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Coupled NSR-SCR systems comprising a Pt-BaO/Al2O3 NSR monolith and Cu/CHA, Cu/ZSM-5 or Cu/BETA SCR catalysts are prepared and tested for NOx removal from diesel and lean burn engines exhaust gases. The Cu/zeolite catalysts are characterized by ICP-AES, XRD, N2 adsorption-desorption, NH3-TPD and H2-TPR. The physico-chemical characteristics of fresh catalysts and aged under 5% steam/Ar at 750 °C for 16 h and are compared, resulting in the Cu/CHA with much higher hydrothermal resistance to the loss of textural and structural properties. The single-SCR, single-NSR and coupled NSR-SCR catalytic performance is studied including the conversion of NO and NH3, slip of NH3, and N2O and NO2 yields. Cu/CHA presents the SCR wider temperature window, eventually 100% NO conversion from 220 to 380 °C, even maintained after severe aging. For application in the NSR-SCR technology, the NH3 generated in the NSR catalyst during the rich period is able to achieve higher NO conversion reducing significantly the slip of NH3 (negligible at 200 °C and above), very few amount of N2O at any temperature, and small production of NO2 only at higher temperatures. This improvement of activity and selectivity is particularly enhanced with the coupled NSR-Cu/CHA system, which is also maintained when the catalyst is deposited on the cordierite monolith substrate, as in the case of real application. ; The authors wish to acknowledge the financial support by the Spanish Economy and Competitiveness Ministry [CTQ2012-32899; MAT2012-3716, and "Severo Ochoa" (SEV 2012-0267)], the Basque Government (IT657-013), and the European Union (SynCatMatch project; ERC-AdG-2014-671093). One of the authors (UDLT) acknowledge to the Basque Government for the PhD Research Grant (BFI-2010-330). ; Peer Reviewed

[EN] Coupled NSR-SCR systems comprising a Pt-BaO/Al2O3 NSR monolith and Cu/CHA, Cu/ZSM-5 or Cu/BETA SCR catalysts are prepared and tested for NOx removal from diesel and lean burn engines exhaust gases. The Cu/zeolite catalysts are characterized by ICP-AES, XRD, N-2 adsorption-desorption, NH3-TPD and H-2-TPR. The physico-chemical characteristics of fresh catalysts and aged under 5% steam/Ar at 750 degrees C for 16 h and are compared, resulting in the Cu/CHA with much higher hydrothermal resistance to the loss of textural and structural properties. The single-SCR, single-NSR and coupled NSR-SCR catalytic performance is studied including the conversion of NO and NH3, slip of NH3, and N2O and NO2 yields. Cu/CHA presents the SCR wider temperature window, eventually 100%NO conversion from 220 to 380 degrees C, even maintained after severe aging. For application in the NSR-SCR technology, the NH3 generated in the NSR catalyst during the rich period is able to achieve higher NO conversion reducing significantly the slip of NH3 (negligible at 200 degrees C and above), very few amount of N2O at any temperature, and small production of NO2 only at higher temperatures. This improvement of activity and selectivity is particularly enhanced with the coupled NSR-Cu/CHA system, which is also maintained when the catalyst is deposited on the cordierite monolith substrate, as in the case of real application. (C) 2016 Published by Elsevier B.V. ; The authors wish to acknowledge the financial support by the Spanish Economy and Competitiveness Ministry [CTQ2012-32899; MAT2012-3716, and "Severo Ochoa" (SEV 2012-0267)], the Basque Government (IT657-013), and the European Union (SynCat-Match project; ERC-AdG-2014-671093). One of the authors (UDLT) acknowledge to the Basque Government for the PhD Research Grant (BFI-2010-330). ; De-La-Torre, U.; Pereda-Ayo, B.; Moliner Marin, M.; González Velasco, JR.; Corma Canós, A. (2016). Cu-zeolite catalysts for NOx removal by selective catalytic reduction with NH3 and coupled to NO ...

