Air Products and Chemicals, Inc.

Iosif Chernyakov

Alexander Schwarz

Thomas Hsiao-Ling Hsiung

James Hsu-Kuang Yang

A method for the separation and recovery of fluorochemicals from a gas stream containing a diluent gas and fluorochemicals by first contacting the gas stream with a membrane system in one or more stages where the membrane(s) is selectively more permeable to the diluent gas than the fluorochemicals to result in a permeate stream rich in diluent gas and retentate rich in fluorochemicals, thereafter subjecting retentate the gas stream to a purification by distillation or adsorption resulting in a product stream enriched in fluorochemicals and a purified diluent stream. The purified diluent stream is used as a purge stream and/or a recycle stream together with the permeate stream to a vacuum pump upstream of the membrane separation step. A product stream can be produced from a similar gas stream containing diluent gas and fluorochemical by an adsorption step combined with a subsequent distillation step where the purified diluent from the adsorption step is used as a purge stream and/or wholly or partial combined with a purified diluent stream from the distillation step as a recycle stream introduced into the process upstream of the adsorption step. Enriched fluorochemical and an enriched diluent streams can be produced from a stream containing diluent gas and fluorochemicals by cryogenic distillation with the enriched diluent stream recycled to the process upstream of the distillation step.

Recovery of perfluorinated compounds from the exhaust of semiconductor

A process for the separation and recovery of fluorochemicals from a gas stream containing a diluent gas and fluorochemicals by contact of the gas stream with a membrane system in combination with an adsorption system, the adsorption system used either before or after the membrane system. In either case the membrane portion of the combined system comprises the steps of: compressing a gas stream containing a diluent gas and fluorochemicals to an elevated pressure; heating the gas stream containing a diluent gas and fluorochemicals to an elevated temperature sufficient to increase the flux of the permeate stream and to increase the selectivity of the membrane for the permeation of the diluent gas relative to the permeation of the fluorochemicals; contacting the gas stream with a membrane which is selectively more permeable to the diluent gas than the fluorochemicals to result in a permeate stream rich in the diluent gas and a retentate rich in fluorochemicals; contacting the gas stream with one or more additional membranes which are selectively more permeable to the diluent gas than the fluorochemicals to result in a second permeate stream rich in the diluent gas and a second retentate rich in fluorochemicals; and recycling the second permeate stream to be compressed with the gas stream containing diluent gas and fluorochemicals to an elevated pressure.

A method for the separation and recovery of fluorochemicals from a gas stream containing a diluent gas and fluorochemicals by contact of the gas stream with a membrane, comprising the steps of: compressing a gas stream containing a diluent gas and fluorochemicals to an elevated pressure; heating the gas stream containing a diluent gas and fluorochemicals to an elevated temperature sufficient to increase the flux of the permeate stream and to increase the selectivity of the membrane for the permeation of the diluent gas relative to the permeation of the fluorochemicals; contacting the gas stream with a membrane which is selectively more permeable to the diluent gas than the fluorochemicals to result in a permeate stream rich in the diluent gas and a retentate rich in fluorochemicals; contacting the gas stream with one or more additional membranes which are selectively more permeable to the diluent gas than the fluorochemicals to result in a second permeate stream rich in the diluent gas and a second retentate rich in fluorochemicals; and recycling the second permeate stream to be compressed with the gas stream containing diluent gas and fluorochemicals to an elevated pressure. Preferably, the second retentate rich in fluorochemicals is further purified by adsorption or low temperature rectification to provide a fluorochemical-rich product stream and a diluent-rich vent stream.

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Fort Lee, NJ, United States of America

Iosif Chernyakov