A novel catalyst-free pyrolysis process of poly-3-hydroxybutyrate (PHB) to crotonic acid (CA) in inert nonpolar solvents was developed. After a simple consecutive process of reaction (210 oC for 5 h...

With the threat of ‘white pollution’, the large‐scale production and application of biodegradable plastics have become crucial. Poly‐3‐hydroxybutyrate (PHB) is the simplest and most used member of the polyhydroxyalkanoate family, with a uniform C4 structural unit (C4H6O2). To reduce the impact of PHB on waste treatment, various recycling strategies have been developed for the tailored conversion of PHB to targeted chemicals and fuels. Given the special structural unit, PHB and its plastic forms have the potential to serve as a sustainable feedstock for producing a series of value‐added chemicals and fuels, including (i) crotonic acid via pyrolysis, (ii) (R)‐β‐hydroxybutyric acid via hydrolysis, (iii) propylene via depolymerization and decarboxylation, (iv) liquid fuels via deoxygenation and oligomerization, (v) n‐biobutanol via catalytic hydrogenolysis, (vi) methyl crotonate via thermolysis and esterification, (vii) (R)‐3‐hydroxybutyrate methyl ester via catalytic methanolysis, and (viii) β‐aminobutyric acid via ammonolysis. This review article provides a systematic review focusing on the reaction pathways, primary applications and market potential of the target products, and the pros and cons of current bio‐refineries in comparison with conventional petroleum refineries. The thermochemical processes developed for PHB degradation and polypropylene (a typical petroleum‐derived plastic to be replaced by PHB) are also comprehensively evaluated to reveal the future opportunities and challenges of PHB's broad‐scale production and utilization. PHB‐derived chemicals and fuels have a mature market already, and it is confirmed that the tailored valorization of PHB is a promising pathway to expand the market and gain more environmental and energy benefits. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

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The valorization and recycling of bioderived polylactic acid (PLA) have garnered significant attentions. In this study, a pioneering approach using hydrogen bromide (HBr) catalysis for the degradation of PLA to 2-bromopropionates and lactates is presented. Both HBr solution and HBr-HAc (acetic acid) solution were found to be efficient for the process. Notably, the HBr solution predominantly yields lactic acid (LA) with an exceptional yield of ≥ 99 mol% at temperatures ranging from 80 to 110 oC. Conversely, the HBr-HAc solution yields both 2-bromopropionic acid (2BA) and LA, with 2BA yield achieving a remarkable yield of 55.2 mol% at 100 oC. Subsequently, esterification of the PLA derived 2BA and LA was conducted, and a serious of 2-bromopropionates and lactates were synthetized. Furthermore, the impact of reaction factors was investigated via multivariate analysis methods.

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