超临界CO_2萃取脱除毛竹木质素的研究

研究了在CO2的超临界流体中,以二氧杂环己烷/水为夹带剂,毛竹木质素的脱除规律。采用4因素3水平的正交试验,对脱木质素效率、纸浆得率、残渣中Klason木质素含量及综纤维素含量的影响因素进行了分析。结果表明,温度是影响脱木质素效率的主要因素,其次是压力,反应时间和夹带剂体积分数对木质素溶出效率的影响相对较小。温度越高,萃取液中Klason木质素含量越高,但其综纤维素含量越低,纸浆得率也越低。在180℃、20 MPa下,采用95%（体积分数）二氧六环水溶液作夹带剂,萃取1 h,可得到较高的脱木质素率,达到84.18%。对不同温度下超临界萃取液的GC-MS分析表明,总离子流图流出峰中存在具有乙氧基的直链或支链以及含氧五元环结构的醇、醛、酮、酸和酯类化合物,也存在如香草醛、对羟基苯甲醛等木质素的基本结构单元。萃取液的组成受温度的影响很大,在较低温度（160℃）下,没有糠醛及香豆酮等的产生,而在较高温度（200℃）下,香豆酮质量分数接近15%,糠醛质量分数可达42%以上。

Delignification of Bamboo with CO_2 Supercritical Fluid Extraction

This paper researched the delignification of bamboo under the supercritical fluid of CO2 with dioxane/water as co-solvent.The experiments were carried out by using an orthogonal experimental design for four factors in three levels.The influence of temperatures（160,180 and 200 ℃）,pressure（16,20 and 24 MPa）,reaction time（30,60 and 90 min） and co-solvent dioxane content（95 %,90 % and 85 %） on delignification extent,pulp yields,Klason lignin content and residual holocellulose contents were analyzed.The results showed that the most important factor that affected the efficiency of delignification was the temperature and next was the pressure.The influences of reaction time and concentrations on delignification were relatively less.From the data,it can be found that the content of Klason lignin in exact liquid would be high and the pulps yield would be low when the temperature rises.Under the condition of 180 ℃ and 20 MPa,the high pulps yield and delignification could be obtained within 60 min with 95 % concentration of dioxane/water as co-solvent and the yield run up to 84.18%.The analysis of the GC-MS of the extract liquor tested under different temperature showed that the linear chain or branch of ethoxy and alcohol,aldehyde,ketone,acid and ester of five-member ring structure were existed.Lignin′s basic structure unit likes vanillin and p-hydroxyl benzaldehyde etc were found.The temperature had a great effect on the extract liquor content.There would be no furfural and benzofuran generated when the temperature was low,such as 160 ℃.But when the temperature increased to 200 ℃,the benzofuran content nearly reached to 15 % and furfural content run up to more than 42 %.