Novel Membranes for Olefin/Paraffin Separation

Ethylene and propylene are major chemical industry raw materials and consume a great deal of energy related to their production. It is estimated that 230 trillion BTU/yr are consumed in olefin/paraffin separations. Significant energy consumption is employed when cryogenically separating ethane from ethylene and propane from propylene. These cryogenic separations are difficult and are both capital and energy intensive. Membrane processes have been previously evaluated for separating ethylene/ethane or propylene/propane. While somewhat encouraging results have been demonstrated, stability problems have led to systems that have been unable to maintain performance. In many cases the use of silver (Ag+) salts were used to preferentially transport the ethylene or propylene. It is proposed to combine the stability features and high gas transport of Compact Membrane Systems proprietary membrane with the high selectivity of Ag+ salts. The membranes have demonstrated superb chemical and thermal stability with the highest gas transport of any known stable polymer. CMS has identified routes to adding Ag+. The introduction of Ag+ sites is likely to result in dramatically higher ethylene and propylene transport and also significant increases in ethylene/ethane and propylene/propane separation. We have demonstrated the feasibility of all the key elements for developing novel gas separation membranes. Key building blocks for program success include membranes that gave excellent results for the separation process of interest. Engineering and economic analysis projections showed that a process combining distillation and membrane separation would result in annual energy savings ranges from 16.8 to 45.6 trillion Btu per year. The resulting membrane/distillation hybrid process offers an energy savings of 15% to 23%, a return on investment up to 67% with a payback time of 1.3 years. In Phase II membranes will be optimized and larger size membrane devices will be fabricated. Testing will be carried out for ruggedness and stability of the membrane for an extended period of time. Membrane performance will be demonstrated at an industrial site and the process via engineering and economic evaluation will be verified. Commercial Applications or other Benefits: CMS has membranes with outstanding olefin/paraffin separation and flux. Economic and engineering analysis of these CMS membranes in a retrofit mode to be added to existing ethylene or propylene plants has projected energy savings of over 40 trillion BTU/yr and reduced separation costs by over $4.00 per 1000 pounds (or more than 12% of the separation costs).