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Nicotinamide adenine dinucleotide NAD(P)H is a prolific cofactor in oxidoreductases biochemistry, but its high cost and the stoichiometric amounts motivates significant research for establishing efficient solutions for regenerating NAD(P)H from NAD(P)+. This study presents nanoparticles of gold/layered double hydroxides (AuNPs/LDH) as nanoplatforms with highly efficient photocatalytic response for solar‐light promoted NADH regeneration. The novel photocatalysts are obtained via self‐assembling of ZnAlLDH and AuNPs by using the manifestation of the "structural memory" of the anionic clay in gold salt solution. The chemical composition, structural, optical and nanotextural features of AuNPs/LDH have been assessed by transmission electron microscopy (TEM), energy dispersive X‐Ray Spectroscopy (EDX), powder X‐ray diffraction (XRD), and UV‐Vis Spectroscopy (UV‐Vis). It was found that, at pH 8 and in the presence of flavin mononucleotide (FMN) as a mediator and using water as an electron donor, the regeneration the NADH under solar light is defined by a rate of 20.5 μM/h. Furthermore, the regenerated NADH cofactor is tested in presence of Horseradish Peroxidase (HRP) enzyme to promote the hydrogen peroxide reduction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First demonstration of efficient glycerol oxidation by laser activation of Gold Nanoparticles. • Glycerol oxidation is induced by thermoplasmonic effect of photoexcited GNPs. • More than 90% of Glycerol are converted after 2 h without any external source of heat. • The laser activation is 2.5 times more efficient than thermal activation at 60 °C. • Hot electron transfer between GNPs and TiO 2 contributes to the enhancement. Abstract In this work, we highlight the feasibility of new efficient catalytic processes by laser excitation, exemplified in the reaction of oxidation of glycerol over catalysts based on supported gold nanoparticles. We show that this catalytic oxidation reaction can efficiently proceed via laser excitation of surface plasmon resonance of gold nanoparticles, inducing local thermal heating effect. While the reaction did not occur in the absence of any external heat source, with this original approach, 88% of glycerol was converted after 2 h, leading to the formation of glyceric acid and tartronic acid as main products. The photonic activation led to 2.5 times more efficient conversion than an equivalent thermal activation by conventional heating source. Investigations of the laser power and the nature of support catalyst revealed a significant contribution of electron transfer from plasmonic nanoparticles to TiO 2 in the oxidation reaction. [ABSTRACT FROM AUTHOR]

Chemisorption of propene and propane was studied in a pulse reactor over a series of cobalt silica-supported Fischer-Tropsch catalysts. It was shown that interaction of propene with cobalt metal particles resulted in its rapid autohydrogenation. The reaction consists in a part of the propene being dehydrogenated to surface carbon and CH x chemisorbed species; hydrogen atoms released in the course of propene dehydrogenation are then involved in hydrogenation of remaining propene molecules to propane at 323-423 K or in propene hydrogenolysis to methane and ethane at temperatures higher than 423 K. The catalyst characterization suggests that propene chemisorption over cobalt catalysts is primarily a function of the density of cobalt surface metal sites. A correlation between propene chemisorption and Fischer-Tropsch reaction rate was observed over a series of cobalt silica-supported catalysts. No propane chemisorption was observed at 323-373 K over cobalt silica-supported catalysts. Propane autohydrogenolysis was found to proceed at higher temperatures, with methane being the major product of this reaction over cobalt catalysts. Hydrogen for propane autohydrogenolysis is probably provided by adsorbed CH x species formed via propane dehydrogenation. Propene and propane chemisorption is dramatically reduced upon the catalyst exposure to synthesis gas (H2/CO = 2) at 323-473 K. Our results suggest that cobalt metal particles are probably completely covered by carbon monoxide molecules under the conditions similar to Fischer-Tropsch synthesis and thus, most of cobalt surface sites are not available for propene and propane chemisorption. [ABSTRACT FROM AUTHOR]

