CH4-H2混合气体还原二氧化钛的热力学研究

Thermodynamics of Reduction of Titania by CH4-H2 Gas Mixture

摘要:

针对钛及碳化钛制备这一全球关注的重要课题，开发了一种基于CH₄-H₂混合气体的新型TiO₂还原工艺，并对其中存在的热力学行为、相平衡和能耗进行了研究。结果表明，在CH₄-H₂混合气氛下，TiO₂的还原过程呈现出独特的逐步转化特征，其反应路径遵循从TiO₂到Ti(C, O)的演变规律，过程中可观察到Magnéli相（Ti_nO_2n-1）和Ti₃O₅等低价氧化物作为重要的中间相存在。与传统的纯CH₄还原体系相比，H₂的引入显著增加了反应难度，这一现象可能与H₂对表面碳沉积的抑制作用有关。在能量消耗方面，获得了具有重要指导意义的数据：在标准条件下，1000 ℃时完全碳化反应的能耗为1159 kJ/mol，当温度升至1100 ℃时能耗显著降低至925 kJ/mol，而继续升温至1200 ℃时却出现能耗回升至977 kJ/mol的反常现象，这可能与高温下气相平衡的移动和副反应增加有关。

Abstract:

Given the considerable global interest in the preparation of Ti and TiC, a novel reduction method for TiO₂ in a CH₄-H₂ atmosphere was proposed, and the reduction thermodynamic behavior, phase equilibrium, and energy consumption of TiO₂ during its reaction with a CH₄-H₂ gas mixture were investigated. The results indicate that the reaction proceeds via a stepwise reduction pathway from TiO₂ to Ti(C, O), with the Magnéli phase (Ti_nO_2n-1) and Ti₃O₅ serving as intermediate phases. Notably, the reduction of TiO₂ by H₂ is more challenging than that by CH₄, which may be attributed to the inhibitory effect of H₂ on the surface carbon precipitation. For the complete carbonization of 1 mol TiO₂, the total energy required at 1000, 1100, and 1200 ℃ is 1159, 925, and 977 kJ/mol, respectively, which may be related to the shift of gas-phase equilibrium and the increase in side reactions at high temperatures.