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Welcome to Africa was the motto when after more than 100 years the flag ship conference series of the Royal Society of Chemistry, the Faraday Discussions was hosted for the first time on the African Continent. Under the fitting topic ‘Catalysis for Fuels’ over 120 delegates followed the invitation by the conference chair Prof. Graham Hutchings FRS (Cardiff Catalysis Institute), his organizing committee and the co-organizing DST-NRF Centre of Excellence in Catalysis c*change (http://www.cchange.ac.za). In the presentations of 21 invited speakers and 59 posters, cutting edge research in the field of catalysis for fuels, designing new catalysts for synthetic fuels, hydrocarbon conversion in the production of synthetic fuels and novel photocatalysis was presented over the two-day meeting. The scene was set by the opening lecture of Prof. Enrique Iglesias (UC Berkeley) and wrapped-up with the concluding remarks by Philip Gibson (SASOL).

We are presenting the use of an alumina supported FeRh alloy catalyst for the formation of nitrogen containing compounds via the CO hydrogenation in the presence of ammonia. In contrast to previous studies on either similar catalyst systems or on an iron-based catalyst, the prepared FeRh material displays a high selectivity to a single nitrogen-containing compound, acetonitrile. The formation of acetonitrile occurs at the expense of oxygenates, mostly ethanol, which form in the absence of ammonia.

We present a newly developed in situ/operando sample presentation device for radiation based characterization techniques. Although originally designed for use on commercial X-ray diffractometers it has also been successfully used in a high energy light source environment. We could show that the device allows monitoring phase and crystallite size changes at elevated temperatures and pressures under various atmospheres, including corroding gases such as steam. In addition and in contrast to most previously described cells the presented device allows for the collection of fully industrially relevant kinetic data from catalytic processes. As an example we show a comparison of the catalytic performance of a cobalt based Fischer-Tropsch catalyst obtained with the developed device which uses a capillary reactor to a performance test conducted in a standard 1/2” stainless steel laboratory scale reactor.

Using an in house developed in situ magnetometer the passivation in diluted oxygen or pure carbon dioxide of a platinum promoted and silica supported cobalt catalyst was studied. No passivation of cobalt was observed after treatment in CO 2 , neither at 30 °C nor at 150 °C. The magnetic cobalt metal phase content remained constant during these treatments and decreased in the subsequent exposure to air. The catalyst exposed to 1% O 2 in N 2 was stable in air at 30 °C. However, no long-term stability was observed. The magnetic measurements during passivation in 1% O 2 indicate partial oxidation of the nanoparticles in form of a CoO layer. The degree of reduction decreased from 89% to 51%, which corresponds to a theoretical oxide layer thickness of 1.3 nm surrounding the metallic core with a diameter of 9.8 nm. Upon re-reduction full recovery of the metal phase was obtained. The re-reduction occurred at significantly lower temperatures than the reduction of the freshly prepared catalyst or the re-reduction of a reduced catalyst after exposure to air without any passivation.

Different supporting procedures were followed to alter the nanoparticle–support interactions (NPSI) in two Co3O4/Al2O3 catalysts, prepared using the reverse micelle technique. The catalysts were tested in the dry preferential oxidation of carbon monoxide (CO-PrOx) while their phase stability was monitored using four complementary in situ techniques, viz., magnet-based characterization, PXRD, and combined XAS/DRIFTS, as well as quasi in situ XPS, respectively. The catalyst with weak NPSI achieved higher CO2 yields and selectivities at temperatures below 225 °C compared to the sample with strong NPSI. However, relatively high degrees of reduction of Co3O4 to metallic Co were reached between 250 and 350 °C for the same catalyst. The presence of metallic Co led to the undesired formation of CH4, reaching a yield of over 90% above 300 °C. The catalyst with strong NPSI formed very low amounts of metallic Co (less than 1%) and CH4 (yield of up to 20%) even at 350 °C. When the temperature was decreased from 350 to 50 °C under the reaction gas, both catalysts were slightly reoxidized and gradually regained their CO oxidation activity, while the formation of CH4 diminished. The present study shows a strong relationship between catalyst performance (i.e., activity and selectivity) and phase stability, both of which are affected by the strength of the NPSI. When using a metal oxide as the active CO-PrOx catalyst, it is important for it to have significant reduction resistance to avoid the formation of undesired products, e.g., CH4. However, the metal oxide should also be reducible (especially on the surface) to allow for a complete conversion of CO to CO2 via the Mars–van Krevelen mechanism.

