铬钒双金属催化剂乙烯聚合反应动力学模型化

双金属催化剂可催化乙烯聚合在单个反应器内制备双峰聚乙烯。考察了新型Cr-iV双金属催化剂及相应的单金属S-2和iV催化剂在不同实验条件下的乙烯均聚反应动力学。通过对Cr-iV催化剂聚合产物分子量分布曲线的解析发现铬钒活性中心之间存在相互作用,铬中心活性受到抑制,钒中心活性得到增强;聚合温度基本不改变铬钒活性中心生成的聚合物的质量分数。采用简化的单中心乙烯均聚动力学模型分别描述铬钒双活性中心的动力学行为,结合双金属催化剂的聚合实验结果确定了各个活性中心的动力学参数。相比单金属催化剂,Cr-iV催化剂中铬活性中心链增长速率常数降低,说明其聚合活性降低;而钒活性中心链失活速率常数减小,稳定性增强,活性提高。     

铬钒双金属催化剂乙烯聚合反应动力学模型化

双金属催化剂可催化乙烯聚合在单个反应器内制备双峰聚乙烯。考察了新型Cr-i V双金属催化剂及相应的单金属S-2和i V催化剂在不同实验条件下的乙烯均聚反应动力学。通过对Cr-i V催化剂聚合产物分子量分布曲线的解析发现铬钒活性中心之间存在相互作用,铬中心活性受到抑制,钒中心活性得到增强;聚合温度基本不改变铬钒活性中心生成的聚合物的质量分数。采用简化的单中心乙烯均聚动力学模型分别描述铬钒双活性中心的动力学行为,结合双金属催化剂的聚合实验结果确定了各个活性中心的动力学参数。相比单金属催化剂,Cr-i V催化剂中铬活性中心链增长速率常数降低,说明其聚合活性降低;而钒活性中心链失活速率常数减小,稳定性增强,活性提高。     

水杨醛亚胺型镍金属烯烃聚合催化剂研究进展

非茂金属烯烃聚合催化剂作为新型烯烃聚合催化剂,具有配体可修饰及过渡金属可选择的优势,拓宽了烯烃聚合催化剂研究领域。综述了水杨醛亚胺型镍金属配合物催化烯烃聚合近二十年研究进展,阐述了配体上取代基电子效应、空间结构及催化乙烯聚合或烯烃共聚性能关系,分析了水杨醛亚胺型镍金属配合物催化烯烃聚合或者共聚特点,指明了此类烯烃聚合催化剂发展应用前景。     

乙烯与极性单体共聚的研究进展

聚烯烃属于非极性聚合物,通过在其分子链上引入极性基团可以将其功能化,从而可以有效地改善聚烯烃的性质,拓宽聚烯烃的商业用途。本文主要从极性单体的种类、乙烯与极性单体共聚的催化剂体系两个方面介绍了乙烯与极性单体共聚合研究的最新进展。Ziegler-Natta催化剂、茂金属催化剂以及后过渡金属催化剂都可用于乙烯与极性单体的共聚合反应。文中重点介绍了后过渡金属催化剂,其催化活性高,聚合能力强,可以催化乙烯与大多数极性单体的共聚反应。     

铬系催化乙烯配位聚合/齐聚分子模拟研究进展

针对工业中广泛应用的Phillips铬系乙烯聚合催化剂和铬系乙烯选择性齐聚催化体系,从分子模拟角度对近期相关研究进展进行综述。主要介绍了分子模拟在Phillips铬系催化剂诱导期内乙烯聚合活性中心向乙烯易位活性中心转换机理、Ti改性Phillips铬系催化剂的乙烯聚合行为、Cr(III)2-EH/PIBAO/DME体系乙烯聚合和三聚转换机理以及Cr-SNS体系去质子化对乙烯三聚活性的影响等方面的研究进展。通过计算机分子模拟和实验手段相结合,可以获得对催化反应机理更为深刻的认识,从而为新型催化剂的设计与开发提供理论指导。     

