Preparation of HMF by dissolving cellulose of rice husk with ionic liquid and its kinetics study

• Main Authors: LIN, YI-FENG, 林義豐
• Other Authors: WU, SHU YII
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/7w2zfd

碩士 === 逢甲大學 === 化學工程學系 === 107 === In this study, HMF was prepared by dissolving lignocellulose materials in ionic liquid. The methods of HMF quantitative analysis are compared, and the reaction kinetics of cellulose to HMF redactions were investigated in this study. The pretreatment of rice husk by alkali resulted in the increasing cellulose recovery, and reducing the ionic liquids utilization during the process and lower the cost of the circular processing. Rice husk was used as raw feed stock for the synthesis of HMF via alkali pretreatment. The concentrations of NaOH and reaction time were 0.5, 1.5, 3.5, 6.5, 10 M and 20, 40, 60, 120, 240 min, respectively in a 3-necked flask at 80°C. The cellulose content was increased from 36.00% to 55.77% after the alkali pretreatment. The crystallinity of cellulose of rice husk was slightly increased from 38.65% to 43.48% according to XRD analysis. Pretreatment effectively remove ash of 96.39% and reduce its silicon content based on EDS analysis. Studies indicate [Bmim]Cl is an effective ionic liquid in converting cellulose into HMF. In this study, HMF was derived from cellulose at different temperatures and cellulose concentrations. According to literature reports, the conversion of cellulose to HMF is a continuous first-order reaction. Thus, the kinetic model for this study was based on this assumption. The kinetic model is as follows. CA = CA0e(-k1t) CG = "k1CA0" /"k2 + k3 - k1" [ e(-k1t) - e(-(k2 + k3)t)] CH = "k1k2CA0" /"k2 + k3 - k1" [ "e(-k1t)" /"k4 - k1" - "e(-(k2 + k3)t)" /"k4 - (k2 + k3)" ] + "k1k2CA0e(-k4t)" /"(k4 - k1)(k4 - k2 - k3) " Reaction k0 Ea (kJ/mol) A → G 3.33 × 1016 142.54 G → H 2.33 × 1012 109.23 G → Hu 2.38 × 1012 107.70 H → Hu 5.53 × 1014 125.33 The degradation rate constant kGl (0.1161) of glucose was greater than the degradation rate constant k1 (0.0999) of cellulose, and the higher the temperature, the greater the difference. The degradation of cellulose was a slow reaction relative to the glucose, and controlled the rate of the entire series of reactions. Preparation of HMF from pretreated rice husk was carried out with 12wt.% of cellulose at 423K. The resulting HMF yield was 12.11%. This study suggests a feasible route to prepare HMF from rice husk in an ionic liquid.