Pd/zeolite passive NO x adsorber (PNA) materials were prepared with solution ion-exchange between NH 4 /zeolites (Beta, and PdCl 2 solutions. The nature of Pd (dispersion, distribution, and oxidation states) in these materials was characterized with Na + ion exchange, TEM imaging, CO titration with FTIR, and in situ XPS. The NO x trapping and release properties were tested using feeds with different compositions. It is concluded that multiple Pd species coexist in these materials: atomically dispersed Pd in the cationic sites of zeolites and PdO 2 and PdO particles on the external surfaces. While Pd is largely atomically dispersed in ZSM-5, the small pore opening for SSZ-13 inhibits Pd diffusion such that the majority of Pd stays as external surface PdO 2 clusters. NO x trapping and release are not simple chemisorption and desorption events but involve rather complex chemical reactions. In the absence of CO in the feed, cationic Pd(II) sites with oxygen ligands and PdO 2 clusters are reduced by NO to Pd(I) and PdO clusters. These reduced sites are the primary NO adsorption sites. In the presence of H 2 O, the as-formed NO 2 desorbs immediately. In the presence of CO in the feed, metallic Pd, "naked" Pd 2+ , and Pd + sites are responsible for NO adsorption. For Pd adsorption sites with the same oxidation states but in different zeolite frameworks, NO binding energies are not expected to vary greatly. However, NO release temperatures do vary substantially with different zeolite structures. This indicates that NO transport within these materials plays an important role in determining release temperatures. Finally, some rational design principles for efficient PNA materials are suggested.

Using a traditional aqueous solution ion exchange method under a protecting atmosphere of N2, a series of Fe/SSZ-13 catalysts with various Fe loadings were synthesized. UV–vis, EPR, and Mössbauer spectroscopic methods, coupled with temperature-programmed reduction and desorption techniques, were used to probe the nature of the Fe sites. The major Fe species are extraframework Fe­(III) species: [Fe­(OH)2]+ (monomeric) and [HO–Fe–O–Fe–OH]2+ (dimeric). Larger oligomers with unknown nuclearity, poorly crystallized Fe oxide particles, together with isolated Fe2+ ions, are minor Fe-containing moieties. Reaction rate and Fe loading correlations, and temperature and Fe loading effects on SCR selectivities, suggest that isolated Fe3+ ions are the active sites for low-temperature standard SCR, and dimeric sites provide the majority of reactivity at higher temperatures. For NO oxidation, dimeric sites are the active centers. NH3 oxidation, on the other hand, is catalyzed by sites with higher nuclearity.

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A novel approach combining biomimetic mineralization and bioadhesion is proposed to prepare robust and versatile organic-inorganic hybrid microcapsules. More specifically, these microcapsules are fabricated by sequential deposition of inorganic layer and organic layer on the surface of CaCO(3) microparticles, followed by the dissolution of CaCO(3) microparticles using EDTA. During the preparation process, protamine induces the hydrolysis and condensation of titania or silica precursor to form the inorganic layer or the biomineral layer. The organic layer or bioadhesive layer was formed through the rapid, spontaneous oxidative polymerization of dopamine into polydopamine (PDA) on the surface of the biomineral layer. There exist multiple interactions between the inorganic layer and the organic layer. Thus, the as-prepared organic-inorganic hybrid microcapsules acquire much higher mechanical stability and surface reactivity than pure titania or pure silica microcapsules. Furthermore, protamine/titania/polydopamine hybrid microcapsules display superior mechanical stability to protamine/silica/polydopamine hybrid microcapsules because of the formation of Ti(IV)-catechol coordination complex between the biomineral layer and the bioadhesive layer. As an example of application, three enzymes are respectively immobilized through physical encapsulation in the lumen, in situ entrapment within the wall and chemical attachment on the out surface of the hybrid microcapsules. The as-constructed multienzyme system displays higher catalytic activity and operational stability. Hopefully, the approach developed in this study will evolve as a generic platform for facile and controllable preparation of organic-inorganic hybrid materials with different compositions and shapes for a variety of applications in catalysis, sensor, drug/gene delivery.

