Sooknoi, Tawan

Preferred name

Sooknoi, Tawan

Alternative Name

Sooknoi, T.

Main Affiliation

School of Science

tawan.so@kmitl.ac.th

Now showing 1 - 10 of 21

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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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Synthesis, preparation and catalytic activities of V-doped TiO2 gel coating on porous α-Al2O3 beads
(2007-01-01)
Jaroenworaluck, A.
;
Panyathanmaporn, T.
;
Soontornworajit, B.
;
Supothina, S.
;
Tawkaew, S.
TiO<inf>2</inf> and V-doped TiO<inf>2</inf> gel were synthesized and coated onto porous α-Al<inf>2</inf>O<inf>3</inf> beads to study the thermal catalytic activities of oxidation reactions. Titanium isopropoxide (Ti(OPr) <inf>4</inf>) and 1,2-butadiol(Bu(OH)<inf>2</inf>) were used as starting chemicals for preparation of TiO<inf>2</inf> gel without V-doping. After aging at ambient temperature for one week, a TiO<inf>2</inf> gel was obtained. The concentration of Ti(OPr)<inf>4</inf> was varied, 0.2, 0.3, 0.7 and 2.4 M was used. For V-doping of the TiO<inf>2</inf> gel, 0.05, 0.20 and 0.75 mole% of V was prepared by ultrasonically dissolving vanadium acetylacetone (V(acac) <inf>2</inf>) in 1,2-butadiol. The solutions were then added to Ti(OPr) <inf>4</inf>. Finally, the mixed solutions were kept under ambient temperature for one week to form the V-doped TiO<inf>2</inf> gel. TiO<inf>2</inf> and V-doped TiO<inf>2</inf> were calcined at 300, 400, 500, 600, 700, and 800°C. XRD analysis, SEM and TEM in conjunction with EDS analysis were used to identify the phases present, grain size and morphology. The TiO<inf>2</inf> grains have a particle size in the nano-scale range. Doping TiO<inf>2</inf> with V could retard growth of the TiO<inf>2</inf> particles and affect phase transformation at higher calcination temperatures. Both the TiO<inf>2</inf> and V-doped TiO<inf>2</inf> gels were prepared and coated onto α-Al <inf>2</inf>O<inf>3</inf> beads to test oxidation reactions in a purpose-designed reactor. The results of the catalytic reactions indicated that V-doped TiO<inf>2</inf> had a higher oxidation activity than the undoped TiO<inf>2</inf> gel. The content of vanadium was related to the reaction efficiency.
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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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Etherification of 2-methyl-pentanal on supported palladium
(2009-12-01)
Pham, Trung T.
;
Crossley, Steven P.
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Sooknoi, Tawan
;
Lobban, Lance L.
;
Resasco, Daniel E.
Dialkyl ethers can be selectively produced from etherification of 2-methyl-pentanal and other oxygenates on supported Pd catalysts. Selectivities of 90% of ether were observed when feeding 2-methyl-pentanal and 2-methyl-pentanol at a molar ratio 1:1. Yields of up to 79 % have also been achieved. The reaction appears to be sensitive to metal particle features and molar feed ratios.
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Deoxygenation of model biofuel compounds over CsNaX zeolite catalyst
(2008-12-01)
Danuthai, Tanate
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Peralta, Maria A.
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Sooknoi, Tawan
;
Osuwan, Somchai
;
Lobban, Lance L.
The deoxygenation of methyl octanoate and benzaldehyde over CsNaX zeolite catalyst has been investigated as a model for reactions for production of hydrocarbon fuels from bio-oxygenates. The CsNaX zeolite used in the study was prepared by ion exchange of NaX with a CsNO<inf>3</inf>/CsOH solution to a 50% exchange level. The decarbonylation activity, selectivity, and stability of the CsNaX catalyst were enhanced when methanol was co-fed for the reaction of methyl octanoate. TPD studies suggest that methyl octanoate first decomposes to an octanoate-like species. The decomposition of such species leads to the formation of heptenes and hexenes as major products. Octenes and hydrogenated products are formed in lesser amounts via hydrogenation / hydrogenolysis using hydrogen produced on the surface from methanol decomposition, but not from gas phase H<inf>2</inf>.
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Reversible interconversion behavior of Ag species in AgHZSM-5: XRD, 1H MAS NMR, TPR, TPHE, and catalytic studies
(2008-07-31)
Ausavasukhi, Artit
;
Suwannaran, Suratsawadee
