甲酸/盐酸胍DES温和高效分离毛竹木质素

Mild and efficient fractionation of moso bamboo lignin based on formic acid / guanidine hydrochloride deep eutectic solvent

摘要:

以毛竹为原料，采用甲酸/盐酸胍酸性低共熔溶剂（DES）温和高效分离木质素，并对其结构、热稳定性和抗氧化性进行了表征。结果表明，甲酸/盐酸胍（摩尔比为4:1）DES实现了温和短时条件下（100 ℃，2 h）高效分离木质素（得率为59.31%），当进一步升温至120 ℃时，得率可达73.98%，其原因是该酸性体系中氢质子使木质素中大量的β-O-4、β-β、β-5连接键断裂，促使木质素大分子解聚成小分子而溶出。分离的木质素纯度高于96.6%，分子量低（Mw=1040~2040 g/mol），多分散系数小于1.5，结构均一，热稳定性好。同时，该木质素抗氧化活性强（IC50=0.016~0.045 mg/ml），优于商业抗氧化剂丁基羟基茴香醚（IC50=0.056 mg/ml）。

Abstract:

The lignin from moso bamboo was fractionated mildly and efficiently using formic acid / guanidine hydrochloride acidic deep eutectic solvent (DES). The structure, thermal stability and antioxidant activity of the lignin were characterized. It was found that formic acid / guanidine hydrochloride (molar ratio was 4:1) DES resulted in a high lignin yield of 59.31% under mild conditions (100 ℃, 2 h) and further increased to 73.98% at 120 ℃. This was attributed to the acidic DES donated active protons to selectively cleave β-O-4、β-β、β-5 bonds and further facilitated a large amount of lignin removal. The following lignin profiling indicated that the lignin had a high purity (>96.6%), low molecular weight (Mw=1040~2040 g/mol), low polydispersity (PDI<1.5), homogeneous structure, excellent thermal stability. The antioxidant performance of the lignin (IC50=0.016~0.045 mg/ml) was better than that of the commercial antioxidant butylated hydroxytoluence (IC50=0.056 mg/ml).