Kraiwattanawong, Kriangsak

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Kraiwattanawong, K.

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School of Engineering

kriangsak.kr@kmitl.ac.th

Now showing 1 - 9 of 9

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Removal of heavy polynuclear aromatics by activated carbons
(2018-01-01)
Pilawan, Wijai
;
Sirikarn, Wisanu
;
Kraiwattanawong, Kriangsak
Heavy polynuclear aromatics (HPNA) is a complex molecules generated during hydrocracking process in waxy oil. HPNA is eliminated by a commercial activated carbon in the absorber to prevent the fouling in the pipelines and the decrease of product yield. In this work, the commercial activated carbons containing the different micropores and the different mesopores were selected to investigate the influence of pore structure on the HPNA removal. Here, the surface area of commercial activated carbons were quite equivalent. The results show that the activated carbon possessing the high mesopores can adsorb HPNA better than the activated carbon having the high micropores in spite of the summation of a micropore volume and a mesopore volume are quite equal. Therefore, the mesopore structure is a major role in the HPNA removal.
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Influence of solvent species used in solvent exchange for preparation of mesoporous carbon xerogels from resorcinol and formaldehyde via subcritical drying
(2011-02-01)
Kraiwattanawong, Kriangsak
;
Tamon, Hajime
;
Praserthdam, Piyasan
Carbon cryogels are dried by 3 days of freeze drying with 6 h of pre-freezing whereas the carbon xerogels are prepared by 1 day of subcritical drying in the selective range of synthesis condition, but the mesoporosity of carbon xerogels are not well controlled. This research is to study the influence of solvent species in the solvent exchange for the preparation of carbon xerogels cooperated by the evaporation drying and the vacuum drying. The good solvent for the high mesoporous properties of carbon xerogels is desirable in the wide range of synthesis condition. The carbon xerogels prepared from resorcinol and formaldehyde were characterized by the nitrogen adsorption apparatus and the field emission scanning electron microscope (FE-SEM). The results illustrate that the mesoporous carbon xerogels in the two subcritical dryings can be easily prepared by solvent exchange. Among the solvents, t-butanol allows the great results in the preparation of high mesoporous carbon xerogels and is well applied in the wide range of synthesis conditions. The FE-SEM images elucidate that the carbon xerogels dried by the vacuum drying contain the particles interconnection larger than the evaporation drying. © 2010 Elsevier Inc. All rights reserved.
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Investigation on porous properties of carbon/carbon composite cryogels by using weighted arithmetic mean
(2016-09-01)
Kraiwattanawong, Kriangsak
;
Sano, Noriaki
;
Tamon, Hajime
Cotton fibers (CF) and resorcinol and formaldehyde (RF) sol were used to synthesize composite cryogels. They were carbonized to prepare carbon/carbon (C/C) composite cryogels. In this work, the molar ratio of resorcinol to sodium carbonate (R/C), the mass concentration of resorcinol to distilled water (R/W) and the mass ratio of CF to RF (CF/RF) were changed as 100 and 200 mol/mol, 0.25 and 0.50 g/cm<sup>3</sup> and 0.00 up to 0.64 g/g, respectively. The C/C composites were characterized by nitrogen adsorption and scanning electron microscopy. The results showed that the mesopore structure of C/C composites could be controlled by the adjustment of an R/W or R/C ratio. Moreover, the mean micropore sizes of C/C composite cryogels were kept equivalently to those of normal carbon cryogels. The weighted arithmetic mean was well applied to the BET surface area and micropore surface area of C/C composites with the deviation of about 21% for the high R/C ratio; however, it poor for the low R/C ratio. The weighted arithmetic mean also estimated the micropore volume of C/C composite cryogels with the deviation of about 20% for the CF/RF ratio smaller than 0.40 g/g. Moreover, the weighted arithmetic mean can be used as a guideline to estimate the mesopore volume.
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Improvement of the textural properties of templated carbon xerogels using cotton fibres as a hard template dehydrated by sulphuric acid
(2019-02-01)
Kraiwattanawong, Kriangsak
Carbon xerogels have generally low textural properties compared with carbon aerogels and carbon cryogels since the gas-liquid interface produces a capillary force in small pores. In this work, the templated carbon xerogels (TCXs), using resorcinol-formaldehyde (RF) and cotton fibres (CFs) as a hard template, were synthesized by CF removal from CF/RF composite hydrogels by sulphuric acid treatment. The TCX precursors were exchanged by t-butanol, dried by evaporation drying, and carbonized at high temperature. Scanning electron microscope images and Hg intrusion data confirm that TCXs possess macropores whose walls are the carbon xerogel scaffold. Their nitrogen adsorption and desorption isotherms also support that TCXs have micropores and mesopores. The quantities of micropores, mesopores and macropores are improved with the increase of CF utilization. X-ray diffraction allows us to know that TCXs have a graphitic structure. The intensity of D to G from the Raman spectra is also investigated.
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Porous properties of carbon/carbon composite xerogels
(2018-01-01)
Kraiwattanawong, Kriangsak
