JPS6225613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering platinum group elements from a platinum-based catalyst using alumina or the like as a carrier.

Due to their strong and special catalytic action, platinum group elements are widely used in the petrochemical industry, automobile exhaust gas purification, etc. However, platinum group elements are not only expensive but also limited in terms of resources. In terms of resource conservation, it is desirable to recover platinum group elements from spent catalysts.

Conventionally, when recovering platinum group elements from a platinum-based catalyst using an activated alumina catalyst carrier, in order to suppress the elution of alumina into the extract solution, the alumina was calcined in air at a temperature of 1000°C or higher, and the alumina was pregelatinized and chemically processed. It undergoes pre-treatment to make it more stable. However, as a result of this firing treatment, the platinum-based elements turn into oxides and become stable substances with respect to the extraction solution, resulting in a decrease in extraction efficiency. In this case, the extraction rate of platinum and palladium can be restored by reduction after firing, but the extraction rate of rhodium and iridium is extremely low even after reduction after firing, and when it comes to osmium and ruthenium, the extraction rate is extremely low. , it is difficult to extract because the oxide is volatile.

The purpose of the present invention is to recover platinum group elements in high yield while suppressing alumina elution from platinum-based catalysts through a simple process. system catalyst
When firing by heating to 1000℃ or higher, select a reducing gas as the atmospheric condition, then treat the fired platinum-based catalyst with an inorganic acid to dissolve and extract the catalyst components to separate the platinum group elements. , is characterized by being recovered.

In this case, it is convenient for the firing temperature to be 1000℃ or higher.
If firing is performed below this temperature, a large amount of alumina will be eluted during extraction. In addition, conventionally used inorganic acids can be used as the extract, and these may be used alone or in combination depending on the purpose, but it is preferable to use aqua regia. Note that since the reducing gas is used to prevent oxidation of platinum group elements, it is preferable to allow a constant amount to flow into the reaction apparatus at all times.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Rhodium (0.015% by weight) on activated alumina carrier,
A catalyst supported with platinum (0.135% by weight) was calcined in water gas at temperatures of 800, 1000, 1200, 1300,
When calcined at 1400°C and extracted with aqua regia, the rhodium extraction rate, platinum extraction rate, and alumina elution rate at each firing temperature were as shown in Figures 1, 2, and 3.

Reference Example 1 A catalyst with the same composition as that used in Example 1 was calcined in air at a temperature of 800, 1000, 1200, 1300, 1400°C.
The rhodium extraction rate, platinum extraction rate, and alumina elution rate at each firing temperature are shown in Figures 1, 2, and 3. It was hot on the street.

Example 1 (A) and Reference Example 1 (B) in each figure
Comparing the results, we find that the recovery rate of rhodium differs greatly between A and B at firing temperatures of 1000°C or higher, with the recovery rate of A always exceeding 50%. Next, regarding the recovery rate of platinum, A shows a somewhat higher value than B at each firing temperature, and tends to gradually increase as the firing temperature increases. In addition, regarding the elution rate of alumina that does not need to be recovered, A and B have almost the same value regardless of changes in the firing temperature, and
The values at 1200 and 1400℃ are very low.

Example 2 Rhodium (0.015% by weight) on activated alumina carrier,
Catalyst supported with palladium (0.07% by weight)
When 6.8g was calcined at 1400℃ in hydrogen gas and extracted with aqua regia, 0.72mg of rhodium and palladium were found.
4.5 mg was recovered.

Reference Example 2 The same amount of catalyst with the same composition as that used in Example 2 was
It was calcined in air at 1400°C, then reduced in hydrogen gas at 700°C, and extracted with aqua regia, recovering 0.26 mg of rhodium and 4.2 mg of palladium.

Comparing the recovery rate results, it can be seen that Example 2 exceeds both rhodium and palladium.

Example 3 6.8 g of a catalyst in which rhodium (0.015% by weight) and platinum (0.135% by weight) were supported on a catalyst carrier in which cerium dioxide (8% by weight) was supported on activated alumina was calcined at 1200°C in hydrogen gas. When extracted with aqua regia, 0.68 mg of rhodium and 8.2 mg of platinum were recovered.

Example 4 Magnesium oxide (20% by weight) on activated alumina
When an experiment was conducted using a catalyst carrier supporting , the same results as in Examples 1 to 3 were obtained.

As can be seen from Examples 3 and 4 above, even if the oxide is supported on the catalyst carrier in advance, the recovery rate of the platinum group elements is not affected.

Example 5 In Examples 1 to 4, hydrocarbons such as propane and propylene were used as the pretreatment firing atmosphere.
When a similar experiment was conducted using carbon monoxide instead of hydrogen gas, the same results as in Examples 1 to 4 were obtained.

In this way, it is possible to increase the recovery rate of not only rhodium but also platinum, palladium, and other platinum group elements while keeping alumina elution from the carrier to an extremely low level.Furthermore, it is possible to increase the recovery rate of platinum group elements such as platinum and palladium, which are difficult to dissolve in aqua regia using conventional methods. Since the atomic structures of ruthenium, osmium, and iridium are extremely similar to rhodium, these elements can also be extracted by the method of the present invention.

As described above, the pretreatment according to the present invention has many advantages, such as being able to significantly increase the recovery rate of platinum group elements while minimizing the elution of carriers such as alumina.

[Brief explanation of the drawing]

Figure 1 shows Example 1 (A) and Reference Example 1 (B).
Figure 2 is a graph showing the platinum recovery rate versus firing temperature at A and B. Figure 3 is a graph showing the alumina elution rate versus firing temperature at A and B. graph,
represents.

Claims (1)

[Claims] 1 Platinum-based catalyst using an alumina catalyst carrier,
A method for recovering platinum group elements from a platinum-based catalyst, which comprises extracting the platinum group elements with an inorganic acid after calcination at 1000°C or higher in a reducing atmosphere.