【作者】 李留忠；

【导师】 郝爱友； 达建文；

【作者基本信息】 山东大学 ， 有机化学， 2012， 博士

【摘要】 聚烯烃树脂作为高分子材料中产量最大、应用最广泛的品种,全球消费量已超过1亿吨/年。由于具有质轻、抗冲、耐腐蚀、电绝缘、透明、无毒、价廉等优点,而且易于成型加工、综合性能优良,因而广泛应用于工业、农业、军事、医疗卫生、日常生活等诸多领域。聚乙烯是聚烯烃中产量最大的树脂产品,其工艺技术的核心在于催化剂,主要包括钛系Ziegler-Natta催化剂、铬系催化剂、茂金属催化剂和后过渡金属催化剂等。其中,铬系催化剂的树脂产品由于含有特定的长支链结构、分子量分布宽、易于加工而具有不可取代的地位。然而,与钛系Ziegler-Natta催化剂相比,铬系催化剂由于对微量水氧等杂质敏感度更高,研究难度更大,其聚合反应机理目前尚不清楚；而且聚合反应动力学,尤其是气相聚合动力学研究未见报道。因此,通过铬系催化剂气相聚合反应机理和动力学研究,进而制备出新型铬系催化剂对于开发高性能、高附加值聚乙烯树脂具有重要意义。此外,后过渡金属镍、钯均相催化剂作为一类新型聚乙烯催化剂,为目前国际聚烯烃领域的研究热点之一,其设计、合成和应用研究具有重要的学术价值和潜在的应用前景。本论文的研究内容主要包括4个部分。第一部分[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂研究采用双三苯基硅烷铬酸酯(BC)作为活性组分,制备了一系列负载型[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂,对催化剂制备过程中的形貌和结构性能进行了表征,对催化剂上乙烯引发反应初始阶段的反应机理进行初步探讨。采用特殊内部结构的聚合反应器和试验方法,首次在实验室进行了铬系催化剂的乙烯气相聚合评价研究,考察了铬含量、Al/Cr比对催化剂和聚合产物性能的影响。选择了典型Al/Cr摩尔比分别为3.0、4.2和6.0的三种CrO2/AlR3/SiO2催化剂,进行了系统的乙烯气相聚合研究。1)催化剂与初始硅胶载体的粒度分布、孔结构和形貌相似,催化剂制备工艺过程对其影响较小,聚合物初级粒子复制催化剂形貌。2)ESR表征结果表明,催化剂上铬价态在接触乙烯前后有明显变化,聚合反应活性中心为低价态铬。接触乙烯前,催化剂中以高价态铬(如Ⅴ和Ⅵ)为主,而接触乙烯引发聚合反应后则以低价态铬(如Ⅱ和Ⅲ)为主。3)催化剂活性随Al/Cr比变化的规律是：随着Al/Cr比的增加,催化剂活性先升高至一个峰值,然后降低,其中Al/Cr比在4.24.6时聚合活性最高。4)乙烯气相聚合过程中,聚合温度升高或者聚合压力降低,催化剂活性增大,聚合物分子量降低。5)对[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂[Al/Cr=4.2]而言,氢气作为一种链转移剂使活性中心上的聚合物链发生链转移反应同时产生Cr-H物种,导致聚合物分子量降低,产品熔体流动速率增大；同时间接造成乙烯分压降低,使催化剂聚合活性降低。共聚单体1-丁烯的加入可以使得聚合物分子链上引入支链而使聚合物密度和结晶度降低,同时1-丁烯也是催化剂的链转移剂,使聚合物的分子量和MFR显著变化。6)三种催化剂动力学曲线规律相似,都是先增长,达到最大聚合反应速率,然后缓慢衰减。比较而言,[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂[Al/Cr=4.2]聚合活性较高,达到最大聚合反应速率的时间较长,需要40min；而[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂[Al/Cr=3.0]和[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂[Al/Cr=6.0]聚合活性较低,达到最大聚合反应速率需要20-25min。第二部分CrOx/AlR3/SiO2催化剂的制备、表征及催化乙烯聚合性能采用低毒性的廉价低价态铬源化合物碱式醋酸铬为原料,通过浸渍、干燥、高温活化和还原等过程制备了CrOx/AlR3/SiO2催化剂。采用FT-IR, TG-DTA, XPS, DSC, SEM和ESR等多种表征手段研究了催化剂负载和活化机理,系统考察了催化剂制备工艺和配方对催化剂性能和聚合产物性能的影响以及气相聚合反应动力学。开发出的新型铬系聚乙烯催化剂CrOx/AlR3/SiO2具有成本低、毒性小、活性高等优点,聚合反应动力学平稳,氢调和共聚性能优良。1)将碱式醋酸铬Cr3(CH3COO)7(OH)2负载硅胶后,其分解温度降低(314→299℃),是由于Cr物种分散度的提高导致其氧化分解反应更容易进行。FT-IR谱图表明其氧化分解在300℃显著加强,在400℃基本完成。反应生成CrO3, H2O和CO2。而生成的Cr03继续与硅羟基发生酯化反应生成铬酸酯。同时FT-IR和TG-DTA结果表明在430-460℃存在Cr03诱导分解为Cr2O3。CrO3负载与否对其分解过程有相当大的影响,这是由于Cr03熔点低,且极易在高温下诱导还原为聚集态的Cr203稳定存在。对于CrO3/SiO2样品而言,其酯化反应在242-304℃温度范围内进行。2)碱式醋酸铬和Cr03在活化温度达到300℃以后,出现了稳定的归属于Cr5+的γ信号,且该信号在活化温度达到600℃时仍稳定存在。这表明在催化剂热活化过程中,大部分的Cr物种和硅羟基作用形成VI价的铬酸酯物种的同时,少量的Cr以V价负载化的形式稳定存在。3)催化剂制备过程中铬含量、Al/Cr、活化温度和还原剂等对催化剂和聚合产品性能产生影响。采用DEAE作为还原剂,催化剂活性适中,聚合物分子量适中；催化剂中铬含量增大,催化剂活性增大,聚合物分子量随之而减小；活化温度在600℃时,催化剂活性最高,聚合物分子量适中；催化剂中Al/Cr比在1.5—8.0范围内,催化剂聚合活性随着Al/Cr比增大而增加,聚合物分子量在Al/Cr比4.5—6.0时比较适中。催化剂和聚合物性能可以通过工艺配方和工艺条件调控。4)聚合温度、聚合压力、氢气和共聚单体对催化剂的聚合行为和聚合物性能产生影响。聚合温度升高,催化剂活性增大,聚合物分子量减小；聚合压力增大,催化剂活性增大,聚合物分子量增加；聚合体系加入氢气,催化剂活性有所降低,聚合物分子量减小；共聚单体1-丁烯在一定范围内使得催化剂活性增大,聚合物密度减小。5)催化剂的气相聚合动力学属于先增长后缓慢衰减型动力学曲线,聚合反应平稳。催化剂制备配方和聚合反应工艺条件如温度、压力、氢气和共聚单体均对聚合反应动力学产生影响。第三部分[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2催化剂研究从CrO3/SiO2催化剂出发,制备了新型铬系[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2催化剂,研究了新型催化剂制备及聚合工艺条件,探求了乙烯聚合的产品性能及最佳反应条件。