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The effect of the LnOx support has been studied for Ni‐based CO2 methanation catalysts. 10 wt.% nickel catalysts with LaOx, CeO2 and PrOx supports have been prepared, characterized by N2 adsorption, XRD, XRF, TG‐MS (N2‐TPD and H2‐TPR) and XPS, and have been tested for CO2 methanation. The catalytic activity follows the trend Ni/CeO2>Ni/PrOx≫Ni/LaOx, all catalysts being very selective towards CH4 formation. The activity depends both on the nature of the catalytic active sites and on the stability of the surface CO2 and H2O species. Ni/CeO2 is the most active catalyst because (i) the Ni2+‐ceria interaction leads to the formation of the highest population of active sites for CO2 dissociation, (ii) the reduced Ni0 sites where H2 dissociation takes place are the most electronegative and active, and (iii) the stability of surface CO2 and H2O species is lowest. Ni/LaOx achieves lower activity because of the strong chemisorption of H2O and CO2, which poison the catalyst surface, and because this support is not able to promote the formation of highly active sites for CO2 and H2 dissociation. The behavior of Ni/PrOx is intermediate, being slightly lower to that of Ni/CeO2 because the formation of active sites is not so efficient and because the stability of chemisorbed CO2 is slightly higher. Thanks for your support: Ni/CeO2 is the most active Ni/LnOx catalyst because (i) the Ni2+‐ceria interaction leads to the formation of the highest population of active sites for CO2 dissociation, (ii) the reduced Ni0 sites where H2 dissociation takes place are the most electronegative and active, and (iii) the stability of surface CO2 and H2O species is lowest. [ABSTRACT FROM AUTHOR]

Abstract: There are two alternative, main technologies for removal of nitrogen oxides (NOx) from vehicle exhaust gases, namely, selective catalytic reduction (SCR) and NOx storage and reduction (NSR). The SCR technology consists of using ammonia (NH3), produced by hydrolysis of urea that is stored into an on‐board tank in the vehicle, to reduce NOx selectively to nitrogen (N2). In the NSR strategy, the conversion of NOx into N2 occurs through a two‐step cyclic operation. During the fuel‐lean stage, the NOx is trapped on the catalyst; then, the engine is switched to a fuel‐rich condition, under which NOx is released and reduced preferentially to N2, although some NH3 can also be produced. The concept of coupling NSR with SCR is based on tuning the operation of the NSR catalyst to produce a controlled amount of NH3, which is stored on the SCR catalyst during the fuel‐rich stage and used to reduce the remaining NOx on the SCR catalyst, placed downstream of the NSR catalyst in a sequential NSR+SCR configuration. Alternatively, the same concept applies to the dual‐layer architecture, which comprises a SCR layer deposited on top of the NSR layer in a single monolith. The internal generation of NH3 in the NSR catalyst avoids the need of external supply from the on‐board tank, but also achieves impressive NOx‐to‐N2 efficiency, apparently allowing zero‐level pollutant emission. [ABSTRACT FROM AUTHOR]

Highlights: [•] NH3 NOx-SCR is studied on Cu-ZSM5 and Cu-BETA prepared by ion exchange and impregnation. [•] CuO and Cu(II) exchanged on tetrahedral and octahedral positions of zeolite framework were found. [•] CuO prevails in high Cu-content on ZSM5. Isolated Cu(II) ions prevail in low Cu-content on BETA catalysts. [•] CuO promotes NOx reduction at low temperature. [•] Isolated Cu(II) ions maintain high NOx conversion at high temperatures. [Copyright &y& Elsevier]

Highlights: [•] The preparation method of Cu-zeolite/cordierite monolith catalysts is optimized. [•] Zeolite washcoating followed by Cu ion-exchange is compared to washcoating with Cu-zeolite. [•] Washcoating with Cu ion-exchanged powder zeolite led to most active SCR catalyst. [•] Cu exchanged home-extruded BETA zeolite monolith achieved high SCR activity. [ABSTRACT FROM AUTHOR]

The NO NH-SCR performance of several Cu and Fe catalysts supported on BETA and ZSM-5 zeolites has been studied in single SCR and double NSR-SCR configuration, and the activity related to the nature and reducibility of metal species on the catalyst surface. Intermediate ammonia formed in NSR improved greatly NO conversion at the exit of the double NSR-SCR configuration, which was practically totally converted to N. [ABSTRACT FROM AUTHOR]

