Application Of Photodeposition Technology In The Synthesis Of Pyridine Base Over Zeolite

Pyridine base（pyridine and its derivatives）,as a type of nitrogen-containing compound,is widely used as basic raw materials in medicine,pesticides,perfumes,rubber,dyes and other fields,and the demand is increasing year by year.At present,the synthesis of pyridine base mainly includes coal tar extraction and chemical synthesis.The coal tar extraction method has been gradually replaced by chemical synthesis because of limited production and cannot meet market demand.In the current industrial production,formaldehyde,acetaldehyde and ammonia are used as raw materials,and ZSM-5 zeolite is used as the main catalyst to prepare pyridine base in aldehyde-ammonia condensation reaction.In this reaction,metal-supported modification methods are commonly used in industry to improve the catalytic performance of zeolite catalysts,but metal modification methods have problems such as high-temperature calcination,easy agglomeration of metals,and low utilization rates.In view of the above problems,this paper studies as follows:（1）Bi₂O₃ is supported on the surface of ZSM-5 zeolite by photo-deposition technology,which is uniformly dispersed,not easy to agglomerate,and has high utilization rate.In the aldehyde-ammonia condensation reaction catalytic experiment,the dominant products are pyridine and 3-methylpyridine.Compared with ZSM-5 zeolite catalyst,the yield of the composite catalyst is significantly improved.Bi₂O₃ improves the catalytic performance by its contribution to the Lweis acid sites.With the increase of Bi loading,the selectivity of pyridine increased,and the selectivity of 3-methylpyridine decreased,which result from the gradual decrease of the micropore diameter.When the Bi amount is 2.5wt.%,The composite catalyst has the best catalytic performance due to the suitable acidic sites and micropore pore size distribution.At the same time,in a single-pass catalyst,when the temperature is 400°C and the mixing mass ratio of prepared catalysts and commercial ZSM-5 is 1:6,the catalytic performance is the best yieldof 54.9%.The effect of temperature on the reaction is also researched,it is found that the yield is reduced at 350°C,but the catalyst life is doubled up to 4h.（2）Titanium silicon zeolite（TS-1）,with the same MFI topology,is used instead of ZSM-5zeolite to catalyze the aldehyde-ammonia condensation reaction.The results show that although TS-1 zeolite has a catalytic effect on aldehyde-ammonia condensation reaction,The catalytic performance of TS-1 is far inferior to ZSM-5 zeolite because of the weak acid sites.Bi Well-dispersed Bi/TS-1 composite catalysts are prepared using photodeposition technology.It was found that agglomeration begin to occur when the Bi load reaches 10wt.%Compared with TS-1,the catalytic performance of the composite catalyst is improved.The catalytic activity is the best at the Bi load of 5wt.%.