Related Experiment Video
Updated: Jan 6, 2026

Ammonia Synthesis at Low Pressure
Published on: August 23, 2017
Ammonia Formation over Pd/Rh Three-Way Catalysts during Lean-to-Rich Fluctuations: The Effect of the Catalyst Aging,
Chengxiong Wang1,2, Jianwei Tan3, Gavin Harle2
1State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals , Kunming Institute of Precious Metals , Kunming 650106 , China.
Abstract:
The formation of ammonia (NH3) as a byproduct during the operation of a three-way catalyst (TWC) in a simulated exhaust stream was investigated using a commercially available Pd/Rh TWC under steady-state and lean/rich cycling conditions. Ion molecular reaction-mass spectrometry was applied to determine NO, NO2, and NH3 concentrations at a time resolution of 0.6 s. Catalyst aging was shown to result in a significant increase in the amount of NH3 formed, which has received limited attention in the literature to date. The selectivity toward NH3 formation has been shown to increase with the decrease in the oxygen storage capacity (OSC) of a TWC induced by thermal aging. NH3 has been shown to mainly form within the exhaust temperature range of 250-550 °C. Typical lambda and rich operational condition duration periods found in vehicle test procedures were also employed to investigate their effects on NH3 formation. The results suggest that a decrease in the lambda and/or an increase in the duration of rich operating conditions will lead to an increase in the selectivity toward NH3 formation. Improving the OSC of TWCs and effectively controlling the lambda near to 1.0 with limited duration in rich operating conditions are therefore significant factors in the reduction of NH3 emissions.
More Related Videos
12:08Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes
Published on: June 24, 2022
10:19Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation
Published on: July 18, 2017
Related Concept Videos
Catalysis
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Reduction of Alkenes: Catalytic Hydrogenation
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...
Preparation of Amines: Alkylation of Ammonia and Amines
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Carboxylic Acids to Methylesters: Alkylation using Diazomethane