Assessment of the stability of LTA zeolites under natural gas drying TSA conditions

[EN] The main features in cationic LTA zeolites that are likely to impact its potential hydrothermal stability are interconnected. The Al content and the compensating cation play an important role in the water adsorption but their influence on the zeolite performance in thermal cycles is yet to be understood. In this study, four LTA zeolite samples were synthetized with distinct Si/Al ratios in sodium and potassium forms. They underwent a Premature Aging Protocol (PAP) that took into account the operating conditions typically found in temperature swing adsorption processes. The Si/Al ratio per se did not impact in the crystallinity upon aging, but the presence of a high amount of potassium cations (Si/Al = 1) led to the amorphization of the zeolite structure. The results from XPS and NMR techniques indicate the Al migration from the outer surface to the inner cages occurs upon aging. Chemical analysis by XRF and ICP-OES associated with 27Al NMR analysis reveal that the presence of EFAl is particularly significant in the sample with the largest Si/Al ratio (5) and is correlated to a much larger C deposition upon aging. TG/DTG and TPD-NH3 experiments suggest that acid sites in the zeolite structures act as a double-edged sword, by enhancing water adsorption while also leading to carbon accumulation. CO2 isotherms at 0 oC reveal the reduction of the microporosity after aging, whereas the Al content is proportional to the water adsorption uptake, particularly at low pressures (below 10 mbar). The material with an intermediate Si/Al ratio and in Na-form (LTAc-SiAl2-Na) combines excellent hydrothermal stability with a high-water affinity and uptake.The authors acknowledge financial support from Petrobras (Brazil) project 2018/00130-5, CAPES (Brazil), particularly in the frame of project CAPES/Print 88887.311867/2018-00 and Servicios Centrales de Apoyo a la Investigacion - SCAI. S.V. and F. R. acknowledge financial support by the Spanish Ministry of Science and Innovation (CEX2021-001230-S grant funded by MCIN/AEI/10.13039/501100011033 and TED2021-130191B-C41 and TED2021-130756B-C31 grants funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe" by the European Union NextGenerationEU/PRTR). Authors thank also the financial support by the Generalitat Valenciana (Prometeo 2021/077). This study forms part of the Advanced Materials programme and was supported by MCIN with partial funding from European Union Next Generation EU (PRTR-C17. I1) and by Generalitat Valenciana (MFA/2022/047 and MFA/2022/012).Moura, P.; Ferracine, E.; Rodríguez-Aguado, E.; Maia, D.; Melo, DC.; Valencia Valencia, S.; Cardoso, D.... (2024). Assessment of the stability of LTA zeolites under natural gas drying TSA conditions. Catalysis Today. 427. https://doi.org/10.1016/j.cattod.2023.11441042

Support effects on NiO-based catalysts for the oxidative dehydrogenation (ODH) of ethane

[EN] We report on the effect of NiO-support interactions on the chemical nature of Ni species in a series of supported NiO catalysts for the ODH of ethane. SiO2, TiO2-anatase, a high surface area TiO2 and a porous clay hetero-structure (PCH) with TiO2 and SiO2 pillars were used as supports, which led to a selectivity to ethylene in the range 30-90% over supported NiO catalysts. The catalysts were characterized by means of XRD, N-2-Adsorption, H-2-TPR, XPS and in situ (under H-2 reductive atmosphere) and ex situ XAS spectroscopy. The catalytic performance of supported materials is discussed in terms of their reducibility and specific reduction kinetics, but also taking into account the specific chemical nature of Ni species on each catalyst. The influence of the particle size and the presence of Ni and O vacancies on the catalytic performance in the ODH of ethane is inferred.Authors would like to thank the DGICYT in Spain CTQ2015-68951-C3-1-R, CTQ2015-68951-C3-3-R, CTQ2012-37925-C03-2 and ENE2017-88818-C2-1-R. Also authors want to acknowledge the ALBA Synchrotron Light Source (Project ID: 2015021258 at CLAESS beamline). Authors from ITQ thank Project SEV-2016-0683 for financial support. D. D. also thanks MINECO and Severo Ochoa Excellence Program for his fellowship (SVP-2014-068669). Authors from UV thank the University of Valencia (UV-INV-AE16-484416 project) and MINECO (MAT2017-84118-C2-1-R project) for funding.Delgado-Muñoz, D.; Sanchís, R.; Cecilia, JA.; Rodríguez-Castellón, E.; Caballero, A.; Solsona, B.; López Nieto, JM. (2019). Support effects on NiO-based catalysts for the oxidative dehydrogenation (ODH) of ethane. Catalysis Today. 333:10-16. https://doi.org/10.1016/j.cattod.2018.07.010S101633

