Deactivation of Pd/SSZ-13 by Potassium and Water for Passive NOx Adsorption

The passive NOx adsorber (PNA) material has been considered an effective candidate for the control of NOx from diesel exhaust during the engine cold start stage, and Pd/SSZ-13 attracts peoples’ attention mainly due to its superior hydrothermal stability and sulfur resistance. However, chemical poisoning tolerance of Pd/SSZ-13 is another key parameter to its practical application and future development. Herein, we prepared potassium-loaded Pd/SSZ-13 and evaluated the influence on NOx adsorption ability. The characterization results revealed that the loading of potassium could not destruct the structure of SSZ-13 but impaired the BET surface area and pore structure through the sintering of Pd species to PdO. Meanwhile, the grown PdO phase restrained the NOx adsorption ability and promoted the generation of NO2 at high temperatures. Moreover, the presence of H2O could also impair the NOx adsorption ability due to the competitive adsorption between H2O and NOx. This work verifies that the design of Pd/SSZ-13 sample with stable Pd species and excellent hydrophobicity is significant for its further application under harsh conditions

Sulfur resistant water gas shift catalyst based on CoMo supported on NbMgAl mixed oxide derived from Nb-modified MgAl-hydrotalcite

National audienc

Hydrogen production by water-gas shift reaction over Co-promoted MoS 2 /Al 2 O 3 catalyst: The intrinsic activities of Co-promoted and unprompted sites

International audienc

Reverse oxygen spillover triggered by CO adsorption on Sn-doped Pt/TiO2 for low-temperature CO oxidation

Abstract The spillover of oxygen species is fundamentally important in redox reactions, but the spillover mechanism has been less understood compared to that of hydrogen spillover. Herein Sn is doped into TiO 2 to activate low-temperature (<100 °C) reverse oxygen spillover in Pt/TiO 2 catalyst, leading to CO oxidation activity much higher than that of most oxide-supported Pt catalysts. A combination of near-ambient-pressure X-ray photoelectron spectroscopy, in situ Raman/Infrared spectroscopies, and ab initio molecular dynamics simulations reveal that the reverse oxygen spillover is triggered by CO adsorption at Pt 2+ sites, followed by bond cleavage of Ti-O-Sn moieties nearby and the appearance of Pt 4+ species. The O in the catalytically indispensable Pt-O species is energetically more favourable to be originated from Ti-O-Sn. This work clearly depicts the interfacial chemistry of reverse oxygen spillover that is triggered by CO adsorption, and the understanding is helpful for the design of platinum/titania catalysts suitable for reactions of various reactants

Role of Citric Acid in Preparing Highly Active CoMo/Al _\textrm2 O _\textrm3 Catalyst: From Aqueous Impregnation Solution to Active Site Formation

International audienc

Effects of Doping Rare Earth Elements (Y, La, and Ce) on Catalytic Performances of CoMo/MgAlM for Water Gas Shift Reaction

Rare earth element (La, Y, and Ce) modified MgAl-hydrotalcites of MgAlM were synthesized from coprecipitation and calcination, and further loaded with CoMo active species to give CoMo/MgAlM catalysts. X-ray powder diffraction, inductively coupled plasma, and N₂ adsorption isotherms indicate that MgAlM possess large BET surface areas (58–91 m²/g), and rare earth elements were successfully introduced into samples. CO₂-TPD (temperature-programmed desorption), NH₃-TPD, H₂-TPR (temperature-programmed reduction), H₂S-TPS (temperature-programmed sulfidation), and Raman spectra indicate the presence of unique interactions between rare earth elements and Mo active species, which strongly affect the reduction and sulfidation behaviors of these catalysts. High resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analysis suggest that the addition of rare earth elements decreases the slab length and stacking numbers of MoS₂ and promotes the sulfidation degree of Mo oxides. The above characteristics make CoMo/MgAlM act as highly active catalysts for the water gas shift reaction (WGSR). This work develops a facile and cost-effective method for rational design of efficient catalysts for WGSR in industrial processes