Ethylene polymerization over (nBuCp)₂ZrCl₂/MAO catalytic system supported on aluminosilicate SBA‐15 mesostructured materials

Abstract

Heterogeneous metallocene catalysts were prepared by incipient wetness impregnation of 15,30, 60, and ∞) mesostructured materials with (nBuCp) 2 ZrCl 2 /MAO. For comparative purposes commercial silica and silica-alumina (Si/Al = 4.8) supports were also impregnated with the MAO/metallocene catalytic system. A combination of X-ray powder diffraction, nitrogen adsorption-desorption isotherms at 77 K, transmission electron microscopy, ICP-atomic emission spectroscopy, and UV-vis spectroscopic data, were used to characterize the supports and the heterogeneous catalysts. Ethylene polymerizations were carried out in a schlenk tube at 70 8C and 1.2 bar of ethylene pressure. The polyethylene obtained was characterized by GPC, DSC, and SEM. Catalysts prepared with mesostructured SBA-15 supports exhibited better catalytic performance than those supported on amorphous silica and silica-alumina. In general, higher ethylene polymerization activity was achieved if (nBuCp) 2 ZrCl 2 /MAO catalytic system was heterogenized using supports with lower pore size in the range of the mesopores and lower Si/Al ratio. All catalysts produced high-density polyethylene, with high crystallinity values and fibrous morphology when SBA-15 mesostructured materials were used as supports. POLYM. ENG. SCI.,

Ethylene/1‐Hexene Copolymers Produced with MAO/(nBuCp)2ZrCl2 Supported on SBA‐15 Materials with Different Pore Sizes

“…30 It has been reported that pore size has a significant effect on the gas-phase ethylene and ethylene-1-hexene polymerization rates with supported MAO/(nBuCp) 2 ZrCl 2 catalysts. [21] In a previous work using aluminosilicate SBA-15, [22] we observed that, apart from chemical surface properties, pore size had a strong influence on catalytic activity. A possible explanation for this phenomenon was suggested by Sano et al, [23][24][25] who proposed that the MAO species responsible for activating metallocenes, consisting of cyclic cage structures made from CH 3 AlO units, are preferentially adsorbed into small pores, or possibly stabilized by interaction with the surfaces of the small pores, by shifting the equilibrium from linear to cyclic MAO.…”

Ethylene polymerization with methylaluminoxane/(nBuCp)2ZrCl2 catalyst supported on silica and silica‐alumina at different AlMAO/Zr molar ratios

“…Concerning solid supports, silica is by far the most common support in the heterogenization of metallocenes because it has high surface area and porosity, has good mechanical properties, and is stable under reaction and processing conditions 11, 12. However, the literature also reports the use of others carriers such as Al 2 O 3 , SiO 2 ‐Al 2 O 3 , AlPO's, Al‐MCM‐41, and Al‐SBA‐15, describing the interaction of metallocenes and MAO with aluminium atoms from the support 14–17. In fact, our previous work18 reported higher polymerization activity for MAO/(nBuCp) 2 ZrCl 2 supported on silica‐alumina instead on conventional silica.…”

Design and synthesis of a new porous organic polymer equipped with N‐propyl sulfamic acid functionalities: As an efficient heterogeneous catalyst for the synthesis of 1,8‐dioxo‐octahydroxanthene derivatives

“…Self-assembly process between phenolic sectors and formaldehyde molecules under high-temperature conditions to afford oligomeric systems like resins [7], monoliths [8], and calixarenes [9,10] have been the focus of interest over recent years. The ability of these systems for being incorporated to various substrates like neutral molecules, cations, and also linking agents make them known as appropriate candidates in heterogeneous catalysis [11][12][13]. In this regard, special attention has been given to the cross-linked polymers based on calix [4]resorcinarene by this research group [13][14][15][16][17][18] as a proper porous material capable of undergoing the post-functionalization process.…”