Kraiwattanawong, Kriangsak

Preferred name

Alternative Name

Kraiwattanawong, K.

Main Affiliation

School of Engineering

kriangsak.kr@kmitl.ac.th

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Preparation of carbon cryogels from wattle tannin and furfural
(2007-01-05)
Kraiwattanawong, K.
;
Mukai, S. R.
;
Tamon, H.
;
Lothongkum, A. W.
Wattle tannin-furfural (TFu) hydrogels were synthesized by the sol-gel polycondensation of wattle tannin with furfural by using three types of base catalysts (NaOH, Na<inf>2</inf>CO<inf>3</inf> and NaHCO<inf>3</inf>). TFu cryogels were prepared by freeze drying of the hydrogels and TFu carbon cryogels were obtained by pyrolysis of the cryogels in an inert atmosphere. The TFu and carbon cryogels were characterized by N<inf>2</inf> adsorption and scanning electron microscope (SEM). The effect of catalysts on porous properties of carbon cryogels resulted in different ways: (1) NaOH enhances increasing mesopore volumes and surface area of carbon cryogels and (2) Na<inf>2</inf>CO<inf>3</inf> and NaHCO<inf>3</inf> cause decreasing those of carbon cryogels. The TFu and carbon cryogels prepared by using NaOH as a catalyst possessed large mesopore volumes comparing with micropore volumes. Even though the TFu cryogels have surface area and mesopore volumes smaller than the resorcinol-formaldehyde (RF) cryogels, the carbon cryogels have unique porous properties differed from the RF carbon gels. The properties are summarized as follows: (1) the mesopore volume changes insignificantly after pyrolysis, (2) the pore radius is increased after pyrolysis and (3) micropores are not greatly developed during pyrolysis. © 2006 Elsevier Inc. All rights reserved.
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Control of mesoporous properties of carbon cryogels prepared from wattle tannin and furfural
(2008-12-01)
Kraiwattanawong, Kriangsak
;
Mukai, Shin R.
;
Tamon, Hajime
;
Lothongkum, Anchaleeporn W.
Wattle tannin-furfural (TFu) carbon cryogels are synthesized by sol-gel polycondensation of wattle tannin with furfural by using sodium hydroxide (NaOH) as a catalyst, dried by freeze-drying technique and then pyrolyzed under inert atmosphere, respectively. The amounts of wattle tannin (T), furfural (Fu), NaOH (C) and distilled water (W) are changed for preparing the mesoporous TFu carbon cryogels. The mole ratio of tannin to catalyst T/C plays a crucial role for the synthesis of TFu organic and carbon cryogels. The results suggest that the T/C ratio should be above 0.25 but <1.0 to prepare the mesoporous and homogeneous cryogels. Although TFu carbon cryogels have the broad mesopore size distribution, the mesoporous structure is controllable by the synthesis conditions. The carbon cryogels possess the mesopore volume less than 0.56 cm<sup>3</sup>/g and the BET surface area less than 600 m<sup>2</sup>/g. Moreover, the ratio of catalyst to water C/W can be used to prepare the homogeneous and mesoporous carbon cryogels, and to control the mesopore radius of carbon cryogels in the range of 1.6-9.6 nm. © 2007 Springer Science+Business Media, LLC.
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Improvement of mesoporosity of carbon cryogels by acid treatment of hydrogels
(2008-11-01)
Kraiwattanawong, Kriangsak
;
Mukai, Shin R.
;
Tamon, Hajime
;
Lothongkum, Anchaleeporn W.
Wattle tannin-furfural (TFu) gels are synthesized by the sol-gel polycondensation of wattle tannin with furfural by using sodium hydroxide as a catalyst and cured at 363 K. After cured, the TFu hydrogels are treated in hydrochloric acid (HCl) solutions with various variables as follows: aging temperature, HCl concentration and pH. TFu cryogels aged are then freeze-dried and pyrolyzed under an inert atmosphere to obtain TFu carbon cryogels. The TFu and carbon cryogels were characterized by N<inf>2</inf> adsorption and scanning electron microscope. The high HCl concentration yields the increase of mesopore volume almost twice especially at high temperature and the mesopore size distribution can be greatly developed sharper and narrower when the high concentration of HCl or/and the high temperature are used. Moreover, this method is the versatile approach for developing the mesopore structure of the low and high porous TFu hydrogels and has no serious problem of weight loss after treatment. © 2008 Elsevier Inc. All rights reserved.
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Some aspects about the nature of surface species on Pt-based and MFI-based catalysts for the selective catalytic reduction of NO by propene under lean-burn condition
(2002-06-29)
Praserthdam, Piyasan
;
Chaisuk, Choowong
;
Panit, Apiwat
;
Kraiwattanawong, Kriangsak
The nature of surface species for the selective catalytic reduction of NO by propene under lean-burn condition is relatively investigated on Pt/Al<inf>2</inf>O<inf>3</inf> and Co-ZSM-5 catalysts. An experimental set of three continuous steps including adsorption, temperature programmed desorption (TPD) and temperature programmed oxidation (TPO) is performed to observe the particular behavior of surface species on both catalysts. The surface species on Pt/Al<inf>2</inf>O<inf>3</inf> are almost totally released during TPD step, whereas those on Co-ZSM-5 are necessarily removed by the oxidizing gas on TPO step. It is suggested that the different nature of surface species on both catalysts should possibly play an important role on the reaction mechanism pathway. For Co-ZSM-5 catalyst, the surface species, which are formed by the interaction of NO, propene and oxygen, are distinctly assigned as the intermediate species in the NO reduction mechanism. On the other hand, for Pt/Al<inf>2</inf>O<inf>3</inf> catalyst, the observation of several surface species and the investigation about their reactivities indicate that several reaction mechanisms are simultaneously proceeded at the same operating condition. © 2002 Elsevier Science B.V. All rights reserved.
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Improvement of mesopore structure of resorcinol and formaldehyde carbon cryogels by acid solution
(2008-01-01)
Kraiwattanawong, K.
;
Kitchaiya, P.
;
Neramittagapong, A.
;
Praserthdam, P.
;
Tamon, H.
Resorcinol and formaldehyde (RF) carbon cryogels are prepared by sol-gel polycondensation by using sodium carbonate (C) as a catalyst with water (W) as solvent, immersed in acid solution, hydrochloric acid (HC1), dried by freeze-drying technique and then carbonized under inert atmosphere, respectively. Compared with their carbon precursors, both V<inf>mes</inf> and mesopore size distributions of all carbon cryogels can be developed since the pore shrinkage is the crucial role in the change of pore structure of carbon gels. HC1 may promote the strength of small pore structure and increase the pore shrinkage of large pore structure. Consequently, the treatment of HC1 does not only enhance the partial collapse of large pore structure, the treatment also increases the strength of small pore structure to inhibit the shrinkage of this structure during carbonization as well. © 2008 Trans Tech Publications, Switzerland.

Kraiwattanawong, Kriangsak

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