单 位：
东北林业大学材料科学与工程学院;东北林业大学生物质材料科学与技术教育部重点实验室
关键词：
离子液体;杂多酸;双效催化降解;麦草碱木质素
摘 要：
采用常规合成法制备了杂多酸H_5PV_2Mo_(10)O_(40),并通过FT-IR、XRD、SEM对其进行表征。研究了[BMIM]Cl单催化与{H_5PV_2Mo_(10)O_(40)+[BMIM]Cl}双效催化体系中,反应时间、温度以及H_5PV_2Mo_(10)O_(40)用量对麦草碱木质素降解的影响,并初步探讨了木质素的降解机理。结果表明:H_5PV_2Mo_(10)O_(40)中P、V、Mo相对原子质量满足1∶2∶10关系,并具有典型的Keggin结构;木质素降解反应中,仅离子液体[BMIM]Cl降解木质素的最佳条件为140℃下反应3 h,降解后固体产物中总羟基由3.49 mol/kg增加到10.92 mol/kg,液体产物中有香草醛与丁香醛生成,分别占2.00%和2.15%;{H_5PV_2Mo_(10)O_(40)+[BMIM]Cl}双效催化体系中,最佳反应条件为加入20%的H_5PV_2Mo_(10)O_(40)120℃下反应6 h,降解后固体产物中总羟基由3.49 mol/kg增加到14.12 mol/kg,摩尔质量由7.691 kg/mol降为1.589kg/mol;液体产物中无丁香醛生成,香草醛占6.97%。初步认为:当单独[BMIM]Cl催化木质素时,H+首先进攻木质素中β-O-4键上的氧原子,正电荷转移到β位,然后水分子中氧原子向带有正电荷的β位进攻,从而催化剂的H+被消除,最后实现了β-O-4键水解断裂,生成愈创木酚,进而侧链发生氧化生成香草醛与丁香醛;当添加H_5PV_2Mo_(10)O_(40)时,[PV2Mo10O40]5-中的VO+2由V(V)→V(IV),故使模型化合物得以单电子的氧化,使木质素脱甲氧基,由紫丁香基木质素转变成愈创木基木质素,液体产物中无丁香醛生成,且香草醛质量分数升高。
译 名：
Experimental evaluation on the ionic liquid [BMIM]Cl and H_5PV_2Mo_(10)O_(40) dual function catalytic degradating wheat straw alkali lignin
作 者：
LIU Xiao-le;REN Shi-xue;HOU Lian-xia;LI Shu-jun;College of Material Science and Engineering,Northeast Forestry University;Key Laboratory of Bio-based Material Science and Technology of Ministry of Education,Northeast Forestry University;
关键词：
ionic liquid;;heteropoly acid;;dual function catalytic degradation;;wheat straw alkali lignin
摘 要：
The H_5PV_2Mo_(10)O_(40)heteropoly acid was prepared by the conventional methods and was characterized [BMIM]Cl single function catalytic system,the effects of reaction time,reaction temperature and the amount of H_5PV_2Mo_(10)O_(40)on the lignin degradation process were studied,and the degradation mechanism was also discussed preliminarily.The results indicated that the contents of P,V,Mo in the synthesis H_5PV_2Mo_(10)O_(40)heteropoly acid accorded with the relationship of 1∶2∶10,and the H_5PV_2Mo_(10)O_(40)heteropoly acid had the typical Keggin structure.Under the optimal reaction condition,i.e.,140℃,3hours,the ionic liquids were used as the catalysts,the contents of total hydroxyl of alkali lignin increased from 3.49 to 10.92 mol/kg after reaction,and the mass fraction of vanillin and syringaldehyde were2.00%and 2.15%in liquid products,respectively.When 20%H_5PV_2Mo_(10)O_(40)was added,the optimal reaction time and temperature were 6 hour and 120℃,and the total hydroxyl increased from 3.49 to14.12 mol/kg in solid degradation products.The molar mass reduced from 7.691 to 1.589 kg/mol.Only vanillin was found in liquid products,and its mass fraction was 6.97%.It was believed that H+attacked oxygen atom on theβ-O-4 bond in lignin firstly when[BMIM]Cl catalyzed lignin alone.At the same time,the positive charge was transferred to theβposition,and then the oxygen atom in the water molecule attacked theβposition which had positive charge.As a result,catalyst H+was eliminated andβ-O-4 bond generated guaiacol due to the hydrolytic cleavage.Then the side chain generated vanillin and syringaldehyde by the oxidation reaction.When H_5PV_2Mo_(10)O_(40)was added,[PV_2Mo_(10)O_(40)]5-released VO_2~+ and its valencestate was changed from V(V)to V(IV).The single electron oxidation model compounds were obtained and the lignin was demethylated.It was thought that the lignin demethoxy group was changed from lignin-type lignin to guaiacol-type lignin,not only without any clove aldehydes were found in the liquid product but also the contents of vanillin were increased.
