was examined by X-ray diffraction, and the peak of α-alumina shifted to the lower angle side.As a result of calculating the lattice constant C, Usually 12.990X is 1
It is clear that it has expanded to 2.9951. Considering these facts, it is generally considered that Rh
20. and α-At20. It is thought that a solid solution of the molecule is formed depending on the conditions. Considering this, in catalysts using alumina as a carrier, Rh is generally supported only in a very small amount, and during calcination, Rh is
It is quite possible that it will form a solid solution in the water.

In this way, AA20. Rh dissolved in α-
Like alumina, it is extremely stable against acids, making recovery by dissolution extraction impossible.

The present invention solves the problems of the prior art described above and provides a method for efficiently recovering rhodium in a spent catalyst. - In the method of dissolving and extracting and recovering dium, a compound of an element that forms a compound with rhodium and prevents solid solution of rhodium in alumina is added to the catalyst, which is calcined and reduced, and then the rhodium is recovered. It is characterized by dissolution and extraction.

In this invention, a compound of an element that forms a compound with rhodium (ah) and prevents solid solution of rhodium in alumina as described above is added to alumina by adding rhodium to the alumina. to be fired. As a compound of such an element, first of all, rhodium and the composite oxide MxR
Metals that produce kyO8 (M is gold), such as salts of lanthanum, calcium (C&), lead (PB), and sodium A (Na), such as chlorides, nitrates, carbonates, and acetates. .

In the method of the present invention, examples of the compound of the element added to the catalyst include the above-mentioned metal salts and, for example, boron oxygen acid (H3BO, etc.).

It is presumed that such a boron oxygen acid generates a compound such as rhodium and RhBOX, thereby preventing solid solution of rhodium in alumina.

A compound of the elements shown above is added to the catalyst and 60%
When calcined at a temperature of 0 to 1300°C, the compounds shown in Table 1 are produced, and when this compound is further subjected to reduction treatment, the compounds shown in Table 1 are produced.
Changes into elements and compounds as shown in the table.

Table 1 By adding compounds of the elements listed above to the catalyst, Rh, 0. In a temperature range lower than 800°C, which is the temperature at which the solid solution of Arunna is estimated to start, rhodium is consumed by the formation of the above-mentioned chemical compounds between rhodium and the compound of the added element. Moreover, this product compound is stable even in the high temperature range of 1200° C. to 1300° C. Since rhodium is not liberated from the product compound in -1, solid solution of rhodium in alumina can be avoided. Furthermore, even when cooled to room temperature, the product compound is stable in terms of α-alkyl structure, and when this product compound is reduced, it becomes a compound that is more soluble in acids than K, so it is possible to efficiently dissolve and extract rhodium. It becomes possible to collect the waste.

After reduction treatment as above, 60dium metal Xaa
When folded, the rhodium metal peak becomes a broad peak, which is thought to be due to the rhodium crystals becoming finer.

The calcination temperature for producing the product compound as described above is preferably 600 to 1300°C, preferably 600°C.
At temperatures below 1, the product compound 1 is formed and separated, while 1
This is because if the temperature exceeds 300°C, other types of product compounds are likely to be produced and it is difficult to produce uniform product compounds.

In this invention, the amount of the compound of the element to be added and contained in order to produce the product compound is as follows:
preferably 0.0 x 4 to 2 moles;
If the content is less than 1 mol, no product will be produced, and if the content is 2 mol, no effect will be obtained even if the content is increased, so it is decided to set the content to 2 mol. This is because it has no special meaning.

According to the method of this invention, rhodium in the catalyst forms the above-mentioned compound with the added element, so it does not form a solid solution in alumina, and the resulting compound is further reduced and dissolved in acid. Moreover, since the rhodium crystals after reduction are finely divided and easily dissolved in acid, rhodium can be easily dissolved and extracted, and rhodium can be recovered efficiently.

