Urban waste upcycling to a recyclable solid acid catalyst for converting levulinic acid platform molecules into high-value products

Abstract

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.

Sustainable Porous Heterogeneous Catalysts for the Conversion of Biomass into Renewable Energy Products

“…For instance, urban waste pine needles-derived acidic catalyst PiNe-SO 3 H has been used by Campana et al for producing a range of levulinates beyond ethyl levulinate (EL). 33 The performance and versatility of the PiNe-SO 3 H catalyst were outstanding, achieving remarkable isolated yields ranging from approximately 46% to 93% through a straightforward process conducted in mild operating conditions. This accomplishment stands as unprecedented within its field.…”

“…Municipal solid waste, including plastics, paper, and organic residues, can be transformed into functional catalysts through pyrolysis, activation, and surface modification techniques. − These catalysts exhibit superior catalytic activity, stability, and recyclability compared to traditional homogeneous or heterogeneous catalysts. For instance, urban waste pine needles-derived acidic catalyst PiNe-SO 3 H has been used by Campana et al for producing a range of levulinates beyond ethyl levulinate (EL) . The performance and versatility of the PiNe-SO 3 H catalyst were outstanding, achieving remarkable isolated yields ranging from approximately 46% to 93% through a straightforward process conducted in mild operating conditions.…”