Search results for " Chemical engineering"
showing 10 items of 2965 documents
Recent Advances in Halogen Bonded Assemblies with Resorcin[4]arenes
2020
Resorcinarenes are cavity-containing compounds when in the crown conformation, from the calixarene family of concave compounds. These easy to synthesize macrocycles can be decorated at the upper rim through the eight hydroxyl groups and/or the 2-position of the aromatic ring. They are good synthons in supramolecular chemistry leading to appealing assemblies such as open-inclusion complexes, capsules and tubes through multiple weak interactions with various guests. Halogen bonding (XB) is a highly directional non-covalent interaction by an electron-deficient halogen atom as a donor that interacts with a Lewis base, the XB acceptor. This tutorial review provides an overview of recent advances…
Total oxidation of VOCs on Au nanoparticles anchored on Co doped mesoporous UVM-7 silica
2012
Abstract Gold deposited on a cobalt containing siliceous mesoporous structure, UVM-7, presents a good catalytic performance in the total oxidation of propane and toluene. The presence of both gold and cobalt is necessary as bimetallic Au/Co-UVM-7 catalysts are remarkably more active than monometallic Au/UVM-7 or Co-UVM-7 catalysts. The improved activity of the bimetallic AuCo-samples if compared to gold free cobalt catalysts can be explained on the basis of the enhanced reducibility of some cobalt species in the presence of gold, which facilitates the redox cycle. This high reducibility of cobalt species in the bimetallic samples is probably due to the formation of Co 3 O 4 domains at the g…
Solvothermal Synthesis of Molybdenum–Tungsten Oxides and Their Application for Photoelectrochemical Water Splitting
2018
Molybdenum and tungsten oxides are of interest as semiconductors for the production of clean and sustainable energy. Here we show that synergistic effects arising from a combination of noncrystalli...
Design of PNIPAAM covalently grafted on halloysite nanotubes as a support for metal-based catalysts
2016
A thermo-responsive polymer such as poly(N-isopropylacrylamide) (PNIPAAM) was covalently grafted on the external surface of halloysite nanotubes (HNTs) by means of microwave irradiation. This nanomaterial was used as a support and stabilizer for palladium nanoparticles. The obtained HNT–PNIPAAM/PdNPs was characterized by means of TGA, SEM, EDS and TEM analyses. The palladium content of the catalyst was estimated to be 0.4 wt%. The stability of the catalytic material at different temperatures (below and above the PNIPAAM lower critical solution temperature) was tested in the Suzuki reaction under microwave irradiation. In addition, TEM analysis after five consecutive runs was performed. The …
Nano-sized I12L6 Molecular Capsules Based on the [N⋅⋅⋅I+⋅⋅⋅N] Halogen Bond
2017
Summary Self-assembly of pre-organized subunits with a concave overall shape is an effective strategy for the synthesis of supramolecular capsules. We report the synthesis of a cavitand-based hexameric capsule held together solely by 12 robust [N⋅⋅⋅I + ⋅⋅⋅N] halogen bonds and its characterization in solution and in the gas phase via 1 H NMR spectroscopy, diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY), and electrospray ionization mass spectrometry. The [N⋅⋅⋅I + ⋅⋅⋅N] halogen-bonded hexameric capsule was efficiently synthesized from the isolobal metallosupramolecular Ag + capsule by application of the [N⋅⋅⋅Ag + ⋅⋅⋅N] → [N⋅⋅⋅I + ⋅⋅⋅N] cation-exchange reaction.
Adsorption and desorption surface dynamics of gaseous adsorbate on silicate-1 by molecular dynamics simulation
2013
The dynamics of adsorption and desorption of gaseous molecules on the external surface of a crystal and a membrane of zeolite silicate-1 is investigated by molecular dynamics simulation. The gases ...
An unexpected ring carboxylation in the electrocarboxylation of aromatic ketones
2006
The electrocarboxylation of various aromatic ketones, carried out in N-methyl-2-pyrrolidone (NMP) in a diaphragmless cell equipped with a carbon cathode and an aluminium sacrificial anode, yielded, among the products, the target hydroxy acids, the corresponding alcohols and pinacols and, quite surprisingly, detectable amounts of substituted benzoic acids and cycloexene carboxylic acids. These compounds arise from a never reported before electrocarboxylation on the aromatic ring, respectively, for substitution of an aromatic hydrogen and from an addition reaction. For example, the electrocarboxylation of acetophenone gave rise to the substituted benzoic acids in ortho, para and meta position…
Promoting the activity and selectivity of high surface area Ni–Ce–O mixed oxides by gold deposition for VOC catalytic combustion
2011
Gold supported on nickel cerium oxide catalysts (Ni–Ce–O) have been studied for the total oxidation of propane, as a model for hydrocarbon volatile organic compound emission control. High surface area Ni–Ce–O catalysts were synthesized using a very simple evaporation method, where cerium and nickel salts were evaporated in the presence of a mixture of methanol and oxalic acid. Gold catalysts were prepared following a deposition–precipitation method. A very efficient catalyst for the oxidation of propane, in terms of both activity and selectivity, was obtained. This high activity has been related to the high surface area of the catalyst (and therefore to the presence of more active sites ava…
Electrostatic phenomena in ion exchange membranes
1971
Abstract Specific and transport properties of a cation and an anion exchange membrane in Na + and Cl - form respectively have been measured in water and dioxane water mixtures. A greater electrolyte absorption and a lesser specific conductivity and counterion transport number in solvents at higher dioxane content indicate strong electrostatic interactions between fixed groups in the membrane and counterions.
Isobaric Vapor−Liquid Equilibria for Water + Acetic Acid + Potassium Acetate
2004
Isobaric vapor−liquid equilibria for water + acetic acid + potassium acetate at different salt concentrations as well as for solvent + potassium acetate binary mixtures have been obtained at 100 kPa. Potassium acetate is more effective in the salting-out effect (on water) than lithium and sodium acetates. The eNRTL-CT model, which is a combination of electrolyte nonrandom two-liquid and chemical theory models, has been used to fit the experimental data. The binary parameters of the model have been obtained from the experimental binary vapor−liquid equilibria which have been used to suitably reproduce the vapor−liquid equilibria (VLE) for water + acetic acid + potassium acetate ternary syste…