Choojun, Kittisak

Preferred name

Choojun, Kittisak

Main Affiliation

School of Science

kittisak.ch@kmitl.ac.th

Now showing 1 - 10 of 37

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Preparation, characterization and photocatalytic properties of rubber-TiO2-rGO composite sheets for dye decomposition in wastewater
(2017-01-01)
Tejangkura, Worapol
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Sriwong, Chaval
;
Choojun, Kittisak
In this work, rubber-TiO<inf>2</inf>-rGO (RT-rGO) composite sheets were successfully prepared by a simple latex mixing-casting method using TiO<inf>2</inf> and natural rubber latex with different amounts of rGO loading. The prepared RT-rGO sheet samples were characterized by XRD, FT-IR, Raman, SEM and EDS techniques. The photocatalytic properties of the prepared RT-rGO sheets as catalyst were evaluated using methylene blue (MB) dye solution under UV light irradiation. The result indicated that all the composite sheets loaded with rGO had better photocatalytic activities than the sheet without rGO loading. RT-rGO6.2% sheet showed the highest removal efficiency of 93.3% which has the rate constant (kapp) as 98.2 times higher than the unloaded sheet. Furthermore, the efficiency of the RT-rGO sheet upon the repeated usage was also studied. The result indicated that the sheet could be easily used, recovered and reused many times with no need for the cleaning in between successive uses. Thus, the RT-rGO sheet appears to be an attractive-material for the wastewater treatment or the water purification industry.
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Highly Dispersed WOx/SiO2Catalysts Derived from W-TRIS Complex for Efficient Biobutadiene Production from Acetylene-Ethylene Cross-Metathesis
(2025-01-01)
Promchana, Pratya
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Choojun, Kittisak
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Wengwirat, Kanokwan
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Limphirat, Wanwisa
;
Sooknoi, Tawan
Renewable 1,3-butadiene was selectively produced via acetylene-ethylene cross-metathesis over highly dispersed WO<inf>x</inf>/SiO<inf>2</inf>catalysts prepared by a simple impregnation method using the molecular precursor (NH<inf>4</inf>)<inf>2</inf>[W<inf>2</inf>O<inf>6</inf>(TRIS)<inf>2</inf>] (W-TRIS). Compared to catalysts derived from ammonium metatungstate (AMT), the TRIS-derived catalysts exhibited superior WO<inf>x</inf>dispersion and catalytic activity, attributed to stronger W–O–Si interactions as evidenced by XRD, DRUV–vis, Raman spectroscopy, and W L<inf>3</inf>-edge XANES/EXAFS. Systematic variation of WO<inf>3</inf>loading revealed that 5 wt % WO<inf>x</inf>/SiO<inf>2</inf>-TRIS offered the optimal balance of activity and selectivity, achieving 60% acetylene conversion, ∼74% selectivity to 1,3-butadiene, and a turnover frequency (TOF) of 23 h–1. Contact time analysis confirmed that 1,3-butadiene was the primary product, while minor byproducts such as cyclohexene and benzene originated from Diels–Alder cycloaddition followed by dehydrogenation. Reaction temperature screening identified 450 °C as the optimal operating condition; higher temperatures led to increased side reactions. Importantly, long-term testing over 100 h under continuous-flow conditions demonstrated high stability with sustained selectivity and negligible coke formation. These findings underscore the practical advantages of the W-TRIS molecular precursor strategy in designing durable WO<inf>x</inf>/SiO<inf>2</inf>catalysts for efficient and sustainable C<inf>4</inf>chemical production from bioethylene.
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Facile synthesis of the atomically dispersed hydrotalcite oxide supported copper catalysts for the selective hydrogenation of 5–hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan
(2023-07-15)
Kumar, Raju
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Lee, Hsin Hui
;
Chen, En
;
Du, Yuan Peng
;
Lin, Chan Yi
