Researchs Of N-formylmorpholine Synthesis By Reactive-Azeotropic Distillation

N-formylmorpholine(NFM), C5H9NO2, is an excellent industrial solvent. It has been applied in aromatic extraction, Butylene purification and natural gas desulfurization, etc al, and it has some advantages such as high boiling point, good dissolvability and thermal stability, safety and low corrosivity, et al. There are some methods to synthesize NFM . According to the different acylating agent, the synthesis can be classified to formic acid method, methyl formate method, formyl chloride method, carboxide acidylation method and morpholine enamine oxygenation method et al. The formyl chloride method has been eliminated because of its serious corrosiveness and pollution. The methyl formate method produces large amounts of methanol needed to be recovered; Carboxide acidylation method need the costly catalyst,et al. The formic acid method is a better choice for its advantages of less side reaction and abundant supply of raw materials.At present, NFM is synthesized by formic acid method in batch with kettle-type reactor and purified with vacuum rectification. The reaction heat is not used efficiently, and the agent must be separated with distillation, which increases the expenditure of energy. The quality of the product is unstable. By analysis present process, a new coupled process for NFM production is proposed, which consists of reactive distillation and azeotropic distillation.This new process is studied the effects of the condition on the recovery of NFM by experiment and simulation. The optimum process conditions are selected: When the mole ratio of morpholine to formic acid is 1.02 the residence time in reaction section is 3.0h, the volume ratio of circulating solvent to charging rate of formic acid is 8, the top temperature is 71.6℃, the bottom temperature is about 111℃in column, the NTP of rectification section and stripping section are 18 and 6 respectively, the average yield of NFM is 99.45%.The reactive-azeotropic distillation process is simulated with similar conditions to experiment by ECSS, the result coincides with experiment data satisfactorily. The equilibrium stage model and the UNIFAC model are of enough exactitude within right process conditions scope, which is helpful in the process design and scaling-up. The crude NFM is purified by flash evaporation to the purity of more than 99.90%, and the one pass yield reached about 99.0%. This method of purifying NFM is simple and feasible.The development of this new process will provide a new way in NFM production massively and continuously. Comparing the present technique, the reaction heat is used efficiently in distillation; the selected azeotropic distillation solvent RA-01 can form heteroazeotrope with water, and is immiscible to NFM,thus solvent can be recovered by demixing with little energy cosumption. Moreover, this process coupled reactive distillation and azeotropic distillation appropriately, which does promote the development of the complex process.