A Synthetic Approach to Active Site Deconvolution in Supported Cr Catalysts for Olefin Polymerization

摘要提案题目：烯烃聚合载体Cr催化剂活性位点反卷积的合成方法提案号：ccs -0500489首席研究员：Susannah L. scott机构：加州大学圣巴巴拉分校分析（决策依据）：该项目的目标是解决一类广泛用于高密度聚乙烯生产的基于铬的催化剂长期存在的复杂问题。这些催化剂在烯烃存在下具有显著的自激活能力。然而，在活性位点的性质已知之前，不太可能确定它们是如何形成的，或者为什么这种催化剂在恢复失活位点方面如此有效。该方法结合了使用Flory分析和动力学建模对非均相催化剂进行活性位点反褶积和使用表面有机金属化学合成单个候选活性位点的方法。将催化剂位点的活性谱和聚合物特征与那些定义明确的有机金属位点相匹配，将使结构与反应性相关联。这样就有可能通过选择在聚乙烯中产生所需物理性质组合的位点组合来重新配制烯烃聚合催化剂。此外，通过阐明负载型金属氧化物催化剂的活化机制，将有可能使自活化更有效。活性位点研究的合成方法是催化剂发现的组合方法的补充。一旦通过筛选（平行或其他）确定并优化了有趣的催化剂配方，进一步的改进取决于操纵活性位点结构的能力。通过合成模型化合物来识别控制反应性的结构特征是均相催化中很有前途的一种方法，但该方法具有创新性，在多相催化中具有较高的风险。由于铬基聚合催化剂在工业上的广泛应用，该项目将产生更广泛的技术影响。该项目将让学生参与到一个非常强大的多学科环境中，特别强调化学工程和化学方法的关键结合，这是前沿催化研究所必需的。由首席研究员进行的研究项目有涉及代表性不足群体的本科生的记录：在过去的10年里，28名学生（包括18名女性）参与了项目，其中13名学生攻读了研究生课程。

AbstractProposal Title: A Synthetic Approach to Active Site Deconvolution in Support Cr Catalysts for Olefin Polymerization Proposal Number: CTS-0500489Principal Investigator: Susannah L. ScottInstitution: University of California-Santa BarbaraAnalysis (rationale for decision): The goal of this project is to solve a longstanding and complex problem related to a class of catalysts based on chromium that have been extensively used for high-density polyethylene production. These catalysts have a remarkable ability to self-activate in the presence of olefin. Until the nature of the active sites is known, however, it is unlikely that it will be possible to determine how they are formed or why this catalyst is so effective at reviving deactivated sites. The proposed approach to this problem combines active site deconvolution for the heterogeneous catalyst using Flory analysis and kinetic modeling with synthesis of individual active site candidates using surface organometallic chemistry. Matching the activity profiles and polymer characteristics of the catalyst sites with those of well-defined organometallic sites will allow correlation of structure with reactivity. It may then be possible to reformulate the olefin polymerization catalysts by selecting combinations of sites that generate desired combinations of physical properties in the polyethylene. Furthermore, by shedding light on the activation mechanisms of the supported metal oxide catalysts, it will be possible to make the self-activation more efficient. The synthetic approach to active site investigation is complementary to combinatorial approaches to catalyst discovery. Once interesting catalyst formulations are identified and optimized by screening (parallel or otherwise), further improvements depend on the ability to manipulate active site structure. Identifying the structural features which control reactivity by synthesizing model compounds has been a promising strategy in homogeneous catalysis, and the approach is innovative and high risk for heterogeneous catalysis.The broader technological impacts of this project will be significant due to the widespread use of chromium-based polymerization catalysts by industry. The project will involve students in a very strong multidisciplinary environment that particularly emphasizes the key combination of chemical engineering and chemistry approaches that have been necessary for leading-edge catalysis research. The research program conducted by the principal investigator has a record of involving undergraduate students from underrepresented groups in research: 28 students including 18 women have been involved in projects during the past 10 years, and 13 of these students have pursued graduate studies.