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    Oxidative extraction of thiophene from n-dodecane over TS-1 in continuous process: A model for non-severe sulfur removal from liquid fuels
    (2009-10-10)
    Napanang, Thasaneeya
    ;
    Sooknoi, Tawan
    Liquid phase oxidation of thiophene in dodecane and subsequently extraction of the oxidized product into a polar solvent were studied in continuous process, as a model for selective removal of sulfur-containing compounds from liquid hydrocarbons under a non-severe condition. Titanium silicalite-1 (TS-1) and 30% of H<inf>2</inf>O<inf>2</inf> were used as catalyst and oxidizing agent, respectively. The reactions were carried out at room temperature and 60 °C at atmospheric pressure. TS-1 was synthesized, calcined at 550 °C and characterized by XRD, ICP-AES, SEM, BET and FT-IR. The continuous stirred tank reactor (CSTR, ∼150 ml) was used for the oxidative extraction in the continuous process. Thiophene (1000, 3000 ppm) in dodecane and H<inf>2</inf>O<inf>2</inf> (1.5 %w) in methanol were fed (10-25 ml/h) by a peristaltic pump into the CSTR (150 ml) containing TS-1 (1.0 and 1.8 g). The use of TS-1 catalyst significantly improves rate of thiophene removal as the oxidized products SO<inf>4</inf><sup>-</sup> species) can be transferred to the solvent, readily faster than the simple thiophene extraction. The reaction using methanol as a solvent showed a higher efficiency of thiophene removal, as compared to that using acetonitrile, acetic acid and water, respectively. The oxidation activity was increased when the solvent/oil ratio was increased. Increasing amounts of catalyst and decreasing feeding rate lead to an increase in oxidative extraction of thiophene. The deactivation of the catalyst is due to the titanium leaching and this can be improved when the calcinations temperature was raised. © 2009 Elsevier B.V. All rights reserved.
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    Ammoximation of cyclohexanone in acetic acid using titanium silicalite-1 catalyst: Activity and reaction pathway
    (2005-07-18)
    Sooknoi, Tawan
    ;
    Chitranuwatkul, Veerachai
    The activity of titanium silicalite (TS-1) and the reaction pathway for the ammoximation of cyclohexanone to produce cyclohexanone oxime were studied using acetic acid as a solvent at 60 °C. The effect of solvent, sources of nitrogen, water content and the active site stability were also evaluated. It was found that, in the reaction using acetic acid as a solvent, the ammoximation of cyclohexanone proceeded mainly via the oxidation of imine, which was primarily formed in situ by the condensation of ketone with ammonia. In addition, the ammonium salts of weak acids, such as acetate, citrate and carbonate, can be used as nitrogen sources for the ammoximation in acetic acid. Water was shown to inhibit the formation of imine, and also prevent the side reactions. Moreover, TS-1 possessed an excellent stability, and can be reused without significant loss of activity. © 2005 Elsevier B.V. All rights reserved.