Search results for "vanA"
showing 10 items of 345 documents
Effect of silica-type sol–gel carrier’s structure and morphology on a supported Ziegler–Natta catalyst for ethylene polymerization
2006
Abstract Silica xerogels with different structures and morphology, synthesized using a sol–gel procedure, were used as a carrier of vanadium catalysts (VOCl 3 /AlEt 2 Cl) for ethylene polymerization. Two techniques of catalyst synthesis were applied: slurry impregnation and gas-phase adsorption and the relevant polymerization methods were then employed. The effect of the carrier structure and morphology on the vanadium loading in the catalysts, the catalyst’s activity and kinetic stability were investigated.
Relationship between bulk phase, near surface and outermost atomic layer of VPO catalysts and their catalytic performance in the oxidative dehydrogen…
2017
Abstract A set of vanadium phosphorous oxide (VPO) catalysts, mainly consisting of (VO) 2 P 2 O 7 , VO(PO 3 ) 2 or VOPO 4 ·2H 2 O bulk crystalline phases, has been investigated for the oxidative dehydrogenation (ODH) of ethane to ethylene, a key potential reaction for a sustainable industrial and socioeconomic development. The catalytic performance on these VPO catalysts has been explained on the basis of the main crystalline phases and the corresponding surface features found by XPS and LEISS at 400 °C, i.e. within the temperature range used for ODH reaction. The catalysts based on (VO) 2 P 2 O 7 phase presented the highest catalytic activity and productivity to ethylene. Nevertheless, the…
Molybdenum–vanadium supported on mesoporous alumina catalysts for the oxidative dehydrogenation of ethane
2006
Abstract Vanadium and/or molybdenum oxides supported on mesoporous alumina have been prepared by a “wet” impregnation method, characterized (by using several physico-chemical techniques TPR, DR-UV–vis, Raman spectroscopies) and tested in the oxidative dehydrogenation (ODH) of ethane. For comparison Mo–V-mixed oxides supported on γ-Al2O3 have also been studied. The characterization results indicate that the main vanadium species in both Mo-free and Mo-containing V-based samples present low aggregation and coordination, whereas molybdenum is present as monomeric or polymeric tetrahedral molybdenum species. Interestingly, no apparent interaction between molybdenum and vanadia takes place. The …
Copolymerization of ethylene with norbornene or 1-octene using supported ionic liquid systems
2016
Copolymerization of ethylene with norbornene (E/NB) and ethylene with 1-octene (E/Oct) is performed using supported ionic liquid (SIL) systems, in which metallocene (Cp2VCl2) or post-metallocene [VCl2(salenCl2)] vanadium catalysts are immobilized in pyridinium chloroaluminate ionic liquid supported on silica. The studied SIL catalysts show higher activities as well as stability than their non-supported analogues. In addition, higher activities and better comonomer incorporation are observed for norbornene (above 30 mol%). The comonomer incorporation has considerable influence on copolymer molecular weight (M w), melting temperature, crystallinity degree, and microstructure of the copolymers…
The effect of the comonomer on the copolymerization of ethylene with long chain α-olefins using Ziegler–Natta catalysts supported on MgCl2(THF)2
2000
Abstract The effect of the type of the comonomer (1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene) on the copolymerization of ethylene with α-olefin over vanadium (VOCl3 and VCl4) and titanium (TiCl4) catalysts supported on MgCl2(THF)2 and activated by Et2AlCl was studied. The results show that the introduction of a longer α-olefin in the ethylene polymerization feed depresses the catalytic activity of all investigated catalysts. The catalyst activity does not depend on the type of the comonomer applied but changes with the comonomer concentration in the feed. The incorporation of α-olefin in the polymer chain was found to be dependent on the type and concentration of the comonomer i…
Vanadium complex with tetradentate [O,N,N,O] ligand supported on magnesium type carrier for ethylene homopolymerization and copolymerization
2009
Immobilization of 1,2-cyclohexylenebis(5-chlorosalicylideneiminato)vanadium dichloride on the magnesium support obtained in the reaction of MgCl 2 .3.4EtOH with Et 2 AlCl gives a highly active precursor for ethylene homopolymerization and its copolymerization with 1-octene. This catalyst exhibits the highest activity in conjunction with MAO, but it is also highly active with AlMe 3 as a cocatalyst. On the other hand, when combined with chlorinated alkylaluminum compounds, Et 2 AlCl and EtAlCl 2 , it gives traces of polyethylene. Moreover, its catalytic activity is strongly affected by the reaction temperature: it increased with rising polymerization temperature from 20 °C to 60 °C, The kine…
Organometallic vanadium‐based heterogeneous catalysts for ethylene polymerization. Study of the deactivation process
1998
Slurry polymerizations of ethylene over vanadium catalysts (based on VCl4 and VOCl3) and their MgCl2(THF)2-supported equivalents were studied. Unsupported vanadium catalysts were found to be unstable while the vanadium active sites deposited on the MgCl2(THF)2 complex are stable. A sharply outlined correlation was found between the concentration of vanadium(III) and catalyst productivity. The high activity and stability of the vanadium catalyst when supported on the magnesium complex is attributed to the increase of resistance to reduction of active vanadium(III) to inactive vanadium(II) by an organoaluminium co-catalyst.
