Bioderived Muconates by Cross-Metathesis and Their Conversion into Terephthalates

Area of Science:

• Chemical Engineering
• Polymer Science
• Sustainable Chemistry

Background:

• Growing demand for 100% bioderived polyethylene terephthalate driven by sustainability regulations.
• Challenges in producing renewable terephthalic acid, particularly the synthesis and purification of muconic acid isomers.

Purpose of the Study:

• To develop an efficient and direct synthesis of renewable terephthalate precursors from biomass-derived compounds.
• To overcome limitations of current methods involving complex separations and isomer transformations.

Main Methods:

• Ruthenium-catalyzed cross-metathesis of bioderived sorbates and acrylates to synthesize dialkyl muconates.
• Diels-Alder cycloaddition of bioderived dimethyl muconate with ethylene.
• Aromatization of the cyclohexene intermediate to dimethyl terephthalate using a Palladium on Carbon catalyst.

Main Results:

• Selective synthesis of trans,trans-dialkyl muconates via cross-metathesis in up to 41% yield, with exclusive formation of the desired isomer.
• High conversion (77-100%) and yield (70-98%) in the Diels-Alder reaction, with methanol and THF as optimal solvents.
• Up to 70% yield in the aromatization step, directly producing dimethyl terephthalate without intermediate purification.

Conclusions:

• Cross-metathesis offers a viable route to bioderived trans,trans-muconates, simplifying precursor synthesis for renewable terephthalates.
• This streamlined process, from muconate synthesis to terephthalate formation, is a significant advancement for the polymer industry.
• The method provides a sustainable alternative for producing key monomers for bio-based polymers.