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《合成树脂及塑料》2017,(2)
研究了4种Ziegler-Natta催化剂在淤浆聚合条件下,助催化剂和外给电子体对其催化丙烯聚合反应动力学行为的影响。结果表明:4种催化剂都有一个短暂的活性中心形成阶段,聚合动力学曲线均为上升-衰减型;4种催化剂活性均随烷基铝用量的增加而降低;所制聚丙烯的等规指数均随烷基铝用量的增加而降低,随外给电子体用量的增加而升高;助催化剂为三乙基铝[n(Al)∶n(Ti)=100],外给电子体为二环戊基二甲氧基硅烷[n(Si)∶n(Ti)=5]时,4种催化剂都具有较高的活性及较慢的聚合反应速率衰减;用催化剂4制备的聚丙烯的等规指数受助催化剂及外给电子体的影响较小。 相似文献
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Ziegler-Natta(Z-N)催化剂是生产等规聚丙烯的最主要的催化剂,其不同组分对Ti活性中心立构选择性都有不同的影响,本文详细论述了MgCl2载体、给电子体和烷基铝助催化剂以及它们之间的相互作用对Z-N催化剂立构选择性的影响。 相似文献
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丙烯聚合用齐格勒-纳塔催化剂的作用机理 总被引:1,自引:0,他引:1
讨论了丙烯聚合用齐格勒-纳塔催化剂的作用机理,以及反应体系内的氯化镁、内给电子体、烷基铝、硅烷和氢气等对丙烯聚合的影响。 相似文献
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聚乙烯生产过程中齐聚物的生成与控制 总被引:1,自引:0,他引:1
分析了聚乙烯装置生产过程中产生的齐聚物组分主要是高沸点饱和直链烷烃,产生齐聚物的影响因素有催化剂种类、烷基铝的用量、催化剂活性以及氢气加入量等。提出了减少烷基铝加入量、提高预聚物收率、及时排出齐聚物等方法,可控制齐聚物的生成,减少其对装置的影响。 相似文献
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自本世纪五十年代,K·齐格勒和 G·纳塔用烷基铝-氧化钛为催化剂创造性地开拓了-α烯烃的立体定向聚合以后,迅速开展了对齐格勒-纳塔催化剂的研究工作。齐格勒和纳塔所用的催化剂一般是由周期表中Ⅰ~Ⅱ族的金属烷基化合物和Ⅳ~Ⅷ族过渡金属化合物所组成。前者如 LiR、AlR_3、AlR_2Cl、MgR_2、BeR_2、ZnR_2,若与 TiCl_4、TiCl_3,VCl_3等过渡金属卤化物,则构成不溶性双金属络合物;但若与(π-C_5H_5)_2TiCl_2、VOCl_3、VO(OR)_3等过渡金属化合物就构成可溶性的催化剂。近年来还发现,某些稀土金属,如钍、钋、铈等 相似文献
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G. L. Tembe A. R. Bandyopadhyay S. M. Pillai S. Satish M. Ravindranathan 《大分子材料与工程》1995,225(1):51-61
The catalytic oligomerization of 1-decene has been carried out employing several transition metal complexes of Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V) in combination with alkyl aluminum halides as cocatalysts. The chromium(III)-Et3Al2Cl3 system exhibits good oligomerizing activity yielding dimers (C20), trimers (C30) and tetramers (C40) of 1-decene. The kinematic viscosities and pour points of hydrogenated oligomers have been determined and compared with those of commercial samples. The probable mechanism of oligomerization of 1-decene on this catalyst is described. 相似文献
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The catalytic reactivity and selectivity of metallic nanoclusters supported on a metal-oxide can be tuned by electronic charge. In this review, different approaches for controlling the electronic properties of metallic nanoclusters and its impact on catalytic reactions are discussed. Electronic charge can transfer from the metal-oxide support to the metallic catalyst and change the metal–reactants interaction and as a consequence modify as-well the catalytic reactivity and selectivity. In other cases, the electronic properties of the metal-oxide have an active role in the catalytic process and the metal oxide can be used as a co-catalyst. Another approach is to directly change the electronic properties of the metallic catalyst. It is demonstrated that dendrimer-encapsulated metallic nanoparticles can be directly oxidized by the addition of an inorganic oxidizer to the solution phase. In this case, even while supported on inert oxides, novel catalytic reactivity and selectivity can be gained by the formation of highly oxidized metal ions. 相似文献