后过渡催化剂催化烯烃与极性单体共聚的研究进展

综述了近年来后过渡金属催化剂催化烯烃与极性单体共聚的研究进展,后过渡金属催化剂催化乙烯与极性单体共聚的反应条件温和。对聚合机理和极性单体的种类进行了探讨,同时还讨论了共聚条件的变化对聚合产物的影响。     

茂金属烯烃聚合催化剂Ⅳ.含杂原子单活性中心催化剂及聚合研究

介绍了含氧，氮等杂原子单活性中心催化剂，包括后过渡金属催化剂，应用于乙烯，α－烯烃，环烯烃及其他极性单体的聚合。     

单活性中心乙烯聚合催化剂的研究进展

单活性中心乙烯聚合催化剂是近年来国内外研究的热点,也是开发聚乙烯新产品的重要手段。本文综述了近年来单活性中心催化剂用于制备功能性聚乙烯材料的研究进展,包括茂金属催化剂、非茂金属催化剂的开发应用。通过对单活性中心催化剂结构的调控,可以得到分子量及分子量分布、分子结构、构象等精确可控的功能性乙烯共聚物,或具有特殊性能的聚乙烯产品。     

三齿配体过渡金属烯烃聚合催化剂研究新进展

介绍了三齿配体结构、中心金属原子、助催化剂、负载化等对催化剂性能的影响;综述了三齿配体过渡金属烯烃聚合催化剂在乙烯齐聚、乙烯聚合、丙烯聚合以及极性单体聚合方面的应用以及三齿配体过渡金属烯烃聚合催化剂的催化机理方面的研究进展。     

乙烯齐聚多产α-烯烃催化剂进展

综述了乙烯齐聚多产α-烯烃催化剂的最新进展,包括前过渡金属中的钛系、锆系和后过渡金属中的镍系、钯系等。从催化剂活性中心结构、配位环境变化、取代基空间位阻变化、助催化剂的影响等角度阐述了不同催化体系催化乙烯齐聚的催化活性、α-烯烃选择性及其对催化体系的影响。     

乙烯齐聚催化体系中的Friedel-Crafts烷基化反应研究进展

采用过渡金属配合物催化乙烯齐聚是制备α-烯烃的一条重要工艺路线,部分催化体系已进入了中试和工业化生产阶段,但近年来的研究工作表明,一些过渡金属催化剂在甲苯溶剂中的齐聚产物可直接与甲苯发生Friedel-Crafts烷基化反应,这将为烷基苯的生产开辟一条新的途径。综述了近年来乙烯齐聚过程中发生Friedel-Crafts烷基化反应的研究进展,详细阐述了催化剂的结构、催化体系、工艺条件等对烷基化反应及烷基化产物分布的影响。同时,给出了乙烯齐聚中Friedel-Crafts烷基化反应的反应过程,对设计可催化乙烯齐聚制备混合烷基苯的催化剂具有重要的意义。     

LLDPE及其催化剂技术进展

综述了线性密度聚乙烯（LLDPE）研究的最进展情况，特别对乙烯原位聚合工艺和后过渡金属镍、钯催化剂进行了详细的叙述，对我国LLDPE的生产提出了自己的看法。     

Studies with High Activity Catalysts for Olefin Polymerization

Catalysis continues to play a vital role in polymerization of such olefins as ethylene and propylene. A voluminous patent and scientific literature describing transition metal catalysts for olefin polymerization has emerged since the original discoveries by Ziegler, Natta, and other workers [1–6], Significant progress in polymerization catalysis has been made in the last 15 years, particularly with the development of methods to increase the efficiency of transition metal catalysts in olefin polymerization. Success in this area has provided the basis of simplified, less costly plant operations which do not require removal of residual catalyst from the polymer [3–9].     

Studies with High Activity Catalysts for Olefin Polymerization

Catalysis continues to play a vital role in polymerization of such olefins as ethylene and propylene. A voluminous patent and scientific literature describing transition metal catalysts for olefin polymerization has emerged since the original discoveries by Ziegler, Natta, and other workers [1-6], Significant progress in polymerization catalysis has been made in the last 15 years, particularly with the development of methods to increase the efficiency of transition metal catalysts in olefin polymerization. Success in this area has provided the basis of simplified, less costly plant operations which do not require removal of residual catalyst from the polymer [3-9].     

