Study On The Synthesis Of Pentaerythritol Catalyzed By Ionic Liqui

The condensation reaction of formaldehyde and acetaldehyde to form pentaerythritol is typical alkali-catalyzed hydroxylaldehyde condensation reaction and Conizzaro reaction.Alkaline ionic liquid has good physical and chemical properties and designability,and has good catalytic activity when widely used as green catalyst for this kind of reaction.Therefore,in the process of sodium pentaerythritol synthesis,by introducing alkaline ionic liquid auxiliary catalysis to improve the synthesis rate of pentaerythritol was studied in this paper.The synthesis and characterization of four basic imidazoles are discussed.Thermodynamic analysis of condensation reaction between formaldehyde and acetaldehyde;A series of related studies on optimization of process conditions for sodium synthesis of pentaerythritol by ionic liquids.First of all,Four basic imidazoles(1-ethyl-3-methyl-imidazoles（[Emim]Ac）,1-butyl-3-methyl-imidazoles（[Bmim]Ac）,1-hexyl-3-methyl-imidazoles（[Hmim]Ac）and methoxy1-ethyl-3-methyl-imidazoles（[Emim]OCH₃）were synthesized by two-step method,respectively A series of characterization analyses were carried out.The results showed that the alkalinity of[Emim]OCH₃、[Emim]Ac、[Bmim]Ac and[Hmim]Ac decreased successively,and the alkalinity decreased slightly with the increase of temperature（28～55℃）.Their electrical conductivity in different solvents increased with the increase of mass concentration（6～20g/L）and temperature（25～60℃）,and was significantly affected by the type of solvent.Their critical micelle concentrations were 9.73、11.46、9.92 g/L and 9.72g/L,respectively.Their solubility increases with increasing polarity of solvent and elongation of side chain alkyl groups.Secondly,the ABWY method was used to estimate the thermodynamic parameters of each component in the reaction system in which formaldehyde and acetaldehyde react to produce pentaerythritose,and the variation of Gibbs free energy and standard chemical equilibrium constant of each step reaction and total reaction in the reaction system with temperature（20～90°C）was investigated.The results showed that the spontaneity of the condensation reaction between formaldehyde and acetaldehyde was significantly affected by temperature.High temperature was not conducive to the forward spontaneous reaction,and pentaerythritose was more conducive to the formation of pentaerythritose at 20～40°C.The value of the standard chemical equilibrium constant decreases with the increase of temperature,that was the conversion rate of the reaction system was significantly affected by temperature.The condensation reaction between Formaldehyde and acetaldehyde hydroxyl aldehyde was more favorable when the reaction temperature is 20～55°C than 55～90°C.Finally,the four basic ionic liquids were used to catalyze the synthesis of pentaerythritol by sodium method.The results show that[Emim]OCH₃ has the best catalytic effect,and the catalytic effect of ionic liquid is greatly affected by its alkalinity.The synthesis of pentaerythritol by sodium method with or without[Emim]OCH₃catalyzed by[Emim]OCH₃ was compared.The results showed that the equilibrium was reached in the absence of[Emim]OCH₃ for 2.5h and in the presence of[Emim]OCH₃for 2h.The introduction of[Emim]OCH₃ increases the reaction rate of pentaerythritol from formaldehyde to acetaldehyde.Furthermore,the process conditions of[Emim]OCH₃ for catalytic synthesis of pentaerythritol by sodium method were optimized by single factor experiment,orthogonal experiment and optimal process repeatability test.The results showed that the optimum synthesis conditions were as follows:[Emim]OCH₃ dosage(n_[Emim]OCH3:n_C2H4O)was 0.02:1、reaction temperature43℃、reaction time 2h;The significant effect of various technological conditions on the yield of pentaerythritol was as follows:reaction temperature>[Emim]OCH₃ dosage>reaction time.