Document Type : Research Paper
Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia. Via Elce di Sotto, 8, 06124 Perugia, Italy.
Dipartimento di Ingegneria, Università degli Studi di Perugia Via G. Duranti 93, 06125, Perugia, Italy.
The conversion of levulinic acid (LA) into alkyl levulinates is highly significant due to the wide range of applications for these products, including their use as fuel additives, solvents, and fragrances. In order to meet the growing need for environmentally friendly chemical production, this study takes a circular economy approach by upcycling a common urban waste, i.e., pine needles, to synthesize a robust heterogeneous acid catalyst, subsequently used to efficiently upgrade LA into levulinates. By utilizing a single-step procedure under mild operating conditions, the resulting PiNe–SO3H catalyst demonstrated good performances and flexibility in synthesizing diverse bio-derived levulinates. In fact, the catalyst showed an exceptionally broad range of applicability, resulting in isolated yields ranging from ̴ 46% to ̴ 93%, which is an unprecedented achievement. The catalyst's ability to be reused was tested, revealing remarkable performance for up to 10 consecutive cycles with negligible loss in efficiency. Additionally, a significant focus was directed towards developing a method that minimizes waste during the isolation process. This involved optimizing reaction conditions and rationalizing work-up procedures, resulting in low Environmental factor (E-factor) values ranging from 1.2 to 8.9. To comprehensively assess the overall environmental sustainability of the process, various additional green metrics were calculated, and the Ecoscale tool was employed as well. Furthermore, mechanistic investigations elucidated the favored reaction pathway, underscoring that, under the optimized conditions, the prevailing mechanism entails direct esterification, as opposed to the generation of a pseudo-ester intermediate.
- One-pot upcycling of urban waste pine needles into an efficient sulphonated catalyst achieved.
- The favored reaction pathway in alkyl levulinates synthesis was investigated.
- Good to excellent levulinates yields (46-93%) were obtained across a broad substrate range.
- Remarkable catalyst durability over a span of 10 consecutive cycles was demonstrated.
- Waste-minimized purification protocol through Amberlyst® A-21 pad was verified by green metrics.