Heterogeneous Catalytic Synthesis Of 1,2,4-butanetriol

As an important chemical intermediate,1,2,4-butanetriol was used in fine chemicals,pharmaceutical chemistry,military materials,polymer materials and other fields.In the military field,1,2,4-butanetriol trinitrate(BTTN),as one of the most significant derivatives of 1,2,4-butanetriol,is a good energetic plasticizer.It can interact with nitroglycerin as a high-energy propellant to solve the safety problems caused by the low-temperature brittleness of nitroglycerin(NG).Therefore,the synthetic method of 1,2,4-butanetriol has been widely investigated.To date,the key synthetic method of 1,2,4-butanetriol is as follows:(1)the 1,2,4-butanetriol is obtained by catalytic hydrogenolysis of 2-butene-1,4-diol epoxide which is acquired by the epoxidation of 2-butene-1,4-diol.However,owing to high price of raw materials,harsh conditions,poor stability of intermediates and the use of a large amount of precious metals in catalytic hydrogenolysis,the large-scale and low-cost synthesis of 1,2,4-butanetriol was greatly limited.In addition,it also be reported that the synthesis of 1,2,4-butanetriol triacetate with propylene acetate via Prins reaction.This method is considered as a strategy that may have potential to replace current1,2,4-butanetriol production methods.For this method,there are still many problems for further investigation,such as difficulty in product separation and environmental pollution caused by the use of a homogeneous catalytic system.In order to achieve low-cost and efficient synthetic method of 1,2,4-butanetriol,this thesis intends to develop a new heterogeneous catalytic system in epoxidation/catalytic hydrogenolysis strategy and Prins reaction with propylene acetate.The specific research contents of this thesis are as follows:(1)For the poor repeatability and stability of epoxidation of 2-butene-1,4-diol,the epoxidation catalyst was screened firstly.As a result,sodium tungstate was used in the reaction.Then many conditions have been optimized,such as the amount of catalyst,the amount of base,the amount of oxidant,the type of solvent and reaction temperature.Finally,the product can be obtained in excellent yield under the optimized condition.This method reveals a new strategy for catalytic epoxidation and achieves the efficient synthesis of the key intermediate 2,3-epoxy-1,4-butanediol in the route of 1,2,4-butanetriol synthesis.(2)Based on the above result,we investigated the heterogeneous catalytic reaction for the hydrogenolysis of 2,3-epoxy-1,4-butanediol.A series of commercially available Pd/C catalysts for hydrogenolysis has been screened.Then a series of Pd/C catalysts with different carbon supports have been prepared,followed by being utilized in hydrogenolysis reaction.Among them,Pd(OH)₂ with carboxylated carbon nanotube as support demonstrated better yield of 1,2,4-butanetriol.Then we optimized the loading of the catalyst and the 1%loading of Pd(OH)₂/carboxylated carbon nanotubes demonstrate best catalytic activity.Then the type of solvent,concentration of reaction,temperature of reaction,hydrogen pressure of reaction and reaction time were optimized.In this process,the amount of Pd was decreased to 0.25%of the mass of the substrate,and the product can be obtained in 87%yield.The recycling evaluation of the recovered catalyst demonstrated that the catalyst after the reaction also has some catalytic effect.(3)Given the use of concentrated sulfuric acid with corrosiveness and environmental pollution,a heterogeneous solid acid catalytic method has been revealed for synthesizing of 1,2,4-butanetriol triacetate by Prins reaction with propylene acetate.Through the screening of a series of solid acid catalysts,we determined that sulfonic acid resin catalyst NKC-9 with strong acidity could be used as catalyst.The sulfonic acid resin catalyst NKC-9 with strong Bronsted acidity was determined as the optimal catalyst.Then the amount of catalyst,temperature of reaction,the amount of paraformaldehyde and the loading time of substrate were all optimized.Under the optimized conditions,the NMR yield was obtained in 50%.Compared with the original patent,this method uses a resin catalyst which is facile to recover,easy to operate and cheap than concentrated sulfuric acid which is environmentally polluting,corrosive.Furthermore,the reaction yield is slightly better than the result of concentrated sulfuric acid catalysis.