Sulfur removal from gasoline by pervaporation: The effect of hydrocarbon species

With the mixtures of different hydrocarbons and thiophene making up the model gasoline, PDMS membrane was used for sulfur removal from gasoline by pervaporation and the impact of different hydrocarbon species on the desulfurization efficiency was investigated experimentally. Experimental results of a series of alkane/thiophene mixtures indicated that, the total fluxes decrease with increase of carbon number in the alkane, while the enrichment factor of thiophene increases simultaneously. With the membrane having a normalized PDMS layer of 15 μm, the total flux for n-octane/thiophene mixture was measured to be about 1.04 kg m−2 h−1, with the corresponding enrichment factor of thiophene 4.4 at 31 °C. Compared with alkanes, one or more double bonds in olefin molecules would provide them with a plane geometry and certainly facilitate their transport through the dense membrane. Pervaporation results of n-hexene/n-hexane/thiophene demonstrated that, the rise of concentration of n-hexene in the feed leads to a larger total flux, but a smaller enrichment factor for thiophene at the same time. In addition, the similar framework and electronic properties of aromatics and the coexisting aromatic sulfur heterocycles would result in negative influence for this desulfurization process. Experimental results indicated that, with the increase of the content of toluene in toluene/n-octane/thiophene mixtures, the total flux would increase while the enrichment factor of thiophene would decrease. For this system, the coupling effect should be taken into consideration for the further understanding or mathematical simulation of the transport process.