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Simultaneous reduction of N2O in the presence of co-existing oxidants, especially NO, from industrial plants, is a challenging task. This study explores the applications of a hydrocarbon reduced Rh/Zr stabilized La doped ceria (Rh/CLZ) catalyst in N2O abatement from oxidant rich industrial exhaust streams e.g. NO, CO2, and O2. The reaction mechanism was studied by the temporal analysis of products. The obtained results revealed that hydrocarbon pretreatment led to the creation of ceria oxygen vacancies and the formation of carbon deposits on the Rh/CLZ catalyst surface. These ceria oxygen vacancies are the active sites for the selective reduction of N2O into N2, while the dissociated O atoms from N2O fill the ceria oxygen vacancies. The oxidation of the deposited carbon via the lattice ceria oxygen generates new ceria oxygen vacancies, thereby extending the catalytic cycle. The reduction of N2O over C3H6 reduced Rh/CLZ is a process combining oxygen vacancy healing and deposited carbon oxidation. The results obtained from fixed-bed reactor experiments demonstrated that the hydrocarbon reduced Rh/CLZ catalyst provided a unique and extraordinary N2O abatement performance in the presence of co-existing competing oxidants (reactivity order: N2O ∼ NO > O2 > CO2 ∼ H2O).

Abstract Mn and Li promoted Rh catalysts supported on SiO2 with a thin TiO2 layer were synthesized by stepwise incipient wetness impregnation approach. The thin TiO2 layer on the surface of SiO2 was proved to stabilize those small Rh nanoparticles and hinder their agglomeration. The reducibility of Rh on these catalysts depends on Rh particle size as well as the position of manganese oxide, and large Rh nanoparticles with MnO on Rh nanoparticles can be only reduced at an elevated temperature. Catalyst with large Rh particles exhibits a higher CO conversion and higher products selectivity towards long chain hydrocarbons and C2-oxygenates at the expense of decreasing methane formation than a similar catalyst with smaller Rh particles. This was attributed to the synergistic effect of Mn and Li promotion and molar ratio between Rh0 and Rhδ+ sites on the surface of Rh nanoparticles. Moreover, Rh nanoparticles on MnO are proved to be more efficient in promoting hydrogenation of acetaldehyde to ethanol than its counterpart with MnO on Rh nanoparticles. Finally, in order to target high C2-oxygenates selectivity, low reaction temperature together with a low H2/CO ratio in the feed is recommended. Graphic Abstract

In this study, the role of the noble metals Pt and Rh (0.5 wt.%) for the selective reduction of NO into N2 is evaluated by the transient TAP technique and in-situ spectroscopy using a commercial stable ceria support (denoted as CZ) and applying isotopically labelled 15NO and 18O2. The transient operation was mimicked by multi-pulse oxidation (using O2 or NO) and reduction cycles (using CO, H2, C3H6 and C3H8), while following quantitatively the catalyst and reactants response. Pt and Rh significantly lowered the temperature of CZ reduction. CO and H2 only reduce the surface of CZ, while a 2.5 times deeper reduction was achieved by the hydrocarbons C3H6 and C3H8, removing also lattice oxygen. Pt and Rh also promoted carbon deposition after surface reduction. Rh was a more active promoter than Pt, while propene was more reactive than propane over both metals. During the NO reduction the pre-reduced CZ support became gradually re-oxidised and after filling 70–80% of the oxygen vacancies the NO started to appear in the product mixture. In the presence of carbon deposits the lattice oxygen of the CZ reacted with the carbon keeping the CZ in a reduced state, extending the NO decomposition process as long as the carbon was present. The reduction of NO over pre-reduced noble metal/CZ showed a selective formation N2, while N2O and NO2 were never observed. During the NO reduction process some unidentified N-species remained on the catalyst, the amount depending on the type of catalyst, but finally all nitrogen was released as N2. The presence of the noble metal led less unidentified N-species on the CZ surface and to a faster N2 formation rate than that over the bare CZ.

Background Inhalation of particulate matter, as part of air pollution, is associated with increased morbidity and mortality. Nanoparticles (< 100 nm) are likely candidates for triggering inflammatory responses and activation of coagulation pathways because of their ability to enter lung cells and pass bronchial mucosa. We tested the hypothesis that bronchial segmental instillation of carbon nanoparticles causes inflammation and activation of coagulation pathways in healthy humans in vivo. Methods This was an investigator-initiated, randomized controlled, dose-escalation study in 26 healthy males. Participants received saline (control) in one lung segment and saline (placebo) or carbon nanoparticles 10 μg, 50 μg, or 100 μg in the contra-lateral lung. Six hours later, blood and bronchoalveolar lavage fluid (BALF) was collected for inflammation and coagulation parameters. Results There was a significant dose-dependent increase in blood neutrophils (p = 0.046) after challenge with carbon nanoparticles. The individual top-dose of 100 μg showed a significant (p = 0.05) increase in terms of percentage neutrophils in blood as compared to placebo. Conclusions This study shows a dose-dependent effect of bronchial segmental challenge with carbon nanoparticles on circulating neutrophils of healthy volunteers. This suggests that nanoparticles in the respiratory tract induce systemic inflammation. Trial registration Dutch Trial Register no. 2976. 11 July 2011. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2976 Electronic supplementary material The online version of this article (10.1186/s12890-017-0463-x) contains supplementary material, which is available to authorized users.

The recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO2 to formate/formic acid, methanol, and dimethyl ether are thoroughly reviewed, with special emphasis on thermodynamics and catalyst design considerations. After introducing the main motivation for the development of such processes, we first summarize the most important aspects of CO2 capture and green routes to produce H2. Once the scene in terms of feedstocks is introduced, we carefully summarize the state of the art in the development of heterogeneous catalysts for these important hydrogenation reactions. Finally, in an attempt to give an order of magnitude regarding CO2 valorization, we critically assess economical aspects of the production of methanol and DME and outline future research and development directions.