In the field of heterogeneous catalysis research, in situ and operando characterization techniques, i.e. characterization techniques which can be applied under realistic reaction conditions and ideally on a working catalyst, become essential in order to generate new knowledge and understanding of structure performance relationships. Only this knowledge will enable researchers to develop or rather design new catalysts for existing and novel processes without relying on an 'educated guess' approach. In combination with ever improving theoretical predictions, operando characterization techniques are expected to be the main drivers in catalyst research and associated material science in the foreseeable future. Fischer-Tropsch (FT) catalyst systems, and specifically the iron based catalysts, are highly dynamic under reaction conditions, making deductions on structure-activity relationships difficult when relying on conventional characterization techniques. In addition, various deactivation mechanisms, such as oxidation, poisoning, sintering, attrition and phase separation have been observed. As such, the FT synthesis encompasses several challenges experienced in some form or other in most catalytic applications and material science studies. The present review therefore aims to provide a comprehensive account of characterization techniques employed under (quasi) in situ and operando conditions for FT catalysts. Together with a description of the respective technique and a critical discussion of the employed reaction cell, the actual research conducted is briefly discussed. We hope that this combination will enable readers not only to get a good impression of the capabilities and limitations of the respective technique and available instrumentation but also to understand their applicability in catalysis research and maybe to be inspired to push current boundaries.

The formation of mixed-metal cobalt oxides, representing potential metal-support compounds for cobalt-based catalysts, has been observed at high conversion levels in the Fischer-Tropsch synthesis over metal oxide-supported cobalt catalysts. An often observed increase in the carbon dioxide selectivity at Fischer-Tropsch conversion levels above 80% has been suggested to be associated to the formation of water-gas shift active oxidic cobalt species. Mixed-metal cobalt oxides, namely cobalt aluminate and cobalt titanate, were therefore synthesised and tested for potential catalytic activity in the water-gas shift reaction. We present a preparation route for amorphous mixed-metal oxides via thermal treatment of metal precursors in benzyl alcohol. Calcination of the as prepared nanoparticles results in highly crystalline phases. The nano-particulate mixed-metal cobalt oxides were thoroughly analysed by means of X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, X-ray absorption near edge structure spectroscopy, extended X-ray absorption fine structure, and high-resolution scanning transmission electron microscopy. This complementary characterisation of the synthesised materials allows for a distinct identification of the phases and their properties. The cobalt aluminate prepared has a cobalt-rich composition (Co1+xAl2-xO4) with a homogeneous atomic distribution throughout the nano-particulate structures, while the perovskite-type cobalt titanate (CoTiO3) features cobalt-lean smaller particles associated with larger ones with an increased concentration of cobalt. The cobalt aluminate prepared showed no water-gas shift activity in the medium-shift temperature range, while the cobalt titanate sample catalysed the conversion of water and carbon monoxide to hydrogen and carbon dioxide after an extended activation period. However, this perovskite underwent vast restructuring forming metallic cobalt, a known catalyst for the water-gas shift reaction at temperatures exceeding typical conditions for the cobalt-based Fischer-Tropsch synthesis, and anatase-TiO2. The partial reduction of the mixed-metal oxide and segregation was identified by means of post-run characterisation using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy energy-dispersive spectrometry.

Herein we present a comparative study on the water-induced formation of metal–support compounds from metallic cobalt in a simulated high conversion Fischer–Tropsch environment. Literature on the de...

