Synthesis Of Merrifield Resin Supported Ionic Liquids And Investigation Of The Desulfurization Properties

The emission of SOx in fuels combustion process contributes to acid rains, global warming effect and serious air pollution, so it is urgent to remove sulfides from fuels. Most of sulfides could be removed by traditional catalytic hydrodesulfurization, but it is a big challenge to remove the aromatic sulfides such as dibenzothiophene and their alkyl derivatives. Ionic Liquids(ILs) became “designer solvents” and showed remarkable sulphur extracting ability,but the operation is complex and the recycling is difficult. In this paper, the immobilized ILs was used as absorbent for desulfurization to overcome these problems, which provided a new way for desulfurization.Merrifield resin was used as solid support, four polymer-supported imidazole ionic liquids were synthesized and the structures were characterized by Fourier transform infrared,elemental analysis, 13 C solid state nuclear magnetic resonance spectroscopy, scanning electron microscope and energy dispersive spectrometer. The results suggested that the ILs had been immobilized on the support and the immobilization influenced the physicochemical properties and morphology of the support greatly.Taking these PSILs as absorbent, static and dynamic desulfurization experiments were investigated. The results suggested that PSILs could remove aromatic sulfides from model oil,and PS[unmim][BF4] with the longest alkyl chain showed the best surfur remove abilities.Adsorption time affected the desulfurization effciency, adsorption temperature and the initial surfur contents have little influence on the desulfurization effciency. Under the defined dynamic desulfurization experimental conditions, the break-through time of PS[unmim][BF4]on thiophene and dibenzothiophene was 30 min and 40 min, and the break-through capacity was 0.134% and 0.274% respectively.Absorption isotherms at different temperature of PS[unmim][BF4] on thiophene and dibenzothiophene were investigated, the adsorption experimental data were correlated byLangmuir, Freundlich and Sips models. Langmuir and Sips models fitted better, which suggested that the adsorption of thiophene and dibenzothiophene were more prone to uniform monolayer adsorption. From the calculation result of thermodynamic parameters, one can get the conclusion that the adsorption was a process of randomness decreased, exothermic physisorption, and the adsorption force was molecular interactions, thiophene adsorbed on PS[unmim][BF4] inclined to vertical adsorption and benzothiophene inclined to parallel. π-πinteraction and electrostatic attraction between PSILs and aromatic sulfides were used to explain the adsorption mechanism.The elemental analysis result of adsorbed PSILs suggested that ILs section of PSILs did not loss under the desulfurization operation. The adsorbed PS[unmim][BF4] was regenerated by the methods of vacuum drying at 80 ℃ and soxhlet extraction with methanol and ethylalcohol as solvents, vacuum drying could not regenerate the absorbent, soxhlet extraction with strong-polar methanol has better regenerative effect.Lastly, PSILs were improved with Zn2+ to enhance desulfurization abilities and found that the desulfurization abilities of improved PSILs were not obvious enhanced, this maybe because π-complexation of Zn2+ is not strong enough or the distribution of Zn2+ is too concentrated that the desulfurization active sites were covered.