A series of Fe-Ti mixed oxide model catalysts containing different Ti/Fe ratios were synthesized and applied as catalysts for the High Temperature Fischer-Tropsch reaction (HTFTS). XRD, H2-TPR and in situ Mossbauer and XAFS spectroscopy were applied to evaluate the role of Ti on the physical and chemical properties of Fe within the mixed metal oxide. It was observed that the Ti/Fe ratio determines the relative amounts of hematite, pseudobrookite, and anatase in the starting materials. The interplay between these phases is responsible for the HTFTS catalytic performance. Our results demonstrate that the presence of pseudobrookite: i) enhances the dispersion of iron; ii) mediates and controls the reduction and carburization degree during the transformation of Fe (III) species to carbides upon activation, and iii) increases the stability under HTFTS conditions by minimizing the re-oxidation of iron carbides. Highest catalytic activity and stability is achieved for the material with Ti/Fe ratio of 1/2.1.

[EN] Isomerisation of allylic alcohols to saturated ketones can be efficiently catalysed by a heterogeneous molecular system resulting from (IrCp)-Cp-III* anchoring to a covalent triazine framework. The obtained catalysts are active, selective, and fully recyclable., Financial support from the Generalitat Valenciana (projects Consolider-Ingenio MULTICAT and AICO/2015/065), the Spanish Ministry of Economy and Competitiveness (MINECO) (program Severo Ochoa SEV20120267), and the Spanish Ministry of Science and Innovation (MICINN) (project MAT2014-52085-C2-1-P) are gratefully acknowledged. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 641887 (project acronym: DEFNET). Also, financial support from the European Union Seventh Framework Programme (FP7/2007-2013) under the grant agreement number 309701, project Eco2CO2 is acknowledged.

The use of two different classes of covalent organic frameworks (covalent triazine and imine linked frameworks) as supports for molecular Ni2+ catalysts is presented. For COFs, a large concentration of N heteroatoms, either in the form of quasi bipyridine or as diiminopyridine moieties, allows for the coordination of NiBr2 to the scaffold of the porous polymers. When applied as catalysts in the oligomerization of ethylene under mild reaction conditions (15 bar, 50 °C), these new catalysts display an activity comparable to those of their homogeneous counterpart and a fivefold higher selectivity to C6 + olefins. Accumulation of long chain hydrocarbons within the porosity of the COFs leads to reversible deactivation. Full activity and selectivity of the best catalysts can be recovered upon washing with dichlorobenzene.

A membrane reactor containing an immobilized heterogeneous catalyst is an alternative for traditional homogeneous-based catalyzed transesterification for biodiesel production. Major problems in homogeneous catalysis are related to catalyst recuperation and soap formation, which can be overcome by using heterogeneous catalysts. Conversion can be increased by a combination of reaction and separation, using membranes with a specific pore size. The aim of this work was to study the performance of different membrane reactors combined with heterogeneous catalysis. The main objectives were: to identify a proper catalyst, to choose the proper immobilization technique, to establish the membrane with the adequate pore size, and to control the reaction and separation process. Amberlyst®15 with acid sites and different types of strontium oxide with basic sites were tested as heterogeneous catalysts. Strontium oxide provided the highest sunflower oil conversion (around 93%) and was easy to immobilize. Two catalytic membrane reactor configurations were investigated, thus confirming the production of several types of methyl esters. The configuration comprising the physical immobilization of the catalyst over the membrane reached a methyl ester yield of > 90 wt%.

Huge efforts have been done in the last years on electrochemical and photoelectrochemical reduction of CO 2 to offer a sustainable route to recycle CO 2 . A promising route is to electrochemically reduce CO 2 into CO which, by combination with hydrogen, can be used as a feedstock to different added-value products or fuels. Herein, perpendicular oriented TiO 2 nanotubes (NTs) on the electrode plate were grown by anodic oxidation of titanium substrate and then decorated by a low loading of silver nanoparticles deposited by sputtering (i.e. Ag/TiO 2 NTs). Due to their quasi one-dimensional arrangement, TiO 2 NTs are able to provide higher surface area for Ag adhesion and superior electron transport properties than other Ti substrates (e.g. Ti foil and TiO 2 nanoparticles), as confirmed by electrochemical (CV, EIS, electrochemical active surface area) and chemical/morphological analysis (FESEM, TEM, EDS). These characteristics together with the role of the TiO 2 NTs to enhance the stability of CO 2 ·- intermediate formed due to titania redox couple (Ti IV /Ti III ) lead to an improvement of the CO production in the Ag/TiO 2 NTs electrodes. Particular attention has been devoted to reduce the loading of noble metal in the electrode(14.5 %w/%w) and to increase the catalysts active surface area in order to decrease the required overpotential.

We describe the co-current flow pattern of gas and liquid through micro-fabricated beds of solid and pillars under variable (i) capillary number, (ii) contact angle or wettability and (iii) pillar arrangement, i.e. modifying the distance between pillars or their size and comparing regular with more chaotic systems. Laser-induced fluorescent microscopy and image analysis are used to study the hydrodynamic interactions in terms of dynamics, liquid hold-up, and gas-liquid interfacial area per reactor volume. Those parameters provide insights into the multiphase flow patterns in these systems, how to control them, maximize mass transfer rate and unlock the potential of microreactors to reveal further intrinsic information.

Sulfur addition is used to probe the role of gold in Au/Fe2O3/ZrO2 catalyst in the water-gas shift (WGS) at high temperature (623-773 K) and pressure (21 bar). Sulfur poisoning unravels the WGS activity contribution by gold nano-particles and gold promotion of iron oxide in Au/Fe2O3/ZrO2. The active site(s) on gold nano-particles are poisoned by sulfur, which is reflected in a suppressed WGS activity of presulfided Au/ZrO2. The same holds for the WGS activity contribution of gold nano-particles in Au/Fe2O3/ZrO2, but the promotion by gold of the Fe2O3 is still present after presulfidation. The WGS performance of Fe2O3/ZrO2 and Au/ZrO2 catalysts with and without sulfur pretreatment are also compared with that of Au/Fe2O3/ZrO2.

A new series of electrocatalysts consisting of Ag nanoparticles supported on graphitic carbon nitride (g-C3N4) are presented. The combination of nanostructured silver and a carbon nitride support results in the direct generation of synthesis gas (CO+H2) during the electrocatalytic reduction of CO2 in water. By using a state-of-the-art electrocatalytic setup, the influence of different operation parameters over the final product composition is shown. The H2/CO product ratio can easily be tuned from 100:1 to 2:1 with high reproducibility by controlling the applied potential and the Ag loading. More importantly, long-term and catalyst reuse experiments demonstrate the robustness of these electrodes, which could be operated for over 20 h time on stream and reused several times without any evident loss of activity or selectivity. Our results highlight the potential of nanostructuring Ag-based catalysts and the relevance of the selected support for the green valorization of CO2.

