Synthesis, modification and gas permeation properties of DD3R zeolite membrane for separation of natural gas impurities (N2 and CO2)

Abstract

A good DD3R zeolite membrane layer was synthesized via secondary growth hydrothermal method, using a different procedure for preparing the membrane synthesis solution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated the formation of DD3R layer on the support. The defects formed in calcination step were blocked by surface treatment of the synthesized membrane via a simple coating technique using polydimethyl siloxane (PDMS) solution. SEM showed a good PDMS polymer coating on the surface of DD3R membrane. The gas separation properties of the membranes were extensively studied for gas permeation of CO2, N2 and CH4 and their mixtures with composition closed to natural gas composition. After applying PDMS, a considerable improvement of perm-selectivity for CO2/CH4 (0.6–220), CO2/N2 (0.8–28) and N2/CH4 (0.75–8) was observed. Furthermore, comparing these perm-selectivities with other modified DD3R membranes in literature showed better separation performance for our membrane both in the separation of CO2 and N2. The membrane selectivity for CO2/CH4 and N2/CH4 mixtures was 80–120 and 7–9 at room temperature respectively. The presence of different species in the binary and ternary mixtures have sufficient effects on the performance of modified membrane in the separation of natural gas impurities.