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Kinetic modeling of titania reduction by a methane-hydrogen-argon gas mixture

Journal Article


Abstract


  • This article describes kinetic modeling of titania reduction and carburization by methane-containing gas, based on experimental data reported previously by Zhang and Ostrovski. A sequence of titania reduction to titanium oxycarbide, TiO2 → Ti5O9 → Ti4O7 → Ti3O5 → Ti2O3 → TiCfO1-f which was observed experimentally, is represented by the following two reactions: TiO2 + (H2 + CH4) → 1/2Ti2O3 + H2O + CO [1] 1/2Ti2O3 + (1/2 + f)CH4 → f(TiC)ss + (1 - f)(TiO)ss + (1/2 +f)CO + (1 + 2f)H2 [2] where ss designates a solid solution and f is the molar fraction of TiC in the solid solution. A two-interface shrinking-core model and a crackling-core model are employed for the kinetic modeling of the reduction and carburization process. The rates of Reactions [1] and [2] are both controlled by the chemical-reaction stage. For the intrinsic chemical-reaction control, the extent of the reaction as a function of reaction time is well described analytically. The two models give close results that are consistent with experimental data obtained at 1473 to 1773 K and a methane partial pressure up to 8 kPa. Reaction [1] is of the first order with respect to methane and of one-half to first order with respect to hydrogen. The apparent activation energy of reaction [1] is 124 kJ/mol for the two-interface shrinking-core model and 126 kJ/mol for the crackling-core model. Reaction [2] is of the first order with respect to methane and is independent of hydrogen concentration. Nevertheless, hydrogen plays an important role in the reduction/carburization process, as it suppresses the decomposition of methane and deposition of solid carbon. The apparent activation energy of the reaction is 161 kJ/mol for the two-interface shrinking-core model and 191 kJ/mol for the crackling-core model.

Publication Date


  • 2001

Citation


  • Zhang, G., & Ostrovski, O. (2001). Kinetic modeling of titania reduction by a methane-hydrogen-argon gas mixture. Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science, 32(3), 465-473. doi:10.1007/s11663-001-0032-8

Scopus Eid


  • 2-s2.0-0035360274

Start Page


  • 465

End Page


  • 473

Volume


  • 32

Issue


  • 3

Abstract


  • This article describes kinetic modeling of titania reduction and carburization by methane-containing gas, based on experimental data reported previously by Zhang and Ostrovski. A sequence of titania reduction to titanium oxycarbide, TiO2 → Ti5O9 → Ti4O7 → Ti3O5 → Ti2O3 → TiCfO1-f which was observed experimentally, is represented by the following two reactions: TiO2 + (H2 + CH4) → 1/2Ti2O3 + H2O + CO [1] 1/2Ti2O3 + (1/2 + f)CH4 → f(TiC)ss + (1 - f)(TiO)ss + (1/2 +f)CO + (1 + 2f)H2 [2] where ss designates a solid solution and f is the molar fraction of TiC in the solid solution. A two-interface shrinking-core model and a crackling-core model are employed for the kinetic modeling of the reduction and carburization process. The rates of Reactions [1] and [2] are both controlled by the chemical-reaction stage. For the intrinsic chemical-reaction control, the extent of the reaction as a function of reaction time is well described analytically. The two models give close results that are consistent with experimental data obtained at 1473 to 1773 K and a methane partial pressure up to 8 kPa. Reaction [1] is of the first order with respect to methane and of one-half to first order with respect to hydrogen. The apparent activation energy of reaction [1] is 124 kJ/mol for the two-interface shrinking-core model and 126 kJ/mol for the crackling-core model. Reaction [2] is of the first order with respect to methane and is independent of hydrogen concentration. Nevertheless, hydrogen plays an important role in the reduction/carburization process, as it suppresses the decomposition of methane and deposition of solid carbon. The apparent activation energy of the reaction is 161 kJ/mol for the two-interface shrinking-core model and 191 kJ/mol for the crackling-core model.

Publication Date


  • 2001

Citation


  • Zhang, G., & Ostrovski, O. (2001). Kinetic modeling of titania reduction by a methane-hydrogen-argon gas mixture. Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science, 32(3), 465-473. doi:10.1007/s11663-001-0032-8

Scopus Eid


  • 2-s2.0-0035360274

Start Page


  • 465

End Page


  • 473

Volume


  • 32

Issue


  • 3