Green Routes to Fluorocarbons

碳氟化合物的绿色路线

• 批准号: RGPIN-2014-05841
• 负责人: Baker, Ralph
• 金额: $ 7.29万
• 依托单位: University of Ottawa
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=644505
• 关键词: Green; Routes; Fluorocarbons

Fluorocarbons are important materials for a variety of applications. Small molecule hydrofluorocarbons (HFCs), for example, have a low ozone depletion potential and have replaced banned chlorofluorocarbons (CFCs) as refrigerants, blowing agents, solvents, etc. More recently, unsaturated HFCs are being marketed that have greatly diminished global warming potential relative to their saturated analogs. Industrial production of these molecules, however, includes use of environmentally problematic chlorocarbons and toxic metals such as antimony. The unique properties of fluoropolymers such as low surface energy, high thermal and chemical stability make them especially useful as thermoplastics, coatings, elastomer membranes and functional materials. Unfortunately, these materials are prepared by energy-intensive radical processes or emulsion polymerization that employs environmentally persistent fluorosurfactants. As a result, for important monomers such as vinylidene fluoride (CH2=CF2) and hexafluoropropene [CF2=CF(CF3)] there is no way to control the insertion regio- and stereoselectivity and thus the polymer microstructure. Moreover, important materials derived from copolymerization of these monomers with tetrafluoroethylene (CF2=CF2) also suffer from a lack of consistent properties resulting from the random nature of the currently employed polymerization methods. In our research program we aim to: 1) Prepare hydrofluoroalkenes (HFAs) from co-pyrolysis of inexpensive bulk polytetrafluoroethylene (PTFE) and difluoromethane, acetylene or syngas (CO/H2) at low pressures (< 20 torr) using a commercial catalytic pyrolysis unit. The carbon-containing gases are activated by the heterogeneous catalyst and then combine with gas phase CF2 generated by the PTFE pyrolysis. Solid bases such as MgO or hydrotalcite will be used to remove HF from CH2F2 to generate CHF carbene, metal catalysts will activate acetylene for CF2 addition or insertion into a C-H bond, and Fisher-Tropsch catalysts will be used to generate CHn units on the catalyst surface for reaction with the gas phase CF2 carbenes. Optimized reaction conditions will be used for scaled-up production of selected HFAs for lab use and subsequent technology transfer to industry partners. *2) Develop base metal complex-catalyzed reactions of HFAs, proceeding through metallacyclopentane intermediates, that will offer greener routes to technologically valuable HFCs. Our promising results with low-coordinate organofluoronickelacycles will be extended to include hemilabile N-heterocyclic carbene-thioether ligands for stabilization of the low-valent catalyst under H2 and bifunctional P-N and P-B ligands for heterolytic cleavage of dihydrogen and reversible C-F bond activation, respectively. Low-coordinate Fe complexes will also be evaluated to compare the d5,6 organofluorometallacycle reactivity with our d7,8 nickel examples, particularly with regard to formation and functionalization of mixed HC/FC metallacycles and development of tandem processes that make productive use of the HF product.*3) Investigate nucleophilic metal fluorocarbenes as initiators for HFA metathesis and polymerization via metallacyclobutane intermediates. Building on newly developed CF2 transfer to low-valent metals using Me3SiCF3 and catalytic NaI, we will synthesize a number of new nucleophilic base metal fluorocarbenes and investigate their cycloaddition reactivity with HFAs and subsequent fluoride abstraction. Target systems include XL2 pincer ligands and metal hydrofluorocarbenes. These fundamental studies will be accompanied by rapid throughput catalytic testing of tandem processes using the silyl reagent to deliver CFRF and CHRF carbenes to low-valent metal precursors and subsequent catalyzed insertion into C-H bonds.

碳氟化合物是多种应用的重要材料。例如，小分子氢氟碳化物 (HFC) 具有较低的臭氧消耗潜能，并已取代禁用的氯氟碳化物 (CFC) 作为制冷剂、发泡剂、溶剂等。最近，不饱和氢氟碳化物正在上市，相对于饱和类似物，它大大降低了全球变暖的可能性。然而，这些分子的工业生产包括使用对环境有问题的氯碳化合物和有毒金属，例如锑。含氟聚合物的独特性能，例如低表面能、高热稳定性和化学稳定性，使其特别适用于热塑性塑料、涂料、弹性体膜和功能材料。不幸的是，这些材料是通过能量密集型自由基工艺或采用环境持久性含氟表面活性剂的乳液聚合来制备的。因此，对于重要单体，如偏二氟乙烯 (CH2=CF2) 和六氟丙烯 [CF2=CF(CF3)] ，无法控制插入区域选择性和立体选择性，从而控制聚合物微观结构。此外，由这些单体与四氟乙烯(CF2=CF2)共聚得到的重要材料也因目前采用的聚合方法的随机性而缺乏一致的性能。在我们的研究计划中，我们的目标是：1) 使用商用催化热解装置，在低压（< 20 托）下，通过廉价的散装聚四氟乙烯 (PTFE) 和二氟甲烷、乙炔或合成气 (CO/H2) 的共热解来制备氢氟烯烃 (HFA)。含碳气体被多相催化剂活化，然后与PTFE热解产生的气相CF2结合。 MgO或水滑石等固体碱将用于从CH2F2中去除HF以生成CHF卡宾，金属催化剂将活化乙炔以进行CF2加成或插入C-H键，费托催化剂将用于在催化剂表面上生成CHn单元以与气相CF2卡宾反应。优化的反应条件将用于扩大生产选定的氢氟酸供实验室使用以及随后向行业合作伙伴转让技术。 *2) 通过金属环戊烷中间体开发 HFA 的贱金属络合物催化反应，这将为生产具有技术价值的 HFC 提供更绿色的途径。我们对低配位有机氟镍环的有希望的结果将扩展到包括半不稳定的N-杂环卡宾硫醚配体，用于在H2下稳定低价催化剂，以及双功能P-N和P-B配体，分别用于二氢的异裂和可逆的C-F键活化。还将评估低配位 Fe 配合物，以将 d5,6 有机氟金属环反应性与我们的 d7,8 镍示例进行比较，特别是在混合 HC/FC 金属环的形成和官能化以及高效利用 HF 产品的串联工艺开发方面。*3) 研究亲核金属氟碳烯作为 HFA 复分解和聚合的引发剂 金属环丁烷中间体。基于新开发的使用 Me3SiCF3 和催化 NaI 将 CF2 转移到低价金属的方法，我们将合成许多新型亲核贱金属氟碳烯，并研究它们与 HFA 的环加成反应性以及随后的氟化物提取。目标系统包括 XL2 钳配体和金属氢氟碳烯。这些基础研究将伴随着串联过程的快速通量催化测试，使用甲硅烷基试剂将 CFRF 和 CHRF 卡宾传递到低价金属前体，并随后催化插入 C-H 键。