Research On Copper-based Catalysts For Hydrogenation-rearrangement Of Furfural To Cyclopentanone And Cyclopentanol

Furfural,as an important biomass platform compound extracted from hemicellulose,had been widely used in the preparation of a variety of high value-added biomass green chemicals.This work prepared a series of copper catalysts doped with alkali or alkaline earth metals（Cu-M/γ-Al₂O₃,M=Ba,Ca,K,Mg,Na）,Cu-M)by using impregnation method,and examined their performance of furfural rearrangement reaction.The mechanism of coke formation and deactivation of catalysts were proposed by studying spent catalysts after hydrogenation-rearrangement reaction,and regeneration effects of calcination regeneration,hydrogen reduction regeneration,Dimethyl sulfoxide（DMSO）extraction regeneration and N,N-Dimethylformamide（DMF）extraction regeneration on catalysts were investigated and principles of each regeneration methods were analyzed.Firstly,the performance of furfural hydrogenation-rearrangement among single metal catalyst Cu and bimetal catalysts modified by alkali or alkali earth metals Cu-M were investigated.The effect of metal loadings of alkali or alkaline earth metals on the catalytic activity was investigated,and results showed that appropriately increased the loading of alkali or alkaline earth metal was beneficial for improving catalytic performance.Cu-Ba catalyst showed the highest catalytic activity under 200℃,1 MPa of hydrogen pressure,and 4 h of reaction time,producing cyclopentanone and cyclopentanol at an 82.6%yield.The yield of Cu-Ba catalyst was 2.5 times of unmodified Cu catalyst.At the same time,Cu-Ba catalyst was used to discuss effects of reaction temperature,hydrogen pressure,reaction time,catalyst mass,water volume and stirring rate on the reactivity.Secondly,a systematic study on spent catalysts from furfural rearrangement under different conditions were conducted,and it was found that catalysts will produce polymeric condensates during the reaction.The structure of condensates was conjugated polymers produced from polyfurfuryl alcohol after a series of transformation.Spent catalysts after the reaction showed active component agglomeration and pore structure destruction,which inevitably resulted in the deactivation of catalysts.The investigation on the mechanism of the polymer formation indicated that a carbocation intermediate was crucial in both hydrogenation reaction and polymerization reaction.Therefore,in a neutral or acidic environment,it was difficult to completely avoid the polymerization of furfuryl alcohol.The introduction of alkali or alkaline earth metals could protect the pore structure of catalysts,improve the stability of carbocation intermediates,and reduce the formation of coke to a certain extent.Last but not least,the effects of regeneration methods including calcination,hydrogen reduction and solvent extraction on spent catalysts from furfural rearrangement were investigated,and results showed that calcination was a better regeneration method compared with hydrogen reduction,DMSO or DMF extraction.After calcination,the catalyst recovered nearly 75%of its catalytic activity.Although hydrogen reduction could also decompose a portion of coke at high temperatures,there is still some coke adsorbed on the catalyst,which might cause incomplete recovery of catalytic reactivity.Solvent extraction showed the worst regeneration performance.