Vanadium-containing modified clays as catalysts for acetaldehyde production by ethanol selective oxidation

This work investigates use of natural clays as a sustainable raw material to prepare supported vanadium catalysts for the aerobic selective oxidation of ethanol to produce acetaldehyde. As dispersion and nature of the supported V species depend on its interaction with the support surface and its specific surface area, montmorillonite extracted from an Argentinian bentonite clay was pillared with titania, and vanadium was added by wet impregnation to get V/Ti-PILC catalysts. The effects of catalyst V content (0.5 – 2 wt%), reaction temperature (250 – 350 ºC) and O2/ethanol molar ratio (0.5 – 1.5) on their performance for this reaction were studied. Characterization by X-ray diffraction (XRD) and N2 adsorption/desorption isotherms showed that the synthesized catalysts maintained the mesoporous structure after the V addition, though their lamellar structure lost regularity. Under the reaction conditions explored, all the V/Ti-PILC catalysts were active and very selective to acetaldehyde (80 %), their activity increasing with V content. The highest activity was associated with the highest dispersion of isolated tetrahedral vanadium centers, identified by diffuse reflectance UV-Vis, Raman and X-ray photoelectron (XPS) spectroscopies. The highest ethanol conversion (87 %), with 85 % selectivity to acetaldehyde, was reached over the catalyst with 2 wt% of V at 350 ºC with O2/ethanol = 1. The acetaldehyde yield and selectivity values reached are comparable with those reported for related mesoporous catalysts, which allows to consider these supports a sustainable alternative for high surface area supported vanadium catalysts.Fil: Sabre, Ema Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Casuscelli, Sandra Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Cánepa, Analía Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Cortés Corberán, Vicente. Consejo Superior de Investigaciones Científicas; Españ

Oxidation of 5-hydroxymethylfurfural on supported ag, au, pd and bimetallic pd-au catalysts: Effect of the support

Fundacao para a Ciencia e Tecnologia (FCT), Portugal, through project UIDB/00100/2020 of the Centro de Quimica Estrutural; Associate Laboratory for Green Chemistry-LAQV,financed by national funds from FCT/MCTES (UIDB/50006/2020); FCT Scientific Employment Stimulus-Institutional Call (CEECINST/00102/2018) and PTDC/QEQ-QIN/3967/2014; Tomsk Polytechnic University Competitiveness Enhancement Program project VIU-RSCBMT-197/2020; Russian Foundation of Basic Research, project 18-29-24037; Tomsk Polytechnic University State Task `Science' (project FSWW-2020-0011) andMICINN project CTQ2017-86170-R (Spain).Oxidation of 5-hydroxymethylfurfural (HMF), a major feedstock derived from waste/fresh biomass, into 2,5-furandicarboxylic acid (FDCA) is an important transformation for the production of biodegradable plastics. Herein, we investigated the effect of the support (unmodified and modified titania, commercial alumina, and untreated and treated Sibunit carbon) of mono-and bimetallic catalysts based on noble metals (Ag, Au, Pd) on selective HMF oxidation with molecular oxygen to FDCA under mild and basic reaction conditions. The higher selectivity to FDCA was obtained when metals were supported on Sibunit carbon (Cp). The order of noble metal in terms of catalyst selectivity was: Ag < Au < Pd < PdAu. Finally, FDCA production on the most efficient PdAu NPs catalysts supported on Sibunit depended on the treatment applied to this carbon support in the order: PdAu/Cp < PdAu/Cp-HNO3 < PdAu/Cp-NH4OH. These bimetallic catalysts were characterized by nitrogen adsorption-desorption, inductively coupled plasma atomic emission spectroscopy, high resolution transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Hammet indicator method and X-ray photoelectron spectroscopy. The functionalization of Sibunit surface by HNO3 and NH4OH led to a change in the contribution of the active states of Pd and Au due to promotion effect of N-doping and, as a consequence, to higher FDCA production. HMF oxidation catalyzed by bimetallic catalysts is a structure sensitive reaction.publishersversionpublishe

Effect of the metal deposition order on structural, electronic and catalytic properties of tio2-supported bimetallic au-ag catalysts in 1-octanol selective oxidation

42-01-09/169/2021-4 CTQ2017-86170-RAu and Ag were deposited on TiO2 modified with Ce, La, Fe or Mg in order to obtain bimetallic catalysts to be used for liquid-phase oxidation of 1-octanol. The effects of the deposition order of gold and silver, and the nature of the support modifying additives and redox pretreatments on the catalytic properties of the bimetallic Au-Ag catalysts were studied. Catalysts were characterized by low-temperature nitrogen adsorption–desorption, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and ultraviolet-visible diffuse reflectance spectroscopy. It was found that pretreatments with hydrogen and oxygen at 300◦C significantly decreased the activity of AuAg catalysts (silver was deposited first) and had little effect on the catalytic properties of AgAu samples (gold was deposited first). The density functional theory method demonstrated that the adsorption energy of 1-octanol increased for all positively charged AuxAgyq (x + y = 10, with a charge of q = 0 or +1) clusters compared with the neutral counterparts. Lanthanum oxide was a very effective promoter for both monometallic and bimetallic gold and silver catalysts in the studied process.publishersversionpublishe

Effect of gold electronic state on the catalytic performance of nano gold catalysts in n-octanol oxidation

