Impact of precursor materials and synthesis procedures on structure and performance of TiO2 supported Pd-catalysts in the gas phase acetoxylation of toluene

The current industrial production of benzyl acetate (BA), a valuable chemical, is based on the environmentally problematic chlorine route. Gas phase acetoxylation of toluene to BA, an eco-friendly reaction, over Pd-based catalysts using molecular oxygen can be an alternative for the production BA. In this work, Pd-Based catalysts were synthesized by using different precursor materials, thermal pretreatments, co-components and supports. Co-components (Cu, Sb, Mn, Co, Au) altered the valance state of Pd and hereby the activity and selectivity of the catalyst. Surprisingly, catalyst with very high selectivity between 95 to 99 % and good long term-stability (> 30 h) was obtained with rutile as support for 10 wt.-% Pd, 16 wt.-% Sb

Facile synthesis of high-surface area platinum-doped ceria for low temperature CO oxidation

International audienceUsing a simple slow decomposition method of nitrate precursors, high-surface area platinum-doped ceria with a crystallite size of 9 nm can be prepared. The catalytic performance of the compound can be tuned by changing the reduction temperature under hydrogen (300°C, 500°C and 700°C). The catalyst treated at 300°C shows the best catalytic performance, being active at room temperature. The materials were analysed using a combination of structural characterization methods (X-ray diffraction (XRD), nitrogen physisorption, high angle annular dark field scanning transmission electron microscopy (HAADF-STEM)), surface sensitive methods (X-ray photoelectron spectroscopy (XPS), H 2-chemisorption and H 2-temperature-programmed reduction (TPR)) and X-ray absorption fluorescence spectroscopy (XAFS). HAADF-STEM and XAFS analysis suggests successful doping of platinum in the ceria lattice. After pretreatment at 300°C, the situation is slightly different. While no defined platinum nanoparticles can be identified on the surface, some platinum is in a reduced state (XPS, H 2-chemisorption)

In situ generated catalyst: Copper (II) oxide and Copper (I) supported on Ca2Fe2O5 for CO oxidation

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Pb²⁺N Bonding Chemistry: Recycling of Polyaniline–Pb Nanocrystals Waste for Generating High-Performance Supercapacitor Electrodes

Understanding of PbN bonding chemistry is not only fundamentally important in the view of relativistic inert-pair effect but also is important for therapeutic as well as environmental applications. In the present study, an unusual reactivity of N-containing π-conjugated polyaniline emeraldine base (EB) toward aqueous Pb²⁺ ions has been identified. In the course of sequestering Pb²⁺ ions by EB, cuboid-shaped nanocrystals were isolated. Synchrotron-based X-ray absorption near-edge structure and extended X-ray absorption fine structure techniques were employed to understand Pb–N bonding chemistry in EB-Pb nanocrystals. The adopted methodology of slow exposure of HCl vapor to EB-Pb nanomaterial facilitated the isolation of polyaniline emeraldine-salt (ES) with unique morphological patterns, porosity and electrical conductivity. The electrochemical device based on recycled ES showed high-capacitance value (∼606 F/g @1 A/g and ∼663 F/g @10 mV/s), high-energy density (∼14.8 Wh/kg at power density of ∼663 W/kg) and excellent-cycling stability (only ∼15% degradation after 1100 continued cycles at current density of 5 A/g). Notably, ES materials prepared directly from EB and upon exposing HNO₃ vapor exhibited greatly inferior device performance

Room-Temperature CO Oxidation Catalyst: Low-Temperature Metal–Support Interaction between Platinum Nanoparticles and Nanosized Ceria

Platinum nanoparticles dispersed on nanosized ceria are active for CO oxidation at room temperature after hydrogen pretreatment. High angular annular dark field scanning transmission electron microscopy (HAADF-STEM) analysis of the reduced catalyst shows spreading of the 1 nm sized platinum particles under the electron beam, characteristic for a two-dimensional strong metal–support interaction. In situ X-ray absorption fluorescence spectroscopy (XAFS) reveals a Pt–O distance of 2.1 Å, which is significantly longer than the Pt–O distance in PtO₂ (2.0 Å). This elongated Pt–O distance can be related to interaction of the platinum species with cerium oxide in the form of a low-temperature active species–support interaction. These findings contribute to the general understanding of catalytic systems operating at low temperature