DD251120A1 - PLATINUM RECOVERY FROM DISABLED MULTIMETAL CARRIER CATALYSTS - Google Patents

Abstract

Process for recovering platinum from deactivated multimetal starter catalysts with the aim of reducing Pt losses. The task of developing such a method is achieved by digesting the spent catalyst with concentrated sodium hydroxide solution or potassium hydroxide solution at 433 to 463 K and pressures of 0.4 to 0.7 MPa and, according to the invention, the sodium hydroxide or potassium hydroxide solution or / and the digestion solution of metal salt solution is added in such an amount that the molar ratio of metal salt to Pt is 0.1 to 10. The metal salts consist of divalent metal ions with chloride or nitrate as counter ions. The alkaline earth metal salts have proved particularly suitable if molar ratios of metal salt to Pt of 0.4 to 5 are maintained.

Description

Field of application of the invention

The invention relates to a process for platinum recovery from spent Pt-Me-A ^ Oy catalysts, wherein Me represents an element of the 7th or 8th subgroup pESE.

Characteristic of the known technical solutions

Platinum-containing supported metal catalysts are used in numerous petroleum processing processes. In most cases, the use of the catalyst leads to irreversible damage to the catalyst, so that platinum recovery is necessary. Various methods are given in the literature for this purpose. In EP 0048823 the energy-consuming separation of the liquid Pt after melting of the catalyst in an electric furnace at 2100 ° C is described.

In the event that no irreversible damage has occurred on the support, a treatment of the spent catalyst with phosgene (FP 1156974, EP 795629, DE-AS 1077642) and AICI ₃ (DE-AS 1 050 734) for the volatilization of the Pt makes sense. In most cases, however, irreversible damage has also occurred on the Al ₂ O ₃ supports after the catalyst has been used. Therefore, wet digestions with alkalis or acids are most often recommended. The digestion procedures are basically carried out in two steps:

1. Remove the Pt from the spent contact by digestion to obtain a Pt concentrate.

2. Work up the platinum concentrate to pure metal.

The second step is the same in almost all cases and is usually carried out by digesting the concentrate with aqua regia or hydrochloric acid-chlorine mixtures and subsequent cementation. The differences of the Pt recovery methods exist mainly in the digestion conditions of the 1st step for obtaining the platinum concentrate. The acidic digests are often coupled with oxidizing treatments for dissolving out the Pt: dissolution with aqua regia (GB-PS 1312438), with hydrochloric acid-bromine mixture (US Pat. No. 3,985,854) or with hydrochloric acid, hydrochloric acid, sodium chlorate or sodium bromate. Mixtures (GB-PS 1517270). According to US-PS 3856912.3672874 and 3855385, the Pt concentrate is obtained after digestion with sulfuric acid. Acid digestion processes have the general disadvantage that the resulting aluminum salt solutions are contaminated with heavy metal ions and used for further processing, eg. As cases of aluminum hydroxides, only extensive cleaning operations must be subjected. In the alkaline digestions most frequently sodium hydroxide solution is used (DE-OS 1758837, DD-PS 143362). The alkaline digestion processes have the advantage over the acid digestions that lower Pt losses occur. However, the known alkaline digestion methods can not be applied without restriction to multimetal Al ₂ O ₃ support catalysts which, in addition to Pt, also contain one or more elements of the 7th or 8th subgroup of the PSE. Thus, in many cases the workup of multimetal Al ₂ O _{3 supported} catalysts for unknown reasons leads to large Pt losses.

Object of the invention

The object of the present invention is to find a method for Pt recovery from Pt / Me-Al ₂ O ₃ catalysts with low Pt losses, where Me is an element of the 7th and 8th subgroup of the PSE.

Explanation of the essence of the invention

The invention is based on the object of Pt-containing catalysts consisting of alumina, Pt and an element of the 7th or 8th subgroup of the PSE to recover the Pt with a high yield.

This task is carried out by alkaline digestion with concentrated sodium hydroxide solution or potassium hydroxide solution at temperatures of 433 to 463K and pressures of 0.4 MPa to 0.7 MPa, diluting the digestion liquor, adding a reducing agent, separating the Pt concentrate and working up the Pt concentrate known solution and precipitation reactions in that according to the invention the sodium hydroxide or potassium hydroxide solution or the digestion solution, a metal salt solution consisting of divalent metal ions with chloride or nitrate as counter ions, is added, wherein the molar ratio of metal salt: Pt 0.1 to -10 is. It is favorable if the metal salt solution consists of chlorides or nitrates of Ba or Ca, the molar ratio of metal salt: Pt being from 0.4 to 5.

