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The Design of Bimetallic Catalysts for the Upgrading of Carboxylic Acids /

Record Type:	Electronic resources : Monograph/item
Title/Author:	The Design of Bimetallic Catalysts for the Upgrading of Carboxylic Acids // Ayodeji Omoniyi.
Author:	Omoniyi, Ayodeji,
Description:	1 electronic resource (323 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-11, Section: B.
Contained By:	Dissertations Abstracts International86-11B.
Subject:	Chemical engineering. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32000196
ISBN:	9798315737117

The Design of Bimetallic Catalysts for the Upgrading of Carboxylic Acids /
Omoniyi, Ayodeji,

The Design of Bimetallic Catalysts for the Upgrading of Carboxylic Acids /Ayodeji Omoniyi. - 1 electronic resource (323 pages)

Source: Dissertations Abstracts International, Volume: 86-11, Section: B.

The next couple of decades are gearing up to be pivotal in reducing our energy reliance on fossil fuels. The environmental consequences of fossil fuel combustion grow increasingly dire, and their reserves are diminishing. To get in front of this, sustainable alternative sources of energy are intensely sought out. Among these, biomass-derived fuels (known as biofuels) show the most potential due to their compatibility with our existing internal combustion engine designs, offering a transitional bridge between current systems and a greener future. However, biomass is initially broken down into raw form called biooils which is unusable due in part to its high oxygen content. Thus, necessitating a second step upgrading of the oxygenated functional groups that populate the biooils, into usable biofuels. Catalytic upgrading strategies, most notably hydrodeoxygenation (HDO) and aqueous phase reforming (APR), have emerged as green and efficient approaches for converting these complex mixtures into higher-quality fuels. Transition metal catalysts are widely employed in these processes, and bimetallic catalysts have been shown to provide promising activity, selectivity, and stability. Yet, critical challenges/knowledge gaps linger: (1) Experimental testing of various bimetallic catalysts to find optimal combinations is time consuming and expensive; (2) Existing computational studies oversimplify what is happening on the catalyst surface, focusing on low coverage conditions inconsistent with experimental realities; (3) Inadequate mechanistic understanding of the connections between nanoscale interactions on the catalyst surface and observed macroscale catalyst performance. These gaps hinder the rational design of more selective catalysts and limits progress toward efficient biofuel production.In this work, I employed multi-scale computational chemistry approaches integrating ab initio modeling with experimental validation to investigate Pt, Ni, and Ru monometallic and bimetallic catalysts for bio-oil upgrading. Seven carboxylic acids were studied as representative undesirable biooil compounds. To demonstrate model accuracy, modeled coverages of key surface intermediates on the monometallic surfaces under a wide range of reaction conditions were validated against experimental adsorption results. Nanoscale insights were then derived by parameterizing adsorption energies into two key components: adsorbate-surface and adsorbate-adsorbate (intermolecular) interactions. Elucidation of such previously unexplored interactions allowed the prediction of these nanoscale interactions on catalyst surfaces and how they influence reaction energies, activation barriers, favored pathways, and the resulting potential energy surfaces for carboxylic acid catalytic upgrading. A key insight that emerged was the identification of two dominant adsorption modes that dictate catalytic behavior: (1) Transition metal catalysts that favor carboxylic acids adsorbing as dimers promote successive early dehydrogenations, hence H2 selectivity, while (2) Transition metal catalysts that favor dissociative adsorption through deprotonation to form bidentate surface carboxylates promote early C-O scissions and pathways more selective toward alkane formation. By balancing these two descriptors on an elliptical Gaussian plot for H2 selectivity, a unified framework that predicts product selectivity trends across a broad range of metals was developed. This allows the improvement of monometallic surfaces through doping for bimetallic and even trimetallic catalyst combinations. Specifically, while scanning different dopants for Pt and Ni as host metals, with a view to obtaining more selective and cheaper Ni-based bimetallic catalysts, it was discovered that Pt-based dopants showed limited improvement on the previously observed selectivity on pure Pt. But they show enough selectivity to foreshadow improved performance through synergistic dopant effects not captured in this model. On the other hand, Ni-based dopants such as Pd, Pt, Ag, Cu, Mo, Fe, and W all seem to markedly increase performance. NiPd and NiPt performed best.Taken together, this work offers an accelerated, insight-driven route for catalyst discovery for sustainable fuel production, one that bridges nanoscale interactions on the catalyst surface with macroscale catalyst performance. These findings not only deepen our fundamental understanding of catalytic upgrading reactions but also advance the transformation process of biomass into commercially viable and sustainable biofuels towards more efficient levels.