Homogeneous catalysts for ethylene polymerization based on bis(imino)pyridine complexes of iron, cobalt, vanadium and chromium

Results of a comparative study of ethylene polymerization activity and the structure of polyethylene (PE) produced over homogeneous catalysts based on bis(imino)pyridine complexes with close ligand frameworks and different transition metal centers (Fe(II), Co(II), Cr(III) and V(III)) are reported. The effects of the activator nature and polymerization conditions on the activity of these complexes and the resulting PE structure (molecular weight, molecular weight distribution, content of methyl and vinyl groups) have been studied. The experimental data obtained under comparable conditions demonstrate a pronounced effect of transition metal center on the catalytic properties of bis(imino)pyridine complexes (polymerization activity, copolymerization reactivity, thermal stability, PE structure, composition of optimal activator, formation of single-site or multiple-site catalytic system).     

乙烯装置废热锅炉焦炭催化燃烧过程的研究

考察了各种金属离子型烧焦催化剂对乙烯装置废热锅炉焦炭燃烧过程的影响 ,讨论了其催化燃烧机理。研究结果表明 :第四周期过渡金属离子型催化剂在焦炭烧焦前期催化效果好 ,后期催化效果不明显 ,其催化机理可用氧传递过程来解释 ;IA族金属离子型烧焦催化剂的催化效果显著 ,能大大提高烧焦速度 ,并促进焦炭完全燃烧 ;IIA族金属离子型催化剂的催化烧焦效果较IA族金属离子型催化剂差。IA族与IIA族金属离子的催化作用效果与金属元素的第一热电离电势成反比     

Rational approach to polymer-supported catalysts: synergy between catalytic reaction mechanism and polymer design

Supported catalysis is emerging as a cornerstone of transition metal catalysis, as environmental awareness necessitates "green" methodologies and transition metal resources become scarcer and more expensive. Although these supported systems are quite useful, especially in their capacity for transition metal catalyst recycling and recovery, higher activity and selectivity have been elusive compared with nonsupported catalysts. This Account describes recent developments in polymer-supported metal-salen complexes, which often surpass nonsupported analogues in catalytic activity and selectivity, demonstrating the effectiveness of a systematic, logical approach to designing supported catalysts from a detailed understanding of the catalytic reaction mechanism. Over the past few decades, a large number of transition metal complex catalysts have been supported on a variety of materials ranging from polymers to mesoporous silica. In particular, soluble polymer supports are advantageous because of the development of controlled and living polymerization methods that are tolerant to a wide variety of functional groups, including controlled radical polymerizations and ring-opening metathesis polymerization. These methods allow for tuning the density and structure of the catalyst sites along the polymer chain, thereby enabling the development of structure-property relationships between a catalyst and its polymer support. The fine-tuning of the catalyst-support interface, in combination with a detailed understanding of catalytic reaction mechanisms, not only permits the generation of reusable and recyclable polymer-supported catalysts but also facilitates the design and realization of supported catalysts that are significantly more active and selective than their nonsupported counterparts. These superior supported catalysts are accessible through the optimization of four basic variables in their design: (i) polymer backbone rigidity, (ii) the nature of the linker, (iii) catalyst site density, and (iv) the nature of the catalyst attachment. Herein, we describe the design of polymer supports tuned to enhance the catalytic activity or decrease, or even eliminate, decomposition pathways of salen-based transition metal catalysts that follow either a monometallic or a bimetallic reaction mechanism. These findings result in the creation of some of the most active and selective salen catalysts in the literature.     

