In this contribution, we report for the first time a process for the conversion of bioethanol into mono- and dihydroxy acid monomers, via a sequential oxidation, aldo-condensation, and epoxidation reactions for the production of PHAs building blocks using a cascade catalytic process. These monomers can be readily employed in the production of polyhydroxyalkanoates (PHA), which are biodegradable and bio-based (renewable) polymers typically produced using genetically modified bacteria. In the first stage, a simple dehydrogenation on Cu and/or Ni catalysts supported on SiO<sub>2</sub> was employed to convert ethanol into acetaldehyde in vapor phase. Then, a series of acid-base solid catalysts were screened for the selective aldol-condensation acetaldehyde to crotonaldehyde in liquid phase using ethanol as reaction solvent. This intermediate was employed as feedstock for the selective oxidation to produce the first end-product (crotonic acid). Further conversion of the α-β-unsaturated acid via Sharpless epoxidation using WO<sub>x</sub>-containing catalysts was employed to produce a reaction intermediate that could readily undergo hydrolysis or hydrogenation to either di- or mono- hydroxy acids. The overall process yield for the unsaturated acid was ~ 69 %, while in the case of the di- and mono- hydroxy acids mixture this yield slightly decreased to ~ 60 %. While these yields are moderately high we believe that this strategy offers a promissing alternative for large-scale production of renewable and biodegradable polymers that can compete with the current bio-conversion processes and increase the wealth of possible products that can be synthesize in current bioethanol plants.

Catalytic multistage process for the production of polyhydroxyalkanoate monomers from bioethanol

255th National Meeting (2018)

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