Synthesis And Desulfurization Performance Of Functional Silica Gel Modified By Polymeric Ionic Liquids

Sulfides from fossil fuels are converted to SOx during combustion and then discharged into the air,furthermore poison the catalyst of tail gas treatment and effect the performance of exhaust converters.At the same time,SOx is the main source of acid rain.Therefore numerous countries recently have mandated a reduction in the sulfur content of motor fuel.In this study,we tried a new method to synthesis an adsorbent which was supported by polymeric ionic liquids.Supported ionic liquids can form complexes by complexation of π-π with aromatic sulfur containing compounds.This approach overcomes many problems,for example,the large consumption of hydrogen,large investment in equipment.Desulfurization performance of the silica gel modified by supported ionic liquids was better than silica gel,which had been studied by our group.In order to improve the desulfurization efficiency,we tried to increase the loading amount of ionic liquids and then load polymeric ionic liquids on the surface of spherical silica gel.Silica gel supported by two types of polymeric ionic liquids – polymeric imidazolium ionic liquids(SPIm ILs-SG)and polymeric pyridine ionic liquids(SPPyILs-SG).Characterization with Fourier transform infrared,elemental analysis,scanning electron microscopy,energy dispersive spectroscopy,gel permeation chromatography,thermogravimetric analysis,and 13 C,29Si magic angle spinning nuclear magnetic resonance demonstrated that polymeric ionic liquids had successfully loaded on the surface of silica gel.Gel chromatography analysis showed that number average molecular weight of SPIm ILs-SG and SPPyILs-SG was 7852 g/mol and 21970 g/mol respectively.Their grafting density was 0.254 μmol/m2 and 0.127 μmol/m2 respectively.Thermal gravimetric analysis of SPImILs-SG showed its decomposition temperature was 350 ?C,which meant SPImILs-SG had high thermal stability.Effects of temperature,time,SPImILs-SG / SPPyILs-SG ratio to fuel on desulfurization rates were tested.Their optimum adsorption times were 0.5 h and 2 h respectively,the optimum temperature was 30 ?C,and SPImILs-SG / SPPyILs-SG to oil ratio was 1:10.Under the same experimental conditions,SPIm ILs-SG / SPPyILs-SG desulfurization rate order was 2-MTS < BT < DBT.Adsorption isotherms at different temperature of SPIm ILs-SG were investigated,and the experimental data were correlated by Freundlich、Langmuir、D-R and BET models.BET models fitted best,which suggested that the adsorption of SPImILs-SG for 2-MTS,BT and DBT were more prone to multi-layer adsorption.Thermodynamic study of the adsorption isotherm equation of SPImILs-SG suggested that adsorption processes were spontaneous,exothermic physical adsorption and entropy decreases at the test temperature.Adsorption isotherms at different temperature of SPPyILs-SG were investigated.Fitting adsorption isotherm with Freundlich、Langmuir、D-R and BET models,it could be find that Langmuir equation best suited,which suggested that SPPyILs-SG was prone to uniform monolayer adsorption.Thermodynamic calculations showed that the adsorption process of SPPyILs-SG for 2-MTS,BT and DBT was similar with SPIm ILs-SG.This was spontaneous,exothermic,entropy reduction process.The molecular of 2-MTS,BT and DBT tended to uniformly arranged on the surface of SPPyILs-SG.SPImILs-SG and SPPyILs-SG were regenerated by the method of soxhlet extraction with methanol as solvent.Recycling number of SPImILs-SG and SPPyILs-SG were 6 and 5 respectively.Desulfurization rates of BT and DBT were reduced with recycling,but the desulfurization rate of 2 – MTS was stable.