(46b) Selective conversion of carboxylic acids without C-C bond cleavage for fuels, chemicals, and hydrogen carriers

Carboxylic acids ranging from small C2 acids, C5-C6 functionalized acids, as well as longer chain fatty acids are excellent building blocks for SAF and other sustainable fuels, as well as many valuable chemicals. Selective activation of acids to yield alcohols is challenging over most catalysts due to nonselective deoxygenation as well as the inherently fast kinetics for sequential conversion of alcohol and aldehyde products over most catalysts. Here we illustrate how MoO3-x catalysts can exhibit remarkable selectivity toward desirable products by modifying catalyst pretreatment and surface coverage to produce primarily aldehydes and alcohols. Rates can be markedly improved by adding dopants that enhance hydrogen dissociation rates as we will show. We present a kinetic model that delineates the kinetic role of the various Mo oxide phases, and illustrate how maintaining a high coverage of acid inhibits undesirable side reactions, while a persistent coverage of surface OH species favors higher rates and selectivity to desired products. Finally, we show how tuning this chemistry in a reversible manner can be useful for reversible hydrogen storage and transport.