【摘要】 采用向二甲基甲酰胺 ( DMF)回收系统加入二甲胺的方法 ,从化学平衡的角度研究了二甲胺在 DMF回收系统中对甲酸生成的抑制作用 ;随着二甲胺与甲酸摩尔比的增大 ,甲酸降低的速率加快。同时 ,在传统的 DMF回收工艺的基础上 ,设计了第一溶剂回收塔顶的二甲胺污水精馏塔 ,以回收第一溶剂回收塔顶的二甲胺 ;该方法只需对原始流程稍加修改就可达到降低“第二回收塔进料中甲酸浓度过高”和“减少第二回收塔底 DMF损失量”的目的。更多还原

【Abstract】 In the DMF (Dimethyl Formamide) solvent reclaim system, the percentage of formic acid is about from 0.6 % to 1.5 % in the feed of the tar column called the 2nd solvent reclaim column. The higher is the formic acid content in the feed, the larger is the amount of DMF loss in the bottom product of the tar column, because the formic acid and DMF can form azeotrope whose boiling point (BP) is 163 ℃ (the BP of DMF is 153 ℃). On the other hand, the high acid content can accelerate the DMF hydrolytic degradation, which causes the further loss of DMF. In the reaction of DMF hydrolytic degradation,the DMF produces DMAM (Dimethylamine) and formic acid. According to the chemical equilibrium, if DMAM were taken out from the reaction system, the DMF hydrolytic degradation rate should become faster. Otherwise, if DMAM were added to the system, the DMF hydrolytic degradation rate should be slower or stop, or the DMAM should react with formic acid to produce DMF. Hence, the theory that the DMAM is added to the system to restrain the DMF loss would be verified in the experiment. The influence of DMAM to restrain the production of formic acid and the reaction time and molar ratio of DMAM to formic acid on the acidity of DMF solution were studied.A universal equation to direct the practical production was gotten by the regression of the experimental data.A new scheme of reconstruction of the DMF solvent reclaim system is provided.更多还原