催化加氢不同预处理玉米秸秆制取多元醇的研究

Study on Catalytic Hydrogenation of Corn Stalk after Various Pretreatment into Polyol

以玉米秸秆为研究对象,采用5%硫酸和5%氢氧化钠对其进行预处理,通过对解聚前后玉米秸秆官能团表征和成分分析,发现酸、碱处理后秸秆中大部分半纤维素和木质素被脱除,其中先碱后酸、先酸后碱处理后秸秆的木质素含量由28.04%分别下降至11.54%和12.14%,而纤维素相对含量由42.02%分别增加到75.12%和77.68%。通过浸渍法制备的非贵金属5%Ni-15%W/MCM-41催化剂用于催化转化预处理秸秆制取多元醇,结果表明:与未经处理的玉米秸秆多元醇得率21.00%相比,先碱后酸、先酸后碱处理的玉米秸秆催化转化多元醇得率分别达到60.72%和61.40%。α-葡萄糖和β-葡萄糖的加氢结果显示乙二醇(EG)和1,2-丙二醇(1,2-PG)得率均相近,说明葡萄糖的旋光构型对催化加氢没有影响。与C6糖加氢产物分布比较,C5糖的产物中除了有EG和1,2-PG,同时还有丙三醇的生成,提出了糖加氢制取多元醇的可能机理。

In the study, corn stalk was pretreated using 5% H2804 or/and 5% NaOH. The functional group and chemical composition of corn stalk before and after pretreatment were characterized and analyzed. Pretreatment of corn stalk removed most of lignin and hemicellulose, the lignin contents in corn stalk were decreased from 28.04% to 11.54% and 12.14% after alkali-acid and acid-alkali pretreatments, thereby the cellulose contents were increased from 42.02% to 75.12% and 77.68%, respectively. The catalyst of 5%Ni-15%W/MCM-41 for catalytic conversion of pretreatment corn stalk into polyol was prepared using an impregnation method. The results showed that the high yields of 60.72% and 61.40% polyol were obtained by catalytic hydrogenation of corn stalk after pretreatment with alkali-acid and acid-alkali, respectively, which were significantly high as compared with 21.00% from the raw corn stalk conversion. The yields of ethylene glycol （EG） and propylene glycol （1, 2-PG） from catalyst conversion of a-and Q-glucose suggested that the opitical isomerization of glucose had no influence on catalytic hydrogenation. Not just EG and 1, 2-PG, as compared with product distributions of C6 sugar, the glycerol was also obtained from C5 sugar catalytic hydrogenation. Based on the above experimental results, a possible reaction mechanism of sugar into polyol was suggested.