Preliminary investigation on the catalytic mechanism of TiF3 additive in MgH2–TiF3 H-storage system

2007 ◽  
Vol 22 (7) ◽  
pp. 1779-1786 ◽  
Author(s):  
Lai-Peng Ma ◽  
Ping Wang ◽  
Xiang-Dong Kang ◽  
Hui-Ming Cheng
Keyword(s):  
Catalytic Activity ◽  
Catalytic Mechanism ◽  
Metastable Phase ◽  
Storage System ◽  
Preliminary Investigation ◽  
Comparative Investigation ◽  
Active Species ◽  
Structure Property ◽  
Catalytically Active ◽  
Combined Structure

A combined structure/property investigation is performed to understand the catalytic effect of TiF3 additive on the absorption/desorption reactions of MgH2. It was found that both TiH2 and MgF2 phases identified by x-ray diffraction cannot explain the observed kinetic enhancement in the MgH2–TiF3 system, whether they are incorporated in a direct or an in situ manner. In combination with the comparative investigation on the catalytic activity of TiF3 and its analog TiCl3, as well as the samples milled under inert and reactive atmospheres, we propose that the catalytically active species is a multicomponent metastable phase composed of host Mg, transition metal Ti, and F anion, the catalytic activity of which is dependent on its interaction with the surrounding chemical environment.

The effect of different metal oxides on the catalytic activity of a Co3O4 catalyst for toluene combustion: importance of the structure–property relationship and surface active species

2019 ◽  
Vol 43 (27) ◽  
pp. 10868-10877 ◽  
Author(s):  
Xuejun Zhang ◽  
Min Zhao ◽  
Zhongxian Song ◽  
Heng Zhao ◽  
Wei Liu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Metal Oxides ◽  
Catalytic Oxidation ◽  
Active Species ◽  
Active Oxygen ◽  
Redox Cycle ◽  
Structure Property ◽  
Property Relationship ◽  
Structure Property Relationship ◽  
Surface Active

The Co–La catalyst was used to the catalytic oxidation of toluene. The LaCoO3 perovskite was detected. The abundance of Co3+ and active oxygen contributed synergistically to the redox cycle reaction, which could improve the catalytic activity.

An ESR study of irradiated mixtures of hydrogen peroxide and Cu(II) complexes at 77 K

1988 ◽  
Vol 53 (12) ◽  
pp. 3080-3088 ◽  
Author(s):  
Pavel Stopka
Keyword(s):  
Hydrogen Peroxide ◽  
High Pressure ◽  
Catalytic Activity ◽  
Oxalic Acid ◽  
Hydroxyl Radicals ◽  
Room Temperature ◽  
Active Species ◽  
Mercury Lamp ◽  
Catalytically Active ◽  
High Concentrations

When aqueous solutions containing hydrogen peroxide and CuSO4 are irradiated by a high-pressure mercury lamp at room temperature and at 77 K, hydrogen peroxide decomposes and hydroxyl radicals generated in high concentrations coordinate to CuSO4. The catalytic activity of Cu(II), which depends on the choice of the ligand (triene, diene, ethylenediamine, ammonia, EDTA, oxalic acid and glycerine) and the proportion between the monomeric and dimeric forms of the Cu(II) complex, shows a maximum at a concentration of 10-4 mol dm-3. The catalytically active species is the monomeric Cu(II) complex, the dimer being inactive.

Asymmetrische Katalysen, 76. Rh-katalysierte enantioselektive Hydrosilylierung von Acetophenon mit einem polymergebundenen Pyridinoxazolin / Asymmetric Catalysis, 76. Rh-Catalyzed Enantioselective Hydrosilylation of Acetophenone by a Polymer-Bound Pyridineoxazoline

1992 ◽  
Vol 47 (5) ◽  
pp. 609-613 ◽  
Author(s):  
Henri Brunner ◽  
Paul Brandl
Keyword(s):  
Catalytic Activity ◽  
Asymmetric Catalysis ◽  
Enantiomeric Excess ◽  
Active Species ◽  
Product Configuration ◽  
Homogeneous Catalyst ◽  
Catalytically Active ◽  
Polymeric Catalyst

In the enantioselective hydrosilylation of acetophenone with diphenylsilane, a polystyrenebound heterogeneous Rh/pyridineoxazoline catalyst achieved higher optical inductions than a comparable homogeneous catalyst. After using the polymeric catalyst 8—10 times, the catalytic activity decreased markedly and an inversion of the product configuration was observed, the enantiomeric excess rising to 92% ee. These results indicate that the polymeric catalyst contains several catalytically active species with different enantioselectivity and stability.

