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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Guidelines to Achieving High Selectivity for the Hydrogenation of α,β-Unsaturated Aldehydes with Bimetallic and Dilute Alloy Catalysts: A Review

Selective hydrogenation of unsaturated aldehydes to unsaturated alcohols is a challenging class of reactions, yielding valuable intermediates for the production of pharmaceuticals, perfumes, and flavorings. On monometallic heterogeneous catalysts, the formation of the unsaturated alcohols is thermodynamically disfavored over the saturated aldehydes. Hence, new catalysts are required to achieve the desired selectivity. In this work, the literature of three major research areas in catalysis is integrated as a step toward establishing the guidelines for enhancing the selectivity: reactor studies of complex catalyst materials at operating temperature and pressure, surface science studies of crystalline surfaces in ultrahigh vacuum, and first-principles modeling using density functional theory calculations. Aggregate analysis shows that bimetallic and dilute alloy catalysts significantly enhance the selectivity to the unsaturated alcohols compared to monometallic catalysts. This comprehensive review focuses primarily on the role of different metal surfaces as well as the factors that promote the adsorption of the unsaturated aldehyde via its C=O bond, most notably by electronic modification of the surface and formation of the electrophilic sites. Furthermore, challenges, gaps, and opportunities are identified to advance the rational design of efficient catalysts for this class of reactions, including the need for systematic studies of catalytic processes, theoretical modeling of complex materials, and model studies under ambient pressure and temperature.

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DOE OSTI2021

Highly Selective Acetylene Semihydrogenation Catalyst with an Operation Window Exceeding 150 °C

The operating window (OW) is a primary performance criterion for the selective hydrogenation of acetylene in excess ethylene. Currently, most state-of-the-art catalyst systems have an OW of less than 50 °C in front-end processes. Selective acetylene hydrogenation catalysts with an OW wider than 100 °C are rare. Here, we demonstrate a facile stepwise chemical method to synthesize calcite-supported PdBi intermetallic compounds (PdBi/Calcite) that feature isolated and electron-rich Pd atoms as active sites for acetylene hydrogenation. Beneficial from the extremely weak ethylene absorption abilities and the stable structures against the formation of β-PdH x , PdBi/Calcite exhibit >99% selectivity to C 2 H 4 in the whole temperature range tested (50–300 °C) and ~100% C 2 H 2 conversion from 150 to 300 °C. Finally, as a result, an operation window exceeding 150 °C has been achieved.

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