Preparation Of Castor Oil-based Surfactant

Recently,oil-based surfactants,prepared from natural renewable resources-animal and vegetable oils instead of fossil raw materials,agree well with the green development concept of"sustainable and environmentally friendly"of surfactants,and have been the focus of research in the surfactant industry.Mono-and diacylglycerol possessing good wettability,solubility and emulsification,can be used as surfactant for their advantages of green and environmental friendly.However,Mono-and diacylglycerol must be obtained by synthesis owing to their low content（<10%）in nature.The limiting factors of the synthesis of mono-and diacylglycerol are as following:（i）The raw materials mainly are edible oils such as soybean oil,corn oil and rapeseed oil,which occupy human food resources;（ii）Traditional alkaline catalysts such as Na OH and KOH,used in the industrial preparation of mono-and diacylglycerol have the disadvantages of high reaction temperature（200～250℃）,unpredictable by-products,and dischargeing waste water polluting the environment.To avoid those problems,nonedible castor oil is used as raw material,and solid super base,amino acid ionic liquid and liquid lipase are use as catalysts in this work,to prepare mono-and diacylglycerol.Firstly,solid superbase catalyzed the glycerolysis of castor oil was investgated.The effects of different base catalysts,reaction time,castor oil-glycerol ratio,catalyst load,and temperature on the glycerolysis were evaluated and optimized by respose surface methodology.Furthermore,the reaction mechanism,kinetics and thermodynamics of the glycerolysis reaction were also explored.Results suggested that,HND-63 solid superbase showed higher catalytic performance,was between KOH and Na OH,and much higher than CH₃ONa and HND-64.In addition,compared with Na OH and CH₃ONa,HND-63 solid superbase catalyzed glycerolysis reaction was characterized by less saponification,high MAG content in the product,and easy to purify the product.The result show that the order of the effect of four single factors on castor oil glycerolysis catalyzed by HND-63 is as follows:temperature>HND-63 loading>reaction time>substrate ratio.Under the conditions of 111℃,10%HND-63 loading,and 1:9.2 substrate ratio,castor oil-based surfactant with MAG content of 72.50±1.70%was obtained after 209 min of reaction.According to the results of kinetic,the activation energy（Ea）and pre-factor A were obtained as 61.37 k J/mol and 6.33×10⁶,respectively.Secondly,nine amnio acid-based ionic liquids（AA-ILs）,consisting of arginine,lysine and histidine,and choline hydroxide（Ch OH）,tetramethylhydroxide ammonium（TMAOH）and tetrabutylammonium hydroxide（TBAOH）,were synthesized via a simple and green chemical route and used as catalysts to catalyze the glycerolysis of castor oil.The effects of the structural composition of AA-ILs,reaction time,castor oil-glycerol ratio,AA-ILs load,temperature and free fatty acid content in castor oil on the glycerolysis were evaluated and optimized by response surface methodology.Results demonstrated that,among the tested AA-ILs,[Ch][Arg],[TMA][Arg]and[TBA][Arg]showed the outstanding catalysis performance.Especially,[Ch][Arg]as reaction catalyst for the glycerolysis of castor oil exhibited the best catalysis activity,and high selectivity toward the formation of MAG.The maximum MAG content（83.33±1.56%）were obtained under the optimized conditions:93.7℃,60.7 min,[Ch][Arg]load 12.3%,and substrate molar ratio 1:6.4.Besides,[Ch][Arg]still had 80%catalytic activity when the free fatty acid content was 20%in castor oil.Kinetic of the glycrolysis was also evaluated.Accordingly,Ea of the glycerolysis was obtained as 59.7 k J/mol.Then,three liquid lipases Eversa Transform 2.0,Candida antartica lipase-B and Thermomyces lanuginosus were used to catalyst the glycerolysis of castor oil and were compared with immobilized lipases.The effects of reaction time,castor oil-glycerol ratio,lipase load,and temperature on the glycerolysis were evaluated and optimized by response surface methodology.Results showed that,among the three liquid lipases,Eversa Transform2.0 showed the best catalytic activity,and was more active than immobilized lipases at low temperature（35℃）.The influence of three variables on DAG content was time>liquid lipase loading>temperature.The optimal glycrolysis conditions were Eversa Transform 2.0loading 9.5%,substrate molar ratio 1:6,reaction time 99 min,and temperature 29℃.The maximum DAG content（49.80±0.58%）was obtained under the optimal conditions.The activation energy for castor conversion was 31.24 k J/mol.Kinetic parameters K’_m and V_maxwere 0.701 mol/L and 5.63×10^-2 mol/（L·min）,respectively.Finally,the properties of castor oil based surfactant products were investigated.Resuts showed that castor oil surfactant has high HLB value（12.20～15.50）,low surface tension,good wettability,can be used as O/W type emulsifier,detergent and solvent-increasing agent.