Surface chemistry of selected supported metallocene catalysts studied by DR-FTIR, CPMAS NMR, and XPS techniques

Atiqullah, Muhammad; Akhtar, M. Naseem; Faiz, M.; Moman, A.; Abu-Raqabah, A. H.; Khan, Janet A.; Wazeer, Mohamed I. M.

doi:10.1002/sia.2452

Cited by 22 publications

(36 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It consisted of a fixed top head and a one-liter jacketed Büchi glass autoclave. The reactor system is detailed in our earlier publications [7,8,22]. The reactor was baked for an hour at about 120°C.…”

Section: Elemental Compositions Of the Synthesized Catalystsmentioning

confidence: 99%

“…The metallocene catalyst [PQ 3030/MAO/( n BuCp) 2 ZrCl 2 ] was synthesized following the procedures detailed in our earlier publications [7,8,22]. The silica (PQ 3030) was dehydroxylated at 250°C for 4 h using a Thermcraft furnace equipped with a vertical quartz glass tube, a digital temperature indicator and controller, a gas flow meter, and a vacuum pump.…”

Section: Synthesis Of Catalystsmentioning

confidence: 99%

“…High purity nitrous oxide-acetylene flame was used for the analyses. The analysis procedures available in the literature were followed [7,8,22,25] Polymerization trials and catalyst activity Ethylene was polymerized using an Imtech laboratory-scale reactor set up. It consisted of a fixed top head and a one-liter jacketed Büchi glass autoclave.…”

Section: Elemental Compositions Of the Synthesized Catalystsmentioning

confidence: 99%

See 2 more Smart Citations

Crystallization kinetics of ethylene homopolymers: a new perspective from residual catalyst and resin molecular weight

et al. 2012

View full text Add to dashboard Cite

Two Ziegler-Natta and one metallocene supported catalysts were prepared that were used to synthesize ethylene homopolymers with different molecular weights. The influence of varying residual catalyst types and molecular weights on the isothermal crystallization kinetics of these polymers was studied using DSC and Avrami model to gain better understanding. The MetCat HomoPE, unlike the Z-N HomoPEs, followed the Avrami model during the entire crystallization. The increase in molecular weights did not affect (i) the decreasing trend of 1/t 1/2 (bulk crystallization rate) and K (crystallization rate constant) with the increase in T c (crystallization temperature), and (ii) the increasing trend of K with the increase in %crystallinity. However, combined with the varying residual catalysts, it differently varied the rate of change of 1/t 1/2 and K; and decreased T c . K and 1/t 1/2 turned out to be asymptotically related up to 1/t 1/2 ≈0.73 min −1 . The residual catalyst type more predominantly affected the crystallization facileness than the molecular weight. Therefore, the Z-N 1 residual catalyst acted as heterogeneous nuclei. In Z-N HomoPE 1 and Z-N HomoPE 2, n ranged from 2.2 to 3.4, and 2.6 to 3.0, respectively as a function of T c . In MetCat HomoPE, it remained constant at 2. Therefore, the MetCat residual catalyst impinged the expected spherulitic crystal growth to a two dimensional one. All these findings were explained considering how the molecular level residual catalysts, with their characteristic surface chemistries and structures, influenced the prevailing heterogeneous nucleation process, and the aliased interaction of G (nuclei growth rate) and Ñ (nucleation rate).

show abstract

Section: Elemental Compositions Of the Synthesized Catalystsmentioning

confidence: 99%

Section: Synthesis Of Catalystsmentioning

confidence: 99%

Section: Elemental Compositions Of the Synthesized Catalystsmentioning

confidence: 99%

See 1 more Smart Citation

Crystallization kinetics of ethylene homopolymers: a new perspective from residual catalyst and resin molecular weight

et al. 2012

View full text Add to dashboard Cite

show abstract

“…We shall use the following two differing anions, unsupported [MAOCl 2 ] − and supported Si−O−[MAOCl 2 ] − , the synthesis of which has been illustrated through Scheme 1 that shows the major relevant reactions [6,20]. Note that the variation in the design of novel co-catalyst anions, which is much easier and less costly than synthesizing new metallocenes, widens the scope of industrial process development.…”

