Study On Synthesis Of Solid Catalyst And Biodiesel Production From Litsea Cubeba Kernel Oil

Litsea cubeba is one of the unique spices resources in China and the main source of natural citral,which is mainly produced by Jiangxi province.Litsea cubeba kernels are the residue of Litsea cubeba after extracting essential oil and the oil content is 40%（more than 85%middle chain fatty acids）.Therefore,with the market demand for Litsea cubeba,it is great significance to develop some new technologies for resource utilization of Litsea cubeba kernel oil（LCKO）.Biodiesel has become a good potential substitute for petrochemical diesel as its excellent lubricity,safety and combustion performance.It can not only reduce production costs,and realize high-value utilization of forestry by-products,but also decrease the environmental pollution when Litsea cubeba kernel oil is used as raw material for biodiesel production.It has excellent theoretical significance,and industrial application value and development prospects.In this paper,biodiesel was synthesized by transesterification of LCKO catalyzed by solid acid catalyst,which are high efficiency,green,economy and easy separation.The extraction process of LCKO was studied systematically,and the chemical composition was analyzed.For the transesterification of LCKO,high efficiency solid acid catalysts were careful synthesized by acid impregnation and metal modification.Furthermore,the morphology,composition,structure and surface properties of the catalysts were analyzed by various characterization techniques,and the catalytic mechanism and reaction mechanism of the transesterification reaction were clarified carefully.Finally,a series of single factor experiments were designed to optimize the reaction conditions of biodiesel production from LCKO,and the optimal process parameters were obtained.The research is summarized as follows:1)The crushed Litsea cubeba seed was extracted with microwave assisted under the petroleum ether solvent for production of LCKO.The effects of microwave treatment time,solid-liquid ratio（Litsea cubeba seed powder:petroleum ether）,extraction temperature,and extraction time were investigated by single factor experiment.The L9（4³）orthogonal experiment design was used to optimize the extraction process.The optimal extraction process was obtained as follows:microwave treatment time was 90 s,solid-liquid ratio was 1:14（g/m L）,extraction temperature was 85°C,and extraction time was 60 min,and the extraction yield of LCKO was 42.23%.The physicochemical properties and the chemical composition of LCKO were analyzed using Chinese standard methods and gas chromatography technology,respectively.The results show that the properties of LCKO is stable,and the composition of fatty acids islauric acid（52.27%）,decanoic acid（19.52%）and lauroleic acid（13.95%）.And the composition proportion of saturated fatty acids and the medium chain fatty acids（C10-C12）is 75.76%and 88.12%,respectively.2)A series of the x SO4^2-/ZrO2 catalysts were prepared through impregnated Zr（OH）4 with different H2SO4 concentration,and applied to transesterification reaction of LCKO.Furthermore,the microstructure of these solid catalysts was systematically characterized by XRD,N2 physical adsorption,FT-IR,ICP,NH3-TPD,py-IR,SEM and TEM.Combined with the characterization and experimental results,the strong acid site was the catalytic active center of the transesterification of LCKO,and the possible mechanism of transesterification reaction over SO4^2-/ZrO2 catalysts was proposed.Meanwhile,the optimized conversion of LCKO of 84.24%and the biodiesel selectivity of 99%was obtained when the reaction was carried out at 130°C for 16 h over0.5SO4^2-/ZrO2 catalyst.In addition,the optimal process conditions of the transesterification were as follows:H2SO4 concentration was 0.5 mol L^-1,reaction time was 20 h,LCKO:methanol was 3:2（mass ratio）,catalyst content was 3 wt%,reaction temperature was 130℃and stirring speed was 400 rpm.Unfortunately,the stability of the catalyst was not good due to the loss of the acid sites during the reaction,and the conversion of LCKO decreased by 63.2%after 5 runs.3)xZn/ZrO2 catalysts were synthesized by incipient-wetness impregnation method,and the catalytic performance was tested in the transesterification reaction of LCKO.Furthermore,the microstructure of supported Zn catalysts was carefully characterized by XRD、Raman、N₂ physical adsorption、FT-IR、NH₃-TPD、SEM、TEM、ICP和XPS.The characterization results exhibited that the introduction of Zn species could promote the catalyst from monoclinic phase to tetragonal phase,which improved the thermal stability.on the other hand,the Zn O active sites were observed on the surface of the support,and Zn OH⁺was formed through the interaction with the ZrO2,which greatly improved the catalytic performance in the transesterification reaction due to the synergistic effect.Therefore,the mechanism of the Zn/ZrO2 catalyst was elucidated from metal catalysis and acid catalysis,respectively.Meanwhile,the optimized conversion of LCKO of 82.5%and the biodiesel selectivity of 99%was obtained when the reaction was carried out at 120°C for 12 h over 7Zn/ZrO2 catalyst.Additionally,the optimal process conditions were as follows:Zn-loading amount was 7 wt%,reaction time was 16 h,LCKO:methanol was 3:2（mass ratio）,catalyst content was 4 wt%,reaction temperature was 130°C and rotation speed was 300 rpm.Although the LCKO conversion was decreased by 30.9%after 5 runs due to the leaching of Zn species during the reaction,it exhibited the better catalytic stability than the SO4^2-/ZrO2 catalyst.4)The physical properties and chemical composition of LCKO-based biodiesel,including density(859 kg m^-3),acid value(0.46 mg KOH g^-1),iodine value(54.8 mg I₂ g^-1),flash point（126℃）,kinematic viscosity(3.212 mm² s^-1),moisture content（0.02%）,ash content（0.01%）and ester（97.2%）,have been measured through Chinese standard methods.The results showed that the physical properties of the as-synthesized biodiesel accorded with the current international biodiesel standards.Therefore,LCKO-based biodiesel has good industrial application and development prospects in the future.