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Improving the selectivity in the oxidative coupling of methane to ethane/ethylene poses a significant challenge for commercialization. The required improvements are hampered by the uncertainties associated with the reaction mechanism due to its complexity. Herein, we report about 90 % selectivity to the target products at 11 % methane conversion over Gd2O3‐based catalysts at 700 °C using N2O as the oxidant. Sophisticated kinetic studies have suggested the nature of adsorbed oxygen species and their binding strength as key parameters for undesired methane oxidation to carbon oxides. These descriptors can be controlled by a metal oxide promoter for Gd2O3. [ABSTRACT FROM AUTHOR]

A setup for dispersive X-ray absorption spectroscopy (XAS) with spatial, temporal and energy resolution is presented. Through investigation of a Mo/HZSM-5 catalyst during the dehydroaromatization of methane we observed a reduction gradient along the packed bed. Our new method represents an unprecedented addition to the analytical toolbox for in situ characterizations. [ABSTRACT FROM AUTHOR]

Correction for 'Time-, space- and energy-resolved in situ characterization of catalysts by X-ray absorption spectroscopy' by Stefan Peters et al., Chem. Commun., 2023, 59, 12120–12123, https://doi.org/10.1039/D3CC03277A. [ABSTRACT FROM AUTHOR]

The synthesis of vitamin precursors via alkyne semi-hydrogenation has been achieved with a lead- and palladium-free catalyst. Cobalt nanoparticles modified by nitrogen doped carbon and supported on silica allow the production of a range of fine chemicals and vitamin precursors. The optimal catalyst could be conveniently recycled and used for at least five runs with consistent activity. Interestingly, this material selectively hydrogenates alkynes in the presence of easily reducible, cyano-, keto-, aldehyde-, and even nitro groups, which shows it to be a versatile catalyst for synthetic organic chemistry. [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]

[Display omitted] • A series of Fe-based catalysts differing in surface Na/Fe ratio were prepared. • The critical role of Na is beyond its promotional effects under stationary operation. • Surface Na/Fe ratio determines the response of performance to fluctuating conditions. • Catalyst dynamics induced by fluctuating reaction conditions were studied. • The effect of Na in securing iron carbides was studied by in situ characterization. Considering the on-going developments of approaches for CO 2 capture, storage, and utilization, CO 2 hydrogenation with renewable H 2 can become sustainable technology to produce value-added chemicals/fuels in future feedstock scenarios. Herein, we investigate temporal behaviors of Fe-based catalysts in CO 2 hydrogenation under externally forced dynamics of reactor operation from the respective of composition and performance. Different catalyst preparation methods were applied to modulate the surface concentration of Na promoter but keeping the bulk concentration constant. The crucial promoter role in reserving catalyst performance and (un)steady-state catalyst composition during dynamic reactor operation was investigated by means of sophisticated catalytic tests combined with in situ and ex situ catalyst characterizations. The surface Na/Fe ratio of spent catalysts was identified as the decisive descriptor for production of the desired products under dynamic CO 2 hydrogenation conditions. The derived knowledge could be useful for redesigning catalysts and optimizing reaction processes when employing fluctuating energy supply. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co/ZrO 2 catalysts with single Co2+ are efficient for C 3 H 8 dehydrogenation to C 3 H 6. • 1Co/ZrO 2 performed durable over multiple dehydrogenation/regeneration cycles. • 1Co/ZrO 2 showed higher activity than a commercial analogue of K-CrO x /Al 2 O 3. • The high activity results from a synergy effect between Co2+ and Zr cus. • Recombination of surface H species is the rate-limiting step in C 3 H 6 formation. Due to the increased production of shale gas containing propane, the share of non-oxidative propane dehydrogenation (PDH) in the large-scale production of propene is expected to continue to grow. There are, however, some ecofriendly and cost shortcomings associated with the currently applied Cr- or Pt-containing catalysts. Against this background, we present here Co/ZrO 2 alternatives and reveal the fundamentals affecting their activity, which can be used for purposeful catalyst design. Co2+ species homogeneously distributed within the lattice of ZrO 2 significantly increase the activity of coordinatively unsaturated Zr4+ for the PDH reaction. The increase is caused by accelerating both the cleavage of CH bonds in propane and the recombination of surface H species, with the latter reaction being the rate-limiting step. The best-performing catalyst outperformed an analogue of commercial K-CrO x /Al 2 O 3 in terms of the rate of propene formation and demonstrated durable performance over a series of 10 PDH/regeneration cycles under industrially relevant conditions. It also outperformed most previously developed Co-containing catalysts in terms of propene productivity. The space–time yield of propene formation achieved at 57 % equilibrium propane conversion at 550 °C was 0.71 kg·h−1·kg cat -1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metallic Co0 species in situ formed are suggested to be the main active sites for PDH. • CoO x but not Co0 is responsible for the formation of undesired products. • Transformation of CoO x to Co0 depends on the strength of CoO x -support interactions. • Co/Silicalite-1 showed the C 3 H 6 space time yield of 1.50 kg·h−1·kg cat −1 at 550 °C. Although Co-containing catalysts show attractive performance in the non-oxidative propane dehydrogenation to propylene (PDH), their tailored development is hindered by the ambiguity in the kind of active sites (Co0 or Co2+O x) responsible for selective and unselective pathways. Herein, we demonstrate that supported CoO x species expends its lattice oxygen through oxidation of C 3 H 8 to CO 2 /C 3 H 6 and are accordingly transformed into Co0 species. The latter are decisive for the selective dehydrogenation of propane to propylene with high activity. The ability of CoO x to in situ form Co0 is affected by metal-oxide-support interactions (MOSI). In addition to the kind of support, defective OH groups (OH nests) in ZSM-5-type zeolites seem to be relevant for the MOSI effect. In comparison with previous studies highlighting the importance of the size of CoO x species and their acidity for coke formation, we could not establish any direct correlation. Nevertheless, the presence of CoO x seems to be relevant for this undesired reaction because the formation of coke is hindered when CoO x species are transformed to Co0 species. Catalyst acidic sites are responsible for cracking reactions. Thus, the derived mechanistic insights reveal the nature of active sites both for selective and unselective pathways and provide fundamentals for catalyst development. From an industrial viewpoint, the developed Co/Silicalite-1 (Co/S-1) catalyst with the weakest MOSI and accordingly highest fraction of Co0 showed the space time yield of propylene formation of 1.50 kg·h−1·kg cat −1 at 67 % equilibrium propane conversion and propylene selectivity of 95.3 % and the Co-related TOF value of 0.145 s−1 at 550 °C. These both activity values exceed those of the state-of-the-art Co-containing catalysts. The productivity of Co/S-1 is comparable or even higher than that of industrially relevant Pt- or Cr-containing catalysts. [ABSTRACT FROM AUTHOR]

