Preparation Of Biofuel By Catalytic Cracking Of Coconut Oil And Its’ Combustion Characteristics

The efficient conversion and utilization of oil is an important path to achieve"carbon reduction"and"carbon neutrality".The biofuel prepared by cracking has many advantages such as simple process,few by-products,high calorific value,wide adaptability of raw materials,and no glycerol.Therefore,the method has attracted more and more attention.However,the biofuel obtained by the direct pyrolysis have high acid value,which aggravate engine wear and cause severe coking.It is necessary to adopt appropriate processes to conduct decarboxylation for pyrolysis oil to improve the fuel quality,then apply efficiently in engines.Therefore,in this present work,coconut oil is used as a raw material to prepare high-grade biofuels through the methods of liquid phase cracking（LPC）and gas phase catalytic cracking（GPCC）.The effects of process parameters such as temperature,air intake rate,reaction time and catalyst content on the liquid yield,acid value are explored.Based on the detailed component analysis,the main reaction mechanism in the cracking process is inferred.Fuel blends C10,C20 and C30 were prepared by mixing 10%,20%and 30%volume fractions of catalytic cracking oil（CCO）with diesel.Fuel blends C5B5,C10B10 and C15B15 were prepared by mixing 5%,10%and 15%volume fractions of CCO,biodiesel with diesel.The main physicochemical properties of diesel and fuel blends were measured.Based on TGA/DSC1 synchronous thermal analyzer,their volatilization and oxidation performances were evaluated in air atmosphere.The applicability of the diesel and fuel blends was explored based on the engine performances tests.The main study is as follows:（1）Effect of process parameters of LPC and GPCC were studied.Set up a reaction device to explore the effects of temperature,gas inlet rate,reaction time,catalyst dosage on the liquid yield and acid value of liquid phase cracking and gas phase catalytic cracking.With LPC of coconut oil,the maximum biofuel yield reaches 76.5%under the pyrolysis temperature of 450℃,intake rate of 30 ml/min and reaction time of 40min.However,the acid value of biofuel is above 100mg KOH/g.The maximum biofuel yield of GPCC with the CaO/bentonit combined catalyst reaches69.5%,and the minimum acid value of biofuel is 2.8mg KOH/g.Based on GC-MS,the major components in the liquid product are alkanes or alkenes,ketones,and acids.Compared with LPC oil,the hydrocarbons of biofuel obtained by GPCC increase by 23.3%,but the acids and ketones decrease by18.8%and 4.6%,respectively.Meanwhile,it is inferred that the process in GPCC mainly occurred three reactions,namely,ester bond cleavage,CaO and carboxylic acid combination,and cyclic reaction.（2）The physicochemical properties of pyrolysis oil were measured,and its evaporation and oxidation performances were evaluated based on thermogravimetryic experiments.The physicochemical parameters such as oxygen content,acid value,viscosity and low calorific value of GPCC biofuel,biodiesel and fuel blends（C5B5,C10,C10B10,C20,C15B15 and C30）were measured and calculated via experiments or empirical formulas.Compared with diesel,fuel blends have higher oxygen content,kinematic viscosity,density,and acid value,but has a lower low calorific value.Compared with binary fuels,low calorific value and acid value of ternary fuels are lower but the kinematic viscosity,density and oxygen content are higher.Based on the analysis of the TGA/DSC1 synchronous thermal analyzer,the TG and DTG curves of CCO are more similar with diesel.The smaller the proportion of biodiesel and CCO in the fuel blends are,the more similar the TG and DTG curves are to diesel.（3）Economy characteristics and combustion characteristics analysis of fuel blends containing different fractions of GPCC biofuel and biodiesel were evaluated.The equivalent specific fuel consumptions(b_eq),effective thermal efficiencies(η_et),in-cylinder pressure,in-cylinder temperature,and instantaneous heat release rate of Diesel,C5B5,C10,C10B10,C20,C15B15 and C30 at 1800 r/min were analyzed.The b_eq of mixed fuel is slightly higher than that of diesel,and the b_eq of binary fuel is lower than that of ternary fuel.However,η_et shows the opposite law.Under 50%load and 100%load conditions,heat release law,in-cylinder pressure,and in-cylinder temperature exist two peaks.In the pre-injection fuel combustion heat release stage,the peaks of initial heat release and in-cylinder pressure of fuel blends are lower than that of diesel,but the in-cylinder temperature curve is almost same with diesel.In the main-injection fuel combustion heat release stage,the former is higher than diesel,but the latter is lower than diesel.Compared with binary fuel,the peaks of instantaneous heat release rate,in-cylinder pressure,and in-cylinder temperature of ternary fuel are slightly lower.However,the combustion characteristics of ternary fuel are more similar with that of diesel.