Preparation Of Copper/Sepiolite Catalyst And Its Application In Synthesis Of P-Hydroxyphenylacetic Acid

This paper makes detailed investigations on the method of sepiolite particles refination and activation, surface modification, copper/sepiolite catalyst preparation and application of this catalyst in synthesis of p-hydroxyphenylacetic acid. Moreover, the method of preparation of copper/sepiolite catalyst by hydrothermal process and its application are the emphasis of this thesis.In order to modify the surface structure of sepiolite particles, refining and acid attacking method are employed. The appearance of processed sepiolite is very different to that of the raw material on SEM photos: those large, gathered fibers have been changed into fine, dispersed ones. However, the original smooth surface of sepiolite becomes very rough, which can lead to uncontrollable particle size when metal is loaded on it. Thus, modify the surface without changing its specific area is needed. On the experiment of modify surface, factors—which can influence the growth of silicate crystal on sepiolite— such as temperature, time and concentration are discussed in detail. From the results of the analyses, findings are presented that temperature and concentration are more important factors then time. From surface configuration, the covered state of well-distributed particles and compact texture are premise and basis to obtain an ideal covering of metal salt over the surface of sepiolite.Preparation of copper/sepiolite catalyst by hydrothermal process, which is the main content in this paper, is influenced by many factors such as concentration of solution, time and temperature of crystallization, temperature of reduction, size of fiber, etc., and the catalysis performance of the product results from these factors. In order to obtain an active catalyst, it is essential to maintain longer hydrothermal time of verdigris, and 12-24 hours is preferred. Adjusting the reducing temperature can control the particle size of copper. Synthesis of p-hydroxyphenylacetic acid—which is an important organic intermediate—with the copper/sepiolite catalyst is another main topic. The hydrolyzing process in alkalescence and p-chlorobenzyl cyanide as a raw material are chosen, and copper/sepiolite catalyst is applied to the hydrolyzing step of sodium p-chlorophenylacetate to sodium p-hydroxyphenylacetate instead of copper. This process developes the new application of such catalyst as metal/sepiolite series. The optimal process conditions are: ratio of sodium hydroxide to sodium p-chlorophenylacetate is 5:1and reaction temperature is 250-270℃and time is 7h, dosage of catalyst is 4%(w%) of p-chlorobenzyl cyanide. Under these conditions, content of p-hydoxyphenylactic acid is more than 98% with yield of 81.2%, greater than those in reference.