CH308889A - Method of making a catalyst. - Google Patents

Description

  

  



  Method of making a catalyst.



   Many catalysts for the selective hydrogenation of triple bonds to double bonds are described in the literature. The preparation of these catalysts is usually cumbersome and the effect is not entirely satisfactory, since double bonds are also hydrogenated despite a certain selectivity.



   According to the process of patent no. 2804616, a catalyst of high selectivity is obtained by reducing the activity of palladium, possibly supported on a support, with lead.



   It has now been found that a very selective catalyst, with the use of which triple bonds to double bonds can be hydrogenated while protecting existing or emerging double bonds, is obtained if the activity of a palladium catalyst in the form of palladium metal with and without supports, for example with barium sulfate , Clay, calcium sulfate, calcium carbonate, magnesium oxide, carbon as a carrier, is lowered with bismuth. Bismuth is used in the form of a salt in aqueous solution or as a suspension by stirring the suspension of the catalyst with a salt of the metal in question and heating it for a short time.



   The subject of the present patent is a palladium catalyst for selective Hy drations, which is characterized by a content of bismuth. It is assumed that the bismuth is alloyed with the palladium and is mainly located in the areas of the individual catalyst particles close to the surface, while the interior of the particles remains free of bismuth.



   The patent also relates to a method for producing a selective palladium catalyst according to the invention, which is characterized in that a non-selective palladium catalyst is brought into contact with a bismuth salt in an aqueous medium.



   The catalyst is easy to prepare, easy to reproduce, not pyrophoric and can be used wherever triple bonds are to be converted into double bonds. In certain cases it is advisable to add a little quinoline mainly when hydrogenating molecules in which there are already several double bonds in addition to the triple bond. The catalyst is particularly suitable for the partial hydrogenation of acetylenic hydrocarbons and acetylenearbinols. For example, acetylene is hydrogenated to ethylene in good yield in acetone solution.



  The partial hydrogenation of vinyl acetylene, an intermediate product of synthetic rubber, is carried out in an analogous manner. Ethylene carbinols, for example 1-oxyethinyl1, 5, 9, 13-tetramethyltetradecane, are reduced to the corresponding ethylene carbinols in an excellent yield.

   With bismuth deactivated catalyst it is possible to obtain 1,6-dioxy 3, 7-dimethyl-9- [trimethyl-eyclohexen- (1 ') -yl] -nonadiene- (2, 7) -yne- (4) with a melting point of 54 up to 56¯ C in petroleum ether in the presence of quinoline with a yield of 85% 1,6-dioxy-3,7-dimethyl-9 - [trimethyl-cyclohexen- (l ') - yl] -nonatriene- (2,4 , 7) from melting point 73 to 74¯ C.



   Example:
20 parts of a 5 percent palladium chloride solution are diluted to 200 parts by volume with hot water, then a 5 percent soda solution is added until all the palladium has precipitated. A sodium formate solution, which is prepared from 1 part of formic acid and 30 parts of 5 percent soda solution, is carefully added dropwise to the hot suspension. After everything has been reduced, the water is decanted from the palladium metal and this is thoroughly washed out by repeated decanting. The palladium is now suspended in 20 parts of water, 1 part of bismuth nitrate is added and the mixture is stirred.

   The bismuth salt is obtained in solution by adding hydrochloric acid. After the mixture has been stirred at 90 ° C. for 1/2 hour, it is filtered off, washed, dried and finely sieved.

 

Claims (1)

PATENT CLAIMS: I. Palladium catalyst for selective Hy drations, characterized by its bismuth content. II. Process for the production of a selective hydrogenation catalyst according to patent claim I, characterized in that a non-selective palladium catalyst is brought into contact with a bismuth salt in an aqueous medium.