scholarly journals Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Ethylene Oligomers and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

Macromol ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 121-129
Author(s):  
Ilaria D’Auria ◽  
Zeinab Saki ◽  
Claudio Pellecchia
Keyword(s):  
Active Species ◽  
Polymerization Catalysts ◽  
Reaction Conditions ◽  
Catalyst Structure ◽  
Variable Content ◽  
Peculiar Behavior ◽  
Number Of Branches ◽  
Ethylene Oligomers

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart’s α-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that Ni(II) complexes bearing aryliminopyridine ligands with bulky substituents both at the imino moiety and in the 6-position of pyridine afford either hyperbranched low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes or both, depending on the ligand structure and the reaction conditions. The formation of multiple active species in situ is suggested by analysis of the post-polymerization catalyst residues, showing the partial reduction of the imino function. Some related arylaminopyridine Ni(II) complexes were also synthesized and tested, showing a peculiar behavior, i.e., the number of branches of the produced polyethylenes increases while ethylene pressure increases.

scholarly journals Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Oligoethylenes and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

2021 ◽  
Author(s):  
Ilaria D'Auria ◽  
Zeinab Saki ◽  
Claudio Pellecchia
Keyword(s):  
Ethylene Polymerization ◽  
Active Species ◽  
Polymerization Catalysts ◽  
Reaction Conditions ◽  
Catalyst Structure ◽  
Variable Content ◽  
Peculiar Behavior ◽  
Number Of Branches

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart's α-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that Ni(II) complexes bearing aryliminopyridine ligands with bulky substituents both at the imino moiety and in the 6-position of pyridine afford either hyperbranched low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes or both depending on the ligand structure and the reaction conditions. The formation of multiple active species in situ is suggested by analysis of the post-polymerization catalyst residues, showing the partial reduction of the imino function. Some related arylaminopyridine Ni(II) complexes were also synthesized and tested, showing a peculiar behavior, i.e. the number of branches of the produced polyethylenes increases while ethylene pressure increases.

Fischer-Tropsch synthesis nanostructured catalysts: understanding structural characteristics and catalytic reaction

2013 ◽  
Vol 2 (5) ◽  
pp. 547-576 ◽  
Author(s):  
Peng Zhai ◽  
Geng Sun ◽  
Qingjun Zhu ◽  
Ding Ma
Keyword(s):  
Structural Characteristics ◽  
Nanostructured Catalysts ◽  
Catalytic Performance ◽  
Tropsch Synthesis ◽  
Fischer Tropsch ◽  
Reaction Conditions ◽  
Catalyst Structure ◽  
Fischer Tropsch Synthesis

AbstractOne key goal of heterogeneous catalysis study is to understand the correlation between the catalyst structure and its corresponding catalytic activity. In this review, we focus on recent strategies to synthesize well-defined Fischer-Tropsch synthesis (FTS) nanostructured catalysts and their catalytic performance in FTS. The development of those promising catalysts highlights the potentials of nanostructured materials to unravel the complex and dynamic reaction mechanism, particularly under the in situ reaction conditions. The crucial factors associated with the catalyst compositions and structures and their effects on the FTS activities are discussed with an emphasis on the role of theoretical modeling and experimental results.

scholarly journals Enzymatic synthesis and phosphorolysis of 4(2)-thioxo- and 6(5)-azapyrimidine nucleosides by E. coli nucleoside phosphorylases

2016 ◽  
Vol 12 ◽  
pp. 2588-2601 ◽  
Author(s):  
Vladimir A Stepchenko ◽  
Anatoly I Miroshnikov ◽  
Frank Seela ◽  
Igor A Mikhailopulo
Keyword(s):  
Purine Nucleoside Phosphorylase ◽  
Reaction Conditions ◽  
E Coli ◽  
No Formation ◽  
Structural Peculiarities ◽  
Substrate Properties ◽  
Nucleoside Phosphorylases ◽  
Derivatives Of

The trans-2-deoxyribosylation of 4-thiouracil (4SUra) and 2-thiouracil (2SUra), as well as 6-azauracil, 6-azathymine and 6-aza-2-thiothymine was studied using dG and E. coli purine nucleoside phosphorylase (PNP) for the in situ generation of 2-deoxy-α-D-ribofuranose-1-phosphate (dRib-1P) followed by its coupling with the bases catalyzed by either E. coli thymidine (TP) or uridine (UP) phosphorylases. 4SUra revealed satisfactory substrate activity for UP and, unexpectedly, complete inertness for TP; no formation of 2’-deoxy-2-thiouridine (2SUd) was observed under analogous reaction conditions in the presence of UP and TP. On the contrary, 2SU, 2SUd, 4STd and 2STd are good substrates for both UP and TP; moreover, 2SU, 4STd and 2’-deoxy-5-azacytidine (Decitabine) are substrates for PNP and the phosphorolysis of the latter is reversible. Condensation of 2SUra and 5-azacytosine with dRib-1P (Ba salt) catalyzed by the accordant UP and PNP in Tris∙HCl buffer gave 2SUd and 2’-deoxy-5-azacytidine in 27% and 15% yields, respectively. 6-Azauracil and 6-azathymine showed good substrate properties for both TP and UP, whereas only TP recognizes 2-thio-6-azathymine as a substrate. 5-Phenyl and 5-tert-butyl derivatives of 6-azauracil and its 2-thioxo derivative were tested as substrates for UP and TP, and only 5-phenyl- and 5-tert-butyl-6-azauracils displayed very low substrate activity. The role of structural peculiarities and electronic properties in the substrate recognition by E. coli nucleoside phosphorylases is discussed.