Abstract: The effect of cobalt precursor and pretreatment conditions on the structure of cobalt species in silica-supported Fischer–Tropsch (FT) catalysts was studied with a combination of characterization techniques (X-ray diffraction, UV–visible, X-ray absorption, X-ray photoelectron spectroscopies, DSC-TGA thermal analysis, propene chemisorption, and temperature-programmed reduction combined with in situ magnetic measurements). The catalysts were prepared via aqueous impregnation of silica with solutions of cobalt nitrate or acetate followed by oxidative pretreatment in air and reduction in hydrogen. It was found that after impregnation and drying cobalt exists in octahedrally coordinated complexes in catalysts prepared from cobalt nitrate or cobalt acetate. Decomposition of the octahedral complexes results in the appearance of Co3O4 crystallites and cobalt silicate species. Cobalt repartition between crystalline Co3O4 and the cobalt silicate phase in the oxidized samples depends on the exothermicity of salt decomposition in air and the temperature of the oxidative pretreatment. Co3O4 crystallite is the dominant phase in the samples prepared via endothermic decomposition of supported cobalt nitrate. Significantly higher cobalt dispersion is found in the catalyst prepared via low-temperature cobalt nitrate decomposition. The uncovered enhanced cobalt dispersion is associated with lower cobalt reducibility. The high exothermicity of cobalt acetate decomposition leads primarily to amorphous, barely reducible cobalt silicate. A more efficient heat flow control at the stage of cobalt acetate decomposition significantly increases the concentration of easy reducible Co3O4 in the oxidized catalysts and the number of cobalt metal active sites after reduction. The catalytic measurements show that FT reaction rates depend on the number of cobalt surface metal sites; a higher concentration of cobalt metal sites in the catalysts prepared from cobalt nitrate or with the use of soft cobalt acetate decomposition results in higher catalytic activity in FT synthesis. [Copyright &y& Elsevier]

The design of an "H"‐shaped reactor has been studied to satisfy the possibility of using a triphasic medium to transform d‐glucose into 5‐hydroxymethylfurfural (HMF) by a hybrid catalytic process using an immobilized glucose isomerase, allowing the isomerization of D‐glucose to d‐fructose, and a heterogeneous chemical catalyst to catalyze the dehydration of d‐fructose to HMF. The various parameters influencing the transport of d‐fructose within the reactor were studied, namely the difference in pH between the two aqueous phases, the agitation and the quantity of 3,4‐DCPBA/Aliquat336® used to extract and transport continuously the d‐fructose. The pH discrepancy, which must be between 5.0 and 5.5, turns out to be the real driving force behind the extraction of D‐fructose. The D‐Fru/3,4‐DCPBA molar ratio of 1/0.25 allowed the transport of more than 80 % of the D‐fructose initially present and shows that the same molecule of 3,4‐DCPBA is involved at least twice in the transport of D‐fructose and that the 3,4‐DCPBA/Aliquat336® couple performs a turnover within the organic phase. Finally, a HMF production yield of 30.9 % and an isomerization yield of 79.1 % were obtained, illustrating the shift in the isomerization equilibrium made possible by a D‐fructose extraction yield of 96.8 %. [ABSTRACT FROM AUTHOR]

In the present study, kinetic analysis and modelling of the glycerol oxidation reaction over unsupported Au particles were performed. The reaction pathways, which were determined in agreement with the experimental results, comprise two types of reactions, namely oxidation and C-C cleavage. A homogeneous catalytic reaction model was proposed by considering the occurrence of the non-catalytic reaction, the effect of the temperature, as well as NaOH and catalyst concentrations. The proposed kinetic model could adequately describe the data. The reaction under basic conditions but in the absence of a catalyst favoured the formation of C-C cleavage products (glycolic and formic acids), while in the presence of unsupported Au particles the oxidation to glyceric acid and the direct oxidation of glycerol to formic acid were promoted. Finally, it was observed that the formation of tartronic acid was not promoted by the catalyst and followed the non-catalytic route. Practical applications: The building of a kinetic model for glycerol oxidation in liquid phase using gold-based catalyst allows to better understand the mechanism leading to oxidation and C-C cleavage responsible to some change of selectivities in the process. The model parameters obtained in this study would be used to scale an industrial unit in a reactor modeling. The present work describes a homogeneous catalytic kinetic model of the glycerol (GLY) oxidation, by using unsupported Au nanoparticles. The proposed model includes the occurrence of the non-catalysed reaction in basic media and the effect of the reaction temperature, NaOH/GLY ratio and GLY/Au ratio. The model predicted well the experimental results. Unsupported Au nanoparticles were selective to glyceric acid and C-C cleavage products like formic and glycolic acids. [ABSTRACT FROM AUTHOR]

