| Biomass is the most abundant and cheap renewable organic carbon resource in nature.γ-Valerolactone（GVL）,as an important biomass-derived compound,has broad application in the fields of fuel,chemical industry,food,etc.,and is one of the recognized important substitutes for basic chemical raw materials.Exploring a green,economical and efficient GVL synthesis route is a hot issues in the field of biomass resource utilization.This article designed and prepared highly efficient nickel-based catalysts and acid catalysts for the synthesis of GVL from ethyl levulinate and furfuryl alcohol.The catalytic reaction rules of metal-acid and double acid site catalysts in the reaction were studied.The main research contents are as follows:（1）A series of support-free magnetic mesoporous Ni-X catalysts with different molar ratios of citric acid and nickel nitrate（C6H8O7/Ni）were prepared by a solid-state grinding and in-situ reduction method using citric acid as the reducing agent and nickel nitrate as the nickel source.Changing the amount of citric acid can change the reduction degree of nickel citrate precursor,and adjust the pore structure and Ni O content of Ni-X catalyst.The Ni catalyst（Ni-1.2）with a molar ratio of C6H8O7/Ni of 1.2:1 had the highest catalytic activity in the transfer hydrogenation of ethyl levulinate（EL）to GVL.Under the optimal reaction conditions,EL was completely converted and the GVL selectivity was 99.1%.The characterization results showed that the excellent catalytic performance of Ni-1.2 can be attributed to:Ni-1.2 has a uniform mesoporous structure and a high specific surface area,which reduces the diffusion resistance of the reaction molecules,making the Ni active center fully utilized,and the Lewis acid sites provided by a small amount of Ni O on the surface of catalyst can activate the carbonyl group of EL and promote the formation of GVL to play a synergistic catalytic role.（2）A series of w-Ni/E-cats catalysts with different nickel loadings were prepared by a solid-state grinding and in-situ reduction method using waste FCC catalyst（E-cat）as a carrier.The Ni/E-cat catalyst（30-Ni/E-cat）with a Ni loading of 30%showed the highest catalytic activity in the transfer hydrogenation of EL to GVL.Under the optimal reaction conditions,the conversion of EL was 90.3%and the selectivity of GVL reached 96.2%.Through XRD,NH3-TPD and SEM characterization analysis,Ni metal active sites play a decisive role in the the conversion of the EL,while acid sites mainly affect the selectivity of the product GVL,when the metal-acid bifunctional catalysts catalyze the reaction.The high activity of the 30-Ni/E-cat catalyst is attributed to the synergistic catalytic effect of uniformly dispersed Ni metal active sites and acid sites in the synthesis of GVL.There are two pathways in the reaction,and the pathway mediated by the intermediate 4-HPE is the main pathway.（3）The bifunctional Zr-P/TS acid catalysts were prepared and their catalytic performance in the conversion of furfuryl alcohol to GVL and the catalytic role of different acid types（B/L）were investigated.According to the distribution and changes of the products,Bronsted acidic phosphotungstic acid promotes the conversion of furfuryl alcohol to isopropyl levulinate via intermediate FE in the reaction,and the Lewis acid site of ZrO2 effectively catalyzes the transfer hydrogenation of isopropyl levulinate to GVL.The corresponding reaction pathway and mechanism were proposed.By optimizing the reaction parameters,the selectivity of isopropyl levulinate and GVL was improved.Under the optimal reaction conditions,furfuryl alcohol was completely converted,the selectivity of isopropyl levulinate was 51.9%,and the selectivity of GVL was 41.1%. |
