The Investigation Of The Synthesis Of Pyridine And Its Derivatives By Modified ZSM-5 Catalysts

The Investigation of the Synthesis of Pyridine and its Derivatives By Modified ZSM-5 CatalystsAbstractPyridine and its derivatives are widely used in pharmaceuticals, insecticides, rubbers and dyestuffs. They are not produced by catalytic synthesis on a large scale and mainly depend on import in our country now. In developed country, such as U.S.A. and Japan, they are synthesized by modified zeolite catalysts. Therefore it is of scientific significance and application importance to substitute the imported products for homely-made ones, based on the research of pyridine and its derivatives.In this paper the reaction of formaldehyde, acetaldehyde with ammonia was carried out by fixed bed heterogeneous catalytic reactor. To get pyridine and its derivatives, twelve catalysts were designed and prepared. The activity of these catalysts was evaluated and the reaction conditions and parameters were also optimized. At latm, 450癈, lOOOh"1, the selectivity of main products was 93.03%, at 83.7% conversion of acetaldehyde over Pb(3. 72%)-ZSM-5 catalyst.The catalysts were studied by XRD, IR, ICP and NH3-TPD methods. The results were as follows:1. There were two kind of acid sites in catalysts, Bronsted acid sites and Lewis acid ones. Bronsted acid sites were active for catalytic synthesis of pyridine and its derivatives.2. Catalysts were calcined at the high temperatures, which resulted in the dehydroxy and dealuminium. The dehydroxy changed the BrOnsted acid sitesinto Lewis acid sites and the dealuminium made the pores of ZSM-5 zeolites contracted, with the result of the decrease in the selectivity of main products.3. There was a limitation to the content of Pb in catalysts. When the content of Pb was over 2. 72%, part of PbO accumulated in catalysts.4. With the increase in content of Pb, strong acid sites reduced gradually, which caused the decrease in the activity of catalysts.