Catalyst For The Synthesis Of Fluoride Pyridine Development And Research

Aromatic fluoride is an important medicine and pesticide intermediate,with high value and good market foreground. Halogen exchange reaction is an effective way to synthesize fluorinated organics. But Halogen exchange usually needs high activation energy. Literature states that tetrafluorochloropyridine and pentafluoropyridine are prepered by reacting pentachloropyridine and KF at a temperature of 350℃, and the yield of tetrafluorotrichloropyridine and pentafluoropyridine are respectively around 35% and 15%. when adding benzonitrile as the impregnant of this reaction, and controling the temperature between 330-360℃, the total yield of ultimate product can achieve to 60%. However, when the temperature is higher than 300℃, the reactant can seriously corrupt equipment made from all kind of materials .Play like that, there are a lot of security risks in the conditions of high-pressure operation, which constraints of its industrialization.This paper relates to a process for preparing pentafluoropyridine and tetrafluorochloropyridine by reacting dichlorotrifluoropyridine and potassium fluoride, and researching a new catalyst to reduce the reaction temperature. Through experiment research, we screen out a new combination of catalyst, and obtain a better experiental results in solvent-free conditions. This research has never been done before,which is the point of innovation.Through to tests the mechanism research , through the cross-portfolio, Tetraphe-nylphosphonium bromide and potassium fluoride portfolioed by a certain percentage can catalyze this reaction at the temperature of 240℃, and the yield of tetrafluorochloropyridine and pentafiuorop- yridine are 15% and 10%, and the rate of recycling of dichlorotrifluoropyridine is 50%. Through process optimization, a better process parameters is found : charged 30g of KF,150g of dichlorotrifluoropyridine,3g of Tetraphenylphosphonium bromi- de ,1g of AlCl₃ the reaction temperature is 240℃, the reaction time is 20h.experimental studies have shown that in the catalyst-free and solvent-free conditions, dichlorotrifluoropyridine and potassium fluoride react for 20 hours at the temperatrue of 340℃. The yield of tetrafluoroch- loropyridine is 0.89 percent. In the catalyst-free conditions , the impregnant of benzonitrile is charged , and the reaction carries out for 20 hours at the temperatrue of 350℃. The yeild of tetrafluorochlorop- yridine and pentafmoropyridine are 17% and 6.5%.The new catalyst is promoted to extensive application, respectively pentachloro-pyridine, 2,3,5-trichloropyridine synthesize dichlorotrifluoropyridine 2,3-Difluoro-5-chloropyridin. The catalyst for halogen exchange in response to fluoride can reduce reaction activation energy, but in a very low solvent selective catalytic.