Method for separating straight-chain conjugated diene
The present invention provides a method for selectively separating a straight-chain conjugated diene with high purity from a mixture containing the straight-chain conjugated diene and at least one type of straight-chain olefin. The method involves separating the straight-chain conjugated diene from the mixture containing the straight-chain conjugated diene and the straight-chain olefin using a zeolite membrane composite. The composite contains a porous support and a zeolite layer formed on the surface and in the fine pores of the support, and the zeolite contains an alkali metal cation.
1. A method for separating a straight-chain conjugated diene comprising separating the straight-chain conjugated diene from a mixture of the straight-chain conjugated diene and at least one type of straight-chain olefin using a zeolite membrane composite comprising a porous support and a zeolite layer formed on the surface and in fine pores of the support wherein the zeolite comprises an alkali metal as a cation.
2. The method for separating a straight-chain conjugated diene according to claim 1 wherein the zeolite comprises a faujasite type zeolite.
3. The method for separating a straight-chain conjugated diene according to claim 1 wherein the alkali metal is at least one type selected from Na, K, Rb and Cs.
4. The method for separating a straight-chain conjugated diene according to claim 1 wherein the alkali metal consists of Na and Cs.
5. The method for separating a straight-chain conjugated diene according to claim 1 wherein the Cs/Na molar ratio of the alkali metal is from 0.1 to 1.5 mol/mol.
6. The method for separating a straight-chain conjugated diene according to claim 1 wherein the straight-chain conjugated diene is butadiene.
7. The method for separating a straight-chain conjugated diene according to claim 1 wherein the zeolite membrane composite has a 1,3-butadine/1-butene separation coefficient of 1.4 or greater at 60° C.
8. The method for separating a straight-chain conjugated diene according to claim 1 wherein the faujasite type zeolite is a Y-type zeolite.
9. The method for separating a straight-chain conjugated diene according to claim 1 wherein the separation is carried out in coexistence of an inorganic gas with the mixture.
10. The method for separating a straight-chain conjugated diene according to claim 9 wherein the inorganic gas is at least one type selected from helium, argon, nitrogen, hydrogen, carbon monoxide, carbon dioxide and oxygen.