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The effect of thermal treatment on the catalyst structure and the CO oxidation performance of a Au/TiO catalyst supported on a carbon composite material has been studied. X-ray absorption spectroscopy shows that the carbon composite stabilises the TiO and prevent agglomeration of the particles. The activity measurements show that both Au and TiO need to be present in order to obtain catalytic activity. The catalytic performance was found to be strongly affected by thermal treatments of the active phase prior to the reaction. The thermal treatments have an effect on the ordering of the TiO structure, and on the CO oxidation activity. Heat treatment after Au deposition has a positive effect on the CO oxidation performance. This is attributed to the introduction of a stronger interaction between the oxide and Au which improves the catalytic activity. This also indicates that the TiO support and the Au-TiO interface play important roles in the CO oxidation reaction. [ABSTRACT FROM AUTHOR]

The impact of thermal treatment at various preparation stages of carbon supported Au/TiO catalysts prior to oxidation of CO in the presence and absence of hydrogen was studied. An increase in catalytic activity for thermally treated samples due to a more ordered structure of TiO was observed. A reversible deactivation of the catalysts occurred in the absence of hydrogen. However, the activity was restored at preferential CO oxidation conditions in presence of hydrogen. [ABSTRACT FROM AUTHOR]

Abstract: The effect of 10 typical biomass-derived synthesis gas impurities on cobalt Fischer–Tropsch catalyst performance was investigated at industrially relevant conditions. Impurities (0–1000ppmw) were introduced ex situ by incipient wetness impregnation to give 23 different compositions. The presence of alkali (Na, K) and alkaline earth elements (Ca, Mg) did not affect the ex situ-measured cobalt surface area but decreased the in situ activity, thereby decreasing the apparent turnover frequency. The C5+ selectivity increased and decreased upon addition of alkali and alkaline earth metals, respectively. Mn, Fe, and P had minor effects on catalyst performance. The presence of Cl decreased cobalt surface without affecting activity, thus increasing the turnover frequency. The changes in turnover frequency correlated with element electronegativity. In situ addition of H2S and (CH3)2S (2.5–10ppm) decreased activity at all concentrations. However, product selectivity was not affected. Addition of NH3 (4ppm) did not change catalytic performance. [Copyright &y& Elsevier]

Abstract: The effect of rhenium on the Fischer–Tropsch synthesis activity and selectivity of γ-Al2O3 supported cobalt catalysts was investigated in fixed-bed reactors at T =483K, P =20bar, and H2/CO=2.0. Catalysts containing 20wt.% cobalt and 0 or 0.5wt.% rhenium were prepared by incipient wetness impregnation of different γ-Al2O3 supports with aqueous solutions of cobalt nitrate hexahydrate and for the Re-promoted catalysts, also perrhenic acid. The γ-Al2O3 supports had very different pore characteristics. The post-calcination Co3O4 crystallite size was predominantly controlled by the γ-Al2O3 support pore diameter. Presence of Re had only a minor effect on the crystallite size. For all catalysts, supported Co3O4 was reduced in two steps to Co0 with CoO as intermediate species. However, while reduction of Co3O4 to CoO took place in the same temperature range for all catalysts, the reduction temperature of CoO to Co0 was dependent on the catalyst properties. Large particles present in wide pores were easier to reduce than small particles located in narrow pores. In addition, Re promoted the reduction of CoO. The effect of rhenium as a reduction promoter was less pronounced at increasing pore size and particle size. Re also had a similar positive impact on the cobalt dispersion of the catalysts. Although Re significantly increased the Fischer–Tropsch synthesis cobalt-time yield, it did not modify the site-time yield. The deactivation rates of all the catalysts were also similar up to 100h on stream. Positive correlations were found between the catalyst pore diameter and the C5+ selectivity and between the cobalt particle size and the C5+ selectivity. Re had a consistent positive, albeit small, effect on the C5+ selectivity. [Copyright &y& Elsevier]

Abstract: Dehydrogenation of propane (DHP) was studied over a series of xCr–SBA-15 and xCr–Al2O3 catalysts, prepared by incipient wetness impregnation, to gain a better understanding of the nature and distribution of Cr species and their catalytic function. To this end, the catalysts were characterized by N2-physisorption, X-ray diffraction (XRD), UV-Raman spectroscopy, scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM–EDXS) and X-ray absorption spectroscopy (XANES and EXAFS). All these characterization techniques indicate that, at ⩽1 wt% Cr, SBA-15 contains exclusively uniform distribution of chromium as isolated Cr(VI) species in tetrahedral () coordination, whilst on γ-Al2O3 a fraction of oligomers (including dimers) is present along with isolated species. At ⩾5 wt% Cr, SBA-15 is dominated by crystalline α-Cr2O3 particles, besides a fraction of isolated Cr(VI) species in coordination. Remarkably, γ-Al2O3 contains mainly oligomers with different degrees of nuclearity and a fraction of isolated species but no Cr2O3 particles. Among xCr–SBA-15 catalysts, those containing exclusively isolated Cr species (i.e., ⩽1 wt% Cr) exhibit higher activity and selectivity with respect to per mole of Cr than the catalyst dominated by crystalline α-Cr2O3 particles (⩾5 wt% Cr). The intrinsic activity of these isolated Cr species is higher than those observed on γ-Al2O3 (⩽1 wt% Cr). Interestingly, among xCr–Al2O3, the catalysts dominated by oligomeric species show the highest activity, indicating the important role of the species in the reaction. In situ XAS studies evidence that active Cr sites are apparently generated on-site during the reaction and that Cr is typically in (III) oxidation state. Based on ex situ and in situ characterization results and catalytic data, it appears that the activity of the Cr species is different in xCr–SBA-15 and xCr–Al2O3. For xCr–SBA-15, isolated Cr(III) sites with coordination number greater than four are more active, selective and stable than Cr sites on the surface of crystalline Cr2O3. In contrast, for xCr–Al2O3, oligomeric Cr species are more active and selective than the isolated Cr sites. [Copyright &y& Elsevier]

