Ultrasonic-assisted secondary growth of deca-dodecasil 3 rhombohedral (DD3R) membrane and its process optimization studies in CO2/CH4 separation using response surface methodology

In the current work, the synthesis duration of DD3R membrane has been successfully reduced from 27 days to 3 days using DD3R seeds prepared in 1 day via ultrasonic irradiation coupled with conventional hydrothermal heating method. Two DD3R membranes have been grown on alpha-alumina support using vacuum-assisted seeding secondary growth method. A DD3R membrane has been synthesized in 2 days at 160 degrees C using DD3R seeds prepared in 1 day via ultrasonic irradiation coupled with hydrothermal heating method. Similarly, another DD3R membrane has also been synthesized in 2 days at 160 degrees C using DD3R seeds prepared in 25 days without ultrasonic irradiation pretreatment. Characterization tools including; XRD and FESEM confirmed the formation of DD3R topology for the resultant membranes. Subsequently, the effect of temperature, pressure and CO2 feed composition on the performance of resultant DD3R membrane in CO2/CH4 separation has been conducted based on the experimental conditions suggested by the statistical tool: response surface methodology. Overall, the single gas permeation result showed that high CO2 permeance of 2.46 x 10(-7) mol/m(2)sPa obtained in the present work was comparable with the CO2 permeance reported in the literature. Besides, DD3R membrane showed ideal CO2/CH4 selectivity about 5.22 which was also comparable with the results reported in the literature. In CO2/CH4 separation study, the experimental data were fitted well with the model suggested by response surface methodology, with R-2 value near to 0.99. The optimum condition for the separation has been obtained at temperature of 30.1 degrees C, feed pressure of 1 bar and CO2 feed composition of 10 vol% which yielded CO2 permeance, CH4 permeance and CO2/CH4 selectivity of 8.23 x 10(-8) mol/m(2)sPa, 4.64 x 10(-8) mol/m(2)sPa and 3.81, respectively. Thus, in the present study, it was concluded that the performance of DD3R membrane still need to be improved in order to meet the industrial requirement for CO2 separation from CH4. (C) 2016 Elsevier B.V. All rights reserved.