Membrane Mediated Extraction Process for Olefin/Paraffin Separation

Ethylene and propylene, two of the most important building blocks of the U.S. petrochemical industry, are produced by steam cracking of ethane, propane, or heavier hydrocarbons and are also a by-product of fluid catalytic cracking. Unfortunately, as produced, these species are always in admixture with other species from which they must be separated. The conventional method of separation is cryogenic distillation, which is extremely energy intensive. In this project, the best features of liquid-liquid extraction and membranes will be combined into a novel membrane-mediated extraction (MME) process. The process will use complexing agents, which are commercially viable and for which their ability to extract olefins has been quantified; their use in a high-surface-area membrane module will enhance their extraction efficiency due to the increased transport area. During Phase I, selected solvents and complexing agents were synthesized and used in batch laboratory extractions. The effect of solvent type, complexing agent composition, feed molecular type, and other parameters were evaluated for the extraction of olefins of commercial interest. During Phase II, the nature of the molecular interactions between olefins of different size and specific complexing agents will be quantified. The optimum complexing-agent/solvent combination will be scaled up and used in a pilot plant, which will be constructed in Phase II. Commercial Applications and other Benefits as described by the awardee: The MME process could be used to effectively recover olefins from waste streams. Correspondingly, the first application for this process will be the recovery of valuable olefin from a waste stream produced by a major chemical company in Texas. The waste stream contains approximately 13 wt % of this olefin in an isoparaffininc solvent and is currently incinerated for lack of a cost-effective method of recovering the olefins. The process also provides environmental credits for eliminating incineration. Once demonstrated on a small scale for this application, the process would be expected to work well for ethane/ethylene or propane/propylene separation in steam cracking operations.