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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]

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]

A quasi-homogeneous solution of gold nanoparticles prepared by the Turkevich method was used as an unconventional catalyst in the oxidation of glycerol (GLY) in the liquid phase. The highest obtained conversion was 100 % after 3 h of reaction at 100 °C under an oxygen atmosphere (5 bar). The main products were glyceric, glycolic, formic, tartronic, and oxalic acid with selectivities of 28, 36, 25, 9, and 2 %, respectively. Traces of hydroxypyruvic and acetic acid were also detected (combined selectivities below 1 %). To elucidate the reaction mechanism and specify the role of gold nanoparticles in the oxidation process, a series of experiments under various reaction conditions were carried out. The effect of reaction temperature, oxygen pressure, gold concentration, and GLY/base molar ratio was investigated. All catalytic results were systematically compared to the corresponding noncatalytic base-induced transformations (blank tests). Such an approach allowed us to separate and clarify the respective driving parameters for the transformation of GLY (presence of a base and activity of the gold catalyst). The reaction mechanism comprised a series of oxidation and CC cleavage reactions, whereas additional oxidation-reduction reactions (of the Cannizzaro type) could also occur in the presence of the base. [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]