过渡金属硫酸盐协同Pd/C高效定向降解木质素的研究

Efficient and Product-controlled Degradation of Lignin Using Transition Metal Sulfates Cooperated with Pd/C

中文关键词:  过渡金属硫酸盐  Pd/C  木质素  定向降解  酚类化合物

Key Words:transition metal sulfate  Pd/C  lignin  product-controlled degradation  phenolic compound

中文摘要:

      以改善当前木质素催化降解存在的降解产物可控性较差、小分子化合物总收率较低、均一化程度不足、难以进一步开发利用等问题为目标，采用过渡金属硫酸盐NiSO₄·6H₂O协同Pd/C催化降解玉米芯酶解木质素，考察了过渡金属离子、反应温度、反应时间、NiSO₄·6H₂O与Pd/C协同作用等对木质素降解率的影响，并分析了降解产物的分布和催化作用机理。结果表明，NiSO₄·6H₂O可有效提高Pd/C对木质素的催化降解效率，如木质素降解率相较于单独使用Pd/C催化降解时提高14.5%，小分子化合物总收率提高39.9%，其中，酚类化合物的得率提高88.6%，且产物的均一化程度提高了35.8%；分析表明，由于NiSO₄·6H₂O的路易斯酸特性和镍离子的高电负性，木质素的醚键可有效地在Pd/C和NiSO₄·6H₂O酸性催化中心上发生裂解，并通过加氢反应，定向生成以酚类为主体的中间产物。

Abstract:

      In order to overcome several obstacles which limit the further development and utilization of degradation products existing in lignin catalytic degradation at present， such as poor product-controlled property， low yield of small molecule compounds， insufficient degree of uniformity， and difficulty for further utilization. NiSO₄·6H₂O cooperated with Pd/C was used to catalyze the degradation of corncob lignin in this study. The effects of transition metal ions， reaction temperature， reaction time， and synergistic effect of NiSO₄·6H₂O and Pd/C on lignin degradation ratio were investigated. Meantime， the degradation products and mechanism were analyzed. The results showed that NiSO₄·6H₂O cooperated with Pd/C could effectively improve the lignin degradation ratio. The degradation ratio was increased by 14.5%， and the yield of small molecules was improved by 39.9%. Especially， the yield of phenolic compounds was increased by 88.6% and the products uniformity was upgraded by 35.8% as well. Due to the properties of Lewis acid and the high electronegativity of Ni²⁺ in NiSO₄·6H₂O， the ether bonds of lignin could be cleaved on the acidic catalytic centers of Pd/C and NiSO₄·6H₂O effectively， and phenolic compounds were formed through the hydrogenation reaction.