Carbon/carbon composite xerogels are prepared by a vacuum drying technique whereas a carbon cryogel is synthesized by a freeze drying technique to compare the effect of these drying methods at the selective synthesis condition. Resorcinol and formaldehyde are used to prepare a matrix phase and cotton fibers are acted as a disperse phase of the carbon/carbon composite xerogels. Here resorcinol and formaldehyde is utilized to synthesize the carbon cryogel only. The carbon/carbon composite xerogels and the carbon cryogel were analyzed by a nitrogen adsorption apparatus and a field emission scanning electron microscope. The results support that the vacuum drying can decrease the pore shrinkage despite of the gas-liquid interface. The porous properties of the carbon xerogel is quite equivalent to the porous properties of the carbon cryogel. When the porous properties of carbon xerogels are considered, their porous properties can be preserved at the high porosity until 0.15 g/g of the cotton fibers/resorcinol ratio. At 0.25 g/g of this ratio, the porous properties start decreasingly.
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Capacitive performance of binder-free carbon/carbon composite cryogels
(2013-01-01)
Kraiwattanawong, Kriangsak
;
Sano, Noriaki
;
Tamon, Hajime
A carbon/carbon (C/C) composite cryogel was prepared by pouring a resorcinol-formaldehyde (RF) sol into vials containing cotton fibers, followed by solvent exchange with t-butanol, freeze drying and pyrolysis under inert atmosphere. The porous properties of C/C composites were analyzed by nitrogen adsorption, and their mesopore texture was observed by a scanning electron microscope. The capacitive performance of C/C composites was also analyzed by galvanostatic charge/discharge method and cyclic voltammetry. The results demonstrate that the capacitance can be increased with the increase of amount of cotton fibers added to C/C composites, because the broader micropore size distribution and the carbon tunnels of C/C composites promote the charge propagation inside the pore structure. The suitable pore texture and the carbon tunnels can play the crucial role relevant to the high surface area in order to obtain the high capacitance value. © 2012 Elsevier Inc. All rights reserved.
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Carbon tunnels formed in carbon/carbon composite cryogels
(2012-05-01)
Kraiwattanawong, Kriangsak
;
Sano, Noriaki
;
Tamon, Hajime
A carbon/carbon (C/C) composite cryogel was prepared by putting almost the maximum content of cotton fibers in vials and then filling them with resorcinol-formaldehyde (RF) sols, followed by solvent exchange with t-butanol, freeze drying and pyrolysis under inert atmosphere. The mesopore structure of C/C composite cryogels was observed by a scanning electron microscope (SEM) and their porous structures were characterized by nitrogen adsorption and mercury porosimetry. The SEM images confirm that the C/C composite cryogels, being heterogeneous carbon materials, possess ordinary carbon cryogels and carbon tunnels. Here, the tunnels are comprised of (i) carbon fibers, (ii) spaces between carbon fibers and nanoporous carbon spheres, (iii) nanoporous carbon spheres with surrounding nanocages, and (iv) dense ring structures. The formation model of carbon tunnels is also proposed. The porous properties of cryogels could be changed by the cotton fiber addition and the synthesis conditions. The results support that the synthesis condition of RF sol determines the porous properties of C/C composite cryogels. © 2011 Elsevier Inc. All rights reserved.
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HCl treatment on micropore and mesopore structures of carbon cryogels from resorcinol and formaldehyde
(2011-02-25)
Kraiwattanawong, Kriangsak
;
Tamon, Hajime
;
Praserthdam, Piyasan
The effect of HCl treatment on the porous properties of carbon cryogels synthesized from resorcinol and formaldehyde (RF) is investigated in this work. The treated and untreated carbon cryogels were analyzed with a nitrogen adsorption-desorption apparatus, scanning electron microscope (SEM) and high performance liquid chromatograph (HPLC). The results show that the HCl treatment can enlarge the micropore diameter which is advantageous to electric double layer capacitors, and can broaden the mesopore diameter, which is advantageous to mesoporous carbon supports of catalysts. The micropore volume, mesopore volume and weight loss of the carbon cryogel are not significantly changed by the HCl treatment. Moreover, SEM images and HPLC chromatograms support that the HCl treatment can promote the Ostwald ripening effect for RF carbon cryogels. © 2011 The Society of Chemical Engineers, Japan.
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Low-cost production of mesoporous carbon/carbon composite cryogels
(2011-09-01)
Kraiwattanawong, Kriangsak
;
Sano, Noriaki
;
Tamon, Hajime
A carbon/carbon (C/C) composite cryogel was prepared by dispersing cotton fibers (CF) in a resorcinol and formaldehyde (RF) sol, followed by solvent exchange with t-butanol, freeze drying and pyrolysis under inert atmosphere. The mass ratio of CF to RF was increased from 0% up to 25% to observe the mesopore structure change of C/C composites under a selected RF synthesis condition. The porous structures were characterized by nitrogen adsorption and mercury porosimetry, and their structure was observed by a scanning electron microscope (SEM). The mesopore diameter of the C/C composites increases slightly with the increase of CF content. The preparation can increase the mesopore volume and also reduce the production cost compared with carbon cryogels prepared without CF. The SEM images show that nanoporous gel spheres appeared after the freeze drying step. These spheres are converted to be nanoporous carbon spheres with surrounding nanocages, and CF are converted into carbon fibers at the same time by pyrolysis. © 2011 Elsevier Ltd. All rights reserved.

Kraiwattanawong, Kriangsak

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