Activation procedure to unleash the power of N2-selective ETS-4 membranes for CH4 upgrading

Abstract

Abstract Microporous ETS-4 zeotype, with its 4Å pore openings, is an adequate material for the kinetic separation of nitrogen from methane. Small-sized ETS-4 was synthesized by a novel method and then utilized as membrane seeding powder. High-quality and uniform ETS-4 membranes were fabrucated utilizing a new recipe and the secondary growth approach on α-alumina supports. XRD, FESEM, and EDX studies were used to analyse the synthesized ETS-4 powder and membranes. The effect of membrane activation temperature (80–140 ºC) on permeance was evaluated. In addition to N2 and CH4, the membrane permeance was also evaluated for O2 and Ar gases. N2 permeance increased gradually as the activation temperature was raised in the 80–120 ºC range, reaching its highest value (i.e., 2.6×10− 8 mol m− 2 s− 1 Pa− 1) after activation at 140 ºC. The permeances of pure N2 and CH4 gases were quantified through the ETS-4 membrane at 30, 50, and 70 ºC, and a pressure difference up to 600 kPa. N2/CH4 permselectivity of 75.19 ( N2 permeance of 1.94 × 10− 8 mol m-2 s− 1 Pa− 1 ) were measured at 30°C and 200 kPa of feed pressure, respectively, which is the highest N2/CH4 permselectivity among all membranes reported in the literature.