Selective oxidation of glycerol over Pt supported on mesoporous carbon nitride in base-free aqueous solution

Abstract

Novel ordered mesoporous carbon nitride (MCN)-supported Pt catalysts were prepared, and then characterized using a combination of powder X-ray diffraction, transmission electron microscopy, N2 adsorption, inductively coupled plasma optical emission spectroscopy, NH3 temperature-programmed desorption, and X-ray photoelectron spectroscopy. These catalysts were evaluated for the selective oxidation of glycerol with molecular oxygen in base-free aqueous solution. The results showed that with increasing N content in the supports, the average Pt particle size in the catalysts decreased, whereas the conversion of glycerol increased. The basicity of the supports is helpful for promoting the oxidation of glycerol to glyceraldehyde and further oxidation to glyceric acid. Glycerol conversion of 63.1% and yields of 58.5% glyceric acid and 24.3% glyceraldehydes were obtained when reacting an aqueous solution of glycerol (0.3M, 20mL) with 0.023g catalyst at 60°C under 0.3MPa O2 for 4h. Upon recycling of the catalyst, the conversion of glycerol gradually decreased. The decrease of catalytic activity during recycling can be attributed to a combination of the growth and oxidation of Pt particles, leaching of N species, and collapse of the ordered mesoporous structure in the carbon nitride support.