Abstract: The challenge of efficient NO x removal from diesel and lean-burn engine exhaust gas by combining NSR and SCR catalyst is studied. Several Cu exchanged zeolites have been prepared, varying the preparation method (ion exchange and impregnation), the copper content (1–6%) and the zeolite (BETA and ZSM5). The prepared catalysts have been characterized, and acidity, surface area, crystallinity and metal reducibility have been compared. SCR experiments under 750ppm NO, 750ppm NH3 and 9.5% O2 (Ar to balance) discriminated low copper loading, prepared by ion exchange catalyst (Z-IE-1.4 and B-IE-2.1) as the most active for NO x conversion (>95%) in ample temperature range (280–450°C). These active SCR catalysts were placed downstream a monolith NSR Pt–BaO/Al2O3 catalyst, running under cycled lean–rich conditions, and the improvement on NO x removal and selectivity to only N2 were determined. In an ample range of temperature, from 200 to 400°C, NO x conversion was increased in more than 30%, also notably increasing the production of nitrogen, and reducing production of ammonia and N2O below 3% and 2%, respectively, when comparing the combined NSR–SCR configuration versus the single NSR catalyst. [Copyright &y& Elsevier]

• Strontium doping enhances NO x storage and reduction performance of bulk LaCoO 3. • 30% is the optimum strontium doping degree for bulk perovskites, La 0.7 Sr 0.3 CoO 3. • A more efficient use of the perovskite can be achieved by supporting it over Al 2 O 3. • Perovskite loading around 30% over Al 2 O 3 maximizes its utilization. • NSR performance was better for Al 2 O 3 supported perovskites than bulk ones. Here we report the effects of strontium doping of perovskites (La 1-x Sr x CoO 3) on NO x storage and reduction (NSR) as well as the effects of supporting the perovskite onto an alumina support. The NSR capacity of La 0.7 Sr 0.3 CoO 3 improved with strontium doping: this material displayed a good balance between NO oxidation capacity and adsorption sites accessibility. Increased accessibility was mainly due to the strontium oxide segregates. In addition, different loadings of La 0.7 Sr 0.3 CoO 3 perovskite (10, 20, 30, 40 and 50%) were impregnated onto alumina in order to increase the exposed surface area of the perovskite. This had the effect of increasing the NSR capacity of the perovskite. The results of X-Ray diffraction, UV–vis–NIR spectroscopy, N 2 adsorption-desorption, electron microscopy, and temperature programmed techniques, demonstrated that the cobalt ions preferably formed cobalt aluminate (CoAl 2 O 4) in the case of low perovskite loadings (<20%). Meanwhile, a well-developed perovskite phase was observed with the higher loadings (>30%). The specific NO oxidation rate per gram of perovskite increased dramatically with the incorporation onto an alumina support. 30% LSCO/Al 2 O 3 sample had an oxidation rate of 138 μmol min-1 (g LSCO)-1 at 350 °C, more than double the rate of the bulk La 0.7 Sr 0.3 CoO 3 (49 μmol min−1 (g LSCO)−1). Likewise, the 30% LSCO/Al 2 O 3 sample had a higher NO x storage capacity than its bulk counterpart at 400 °C: 306 vs. 115 μmol (g LSCO)−1. The higher oxidation capacity of the alumina-supported samples also facilitated the diffusion of the intermediate compounds from oxidation to adsorption sites. Impregnating alumina with perovskite could be used to improve the efficiency of perovskite mediated NO x removal in automobile applications. Furthermore, adding palladium onto optimum alumina-supported perovskite sample, i.e. 1.5% Pd-30% LSCO/Al 2 O 3 , resulted in a clear improvement in NO x storage and reduction capacity. This last sample demonstrated a nitrogen yield as high as 65%, an improvement over the model Pt-based NSR catalyst. [ABSTRACT FROM AUTHOR]

Cu/SAPO-34 catalysts are prepared using solid-state ion exchange (SSIE) and liquid ion exchange (LIE). SSIE is conducted by calcining a physical mixture of H-SAPO-34 zeolite and CuO nanoparticles at elevated temperatures (500-800 °C). The conventional LIE method is conducted by exchanging Na-SAPO-34 with Cu(COOCH 3 ) 2 aqueous solution with a final calcination step at 500 °C. Catalysts were fully characterized, focusing on Cu species identification. The NH 3 -SCR activity is evaluated for NO x removal. Cu/SAPO-34 catalysts synthesized by SSIE at 700 °C achieved an optimal reaction rate, which was correlated with a higher proportion of Cu 2+ ions. The activation energies of Cu/SAPO-34 catalysts prepared by SSIE and LIE with varying copper loadings are 32-38 and 42-47 kJ mol -1 , respectively. The SSIE catalysts achieve higher turnover frequency than LIE catalysts for a similar copper content, which decreases on increasing the copper loading. These results provide evidence that Cu ions exchanged into the Cu/SAPO-34 catalysts synthesized by SSIE present higher activity than those prepared by LIE for NO x removal by NH 3 -SCR., Competing Interests: The authors declare no competing financial interest.