Dichlorovanadium(IV) diamine-bis(phenolate) complexes for ethylene (co)polymerization and 1-olefin isospecific polymerization
2018
Abstract Two vanadium complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor, [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)2}Cl2] (1) and [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)(CH2-2-O-C6H4)}Cl2] (2), were synthesised and characterized by FTIR and 1H NMR spectroscopy. Upon activation with Al(iBu)3/Ph3CB(C6F5)4, these complexes became active catalysts for 1-octene polymerization giving highly stereoregular polymers (mmmm ∼ 90%) having regioirregularly arranged units. The catalytic activity of the catalysts in ethylene homo- and copolymerization, and their ability to incorporate a comonomer were highly dependent on both the activator type and the complex structure. 1/EtAlCl2 exhi…
Projekts: Tirdzniecības uzņēmuma "DĀRSIJA" dibināšana
2016
Maģistra darba mērķis ir uzņēmuma dibināšanas projekta izstrāde un novērtēšana, veicot ieņēmumu un izdevumu aprēķināšu, sastādot un veicot uzņēmuma finanšu pārskatu analīzi. Projekta ideja, kura aprakstīta maģistra darba pirmajā nodaļā, ir konkurētspējīga uzņēmuma dibināšana, kurš veiksmīgi darbojas ziedu tirdzniecības nozarē, bet uzņēmuma galvenie mērķi ir, apmācot jaunos darbiniekus, veicot sadarbību ar piegādātājiem, atvērt ziedu salonu un 3 gadu laikā sasniegt stabila uzņēmuma tēlu, bet, izmantojot dažādas reklāmas kampaņas un konkursus, 5 gadu laikā ieņemt vadošo pozīciju ziedu tirdzniecībā. Paplašināt uzņēmumu un radīt jaunas darba vietas kā arī dot labumu Latvijas ekonomikai. Uzņēmum…
Projekts: Uzņēmuma SIA "Flower Pot Style" dibināšana
2019
Maģistra darba mērķis ir jauna uzņēmuma dibināšana – ziedu veikals Tukuma pilsētā. Ziedu veikals būs unikāls ar savu piedāvāto preču un pakalpojumu daudzveidību. Maģistra darba laikā tika izvērtēts jauna uzņēmuma dibināšanas process un veikta tā pirmo trīs darbības gadu finanšu analīze. Projekta ideja ir dibināt ziedu mazumtirdzniecības uzņēmumu Tukumā. Jaunatvērtais veikals paplašinās jau pieejamo ziedu tirdzniecības klāstu, kā arī piedāvās Tukumā vēl iepriekš nepiedāvātas preces un pakalpojumus. Patērētāji lielāku priekšroku dod paštaisītām un orģinālām lietām. Sekojot patērētāju vēlmēm ziedu veikala piedāvājumā tiks iekļauti ne tikai jau pierastie grieztie ziedu un to kompozīcijas, bet a…