Construction Of 3D Layered Biochar Solid Acid And Its Efficient Catalytic Preparation Of Biodiese

With the rapid development of global industrialization,global fossil energy consumption is expected to increase by 28%between 2015 and 2040,resulting in a gradual reduction of fossil energy reserves.At the same time,people‘s environmental awareness and growing energy demand are inspiring countries around the world to seek renewable energy.As a clean and renewable energy source with low sulfur content,biodiesel stands out among many renewable energy sources and has been widely used.It has long been regarded not only as a sustainable green fuel,but also as a raw material or intermediate for the synthesis of fine chemicals（e.g.,industrial solvents,surfactants and lubricants）.Biochar catalysts are widely used in the catalytic preparation of biodiesel because of its environmentally friendly,economical and renewable characteristics.However,traditional pyrolysis methods（e.g.,pyrolysis,gasification and hydrothermal carbonization）directly treat biomass under high-temperature conditions to prepare biochar with small specific surface area,low acid content（e.g.,-OH,-COOH,and-SO₃H）,high energy consumption and agglomeration.Therefore,based on the existing problems of biochar catalysts,this study developed a new strategy for the preparation of biochar,and prepared layered biochar catalysts with large specific surface area,high acid density and loose pores at a low temperature,so as to achieve efficient catalytic preparation of biodiesel from oil/fatty acids.（1）Acidic biochar catalysts were prepared at a low temperature（80℃）using different lignin-derived monomers（e.g.,4-methylphenol,4-ethylphenol,4-propylphenol）as carbon sources.A series of characterization（e.g.,XPS,FT-IR,AFM,Raman,SEM,HR-TEM and BET）and activity tests were carried out for the catalysts.The carbonaceous catalyst（PPR-SO₃H-80）was found to be composed of irregular particles accumulated by lamellar carbon,and have a large specific surface area（165.2 m²/g）and good thermal stability.Meanwhile,PPR-SO₃H-80 had a high density of-SO₃H（3.56 mmol/g）,which increases with the degree of carbon defects.Importantly,the conditions for the esterification of oleic acid to biodiesel（FAMEs）were optimized by response surface methodology（RSM）.Under the optimal conditions（CA=2.2wt.%,t=2.8 h,T=78℃,M/O molar ratio=14:1）,the yield of FAMEs was as high as 97.1%.The results showed that the co-existence of-OH and-COOH in a certain amount with-SO₃H on PPR-SO₃H-80 could significantly promote the production of biodiesel.In addition,the kinetics of the esterification reaction system was studied,and the activation energy was calculated to be 27.7k J/mol,which was much lower than previous studies.Moreover,PPR-SO₃H-80showed good stability and could be recycled for 4 times,with the biodiesel yield of90.3%.（2）On the basis of（1）,the prepared acidic biochar catalyst was improved to obtain an acidic biochar catalyst（PAP-MEPP-C）with higher efficiency and more universal applicability.The interlayer spacing of the biochar catalyst was adjusted by adjusting the mixing ratio of lignin-derived monomers to adjust its acid density and specific surface area,thereby improving its catalytic efficiency.A series of characterizations（e.g.,XPS,FT-IR,AFM,Raman,SEM and BET）of the prepared catalysts were further carried out and used to efficiently produce biodiesel from non-edible Jatropha oil（JO）.The characterization results showed that the structure of PAP-MEPP-C biochar catalyst was a layered three-dimensional structure,and its acidity could be controlled by changing the monomer composition.The reaction conditions for the preparation of biodiesel catalyzed by PAP-MEPP-C were optimized by response surface methodology（RSM）,and the obtained maximum biodiesel yield was 97.2%.The PAP-MEPP-C catalyst was used for esterification different fatty acids（lauric acid,myristic acid,palmitic acid and stearic acid）,and transesterification of chlorella oil and methanol to prepare biodiesel.Under the optimum conditions of RSM optimization,the conversion of fatty acids and chlorella oil catalyzed by PAP-MEPP-C could afford high biodiesel yields（>96%）,indicating that PAP-MEPP-C had good catalytic activity and universal applicability.In addition,compared with other tested acid catalysts,its excellent catalytic performance could be further demonstrated by a relatively low activation energy（36 kJ/mol）.The PAP-MEPP-C catalyst had high stability,and the obtained biodiesel yield still exceeded 90%after recycling for 4 times...