In this study, 5-hydroxymethylfurfural (HMF) oxidation was carried out via both the catalytic and the photocatalytic approach. Special attention was devoted to the preparation of the TiO₂-based ...catalysts, since this oxide has been widely used for catalytic and photocatalytic application in alcohol oxidation reactions. Thus, in the catalytic process, the colloidal heterocoagulation of very stable sols, followed by the spray-freeze-drying (SFD) approach, was successfully applied for the preparation of nanostructured porous TiO₂-SiO₂ mixed-oxides with high surface areas. The versatility of the process made it possible to encapsulate Pt particles and use this material in the liquid-phase oxidation of HMF. The photocatalytic activity of a commercial titania and a homemade oxide prepared with the microemulsion technique was then compared. The influence of gold, base addition, and oxygen content on product distribution in the photocatalytic process was evaluated.
The coupling of methane to C2 hydrocarbons by means of non-thermal plasma is a recognized process as it is performed at room temperature, through the generation of radical species, but it still ...presents a major disadvantage of carbon deposition. The main goal of the study is to better control the chemistry and avoid C deposit. For that purpose, the addition of hydrogen as co-feed in a Dielectric Barrier Discharge plasma reactor was proposed. Experiments were carried out at a fixed deposited power of 8 W in the presence and absence of helium. As expected the conversion of methane was low without helium (6.5% for pure CH
4
against 22.3% for He/CH
4
: 30/10 mL min
−1
). A high selectivity into hydrocarbons was achieved by adding H
2
to CH
4
(75% for H
2
/CH
4
= 1 against 62% without H
2
), the main product being ethane (selectivity of 60%). An increase of the deposited power from 8 to 21 W favoured methane transformation and the hydrocarbons yield reached 9.1%. Surprisingly, the carbon deposition was limited at high deposited power. It could result from the hydrogenation of coke precursor (ethylene, acetylene) or reaction of H
2
with C deposit. The beneficial action of hydrogen on the reaction to reach high C2 selectivity has been demonstrated and a reaction mechanism is proposed.
The photocatalytic oxidation of biomass-derived building blocks such as 5-hydroxymethylfurfural (HMF) is a promising reaction for obtaining valuable chemicals and the efficient long-term storage of ...solar radiation. In this work, we developed innovative TiO2-based materials capable of base-free HMF photo-oxidation in water using simulated solar irradiation. The materials were prepared by combining microemulsion and spray-freeze drying (SFD), resulting in highly porous systems with a large surface area. The effect of titania/silica composition and the presence of gold-copper alloy nanoparticles on the properties of materials as well as photocatalytic performance were evaluated. Among the lab-synthesized photocatalysts, Ti15Si85 SFD and Au3Cu1/Ti15Si85 SFD achieved the higher conversions, while the best selectivity was observed for Au3Cu1/Ti15Si85 SFD. The tests with radical scavengers for both TiO2-m and Au3Cu1/Ti15Si85 SFD suggested that primary species responsible for the selective photo-oxidation of HMF are photo-generated electrons and/or superoxide radicals.
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•High surface area anatase and rutile TiO2 were obtained by microemulsion synthesis.•Glycerol photo-reforming was examined using commercial and lab-synthesized TiO2.•The effect of ...different deposition methods of Pt nanoparticles was demonstrated.•Both hydrogen and liquid phase intermediates productions were studied.•Phase composition influences a mechanism in liquid phase and a productivity of H2.
Reverse microemulsion-based synthesis was successfully applied to the preparation of nanosized TiO2 particles in anatase and rutile crystalline phases. The resulted nano-oxides were found to have smaller average crystalline size, higher surface area and narrower band gap than commercial TiO2 samples, P25 and DT-51. All the TiO2 materials were used as supports for platinum nanoparticles prepared by incipient wetness impregnation and deposition-precipitation methods. The photo-catalytic activities of these materials were compared in the reaction of glycerol photo-reforming in aqueous media using simulated solar light. The results showed that different crystalline phases of titania have different effects on hydrogen production and selectivity of intermediate products. Anatase was found to be more selective towards glyceraldehyde, while the presence of rutile promoted a more selective reaction towards glycolaldehyde. Rutile also exhibited a higher productivity of hydrogen compared to anatase.
A series of four catalysts, CeO2, CePO4 and LaPO4 in a nanorod structure and CePO4 nanospheres were assessed for the oxidative coupling of methane (OCM) reaction in an electric field at room ...temperature. The applied current of 3 mA was kept constant throughout the study. The cerium and lanthanum phosphates showed similar and high activity for OCM in the electric field, while CeO2 was not active for OCM reaction, and led only to total oxidation into CO2. C2 selectivity was improved as methane content increased in the feed and reached 27.6 % at a CH4/O2 ratio of 3. Switching the polarity of the current from positive to negative shifted the C2 selectivities to acetylene (18.2 %) for CePO4. It was suggested that this shift was related to the deposited power due to the polarity switch rather than the polarity effect on the electric field. Changing the structure of the CePO4 catalyst from nanorod to nanosphere did not alter the conversion or selectivities, indicating that the morphology does not compromise the reactivity.
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•Electric field promotes OCM reaction on CePO4 and LaPO4 nanorods catalysts.•CH4 conversion and C2H2 selectivity is enhanced under an electric field with negative polarity.•Conversion and selectivities are not affected by the CePO4 morphology.•Conversion and C2H2 selectivity are linked to the electric field power.
