Flow synthesis of N-alkyl-5-methyl-2-pyrrolidones over Ni2P/SiO2 catalyst

Effect of Phosphorus Precursor, Reduction Temperature, and Support on the Catalytic Properties of Nickel Phosphide Catalysts in Continuous-Flow Reductive Amination of Ethyl Levulinate

“…The variation of these parameters significantly changes the activity of supported nickel phosphides in hydrodeoxygenation [29][30][31][32] and hydrodesulfurization [33] reactions. In our previous work, it was shown that 6.3% of the Ni 2 P/SiO 2 catalyst prepared by impregnation of silica with aqueous solutions of Ni(CH 3 COO) 2 and (NH 4 ) 2 HPO 4 provides continuous-flow reductive amination of EL to N-alkyl-5-methyl-2-pyrrolidones with the yield up to 94% [24]. Isolation of the target product from the reaction medium is a difficult task, the solution of which is facilitated by an increase in the yield.…”

“…The Ni 2 P/SiO 2 _A600 catalyst shows the formation of HMP with 96% selectivity at 98% conversion of EL [24]. A decrease in the reduction temperature to 500-550 • C leads to a decrease in the hydrogenation activity that, in turn, gives a lower yield of HMP (Table 2, entries 1−4).…”

“…Before the experiments, the precursor was reduced in situ in a hydrogen flow (100 mL min −1 ) at atmospheric pressure. The samples were heated to 450-600 • C (for Ni 2 P/SiO 2 and Ni 2 P/Al 2 O 3 ) or to 400 • C (for Ni/SiO 2 and Ni/Al 2 O 3 ) at a heating rate of 1 • C min −1 and kept at the reduction temperature for 1 h or 2 h, respectively [24,[29][30][31]34].…”

“…Reductive amination of LA or levulinates with primary amines over heterogeneous metal catalysts using molecular hydrogen as a reducing agent is a promising method for the synthesis of N-substituted-5-methyl-2-pyrrolidones [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], which are an alternative to the carcinogenic solvent N-methyl-2-pyrrolidone (NMP) used in large volumes in industry [3]. Due to the high cost and limited availability of precious metals, the use of non-noble metal catalysts is of particular interest [1,[20][21][22][23][24][25].…”

“…In the case of EL, the process begins with the condensation of EL and amine to the corresponding imine, which reacts with hydrogen over metal sites to form 4-aminopentanoate, and further intramolecular amidation leads to pyrrolidone. The conversion of imine can 2 of 11 also occur via imine-enamine equilibrium, followed by the elimination of EtOH and hydrogenation to the desired product [9,13,17,24]. At the same time, hydrogenation of EL with the subsequent cyclization gives γ-valerolactone (GVL) in a side reaction (Scheme 1).…”