Green Extraction Of Litsea Cubeba Kernel Oils And Its Application In Biolubricant Base Oil Preparation

Litsea cubeba is an indigenous industrial crop in China with fruits possessing interesting essential oil content of 3-5%,which production leads to a large number of kernels as wastes.In this study,innovative techniques and solvents for the extraction of oils from Litsea cubeba kernels and dried fruits were developed to obtain the optimal extraction technology as compared to traditional techniques,which can provide theoretical and experimental database for the green extraction of Litsea cubeba oils.Besides,such oil as a new lauric acid source could synthesize its trimethylolpropane fatty acid ester,which showed its potential to be a biodegradable and frigostable biolubricant base oil.The main contents are as follows:(1)The effect investigation of traditional pressing,solid-liquid solvent extraction and ultrasound-assisted extraction in terms of acylglycerol and fatty acid compositions,physicochemical properties and total phenolic content in Litsea cubeba fruit and kernel oils,as well as their decolorization and deacidification,were carried out.The results showed that Litsea cubeba kernel oil with a higher saturation level could be used as a new oil source of natural lauric acid(>50%).Compared to pressing and solid-liquid extraction,the ultrasound-assisted extraction had the best extraction rate of Litsea cubeba oils with no significant difference concerning the acylglycerols composition,density,refractive index and melting point.Litsea cubeba peel oil was rich in palmitic and linoleic acids,its high free fatty acid content led to the higher acid value in fruit oils than in kernel oils.Moreover,the fruit oil was more difficult to process due to its darker color and larger viscosity.The activated clay and alkali deacidification had significant effects on Litsea cubeba kernel oil resulting in a relatively low yield due to the large loss rate of raw materials.(2)The effect investigation of four alternative solvents on the extraction of Litsea cubeba kernel oils in comparison with n-hexane as the reference solvent.Regardless of the solvent used,all extracted oils were qualitatively and quantitatively analyzed,where solvent-solute interactions were also theoretically studied by Hansen solubility parameters.The results showed that green solvents(dimethyl carbonate and cyclopentyl methyl ether)were preferred to alcoholic solvents(ethanol and isopropanol)considering their higher extraction yields,higher micronutrients and similar fatty acid and acylglycerol compositions to oils extracted by n-hexane.CPME performed the best for Litsea cubeba kernel oil extraction,which was expected to become a green alternative to n-hexane for other plant oil extractions.(3)The Litsea cubeba kernel oil was processed by decolorization,esterification and transesterification.The purified methyl ester by molecular distillation was transesterified with trihydroxypropane to prepare a trihydroxypropane fatty acid trimester,which was subjected to the measurement of physicochemical properties and attenuated total reflectance-fourier transform infrared spectroscopy(ATR-FTIR)analysis.The results showed that the esterification of Litsea cubeba oils significantly reduced the acid value,which helped to synthesize their high-purity fatty acid methyl esters.The product of trihydroxypropane fatty acid triester(TFATE)as the biolubricant base oil was obtained with a mass fraction of 84% by the reaction under the vacuum of less than 100 Pa,which content could improve to 92% after molecular distillation.The product obtained had low crystallization starting point and low-temperature dynamic viscosity corresponding to its good cold starting-up performance and low-temperature stability.The viscosity index of TFATE could meet the criteria of multi-grade lubricating oil products.