Pervaporation and sorption behavior of zeolite-filled polyethylene glycol hybrid membranes for the removal of thiophene species

Polyethylene glycol (PEG)–CuY zeolite hybrid membranes were prepared for sulfur removal from gasoline feed. The sorption and diffusion behavior of typical gasoline components through the hybrid membranes has been investigated by systematic studies of dynamic sorption curves. Influencing factors including feed temperature, permeate pressure, and zeolite content in the membranes on membrane performance have been evaluated. Immersion experiments results showed the preferential sorption of thiophene, which is key in fulfilling the separation of thiophene/hydrocarbon mixtures. The sorption, diffusion, and permeation coefficients of gasoline components in filled membranes are higher than those in unfilled membranes. Pervaporation (PV) and gas chromatography (GC) experiments results corresponded to the discussions on dynamic sorption curves. PV experiments showed that lower permeate pressure meant higher separation performance. The optimum temperature occurred at 383 K, and an Arrhenius relationship existed between permeation flux and operating temperature. The CuY zeolite filling led to a significant increase of flux since the porous zeolite provides for more diffusion for small molecules in mixed matrix membranes. The sulfur enrichment factor increased first and then decreased with the increasing zeolite content, which was attributed to the combined influence of complexation force between CuY and thiophenes as well as the trade-off phenomenon between flux and selectivity. At 9 wt% CuY content, a higher permeation flux (3.19 kg/(m2 h)) and sulfur enrichment factor (2.95) were obtained with 1190 μg/g sulfur content level in gasoline feed.

Dynamic sorption curves for typical gasoline components in membranes: thiophene has higher sorption and permeation coefficients than hydrocarbons, which is key in fulfilling the separation of thiophene/hydrocarbon mixtures.Figure optionsDownload high-quality image (64 K)Download as PowerPoint slideResearch highlights
► Zeolite filling promotes permeation of small molecules in membrane.
► Higher sorption speed of thiophene than hydrocarbons is the key on their separation.
► Trade-off phenomenon exists for PEG/CuY hybrid desulphurization membranes.