scholarly journals A Four Coordinated Iron(II)-Digermyl Complex as an Effective Precursor for the Catalytic Dehydrogenation of Ammonia Borane

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 29
Author(s):  
Yoshinao Kobayashi ◽  
Yusuke Sunada
Keyword(s):  
Catalytic Activity ◽  
Ammonia Borane ◽  
Active Species ◽  
Catalytic Dehydrogenation ◽  
Reduction Reactions ◽  
Catalytically Active ◽  
One Step

A coordinatively unsaturated iron(II)-digermyl complex, Fe[Ge(SiMe3)3]2(THF)2 (1), was synthesized in one step by the reaction of FeBr2 with 2 equiv of KGe(SiMe3)3. Complex 1 shows catalytic activity comparable to that of its silicon analogue in reduction reactions. In addition, 1 acts as an effective precursor for the catalytic dehydrogenation of ammonia borane. Catalytically active species can also be generated in situ by simple mixing of the easy-to-handle precursors FeBr2, Ge(SiMe3)4, KOtBu, and phenanthroline.

scholarly journals Activation Mechanism of Nickel(0) N-Heterocyclic Carbene Catalysts Stabilized by Fumarate Ligands

2021 ◽  
Author(s):  
Michael Robo ◽  
Amie Frank ◽  
Ellen Butler ◽  
Alex Nett ◽  
Santiago Canellas ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ligand Exchange ◽  
Active Species ◽  
Heterocyclic Carbenes ◽  
Activation Mechanism ◽  
Catalyst Stability ◽  
Activation Process ◽  
Catalytic Activities ◽  
Computational Evaluation ◽  
Catalytically Active

Nickel(0) catalysts of N-heterocyclic carbenes (NHCs) that are stabilized by electronic deficient alkenes possess desirable properties of air tolerance and ease of handling while also retaining high catalytic activities. Since catalyst stability often comes at the expense of catalytic activity, we have undertaken a detailed study of the activation mechanism of a new IMes-nickel(0) catalyst stabilized by di-(o-tolyl) fumarate that converts the stable pre-catalyst form into a catalytically active species. Computational evaluation provided evidence against a simple ligand exchange as the activation mechanism, and a stoichiometric activation process that covalently modifies the stabilizing ligand was identified. A detailed computational picture for the activation process was developed, with predictive insights that explain the catalyst features that lead to both active and inactive precatalysts.

Sewage sludge as a precursor of adsorbents/catalysts for environmental applications

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
A. Ros ◽  
C. Canals-Batlle ◽  
M.A. Lillo-Ródenas ◽  
E. Fuente ◽  
M. A. Montes-Morán ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Room Temperature ◽  
Waste Water Treatment ◽  
Textural Properties ◽  
Active Species ◽  
Elemental Sulphur ◽  
Gaseous Emissions ◽  
Removal Experiments ◽  
Catalytically Active

This paper focuses on the valorisation of solid residues obtained from the thermal treatment of sewage sludge. In particular, sewage sludge samples were collected from two waste water treatment plants (WWTPs) with different sludge line basic operations. After drying, sludges were heated up to 700 °C in appropriate ovens under diluted air (gasification) and inert (pyrolysis) atmospheres. The solids obtained, as well as the dried (raw) sludges, were characterised to determine their textural properties and chemical composition, including the speciation of their inorganic fraction. All the materials under study were employed as adsorbents/catalysts in H2S removal experiments at room temperature. It was found that, depending on the particular sludge characteristics, outstanding results can be achieved both in terms of retention capacities and selectivity. Some of the solids outperform commercially available sorbents specially designed for gaseous emissions control. In these adsorbents/catalysts, H2S is selectively oxidised to elemental sulphur most likely due to the presence of inorganic, catalytically active species. The role of the carbon-enriched part on these solids is also remarked.

