Premium
Supporting mechanism of non‐toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalysts
Author(s) -
Qiu Pengyuan,
Li Xiaofang,
Zhang Shiliang,
Cheng Ruihua,
Dong Qi,
Liu Boping,
Li Liuzhong,
Yu Yongling,
Tang Yan,
Xie JianLing,
Wang Wenqing
Publication year - 2009
Publication title -
asia‐pacific journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.348
H-Index - 35
eISSN - 1932-2143
pISSN - 1932-2135
DOI - 10.1002/apj.314
Subject(s) - chromium , catalysis , chromate conversion coating , thermogravimetry , thermal decomposition , chemistry , decomposition , ethylene , differential thermal analysis , silica gel , inorganic chemistry , nuclear chemistry , organic chemistry , physics , diffraction , optics
Phillips catalyst is an important kind of industrial polyethylene catalyst. As early as in the late 1970s, CrO 3 was substituted by chromium (III) acetate for the preparation of Phillips catalyst on the industrial scale owing to health and environmental considerations. There is still considerable research focusing on the relations between the preparation process and catalyst properties in academics. In this work, the supporting mechanism of chromium (III) acetate on silica has been studied by Thermogravimetry–Differential Thermal Analysis (TG‐DTA), and Electron Spin Resonance (ESR), in comparison with that of supporting CrO 3 on SiO 2 . The basic chromium (III) acetate supported on high surface area silica gel decomposed differently from that for bulk basic chromium acetate when decomposition temperature was decreased by 15 °C. The decomposition temperature was 299 °C for Cr 3 (OH) 2 (Ac) 7 /SiO 2 catalyst precursor, which would be firstly transferred into CrO 3 followed by supporting on silica surface as chromate species. The further weight loss came from thermal inductive reduction of chromate species into Cr 2 O 3 , which was also supported by the results of colors of catalysts. Moreover, with the increase of chromium loading of Cr 3 (OH) 2 (Ac) 7 /SiO 2 , such thermal inductive reduction became more severe. ESR spectra of Cr 3 (OH) 2 (Ac) 7 /SiO 2 and CrO 3 /SiO 2 catalyst precursors showed that a small amount of supported Cr 5+ can exist stably on silica gel surface at temperatures higher than 200 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.