NO reduction with H2 in the presence of excess O2 over Pd/MFI catalyst

Excellent activity and selectivity of Pd/ZSM-5 catalyst in the selective catalytic reduction of NOx by H2

Superior de-NO_x activity and N₂ selectivity of the Pd/ZSM-5 catalyst was observed at low temperature (<200 °C) for the selective catalytic reduction of NO_x by H₂ (H₂-SCR). Various Pd/ZSM-5 catalysts were prepared by calcinating at different temperatures (e.g., 500 °C, 650 °C, 750 °C, and 850 °C) and treated at reductive conditions before the H₂-SCR reaction was performed. Among the prepared catalysts, the one prepared at the calcination temperature at 750 °C resulted in 96.7% NO_x conversion and 96.8% N₂ selectivity at 150 °C. Based on the H₂-O₂ reaction, the higher activity of the Pd/ZSM-5 catalyst calcined at 750 °C was attributed to its superior H₂ activation ability for the H₂-SCR reaction. The combined X-ray diffraction (XRD), temperature-programmed hydride decomposition (TPHD), and transmission electron microscopy (TEM) results revealed that highly dispersed Pd particles were generated on the catalyst calcined at 750 °C, while large Pd agglomerates were formed on the one calcined at 500 °C. It can be concluded that the catalytic activity of Pd/ZSM-5 improves by optimizing the calcination temperature, resulting in high Pd dispersion. Moreover, the Pd catalyst calcined at 750 °C showed high resistance to CO, maintaining >94% NO_x conversion at 175 °C under 1000 ppm CO in the feed gas. Therefore, the catalyst calcined at 750 °C can be potentially used for industrial applications because of its simple preparation method and high resistance to CO.

Selective Catalytic Reduction with Hydrogen for Exhaust gas after-treatment of Hydrogen Combustion Engines

In this work, two palladium-based catalysts with either ZSM-5 or Zeolite Y as support material are tested for their performance in selective catalytic reduction of NOx with hydrogen (H2-SCR). The ligh-toff measurements in synthetic exhaust gas mixtures typical for hydrogen combustion engines are supplemented by detailed catalyst characterization comprising N2 physisorption, X-ray powder diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR) and ammonia temperature programmed desorption (NH3-TPD). Introducing 10% or 20% TiO2 into the catalyst formulations reduced the surface area and the number of acidic sites for both catalysts, however, more severely for the Zeolite Y-supported catalysts. The higher reducibility of the Pd particles that was uncovered by H2-TPR resulted in an improved catalytic performance during the light-off measurements and substantially boosted NO conversion. Upon exposition to humid exhaust gas, the ZSM-5-supported catalysts showed a significant drop in performance, whereas the Zeolite Y-supported catalyst kept the high levels of conversion while shifting the selectivity from N2O more toward NH3 and N2. The 1%Pd/20%TiO2/HY catalyst subject to this work outperforms one of the most active and selective benchmark catalyst formulations, 1%Pd/5%V2O5/20%TiO2-Al2O3, making Zeolite Y a promising support material for H2-SCR catalyst formulations that allow efficient and selective NOx-removal from exhaust gases originating from hydrogen-fueled engines.

Methanol reforming denitration over an integrated bifunctional CuZnOx–X–MnPdOz@Ni catalyst at low temperature

Severe conditions involved in hydrogen storage and transportation limit the practical applications of hydrogen denitration reaction.

Understanding the promotional effect of 3d transition metals (Fe, Co, Cu) on Pd/TiO2 for H2-SCR

The addition of 3d transition metal (Fe, Co, Cu) oxides on Pd/TiO₂ catalysts show that the formation of monodentate nitrates is the rate limiting step in the formation of NH_x species, which is active intermediate for the enhancement of H₂-SCR activities.

Three pathways to selective catalytic reduction of NO over Pt/Nb-AlMCM-41 under H2 with excess O2

NO was reduced on Pt/Nb-AlMCM-41 through decomposition, SCR with produced NH₃, and oxidation of NH₃.