Sustainable synthesis and extraction of 5-methyl-N-phenyl-2-pyrrolidone produced via reductive amination of levulinic acid

Abstract

5-methyl-N-substituted-2-pyrrolidones (5MPs) have been proposed as alternatives to N-methyl-2-pyrrolidone, a solvent with industrial and commercial applications which is considered hazardous and undesired by regulators. 5MPs are produced via reductive amination of levulinic acid with a catalyst and a reducing agent like H2. However, the separation of 5MPs from the reaction media is scarcely studied to understand industrial and commercial viability. This work is centered on producing 5-methyl-N-phenyl-2-pyrrolidone from levulinic acid via reductive amination followed by its liquid-liquid extraction using specifically selected extracting solvents. The extraction step considers not only the separation performance but also the environmental, health, and safety (EHS) criteria of the selected solvents. Thus, COSMO-RS, along with EHS guides, were used to screen solvents to extract 5-methyl-N-phenyl-2-pyrrolidone from methanol or water, which are used as reaction solvents. Some promising extracting solvents were studied in ternary liquid-liquid equilibrium experiments based on the partition of 5-methyl-N-phenyl-2-pyrrolidone and the reactants in the extracting solvent + (water or methanol) biphasic system. Subsequently, the solvents were tested for the extraction of the 5-methyl-N-phenyl-2-pyrrolidone from a real reaction mixture, produced by a Pt/TiO2 catalyzed reductive amination at 25 degrees C and 1.013 bar. Predictions and further validations of the distribution coefficients and selectivities for the solute show that anisole and limonene are favorable solvents for extracting 5-methyl-N-phenyl-2-pyrrolidone from water and methanol media, respectively. Both solvents are attractive alternatives due to their biobased nature, with the former ranked as recommended by EHS guides and the latter having some concerns with environmental criteria. However, both solvents show advantages for a scale-up of the reaction + separation process.