TiO_2-CeO_2光催化吸附协同脱除柴油中的有机硫

Synergy of photocatalysis and adsorption on TiO_2-CeO_2 for the removal of organosulfur compounds from diesel fuel

采用共沉淀法制备TiO_2-CeO_2光催化吸附脱硫材料,通过低温N2吸附脱附和X射线衍射等技术对TiO_2-CeO_2的物理化学性质进行了表征。结果表明,紫外光辐射显著提高了TiO_2-CeO_2的吸附脱硫性能;柴油中有机硫在TiO_2-CeO_2表面发生了光催化氧化转化为极性较强的砜类,可选择性地吸附在材料表面而被脱除。当TiO_2-CeO_2材料中钛铈物质的量比为9∶1、煅烧温度为500℃时,其光催化吸附协同脱硫效果最好;在紫外光辐射下反应5 h,油品中DBT的脱除率高达99.6%。TiO_2-CeO_2光催化吸附协同脱硫工艺可有效解决吸附脱硫工艺中芳烃竞争吸附导致吸附脱硫选择性低的问题;在模拟油品中添加质量分数为25%的甲苯,反应7 h后油品脱硫率仍高达96.6%。TiO_2-CeO_2对不同硫化物的光催化吸附协同脱硫效果顺序为:4,6-DMDBT>DBT>BT。TiO_2-CeO_2经四次再生循环使用后,脱硫率没有明显降低。

TiO2- CeO2 mixed oxides were prepared by urea gelation and co-precipitation method and then characterized by N2 sorption and X-ray diffraction （XRD）. The synergy of photocatalysis and adsorption on TiO2- CeO2 adsorbents for the removal of organosulfur compounds from diesel fuel was investigated. The results show that the UV irradiation can greatly enhance the adsorption of organosulfur in model fuel on TiO - CeO2; the organosulfur compounds is first photocatalytically oxidized to polar sulfoxides and sulfones over TiO2- CeO2, which are then selectively adsorbed on the bifucntional TiO2- CeO2 material due to their much higher polarities than the original oranosulfur compounds and other organic compounds in the diesel fuel. The TiO2- CeO2 material with a Ti/Ce molar ratio of 9：1 and calcined at 500 益 exhibits the highest synergistic photocatalysis-adsorption desulfurization performance; over it the sulfur removal rate reaches 99. 6% for a model fuel after reaction for 5 h under UV irradiation. The low desulfurization selctivity because of the strongly competitive adsorption of aromatics in the diesel fule could be greatly improved by employing the synergistic photocatalysis-adsorption desulfurization process; the sulfur removal rate is still higher than 96. 6% for the model fuel containing 25% toluene after reaction for 7 h under UV irradiation. The desulfurization performance of TiO 2- CeO 2 for different organosulfur compounds in the diesel fuel follows the order of 4’6-DMDBT 〉 DBT 〉 BT. Moreover’ TiO 2- CeO2 can be well regenrated by washing with acetonitrile followed by heat treatment in air; it still gives a high synergistic photocatalysis-adsorption desulfurization performance even after four regeneration cycles.