Monomer

NMP can be recycled using a multi-stage distillation process to separate solvents into its components at lower-than-boiling point temperatures. Waste is removed and clean solvent is left. You can expect to recover up to 95% of the used NMP. The battery manufacturer may use upwards of 10,000 to 20,000 NMP per month, which in a year can translate to over 240,000 NMP.
Recycling is an environmental and cost-friendly alternative to buying new NMP and disposing of the used solvent after one use.
With solvent recycling, wasted NMP can be recovered and reused, reducing the cost of buying and disposing of single-use solvent. The recyclability of NMP is a huge benefit as a solvent as it does not pose as a dangerous environmental threat like other solvents when they have been used.

N-methylpyrrolidone (NMP) is a polar aprotic solvent. It has the advantages of high boiling point, strong polarity, low viscosity, strong solubility, non-corrosion, low toxicity, good chemical and thermal stability, etc. It is mainly used It is used in the fields of aromatic extraction, purification and separation of acetylene, olefins, and diolefins, polymer solvents and polymerization solvents. With the rapid development of domestic polyamide, polyimide, polyphenylene sulfide and other high-strength engineering plastics and high-strength fibers, the quality and demand of N-methylpyrrolidone have been put forward higher requirements.

At present, there are three main industrial production processes for N-methylpyrrolidone: a) γ-butyrolactone (GBL) and monomethylamine (MMA) are reacted to synthesize N-methylpyrrolidone; b) γ-butyrolactone and mixed amines Synthesis of N-methylpyrrolidone by reaction; c) 1,4-Butanediol dehydrogenation-amination to prepare N-methylpyrrolidone. The production capacity of foreign N-methylpyrrolidone is mainly concentrated in the hands of a few large companies. There are more than 10 domestic enterprises engaged in the production of N-methylpyrrolidone, but the scale of the equipment is relatively small, the source of raw materials is many, and the product quality stability is poor , The production technology needs to be improved. At present, the domestic apparent N-methylpyrrolidone annual output is 53 kt/a, and it is growing at an annual rate of 6% to 8%. The prospect of NMP is relatively broad.

NMP (C5H9NO, molecular weight 99, boiling point 203°C) has a pH=7~9. It is weakly alkaline with a slight ammonia smell. It is a colorless to light yellow transparent oily liquid belonging to nitrogen heterocyclic compounds. It has good chemical stability. It is relatively stable in a neutral environment. Due to the pyrrole ring in its molecular structure, NMP is prone to hydrolysis in an alkaline environment. NMP can be oxidized by hydroxyl in the water phase to generate 66 products, of which 24 can be identified. NMP undergoes a hydrolysis reaction in an acidic environment with water to generate 4-methylaminobutyric acid, which is further decomposed into succinic acid semiamide.

And it has high thermal stability. In the absence of water and air, the decomposition temperature is about 350°C. Although the color of NMP turns yellow at 200°C, it does not affect its use. When NMP encounters air and water during use, it is prone to decomposition reaction. In the presence of oxygen and water at the same time, NMP can undergo hydrolysis and oxidation reactions at a low temperature of about 120-200°C.

NMP, also known as N-methyl-α-pyrrolidinone; N-methyl-α-pyrrolidone, N-methyl-γ- butyrolactam, N-methyl-2-pyrrolidinone, N-methyl-2-pyrrolidone, n-methylpyrrolidinone, 1-methyl-2-pyrrolidinone and 1-methyl-2-pyrrolidone, is a derivative of γ-butyrolactone. Molecular formula: C5H9NO, molecular weight: 99.1311. NMP is a colorless and transparent liquid with a slight ammonia smell. It is a highpolarity, chemically and thermally stable high-boiling solvent (boiling point: 202 °C). It is completely miscible with water, alcohol, ether, ketone, ethyl acetate, chloroform, and benzene. The solubility of unsaturated hydrocarbons such as alkynes, olefins, and diolefins in NMP is higher than that of saturated hydrocarbons. In addition, a variety of polymers can also be dissolved in NMP.

