Preparation Of Copper-Based MOF Catalyst And Its Application In Biodiesel Catalysis

Biodiesel is a kind of green,renewable and degradable fuel,which has the advantages of non-toxic and sulfur free,high flash point,and is considered as an ideal substitute for fossil fuels.Heterogeneous catalysts play an important role in biodiesel preparation,among which MOFs are ideal catalysts for biodiesel preparation due to their many advantages.However,most MOFs exhibit poor hydrothermal stability,and the catalytic activity and reusability are often reduced due to hydrolysis in the process of biodiesel preparation,resulting in higher cost,which limits their application.In this paper,the solvothermal method was used to prepare copper organic framework（Cu MOF）catalyst,and then the functional design of Cu MOF was carried out.Two solid catalysts,magnetic copper MOFs（Fe₃O₄@Cu MOF）and amino acid hydrophobic copper MOFs（ILe@Cu MOF）,were prepared.Fourier transform spectroscopy（FTIR）,scanning electron microscopy（SEM）,energy spectrum analysis（EDS）,X-ray diffraction（XRD）,N₂ adsorption and desorption（BET）,thermogravimetric analysis（TG）and other characterization methods were used to analyze the microstructure and thermal stability of the catalysts.The three catalysts were respectively used in the preparation of biodiesel from Xanthoceras sorbiflia bunge seed oil.The main contents and research results are summarized as follows:1.Cu MOF mainly contains Cu,O,C and N elements,and has a highly crystalline cube structure,with an average size of 4-8μm,a specific surface area of 5.07m²/g,and an average pore size of 23.64nm,belonging to mesoporous materials.In addition,the use of Cu MOF temperature should not exceed 310℃,otherwise it will lead to the collapse of Cu MOF structure.The optimum preparation conditions of Cu MOF were as follows:10%Cu SO₄ solution 100m L,10%p-Phthalic acid dimethylformamide（DMF）solution 100ml.The catalytic activity of Cu MOF catalyst was the highest,and the yield of biodiesel reached 72.36%.The optimum conditions for preparing biodiesel were as follows:catalyst dosage of 3wt%,molar ratio of alcohol to oil 20:1,reaction temperature of 60℃,reaction time of 3h,and biological yield of 84.75%.The yield of Cu MOF reached 65.68%after five cycles.2.Fe₃O₄@Cu MOF mainly contains Cu,O,C,Fe and other elements,the content of Cu element was low,the content of Fe element was high,because iron coordination ability is stronger than copper,so that most copper ion sites were occupied by iron ions.Fe₃O₄@Cu MOF catalyst has rough and porous surface area of 206.239m²/g and average pore size of 6.64nm,which belongs to mesoporous materials.Fe₃O₄@Cu MOF has a saturation magnetization of 12.6emu/g and was easy to separate and recover.The optimal preparation conditions of Fe₃O₄@Cu MOF are as follows:when Cu MOF is 0.4g,Fe Cl₃·6H₂O and Fe Cl₂·4H₂O are 1.6g and 0.6g,respectively,the catalytic activity of Fe₃O₄@Cu MOF catalyst is the highest,and the biodiesel yield reaches 72.31%.The optimum conditions for preparing biodiesel were as follows:catalyst dosage of 3wt%,molar ratio of alcohol to oil 20:1,reaction temperature of 60℃,and reaction time of 2h.Under this condition,the maximum biodiesel yield was 75.0%.Fe₃O₄@Cu MOF was recycled for five times,and the yield still reached 69.25%.3.ILe@Cu MOF catalyst surface was attached to isoleucine（ILe）in sheet structure,mainly containing Cu,O,C,N elements,specific surface area of 19.687m²/g,average pore size of 31.74nm,belonging to mesoporous materials.The pyrolysis temperature of ILe@Cu MOF reached 360℃,indicating that grafting ILe had protective effect on Cu MOF and increased the pyrolysis temperature of Cu MOF.At the same time,the contact Angle of water increased from 86°to 121°,indicating that the material was hydrophobic.The optimal addition of ILe@Cu MOF catalyst ILe was 45wt%Cu MOF,and the catalytic activity of ILe@Cu MOF catalyst was the highest,and the biodiesel yield could reach 71.99%.The optimum conditions for preparing biodiesel were as follows:catalyst dosage of 3wt%,alcohol oil molar ratio of 35:1,reaction temperature of 50℃,reaction time of 4h,the highest biodiesel yield of 82.85%.ILe@Cu The yield of MOF reached73.4%after five cycles.