We present a study in which the suitability of potassium promoted iron-based Fischer–Tropsch (FT) catalysts for the generation of synthetic natural gas additives via the hydrogenation of carbon dioxide through a combined reverse water gas shift (WGS) and FT reaction is studied. Using novel in situ instrumentation based on XRD and magnetometry techniques the reversible conversion of metallic iron to Hagg carbide under reaction conditions and its decomposition in hydrogen could be monitored. The facilitating effect of potassium in the formation of iron carbide could be exposed as function of time on stream. While the FT reaction was reduced in the presence of high potassium loadings the reverse WGS reaction seemed to be unperturbed. A faster activation of an iron phase obtained via the decomposition of iron carbide, compared to the initial activation of a pristine iron phase obtained via the reduction of iron oxide was witnessed.

The effect of ammonia on activity and selectivity of a low temperature, iron-catalyzed slurry phase Fischer–Tropsch process was studied. The ammonia content in the feed was varied systematically from 0 to 10 vol% while the total pressure was adjusted simultaneously in order to keep partial pressures constant. In addition to standard Fischer–Tropsch synthesis (FTS) products, long chained aliphatic amines, nitriles and amides were formed; the latter two product classes had not been observed by others before with iron based catalysts. The selectivities toward nitrogen containing compounds increased with increasing ammonia content while the formation rates of alcohols, aldehydes and organic acids were reduced possibly suggesting that nitrogen containing compounds are formed via oxygenates or their precursors. Common FTS descriptors such as methane selectivity, chain growth probability, olefin to paraffin ratio and double bond shift were largely unaffected at the studied levels of ammonia addition, while the activity at ammonia levels above 2 vol% decreased over and above the intrinsic deactivation rate. Although this deactivation seems reversible upon removal of ammonia from the feed gas, the selectivity is shifted toward higher water gas shift reactivity.

Using well-defined supported cobalt nanocrystallites in a novel in situ sample presentation device for laboratory X-ray diffractometers, we investigated the extensively studied structure sensitivity of Fischer–Tropsch (FT) catalysts under simulated high conversion conditions, that is, at high water to synthesis gas ratios. This study has to be regarded as a further small step toward a full understanding of the various processes governing FT activity and selectivity. We were able to show, for two different crystallite sizes, that water has an overall enhancing effect on carbon monoxide conversion and surface specific turnover frequency on metallic surfaces and improves the overall product selectivity with a decrease of methane selectivity. For small crystallites oxidation was observed at elevated water partial pressures, which caused a decrease of activity. The selectivity to the undesired product methane is suppressed in favor of chain growth. This influence on the selectivity might originate from water-i...

A major obstacle in the development of industrial catalysts is the scalability of both catalyst performance and synthesis. While utilizing pilot-scale test reactors allows for a direct transfer from the development stage to the application, it comes at the cost of flexibility. The amount of catalyst required in a pilot-scale test reactor often surpasses the yields of novel synthesis procedures, requiring extensive scale-up efforts. Here, pilot-scale reactors are combined with small lab-scale reactors, using the example of oxidation of o-xylene to phthalic anhydride.

In recent years, several groups have invested significant research capacity to investigate the effect of the metal crystallite size on the various primary and secondary reactions taking place during the Fischer–Tropsch synthesis. Most publications agree that with decreasing crystallite size (dcryst

The utilization of metal nanoparticles traverses across disciplines and we continue to explore the intrinsic size-dependent properties that make them so unique. Ideal nanoparticle formulation to improve a process’s efficiency is classically presented as exposing a greater surface area to volume ratio through decreasing the nanoparticle size. Although, the physiochemical characteristics of the nanoparticles, such as phase, structure, or behavior, may be influenced by the nature of the environment in which the nanoparticles are subjected1, 2 and, in some cases, could potentially lead to unwanted side effects. The degree of this influence on the particle properties can be size-dependent, which is seldom highlighted in research. Herein we reveal such an effect in an industrially valuable cobalt Fischer–Tropsch synthesis (FTS) catalyst using novel in situ characterization. We expose a direct correlation that exists between the cobalt nanoparticle’s size and a phase transformation, which ultimately leads to catalyst deactivation.