The selective hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) using the atomically dispersed supported copper catalyst is investigated. The hydrotalcite oxide supported copper materials (Cu<inf>(x)</inf>HTO) are facilely prepared by coprecipitating metal precursors in a methanolic solution under a tuned pH. The surface characterization involving PXRD, TEM, H<inf>2</inf>/N<inf>2</inf>O-TPR, and XAS reveals unequivocal evidence for the presence of the atomically dispersed copper on HTO surface. XAS specifically indicates the formation of mononuclear copper species, and H<inf>2</inf>/N<inf>2</inf>O-TPR strongly supports the copper atoms of Cu<inf>(5)</inf>HTO are evenly distributed in 99% dispersion. Moreover, the reduced Cu<inf>(5)</inf>HTO (r-Cu<inf>(5)</inf>HTO) enables to completely hydrogenate HMF to BHMF under mild conditions, in comparison to the poor reactivity catalyzed by the hydrotalcite oxide supported copper nanoparticles (r-Cu<inf>(4)</inf>@HTO). The dramatic enhancement of HMF hydrogenation catalyzed by r-Cu<inf>(5)</inf>HTO can be attributed to the fine distribution of copper atoms which are situated homogeneously over HTO surface as well as chemically reactive for the carbonyl group.
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High photocatalytic performance of 3D porous-structured TiO2@natural rubber hybrid sheet on the removal of indigo carmine dye in water
(2019-08-01)
Sriwong, Chaval
;
Choojun, Kittisak
;
Sriwong, Sukanpirom
Due to the high efficiency of photocatalytic process for the environmental treatments, titanium dioxide (TiO<inf>2</inf>) is a popular used as photocatalyst material. However, the practical uses of TiO<inf>2</inf> in powder form have some drawbacks as well as the difficult reusability. In this work, 3D porous-structured TiO<inf>2</inf>@natural rubber (TNR) hybrid sheets with high photocatalytic performance were presented. TNR hybrid sheets prepared by a facile and low-cost method, which is based on the mixing of natural rubber (NR) latex (60% high ammonia) and ammoniacal TiO<inf>2</inf> (P25) suspension, followed by vacuum filtration through a sintered glass template to make a 3D porous network structure on the surface of the sheets. The obtained TNR sheet samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), X-ray diffractometer (XRD) and reflection Fourier transformed infrared spectroscopy (FT-IR) techniques. The results showed that the surface morphologies of TNR hybrid sheets appeared as porous-structured which had high roughness and with various tiny pores on the surface. The photocatalytic properties of the prepared TNR hybrid sheets were tested using indigo carmine (IC) dye under UV light irradiation. It was found that the highest photodegradation efficiency was achieved with the TNR_5 wt% hybrid sheet sample. Compared with the sheets reported in previous works, the TNR sheet shows higher efficiencies than those sheets due to its higher amount of TiO<inf>2</inf> particles at the surface, more porous structure with high rough surface, and abundance of tiny pores on the TNR sheet surface. Moreover, the recyclability and stability of TNR sheet indicated that upon using 10 cycles (remains 98% efficiency), in which the stability of the sheet surface well-confirmed by SEM and XRD techniques, as well. From above the study, this 3D porous-structured TNR hybrid sheet could be a new alternative strategy for the water or wastewater treatment in industry concerning with the easy use, recovery, reusability and stability of the photocatalysts.
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Tailoring the First Coordination Shell of Isolated Ti(IV) Active Sites in Zeolite Frameworks Boosting Catalytic Activity in Epoxidation
(2025-05-08)
Klinyod, Sorasak
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Yomthong, Krissanapat
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Suttipat, Duangkamon
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Pornsetmetakul, Peerapol
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Kidkhunthod, Pinit
We present a strategy to precisely tune the local structure of the tetrahedrally coordinated titanium (Ti) sites incorporated in the zeolite framework via a one-pot hydrothermal synthesis with the aid of NH<inf>4</inf>F without any further postmodification step. This approach effectively prevents typical issues observed in postsynthetic methods, such as Ti leaching and zeolite framework degradation. By optimizing the NH<inf>4</inf>F concentration in the synthesis precursor, the formation of open Ti(OSi)<inf>3</inf>OH and Ti(OSi)<inf>3</inf>F active species can be precisely controlled. To elucidate the relationship between various Ti active species, including closed Ti(OSi)<inf>4</inf>, open Ti(OSi)<inf>3</inf>OH, and open Ti(OSi)<inf>3</inf>F sites and their catalytic performances in methyl oleate (MO) epoxidation, we employed ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), fluorine X-ray absorption near edge structure spectroscopy (F-XANES), and density functional theory (DFT) calculations. Our findings reveal that increased positive charges on Ti active centers, in the order of closed Ti(OSi)<inf>4</inf> < open Ti(OSi)<inf>3</inf>OH < open Ti(OSi)<inf>3</inf>F, correlate with enhanced catalytic performance in MO epoxidation. However, an excessive proportion of Ti(OSi)<inf>3</inf>F species in the framework can diminish catalytic performance by promoting undesired side reactions. Therefore, we propose an optimized balance between open Ti(OSi)<inf>3</inf>OH and open Ti(OSi)<inf>3</inf>F species in the zeolite structure to maximize the catalytic activity of epoxidation.
