Aniline is a group of important platform molecules that has been widely used in the synthesis of other high-value chemicals and pharmaceutical products. How to produce high-value anilines as the high-value chemical intermediates more efficiently and environmentally has always been a research topic in the industry. Catalytic hydrogenation is an environmentally friendly method for preparing halogenated anilines. Traditional noble metal catalysts face the problems of cost and noble metals residue. To improve the purity of the product as well as the activity and recyclability of the catalyst, we prepared a Pd/Fe magnetic bimetallic catalyst supported on N-doped carbon materials to reduce nitrobenzene to aniline under mild conditions. The catalyst has a low Pd loading of 2.35%. And the prepared bimetallic Pd/Fe@N/C catalyst showed excellent catalytic reactivity with the nitrobenzene conversion rate of 99%, and the aniline selectivity of 99% under mild reaction conditions of 0.8 MPa H and 40 °C. A variety of halogenated and aliphatic nitro compounds were well tolerated and had been transformed to the corresponding target amine products with excellent selectivity. In addition, the novel N-doped graphene-encapsulated bimetallic magnetic Pd/Fe@N/C catalyst not only had magnetic physical properties, which was easy to separate, recover, and used for the recycling of the catalyst without metal leaching but also catalyzed highly selective reductive amination of aromatics was a green, economical and environmentally friendly reaction with the only by-product of HO.

Here we report some results on a 3 steps benzene caprolactam process via amination, aniline Hydroxymation and Beckmann rearrangement. The amination proceeds with hydroxylamine trifluoroacetate, with 97% of conversion and selectivity of 90%, catalyzed by V compounds. We achieve 98% of conversion and 95% of selectivity in the hydroxymation of aniline in the presence of hydroxylamine trifluoroacetate, sulfonic resin and Pd/C. While in the absence of the resin, hydrogenation of hydroxylamine trifluoroacetate occurs readily to the ammonium salt. The reaction occurs likely by the exchanged hydroxylamine and the aniline reduction intermediate. The use of hydroxylamine trifluoroacetate, instead of the chloride, favors the sustainability of the process by avoiding the ammonium chloride formation. The absence of salt except those derived from the trifluoroacetic acid allows a complete reuse of the trifluoroacetic acid and the only byproduct is ammonium nitrate obtained by resin regeneration. Beckmann rearrangement of the so produced cyclohexanone oxime occurs easily after diethyl ether evaporation and additions of a solution trifluoroacetic acid acetonitrile in high yield and selectivity.

Ambient-pressure photoelectron spectroscopy (APPES) and microscopy are at the frontier of modern chemical analysis at liquid-gas, solid-liquid and solid-gas interfaces, bridging science and engineering of functional materials. Complementing the current state-of-the art of the instruments, we survey in this short review several alternative APPES approaches, developed recently in the scanning photoelectron microscope (SPEM) at the Elettra laboratory. In particular, we report on experimental setups for dynamic near-ambient pressure environment, using pulsed-gas injection in the vicinity of samples or reaction cells with very small apertures, allowing for experiments without introducing additional differential pumping stages. The major part of the review is dedicated to the construction and performance of novel environmental cells using ultrathin electron-transparent but molecularly impermeable membranes to isolate the gas or liquid ambient from the electron detector operating in ultra-high vacuum (UHV). We demonstrate that two dimensional materials, such as graphene and derivatives, are mechanically robust to withstand atmospheric - UHV pressure differences and are sufficiently transparent for the photoelectrons emitted from samples immersed in the liquid or gaseous media. There are many unique opportunities for APPES using X-rays over a wide energy range. We show representative results that illustrate the potential of these 'ambient-pressure' approaches. Combined with the ca 100 nm lateral resolution of SPEM, they can overcome the pressure gap challenges and address the evolution of chemical composition and electronic structure at surface and interfaces under realistic operation conditions with unprecedented lateral and spectral resolution.

Proton reduction and H oxidation are key elementary reactions for solar fuel production. Hydrogenases interconvert H and H with remarkable efficiency and have therefore received much attention in this context. For [FeFe]-hydrogenases, catalysis occurs at a unique cofactor called the H-cluster. In this article, we discuss ways in which EPR spectroscopy has elucidated aspects of the bioassembly of the H-cluster, with a focus on four case studies: EPR spectroscopic identification of a radical to the CO and CN ligands of the H-cluster, tracing Fe from the maturase HydG into the H-cluster, characterization of the auxiliary Fe-S cluster in HydG, and isotopic labeling of the CN ligands of HydA for electronic structure studies of its H state. Advances in cell-free maturation protocols have enabled several of these mechanistic studies, and understanding H-cluster maturation may in turn provide insights leading to improvements in hydrogenase production for biotechnological applications.

