Search results for "Heterogeneous catalysis"

Catalytic activity of rare-earth-supported catalysts in Friedel–Crafts acylations

1999

Abstract Friedel–Crafts acylations are catalysed by rare-earth-supported catalysts. The preparation, characterization and performance of these solid catalysts in a test acylation reaction and in a variety of syntheses of aromatic ketones are reported. In contrast to the reactions using AlCl3, the experimental conditions are non-polluting and the final work-up does not require any aqueous treatment.

Gas-phase hydrogenation of propionitrile on copper-lanthanide oxides

2009

Abstract The hydrogenation of propionitrile on copper-lanthanide oxide catalysts (2Cu·CeO 2 and 4Cu·Ln 2 O 3 (Ln = La, Pr, Nd)) was studied in the gas phase. The activity of the catalysts varies with the lanthanide in the order 2Cu·CeO 2  > 4Cu·Pr 2 O 3  > 4Cu·La 2 O 3  ≥ 4Cu·Nd 2 O 3 , while the activation energies varies in the opposite order, except for 2Cu·CeO 2 . The main product was the primary amine, n -propylamine. The formation of the unstable imine CH 3 CH 2 N CHCH 3 as a major product over 2Cu·CeO 2 seems to be consistent with the acidity of the catalyst. The catalysts were more selective than conventional copper impregnation catalysts, Cu (10 wt.%) on SiO 2 , La 2 O 3 or CeO 2 ,…

Comparison of the photocatalytic degradation of 2-propanol in gas–solid and liquid–solid systems by using TiO2–LnPc2 hybrid powders

2009

Photocatalytic degradation of 2-propanol was carried out as a probe reaction both in gas–solid and in liquid–solid systems in the presence of TiO2 both bare and impregnated with lanthanide (Sm, Gd, Ho) bis-phthalocyanines (LnPc2) used as sensitizers. Continuous and batch photo-reactors, irradiated with an equal flux of photons, were used in gas–solid and in liquid–solid systems, respectively. Propanone and acetaldehyde were the main intermediates found in both systems during 2-propanol oxidation, whereas carbon dioxide and water were the final oxidation products exclusively in the gas–solid regime. The photocatalysts exhibited significantly higher activity in the liquid–solid system than in…

Supported Ionic Liquids: A Versatile and Useful Class of Materials.

2017

Supported ionic liquids (SILs) represent a class of materials with peculiar properties and a huge potential regarding their possible applications in different fields of chemistry. Herein, we report our ongoing research about the use of SILs as support for organocatalysts, their role as catalysts themselves, and their application as support and stabilizers of palladium nanoparticles (PdNPs). The use of SILs based materials allowed achieving good results. Moreover, in some cases, after the functionalization of the catalytic species with an ion-tag moiety, a release and catch approach was employed in order to improve the catalytic activity and to facilitate the recovery of the hybrid system fo…

Porous Materials Based on 3-Dimensional Td-Directing Functionalized Adamantane Scaffolds and Applied as Recyclable Catalysts

2018

Porous materials have been of high scientific and technological interest owing to their unique performances in many topical applications related to multiphasic functional systems: gas separation and storage, heterogeneous catalysis, energy conversion, etc. We review herein the synthetic strategies applied for using functionalized adamantane derivatives as polyhedral (mainly tetrahedral, Td-directing) building units of three-dimensional (3-D) porous supramolecular structures and nanomaterials, either purely organic or within metal hybrid frameworks. The resulting materials are currently used in varied heterogeneous (or supported) transition metal catalysis and organocatalysis, including rece…

Synthesis of Densely Packaged, Ultrasmall Pt02Clusters within a Thioether-Functionalized MOF: Catalytic Activity in Industrial Reactions at Low Tempe…

2018

The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt02 clusters, homogenously distributed and densely packaged within the channels of a metal-organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO2 methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal c…

Hybrid catalysts for CO 2 conversion into cyclic carbonates

2019

The conversion of carbon dioxide into valuable chemicals such as cyclic carbonates is an appealing topic for the scientific community due to the possibility of valorizing waste into an inexpensive, available, nontoxic, and renewable carbon feedstock. In this regard, last-generation heterogeneous catalysts are of great interest owing to their high catalytic activity, robustness, and easy recovery and recycling. In the present review, recent advances on CO 2 cycloaddition to epoxide mediated by hybrid catalysts through organometallic or organo-catalytic species supported onto silica-, nanocarbon-, and metal-organic framework (MOF)-based heterogeneous materials, are highlighted and discussed.

Bismuth-Catalyzed Growth of SnS2 Nanotubes and Their Stability

2009

Heterogeneous Photocatalysis and Catalysis

2019

Abstract General definitions of heterogeneous catalysis and photocatalysis are reported together with parameters to assess the catalytic and photocatalytic performances. Some features of catalytic and photocatalytic reactions, the importance of amorphous and crystalline phases of the solid photocatalysts, and reactors and photoreactors with the most important kinetic aspects are presented.

DFT calculations on subnanometric metal catalysts: a short review on new supported materials

2018

Metal clusters have been used in catalysis for a long time, even in industrial production protocols, and a large number of theoretical and experimental studies aimed at characterizing their structure and reactivity, either when supported or not, are already present in the literature. Nevertheless, in the last years the advances made in the control of the synthesis and stabilization of subnanometric clusters promoted a renewed interest in the field. The shape and size of sub-nanometer clusters are crucial in determining their catalytic activity and selectivity. Moreover, if supported, subnanometric clusters could be highly influenced by the interactions with the support that could affect geo…