Designing ionic liquids to enhance ethylene/ethane separations

Abstract

Separation of light olefins from their paraffin counterparts has been described as one of the seven chemical separations to change the world. Global annual production of light olefins exceeds 200 million tons, about 30 kg for each person on the planet. The current method for their separation is cryogenic distillation, one of the most energy-intensive processes in the industry. Alternative methods focus primarily on forming stronger interactions on either the olefin or paraffin. For the paraffin this is typically through physical interactions (physisorption), and for the olefin this can be physical interactions but also chemical interactions (chemisorption).One class of alternative sorbents are ionic liquids. So far, physisorbent ionic liquids have not demonstrated sufficient efficiency in either selectivity or capacity to compete with current technologies. Complexation of ethylene through its double bond with silver and copper ions has been used in the literature for chemical separation of olefins and paraffins. However, other components of raw gas feeds, such as acetylene, can react with the silver and become explosive. This has prevented the uptake of these materials into large scale processes.The objective of this work is to develop and try to create new chemisorbent materials for the separation of light olefins and paraffins; to achieve high capacity combined with selectivity for ethylene. Several groups of ionic liquids have been investigated including phosphorous containing ionic liquids, nitrile based ionic liquids (including cyanopyridinium ionic liquids) and ionic liquids mixed with metal species. This will involve the investigation of ethylene and ethane solubility and interactions in these ionic liquids, using characterisation studies including nuclear magnetic resonance spectroscopy (1D/2D spectras), thermal analysis, and viscosity/density measurements.

Date of Award	Dec 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Engineering and Physical Sciences Research Council
Supervisor	John Holbrey (Supervisor) & Leila Moura (Supervisor)