Ir/ZSM-5/cordierite monolith for catalytic NOx reduction from automobile exhaust

Abstract

Ir/ZSM-5/cordierite was studied as promising catalyst for the reduction of nitrogen oxides from automobile exhaust under both stoichiometric combustion and lean conditions. ZSM-5 was in situ synthesized on the surface of honeycomb cordierite substrate and iridium was introduced to ZSM-5/cordierite by wet impregnation. Under stoichiometric combustion, Ir/ZSM-5/cordierite exhibited good catalytic activity approaching commercial three-way catalysts, and the three main pollutants nitrogen oxides, carbon monoxide and unburned hydrocarbons could be purified simultaneously. Under lean conditions, Ir/ZSM-5/cordierite also exhibited quite good deNOx activities though excess oxygen showed inhibition effect on NOx reduction.

Insight into the Mechanism of Selective Catalytic Reduction of NO by CO over a Bimetallic IrRu/ZSM-5 Catalyst in the Absence/Presence of O2 by Isotopic C13O Tracing Methods

“…The peaks in the range of 1550–1650 cm –1 are assigned to the nitrate species adsorbed on the cation sites in ZSM-5. , Moreover, the peak at 1727 cm –1 could be assigned to the N 2 O 4 species . Notably, the peak at 1820 cm –1 was assigned to NO linearly adsorbed on the Ir 0 atop sites, which could not dissociate into N and O. ,, Previous reports have demonstrated that NO is mainly adsorbed on the atop sites and hollow sites of Ir. − NO adsorbed on the hollow sites could dissociate into N and O at low temperatures, whereas NO adsorbed on the atop sites is more stable than that on the hollow sites. ,, Thus, the peak of NO adsorbed on the Ir 0 hollow sites did not appear in this spectrum. Furthermore, the NO adsorption species in the presence of O 2 on different catalysts were also investigated (Figure S11).…”

“…Moreover, tungsten oxide could also serve as a promoter to improve the CO-SCR performance of Ir/SiO 2 catalysts due to the interaction between Ir and WO x . Recently, Song and co-workers reported a bimetallic IrRu/Al 2 O 3 catalyst for CO-SCR in the presence of O 2 , where the excellent catalytic performance of this catalyst at low temperatures was attributed to the formation of an IrRu alloy. ,, Furthermore, Wang et al reported that Ir/ZSM-5 is an efficient catalyst for the CO-SCR in the presence of excess O 2 . − …”

Characterization and Activity of Pd–Ir Catalysts in CO and C3H6 Oxidation Under Stoichiometric Conditions

“…The reason could be volatility of Ir compounds, especially, if halogenated precursors have been used in the preparation of Ir phase [28,29]. Over the Al 2 O 3 -SiO 2 support Ir has displayed a good dispersion [30] and a high activity for reduction of nitrogen oxide over CeO 2 under stoichiometric conditions on TWCs [31].…”

Selective catalytic reduction of NO over hierarchical Cu ZSM-5 coated on an alumina foam support

“…10 Landong et al and L. Li et al synthesized Cu ZSM-5, Cutitanium silicate, and Ir ZSM-5 on a honeycomb cordierite monolith and studied SCR of NO x from automobile exhaust. 2,11 Kryca et al compared the heat and mass transfer properties and pressure drop of packed bed reactors, Kanthal foam, monoliths, and honeycomb reactors. They concluded that packed bed reactors offer high mass transfer but with high-pressure drop and monolithic reactors exhibit lowpressure drop but with poor mass transfer.…”