Ethylene polymerization over chromium supported onto SBA-15 mesoporous materials

Abstract

Ethylene polymerization catalysts have been prepared by incorporation of chromium (III) acetylacetonate onto siliceous SBA-15 swelled mesoporous materials. Catalysts characterization includes DRX, FTIR, UV-vis spectroscopy, nitrogen physisorption, TGA and ICP analysis. Chromium anchorage through H-bonds was observed in Cr/SBA-15 catalyst prepared by incipient wetness impregnation. On the contrary, when catalysts were prepared by grafting, a ligand exchange reaction may occur. For similar chromium contents, catalyst prepared by grafting showed higher polymerization activity than catalyst prepared by incipient wetness impregnation. Regarding polymer properties, Cr/SBA-15 catalyst prepared by impregnation gave polyethylene with slightly higher molecular weight, polydispersity, bulk density and melting temperature than polyethylene obtained from grafted catalyst