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Chain transfer with adsorbed aluminium alkyl has been investigated for the system VCI3/AIR3/4-methylpentene-1, where adsorption of the metal alkyl onto the catalyst surface is described by a Langmuir type adsorption isotherm. Rate constants for chain transfer with metal alkyl and equilibrium constants for adsorption of a series of aluminium alkyls and 4-methylpentene-1 onto the transition metal halide surface have been determined. The activation energy for the chain transfer process with tri-isobutylaluminium has also been evaluated. The number of active centres is found to be reduced at low monomer concentrations probably because of slow initiation by monomer. Quantitative verification of a previously presented kinetic scheme has been effected. 相似文献
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Modification of ethyl‐iso‐butylaluminoxanes (EBAOs) with alkyl boronic acid resulted in different co‐catalytic performances when combined with iron complexes for ethylene polymerization, in particular the preferred high‐temperature performance. The changes in polymerization activity and molecular weight distribution of the resulting polymer derived from the variation of aluminoxane were investigated. The varying performance of the iron complex with different aluminoxanes has proved that the interaction between the late transition metal complex and aluminoxane greatly affects the performance of such bicomponent catalyst systems Copyright © 2003 Society of Chemical Industry 相似文献
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煤催化气化工艺中碱金属催化剂的引入加剧了气化炉的结渣,直接影响了流化床气化炉的正常操作。煤灰的烧结特性是流化床气化炉结渣的主要影响因素之一。通过自制的压差法烧结温度测定实验装置,并结合XRD 等分析表征及Factsage热力学软件模拟计算,考察了不同添加剂对煤灰烧结特性及气化性能的影响,并从矿物学角度探讨了添加剂对煤灰结渣特性及气化工艺的影响。结果表明,添加硅铝系添加剂可提高煤灰的烧结温度;相比硅系添加剂,添加高铝系添加剂对改善煤灰的烧结温度效果更明显;高铝系添加剂可作为一种高效的阻熔剂,但因在气化过程中容易同催化剂反应,导致催化剂催化性能降低,对煤的气化活性及催化剂回收率产生不利影响;添加氧化钙添加剂,煤的灰熔温度及烧结温度均增加,随氧化钙含量增加,灰熔点及烧结温度均升高,且对气化活性及催化剂回收率有良性作用;氧化钙可作为改善煤种结渣性的添加剂用于催化气化工艺中,需根据煤种性质及工艺特点确定适宜的添加量。 相似文献
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分别以碱及碱土金属、过渡金属以及稀土金属3种常见助剂类型,探讨了不同助剂对镍基催化剂催化生物质裂解及气化重整制氢催化活性、催化剂物化特性及催化剂失活特性的影响。添加碱金属组分后,生物质热解反应速率会大幅上升,生物质焦的水蒸气气化反应得到促进,并且达到最大热解速率所需的温度也有所降低,热解产物趋向于小分子量产物;过渡金属对生物质气化过程中生成焦油的催化裂解重整具有较好的催化活性;稀土元素对甲醇水蒸气重整等催化反应有着重要的作用,镍基催化剂中加入Ce和Pr能提高甲醇转化率、改善产气组分、提高H2的选择性。结合国内外的研究情况发现钴、镧等金属助剂有利于提升镍基催化剂重整制氢活性,催化剂积炭及表面活性颗粒的聚集是造成催化剂失活的主要原因。 相似文献
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含氯挥发性有机化合物(CVOCs)是一类重要的大气污染物,催化燃烧是实现CVOCs高效减排的一种主流处理技术,但工艺过程中存在氯元素易吸附在催化剂表面致使催化剂失活的问题。本文从催化燃烧CVOCs的反应机理、催化剂活性组分、催化剂载体等几个方面,对近年来催化燃烧处理CVOCs的研究进行了综述,其中催化活性组分可分为以钌、钯为主的贵金属催化剂和集中在高活性的过渡金属复合氧化物、钙钛矿型非贵金属催化剂,并重点阐述了水蒸气对催化燃烧CVOCs反应活性的影响及机制。根据国内外研究状况和技术水平,提出了催化燃烧技术的研究及发展方向,充分利用一定浓度水蒸气的优点抑制催化剂氯中毒及产生较低含量的副产物,为CVOCs高效工业化处理提供了重要的参考。 相似文献
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In this study, with Mo-based catalytic systems consisting of molybdenum pentachloride (MoCl5) as the main catalyst, alkyl aluminum as the cocatalyst and organophosphorus compound as the ligand, high 1,2-orientation butadiene (Bd)-styrene (St) copolymers were prepared by the coordination polymerization. The effects of phosphorous ligand, alkyl aluminum, polymerization temperature, polymerization time and monomers feed ratios on the monomer conversion and intrinsic viscosity of copolymers were explored in detail. The experimental results indicated that with MoCl5•TBP (tributyl phosphate)/Al(OPhCH3)(i-Bu)2 as the catalytic system to initiate Bd-St copolymerization, the reactivity ratios of butadiene and styrene monomers are 3.64 and 0.16, and the 1,2-structural content in the resulting copolymers is over 80%, regarded as high 1,2-orientation Bd-St copolymers. All these results provided a basis for the design of catalyst used to prepare high 1,2-orientation Bd-St rubber. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48897. 相似文献