(521k) Non-Enzymatic, Resonance-Promoted Bio-Renewable Polymer Production Under Mild Conditions.

Recent advances in resonance-promoted catalysis opened up a new direction in heterogenous catalyst research: the time-resolved modulation of binding energies by application of forced, cyclical external stimuli to balance rates of chemical reactions at surfaces with rates of product desorption, resulting in rates and selectivities not previously reported over similar catalysts in the absence of external stimuli. Following these, it is now possible to revisit previously reported catalytic systems wherein selectivity to desired products has been maximized, but rates are onerously slow (~24 hours reaction time at low temperature). In select cases (namely, when the catalyst system can be supported by a conducting material), we can apply concepts drawn from catalytic resonance theory to intensify these processes or increases their throughput, therefore enhancing their economic feasibility and accelerating their progression toward commercialization. An important family of chemical reaction wherein resonance promoted catalysis could enable a step-change improvement in rates and yields is the electrochemical oxidation of renewable, biomass-derived molecules into lower-carbon and sustainable specialty products, like bio-based and bio-degradable polymers. For example, the bio-degradable polymer precursor 3-hydroxybutyrate (HBA) is conventionally produce via enzymatic routes, which are costly to operate. Alternatively, PtSb alloys supported on activated carbon have been reported to oxidize 1,3-butanediol into HBA with near quantitative selectivity; but the reaction requires lower temperatures, and therefore long reactions times (~14 hours). Here, we report the effects of applying time-dependent, oscillating voltages to an electrochemical cell where the working electrode is decorated with Pt-based alloys supported on activated carbon. We quantify the effects of voltage amplitude, frequency and wave form on the rates and selectivities of 1,3-butanediol conversion at temperatures between 25-70 degrees Celsius. This work represents one important front in the new field of dynamic or resonance-promoted catalysis: de-bottlenecking of biomass-derived small molecule oxidations into renewable and bio-degradable polymers.