Influence of metal-support interaction on nitrate hydrogenation over Rh and Rh-Cu nanoparticles dispersed on Al 2 O 3 and TiO 2 supports

Enhancing CO and H2 Production in Propane Dry Reforming in Excess of CO2

This study focuses on addressing the challenges in the dry reforming of propane, a process historically marked by low syngas yields and only moderate conversions of CO2 and propane. The primary objective was to enhance CO2 utilization and boost the selectivity of syngas (CO and H2) production using titania-based catalysts. For synthesizing these catalysts, an impregnation method was employed with subsequent characterization through X-ray diffraction (XRD), N2 adsorption-desorption, ammonia temperature-programmed desorption (TPD), and hydrogen temperature-programmed reduction (TPR). The titania-based catalysts generally possess weak acidic strength, with each catalyst displaying a unique reduction profile. The dry reforming process using these catalysts resulted in varying levels of propane conversion, with V/Ti, Ir/Ti, Al/Ti, and Zr/Ti catalysts showing distinct efficiencies. Notably, the Ir/Ti and V/Ti oxide catalysts achieved the lowest selectivity for generating intermediate byproducts such as methane, ethane, ethylene, and propylene while successfully promoting higher syngas CO and H2 production alongside stable propane conversion. When exposed to excess CO2, each catalyst consumed differing amounts of CO2 molecules. Particularly, the Ir/Ti and V/Ti oxide catalysts demonstrated enhanced activity in promoting CO2 reactions with intermediate radical species, facilitating carbon-carbon (C-C) bond dissociation and leading to increased syngas production. This study offers valuable insights into the potential of titania-based catalysts in improving the efficiency and selectivity of propane dry reforming processes for blue hydrogen.

Advancements on Basic Working Principles of Photo-Driven Oxidative Degradation of Organic Substrates over Pristine and Noble Metal-Modified TiO2. Model Case of Phenol Photo Oxidation

The specific roles played by both support and noble metals in light absorption, charge separation, and the formation of ·OH and O2− (ROS) are analyzed for light-triggered oxidation of phenol (Ph) over pristine and over noble metal (Ag, Au, Pt) -loaded TiO2. Experiments show that the supported noble metals act as a light visible absorber, assist the separation of photo-charges and reduction of O2 to O2−. The O2− oxidizes mildly Ph to oxygenated products (hydroquinone, benzoquinone, and 1,2-dihydroxibenzene). In a parallel process, ·OH radicals, yielded by TiO2, mineralize Ph to CO2 by fast reaction sequences. Radical quenching and photo electrochemical measurements (surface photovoltage) confirm independently that the production of ·OH and O2− scale with oxidative conversion of Ph. The selectivity to CO2 and mild oxidation products is the result of the interplay between catalyst activity for ·OH and for O2− production.

Effect of Nanoparticle Size in Pt/SiO2 Catalyzed Nitrate Reduction in Liquid Phase

Effect of platinum nanoparticle size on catalytic reduction of nitrate in liquid phase was examined under ambient conditions by using hydrogen as a reducing agent. For the size effect study, Pt nanoparticles with sizes of 2, 4 and 8 nm were loaded silica support. TEM images of Pt nanoparticles showed that homogeneous morphologies as well as narrow size distributions were achieved during the preparation. All three catalysts showed high activity and were able to reduce nitrate below the recommended limit of 50 mg/L in drinking water. The highest catalytic activity was seen with 8 nm platinum; however, the product selectivity for N₂ was highest with 4 nm platinum. In addition, the possibility of PVP capping agent acting as a promoter in the reaction is highlighted.

Correlation of Rh Particle Size with CO Chemisorption: Effect on the Catalytic Oxidation of MTBE

This study was conducted to identify the correlation between the CO chemisorption (linear interaction and gem dicarbonyl) and the specific size of rhodium particles, and further to determine the influence of this relationship on the catalytic oxidation reaction of methyl tert-butyl ether (MTBE). During the synthesis, first, TiO2 was developed by the sol-gel method under acidic conditions. Second, Rh was deposited (1 wt %) by the incipient wetness impregnation method. Later, with the aim of controlling the particle size, the Rh/TiO2 materials were crystallized at different reduction conditions during 3 h heat treatment. The results obtained by TEM micrographs indicated that the average particle size varies between 1.0 and 8.1 nm, depending on the conditions of heat treatment. From the histogram analysis of each TEM micrograph, two correlations were made: (i) the gem-dicarbonyl interaction was typical of Rh particles ≤ 1.5 nm, and (ii) a linear interaction, bridged interaction and dentate interaction were observed in particles ≥ 1.6 nm. The gem-dicarbonyl interaction (particle size ≤ 1.5 nm) was the most active in the oxidation reaction of MTBE.

Green method for efficient PdNPs deposition on carbon carrier in the microreactor system

The synthesis of palladium nanoparticles and conditions of their deposition on active carbon fibers in the microreactor was described. All processes related with metal ion reduction, nucleation, and autocatalytic growth of particles as well as their deposition were carried out in the microreactor in only one cycle. Synthesis of palladium nanoparticles was carried out under different conditions, i.e., changing the initial concentration of metal ions and the reductant, at 40 °C. Depending on the conditions imposed, the nanoparticles of different size (hydrodynamic radius change from 12 to 37 nm) and shape (spherical, cube, pyramid) were obtained. It was also shown that flow conditions allow for much more efficient Pd deposition on active carbon fibers than the process carried out in the batch. It was observed that for concentrations of Pd(II) ions higher than 0.2 mM, the degree of fiber surface coverage increased significantly in comparison with the batch process.