Influences of methylaluminoxane separated by porous inorganic materials on the isospecific polymerization of propylene

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

“…SBA-15 has a wall thickness of 3.8 nm, while in SBA-15 synthesized with decane the wall thickness is 2.2 nm; for the 22.7 nm support was not possible to calculate the wall thickness due to the weak reflexions in the diffractogram. Moreover, a pore diameter around 11 nm must be an optimum pore size for SBA-15 materials and MAO/(nBuCp) 2 ZrCl 2 system in slurry ethylene polymerization, since it should be small enough for MAO stabilization through the carrier sieve effect, as mentioned in the introduction section according to Sano et al [23][24][25] On the contrary, at higher 1-hexene concentrations, the silica supported catalyst is the most active. The polymer that grows at such 1-hexene concentrations is less crystalline and consequently, less rigid to fragment the support particles effectively, so a support with bigger pore volume and therefore, the more brittle one will lead to higher catalytic activities.…”

“…On the other hand, the different natures of S ext and S int sites could be also explained according to Sano et al, [23][24][25] who proposed changes in the MAO structure due to the pore size. Therefore, it is possible that, as a result of the different MAO structures existing in the pore openings and inside, the 1-hexene reactivity ratio of S ext and S int sites is different.…”

“…[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 over (nBuCp)2ZrCl2/MAO catalytic system supported on aluminosilicate SBA‐15 mesostructured materials

“…Interaction between MAO/metallocene catalytic system and silica-alumina surface. (nBuCp) 2 ZrCl 2 supported on MAO-treated mesoporous molecular sieves and, by Sano et al [29][30][31][32] for the slurry polymerization of ethylene with Cp 2 ZrCl 2 supported on mesoporous materials that have been soaked in a MAO solution. Several works proposed that the MAO species responsible for activating metallocenes consist of a cyclic cage structure made from (AlOCH 3 ) 12 units [33][34][35], which could interact with the support pore surface.…”