Construction Of Hydrophobic MOFs-based Functional Materials And Their Low-temperature Catalytic Synthesis Of Biodiese

Biodiesel is being deemed a kind of important renewable energy source and also shows the great potential to replace fossil fuels to respond to global primary energy demands.However,by-product water generated during the esterification reaction of biodiesel production is not conducive to the forward progress of the reaction,and even affects the pristine structure and activity of the employed catalytic material.In this work,a hydrophobic solid acid catalyst FDCA/SA-Ui O-66(Zr)was prepared by a solvent-free method using Zr as the metal precursor,biomass-based2,5-furandicarboxylic acid as the connector,and stearic acid as the hydrophobic ligand.The effect of Lewis acid sites in the hydrophobic environment on the catalytic activity of the fatty acid methyl ester production process was clarified,the catalytic activity of the catalyst was tested,and its reaction mechanism and mechanism of action were studied.The structure of FDCA/SA-Ui O-66(Zr)was analyzed by HR-TEM,STEM-Mapping,SEM,AFM,XPS,FT-IR,XRD,TG,TPD and water contact angle measurement.The results show that the material has good particle size and high hydrophobic network(136.4°).Compared with traditional solid acid catalysts and liquid acid catalysts,it exhibits superior or comparable catalytic performance in the esterification of long alkyl chain fatty acids.Through the test of single factor and response surface method,the yield of FAME can reach 98.4% at 60.2 °C,atmospheric pressure and 6.1 wt% catalyst.Further studies confirmed that the hydrophobic environment promoted the adsorption of lipophilic acid on the Lewis acid site,which significantly promoted the esterification reaction.In addition,the structure of FDCA/SA-Ui O-66(Zr)catalyst was stable during continuous recycling.After 6 cycles,the yield of FAME could still reach 92.5%,and the reusability was good.Secondly,FDCA/SA-Hf was prepared by using hafnium instead of zirconium to catalyze the preparation of biodiesel,and the reaction conditions were optimized to further explore the reaction mechanism.FDCA/SA-Hf exhibited high catalytic activity,structural stability and excellent hydrophobic network(131.5°)similar to FDCA/SA-Ui O-66(Zr).The chemical grafting of stearic acid increased its Lewis acidity,promoted the adsorption of free fatty acids and the desorption of water.Importantly,under the esterification of FDCA/SA-Hf,the yield of biodiesel can reach98.6%(49 °C,4.1 wt%).Even in the presence of 6 wt% water or after 6 cycles,the yield of biodiesel can still reach 90%,which is due to its high hydrophobicity and stability.In addition,the effect of catalyst acidity on the catalytic effect and the directional control method of acidity were studied.Based on FDCA/SA-Hf,the acidity of the catalyst was adjusted by metal cation exchange,and the effect of different acidity of the catalyst on the yield of biodiesel was studied to meet the production needs of different raw materials and different environments.FDCA/SA-Hf has great potential in the field of heterogeneous acid catalysis,especially in biodiesel production.It is a promising biomass-derived heterogeneous catalyst that can be used to produce biodiesel from cheap crude oil sources.This strategy can achieve green and efficient production of biodiesel under mild conditions.