The activity of four different noble metals (Ag, Au, Pd and Pt) in the liquid phase oxidation of pure glycerol was confronted with the results obtained with a crude glycerol fraction, received from a large-scale biodiesel production plant. The catalysts were characterized by numerous techniques, giving insight into actual metal loading (elemental analysis by ICP and XRF), surface morphology (nitrogen absorption methods—BET and porosity), chemical state of both the support and the metal (XRD and XPS), and, finally, the metal particle size distribution (TEM microscopy). A good dispersion of totally reduced noble metal particles of a nanometric size (an average metal diameters were equal 3.5 nm, 4.2 nm, 4.7 nm and 21.2 nm for respectively Pd, Pt, Au and Ag) was accompanied with a comparable values of total metal loadings on the alumina support (from 0.95 and 0.96 wt.% for Pt and Pd, up to 0.98 and 1.13 wt.% for Au and Ag supported catalysts, respectively). In terms of initial reaction rate, the most active sample was the Au/Al 2 O 3 catalyst, both using pure (12976 mol h −1 mol Au −1 ) or crude glycerol (1230 mol h −1 mol Au −1 ). However, comparison of the selectivities and conversions after 1–2 h shows that the most robust and resistant catalyst – toward the impurities present in crude glycerol – is Pd/Al 2 O 3 , with a loss of conversion less than 50% (in respect to analogous reaction using pure glycerol) and almost unchanged high selectivity to glyceric acid (close to 80–90%). Ag/Al 2 O 3 also showed a relatively high resistance to impurities in terms of glycerol conversion, but with a drastic modification of its selectivity. The activity of the two other catalysts was dramatically affected with a conversion divided by ca. 4 and even 10 for the Pt and the Au catalysts, respectively, when using crude glycerol instead of pure glycerol. Finally, the effect of each main impurity (MONG-NM, i.e. , matter organic non-glycerol and non-methanol; ash; methanol; sulphur compounds) was independently studied. In any case, the sulphur compounds and MONG-NM were the impurities the most detrimental for the performances of catalysts. Thus, they should be removed in priority from crude glycerol fractions before reaction, while ashes and methanol should not be considered as completely undesirable. [ABSTRACT FROM AUTHOR]

Abstract: A new reaction setup using a gold-based catalytic microcapillary reactor was developed. In order to immobilize the gold nanoparticles onto the fused silica inner wall, two different linkers were used: (3-aminopropyl)triethoxysilane (APTES) and (3-mercaptopropyl)triethoxysilane (MPTES). Three different types of gold nanoparticles: (i) Turkevich gold nanoparticles (Citrate–Au), (ii) polyvinylpyrrolidone stabilized gold nanoparticles (PVP–Au) and (iii) polyvinylalcohol stabilized gold nanoparticles (PVA–Au) were synthesized to be anchored on the microcapillary internal surface. The catalytic efficiency of these new microsystems has been investigated for oxidation as a function of the nature of the linkers and/or the type of gold nanoparticles. The oxidation of benzyl alcohol in the presence of H2O2 was used to evaluate the catalytic performance of these microreactors. Under the reaction conditions (80°C, resident time=639s), the Citrate–Au nanoparticles leaked out slightly from the capillary reactor, whereas high conversions (>90%) and high selectivity to benzoic acid were achieved with PVP–Au and PVA–Au nanoparticles. A catalytic microreactor based on MPTES/PVP–Au functionalization proved to be the most effective for this reaction. [Copyright &y& Elsevier]

