关键词: 纤维素, 化学链, 纳米粒子, 载氧体, 气化, 分子模拟

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