A novel SiO2-supported inorganic and organic hybrid chromium-based catalyst for ethylene polymerization

In this work, a novel SiO2-supported hybrid chromium-based catalyst for ethylene and ethylene/1-hexene polymerization was prepared by using the residual surface hydroxyl groups in Phillips catalyst to further support bis(triphenysilyl) chromate (BC) in order to get the merits from two important chromium-based catalysts namely inorganic Phillips and organic S-2 catalysts. By characterization of the catalysts, investigation of the polymerization behavior and the microstructures of polymers, several vital factors such as cocatalyst, the addition amount of BC, calcination temperature, total chromium loading, polymerization temperature, pressure and hydrogen were systematically investigated. The proper addition weight amount of BC was CrBC ≤ 0.25 wt%. The suitable calcination temperature and total chromium loading were ≤600 °C and ≤0.5 wt%, respectively. With increasing the relative addition amount of CrBC from 0 to 20, 50, 80 and 100 wt% (corresponding from Phillips to HCat-1, HCat-2, HCat-3 and S-2 catalysts), the copolymerization abilities of the above catalysts showed a decreasing tendency. By comparing different chromium catalysts, HCat-2 catalyst showed higher activity than S-2 catalyst and its polymer had higher average molecular weight (MW) than that obtained from Phillips catalyst. HCat-2 catalyst got well-balanced properties mainly including activity, MW of polymers and copolymerization ability.

Graphical abstractA novel SiO2-supported inorganic and organic hybrid chromium-based catalyst for ethylene polymerization was prepared by using the residual surface hydroxyl groups in Phillips catalyst to further support bis(triphenysilyl) chromate.Figure optionsDownload full-size imageDownload high-quality image (169 K)Download as PowerPoint slideHighlights► A novel SiO2-supported chromium-based catalyst for ethylene polymerization. ► Hybridizing inorganic Phillips and organic S-2 catalysts. ► Suitable calcination temperature ≤600 °C and total Cr loading ≤0.5 wt%. ► Proper addition amount of organic bis(triphenysilyl) chromate was CrBC ≤ 0.25 wt%. ► Effects of cocatalyst, temperature, pressure and hydrogen on polymerization.