一锅三步法固定化脂肪酶催化环己酮合成聚ε-己内酯

Preparation of polyε-caprolactone from cyclohexanone catalyzed by immobilized lipase in one pot using three steps process

采用固定化T.laibacchii脂肪酶催化一锅三步法制备聚ε-己内酯(PCL)。所得最优聚ε-己内酯产率为96.5%,平均摩尔质量为2912 g/mol。首先,采用脂肪酶催化乙酸乙酯(EtOAc)与尿素过氧化氢(UHP)的反应,生成乙酸;然后,采用原位反应生成的过氧乙酸,将环己酮以非酶方式酯化为ε-己内酯(CL),同时,反应生成的乙酸与UHP反应生成过氧乙酸;最后,CL经酶催化开环聚合,原位生成聚ε-己内酯。采用响应面法(Response Surface Methodology,RSM)进行了实验设计和优化,建立了聚ε-己内酯产率模型,其相关系数R2为0.9997。反应中生成的乙酸与UHP反应生成过氧乙酸,有效减少了UHP用量,进而降低了UHP浓度,减弱了UHP对脂肪酶的抑制作用,加快了反应速度。经RSM优化得到的最佳条件为:脂肪酶用量23.55 mg,反应温度59.4℃,UHP/环己酮的摩尔比1.31。聚ε-己内酯高产率的原因有:采用交联固定化脂肪酶;在步骤3中添加脂肪酶;将UHP初始浓度由2.50 mol/L降至1.63 mol/L。

Polyε-caprolactone has very good biocompatibility.One-pot ring-opening polymerization(ROP)was used to prepare polyε-caprolactone from cyclohexanone(CHN)catalyzed and immobilized T.laibacchii lipase was carried out.The yield of PCL and number-average molar mass(Mn)were 96.5%and 2912 g/mol.The one-pot ROP consists three steps:first,ethyl acetate(EtOAc)reacts with UHP to generate peracetic acid catalyzed by lipase;then,CHN is lactonized toε-caprolactone(CL)with peracetic acid in situ generated in nonenzymatic,and acetic acid formed reacts with UHP to form peracetic acid;finally,CL suffers from enzymatic ROP to in situ generate polyε-caprolactone.RSM was used to design and optimize the experiment,and a polyε-caprolactone yield model was established.The correlation coefficient R2 was 0.9997.The acetic acid generated in the reaction reacts with UHP to produce peracetic acid,which effectively reduces the amount of UHP,thus reducing the concentration of UHP,reducing the inhibition of UHP on lipase,and speeding up the reaction.The optimal conditions by using response surface methodology(RSM)were obtained as follows:the supplement of lipase,23.55 mg,the reaction temperature,59.4℃and the molar ratio of urea hydrogen peroxide(UHP)to CHN,1.31∶1.There are three factors contributing to the high yield:cross-linked immobilized lipase employed,the supplement of lipase added in step 3 of ROP and the initial concentration of UHP reduced from 2.50 mol/L to 1.63 mol/L.