Topographic and wetting properties of Inconel 718 (IN718) surfaces were modified via nanosecond laser treatment. In order to investigate surface wetting behavior without additional post treatment, three kinds of microstructures were created on IN718 surfaces, including line pattern, grid pattern and spot pattern. From the viewpoint of surface morphology, the results show that laser ablated grooves and debris significantly altered the surface topography as well as surface roughness compared with the nontreated surfaces. The effect of laser parameters (such as laser scanning speed and laser average power) on surface features was also discussed. We have observed the treated surface of IN718 showed very high hydrophilicity just after laser treatment under ambient air condistion.And this hydrophicility property has changed rapidly to the other extreme; very high hydrophobicity over just about 20 days. Further experiments and analyses have been carried out in order to investigate this phenomena. Based on the XPS analysis, the results indicate that the change of wetting property from hydrophilic to hydrophobic over time is due to the surface chemistry modifications, especially carbon content. After the contact angles reached steady state, the maximum water contact angle (WCA) for line-patterned and grid-patterned surfaces increased to 152.3  1.2° and 156.8  1.1° with the corresponding rolling angle (RA) of 8.8  1.1° and 6.5  0.8°, respectively. These treated IN718 surfaces exhibited superhydrophobic property. However, the maximum WCA for the spot-patterned surfaces just increased to 140.8  2.8° with RA above 10°. Therefore, it is deduced that laser-inscribed modification of surface wettability has high sensitivity to surface morphology and surface chemical compositions. This work can be utilized to optimize the laser processing parameters so as to fabricate desired IN718 surfaces with hydrophobic or even superhydrophobic property and thus extend the applications of IN718 material in various fields.

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Experiments and density functional theory (DFT) models are combined to develop a unified, quantitative model of the mechanism and kinetics of fast selective catalytic reduction (SCR) of NO/NO2 mixtures over H-SSZ-13 zeolite. Rates, rate orders, and apparent activation energies collected under differential conditions reveal two distinct kinetic regimes. First-principles thermodynamics simulations are used to determine the relative coverages of free Brønsted sites, chemisorbed NH4 +, and physisorbed NH3 as a function of reaction conditions. First-principles metadynamics calculations show that all three sites can contribute to the rate-limiting N–N bond forming step in fast SCR. The results are used to parametrize a kinetic model that encompasses the full range of reaction conditions and recovers observed rate orders and apparent activation energies. Observed kinetic regimes are related to changes in most-abundant surface intermediates.

We investigated the steady-state and transient effects of reductants (CO, H 2 and C 3 H 6 ) on NO 2 reduction, NH 3 -SCR (selective catalytic reduction), NH 3 adsorption and oxidation, and N 2 O production on a Cu-SSZ-13 monolithic catalyst. The three reductants affect to different extents the standard SCR (NO + NH 3 + O 2 ), fast SCR (NO + NH 3 + NO 2 ), and slow SCR (NH 3 + NO 2 ). This study underscores the importance of accounting for the impact of reducing agents on conventional NH 3 -SCR reaction mechanism when SCR catalyst is subjected to either rich regeneration of integrated systems (LNT + SCR, SCR on DPF) or cold-start. Propylene is most effective in promoting NO 2 reduction to NO by formation of organic intermediates. CO effectively reduces nitrates to nitrites that then react with NO 2 , releasing NO. H 2 can follow a similar pathway as CO but is less effective. In addition, H 2 can also enable a H 2 -based SCR pathway through the reduction of Cu cations to Cu 0 which then catalyze the NOx reduction. This pathway is particularly evident at high temperatures and low O 2 levels. As for NH 3 -SCR reactions, propylene competes with NH 3 for adsorbed NO 2 , which generates NO and thus increases the NO/NOx ratio. This leads to the dominance of either fast or standard SCR for a slow SCR (NH 3 + NO 2 ) feed condition when C 3 H 6 is present. CO has only a minor effect on both standard and fast SCR but a promoting effect on slow SCR. The ineffective reduction of NO 2 to NO by H 2 at low temperature (T < 250 o C) results in a negligible effect on slow SCR. In contrast to steady-state operation, lean/rich cycling enhances cycle-averaged NOx conversion for each of the NH 3 -SCR reactions when adding either C 3 H 6 or a CO + H 2 mixture in the rich phase. A decreased N 2 O generation rate from the slow SCR reaction is observed when any of the three reductants are present due in part to their reaction with ammonium nitrates.