Gold-based catalysts have shown high catalytic activity for reverse water gas shift (RWGS) reactions at low temperatures. Despite extensive studies, the RWGS reaction on Au-based catalysts with very low Au content (< 0.1 wt%) has not yet been investigated. In this study, TiO 2 and ZrO 2 supported gold catalysts with such low gold loading have been synthesized and tested for RWGS. The catalysts were investigated by a series of in/ex-situ characterization techniques, including ICP-OES, XRD, BET, XPS, STEM, STEM-EELS, TAP, in-situ DRIFTS and in-situ EPR. At 250 oC, the Au/TiO 2 catalyst showed almost 10 times higher activity than Au/ZrO 2. In-situ DRIFTS results suggest that the formate mechanism is the predominant mechanism over Au/ZrO 2 , while over Au/TiO 2 the reaction proceeds via the formation of hydroxycarbonyl intermediates. A combined study including STEM, STEM-EELS, XPS, and in-situ EPR suggests that the interfacial Au–O v –Ti3+ sites are responsible for the superior activity of Au/TiO 2. [Display omitted] • Au/TiO 2 exhibited superior activity and CO selectivity. • Ti3+formation and oxygen vacancies on Au/TiO 2 contribute to its superior activity. • The weak adsorption strength of CO is responsible for the superior CO selectivity. • An Oxygen-vacancies-engaged reaction mechanism is proposed for RWGS over Au/ZrO 2. • The decomposition of formate seems to be the rate-limiting step in the CO formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gd, La and Sc improve stability of low Ni content Al 2 O 3 -MgO catalysts in DRM. • Rare earth elements stabilize Ni dispersion and promote CO 2 activation. • Gd sufficiently establishes both effects. • Outstanding stability in excess methane (CH 4 /CO 2 = 2) at 630 and 750 °C. • Successful exceptional long-term tests over 100 h at high space velocity. Biogas consists of a larger part of methane and a smaller part of carbon dioxide. Reforming biogas is highly desirable due to the direct conversion of the two components, yet not possible due to the current state of catalyst development. For such dry reforming of methane-rich gases (CH 4 /CO 2 = 2) we now present catalysts with low Ni loading (2.5 wt%) modified with Gd, Sc, or La. The best catalyst reaches 49% CH 4 conversion and 95% CO 2 conversion at 750 °C. The La-modification only shows limited influence on coking and protection against catalyst deactivation although this catalyst exposed highest basicity. On the other side, Sc- and especially Gd-modified catalysts exposed stronger metal-support interaction and thus enhanced stabilization of fine Ni particles during the reaction, which is critical to preserve high performance in CH 4 -rich DRM. This suppressed carbon deposition and the growth of structured carbon as evidenced by STEM images and TPO of spent catalysts. In this way, exceptionally high specific H 2 productivity (94 l/(g cat ·h)) compared to literature was obtained on Gd-modified catalyst, and, most noteworthy, after extending the time on stream from 8 to 100 h the amount of deposited coke increased only from 3 to 4 wt%. [ABSTRACT FROM AUTHOR]

• Rh supported large pore Zr-MOFs with different pore structure were prepared and characterized. • The catalysts show markedly different catalytic effects in the hydroformylation reaction with different framework types. • All catalysts show superior activity at low rh content as expected from rh single site catalysts. • A markedly impact of the pore structure on selectivity to aldehydes and enones is observed. • Catalytic differences are due to different accessibility of rh located in various framework sites. Three large pore crystalline zirconium-based metal-organic frameworks (Zr-MOFs) of different pore sizes (6–18 Å) and structure were synthesized and used for the preparation of the Rh-supported catalysts Rh@UiO-66, Rh@UiO-67, and Rh@MOF-808. The materials were characterized by XRD, FTIR, SEM/TEM, XPS, and nitrogen adsorption/desorption measurements. The catalytic performance was studied in the hydroformylation of olefins to the corresponding aldehydes. A series of n-alk-1-enes of different chain length was used to study the influence of the pore size and structure. The results show that the Zr-MOF-based catalysts are very active and show high aldehyde selectivity. The superior catalytic properties are assigned to the presence of highly dispersed active Rh sites located at the isolated zirconia moieties and the enhanced accessibility of sites via the large pores. Nevertheless, marked differences in the catalytic performance of the catalysts are observed, which are assigned to the different accessibility of Rh located at various secondary building units. [Display omitted] [ABSTRACT FROM AUTHOR]