Study On The Catalyst La_0.7Ce_0.3NiO₃ In Steam Reforming Of Glycerol

With the declining fossil fuels and a series of problems caused by its exploitation and combustion,the development and utilization of renewable energy are particularly important and urgent.Biodiesel has been vigorously developed and promoted,with producing by-product of crude glycerol accounting for about 10%of the total weight of biodiesel.However,in the face of a large volume of crude glycerol,it is necessary to develop high value-added products in order to reduce the cost of producing biodiesel.Obviously hydrogen production by glycerol is a potential advantage way.So far,there are many ways to produce hydrogen from glycerol:steam reforming,autothermal reforming,partial oxidation,aqueous-phase reforming,supercritical water reforming.Among them,the steam reforming of glycerol at atmospheric pressure has been extensively investigated due to providing high hydrogen yield,relatively few by-products and similar catalyst process and technology to the steam reforming of methanol or ethanol,which can provide an important reference for further large-scale production in the future.This dissertation summarizes the research on the steam reforming of glycerol.The catalytic steam reforming of glycerol and enhanced process of steam reforming are widely studied.However,there are relatively few studies on the reaction kinetics and mechanism.In addition,the catalytic steam reforming of glycerol focuses mainly on the study on catalyst,including active phase,carrier,promotor and preparation conditions.Enhanced process is mainly achieved by adsorption enhancement,chemical loop,membrane reactor,and adsorption-enhanced chemical loop,adsorption-enhanced membrane reactor.In this work,only solution concentration and calcination temperature were varied in the co-precipitation procedure,and the molar ratio of 0.7:0.3:1:5 for La³⁺,Ce³⁺,Ni²⁺and HCO3^-was kept constant.And then a series of catalysts La0.7Ce0.3NiO3 with perovskite structure were obtained.The activity and stability of catalysts were evaluated in the steam reforming of glycerol.It was found that the catalyst L700-0.3-0.6 had excellent catalytic performance at calcination temperature of 700°C and moderate solution concentration.After 21.5 h reaction,hydrogen yield was kept at about 70%over catalyst L700-0.3-0.6.This result is attributed to the high density of basic site,the highest mass of La2O2CO3 phase,CeO2 with more lanthana doping and smaller particles of CeO2 for catalyst L700-0.3-0.6.The influence of reaction temperature on the catalyst L700-0.3-0.6 was studied in the steam reforming of glycerol.The results exhibited that CH4 yield was very low,which showed that the catalyst had enough capacity to reform the CH4 to generate hydrogen and carbon oxides.The macroscopic and intrinsic kinetics of steam reforming of glycerol catalyzed by catalyst La0.7Ce0.3NiO3 was investigated at a temperature range of 475?to 525?and a molar ratio of water to glycerol of 15?STGR?23.Under the studied conditions,the apparent reaction order of glycerol was 0.37 and the apparent reaction order of water,hydrogen and carbon dioxide were zero by the power-law model.The apparent activation energy of overall reaction was 55.0 kJ mol-1.