Organic Catalysts For Biodiesel Production And Utilization Of Crude Glycerol Form Biodiesel Production

Biodiesel,fatty acid alkyl ester,is not only environmental friendly but also renewable.It has been proved to be the ideal alternative for diesel.The chemical process by which biodiesel is produced is mainly recognized as the catalyzed transesterification reaction.The catalysts used usually are homogeneous or heterogeneous acid or alkaline and lipase.The transesterification reaction catalyzed by homogeneous catalyst has the advantages of short reaction time and small amount of alcohol loading,however,the purification process of biodiesel product is complicated.The heterogeneous catalyst catalyzed process has the merits of environmental friendly,easy continuous operation and recycle,less corrosion,and so on.But comparing with its counterpart,homogeneous process,most of the disclosed heterogeneous processes usually have lower reaction rate and requires higher methanol amount and catalyst amount to maintain the high productivity.Most reported heterogeneous catalysts contain metal,therefore,their production cost is high.Organic catalyst is attractive alternative for the catalysts contained metal.The utilization of crude glycerol from biodiesel production can reduce the biodiesel production cost in terms of systematic utilization and relieve the effects of crude glycerol on glycerol market.In order to investigate better biodiesel production methods and possible value-added utilization ways for crude glycerol,this research focused on new organic catalysts N-Heterocyclic Carbenes(NHC)and Br￠nsted acidic ionic liquids for biodiesel production and utilization of crude glycerol from biodiesel production.The main results of this research are as followings:1.Investigation of the reaction kinetics of transesterification reaction of soybean oil and methanol catalyzed by self-prepared NHC was carried out by methods involving aliquot sampling during reaction processes,1H NMR analysis and simplifying reaction process to one overall reaction.The obtained experimental data during the methanolysis process were fitted with Boltzman functions.The obtained correlation coefficients were over 0.975.The obtained change trend of reaction kinetics plot of the fatty acid methyl esters formation is similar with that of traditional alkaline catalyst catalyzed transesterification reaction between vegetable oils and methanol.Under the reaction conditions of molar ratio of alcohol and oil 3.4:1 and catalyst amount 4 mol%(based on feedstock oil loading amount),the reaction has significantly approached equilibrium after 10 min when reaction temperature was 40℃.The biodiesel yield was over 97.5%when the methanolysis reaction was carried out at 50℃ for 1 h.The reaction activation energy is 121.64 KJ/mol.2.The catalytic activity of six elf-prepared imidazolium-based SO3H-functionalized Br￠nsted acidic ionic liquids for esterification reaction of oleic acid and methanol and transesterification reaction of soybean oil and methanol showed that the ionic liquids 3,3’-(dodecane-1,12-diyl)bis(1-(2,6-dimethylphenyl)-1 H-imidazol-3-ium)hydrogensulfate[IXyC6]2[SO4H]2)has higher catalytic activity for catalyzing oleic acid esterification reaction and soybean oil methanolysis reaction.Under the reaction conditions of molar ratio of alcohol and oil 8:1 and reaction time 5h,the optimum catalyst loading amount and reaction temperature for the ionic liquids[IXyC6]2[SO4H]2 catalyzed beef tallow methanolysis were 5 mol%and 75℃,respectively.Under these optimized reaction conditions,the yield of beef tallow biodiesel was 93.1%and the ionic liquids[IXyC6]2[SO4H]2 could be reused at least 3 times.3.Supercritical water gasification of crude glycerol from biodiesel production for hydrogen(H2)production was systematically studied employing central composite design and response surface methodology.High temperature and KOH concentration favored H2 production.Too high glycerol concentration in the reactant had a negative effect on H2 production.The gasification of crude glycerol under supercritical water was pretty fast and the reaction time had little effect on H2 yield.During the KOH catalyzed supercritical water gasification of crude glycerol,hydrogen was the main component in the gas products,its purity was about 90 vol.%.However,too high temperature reduced its purity.The quantity of hydrogen and carbon dioxide is nearly equal during the process without KOH.The oily products amount obtained from uncatalyzed process was higher than that from catalyzed process.But the amount of the solid product from uncatalyzed process was lower than that from the catalyzed process.The method of least squares and the software SAS 9.2 were employed for regression analyses of the experimental data to evaluate the linear,quadratic and interaction effects of each experimental factor on hydrogen yield and carbon monoxide yield.The R squares of the model equations of H2 mole fraction yield and CO mole fraction yield were 0.936 and 0.9757,respectively.The lack-of-fit of the model for H2 mole fraction yield and CO mole fraction yield were 0.2386 and 0.084.The P values of the developed models were less than 0.0001The optimum reaction conditions for maximizing H2 production were 500℃ temperature,7 wt.%glycerol concentration,and 2.39 mol/l KOH concentration.The corresponding operating pressure was 45 MPa.Under optimum conditions,the H2 yield from crude glycerol reached 27.99±0.22 mol%.