In this combined in situ XAFS, DRIFTS, and Mossbauer study, we elucidate the changes in structural, electronic, and local environments of Fe during pyrolysis of the metal organic framework Fe-BTC toward highly active and stable Fischer–Tropsch synthesis (FTS) catalysts (Fe@C). Fe-BTC framework decomposition is characterized by decarboxylation of its trimesic acid linker, generating a carbon matrix around Fe nanoparticles. Pyrolysis of Fe-BTC at 400 °C (Fe@C-400) favors the formation of highly dispersed epsilon carbides (e′-Fe2.2C, dp = 2.5 nm), while at temperatures of 600 °C (Fe@C-600), mainly Hagg carbides are formed (χ-Fe5C2, dp = 6.0 nm). Extensive carburization and sintering occur above these temperatures, as at 900 °C the predominant phase is cementite (θ-Fe3C, dp = 28.4 nm). Thus, the loading, average particle size, and degree of carburization of Fe@C catalysts can be tuned by varying the pyrolysis temperature. Performance testing in high-temperature FTS (HT-FTS) showed that the initial turnover fr...

In catalyst activity testing, micro-packed-bed reactors are the most commonly used devices. However, the small particle sizes (typically 0.05–0.2 mm) inherent with these microreactors in multiphase systems do exhibit special hydrodynamics characteristics, that are not generally recognized. Cold three-phase model investigations show that in micro-packed-bed reactors segregated flows of gas and liquid occur in a broad range of conditions. This situation is dramatically different from the hydrodynamics in industrial-scale trickle-bed reactors. Since in a broad range of conditions the gas flow follows preferential pathways through the micro-packed bed, the average thickness of the liquid layers is relatively large. Because the transport through these layers occurs mainly by molecular diffusion, the observed reaction rate potentially will be limited, resulting in poor radial dispersion. Even for a rather slow reaction as the hydrodesulfurization of dibenzothiophene (HDS), radial mass-transfer limitations were observed. This counterintuitive result is due to the combination of (i) the presence of apparent stagnant liquid layers with several particle diameters thickness, (ii) the low rate of radial transport, and (iii) the strong inhibition by the reaction product H 2 S. A general criterion, analogous to the Weisz–Prater criterion for internal diffusion limitations, is proposed for the estimation of the influence of poor radial dispersion in catalyst performance testing in micro-packed-bed reactors. For use in practice, it is advised to start with a worst-case scenario and dependent on the outcome to relax this strict criterion.

Nitrogenoxides (NOx, including NO and NOx) are a group of hazardous, toxic and harmfulgasses, which have an adverse effect on both environment and human health,e.g., acid rain, photochemical smog, and affecting the human respiratorysystem. The NOx concentration in most of the EUcities exceeds the EU annual limit value (40 μg/m3). Around40% of the emitted NOx is attributedto transport related emissions. In currently applicable Euro 6, the real NOx emissionfrom a diesel car is on average 400% than the Euro 6 regulation limit allows ifmeasured under more realistic driving conditions. Although NSR and SCR DeNOx systemshave been broadly investigated and commercially applied with the aim to reduceNOx emissions from lean burn engines,some common problems still exist, e.g., a narrow temperature window and a lowgas hourly space velocity (up to 50.000 L/L/h)in order to convert the NOx selectivelyinto Nx. Due to the in practice high NOxemissionfrom September 2017 additional legislation will be in force to arrive at a morerealistic determination of the highly dynamic NOxemissionby among others the introduction of the real driving emission (RDE) test in thecertification procedure. The Di-Air (Diesel NOxaftertreatment by Adsorbed Intermediate Reductants) system was developed by Toyota(2011-2012) and is still under development. This Di-Air system showed promiseby yielding a high NOx conversion,especially at high temperature (up to 600 ∘C) and high gas hourly space velocity (up to 125.000 L/L/h).This system opts to meet the future stringent NOxreductionrequirements under RDE test conditions (Chapter 1)…

The influence of potassium in Rh on a lanthium promoted zirconia stablised ceria (CZ) catalysts was studied toward NOxreduction reactivity and selectivity. The results are compared with a Rh/CZ catalyst. The samples were characterised by N2 adsorption, XRD, SEM, ICP, and H2-TPR. The study highlighted the importance of stored NOx regeneration over potassium in determining the overall performance of the Rh/K/CZ catalyst. The NOx stored over Rh/K/CZ in the previous NO gas stream cannot be regenerated sufficiently during the C3H6 gas stream, and stored NOxgradually decreased from one cycle to the next, resulting in deteriorating performance of Rh/K/CZ. Besides, problem of NOx slip, the formation of both NH3 and N2O (selectivities up to 30% for each side product) were observed by the addition of potassium into the Rh/CZ catalyst system, depending on the reaction conditions applied and the severity of the catalyst deactivation.

Toyota's Di-Air DeNOx system is a promising DeNOx system to meet NOx emission requirement during the real driving, yet, a fundamental understanding largely lacks, e.g. the benefit of fast frequency fuel injection. Ceria is the main ingredient in Di-Air catalyst composition. Hence, we investigated the reduction of ceria by reductants, e.g. CO, H2, and hydrocarbons (C3H6 and C3H8), with Temporal Analysis of Product (TAP) technique. The results show that the reduction by CO yielded a faster catalyst reduction rate than that of H2. However, they reached the same final degree of ceria reduction. Hydrocarbons generated almost three times deeper degree of ceria reduction than that with CO and H2. In addition, hydrocarbons resulted in carbonaceous deposits on the ceria surface. The total amount of converted NO over the C3H6 reduced sample is around ten times more than that of CO. The deeper degree of reduction and the deposition of carbon by hydrocarbon explain why hydrocarbons are the most powerful reductants in Toyota's Di-Air NOx abatement system.

