Catalytic Conversion Of 5-Hydroxymethylfurfural To Cyclopentanone Derivatives Over CuZnAl Catalyst

Fossil resources such as coal,oil and natural gas are limited,and their sustainable and stable supply is facing great challenges.Biomass is a renewable organic carbon resource in nature with abundant reserves.The efficient development and utilization of biomass platform compounds to prepare organic chemicals needed in production and life has important scientific significance and application background for reducing greenhouse effect,decreasing environmental pollution and alleviating energy crisis.3-(hydroxymethyl)cyclopentone(HCPN)and 3-(hydroxymethyl)cyclopentanol(HCPL)as cyclopentanone derivatives are important fine chemical intermediates for the preparation of drugs,polymers,perfumes and other chemicals.They are mainly synthesized by multi-step reactions of petroleum-based chemicals or obtained by hydrogenation and rearrangement of 5-(hydroxymethyl)furfural(HMF)in the aqueous phase.At present,there are some problems in the synthesis of cyclopentanone derivatives from HMF by hydrogenation and rearrangement,such as complex catalyst preparation and catalytic system,increasing reaction cost of noble metal catalyst,poor cyclic stability of catalyst and low reactant concentration.In this paper,the existing problems were studied,the inexpensive metal catalyst with high catalytic activity was selected,and the reaction conditions were optimized.At the same time,the stability of the catalyst was investigated and the causes of catalyst deactivation were analyzed to provide a theoretical basis for the large-scale production of cyclopentanone derivatives.The main contents of this thesis are as follows:Firstly,the inexpensive metal catalysts for the synthesis of cyclopentanone derivatives from HMF were screened.The results showed that the active metal species was an important factor affecting the catalytic activity,among which CuZnAl had the best catalytic effect.The selective attraction of the Cu reduced metal phase to the carbonyl group and the strong repulsion towards the furan ring,making the C=C bond in furan ring difficult to be hydrogenated,thereby improving the selectivity of the target product.At the same time,the copper particles were highly dispersed,which was conducive to the reaction.The content of each component in the catalysts and the preparation method of the catalysts also affected the catalytic effect.The catalyst prepared by coprecipitation method with Cu:Zn:Al molar ratio of 1:4:5 had the highest catalytic activity.At a reaction temperature of 140?,a H2 pressure of 4 MPa,and a reaction time of 4 h,HMF was completely converted,and the yields of HCPN and HCPL reached 57.7%and 21.9%,respectively.Through characterization,it was found that the physical structure properties and the surface acid strength of the catalysts had no significantly relationship with the catalytic activity,while the amount of surface acid was negatively related to the activity of the catalyst,that is,the catalytic activity increased as the amount of surface acid decreased.During the synthesis of HCPN by HMF,the increase of Cu content,reaction temperature,H2 pressure and reaction time will lead to the excessive hydrogenation of HCPN,thus reducing its selectivity.If the reaction temperature is too high,the C-C bond will be easily broken and carbon deposits will be generated;the generated active intermediate will also undergo polymerization and coking.By optimizing the reaction conditions,the yield of HCPN was up to 69.9%,and the conversion of HMF was 100%.Under the catalytic reaction system of this paper,the reaction route for the synthesis of cyclopentanone derivatives from HMF was presumed as follows:firstly,the catalyst hydrogenates the aldehyde group of HMF to generate 2,5-dihydroxymethyl furan(BHMF),and then BHMF undergoes a ring-opening reaction to produce 1-hydroxy-3-hexene-2,5-dione(HHED),most of HHED was condensed to 4-hydroxy-4-hydroxymethyl-2-cyclopentenone(HHCPEN)by intramolecular aldol condensation,and HCPN was obtained through dehydration and hydrogenation.On the other hand,HHED can generate 1-hydroxy-2,5-hexanedione(HHD)by hydrogenation,and generated 3-hydroxymethyl-2-cyclopentenone(HCPEN)by intramolecular aldol condensation,and then hydrogenated to HCPN.The C=O bond in HCPN can be further hydrogenated to generate HCPL.During the synthesis of HCPL by HMF,the reaction temperature was the main factor affecting the yield of HCPL.With the increased of reaction temperature,the yield of HCPL showed an increasing trend,and then gradually tended to be stable.H2 pressure and reaction time were not significantly correlated with HCPL yield.By optimizing the reaction conditions,the highest yield of HCPL was 67.2%,and HMF was completely converted.The stability of CuZnAl catalysts showed that the conversion of HMF and the total yield of cyclopentanone derivatives remained unchanged after three cycles.The total yield of the target product decreased from about 87%to 47.0%during the fourth reaction.The decrease of catalytic activity can be attributed to the serious agglomeration caused by the increase of catalyst particles after the reaction,and at the same time a serious carbon deposition on the catalyst surface caused the catalyst to deactivate.On the other hand,Cu0 component,which played a major catalytic role,was oxidized during the process of reaction and the recovery of catalyst,thus reducing the catalyst activity.