Experimental kinetic analysis of ethylene absorption in ionic liquid [Bmim]NO3 with dissolved AgNO3 by a semi-continuous process

The ability of silver ions to form reversible π-bond complexation with unsaturated hydrocarbons can be utilized to separate olefins from paraffins using a solution of AgNO3 dissolved in an ionic liquid (IL). The process is suggested because of zero vapor pressure of the solvent, which results in higher purity of the separated product in comparison to when an aqueous AgNO3 solution is applied. In the present study, 1-butyl-3-methylimidazolium nitrate ([Bmim]NO3), an IL that can dissolve AgNO3, is applied as the solvent. The absorption of ethylene from a gaseous mixture of ethylene/ethane with constant flowrate in the silver nitrate dissolved media is investigated in silver nitrate concentrations of 1, 2 and 5 M, and temperatures within the range of 5–35 °C. The absolute absorptivity of ethylene is increased from 1.12 to 5.68 g l−1 at 25 °C when the concentration of AgNO3 is increased from 1 to 5 M. Maximum absorption of ethylene is found at near ambient temperatures (15 °C). The absorption selectivity of ethylene to ethane increases with increase of AgNO3 concentration and decrease with increasing temperature. The capacity of ethylene absorption in the reactive media at 25 °C and 5 M concentration of AgNO3 is about 0.43 of that for the aqueous AgNO3 solution. The results of an applied theoretical model for prediction of total ethylene absorption can be verified by the experimental results.