CO2 photo-reduction: insights into CO2 activation and reaction on surfaces of photocatalysts

2016 ◽  
Vol 9 (7) ◽  
pp. 2177-2196 ◽  
Author(s):  
Xiaoxia Chang ◽  
Tuo Wang ◽  
Jinlong Gong
Keyword(s):  
Reaction Mechanism ◽  
Heterogeneous Catalysts ◽  
Current Understanding ◽  
Co2 Activation

This review describes the current understanding of CO2 photoreduction on the surface of heterogeneous catalysts with a particular focus on the reaction mechanism and pathways as well as the adsorption/activation of CO2.

scholarly journals Rhodium-catalyzed asymmetric 1,4-addition reactions of aryl boronic acids with nitroalkenes: reaction mechanism and development of homogeneous and heterogeneous catalysts

2017 ◽  
Vol 8 (12) ◽  
pp. 8362-8372 ◽  
Author(s):  
Hiroyuki Miyamura ◽  
Kohei Nishino ◽  
Tomohiro Yasukawa ◽  
Shū Kobayashi
Keyword(s):  
Reaction Mechanism ◽  
Heterogeneous Catalysts ◽  
Bimetallic Nanoparticles ◽  
Boronic Acids ◽  
Addition Reactions ◽  
Rhodium Complexes ◽  
Tertiary Butyl ◽  
Arylboronic Acids

Asymmetric 1,4-additions of arylboronic acids with nitroalkenes catalyzed by rhodium complexes or heterogeneous Rh–Ag bimetallic nanoparticles with a chiral diene ligand bearing a tertiary butyl amide moiety are developed.

Adenine-Based Zn(II)/Cd(II) Metal–Organic Frameworks as Efficient Heterogeneous Catalysts for Facile CO2Fixation into Cyclic Carbonates: A DFT-Supported Study of the Reaction Mechanism

2019 ◽  
Vol 58 (17) ◽  
pp. 11389-11403 ◽  
Author(s):  
Yadagiri Rachuri ◽  
Jintu Francis Kurisingal ◽  
Ramesh Kumar Chitumalla ◽  
Srimai Vuppala ◽  
Yunjang Gu ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Heterogeneous Catalysts ◽  
Metal Organic Frameworks ◽  
Cyclic Carbonates ◽  
Metal Organic

Reaction mechanism of low-temperature catalysis by surface protonics in an electric field

2020 ◽  
Author(s):  
Yasushi Sekine ◽  
Ryo Manabe
Keyword(s):  
Energy Consumption ◽  
Reaction Mechanism ◽  
Electric Field ◽  
Steam Reforming ◽  
Heterogeneous Catalysts ◽  
Electrical Energy ◽  
Electrical Energy Consumption ◽  
Catalytic Activities ◽  
Mild Conditions ◽  
Dc Electric Field

The process combining heterogeneous catalysts and DC electric field can achieve high catalytic activities, even under mild conditions (<500 K) with less electrical energy consumption. Hydrogen production by steam reforming...

Mechanistic study and catalyst development for selective carbon monoxide methanation

2015 ◽  
Vol 5 (6) ◽  
pp. 3061-3070 ◽  
Author(s):  
S. Tada ◽  
R. Kikuchi
Keyword(s):  
Carbon Monoxide ◽  
Reaction Mechanism ◽  
Heterogeneous Catalysts ◽  
Mechanistic Study ◽  
Co Methanation ◽  
Catalyst Development ◽  
Selective Co Methanation

As for selective CO methanation over heterogeneous catalysts, numerous investigations of the reaction mechanism and catalyst development are reviewed.

scholarly journals Tritiation of aryl thianthrenium salts with a molecular palladium catalyst

Nature ◽  
2021 ◽  
Vol 600 (7889) ◽  
pp. 444-449
Author(s):  
Da Zhao ◽  
Roland Petzold ◽  
Jiyao Yan ◽  
Dieter Muri ◽  
Tobias Ritter
Keyword(s):  
Reaction Mechanism ◽  
Palladium Catalyst ◽  
Palladium Catalysts ◽  
Heterogeneous Catalysts ◽  
Receptor Occupancy ◽  
Inert Atmosphere ◽  
Leaving Group ◽  
Dry Conditions ◽  
Leaving Groups ◽  
Pseudo Halides