In situ synthesis of hierarchical nitrogen-doped MoS2 microsphere with an excellent visible light-driven photocatalytic nitrogen fixation ability

2020 ◽  
Vol 13 (05) ◽  
pp. 2051031
Author(s):  
Abulikemu Abulizi ◽  
Hujiabudula Maimaitizi ◽  
Dilinuer Talifu ◽  
Yalkunjan Tursun
Keyword(s):  
Visible Light ◽  
High Performance ◽  
Nucleation Site ◽  
Active Species ◽  
Nitrogen Doped ◽  
Photogenerated Electrons ◽  
The Hierarchical Structure ◽  
Visible Light Driven

A photocatalyst of high-performance hierarchical nitrogen-doped MoS2 (N-MoS2) microsphere was fabricated by an in situ hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB). The as-prepared N-MoS2 microsphere was self-assembled by extremely thin interleaving petals, where CTAB acts as a nucleation site for the formation of the interleaving petals due to the strong interaction between CTA+ and [Formula: see text]. N-MoS2 showed higher N2 fixation ability (101.2 [Formula: see text] mol/g(cat)h) than the non-doped MoS2 under the visible light irradiation, and the improved photocatalytic activity could be ascribed to that the doped N narrows the band gap, and the surface reflecting and scattering effect caused by the hierarchical structure enhance the light adsorption. The trapping experiment of active species was also investigated to evaluate the role of photogenerated electrons in the photocatalytic reaction process. Meanwhile, the possible mechanism for the formation and excellent photocatalytic performance of N-MoS2 microsphere were also presented.

Immobilization of a rhodium catalyst using a diphosphine-functionalized ionic liquid in RTIL for the efficient and recyclable biphasic hydroformylation of 1-octene

2016 ◽  
Vol 190 ◽  
pp. 219-230 ◽  
Author(s):  
Yong-Qi Li ◽  
Huan Liu ◽  
Peng Wang ◽  
Da Yang ◽  
Xiao-Li Zhao ◽  
...  
Keyword(s):  
High Pressure ◽  
Ionic Liquid ◽  
Spectral Analysis ◽  
Catalytic System ◽  
Active Species ◽  
Rhodium Catalyst ◽  
Functionalized Ionic Liquid ◽  
Ft Ir

A highly efficient and stable Rh–P catalytic system in the RTIL of [PEmim]BF4 was developed for the biphasic hydroformylation of 1-octene by using the diphosphine-functionalized ionic liquid (FIL) of 2. While 2-Rh(acac)(CO)2 was immobilized in [PEmim]BF4 (solvent), a typical biphasic catalysis was fulfilled with advantages of facile separation and recycling ability – 9 runs without any loss of activity. It was found that not only the acquired π-acceptor character of 2, but also the synergetic role of the piperidyl group in [PEmim]BF4 as an N-containing donor, cooperatively contributed to the efficient hydroformylation due to the facilitated formation and stability of the Rh-H active species (ν 2045 cm−1). This was supported by the in situ high-pressure FT-IR spectral analysis.

scholarly journals Conductive Cotton by In Situ Laccase-Polymerization of Aniline

Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1023 ◽  
Author(s):  
Jing Su ◽  
Euijin Shim ◽  
Jennifer Noro ◽  
Jiajia Fu ◽  
Qiang Wang ◽  
...  
Keyword(s):  
Cotton Fabrics ◽  
Wearable Electronics ◽  
Polymerization Degree ◽  
Reaction Conditions ◽  
Ultrasonic Bath ◽  
Potential Applications ◽  
Aniline Oxidation ◽  
Conductive Textile

Conductive cotton fabrics were obtained via in situ aniline polymerization by laccase from Myceliophthora thermophila under mild reaction conditions without the addition of strong proton acids. The reactions were conducted using two types of reactors, namely a water bath (WB) and an ultrasonic bath (US), and the role of a mediator, 1-hydroxybenzotriazol (HBT), on the laccase-assisted polymerization of aniline was investigated. A similar polymerization degree was obtained when using both reactors—however, the ultrasonic bath allowed the experiments to be conducted in shorter periods of time (24 h for WB vs. 2 h for US). The data obtained also revealed that the mediator (1-hydroxybenzotriazol-HBT) played a crucial role in aniline oxidation. A higher conversion yield and polymerization degree were obtained when the reaction was conducted in the presence of this compound, as confirmed by MALDI-TOF analysis. The cotton fabrics coated with polyaniline presented deep coloration and conductivity, especially when the mediator was included on the reactional system. The results obtained are a step forward in the enzymatic polymerization of aniline with the purpose of obtaining coloured conductive textile surfaces, with potential applications in wearable electronics.

{10-12} Twinning Mechanism During In Situ Micro-Tensile Loading of Pure Mg: Role of Basal Slip and Twin-Twin Boundary Interaction

2020 ◽  
Author(s):  
Nicolò Maria della Ventura ◽  
Szilvia Kalácska ◽  
Daniele Casari ◽  
Thomas Edward James Edwards ◽  
Johann Michler ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Basal Slip ◽  
Tensile Loading ◽  
Boundary Interaction

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.

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