Abstract:

The chemical looping gasification (CLG) process of cellulose under the action of nano-iron oxide particles was studied by combining experiments with molecular simulation. Thermogravimetric experimental results show that iron oxide can accelerate the thermal decomposition of cellulose and reduce the peak temperature of thermal mass loss rate. The molecular dynamic modeling results show that cellulose begins to decompose and tar/volatile compounds are produced at 1500 K. Cellulose is almost completely decomposed, producing a large amount of fragmented molecules at 3000 K. The presence of iron oxide nanocluster promotes the shift of cellulose pyrolysis reactions towards lower temperatures and accelerates cellulose chain cleavage. Furthermore, tar and char conversion is enhanced through in situ oxygen supply. When the temperature reaches 3000 K, all cellulose is gasified with no remaining char. The gas yield and tar yield are 91.28%(mass) and 9.49%(mass) respectively. Individual product yields indicate that Fe₂O₃ nanocluster restricts the formation of tar compounds, while enhances the yield of CO and H₂O. Radial distribution function (RDF) results of Fe₂O₃ nanocluster prove that iron atoms and oxygen atoms generally tend to separate from each other at high temperature. Lattice oxygen tends to move to the surface. Finally, the detailed reactions during CLG of cellulose were discussed at molecular level. A four-step mechanism was proposed for the CLG of cellulose by Fe₂O₃ nanocluster.

Key words: cellulose, chemical looping, nanoparticles, oxygen carrier, gasification, molecular simulation

摘要：

采用实验与分子模拟相结合的方法，对纳米氧化铁颗粒作用下的纤维素的化学链气化过程进行研究。热重实验结果表明，氧化铁能够加速纤维素的热分解，同时使得热失重速率峰值温度降低。分子动力学模拟结果表明纳米氧化铁颗粒的存在使得纤维素解聚温度降低，同时，氧化铁载氧体的原位供氧加强了焦油和焦炭的转化。当模拟温度达到3000 K时，固体焦炭完全转化，焦油和气体的产率分别为9.49%（质量分数）和91.28%（质量分数）。单组分产物结果表明，纳米氧化铁载氧体抑制了焦油的生成，同时促进了CO和H₂O的生成。径向分布函数结果表明，高温下，纳米氧化铁颗粒中氧原子与铁原子容易发生分离，晶格氧倾向于向颗粒表面迁移，促进原位供氧。

关键词: 纤维素, 化学链, 纳米粒子, 载氧体, 气化, 分子模拟