Experimental study on distillation and purification of reclaimed NMP

With the proposal of double carbon target, NMP is widely used in lithium battery industry, chemical process, petroleum industry and other industries. Its purity directly affects the production and quality of products. In this paper, the NMP recovered liquid is taken as the experimental object, and the atmospheric and vacuum distillation methods are used to distill the recovered liquid for many times to remove impurities, so as to reduce the content of impurity elements such as Ca, Na, Si and water molecules. The Karl Fischer moisture meter, ICP-OES and ultraviolet photometer are used to detect and compare the experimental results. It is found that the moisture in the NMP recovered by distillation can be gradually reduced. Through UV analysis, in the second temperature step of distillation, 274 nm and 325 nm impurity peaks can be removed to achieve the purpose of removing impurity peaks and effectively reduce the impurity content in NMP recovery solution. The experimental method for removing impurities of Ca, Na, Si elements and water molecules in NMP recovery solution proposed in this paper provides a certain reference for NMP purification research.