Challenge

Menthol is one of the most economically important monoterpenes and is used in pharmaceuticals, cosmetics, toothpaste, and chewing gum production. L-(-)-menthol is the menthol isomer responsible for the typical menthol taste. At present, it is mainly obtained from mineral oil. A renewable raw material that would be suitable as a starting material for L-(-)-menthol production is turpentine oil, which is a waste product from paper production. More specifically, a component of turpentine oil called 3-carene could be used for this purpose. Developing a method to process a natural product that consists of a large number of compounds with similar boiling points is, however, challenging. In addition, the composition of this starting material can vary considerably.

Goals and procedure

The aim of the Waste2Menthol project is to develop a thermal separation process that enables the extraction of 3-carene as a starting material for menthol synthesis with high yield and purity from turpentine paper industry waste. In addition, a technical synthesis process for the production of menthol based on 3-carene will be developed and investigated. Thermal separation is to be conducted in a sustainable manner, i.e. with minimized energy requirements. As energy requirements and operational effort increase disproportionately with the desired purity and yield, the aim is to find an optimum for these variables. Organophilic nanofiltration will also be used in the process; this novel membrane process can separate large molecules in advance and thus relieves the subsequent counterflow distillation. A further step in the project is to identify the most suitable starting material because turpentine oil is produced in varying quality during the different steps of cellulose processing.

Innovations and perspectives

With the results from the Waste2Menthol project, a renewable raw material could replace mineral oil as a precursor in L-(-)-menthol production. The production process is, moreover, not in competition with food production as the raw material is a mere waste product from the paper industry. From an ecological, economic, and social point of view it is therefore an ideal starting material.

The project partners estimate the economic prospects for success as good. The results of the project are to be exploited through patents and communicated through publications in specialist journals. In addition, the project partners are continuously examining whether there are useful applications for other components of the starting mixture that cannot be converted into L-(-)-menthol.