Metathesis Catalyst WOCl4/Ph4Sn: The Chemistry of Ripening and Transformation to Polymerization Active Species

1994 ◽  
Vol 59 (11) ◽  
pp. 2454-2471 ◽  
Author(s):  
Jan Sedláček ◽  
Jiří Vohlídal ◽  
Jiří Kareš ◽  
Marta Pacovská ◽  
Bohumil Máca
Keyword(s):  
Homogeneous Solution ◽  
Active Species ◽  
Active Particles ◽  
Metathesis Catalyst ◽  
Catalytically Active ◽  
Tungsten Species ◽  
To Come ◽  
Binary Catalyst ◽  
Derivatives Of ◽  
Stoichiometric Relation

Ripening of WOCl4/Ph4Sn binary catalyst of composition from 1 : 1 to 1 : 4 in benzene and toluene is a complex reaction in which initially homogeneous solution of the catalyst components continually changes to a colloidal solution, and utterly to a suspension of catalytically active particles consisted of lower-valent tungsten species in the solution of biphenyl, Ph3SnCl and, eventually, unreacted Ph4Sn (at composition 1 : 4). The yield of biphenyl is in a simple stoichiometric relation with the initial concentration of WOCl4 and a proof is given that the phenyl groups constituting biphenyl molecules come from Ph4Sn cocatalyst. The mechanism of the overall process is suggested. Above twenty, mostly phenylated derivatives of phenylacetylene (PhA) and oligomers of two degrees of unsaturation were detected as by-products of PhA reaction with the ripened catalyst formed in addition to main product, poly(phenylacetylene). The excess phenyls built in the oligomers are demonstrated to come from the supplied Ph4Sn. The mechanism is suggested for formation of the both oligomeric derivatives and growing carbene centers in which oxo ligands of tungsten centers are proposed to play a central role.

scholarly journals Non-equilibrium phase separation in mixtures of catalytically active particles: size dispersity and screening effects

2021 ◽  
Vol 44 (9) ◽  
Author(s):  
Vincent Ouazan-Reboul ◽  
Jaime Agudo-Canalejo ◽  
Ramin Golestanian
Keyword(s):  
Phase Separation ◽  
Alternative Pathway ◽  
Effective Interaction ◽  
Equilibrium Phase ◽  
Active Species ◽  
Biologically Relevant ◽  
Active Particles ◽  
Catalytically Active ◽  
Non Equilibrium ◽  
In Cells

Abstract Biomolecular condensates in cells are often rich in catalytically active enzymes. This is particularly true in the case of the large enzymatic complexes known as metabolons, which contain different enzymes that participate in the same catalytic pathway. One possible explanation for this self-organization is the combination of the catalytic activity of the enzymes and a chemotactic response to gradients of their substrate, which leads to a substrate-mediated effective interaction between enzymes. These interactions constitute a purely non-equilibrium effect and show exotic features such as non-reciprocity. Here, we analytically study a model describing the phase separation of a mixture of such catalytically active particles. We show that a Michaelis–Menten-like dependence of the particles’ activities manifests itself as a screening of the interactions, and that a mixture of two differently sized active species can exhibit phase separation with transient oscillations. We also derive a rich stability phase diagram for a mixture of two species with both concentration-dependent activity and size dispersity. This work highlights the variety of possible phase separation behaviours in mixtures of chemically active particles, which provides an alternative pathway to the passive interactions more commonly associated with phase separation in cells. Our results highlight non-equilibrium organizing principles that can be important for biologically relevant liquid-liquid phase separation. Graphic abstract

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.

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 Shedding light on the nature of the catalytically active species in photocatalytic reactions using Bi2O3 semiconductor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Paola Riente ◽  
Mauro Fianchini ◽  
Patricia Llanes ◽  
Miquel A. Pericàs ◽  
Timothy Noël
Keyword(s):  
Experimental Studies ◽  
Heterogeneous Photocatalysis ◽  
Active Species ◽  
Organic Transformations ◽  
Alkyl Bromides ◽  
Catalytically Active ◽  
Visible Light Driven ◽  
Photocatalytic Reactions ◽  
Insight Into ◽  
Photocatalytic Processes

AbstractThe importance of discovering the true catalytically active species involved in photocatalytic systems allows for a better and more general understanding of photocatalytic processes, which eventually may help to improve their efficiency. Bi2O3 has been used as a heterogeneous photocatalyst and is able to catalyze several synthetically important visible-light-driven organic transformations. However, insight into the operative catalyst involved in the photocatalytic process is hitherto missing. Herein, we show through a combination of theoretical and experimental studies that the perceived heterogeneous photocatalysis with Bi2O3 in the presence of alkyl bromides involves a homogeneous BinBrm species, which is the true photocatalyst operative in the reaction. Hence, Bi2O3 can be regarded as a precatalyst which is slowly converted in an active homogeneous photocatalyst. This work can also be of importance to mechanistic studies involving other semiconductor-based photocatalytic processes.

In Search of Catalytically Active Species in the Surfactant-Mediated Biphasic Alkene Epoxidation with Mimoun-Type Complexes

2001 ◽  
Vol 3 (3) ◽  
pp. 329-332 ◽  
Author(s):  
Dirk V. Deubel ◽  
Jörg Sundermeyer ◽  
Gernot Frenking
Keyword(s):  
Active Species ◽  
Catalytically Active

scholarly journals Surprisingly high sensitivity of copper nanoparticles toward coordinating ligands: consequences for the hydride reduction of benzaldehyde

2018 ◽  
Vol 8 (19) ◽  
pp. 5073-5080 ◽  
Author(s):  
Xavier Frogneux ◽  
Ferenc Borondics ◽  
Stéphane Lefrançois ◽  
Florian D'Accriscio ◽  
Clément Sanchez ◽  
...  
Keyword(s):  
Copper Nanoparticles ◽  
High Sensitivity ◽  
Active Species ◽  
Hydride Reduction ◽  
Catalytically Active

Depending on the ligand, ligand-induced leaching of copper nanoparticles may produce catalytically active species for the reduction of benzaldehyde.

scholarly journals Self-Propulsion Strategies for Artificial Cell-Like Compartments

Nanomaterials ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1680 ◽  
Author(s):  
Ibon Santiago ◽  
Friedrich C. Simmel
Keyword(s):  
Synthetic Biology ◽  
Biomedical Engineering ◽  
Recent Progress ◽  
Emulsion Droplet ◽  
Artificial Cells ◽  
Droplet Motion ◽  
Active Particles ◽  
Artificial Cell ◽  
Catalytically Active ◽  
A Current

Reconstitution of life-like properties in artificial cells is a current research frontier in synthetic biology. Mimicking metabolism, growth, and sensing are active areas of investigation; however, achieving motility and directional taxis are also challenging in the context of artificial cells. To tackle this problem, recent progress has been made that leverages the tools of active matter physics in synthetic biology. This review surveys the most significant achievements in designing motile cell-like compartments. In this context, strategies for self-propulsion are summarized, including, compartmentalization of catalytically active particles, phoretic propulsion of vesicles and emulsion droplet motion driven by Marangoni flows. This work showcases how the realization of motile protocells may impact biomedical engineering while also aiming at answering fundamental questions in locomotion of prebiotic cells.

Sign in / Sign up

Export Citation Format

Share Document