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The mild catalytic hydrogen‐transfer hydrodechlorination (HDC) of 4‐chlorophenol (4‐CP) was studied in heterogeneous batch mode. The applied catalyst was prepared by impregnation of γ‐Al2O3 with preformed Pt nanoparticles (1.0 % w/w). Analytical data of both the Pt nanoparticles and the final catalyst are presented. 96.8 % conversion of 4‐chlorophenol was obtained in isopropanol after 24 h at 82 °C and atmospheric pressure in the presence of potassium tert‐butoxide (tBuOK). Phenol was the only reaction product formed and hydrogenation of the aromatic ring did not occur. The Pt/γ‐Al2O3 catalyst was also evaluated under varying reaction conditions (temperature, base, time) and it shows during 5 hydrodechlorination/regeneration cycles only slight deactivation (24 h at 82 °C, X=87.3 % after the fifth cycle). [ABSTRACT FROM AUTHOR]

Understanding and enhancing the activity of heterogeneous single‐atom catalysts (SACs) are indispensable aspects to use them in industrial applications. Among these, low‐temperature CO oxidation is considered as a model reaction for testing a wide‐range of oxidation catalysts, and as an essential process for the exhaust aftertreatment in modern combustion engines. This study demonstrates that the activity of heterogeneous Cu/CeO2−TiO2 SAC catalysts can be fine‐tuned by controlling the Ce/Ti ratio in CeO2−TiO2 supports, with the highest catalytic activity achieved for a Ce/Ti molar ratio of 0.18. Based on DRIFT, EEL, and EPR spectroscopies, together with high‐resolution electron microscopy and H2‐TPR measurements, it is inferred that the optimized Ce/Ti ratio correlates with i) highest dispersion of separate CeO2 particles on TiO2 surface, ii) more facile reduction of Ce4+ to Ce3+, and iii) enhanced formation of −Cu2+−O−Ce4+−⇆−Cu+−□−Ce3+− redox shuttles, which play a dual role for CO adsorption and O2‐activation. These results extend the understanding of heterogeneous metal single‐atom catalysts and constitute a robust approach for the rational control of their catalytic performance in technically relevant applications. [ABSTRACT FROM AUTHOR]

Hydrogen storage materials and technologies are deemed as the cornerstone towards a world economy less reliant on, and ultimately independent of fossil resources. Ammonia is considered among the most efficient carbon‐free hydrogen carriers because of its relatively high gravimetric and volumetric hydrogen storage capacities and, equally important, ease of transport and storage. In addition, the well‐established chemical production of ammonia (preferably a green Haber‐Bosch process) would accelerate the immediate introduction of hydrogen into energy infrastructure. Thermocatalytic decomposition of ammonia yields clean, COx‐free hydrogen, but is energy intensive and currently performed with expensive Ru‐based catalysts. The development of more efficient catalysts based on more abundant and cheaper elements is indispensable for future wide‐scale industrial application. Therefore, the conceptualization of strategies and challenges for material developments, study and optimization of ammonia decomposition catalysts as well as their in situ/operando characterizations are pivotal aspects to be considered. [ABSTRACT FROM AUTHOR]

A heterogeneous single‐atom catalyst (SAC) based on a tiny Cu loading (0.05 wt.%) supported on CeO2−TiO2 (Ce/Ti=0.18) shows very high Cu mass‐normalized CO oxidation activity, 100 % selectivity for CO2 between 60 and 100 °C and essentially no deactivation during 17 h on stream in the preferential oxidation of CO (PROX) at 120 °C. Based on state of the art, this catalyst is among the most active and PROX‐selective catalysts. Employing a combination of ex‐situ and operando methods, we infer that the isolated Cu single sites are incorporated with redox‐active Cu2+−O−Ce4+⇆Cu+−□−Ce3+ moieties connected by labile oxygen and are exposed on the surface of highly dispersed ceria. This high dispersion is promoted by TiO2 which itself does not participate in redox steps during PROX, as Ti ions remain essentially tetravalent while Cu and Ce undergo reversible redox shuttles. [ABSTRACT FROM AUTHOR]