Abstract Electric field‐induced decomposition of ammonia into hydrogen and nitrogen was investigated over CeO 2 , Fe‐, Ru‐ deposited CeO 2 , CePO 4 and Sr‐doped CePO 4 , and CeZrO 4 in a packed bed ...down‐flow reactor. The effect of applied current, concentration of ammonia in a feed, and residence time was examined using CeO 2 alone. The conversion of ammonia was also studied with respect to a reduction temperature, loading and a type of the deposited metal. The activity results have been analyzed in terms of surface, morphological and electrical characterization of the catalysts. Among metal‐deposited catalysts, ammonia decomposition result at 4 mA was the best for 1 wt % Fe/CeO 2 reduced at 550 °C, showing 22 % of conversion with 0.18 mmol of converted ammonia per kJ of energy consumed. The activity of studied Ce‐based catalysts normalized per mass of loaded catalyst showed an accordance in activity‐porosity relation.
The oxidative photo-dehydrogenation of glycerol to produce H2 and other valuable chemicals was studied using different materials. In particular, Pt nanoparticles were deposited on ...microemulsion-synthesized TiO2 via surface organometallic chemistry (SOMC) and compared with photocatalysts obtained using more conventional methods. Well-defined Pt(II) single-site titania-grafted were prepared reacting the surface hydroxyl groups of TiO2 nano-oxides with the organometallic Pt(COD)Me2 complex. Sample reduction under H2 generated ultrafine Pt nanoparticles well-dispersed on titania surface. Its performance under simulated solar light showed superior activity when compared to analogous Pt-containing catalysts prepared by other methods. Improved dispersion of Pt metal on titania surface was among the primary reasons of a better overall activity, providing relatively high rates of hydrogen productivity. Moreover, an increase of glyceraldehyde productivity in liquid phase was observed with the increase of Pt dispersion, demonstrating that the metal dispersion can strongly affect the selectivity of chemicals produced in the reaction. Comparison with state of the art shows that the present material exhibits excellent performance for a combined positive effect of the high specific surface area of titania prepared by microemulsion, giving access to the increased densities of active sites and the high dispersion of Pt nanoparticles given by the SOMC technique.
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•Surface chemistry of microemulsion-synthesized titania was studied.•Ultrafine Pt NPs well-dispersed on titania were obtained using SOMC approach.•Prepared samples outperformed in the photo-dehydrogenation of glycerol using solar light.•Pt dispersion strongly affected the production of liquid phase chemicals and H2.
Electric field‐induced decomposition of ammonia into hydrogen and nitrogen was investigated over CeO2, Fe‐, Ru‐ deposited CeO2, CePO4 and Sr‐doped CePO4, and CeZrO4 in a packed bed down‐flow reactor. ...The effect of applied current, concentration of ammonia in a feed, and residence time was examined using CeO2 alone. The conversion of ammonia was also studied with respect to a reduction temperature, loading and a type of the deposited metal. The activity results have been analyzed in terms of surface, morphological and electrical characterization of the catalysts. Among metal‐deposited catalysts, ammonia decomposition result at 4 mA was the best for 1 wt % Fe/CeO2 reduced at 550 °C, showing 22 % of conversion with 0.18 mmol of converted ammonia per kJ of energy consumed. The activity of studied Ce‐based catalysts normalized per mass of loaded catalyst showed an accordance in activity‐porosity relation.
Electric field‐induced decomposition of ammonia into hydrogen and nitrogen was performed over CeO2, Fe‐, Ru‐ deposited CeO2, CePO4 and Sr‐doped CePO4, and CeZrO4; It seems that the electrical characteristics determine ammonia conversion in case of non‐porous systems whereas, the porosity and surface area are more influencing criteria than permittivity when it comes to the porous materials.
The photocatalytic oxidation of biomass-derived building blocks such as 5-hydroxymethylfurfural (HMF) is a promising reaction for obtaining valuable chemicals and the efficient long-term storage of ...solar radiation. In this work, we developed innovative TiO
-based materials capable of base-free HMF photo-oxidation in water using simulated solar irradiation. The materials were prepared by combining microemulsion and spray-freeze drying (SFD), resulting in highly porous systems with a large surface area. The effect of titania/silica composition and the presence of gold-copper alloy nanoparticles on the properties of materials as well as photocatalytic performance were evaluated. Among the lab-synthesized photocatalysts, Ti
Si
SFD and Au
Cu
/Ti
Si
SFD achieved the higher conversions, while the best selectivity was observed for Au
Cu
/Ti
Si
SFD. The tests with radical scavengers for both TiO
-m and Au
Cu
/Ti
Si
SFD suggested that primary species responsible for the selective photo-oxidation of HMF are photo-generated electrons and/or superoxide radicals.
Screening pathogenic variants in the SLC26A4 gene is an important part of molecular genetic testing for hearing loss (HL) since they are one of the common causes of hereditary HL in many populations. ...However, a large size of the SLC26A4 gene (20 coding exons) predetermines the difficulties of its complete mutational analysis, especially in large samples of patients. In addition, the regional or ethno-specific prevalence of SLC26A4 pathogenic variants has not yet been fully elucidated, except variants c.919-2A>G and c.2168A>G (p.His723Arg), which have been proven to be most common in Asian populations. We explored the distribution of currently known pathogenic and likely pathogenic (PLP) variants across the SLC26A4 gene sequence presented in the Deafness Variation Database for the selection of potential diagnostically important parts of this gene. As a result of this bioinformatic analysis, we found that molecular testing ten SLC26A4 exons (4, 6, 10, 11, 13−17 and 19) with flanking intronic regions can provide a diagnostic rate of 61.9% for all PLP variants in the SLC26A4 gene. The primary sequencing of these SLC26A4 regions may be applied as an initial effective diagnostic testing in samples of patients of unknown ethnicity or as a subsequent step after the targeted testing of already-known ethno- or region-specific pathogenic SLC26A4 variants.
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