A Study Of Copper-based Catalysts For The Hydrogenation Of Dimethyl 1,4-Cyclohexane Dicarboxylate To 1,4-Cyclohexane Dimethanol

The inexpensive Cu-based catalyst is proved to be highly active for the hydrogenation of carbon-oxygen bonds,which is widely used in the hydrogenation reaction of various esters.However,the conventional Cu-based catalyst presents a decreasing tendency during the hydrogenation reactions,which affects its application in industrial production.In this work,we chose the hydrogenation of dimethyl 1,4-cyclohexane dicarboxylate(DMCD)to 1,4-cyclohexane dimethanol(CHDM)as a target reaction,then synthesised a copper phyllosilicate nanotubes(CSNTs).CSNTs were employed as a precursor in this study to prepare a type of Cu-based catalyst with copper nanoparticles socketed into the parent CSNTs through in situ reduction exsolution under the H2 atmosphere.The catalyst possessed uniform particle size distribution,high Cu dispersion,strong metal-support interactions,and optical ratio of Cu+ species,thereby exhibiting excellent performance and stability for the chemoselective hydrogenation of esters to alcohols.The main research contents are as follows:1.The copper phyllosilicate nanotubes precursor,which exhibits uniform thin nanotube morphologies and high specific surface area,were prepared by hydrothermal method.After the reduction,the Cue+/Cu+ in CSNTs crystal lattice was reduced to Cu0 while SiO2 appeared in the surrounding.To understand the status of Cu nanoparticles exsoluted in situ during the reduction,the CSNTs were reduced in 5%H2-95%N2 at different temperatures to afford the catalyst CSNTs-T,where T represents the reduction temperature.Morphology,surface properties and catalytic activity of CSNTs-T were investigated.The suitable temperature ranges from 523 K to 723 K,affording a richer surface Cu+ concentration and exhibiting an excellent catalytic performance for ester hydrogenation.The DMCD conversion and CHDM selectivity over CSNTs-623 maintained up to 95%under the optimal conditions.Further increasing the reduction temperature,the nanotube structure of CSNTs can cause partial destruction,lead to surface Cu+ ratio and catalytic activity decreasing.2.The comparison catalysts were prepared by traditional methods,such as deposition precipitation(DP)and urea-assisted gelation(UG),labeled as D-Cu/Si02 and U-Cu/SiO2,respectively.The catalytic performance and thermal stability of three samples reduced at 623 K were investigated for vapour-hydrogenation of DMCD.A variety of characterizations,TEM,XRD,XPS,H2-TPR,were found the reasons of different activity.CSNTs-623 has a higher Cu+/(Cu++Cu0)ratio,lead to superior catalytic properties and stability of mon-metallic.Because the in situ exsolution of Cu nanoparticles from CSNTs with highly metal dispersion and strong metal-support interactions are beneficial to maintain its particle size and Cu+ species during reaction.The yield of CHDM remained up to 95%during 1000 h under optimal conditions.The hydrogenation reactions over CSNTs-623 were investigated by various esters,which showed a potential application in high-temperature hydrogenation reactions.