Seeded-gel synthesis of SAPO-34 single channel and monolith membranes, for CO2/CH4 separations

Abstract

▸ SAPO-34 zeolite membranes were synthesized on 7-channel alumina monolith supports. ▸ The membranes had high CO 2 /CH 4 selectivities even at high pressures. ▸ SAPO-34 seeds were added to the synthesis gel instead of seeding the support surface. ▸ Seeding the gel simplified synthesis and improved reproducibility. SAPO-34 zeolite membrane synthesis was scaled up by preparing membranes on seven-channel monolith alumina supports. These monoliths have CO 2 permeances and CO 2 /CH 4 separations selectivities at 4.6 MPa feed pressure that were similar to SAPO-34 membranes on single channel supports. They also exhibited the same pressure dependence. SAPO-34 membrane preparation was improved by adding SAPO-34 seed crystals to the synthesis gel instead of placing seeds on the support surface. Membranes prepared by seeded-gel synthesis had higher CO 2 permeances, higher CO 2 /CH 4 separation selectivities, and smaller standard deviations for these values. Using seeded-gel synthesis also decreased the number of synthesis steps, but increased the amount of seeds needed by two orders of magnitude.