Examples 1 to 5 Granular r = *z2o, a catalyst for purifying automobile exhaust gas in which the carrier contained 0.014 weight of rhodium and 0.131 weight of platinum was added as an additive compound, La (No, ),
was impregnated at a ratio of 0.01 mol/l to 2.0 mol/l catalyst, calcined in air at a temperature of 1200°C for 1 hour, and then subjected to reduction treatment with a sodium borohydride (NoBHa) solution. Regarding this treated product, HCA and town 0
Perform dissolution extraction of rhodium and platinum with the two mixed liquids,
The dissolution extraction rate (4) of each was measured. As a result, Table 2 shows the amount of La (NOs)s impregnated (mol/!
(catalyst) and the corresponding Rh dissolution extraction rate (■) and Pt dissolution extraction rate (-).

For comparison, as Comparative Example 1, the same catalyst as above was treated in the same manner as above without being impregnated with La(Nos)i. Perform dissolution and extraction, measure the dissolution and extraction rate of each dye, and record the results in 2nd #I.9.

As is clear from the results shown in Table 2, the Rh dissolution and extraction rate by the methods of Examples 1 to 5 is higher than the Rh dissolution and extraction rate by the method of Comparative Example 1, which does not use La(NO3),5. It was something. In addition, the Pt dissolution and extraction rate is also La(NO,)
In the cases where Rh 3 was used (Examples 1 to 5), there was a slight increase compared to the case where Rh was not used (Comparative Example 1), but no increase was observed in the Rh dissolution extraction rate.

Examples 6 to 10 La was added to the same catalyst as in Examples 1 to 5 as an additive compound.
(No.) was impregnated at a ratio of 1.0 mol/l catalyst and calcined in air at a temperature of 600°C to 1300°C as shown in Table 3 for 1 hour. For those treated in the same manner, rhodium was dissolved and extracted in the same manner as in Examples 1 to 5. In addition, as Comparative Examples 6 to 10, the same catalysts as those described above were treated with K without being impregnated with La (No, ), and the treatment conditions were conducted under the treatment conditions corresponding to Examples 6 to 10, respectively, and these treated products were Rhodium was similarly dissolved and extracted. 31st! 1 shows the Rh dissolution and extraction rates for these Examples and Comparative Examples.

Table 3 The results of Table 3 are as follows: 1. When compared at the same firing temperature, the Rh dissolution and extraction rate was higher when I, a (No, ) was used than when it was not used. In particular, when the temperature exceeds 800°C, Ll(NO,
), the result was much larger.

Examples 11-25 Granular r-At20. An automobile exhaust gas purification catalyst containing 0.016 tcs of rhodium in the carrier was added with NaNO3, ca (No, ), Pb (No.
s), and 0.0.2 mol/l each of H, BO,
Impregnated with catalyst ~ 2 mol/l catalyst, 1200 in air
After firing at a temperature of 300°C for 1 hour, reduction treatment was performed in hydrogen at a temperature of 300°C for 1 hour.This treated product was subjected to dissolution extraction of rhodium with a mixed solution of HCl and H2O2 to obtain a Rh dissolution extraction rate (4 ) was measured. Table 4 shows the type and impregnated amount of the added compound and the corresponding Rh dissolution and extraction rate (a). For comparison, as Comparative Example 7, the same catalyst as above was used without impregnating the additive compound.
The same treatment as above was carried out, and for this treated product, HC
Rhodium was dissolved and extracted using a mixture of H2O2 and H2O2, and the Rh dissolution and extraction rate (maximum) was measured.

The results are also listed in Table 4.

Table 4 As is clear from the results in Table 4, compared to the case where no additive compound is used (Comparative Example 7), the method of this invention (
In Examples 11 to 25), the dissolution and extraction rate of Rh was high.

