Modification And Pervaporation On Desulfurization Performance Study Of PEG/PVDF Composite Membrane

In the modern society,more and more motor vehicles resulted in antomobile emissions of toxic gases such as SOx and the like,which can not only damage the human’s health,but also pollute the environment seriously.According to the report in 2014,the regulation of sulfur content in gasoline was restricted to less than 10 ppm in china,but the current sulfur content in China’s gasoline is much higher than 10 ppm.Therefore,it must be intensified to develope new and more efficient desulfurization technology.Pervaporation,as a new separation technology with many potential advantages,has been widely used to separate liquid mixtures.In the pervaporation process,the membrane is the core component of the separation.In this paper,polyethylene glycol(PEG),which has a good effect on removing thiophene from gasoline,is selected from the membrane material as the separation active layer.Then the PEG membrane was further modified to improve the desulfurization performance.First of all,the effect of PEG molecular weight on desulfurization performance of PEG composite membranes was studied.We prepared PEG/PVDF composite membranes of three different molecular weights for separating organosulphur compounds from simulated gasoline solution by pervaporation.All the PEG/PVDF composite membranes were systemly characterized by Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),X-ray diffraction(XRD),and positron annihilation spectroscopy(PAS).A mixed solution of thiophene,2-methylthiophene and 2,5-dimethylthiophene with n-heptane was used as a simulated gasoline system,the effects of operating temperature,feed sulphur content,and organosulphur species on performance of PEG/PVDF composite membranes with different molecular weights were investigated.The results showed,when the feed organosulphur was thiophene,the permeate fluxes decreased with an increase in PEG molecular weight.PEG membrane with molecular weight of 35000 exhibited the optimum desulfurization performance,the enrichment factor was 12.59 for thiophene when the temperature is 85 ℃.When the feed.organosulphur was 2-methylthiophene or 2,5-dimethylthiophene,it was found that the PEG membrane with molecular weight of 100000 showed the higher enrichment factor.The results showed that PEG molecular weight has a considerable effect on separation performance for pervaporation desulphurization.Then,the PEG/PVDF composite membrane was modified by physically filling inorganic particles.We prepared AC-PEG/PVDF hybrid membranes with different activated carbon(AC)loading.All the AC-PEG/PVDF hybrid membranes were systemly characterized by Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),X-raydiffraction(XRD)and Raman spectra.The thiophene/n-heptane mixture was used as a simulated gasoline system,the effects of different operating conditions on desulfurization of membranes were studied.The results showed that the total flux of all the AC-PEG/PVDF hybrid membranes were all improved under each conditions,and with litter fluctuations in sulfur enrichment factor when diverse concentrations of activated carbon were added.Specifically,when the content of activated carbon is 5%and the temperature is 85 ℃,the permeation flux and sulfur enrichment factor of the unfilled PEG/PVDF membrane were improved to 1.14 kg·m-2·h-1 and 9.47 respectively.This indicates that the desulfurization performance of PEG/PVDF composite membrane can be improved significantly at the appropriate amount of activated carbon.