UIDB/50006/2020 project VIU-RSCBMT-65/2019 project 18-29-24037 (Russia) MINECO project CTQ2017-86170-R (Spain)This study aims to identify the role of the various electronic states of gold in the catalytic behavior of Au/MxOy/TiO2 (where MxOy are Fe2O3 or MgO) for the liquid phase oxidation of n-octanol, under mild conditions. For this purpose, Au/MxOy/TiO2 catalysts were prepared by deposition-precipitation with urea, varying the gold content (0.5 or 4 wt.%) and pretreatment conditions (H2 or O2), and characterized by low temperature nitrogen adsorption-desorption, X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDX), scanning transmission electron microscopy-high angle annular dark field (STEM HAADF), diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy of CO adsorption, temperature-programmable desorption (TPD) of ammonia and carbon dioxide, and X-ray photoelectron spectroscopy (XPS). Three states of gold were identified on the surface of the catalysts, Au0, Au1+ and Au3+, and their ratio determined the catalysts performance. Based on a comparison of catalytic and spectroscopic results, it may be concluded that Au+ was the active site state, while Au0 had negative effect, due to a partial blocking of Au0 by solvent. Au3+ also inhibited the oxidation process, due to the strong adsorption of the solvent and/or water formed during the reaction. Density functional theory (DFT) simulations confirmed these suggestions. The dependence of selectivity on the ratio of Brønsted acid centers to Brønsted basic centers was revealed.publishersversionpublishe

Oxidative dehydrogenation of hydrocarbons on nanostructured catalysts

Trabajo presentado en la III International scientific school-conference for young scientists catalysis: from science to industry, celebrada en Tomsk (Rusia) del 26 al 30 de octubre de 2014.Peer Reviewe

Heterogeneous selective oxidations with nanostructured catalysts

Trabajo presentado en el 1st CZM Workshop on Catalysis, celebrado en Clausthal (Alemania) del 22 al 23 de noviembre de 2013.Peer Reviewe

Selectivity Control in Oxidation of 1-tetradecanol on Supported Nano Au Catalysts

Trabajo presentado en el 12th European Congress on Catalysis (EuropaCat-XII), celebrado en Kazan (Rusia) del 30 de agosto al 4 de septiembre de 2015.Selective oxidation of tetradecanol, a representative higher fatty alcohol, has received little attention despite the great industrial interest of its products, myristaldehyde (tetradecanal) and myristyl myristate (tetradecyl tetradecanoate). We investigate here the effect of operation conditions (temperature, run time and alcohol/metal (A/M) ratio) on the catalytic performance of Au/CeO2-Al2O3 catalyst to assess the factors that control selectivity. The results confirm the previous hypothesis that the acid formation only starts when the produced water saturates the hydrophilic surface of the support and becomes available as reactant. This makes A/M a critical factor to control selectivity to aldehyde and acid. Nevertheless, by proper selection of operation parameters, high yields to either aldehyde or acid can be reached with high selectivity. Selectivity to the ester is less sensible to operation parameters.Peer Reviewe

Selectivity control in oxidation of 1-tetradecanol on supported nano Au catalysts

Selective oxidation of tetradecanol, a model higher fatty alcohol, on Au/CeO-AlO catalyst has been investigated to assess the factors that control selectivity. The analysis of the effect of operation conditions (temperature, run time and alcohol/metal (A/M) ratio) on catalytic performance revealed a quite complex reaction network, in which acid formation starts only after a certain level of conversion is reached. This level depends linearly on the total support surface available, indicating that it must be saturated by species generated by the reaction itself to allow acid formation to start. Addition of water to reaction medium did not modify this level, indicating that such species is not adsorbed water, as previously hypothesized, but probably spilled over hydrogen species. The resulting drastic change in the selectivity trends makes the ratio A/M a critical factor to control selectivity to aldehyde and to acid. Selectivity to ester is less sensible to operation parameters. It is noteworthy that aldehyde yields up to 27% with 90% selectivity, and acid yields up to 40% with 81% selectivity can be reached by proper selection of operation parameters.Funding of this work by CSIC (project 201480E070) and MINECO (project CTQ2013-41507-R) is greatfully acknowledged

Causes of Activation and Deactivation of Modified Nanogold Catalysts during Prolonged Storage and Redox Treatments

The catalytic properties of modified Au/TiO2 catalysts for low-temperature CO oxidation are affected by deactivation and reactivation after long-term storage and by redox treatments. The effect of these phenomena on the catalysts was studied by HRTEM, BET, SEM, FTIR CO, XPS and H2 TPR methods. The main cause for the deactivation and reactivation of catalytic properties is the variation in the electronic state of the supported gold, mainly, the proportion of singly charged ions Au+. The most active samples are those with the highest proportion of singly charged gold ions, while catalysts with a high content of trivalent gold ions are inactive at low-temperatures. Active states of gold, resistant to changes caused by the reaction process and storage conditions, can be stabilized by modification of the titanium oxide support with transition metals oxides. The catalyst modified with lanthanum oxide shows the highest stability and activity.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).This work was funded by CONACYT project 260409 and PAPIIT-UNAM project IT200114 (Mexico); CSIC project 201180E104 and MINECO project CTQ2013-41507-R (Spain); and Government Program “Science” of Tomsk Polytechnic University, grant No. 4.1187.2014/K (Russia)