质谱学报2018，Vol.39Issue(3)：268-277,10.DOI:10.7538/zpxb.2017.0064
在线热解-光电离质谱法研究Li2CO3对松木热解的影响
On-line Study on the Catalytic Pyrolysis of Pine Wood over Li2CO3 Using Pyrolysis-Photoionization Mass Spectrometry
摘要
Abstract
The catalytic effect of Li2CO3on pine wood pyrolysis was studied by thermo-gravimetry (TG)and homemade pyrolysis-photoionization mass spectrometry (Py/PI-MS).The TG and derivative thermogravimetry(DTG)curves indicated that the pyroly-sis temperature of pine wood was reduced and the yield of coke didn't increase signifi-cantly in the presence of Li2CO3.The DTG curve of pure pine wood was characterized by a shoulder peak.Since the pyrolysis temperature of hemicellulose was lower than that of cellulose,the peak and shoulder peak were mainly attributed to the decomposi-tion of cellulose and hemicellulose,respectively.The shoulder peak in the DTG curve of pine wood/Li2CO3disappeared,indicating the pyrolysis temperature of cellulose was reduced obviously and the pyrolysis temperature of hemicellulose decreased slightly. Py/PI-MS is an on-line analytical method which combines pyrolysis furnace with photoionization mass spectrometry.Thanks to the"soft"ionization method (10.6 eV), nearly few or no fragments are produced in the mass spectra.The experiment was car-ried out in two modes:(1)In temperature-fixed mode,the mass spectra of pine wood and pine wood/Li2CO3pyrolyzates at different temperatures as well as the time-evolved profiles were obtained.(2)In temperature-programmed mode,the temperature-evolved profiles of pine wood and pine wood/Li2CO3pyrolyzates were obtained.The results of Py/PI-MS showed that the three primary components of pine wood,i.e.,cellulose, hemicellulose and lignin had different responses to the added catalyst,Li2CO3.The yield of pyrolyzates from cellulose and hemicellulose were decreased,while pyrolyzates yields from lignin increased significantly.From time-evolved profiles,the time to reach the maximum reaction rate of pyrolyzates were advanced in the presence of Li2CO3. From temperature-evolved profiles,the temperature to reach the maximum reaction rate of pyrolyzates were advanced due to added Li2CO3.The major pyrolysis products of hemicellulose had only one peak,which was consistent with their generation paths.The pyrolysis products of cellulose and lignin had two peaks,indicating that they had multi-ple different generation paths,which were also consistent with their generation paths. As mentioned above,Li2CO3had a profound effect upon the pyrolysis of pine wood.It has been investigated by considering the effect of Li+on the reaction energy barrier for the decomposition of pyrolyzates.The possible catalytic mechanism was proposed that the bond energy of C—O of pyrolyzates were reduced in the presence of Li+,thus promoting the decomposition of pyrolyzates.Pine wood pyrolyzates showed different responses to the catalyst,which were closely related to their different structures.This work provides the basis for the research of biomass catalytic pyrolysis mechanism and the potential of industrial application.关键词
Li2CO3/松木/热解/热重/光电离质谱/在线Key words
Li2CO3/pine wood/pyrolysis/thermogravimetry/photoionization mass spectrometry/online分类
化学化工引用本文复制引用
陈夏敏,李亚敏,文武,朱亚楠,杨玖重,潘洋..在线热解-光电离质谱法研究Li2CO3对松木热解的影响[J].质谱学报,2018,39(3):268-277,10.基金项目
国家自然科学基金(91545120) （91545120）
中央高校基本科研业务费专项资金资助 （）
