Ribeiro Susana O, Duarte Beatriz, de Castro Baltazar, Granadeiro Carlos M, Balula Salete S
LAQV-REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal.
Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
Materials (Basel). 2018 Jul 12;11(7):1196. doi: 10.3390/ma11071196.
Different methodologies were used to increase the oxidative desulfurization efficiency of the Keggin phosphotungstate [PWO] (PW). One possibility was to replace the acid proton by three different ionic liquid cations, forming the novel hybrid polyoxometalates: [BMIM]₃PW (BMIM as 1-butyl-3-methylimidazolium), [BPy]₃PW (BPy as 1-butylpyridinium) and [HDPy]₃PW (HDPy as hexadecylpyridinium. These hybrid Keggin compounds showed high oxidative desulfurization efficiency in the presence of [BMIM]PF₆ solvent, achieving complete desulfurization of multicomponent model diesel (2000 ppm of S) after only 1 h, using a low excess of oxidant (H₂O₂/S = 8) at 70 °C. However, their stability and activity showed some weakness in continuous reused oxidative desulfurization cycles. An improvement of stability in continuous reused cycles was reached by the immobilization of the Keggin polyanion in a strategic positively-charged functionalized-SBA-15 support. The PW@TM⁻SBA-15 composite (TM is the trimethylammonium functional group) presented similar oxidative desulfurization efficiency to the homogeneous IL⁻PW compounds, having the advantage of a high recycling capability in continuous cycles, increasing its activity from the first to the consecutive cycles. Therefore, the oxidative desulfurization system catalyzed by the Keggin-type composite has high performance under sustainable operational conditions, avoids waste production during recycling and allows catalyst recovery.
采用了不同的方法来提高Keggin型磷钨酸盐[PWO]（PW）的氧化脱硫效率。一种可能性是用三种不同的离子液体阳离子取代酸质子，形成新型杂化多金属氧酸盐：[BMIM]₃PW（BMIM为1-丁基-3-甲基咪唑鎓）、[BPy]₃PW（BPy为1-丁基吡啶鎓）和[HDPy]₃PW（HDPy为十六烷基吡啶鎓）。这些杂化Keggin化合物在[BMIM]PF₆溶剂存在下表现出高氧化脱硫效率，在70℃下仅使用少量过量的氧化剂（H₂O₂/S = 8），1小时后就能实现多组分模型柴油（硫含量2000 ppm）的完全脱硫。然而，它们在连续重复使用的氧化脱硫循环中的稳定性和活性表现出一些弱点。通过将Keggin多阴离子固定在具有策略性正电荷功能化的SBA-15载体上，实现了连续重复使用循环中稳定性的提高。PW@TM⁻SBA-15复合材料（TM是三甲基铵官能团）表现出与均相IL⁻PW化合物相似的氧化脱硫效率，具有在连续循环中高回收能力的优点，其活性从第一个循环到连续循环不断增加。因此，由Keggin型复合材料催化的氧化脱硫系统在可持续操作条件下具有高性能，避免了回收过程中的废物产生，并允许催化剂回收。
