关键词: 杂交狼尾草, 木质纤维素, 稀硫酸预处理, 最佳工艺

Abstract:

【Objective】 Study the effects of H₂SO₄ concentration, solid-liquid ratio, treatment time and temperature on lignocellulose degradation efficiency of hybrid pennisetum under dilute sulfuric acid pretreatment, analyze the mechanism of dilute sulfuric acid on lignocellulose degradation, and screen the best pretreatment process.【Method】 Four single factors: H₂SO₄ concentration (0.5%, 1.0%, 1.5%, 2.0%, 2.5%), solid-liquid ratio (1﹕6, 1﹕8, 1﹕10, 1﹕12, 1﹕14), time (15, 30, 45, 60, 90 min) and temperature (80, 100, 110, 120, 125℃) were tested. Five levels of each factor were selected and repeated three times to analyze the effects of single factor on solid decomposition rate, cellulose degradation rate, hemicellulose degradation rate, lignin removal rate and hydrolyzed sugar. On the basis of single factor experiment, L₈ (2⁴) orthogonal test with 4 factors and 2 levels was used to determine the main influencing factors, and SEM and XRD analysis were carried out for the hybrid pennisetum under the optimal processing conditions. 【Result】 The results of single factor test showed that the degradation rate of hemicellulose was higher than that of lignin under all factors. With the increase of H₂SO₄ concentration, the degradation rate of cellulose and hemicellulose increased, and the lignin removal rate decreased; the yield of glucose produced by cellulose hydrolysis increased with the increase of concentration, but the content of xylose decreased gradually. The low concentration of H₂SO₄ (0.5%-1.5%) promoted the degradation and digestion of solid substances of hybrid pennisetum, increased concentration (>1.5%) further did not significantly change the solid degradation. The influence of solid-liquid ratio on each index was small,and when the solid-liquid ratio increased to 1﹕10, the solid decomposition rate, hemicellulose and lignin removal reached the maximum. The pretreatment time had no obvious effect on solid decomposition rate, hemicellulose and lignin degradation, but promoted hemicellulose degradation and glucose production. Temperature has obvious effects on solid decomposition rate, degradation of cellulose, hemicellulose and lignin, and yield of hydrolyzed sugar, and 100℃ is an important critical value, and effective degradation of lignocellulose need temperature above 100℃. The orthogonal test results showed that the factors affecting hemicellulose degradation were temperature - concentration - time - solid - liquid ratio. After pretreatment with dilute sulfuric acid, the structure of lignocellulose collapsed, non-cellulose was removed, cellulose bundles were exposed (SEM), and the degree of crystallization and polymerization of cellulose was increased (XRD). 【Conclusion】 Hemicellulose was mainly degraded by dilute sulfuric acid pretreatment, but lignin was poorly degraded. Temperature is the most important factor, followed by H₂SO₄ concentration. Under the influence of four factors, the optimum technological conditions are as follows: concentration 1.5%, solid-liquid ratio 1﹕6, time 15 min, temperature 120℃.

Key words: hybrid pennisetum, lignocellulose, dilute sulfuric acid pretreatment, optimal conditions