Search results for "catalyst"

Synthesis of oxide-supported vanadium catalysts and their activity in ethylene polymerization

1999

The activity of oxide-supported vanadium-based catalyst systems (VOCl 3/Et 2AlCl) in low-pressure ethylene polymerization and the properties of the resulting polyethylenes were studied in relation to the type and mode of modification of the oxide support. Alumina, silica and an un"conventional silica-type material prepared by the sol-gel process were used as supports. Results are compared with those obtained earlier with a catalyst supported on MgCl 2(THF) 2. Of the oxides studied, the silica-type sol-gel material dehydrated and subsequently modified with Et 2AlCl proved to be the best carrier for a vanadium catalyst. The polyethylene prepared by using this catalyst support was found to exh…

SUPERHYDROPHOBIC TIO2-FLUORINATED POLYSILOXANE NANOCOMPOSITES WITH PHOTOCATALYTIC CLEANING ACTIVITY FOR CULTURAL HERITAGE APPLICATIONS

Preparation of tungstophosphoric acid/cerium-doped NH2-UiO-66 Z-scheme photocatalyst: a new candidate for green photo-oxidation of dibenzothiophene a…

2021

International audience; The goal of this study was to introduce an effective visible-light induced photocatalytic system with a good ability for photocatalytic oxidative desulfurization (PODS) and denitrogenation (PODN) using molecular oxygen (O2) as an oxidant. In this regard, tungestophosphoric acid (PW12) was supported onto cerium-doped NH2-UiO-66 (PW12/Ce-NUiO-66) and employed for the photo-oxidation of dibenzothiophene (DBT) and quinoline (Qu). Herein, using cerium (Ce) as a “mediator” facilitated the separation of charge carriers, while NH2-UiO-66 remarkably enhanced the surface area with plentiful adsorption sites and shifted the adsorption edge of PW12to the visible region. The sum …

Comparison of imidazolium and pyridinium ionic liquids as the media for biphasic ethylene polymerization in the presence of titanocene catalyst

2009

Chloroglinianowe ciecze jonowe z kationem 1-n-oktylo-3-metylopirydyniowym [C8-β-mpy]+[AlCl4]- lub 1-n-oktylo-4-metylopirydyniowym [C8-γ-mpy]+[AlCl4]- zastosowano jako jedną z faz w dwufazowej polimeryzacji etylenu w układzie ciecz jonowa/heksan, prowadzonej wobec katalizatora tytanocenowego (Cp2TiCl2) aktywowanego AlEtCl2. Wydajności polimeryzacji i właściwości polimerów otrzymanych z udziałem wymienionych cieczy jonowych porównano z odpowiednimi wielkościami uzyskanymi wcześniej przy udziale cieczy imidazoliowej ([C8-mim]+ [AlCl4]-) (tabele 1 i 2). Stwierdzono, że wprowadzenie do układu pirydyniowych zamiast imidazoliowych cieczy jonowych skutkuje wzrostem całkowitej wydajności procesu, wi…

Defying Stereotypes with Nanodiamonds: Stable Primary Diamondoid Phosphines

2016

International audience; Direct unequal C-H bond difunctionalization of phosphorylated diamantane was achieved in high yield from the corresponding phosphonates. Reduction of the functionalized phosphonates provides access to novel primary and secondary alkyl/aryl diamantane phosphines. The prepared primary diamantyl phosphines are quite air stable compared to their adamantyl and especially alkyl or aryl analogues. This finding is corroborated by comparing the singly occupied molecular orbital energy levels of the corresponding phosphine radical cations obtained by density functional theory computations.

Sustainable Recycling of Insoluble Rust Waste for the Synthesis of Iron-Containing Perovskite-Type Catalysts

2019

Insoluble rust waste from the scraping of rusted iron-containing materials represents a cheap, eco-friendly, and available source of iron. LaFeO3 perovskite-type powders were successfully prepared by solution combustion synthesis using rust waste from an electricity transmission tower manufacturer. Solution combustion synthesis enabled introduction of this insoluble iron precursor directly into the final product, bypassing complex extraction procedures. Catalytic activity in the propylene oxidation of the waste-derived LaFeO3 with stoichiometric Fe/La ratio was almost identical to the commercial iron nitrate-derived LaFeO3 , thus demonstrating the viability of this recycling solution. The a…

Metal salen complexes as ethylene polymerization catalysts - effect of catalytic system composition on its activity and properties of polymerization …

2008

Zsyntetyzowano i zastosowano [po aktywacji metyloaluminoksanem (MAO) lub Et2AlCl] w charakterze katalizatorów niskociśnieniowej polimeryzacji etylenu serię salenowych kompleksów metali przejściowych różniących się rodzajem atomu centralnego (M=Ti, Zr lub V) i budową chemiczną ligandu (schemat A). Stwierdzono, że salenowe kompleksy cyrkonu są aktywne w polimeryzacji jedynie wówczas, gdy aktywator stanowi MAO, natomiast kompleksy tytanu i wanadu są aktywniejsze w przypadku gdy kokatalizatorem jest typowy związek glinoorganiczny - dietylochloroglin. Aktywność kompleksów w układzie z Et2AlCl zmienia się w szeregu V>Ti>>Zr?0, podczas gdy w odniesieniu do kompleksów aktywowanych MAO maleje ona w …

Polystyrene-supported organocatalysts for alfa-selenenylation and Michael reactions. A common post-modification approach for catalytic differentiation

2011

Three different resin-supported catalysts have been prepared by using the well established post-modification approach by means of thiol-ene coupling reaction. Two catalysts were tested for the first time in the asymmetric α-selenenylation of propanal, while the third catalyst was used in the Michael addition reaction. While the preliminary results are not encouraging in the case of supported Jørgensen’ catalyst, interesting data have been collected with both for the supported MacMillan and prolyl-prolinol catalysts. In fact, these catalysts displayed good activity and selectivity. A reversed enantioselectivity in the α-selenenylation was observed by changing the polarity of the solvent. Fin…

From covalently linked catalysts to "release and catch" catalytic systems

2014

Silica powder obtained by sol-gel method as a support of organometallic vanadium catalyst for ethylene polymerization

2004

Sol-gel technique was employed to obtain the silica-type powder, which after modification procedure was applied as asupport of organometallic catalytic system for ethylene polymerization. The powder product was synthesized using hydrolysis and condensation of TEOS, catalyzed by ammonia. Obtained material and a reference support (commercial silica Davisil) were characterized to determine their particle size distributions, BET surface area, pore volume and diameter. Gas-phase adsorption of vanadium catalyst on analyzed support materials as well as adsorption from the solution in hexane were carried out. Both carrier materials were thermally pretreated prior catalytic systems syntheses and the…