Exploration of new synthesis process of pentalactam
Pentanolactam was prepared by mixing cyclopentanone and reaction auxiliary cyclohexanone in a certain proportion as raw materials,followed by aminooximation reaction,separation of oxime products,Beckmann rearrangement reaction,hydroly-sis neutralization reaction,separation and purification.The synthesis process conditions of pentanolactam were investigated through single factor experiments.The results showed that the mass fraction of oxime in the separated ammonia oxime wastewater from aminooximation separation unit could decrease to below 0.1%by adding the reaction auxiliary cyclohexanone to cyclopen-tanone at a molar ratio of above 4.0,and a solution with a mass fraction of lactam higher than 30%in benzene could be obtained by using benzene to extract the oil phase of caprolactam and pentalactam produced during hydrolysis neutralization;the conversion rate of ketone and the selectivity of oxime were both higher than 99.8%when the aminooximation reaction conditions of cyclopen-tanone and cyclohexanone mixture were optimized as followed:reaction temperature of 80-85℃,hydrogen peroxide-to-ketone molar ratio of 1.08-1.12,ammonia-to-ketone molar ratio of 1.4-1.6,3.0%-4.0%catalyst in reaction system by mass fraction and reaction residence time of 90 min;the conversion rate of oxime and the selectivity of the product were both above 99.8%when the reaction conditions for Beckman rearrangement and hydrolysis neutralization reaction were optimized as followed:rear-rangement reaction temperature of 90-110℃,acid-to-oxime molar ratio of 1.12-1.20,hydrolysis neutralization reaction temper-ature of 40-50℃and pH value of 5;and the new process for synthesizing pentanolactam not only can provide high conversion rate and selectivity,but also can reduce the oxime content of ammonia oxime wastewater,depress the loss of oxime,and solve the problem of low extraction efficiency of pentalactam with benzene.
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