A facile and efficient methodology is described for the solvothermal synthesis of size‐tunable, stable, and uniform NiCu core–shell nanoparticles (NPs) for application in catalysis. The diameter of the NPs is tuned in a range from 6 nm to 30 nm and to adjust the Ni:Cu ratio from 30:1 to 1:1. Furthermore, the influence of different reaction parameters on the final NPs is studied. The NPs are structurally characterized by a method combination of transmission electron microscopy, anomalous small‐angle X‐ray scattering, X‐ray absorption fine structure, and X‐ray photoelectron spectroscopy. Using these analytical methods, it is possible to elucidate a core–shell–shell structure of all particles and their chemical composition. In all cases, a depletion from the core to the shell is observed, with the core consisting of NiCu alloy, surrounded by an inner Ni‐rich shell and an outer NiO shell. The SiO2‐supported NiCu core–shell NPs show pronounced selectivity of >99% for CO in the catalytic reduction of CO2 to CO using hydrogen as reactant (reverse water–gas shift reaction) independent of size and Ni:Cu ratio. [ABSTRACT FROM AUTHOR]

Purification of gases by membranes can provide enormous energy savings. Inorganic membranes offer good stability and regenerability, but large margin manufacturing is limited. Silica membranes are an exception since they can be produced by coating with molecular precursors. However, such membranes do not have a defined pore structure, which limits their applicability in mass separation. Nevertheless, it is possible to fill the pores of silica membranes with condensate of a component to be separated from gas mixtures. In this work, this applicability of a micro‐mesoporous silica membrane was demonstrated exemplarily by the separation of n‐butane (C4) from mixtures containing methane (C1). The main result, which was supported by grand canonical Monte Carlo (GCMC) simulations, is that capillary condensation contributes significantly to the performance. The experimental results showed that the n‐butane separation efficiency (permeate flux and separation selectivity) through the silica membrane under the condensation conditions is excellent and thus can serve as a model for similar separation tasks. [ABSTRACT FROM AUTHOR]

Highly active and coking‐resistant Ni catalysts suited for the dry reforming of CH4‐rich gases (70 vol %, e. g. biogas or sour natural gas) were prepared starting from a Mg‐rich Mg−Al hydrotalcite support precursor. Calcination at 1000 °C yields two phases, MgO and MgAl2O4 spinel. Complexation‐deposition of Ni with citric acid on the preformed support as well as lanthanum addition yields a catalyst with remarkably low carbon accumulation over 100 h on stream attributed to both high Ni dispersion and preferred interactions of Ni with MgO on MgAl2O4. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Phosphate surface groups on CeO2–ZrO2 solid solutions were generated by treating Ce–Zr–hydroxide precursors with phosphoric acid. In the catalytic formation of dimethyl carbonate (DMC) from methanol and CO2, the performance of the P‐modified samples was markedly affected relative to that of the unmodified ones: Phosphate treatment caused remarkable changes in the phase composition, acid–base properties, and the ability to form monodentate methoxy intermediates. The DMC yield (1.6 %) was successfully improved from 0.24 to 1.6 % by phosphate modification of CeO2–ZrO2 (Ce/Zr=4.7, P/Zr=0.13) and by performing the reaction at 170 °C and 6.5 MPa for 1 h. [ABSTRACT FROM AUTHOR]

Operational criteria for the adsorption based separation of alkanes by MFI zeolite membranes were evaluated using the model system n-butane in methane. The influence of operation parameters is rather case sensitive and the separation is determined by the interplay between mobility of adsorbed molecules across the membrane and the depletion of the preferred adsorptive agent, n-butane, along the membrane. Different aspects in the operational design for the separation of alkanes by zeolite membranes were illuminated, namely separation task, stationarity, and membrane surface. [ABSTRACT FROM AUTHOR]

