1. Department of Chemical Engineering, Faculty of EngineeringFerdowsi University of Mashhad Mashhad P.O. Box 91775‐1111 Iran
2. Khorasan Razavi Gas Company Mashhad P.O. Box 4694‐11365 Iran
3. Advanced Membrane Technology Research Centre (AMTEC)Universiti Teknologi Malaysia Skudai Johor 81310 Malaysia
4. Department of Chemical and Biological EngineeringUniversity of Ottawa Ottawa K1N 6N5 Canada