The SCR of NOx with NH3 has been studied by using different Cu zeolite catalysts, prepared both with ZSM5 and BETA zeolite supports by ionic exchange or by impregnation. The catalysts were characterized by ICP-AES, N2 adsorption at −196 °C, XRD, TEM, XPS and H2-TPR. The catalysts characterization confirmed the presence of different Cu(II) species on all catalyst (CuO and Cu(II) exchanged on tetrahedral and octahedral positions of the zeolites framework). Clear evidences of Cu(I) or Cu(0) species were not obtained. CuO was more abundant in high copper-content catalysts and in ZSM5 catalysts, due to its lower ionic exchange capacity, while isolated Cu(II) ions are more abundant in low copper-content catalysts and in BETA catalysts. It was concluded that CuO catalyzes the oxidation of NO to NO2, and this favors the reduction of NOx at lower temperature (the NH3-NO2 reaction is faster than the NH3-NO reaction because NO2 is much more oxidizing than NO), whereas isolated Cu(II) ions maintain high NOx conversion at high temperatures. ; Financial support provided by the Spanish Ministry of Economy and Competitiveness (CTQ2012-30703), the Basque Government (IT-657-13) and the UPV/EHU (UFI11/39). One of the authors (UDLT) wants to acknowledge to the Basque Government for the PhD Research Grant (BFI-2010-330).

The hydrogenation of CO2 into CH4 from H2 produced by renewable energy is considered an interesting alternative in order to promote the development of such green energies. In the present work, the effect of Ni and Ru loadings on the catalytic performance of alumina-supported catalysts is studied for CO2 methanation reaction. All catalysts were prepared by wetness incipient impregnation, characterized by several techniques (N2-physisorption, CO2-TPD, XRD, H2-chemisorption, XPS and H2-TPR) and evaluated for CO2 methanation in a fixed bed reactor at GHSV=10,000 h−1 and W/FCO2 0 = 4.7 (g cat.) h mol−1. Characterization results showed that addition of increasing loadings of Ni and Ru lead to the formation of both CO2 adsorption and H2 dissociation active sites, which are necessary to carry out CO2 hydrogenation into methane. Easily reducible ruthenium was dispersed on γ-Al2O3 in form of large agglomerates, whereas Ni was better dispersed presenting a great interaction with the support. 12% Ni and 4% Ru resulted to be the optimal contents providing metal surfaces of 5.1 and 0.6m2 g−1, T50 values of 340 and 310 °C and activity being quite stable for 24 h-on-stream. In terms of turnover frequency (TOF), 4%Ru/Al2O3 catalyst was quite more efficient than 12%Ni/Al2O3, probably due to a greater ability of ruthenium to dissociate hydrogen. The apparent activation energies for alumina supported Ni and Ru were 129 and 84 kJ mol−1, respectively. ; The support from the Economy and Competitiveness Spanish Ministry (CTQ2015-67597-C2-1-R and CTQ2015-67597-C2-2-R MINECO-FEDER), the Basque Government (IT657-13 and IT1297-19) and the SGIker (Analytical Services) at the University of the Basque Country are acknowledged. One of the authors (AQ) also acknowledges University of the Basque Country by his PhD grant (PIF-15/351).

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. ; The authors thank the financial support of Basque Government (Consolidated Group IT657-13), Spanish Ministry of Economy and Competitiveness (Projects CTQ2015-67597-C2-1-R and CTQ2015-67597-C2-2-R), and the EU (FEDER funding). ADQ thanks the Spanish Ministry of Education, Culture and Sports (grant FPU14/01178) and AQ the University of the Basque Country (grant PIF15/351).

The CO2 methanation mechanism was studied for Ni/CeO2 and Ni/Al2O3 catalysts. The higher methanation activity and selectivity of Ni/CeO2 is attributed to: i) Ni/CeO2 combines two types of active sites efficient for CO2 dissociation at the NiO-Ceria interface and for H2 dissociation on Ni0 particles; ii) water desorption is the slowest mechanism step, and, due to the high oxygen mobility throughout the ceria lattice, water is not necessarily formed on the same active sites that chemisorb CO2, i.e., the CO2 chemisorption sites are not blocked by water molecules; iii) the Ni/CeO2 surface does not accumulate carbon-containing species under reaction conditions, which allows faster chemisorption and dissociation of CO2. The Ni/Al2O3 catalyst handicaps are that all the steps of the mechanism take place on the same active sites, and the slow release of water and the accumulation of surface formates on these sites delay the chemisorption of further CO2 molecules. ; Financial support of: - Economy and Competitiveness Spanish Ministry: Projects CTQ2015-67597-C2-1-R and CTQ2015-67597-C2-2-R MINECO-FEDER) and grant of EBG FJCI-2015-23769. - Generalitat Valenciana: Project PROMETEO/2018/076 and PhD grant of ACA GRISOLIAP/2017/185. - The Basque Government: Project IT657-13. - SGIker (Analytical Services) at the University of the Basque Country. - Spanish Ministry of Education, Culture and Sports grant of ADQ FPU14/01178. - University of the Basque Country PhD grant of AQ PIF-495 15/351.