Fe(NO_3)_3催化乙酸预处理玉米秸秆的研究

Acetic acid pretreatment of corn stack by using Fe(NO_3)_3 as the catalytic agent

采用Fe(NO3)3催化乙酸对玉米秸秆进行预处理,以提高水解反应的效率,考察了乙酸初始质量分数和预处理时间对玉米秸秆水解反应的影响。结果表明,Fe(NO3)3可有效提高乙酸预处理秸秆的水解率。当使用0.05 mol/L Fe(NO3)3催化5%乙酸预处理秸秆15min时,与单独乙酸预处理玉米秸秆相比,水解液中葡萄糖、木糖和阿拉伯糖的质量浓度分别提高了110%、250%和10%,同时秸秆中半纤维素和纤维素的水解率分别提高了49%和14%;与单独0.05 mol/L Fe(NO3)3预处理玉米秸秆相比,水解液中相应的各单糖质量浓度分别提高了131%、68%和61%。随乙酸初始质量分数增加,水解反应中各产物的质量浓度均逐渐增加。乙酸初始质量分数从1%增加到5%,水解玉米秸秆15 min时,水解液中葡萄糖、木糖和阿拉伯糖的质量浓度分别从8.67 g/L、11.68 g/L和3.19 g/L升高到11.86 g/L、13.78 g/L和3.23 g/L。延长预处理时间有利于秸秆的水解反应,但太长会导致玉米秸杆中半纤维素和纤维素的水解率增加变缓。当采用0.05 mol/L Fe(NO3)3催化5%乙酸时,预处理时间从15 min延长到60 min,半纤维素的水解率从74.7%逐渐升高到92.9%,而纤维素的水解率没有变化,稳定在26%。

The present paper is inclined to investigate an improved method for pretreating the corn stack by enhancing the effect of the acetic acid concentration and pretreatment time on its hydrolysis be- havior with Fe（NO3）3 as its catalytic agent. In so doing, it is expected to increase its sugar yield in the hydrolysis. The results of our in- vestigation show that Fe（NO3 ）3 tends to be effective for enhancing the acetic acid pretreatment. The practical procedure we have developed can be shown as follows： Taking 5% （w/w） acetic acid catalyzed by 0.05 mol/L Fe（NO3）3 for 15 min, the concentration of glucose, xylose and arabinose in the hydrosates are expected to be enhanced by 110%, 250% and 10%, respectively, with the hemicellulose hydrolysis efficiency increased by 49 % and that of cellulose enhanced by 14% as compared with the case pretreated by acetic acid alone, whereas the concentration of corresponding monosaccharide in the hydrolysates is expected to be improved by 131% , 68 % and 61% as compared with the pretreatment results by merely 0.05 moL/L Fe（NO3）3. With the increase of the acetic acid concentration, the concentration of products in the hydrolysis tends to increase gradually, to0. In addition, when the initial concentration of acetic acid in- creased by 5% （w/w） from 1% （w/w）, the concentration of glucose, xylose and arabinose in the hydrosates can be expected to increase by 11.86 g/L, 13.78 g/L and 3.23 g/L from 8.67 g/L, 11.68 g/L and 3.19 g/L, respectively, through a 15 min pretreatment. Moreover, it can be found that prolonging the pretreatment time is benefited to increase the hydrolysis of the corn stack, nevertheless, too long extending of the pretreating time is likely to lead to a slow increase of the hemicellulose and cellulose hydrolysis efficiency in the corn stack. For example, if the prctreatment proceeding from 15 min to 60 min, the hemicellulose hydrolysis efficiency tends to increase to 92.9% from 74.7% gradually, but that of cellulose wouldn＇t vary and then get stabilized at 26% with a 5% （w/w） of acetic acid as the catalytic agent by 0.05 mol/L Fe（NO3）3.