Periodic and molecular density functional theory calculations have been applied to elucidate the associative mechanism for hydrazine and ammonia synthesis in the gas phase and hydrazine formation on CoMoN. We find that there are two activation barriers for the associative gas phase mechanism with barriers of 730 and 658 kJ/mol, corresponding to a hydrogenation step from N to NNH and HNNH to HNNH, respectively. The second step of the mechanism is barrierless and an important intermediate, NNH, can also readily form on CoMoN surfaces via the Eley-Rideal chemisorption of H on a pre-adsorbed N at nitrogen vacancies. Based on this intermediate a new heterogeneous mechanism for hydrazine synthesis is studied. The highest relative barrier for this heterogeneous catalysed process is 213 kJ/mol for CoMoN containing nitrogen vacancies, clearly pointing towards a low-energy process for the synthesis of hydrazine via a heterogeneous catalysis route.

The catalytic (Pd/AlO and Pd/C; mean Pd size 2.5-3.0 nm from (S)TEM analysis) synthesis of di-butylamine (DBA) and tri-butylamine (TBA) from mono-butylamine (MBA) and DBA, respectively, in continuous gas phase operation is demonstrated. Exclusive production of DBA (from MBA) has been established over both catalysts where 453 ≤  ≤ 523 K (∆E = 79 kJ mol). Greater activity for Pd/C is associated with higher levels of surface acidity (from NH chemisorption/TPD) and spillover hydrogen (from H TPD). Reaction of DBA over both catalysts when configured in series delivered full selectivity to TBA. Our results establish a novel clean alternative route for the continuous production of higher (secondary and tertiary) amines.

The catalytic behaviour of CoMoC, CoMoC, CoMoN and CoMoN for methane cracking has been studied to determine the relationship between the methane cracking activity and the chemical composition. The characterisation of post-reaction samples showed a complex phase composition with the presence of CoMoC, α-Co and β-MoC as catalytic phases and the deposition of different forms of carbon during reaction.

We have examined the role of support oxygen vacancies in the gas phase hydrogenation of furfural over Au/TiO and Au/CeO prepared by deposition-precipitation. Both catalysts exhibited a similar Au particle size distribution (1-6 nm) and mean (2.8-3.2 nm). Excess H consumption during TPR is indicative of partial support reduction, which was confirmed by O titration. Gold on CeO with a higher redox potential exhibited a greater oxygen vacancy density. A lower furfural turnover frequency () was recorded over Au/CeO than Au/TiO and is linked to suppressed H chemisorption capacity and strong -C=O interaction at oxygen vacancies that inhibited activity. Gold on non-reducible AlO as benchmark exhibited greater H uptake and delivered the highest furfural . Full selectivity to the target furfuryl alcohol was achieved over Au/TiO and Au/AlO at 413 K and over Au/CeO at 473 K with hydrogenolysis to 2-methylfuran at higher reaction temperature (523 K). A surface reaction mechanism is proposed to account for the activity/selectivity response.

Surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) were until recently limited in their applicability to the majority of heterogeneous catalytic reactions. Recent developments begin to resolve the conflicting experimental requirements for SERS and TERS on the one hand, and heterogeneous catalysis on the other hand. This article discusses the development and use of SERS and TERS to study heterogeneous catalytic reactions, and the exciting possibilities that may now be within reach thanks to the latest technical developments. This will be illustrated with showcase examples from photo- and electrocatalysis.

The catalytic H oxidation reaction on stepped Rh surfaces in the 10 mbar pressure range was studied in situ on individual high-Miller-index domains of a polycrystalline Rh foil by PEEM (photoemission electron microscopy) and on a Rh nanotip by FIM/FEM (field-ion/field-emission microscopy). The activity, particularly the tolerance to poisoning by oxygen, was found to strongly depend on the density of steps and defects, as well as on the size of the catalytically active surfaces.

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In this work, a new viral protein cage based nanoreactor was successfully constructed via encapsulating Tween 80 stabilized palladium nanoparticles (NPs) into rotavirus capsid VP2 virus-like particles (i.e. Pd@VP2). The effects of stabilizers including CTAB, SDS, Tween 80 and PVP on controlling the particle size of Pd NPs were investigated. They were further immobilized on graphene oxide (i.e. Pd@VP2/GO) by a simple mixing method. Some characterizations including FT-IR and XPS were conducted to study adsorption mode of Pd@VP2 on GO sheets. Their catalytic performance was estimated in the reduction of 4-nitrophenol (4-NP). Results showed that Tween 80 stabilized Pd NPs with the molar ratio of Pd to Tween 80 at 1:0.1 possessed the smallest size and the best stability as well. They were encapsulated into viral protein cages (mean size 49 ± 0.26 nm) to assemble confined nanoreactors, most of which contained 1-2 Pd NPs (mean size 8.15 ± 0.26 nm). As-prepared Pd@VP2 indicated an enhanced activity (apparent reaction rate constant  = (3.74 ± 0.10) × 10 s) for the reduction of 4-NP in comparison to non-confined Pd-Tween80 colloid (  = (2.20 ± 0.06) × 10 s). It was logically due to confinement effects of Pd@VP2 including high dispersion of Pd NPs and high effective concentration of substrates in confined space. Pd@VP2 were further immobilized on GO surface through C-N bond. Pd@VP2/GO exhibited good reusability after recycling for four runs, confirming the strong anchoring effects of GO on Pd@VP2.

