Efficient and reversible separation of NH3 by deep eutectic solvents with multiple active sites and low viscosities

Abstract

The efficient separation and collection of ammonia (NH3) during NH3 synthesis process is essential to improve the economic efficiency and protect the environment. In this work, ethanolammonium hydrochloride (EtOHACl) and phenol (PhOH) were used to prepare a novel class of deep eutectic solvents (DESs) with multiple active sites and low viscosities. The NH3 separation performance of EtOHACl + PhOH DESs was analyzed completely. It is figured out that the NH3 absorption rates in EtOHACl + PhOH DESs are very fast. The NH3 absorption capacities are very high and reach up to 5.52 and 10.74 mol·kg−1 at 11.2 and 100.4 kPa under 298.2 K, respectively. In addition, the EtOHACl + PhOH DESs present highly selective absorption of NH3 over N2 and H2 and good regenerative properties after seven cycles of absorption/desorption. The intrinsic separation mechanism of NH3 by EtOHACl + PhOH DESs was further revealed by spectroscopic analysis and quantum chemistry calculations.