Identifying the active site on the surface of a heterogeneous catalyst is one of the biggest challenges in the field of catalysis research. Especially, in the case of structure sensitive and heterogeneously catalyzed reactions, the knowledge of the active site/ensemble would result in a great advantage in the quest to design tailored catalyst displaying the desired activity and selectivity. In the Fischer–Tropsch synthesis, the multitude of reaction products as well as the large number different reaction pathways does result in additional difficulties in the search for the active site/ensemble. In the here presented work, we were able to conduct a thorough study of the CO hydrogenation reactions on nano-sized alumina supported cobalt crystallite model catalysts. By evaluating the full product spectrum, it was possible to deconvolute the structure sensitivity of the various reactions and to gain further insight into the nature of the present reaction mechanisms. It was therefore possible to measure decreasing carbon monoxide turn over frequency with decreasing cobalt crystallite site, paralleled with an increased selectivity toward methane and branched hydrocarbons at a constant olefin selectivity. Although these trends were observed to be independent of time on stream, the activity did change drastically upon the initial exposure to reaction conditions. CO-TPD studies provided direct evidence for the observed size dependencies.

Highly monodisperse cobalt crystallites, supported on Stöber silica spheres, as model catalysts for the Fischer–Tropsch synthesis were exposed to simulated high conversion environments in the presence and absence of CO utilising an in house developedin situmagnetometer. The catalyst comprising the smallest crystallites in the metallic state (average diameter of 3.2 nm) experienced pronounced oxidation whilst the ratio of H2O to H2was increased stepwise to simulate CO conversions from 26% up to complete conversion. Direct exposure of this freshly reduced catalyst to a high conversion Fischer–Tropsch environment resulted in almost spontaneous oxidation of 40% of the metallic cobalt. In contrast, a model catalyst with cobalt crystallites of 5.3 nm only oxidised to a small extent even when exposed to a simulated conversion of over 99%. The largest cobalt crystallites were rather stable and only experienced measurable oxidation when subjected to H2O in the absence of H2. This size dependency of the stability is in qualitative accordance with reported thermodynamic calculations. However, the cobalt crystallites showed an unexpected low susceptibility to oxidation,i.e.only relatively high ratios of H2O to H2partial pressure caused oxidation. Similar experiments in the presence of CO revealed the significance of the actual Fischer–Tropsch synthesis on the metallic surface as the dissociation of CO, an elementary step in the Fischer–Tropsch mechanism, was shown to be a prerequisite for oxidation. Direct oxidation of cobalt to CoO by H2O seems to be kinetically hindered. Thus, H2O may only be capable of indirect oxidation,i.e.high concentrations prevent the removal of adsorbed oxygen species on the cobalt surface leading to oxidation. However, a spontaneous direct oxidation of cobalt at the interface between the support and the crystallites by H2O forming presumably cobalt silicate type species was observed in the presence and absence of CO. The formation of these metal–support compounds is in accordance with conducted thermodynamic predictions. None of the extreme Fischer–Tropsch conditions initiated hydrothermal sintering. Seemingly, the formation of metal–support compounds stabilised the metallic crystallites and/or higher partial pressures of CO are required to increase the concentration of mobile, cobalt oxide-type species on the metallic surface.

