Ethylene and Propylene are two primary feedstocks for manufacture of petrochemicals. Therefore, there is significant economic benefit in increasing capacity of existing distillation operations while simultaneously reducing costs. Existing distillation for separation of olefins from paraffins (e.g., propylene from propane) is very difficult requiring large distillation columns and significant energy consumption. In principle membranes are small and should be easily retrofitable into distillation columns.
A hybrid distillation-membrane process that can efficiently separate and recover the olefin from the paraffin would provide substantial economic benefit to these polymerization processes. Membrane processes have been previously evaluated for separating ethylene/ethane or propylene/propane. In many cases, silver salt facilitating agents have been incorporated into membranes to preferentially transport ethylene or propylene. Historically with earlier membranes, while good separations have been initially demonstrated in the laboratory, membrane stability problems have prevented development of commercial systems.
Using customized amorphous fluoropolymer (CAF) membranes, Compact Membrane Systems has developed stable olefin-paraffin separation membranes with very good propylene flux and propylene/propane selectivity. The permeance and selectivity combination of the membranes are above the industry Robeson curve. In addition results were stable when exposed to high levels of conventional foulants (e.g., sulfur containing gases) in the laboratory. Using basic data from these laboratory results payback times for hybrid distillation-membrane processes were calculated to be less than 1-2 years. Laboratory experimental data and hybrid distillation –membrane system modeling results will be discussed more extensively at the presentation.