Pervaporation characteristics of PDMS/PMHS nanocomposite membranes inclusive multi-walled carbon nanotubes for improvement of acetic acid–methanol esterification reaction

Abstract

Cross-linked poly(dimethyl siloxane)–poly(methyl hydrogen siloxane) nanocomposite membranes selective to esters were prepared using different concentrations of multi-walled carbon nanotubes (CNTs) (0, 0.2, 0.5 and 1 wt%) and then used in the hybrid pervaporation reaction process. In this reaction, methyl acetate was produced by pervaporation–esterification reaction in a batch membrane reactor using heterogeneous catalyst of Amberlyst 15. The synthesized membranes were characterized by Fourier transform infrared spectroscopy, scanning electronic microscopy (SEM), X-ray diffraction and thermal gravimetric analysis. The SEM micrographs showed the nanometric distribution of the hybrid membranes. The thermal stability of the prepared membranes showed that the appropriate incorporation of CNT could improve the thermal stability of the prepared membranes. The effects of catalyst loading, CNT content in membranes, temperature and initial molar ratio of reactants were examined. Results showed that the flux and separation factor were varied depending on the studied parameters. Using the hybrid membrane with 0.2 wt% CNT content resulted in an acid conversion rate of 88.7% after 90 min, for an alcohol/acid molar ratio of 4:1 and with catalyst loading of 15 wt% relative to initial weigh of acid in the feed mixture at 50 °C.