The performance of Au/TiO2 P25 synthesized at different pH's (8, 9 and 10) is studied over time-on-stream in low temperature water–gas shift (WGS) at 21 bar under semi-industrial conditions. Furthermore, their performance is compared with a commercial CuO/ZnO/Al2O3 low temperature WGS catalyst and AUROlite 1 wt.% Au/TiO2 as a reference. Sulfur severely poisons the Au/TiO2 catalyst, which is irreversible over time-on-stream under high pressure (21 bar) WGS conditions. The Au/TiO2 P25 catalysts are synthesized using deposition precipitation to a targeted loading of gold close to 1 wt.% and are carried at three different pH (8, 9 and 10) under controlled conditions. The influence of parameters such as final pH, rate of addition of basic solution, type of basic solution are discussed. A higher final pH resulted in smaller gold particles deposited on TiO2-P25. The Au/TiO2-P25 catalyst prepared at the higher final pH (pH 10) showed higher WGS activity which relates to the averaged smaller particle size of the gold on TiO2-P25. The Au/TiO2-P25 catalyst prepared at lower final pH (pH of 8) is stable, while the catalysts prepared at pH of 9 and 10 deactivate over 130 h timeon stream.

Iron oxide and ceria are known to have redox properties and their performance as a water–gas shift (WGS) catalyst is investigated at low H2O/CO ratio (∼2) in the temperature range of 623–773 K at 21 bar with space velocities relevant for industrial applications. The WGS activity of supported iron oxide is higher than that of supported ceria. The addition of rhodium to supported iron oxide (Rh/Fe2O3/ZrO2) enhances the WGS activity while for supported ceria (Rh/CeO2/ZrO2) rhodium enhances the methanation activity at high pressure (21 bar) WGS conditions. The improved hydrogen production by enhancement of the WGS activity over Rh/CeO2/ZrO2 due to rhodium is undone by the consumption of hydrogen in the methane production. Methane is produced over Rh/Fe2O3/ZrO2 and Rh/CeO2/ZrO2 catalysts due to the presence of rhodium. Rhodium nitrate as precursor results in a better WGS activity performance over Rh/Fe2O3/ZrO2 and a better methanation activity is obtained over Rh/CeO2/ZrO2 in comparison with the use of rhodium chloride precursor. The presence of residual chlorine suppresses the promotional WGS activity due to rhodium as well as the methanation activity. In both ex-nitrate and ex-chloride catalysts the smaller rhodium particles are highly active for methane formation.

The kinetics of the water–gas shift (WGS) over three newly developed chromium-free catalysts Fe2O3/ZrO2, Rh/ZrO2, and Rh/Fe2O3/ZrO2 were investigated in a parallel six-flow reaction unit in the temperature range of 623–773 K at a total pressure of 21 bar. Different kinetic models based on redox and associative WGS mechanisms depending on the type of catalyst were evaluated to represent the kinetic data. An aging pretreatment at 793 K for 48 h time-on-stream (TOS) under WGS conditions was applied before recording the kinetic data. The deactivation of the catalysts observed during the kinetic runs was described by a TOS exponential decay in the apparent rate constant of the kinetic model at different temperatures. All data satisfied the requirements for absence of transport limitations and plug flow reactor behavior. The Fe-based catalysts showed a higher activation energy (105–111 kJ mol−1) than that of the Rh catalyst (64 kJ mol−1), indicating that the reaction on both iron oxide based catalysts proceed through the redox mechanism. The addition of Rh to the Fe catalyst increased the rate fivefold and introduced a strong CO2 inhibition, while it reduced the dependency on CO and increased the dependency on H2O. The dependency on hydrogen is weak for all catalysts. The selected kinetic model for the Fe2O3/ZrO2 and Rh/ZrO2 catalysts, based on statistical analysis of the results (minimum sum of squared residuals, parameter significance, normal and randomly distributed residuals) agree with the expected WGS mechanism over these catalysts, the redox and the associative mechanism, respectively. For the rhodium promoted iron based catalyst Rh/Fe2O3/ZrO2 no clear preference for a mechanism could be concluded.

A heterogeneous molecular catalyst based on Ir(III) Cp* (Cp*=pentamethylcyclopentadienyl) attached to a covalent triazine framework (CTF) is reported. It catalyses the production of hydrogen from formic acid with initial turnover frequencies (TOFs) up to 27,000 h(-1) and turnover numbers (TONs) of more than one million in continuous operation. The CTF support, with a Brunauer-Emmett-Teller (BET) surface area of 1800 m(2) g(-1), was constructed from an optimal 2:1 ratio of biphenyl and pyridine carbonitrile building blocks. Biphenyl building blocks induce mesoporosity and, therefore, facilitate diffusion of reactants and products whereas free pyridinic sites activate formic acid towards β-hydride elimination at the metal, rendering unprecedented rates in hydrogen production. The catalyst is air stable, produces CO-free hydrogen, and is fully recyclable. Hydrogen production rates of more than 60 mol L(-1) h(-1) were obtained at high catalyst loadings of 16 wt % Ir, making it attractive towards process intensification.

We tailored the size distribution of Pt nanoparticles (NPs) on graphene nanoplatelets at a given metal loading by using low-temperature atomic layer deposition carried out in a fluidized bed reactor operated at atmospheric pressure. The Pt NPs deposited at low temperature (100 °C) after 10 cycles were more active and stable towards the propene oxidation reaction than their high-temperature counterparts. Crucially, the gap in the catalytic performance was retained even after prolonged periods of time (>24 hours) at reaction temperatures as high as 450 °C. After exposure to such harsh conditions the Pt NPs deposited at 100 °C still retained a size distribution that is narrower than the one of the as-synthesized NPs obtained at 250 °C. The difference in performance correlated with the difference in the number of facet sites as estimated after the catalytic test. Our approach provides not only a viable route for the scalable synthesis of stable supported Pt NPs with tailored size distributions but also a tool for studying the structure-function relationship.

A quasi chemical vapor deposition method for the manufacture of well-defined covalent triazine framework (CTF) coatings on cordierite monoliths is reported. The resulting supported porous organic polymer is an excellent support for the immobilization of two different homogeneous catalysts: (1) an IrIIICp∗-based catalyst for the hydrogen production from formic acid and (2) a PtII-based catalyst for the direct activation of methane via Periana chemistry. The immobilized catalysts display a much higher activity in comparison with the unsupported CTF operated in slurry because of improved mass transport. Our results demonstrate that CTF-based catalysts can be further optimized by engineering at different length scales.

