Interaction between Nickel Oxide and Support Promotes Selective Catalytic Reduction of NO_x with C₃ H₆

Area of Science:

• Heterogeneous catalysis
• Environmental chemistry
• Materials science

Background:

• Nitrogen oxides (NOx) are major air pollutants contributing to environmental degradation.
• Selective Catalytic Reduction (SCR) using hydrocarbons like propylene (C3H6) is a promising NOx abatement technology.
• Nickel oxide (NiO) catalysts supported on metal oxides are explored for C3H6-SCR applications.

Purpose of the Study:

• To investigate the performance of NiO catalysts supported on various metal oxides for C3H6-SCR.
• To elucidate the role of metal-support interactions, particularly with alumina, on catalytic activity.
• To understand the reaction mechanism and intermediate species involved in the C3H6-SCR process.

Main Methods:

• Synthesis and characterization of NiO catalysts on different metal oxide supports.
• Evaluation of NOx conversion and C3H6 oxidation activity in a temperature range.
• Temperature-programmed NO oxidation and in-situ transient reaction studies to probe reaction mechanisms.

Main Results:

• NiO/γ-Al2O3 catalyst formed a NiAlOx mixed oxide phase with strong Ni-Al interaction, leading to Ni in a high oxidation state.
• NiO/γ-Al2O3 exhibited superior NOx conversion above 450°C compared to other NiO catalysts, despite lower C3H6 oxidation.
• Evidence of rapid nitrate formation and stability, along with well-preserved C3H6-SCR intermediates, on NiO/γ-Al2O3.

Conclusions:

• The strong metal-support interaction in NiO/γ-Al2O3 is crucial for high NOx conversion in C3H6-SCR.
• The catalyst facilitates the Langmuir-Hinshelwood mechanism, involving adsorption and activation of both NO and C3H6.
• NiO/γ-Al2O3 demonstrates significant potential for efficient NOx abatement via C3H6-SCR at high temperatures.