NOVELTY - A porous support is provided and silicoaluminophosphate-34 synthesis mixture comprising aqueous silicoaluminophosphate-34 forming gel and silicoaluminophosphate-34 crystals having average size of 50-5000 nm is prepared. At least one surface of the porous support is contacted with the synthesis mixture. Then, porous support and synthesis mixture are heated, to obtain continuous layer of silicoaluminophosphate-34 crystals on the surface of the support. The silicoaluminophosphate-34 layer is heated and templating agent is removed, to obtain crystalline silicoaluminophosphate-34 memrane.    USE - Preparation of crystalline silicoaluminophosphate-34 membrane used for separating gas components e.g. separating carbon dioxide and methane (all claimed).    ADVANTAGE - The crystalline silicoaluminophosphate-34 membrane having excellent selectivity and permeance performance is prepared.    DETAILED DESCRIPTION - A porous support is provided and silicoaluminophosphate-34 synthesis mixture comprising aqueous silicoaluminophosphate-34 forming gel and silicoaluminophosphate-34 crystals having average size of 50-5000 nm is prepared. At least one surface of the porous support is contacted with the synthesis mixture. Then, porous support and synthesis mixture are heated at 450-515 K for less than 20 hours, to obtain continuous layer of silicoaluminophosphate-34 crystals on the surface of the support. The silicoaluminophosphate-34 layer is heated and templating agent is removed, to obtain crystalline silicoaluminophosphate-34 memrane. The gel comprises aluminum, phosphorus, silicon, oxygen and templating agent. The ratio of silicon and aluminum in gel is more than 0.1 to 0.6. The overall concentration of silicoaluminophosphate-34 crystals in the gel is 0.5-10 mg crystals per gram of gel. The average pore size of porous support at the surface is less than 5 microns. An INDEPENDENT CLAIM is included for method for separating gas component (g1) from gas mixture comprising gas component (c1) and gas component (c2), which involves providing membrane having feed and permeate side, applying feed stream comprising gas component (g1) and gas component (g2) to the feed side of the membrane and producing permeate stream enriched in the gas component (g1) from the permeate side of the membrane by providing driving force sufficient for permeation of the gas component (g1) through the membrane. The membrane is selectively permeable to the gas component (g1) over gas component (g2).