基于TG-FTIR-MS技术的酶解木质素热解行为分析

Pyrolysis Behavior Analysis of Enzymolysis Lignin Based on TG-FTIR-MS Technology

为了给磷酸法制备木质素基活性炭活化条件分析提供理论基础,实验对酶解木质素(EL)、磷酸浸渍酶解木质素(EL-P)进行恒速升温热重分析,以及模拟制备活性炭过程中的实验条件的变速升温热重分析。恒速升温热重分析发现EL热解过程主要发生在300~360℃,EL-P热解温度提前,证明磷酸在低温下即与EL发生反应。变速升温增加了木质素热解反应时间,主要失重峰从EL恒速升温过程的一个分裂为两个峰,木质素热解更加充分,EL-P热解产物残留量从恒速升温的57.42%降低到39.93%。变速热解与恒速热解相比,增加了恒温过程,最终热解产物残留量下降,更多物质以气体形式被释放,说明热解反应更充分,从而验证了在活性炭制备过程中浸渍及活化阶段恒温一段时间的必要性。通过释放成分的化学分析可知,木质素热解产物主要包括CO、CO_(2)、CH_(4)、甲醇、丙醛及芳香族化合物等,磷酸浸渍后,木质素热解释放产物含量减少,但成分大致相同。

The thermogravimetric analysis of enzymolysis lignin(EL)and phosphoric acid impregnated enzymolysis(EL-P)lignin was carried out at constant heating speed and variable heating speed to simulate the preparation conditions of activated carbon and provide a theoretical basis for analysis.The constant heating speed thermogravimetric experiments found that the EL pyrolysis process mainly occurred at 300-360℃,the EL-P pyrolysis temperature was advanced,which proved that phosphoric acid would interact with EL at low temperature.Variable heating speed increased the pyrolysis reaction time of lignin.The main weight loss peaks in the constant-rate heating process of EL split into two weight loss peaks,and the pyrolysis of lignin was more complete.The residual amount of EL-P pyrolysis products was reduced from 57.42%at the constant heating speed to 39.93%at the variable weating speed.Compared with constant speed pyrolysis,variable speed pyrolysis added the constant temperature process,the final pyrolysis residue decreased,more substances were released as gas,which indicated that the pyrolysis reaction was more sufficient.It verified the necessity of holding a constant temperature for a period of time during the impregnation and activation stages of the activated carbon preparation process.The chemical analysis of the released components showed that the pyrolysis of ligin mainly included CO,CO_(2),CH_(4),methanol,propionaldehyde and aromatic compound and so on.After H_(3)PO_(4) impregnation,the content of pyrolysis products of EL-P reduced and the components were roughly the same.