Based on the raw materials used, several processes such as succinonitrile route, condensation of γ-butyrolactone and methylamine, 4-oxidized methyl butyrate method, and 1,4-succinic acid route for manufacture of NMP were developed. However, the only process currently employed in the industry is the condensation from γ-butyrolactone and methylamine. The process technologies are similar in all NMP producers, yet the main difference is the production method for γ-butyrolactone intermediate. developed a process that included dehydrogenating BDO to γ-butyrolactone and then condensing with methylamine to produce NMP. Mitsubishi Chemical Corporation of Japan developed a process that included hydrogenation of maleic anhydride to γ-butyrolactone and condensation with methylamine to yield NMP. Synthesis of NMP by the condensation of γ-butyrolactone and methylamine in the absence of a catalyst was developed. γ-Butyrolactone and methylamine are reacted at a temperature of 240–285 °C and a pressure of 5.0–8.0 MPa for 2–3 h, and the resulting NMP is purified by fractional distillation to obtain a high-purity product. Its reaction equation is as follows:

The reaction is carried out in two steps. The first step is the reaction of γ-butyrolactone with methylamine to form N-methyl-γ-hydroxybutanamide, which is a reversible reaction and can be carried out at lower temperatures and lower pressure. The second step is dehydrating and cyclizing N-methyl-γ-hydroxybutanamide to NMP under higher temperatures and pressure. The two-step reactions can be carried out batch-wise in an autoclave or continuously in a tubular reactor.

Since the boiling point of NMP (204 °C) is very close to that of the raw material γ-butyrolactone (206 °C), separating them by fractional distillation is difficult. Therefore, a large excess of methylamine is applied in the reaction (molar ratio of methylamine to γ-butyrolactone from 1.5 to 1.8) for complete conversion of γ-butyrolactone, simplifying the product separation process. Anhydrous methylamine can be used as the raw material, but adding some water to the reaction system can increase the selectivity of NMP. The reaction solution is subjected to fractional distillation in the amine removal tower, in which the unreacted methylamine is distilled from the top and recycled to the reactor. The bottom product of the tower is introduced into the light fraction removal tower, and all the remaining water is distilled from the top of the tower. The light fraction is collected from the sideline on the tower's upper section. The bottom product of the light fraction removal tower is introduced into the heavy fraction removal tower. The heavy fraction is removed from the bottom of the tower, and NMP of high purity is obtained from the top. The yield of NMP is up to 99% based on γ-butyrolactone.

N-Methyl-2-pyrrolidone is easily absorbed from the human skin gastrointestinal and respiratory tracts. The permeability of commercial solvents through human skin has been investigated in a study, and the permeability rate of N-Methyl-2-pyrrolidone was found to be higher than that of other solvents. It is quickly distributed in most organs, with a relatively high concentration in the sexual organs. Repeated exposures may be one of the reasons for infertility. The volume of distribution (Vd) of N-Methyl-2-pyrrolidone is 0.7 L/kg, and the half-life of unchanged N-Methyl-2-pyrrolidone in the plasma after oral or dermal administration and inhalation exposure are 9–12 h and 4 h, respectively. N-Methyl-2-pyrrolidone is hyroxylated to 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) by the isoform 1E of cytochrome P450 (CYP1E) and oxidized to N-methylsuccinimide (MSI); MSI is then hyroxylated to 2-hydroxy-N-methylsuccinimide (2-HMSI). 2-Pyrrolidone is reported as another metabolite of N-Methyl-2-pyrrolidone.
In rats, it is absorbed rapidly after inhalation, oral, and dermal administration, distributed throughout the organism, and eliminated mainly by hydroxylation to polar compounds, which are excreted via urine. About 80% of the administered dose is excreted as it and its metabolites within 24 hours. A probably dose dependent yellow coloration of the urine in rodents is observed. The major metabolite is 5-hydroxy-N-methyl-2-pyrrolidone.