Search results for "PLE"
showing 10 items of 22773 documents
Vanadium complex with tetradentate [O,N,N,O] ligand supported on magnesium type carrier for ethylene homopolymerization and copolymerization
2010
Immobilization of 1,2‐cyclohexylenebis(5‐chlorosalicylideneiminato)vanadium dichloride on the magnesium support obtained in the reaction of MgCl2·3.4EtOH with Et2AlCl 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 AlMe3 as a cocatalyst. On the other hand, when combined with chlorinated alkylaluminum compounds, Et2AlCl and EtAlCl2, 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 kinetic curve…
Effect of sample preparation on gel permeation chromatography results of determination of molecular weight of polyethylene obtained with using of zir…
2003
Molecular weights of polyethylene (PE) obtained with using of zirconocene catalyst activated with large excess of methylaluminoxane (MAO) were determined by gel permeation chromatography (GPC) method. It was found that repeatability of the measurements is strongly influenced by MAO remained in PE samples as well as time of sample keeping in the apparatus (dissolution + measurement time) at temp. 142 °C. A method of MAO removing from PE samples, before GPC measurement, based on additional washing of the sample with HF in methanol solution has been proposed. This modification leads to better both authenticity and repeatability of the results. Studies on the influence of time of sample keeping…
Ethylene polymerization with FI complexes having novel phenoxy‐imine ligands: Effect of metal type and complex immobilization
2011
A series of bis(phenoxy‐imine) vanadium and zirconium complexes with different types of R3 substituents at the nitrogen atom, where R3 = phenyl, naphthyl, or anthryl, was synthesized and investigated in ethylene polymerization. Moreover, the catalytic performance was verified for three supported catalysts, which had been obtained by immobilization of bis[N‐(salicylidene)‐1‐naphthylaminato]M(IV) dichloride complexes (M = V, Zr, or Ti) on the magnesium carrier MgCl2(THF)2/Et2AlCl. Catalytic performance of both supported and homogeneous catalysts was verified in conjunction with methylaluminoxane (MAO) or with alkylaluminium compounds (EtnAlCl3−n, n = 1–3). The activity of FI vanadium and zirc…
Synteza bimetalicznego silseskwioksanowego kompleksu tytanu(IV) i jego polimerycznego odpowiednika oraz ich właściwości katalityczne w polimeryzacji …
2016
Zsyntetyzowano, a następnie scharakteryzowano dwa tytanosilseskwioksany: nowy, nieznany dotąd z literatury, tetrachloroditytanosilseskwioksan (2) i jego polimeryczny odpowiednik (3). Zbadano właściwości katalityczne otrzymanych związków w polimeryzacji etylenu i 1-oktenu. Obydwa prekatalizatory, po aktywacji za pomocą Et2AlCl lub EtAlCl2, katalizują polimeryzację etylenu do polietylenu (PE) o małej masie molowej, która zmniejsza się zarówno ze wzrostem temperatury reakcji, jak i stosunku molowego Al:Ti. Kompleks (2) w połączeniu z metyloaluminoksanem lub związkami boru jest także aktywny w polimeryzacji 1-oktenu.
Ethylenebis(5‐chlorosalicylideneiminato)vanadium dichloride immobilized on MgCl2‐based supports as a highly effective precursor for ethylene polymeri…
2009
Ethylenebis(5‐chlorosalicylideneiminato)vanadium dichloride supported on MgCl2(THF)2 or on the same carrier modified by EtnAlCl3−n, where n = 1–3, was used in ethylene polymerization in the presence of MAO or a common alkylaluminium compounds as a cocatalyst. The support type alter vanadium loading and also change the characteristic of the catalytic active sites. Et2AlCl is the best activator for a catalyst which has been immobilized on a nonmodified support, whereas the systems which contain a carrier which has been modified by an organoaluminium compound reveal the highest activity in conjunction with MAO. That difference, together with different temperature effects on polymerization effi…
Dichlorovanadium (IV) complexes with salen‐type ligands for ethylene polymerization
2008
Vanadium complexes with tetradentate salen‐type ligands were first time explored in ethylene polymerizations. The effects of the vanadium complex structure, the alkyl aluminum cocatalysts type (EtAlCl2, Et2AlCl, Et3Al, and MAO), and the polymerization conditions (Al/V molar ratio, temperature) on polyethylene yield were explored. It was found that EtAlCl2 in conjunction with investigated vanadium complexes produced the most efficient catalytic systems. It was shown, moreover, that the structural changes of the tetradentate salen ligand (type of bridge which bond donor nitrogen atoms and type of substituent on aryl rings) affected activity of the catalytic system. The complexes containing li…
Complex formation of copper(II) and cadmium(II) with pectin and polygalacturonic acid in aqueous solution. An ISE-H + and ISE-Me 2+ electrochemical s…
2012
The acid-base properties of pectin and its ability to complex with copper(II) or cadmium(II) were quantitatively determined in order to define the ability of this natural polyelectrolyte to sequester metal ions. Potentiometric measurements carried out at different ionic strengths (0.1 - 0.7 mol L-1, in Na+ ionic medium) allowed us to define the acid-base properties of pectin together with the dependence of the protonation constants on ionic strength and to calculate the protonation constant at infinite dilution. The formation of complex species between pectin and copper(II) or cadmium(II) was investigated potentiometrically (using H+, Cu2+ and Cd2+ Ion Selective Electrodes, ISEs) in NaNO3 a…
Revista Fuentes
2018
La crisis economica sufrida en los ultimos anos, y en concreto en Espana, ha transmitido una cierta desconfianza en la sociedad acerca del valor que posee la educacion para la integracion y promocion socio-laboral de los jovenes, asi como en relacion al impacto que esta tiene para prevenir de la exclusion social a lo largo de la vida. Por desgracia en Espana, aun en la actualidad, que se considera que la crisis economica esta en proceso de superacion, hay una gran cantidad de jovenes que se les identifica como “sobre - formados” y que no encuentran un empleo adecuado a su formacion. Unos acaban trabajando en empleos que requieren menor formacion academica, mientras que otros acaban en el p…
Solución al actual problema del desempleo: ¿Políticas activas de empleo local?
2009
La evolución del mercado de trabajo a lo largo de los últimos años, con la exclusión del mismo de los colectivos más sensibles, a la vez que aumentaba la dificultad de su acceso al empleo, el desempleo y las tasas de temporalidad en la contratación y la acentuación de los desequilibrios territoriales, han supuesto una de las preocupaciones más importantes de las diferentes administraciones (nacional, regional y local) implicadas en la creación de empleo.
Economia del treball. Guions de seguiment
2013
Aquest material ha rebut l'ajut del Servei de Política Lingüística de la Universitat de València. Guions de seguiment de l'assignatura Economia del Treball, impartida al Grau en Relacions Laborals i Recursos Humans. Els temes abordats són els següents: 1. El mercat de treball des d'un punt de vista estructural: determinants de la demanda i oferta de treball, segmentació laboral. 2. L'anàlisi econòmica de les causes de l'atur i les polítiques d'ocupació: enfocament microeconòmic convencional sobre l'atur, enfocament macroeconòmic de l'atur, l'atur des d'un punt de vista estructural. 3. La determinació dels salaris. 4. Visió global del mercat laboral a Espanya: principals tendències i transfo…