Significant Reduction of the Formation of N₂O and NH₃ on an Efficient Three-Way PtRh Catalyst Modified by LaFeCu Perovskite

Abstract

This work designed a series of three-way catalysts (TWCs) with and without the modification by La 0.67 Fe 0.83 Cu 0.17 O 3 (LaFeCu) perovskite to reduce the formation of N 2 O and NH 3 emissions from natural gas vehicles (NGVs). The modified PtRh catalyst was found to have an efficient TWC performance and to reduce the formation of N 2 O and NH 3 significantly. The Xray diffraction and CO-Fourier transform infrared results demonstrated the formation of Rhx species, which would reduce the formation of NCO*, the main precursor of NH 3 . In situ diffuse reflectance infrared Fourier transform spectroscopy was used to confirm that no NCO* groups were found on the modified catalyst. The X-ray photoelectron spectroscopy results revealed the increase in the Pt 2+ content on the modified catalyst, promoting the decomposition of N 2 O. Also note that the modified catalyst produced far fewer N 2 O than the catalyst without modification in the model reaction of CO + NO. Our work would provide a solution to develop an advanced TWC for NGVs.

Regeneration of Sulfur-Poisoned Pd-Based Three-Way Catalysts for Stoichiometric Natural Gas Vehicles

“…The flow capacity of gas entering the reactor was regulated by a calibrated mass flowmeter. The λ-values of the reaction gas were calculated by eq , which represents the ratio between the available oxygen provided by the reactant and the oxygen required for the complete conversion of the reactant into CO 2 , H 2 O, and N 2 . λ = ( 2 false[ O 2 false] + 2 false[ CO 2 false] + false[ CO false] + false[ NO false] + false[ H 2 normalO false] ) / ( 2 false[ CO 2 false] + 2 false[ CO false] + 4 false[ CH 4 false] + false[ H 2 normalO false] ) In the experiment, λ = 1.000, corresponding to the stoichiometric NGVs’ simulation exhaust containing 1000 ppm CH 4 , 4800 ppm CO, 960 ppm NO, 3128 ppm O 2 , 10 vol % H 2 O, and 10 vol % CO 2 and N 2 . The total gas flow rate was 1750 mL/min and the gas hourly space velocity (GHSV) was 50,000 h –1 .…”

“…The flow capacity of gas entering the reactor was regulated by a calibrated mass flowmeter. The λ-values of the reaction gas were calculated by eq 3, 25 which represents the ratio between the available oxygen provided by the reactant and the oxygen required for the complete conversion of the reactant into CO 2 , H 2 O, and N 2 .…”