Preparation and characterisation of calcined Mg/Al hydrotalcites impregnated with alkaline nitrate and their activities in the combustion of particulate matter

The effect of incorporating alkaline nitrates in hydrotalcites for use in the combustion of particulate matter from diesel emissions has been studied. The catalysts were characterised by X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), atomic absorption spectrophotometry (AAS) temperature programmed reduction (TPR) and Fourier transform infrared spectroscopy (FTIR). Activity measurements were carried out using a thermobalance in air and using a fixed-bed reactor with a NO/O2 flow. The observed activities decreased in the following order: HTMgAlcCs > HTMgAlcK > HTMgAlcLi > HTMgAlc.Fil: Comelli, Nora Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Ruiz, Maria Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Merino, Nora Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Lick, Ileana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Rodríguez Castellón, E.. Universidad de Málaga. Facultad de Ciencias. Departamento de Química Inorgánica, Cristalografía y Mineralogía; EspañaFil: Jiménez López, A.. Universidad de Málaga. Facultad de Ciencias. Departamento de Química Inorgánica, Cristalografía y Mineralogía; EspañaFil: Ponzi, Marta Isabel

Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane

[EN] NiO and metal-promoted NiO catalysts (M-NiO, with a M/(M+Ni) atomic ratio of 0.08, with M = Nb, Sn, or La) have been prepared, tested in the oxidative dehydrogenation (ODH) of ethane, and characterized by means of XRD, TPR, HRTEM, Raman, XPS, and in situ XAS (using H-2/He, air or C2H6/He mixtures). The selectivity to ethylene during the ODH of ethane decreases according to the following trend: Nb NiO Sn NiO > La NiO > NiO, whereas the catalyst reducibility (determined by both TPR and XAS using H-2/He mixtures) shows the opposite trend. However, different reducibility and catalytic behavior in the absence of oxygen (ethane/He mixtures) have been observed, especially when comparing Nb- and Sn-promoted NiO samples. These differences can be ascribed mainly to a different phase distribution of the promoter. The results presented here are discussed in terms of the nature of active and selective sites for ODH of ethane in selective and unselective catalysts, but also the role of promoters and the importance of their phase distribution.The authors would like to acknowledge the DGICYT in Spain CTQ2012-37925-C03-2, CTQ2015-68951-C3-1-R, and CTQ2015-68951-C3-3-R. Authors thank European Synchrotron Radiation Facility, ESRF (Project CH-4512; BM25-SpLine Beamlime). Authors from ITQ also thank Project SEV-2016-0683 for financial support. D.D. thanks MINECO and Severo Ochoa Excellence Program for his fellowship (SVP-2014-068669). B.S. also thanks UV-INV-AE16-484416. Finally, the authors thank the Electron Microscopy Service of Universitat Politecnica de Valencia for their support.Delgado-Muñoz, D.; Solsona Espriu, BE.; Ykrelef, A.; Rodriguez-Gomez, A.; Caballero, A.; Rodríguez-Aguado, E.; Rodriguez-Castellón, E.... (2017). Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane. The Journal of Physical Chemistry C. 121(45):25132-25142. https://doi.org/10.1021/acs.jpcc.7b07066S25132251421214

Preparation and characterisation of calcined Mg/Al hydrotalcites impregnated with alkaline nitrate and their activities in the combustion of particulate matter

The effect of incorporating alkaline nitrates in hydrotalcites for use in the combustion of particulate matter from diesel emissions has been studied. The catalysts were characterised by X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), atomic absorption spectrophotometry (AAS) temperature programmed reduction (TPR) and Fourier transform infrared spectroscopy (FTIR). Activity measurements were carried out using a thermobalance in air and using a fixed-bed reactor with a NO/O2 flow. The observed activities decreased in the following order: HTMgAlcCs>HTMgAlcK>HTMgAlcLi>HTMgAlc.Centro de Investigación y Desarrollo en Ciencias Aplicada

