Heterogeneous Catalytic Conversion Of Biomass Glycerol To Lactic Acid Over Copper And Nickel Based Catalysts And Reaction Kinetics

The demand of energy is increasing with the rapid development of society,the traditional fossil energy storage capacity is limited which will inevitably accelerate the depletion of fossil energy.The excessive use of fossil fuels has led to the extreme deterioration of environment,so searching for green renewable clean energy is imminent.Biodiesel,a representative for new energy and produced by the transesterification between methanol and animal fat or vegetable oil has been used worldwide as a renewable and sustainable source of fuel in virtue of limiting greenhouse gas emission,diminishing pollution,and improving air quality.Accompanied with the biodiesel production,glycerol is formed on a large scale.So the conversion of glycerol to prepare more value-added chemicals attracted the attention of researchers.Among the value-added chemicals,lactic acid is an important chemical because it can be used as the monomer for the synthesis of biodegradable polylactic acid plastics and biocompatible medical materials.Therefore,the catalytic conversion of glycerol to lactic acid has important environmental and economic value.In this paper,catalytic conversion of glycerol to lactic acid catalyzed by supported copper,Cu nanoparticles and supported nickel with the raw material of glycerol,the alkali source of NaOH was studied at a certain temperature.In the process of catalytic conversion of glycerol to lactic acid,the effect of the concentrations of glycerol and NaOH,reaction time,reaction temperature and catalyst loading on the reaction was researched.In order to investigate the reaction mechanism,A power-law expression reaction kinetic equation was used to evaluate the data obtained from the experiments,and good fit results were obtained.1.According to the incipient wetness impregnation method,MgO,ZrO2 and HAP used as the support of Cu0 which was the active site were prepared.In a stainless steel autoclave,all the experiments were carried out.From the results,it was found Cu/MgO and Cu/HAP catalysts hold high basicity exhibited higher catalytic activities for the hydrothermal conversion of glycerol to lactic acid than Cu/ZrO2 catalyst hold low basicity.When the Cu?16?/HAP was used as catalyst to catalytic conversion glycerol(1.0 mol L^-1)to lactic acid with NaOH concentration of 1.1 mol L^-1,the selectivity of lactic acid and the conversion of glycerol were 90% and 91%,respectively.The Cu?16?/HAP catalyst exhibited good recycling performance in the hydrothermal conversion of glycerol to lactic acid.A power-law expression kinetic equation was used to evaluate the effect of glycerol and NaOH concentrations and reaction temperature on the alkaline hydrothermal conversion of glycerol to lactic acid over the Cu?16?/HAP catalyst.The intrinsic reaction activation energy,Ea,was 117.2 kJ mol-1.2.Different-sized metallic Cu0 nanoparticles were prepared by the wet chemical reduction method with organic modifiers.The small-sized Cu0 nanoparticles?CuPEG?prepared by using polyethylene glycol as the organic modifier exhibited high catalytic activity for the hydrothermal conversion of glycerol to lactic acid.When the reaction was carried out with the initial glycerol and NaOH concentrations of 1.0 and 1.1 mol L^-1 at 230 ? for 4 h,the lactic acid selectivity reached 91.9% at the glycerol conversion of 98.0%.Over CuPEG?36.9 nm?and Cublank?118.3 nm?catalysts,the reaction activation energies were 76.3 and 86.5 kJ mol-1,respectively.3.Catalytic conversion of biomass glycerol to lactic acid is an alternative to the conventional fermentation process starting from carbohydrate.Graphite-supported metallic Ni0 nanoparticles effectively catalyzed the hydrothermal conversion of glycerol to lactic acid in NaOH aqueous solution.Ni0 nanoparticle and NaOH synergistically catalyzed the glycerol conversion to lactic acid.When the reaction was carried out with the initial glycerol and NaOH concentrations of 1.0 and 1.1 mol L^-1 at 230 ? for 3 h over Ni0.3/graphite catalyst,the selectivity of lactic acid was 92.2% at the glycerol conversion of 97.6%.The reaction activation energy,Ea,was 69.2 kJ mol-1.The results shown that the copper and nickel-based catalysts exhibited good catalytic activity for the catalytic conversion of glycerol to lactic acid.The preparation of lactic acid with biomass glycerol as raw material has the advantage of substituting traditional saccharide fermentation.