Hydrogen peroxide decomposition on a two-component CuO-Cr2O3 catalyst

1988 ◽  
Vol 53 (8) ◽  
pp. 1636-1646 ◽  
Author(s):  
Viliam Múčka ◽  
Kamil Lang
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Extreme Values ◽  
Catalytic Properties ◽  
Active Components ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Peroxide Decomposition ◽  
Two Component ◽  
Catalytically Active

Some physical and catalytic properties of the two-component copper(II)oxide-chromium(III)oxide catalyst with different content of both components were studied using the decomposition of the aqueous solution of hydrogen peroxide as a testing reaction. It has been found that along to both basic components, the system under study contains also the spinel structure CuCr2O4, chromate washable by water and hexavalent ions of chromium unwashable by water. The soluble chromate is catalytically active. During the first period of the reaction the equilibrium is being established in both homogeneous and heterogeneous catalytic systems. The catalytic activity as well as the specific surface area of the washed solid is a non-monotonous function of its composition. It seems highly probable that the extreme values of both these quantities are not connected with the detected admixtures in the catalytic system. The system under study is very insensitive with regard to the applied doses of gamma radiation. Its catalytic properties are changed rather significantly after the thermal treatment and particularly after the partial reduction to low degree by hydrogen. The observed changes of the catalytic activity of the system under study are very probably in connection with the changes of the valence state of the catalytically active components of the catalyst.

scholarly journals ZnCDs/ZnO@ZIF-8 Zeolite Composites for the Photocatalytic Degradation of Tetracycline

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 934
Author(s):  
Yong Cheng ◽  
Xiuxiu Wang ◽  
Yu Mei ◽  
Dan Wang ◽  
Changchun Ji
Keyword(s):  
Catalytic Activity ◽  
Photocatalytic Degradation ◽  
Photocatalytic Performance ◽  
Active Species ◽  
Degradation Efficiency ◽  
Experimental Result ◽  
Porous Nanostructure ◽  
Resultant Material

Considering the photocatalytic performance of CDs, ZnO, and the unique porous nanostructure and stability of ZIF-8, we prepared ZnCDs/ZnO@ZIF-8 zeolite composites. The resultant material represented an enhanced ability for the photodegradation of TC compared with that of ZnCDs and ZnO. The photocatalytic degradation efficiency reached over 85%. The catalytic activity of the composites was maintained after four cycles. The experimental result indicated that ×O2 radical was the active species in the reaction.

Probing the Catalytically Active Species in POM‐catalysed DNA‐model Hydrolysis

2021 ◽  
Author(s):  
Frederico F Martins ◽  
Ángel Sánchez-González ◽  
Jose Lanuza ◽  
Haralampos N. Miras ◽  
Xabier Lopez ◽  
...  
Keyword(s):  
Active Species ◽  
Catalytically Active

scholarly journals Serine protease dynamics revealed by NMR analysis of the thrombin-thrombomodulin complex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Riley B. Peacock ◽  
Taylor McGrann ◽  
Marco Tonelli ◽  
Elizabeth A. Komives
Keyword(s):  
Active Site ◽  
Serine Proteases ◽  
Protein C ◽  
Catalytic Mechanism ◽  
Bond Cleavage ◽  
Peptide Bond ◽  
Peptide Bond Cleavage ◽  
Exchange Mass Spectrometry ◽  
Catalytically Active ◽  
Hydrogen Deuterium

AbstractSerine proteases catalyze a multi-step covalent catalytic mechanism of peptide bond cleavage. It has long been assumed that serine proteases including thrombin carry-out catalysis without significant conformational rearrangement of their stable two-β-barrel structure. We present nuclear magnetic resonance (NMR) and hydrogen deuterium exchange mass spectrometry (HDX-MS) experiments on the thrombin-thrombomodulin (TM) complex. Thrombin promotes procoagulative fibrinogen cleavage when fibrinogen engages both the anion binding exosite 1 (ABE1) and the active site. It is thought that TM promotes cleavage of protein C by engaging ABE1 in a similar manner as fibrinogen. Thus, the thrombin-TM complex may represent the catalytically active, ABE1-engaged thrombin. Compared to apo- and active site inhibited-thrombin, we show that thrombin-TM has reduced μs-ms dynamics in the substrate binding (S1) pocket consistent with its known acceleration of protein C binding. Thrombin-TM has increased μs-ms dynamics in a β-strand connecting the TM binding site to the catalytic aspartate. Finally, thrombin-TM had doublet peaks indicative of dynamics that are slow on the NMR timescale in residues along the interface between the two β-barrels. Such dynamics may be responsible for facilitating the N-terminal product release and water molecule entry that are required for hydrolysis of the acyl-enzyme intermediate.

Sign in / Sign up

Export Citation Format

Share Document