Study On The Decarboxylation Mechanism Of Fatty Acid Salt Under Microwave Polarization And Hydrogen Donation

Due to the reduction in supply and the environmental pollution caused by fossil fuels,alternative fuel development becomes more important for securing the supply of future transportation fuels,as well as for cleaner environment.Therefore,the development and use of renewable energy sources has attracted attention around the world,and research and development of high calorific value renewable hydrocarbon fuels are.underway.Different from fossil fuel which is unrenewable,biomass fuel is reproducible,and the non-edible oils are the most important raw material for biofuel production.It is widely used for inedible oils to produce biodiesel by transesterification.However,many defects of the biodiesel still exist:it has high cloud point and condensation point,and shows no good fluidity at the low temperature,therefore not suitable in cold weather,and could be harmful to some engine;Due to the oxygen-containing functional groups,its calorific value is 9%to 13%lower than that of fossil diesel;also it shows no advantage in the thermal stability and storage stability due to prone to oxidation and deterioration.Recently,research reports show a product with higher energy density,lower oxygen and renewability was obtained by that pyrolysis of inedible oils which can be a perfect substitute for fossil fuel.Due to the fact that the inedible oils hydrolyzate is the fatty acid salt,microwave-assisted production of hydrocarbon fuels was used for the decarboxylation of acid salts(saponification of fatty matter).The GC-MS and FTIR method were used to analyze the cracked liquid and solid products,the effects of different saturation,number of carbon atoms,and the catalyst on the pyrolysis product of the fatty acid salt and decarboxylation reaction mechanism were explored.First,a study on pyrolysis of sodium oleate was carried out.The effect of different temperatures and microwave power input on the cleavage product and decarboxylation mechanism were studied.The carboxyl terminus of sodium oleate showed strong polarity,easier dipolar polarization and ionic conduction in the microwave field,therefor,more selective microwave heating of carboxy-terminal,and therefore more conducive to decarboxylation.The viscosity and density of the cracked liquid product were 2.40-2.55 mm2/s,0.870-0.885 g/cm3,respectively,and the physical properties of the prepared biofuel are very similar to the diesel fuel,proving the feasibility of renewable hydrocarbon fuels production through microwave pyrolysis of sodium decarboxylation.In the research,Sodium stearate,sodium oleate,sodium linoleic acid were chosen as the research objects and microwave-assisted pyrolysis technology was used to explore impacts of the amount of C=C double bond on cleavage products and response mechanisms.GC-MS was used to analysis the cleavage products.It shows that the amount of C=C double bond has impact to microwave-assisted pyrolysis of unsaturated fatty acids of sodium to a certain degree and wax was obtained in the pyrolysis of sodium stearate cracking process with no C=C double bond.More oxygen-containing compounds were obtained in the pyrolysis of linoleic acid sodium containing two C=C double bond,which is due to the existence of two C=C double bonds decreases bond dissociation energy of two adjacent C-C bonds,especially decreases that of two C=C single bond between C=C bond,resulting in single bond cleavage reaction occurs first of some part if linoleic sodium,so relatively more oxygen-containing compounds were produced.Sodium stearate,sodium palmitic acid,myristic acid sodium,sodium laurate were used as the research objects,microwave assisted cracking technology was applied to research the effects of number of carbon atoms on the decarboxylation products and reaction mechanism.Pyrolysis products of saturated fatty acid sodium salt are mainly alkanes and olefins containing carbon atoms from 9 to 18,which are more than 80%.Less kinds of hydrocarbon are produced from that of less carbon atoms.It shows that the longer the carbon chain,the more complicated pyrolysis products will produce.Potassium stearate was used as model compounds,alkali magnesium aluminum hydrotalcite as catalyst to research the cracking in the microwaves.It shows that the addition of magnalium hydrotalcite promoted the decarboxylation at carboxyl of stearic acid potassium,reduced the content of oxygen containing compounds in the liquid product,also prompted cyclization reaction of the long-chain alkenes generating naphthene,also increased the amount of saturated alkane in the pyrolysis oil and improved its stability.It lays the foundation of the further refining of aviation kerosene.