Synthesis of polyoxymethylene dimethyl ethers from dimethoxymethane and trioxymethylene over graphene oxide: Probing the active species and relating the catalyst structure to performance

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.

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Synergistic Removal of Bromate and Ibuprofen by Graphene Oxide and TiO2 Heterostructure Doped with F: Performance and Mechanism

Journal of Nanomaterials ◽

10.1155/2020/6094984 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9

Author(s):

Yan Zhang ◽

Jiarong Li ◽

Hongyuan Liu

Keyword(s):

Graphene Oxide ◽

Photocatalytic Oxidation ◽

Removal Rate ◽

Active Species ◽

Main Role ◽

Reaction Rate Constants ◽

First Order Kinetics ◽

Oxidation Reduction ◽

Synergistic Degradation ◽

Performance And Mechanism

The batch experiments of photocatalytic oxidation-reduction of bromate and ibuprofen (IBP) by graphene oxide (GO) and TiO2 heterostructure doped with F (FGT) particles were conducted. The performance and mechanism of synergistic removal of bromate and IBP by FGT were discussed. The results show that a demonstrable synergistic effect and excellent removal rate of bromate and IBP by FGT were exhibited. When pH is 5.2 and the dosage of FGT is 0.1 g/L, the reaction rate constants of bromate and IBP increased from 0.0584 min-1 and 0.4188 min-1 to 0.1353 min-1 and 0.4504 min-1, respectively, compared with the degradation of bromate or IBP alone. The reaction of photocatalytic synergistic degradation is appropriately fitted through Langmuir-Hinshelwood first-order kinetics. The mechanism of synergistic removal of bromate and IBP by FGT was discussed. And electrons (e-), hydroxyl radical (⋅OH), and superoxide radical (⋅O2-) are the main active species. The electrons play a main role in the bromate reduction, and bromine is the only reduction product, while the oxidation of IBP is the result of ⋅OH and ⋅O2-, and ⋅OH plays a key role. The recombination of electrons and holes is inhibited by simultaneous consumption of bromate and IBP, which makes full use of the redox properties of FGT and plays a synergistic role in the removal of pollutants. The results indicate that photocatalytic oxidation-reduction by FGT is a promising, efficient, and environmental-friendly method for synchronous removal of combined pollution in water.

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Highly regioselective osmium-catalyzed hydroformylation

Chemical Communications ◽

10.1039/c4cc05626d ◽

2015 ◽

Vol 51 (15) ◽

pp. 3080-3082 ◽

Cited By ~ 16

Author(s):

Lipeng Wu ◽

Qiang Liu ◽

Anke Spannenberg ◽

Ralf Jackstell ◽

Matthias Beller

Keyword(s):

Active Species ◽

Phosphine Ligands ◽

Catalyst Structure ◽

Osmium Carbonyl

Osmium carbonyl combined with 2-imidazoyl-substituted phosphine ligands forms active species for the highly regioselective and general hydroformylation of alkenes to produce aldehydes in good yields and excellent regioselectivities. An unusual phosphido bridged trinuclear osmium catalyst structure was obtained.

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Boosting ethanol electrooxidation via photothermal effect over palladium/reduced graphene oxide

Journal of Materials Chemistry A ◽

10.1039/c8ta08006b ◽

2018 ◽

Vol 6 (38) ◽

pp. 18426-18429 ◽

Cited By ~ 6

Author(s):

Yongmeng Wu ◽

Shuhe Han ◽

Yi Huang ◽

Yanmei Shi ◽

Bin Zhang

Keyword(s):

Graphene Oxide ◽

Reduced Graphene Oxide ◽

Active Species ◽

Photothermal Effect ◽

Ethanol Electrooxidation ◽

Reduced Graphene ◽

Alcohol Electrooxidation

A photothermal effect strategy to combine the model thermal material, namely, reduced graphene oxide with active species (Pd) was developed to greatly improve the activity and stability of the alcohol electrooxidation reaction.

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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 ◽

10.3390/macromol1020010 ◽

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.

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