新型催化剂制备方法简单,成本低廉,采用三价醋酸铬为铬源,取代传统的高毒性双(三苯基硅烷)铬酸酯原料,降低了催化剂制备操作中的危害1)铬系[(C6H5)3SiO]2/CrO2/AlR3/SiO2催化剂表征、聚合试验和聚合物表征结果以及原料成本方面综合考虑,优化的TPS加入量为1.5(Si/Cr)。2)催化剂活性和助催化剂加入量的结果表明,TEA是新型催化剂体系适宜的助催化剂体系；使用MAO作助催化剂时,乙烯在[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2催化剂上的聚合活性比[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂提高一倍。3)[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2催化剂淤浆浓度对聚合活性有明显的影响,淤浆浓度低对反应的活性有利。4)[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2催化剂的共聚和氢调性能试验结果表明,随着己烯共聚单体的加入,聚合物DSC熔融峰变宽,产生双峰,且随着共聚单体加入量的增加,熔点较低的峰越来越大,表明插入的短支链数量增加；[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2催化剂的氢调敏感性与[(C6H5)3SiO]2CrO2/AlR3/SiO2催化剂相当。第四部分新型P(?)N配体及其Ni、Pd配合物的合成、表征及乙烯催化反应立足于新型过渡金属乙烯反应催化剂配体以及配合物的设计与合成,成功合成了两种含有强吸电子基大体积—双(2,4,6-三(三氟甲基)苯基)膦吡啶p(?)N配体,用这些配体与过渡金属Ni，Pd盐反应得到相应的中性或阳离子配合物,这些配合物表现出乙烯聚合或齐聚催化活性。对配体上取代基的电子效应、空间位阻效应与催化性能间的相互关系进行了研究。1)首次合成了两种含有强吸电子基大体积—双(2,4,6-三(三氟甲基)苯基)膦吡啶p(?)N配体。在双(2,4,6-三(三氟甲基)苯基)氯化膦合成过程中,把反应副产物2,4,6-三(三氟甲基)苯基二氯化膦与2,4,6-三(三氟甲基)苯基锂盐继续反应的方法,成功地把目标产物的收率从35%提高到90%,为进一步的研究提供了充足的原料；解决了三乙胺与双(2,4,6-三(三氟甲基)苯基)氯化膦作用导致反应无法进行的难题,采用正丁基锂活化吡啶醇类化合物的方法,实现了双(2,4,6-三(三氟甲基)苯基)膦吡啶p(?)N配体的合成。2)合成了一种含有上述配体的中性镍配合物,并进行了初步1H NMR和31PNMR表征以及催化乙烯反应研究。1H NMR和31P NMR谱图中均出现宽峰,表明中性镍配合物具有顺磁性,空间构型应为以金属镍为中心的四面体构型。以MAO为助催化剂,研究了镍配合物的乙烯催化反应性能。结果表明,镍配合物具有乙烯聚合活性,在室温1atm乙烯压力下催化剂寿命较长(反应3.5hr仍然保持活性),而且随着Al/Cr从140提高到350,催化剂TOF从130molC2H4/molNi.h增大到151molC2H4/molNi.h。3)合成了两种含有上述配体的中性和阳离子钯配合物,并对这些配合物进行了1H NMR、31P NMR、单晶结构表征和元素分析。晶体结构证明,该配合物为p(?)N配位以金属钯为中心的平行四边形几何构型。阳离子钯配合物可催化乙烯齐聚反应,20℃,1atm乙烯压力,1.0hr时,TOF≈30—50molC2H4/molPd.h;20℃,2.0MPa,1.0hr, TOF≈200—350molC2H4/molPd.h,产物以CH3CH=CHCH3内烯烃为主。吡啶邻位亚甲基上的氢被甲基取代后,配合物空间位阻增大,对中心金属钯的覆盖增强,导致阳离子配合物催化乙烯齐聚活性降低,但一定程度上也阻碍了β-H消除反应,使齐聚产物中C6烯烃含量有所提高。更多还原

【Abstract】 With the highest production capacity and the widest application areas within all the polymer materials, polyolefin resins have exceeded100million metric tons of consumption per year in the world. Nowadays, polyolefins are widely used in many fields such as industry, agriculture, military, medical hygiene and everyday life because of their light mass, impact resistance, erosion resistance, insulation, transparency, non-toxicity and low price etc. Polyethylene (PE) has the highest production of the polyolefins. The catalysts are the key technology of the polyethylene production process, which mainly consist of Ziegler-Natta type titanium-based catalyst, chromium-based catalyst, metallocene catalyst and late transition metal catalyst etc. Therein, chromium-based catalyst resin has the unique role for its special long chain branched structure, broad molecular distribution, easy-processing behavior. However, chromium-based catalysts are more sensitive to trace of moisture and oxygen compared with titanium-based catalysts, which leads to the difficulty of research and development. The polymerization mechanism upon chromium-based catalysts is still unknown and the research of the polymerization kinetics, especially gas phase polymerization kinetics, is not reported yet. Therefore, it is indispensable to prepare new chromium-based catalysts and to develop high property and value-added PE resins