Supporting mechanism of non‐toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalysts
Supporting mechanism of non‐toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalysts
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DOI：
10.1002/apj.314
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发表时间：
2009-09
影响因子：
1.8
通讯作者：
Pengyuan Qiu;Xiaofang Li;Shiliang Zhang;R. Cheng;Qi Dong;Bo-ping Liu;Liuzhong Li;Yongling Yu;Yan Tang;Jianling Xie;Wenqing Wang
中科院分区：
文献类型：
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作者：
Pengyuan Qiu;Xiaofang Li;Shiliang Zhang;R. Cheng;Qi Dong;Bo-ping Liu;Liuzhong Li;Yongling Yu;Yan Tang;Jianling Xie;Wenqing Wang
菲利普斯催化剂是一种重要的工业聚乙烯催化剂。早在20世纪70年代末，出于健康和环境方面的考虑，工业规模的菲利普斯催化剂的制备就用醋酸铬代替了CrO_3。目前学术界仍有相当多的研究集中在制备工艺与催化剂性能之间的关系上。用热重-差热分析(TG-DTA)和电子自旋共振(ESR)研究了醋酸铬在SiO_2上的负载机理，并与CrO_3在SiO_2上的负载机理进行了比较。当分解温度降低15℃时，担载在高比表面积硅胶上的碱性醋酸铬的分解温度与体相碱性醋酸铬不同，Cr3(OH)2(Ac)7/SiO_2催化剂前驱体的分解温度为299℃，首先转化为CrO_3，然后以铬酸盐物种的形式负载在二氧化硅表面。进一步的失重来自于铬酸盐物种的热诱导还原为Cr2O_3，这也得到了催化剂颜色的结果的支持。此外，随着Cr3(OH)2(Ac)7/SiO_2中铬负载量的增加，这种热感应还原现象变得更加严重。Cr3(OH)2(Ac)7/SiO_2和CrO_3/SiO_2催化剂前驱体的ESR谱表明，在高于200°C的温度下，少量负载型Cr5+可以稳定地存在于硅胶表面。版权所有©2009科廷理工大学和John Wiley&Sons，Ltd.
Phillips catalyst is an important kind of industrial polyethylene catalyst. As early as in the late 1970s, CrO3 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 CrO3 on SiO2. 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 Cr3(OH)2(Ac)7/SiO2 catalyst precursor, which would be firstly transferred into CrO3 followed by supporting on silica surface as chromate species. The further weight loss came from thermal inductive reduction of chromate species into Cr2O3, which was also supported by the results of colors of catalysts. Moreover, with the increase of chromium loading of Cr3(OH)2(Ac)7/SiO2, such thermal inductive reduction became more severe. ESR spectra of Cr3(OH)2(Ac)7/SiO2 and CrO3/SiO2 catalyst precursors showed that a small amount of supported Cr5+ can exist stably on silica gel surface at temperatures higher than 200 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.