Stereo-selective Hydrogenation of Paracetamol to 4-trans-acetamidocyclohexanol on Carbon Supported Ru-M (M=Co, Ni) Bimetallic Catalysts

摘要

4-trans-Acetamidocyclohexanol is an important intermediate in the synthesis of pharmaceutical compounds such as the broncosecretolytic drug Ambroxol. It can be prepared from the catalytic hydrogenation of the aromatic ring of 4-acetamidophenol (paracetamol). The stereoselectivity on this reaction, as far as the cis and trans isomers ratio is concerned, depends on the metal catalyst, the type of support, and the employed reaction conditions. Many patents deal with the use of noble and non-noble metals supported on alumina. It is well known that acidic oxide supports leads to strong metal-support interactions causing metal segregation in bimetallic catalysts. To avoid such effects, as well as secondary reactions associated with the surface acidity of supports, we have selected a high surface area graphite and a carbon molecular sieve as supports of Ru, Co, and Ni monometallic catalysts. Also some Ru-Co and Ru-Ni bimetallic catalysts have been prepared and tested on the title hydrogenation reaction. In order to obtain information of the number of surface sites on these catalysts, CO chemisorption determinations were performed.