English

ISBN: 9798315737117Subjects--Topical Terms:

560457
Chemical engineering.
Subjects--Index Terms:

Aqueous-phase reforming

The Design of Bimetallic Catalysts for the Upgrading of Carboxylic Acids /
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520 $a The next couple of decades are gearing up to be pivotal in reducing our energy reliance on fossil fuels. The environmental consequences of fossil fuel combustion grow increasingly dire, and their reserves are diminishing. To get in front of this, sustainable alternative sources of energy are intensely sought out. Among these, biomass-derived fuels (known as biofuels) show the most potential due to their compatibility with our existing internal combustion engine designs, offering a transitional bridge between current systems and a greener future. However, biomass is initially broken down into raw form called biooils which is unusable due in part to its high oxygen content. Thus, necessitating a second step upgrading of the oxygenated functional groups that populate the biooils, into usable biofuels. Catalytic upgrading strategies, most notably hydrodeoxygenation (HDO) and aqueous phase reforming (APR), have emerged as green and efficient approaches for converting these complex mixtures into higher-quality fuels. Transition metal catalysts are widely employed in these processes, and bimetallic catalysts have been shown to provide promising activity, selectivity, and stability. Yet, critical challenges/knowledge gaps linger: (1) Experimental testing of various bimetallic catalysts to find optimal combinations is time consuming and expensive; (2) Existing computational studies oversimplify what is happening on the catalyst surface, focusing on low coverage conditions inconsistent with experimental realities; (3) Inadequate mechanistic understanding of the connections between nanoscale interactions on the catalyst surface and observed macroscale catalyst performance. These gaps hinder the rational design of more selective catalysts and limits progress toward efficient biofuel production.In this work, I employed multi-scale computational chemistry approaches integrating ab initio modeling with experimental validation to investigate Pt, Ni, and Ru monometallic and bimetallic catalysts for bio-oil upgrading. Seven carboxylic acids were studied as representative undesirable biooil compounds. To demonstrate model accuracy, modeled coverages of key surface intermediates on the monometallic surfaces under a wide range of reaction conditions were validated against experimental adsorption results. Nanoscale insights were then derived by parameterizing adsorption energies into two key components: adsorbate-surface and adsorbate-adsorbate (intermolecular) interactions. Elucidation of such previously unexplored interactions allowed the prediction of these nanoscale interactions on catalyst surfaces and how they influence reaction energies, activation barriers, favored pathways, and the resulting potential energy surfaces for carboxylic acid catalytic upgrading. A key insight that emerged was the identification of two dominant adsorption modes that dictate catalytic behavior: (1) Transition metal catalysts that favor carboxylic acids adsorbing as dimers promote successive early dehydrogenations, hence H2 selectivity, while (2) Transition metal catalysts that favor dissociative adsorption through deprotonation to form bidentate surface carboxylates promote early C-O scissions and pathways more selective toward alkane formation. By balancing these two descriptors on an elliptical Gaussian plot for H2 selectivity, a unified framework that predicts product selectivity trends across a broad range of metals was developed. This allows the improvement of monometallic surfaces through doping for bimetallic and even trimetallic catalyst combinations. Specifically, while scanning different dopants for Pt and Ni as host metals, with a view to obtaining more selective and cheaper Ni-based bimetallic catalysts, it was discovered that Pt-based dopants showed limited improvement on the previously observed selectivity on pure Pt. But they show enough selectivity to foreshadow improved performance through synergistic dopant effects not captured in this model. On the other hand, Ni-based dopants such as Pd, Pt, Ag, Cu, Mo, Fe, and W all seem to markedly increase performance. NiPd and NiPt performed best.Taken together, this work offers an accelerated, insight-driven route for catalyst discovery for sustainable fuel production, one that bridges nanoscale interactions on the catalyst surface with macroscale catalyst performance. These findings not only deepen our fundamental understanding of catalytic upgrading reactions but also advance the transformation process of biomass into commercially viable and sustainable biofuels towards more efficient levels.
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653 $a Carboxylic acid upgrading
653 $a Density functional theory
653 $a Heterogeneous catalysis
653 $a Hydrodeoxygenation
653 $a Transition metal catalysts
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710 2 $a Stevens Institute of Technology. $b Chemical Engineering. $e degree granting institution. $3 3824620
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