Alkaline‐Earth‐Promoted CO Homologation and Reductive Catalysis

Reaction between a β‐diketiminato magnesium hydride and carbon monoxide results in the isolation of a dimeric cis‐enediolate species through the reductive coupling of two CO molecules. Under catalytic conditions with PhSiH₃, an observable magnesium formyl species may be intercepted for the mild reductive cleavage of the CO triple bond.     

Functionalized Natural Carbon‐Supported Nanoparticles as Excellent Catalysts for Hydrocarbon Production

We report a one‐pot and eco‐friendly synthesis of carbon‐supported cobalt nanoparticles, achieved by carbonization of waste biomass (rice bran) with a cobalt source. The functionalized biomass provides carbon microspheres as excellent catalyst support, forming a unique interface between hydrophobic and hydrophilic groups. The latter, involving hydroxyl and amino groups, can catch much more active cobalt nanoparticles on surface for Fischer–Tropsch synthesis than chemical carbon. The loading amount of cobalt on the final catalyst is much higher than that prepared with a chemical carbon source, such as glucose. The proposed concept of using a functionalized natural carbon source shows great potential compared with conventional carbon sources, and will be meaningful for other fields concerning carbon support, such as heterogeneous catalysis or electrochemical fields.     

Non‐Thermal Plasma Activation of Gold‐Based Catalysts for Low‐Temperature Water–Gas Shift Catalysis

Non‐thermal plasma activation has been used to enable low‐temperature water‐gas shift over a Au/CeZrO₄ catalyst. The activity obtained was comparable with that attained by heating the catalyst to 180 °C providing an opportunity for the hydrogen production to be obtained under conditions where the thermodynamic limitations are minimal. Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), structural changes associated with the gold nanoparticles in the catalyst have been observed which are not found under thermal activation indicating a weakening of the Au−CO bond and a change in the mechanism of deactivation.     

hcp‐Co Nanowires Grown on Metallic Foams as Catalysts for Fischer–Tropsch Synthesis

The Fischer–Tropsch synthesis (FTS) is a structure‐sensitive exothermic reaction that enables catalytic transformation of syngas to high quality liquid fuels. Now, monolithic cobalt‐based heterogeneous catalysts were elaborated through a wet chemistry approach that allows control over nanocrystal shape and crystallographic phase, while at the same time enables heat management. Copper and nickel foams have been employed as supports for the epitaxial growth of hcp‐Co nanowires directly from a solution containing a coordination compound of cobalt and stabilizing ligands. The Co/Cu_foam catalyst was tested for Fischer–Tropsch synthesis in a fixed‐bed reactor, showing stability and significantly superior activity and selectivity towards C5+ compared to a Co/SiO₂‐Al₂O₃ reference catalyst under the same conditions.     

One Hundred Years of the Max‐Planck‐Institut für Kohlenforschung

This Essay is an account of the institutional and scientific development of the Max‐Planck‐Institut für Kohlenforschung in Mülheim an der Ruhr (Germany), which is the successor to the Kaiser‐Wilhelm‐Institut für Kohlenforschung founded in 1914. The Essay is divided into four main parts, corresponding to the four major periods which are closely associated with the respective Directors of the Institute from 1914 to 2014: 1) Franz Fischer; 2) Karl Ziegler; 3) Günther Wilke; and 4) the period beginning with Manfred T. Reetz, who established a directorate comprising five Directors of equal status, each heading a different research department under the banner of catalysis. Along with key historical events associated with the Institute, research highlights of the four periods are featured.     