The preferential oxidation of carbon monoxide has been identified as an effective route to remove trace amounts of CO (approx. 0.5-1.0 vol%) in the H

B-cell epitope sequences from Zika virus (ZIKV) NS1 protein have been identified using epitope prediction tools. Mapping these sequences onto the NS1 surface reveals two major conformational epitopes and a single linear one. Despite an overall average sequence identity of ca. 55% between the NS1 from ZIKV and the four dengue virus (DENV) serotypes, epitope sequences were found to be highly conserved. Nevertheless, nonconserved epitope-flanking residues are responsible for a dramatically divergent electrostatic surface potential on the epitope regions of ZIKV and DENV2 serotypes. These findings suggest that strategies for differential diagnostics on the basis of short linear NS1 sequences are likely to fail due to immunological cross-reactions. Overall, results provide the molecular basis of differential discrimination between Zika and DENVs by NS1 monoclonal antibodies.

The Faraday Discussion on the design of new heterogeneous catalysts took place from 4-6 April 2016 in London, United Kingdom. It brought together world leading scientists actively involved in the synthesis, characterisation, modelling and testing of solid catalysts, attracting more than one hundred delegates from a broad spectrum of backgrounds and experience levels-academic and industrial researchers, experimentalists and theoreticians, and students. The meeting was a reflection of how big of an impact the ability to control and design catalysts with specific properties for particular processes can potentially have on the chemical industry, environment, economy and society as a whole. In the following, we give an overview of the topics covered during this meeting and briefly highlight the content of each presentation.

To obtain nano-sized metal and metal salt crystallites with a narrow size distribution synthesis methods utilizing water in oil (w/o) microemulsions, i.e. reverse micelles, have been widely applied and reported in literature. In this study we show the effect of support addition at different stages of the reverse micelle based preparation of cobalt oxide on alumina model catalysts. All catalysts were characterized with X-ray powder diffraction and Raman spectroscopy indicating the presence of Co3O4 on the Al2O3 support. Studies of the reduction behaviour and X-ray photoelectron spectroscopy however revealed the presence of difficult to reduce cobalt aluminate species in the samples where the support was added during or shortly after the precipitation step in the synthesis process. It can therefore be assumed that if the alumina support is added to the reverse micelle solution unprecipitated Co2+ ions and partially dissolved Al3+ combine and form cobalt aluminates. In the preparations where the solid cobalt precipitates are recovered from the microemulsion and then supported on the carrier, no metal-aluminate formation could be observed. This study therefore gives important information how metal-support interaction can be affected during catalyst preparation using reverse micelles.

In order to study the role of the crystallite size of an active phase in a catalytic reaction it is of utmost importance to be able to synthesise pure phases of crystallites in the desired size range with a narrow size distribution. In this paper we describe a new method to produce Co3O4 crystallites in the nanometer size range (average sizes: 3–10 nm) utilising reverse micelles as nano reactors. To prepare suitable model catalysts for studies on effects of crystallite size these crystallites can be deposited onto a variety of carriers, in this work an alumina support was used. It is further shown that the supported cobalt oxide crystallites prepared in this study do not undergo extensive sintering under reductive conditions (H2 flow and temperatures between 375 and 450 °C) so that also a series of model catalysts with metallic cobalt crystallites of varied size could be prepared. The resulting metal phase only shows the diffraction pattern of a face-centred cubic (fcc) crystal phase, while normally mixtures of fcc an hcp cobalt were obtained in previous studies. Furthermore, almost complete reduction of the catalyst could be obtained for all crystallite sizes and no Co-aluminate formation was observed. These model catalyst systems allow the study of structure sensitive reactions with an industrially relevant catalyst system in the absence of the commonly encountered difficulties like the formation of strong metal support interactions, co-existence of different metal crystallite phases, an incomplete reducibility and crystallite growth upon exposure to reduction/reaction conditions.

