Study On The Lowering Of Five-membered Ring Impurities During The Synthesis Of Vitamin E

The five-membered ring impurities are the main byproduct of the synthesis reaction of vitamin E and are difficult to separate from the reaction mixture due to the isomerism. The content of five-membered ring impurities directly affect the quality of vitamin E and determine the possibility to meet the demand of upscale pharmaceutical market, which exhibits the necessity and importance of the study on reducing the amount of five-membered ring impurities. The formation mechanism and various reaction conditions of five-membered ring impurities were explored in this paper.Combined with reaction mechanism analysis of five-membered ring impurities effect of reaction temperature, time, catalyst, water and solvent on the formation of five-membered ring impurities were studied through single factor experiments. The researches show that when reaction temperature, initial moisture content of the system, and catalyst concentration rise, and reaction time is shortened more are produced. The effect of the factors on the content of five-membered ring impurities always exist because too low temperature leads to un-complete reaction and too long reaction time such as5hr causes little change of five-membered ring impurities content.It is also found in this paper that phosphoric acid alone or compounded with hydrochloric acid can decrease the amount of five-membered ring impurities based on the mechanism analyzing, single factor experiments and further verifying experiments. The five-membered ring impurities content is lowered to about0.6%.