Search results for "Catalysis"
showing 10 items of 5944 documents
Hydrogen-ion driven molecular motions in Cu2+-complexes of a ditopic phenanthrolinophane ligand
2004
One of the first kinetic evaluations of a metal ion interchange between the two coordination sites of a ditopic macrocycle is presented. Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es ; Soriano Soto, Concepción, Concepcion.Soriano@uv.es ; Verdejo Viu, Begoña, Begona.Verdejo@uv.es
Hydrogen Sorption Properties of Metal Hydride and Glass Phase
2009
This work is devoted to the development of a new composite material for hydrogen storage and to investigation of physical and chemical characteristics of material. The new composite material is formed by combination of AB5 type lanthanum nickel alloy with a glass based on silica. Thermogravimetric and XRD measurements prove that the new material absorbs more hydrogen than both constituents separately. That is explained by hydrogen sorption in the composite material due to the hydrogen spillover phenomena, where the hydrogen molecules dissociated on the surface of catalyst in atoms and spills over to the inert surface. That causes the increase of catalytic activity of an alloy and the presen…
H2 and value added chemicals from photocatalytic conversion of glucose
2015
Commercial and home prepared bare and Pt-supported TiO2 samples were used as the photocatalysts for the aqueous aerobic and anaerobic photo-conversion of glucose at ambient pressure and temperature. H2 and valuable chemicals were the obtained products. The home prepared samples resulted more active than the commercial ones
Valorization of alginate for the production of hydrogen via catalytic aqueous phase reforming
2018
Abstract Alginate, a carbohydrate abundant in the outer cell wall of macroalgae, was subjected to catalytic aqueous phase reforming (APR) to produce hydrogen using a 3% Pt/C commercial catalyst. The performance of the process was evaluated according to the conversion of the carbon to gas, the hydrogen yield and the hydrogen selectivity. The catalyst and feed amount, temperature, reaction time, pH and the presence of H2 were modified to understand the dependence of the outcome of the process on these parameters. The presence of the catalyst was fundamental in order to increase the hydrogen yield compared to the uncatalyzed reaction, and it can be reused without activity loss. In addition, it…
Structural reorganization in a hydrogen-bonded organic framework
2018
Self-recognition of 3,3′,5,5′-azobenzenetetracarboxylic acid drives the formation of a grid-like anionic hydrogen-bonded framework with channels occupied by organic cations. This supramolecular solid is capable of reorganizing its connectivity in the presence of specific guests into a different crystalline architecture by sequential dissolution and recrystallization.
Neutral nido-heteroboranes with non ionisable hydrogen as arenes in coordination
2003
Designed ligands have been synthesised to produce the first arene-like metallacarborane. For arene-like coordination the number of electronegative elements on the coordinating site must be kept to a minimum. Choosing ligands with bulky substituents on the heteroatom allows easy rearrangement and arene-like coordination. This is more hampered the higher the number of hetereoatoms to be re-located.
DFT studies on catalytic properties of isolated and carbon nanotube supported Pd9 cluster–I: adsorption, fragmentation and diffusion of hydrogen
2009
The processes of adsorption, fragmentation and diffusion of hydrogen on a small palladium cluster have been investigated by means of DFT and DFT/MM approaches. These studies have been performed by considering a D(3h) symmetry Pd(9) in the isolated state as well as when supported on a portion of single-walled armchair(6,6) carbon nanotube. The hydrogen fragmentation process easily occurs on the bare Pd(9) cluster, involving energy barriers of 25-35 kJ mol(-1) and the drop in spin multiplicity on passing from the reactant to the product. The atomic hydrogen diffuses through the cluster atoms with energy barriers, which do not exceed 20 kJ mol(-1), with some positions clearly identifiable as t…
Bio-inspired Ni dinuclear complexes as heterogeneous catalysts for hydrogen evolution
2021
Abstract A major challenge in the sustainable production of hydrogen is lowering the electrochemical overpotential and the activation energy of the hydrogen evolution reaction. Some enzymes have two metallic Ni centers and catalyze this reaction with high activity. Taking inspiration from them, we have developed two novel dinuclear Ni(II) complexes, Ni-PATIO and Ni-PACO, with promise as molecular catalysts. Ni-PACO exhibits a square-planar geometry for both Ni(II) and two-fold rotational symmetry both in solid and solution states, whereas Ni-PATIO displays one square-planar Ni(II) center and one octahedral Ni(II) configuration, which confer it magnetic properties. We show that both complexe…