Challenges and Opportunities in the Catalytic Synthesis of Diphenolic Acid and Evaluation of Its Application Potential

Abstract

Diphenolic acid, or 4,4-bis(4-hydroxyphenyl)pentanoic acid, represents one of the potentially most interesting bio-products obtainable from the levulinic acid supply-chain. It represents a valuable candidate for the replacement of bisphenol A, which is strongly questioned for its toxicological issues. Diphenolic acid synthesis involves the condensation reaction between phenol and levulinic acid and requires the presence of a Brønsted acid as a catalyst. In this review, the state of the art related to the catalytic issues of its synthesis have been critically discussed, with particular attention to the heterogeneous systems, the reference benchmark being represented by the homogeneous acids. The main opportunities in the field of heterogeneous catalysis are deeply discussed, as well as the bottlenecks to be overcome to facilitate diphenolic acid production on an industrial scale. The regioselectivity of the reaction is a critical point because only the p,p′-isomer is of industrial interest; thus, several strategies aiming at the improvement of the selectivity towards this isomer are considered. The future potential of adopting alkyl levulinates, instead of levulinic acid, as starting materials for the synthesis of new classes of biopolymers, such as new epoxy and phenolic resins and polycarbonates, is also briefly considered.

Catalytic Transformation of Carbohydrates into Renewable Organic Chemicals by Revering the Principles of Green Chemistry

“…179 Even though phenol and acetone can be synthesized from biomass (or carbohydrates) for renewable BPA, the focus is explicitly given to DPA as a safer and more efficient product following the fourth principle of green chemistry. 180 The latest research in producing DPA focused on developing efficient and eco-friendly acid catalysts while aiming for higher selectivity and yield. Dimethyl isosorbide (DMI) is a promising ether-based biorenewable solvent being examined for various organic transformations, biomass pretreatment, and an electrolyte in battery applications.…”

“…Even though phenol and acetone can be synthesized from biomass (or carbohydrates) for renewable BPA, the focus is explicitly given to DPA as a safer and more efficient product following the fourth principle of green chemistry. 180 The latest research in producing DPA focused on developing efficient and eco-friendly acid catalysts while aiming for higher selectivity and yield. 181 …”