petrochemical industrial applications of N-methyl pyrrolidone

With the development of chemical technology and industrial modernization, the quality requirements for lubricants have gradually increased. Lubricant base oils contain a large number of polycyclic aromatic hydrocarbons, alkanes, and highly polar substances that affect their viscosity and oxidation. The traditional refining method uses phenol and furfural as raw materials to extract its aromatics, but due to its poor solubility and insufficient refining depth, it is gradually replaced by the NMP refining process. As early as the mid 1970s, due to its outstanding advantages, foreign countries attach great importance to the development of N-methyl pyrrolidone refining processes and realize the industrialization of NMP refining processes. Krishna et al. [5] of the Indian Institute of Petroleum, respectively, adopted NMP refining methods and furfural refining The method was used to experimentally study the spindle oil fractions of Oman crude oil.

The results showed that NMP Solvent outperformed furfural in terms of refining yield, oxidation resistance, and oil-to-mass ratio. Subsequently, the NMP refining process developed rapidly abroad. By the early 1990s, the N-Methyl-2-Pyrrolidone refining process had exceeded one and a half in the United States. At the same time, China ’s NMP plant gradually replaced furfural refining equipment, and some companies are also retrofitting phenol and furfural units. When the refined oil meets the same quality requirements, the NMP refining process not only reduces the upper temperature and the volume ratio of the agent to the oil, but also improves the lubricating oil yield. The scientific research results show that compared with furfural, it has stable chemical properties and high yields of essential oils, and is an excellent extraction solvent for refined high viscosity lubricants. It was confirmed that too high water content and temperature are not conducive to the refining of distillate oils. Only a proper increase in temperature can improve the quality of lubricating base oils. At the same time, it shows that the use of NMP refined lubricants has good development prospects and practical value. Due to the corrosion problems of some parts and equipment of NMP refining equipment, Sinopec Lanzhou General Plant has carried out research on corrosion causes and protective measures from various aspects such as technology and equipment. At the same time, it draws on the anti-corrosion experience of similar equipment in foreign countries to make process improvements and Equipment modification, adopting measures such as 254S M steel with higher key content and nitrogen sealing, basically solved the corrosion problem of the device, reduced the loss of the device, met the requirements of environmental protection, extended the operating cycle of the device, The rapid improvement has accumulated valuable experience. Compared with phenol and furfural, NMP has the characteristics of strong dissolving power, low energy consumption, low extraction temperature, high refining yield, etc., compared with phenol and furfural Solvent.

The effect of water on hydrolysis of N methyl pyrrolidone

At room temperature, due to the formation of hydrogen bonds between N-Methyl-2-Pyrrolidone and water, the hydrolysis rate of NMP is about 1%, and at high temperatures due to the destruction of hydrogen bonds, the hydrolysis rate of NMP remains at about 2.5%, so when only water is present in NMP The hydrolysis rate is small at both high temperature and room temperature. After adding NaOH, in the NMP containing NaOH solution at room temperature, water inhibits the hydrolysis of NMP to a certain extent, but after a certain amount, due to dissolution Partially non-ionized NaOH, the alkaline environment reduces the activation energy required for NMP to break the C-N bond, thereby intensifying the hydrolysis of NMP.

Through orthogonal experiments, it was found that because NMP hydrolysis needs to break the C-N bond to open the ring and needs to absorb energy, the temperature has the greatest impact on NMP hydrolysis.Secondly, the activation energy of NMP hydrolysis is reduced due to the alkaline environment caused by NaOH. NMP can achieve a higher hydrolysis rate at lower temperatures; the smallest factor that affects NMP hydrolysis is water.The formation of hydrogen bonds between water and NMP at low temperatures plays a role in protecting NMP, but at the high temperature, the presence of NaOH solution Under the influence of hydrogen bonds, the hydrolysis rate of NMP rises.