共查询到19条相似文献,搜索用时 62 毫秒
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树枝状过渡金属催化剂是在树枝状大分子上负载上过渡金属活性中心,因此,此类催化剂既具有树枝状大分子特有的艺术结构,同时还具有过渡金属配合物的功能化性能,使其两者能够协同发挥作用,兼具均相和非均相催化体系的特点,在催化烯烃聚合方面具有较高的催化活性和良好的催化稳定性,近年来备受关注,催化乙烯聚合就是其中的研究热点之一。本文按其过渡金属活性中心进行分类,综述了近年来国内外树枝状过渡金属催化剂在这乙烯聚合方面的进展,阐述了多种树枝状效应产生的原因,并且对乙烯聚合用树枝状过渡金属催化剂的发展前景进行了展望。 相似文献
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按照乙烯聚合反应机理,论述了Ziegler催化剂铝/钛比降低,对乙烯聚合反应及产品性能的影响,并对所得结果进行了讨论。 相似文献
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乙烯齐聚合锆系催化剂研究进展 总被引:1,自引:0,他引:1
综述了锆系催化体系的特点和研究进展,并对各种配体对催化活性和选择性的影响进行了分析比较。在乙烯齐聚合的催化体系中,不同有机铝对催化乙烯齐聚合的活性和选择性有较大的影响。在锆系催化剂中加入第三组分对乙烯齐聚物的相对分子质量分布有明显的调变作用。 相似文献
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概述了茂金属有机络合物的发展,重点介绍了无助催化剂的非桥二茂稀土金属络合物、桥联二茂稀土金属络合物和加助催化剂的非桥二茂稀土金属络合物三类二茂型稀土金属络合物对乙烯聚合的催化活性的研究进展,说明二茂型有机稀土络合物在催化乙烯聚合反应中有优良活性并极具开发价值。 相似文献
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合成了一种新型后过渡金属络合物——镍二亚胺配合物,并以蒙脱土为载体,制备了蒙脱土载体镍催化剂,在甲基铝氧烷(MAO)、三乙基铝(TEA)和三正辛基铝(TNOA)对丙烯酸甲酯分子中的极性基团保护下,用MAO和TEA作助催化剂催化乙烯-丙烯酸甲酯(E-MA)共聚合,考察了催化剂配体、载体化、聚合条件等对催化剂催化E-MA共聚合的影响。结果表明:随保护剂的不同,催化剂的活性从大到小依次为TEA,MAO,TNOA;适宜条件下,该络合物催化活性可达576kg/(mol·h),负载后的催化剂改善了共聚物形态。 相似文献
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聚丙烯催化剂研究进展 总被引:10,自引:0,他引:10
综述了Ziegler-Natta聚丙烯催化剂技术的发展历史与研究动态,介绍了茂金属催化剂和后过渡金属催化剂的研究进展,展望了未来聚丙烯催化科技术的发展前景.提出了我国发展聚丙烯催化剂的建议。 相似文献
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A new iron‐based catalyst, 2,6‐bis[(1‐naphthanylimino)ethyl]pyridine iron(II) chloride I, has been successfully synthesized and characterized. Ethylene was polymerized by I/methylaluminoxane to give branched, low‐density polymers with good activity. The result shows that the new diimino ligand has improved the characteristics of the resulting polyethylene. © 2000 Society of Chemical Industry 相似文献
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Zhi Ma Wen‐Hua Sun Ning Zhu Zilong Li Changxing Shao Youliang Hu 《Polymer International》2002,51(4):349-352
A Correction has been published for this article in Polymer International 51(6) 2002, 561 The late transition metal catalyst 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine iron(II) chloride was supported on silica. Fourier transform infrared spectroscopy, scanning electronic micrograph and X‐ray photoelectron spectroscopy measurements were utilized to examine the process of supporting catalyst on silica and investigate the possible mechanism of support. Furthermore, ethylene polymerizations with the supported catalysts were carried out in various conditions such as different reaction temperatures and Al/Fe molar ratios. The results showed that MAO first reacted with the hydroxyl of silica forming Si? O? Al bonds and then the catalyst was bridged through MAO on the surface of silica. Compared with homogeneous catalysts, the supported catalysts show some decrease in catalyst activity. However, they can show good activity at a lower Al/Fe molar ratio with MAO as co‐catalyst and give rise to higher molecular weight and melting temperature of the polymer. Better morphology of polyethylene was obtained by a supported catalyst than by its corresponding homogeneous catalyst. The late transition metal catalyst 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine iron(II) chloride was supported on silica. Fourier transform infrared spectroscopy, scanning electronic micrograph and X‐ray photoelectron spectroscopy measurements were utilized to examine the process of supporting catalyst on silica and investigate the possible mechanism of support. Furthermore, ethylene polymerizations with the supported catalysts were carried out in various conditions such as different reaction temperatures and Al/Fe molar ratios. The results showed that MAO first reacted with the hydroxyl of silica forming Si? O? Al bonds and then the catalyst was bridged through MAO on the surface of silica. Compared with homogeneous catalysts, the supported catalysts show some decrease in catalyst activity. However, they can show good activity at a lower Al/Fe molar ratio with MAO as co‐catalyst and give rise to higher molecular weight and melting temperature of the polymer. Better morphology of polyethylene was obtained by a supported catalyst than by its corresponding homogeneous catalyst. © 2002 Society of Chemical Industry 相似文献
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综述了钛改性铬系催化剂的国内外研发现状、制备方法、性能以及对乙烯聚合性能的影响。与用表面浸渍法制备的钛改性铬系催化剂相比,用共凝胶法制备的钛改性铬系催化剂可以缩短诱导期,提高聚乙烯(PE)的熔体流动速率。钛改性铬系催化剂中的钛可阻止α-烯烃在PE的低相对分子质量部分插入,有效降低了含支链低相对分子质量PE的含量。随着钛的加入,低相对分子质量部分的共聚支链减少,从而可改变PE的支链分布。钛改性铬系催化剂的聚合性能明显改善,制备的聚乙烯性能优异。 相似文献