Fully Renewable Diphenolic Acid Synthesis in Batch and Continuous Reactors in the Presence of New Biomass Derived Acid Catalysts and LCA Evaluation

Diphenolic acid is emerging as a promising "green" alternative to bisphenol A. The diphenolic acid synthesis involves a condensation reaction between phenol and levulinic acid, catalyzed by Brønsted acid catalysts, in particular mineral ones, which lead to significant corrosion issues and difficult catalyst recycling. Therefore, it is paramount to move towards heterogeneous systems, especially those derived from renewable resources. In this specific domain, the PRIN 2020 LEVANTE project focuses on synthesizing a fully renewable p,p’-diphenolic acid. The possibility of using biomass-derived catalysts offers the opportunity to make the entire DPA synthesis fully renewable. In order to achieve these goals, new ad-hoc acid catalysts have been synthesized by sulfonating xylose- and glucose- derived hydrochars, and tested for the selective production of p,p'-diphenolic acid in batch and continuous reactors. Under the best reaction conditions, in batch reactors p,p'-diphenolic acid yields about 20-25 mol% were reached, whereas in continuous reactors very high selectivity, equal to 85 mol%, were obtained toward the target isomer p,p'-diphenolic acid. At the same time, the Life Cycle Assessment evaluation was performed to compare environmental impacts associated to the new developed preparation of diphenolic acid in batch with those of the consolidated process which involves mineral acids as catalysts.