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This study explores the performances of nickel‐based materials for the dry reforming of methane (DRM), an important process for hydrogen and syngas productions. Ni nanoparticles are issued from porous phyllosilicate phase exolution under reducing conditions (in situ or ex situ). Phyllosilicate precursors were obtained by deposition/precipitation with urea onto SBA‐15 porous silica, with metal loading up to 40 wt.%. Reaction was performed at 600–700 °C. The successful formation and stabilization of highly dispersed nanoparticles (2–6 nm) is revealed, even for highly loaded formulations (20 wt.% and 40 wt.%). In DRM‐700 (CH4/CO2=1, 20 % CH4, 480,000 mL gcat−1 h−1) the formulation at 20 wt.% metal loading (Ni_20 %) activated during reaction affords 50 % and 65 % of CH4 and CO2 conversions respectively at 700 °C. Ni_20 % is showing excellent resistance toward sintering after DRM stability test of 80 h. Characterizations made for spent catalyst show high resistance toward sintering and limited carbon formation. [ABSTRACT FROM AUTHOR]

Lanthanum orthoferrite, a highly potential 3‐way catalyst, shaped as a polycrystalline thin film has been comprehensively analysed by combining bulk and surface characterization techniques. The possibility to accomplish unprecedented surface information has been presented, thanks to the combined use of LEIS, XPS, and ToF‐SIMS. The structural, morphological, and surface properties at nanometric scale make such thin films indistinguishable from powdered solids. Thus, the relevance of using such model materials for advanced surface investigations of LaFeO3±δ‐based 3‐way catalysts has been demonstrated. [ABSTRACT FROM AUTHOR]

Ceria supported copper oxide catalysts were produced by a deposition–precipitation method, at a high copper loading (up to ＞25 wt%). These materials demonstrated excellent properties for glycerol selective conversion to lactic acid, with a conversion reaching up to 87% with a selectivity to lactic acid of 74% (8 h reaction, 220 °C, under N2 pressure). These catalysts also exhibited high stability upon 5 successive reaction cycles. The formation of a crystalline CuO phase was demonstrated in the nanocomposites at a high Cu loading, with elongated shaped particles formed on the cerium oxide surface. Such particles were however, not observed at low Cu loadings. XPS analysis revealed that Cu(ii) was the main Cu species on the fresh catalyst, and that this species was reduced to Cu(i) during the reaction. Complementary characterization over the spent catalyst clearly showed the morphological modifications of the CuO phase, however, did not impact significantly either glycerol conversion or selectivity to lactic acid upon recycling. For instance, apparently, the catalytic activity of CuO largely depends on the Cu(ii) species. [ABSTRACT FROM AUTHOR]

The Guerbet reaction of ethanol to heavier products was performed over a series of extensively characterized Sr-substituted hydroxyapatites (HAPs) with different (Ca+Sr)/P ratios, and thus different structural, textural, and acid-base properties. The acid-base properties were correlated with the reactivity of the solids and an optimal ratio between the amount of acid and basic sites was determined (ca. 4), whereas the ethanol conversion was mainly depending on the specific surface area of the solids. The stoichiometric 100 mol % Sr-substituted sample (SrAp-100) was especially efficient in higher alcohols production, which can be illustrated by a total alcohol selectivity (76.4 %) higher than that of all the other solids at a 13 % ethanol isoconversion. [ABSTRACT FROM AUTHOR]

Ammoxidation of acrolein to acrylonitrile was studied using multicomponent (MC) BiMoO x catalysts in the presence of ammonia and oxygen. The MC catalysts containing bivalent and trivalent metal promoters were found to be highly active and selective to acrylonitrile. The corresponding MC catalysts were characterized by X-ray diffraction, nitrogen physisorption, X-ray photoelectron spectroscopy, ICP-MS and UV-visible diffuse reflectance spectroscopy. It was observed that, among the bivalent cations, the catalysts containing both Co-Ni showed superior performances due to the presence of the metastable β-CoNiMoO phase. The presence of a trivalent cation, and especially of iron, promoted the formation of both the γ-BiMoO active phase and the active β-phase of bivalent metal molybdate. Further, optimization of the reaction conditions enabled the achievement of a 59 % acrylonitrile yield. [ABSTRACT FROM AUTHOR]

The ammoxidation of allyl alcohol was demonstrated over antimony–iron oxide catalysts with a Sb/Fe ratio of 0.6 and 1. Both catalysts showed high performance with 83 and 84% yield of acrylonitrile, respectively, whereby the main difference was found in the initial performance. This was ascribed to the in-operando formation of the SbFeO4 mixed oxide on the catalyst surface under reaction conditions, as proven by XPS analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stable and selective bimetallic Ni-Fe catalyst was study in the aqueous phase hydrogenation of xylose to xylitol. • The benefits of using Fe as a promoter of Ni: increasing the catalyst activity and chemical stability of the catalyst. • Reduced Fe at the surface increased both the first-order apparent rate constant and the adsorption constant of xylose. • The restructuring of the bimetallic nanoparticles occurred as the metal particles sizes and the Fe proportion in the surface layers increased. A monometallic Ni and a bimetallic Ni-Fe catalyst were used in the aqueous phase hydrogenation of xylose in batch conditions (T = 50–150 °C, P H2 = 10–30 bar, xylose mass fraction in water = 3.7–11.0 wt.%) to evidence the benefits of promoting Ni by Fe. The activity of the catalysts increased with temperature, but a temperature of 80 °C allowed minimizing nickel leaching at full conversion. The presence of reduced Fe at the surface of the bimetallic nanoparticles increased both the first-order apparent rate constant and the adsorption constant of xylose. The catalytic activity of Ni/SiO 2 strongly declined and no deactivation was found for the Ni-Fe catalyst. A restructuring of the bimetallic nanoparticles took place, as the size of the metal particles and the Fe proportion in the surface layers increased, suggesting a flattening and coalescing of the particles over the silica surface. [ABSTRACT FROM AUTHOR]

