稻草和毛竹CO_2超临界流体萃取脱木质素研究

Delignification of bamboo and straw using CO_2 supercritical fluid extraction technology

采用CO2超临界流体萃取技术脱除稻草和毛竹的木质素,利用正交试验对脱木质素率与综纤维素含量等指标进行了评价;采用气相色谱-质谱联用方法(GC-MS)分析了萃取液的组成,讨论了萃取液组成与萃取条件(温度、压力和时间)的关系;利用透射电镜-能谱联用技术(TEM-EDXA)考察了萃取前后材料中木质素分布的超微结构。结果表明:温度、压力和时间是影响稻草和毛竹脱木质素的主要因素;温度越高、压力越大、时间越长,脱木质素程度越大,综纤维素含量越低。萃取液中主要含有来自纤维素结构的五元环、烷氧基醇和脂肪酸以及来自于H、G、S型木质素典型结构单元的降解产物。经CO2超临界萃取后,在160℃、16MPa、60min条件下,稻草细胞壁分层已不明显;在200℃、16MPa、60min条件下,毛竹细胞壁胞间层和细胞角隅中的木质素已全部溶出。

A technology of CO2 supercritical fluid extraction was adopted to remove the lignin in straw and bamboo.The content of Klason lignin and holocellulose was evaluated through orthogonal experiments.Extraction liquid composition was analyzed by GC/MS.The relationship between extraction liquid composition and experimental conditions was discussed.The ultrastructure of lignin distribution before and after extraction was analyzed by transmission electron microscopy（TEM） and energy dispersive X-ray analysis（EDXA）.Results showed that temperature and time were major factors affecting delignification of straw and bamboo.The higher the temperature and the longer the time,the higher the delignification and the lower the holocellulose content.The extraction liquid consisted of five-membered rings,alkoxyl groups and aliphatic acids from cellulose and lignin degradation products（H-,Gand S-type structure units）.TEM-EDXA analysis showed that after CO2 supercritical fluid extraction,cell wall delamination of straw was unobvious and the lignin of middle lamella and CCML in bamboo cell wall was removed at 200℃ and 16MPa.