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1,391 results on '"Vlachos, Dionisios G."'

1. Thermodynamic and Transport Properties of Binary Mixtures of Polyethylene and Higher n-Alkanes from Physics-Informed and Machine-Learned Models

Author

Ley-Flores, Maria, Alessandri, Riccardo, Najmi, Sean, Valsecchi, Michele, Jackson, George, Galindo, Amparo, Korley, LaShanda, Vlachos, Dionisios G., and de Pablo, Juan J.

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

The thermodynamics and transport properties of polymeric materials are essential for the design of reactors and for the development of polymer deconstruction processes. Existing property prediction tools such as correlations based on entropy scaling, kinetic gas theory, and free-volume model are inadequate for polymers. In this paper, we introduce a data-driven model for polyolefins based on data from molecular dynamics simulations that can accurately predict the transport properties of polyethylenes and their binary mixtures with higher n-alkanes across a range of temperatures, pressures, concentrations, and oligomer molecular weights.

Published
2024

2. A US perspective on closing the carbon cycle to defossilize difficult-to-electrify segments of our economy

Author

Shaw, Wendy J, Kidder, Michelle K, Bare, Simon R, Delferro, Massimiliano, Morris, James R, Toma, Francesca M, Senanayake, Sanjaya D, Autrey, Tom, Biddinger, Elizabeth J, Boettcher, Shannon, Bowden, Mark E, Britt, Phillip F, Brown, Robert C, Bullock, R Morris, Chen, Jingguang G, Daniel, Claus, Dorhout, Peter K, Efroymson, Rebecca A, Gaffney, Kelly J, Gagliardi, Laura, Harper, Aaron S, Heldebrant, David J, Luca, Oana R, Lyubovsky, Maxim, Male, Jonathan L, Miller, Daniel J, Prozorov, Tanya, Rallo, Robert, Rana, Rachita, Rioux, Robert M, Sadow, Aaron D, Schaidle, Joshua A, Schulte, Lisa A, Tarpeh, William A, Vlachos, Dionisios G, Vogt, Bryan D, Weber, Robert S, Yang, Jenny Y, Arenholz, Elke, Helms, Brett A, Huang, Wenyu, Jordahl, James L, Karakaya, Canan, Kian, Kourosh Cyrus, Kothandaraman, Jotheeswari, Lercher, Johannes, Liu, Ping, Malhotra, Deepika, Mueller, Karl T, O’Brien, Casey P, Palomino, Robert M, Qi, Long, Rodriguez, José A, Rousseau, Roger, Russell, Jake C, Sarazen, Michele L, Sholl, David S, Smith, Emily A, Stevens, Michaela Burke, Surendranath, Yogesh, Tassone, Christopher J, Tran, Ba, Tumas, William, and Walton, Krista S

Subjects
Chemical Sciences, Climate Action, Responsible Consumption and Production, Chemical sciences
Abstract

Electrification to reduce or eliminate greenhouse gas emissions is essential to mitigate climate change. However, a substantial portion of our manufacturing and transportation infrastructure will be difficult to electrify and/or will continue to use carbon as a key component, including areas in aviation, heavy-duty and marine transportation, and the chemical industry. In this Roadmap, we explore how multidisciplinary approaches will enable us to close the carbon cycle and create a circular economy by defossilizing these difficult-to-electrify areas and those that will continue to need carbon. We discuss two approaches for this: developing carbon alternatives and improving our ability to reuse carbon, enabled by separations. Furthermore, we posit that co-design and use-driven fundamental science are essential to reach aggressive greenhouse gas reduction targets.

Published
2024

7. Facet-dependent strong metal-support interactions control the C–O bond activation

Author

Shi, Song, Lee, Seungyeon, Dun, Chaochao, Zheng, Weiqing, Urban, Jeffrey J, Caratzoulas, Stavros, and Vlachos, Dionisios G

Subjects
Inorganic Chemistry, Chemical Sciences
Abstract

Reducible metal oxides are selective and effective for C–O bond scission of hydrodeoxygenation reactions via the reverse Mars-van Krevelen mechanism. Creating efficient redox centers while minimizing metal surfaces leads to highly selective catalysts. Single noble metal atoms activate the surface M–O bond, but the catalyst activity is limited due to low loading. Here, we report that the strong metal-support interaction between Ir and CeO2 is facet sensitive, and certain facets regulate the C–O bond cleavage. At 300°C reduction, Ir is mostly encapsulated on an octahedron by (111) facets but remains exposed by (110) facets. The former is selective, whereas the latter is not. Density functional theory indicates that Ir encapsulation is favored on (111) under reaction conditions, and oxygen vacancies more readily form on encapsulated Ir than on pristine ceria.

Published
2023

10. Selective hydrogenation via precise hydrogen bond interactions on catalytic scaffolds

Author

Shi, Song, Yang, Piaoping, Dun, Chaochao, Zheng, Weiqing, Urban, Jeffrey J, and Vlachos, Dionisios G

Subjects
Inorganic Chemistry, Engineering, Chemical Sciences, Bioengineering
Abstract

The active site environment in enzymes has been known to affect catalyst performance through weak interactions with a substrate, but precise synthetic control of enzyme inspired heterogeneous catalysts remains challenging. Here, we synthesize hyper-crosslinked porous polymer (HCPs) with solely -OH or -CH3 groups on the polymer scaffold to tune the environment of active sites. Reaction rate measurements, spectroscopic techniques, along with DFT calculations show that HCP-OH catalysts enhance the hydrogenation rate of H-acceptor substrates containing carbonyl groups whereas hydrophobic HCP- CH3 ones promote non-H bond substrate activation. The functional groups go beyond enhancing substrate adsorption to partially activate the C = O bond and tune the catalytic sites. They also expose selectivity control in the hydrogenation of multifunctional substrates through preferential substrate functional group adsorption. The proposed synthetic strategy opens a new class of porous polymers for selective catalysis.

Published
2023

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