Study On Preparation And Desulfurization Performance Of MOFs-polyethylene Glycol Mixed Matrix Membranes

Sulfur compounds in gasoline can converted into sulfur dioxide during combustion process,which causes great harm to the natural environment and human health.With the further restrictions on the sulfur content of gasoline in environmental protection laws in the world,the study of deep desulfurization technology has become an inevitable trend in gasoline-related industries.Nearly 80%of the vehicle blended gasoline used in China is catalytic cracking（FCC）gasoline,and the organic sulfur compounds in gasoline mainly come from FCC gasoline.Therefore,reducing the organic sulfur compounds in FCC gasoline is the key to the production of ultra-low sulfur gasoline.Pervaporation,as an emerging membrane separation technology,has received extensive attention for the desulfurization of gasoline because of its advantages of low energy consumption,flexible operation,low cost and environmentally friendly.Polyethylene glycol（PEG）is an excellent desulfurization membrane material due to its excellent characteristics such as easy film-forming properties,good mechanical strength,and satisfied pervaporation performance.Therefore,the metal-organic frameworks（MOFs）materials were selected as fillers to modify PEG membrane in this paper,which improved the desulfurization performance of the pristine PEG membrane.The metal-organic framework MOF-505 particles were synthesized and incorporated into the PEG matrix to prepare mixed matrix membranes.The as-synthesized MOF-505 particles were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared spectrum（FTIR）and N₂ desorption,and the structure and morphology of the composite membranes were characterized by XRD,FTIR,X-ray photoelectron spectroscopy（XPS）,SEM and positron annihilation spectroscopy（PAS）.Taking the thiophene/n-heptane binary system as simulated gasoline,pervaporation experiments were conducted to explore the effects of particle filling amount,operating temperature,sulfur content in feed liquid on membrane desulfurization performance.The results showed that the MOF-505/PEG separation layer and support layer were closely connected,and the introduction of MOF-505 increased the free volume of membrane separation layer.The operating conditions of the pervaporation experiment had a significant effect on the membrane performance.When the operating temperature was 75^oC and the feed concentration was 200 ppm,the membrane with 3 wt%MOF-505 showed the optimal desulfurization performance When the operating temperature was kept at 75^oC and the thiophene concentration in the simulated gasoline was 200 ppm,the 3-MOF-505/PEG membrane showed the best pervaporation performance.Compared with the pristine PEG membrane,the flux and the sulfur rich factor were improved by 158%and 25%,respectively.IFMC-16 particles were synthesized to prepare IFMC-16/PEG membrane by physical blending,which was used to separate thiophene/n-heptane simulated gasoline.The XRD,FTIR and N₂ adsorption-desorption were used to characterize the IFMC-16 particles,and the results showed that the IFMC-16 particles constructed by mixed ligands had larger BET surface area,pore volume and pore size than MOF-505.The IFMC-16/PEG membranes were characterized by XRD,FTIR,XPS and SEM,and the effects of particle amount and pervaporation experimental conditions on the desulfurization performance of the IFMC/PEG MMMs were investigated.It can be found from the results that the IFMC-16 particles filling amount of 4 wt%showed excellent permeability,the flux was 2.84 kg/（m²·h）,which was175%higher than that of PEG membrane,and the sulfur enrichment factor reflecting membrane selectivity was also increased by 59.8%.