氧化铁(Ⅲ)还原动力学研究

氧化铁是制造磁性材料、涂料和催化剂的基本原料,用途广泛。许多工业过程如钢铁冶炼以及催化剂活化均与其价态和还原行为密切相关。因此,研究其还原动力学,不仅具有理论意义,而且有很重要的应用价值。金属氧化物包括氧化铁的还原反应,前人已作了不少研究,然而有些基本问题还不够明确,或存在分歧意见。本文通过等温和程序升温还原实验,考察了α-Fe_2O_3和γ-Fe_2O_3的还原行为,对动力学模型和还原机制加以探讨。

STUDIES ON KINETICS OF REDUCTION OF IRON (Ⅲ) OXIDES

The kinetic behavior of reduction for iron (III) oxides was studied by means of TG-DTA thermal analyzer under temperature programed and isothermal conditions with Hydrogen as the reducing gas. The main results show that: (I) using single kinetic model to fit the overall reductive reactions is impossible. The reduction by hydrogen proceeds in several steps: Fe_2O3 ~A→Fe_3O_4 ~B→FeO ~C→FeIt can be treated with different kinetic equations for different periods. (II) During the first period (including the step A and step B), the main process is nucleation, growth and transformation of Fe_3O_4; the Erofeev equation is better than the Contracting Sphere Model. During the second period (Step C), the main process is reduction of FeO, the Cubic Net Model may be satisfied.(III) The Fe_3O_4 and FeO are formed as intermediates. The transformation of Fe_3O_4 is the controlling step. FeO may react and vanish rapidly at higher temperature.(IV) The kinetic parameters in different periods were obtained. The machanism of the reaction was proposed and explained in some detail.