The CO2 that comes from the use of fossil fuels accounts for about 65% of the global greenhouse gas emission, and it plays a critical role in global climate changes. Among the different strategies that have been considered to address the storage and reutilization of CO2, the transformation of CO2 into chemicals or fuels with a high added-value has been considered a winning approach. This transformation is able to reduce the carbon emission and induce a “fuel switching” that exploits renewable energy sources. The aim of this brief review is to gather and critically analyse the main efforts that have been made and achievements that have been made in the electrochemical reduction of CO2 for the production of CO. The main focus is on the prospective of exploiting the intrinsic nature of the electrolysis process, in which CO2 reduction and H2 evolution reactions can be combined, into a competitive approach, to produce syngas. Several well-established processes already exist for the generation of fuels and fine-chemicals from H2/CO mixtures of different ratios. Hence, the different kinds of electrocatalysts and electrochemical reactors that have been used for the CO and H2 evolution reactions have been analysed, as well as the main factors that influence the performance of the system from the thermodynamic, kinetic and mass transport points of view.

We studied the mechanism of NO reduction as well as its selectivity and reactivity in the presence of excess O2. Results show that fuel injection and/or pretreatment are important for ceria catalyst reduction and carbon deposition on the catalyst surface. Oxygen defects of reduced ceria are the key sites for the reduction of NO into N2. The deposited carbon acts as a buffer reductant, i.e., the oxidation of carbon by lattice oxygen recreates oxygen defects to extend the NO reduction time interval. A small amount of NO showed a full conversion into only N2 both on the reduced Zr-La doped ceria and reduced Pt-Zr-La doped ceria. Only when the catalyst is oxidised NO is converted into NO2.

The structure and elementary composition of various commercial Fe-based MOFs used as precursors for Fischer–Tropsch synthesis (FTS) catalysts have a large influence on the high-temperature FTS activity and selectivity of the resulting Fe on carbon composites. The selected Fe-MOF topologies (MIL-68, MIL-88A, MIL-100, MIL-101, MIL-127, and Fe-BTC) differ from each other in terms of porosity, surface area, Fe and heteroatom content, crystal density and thermal stability. They are re-engineered towards FTS catalysts by means of simple pyrolysis at 500 °C under a N2 atmosphere and afterwards characterized in terms of porosity, crystallite phase, bulk and surface Fe content, Fe nanoparticle size and oxidation state. We discovered that the Fe loading (36–46 wt%) and nanoparticle size (3.6–6.8 nm) of the obtained catalysts are directly related to the elementary composition and porosity of the initial MOFs. Furthermore, the carbonization leads to similar surface areas for the C matrix (SBET between 570 and 670 m2 g−1), whereas the pore width distribution is completely different for the various MOFs. The high catalytic performance (FTY in the range of 1.9–4.6 × 10−4 molCO gFe−1 s−1) of the resulting materials could be correlated to the Fe particle size and corresponding surface area, and only minor deactivation was found for the N-containing catalysts. Elemental analysis of the catalysts containing deliberately added promoters and inherent impurities from the commercial MOFs revealed the subtle interplay between Fe particle size and complex catalyst composition in order to obtain high activity and stability next to a low CH4 selectivity.

Relevant carbon-based materials, home-made carbon-silica hybrids, commercial activated carbon, and nanostructured multi-walled carbon nanotubes (MWCNT) were tested in the oxidative dehydrogenation of ethylbenzene (EB). Special attention was given to the reaction conditions, using a relatively concentrated EB feed (10 vol.% EB), and limited excess of O-2 (O-2:EB = 0.6) in order to work at full oxygen conversion and consequently avoid O-2 in the downstream processing and recycle streams. The temperature was varied between 425 and 475 degrees C, that is about 150-200 degrees C lower than that of the commercial steam dehydrogenation process. The stability was evaluated from runs of 60 h time on stream. Under the applied reactions conditions, all the carbon-based materials are apparently stable in the first 15 h time on stream. The effect of the gasification/burning was significantly visible only after this period where most of them fully decomposes. The carbon of the hybrids decomposes completely rendering the silica matrix and the activated carbon bed is fully consumed. Nano structured MWCNT is the most stable; the structure resists the demanding reaction conditions showing an EB conversion of similar to 30% (but deactivating) with a steady selectivity of similar to 80%. The catalyst stability under the ODH reaction conditions is predicted from the combustion apparent activation energies. (C) 2014 Elsevier Ltd. All rights reserved.

A study is carried out to analyze the activity contribution of the redox and associative mechanism in the water–gas shift (WGS) over a new catalyst system (Rh/Fe 2 O 3 /ZrO 2 ). The catalyst performance was evaluated at low H 2 O/CO ratio (∼2) in the temperature range of 623–773 K at 1 bar and 21 bar, and space velocities relevant for industrial applications, and complemented by kinetic measurements at 21 bar, and physico-chemical characterization techniques. In zirconia supported iron oxide (Fe 2 O 3 /ZrO 2 ), the redox mechanism is considered to be operational and over zirconia supported rhodium associative mechanism is dominant. Rhodium in Rh/Fe 2 O 3 /ZrO 2 enhances the WGS activity by promoting the redox mechanism in iron oxide and also contributes to its activity through associative mechanism over rhodium particles. Small amounts of methane are produced as a side product due to the presence of rhodium. The WGS activity is inhibited by CO 2 in the presence of rhodium in Rh/Fe 2 O 3 /ZrO 2 and similarly as over Rh/ZrO 2 . Methane formation is suppressed by H 2 O over Rh/ZrO 2 and Rh/Fe 2 O 3 /ZrO 2, while CO inhibition in the methane formation is observed only over Rh/ZrO 2 and not over Rh/Fe 2 O 3 /ZrO 2 .

Drastic improvements in styrene yield and selectivity were achieved in the oxidative dehydrogenation of ethylbenzene by staged feeding of O-2. Six isothermal packed bed reactors were used in series with intermediate feeding of O-2, while all EB was fed to the first reactor, diluted with helium or CO2 (1:5 molar ratio), resulting in total O-2:EB molar feed ratios of 0.2-0.6. The two catalyst samples, gamma-Al2O3 and 5P/SiO2, that were applied both benefitted from this operation mode. The ethylbenzene conversion per stage and the selectivity to styrene were significantly improved. The production of COx was effectively reduced, while the selectivity to other side products remained unchanged. Compared with co-feeding at a total O-2:EB molar feed ratio of 0.6, by staged feeding the EB conversion (+15% points for both catalysts), ST selectivity (+4% points for both samples) and O-2 (ST) selectivity (+9% points for gamma-Al2O3 and +17% points for 5P/SiO2) all improved. The ethylbenzene conversion over 5P/SiO2 can be increased from 18% to 70% by increasing the number of reactors from I to 6 with each reactor a total amount of 02 of 0.1 without the loss of ST selectivity (93%). For 5P/SiO2 a higher temperature (500 degrees C vs. 450 e C for Al2O3) is required. Essentially more catalyst (5P/SiO2) was required to achieve full O-2 conversion in each reactor. Staged feeding of O-2 does not eliminate the existing issues of the catalyst stability both in time-on stream and as a function of the number of catalyst regenerations (5P/SiO2), or the relatively moderate performance (relatively low styrene selectivity for gamma-Al2O3). (C) 2014 Elsevier B.V. All rights reserved.