Alkylbenzenes have a wide range of uses and are the most demanded aromatic chemicals. The finite petroleum resources compels the development of production of alkylbenzenes by non-petroleum routes. One-pass selective conversion of benzene and syngas to alkylbenzenes is a promising alternative coal chemical engineering route, yet it still faces challenge to industrialized applications owing to low conversion of benzene and syngas. Here we presented a Cu-ZnO-AlO/ZSM-5 bifunctional catalyst which realizes one-pass conversion of benzene and syngas to alkylbenzenes with high efficiency. This bifunctional catalyst exhibited high benzene conversion (benzene conversion of 50.7%), CO conversion (CO conversion of 55.0%) and C7&C8 aromatics total yield (C7&C8 total yield of 45.0%). Characterizations and catalytic performance evaluations revealed that ZSM-5 with well-regulated acidity, as a vital part of this Cu-ZnO-AlO/ZSM-5 bifunctional catalyst, substantially contributed to its performance for the alkylbenzenes one-pass synthesis from benzene and syngas due to depress methanol-to-olefins (MTO) reaction. Furthermore, matching of the mass ratio of two active components in the dual-function catalyst and the temperature of methanol synthesis with benzene alkylation reactions can effectively depress the formation of unwanted by-products and guarantee the high performance of tandem reactions.

In this work, macroscopic TiO monoliths are proposed to serve simultaneously as support and co-catalyst in a continuous flow photoreactor. The impregnation via one-pot of mesoporous TiO with CdS (m-TiO/CdS) and CuO (m-TiO/CuO) nanoparticles enabled the formation of photocatalytic heterojunctions retaining high specific surface area (~ 100 m/g). The impregnated monoliths of 2-3 mm in size were employed as photocatalysts to inactivate airborne bacteria under blue light, reducing the emission of living airborne bacteria up to 0.1% and 37.7% when using m-TiO/CdS and m-TiO/CuO, respectively. Bacteria were characterized and quantified by flow cytometry and cell lysis was confirmed by SEM, detecting collapsed bacteria. Along 96 h of continuous photocatalysis at a flow rate of 2.2 L/min, the cell concentration presented maxima and minima due to the adsorption-desorption stages of bioaerosols over the catalysts, in concordance with thermal gravimetric analysis. The reactivation of catalysts was achieved by calcination at 400 °C, however, after a third re-cycle, the photocatalytic activity for all monoliths was practically negligible because the physicochemical surface changes hinder the adequate bioaerosol adsorption. These porous systems could emerge as promising gas-phase catalysts since the mass transport is facilitated by porosity and the release of catalyst nanoparticles is avoided by the active support, providing a safe and viable model for bioaerosols inactivation to improve indoor air quality with the use of interior lighting.

A surface science based approach was applied to model carbon supported Pd nanoparticle catalysts. Employing physical vapour deposition of Pd on sputtered surfaces of highly oriented pyrolytic graphite (HOPG), model catalysts were prepared that are well-suited for characterization by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Analysis of the HOPG substrate before and after ion-bombardment, and of Pd/HOPG before and after annealing, revealed the number of "nominal" HOPG defects (~ 10 cm) as well as the nucleation density (~ 10 cm) and structural characteristics of the Pd nanoparticles (mean size/height/distribution). Two model systems were stabilized by UHV annealing to 300 °C, with mean Pd particles sizes of 4.3 and 6.8 nm and size/height aspect ratio up to ~ 10. A UHV-compatible flow microreactor and gas chromatography were used to determine the catalytic performance of Pd/HOPG in ethylene (CH) hydrogenation up to 150 °C under atmospheric pressure, yielding temperature-dependent conversion values, turnover frequencies (TOFs) and activation energies. The performance of Pd nanocatalysts is compared to that of polycrystalline Pd foil and contrasted to Pt/HOPG and Pt foil, pointing to a beneficial effect of the metal/carbon phase boundary, reflected by up to 10 kJ mol lower activation energies for supported nanoparticles.

