Experimental Study Of Aldol Condensation-Hydrogenation Of Ketones From Biomass To Produce Aviation Fuel

With the increasingly strict carbon emission and the increasing demand for aviation fuel,the traditional single source fossil fuel-based aviation fuel will be difficult to meet the normal operation requirements of human society in the future.Therefore,it is very important to develop alternative aviation fuel preparation technology.The short chain aldehydes and ketones obtained from biomass after treatment can increase the carbon chain through aldol condensation reaction,and then through hydrodeoxygenation,the bio aviation fuel meeting the use requirements can be finally prepared.The details are as follows:Cyclopentanone from biomass pyrolysis was used as platform compound,Mg-Al-O as condensation catalyst,Ni/?-Al₂O₃ as hydrogenation catalyst,in order to master the condensation hydrogenation characteristics of cyclopentanone.In the aldol condensation reaction,the catalyst with Mg/Al ratio of 3:1 has the best condensation performance,which is attributed to its strong weak base and medium base position.Proper amount of water?<8wt%?can promote the self-condensation of cyclopentanone.The self-condensation of cyclopentanone is a series reaction,and the high temperature of 170?will promote the reaction.In the hydrogenation reaction,Ni/?-Al₂O₃ with10wt%Ni loading has uniform and sufficient metal sites,and the effect of catalytic hydrogenation is the best.Under the hydrogenation conditions of 4.5MPa,12h and260°C,the highest yield of target alkane of 83.8%was achieved.The increase of hydrogen pressure and reaction temperature increased the activity of the catalyst,which was propitious to the hydrogenation.In order to realize the synthesis of aviation fuel components by integrated condensation hydrogenation,it is necessary to find a cheap and efficient dual functional catalyst for condensation-hydrogenation.Firstly,according to the performance of three kinds of condensation catalysts?MgO,Cao,NaY zeolite?,the best composite metal oxide catalyst Mg-Al-O was determined.Four cheap metal catalysts?Fe,Cu,Co and Ni?were prepared.It was found that the total yield of target alkane was the highest?83.8%?under the catalysis of Ni/?-Al₂O₃.Ni/Mg-Al-O,a condensation and hydrogenation bifunctional catalyst,was initially determined.It was found that the selectivity of hydrogenation intermediate products was very high,which was closely related to the lower specific surface area of the support and the poor pore structure.Therefore,Ni/Mg-Al-O/AC bifunctional catalyst was prepared by using active carbon?AC?as support.The total yield of alkane reached 81.1%by optimizing Ni loading,calcination and activation temperature of catalyst.However,the target hydrocarbon yield decreased by 62%after 5 times of catalyst use.The results of X-ray diffraction show that the hydration of Ni/Mg-Al-O/AC occurs obviously,and the boehmite formed covers the active site of the catalyst.In order to maintain the high activity of the catalyst and optimize the one pot aviation fuel system,hydrophobic solvent and one-step strategy were considered.By introducing solvent such as n-pentane,it was found that n-pentane with polarity of 0has the best effect,and the best ratio of cyclopentanone to solvent is 1:2.In n-pentane solvent system,the yield of target alkane is stable at 70%after 5 times of reuse of Ni/Mg-Al-O/AC.In order to avoid secondary heating,a one-step method was proposed to prepare the target alkane,but cyclopentanone was easily converted to cyclopentanol at high temperature.Therefore,on the premise of hydrogen first,a one-step low-temperature condensation high-temperature hydrogenation strategy is adopted,that is,condensation test is carried out at 170?,and then hydrogenation is carried out at 260?,and the yield of the target alkane is 70.7%.The results show that the condensation and hydrogenation time of the bifunctional catalysts are significantly reduced,which shows that the condensation hydrogenation capacity of the bifunctional catalysts is significantly improved coMPared with Mg-Al-O and Ni/?-Al₂O₃ single functional catalysts.