Study On Synthesis Of Biomass-based High-density Fuels Via Ring-Increasing Reactions

High-density hydrocarbons can significantly improve the flight distance,speed and loading capacity of aerospace vehicles such as missiles and rockets.With the increasingly severe environment and energy crisis,the implementation of sustainable development strategy is imminent and it is of great significance to produce high-energy-density fuels by using renewable biomass resources.Based on the molecular structure-activity relationship of high-density fuels,several biomass derived high-density fuels including novel high-density spiro-fuels,highly strained four-membered ring hydrocarbons and methyl substituted decalin fuel were synthesized by ring-increasing strategy and subsequent hydrodeoxygenation reactions.High-density spiro-fuels were synthesized from cyclic ketones(cyclopentanone and cyclohexanone)through reductive coupling,pinacol rearrangement and Wolff-Kishner-Huang reduction.The effects of amounts of catalyst,the solvents on the reductive coupling reaction and the effect of different bases on the carbonyl reduction were discussed.The spiro-fuels show higher density,higher volumetric neat heat of combustion and lower freezing point than the bicyclic alkane fuels synthesized from directly C-C coupling of cyclic ketones due to their compact molecular structure.One-pot Mannich-Diels-Alder reaction was developed for synthesis of high-density spirocycloalkane from biomass and petroleum derived cyclopentanone,formaldehyde,and cyclopentadiene catalyzed by HZSM-5 zeolites.The structure-activity relationship between catalysts and reactivity were discussed through the effects of different acid catalysts,different Si/Al ratios,pore structures,acidity and acid amounts on the Mannich-Diels-Alder reaction.It was found that the appropriate ratio of Lewis to Br(?)nsted acid sites and the mass transfer effect of porous zeolite played a synergy effect on the product distribution of the reaction.HZSM-5 zeolite with Si/Al molar ratio of 130 exhibited the best catalytic activity,along with good recycling ability.The obtained spirocycloalkane has much higher density and volumetric neat heat of combustion(0.952 g/cm3,40.18 MJ/L)than the wildly used JP-10 fuel(0.936 g/cm3,39.41 MJ/L).Photoinduced cycloaddition process was developed for synthesis of biomass-derived high-density spiro-fuel from isophorone and ?-pinene.A triplet sensitized mechanism was disclosed by a combination of wavelength optimization,triplet quenching,phosphorescence quenching,Stern-Volmer kinetic analysis,DFT calculations and photochemical kinetic studies.Meanwhile,the effects of reactant molar ratio,reaction temperature and light intensity on the self-sensitized cycloaddition reaction were discussed.The synthesized spiro-fuel possesses both high density(0.911 g/cm3)and low freezing point(-51 ?),much better than the fuel of similar structure and the fuel derived from same feedstocks.Self-sensitized[2+2]cycloaddition reaction was conducted for synthesis of highly strained four-membered ring hydrocarbons from biomass-derived ketenes and olefins.Combined with triplet quenching,DFT calculations and photochemical kinetic studies,isophorone self-cycloaddition and isophorone/cyclohexene co-cycloaddition was comprehensively compared and investigated through the study of reaction conditions such as wavelength,solvent,light intensity and reaction temperature.It was found that isophorone played a dual role as a photosensitizer and a reactant in the reaction.The isophorone/cyclohexene co-cycloaddition possesses much lower energy barrier,higher conversion and quantum yield than that of isophorone self-cycloaddition.Meanwhile,the substrate universality of the[2+2]cycloaddition and performance of the obtained four-membered ring fuel were investigated.TiO2-mediated photosensitized cation radical Diels-Alder process was developed for synthesis of methyl substituted decalin fuel from biomass-derived furans and isophorone.The neoteric photosensitized electron transfer cationic radical mechanism of 2-methylfuran and isophorone was comprehensively uncovered by a combination of control experiments,cyclic voltammetry experiment,steady-state and time-resolved photoluminescence spectra,energy levels calculations,radical quenching and capture,and EPR signals of Ti3+.During the photoreaction isophorone serves as reactant and excellent photosensitizer,and excited enone can transfer electron to the conduction band of TiO2 to form an active cationic radical and further induce the DA reaction.TiO2 can promote the generation of isophorone cation radical and strengthen the reaction.Meanwhile,the substrate universality of the cation radical Diels-Alder reaction and performance of the obtained methyl substituted decalin fuel were studied.