DE1143335B - Process for the recovery of noble metal from deactivated catalysts - Google Patents

Description

Process for the recovery of precious metal from deactivated catalysts Catalysts that contain precious metals, especially platinum, are used in industry for many reactions, e.g. B. cyclization, hydrogenation, dehydrogenation, isomerization, Aromatization, sulfonation and dehydrocyclization. Such catalytic Masses usually deactivate themselves after a long period of use, which can result in various Causes, e.g. B. Change in the physical state of the catalytic components, Loss of such components or deposition of solid impurities, especially of coke or other carbonaceous material.

Such deposits are often deactivated by burning off the Catalyst in a medium containing free oxygen, such as air, removed, and the catalyst is usually reactivated to a greater or lesser extent in this way. With each regeneration, however, the activity somewhat decreases, and eventually becomes it is necessary to replace the catalytic converter with a new one. The high value of the precious metal does not usually allow the inactivated catalytic mass to be thrown away, even if the concentration of the precious metal is relatively low.

The invention is based on the recovery of precious metals from deactivated, Precious metal-containing, catalytic masses directed, which are no longer in economic Way can be regenerated.

Although this method focuses particularly on the recovery of platinum from deactivated catalytic masses, the platinum, alumina and fluoride contain, it can also be used with advantage for the recovery of other precious metals, such as Iridium, osmium, palladium, rhodium, rhenium, ruthenium, but especially of palladium from similar masses.

Such catalytic masses can in addition to the refractory inorganic Oxide in addition to the noble metal and the fluoride, for example, other metals, such as Iron, tungsten, sodium, nickel, cobalt, molybdenum, copper, chromium or mixtures same, have. Sulphides, nitrates, oxides and other metal salts can also be used to be available.

It is known that such noble metals from alumina-noble metal catalysts can be recovered by having the catalyst with a main part the amount of sulfuric acid dissolving alumina at elevated temperature, preferably at at least 120 "C, treated the resulting solution of a precious metal and Separating the sludge containing carrier residues, the sludge undergoes another sulfuric acid treatment subject and then from the undissolved residue, if necessary, after Washing with water absorbs the precious metal in a solvent. With this one known processes, the alumina carrier is practically quantitatively brought into solution, while the platinum metal accumulates almost quantitatively in the residue.

However, if the catalyst that makes up the precious metal, such as platinum, is to be recovered, a fluoride - usually it is such Catalysts around a fluorine concentration of about 0.01 to about 8.0 percent by weight - so the known way of working does not lead to economic success.

Fluorine appears to be less easily removed from the catalyst than other halogens, and therefore particular difficulties arise when platinum or other noble metal from the fluoride-containing catalyst by dissolving it out the clay is to be recovered using sulfuric acid; because the fluorine remains back with the platinum in an undissolved state. If so, then the precious metal from the mud z. B. is dissolved out by means of aqua regia, so is the fluorine released. To avoid contamination of the resulting platinum-containing solution or of chloroplatinic acid as a result of attack by aqua regia on the inner walls of the vessels To avoid this, the digestion vessels are generally lined with glass because of this is insensitive to aqua regia. But if the platinum-containing mud, that is to be brought into solution also contains fluoride, so is used in the treatment with aqua regia too Hydrogen fluoride is released from the glass lining attacks. As a result, results in the recovery of platinum or otherwise Noble metals from a fluoride-containing catalyst have particular problems associated with do not appear after the reprocessing of a fluoride-free alumina-noble metal catalyst and do not require any consideration.

The invention is based on the surprising finding that the sulfuric acid when used in a practically stoichiometric amount in proportion to the clay, the latter dissolves to a large extent with the formation of aluminum sulfate before it attacks the bound fluoride. The presence of active sulfuric acid will also be present pushed back as a result of continuous dilution by the aluminum sulfate formed, the solution becomes approximately neutral, and the tendency of sulfuric acid to be bound Dissolving fluoride is decreased at the same time. On the other hand, as it is known that fluorides can be brought into solution by means of sulfuric acid, one had first of all assume that the recovery of precious metal from one the precious metal and at the same time Deactivated catalyst containing fluoride on an alumina support by dissolution the alumina with sulfuric acid and later release of the precious metal from the remaining Mud would be impractical.