via the research of gas phase polymerization mechanism and kinetics of chromium-based catalysts. Moreover, as a new type of polyethylene catalysts, late transition metal catalyst mainly including nickel and palladium homogeneous catalysts is attracting more and more attention in polyolefin field. The design, synthesis and application of new nickel and palladium catalysts possess the significant academic value and potential application.The dissertation is mainly comprised of four parts.Part one:Research of [(C6H5)3SiO]2CrO2/AlR3/SiO2catalystA series of supported [(C6H5)3SiO2CrO2AlR3/SiO2catalysts were prepared using bis(triphenylsilyl)chromate(BC) as the active component. The catalyst morphology and structural properties were characterized and the possible mechanism of initiation reaction at the early stage of ethylene polymerization upon the catalyst was discussed. By special inner structure polymerization reactor and experimental procedure, gas phase ethylene polymerization upon the chromium catalyst in the lab was conducted for the first time, and chromium content and Al/Cr molar ratio effects on the catalyst and polymer properties were also investigated. Moreover, gas phase ethylene polymerization of the three typical [(C6H5)3SiO]2CrO2AlR3/SiO2catalysts of Al/Cr molar ratio3.0,4.2,6.0were systematically investigated.1) The particle size distribution, pore structure and morphology of the catalyst and the initial silica support are similar, which are not affected by the preparation procedure of the catalyst. The produced initial polymer particle duplicates the catalyst particle morphology.2) ESR characterization results show that chromium valence of the catalyst changes dramatically before and after exposure to ethylene. The polymerization active sites are low valence states of the chromium. Before exposure to ethylene, high valence states such as CrⅥ and CrⅤ are the major states of the catalyst while low valence states such as CrⅡ and CrⅢ are the dominating states after exposure to ethylene and initiation of polymerization.3) The activity of the catalyst with the Al/Cr molar ratio as follows:catalyst activity rises firstly, reaches the maximum value and then decreases with the Al/Cr molar ratio increases. The highest activity occurs at the Al/Cr mole ratio being4.2-4.6.4) During the gas phase ethylene polymerization process, the catalyst activity rises and molecular weight of the produced polymer lowers when the polymerization temperature increases or the polymerization pressure decreases.5) As for [(C6H5)3SiO]2CrO2/AlR3/SiO2catalysts of Al/Cr molar ratio4.2, hydrogen as a chain transfer agent attacks the Cr-polymer bond to produce Cr-H species, which leads to lower molecular weight and higher melt fluid index of the produced polymer. At the same time, hydrogen results in ethylene partial pressure reduction and decrease of catalyst activity.1-Butene as the comonomer can introduce the short chain branches in the main chain and reduce density and crystallinity of the produced polymer, while1-Butene as the chain transfer