Tailor-Made Mesoporous Ti-SBA-15 Catalysts for Oxidative Desulfurization of Refractory Aromatic Sulfur Compounds in Transport Fuel

摘要

We propose large-pore titanium-containing organosilylated mesoporous silica (Ti-SBA-15) as a highly efficient catalyst for the oxidative desulfurization (ODS) of refractory aromatic sulfur compounds with the aim to produce ultra-low sulfur diesel. To achieve this, we synthesized a series of mesoporous Ti-SBA-15 catalysts according to a new procedure. The procedure is based on the controlled grafting of titanium chelates on SBA-15 silica at low temperatures (5 degrees C). This specific synthesis procedure ensured a high dispersion of the required 4-coordinate tetrahedral Ti4+ sites located on the mesopore surface. To substantiate the influence of the titanium content and mesopore size on the ODS performance of the catalysts, the parameters were varied in the range of 0.7 to 4.7 mol?% (Si/Ti) and 5.1 to 9.0 nm, respectively. The resulting Ti-SBA-15 catalysts were then tested in the oxidative desulfurization (ODS) of model sulfur-containing compounds in the presence of cumene hydroperoxide (CHP) as the organic oxidant. The ODS of a real industrial diesel fuel was also carried out in a continuous fixed bed reactor with the same Ti-SBA-15 catalysts and CHP. The catalytic results revealed that the Ti-SBA-15 catalysts with the largest pore sizes (>7.3 nm) and highest Ti contents (>2.8 mol?%) were highly active catalysts for ODS reactions. Moreover, the catalysts with large pores and high Ti loadings appeared to be stable for over 30 h and were far less prone to deactivation than their equivalent Ti-SBA-15 samples with smaller pore diameters and lower Ti contents.