Synthesis Of Cyanoacetamide In The Microreactor

Cyanoacetamide is an important and wildly-used raw material in chemical,especially in pharmaceutical industry.Two major synthetic routes can produce cyanoacetamide.Two route refers to the reaction between cyanoacetate and ammonia-water solution,or ammonia-methanol solution respectively.Both methods are only performed in batchwise reactors currently,thus suffer from the long reaction time and the low yield.To avoid these shortcomings,the synthesis of the target molecule was studied in the microreactors;and an engineering design of productive scale was carried out at the last part of the thesis.The research first studied the reaction of methyl cyanoacetate with ammonia in a flask reactor,The product content,conversion rate and impurity level at different reaction temperatures were obtained.The reactions of methyl cyanoacetate with ammonia-water,and with ammonia-ethanol in a microreactor were studied,The product content,conversion rate and impurity level under different pressure,reaction temperature,mixing effect,material ratio and reaction time were obtained.Through the comparison and analysis of the experimental results,the effects of reactor type,raw material ratio,reaction temperature,reaction pressure,reaction time,mixing effect,presence of hydrogen oxide ion on the conversion and selectivity of the reaction were obtained.The study shows that the reaction temperature plays an important role in the synthesis of cyanoacetamide,while the change of pressure has little effect on the reaction.The conversion of raw materials were boosted with an advanced temperature;however,when the temperature reaches a certain value,the side reaction was intensified,impurities increased,and the content of cyanoacetamide compressed.The increase of the molar ratio of reactants can promote the reaction,but just to a certain extent.The reaction time of microreactor is significantly shorter than that of batch reactor.The results also show that the reaction of the cyanoacetate with ammonia-methanol works better than that with ammonia-water,in both reaction yield and impurity level.The best reaction conditions in the microreactors were determined as following:methyl cyanoacetate and ammonia-methanol(27%w/w)were mixed in a T-type micro-mixer at 10 ml/min and 12.5 ml/min respectively(mole ratio 1:1.27),and then pumped into a 30 m-long capillary microreactor.The reaction was carried out at the bath temperature of 15 ℃and the reaction pressure of 0.45 MPa,and the retention time was 16.5 s.As a result,the product content was 99.1%,the residual raw material was 0.053%,and the impurity 0.319%.Based on these data,the microreactor system with a capacity of 500 tons of cyanoacetamide per year is designed in the last chapter.Compared with the batch reactor with the same capacity,the microreactors have several advantages:continuous-flow process,convenient operation,labor saving and as lower annual operation cost as 100,000 CNY annually.The microreactor system need also less investment on equipment(28.9%lower),as well as less chemicals.The heat transfer area of the microreactor is much larger,and thus the reaction inside is much more safe;the microreactor system is closed and does not need to vent materials,so it is much more environmental-friendly.Therefore,the application of microreactor in the synthesis of cyanoacetamide from methyl cyanoacetate and ammonia-methanol(27%)has showed significant advantages.