;
Limtrakul, Jumrus
;
Sooknoi, Tawan
<sup>1</sup>H MAS NMR, XRD, TPR, TPHE (temperature-programmed hydrogen evolution) techniques, and catalytic characterization by ethanol conversion were employed to investigate the reducibility and reversible interconversion behavior of Ag species in Ag-modified HZSM-5 (3 wt.%). The samples were prepared by ion-exchange of ZSM-5 with AgNO<inf>3</inf> (aq). It was found that charge-balancing Ag cations in AgHZSM-5(Si/Al ∼11) and AgHZSM-5(Si/Al ∼28) can be readily reduced to "cationic Ag clusters" at ∼220 °C, while a higher temperature is required for the Ag species in AgHZSM-5(28) to be reduced to "metallic Ag clusters", as compared with that for AgHZSM-5(11). Both cationic and metallic Ag clusters formed can be reversibly conversed into charge-balancing Ag cations by the reaction with neighboring Brønsted acid sites (reversible interconversion). The metallic Ag clusters were found to be more resistant to the reversible interconversion than the cationic Ag clusters. Under hydrogen stream, the reduced Ag species could be preserved and "silver hydride" species were observed, together with the active Brønsted acid sites. This phenomenon is suggested to play a decisive role on the catalytic activity of AgHZSM-5 towards BTX formation in the presence/absence of hydrogen. © 2008 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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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.
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Mediating effect of CO2 in base-catalysis by zeolites
(2000-01-01)
Sooknoi, Tawan
;
Dwyer, John
Effect of acidic carbon dioxide on alkylation with methanol over basic zeolite catalysts were studied. The catalysts, prepared by ion-exchange NaX zeolites with CsOH solution, were believed to contain excess amount of cesium salts on external surfaces and in the micropores. The alkylations of acetonitrile/toluene with methanol were conducted at 350°C using fixed-bed down flow reactor. Helium was used as carrier gas at atmospheric pressure. Gas chromatography was employed to analyse and quantify the products. Infrared spectroscopy was applied to investigate the adsorption of substrate on the basic sites. It was found that substrate electrophilicity played an important role in the alkylation over basic zeolites. For the alkylation of toluene with methanol, the activity was markedly decreased on application of carbon dioxide into the reactant stream. This is due to the competitive adsorption of acidic carbon dioxide over toluene on basic sites. In contrast, enhanced activity was observed in the reaction of more electrophilicity substrates, acetonitrile. It is suggested, in this work, that acetonitrile possess stronger adsorption strength, as compared to carbon dioxide, and it may well react with carbon dioxide to form an intermediate which is relatively more active in the alkylation with methanol. Together with infrared spectroscopy, there was an evidence that adsorption of substrates on basic sites was the rate determining step and the mechanism for the mediating of carbon dioxide in alkylation of acetonitrile was also suggested to increase reaction activity. © 2000 Elsevier Science B.V. All rights reserved.
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Oligomerization of propionaldehyde on novel basic catalysts
(2008-12-01)
Amen, Q. V.
;
Sooknoi, T.
;
Lobban, L. L.
;
Mallinson, R. G.
;
Resasco, Daniel E.
Vapor-phase oligomerization of propanal to 2-methyl-2-pentenal and 2-ethyl-3,5-dimethylcyclo-2-pentenone over basic zeolite catalysts (NaX, KNaX, KX, and CsNaX), as well as more traditional solid basic catalysts (MgO and MgO-Al2O3 hydrotalcites), was studied in an integral flow reactor at atmospheric pressure. Conversion and carbon yield based on catalyst properties (basicity, acidity) are reported. The highest stable activity was over KX, with the highest selectivity to the primary product, 2-methyl-2-pentenal (dehydrated aldol dimer of propanal) and the second highest selectivity to the secondary product, 2-ethyl-3,5-dimethylcyclo-2-pentenone (a non-aromatic cyclic trimer), with essentially no other products. Promotion of Zeolite X with various alkali metals also affected the acid and base site strengths, which had an effect on the conversion and selectivity.

Sooknoi, Tawan

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