201. Analysis of thermodynamics, kinetics, and reaction pathways in the amination of secondary alcohols over Ru/SiO2.
- Author
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Gao, Xin, Sahsah, Dia, Heyden, Andreas, and Bond, Jesse Q.
- Subjects
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ALCOHOL , *AMINATION , *THERMODYNAMICS , *PARTIAL pressure , *LIQUID ammonia , *MOLECULAR structure , *AMINES - Abstract
[Display omitted] • The selective amination of secondary alcohols with ammonia to form primary amines is demonstrated over Ru/SiO 2 in gas- and liquid-phases with and without a hydrogen cofeed. • Thermodynamic constraints are mapped for the overall reactions of alcohol amination, identifying conditions where near-quantitative yields of primary amines are feasible. • Operating conditions are correlated with rate and selectivity, facilitating optimization. • Amination is demonstrated for heterocylic secondary alcohols to produce multifunctional heterocycles (aminofurans, aminopyrans). • Amination rates are low for heterocylic alcohols, with product inhibition implicated in the apparent loss of activity. • Variations in amination rate are quantified upon perturbations to molecular structure, extending kinetic insights to a modest substrate scope (8 alcohols) This work considers the Ru-mediated amination of secondary alcohols with ammonia in vapor and liquid media. We map thermodynamic constraints, and we probe the impacts of species partial pressure, residence time, and reaction temperature on rate, selectivity, and catalyst stability. Alcohol amination consumes no H 2 , and H 2 has no significant impact on amination kinetics; however, operating under H 2 benefits Ru stability. Primary amine selectivity increases with ammonia pressure and alcohol conversion, and the latter observation is consistent with the formation of primary amines through a network of sequential reactions. Unfortunately, primary amines are susceptible to secondary deamination to form hydrocarbons. As is typical of processes that seek to isolate a reactive intermediate, the main selectivity challenge here is identifying residence times that are long enough to accumulate high substrate conversion but short enough to avoid secondary deamination. In general, moderate residence times will maximize the production of primary amines. Insights extend across a broad substrate scope, and we observe 70 – 90% yield of primary amines from linear, cyclic, and heterocyclic alcohols. That said, heterocyclic alcohols appear susceptible to product inhibition, so achieving high conversions requires longer residence times and/or increased ammonia pressures. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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