Bifunctional Catalysts Containing Sites of Controlled Accessibility

含有受控可及性位点的双功能催化剂

• 批准号: 9629963
• 负责人: Wolfgang Sachtler
• 金额: $ 22.8万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-10-01 至 2000-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9629963&HistoricalAwards=false
• 关键词: Bifunctional; Catalysts; Containing; Sites; Controlled

ABSTRACT CTS-9629963 This is an exploration of a novel concept of catalyst design intended to improve selectivity in bifunctional catalysts. The proposed catalysts contain two types of active sites: one type that is in contact with all molecules in the fluid (gas or liquid) medium, and another type, typically metal clusters, effectively inaccessible to most reactants but reachable by small molecules such as hydrogen. This situation should minimize undesired reactions such as metal-catalyzed carbon-carbon bond fission. The restricted accessibility of the metal clusters is achieved by depositing them in a zeolite with one-dimensional micropores that are filled with a physisorbed vapor; it is desired to obtain steady-state conditions characteristic of single-file diffusion. The physisorbed molecules may be converted to carbonaceous materials which would more thoroughly isolate the metal clusters from large molecules while leaving largely unchanged their ability to dissociate hydrogen. The hydrogen atoms can then migrate over the zeolite surface to the more accessible site ("spillover"). This approach if successful would have application to many existing and potential industrial processes, including production of aldehydes from carboxylic acids, ethers from esters, and nitroso compounds from nitro compounds. It could also have utility for enantioselective hydrogenation or hydroformylation. These processes are of great economic importance to the chemical, drug, cosmetic, and agrochemical industries.

CTS-9629963是对一种新的催化剂设计概念的探索，旨在提高双功能催化剂的选择性。所提出的催化剂包含两种类型的活性中心：一种类型与流体(气体或液体)介质中的所有分子接触，另一种类型通常是金属团簇，大多数反应物实际上无法接触到，但氢等小分子可以接触到。这种情况应该会最大限度地减少不受欢迎的反应，如金属催化的碳-碳键分裂。金属团簇的受限可访问性是通过将它们沉积在具有一维微孔的沸石中来实现的，该一维微孔填充了物理吸附的蒸汽；期望获得具有单文件扩散特征的稳态条件。物理吸附的分子可以转化为碳质材料，这将更彻底地将金属团簇从大分子中分离出来，同时基本上保持它们解离氢的能力不变。然后，氢原子可以通过沸石表面迁移到更容易接近的位置(“溢出”)。这种方法如果成功，将适用于许多现有的和潜在的工业过程，包括从羧酸生产醛，从酯生产醚，以及从硝基化合物生产亚硝基化合物。它还可用于对映体选择性氢化或氢甲酰化。这些工艺对化学、制药、化妆品和农用化学工业具有重要的经济意义。