Inelastic neutron scattering (INS) is used to investigate a ZSM-5 catalyst that has been exposed to methanol vapour at elevated temperature. In-line mass spectrometric analysis of the catalyst exit stream confirms methanol-to-gasoline chemistry, whilst ex situ INS measurements detect hydrocarbon species formed in/on the catalyst during methanol conversion. These preliminary studies demonstrate the capability of INS to complement infrared spectroscopic characterisation of the hydrocarbon pool present in/on ZSM-5 during the MTG reaction.

To focus on the influence of the intermetallic compound-oxide interface of Pd-based intermetallic phases in methanol steam reforming (MSR), a co-precipitation pathway has been followed to prepare and subsequently structurally and catalytically characterize a set of nanoparticulate GaO- and InO-supported GaPd and InPd catalysts, respectively. To study the possible promoting effect of InO, an InO-doped GaO-supported GaPd catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the GaO support is strikingly different: rhombohedral and spinel-like GaO phases, as well as hexagonal GaInO and rhombohedral InO phases are observed locally on the materials prior to methanol steam reforming by high-resolution transmission electron microscopy. Overall, the structure, phase composition and morphology of the co-precipitated catalysts are much more complex as compared to the respective impregnated counterparts. However, this induces a beneficial effect in activity and CO selectivity in MSR. Both GaO and InO catalysts show a much higher activity, and in the case of GaPd-GaO, a much higher CO selectivity. The promoting effect of InO is also directly detectable, as the CO selectivity of the co-precipitated supported GaO-InO catalyst is much higher and comparable to the purely InO-supported material, despite the more complex structure and morphology. In all studied cases, no deactivation effects have been observed even after prolonged time-on-stream for 12 h, confirming the stability of the systems.

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The versatility of MOFs as highly porous Lewis acidic supports for precious metal nanoparticles has been exploited for one-pot tandem reductive amination catalysis. MIL-101(Cr) loaded with Pd nanoparticles ca. 3 nm in size at 0.2-1 wt% has been used to catalyse the reaction of 4'-fluoroacetophenone with benzylamine under 10 bar of H to give the secondary amine, 4'-fluoro-α-methyl--phenylmethylbenzenemethanamine. For the highest Pd loading, major hydrogenolysis of the secondary amine occurs in a second tandem reaction, but by changing the ratio of Pd to Lewis acidic Cr active sites it is possible to tune the catalytic selectivity to the desired 2° amine product. An empirical kinetic analysis was performed to demonstrate this active site complementarity.

CeO was synthesized by combined sol-gel and solvothermal processing of gels obtained from acetaldoximate-modified cerium(IV) -butoxide in the presence of the non-ionic surfactant Pluronic F127. The use of cerium(IV) -butoxide as precursor contrasts very favorably with the often used ceric ammonium nitrate and results in more reliable and tailorable properties of the final materials. The kind of post-synthesis treatment of the gels and the composition of the precursor mixture proved to be crucial for obtaining high surface area ceria with a high Ce proportion. Calcination in air or under nitrogen was compared with solvothermal treatment in ethanol or water and a combination of solvothermal treatment and calcination. The obtained materials are composed of 3.5-5.5 nm ceria nanoparticles. The highest specific surface area of 277 m/g was obtained after solvothermal treatment, and 180 m/g when solvothermal treatment was followed by calcination in air to remove residual organic groups. The highest Ce proportion was 18 % after solvothermal treatment in ethanol and additional calcination in air. CO oxidation on selected samples indicated that activity scaled with surface area and thus was largest for samples solvothermally treated in ethanol. The reaction rate of the best sample was about 75-times larger than that of commercial ceria.

In this article we shed light on newly emerging perspectives to characterize and understand the interplay of diffusive mass transport and surface catalytic processes in pores of gas phase metal catalysts. As a case study, nanoporous gold, as an interesting example exhibiting a well-defined pore structure and a high activity for total and partial oxidation reactions is considered. PFG NMR (pulsed field gradient nuclear magnetic resonance) measurements allowed here for a quantitative evaluation of gas diffusivities within the material. STEM (scanning transmission electron microscopy) tomography furthermore provided additional insight into the structural details of the pore system, helping to judge which of its features are most decisive for slowing down mass transport. Based on the quantitative knowledge about the diffusion coefficients inside a porous catalyst, it becomes possible to disentangle mass transport contributions form the measured reaction kinetics and to determine the kinetic rate constant of the underlying catalytic surface reaction. In addition, predictions can be made for an improved effectiveness of the catalyst, i.e., optimized conversion rates. This approach will be discussed at the example of low-temperature CO oxidation, efficiently catalysed by npAu at 30 °C. The case study shall reveal that novel porous materials exhibiting well-defined micro- and mesoscopic features and sufficient catalytic activity, in combination with modern techniques to evaluate diffusive transport, offer interesting new opportunities for an integral understanding of catalytic processes.