Design of biomimetic catalysts by molecular imprinting in synthetic polymers: the role of transition state stabilization

The impressive efficiency and selectivity of biological catalysts has engendered a long-standing effort to understand the details of enzyme action. It is widely accepted that enzymes accelerate reactions through their steric and electronic complementarity to the reactants in the rate-determining transition states. Thus, tight binding to the transition state of a reactant (rather than to the corresponding substrate) lowers the activation energy of the reaction, providing strong catalytic activity. Debates concerning the fundamentals of enzyme catalysis continue, however, and non-natural enzyme mimics offer important additional insight in this area. Molecular structures that mimic enzymes through the design of a predetermined binding site that stabilizes the transition state of a desired reaction are invaluable in this regard. Catalytic antibodies, which can be quite active when raised against stable transition state analogues of the corresponding reaction, represent particularly successful examples. Recently, synthetic chemistry has begun to match nature's ability to produce antibody-like binding sites with high affinities for the transition state. Thus, synthetic, molecularly imprinted polymers have been engineered to provide enzyme-like specificity and activity, and they now represent a powerful tool for creating highly efficient catalysts. In this Account, we review recent efforts to develop enzyme models through the concept of transition state stabilization. In particular, models for carboxypeptidase A were prepared through the molecular imprinting of synthetic polymers. On the basis of successful experiments with phosphonic esters as templates to arrange amidinium groups in the active site, the method was further improved by combining the concept of transition state stabilization with the introduction of special catalytic moieties, such as metal ions in a defined orientation in the active site. In this way, the imprinted polymers were able to provide both an electrostatic stabilization for the transition state through the amidinium group as well as a synergism of transition state recognition and metal ion catalysis. The result was an excellent catalyst for carbonate hydrolysis. These enzyme mimics represent the most active catalysts ever prepared through the molecular imprinting strategy. Their catalytic activity, catalytic efficiency, and catalytic proficiency clearly surpass those of the corresponding catalytic antibodies. The active structures in natural enzymes evolve within soluble proteins, typically by the refining of the folding of one polypeptide chain. To incorporate these characteristics into synthetic polymers, we used the concept of transition state stabilization to develop soluble, nanosized carboxypeptidase A models using a new polymerization method we term the "post-dilution polymerization method". With this methodology, we were able to prepare soluble, highly cross-linked, single-molecule nanoparticles. These particles have controlled molecular weights (39 kDa, for example) and, on average, one catalytically active site per particle. Our strategies have made it possible to obtain efficient new enzyme models and further advance the structural and functional analogy with natural enzymes. Moreover, this bioinspired design based on molecular imprinting in synthetic polymers offers further support for the concept of transition state stabilization in catalysis.     

Precision control of radical polymerization via transition metal catalysis: from dormant species to designed catalysts for precision functional polymers

In the past decade, living radical polymerization has provided one of the most versatile methods to precisely construct designed polymer architectures with complexity and polar functionality. This process takes advantage of carbon-radical intermediates, which tolerate a variety of functional groups in monomers and reaction media. "Transition metal-catalyzed living radical polymerization", one of these living systems, has widely been employed for precision polymer synthesis. Not only can this process produce well-defined functional polymers, but it can also generate hybrids or conjugates with other (often biological) materials. Metal-catalyzed systems retain the advantages of conventional radical polymerization but distinguish themselves through a catalytic reversible halogen exchange equilibrium: the growing radical exists alongside a dormant speciesa covalent precursor capped with a terminal halogen from an initiator. The catalyst dictates the selectivity, exchange rate, and control over the polymerization. This Account provides an updated overview of our group's efforts in transition metal-catalyzed living radical polymerization with specific emphasis on the design of metal catalysts and the resulting precision polymer syntheses. With increasing use of the living processes as convenient tools for materials synthesis, researchers are currently seeking more active and versatile metal catalysts that are tolerant to functional groups. Such catalysts would enable a wider range of applications and target products, would have low metal content, could be readily removed from products, and would allow recycling. Since we first developed the "transition metal-catalyzed living radical polymerization" with RuCl 2(PPh 3) 3, FeCl 2(PPh 3) 2, and NiBr 2(PPh 3) 2, we have strived to systematically design metal catalysts to meet these new demands. For example, we have enhanced catalytic activity and control through several modifications: electron-donating or resonance-enhancing groups, moderate bulkiness, heterochelation via a ligand, and halogen-donor additives. For some catalysts, the use of amphiphilic and polymeric ligands allow efficient recovery of catalysts and convenient use in aqueous media. We have also used ligand design (phosphines) and other methods to improve the thermal stability of iron- and nickel-based catalysts and their tolerance to functional groups.