Oxygen removal to very low residual contents in methane-rich gas streams and carbon dioxide as co-component (simulated biogas) was achieved via three different methods at various temperatures, namely, by reduction with hydrogen admixtures on Pt/ γ-Al2O3 catalysts, by oxygen absorption affinity of YBaCo4O7+ δ, and by the catalytic reaction with methane on both the materials, respectively. The three methods have characteristic advantages and disadvantages which are discussed in the context of existing methods for gas treatments focused on oxygen removal. Finally, the advantage of dielectric radio-frequency heating on the powdered functional materials is suggested as alternative to conventional routes. [ABSTRACT FROM AUTHOR]

Keywords: CO oxidation; Cu/CeO2-TiO2; heterogeneous single-atom catalyst; operando spectroscopy; redox properties EN CO oxidation Cu/CeO2-TiO2 heterogeneous single-atom catalyst operando spectroscopy redox properties 1 1 1 04/26/23 20230421 NES 230421 B The Front Cover b presents a surface-science approach to understanding and steering the catalytic properties of heterogeneous single-atom catalysts (SACs) aiming to step them up for industrial applications. In their Research Article, A. M. Abdel-Mageed et al. show that the CO oxidation activity of Cu/CeO SB 2 sb -TiO SB 2 sb SACs can be fine-tuned by modulating the Ce/Ti ratio. CO oxidation, Cu/CeO2-TiO2, heterogeneous single-atom catalyst, operando spectroscopy, redox properties. [Extracted from the article]

Ammonia decomposition, carbon-free hydrogen, hydrogen storage, fuel cells, heterogeneous catalysis Cover Feature: Thermocatalytic Ammonia Decomposition - Status and Current Research Demands for a Carbon-Free Hydrogen Fuel Technology (ChemCatChem 2/2023) Keywords: ammonia decomposition; carbon-free hydrogen; hydrogen storage; fuel cells; heterogeneous catalysis EN ammonia decomposition carbon-free hydrogen hydrogen storage fuel cells heterogeneous catalysis 1 1 1 01/27/23 20230120 NES 230120 B The Cover Feature b shows a possible pathway for the application of ammonia as a renewable hydrogen and energy vector. [Extracted from the article]

Copyright of Chemie Ingenieur Technik (CIT) is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Molecularly defined Ir complexes and different samples of supported IrO2 nanoparticles have been tested and compared in the catalytic water oxidation with cerium ammonium nitrate (CAN) as the oxidant. By comparing the activity of nano-scaled supported IrO2 particles to the one of organometallic complexes it is shown that the overall activity of the homogeneous Ir precursors is defined by both the formation of the homogeneous active species and its conversion to IrIV -oxo nanoparticles. In the first phase of the reaction the activity is dominated by the homogeneous active species. With increasing reaction time, the influence of nano-sized Ir -oxo particles becomes more evident. Notably, the different conversion rates of the homogeneous precursor into the active species as well as the conversion into Ir-oxo nanoparticles and the different particle sizes have a significant influence on the overall activity. In addition to the homogeneous systems, IrO2@MCM-41 has also been synthesized, which contains stabilized nanoparticles of between 1 and 3 nm in size. This latter system shows a similar activity to IrCl3 ⋅ xH2O and complexes 4 and 5. Mechanistic insights were obtained by in situ X-ray absorption spectroscopy and scanning transmission electron microscopy. [ABSTRACT FROM AUTHOR]

A heterogeneous single‐atom catalyst (SAC) based on a tiny Cu loading (0.05 wt.%) supported on CeO2−TiO2 (Ce/Ti=0.18) shows very high Cu mass‐normalized CO oxidation activity, 100 % selectivity for CO2 between 60 and 100 °C and essentially no deactivation during 17 h on stream in the preferential oxidation of CO (PROX) at 120 °C. Based on state of the art, this catalyst is among the most active and PROX‐selective catalysts. Employing a combination of ex‐situ and operando methods, we infer that the isolated Cu single sites are incorporated with redox‐active Cu2+−O−Ce4+⇆Cu+−□−Ce3+ moieties connected by labile oxygen and are exposed on the surface of highly dispersed ceria. This high dispersion is promoted by TiO2 which itself does not participate in redox steps during PROX, as Ti ions remain essentially tetravalent while Cu and Ce undergo reversible redox shuttles. [ABSTRACT FROM AUTHOR]