Public Abstract

DE-SC0016192: Catalytic Reactions at Solid-Liquid Interfaces: From Water to Liquid Metals

Award Status: Active

Institution: The Pennsylvania State University, University Park, PA
UEI: NPM2J7MSCF61
DUNS: 003403953

Most Recent Award Date: 08/07/2024
Number of Support Periods: 9
PM: Schwartz, Viviane

Current Budget Period: 09/01/2024 - 08/31/2025
Current Project Period: 09/01/2024 - 08/31/2027
PI: Rioux, Robert

Supplement Budget Period: N/A

Public Abstract

Catalytic Reactions at Solid-Liquid Interfaces: From Water to Liquid Metals Robert M Rioux Department of Chemical Engineering Department of Chemistry The Pennsylvania State University University Park, PA 16802-4400 The objectives of this proposal are to understand the impact of solvent effects during acid-catalyzed and high-temperature metal-catalyzed heterogeneous reactions which will be accomplished by a combination of explicit thermodynamic and kinetic measurements. Liquid-phase isothermal titration calorimetry will probe the interaction of acid site titrants and alkanol substrates (for eventual catalytic dehydration) in water to quantify the thermodynamic description of adsorption from the solvent phase to the intrapore space of different zeolite frameworks. Thermochemical Born-Haber cycles will be constructed to rationalize the influence of solvent on apparent thermodynamics and by utilizing additional information from gas-phase adsorption calorimetry, equilibrium adsorption isotherms and solution thermodynamics. Reaction rates quantified per available acid site for alkanol (cyclohexanol and n-propanol) dehydration will be measured under conditions of variable intrapore solvent concentration and structure, from solvent-free (gas-phase) to the incipient intrapore condensation. Apparent differences in acid site availability (“missing acid sites” based on solvent structure included in zeolite pores will be probed by combined liquid-/gas- phase calorimetry and in-situ titration during catalytic turnover. We expand the notion of a solvent effect in heterogeneous catalysis to high temperature, employing liquid metals in (de)hydrogenation catalysis. A unique high-temperature solvent effect will be examined utilizing liquid metals and alloys thereof containing small quantities of catalytic metal as a preferential solvent for H2 absorption (i.e., H2 acceptor) during the dehydrogenation of (cyclo)alkanes. The identity of the liquid metal impacts H2 solubility, defining a “global” solvent effect, displacing equilibrium-limited dehydrogenation reactions to increase conversion. The results from this proposal will impact our understanding of solvent effects in acid- and metal-catalyzed heterogeneous reactions. A quantitative approach based on calorimetry for assessing the impact of solvent identity on the energetics and availability of adsorption sites has been developed and is applicable to related disciplines. The extent to which thermodynamically non-idealities influence the kinetics of elementary steps in a catalytic cycle will increase our understanding of how solvent impacts intrinsic kinetic barriers and how the selection of solvent influences catalytic activity and selectivity. The proposed condensed-phase chemistries to be studied are motivated by biomass valorization, but the proposed methods and reported results will be applicable to catalytic chemistries in non-aqueous condensed-phase systems, such as plastic upcycling and catalysis for fine and bulk chemical production. High-temperature solvent effects based on liquid metals are relevant to hydrocarbon dehydrogenation reactions where intrinsic preferential solvation of hydrogen over hydrocarbon leads to enhanced kinetics and/or favorable equilibrium displacement.

Catalytic Reactions at Solid-Liquid Interfaces: From Water to Liquid Metals

Robert M Rioux
Department of Chemical Engineering
Department of Chemistry
The Pennsylvania State University
University Park, PA 16802-4400

The objectives of this proposal are to understand the impact of solvent effects during acid-catalyzed and high-temperature metal-catalyzed heterogeneous reactions which will be accomplished by a combination of explicit thermodynamic and kinetic measurements. Liquid-phase isothermal titration calorimetry will probe the interaction of acid site titrants and alkanol substrates (for eventual catalytic dehydration) in water to quantify the thermodynamic description of adsorption from the solvent phase to the intrapore space of different zeolite frameworks. Thermochemical Born-Haber cycles will be constructed to rationalize the influence of solvent on apparent thermodynamics and by utilizing additional information from gas-phase adsorption calorimetry, equilibrium adsorption isotherms and solution thermodynamics. Reaction rates quantified per available acid site for alkanol (cyclohexanol and n-propanol) dehydration will be measured under conditions of variable intrapore solvent concentration and structure, from solvent-free (gas-phase) to the incipient intrapore condensation. Apparent differences in acid site availability (“missing acid sites” based on solvent structure included in zeolite pores will be probed by combined liquid-/gas- phase calorimetry and in-situ titration during catalytic turnover. We expand the notion of a solvent effect in heterogeneous catalysis to high temperature, employing liquid metals in (de)hydrogenation catalysis. A unique high-temperature solvent effect will be examined utilizing liquid metals and alloys thereof containing small quantities of catalytic metal as a preferential solvent for H2 absorption (i.e., H2 acceptor) during the dehydrogenation of (cyclo)alkanes. The identity of the liquid metal impacts H2 solubility, defining a “global” solvent effect, displacing equilibrium-limited dehydrogenation reactions to increase conversion.

The results from this proposal will impact our understanding of solvent effects in acid- and metal-catalyzed heterogeneous reactions. A quantitative approach based on calorimetry for assessing the impact of solvent identity on the energetics and availability of adsorption sites has been developed and is applicable to related disciplines. The extent to which thermodynamically non-idealities influence the kinetics of elementary steps in a catalytic cycle will increase our understanding of how solvent impacts intrinsic kinetic barriers and how the selection of solvent influences catalytic activity and selectivity. The proposed condensed-phase chemistries to be studied are motivated by biomass valorization, but the proposed methods and reported results will be applicable to catalytic chemistries in non-aqueous condensed-phase systems, such as plastic upcycling and catalysis for fine and bulk chemical production. High-temperature solvent effects based on liquid metals are relevant to hydrocarbon dehydrogenation reactions where intrinsic preferential solvation of hydrogen over hydrocarbon leads to enhanced kinetics and/or favorable equilibrium displacement.