Study On Preparation Of Supported Bimetallic Nano-catalysts And The Selective Oxidation Of Glycerol

It is feasible that producing the high value-added lactic acid from a large number of glycerol—the by-product of biodiesel.This path can solve the problem of the comprehensive utilization of glycerol and the pollution in the production of lactic acid using chemical method and the low efficiency in the production of lactic acid using fermentation method.A series of bimetallic nanoparticles(NPs)catalysts,consisting of the base metal Ni,Co,Fe,Zn,Cu,Sn and the noble metal Pt,Pd,were made with the aid of high intensity ultrasound.These samples are characterized by ICP-AES?TEM?XPS and applied to the oxidation of glycerol.The characterization results that the metal nanoparticles are dispersed well.And the size of the NPs was tailored in the range 2-5nm.The particle size of the nanoparticles containing Ni is less than Pt or Pd nanoparticles without Ni.When the ratio of Pt,Ni differs,the Pt,Ni bimetallic catalyst particle size is similar.In the Pt-Ni NPs,Pt exists in the form of Pt0 and PtO,Ni exists in the form of NiO and Ni(OH)2.The binding energy of Pt4f peaks and the binding energy of Ni2p peaks are also gradually increased with the addition of the proportion of Ni.The XPS analysis demonstrated that the surface Pt:Ni molar ratio was lower than that of the total Pt:Ni ratio determined by ICP analysis.This suggests that Pt was present as the core and Ni oxide or Ni hydroxide enriched outside the Pt particles in the Pt-Ni particles.These catalysts can catalyze glycerol to lactic acid at conditions of low temperature(363K)with the present of alkaline,and Ni promotes Pt and Pd catalysts for glycerol oxidation to lactic acid.When the Pt:Ni molar ratio is 1,the selectivity of lactic acid reached 73.7%and the rate of glycerol conversion up to 58%at the same time.When the Pt:Ni molar ratio lower,the activity of the catalysts and selectivity of lactic acid also decrease.At last,the adding of base metal Ni can reduce the cost of the catalyst greatly.The P25 has no effect on the oxidation of glycerol.And NaOH solution,which as the reaction medium,increase the reaction rate of glycerol to glyceraldehyde and glyceraldehyde to lactic acid.