化学链燃烧过程Fe_(2)O_(3)/Al_(2)O_(3)载氧体表面CH_(4)反应:ReaxFF-MD模拟

Reaction process of CH_(4) on the surface of Fe_(2)O_(3)/Al_(2)O_(3) oxygen carrier in chemical looping combustion:ReaxFF-MD simulation

借助ReaxFF-MD方法,对化学链燃烧过程Al_(2)O_(3)负载Fe_(2)O_(3)载氧体(Fe_(2)O_(3)/Al_(2)O_(3))表面CH_(4)反应过程模拟,探究Al_(2)O_(3)惰性载体对Fe_(2)O_(3)-CH_(4)体系燃烧过程的调控机制。研究发现添加Al_(2)O_(3)惰性载体改变了化学链燃烧过程中Fe_(2)O_(3)载氧体反应性和Fe_(2)O_(3)/Al_(2)O_(3)-CH_(4)反应体系的热力学和动力学行为。主要是促进了Fe_(2)O_(3)载氧体表面CH_(4)氧化,并对CH_(4)反应过程、中间体、产物及其反应速率和放热量等均具有显著促进和调控作用。原因在于Al_(2)O_(3)惰性载体对Fe_(2)O_(3)活性相中晶格氧的活化作用促进了晶格氧的迁移-扩散-释放。添加惰性载体增强了Fe_(2)O_(3)载氧体在化学链燃烧过程晶格氧释放速率和释放量,有利于CH_(4)氧化燃烧向合成气的高效、清洁转化,强化了化学链燃烧过程,满足当前能源高效转化和碳减排目标。

This work simulated the reaction process of CH_(4) on the surface of Al_(2)O_(3) supported Fe_(2)O_(3) oxygen carrier(denoted as:Fe_(2)O_(3)/Al_(2)O_(3))in chemical looping combustion(CLC)by using ReaxFF-MD method,and explored the regulation mechanism of Al_(2)O_(3) inert support on the combustion process of Fe_(2)O_(3)/Al_(2)O_(3)-CH_(4) system.It was found that the addition of Al_(2)O_(3) inert carrier changed the reactivity of Fe_(2)O_(3) oxygen carrier and the thermodynamic and kinetic behaviors of Fe_(2)O_(3)/Al_(2)O_(3)-CH_(4) reaction system during CLC.The main purpose is to promote the oxidation of CH_(4) on the surface of Fe_(2)O_(3) oxygen carrier,and to significantly promote and regulate the CH_(4) reaction process,intermediates,products and their reaction rates and heat release.ReaxFF-MD simulation showed that the activation effects of Al_(2)O_(3) inert support on the lattice oxygen in Fe_(2)O_(3) active phase facilitated the migration-diffusion-release of the lattice oxygen.These findings show that the addition of inert support can enhance the lattice oxygen release of the Fe_(2)O_(3) oxygen carriers in CLC,and favor the efficient and clean conversion of CH_(4) to the syngas,and strengthen the CLC process,as well as satisfy the goals of the current energy efficient conversion and carbon emission reduction targets.