AbstractTritium labelling is a critical tool for investigating the pharmacokinetic and pharmacodynamic properties of drugs, autoradiography, receptor binding and receptor occupancy studies1. Tritium gas is the preferred source of tritium for the preparation of labelled molecules because it is available in high isotopic purity2. The introduction of tritium labels from tritium gas is commonly achieved by heterogeneous transition-metal-catalysed tritiation of aryl (pseudo)halides. However, heterogeneous catalysts such as palladium supported on carbon operate through a reaction mechanism that also results in the reduction of other functional groups that are prominently featured in pharmaceuticals3. Homogeneous palladium catalysts can react chemoselectively with aryl (pseudo)halides but have not been used for hydrogenolysis reactions because, after required oxidative addition, they cannot split dihydrogen4. Here we report a homogenous hydrogenolysis reaction with a well defined, molecular palladium catalyst. We show how the thianthrene leaving group—which can be introduced selectively into pharmaceuticals by late-stage C–H functionalization5—differs in its coordinating ability to relevant palladium(II) catalysts from conventional leaving groups to enable the previously unrealized catalysis with dihydrogen. This distinct reactivity combined with the chemoselectivity of a well defined molecular palladium catalyst enables the tritiation of small-molecule pharmaceuticals that contain functionality that may otherwise not be tolerated by heterogeneous catalysts. The tritiation reaction does not require an inert atmosphere or dry conditions and is therefore practical and robust to execute, and could have an immediate impact in the discovery and development of pharmaceuticals.

Advances in Catalytic Conversion of Syngas to Ethanol and Higher Alcohols

2016 ◽  
pp. 177-215
Author(s):  
Jie Sun ◽  
Shaolong Wan ◽  
Jingdong Lin ◽  
Yong Wang
Keyword(s):  
Catalytic Activity ◽  
Reaction Mechanism ◽  
Large Scale ◽  
Heterogeneous Catalysts ◽  
Higher Alcohols ◽  
Fischer Tropsch ◽  
Homogeneous Catalysts ◽  
High Productivity ◽  
Synthesis Catalysts ◽  
Prohibitive Cost

Ethanol and higher alcohols (C2+OH) have attracted much attention owing to their wide applications. They can be produced from syngas using homogeneous and heterogeneous catalysts. Although homogeneous catalysts exhibit high productivity and selectivity of C2+OH, difficulties in separating and recycling homogeneous catalysts remain challenging. Among heterogeneous catalysts, Rh-based catalysts show promising higher selectivity of C2+OH. However, prohibitive cost of Rh metal hinders its large-scale application. Non-noble metal based heterogeneous catalysts include modified methanol synthesis catalysts, modified Fischer-Tropsch (F-T) synthesis catalysts, and Mo/MoS2-based catalysts. Compared with the modified F-T synthesis catalysts and Mo/MoS2-based catalysts, production of undesired byproducts on modified Cu-based catalysts can be well suppressed. Here, the influences of additives and supports on catalytic activity of modified Cu-based catalysts are discussed. Reaction mechanism and development of novel reactors are also included.

What catalysis needs from the electron microscopist

1988 ◽  
Vol 46 ◽  
pp. 694-695
Author(s):  
Alexis T. Bell
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Surface Composition ◽  
Internal Surface ◽  
Active Phase ◽  
Atomic Scale ◽  
Metal Catalyst ◽  
Internal Surface Area ◽  
Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

Electron holography of catalysts

1995 ◽  
Vol 53 ◽  
pp. 416-417
Author(s):  
A. K. Datye ◽  
D. S. Kalakkad ◽  
L. F. Allard ◽  
E. Völkl
Keyword(s):  
Heterogeneous Catalysts ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Scale ◽  
Nano Particles ◽  
Phase Image ◽  
Electron Holography ◽  
Specimen Thickness ◽  
Phase Information ◽  
Particle Structure

The active phase in heterogeneous catalysts consists of nanometer-sized metal or oxide particles dispersed within the tortuous pore structure of a high surface area matrix. Such catalysts are extensively used for controlling emissions from automobile exhausts or in industrial processes such as the refining of crude oil to produce gasoline. The morphology of these nano-particles is of great interest to catalytic chemists since it affects the activity and selectivity for a class of reactions known as structure-sensitive reactions. In this paper, we describe some of the challenges in the study of heterogeneous catalysts, and provide examples of how electron holography can help in extracting details of particle structure and morphology on an atomic scale.Conventional high-resolution TEM imaging methods permit the image intensity to be recorded, but the phase information in the complex image wave is lost. However, it is the phase information which is sensitive at the atomic scale to changes in specimen thickness and composition, and thus analysis of the phase image can yield important information on morphological details at the nanometer level.

Quantitative nano-characterization of heterogeneous catalysts

1995 ◽  
Vol 53 ◽  
pp. 398-399
Author(s):  
P.A. Crozier ◽  
M. Pan
Keyword(s):  
Heterogeneous Catalysts ◽  
Low Dose ◽  
Imaging Techniques ◽  
Structural Features ◽  
Catalyst Characterization ◽  
New Developments ◽  
Double Phase ◽  
Phase Systems ◽  
Dose Imaging

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

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