TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Composition: The gases or liquids comprise a mixture of at least one pair of gases chosen from nitrogen and oxygen, carbon dioxide and methane, and hydrogen and methane, a mixture of carbon monoxide, helium and methane, methane and at least one gas component selected from carbon dioxide, oxygen, nitrogen, water vapor, hydrogen sulfide, helium and other trace gases, hydrocarbon gases, carbon dioxide, hydrogen sulfide and their mixtures, mixture of olefin and paraffin, or mixture of isoparaffin and normal paraffin.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The blend polymer membrane is further crosslinked. The blend polymer membrane is further subjected to UV radiation or reaction with a chemical crosslinking composition. Preferred Polymer: The aromatic polyimide comprises several nitrogen-containing repeating units of formula (I).X1=aromatic group(s) of formulae (1-12), preferably group of formula (1-3);X2=cyclic group(s) of formulae (13-18);andR=-C(-CF3)(-CF3)-, -C(-CH3)(-CH3)-, -S(=O)(=O)-, -O-, -S- and/or their mixture.The secondary polymer is chosen from polysulfone, sulfonated polysulfone, polyethersulfone, sulfonated polyethersulfone, polyetherimide, or polyimide including poly(3,3',4,4'-benzophenone tetracarboxylic dianhydride-pyromellitic dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline), poly(3,3',4,4'-benzophenone tetracarboxylic dianhydride-pyromellitic dianhydride-4,4'-oxydiphthalic anhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline), poly(3,3',4,4'- diphenylsulfone tetracarboxylic dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline), poly(3,3',4,4'-benzophenone tetracarboxylic dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline), and poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-pyromellitic dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline). The secondary polymer is chosen from polysulfone, sulfonated polysulfone, polyethersulfone, sulfonated polyethersulfone, polyvinylpyrrolidone, polyetherimide, cellulosic polymer, polyamide, polyimide, polyamide/imide, polyketone, polyether ketone, poly(vinyl amide), poly(vinyl amine), poly(vinyl urethane), poly(vinyl urea), poly(vinyl phosphate), poly(vinyl sulfate), poly(benzobenzimidazole), polyhydrazide, polyoxadiazole, polytriazole, polycarbodiimide, polyphosphazene, and intrinsic microporous polymer. The aromatic polyimide is chosen from poly(2,2'-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane), poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane), poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-3,3'-dihydroxy-4,4'-diamino-biphenyl), poly(4,4'-oxydiphthalic anhydride-2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane), poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane), poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-3,3'-dihydroxy-4,4'-diamino-biphenyl), poly(2,2'-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride-3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane), poly(4,4'-oxydiphthalic anhydride-2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane-3,3'-dihydroxy-4,4'-diamino-biphenyl), poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane-3,3'-dihydroxy-4,4'-diamino-biphenyl), poly(2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-3,3'-dihydroxy-4,4'-diamino-biphenyl), and poly(4,4'-bisphenol A dianhydride-3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane).