Search results for "Catalyst"

Dichlorovanadium(IV) diamine-bis(phenolate) complexes for ethylene (co)polymerization and 1-olefin isospecific polymerization

2018

Abstract Two vanadium complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor, [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)2}Cl2] (1) and [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)(CH2-2-O-C6H4)}Cl2] (2), were synthesised and characterized by FTIR and 1H NMR spectroscopy. Upon activation with Al(iBu)3/Ph3CB(C6F5)4, these complexes became active catalysts for 1-octene polymerization giving highly stereoregular polymers (mmmm ∼ 90%) having regioirregularly arranged units. The catalytic activity of the catalysts in ethylene homo- and copolymerization, and their ability to incorporate a comonomer were highly dependent on both the activator type and the complex structure. 1/EtAlCl2 exhi…

Hydrogen Arrangements on Defective Quasi-Molecular BN Fragments

2019

Considering the ever-increasing interest in metal-free materials, some potential chemical applications of quasi-molecular boron nitride (BN) derivatives were tested. Specifically, the behavior of BN fragments was analyzed when given defects, producing local electron density changes, were introduced by using topological engineering approaches. The inserted structural faults were Schottky-like divacancy (BN-d) defects, assembled in the fragment frame by the subtraction of one pair of B and N atoms or Stone-Wales (SW) defects. This study is aimed at highlighting the role of these important classes of defects in BN materials hypothesizing their future use in H-2-based processes, related to eith…

Counter anion binding in the phenoxyimine, salan and metallocene olefin polymerization catalysts activated with perfluorophenylborate

2012

Abstract Ion pair separation is a process that may influence the activity of homogeneous catalysts of olefin polymerization. We have studied the energy of separation for selected titanium and zirconium metallocene and post-metallocene catalytic ion pairs by means of DFT, dispersion-corrected DFT and Paired Interacting Orbitals method (PIO). Unusually weak cation–anion interactions in the bis(phenoxyimine) systems were attributed to strong electron-donating properties of the phenoxyimine ligands. Energy decomposition analysis (EDA) revealed that almost 70% of the counter ion binding energy results from electrostatic interactions. The PIO method made it possible to analyze the nature of the c…

(Photo)catalyst characterization techniques: Adsorption isotherms and BET, SEM, FTIR, UV-Vis, photoluminescence, and electrochemical characterizations

2019

This chapter reports on some characterization techniques that are commonly used for catalysts and photocatalysts. Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), UV-visible (UV-Vis), photoluminescence (PL), and electrochemical characterization techniques are presented with experimental details and actual case studies from literature are discussed. The chapter starts with adsorption phenomena on (photo)catalysis and adsorption isotherms are presented. Then BET analysis technique and its applications in (photo)catalysis are explained. Morphological properties (SEM), functional groups, and the interaction of substrate (and inter…

Fabrication of Porous Hydrogenation Catalysts by a Selective Laser Sintering 3D Printing Technique

2019

Open in a separate window Three-dimensional selective laser sintering printing was utilized to produce porous, solid objects, in which the catalytically active component, Pd/SiO2, is attached to an easily printable supporting polypropylene framework. Physical properties of the printed objects, such as porosity, were controlled by varying the printing parameters. Structural characterization of the objects was performed by helium ion microscopy, scanning electron microscopy, and X-ray tomography, and the catalytic performance of the objects was tested in the hydrogenation of styrene, cyclohexene, and phenylacetylene. The results show that the selective laser sintering process provides an alte…

Catalytic hydrothermal liquefaction of municipal sludge assisted by formic acid for the production of next-generation fuels

2021

Abstract Hydrothermal liquefaction (HTL) of municipal sludge (MS) was studied at 325 °C and 30 min at 10 and 30% w/w concentration of MS using formic acid (FA) as a green liquid hydrogen donor both in the absence and in the presence of heterogeneous catalysts. Pellets of commercial NiMo/Al2O3, CoMo/Al2O3 and felt of activated carbon ACF 1600 were used as catalysts. The addition of FA at high MS loading allowed to increase the yields in BC from 41 to 62% and its H/C ratio from 1.80 to 2.01 leading to energy recovery (ER) higher than 100%.When heterogeneous catalysts were used together with FA, a marked improvement of BC yields and quality was obtained at 10% MS loading. This behavior was not…

How Proximal Nucleobases Regulate the Catalytic Activity of G-Quadruplex/Hemin DNAzymes

2018

International audience; G-quadruplexes (G4s) are versatile catalytic DNAs when combined with hemin. Despite the repertoire of catalytically competent G4/hemin complexes studied so far, little is known about the detailed catalytic mechanism of these biocatalysts. Herein, we have carried out an in-depth analysis of the hemin binding site within the G4/hemin catalysts, providing the porphyrinic cofactor with a controlled nucleotidic environment. We intensively assessed the position-dependent catalytic enhancement in model reactions and found that proximal nucleobases enhance the catalytic ability of the G4/hemin complexes. Our results allow for revisiting the mechanism of the G4/hemin-based ca…

GaP/TiO2 Composite Photocatalyst for CO2 Reduction in Gas-Solid Regime under Simulated Solar Light Irradiation

2014

3D Ruthenium Nanoparticle Covalent Assemblies from Polymantane Ligands for Confined Catalysis

2020

International audience; The synthesis of metal nanoparticle (NP) assemblies stabilized by functional molecules is an important research topic in nanoscience, and the ability to control interparticle distances and positions in NP assemblies is one of the major challenges in designing and understanding functional nanostructures. Here, two series of functionalized adamantanes, bis-adamantanes, and diamantanes, bearing carboxylic acid or amine functional groups, were used as building blocks to produce, via a straightforward method, networks of ruthenium NPs. Both the nature of the ligand and the Ru/ligand ratio affect the interparticle distance in the assemblies. The use of 1,3-adamantanedicarb…

Vanadium‐Doped Zircon and Zirconia Materials Prepared from Gel Precursors as Site‐Selective Electrochemical Sensors

2003

Abstract Polymer film electrodes incorporating vanadium‐doped zircon (V x ZrSiO4, 0.00 < x < 0.10) and vanadium‐doped monoclinic and tetragonal zirconias (V x ZrO2, 0.00 < x < 0.15), prepared by heat treatment of gel precursors, exhibit a significant site‐selective electrocatalytic activity towards the oxidation of amino acids, polyalcohols, and polyhydroxycarboxylic acids in alkaline media. Catalysis of the oxidation of carboxylate and alcohol groups involves a relatively slow chemical reaction between the substrate and vanadium centers, while the oxidation of thiolate in cysteine can be attributed to the oxidation of an adduct formed by vanadium centers and the substrate.