Section: Article In Pressmentioning

confidence: 99%

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

Adamu

Atiqullah

Malaibari

et al. 2016

Journal of the Taiwan Institute of Chemical Engineers

View full text Add to dashboard Cite

Keywords:Metallocene catalyst Pseudo-homogeneous and in-situ heterogeneous isomeric ethylene−α-olefin copolymerization Hydrodynamic boundary layer mass transfer Inter-and intra-chain backbone composition distribution Lamellar thickness distribution Thermal properties a b s t r a c t This study reports a novel conceptual framework that can be easily experimented to evaluate the effects of hydrodynamic boundary layer mass transfer, methylaluminoxane (MAO) anion design, and comonomer steric hindrance on metallocene-catalyzed ethylene polymerization. This approach was illustrated by conducting homo-and isomeric copolymerization of ethylene with 1-hexene and 4-methyl-1-pentene in the presence of bis(n-butylcyclopentadienyl) zirconium dichloride ( n BuCp) 2 ZrCl 2 , using (i) MAO anion 1 (unsupported [MAOCl 2 ] − ) and pseudo-homogeneous reference polymerization, and (ii) MAO anion 2 (supported Si−O−[MAOCl 2 ] − ) and in-situ heterogeneous polymerization. The measured polymer morphology, catalyst productivity, molecular weight distribution, and inter-chain composition distribution were related to the locus of polymerization, comonomer effect, in-situ chain transfer process, and micromixing effect, respectively. The peak melting and crystallization temperatures and %crystallinity were mathematically correlated to the parameters of microstructural composition distributions, melt fractionation temperatures, and average lamellar thickness. These relations showed to be insightful. The comonomer-induced enchainment defects and the eventual partial disruption of the crystal lattice were successfully modeled using Flory and GibbsThompson equations. The present methodology can also be applied to study ethylene−α-olefin copolymerization, performed using MAO-activated non-metallocene precatalysts.

show abstract

“…25 The functionalized silica was slurried by adding 20.0 mL of dry toluene to it. Then 9.8 mL of the as-received 30 wt % MAO was slowly added to the above slurry at room temperature and was continuously stirred for 60 min.…”

Section: Catalyst Synthesismentioning

confidence: 99%

Supported SiO₂‐ⁿBuSnCl₃/MAO/(ⁿBuCp)₂ZrCl₂ catalyzing MAO cocatalyst‐free ethylene polymerization: Study of hydrogen responsiveness

Atiqullah

Moman

Akhtar

et al. 2007

J of Applied Polymer Sci

Self Cite

View full text Add to dashboard Cite

A supported metallocene catalyst was synthesized by sequentially loading methylaluminoxane (MAO) (30 wt % in toluene) and ( n BuCp) 2 ZrCl 2 on partially dehydroxylated silica ES 70 modified by n BuSnCl 3 . Its shock load hydrogen responsiveness was evaluated by polymerizing ethylene for 1 h at 8.5 bar (g) and 758C without separately feeding the MAO cocatalyst. The shock load hydrogen feeding increased the ethylene consumption (at a fairly constant rate), catalyst productivity, as well as the resin bulk density and average particle size at DP (of hydrogen) $3.0 psi. The bulk density increased from 0.25 to 0.31 g/cm 3 . This shows a procedure for overcoming the inherent drop in catalyst productivity caused by heterogenization of metallocenes (that is a method for catalyst activation) and improving the resulting resin bulk density. The volume-weighted mean particle diameter of the resulting polyethylenes was found to be 5.80-11.12-fold that of the catalyst corresponding to DP 5 0.00-7.11 psi, respectively. The resulting kinetic profiles showed to be fairly stable. However, M w and polydispersity index were not affected. The particle size distribution, average particle size, and the scanning electron microscope photographs of the resulting resin particles confirmed the occurrence of the replication phenomenon. On the basis of the above findings, the mechanism of ethylene polymerization under the present experimental conditions has been revisited.

show abstract

Surface chemistry of selected supported metallocene catalysts studied by DR-FTIR, CPMAS NMR, and XPS techniques

Cited by 22 publications

References 44 publications

Crystallization kinetics of ethylene homopolymers: a new perspective from residual catalyst and resin molecular weight

Crystallization kinetics of ethylene homopolymers: a new perspective from residual catalyst and resin molecular weight

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

Supported SiO₂‐ⁿBuSnCl₃/MAO/(ⁿBuCp)₂ZrCl₂ catalyzing MAO cocatalyst‐free ethylene polymerization: Study of hydrogen responsiveness

Contact Info

Product

Resources

About

Surface chemistry of selected supported metallocene catalysts studied by DR-FTIR, CPMAS NMR, and XPS techniques

Cited by 22 publications

References 44 publications

Crystallization kinetics of ethylene homopolymers: a new perspective from residual catalyst and resin molecular weight

Crystallization kinetics of ethylene homopolymers: a new perspective from residual catalyst and resin molecular weight

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

Supported SiO2‐nBuSnCl3/MAO/(nBuCp)2ZrCl2 catalyzing MAO cocatalyst‐free ethylene polymerization: Study of hydrogen responsiveness

Contact Info

Product

Resources

About

Supported SiO₂‐ⁿBuSnCl₃/MAO/(ⁿBuCp)₂ZrCl₂ catalyzing MAO cocatalyst‐free ethylene polymerization: Study of hydrogen responsiveness