Search results for "Catalyst"
showing 10 items of 516 documents
HYDROTHERMAL LIQUEFACTION OF MICROALGAE IN THE PRESENCE OF HOMOGENEOUS AND HETEROGENEOUS CATALYSTS
2015
The continuous raise in the prices of fossil fuels and the awareness of the society challenges related to their use has recently driven a strong growth of interest on the investigation of different biochemical or thermochemical processes for the production of liquid biofuels .
Halloysite Nanotubes: Smart Nanomaterials in Catalysis
2022
The use of clay minerals as catalyst is renowned since ancient times. Among the different clays used for catalytic purposes, halloysite nanotubes (HNTs) represent valuable resources for industrial applications. This special tubular clay possesses high stability and biocompatibility, resistance against organic solvents, and most importantly be available in large amounts at a low cost. Therefore, HNTs can be efficiently used as catalysts themselves or supports for metal nanoparticles in several catalytic processes. This review reports a comprehensive overview of the relevant advances in the use of halloysite in catalysis, focusing the attention on the last five years.
Iron Porphyrins as Models of Cytochromec Oxidase
2001
A series of iron porphyrins has been synthesized as models of cytochrome c oxidase; their activity as 4 e− catalysts in the reduction of dioxygen has been studied at pH 7. These compounds have been obtained by grafting very different residues onto the same iron complex, namely tripodal tetraamines, pickets, and straps, in order to change the environment of the metal center. In the case of porphyrins bearing a tripodal cap, the secondary amines have been alkylated with different substituents so as to modify the electronic environment of the distal pocket. Surprisingly, when the iron porphyrin is functionalized with four identical acrylamido pickets, the resulting complex exhibits biomimetic …
POSS-based 3D functional networks as catalysts for the conversion of carbon dioxide
2023
Oggi lo sviluppo di processi sostenibili è al centro dell'attenzione a causa delle emergenze climatiche. La Chimica Verde, con i suoi dodici principi sviluppati da Paul Anastas, si concentra sullo sviluppo di processi alternativi e più rispettosi dell'ambiente. Questa branca della chimica mostra come concetti quali la prevenzione dei rifiuti, l'uso di materie prime rinnovabili e la catalisi siano di grande importanza per rendere un processo più sostenibile. In questo contesto, l'anidride carbonica (CO2) rappresenta una delle materie prime più abbondanti, non tossiche e rinnovabili. La possibilità di riutilizzare la CO2 e di trasformare questa molecola in prodotti a valore aggiunto come i ca…
New Hybrid Organic-inorganic Multifunctional Materials Based on Polydopamine-like Chemistry
2021
Taking inspiration from the chemistry of dopamine, a simple and economic synthetic approach toward the synthesis of a series of silica-based polydopamine-like materials has been developed. Mild conditions and easy manipulation are the strongest aspects of this methodology. Such hybrid materials were successfully used as recyclable catalysts for Knoevenagel reactions.
Enhanced Heterogeneously Catalyzed Suzuki-Miyaura Reaction over SiliaCat Pd(0)
2013
Abstract The SiliaCat Pd(0) solid catalyst can be efficiently employed in the Suzuki–Miyaura cross-coupling of an ample variety of haloarenes, including economically viable chloroarenes. The catalyst can be extensively recycled without loss of activity and with low leaching of valued palladium, opening the route to widespread utilization of the method to afford high yields of biaryls devoid of contaminating by-products.
Heterogeneous photocatalysis for selective partial oxidation reactions in aqueous suspension
2018
Heterogeneous photocatalysis for selective partial oxidation reactions in aqueous suspension
Hydrogen trapping: Synergetic effects of inorganic additives with cobalt Sulfide absorbers and reactivity of cobalt polysulfide
2012
International audience; The biphasic product CoS2 + Co(OH)(2) obtained by oxidation of cobalt sulfide is known to trap hydrogen at room temperature and low pressure according to a balanced reduction equation. Adding various inorganic compounds to this original absorber induces their reduction by hydrogen in the same conditions at a significant rate: (i) excess cobalt hydroxide is reduced to metallic cobalt; (ii) nitrate ions are reduced to ammonia; (iii) sulfur and sodium thiosulfate are reduced to H2S or NaHS and Na2S, respectively. Without a hydrogen absorber these inorganic compounds are not reduced by H-2, suggesting synergetic effects involving H-2 and the hydrogen absorber. Amorphous …
Low temperature conversion of levulinic acid into γ-valerolactone using Zn to generate hydrogen from water and nickel catalysts supported on sepiolite
2020
1 scheme, 2 tables, 7 figures.-- Supplementary material available.
DFT and kinetic evidences of the preferential CO oxidation pattern of manganese dioxide catalysts in hydrogen stream (PROX)
2022
Abstract The oxidation functionality of Mn(IV) sites has been assessed by density functional theory (DFT) analysis of adsorption and activation energies of CO, H2 and O2 on a model Mn4O8 cluster. DFT calculations indicate that Mn(IV) atoms prompt an easy CO conversion to CO2 via a reaction path involving both catalyst and gas-phase oxygen species, while much greater energy barriers hinder H2 oxidation. Accordingly, a MnCeOx catalyst (Mnat/Ceat, 5) with large exposure of Mn(IV) sites shows a remarkable CO oxidation performance at T ≥ 293 K and no H2 oxidation activity below 393 K. Empiric kinetics disclose that the catalyst-oxygen abstraction step determines both CO and H2 oxidation rate, al…