生物基极性非质子溶剂/对甲苯磺酸耦合体系中竹粉定向解聚研究

Directional Decomposition of Bamboo Powder in Bio-based Polar Aprotic Solvent/Aqueous p-Toluenesulfonic Acid Coupling Systems

以两种生物基极性非质子溶剂γ-戊内酯(GVL)和二氢左旋葡萄糖酮(Cyrene),分别与对甲苯磺酸水溶液(TsOH aq)构成耦合体系,对竹粉定向解聚及其酶解过程开展了研究。实验结果表明:质量浓度为75 g/L的TsOH,溶剂体积比为4∶1的GVL/TsOH aq体系在130℃预处理毛竹60 min后,半纤维素和木质素分离效率更高,半纤维素分离率(S_(H))和木质素分离率(S_(L))分别达到98.5%和98.4%,同时纤维素保留率(R_(C))为91.5%;而质量浓度为30 g/L的TsOH,溶剂体积比为0.8∶1的Cyrene/TsOH aq体系在120℃预处理毛竹60 min后,R_(C)达到87.3%,S_(H)和S_(L)仅为85.5%和79.4%。预处理后固体样品的表征结果表明:竹粉经GVL/TsOH aq预处理后的样品木质纤维致密结构被有效破坏,无定形的半纤维素和木质素绝大部分被分离,结晶度达68.27%,结构更接近于微晶纤维素,同时暴露出更多的游离羟基,有利于后续酶解。而酶解结果进一步证明:GVL/TsOH aq预处理后样品的酶解葡萄糖产率773 mg/g,显著高于Cyrene/TsOH aq预处理后样品(306 mg/g),达到毛竹原料酶解效率的19.3倍。两种溶剂体系均可高效回收利用,其中GVL/TsOH aq体系循环使用3次后,S_(L)仍达90.3%以上,S_(H)不低于91.3%,R_(C)不低于91.5%,能回收94.8%的溶剂。

The effects of pretreatment withγ-valerolactone/p-toluenesulfonic acid aqueous solution coupling system(GVL/TsOH aq)and Cyrene/p-toluenesulfonic acid aqueous solution coupling system(Cyrene/TsOH aq)on the chemical composition and enzymatic hydrolysis of maso bamboo were studied.The results showed that the hemicellulose separation rates(S_(H))and lignin separation rate(S_(L))in GVL/TsOH aq system with 75 g/L TsOH and the solvent volume ratio of 4∶1 were 98.5%and 98.4%,respectively,after pretreatment at 130℃for 60 min,and the cellulose retention rate(R_(C))was 91.5%.In contrast,the Cyrene/TsOH aq system with 30 g/L TsOH and the solvent volume ratio of 0.8∶1 was pretreated maso bamboo at 120℃for 60 min,the R_(C) was 87.3%,while the S_(H) and S_(L) were 85.5%and 79.4%,respectively.Characterization results of solid samples after pretreatment showed that after pretreatment with GVL/TsOH aq,the dense structure of lignocellulose of the samples was effectively destroyed,and most of the amorphous hemicellulose and lignin were separated,with a crystallinity of 68.27%.Besides,the structure was closer to microcrystalline cellulose,and more free hydroxyl groups were exposed,which was conducive to the subsequent enzymatic hydrolysis and saccharification process.The enzymatic hydrolysis results demonstrated that the glucose yield of the solid sample obtained by GVL/TsOH aq pretreatment(773 mg/g)was significantly higher than that of the sample obtained by Cyrene/TsOH aq(306 mg/g),which was 19.3 times of that of bamboo.The two solvent systems could be effectively recycled,and the separation rate of lignin and the retention rate of cellulose in GVL/TsOH aq system could reach 90.3%and 91.5%respectively,and 94.8%of solvent could be recovered after three cycles.