| The development of bio-aviation oil replace traditional petrochemical aviation oil is of great significance for energy conservation,emission reduction and low-carbon economy.Microalgae have the characteristics of high growth rate and high oil content.Therefore,the use of microalgae oils to convert biological aerosol(C8-C16)has become a research hotspot at home and abroad.In this paper,the mechanism of deoxygenation and hydrocracking of microalgae oils was revealed by quantum chemical calculations,a zeolitic imidazole metal framework nickel-based catalyst and a nickel-based mesoporous Y zeolite catalyst were prepared to improves the conversion rate and selectivity of the jet fuel product.In this paper,the sixteen fatty acids,which are the typical components of microalgae oil,are taken as an example.Based on the experimental results of the main product of deoxygenation and hydrocracking,the competitive reaction mechanism of deoxygenation and debonding is revealed by quantum chemical calculations.Two competing reaction pathways for the deoxygenation and hydrocracking of the sixteen fatty acids were proposed,and the chemical bond lengths and reaction energy barriers of intermediate products and end products were calculated.When Ni-H is added to the carbon atom in the carbonyl group,the bond length of the carbonyl carbon atom and the ortho carbon atom is extended from 0.08007 nm to 0.08132 nm,which contributes to the deoxygenation and hydrocracking of the sixteen fatty acids;meanwhile,Ni-H addition The reaction enthalpy on carbon atoms in the carbonyl group becomes-40.75904 KJ/mol,which is lower than the reaction enthalpy of Ni-H added to the oxygen atom in the carbonyl group of 157.876114 KJ/mol,so the decarboxylation reaction is more likely to follow the Ni-H add to the carbon atom path in the carbonyl proceed.In this paper,a zeolitic imidazole metal framework nickel-based catalyst was prepared,and the conversion rate and selectivity of the microalgae biomass and its hydrothermal extracted oils through deoxygenation and hydrocracking to produce jet fuel were studied.XRD,XPS,SEM,BET,etc.were used to characterize the micro-physical properties of the catalyst: when the zeolite imidazole metal skeleton was loaded with nickel metal,the content of cobalt-oxygen cobalt in the metal skeleton decreased and the nickel content increased to 22.25%,and the XRD characteristic peak appeared to shift.The strength is weakened because the electronic portion of cobalt in the metal skeleton is transferred to the successfully loaded nickel metal.The microalgae hydrothermal extraction oil(C50-C60 triglyceride in microalgae cells is extracted by subcritical hydrolysis to obtain C16-C24 fatty acid)is deoxygenated and hydrocracked by zeolite imidazole metal skeleton nickel-based catalyst to obtain aviation fuel product.The conversion rate and selectivity were 90.51% and 37.83%,respectively,which were significantly higher than the aviation fuel products prepared by direct catalytic conversion of microalgae biomass.In order to solve the problem of the acidity of the zeolitic imidazole metal framework nickelbased catalyst,a nickel-based mesoporous Y zeolite catalyst with acid center was prepared and microscopically characterized.The use of the catalyst to produce jet biofuel derived from microalgae lipids through deoxygenation and hydrocracking significantly improves the conversion rate and selectivity of the jet fuel product.The oil extracted by microalgae hydrothermally produced 99.72% of aviation oil product and the selectivity increased to 50.79% at 390°C under the action of nickel-based gradient mesoporous Y zeolite catalyst.The selectivity of alkane was 43.21%,which was significantly higher than the bio-jet oil produced by direct conversion of microalgal biomass using this catalyst. |
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