DE2009114A1 - Palladium-carrier catalyst regeneration with - Google Patents

Abstract

Palladium-carrier catalyst regeneration with chlorine and chloroform. Catalyst, Pd, on any carrier, e.g. SiO2 gel, CaCO3, BaCO3, charcoal, is suspended in organic solvent, pref. CHCl3, and reactivated by passing Cl2 gas into suspension. Treatment is esp. suitable for hydrogenation catalysts. Process is simple and avoids use of conc. acids, separation of noble metal from carrier and use of deactivating temp. range. Deactivating organic constituents are removed from surface, whilst crystal structure of Pd is completely re-formed.

Description

Process for the regeneration of supported palladium catalysts The invention relates to a process for the regeneration of palladium catalysts on supports which are used in particular for catalytic hydrogenation.

Due to the wide range of applications of noble metal catalysts in a wide variety of catalytic processes such as catalitic hydrogenation or hydrogenolysis organic-chemical compounds in the synthesis of natural substances or in the plastics industry or for example with catalytic detoxification of exhaust gases and others catalytic reaction is the interest in processes for the regeneration of noble metal catalysts Particularly large, It is known that noble metal catalysts that have become inactive through use be regenerated by the ion dissolving the noble metal and the catalyst after the re-establishes the respective regulation, 1) Through single or multiple use Palladium catalysts that have become partially or completely inactive are predominant processed using Königwasser. 2). 3) It is also known about that metallic palladium dissolved with hydrochloric acid in the presence of an oxidizing agent can be, e.g. B. with HC1 + O2, HCl + Cl2, HCl + H2O2, HCl + HClO3, 4) With these known regeneration processes, it is necessary to remove the precious metal from the carrier separate. Depending on the chemical nature of the carrier, this is sighted through selective Dissolving the carrier and then the noble agent, e.g. B. with CaCO as a carrier or by Dissolving the noble metal and subsequent separation by filtration z. B. with silica gel as a Tröger or even burning the carrier and then loosening, z. B. at Precious metal-coal catalysts.

This elaborate way of working is, for example, at dc. particularly Frequently used carrier silica gel due to the aggressive solvent aqua regia or hydrochloric acid with oxidizing agent and the finest dispersion in it z. B. by filtration or centrifugation to be separated support material technically problematic as special equipment is required for this.

After the noble metal has been dissolved, the solution is separated It is necessary for the carrier to also blast the strongly acidic filtrate several times. To Puche5), when palladium is dissolved in aqua regia, some PdCl4 is always formed. 2NOCl, which is difficult to obtain by repeated smoking with conc.

Hydrochloric acid can be removed and which is then necessary again Catalyst manufacturing process leads to incomplete noble metal precipitation.

With these regeneration processes, precious metal losses are inevitable through the many operations that must be carried out. Besides. permit dissolved or burned carriers such. B. Do not reuse caCO3 or coal.

It is also known6), catalysts by treatment with oxygen-containing To reactivate gases at increased temperature, whereby under higher temperature " mostly a combustion of the organic impurities that inactivate the catalyst is understood. However, this occurs in particular with highly active hydrogenation catalysts a loss of activity a 6) Since, however, the inactivation of the catalyst is not solely on the covering of the catalyst surface with organic substances, rather mainly on a coarsening of the crystal structure during catalysis is due, for this reason, according to Houben-Weyl), highly active catalysts lose z. B. hydrogenation catalysts also have a part of their previous effectiveness, if they are regenerated with oxygen-containing gases at an elevated temperature.

The invention is based on the object of a technically easy to implement To develop a process for the regeneration of palladium catalysts that allows to reactivate the catalyst used without using concentrated acids ilisson without separating the precious metal vou carrier and without being in an inactivating It was found that palladium catalysts were used can reactivate aui carriers by z. B. the black by reduced palladium colored catalyst in an organic solvent, especially chloroform suspended and chemically reacted by introducing chlorine gas.