According to the invention, the particular object is recovery of noble metal from a fluoride-containing catalyst, however, dissolved by that one such a catalyst initially with a in the range of 90 to 1100 / o of the stoichiometric equivalent of the alumina amount of sulfuric acid in the catalyst treated and containing the resulting clay, precious metal and fluoride Sludge by digesting at elevated temperature with a greater than that for the dissolving of the clay contained in the sludge required amount of an aqueous Sulfuric acid from 15 to 80% concentration practically freed from fluoride.

In the method according to the invention is preferably a by Treatment of the catalyst at a temperature between 120 and 175 ° C with a preferably about less than the stoichiometric alumina content of the catalyst equivalent amount of acid, in particular with about 950 / o of the stoichiometric equivalent obtained sludge first washed with hot water, and then 1 to 12 hours long with an excess of aqueous sulfuric acid of 45 to 750 / o concentration digested at a temperature in the range from 85 to 150 "C with constant stirring. In this case it is expedient to use the remaining after separation of the fluoride-containing solution Wash solid residue with deionized water and then remove the precious metal to dissolve the residue washed in this way in aqua regia.

Before treating the deactivated catalyst with sulfuric acid it is often expedient to remove as many of the other impurities as possible, such as metallic Impurities as well as carbon and other carbonaceous material, too remove, usually by washing out the metallic contamination with deionized Water, drying and then oxidation at high temperature in the presence of air happens to remove the carbon and the carbonaceous material.

The treatment with sulfuric acid is then carried out in accordance with the invention. If an essential Licher excess sulfuric acid is used, so that all of the clay and metallic components are dissolved and practical all the solid material left behind is made of precious metal is the accruing Solution strongly acidic, causing serious difficulties in the following stages of the process leads, be it that the solution is discarded as waste or into a tradable by-product, for example for reuse in the production of new catalyst carrier material, should be converted.

On the other hand, if a substantial deficit of sulfuric acid is used so will the amount of undissolved alumina and undissolved fluoride that comes with the Precious metal is left behind for effective and economical removal during The digestion in the next stage of the process will be too great, and the benefits of the invention are completely or at least largely lost.

If the sulfuric acid - but is used in such an amount that the solution, which consists mainly of aluminum sulfate, is neither strongly alkaline nor is acidic, the remaining platinum-containing sludge can be as small as Contains 12% or less of the solids weight except platinum.

The concentration of both treatment of the deactivated catalyst sulfuric acid used can be, for example, 20 to 90 percent by weight.

The treatment is generally desired within 1 to 7 hours Extent going on. Preferably the mixture is made from deactivated catalyst and sulfuric acid kept stirring constantly. If desired, the Mixture is kept at the desired temperature by direct introduction of steam will. The dissolution of only a major part, in particular 80 to 95 percent by weight, the clay in this stage of the present process leaves virtually the total fluorine content of the deactivated catalyst in the sludge.

Digestion with hot water one or more times before using further sulfuric acid is digested, practically all of it is removed from the sludge bound fluoride and causes a sharp decrease in the amount of solids, which except the precious metal is contained in it.

Example 1 84 kg of deactivated catalyst with about 0.4% platinum and about 3.8% fluorine on an alumina support became after previous treatment to remove soluble metal salts, coke and other carbonaceous material in a jacketed reaction vessel with approximately 415 liters of water and 255 liters kg 96 above sulfuric acid (106 0 / o of the stoichiometric equivalent of the clay) offset; Steam was passed through the vessel jacket to bring the contents to 152 "C bring and hold for 4 hours while the contents were stirred. The contents of the vessel was cooled, diluted with water and allowed to settle for 1 hour. The resulting Aluminum sulfate solution was poured from the sludge and filtered.

Analysis of the filtrate showed that there was no soluble platinum in the Solution existed.

A 100 g sample of the platinum-containing sludge that is 4.17 weight percent Contained solids other than platinum and contaminated with 35 parts per million fluoride was placed in a beaker containing 77.5 ml of a 96 weight percent solution sulfuric acid was added. This amount of sulfuric acid resulted a concentration of 60 percent by weight sulfuric acid. The resulting mixture was on a hot plate for 4 hours at a temperature of about 37 to 39 ° C digested. 250 ml of water were then added and the solution was allowed to cool and let them settle. The liquid phase was poured off and the residue four times washed with 100 ml aliquots of deionized water. The liquid phase was poured off every time. The digested and washed sludge was left on overnight a temperature of 110 ° C and then allowed to dry to fluoride concentration and Percent solids other than platinum analyzed.

