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

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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.