Preparation And Catalytic Properties Of Transition-Metal-Containing Hydrotalcite-like Compounds

Hydrotalcite-like compounds (HTlcs), which is called layered double hydroxides (LDHs), is a kind of anionic clays. It has a lot of functions for its double layered structure. Scientists began to study the structures and properties systematically from the middle of last century and have put into use in many areas. They also prepared kinds of HTlcs which contain transition rnetals or various anions by different methods, which extends the application areas. At the moment, HTlcs have showed great protentials in catalysis, pharmaceutical industry and environmental protection and so on. HTlcs which contain transition mentals have big advantages in catalytic reactions.4,4’-dinitrostilbene-2,2’-disulfonic acids (DNS) was the intermediate for the preparation of4,4’-diaminostilbene-2,2’-disulfonic acids (DSD), which is an important raw material in dye industry. At present, DNS is prepared by the oxidation of2-methyl-5-nitrobenzenesulfon-ic acid (NTS) in alkaline solution catalyzed by transition metal salts like MnS04. Because of the use of the alkaline solution and the transition metal salts, this production process was environmentally harmful. Therefore, the invention of a recyclable catalytic system to replace the existing process is needed.Four series of HTlcs containing different kinds of transition metals were prepared by coprecipitation method and were used to catalyze the oxidation of NTS to synthetize DNS. Catalytic active sites as well as basic sites are favorable for the reaction. The results showed that the four series of HTlcs were effective for the reaction, especially the catalysts containing Fe was the most favorable serie, which has the biggest potential.