Study On Catalytic Esterification Of Low Molecular Organic Aldehydes

Esters are widely used in fragrances,pharmaceuticals,adhesives,and so on.Currently,MMA are mainly produced by the acetone cyanohydrin process.The method needs a multi-step process,which produces the acids or their derivatives.It not only corrodes the equipment but also yields a large amount of by-products.Therefore,it is particularly important to develop a green production line for MMA.Without adding any toxic or corrosive compounds,oxidative esterification of MAL with methanol to MMA,which is a green and sustainable production method.Au catalysts have unique catalytic properties,causing more and more attention.In this paper,we prepared supports of different properties and nano-gold catalysts,investigated their catalytic performance for aldehyde oxidation and esterification,and studied the effects of physicochemical properties and pore structure of supports on catalytic performance.The main research contents are as follows:1.A series of Au-supported cerium oxide binary composite oxides doped with different metals(M = Mn,Cu,Ni,Co)were synthesized and applied to the oxidative esterification of MAL with Me OH to MMA.The Ce-Mn solid solution as support has the highest activity.The effects between metal additives in the support and material properties and the performance of gold catalyst for oxidative esterification had been investigated.The structural properties and states of the supports and catalysts were characterized by XRD,BET,XPS,ICP-Mass and TEM.The reducibility and basicity of Au/Mn Ce Ox solid solution were tested by H2-TPR and CO2-TPD.The correlation between basicity and activity of catalyst was confirmed.And the cycling performance of the catalyst was also investigated.2.Au/Mn Ce Ox with the highest activity was selected as catalyst.The effects of alcoholaldehyde ratio,catalyst dosage,reaction temperature,oxygen flow rate and reaction pressure on the catalytic performance were investigated,and the optimum reaction conditions were obtained.After eliminating the effects of internal and external diffusion,the kinetics of the reaction was studied and the macro reaction rate equation was obtained.4.Porous nanorods of Mn Ce Ox solid solutions(PN-Mn Ce Ox)with different pore sizes were prepared by using ionic liquids with different carbon chain lengths.Au/PN-Mn Ce Ox were synthesized and applied to the oxidative esterification of aldehydes to esters,Strong metalsupport interaction and restriction of support pores on nano-Au enables the high catalytic activity and stability of as-synthesized catalysts for oxidative esterification of methacrolein to methyl methacrylate.And the universality and cycle performance of the catalysts were also investigated.