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Bio-derived butadiene from cross-metathesis over silanol rich WO3 catalysts obtained from copper phyllosilicate
(2025-03-20)
Wengwirat, Kanokwan
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Choojun, Kittisak
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Promchana, Pratya
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Limphirat, Wanwisa
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Sooknoi, Tawan
Bio-butadiene can be produced from cross-metathesis of bioethanol-derived acetylene/ethylene over supported WO<inf>3</inf> on silanol-rich silica prepared with Cu-leached copper phyllosilicate (CuPS). 20CuPS and 30CuPS were preliminarily reduced before Cu-leaching under an acidic solution (1 M HCl). Compared with fumed SiO<inf>2</inf>29Si CPMAS NMR spectroscopy showed an increase in surface silanols, particularly the isolated silanols (Q<inf>3</inf>), from removing Cu2+ octahedral sites (Cu2+(OSi)<inf>6</inf>) encapsulated within tetrahedral silica layers of CuPS. The surface silanols in fumed SiO<inf>2</inf>, 20CuPS-Le, and 30CuPS-Le adequately accommodate single-site and polymeric WO<inf>3</inf> species, leading to a similar 1,3-butadiene production rate (∼4.7 mmol h−1 g<inf>cat</inf>) at 5 wt% loading. Only 30CuPS-Le sufficiently provides the exposed silanols to disperse 8 wt% WO<inf>3</inf> loading without bulk WO<inf>3</inf> formation. The cross-metathesis activity depends on the relative amounts of exposed silanols. Accordingly, the steady 1,3-butadiene production was obtained in the order of 8WO<inf>3</inf>/30CuPS-Le (6.3 mmol h−1 g<inf>cat</inf>) > 8WO<inf>3</inf>/20CuPS-Le (5.1 mmol h−1 g<inf>cat</inf>) > 8WO<inf>3</inf>/SiO<inf>2</inf> (2.5 mmol h−1 g<inf>cat</inf>).
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Tuning Cu+ species/Brønsted acids of copper phyllosilicate by K+ doping for selective hydrogenation of methyl palmitate to hexadecanol
(2023-12-01)
Prasanseang, Warot
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Choojun, Kittisak
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Poo-arporn, Yingyot
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Huang, Ai Lin
;
Lin, Yu Chuan
Selective hydrogenation of methyl palmitate to hexadecanol can be manipulated by tuning Cu+ species and Brønsted acid sites (BAS) of copper phyllosilicate (CuPS) catalysts with K+ doping. The catalysts were prepared by impregnating K+ onto reduced and non-reduced CuPS. The reactions were carried out in a fixed-bed flow reactor at 250 °C under atmospheric H<inf>2</inf>. In situ TR-XANES and Py-IR suggest that the presence of K+ could stabilize Cu+ species and neutralize BAS. As compared to the non-reduced sample, K+ loading (0.01–0.10 wt%) on the reduced CuPS provide higher Cu+ fraction (10–16%), lower BAS (0.82 to 0.16μ mol/g) and lower Cu dispersion (75 to 52%). A balance between Cu0 active surface and Cu+ content provides an optimum hydrogenation activity (up to 80 %). The increased Cu+ species, together with the decreased BAS, does not only enhance the catalyst stability, but also hexadecanol selectivity (from 35 to 60%, at ∼50% conversion).
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Iridium(III) coordination compounds based on organophosphorus ancillary ligands showing cytotoxicity against breast cancer cells and Fe(III) luminescent sensing
(2025-01-15)
Klaimanee, Ekkapong
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Temram, Thitirat
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Ratanaphan, Adisorn
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Saithong, Saowanit
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Sooksawat, Dhassida
