Sustainable production 3-bromobutyrates and 3-hydroxybutyrates from bioderived poly-3-hydroxybutyrate

Abstract

The efficient and effective degradation of bio-polymer poly-3-hydroxybutyrate (PHB) has emerged as a prominent research focus. In this investigation, we explored the valorization of PHB to 3-bromobutyrates and 3-hydroxybutyrates employing hydrogen bromide (HBr) as a catalyst at relatively mild temperatures (70–110 °C). Comprehensive investigations were conducted on reaction solvent systems (HBr solution and HBr-HAc (acetic acid) solution) along with process parameters. The impact of these variables is systematically assessed using JMP13 software. In the HBr solution, both 3-hydroxybutyric acid (3HA) and 3-bromobutyric acid (3BA) are identified as the primary products. Remarkably, a high 3HA yield of up to 96.3 mol% is achieved at 70 °C, while the 3BA yield remains below 52 mol% within the tested temperature range. Conversely, the HBr-HAc solution yields a favorable 3BA (>99 mol%). Furthermore, we demonstrate a strategy for synthesizing various 3-bromobutyrates through a tandem degradation-esterification process. The utilization of HBr catalysis presents compelling advantages, including a straightforward process conducted under mild conditions, facilitating the complete degradation of PHB into the desired target products with notably high molar yields.