Search results for "Natta"
showing 10 items of 76 documents
Psychometric Properties of the Spanish Version of the Nonattachment Scale (NAS) and Its Relationship with Mindfulness, Decentering, and Mental Health
2016
Abstract Nonattachment is a Buddhism-rooted construct, which can be defined as the relative absence of fixation on ideas, images, or sensory objects, as well as an absence of internal pressure to get, hold, avoid, or change circumstances or experiences. The present study was aimed at exploring the psychometric properties of the Spanish version of the Nonattachment Scale (NAS) and at delimitating the relationship between the NAS and measures of mindfulness, decentering, and negative emotional symptoms. Pooling the NAS data from Spanish meditators (n = 335) and nonmeditators (n = 270), we performed an exploratory factor analysis and then estimated the fit of two competing models (one-factor m…
Quantification of poisons for Ziegler Natta catalysts and effects on the production of polypropylene by gas chromatographic with simultaneous detecti…
2020
[EN] This article describes a new simultaneous method for the analysis of sulfur-type poisons, hydrocarbons and permanent gases affecting the productivity of the Ziegler Natta catalyst during the synthesis of polypropylene on an industrial scale in a fluidized-bed reactor. The identification was achieved employing a configuration of the seven-valve chromatographic system, with events at different times, allowing distribution of the sample through multiple columns, and finally reaching the helium ionization detectors of pulsed discharge, flame ionization and mass spectrometry. The results obtained show a good precision of the method used because the variability was less than 1.02% in area an…
Multidentate Tetrahydrofurfuryloxide Ligand in a Ziegler−Natta Catalyst Studied by Molecular Modeling
2008
The transition from a generation III Ziegler-Natta catalyst with a monodentate Lewis base to a more modem generation 1V/V system, containing a tetrahydrofuran derivative, the tetrahydrofurturyloxide C 4 H 7 O-CH 2 O - bidentate ligand (THFFO), was studied by means of molecular modeling and DFT calculations. This particular ligand was carefully chosen so that it remained in the titanium coordination sphere in the model active site. With such a constraint, the dual role of tetrahydrofurfuryloxide was identified: it was demonstrated how the presence of this ligand limits the number of isomeric active sites as well as enhances the selectivity of the species that can still exist. The results ind…
DFT analysis of titanium complexes with oxygen-containing bidentate ligands
2003
Strength of the TiO co-ordinate bond in several titanium complexes with bidentate ligands has been investigated by means of DFT. Mutual interaction of particular donors and their influence on Lewis acidity of the central atom have also been studied. The energy of ligand binding ranges from −19 to −454 kJ/mol, depending on the kind of donors. Calculations confirm that a strong donor, alkoxide anion, co-ordinatively saturates the titanium and makes binding of new ligands less exoenergetic. On the contrary, two oxygen atoms of similar donor number do not have much influence on each other. Strength of the TiO bonds in titanium complexes with certain oxygen-containing bidentate ligands has bee…
To survive or succeed? : An analysis of biotechnology firms
2017
In this paper, we address the question whether there exists differences in the determinants that support survival versus success of small and medium-sized high-tech firms. We examine this question in the context of Finnish biotechnology industry by analyzing the survival of all dedicated biotechnology firms in the period of 1978–2008. We argue and show that the success and survival of firms are not necessarily driven by similar determinants. Specifically, we find that while the role of different types of alliances, focused market scope as well as legitimacy of the industry seem to be important both ensuring in survival and enhancing successful performance, determinants related to sources of…
Impacts of sovereign risk premium on bank profitability: Evidence from euro area
2021
We analyse the effects of low and negative interest rates and sovereign risk premium on bank profitability among 154 Eurozone banks during the period 2005–2019. In contrast to some of the results in the previous literature, we find that the euro area banks have not suffered too much from the extremely low and negative interest rate era regarding their net interest margins. However, the overall profitability has lowered clearly during the sample period, and the sovereign risk premium has a robust negative effect on all the overall profitability measures, both with risk-adjustment and without it, but it seems to have an increasing effect on the degree of wholesale funding and loan loss provis…
Keep the faith in banking : New evidence for the effects of negative interest rates based on the case of Finnish cooperative banks
2021
This paper analyses the profitability of Finnish cooperative banks during the period of negative nominal interest rates. Contrary to expectations, the continuous decline in money market interest rates between 2009 and 2014, and the following negative rate era, did not have adverse effects on the profitability of banks at the beginning of negative interest rate period. Based on especially using a risk-adjusted measure for bank profitability, these results contrast with previous findings. In our findings, the increasing wholesale funding (WSF) ratio seems to be an important factor. However, after 2017 the banks have not been able to improve especially their risk-adjusted profitability so stro…
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.
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…
Studies on the microstructure of ethylene/1-hexene copolymers prepared over heterogeneous Ziegler - Natta catalysts
2000
Three MgCl 2(THF) 2-supported, AlEt 2Cl-activated VOCl 3, VCl 4 and TiCl 4 Ziegler - Natta catalysts were used to copolymerize ethylene with 1-hexene in the presence of hydrogen to prepare low-M well-soluble copolymers that could be analyzed by 13C-NMR. The spectra (Fig. 1) showed resonance signals due to ethylene and 1-hexene units in positions unaffected by catalyst type and with intensities related to the degree of comonomer incorporation into the copolymer. The triad sequence distribution and comonomer reactivity ratios (r) were calculated by the Randall method [11] and Bernoulli statistics based on the known copolymer composition. The latter appeared to be the more valid in predicting …