Promotion of the Selective Hydrogenation of Unsaturated Aldehydes with Pt-Cu Bimetallics: From Surface Science to Nanostructured Catalysts

多相催化在许多工业化学过程中使用，以使化学反应通过更有选择性和更有效的化学途径发生，并且有助于实现这些化学转化的固体材料多相催化剂的设计是深入研究的领域。 加州大学河滨分校的弗朗西斯科扎埃拉博士正在研究铜铂合金的性质，以确定向活性很高但选择性不高的铂催化剂中添加铜的效果，目的是提高其选择性，以生产所需产品，同时限制不需要的副产物的产生。 Zaera博士的目标是设计一种催化剂，可以使碳-氧（C=O）键反应成醇，而不影响分子中的其他键。 他执行了三管齐下的方法来理解这些反应的机制;在模型系统上进行动力学测量，这些模型系统具有很少的，明确的表面位置，可以在明确的低压条件下探测Cu-Pt材料的表面层组成和反应性;在模型催化剂上进行的反应和在实际催化条件下的反应;使用结构和复杂性与工业催化剂最相似的定义明确的负载型催化剂进行研究。 这项工作的更广泛的影响来自于对混合金属表面的分子水平化学的基本理解。 从这项工作中获得的知识在教育方面也有更广泛的影响，通过提供数据来说明本科生和研究生班的动力学和催化的基本原理。 PI还积极促进与拉丁美洲研究团体的合作，并招募STEM领域代表性不足的群体的学生，特别是西班牙裔学生参加研究活动。加州大学河滨分校的弗朗西斯科扎埃拉博士得到化学催化计划的支持，研究铜铂合金在C=O键选择性氢化中的催化性能。 催化的主要挑战之一是实现对所需产物的高选择性。已经表明，可以通过混合两种或更多种金属来控制选择性，这是一种在许多工业应用中使用但尚未完全理解的方法。该提案的重点是帮助解决与电子催化有关的一些悬而未决的问题，包括确定电子效应与几何效应的贡献，以及根据金属混合程度和组成元素的氧化态确定最活跃的表面。 Zaera博士将反应机理细节的基础表面科学研究与现实催化剂的设计和评估相结合。.涉及三种类型的相互关联的实验：（1）在模型系统上的动力学测量，使用高通量分子束在特定表面上模拟接近大气压的局部压力，同时保持其受控制备和表征所需的超高真空（UHV）环境;（二）通过结合动力学测量与质谱检测和表面中间体的表征，在操作模式下研究模型系统，红外吸收光谱法;和（3）通过使用胶体和其他纳米技术制备的明确的负载型催化剂的动力学测量。 更广泛的影响，研究结果的催化选择性，这转化为更有效的加氢催化剂，特别是对精细化学品的工业生产的理解。更广泛的影响也在课程开发提供数据，说明动力学，催化和纳米粒子合成的本科生和研究生班的基本原则。PI还积极与拉丁美洲研究团体建立合作关系，并从STEM研究领域代表性不足的群体中招募学生，特别关注西班牙裔。

Heterogeneous catalysis is used in many industrial chemical processes to make the chemical reactions occur through more selective and efficient chemical pathways, and the design of the solid material heterogeneous catalysts that help to effect these chemical transformations is a field of intensive study. Dr. Francisco Zaera of the University of California-Riverside is investigating the properties of Cu-Pt alloys to determine the effect of adding copper to very active but not particularly selective platinum catalysts with the aim of improving their selectivity to produce desired products while limiting the creation of unwanted byproducts. Dr. Zaera's goal is to design a catalyst that can bring about the reaction of carbon-oxygen (C=O) bonds to alcohols, without affecting other bonds in the molecule. He performs a three-pronged approach to understand the mechanisms in these reactions; kinetic measurements on model systems with few, well-defined surface sites that probe the surface-layer composition and reactivity of the Cu-Pt materials under well-defined, low-pressure conditions; reactions performed on model catalysts and reactions under actual catalytic conditions and; studies with well-defined, supported catalysts that most closely resemble industrial catalysts in their structure and complexity. Broader impacts of this work result from an enhanced fundamental understanding of the molecule-level chemistry of mixed-metal surfaces. The knowledge deriving from this work has broader impact in education as well, by providing data to illustrate basic principles in kinetics and catalysis for undergraduate and graduate classes. The PI is also active in promoting collaborations with Latin American research groups and recruits students from groups underrepresented in STEM fields, Hispanics in particular, to participate in research activities.Dr. Francisco Zaera of the University of California-Riverside is supported by the Chemical Catalysis Program to investigate the catalytic properties of Cu-Pt alloys in the selective hydrogenation of C=O bonds. One of the major challenges in catalysis is to achieve high selectivity toward the desired products. It has been shown that selectivity may be controlled by mixing two or more metals, an approach that is used in many industrial applications but not fully understood. The focus of this proposal is to help resolve some pending issues associated with bimetallic catalysis, including the determination of the contributions of electronic versus geometrical effects and the identification of the most active surface in terms of the degree of metal intermixing and the oxidation states of the constituent elements. Dr. Zaera combines fundamental surface-science studies on the mechanistic details of the reactions with the design and evaluation of realistic catalysts. . Three types of interconnected experiments are involved : (1) kinetic measurements on model systems using high-flux molecular beams to emulate close-to-atmospheric pressures locally at specific surfaces while maintaining the ultrahigh vacuum (UHV) environment necessary for their controlled preparation and characterization; (2) research of model systems in operando mode by combining kinetic measurements with mass spectrometry detection and characterization of the surface intermediates using infrared absorption spectroscopy; and (3) kinetic measurements with well-defined supported catalysts made by using colloidal and other nanotechnologies. Broader impacts of the research result for an improved understanding of catalytic selectivity, which translates into more efficient hydrogenation catalysts particularly important to the industrial production of fine chemicals. Broader impacts are also made in curriculum development by providing data to illustrate basic principles in kinetics, catalysis, and nanoparticle synthesis for undergraduate and graduate classes. The PI is also active in forging collaborations with Latin American research groups, and in the recruitment of students from groups underrepresented in STEM research fields, with a particular focus on Hispanics.