Selective Transformation of Syngas into Gasoline‐Range Hydrocarbons over Mesoporous H‐ZSM‐5‐Supported Cobalt Nanoparticles

Bifunctional Fischer–Tropsch (FT) catalysts that couple uniform‐sized Co nanoparticles for CO hydrogenation and mesoporous zeolites for hydrocracking/isomerization reactions were found to be promising for the direct production of gasoline‐range (C_5–11) hydrocarbons from syngas. The Brønsted acidity results in hydrocracking/isomerization of the heavier hydrocarbons formed on Co nanoparticles, while the mesoporosity contributes to suppressing the formation of lighter (C_1–4) hydrocarbons. The selectivity for C_5–11 hydrocarbons could reach about 70 % with a ratio of isoparaffins to n‐paraffins of approximately 2.3 over this catalyst, and the former is markedly higher than the maximum value (ca. 45 %) expected from the Anderson–Schulz–Flory distribution. By using n‐hexadecane as a model compound, it was clarified that both the acidity and mesoporosity play key roles in controlling the hydrocracking reactions and thus contribute to the improved product selectivity in FT synthesis.     

Gas‐Phase Thermodynamics as a Validation of Computational Catalysis on Surfaces: A Case Study of Fischer–Tropsch Synthesis

Density functional theory has become a valuable tool to study surface catalysis. However, due to the scarcity of clean and reliable experimental data on surfaces, the theoretical methods employed to explore heterogeneous catalytic mechanisms are usually less well validated than those for gas‐phase reactions. We argue herein that gas‐phase reactions and the corresponding surface reactions are related through the Born–Haber cycle and computational catalysis on surfaces will be less meaningful if gas‐phase behavior cannot first be suitably determined. In this contribution, we have constructed a set of gas‐phase reactions relevant to the Fischer–Tropsch synthesis as a case study. With this set, we have tested the validity of the widely used PBE and B3LYP functionals and found that neither of them are capable of describing all kinds of gas‐phase reactions properly, such that some surface reactions may be biased falsely against the others. Significantly, XYG3, which is a double‐hybrid functional that includes Hartree–Fock‐like exchange and many‐body perturbation correlation effects, presents a significant improvement for all of the gas‐phase reactions, holding promise for further development for surface catalysis.     

Capturing the Genesis of an Active Fischer–Tropsch Synthesis Catalyst with Operando X‐ray Nanospectroscopy

A state‐of‐the‐art operando spectroscopic technique is applied to Co/TiO₂ catalysts, which account for nearly half of the world's transportation fuels produced by Fischer–Tropsch catalysis. This allows determination of, at a spatial resolution of approximately 50 nm, the interdependence of formed hydrocarbon species in the inorganic catalyst. Observed trends show intra‐ and interparticular heterogeneities previously believed not to occur in particles under 200 μm. These heterogeneities are strongly dependent on changes in H₂/CO ratio, but also on changes thereby induced on the Co and Ti valence states. We have captured the genesis of an active FTS particle over its propagation to steady‐state operation, in which microgradients lead to the gradual saturation of the Co/TiO₂ catalyst surface with long chain hydrocarbons (i.e., organic film formation).     

Graphenes as Efficient Metal‐Free Fenton Catalysts

Reduced graphene oxide exhibits high activity as Fenton catalyst with HO^. radical generation efficiency over 82 % and turnover numbers of 4540 and 15023 for phenol degradation and H₂O₂ consumption, respectively. These values compare favorably with those achieved with transition metals, showing the potential of carbocatalysts for the Fenton reaction.     

IR‐Monitored Photolysis of CO‐Inhibited Nitrogenase: A Major EPR‐Silent Species with Coupled Terminal CO Ligands