The synthesis of single-atom catalysts and the control of the electronic properties of catalytic sites to arrive at superior catalysts is a major challenge in heterogeneous catalysis. A stable supported single-atom silver catalyst with a controllable electronic state was obtained by anti-Ostwald ripening. An electronic perturbation of the catalytic sites that is induced by a subtle change in the structure of the support has a strong influence on the intrinsic reactivity. The higher depletion of the 4d electronic state of the silver atoms causes stronger electronic metal-support interactions, which leads to easier reducibility and higher catalytic activity. These results may improve our understanding of the nature of electronic metal-support interactions and lead to structure-activity correlations.

A molecular modelling study, using standard DFT B3LYP/6-31G*, was carried out to develop a better understanding of sorbitol dehydration into isosorbide in ZnCl2 molten salt hydrate medium. Catalysis of sorbitol dehydration by ZnCl2 most likely starts with complexation of the sugar alcohol functions to Zn, followed by an internal SN2 mechanism of a secondary alcohol function attacking a primary alcohol function with the Zn-complex acting as a favourable leaving group. The dehydration reactions to 1,4- and 3,6-anhydrosorbitol show a very similar activation barrier in good accordance with experimental results. The same holds for the formation of isosorbide from 1,4- and 3,6-anhydrosorbitol, albeit with a slightly higher activation barrier. The relative level of the activation barriers reflects the increased strain in the sorbitol skeleton in the corresponding transition states. ZnCl2 turns the dehydration reaction from an endothermic one to an exothermic one by forming a strong complex with the released water. Finally, the ZnCl2–H2O system has been compared with HCl–H2O, which could have been an alternative; it, however, turned out not to be the case.

Ceria-based catalysts with different topological and textural properties have been prepared to study the role of the soot-catalyst contact on the soot oxidation reaction. The physico-chemical features of the catalysts have been investigated by means of complementary techniques, such as powder XRD, N2 physisorption at -196 °C, optical microscopy at variable temperature, FESEM, TEM, and thermogravimetric analysis.As a whole, the best catalytic activity has been obtained with the CeO2-nanocubes (denoted to as "Ce-NC") because of their higher intrinsic reactivity. On the other hand, high-surface area materials prepared by the cerium nitrate decomposition (denoted to as "Ce-ND") or hydrothermal route (CeO2-stars, referred to as "Ce-SAS") resulted less effective toward the soot combustion, confirming the surface-sensitivity for this reaction.Moreover, it has been proven a higher dependence of the oxidation activity on the catalyst-to-soot ratio (wt./wt.) for the nanostructured catalyst (Ce-NC) exhibiting the lowest BET specific surface area (SBET = 4 m2 g-1). On the other hand, the accessible (real) surface area, at variance of the BET surface area, seems to play a relevant role for this solid-solid reaction mediated by gas-phase oxygen.

The main advantages and limitations of the use of mesoporous H-ZSM-5 as Co support in Fischer–Tropsch synthesis (FTS) are identified by combining a detailed catalyst performance evaluation with a thorough characterization. Mesostructures were created in H-ZSM-5 crystallites by demetalation via subsequent base and acid treatments. Desilication through base treatment provides H-ZSM-5 with pore sizes and volumes similar to amorphous SiO2 (a conventional carrier), while acid treatment removes the produced extraframework aluminum and boosts the FTS catalyst activity. Model acid-catalyzed reactions and induced deactivation of zeolite acid sites confirm that hydrocracking of primary FTS hydrocarbons at the zeolite strongly increases the selectivity toward C5–C11 (gasoline fraction). On the other hand, the strong Co–zeolite interaction as revealed by TPR(H2) results in the stabilization of lower coordinated Co sites (as revealed by IR-assisted CO adsorption) and in a higher selectivity toward methane. n-Hexane conversion reactions suggest that the latter is due to increased activity for hydrogenation and hydrocarbon hydrogenolysis reactions at such coordinatively unsaturated Co sites.

Operando infrared spectroscopy in combination with a kinetic study is used to elucidate the role of potassium on the conversion of carbon monoxide over K-promoted MoS2 catalysts. More specifically, the initial break-in transient has been studied in detail. Stabilization of reaction intermediates, and effect of promoter on the intrinsic properties of MoS2 are discussed. Adsorbed alkoxy species were found to play an important intermediate role in the syngas to alcohol route, and it was found that potassium stabilizes these species. Moreover, the electronic properties of MoS2 change upon promotion, thereby allowing for a relatively easier activation of the CO molecule and a reduced hydrogenation activity toward alkanes.

The performance of supported CeO2/HZSM-5 catalysts with a nominal CeO2 loading of 10 wt.% was evaluated for the oxidation of one of the most common chlorinated pollutants found in waste streams, namely 1,2-dichloroethane. The influence of the preparation method, such as impregnation in different media (water and ethanol), precipitation and ion exchange, was examined. Structural, morphological and physico-chemical changes caused as a function of the synthesis procedure were analysed by atomic emission spectroscopy, X-ray diffraction, BET measurements, transmission electronic microscopy, X-ray photoelectron spectroscopy, NH3-temperature-programmed desorption, adsorption of CO at low temperature followed by infrared spectroscopy, temperature-programmed reduction with hydrogen, energy dispersive X-ray spectroscopy and dynamic thermogravimetry coupled to mass spectrometry. The enhancement of the catalytic behaviour of the resulting ceria loaded samples with respect to plain H-ZSM5 could be explained on the basis of the synergetic effects of oxygen mobility and acid sites. In particular, the procedure based on impregnation with ethanol led to a highly dispersed ceria catalyst with a larger amount of oxygen vacancies. As a result, this catalyst required a temperature lower than 200 °C for attaining 50% conversion.

