Oxidative Desulfurization of Model Oil over Au/Ti-MWW
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Oxidative Desulfurization of Model Oil over Au/Ti-MWW Xiaojuan Si Æ Shifu Cheng Æ Yong Lu Æ Guohua Gao Æ Ming-Yuan He
Received: 18 September 2007 / Accepted: 5 December 2007 / Published online: 22 December 2007 Ó Springer Science+Business Media, LLC 2007
Abstract Au/Ti-MWW catalysts were prepared by the impregnation of HAuCl4 on Ti-MWW. Its structure and properties were characterized by X-ray diffraction, N2 adsorption and UV-visible. The oxidation reactions of thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyl-dibenzothiophene (DMDBT) were investigated at mild reaction conditions using H2O2 as oxidant. The results showed that Au loading could significantly promote the activity of Ti-MWW for oxidative desulfurization. Keywords Au/Ti-MWW Oxidative desulfurization Sulfur compounds H2O2
1 Introduction The removal of sulfur compounds in fuels has been a challenge for many years, due to the more stringent emission restriction standards in most countries [1–3]. Presently, the commercial process for desulfurization is hydrogenation desulfurization (HDS), which is carried out at high temperatures and elevated pressures. However, HDS is difficult to remove polyaromatic sulfur compounds, such as benzothiophene (BT), dibenzothiophene (DBT) and their derivatives, owing to their steric hindrance and stronger C–S bond energy, which make them difficult to broken down by hydrotreatment [4].
X. Si S. Cheng Y. Lu G. Gao (&) M.-Y. He Department of Chemistry, Shanghai Key Laboratory of Green Chemistry and Chemical Process, East China Normal University, Shanghai 200062, China e-mail: [email protected]
To overcome the limitations of HDS, several new approaches such as oxidation desulfurization (ODS) [5–10], adsorption desulfurization [3], and extraction desulfurization [11, 12] have been studied in recent years. Among those methods, oxidative desulfurization combined with extraction/adsorption has been paid more and more attention due to its mild reaction conditions and high sulfur removal. As high active oxidation catalysts, Ti-containing molecular sieves were used to catalyze the oxidation of sulfur compounds at mild conditions. Although the catalytic activity of TS-1 for the oxidation of thiophene using hydrogen peroxide is high [5, 8, 9], whereas the catalytic activity for the oxidation of benzothiophene and dibenzothiophene is very low due to the small pore size of TS-1. Other titanium-containing zeolites such as Ti-beta [5], Ti-HMS [6, 8] with larger pore size have been used as catalysts for the oxidation of thiophenes, they were also found with low activity or poor stability. We found that TiMWW [13] had high oxidative activity for benzothiophene and dibenzothiophene. The superior activity probably due to the structure of Ti-MWW. It consists of 12-membered ring side cups and two independent interlayer and intralayer 10-membered ring channels, one of which contains supercages of 0.71 9 1.8 nm in dimension [13, 14]. In view of the disadvantage of zeolites, there is an increasing inter
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