At the same time, those covering the catalyst surface are inactivating active organic components dissolved. The reactivated intalystor is made by chloroform sucked off, dried and can be used again for catalysis.

Other organic solvents can also be used in place of chloroform can be used, such as methylene chloride, tetra, dichloroethane, chlorobenzene, benzene and other. However, it was found that the palladium nar when using chloroform practically completely and when using methylene chloride almost completely am Carrier sticks, while palladium compounds soluble in other organic solvents occur again as active palladium on the carrier in an H2 atmosphere knock down, It was also found that a complete chemical change of the palladium on the carrier within a short time only when using chloroform and methylene chloride is achieved, while other solvents have longer exposure times to chlorine required are.

In addition, it was found that palladium catalysts were used can reactivate on carriers, in which one -fl. -the reduced one becomes inactive through use which has become a catalyst in an atmosphere which, in addition to chlorine gas, also contains air and / or other non-oxidizing gases e.g. B. nitrogen and / or vaporous organic Solvents, e.g. B. chloroform, may contain, chemically reacted. The one so reactivated Catalyst can be used again immediately for catalysis.

Instead of chloroform, other organic vapors can also be used Solvents can be used.

In the method according to the invention, the chemical change of palladium completely reforms the crystal structure for catalysis take place, as otherwise only by dissolving the precious metal and when manufacturing it again of the catalyst is possible according to the respective regulation.

The particular advantages of the method according to the invention exist as is the case with patent application WP 12 g / 138 098 in the practically lossless one Activation process without separation of the precious metal from the carrier, without application concentrated acids and inactivating temperatures. especially for coarsely dispersed catalysts, moldings, etc., that you can reactivate can only be carried out in the simplest technical way by gassing the solid and that there is no further work-up process or the removal of solution or Make suspension means necessary.

Example 1 10.0 g drier, for the analytical hydrogenolysis of Palladium catalyst used organischon bromine compounds (17.5% palladium on silica gel) are suspended in 20 ml of chloroform at room temperature.

After 15 minutes, chlorine gas was passed over the stirred suspension the previously black catalyst has turned brown. The chloroform is sucked off off, washed with the same solvent and dried for renewed catalysis enabled catalyst.

Example 2 10 g of dry material used several times for catalytic hydrogenation Palladium catalyst (2% palladium on CaCO3) are in 30 ml Suspended in chloroform. Chlorine gas is passed over the stirred suspension for 5 minutes, sucks off the chloroform, washes with the same solvent and dries the Catalyst 1 hour at 120 ° C.

Example 3 1 g of used palladium catalyst (17.5% palladium Silica gel) is slurried in 3 ml of methylene chloride at room temperature. After this After chlorine gas has been passed over the suspension for 1 hour, it is filtered off with suction and washed with methylene chloride and dries the ready-to-use catalyst.

Example 4 1 g of used palladium catalyst (2% plladium on CaC03) in benzene suspension is treated with chlorine gas and then refluxed for 1 hour cooked. The suspension can be used for catalytic hydrogenation.

Example 5 A weak stream of chlorine is passed through heated or boiling Blown chloroform and together with a gentle stream of nitrogen on the in an inactive palladium catalyst (e.g. 2% palladium aui aluminum oxide moldings). After about 2 hours, the chlorine gas is displaced containing atmosphere by air or nitrogen and heated the reactivated and a catalyst capable of renewed catalysis to remove the chlorine for 2 hours 60 to 80 OC or gassed for a while with nitrogen or air at room temperature.

Claims (2)

Claims 1. Process for the regeneration of palladium catalysts on carriers, characterized in that the catalyst, palladium, on any supports, such as B. silica gel, CaC03, BaCO3, carbon, in an organic solvent, preferably Chloroform, suspended and reactivated by introducing chlorine gas into the suspension. 2. The method according to claim 1, characterized in that .an the Reactivation with chlorine gas and another gas or Gasge wipe, z. B. nitrogen or air and / or a vaporous solvent, preferably chloroform.