Abstract

In this work, sulfonated expanded polystyrene waste (WEPS), obtaining from recycling of the expanded polystyrene (EPS) waste by low-cost sulfonation reaction, were successfully applied as environmentally benign acid solid in the liquid-phase cyclization of (+)-citronellal (1), under mild reaction conditions. (-)-Isopulegol (2) and (+)-neoisopulegol (3) were obtained with a total yield equal to 80%. Products 2 and 3 have direct industrial application in the composition of fragrances and flavorings. (-)-Isopulegol is also used as a synthesis intermediate of (-)-menthol. It was not observed the leaching of acid sites from WEPS to reaction solution, thereby, this process presented heterogeneuos nature. The WEPS was stable in the reaction medium and presented little significant loss of its performance in consecutive reactions of its reuse. In addition, WEPS showed better performance than commercial resin Amberlyst-15, in the same reaction conditions. The use of WPES as acid solid in reactions of industrial interest is an attractive, low-cost and environmentally friendly alternative for application of this material, obtained by recycling EPS waste, for adding value to natural ingredients obtained from biomass.

Graphic Abstract

中文翻译：

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磺化膨胀聚苯乙烯废料促进（+）-香茅素环化反应：生物量平衡的可持续替代方法

摘要

在这项工作中，通过低成本的磺化反应回收膨胀聚苯乙烯（EPS）废料获得的磺化膨胀聚苯乙烯废料（WEPS）作为环境良性酸固体成功地应用于（+）-香茅醛的液相环化中（1）在温和的反应条件下。获得（-）-异胡薄荷醇（2）和（+）-新异胡薄荷醇（3），总产率等于80％。产品2和3在香料和调味剂的组成上有直接的工业应用。（-）-异薄荷醇也用作（-）-薄荷醇的合成中间体。没有观察到酸性位点从WEPS到反应溶液中的浸出，因此，该过程呈现出异质性。WEPS在反应介质中是稳定的，并且在其重复使用的连续反应中几乎没有明显降低其性能。此外，在相同的反应条件下，WEPS的性能优于市售树脂Amberlyst-15。在工业上感兴趣的反应中，将WPES用作酸性固体是一种有吸引力的，低成本和环保的替代方法，可用于通过回收EPS废料而获得的这种材料的应用，以增加从生物质获得的天然成分的价值。

图形摘要