Philip Davies opened the discussion of the introductory lecture by Avelino Corma: Themetal nanoparticles inside the zeolites are in a different environment from those outside. Is there any difference in their chemistry and their catalytic behaviour? Avelino Corma answered: We were not able to determine the differences in reactivity, other than the accessibility of reactants with different sizes. It should be said that we did not use molecules specifically suited for showing potential electronic–entropic differences. I agree that this is an important point to be considered. What we clearly observed is that the clusters inside the channels were stable towards sintering. Cynthia Friend asked: Have you considered the possible effect of ligands bound to your clusters? Have van der Waals’ interactions been explicitly included? Avelino Corma replied: The theoretical calculation of the interactions of nitrobenzene with the nanoparticles includes the interactions with the support and van der Waals’ interactions. In the case of clusters, H2 dissociation has been carried out on isolated Pt, Au and Au-Pt clusters and van der Waals’ interactions were not considered. Graham Hutchings continued: You rightly point out in your design strategy that the adsorption of the reactant is the key factor, and that adsorption occurs.

Metal–support interactions in the form of iron–silicate were investigated by an inverse approach, that is, modification of nano-sized iron oxide with surface silicate groups. The presence of surface silicate groups in the calcined catalyst precursor was confirmed using diffuse reflectance infra-red Fourier transform analysis. The genesis of the various iron phases in the presence of surface silicate groups after H 2 -activation and the Fischer–Tropsch synthesis was followed. The surface silicate groups are preserved after a hydrogen treatment at 350 °C for 16 h, and these surface ligands are associated with the residual iron oxide phase, wustite. During the Fischer–Tropsch synthesis, α-Fe is mostly converted into χ-Fe 5 C 2 , whereas FeO is the main source for e-Fe 2 C. The activity per unit surface area of hexagonal carbide, e-Fe 2 C, is ca. 25% higher than that of χ-Fe 5 C 2 . The presence of surface silicate ligands on e-Fe 2 C results in a further enhancement of the rate per unit surface area of e-Fe 2 C by a factor of ca. 3. This is being ascribed to the enhanced availability of hydrogen on the surface due to the presence of the surface silicate groups, which also results in an increase in the methane selectivity, a decrease in the olefin content and a decrease in formation of branched product compounds.

The selective conversion of syngas to higher alcohols is an attractive albeit elusive route in the quest for effective production of chemicals from alternative carbon resources. We report the tandem integration of solid cobalt Fischer–Tropsch and molecular hydroformylation catalysts in a one-pot slurry-phase process. Unprecedented selectivities (>50 wt %) to C alcohols are achieved at CO conversion levels >70 %, alongside negligible CO side-production. The efficient overall transformation is enabled by catalyst engineering, bridging gaps in operation temperature and intrinsic selectivity which have classically precluded integration of these reactions in a single conversion step. Swift capture of 1-olefin Fischer–Tropsch primary products by the molecular hydroformylation catalyst, presumably within the pores of the solid catalyst is key for high alcohol selectivity. The results underscore that controlled cooperation between solid aggregate and soluble molecular metal catalysts, which pertain to traditionally dichotomic realms of heterogeneous and homogeneous catalysis, is a promising blueprint toward selective conversion processes., This work received funding from the German Ministry for Education and Research (BMBF, 01DG17019 CAT2BIOL) and the European Research Council (ERC-2019-COG 864195, TANDEng). Parts of this research have also received funding from the Spanish Ministry of Science and Innovation (RTI2018-096399-A-100), the EU Horizon 2020 research and innovation programme under Grant Agreement no. 817612 (REDIFUEL) and the Max Planck Society. W.L. acknowledges the “Fuel Science Center”, funded by the German Research Foundation (DFG) (grant Nr. 390919832), for continuing support. Sasol and Eurosupport are thanked for the provision of Al2O3 precursors. Prof. F. Schüth (MPI-KOFO) is gratefully thanked for lab space allocation and supportive access to research instrumentation. A. Gurowski (MPI-CEC), N. Pfänder (MPI-CEC), V. Dietl (MPI-KOFO) and M. Fadlalla (UCT) are acknowledged for contributions to ICP-MS, STEM/EDS, offline GC and 2DGC analyses, respectively. Staff of the EM unit at the UPV are acknowledged for technical assistance with microscopy characterization. Open Access funding enabled and organized by Projekt DEAL.