agent can also changes the molecular weight and MFR of the produced polymer drastically.6) The three catalysts have similar kinetic curves as follows:firstly rise, reach the maximum value and decline slowly. In comparison,[(C6H5)3SiO]2CrO2AlR3/SiO2catalysts of Al/Cr molar ratio4.2has the higher activity and longer time to the maximum polymerization rate (40mins), while [(C6H5)3SiO]2CrO2/AIR3/SiO2 catalysts of Al/Cr mole ratio3.0and [(C6H5)SiO]2CrO2/AlR3/SiO2catalysts of Al/Cr mole ratio6.0have lower activity and shorter time to the maximum activity value (20-25mins).Part two:Preparation, characterization and catalytic ethylene polymerization of CrOx/AlR3/SiO2catalystSupported CrOx/AlR3/SiO2catalyst was prepared via impregnation, dryness, activation and reduction steps using cheap and low toxic alkaline chromium acetate as the starting material. By a series characterization techniques of FT-IR, TG-DTA, XPS, DSC, SEM and ESR, we systematically investigated the mechanism of the catalyst supporting and activation, and studied on the effects of catalyst preparation procedure and formula on the catalyst and produced polymer properties and gas phase polymerization kinetics. The new chromium catalyst CrOx/AlR3/SiO2possesses the following advantages such as low cost, low toxicity, high activity, hydrogen sensitivity and good copolymerization behavior.1) The decomposition temperature of alkaline chromium acetate supported on the silica decreases from314℃to299℃because higher Cr species dispersion on silica results in easier decomposition of chromium compound. FT-IR results show that oxidation decomposition of Cr3(CH3COO)7(OH)2strengthens at300℃and almost end at400℃. The process produces CrO3, H2O and CO2, and CrO3goes on esterification with surface silanol group to produce chromate species. Meanwhile, FT-IR and TG-DTA results show that inductive decomposition of CrO3to Cr2O3occurs at430-460℃. CrO3supported or not has dramatic effect on its decomposition because of its low melting point and tendency of inductive reduction to stable aggregation of Cr2O3at high temperature. As for CrO3/SiO2sample, the esterification is liable to occur at242-304℃.2) Alkaline chromium acetate and CrO3exhibit stable Y signal assigned to Cr5+when the activation temperature is at300℃and this signal still exists stably when the temperature is at600℃. The result indicates that during the catalyst activation process most of Cr species react with surface silanol to produce chromate species of VI valence state while a small portion of Cr exists stably as the supported form of V valence state.3) During the catalyst preparation process, chromium content, activation temperature and reduction agent have some effects on catalyst and produced polymer properties. Using DEAE as reduction agent, prepared catalyst exhibits medium activity and produced polymer has medium molecular weight. With chromium content of the catalyst increase, catalyst activity rises and molecular weight of the produced polymer reduces. Activation temperature at600℃, the catalyst exhibits maximum