Reduction of esters to ethers may provide the means to modify hydrolytic stability, viscosity, and mechanical properties of advanced materials created from renewably sourced carbon derived from sugars. This reaction is challenging and previous attempts often involve low selectivities to ether products, the use of impractical homogeneous catalysts and expensive stoichiometric metal hydride reagents, or have limited scope of substrates. Here we intend to develop heterogeneous catalysts that use inexpensive sources of hydrogen as reductants (e.g., H2 or regenerable alcohols as H-donors) to selectively reduce and remove O-atoms from the carbonyl functions of esters and leave ether O-atoms intact. Steady-state rates of catalysis are collected in both the liquid and gas phase, and the rates of alcohol and ether products formed by hydrogenolysis of ester reactants (e.g., ethyl acetate, ethyl propionate, and butyl butyrate) are measured as functions of reactant pressures, temperature and conversion to identify primary and secondary reaction pathways that form these species. Re and PdRe nanoparticles supported on γ-Al2O3, silica, and carbon supports provide distinct selectivities to these products. Changes in product selectivities in response to the presence of protic molecules, the pressure of gaseous H2, and the conversion of the ester reactant all indicate that the pathways that cleave the -C=O bond of the ester function to yield the ether product, and those that rupture the -C-O-C linkages to form alcohols, proceed by distinct mechanisms and possess different site requirements.

Catalytic reductions of esters with Re and PdRe nanoparticles

2019 Fall National Meeting

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