Iman Tirooni - Faculty engineering, Ferdowci of Mashhad, Mashhad ,Iran
Majid Pakizeh - Faculty engineering, Ferdowci of Mashhad, Mashhad ,Iran
Morteza Sadeghi - Faculty of chemical engineering. Isfahan university of technology,Isfahan, Iran
Ali Jalali - Faculty of agriculture engineering. Tabriz university, Tabriz, Iran

Natural gas mainly Contains 70-95 percent methane, as well as Useful compounds such as ethane, propane and butane that come out of the well with methane. The transformations thesegases, due to the higher heating value than methane isbeneficial, therefore separation of these compounds from methane is remarkable in the industry. Today, membrane operations because of its benefits can be considered as a good alternative for gas separation, instead of conventional operations. On the other hand, appropriate Membrane selection for the desired operation, is so important due todiversity of membranes [1]. Dense polymer membrane is used for gas separation which is classified as two categories; Rubber and Glass membranes. Transportation properties in the rubber membrane is controlled by the solubility. The greater molecular size results in enhancement of the ability to passthrough the membrane. In this study gas separation using the Polyurethane rubber membrane on the base ofPolytetramethylene glycol (PTMG) was investigated.Polyurethane are the group of polymers that are considered as a membrane in the different separation fields, because of their good mechanical, chemical and thermal properties [2-3].