Deep Deterpenation Of Citrus Essential Oils Via In-situ Formation Of Deep Eutectic Solvent

As the demand for natural products is increasing,essential oils,as a kind of natural product from plants,are widely used in spice,food,cosmetic and medicine industries due to their characteristic aroma,antioxidant,antibacterial and insecticidal properties.Among them,citrus essential oil is the most commonly used,where the main components are terpenes and oxygenated terpenes.Because the terpene contributes less to the aroma of essential oils and is unstable,it will affect the commercial value of essential oils.Therefore,deterpenation of essential oils(i.e.separating terpenes from oxygenated terpenes)is required to improve the content of oxygenated terpenes,which will improve the performance of essential oil products.The paper proposes a deep deterpenation method of the citrus essential oil,of which the process includes an associative extraction and a two-step reextraction.In this work,the citrus essential oil was simulated as a mixture of limonene(representing terpenes)and linalool(representing oxygenated terpenes).In the associative extraction,based on COSMO-RS calculations and associative extraction pre-experiments,tetrabutylammonium chloride(hydrogen bond acceptor)was selected as the associative extractant,and then this extractant was used to in-situ form a deep eutectic solvent(DES)with linalool(hydrogenbond donor),which enabled high efficient extraction of linalool with high selectivity.For the first-step reextraction,n-hexane was selected as the anti-extractant by COSMO-RS simulation,and five-stage cross-flow reextraction was utilized to completely remove limonene from the extraction phase(DES phase)of the associative extraction,which would achieved deep deterpenation.In the second-step reextraction,a two-phase system of n-hexane and water was used to extract linalool and tetrabutylammonium chloride in the DES phase,respectively.Then by vacuum distillation,linalool and tetrabutylammonium chloride were recovered from n-hexane and water,respectively.High-purity linalool(terpeneless product)was finally obtained with mass fraction of 98.76%and reusable tetrabutylammonium chloride was also acquired.The deep deterpenation process of citrus essential oils based on in-situ formation of deep eutectic solvent proposed in the work demonstrates excellent performance,which provides with a new technology for deterpenation process of essential oil and separation systems of natural products.