The kinetics of the gas-phase dehydrogenation of propane over Pt-Sn (1 : 1 mol ratio) supported on Al2O3 was investigated for the first time over the high range of reactant/products partial pressures (up to 0.875 atm). The Pt precursor was reduced to metallic form after a temperature-programmed reduction (TPR) at 873 K. X-ray photoelectron spectroscopy (XPS) analysis suggests that a Pt-Sn surface alloy forms, decreasing the H-2 adsorption on the Pt-Sn sites (5.6 nm in average size) relative to monometallic Pt (6.8 nm). We performed kinetic studies in the absence of mass/heat transfer limitations. The incorporation of Sn into Pt in Pt-Sn/Al2O3 enhanced the catalytic activity and stability when compared to Pt/Al2O3. We attribute this response to the surface electronic interaction between Pt and Sn. The initial propane consumption rate increases with the partial pressure of propane and decreases with the partial pressure of propene, while varying that of hydrogen has a negligible effect. Applying the Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach, the most likely kinetic model is non-dissociative adsorption of propane with simultaneous release of H-2, where surface reaction is the rate-limiting step. Our results of the kinetic aspects provide practical insights relevant to propane dehydrogenation.

Commercially available gamma-Al2O3 was calcined at temperatures between 500 and 1200 degrees C and tested for its performance in the oxidative ethylbenzene dehydrogenation (ODH) over a wide range of industrially-relevant conditions. The original gamma-Al2O3, as well as Z- and alpha-Al2O3, were tested. A calcination temperature around 1000/1050 degrees C turned out to be optimal for the ODH performance. Upon calcination the number of acid sites (from 637 to 436 mu mol g(-1)) and surface area (from 272 to 119 m(2) g(-1)) decrease, whereas the acid site density increases (from 1.4 to 2.4 sites per nm(2)). Less coke, being the active catalyst, is formed during ODH on the Al-1000 sample compared to gamma-Al2O3 (30.8 wt% vs. 21.6 wt%), but the coke surface coverage increases. Compared with gamma-Al2O3, the EB conversion increased from 36% to 42% and the ST selectivity increased from 83% to 87%. For an optimal ST selectivity the catalyst should contain enough coke to attain full conversion of the limiting reactant oxygen. The reactivity of the coke is changed due to the higher density and strength of the Lewis acid sites that are formed by the high temperature calcination. The Al-1000 sample and all other investigated catalysts lost ODH activity with time on stream. The loss of selectivity towards more COX formation is directly correlated with the amount of coke.

Fluid catalytic cracking (FCC) of Fischer–Tropsch (FT) waxes and vegetable oils could be an attractive option to produce transportation fuels and light olefins. For FT waxes, the catalytic cracking using commercial FCC catalysts revealed that a particular product slate (gasoline, diesel or light olefins) with high selectivity can be obtained by selecting an appropriate catalyst and operating conditions. FT wax is an outstanding feedstock in providing a high-value petrochemical feedstock, propene, with yields about 25 wt.% by employing pure ZSM-5 or ZSM-5/FCC catalyst (Y-zeolite-based) mixture. Similar amounts of butenes are also obtained. For the catalytic cracking of vegetable oils, the product distribution primarily depends on the degree of unsaturation (double bonds) of vegetable oils. For gasoline with high selectivity, saturated vegetable oils are more preferable. Irrespective of the degree of unsaturation, the aromatic content of the product fractions is relatively high compared to those from the conventional FCC feedstocks (VGO). Further modification of a FCC catalyst with a suitable metal (nickel) along with co-feeding H2 tremendously increases the gasoline and light olefins yields from a vegetable oil. Thus, development of a novel catalyst and/or tuning catalyst characteristics is still a promising research area to focus onto improve the cracking performance of vegetable oils. The cracking data of FT waxes/vegetable oils with VGO showed that co-processing of renewable feedstocks with the conventional FCC feedstocks is promising and no significant interactions exist between conventional and renewable feedstocks. Consequently, the prediction of the cracking performance at different blend ratios is straightforward.

Background Clinical studies investigating medicinal products need to comply with laws concerning good clinical practice (GCP) and good manufacturing practice (GMP) to guarantee the quality and safety of the product, to protect the health of the participating individual and to assure proper performance of the study. However, there are no specific regulations or guidelines for non-Medicinal Investigational Products (non-MIPs) such as allergens, enriched food supplements, and air pollution components. As a consequence, investigators will avoid clinical research and prefer preclinical models or in vitro testing for e.g. toxicology studies. The aim of this article is to 1) briefly review the current guidelines and regulations for Investigational Medicinal Products; 2) present a standardised approach to ensure the quality and safety of non-MIPs in human in vivo research; and 3) discuss some lessons we have learned. Methods and results We propose a practical line of approach to compose a clarifying product dossier (PD), comprising the description of the production process, the analysis of the raw and final product, toxicological studies, and a thorough risk-benefit-analysis. This is illustrated by an example from a human in vivo research model to study exposure to air pollutants, by challenging volunteers with a suspension of carbon nanoparticles (the component of ink cartridges for laser printers). Conclusion With this novel risk-based approach, the members of competent authorities are provided with standardised information on the quality of the product in relation to the safety of the participants, and the scientific goal of the study. Electronic supplementary material The online version of this article (doi:10.1186/s12931-016-0413-9) contains supplementary material, which is available to authorized users.

A facile one-step method to shape covalent triazine frameworks (CTFs) for catalytic applications is reported. Phase inversion of the CTF powder by using a polyimide as a binder in a microfluidic device results in the formation of composite spheres with accessible CTF porosity and a high mechanical and thermal stability. The fabricated spheres can be used to host organometallic complexes. The obtained shaped catalysts, Ir@CTF spheres, are active and fully recyclable in the direct hydrogenation of carbon dioxide into formic acid under mild reaction conditions (20 bar and 50–90 °C) and in the dehydrogenation of formic acid.

