EXTRACTION OF R-(+)-LIMONENE FROM ORANGE PEELS: ASSESSEMENT AND OTIMIZATION OF THE GREENNESS OF TRADITIONAL EXTRACTION PROCESSES

This article reports a study, performed in educational context, to increase the greenness of the extraction of R-(+)-limonene from orange peels. Protocols from the literature were evaluated with the green star (GS)metric and new protocols, based in them, were designed to increase the overall greenness. These were tested in the laboratory and their greenness was assessed by traditional greenness metrics and metrics inspired in the industrial activity. Results showed that the steam distillation technique presents the largest overall greenness when evaluated by the GS, because organic solvents are not involved, but mass and energy metrics indicate that the extractions by solvent techniques are greener. This conflict denotes the complexity of the concept of chemical greenness and the need of using several types of metrics when greenness evaluation is at stake. The results show that the inclusion of experiments on the R-(+)-limonene extraction in the educational laboratory is efficient to show the difficulties of assessing the greenness of chemistry and of implementing Green Chemistry.

本文报道了一项面向教育场景开展的研究，旨在提升从橙皮中提取R-(+)-柠檬烯（R-(+)-limonene）的绿色性。研究采用绿色星级（Green Star, GS）指标对已有文献中的提取方案进行评估，并在此基础上设计新方案以提升整体绿色性。随后在实验室中对新方案进行测试，并通过传统绿色性指标以及源自工业活动的指标评估其绿色性。研究结果显示，采用GS指标评估时，水蒸气蒸馏法整体绿色性最优，因其未使用有机溶剂；但从物质与能量指标来看，溶剂萃取法的绿色性更强。这一矛盾凸显了化学绿色性概念的复杂性，也说明在开展绿色性评估时，需综合运用多类指标。研究结果表明，在教育实验室中开设R-(+)-柠檬烯提取实验，可有效展现化学绿色性评估以及绿色化学实践所面临的诸多困境。