p-TsOH对稻草的组分分离动力学及分离产物性质

在当前资源短缺和能源危机问题的背景下,用稻草等非木质纤维素原料制备生物质基材料等的研究备受重视。使用质量分数20%～60%的对甲苯磺酸,在60～80℃的反应温度、15～60 min的时间内对稻草进行组分分离,得到的纤维固体产物的得率基本在60%以上,灰分含量在10%以上。通过固体产物与废液等的化学成分分析,得到组分分离的脱木质素反应动力学曲线、半纤维素降解动力学曲线和反应动力学方程相应的参数值。分析了反应的联合脱木质素因子(CDF)跟固体产物的纤维组成、形态和表面电荷等之间的关系。根据反应剧烈程度,把CDF曲线分成3部分:当CDF值小于3 000 min·mol/L时,纤维分离不彻底;当CDF值为3 000～6 000 min·mol/L时,纤维分离程度较好;当CDF值大于6 000 min·mol/L时,纤维虽分离良好,但纤维断裂较多,碎片化严重。CDF因子越高,纤维表面Zeta电位绝对值越高,但红外光谱和羧基含量结果显示纤维的官能团类型没有变化。CDF曲线转折点附近的P30T80t30和P45T70t60条件下的纤维得到了有效的分离,并较好地保持了纤维形态,适用于造纸。

p-TsOH fractionation kinetics of rice straw and its effect on properties of fraction products

As one of the most abundant,renewable,and low-cost agricultural wastes in the world,rice straw is residuum of rice production.The general way that enterprises adopted is burning,which reduces the utilization value of lignin and causes pollutions to the environment.Research of biomass-based materials from non-lignocellulosic materials such as rice straw has attracted much attention because of the resource shortage and energy crisis.p-Toluene sulfonic acid(p-TsOH)is an efficient hydrotrope for biorefining pretreatment.p-TsOH hydrotropic fractionation of lignocellulose is an environmentally friendly and efficient technology.Rice straw fractionation under the different conditions with the p-TsOH concentration of 20%-60%,temperature of 60-80℃,and duration of 15-60 min was studied.The p-TsOH treated pulp yield was more than 60%.The ash content of the pulp was more than 10%.The zeta potential of pulp showed the negative charge.Conductometric titration showed that the carboxyl content of the hydrotropic rice straw pulp was much lower than that of traditional wood pulp.The Fourier transform infrared spectroscopy(FT-IR)showed that the peak wave number of the main functional groups remained unchanged after the p-TsOH treatment,so the types of functional groups did not change.The p-TsOH fractionation kinetics of rice straw was evaluated by the combined delignification factor(CDF)and the combined hydrolysis factor(CHF).The delignification curve,hemicellulose hydrolysis curve and the reaction equation were obtained after the chemical composition analyzation.Microscopes images showed that the p-TsOH treated pulp could be divided into three groups based on the CDF,i.e.,incomplete separated(CDF<3000 min·mol/L),well separated(3000 min·mol/L6000 min·mol/L).The trends of the CHF curve and CDF curve were similar.The high CDF or CHF meant the high reaction severity.The p-TsOH fractionation can be divided into two stages,i.e.,fast reaction and slow reaction.The reaction conditions at the turning point of the CDF curve was P45T70t60,and the turning point of CHF curve was also near P45T70t60.It was the intersection between fast reaction and slow reaction,or the intersection between the high severity and low severity.The zeta potential of pulp of became more negative with the increase in CDF.High yield of rice straw pulp can be obtained by properly controlled CDF and CHF such as P30T80t30 and P45T70t60 around the turning point of CDF curve,of which,these fibers were well separated,and the fiber length and the fiber morphology of the pulp were qualified for papermaking.