Separation of p‐xylene from ternary xylene mixture using silicalite‐1 membrane: process optimization studies

BACKGROUND: The design of experiments (DoE) is applied to the process optimization of p‐xylene (pX) separation from its isomers m‐xylene (mX) and o‐xylene (oX) mixture using silicalite‐1 membrane supported on α‐alumina. A central composite design (CCD) coupled with response surface methodology (RSM) was used to correlate the effect of two separation process variables, temperature (150–250 °C) and pX feed partial pressure (0.10–0.26 kPa) to three responses: (i) pX flux; (ii) pX/oX separation factor; and (iii) pX/mX separation factor. The significant factors affecting each response were elucidated from the analysis of variance (ANOVA). The interaction between two variables was investigated systematically based on three‐dimensional response surface plots. RESULTS: The optimization criteria were used to maximize the value of pX flux, pX/mX separation factor and pX/oX separation factor. The optimum pX flux of 5.94 × 10^?6 mol m^?2 s^?1, pX/oX separation factor of 19 and pX/mX separation factor of 20 were obtained at a temperature of 198 °C and pX feed partial pressure of 0.22 kPa. CONCLUSIONS: The experimental results were in good agreement with the simulated values obtained from the proposed models, with an average error of ± 2.90%. In comparison with the conventional approach, DoE provides better flexibility of the process studies and a useful guideline for the membrane process operation for pX separation. Copyright © 2009 Society of Chemical Industry