Surprisingly, it has been found that the Pt losses are significantly reduced in the workup by the novel process. It is irrelevant whether the addition of metal salt to the sodium hydroxide solution or digestion solution takes place. For practical reasons, however, it has proven to be expedient if the metal salt is added as an approximately saturated solution while stirring the digestion solution. It is essential that the molar ratio of metal salt to R is in the range of 0.1 to 10.

EXAMPLES Comparative Example

100g of the aged catalysts A and B (Cat.A: 0.5Ma .-% Pt, 0.3Ma .-% Re on γ-ΑΙ ₂ Ο ₃ , Cat.B: 0.5Ma .-% Pt, 0.03Ma % Of Ir on 7-Al ₂ Cy are each treated with 280 ml of concentrated sodium hydroxide solution at 463K and 0.7 MPa for 10 hours After cooling, the digestion solutions are diluted in a volume ratio of 1: 1 with water and admixed with 1.5 ml of formalin. After settling the Pt concentrate, the clarified solutions are decanted, and the remaining Pt concentrate is again washed in water (700 ml) to which 1 ml of formalin has been previously added, after which the Pt concentrates are converted to Pt by a method known per se The Pt yields are given in Table 1.

Embodiment 1

100 g of an aged Pt-lr-Al ₂ O ₃ catalyst (Cat.B Comparative Example) are digested for 10 h at 463 K and 0.7 MPa with 280 ml of concentrated sodium hydroxide solution. After cooling, the digestion solution is diluted with water in a volume ratio of 1: 1. Thereafter, 1.5 ml Formally-in as well as 2.5 g of BaCl 2 · H ₂ O, where ₂ in the form of a solution saturated at room temperature, aqueous BaCl ₂ solution with stirring to dilute pulping solution. After settling the Pt concentrate is decanted and the Pt concentrate washed again with 700 ml of water and 1 ml of formalin. The Pt concentrate obtained after settling and decantation is worked up to Pt by a conventional method as in Comparative Example. The Pt yield is included in Table 1.

Embodiment 2

100 g of an aged Pt-lr-Al ₂ O ₃ catalyst (Cat.B of the comparative example) are digested at 463 K and 0.7 MPa with 280 ml of concentrated potassium hydroxide solution over a period of 10 h. The cooled digestion liquor is diluted with water in a volume ratio of 1: 1. While stirring, 1.5 ml of formalin and 2 g of CaCl ₂ · 6H ₂ O in the form of an aqueous CaCl ₂ solution saturated with room temperature are added to this dilute digestion solution. After settling the Pt concentrate, decantation is carried out. The Pt concentrate is then washed again with 700 ml of water and 1 ml of formalin and worked up by a conventional method as in Comparative Example to Pt. Table 1 contains the Pt yield.

Embodiment 3

100 g of an aged Pt-Re-Al ₂ O ₃ catalyst (Cat.A of the comparative example) are added for 10 h at 463 K and 0.7 MPa with 280 ml of concentrated sodium hydroxide to which 2.5 g of BaCl ₂ · 2H ₂ O have previously been added. open minded. After cooling, the digestion liquor is diluted with water in a volume ratio of 1: 1 and treated with 1.5 ml of formalin. After settling the Pt concentrate is decanted. Subsequently, the Pt concentrate is washed again with 700 ml of water and 1 ml of formalin. The Pt concentrate obtained after settling and decantation is worked up to Pt by a conventional method as in Comparative Example. The Pt yield is included in Table 1.

Table 1

Pt yields of the work-up procedures

Method Pt yield in%

Comparative Example Cat.A 97.9

Comparative Example Cat. B 98.1

Example 1 Cat. B 99.7

Example 2 Cat. B 99.6

Embodiment 3 Cat. A 99.7

A comparison of the Pt yields in Table 1 illustrates the advantage of the inventive embodiments 1 to 3. Another advantage of the method according to the invention is a significant reduction in the time of the workup of Pt.

Claims (2)

1. A method for Pt recovery from Pt-Me-A ^ C ^ catalysts, wherein Me is an element of the 7th or 8th subgroup, by alkaline digestion with concentrated sodium hydroxide or potassium hydroxide solution at temperatures of 433 to 463 K and pressures from 0.4 to 0.7 MPa, dilution of the digestion liquor, addition of a reducing agent, separation of the Pt concentrate and workup of the Pt concentrate by per se known solution and precipitation reactions, characterized in that the sodium hydroxide or potassium hydroxide solution or the Aufschiusslösung a metal salt solution consisting of divalent metal ions with chloride or nitrate as counter ions, is added, wherein the molar ratio of metal salt: Pt is 0.1 to 10. 2. The method according to Pkt. ^, Characterized in that the metal salt solution consists of chlorides or nitrates of Ba or Ca, wherein the molar ratio of metal salt: PtO, 4bis5.