Experimental And Mechanism Study On The Production Of Aviation Biofuels

The world is changing and so is the aviation industry. Now with decliningpetroleum resources, shocking surge in the price of fuel, combined with the increasein political and environmental concerns, it is imperative for aviation industries todevelop clean and energy-efficient technologies of producing sustainable alternativebiofuels. In present study, an innovative but simple and effective method wasdeveloped for the production of aviation biofuels by Kolbe electrosynthesis coupledwith catalytic cracking reaction from fatty acid methyl esters （biodiesel） or saturatedfatty acids. The aviation biofuels produced showed good properties even at extremelycritical conditions.For the preparation of long carbon chain hydrocarbons by Kolbe reactions fromsaturated fatty acids. Several reaction conditions （such as potential, solvent, supportelectrolyte, reaction time, and electrode materials） were evaluated to optimize theKolbe electrosynthesis. The optimum conditions for Kolbe reaction were: thepotential higher than7.5V and20wt.%of KOH used as the support electrolyte withtemperature of45±5oC, while the methanol as solvent. Besides, the mechanism wasalso proposed according to the electrochemical tests （cyc1ic voltammetry tests, linearsweep voltammetry tests, and tafel tests）. The results show that it is a very promisingchoice for the preparation of aviation jet fuel by Kolbe processes, which are energyefficient as the reactions are conducted mostly at ambient pressure and temperature.In order to get higher conversion ratio and higher jet fuel yield in the catalyticcracking reaction,15g NKC-7catalyst was used while the feedstock flow rate was0.600mL/min under485oC after1h when the catalyst has stable react activation. Also,a detailed lumping procedure for obtaining a kinetic model of catalytic crackingreaction is developed. The kinetic constants were estimated by nonlinear least squaresfitting method.In order to estimate the cost of producing aviation biofuel, technical andeconomic analysis on a conceptual design of an aviation biofuel production plant（with a capacity of10,000tonnes per year） was made. The estimated total capital costand annual operating cost were approximately RMB24.10million and RMB77.8million, respectively. The present results demonstrated that the industrial scale plant would be promisingly competitive in the market using waste cooking oils and animalfats as raw material.A life cycle assessment was carried out to quantify and compare theenvironmental impacts by producing and utilizing of biofuels derived from the bestfeedstock options available in the short and medium term （palm oil, jatropha oil, andmicroalgae oil） referring to China conditions. According to the well-to-pump （WTP）and pump-to-wheels （PTW） results, the total amount of CO₂emitted for both casescenarios is different, arranging from0.285kg eq-CO₂/MJ biofuel to0.730kgeq-CO₂/MJ biofuel based on the production of1MJ biofuel. The new generationrenewable materials （especially microalgae） and waste cooking oil appear to be themost likely feedstock for aviation biofuels in medium and long term of China.Considering the extensive application of microalgae and waste cooking oil forbiofuels production, new market will be opened up and there will be real andpotentially very promising impacts on ecosystems and on society.