activity and produced polymer has medium molecular weight. Al/Cr molar ratio of the catalyst between1.5and8.0, with Al/Cr molar ratio increase, the catalyst activity rises and produced polymer has the medium molecular weight when Al/Cr mole ratio between4.5and6.0. Therefore, catalyst and produced polymer properties can be adjusted through preparation formula and process conditions.4) Polymerization temperature, pressure, hydrogen and comonomer have some effects on the catalytic polymerization behavior and properties of produced polymer. With the polymerization temperature increase, catalyst activity rises and produced polymer molecular weight lowers. With the polymerization pressure increase, catalyst activity rises and produced polymer molecular weight increases. With the addition of hydrogen to polymerization system, catalyst activity reduces somewhat and polymer molecular weight lowers. Comonomer of1-butene within a certain range can enhance the catalyst activity and lower polymer density.5) Gas phase polymerization kinetics of the catalyst belongs to a type of increase first and then slow decline curve, which is stable reaction. Catalyst formula and polymerization process conditions such as temperature, pressure, hydrogen and comonomer have some effects on the polymerization kinetics.Part three:Research of [(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2catalystBased on CrO3/SiO2catalyst,[(C6H5)SiO]2CrO2CrOx/AlR3/SiO2catalyst was prepared. New catalyst preparation and polymerization process conditions were investigated, and the produced polymer properties and optimum reaction conditions were also studied. The new catalyst was prepared by chromium acetate of III valence state as the starting material instead of the traditional toxic bis(triphenylsilyl)chromate, which decreases harm during catalyst preparation and new catalyst has simple preparation method with low cost.1) On the basis of [(C6H5)3SiO]2CrO2/CrOx AlR3/SiO2catalyst characterization, polymerization, produced polymer and starting material cost, the optimum value of TPS addition should be Si/Cr=1.5.2) The experimental results of catalyst activity and cocatalyst amount show that TEA is the suitable cocatalyst for the new catalyst system. AlR3/SiO2catalyst by MAO as cocatalyst exhibits one times higher activity of ethylene polymerization than [(C6H5)3SiO]2CrO2/AlR3/SiO2catalyst.3)[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2catalyst content has drastic effect on the catalyst activity. Low slurry concentration of catalyst content favors to its activity.4) The hydrogen and comonomer experimental results of [(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2catalyst show that with the comonomer of1-hexene addition, melt peak of produced polymer become broader and bimodal. And with addition amount of1-hexene increase, the low melt peak become bigger, which indicates the number of short chain branch rises.