Copper-Based Ionic Liquids For Ethylene/ Ethane Separations

The paraffin and olefins separation are of primary importance for the chemical industry because many mono-olefins such as ethylene and propylene are used for the production of polymers and other specialty chemicals. To achieve the required degree of separation, distillation towers with an enormous number of trays are required for separating the close boiling point mixture of olefin/paraffin that increases the capital and operational cost of a plant. If such a technique for olefin/paraffin separation is developed that is more efficient than cryogenic distillation, it certainly can save high capital and energy cost and holds a potential to apply practically. The olefin-metal π-complexes research certainly has a broad history of ethylene-ethane separation. Furthermore, ionic liquids have replaced traditional difficulties associated with organic solvents such as volatility and toxicity.This research was focused on the design of isochoric gas absorption equipment to study the separation of ethylene/ethane mixture by copper based ionic liquids having imidazolium and pyrrolidone cations. The different molar ratios of Cu (I) salt to each organic cation have synthesized three ionic liquids such as:1-butyl-3-methyl imidazolium chloride-cuprous chloride BmimCl-CuCl,2BmimCl-CuCl and 3BmimCl-CuCl; and:N-methyl pyrrolidone chloride-cuprous chloride HNMPCl-CuCl,2HNMPCl-CuCl and 3HNMPCl-CuCl. These ionic liquids have the advantage of stabilized Cu (I) that can selectively remove ethylene from the mixture of ethylene/ethane by the mechanism of π complexation. Moreover, the kinetics of absorption was also studied and absorption coefficients were calculated.The results have shown that ILs based on imidazole have higher separation efficiency for ethylene/ethane with BmimCl-CuCl performing the best. At 298K, and 0.8 Mpa, the selectivity and capacity of BmimCl-CuCl reached upto 7.1 and 1.18mol/L respectively. But at same temperature and pressure the selectivity and capacity of 2BmimCl-CuCl and 3BmimCl-CuCl was only 5.3,4.2 and 0.86mol/L,0.69mol/L respectively. The equilibrium rate constant of BmimCl-CuCl was 0.065/min at 298K but decreased to 0.147/min and 0236/min at 313K and 328K respectively. At 298K, and 0.8 Mpa, the capacity of three pyrrolidone based ionic liquids HNMPCl-CuCl, 2HNMPCl-CuCl, and 3HNMPCl-CuCl was around 0.35 mol/L indicating that Cu (I) concentration have no pronounced effect on ethylene absorption.