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Nb(0.05 moles%)-zeolites prepared via a post synthesis methodology (BEA, Y, ZSM-5), or a direct sol-gel method (Silicalite-1) were investigated in the hydroxymethylfurfural (HMF) oxidation by both molecular oxygen, in aqueous phase, and organic peroxides, in acetonitrile. The catalysts prepared through the post synthesis methodology (i.e., Nb-Y5, Nb-ZSM25, Nb-Y30, Nb-BEA12, and Nb-BEA18) displayed a mono-modal mesoporosity and contain residual framework Al-acid sites, extra framework isolated Nb(V)O-H and Nb2O5 pore-encapsulated clusters, while Nb-Sil-1, prepared through a direct synthesis procedure, displayed a bimodal micro-mesoporosity and contains only –Nb=O species. These modified zeolites behave as efficient catalysts in both HMF/glucose wet oxidation to succinic acid (SA) and HMF oxidation with organic peroxides to the 2,5-furandicarboxylic acid (FDCA). The catalytic behavior of these catalysts, in terms of conversion and especially the selectivity, mainly depended on the base/acid sites ratio. Thus, the HMF/glucose wet oxidation occurred with a total conversion and a selectivity to SA of 37.7% (from HMF) or 69.1% (from glucose) on the Nb-Y5 catalyst, i.e., the one with the lowest base/acid sites ratio. On the contrary, the catalysts with the highest base/acid sites ratio, i.e., Nb-ZSM25 and Nb-Sil-1, afforded a high catalytic efficiency in HMF oxidation with organic peroxides, in which FDCA was produced with selectivities of 61.3–63.8% for an HMF conversion of 96.7–99.0%.

The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study.

Methane oxidation has been studied on Rh/Ce x Zr 1− x O 2 . Catalytic performances were found highly sensitive to the preparation method of Ce x Zr 1− x O 2 support. Coprecipitation method leads to the highest conversion and the lowest activation barrier suggesting improved metal-support interaction. In contrast, weak resistance to thermal aging is observed. Finally aged coprecipitated Rh/Ce x Zr 1− x O 2 mimics the kinetic behavior of catalysts prepared by crystal templating method. Kinetic measurements performed on this latter catalyst show that a single site reaction mechanism is more appropriate compared to dual site mechanism which agrees with the assumption that deactivation of coprecipitated samples would be related to the suppression of the metal-support interface.

The catalytic combustion of methane is a key reaction taking place on Natural Gas Vehicle three-way catalysts in unfavorable stoichiometric and rich operating conditions. Pd-doped La x MnO 3 based materials have been developed. Their efficacy has been studied on the basis of the following parameters: La-composition ( x  = 0.7 or 1), homogeneity of perovskite composition according to the protocol synthesis (sol–gel vs. combustion method), strategy for Pd incorporation. The control of Pd dispersion is closely related to the method used for Pd addition. Stabilization of Pd inside the perovskite lattice through a sol–gel route outperforms classical wet impregnated samples in terms of catalytic activity. This trend is accentuated on La-deficient composition as the creation of defective sites can strengthen the Pd–La x MnO 3 interaction. The best compromise was found on La 0.7 Mn 0.98 Pd 0.02 O 3 .

Exhaust car emissions increase significantly at particular gasoline engine driving cycle such as cold-start when the three-way catalyst has not reached its light-off temperature. More efficient technologies are needed to reduce these extra emissions. This study focuses on comparing two strategies to lower cold-start pollutants on a commercial monolithic catalyst: (i) a high content of PGMs (Pd and Rh) loading with a variable concentration distribution along the catalyst, called zone-coating, was investigated in order to take advantages of an in situ pre-heating due to exothermic oxidation processes. And (ii) the use of external device for heating the monolith with the aim to shorten the laps of time to reach the required temperature for their conversion. Both approaches were compared below 300 °C in terms of NO, CO and hydrocarbons conversions as well as N 2 O formation with respect to homogeneously wash-coated catalyst. For evaluation, complex exhaust gas compositions were considered at different steady-state air-to-fuel λ ratios and high frequency transient lean/rich regime to mimic real operation in gasoline engine exhaust. Results show that a pre-heating of the catalyst at 300 °C is necessary to avoid completely N 2 O formation from NO reduction with CO. Remarkably higher NO and CH 4 conversions were observed during transient regime rather than steady-state lean, rich or stoichiometric conditions at 200 and 300 °C.