A second 100 g aliquot of the platinum-containing sludge was Digested in a 60% sulfuric acid solution at 135 to 140 ° C for 4 hours.

The resulting liquid phase was poured off, and the solids were completely washed with deionized water as before. The residue was dried overnight at 110 ° C and then to fluoride concentration and percent solids other than platinum analyzed.

The analytical results thus obtained are shown below Table from which it is easy to see that the method according to the invention the Concentration of solids other than platinum is significantly reduced and the bound Fluoride removed practically completely.

Table I. Part 1 Part 2 Sulfuric acid in weight percent .............. 60 60 Digestion time in hours. 4 4 Digestion temperature in ° C. . 90 to 95 135 to 140 Fluoride concentration in Share per million ...... 2.4 1 Removed fluoride in Weight percent .. .. 93.2 97.0 Solids after treatment in percent by weight * ... 2.29 0.83 *) Solids except platinum, based on the moist sludge.

Example 2 The procedure of Example 1 was followed in the treatment another batch of the same deactivated catalyst, but were followed only 230 kg of 96% sulfuric acid corresponding to 95% of the stoichiometric equivalent the clay used. The resulting sludge contained 11.9 percent by weight solids except platinum and 123 parts fluorine per million.

202 g of this sludge were in a 19.5 ml beaker with 96 Weight percent sulfuric acid added, so that a concentration of 16.5 Weight percent sulfuric acid in the aqueous phase of the sludge resulted. The accruing Mixture was digested on a hot plate for 4 hours at 100-105 ° C. Then the liquid phase was poured off and the remaining solid with deionized Water washed. The residue was dried overnight and then on Fluoride- Analyzed concentration and content of solids other than platinum.

A second portion of the platinum-containing sludge (123 parts per million fluoride) was digested using a 60 weight percent sulfuric acid solution at 135-140 ° C. As described above, the resulting solid was washed, dried and then analyzed for fluoride concentration and percent solids other than platinum. The analysis results for the platinum-containing sludge contaminated with 123 parts fluoride per million can be found in Table II below Part 1 Part 2 Sulfuric acid in weight percent .............. 16.5 60 Digestion time in hours. . . 4 4 Digestion temperature in ° C. . 100 to 105 135 to 140 Fluoride concentration in Parts per million 14.2 2.4 Removed fluoride in Weight percent ...... 88.5 98.0 Solids after treatment in percent by weight * ... 3.58 2.37 *) Solids except platinum, based on the moist sludge.

The above examples illustrate the improvement and the advantageous Results that the process for the recovery of precious metals, in particular Platinum, by using the method according to the invention.

Claims (3)

PATENT CLAIMS: 1. Process for the recovery of precious metal, in particular Platinum, from a deactivated one containing the noble metal on an alumina carrier Catalyst in which the catalyst is dissolved with a major part of the alumina Amount of sulfuric acid treated at an elevated temperature, preferably at at least 120 "C, the resulting solution of a noble metal and carrier residues containing sludge separates, the sludge again subjected to a sulfuric acid treatment and then from the undissolved residue, if necessary after washing out with water, takes up the noble metal in a solvent, characterized in that one a fluoride-containing catalyst initially with a in the range of 90 to 110 01o of the stoichiometric equivalent of the alumina amount of sulfuric acid in the catalyst treated and containing the resulting clay, precious metal and fluoride Sludge by digesting at elevated temperature with a greater than that for the dissolving of the clay contained in the sludge required amount of an aqueous Sulfuric acid from 15 to 800 / o concentration practically freed from fluoride. 2. The method according to claim 1, characterized in that a through Treatment of the catalyst at a temperature between 120 and 175 ° C with a preferably slightly less than that the alumina content of the catalyst stoichiometrically equivalent amount of acid, in particular with about 950/0 of the stoichiometric The equivalent obtained sludge is first washed with hot water and then 1 for up to 12 hours with an excess of aqueous sulfuric acid of 45 to 75 ° / 0 Concentration at a temperature in the range from 85 to 150 "C with constant stirring is digested. 3. The method according to claim 1 or 2, characterized in that the solid residue remaining after separation of the fluoride-containing solution with deionized water and then the noble metal from the residue washed in this way is dissolved in aqua regia. Documents considered: German Auslegeschrift No. 1 051 510.