Examples 26-30 γ-Aj20. containing 0.051% by weight of rhodium, 0.53% by weight of platinum and 1.03% by weight of radium.
Powder 1011 contains LaCl3 and La as additive compounds.
(No,),,H,BO,,Ca(OH)2 and C
aCO5 was added and mixed at a ratio of 1.0 mol/1 kg powder, water was added to form a slurry, and the mixture was dried and calcined in air at a temperature of 1200° C. for 1 hour. After cooling the calcined product, a NaBH4 solution was added to reduce the product, and the solution was extracted with aqua regia to measure the dissolution/extraction ratio (4) of rhodium, platinum, and /9 radium. The results are shown in Table 5. For comparison, as Comparative Example 8, the same powder □ as above was treated in the same manner as above without adding the above additive compound, and this treated product was dissolved and extracted with aqua regia. The dissolution and extraction rates of rhodium, platinum and/or nickel were measured. Combined with the results, the fifth
Shown in the table.

As is clear from the results in Table 5, compared to the case where no additive compound was added (Comparative Example 8), the method of the present invention in which various additive compounds were added (Examples 26 to 30) The Rh dissolution and extraction rate was significantly superior. Also, Pt
Regarding the dissolution and extraction rate of Pd, the dissolution and extraction rate increased when various additive compounds were used compared to when they were not used, but in the case of Rh, it did not increase to t1.

“Examples 31 to 32 A catalyst for purifying automobile exhaust gas containing 0.031 iJll of rhodium and 0.13 wt of platinum on a honeycomb structure carrier coated with r-aluminum on cordierite. A piece with a length of 50 cm is punched out, and this one Ic, La (NOx) i and c a (No
s)2 were each supported at a ratio of 1.0 mol/j catalyst and calcined in air at a temperature of 800° C. for 1 hour. After cooling the fired product, H, BO, 0.05 mol/! After being supported at the same proportion as the catalyst, it was calcined in air at a temperature of 1200°C for 1 hour, and further reduced in hydrogen at a temperature of 300°C for 1 hour.

Regarding this reduced product, rhodium and platinum were dissolved and extracted using a mixed solution of HCA and HCto, and the respective dissolution and extraction rates (4) were measured, and the results are shown in Table 6. For comparison, as Comparative Example 9, 1200
℃ temperature for 1 hour, and further reduced in hydrogen at 300℃ temperature for 1 hour, dissolution extraction was performed in the same manner as above, and the dissolution extraction rate of rhodium and platinum was measured. The results are also listed in Table 6.

Table 6 As is clear from the results in Table 6, both the dissolution and extraction rates of Rh and Pt were lower in the case of the method of the present invention using an additive compound (Examples 31 to 32) than in the case of not using an additive compound. (Comparative Example 9) In particular, the Rh dissolution and extraction rate was much better when the former additive compound was used than when the latter was not used.

Examples 33 to 37 The same catalyst as in Examples 11 to 25 was added with L as an additive compound.
a(CH,C00) and Pb(CH,C00)2 were each impregnated at a ratio of 0.01 mol/l catalyst to 0.5 mol/l catalyst, and the same treatment as in Example 11'-25 was performed. Rhodium was dissolved and extracted using the same method as in Examples 11 to 25, and the Rh dissolution and extraction rate (%) was measured. The results are shown in Table 7. For comparison, the results of the comparative example/θX described above are also listed in Table 7.

The Rh dissolution and extraction rate was superior to that in Table 7 (comparative example, r).

Applicant's agent: Patent attorney Suzue Takehiko,)I

Claims (1)

[Claims] (1) In a method for dissolving and extracting rhodium from a catalyst containing rhodium in an alumina-based carrier, a compound with rhodium is generated to prevent solid solution of rhodium in alumina. A method for recovering rhodium, which involves adding a compound of the element to a catalyst, firing and reducing the compound, and then dissolving and extracting rhodium. (2) The method according to claim 1, wherein the compound of the element is a chloride, nitrate, carbonate or acetate of lanthanum, calcium, lead or sodium. (3) The compound of the element is boron and oxygen. The method according to claim 1, wherein the acid is an acid. (4) The method according to claim 1, which is carried out at a temperature of 600° C. to 1300° C. in the firing tube. (5) The addition lid of the compound of the element is Catalyst 1 no. 0.01
The method according to claim 1, wherein the amount is mol to 2 mol.