Characterization and reactivity of γ-Al2O3 supported Pd–Ni bimetallic nanocatalysts for selective hydrogenation of cyclopentadiene

Manganese catalyzed chemo-selective synthesis of acyl cyclopentenes: a combined experimental and computational investigation

Cyclopentenes serve as foundational structures in numerous natural products and pharmaceuticals. Consequently, the pursuit of innovative synthetic approaches to complement existing protocols is of paramount importance. In this context, we present a novel synthesis route for acyl cyclopentenes through a cascade reaction involving an acceptorless-dehydrogenative coupling of cyclopropyl methanol with methyl ketone, followed by a radical-initiated ring expansion rearrangement of the in situ formed vinyl cyclopropenone intermediate. The reaction, catalyzed by an earth-abundant metal complex, occurs under milder conditions, generating water and hydrogen gas as byproducts. Rigorous control experiments and detailed computational studies were conducted to unravel the underlying mechanism. The observed selectivity is explained by entropy-driven alcohol-assisted hydrogen liberation from an Mn-hydride complex, prevailing over the hydrogenation of unsaturated cyclopentenes.

Elucidating the Structure and Composition of Individual Bimetallic Nanoparticles in Supported Catalysts by Atom Probe Tomography

Understanding and controlling the structure and composition of nanoparticles in supported metal catalysts are crucial to improve chemical processes. For this, atom probe tomography (APT) is a unique tool, as it allows for spatially resolved three-dimensional chemical imaging of materials with sub-nanometer resolution. However, thus far APT has not been applied for mesoporous oxide-supported metal catalyst materials, due to the size and number of pores resulting in sample fracture during experiments. To overcome these issues, we developed a high-pressure resin impregnation strategy and showcased the applicability to high-porous supported Pd-Ni-based catalyst materials, which are active in CO2 hydrogenation. Within the reconstructed volume of 3 × 105 nm3, we identified over 400 Pd-Ni clusters, with compositions ranging from 0 to 16 atom % Pd and a size distribution of 2.6 ± 1.6 nm. These results illustrate that APT is capable of quantitatively assessing the size, composition, and metal distribution for a large number of nanoparticles at the sub-nm scale in industrial catalysts. Furthermore, we showcase that metal segregation occurred predominately between nanoparticles, shedding light on the mechanism of metal segregation. We envision that the presented methodology expands the capabilities of APT to investigate porous functional nanomaterials, including but not limited to solid catalysts.

Preparation and Catalytic Hydrodechlorination Property of Nano Bimetallic Catalyst Pd–Ni/γAl2O3–SiO2

Pd–Ni bimetallic catalyst supported on a composite carrier of γAl2O3 and SiO2 was prepared by chemical precipitation methodology enhanced with an ultrasonic wave. In the present paper, the influence of dispersant, carrier, ultrasonic time and intensity on the dechlorination property of the catalysts obtained are investigated. The appearance, morphology and structure of the prepared catalysts were characterized using X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), N2 adsorption–desorption isotherm and X-ray photoelectron spectroscopy spectrometer (XPS). The chemical composition of active gradients in the catalysts was tested with inductively coupled plasma-atomic emission spectrometry (ICP-AES). The metal dispersion and mean particle size of the metallic phase of the prepared catalysts were also determined with CO chemisorption. Results indicate that a nano bimetal Pd–Ni catalyst on an average particle size of 2.45 nm with a distribution range of 1–7 nm supported on a composite carrier of γAl2O3 and SiO2 can be effectively prepared, and that the chlorine content of shellac dechlorinated with the obtained catalyst is 0.18 wt%, which is lower than that reported in the previous literature, indicating the perfect dechlorination property of the catalyst.

Alloying Effect of Silver on Zirconia Support Manipulated Palladium Catalyst for Methane Combustion

PdAg/ZrO2 alloy catalysts calcined at different temperatures were employed to elucidate the effect of support-metal interaction (SMI) on methane combustion. Combustion activity was depressed when the sample was calcined at an elevated temperature from 500 °C to 700 °C. However, calcination at 850 °C enhanced the beneficial SMI, which facilitated a more active phase for the oxidation reaction. The high-resolution transmission electron microscopy experiments show that a special micro-domain structure at the interface is formed during the reduction pretreatment. H2-TPR and O2-TPD measurements illustrate that the active phase would undergo reconstruction upon redox cycles. The active phase manipulated by the support is more suitable for combustion reaction in the course of temperature altering.

Monolith catalyst design via 3D printing: a reusable support for modern palladium-catalyzed cross-coupling reactions

The use of an additive manufacturing procedure for the modification of catalytic structures is currently gaining popularity in the field of catalysis.

The effect of water on methane oxidation over Pd/Al2O3 under lean, stoichiometric and rich conditions

Methane conversion during cooling ramp: water inhibits methane conversion more severely in high oxygen concentration.

Synthesis and use of bimetals and bimetal oxides in contaminants removal from water: a review

This paper gives an overview of the recent advances of the synthesis methods of bimetals and bimetal oxides and applying them in contaminant removal from water.