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Direct conversion of glycerol to acrylic acid via integrated dehydration-oxidation bed system
(2012-01-31)
Witsuthammakul, Ayut
;
Sooknoi, Tawan
Acrylic acid can be successfully produced in a single reactor via subsequent oxidation of the glycerol-dehydrated products. Selective dehydration of glycerol to acrolein was studied at 275-400 °C over HZSM-5, HBeta, HMordenite and HY. The V-Mo oxides (15-70 mol%V) on silicic acid support (20-100 wt% mixed oxides loading) were then included as a second bed for subsequent oxidation of the dehydrated products. Over the acid zeolites, acrolein and acetol are mainly generated, together with acetaldehyde, propionaldehyde, pyruvaldehyde and other oxygenates as secondary products. A complete conversion of glycerol with high selectivity to acrolein (up to 81 mol%) can be obtained when medium pore zeolites (HZSM-5) and low glycerol concentration (10-30 wt%) was used at 300 °C. A separated-sequential bed system provides high selectivity for acrylic acid with small amount of acetic acid and acetaldehyde (∼15 mol%). The catalyst with high V content promotes total oxidation of the dehydrated products to CO while that with highly dispersed V-Mo-O phases affords 98% selectivity to acrylic acid with 48% acrolein conversion. © 2011 Elsevier B.V.
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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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Oxidation of saturated hydrocarbons to alkyl hydroperoxides by a 'H 2O2/titanosilicalite-1/NaOH/MeCN' system
(2008-06-01)
Shul'pin, Georgiy B.
;
Kirillova, Marina V.
;
Sooknoi, Tawan
;
Pombeiro, Armando J.L.
Hydrogen peroxide oxidizes alkanes at room temperature to produce the corresponding alkyl hydroperoxides in the presence of titanosilicalite-1, NaOH and acetonitrile. The reaction proceeds with low regio- and bond-selectivity and its mechanism apparently involves the formation of hydroxyl radicals. © 2008 Springer Science+Business Media, LLC.
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Activity enhancement by acetic acid in cyclohexane oxidation using Ti-containing zeolite catalyst
(2002-07-10)
Sooknoi, Tawan
;
Limtrakul, Jumras
Titanium silicalite (TS-1) was hydrothermally crystallised from a titanosilicate gel. The solid material was characterised by XRD, IR, and SEM, and then used as a catalyst in the liquid phase oxidation of cyclohexane with hydrogen peroxide. The reaction was carried out for 6 h, at the temperature between 40 and 80 °C. It was found that a marked increase in the catalytic activity was observed in the reaction using acetic acid as the solvent, as compared to those using no solvent and methyl ethyl ketone. Further investigation was made on the cause of activity enhancement, and it was shown that acetic acid was readily oxidised to peracetic acid. This compound was believed to facilitate the complexation of the framework titanium active sites, and subsequently serve as a better oxidising agent, as compared to the original hydrogen peroxide. However, leaching of the titanium species was also observed in small amounts, from the reaction using acetic acid as the solvent. In the mechanistic point of view, there was an evidence suggesting that cyclohexanol might be a primary product from the cyclohexane oxidation, and can be consecutively re-oxidised to form cyclohexanone. It is noted that the direct oxidation from cyclohexane to cyclohexanone cannot be excluded. © 2002 Elsevier Science B.V. All rights reserved.

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