Citric acid modified Ni3P as a catalyst for aqueous phase reforming and hydrogenolysis of glycerol to 1,2-PDO

Abstract

Citric acid (CA) modified Ni₃P catalysts with small particle sizes were prepared by H₂ temperature-programmed reduction (H₂-TPR) of the precursors, which were prepared by co-precipitation with Ni(NO₃)₂·6H₂O and (NH₄)₂HPO₄, using citric acid as the chelating agent and calcining under a N₂ atmosphere. The catalytic activity of the prepared catalysts was tested in the aqueous phase reforming (APR) and hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). The effects of the CA/Ni molar ratio and reaction conditions (temperature, pressure, and time) on APR and hydrogenolysis of glycerol were investigated. The CA(1)–Ni₃P catalyst exhibited the best performance at 220 °C, 0.5 MPa N₂, and 8 h with 74.6% glycerol conversion and 43.2% selectivity of 1,2-PDO. The prepared CA(x)–Ni₃P catalysts were characterized by XRD, N₂ adsorption, Raman spectroscopy, CO-chemisorption and TEM. The addition of CA significantly enhanced the dispersion of Ni species in the precursors and enlarged the surface area of the catalyst. The residual carbonaceous species after calcination in N₂ prevented the aggregation of Ni₃P particles and promoted the reduction of the precursors. Compared with the unmodified Ni₃P and CA(x)–Ni₃P calcined in air, the CA(x)–Ni₃P calcined in N₂ with a smaller average particle size exhibited higher catalytic activities.