Selective Adsorption Of Thiophenic Compounds From Fuel Over Y Zeolite-based Adsorbents And Regeneration By Non-thermal Plasma Processing

Selective adsorption, as one of the promising new approaches for deepdesulfurization, has attracted more and more attention, because it does not need toconsume H₂ and can be performed at ambient temperatures and pressures. In thisdissertation, a series of single-metal exchanged Y zeolites and co-metal exchanged Yzeolites were prepared by microwave promoted liquid ion-exchange method, then thephysical and chemical characteristics of the adsorbents, adsorption properties of sulfurcompounds and adsorption mechanism were systematically studied. Also,investigation of regeneration of adsorbents by non-thermal plasma processing wasconducted.Firstly, several single-metal exchanged Y zeolites, namely H, Co, Ni, Cu, Zn, Ag,La and Ce-Y based on Na-Y, were prepared and evaluated for the adsorption ofthiophene from model fuel using dynamic monocomponent and competitiveadsorption experiments. The physical and chemical characteristics of the adsorbentsas well as desorption behaviors of thiophene from adsorbents by means oftemperature-programmed desorption technique, were also investigated. The resultsindicated that the increase of Lewis acid sites and the enhancement of soft acid of thezeolites would benefit to the removal of thiophene from model fuel. Both Cu-Y andAg-Y zeolites showed an excellent desulfurization performance, with comparablyhigher adsorption capacity and better adsorption selectivity. Then Cu-Y and Ag-Yzeolites were further studied, and it was showed that the binding affinity of thiopheneon the sorption sites on Cu-Y zeolites followed an order of Cu(â… )> Cu(â…¡)> Cu⁰ and onAg-Y zeolites followed an order of Ag⁰> Ag(â… ).Based on the research of single-metal exchanged zeolites for desulfurization,several co-exchanged Y zeolites, namely Ag/Ni-Y, Ag/Zn-Y, Ni/Zn-Y, Cu/Ni-Y,Cu/Zn-Y and Cu/Ag-Y, were prepared and evaluated for the adsorption of thiophenefrom model fuel. It was found that the modification of Y zeolites with Cu and Ag hadsynergistic effect on the adsorption of thiophene from n-heptane and the interaction between thiophene and Ag-Y zeolites seems to be governed by S-M interaction. Ascompared to Cu-Y zeolites and Ag-Y zeolites, refractory sulfur compounds could beremoved more effectively on Cu/Ag-Y zeolites and phenyl compounds had lessinfluence on the desulfurization process, probably due to the synergistic interactionbetween Cu and AgThen the Cu/Ag-Y zeolites saturated with organosulfur compounds wereregenerated by non-thermal plasma processing. The operation parameters,regeneration mechanism in addition to regeneration constancy were studied It wasfound that the adsorbents could be well regenerated in afterglow area at 60℃with 60ml/min flowing oxygen when the input power was 95 W. Ozone plays a dominant rolein the oxidative degradation of sulfur compounds adsorbed on Cu/Ag-Y zeolites.However, the role of other active species can not be neglected. Compared to thermalregeneration and extraction regeneration methods, adsorbents treated withnon-thermal plasma can recover its adsorption property in a shorter time, and also thismethod can maintain its adsorption property after several cycle usages.Finally, quantum chemical parameters were calculated by the density functionaltheory (DFT) method with Gaussian 03 W. The correlation of the logarithm value ofk' and structure parameters were researched and quantitative structure propertyrelationship (QSPR) model was developed credibly The model showed that theE_LUMO had a greater influence on the degradation of organosulfur compounds onzeolites, followed byχ,ZPE and E_HOMO. The model could acceptably predict thedegradation of different organosulfur compounds on Cu/Ag-Y zeolites.