Fourier transform infrared spectroscopy (FTIR) was used to observe the photolysis and recombination of a new EPR‐silent CO‐inhibited form of α‐H195Q nitrogenase from Azotobacter vinelandii. Photolysis at 4 K reveals a strong negative IR difference band at $\tilde \nu $ =1938 cm^?1, along with a weaker negative feature at 1911 cm^?1. These bands and the associated chemical species have both been assigned the label “Hi‐3”. A positive band at $\tilde \nu $ =1921 cm^?1 was assigned to the “Lo‐3” photoproduct. By using an isotopic mixture of ¹²C ¹⁶O and ¹³C ¹⁸O, we show that the Hi‐3 bands arise from coupling of two similar CO oscillators with one uncoupled frequency at approximately $\tilde \nu $ =1917 cm^?1. Although in previous studies Lo‐3 was not observed to recombine, by extending the observation range to 200–240 K, we found that recombination to Hi‐3 does indeed occur, with an activation energy of approximately 6.5 kJ mol^?1. The frequencies of the Hi‐3 bands suggest terminal CO ligation. This hypothesis was tested with DFT calculations on models with terminal CO ligands on Fe2 and Fe6 of the FeMo‐cofactor. An S=0 model with both CO ligands in exo positions predicts symmetric and asymmetric stretches at $\tilde \nu $ =1938 and 1909 cm^?1, respectively, with relative band intensities of about 3.5:1, which is in good agreement with experiment. From the observed IR intensities, Hi‐3 was found to be present at a concentration about equal to that of the EPR‐active Hi‐1 species. The relevance of Hi‐3 to the nitrogenase catalytic mechanism and its recently discovered Fischer–Tropsch chemistry is discussed.     

Selective Hydrogenation of Acrolein Over Pd Model Catalysts: Temperature and Particle‐Size Effects

The selectivity in the hydrogenation of acrolein over Fe₃O₄‐supported Pd nanoparticles has been investigated as a function of nanoparticle size in the 220–270 K temperature range. While Pd(111) shows nearly 100 % selectivity towards the desired hydrogenation of the C=O bond to produce propenol, Pd nanoparticles were found to be much less selective towards this product. In situ detection of surface species by using IR‐reflection absorption spectroscopy shows that the selectivity towards propenol critically depends on the formation of an oxopropyl spectator species. While an overlayer of oxopropyl species is effectively formed on Pd(111) turning the surface highly selective for propenol formation, this process is strongly hindered on Pd nanoparticles by acrolein decomposition resulting in CO formation. We show that the extent of acrolein decomposition can be tuned by varying the particle size and the reaction temperature. As a result, significant production of propenol is observed over 12 nm Pd nanoparticles at 250 K, while smaller (4 and 7 nm) nanoparticles did not produce propenol at any of the temperatures investigated. The possible origin of particle‐size dependence of propenol formation is discussed. This work demonstrates that the selectivity in the hydrogenation of acrolein is controlled by the relative rates of acrolein partial hydrogenation to oxopropyl surface species and of acrolein decomposition, which has significant implications for rational catalyst design.     

CO2 Hydrogenation over Oxide‐Supported PtCo Catalysts: The Role of the Oxide Support in Determining the Product Selectivity

By simply changing the oxide support, the selectivity of a metal–oxide catalysts can be tuned. For the CO₂ hydrogenation over PtCo bimetallic catalysts supported on different reducible oxides (CeO₂, ZrO₂, and TiO₂), replacing a TiO₂ support by CeO₂ or ZrO₂ selectively strengthens the binding of C,O‐bound and O‐bound species at the PtCo–oxide interface, leading to a different product selectivity. These results reveal mechanistic insights into how the catalytic performance of metal–oxide catalysts can be fine‐tuned.     

Revisiting alternative pathways in the Fischer–Tropsch process: Accurate density functional theory calculations on “magic” Ru12 clusters

Models of the Fischer–Tropsch reaction typically focus on two proposed mechanisms for the initial carbon monoxide dissociation: unassisted dissociation (carbide mechanism), and hydrogen‐assisted dissociation via an adsorbed oxymethylidene (HCO*) intermediate. Much evidence for hydrogen‐assisted dissociation comes from density functional theory calculations modeling ruthenium nanoparticle catalysts as infinite, periodic metal slabs. However, the generalized gradient approximations (GGAs) used in these calculations can make significant errors in reaction barrier heights. How these errors affect the predicted selectivity to unassisted vs. hydrogen‐assisted dissociation is not well understood. We address the problem by considering a different regime, applying GGA and beyond‐GGA approximations to CO dissociation on a “magic” nonmagnetic Ru₁₂ cluster modeling supported nanoparticle catalysts. Both approximations concur that hydrogen‐assisted dissociation is facile on this cluster, providing additional support for its potential role in real catalysts.