[(C6H5)3SiO]2CrO2/CrOx/AlR3/SiO2catalyst exhibits equivalent hydrogen response with [(C6H5)SiO]2CrO2/AlR3/SiO2catalyst.Part four:Preparation, characterization and catalytic ethylene polymerization of new P^N ligands and their Ni, Pd complexesOn the basis of design and synthesis of new transition metal complexes for catalytic ethylene reaction, two new P^N ligands bearing bulky strong electron-withdrawing group-bis(2,4,6-tris(trifluromethyl)phenyl)phospino pyridine were successfully prepared. The transition metal complexes of nickel and palladium were prepared by the reaction of corresponding ligands and metal halide. These complexes are active for ethylene oligomerization and/or polymerization. The relationship between the ligand environment of electronic and steric effects and the catalytic activity were elucidated.1) Two new bearing bulky strong electron-withdrawing group-bis (2,4,6-tris (trifluromethyl)phenyl)phospino pyridine were initially prepared. In order to prepare bis(2,4,6-tris(trifluromethyl)phenyl)phospino chloride, the side product2,4,6-tris (trifluromethyl)phenyl phospino dichloride was conducted to keep on reacting with tris(trifluromethyl)phenyl lithium salt and the target compound yield was successfully increased from35%to90%, which supplied enough material for the further synthesis of the ligands. Pyridine alcohol compound was activated through n-butyl lithium to accomplish the preparation of bis(2,4,6-tris(trifluromethyl) phenyl)phospine P^N ligands, which solved the difficulty of triethylamine reacting with bis(2,4,6-tris (trifluromethyl)phenyl)phospino chloride.2) A neutral nickel complex containing the above ligand was prepared, and the relevant1H NMR,31P NMR and catalytic ethylene reaction were briefly studied.1H NMR and31P NMR spectra show broad peak. The results indicate that the neutral nickel complex is paramagnetic and the space configuration is tetrahedron centered metal nickel. The nickel complex is active for ethylene reaction activated by MAO. The results show that the nickel complex is active for ethylene polymerization. The catalytic life is for about3.5hr at latm of ethylene pressure and room temperature. The catalytic activity of the complex was improved from130to151molC2H4/molNi.h by elevation of Al/Cr molar ratio from140to350.3) Two neutral and cationic palladium complexes bearing the above ligands were synthesized and characterized. X-ray crystal determination of the complexes verified that the complexes are ligated by P^N and their geometries around the metal centers are square planar. The cationic complexes are active for ethylene oligomerization. The catalytic activity of the complex exhibits30-50molCaH4/molPd.h at latm of ethylene pressure and20℃while showes200-350molC2H4/molPd.h at20atm of ethylene pressure and20℃. The inner olefins like CH3CH=CHCH3are the major products. Ortho-H of pyridine substituted by methyl, steric effect of the corresponding complex and coverage to central palladium strengthen and the cationic complex catalytic reactivity for ethylene oligomerization lowers. On the other hand, the steric effect also hinders β-H elimination which leads to increased C6olefins content of oligomeric product.更多还原