Increasingly stricter regulations for vehicle emissions require more competitive exhaust emission control systems. Three-way catalysis is a major up-to-date emission control technology, though the activity could be limited during the cold start as well as steady state operation including the three regimes: rich (λ<1), lean (λ>1), and stoichiometric (λ=1). Periodic rich/lean switching emerges as a promising strategy to address this challenge. In this work, we investigate the influence of the switching process, using a fixed lambda air-to-fuel ratio amplitude of λ = 1±0.02 (0.5 Hz), on pollutant conversion from 100 to 400 °C, under a complex matrix including nitrogen monoxide (NO), carbon monoxide (CO), hydrogen (H 2 ), and hydrocarbons (C 1 -C 5 ), simulating the typical car exhaust gas. Moreover, two catalysts were tested: one homogeneously coated with Pd, and another zone-coated with Pd, both containing the same total amount of Pd, in order to identify the effect of the catalyst zone-coating and rationalize the use of increasingly scarce platinum group metals. Simple binary pollutant oxidation reactions were also performed to determine the reactivity of individual pollutant gases. Interestingly, NO, CH 4 and C 5 H 12 displayed highest conversions during the switching regime compared to steady-state periods, attributed to the beneficial balance between active site poisoning/regeneration during the rich/lean regimes respectively. The zone-coated catalyst showed an overall higher activity under the full gas mixture that could be explained by a slightly higher Pd content, more effective Pd-support interactions, exothermic effect or the better OSC properties.

The ammonia-SCR catalytic activity of unsupported CeVO 4 with an excess of CeO 2 was investigated in standard and fast-SCR conditions. Solids were obtained from a hydrothermal synthesis route under a mild condition and then stabilized after aging in a wet atmosphere at 600 and 850 °C. Particular attention was paid to the role of excess CeO 2 and the consequences of hydrothermal aging on physical–chemical properties and catalytic activity. The XRD patterns put into evidence the formation of the zircon-type structure of CeVO 4 in agreement with a segregation of cubic face-centered structure of ceria (CeO 2 ). Along with adding an excess of CeO 2 , high specific surface area (102 m 2 /g) for the 11wt% CeO 2 /CeVO 4 solid was obtained. The presence of CeO 2 nanoparticles in addition to CeVO 4 nanoparticles have limited the decrease in the specific surface area after aging at 600 and 850 °C. The catalyst with 11wt% CeO 2 /CeVO 4 exhibited the best catalytic performances in standard and fast SCR conditions after thermal aging at 600 °C. Graphic Abstract

The ammonia-SCR catalytic activity of unsupported CeVO.sub.4 with an excess of CeO.sub.2 was investigated in standard and fast-SCR conditions. Solids were obtained from a hydrothermal synthesis route under a mild condition and then stabilized after aging in a wet atmosphere at 600 and 850 °C. Particular attention was paid to the role of excess CeO.sub.2 and the consequences of hydrothermal aging on physical-chemical properties and catalytic activity. The XRD patterns put into evidence the formation of the zircon-type structure of CeVO.sub.4 in agreement with a segregation of cubic face-centered structure of ceria (CeO.sub.2). Along with adding an excess of CeO.sub.2, high specific surface area (102 m.sup.2/g) for the 11wt% CeO.sub.2/CeVO.sub.4 solid was obtained. The presence of CeO.sub.2 nanoparticles in addition to CeVO.sub.4 nanoparticles have limited the decrease in the specific surface area after aging at 600 and 850 °C. The catalyst with 11wt% CeO.sub.2/CeVO.sub.4 exhibited the best catalytic performances in standard and fast SCR conditions after thermal aging at 600 °C.

Kinetics and reactor modeling for heterogeneous catalytic reactions are prominent tools for investigating, and understanding, the catalyst functionalities at nanoscale, and related rates of complex reaction networks [...]

In this paper, we report on the pharmacological and functional profile of SSR180711 (1,4-Diazabicyclo[3.2.2]nonane-4-carboxylic acid, 4-bromophenyl ester), a new selective α7 acetylcholine nicotinic receptor (n-AChRs) partial agonist. SSR180711 displays high affinity for rat and human α7 n-AChRs (Ki of 22±4 and 14±1 nM, respectively). Ex vivo 3[H]α-bungarotoxin binding experiments demonstrate that SSR180711 rapidly penetrates into the brain (ID50=8 mg/kg p.o.). In functional studies performed with human α7 n-AChRs expressed in Xenopus oocytes or GH4C1 cells, the compound shows partial agonist effects (intrinsic activity=51 and 36%, EC50=4.4 and 0.9 μM, respectively). In rat cultured hippocampal neurons, SSR180711 induced large GABA-mediated inhibitory postsynaptic currents and small α-bungarotoxin sensitive currents through the activation of presynaptic and somato-dendritic α7 n-AChRs, respectively. In mouse hippocampal slices, the compound increased the amplitude of both glutamatergic (EPSCs) and GABAergic (IPSCs) postsynaptic currents evoked in CA1 pyramidal cells. In rat and mouse hippocampal slices, a concentration of 0.3 μM of SSR180711 increased long-term potentiation (LTP) in the CA1 field. Null mutation of the α7 n-AChR gene totally abolished SSR180711-induced modulation of EPSCs, IPSCs and LTP in mice. Intravenous administration of SSR180711 strongly increased the firing rate of single ventral pallidum neurons, extracellularly recorded in anesthetized rats. In microdialysis experiments, administration of the compound (3–10 mg/kg i.p.) dose-dependently increased extracellular acetylcholine (ACh) levels in the hippocampus and prefrontal cortex of freely moving rats. Together, these results demonstrate that SSR180711 is a selective and partial agonist at human, rat and mouse α7 n-AChRs, increasing glutamatergic neurotransmission, ACh release and LTP in the hippocampus.