CAREER: Rational Design of Nanoporous Catalysts for Carbonylation Reactions

每年，数百万吨的醇和羧酸（用于制造聚合物、食品添加剂、溶剂和药品）通过催化羰基化在工业上生产。由于该工艺使用昂贵的稀有金属催化剂，并需要腐蚀性化学剂来促进所需的反应，因此其结果是严格且昂贵的反应器设计，复杂的催化剂回收方案，以及对环境不利的废物流。该项目旨在发现有效的多孔固体酸催化剂，作为一种技术上和环境上有吸引力的替代品。然而，设计一种最佳的固体酸是一项具有挑战性的任务，因为有数百种潜在的结构可供选择，每种结构都有独特的分子尺度空腔，可以稳定或防止不同的反应。该项目将开发计算机模型，使我们能够准确预测将发生哪些化学反应，从而实现催化剂设计的高效计算方法。这些发展将积极影响以羰基化化学为基础的制造过程，以及为现代社会创造化学产品的许多其他大规模工业过程。研究工作与教育和外展活动紧密结合，以服务于我们的总体目标，即在培训下一代劳动力时提高计算能力，促进多样性和扩大代表性不足的学生在STEM领域的参与。最近的实验工作表明，具有8元环的纳米多孔沸石具有高选择性催化羰基化反应的潜力，为传统的稀有金属基催化剂体系提供了令人注目的替代方案。尽管具有诱人的潜力，但根本性的重要问题仍然存在，包括：在不同的沸石结构中，什么样的结构基序将使小的甲氧基与大的碳正离子有效羰基化成为可能？如何通过选择性抑制不希望发生的反应来控制酸催化的副反应？在这些纳米多孔固体酸中，是什么机制决定了启动剂和投毒剂的功能？该研究项目将通过开发和应用集成量子化学和基于力场的分子尺度模拟的计算工具来解决这些问题。该项目将对纳米多孔催化剂的限制效应产生根本性的见解，并将使合理设计选择性靶向反应的催化剂成为可能。一个成功的结果不仅可能导致工业上可行的、环境友好的用于合成乙醇和乙酸的固体酸，而且还可能为在其他有机合成中使用固体酸和在许多现有的大规模固体酸催化过程中控制副反应提供一般策略。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Annually, millions of tons of alcohols and carboxylic acids (used to create polymers, food additives, solvents, and pharmaceuticals) are produced industrially via catalytic carbonylation. Because this process makes use of expensive rare-metal catalysts and requires corrosive chemical agents to promote the desired reactions, the result is stringent and costly reactor designs, complex catalyst recycling schemes, and environmentally unfriendly waste streams. This project aims to discover effective porous solid-acid catalysts as a technologically and environmentally appealing alternative. Designing an optimal solid acid, however, is a challenging task, as there are hundreds of potential structures to choose from, each with unique, molecular-scale cavities that can stabilize or prevent different reactions. This project will develop computer models that allow us to make accurate predictions of which chemical reactions will take place, enabling a computationally efficient approach to catalyst design. These developments will positively impact manufacturing processes based on carbonylation chemistry, and also many other large-scale industrial processes that create the chemical products for our modern society. The research efforts are closely integrated with educational and outreach activities to serve our overarching goals of improving computational competency in the training of the next-generation workforce and promoting diversity and broadening participation of underrepresented students in STEM fields.Recent experimental work has demonstrated that nanoporous zeolites with 8-membered rings can potentially catalyze the carbonylation reaction with high selectivity, providing a compelling alternative to traditional rare metal-based catalyst systems. Despite the tantalizing potential, fundamentally important questions remain, including: What are the structural motifs that will make possible effective carbonylation of small methoxy groups versus larger carbocations in different zeolite architectures? How can acid-catalyzed side reactions be controlled by selectively suppressing undesired reactions? What are the mechanisms that determine the function of promoters and poisoners in these nanoporous solid acids? This research program will address these questions by developing and applying computational tools that integrate quantum chemical and forcefield-based molecular-scale simulations. The project will generate fundamental insights into confinement effects in nanoporous catalysts and will make possible the rational design of catalysts that target reactions selectively. A successful outcome may not only lead to industrially feasible, environmentally friendly solid acids for the synthesis of ethanol and acetic acid, but also provide general strategies for using solid acids in other organic syntheses and for controlling side reactions in many existing, large-scale solid acid catalytic processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.