Continuous synthesis of NaA zeolite membranes

Zeolite NaA membranes were obtained by using a continuous recirculating flow, 0.25–5 ml min−1 of synthesis solution along the inner side of asymmetric porous alumina tubular supports. The membranes of 5 μm in thickness showed a N2 permeance of 5 × 10−7–1 × 10−6  m−2 s−1 Pa−1. The procedure developed in this work provides control of the synthesis and crystallization conditions at any position on the tubular support, thus implying scale-up.