The Supported Au-based Catalyst Selectively Catalyzes The Oxidation Of Glycerol

With the progressive depletion of non-renewable resource,the development and utilization of renewable resources have been devoted much attention.As one of the renewable resource,the output of bio-diesel is increasing.However,as the main byproduct during the production of bio-diesel,glycerol has been hindering the development of bio-diesel industry severely.Therefore,the proper use of the glycerol has been taken as the most important approach to the economic utility of bio-diesel.The technology of catalytic oxidation has been adopted in view of its mild reaction conditions,the products easy separation,renewable catalysts and high-added-value products etc.In this thesis,our research concentrates on the following fields.Selective catalytic oxidation of glycerol was investigated using single metal oxides and composite metal oxides supported monometallic Au or bimetallic Au-M catalysts,and dihydroxyacetone(DHA)or lactic acid were obtained as the predominant product.Meanwhile,various characterizations were taken to investigate the structure and composition of these catalysts and the influence on the reactivity of glycerol oxidation.Main conclusions are as follows:1.The as synthesized catalysts were evaluated in the selective catalytic oxidation of glycerol to DHA under base-free conditions.The Au/CuO catalyst showed the best catalytic activity and the good selectivity followed by Au/ZnO.The TEM analysis results indicate that in Au/CuO catalyst Au particles are smaller than Au/ZnO catalyst,which guarantees a larger surface of Au can be exposed.Moreover,through characterization we found that the CuO is easy to be reduced which could provide the lattice oxygen species for the reaction.This could be the reason for the highest catalytic activity.The preparation methods of Au/CuO would influence the performance of catalysts greatly.Au/Al2O3 catalyst has great selectivity toward DHA but low catalytic activity,because the existence of oxidic Au species in the catalyst.With the progress of the reaction,the catalytic activity of Au/ZnO catalyst and Au/CuO catalyst decreased greatly.For the Au/ZnO catalyst,it attributes to the changed carrier structure which causes the loss of Zn element and the increase Au particles size.In addition,the surface carbon depositions and the change of Cu valent are possible reasons for activity reduction.2.The molar ratios of Cu/Al in the CuAlO composite metal oxide affect the content of the reactive oxygen species and in turn catalytic activity of catalytic oxidation glycerol using Au/CuAlO-x catalysts.When the molar ratios of Cu/Al reached to 5:1,the supported catalyst has the best catalytic activity.Oxygen partial pressure,reaction temperature and time etc.correlate with the catalytic activity and product selectivity.Au/CuAlO-3 catalyst gets the optimal performance in which the conversion of glycerol and product selectivity of DHA reach to 76.7%and 97.3%respectively with the initial O2 pressure(PO2)of 10 bar,at 80 ? for 2 h.Au/CuAlO-3 is deactivated in the process of recycling due to the loss of Cu and Al,which causes the change of correlation between Au and its support,the carbon deposition and the increase of Au particles.3.Bimetallic Au-Pt loaded on various MgMO(M = Al,La,Ce)composite metal oxides have unremarkable difference on the catalytic oxidation of glycerol to lactic acid in the presence of NaOH.The category of the second active component has great influence on the catalytic activity of Au-M/MgLaO(M = Pt,Pd,Cu,Ir,Ag)catalysts.The Au-Pt/MgLaO catalyst has the optimal catalytic activity and selectivity.Meanwhile,the Au-Pt/MgLaO catalyst also shows great performance in recyclability without any obvious decrease of catalytic activity,but little reduction of selectivity after 7 times of cycling.