Gas separation using molecular sieve SSZ-74

In a process for separating gasses using a membrane containing a molecular sieve, the improvement comprising using as the molecular sieve a crystalline molecular sieve having a mole ratio greater than about 15 of (1) an oxide of a first tetravalent element to (2) an oxide of a trivalent element, pentavalent element, second tetravalent element which is different from said first tetravalent element or mixture thereof and having, after calcination, the X-ray diffraction lines of Table II.