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Abstract: Self-metathesis of 1-hexene was carried out at 40°C over Re2O7 supported on two micelle templated aluminas (sol–gel mesoporous alumina (SGAL) and MSU), prepared with cationic and neutral surfactant, respectively, and a reference Re2O7/γ-Al2O3 catalyst with the same rhenium oxide content (∼9wt%). Both mesostructured catalysts (Re2O7/MSU and Re2O7/SGAL) showed similar activity and far higher than that of the reference Re2O7/γ-Al2O3 catalyst, with a selectivity towards the self-metathesis products above 99%. Among the tested solvents, dodecane yielded the highest conversion likely because of its low polarity and better product removal. Similar TOF values were obtained for Re2O7/SGAL catalysts with mesopore diameter within the 5.0–12.0nm range. In relation with the rhenium content, an optimum in TOF values was detected for rhenium oxide loadings within 6–10wt%. The increase in activation temperature within 550–700°C led towards a greater rise in activity over Re2O7/SGAL catalysts than over Re2O7/γ-Al2O3. DRIFT chemisorbed pyridine spectra disclosed only Lewis acid sites over the activated catalysts and in higher amounts over both mesostructured catalysts. 31P MAS NMR spectra of chemisorbed triethylphosphine oxide (TEPO) indicated the presence of three kind of acid sites (δ ∼58, 68 and 80ppm), with a higher content of strong Lewis acid sites (80ppm) over both mesostructured catalysts. The remarkable performance of both ordered mesoporous catalysts was ascribed to the presence of these strong Lewis acid sites, likely stemming from the interaction of linked rhenium species with the weak Lewis acid sites of the support. [Copyright &y& Elsevier]

Abstract: The polymerization of ethylene in n-heptane with (nBuCp)2ZrCl2 supported over mesoporous SBA-15 catalysts functionalized with propyl or aryl sulfonic acid groups and impregnated with either MAO or TMA was investigated and compared with reference samples. All the supports showed mesoscopic ordering with pore sizes of 7.8–6.6nm, BET surface areas around 700m2 g−1, sulfonic acid loadings between 10 and 20 wt% and an acidity of roughly 1–1.7mmol H+ g−1. None of the catalysts were capable of polymerizing ethylene in the absence of MAO in spite of using TMA or TIBA as scavengers. The addition of MAO (Al/Zr=800 or 5000) led towards ethylene polymerization, being the activity dependent on Al/Zr molar ratio (higher for Al/Zr=5000). The catalysts treated with TMA during the impregnation exhibited considerable leaching, unlike those treated with MAO wherein the leaching was low (<9 wt%). The presence of the sulfonic acid moiety enhanced the activity of the catalysts. In addition, the activity was also augmented with the increase of the sulfonic acid content from 10 to 20 wt%. Interestingly, the molecular weight of the polyethylene synthesized with the SBA-15 functionalized with sulfonic acid groups were 1.5–2.5 times higher, especially with the propyl moiety which leads towards M w ∼350,000gmol−1 at 1.2barg. The results were explained through an interaction between the sulfonic acid moiety and the chlorinated MAO species, which activates the metallocene. [Copyright &y& Elsevier]