Wax Esters Synthesis And Long-Chain Ester Modification Catalyzed By Lipase

Wax esters are long-chain esters derived from fatty acids and alcohols, both with chain lengths of twelve carbons or more. There are saturated wax esters and unsaturated wax esters according to their chemical structures. Saturated wax esters have extensive sources, most of which are derived from animal wax and vegetable wax. Unsaturated wax esters also called liquid wax are biodegradability, good lubricity at high temperature and high pressure and high speed. They are widely used in super Techlon lubricant and senior embellish skin oil. However, the natural unsaturated wax esters are too scare and expensive to commercial use. Thus, we are trying to synthesize wax esters by esterification of natural fatty acids and alcohols catalyzed by immobilized lipase Candida sp.99-125 in solvent free system.First, reaction conditions were optimized using oleic acid and cetyl alcohol, and the reactions were carried out in 50 mL cone-shaped bottles with plug. The reaction system, acid/alcohol molar ratio, lipase dosage, reaction time and water removing method were investigated. The optimized conditions were as follows:solvent free system, acid/alcohol molar ratio 1/0.9, immobilized lipase membrane usage 10%(w/w), open reaction for water removing, the convertion rates were above 95% after 8 h reaction time. The reaction was scaled up to one liter stirred tank reactor, and the optimized conditions were:solvent free system, acid/alcohol molar ratio 1/0.9, lipase membrane dosage 2.5%(w/w) or powder lipase 0.7-0.8% (w/w),200-250 rpm agitation speed, temperature 40℃, and 24 h reaction time. The convertion rate was above 95% at the optimized conditions. The lipases could be reused for 6-7 batches.The fatty acids mixture and long chain alcohols mixture were also used as the substrates of esterification. The optimized conditions were the same as described above. In 50 mL cone-shaped bottles with plug, oleic acid and mixture alcohols (with chain length of 8C-16C) were used as substrates and the conversion rate reached 95%. In 500 mL stirred tank reactor, industrial grade soybean oil fatty acid and cetyl alcohol were used as substrates and the convertion rate also reached 95%. The lipase Candida sp.99-125 could also be used in lanolin modification by estrification with suitable alcohols. The lanolin acid could react with short chain alcohols, and conversion rate reached 80% when reacted with amyl alcohol at the optimized conditions.The purification process was also studied:ethanol was used for cetyl alcohol removing and saturated sodium carbonate solution was selected for fatty acids removing. After purification, the physicochemical properties of esters with different chain length were tested. The results showed that the physicochemical properties of the wax esters could be adjusted by selecting the chain length of fatty acids and fatty alcohols. The esters could be used as the substitute of natural sperm whale oil.