Investigation of the catalytic performances of supported noble metal based catalysts in the NO+H2 reaction under lean conditions

Selective Catalytic Reduction of NOx over Perovskite-Based Catalysts Using CxHy(Oz), H2 and CO as Reducing Agents-A Review of the Latest Developments

Selective catalytic reduction (SCR) is probably the most widespread process for limiting NO_x emissions under lean conditions (O₂ excess) and, in addition to the currently used NH₃ or urea as a reducing agent, many other alternative reductants could be more promising, such as C_xH_y/C_xH_yO_z, H₂ and CO. Different catalysts have been used thus far for NO_x abatement from mobile (automotive) and stationary (fossil fuel combustion plants) sources, however, perovskites demand considerable attention, partly due to their versatility to combine and incorporate various chemical elements in their lattice that favor deNO_x catalysis. In this work, the C_xH_y/C_xH_yO_z⁻, H₂⁻, and CO-SCR of NO_x on perovskite-based catalysts is reviewed, with particular emphasis on the role of the reducing agent nature and perovskite composition. An effort has also been made to further discuss the correlation between the physicochemical properties of the perovskite-based catalysts and their deNO_x activity. Proposed kinetic models are presented as well, that delve deeper into deNO_x mechanisms over perovskite-based catalysts and potentially pave the way for further improving their deNO_x efficiency.

Dopant-driven tuning of toluene oxidation and sulfur resistance at the B-site of LaCo1−xMxO3 (M = Fe, Cr, Cu) perovskites

The optimization effect of Fe dopant on toluene oxidation and sulfur resistance is better than that of Cr and Cu dopants.

Surface hydrogen bond network spatially confined BiOCl oxygen vacancy for photocatalysis

Rational engineering of oxygen vacancy (V_O) at atomic precision is the key to comprehensively understanding the oxygen chemistry of oxide materials for catalytic oxidations. Here, we demonstrate that V_O can be spatially confined on the surface through a sophisticated surface hydrogen bond (HB) network. The HB network is constructed between a hydroxyl-rich BiOCl surface and polyprotic phosphoric acid, which remarkably decreases the formation energy of surface V_O by selectively weakening the metal-oxygen bonds in a short range. Thus, surface-confined V_O enables us to unambiguously distinguish the intrafacial and suprafacial oxygen species associated with NO oxidation in two classical catalytic systems. Unlike randomly distributed bulk V_O that benefits the thermocatalytic NO oxidation and lattice O diffusion by the dominant intrafacial mechanism, surface V_O is demonstrated to favor the photocatalytic NO oxidation through a suprafacial scheme by energetically activating surface O₂, which should be attributed to the spatial confinement nature of surface V_O.

Perovskite-based catalysts for the control of nitrogen oxide emissions from diesel engines

Nitrogen oxides removal over a wide range of perovskite-based catalysts together with their property-activity relationships.

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.

CFD simulations, experimental validation and parametric studies for the catalytic reduction of NO by hydrogen in a fixed bed reactor

CFD simulations and parametric studies of the NO reduction process in a fixed bed catalytic reactor.

Enhanced performance in NOx reduction by NH3 over a mesoporous Ce–Ti–MoOx catalyst stabilized by a carbon template

The mesopore Ce–Ti–MoO_x catalyst stabilized by an in situ formed carbon template showed more than 90% NO_x conversion at 175–425 °C for SCR of NO_x with NH₃. Increasing temperature in the presence of carbon template contributed to the narrow mesoporous distribution and excellent low-temperature SCR activity.

Strontium-doped perovskites rival platinum catalysts for treating NOx in simulated diesel exhaust

The high cost and poor thermal durability of current lean nitrogen oxides (NOx) aftertreatment catalysts are two of the major barriers to widespread adoption of highly fuel-efficient diesel engines. We demonstrated the use of strontium-doped perovskite oxides as efficient platinum substitutes in diesel oxidation (DOC) and lean NOx trap (LNT) catalysts. The lanthanum-based perovskite catalysts coated on monolith substrates showed excellent activities for the NO oxidation reaction, a critical step that demands heavy usage of platinum in a current diesel aftertreatment system. Under realistic conditions, La(1-x)SrxCoO3 catalysts achieved higher NO-to-NO2 conversions than a commercial platinum-based DOC catalyst. Similarly, a La(0.9)Sr(0.1)MnO3-based LNT catalyst achieved NOx reduction performance comparable to that of a commercial platinum-based counterpart. The results show promise for a considerably lower-cost diesel exhaust treatment system.

Impact of thermal aging on the kinetic parameters of the NO/H(2) reaction on Pd/LaCoO(3)

This paper deals with the kinetics of the reduction of NO by H(2) on Pd supported over reducible supports, such as LaCoO(3). An extensive kinetic investigation was performed on aged catalysts after exposure to successive reductive and oxidative atmospheres at a high temperature (T = 500 degrees C). Typically, Pd/LaCoO(3) was reduced in pure H(2) and then aged under reactive conditions in the presence of an excess of O(2). Both thermal treatments are accompanied by significant bulk and surface reconstructions characterized by X-ray diffraction and X-ray photoelectron spectroscopy. Pd/LaCoO(3) is extensively reducef to Pd(0)/CoO(x)/La(2)O(3) after H(2) exposure. It was previously found that the NO/H(2) reaction on Pd(0)/CoO(x)/La(2)O(3) involved the Pd/support interface. This study reports that subsequent thermal aging under oxidative conditions leads to the restoration of the perovskite structure with parallel changes in the chemical environment of oxidic palladium species. The NO reduction by hydrogen was used as a probe reaction to investigate related modifications of the surface properties. It was found that significant changes in the kinetic features of Pd/LaCoO(3) occur after thermal aging, compared to the prereduced catalyst, because of surface modifications that might alter the adsorptive properties of Pd and more significantly the nature of the dissociation step of NO. These surface modifications induce a selectivity enhancement to the formation of nitrogen.