• Co-deposition of Ni(II) and Fe(II) by DPU requires the absence of oxidizing species. • The result is an ill-crystallized Fe-containing Ni(II) 1:1 phyllosilicate phase. • Fe reduction is triggered by Ni reduction but needs high temperatures to be complete. • fcc Fe-Ni particles are formed with a standard deviation in composition of 8 at %. • A surface enrichment in Fe is evidenced by Mössbauer spectroscopy. Supported Fe-Ni catalysts have been reported for their activity and selectivity in the hydrogenation of unsaturated organic molecules. However, the control of the size and composition of the bimetallic nanoparticles remains a bottleneck when oxide-supported catalysts are prepared by impregnation, and alternative procedures should be investigated. Starting with Ni(II) and Fe(II) sulfates as precursor salts, deposition-precipitation with urea (DPU) on SiO 2 in an inert atmosphere initially leads to the formation of an ill-crystallized Fe-containing Ni(II) 1:1 phyllosilicate, which reduces under hydrogen at 700 °C into bimetallic fcc Fe-Ni nanoparticles of 5.4 nm in average. Compared with the composition of the DPU solution (50 Fe at %, 50 Ni at %), an excess of Ni is detected on the catalyst (38 Fe at %, 62 Ni at %), due to the preferential reaction of Ni2+ ions with silica. In situ X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy show that the reduction of Fe ions to the metallic state is triggered by the formation of reduced Ni centers above 350 °C, and, from then, proceeds progressively, resulting in an excess of Fe in the outer shells of the bimetallic particles. The composition of individual Fe-Ni particles evidences a standard deviation of 8%. The bimetallic Fe-Ni/SiO 2 catalyst gives high yields in furfuryl alcohol in the hydrogenation of furfural, in contrast with an analog Ni/SiO 2 catalyst that favours side-reactions of etherification, hydrogenolysis and hydrogenation of the furan ring. [ABSTRACT FROM AUTHOR]

Notably available from the cellulose contained in lignocellulosic biomass, glucose is a highly attractive substrate for eco-efficient processes towards high-value chemicals. A recent strategy for biomass valorization consists on combining biocatalysis and chemocatalysis to realise the so-called chemo-enzymatic or hybrid catalysis. Optimisation of the glucose conversion to 5-hydroxymethylfurfural (HMF) is the object of many research efforts. HMF can be produced by chemo-catalyzed fructose dehydration, while fructose can be selectively obtained from enzymatic glucose isomerization. Despite recent advances in HMF production, a fully integrated efficient process remains to be demonstrated. Our innovative approach consists on a continuous process involving enzymatic glucose isomerization, selective arylboronic-acid mediated fructose complexation/transportation, and chemical fructose dehydration to HMF. We designed a novel reactor based on two aqueous phases dynamically connected via an organic liquid membrane, which enabled substantial enhancement of glucose conversion (70%) while avoiding intermediate separation steps. Furthermore, in the as-combined steps, the use of an immobilized glucose isomerase and an acidic resin facilitates catalyst recycling. [ABSTRACT FROM AUTHOR]

Through biomass valorization, sugars can become a major carbon resource for the production of fuels and chemicals by using catalysis. Hybrid catalysis, a direct combination of biocatalysis and chemocatalysis, may yield innovative solutions. 5-Hydroxymethylfurfural (5-HMF) is a platform molecule derived from glucose, for which fructose is a key intermediate. To overcome the thermodynamic enzymatic equilibrium between glucose and fructose, two methodologies based on hybrid catalysis are described herein. In the first method, the glucose isomerase and fructose-to-5-HMF dehydration chemocatalysts are simultaneously implemented in a multiphasic way to imply the complexation and transport of fructose. The second method proposes a route through sorbitol, obtained by the hydrogenation of glucose. Sorbitol is then enzymatically converted into fructose, whereas regeneration of the cofactor is performed in situ with an organometallic complex as a chemocatalyst. [ABSTRACT FROM AUTHOR]

Highlights: [•] Three methods for fine control of the deposition of gold nanoparticles on oxide supports are compared. [•] Thiol moieties inhibit the oxidation reaction more strongly than conventional antioxidants do. [•] Glycerol oxidation is blocked by the presence of SH groups on the catalysts surface. [Copyright &y& Elsevier]

Due to its three hydroxyl groups, glycerol is a potential starting material for various high value fine chemicals such as dihydroxyacetone, tartronic acid and mesoxalic acid. The corresponding oxidation reactions are catalysed by various metals such as palladium, platinum, bismuth or gold. Nevertheless, the selectivity not only depends on the type of the active phase, but is also influenced by numerous parameters such as the metal particles size, the pore size of the support and the pH of the reaction medium. This review not only describes the recent developments in the field of research for new catalysts but also spotlights the role of the reaction conditions as well as the possible transport limitations in this tri-phasic system. Furthermore, an economical analysis of some processes is given, which shows that this is realistic to envision sustainable production of, e.g., dihydroxyacetone. [ABSTRACT FROM AUTHOR]

[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]