Ordered mesoporous silica SBA-15 and KIT-6 supported Ni/ZrO 2 catalysts are evaluated for the hydrodeoxygenation of guaiacol (stirred batch reactor, 300 °C, 50 bar of H 2), guaiacol being a model compound of bio-oil issued from the lignin fraction of biomass liquefaction. ZrO 2 and Ni are dispersed using incipient-wetness impregnation (IWI) or two-solvent (TS) method over mesoporous silica. Mesoporous zirconia (nanocasting method) and conventional zirconia were also used as supports. Cyclohexane, cyclohexanol and methoxycyclohexanol are the main products of reaction. Significant differences in cyclohexane yield are measured (after 8 h reaction, with conversion in most cases above 85%): NiZr-KIT-TS, 71.6% > NiZr-SBA-TS, 63.3% ≫ Ni/meso-Zr, 7.8% > NiZr-SBA-IWI, 5.2% > Ni/ZrO 2 , 1.6%. Tetragonal ZrO 2 phase, acting as oxophilic phase for guaiacol/oxygenated intermediates adsorption and activation, is observed whatever the approach selected for the preparation. However, when nickel is supported over pure zirconia, low selectivity to cyclohexane is obtained, while the main product becomes cyclohexanol with yields reaching ~40%. Better activities and selectivities toward total deoxygenation (cyclohexane production) are obtained for the silica supported Ni–ZrO 2 catalysts, especially when the catalyst is prepared by the two-solvent approach. Improvement is associated to the proximity between Ni and ZrO 2 particles when confined in the silica mesopores. Finally, conversion and yield to cyclohexane obtained with NiZr-KIT-TS are stable during 5 successive catalytic cycles demonstrating the absence of significant modification of the catalyst during reaction. These results are evidencing that the confining strategy is efficient to improve stability of active elements during HDO reaction. Image 1 • Impregnation over ordered mesoporous silica leads to tetragonal phase ZrO 2. • Mesopore confined Ni–ZrO 2 nanoparticles promoted the HDO of guaiacol to cyclohexane. • Two-solvent method is more appropriate than incipient wetness impregnation for obtaining efficient catalysts. • Mesoporous silica supported Ni–ZrO 2 catalysts are stable during 5 reaction cycles of guaiacol HDO. [ABSTRACT FROM AUTHOR]

Abstract: Novel rhenium oxide catalysts have been prepared by impregnation of mesoporous TiO2-anatase support using amounts of homometallic, such as Re4O4(OEt)12, and heterometallic, such as Ta4O2(OEt)14(ReO4)2, rhenium alkoxide solutions with subsequent thermal treatment. The structure of the produced catalytic centers was investigated by X-ray diffraction, XPS, and IR spectroscopy in order to examine the role of Re in enhancing catalytic activity. It has been demonstrated that rhenium is mostly present as perrhenate ligands attached via an oxo-bridge to an oxide surface. The catalytic activity was studied for the selective oxidation of methanol as model reaction, revealing selectivity strongly dependent on the nature of the molecular precursor: in case of ReO x /TiO2, the catalysts are showing selectivity to formaldehyde, and in case of ReO x /Ta2O5/TiO2 to DMM in rich conditions. [Copyright &y& Elsevier]

[Display omitted] • The structure and surface composition of Cu- and Mn-doped La 0.7 FeO 3 was refined using both bulk and surface characterization techniques • The CuO segregated phase plays the role of redox-active center in Cu-LaFeO 3 material. • Mn 3 + cations embedded at B-site of the perovskite lattice are the major redox-active centers in Mn-doped La 0.7 FeO 3. The present work aims at presenting our investigations on the redox behaviour of Cu- or Mn-doped LaFeO 3 -based perovskite powders under three-way catalysis (TWC) relevant conditions. Two distinct La-deficient catalysts of generic formula La 0.67 Fe 0.8 Mn 0.2 O 3 and La 0.67 Fe 0.8 Cu 0.2 O 3 denoted as Mn-dLFO and Cu-dLFO, respectively, were prepared based on the conventional citrate complexation route and systematically investigated using complementary characterisation techniques. This study has made it possible to highlight fundamentally different structures. In Cu-dLFO, most Cu 2 + cations are expelled from the LaFeO 3 perovskite lattice in the form of a segregated CuO phase. On the other hand, in the case of Mn-dLFO, majority of Mn 3 + cations are stabilised within the perovskite solid solution, while substantial iron exsolution in the form of an additional α -Fe 2 O 3 phase was evidenced. The evolution of both catalysts during CO-TPR using operando Raman revealed the formation of polycyclic aromatic hydrocarbons (PAHs) besides the relative structural stability of the LaFeO 3 lattice. The reduction of Mn 3 + to Mn 2 + , indirectly suggested by Raman analysis, is further supported by a quasi- in situ XPS study. The latter also evidenced the reduction of CuO to metal copper to a large extent in Cu-dLFO. In addition, a share of the α -Fe 2 O 3 phase present in Mn-dLFO is reduced to metal Fe 0 during CO oxidation, and is fully re-oxidised upon NO reduction. Our investigation thus evidences that both copper and manganese sites in Cu-dLFO and Mn-dLFO, respectively, are redox-active centres upon CO oxidation/NO reduction with, however, varying operating modes underpinned by their fundamentally different structures. [ABSTRACT FROM AUTHOR]