Ceria–zirconia-copper oxide catalysts for CO removal from H2-rich streams under PEMFC operating conditions

On-board hydrogen production from hydrocarbons or alcohols has been proposed as the most efficient process to obtain hydrogen for feeding proton-exchange membrane fuel cells (PEMFCs). However, the gas produced after reforming and water gas-shift processes still presents in most cases a relatively high CO concentration, that disallows efficient handling of the fuel by the Pt anode usually employed in the PEMFCs. Preferential oxidation of carbon monoxide (CO-PROX) has been recognized as one of the most straightforward and cost-effective methods to achieve acceptable CO concentrations (<10 ppm). Among different types of catalysts for the PROX reaction, those based on Ce-Zr-Cu oxides 1-3 have shown promising properties in terms of activity, selectivity and resistance to CO2 and H2O. In this work, a series of Ce–Zr–Cu mixed oxide systems, with different atomic ratios among cations, were prepared by slow co-precipitation with the aim to investigate the influence of the presence of very small amounts of zirconium on the performances of these three-component catalysts. The activity of these materials was evaluated in the CO preferential oxidation in hydrogen-rich gas stream (1.2% CO, 1.2% O2, 50% H2, He balance) in the absence and presence of CO2 and H2O, in the 40-190°C temperature range. Correlations between catalytic activity and physico-chemical properties of the materials were made by X-ray Powder Diffraction (XRPD), N2 physisorption, Temperature-Programmed Reduction (H2-TPR), X-ray Photoelectron Spectroscopy (XPS)

Copper supported on mixed alumina/gallium oxide pillared a-tin phosphate for De-NO x applications

Alumina-and mixed alumina/gallium oxide-pillared a-tin phosphate have been impregnated with different amounts of copper via the incipient wetness method. Their characterization by X-ray photoelectron spectroscopy, H 2 temperature-programmed reduction and NO temperature-programmed desorption has allowed to gain insight into the nature of the copper species. These are present as small CuO clusters (not detectable by XRD) as well as forming part of spinel-like structures. NO-TPD studies show that only NO is desorbed from all the catalysts. Ga 3 Al 11 -SnP with 4.9 wt% Cu interacts most strongly with NO and this catalyst exhibits the highest degree of reduction of Cu 2+ to Cu + after the catalytic reaction. The catalysts are active for the selective catalytic reduction (SCR) of nitric oxide with propane in the presence of excess oxygen

Efficient low-loaded ternary Pd-In2O3-Al2O3 catalysts for methanol production

Pd-In2O3 catalysts are among the most promising alternatives to Cu-ZnO-Al2O3 for synthesis of CH3OH from CO2. However, the intrinsic activity and stability of In2O3 per unit mass should be increased to reduce the content of this scarcely available element and to enhance the catalyst lifetime. Herein, we propose and demonstrate a strategy for obtaining highly dispersed Pd and In2O3 nanoparticles onto an Al2O3 matrix by a one-step coprecipitation followed by calcination and activation. The activity of this catalyst is comparable with that of a Pd-In2O3 catalyst (0.52 vs 0.55 gMeOH h−1 gcat-1 at 300 °C, 30 bar, 40,800 mL h−1 gcat-1) but the In2O3 loading decreases from 98 to 12 wt% while improving the long-term stability by threefold at 30 bar. In the new Pd-In2O3-Al2O3 system, the intrinsic activity of In2O3 is highly increased both in terms of STY normalized to In specific surface area and In2O3 mass (4.32 vs 0.56 g gMeOH h−1 gIn2O3-1 of a Pd- In2O3 catalyst operating at 300 °C, 30 bar, 40,800 mL h−1 gcat-1).The combination of ex situ and in situ catalyst characterizations during reduction provides insights into the interaction between Pd and In and with the support. The enhanced activity is likely related to the close proximity of Pd and In2O3, wherein the H2 splitting activity of Pd promotes, in combination with CO2 activation over highly dispersed In2O3 particles, facile formation of CH3OH