(532as) Selective Electrochemical Hydrogenation of Cis, Cis – Muconic Acid on Transition Metals

The abundance of biomass in the midwestern United States has motivated significant recent effort to synthesize sustainably-sourced novel and commodity chemicals.^1,2 Muconic acid has been recently identified as a platform molecule with the potential to produce compounds such as adipic acid, caprolactum, and terephthalic acid, with adipic acid of particular interest as a precursor to nylon 6,6.³ The use of electrochemistry offers a mechanism for more finely controlling the selectivity of muconic acid hydrogenation while taking advantage of “clean” energy generated by midwestern wind farms. Based on the current literature,⁴ the requirement of highly acidic conditions in the presence of Pd/C catalyst is a bottleneck for scale-up of this process. The development of a novel, inexpensive, and highly selective catalyst material at more neutral pH can be accelerated through collaborative efforts of theorists and experimentalists to fundamentally understand the reaction mechanism for conversion of cis, cis-muconic acid to adipic acid.

In this presentation, we will share DFT calculations of the detailed reaction thermochemistry of the possible elementary steps involved in the selective hydrogenation of cis, cis – muconic acid to form adipic acid on Pd(111) and Pt(111) surfaces. We will also provide a comparison of the reaction energetics on the catalytic surfaces with the corresponding energetics in the solution phase. Based on this comparison, we elucidate a thermodynamically preferred reaction pathway. The dependence of the preferred reaction pathway on the external cell potential and pH of the reaction environment will also be elucidated.

References

1. Dell’Anna, M. N. et al. Green Chem. 23, 6456–6468 (2021).
2. Abdolmohammadi, S. et al. Macromolecules 54, 7910–7924 (2021).
3. Khalil, I. et al. Green Chem. 22, 1517–1541 (2020).
4. Matthiesen, J. E. et al. ACS Sustain. Chem. Eng. 4, 3575–3585 (2016).