In situ X-ray absorption spectroscopy (XAS) has been performed to investigate the active site on Au-based catalysts in the water-gas shift (WGS) reaction. The surface area and hence the WGS activity is higher for AuTiO2 catalysts supported on carbon nanofibres (CNF) than TiO2. The WGS reaction rate depends on the Au coordination number with an apparent maximum close to eight which corresponds to a particle size of approximately 2.5–3.0 nm. A likely cause for the changes in the electronic structure of Au is the adsorption of CO on the surface, which also creates a small positive charge in the Au atoms. The catalytic activity significantly improves when titania is present compared to Au deposited directly on CNF. [ABSTRACT FROM AUTHOR]

Abstract: Au catalysts have been prepared (i) on TiO2, (ii) on carbon nanofibres (CNF) and (iii) on TiO2 deposited onto CNF. Catalysts prepared from deposition-precipitation (DP) and from colloid solutions have been characterised using XRD, TEM, TGA and XAS and tested in the water–gas shift (WGS) reaction. DP yields large Au particles (>50nm) on CNF-containing supports. High Au dispersion on carbon nanofibres requires preparation via other methods such as colloid formation. Au particle growth is more pronounced during the synthesis steps than during thermal treatments. This increase is not observed for the Au particles on TiO2 but only when CNF is present, indicating that the surface properties of TiO2 are altered by the CNF. TiO2 XANES analyses show that distortions in the lattice symmetry of TiO2 are introduced when the oxide is deposited on CNF. The distortion of the TiO2 structure by the CNF may also introduce changes that promote the turnover frequencies. The WGS activity significantly improves when titania is present. This shows that coexistence of Au and TiO2 is needed to obtain high catalytic activity in the WGS reaction, indicating that the active sites are either on the Au–TiO2 interface or that the reaction follows a bifunctional mechanism. [Copyright &y& Elsevier]

Abstract: The catalytic activity and stability in the water–gas shift reaction have been tested for Au-based catalysts prepared by deposition of Au from colloid solutions. The supports that have been used are TiO2, TiO2 supported on carbon nanofibres (CNF) and CNF. Thermal treatments of the samples show that the Au particle size depends on the support material and hence the interaction between the Au particles and the support. In situ X-ray absorption spectroscopic (XAS) measurements during the water–gas shift reaction show no changes in the first Au–Au coordination number for the catalysts containing CNF. Furthermore, improved short-time stability is obtained compared to the AuTiO2 catalysts. The improved stability is achieved by the CNF stabilising small TiO2 particles and hence prevent subsequent sintering of the Au particles. [Copyright &y& Elsevier]

The HUNT Biobank in Norway holds biological samples from 110,000 participants in the HUNT Study. The biobank contains a variety of samples, including blood, DNA, urine, and fecal samples, which are available for research purposes. The biobank has a unique identification number for each participant, allowing for linkage to local and national registries. The data and samples from the biobank are accessible to national and international research groups. The HUNT Study is a valuable resource for epidemiological studies, disease risk prediction, and clinical translation. The biobank collects and stores various types of samples, which are processed and stored at specific temperatures. The biobank uses a Laboratory Information Management System to manage and track the samples. The storage facilities include liquid nitrogen freezers, chest freezers, and automatic storage systems. The biobank also conducts DNA and RNA extractions, quality assurance, and biomarker analyses. The data and samples from the HUNT Biobank are accessible to researchers with approval from the Regional Committee for Medical and Health Ethics. [Extracted from the article]

Highlights: [•] High energy XAFS is demonstrated as an attractive option for in situ studies of catalysis at demanding conditions. [•] Both sets of experiments (Re K and LIII edges) indicate that Re is atomically distributed inside the bulk Co particles. [•] The local distortion of the Co environment in intimate contact with the Re atoms may give rise to the enhanced activity of Re-promoted catalysts. [Copyright &y& Elsevier]

Abstract: The surface properties of fishbone (FB) carbon nanofibers (CNFs) were altered. This was achieved by H2O-plasma treatment (FB-plasma) and oxidation in HNO3 (FB-HNO3). By zeta-potential measurements, the surfaces of as-grown and acid treated CNFs were found to be negatively charged at all pHs. Meanwhile, basic entities were introduced by H2O-plasma treatment, indicated by an isoelectric point of pH 4.6. Ultraviolet–visible measurements indicated the successful deposition of negatively charged Au colloids on FB-plasma, and incomplete deposition on FB-HNO3. The nature of the basic sites accommodating colloid deposition is discussed based on X-ray photoelectron spectroscopy (XPS) results. The XPS study indicated significant differences in the type and amount of surface groups. Also, a variation in the fraction of defect and/or edge sites was found. The possible sites responsible for colloid immobilization are discussed based on the XPS results. Plasma treatment is demonstrated as a simple and effective procedure for altering the surface characteristics of CNFs. [Copyright &y& Elsevier]