Tetraethylammonium Amino Acid Ionic Liquids and CO₂ for Separation of Phenols from Oil Mixtures

Abstract

Phenols have wide applications and much commercial value, and they are obtained from oil mixtures by separation. However, the previous separation agents have low separation efficiency or corrosive halide ions or are difficult to be regenerated. In this work, we designed several tetraethylammonium amino acid (TAAA) ionic liquids (ILs) without corrosive halide ions and found that the ILs could separate phenols from oil mixtures with much higher extraction efficiency and could be regenerated using CO2. The effects of separation time, initial phenol content, TAAA type, water content in TAAA, and phenol type on separation were investigated. It has been found that TAAA can separate phenols with high separation efficiencies, and the maximum separation efficiency of phenol can reach up to 99.0% at a TAAA:phenol mole ratio of 0.60. Meanwhile, ultimate phenol contents can reach as low as 1.40 g/dm3. The initial phenol content almost has no influence on the ultimate phenol contents. For real coal tar oil mixtures, the separation efficiency of phenols can reach up to 98.6%. The TAAAs can be regenerated and reused without significant decreases in separation efficiency of phenols. The separation mechanism has also been proposed based on chemical reactions.

Phenol Recovery from Aromatic Solvents by Formation of Eutectic Liquids with Trialkyl-2,3-dihydroxypropylammonium Chloride Salts

“…The addition of one molar equivalent of tributyl-2,3-dihydroxypropylammonium chloride (3) to a 0.1 M phenol solution in toluene resulted in an 84% extraction of phenol as the eutectic and a residual phenol concentration in the toluene phase of 0.016 M ([phenol] f inal = 1.5 g L −1 ). This compares favourably with the best recent data from the literature, where dicationic salts ([phenol] f inal = 3.9 g L −1 ) [17,18], zwitterionic betaines ([phenol] f inal = 4.8 g L −1 ) [19], and tetraethylammonium amino acid ionic liquids ([phenol] f inal = 1.4 g L −1 ) [14] have been developed.…”

“…To address these restrictions, a range of ionic liquids [14][15][16][17][18], zwitterions [19][20][21], pre-formed deep eutectic solvents [22], and other eutectic-forming hydrogen bond acceptors [23][24][25] have been explored. In particular, gemini dicationic salts [17,18] and choline chloride derivatives that incorporate a single longer alkyl-substituent (ethyl to octyl) [26] have been examined in order to enhance phenol extraction efficiency and selectivity while retaining the immiscibility of the formed eutectic with aromatic oils.…”

Halogen-free ionic liquids as high performance extractants for phenols separation

“…26,27 HFILs have been employed in many elds, especially in the absorption of NO, 28 CO 2 , 29,30 SO 2 , 31 or H 2 S 32 and the separation of organic compounds. 10,33 HFILs tend to show better performances than normal ILs in the eld of separation. In the structure of phenols, as we know, the O atom in the hydroxyl group shows strong electronegativity.…”

Ionic liquids and deep eutectic solvents for the recovery of phenolic compounds: effect of ionic liquids structure and process parameters

“…Different types of tetraethylammonium amino acid (TAAA) based ILs, having no corrosive halide, were synthesized for the extraction of phenol from the oil mixture. 183 The effect of process parameters such as extraction time, phenol concentration, ILs type, types of phenol, water contents in phenol on the extraction of phenol using amino acid-based ILs were investigated. The extraction efficiency of 99.0% was achieved using IL:phenol mole ratio of 0.60.…”