Temporal analysis of product (TAP) is used to investigate the effectiveness of CO, C3H6, and C3H8 in the reduction of a La–Zr doped ceria catalyst and NO reduction into N2 over this pre-reduced catalyst. Hydrocarbons are found to be substantially more effective in the reduction of this catalyst at high temperature (above 500 °C) as compared to CO. NO decomposes over oxygen anion defects created upon catalyst reduction. Deposited carbon, in case the catalyst is reduced by C3H6 or C3H8, acts as a delayed or stored reductant and is not directly involved in NO reduction. Instead the oxidation of deposited carbon by an oxygen species derived from lattice oxygen (re)creates the oxygen anion defects active in NO reduction. In situ Raman, in which NO is flown over C3H6 pre-reduced La–Zr doped ceria at 560 °C, additionally shows that re-oxidation of the La–Zr doped ceria catalyst starts prior to the oxidation of deposited carbon, which confirms our TAP findings that firstly NO re-oxidized the La–Zr doped ceria catalyst and that secondly the oxidation of deposited carbon only commences at a higher ceria oxidation state. These findings create a new perspective on the operating principle of Toyota’s Di-Air system.

Methyl mercaptan, CH3SH, is an industrial waste as well as the reactive product of several H2 and H2S induced catalytic hydrogenation processes of COS and CS2. Its coupling into value added products is of great importance in monetizing sour natural gas. In the present work, the full theoretical cycle of catalytic CH3SH coupling to form ethene was investigated by means of density functional theory (DFT) using chabazite as a model catalyst with emphasis on the first C-C bond formation. Calculated thermodynamics were compared with those of analogous and well established CH3OH processes to identify the similarities and differences in the reactive pathways. With few exceptions, CH3SH catalytic transformations are of higher free energy when compared to those of CH3OH. The trimethylsulfonium ion, TMS, isostructural with that of the trimethyloxonium ion, TMO, is shown to be a key reactive intermediate and a thermodynamically stable species leading to ethene formation.

A strategy to enhance the thermal stability of C/SiO2 hybrids for the O2-based oxidative dehydrogenation of ethylbenzene to styrene (ST) by P addition is proposed. The preparation consists of the polymerization of furfuryl alcohol (FA) on a mesoporous precipitated SiO2. The polymerization is catalyzed by oxalic acid (OA) at 160°C (FA:OA = 250). Phosphorous was added as H3PO4 after the polymerization and before the pyrolysis that was carried out at 700°C and will extend the overall activation procedure. Estimation of the apparent activation energies reveals that P enhances the thermal stability under air oxidation, which is a good indication for the ODH tests. Catalytic tests show that the P/C/SiO2 hybrids are readily active, selective and indeed stable in the applied reactions conditions for 60 h time on stream. Coke build-up during the reaction attributed to the P-based acidity is substantial, leading to a reduction of the surface area and pore volume. The comparison with a conventional MWCNT evidences that the P/C/SiO2 hybrids are more active and selective at high temperatures (450-475°C) while the difference becomes negligible at lower temperature. However, the comparison with reference P/SiO2 counterparts shows a very similar yield than the hybrids but more selective to ST. The benefit of the P/C/SiO2 hybrid is the lack of stabilization period, which is observed for the P/SiO2 to create an active coke overlayer. For long term operation, P/SiO2 appears to be a better choice in terms of selectivity, which is crucial for commercialization.

The addition of CO 2 to the dehydrogenation of ethylbenzene (EB) to styrene over promoted and un-promoted vanadia, iron, and chromia catalysts on alumina improves the yield of styrene, in comparison with the use of N 2 as diluent. Depending on the catalyst, EB conversion increases 5–10%, while selectivity does not change significantly. The potassium promoted vanadium catalyst shows the highest CO 2 conversion for dehydrogenation with the largest increase in EB conversion. The activity of these catalysts in the reverse water–gas-shift (RWGS) reaction, in the presence and absence of the dehydrogenation, is very different. Vanadium catalysts exhibit the lowest CO 2 RWGS activity. The presence of coke on the catalyst suppresses the RWGS reaction over chromium and iron catalysts, but improves the activity of the vanadium catalyst. This is attributed to hydrogen spill-over from the coke to the metal catalyst. A two-step mechanism with a hydrogen spill-over is proposed for the EB dehydrogenation in CO 2 . Step-response experiments show that the redox mechanism for the RWGS and the two-step pathway for dehydrogenation in CO 2 are the dominant routes. A slight RWGS activity of the bare alumina support is attributed to an associative mechanism.

Bare alumina support transforms into an active catalyst for the dehydrogenation of ethylbenzene to styrene in CO2 or N2. During the first 15 h time on stream in CO2, or the first 10 h time on stream in N2, the alumina shows an increase in ethylbenzene conversion and styrene selectivity from 15% to 60% and from 60% to 92%, respectively, under industrially relevant conditions of 600 °C and 10 vol% ethylbenzene. Thereafter, the system slowly deactivates, but remains highly selective. TGA analysis shows an increase in coke content. The specific surface area and pore volume show a decrease with time on stream. TEM-imaging reveals that the spent catalyst surface is completely covered by several layers of coke. These results combined suggest that the carbon deposits on the alumina are responsible for the increase in activity and selectivity, and also are the cause of deactivation once a monolayer of carbon is deposited on the support surface. Similar trends are observed for zirconia support. Supported vanadium and chromium oxides on alumina all give similar results, but after a faster activity development. Also for these supported catalysts and even carbon samples, deposited coke is the active and selective phase.

This work investigates the feasibility of ultra-deep hydrodesulfurization ( i.e. ⩽1 ppm of sulfur content) of several diesel feedstocks, viz., regular (R), premium (P) and hydrotreated straight-run (HSR) at low pressures, i.e. 10 bar, to lower significantly the operation costs. The premium and regular diesel contain additive packages with several components such as cetane boosters, antioxidants that show to negatively affect the sulfur conversion at low pressures. In the hydrotreated straight-run diesel fuel, which does not contain an additive package, total desulfurization can be obtained at 10 bar, T = 340 °C and LHSV = 1 h −1 . As a model for the additive package, FAME (fatty acid methyl ester), an ingredient that encounters the demands of a sustainable future, was added to the hydrotreated straight-run diesel (HSR + FAME) in order to check its influence on the total sulfur conversion. Results show that this biofuel component hindered tremendously the sulfur removal process by lowering the sulfur removal from 98% to zero at 10 bar, probably by competitive adsorption. At higher pressures, e.g. 30 bar, when FAME was present, new sulfur compounds were formed during the HDS process and the effective sulfur removal was very low.