Three phosphorescent iridium(III) complexes consisting bis-diphosphine ligands were prepared and characterized by single-crystal XRD, CHN analysis, spectroscopic techniques, cyclic voltammetry, and DFT. The synthesized complexes were the three monomeric [Ir(ppy)<inf>2</inf>(L<inf>1</inf>)Cl] (1), [Ir(ppy)<inf>2</inf>(L<inf>2</inf>)]Cl (2) and [Ir(ppy)<inf>2</inf>(L<inf>3</inf>)]Cl (3) where L<inf>1</inf> = bis-(diphenylphosphino)methane (dppm), L<inf>2</inf> = bis-(diphenylphosphino)propane (dppp) and L<inf>3</inf> = bis-(diphenylphosphino)benzene (dppbe). Complexes 1–3 gave an absorption band between 240 to 380 nm in both CH<inf>2</inf>Cl<inf>2</inf> and DMSO, which is assigned as a charge transfer transition based on theoretical calculation. They showed a blue-green emission at 460–520 nm in DMSO with an absolute quantum efficiency of 0.013–0.046 at room temperature. The selective photo-induced electron transfer (PET) by Fe3+ in DMSO, was studied to obey the Rehm-Weller principle. The 1:1 binding soichiometry between 1–3 and Fe3+ was established by Job's plot. The binding constants (K<inf>a</inf>) were determined using the Benesi-Hildebrand plot. All the complexes are extremely more potent than cisplatin for in vitro antiproliferative activity towards the human breast cancer cells, HCC1937, MCF-7, and MDA-MB-231. The values of IC<inf>50</inf> were in the range of 0.077–0.485 μM, and 1 exhibited the most effective IC<inf>50</inf> against MDA-MB-231 cell line, the triple-negative breast cancer cell. Their lipophilicities (log P) were also examined to explain the penetration ability of the studied complexes towards cell barriers, and transport to the molecular target.
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Reversible Hydrogenation-Dehydrogenation of Acetylpyridine-Pd-MIL-101(Cr) for Chemical Hydrogen Storage
(2020-10-07)
Makmeesub, Nuttapong
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Ritvirulh, Chonlada
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Choojun, Kittisak
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Chen, Teng Hao
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Poo-Arporn, Yingyot
3-Acetylpyridine (AcP), as an organic hydrogen carrier, and Pd nanoparticles, as a catalyst, were incorporated into MIL-101(Cr) for chemical hydrogen storage. AcP was first grafted into MIL-101(Cr), and then Pd (0.5-4.0 wt %) was encapsulated by a double-solvent adsorption process. Thermogravimetric analysis, inductively coupled plasma-optical emission spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, in situ X-ray adsorption near-edge structure analysis, 1H nuclear magnetic resonance (NMR), and elemental analysis suggested the existence of AcP and Pd nanoparticles (NPs) inside the MIL-101(Cr) cages. The chemical hydrogen storage of samples was evaluated by H2 temperature-programmed reaction. In situ Fourier transform infrared and 1H NMR techniques verified the hydrogenated and dehydrogenated forms of AcP upon hydrogen uptake. Reversible hydrogenation/dehydrogenation can be readily regulated by H2 partial pressure and temperature. The chemical hydrogen storage could be accomplished only when AcP and Pd NPs were adjacently present. The chemical hydrogen storage was enhanced with an increased Pd loading up to 0.33 mmol H2·g-1 per cycle. With the manipulation of hydrogenation and dehydrogenation temperatures at 150 °C, the chemical hydrogen storage can be maintained for up to 10 cycles. The material reported herein is one of the noncryogenic chemical hydrogen storages that can be operated at constant temperature and atmospheric pressure.
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Removal of methylene blue dye using metal-free g-C3N4 photocatalyst over natural sunlight irradiation
(2020-01-01)
Sriwong, Chaval
;
Choojun, Kittisak
This work presented the high activity of metal-free g-C<inf>3</inf>N<inf>4</inf> photocatalyst for methylene blue (MB) removing over natural sunlight irradiation. These g-C<inf>3</inf>N<inf>4</inf> photocatalysts materials were synthesized by a conventional thermal condensation method using melamine as a precursor under treated at the various annealing temperatures (450 °C, 500 °C, 550 °C, 600 °C and 650 °C). All assynthesized samples were characterized and confirmed by a several techniques, such as, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectrometer (DRS), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) specific surface area. XRD and FTIR results confirmed that the as-synthesized g-C<inf>3</inf>N<inf>4</inf> samples were completely synthesized at annealing temperature of 500 °C. SEM images showed the morphologies of the g-C<inf>3</inf>N<inf>4</inf> samples had more flake-like structures upon the increasing of annealing temperatures. WhileDRS results indicated that the absorption edges of as-synthesized g-C<inf>3</inf>N<inf>4</inf> samples were shifted to visible-light region, except the sample as-synthesized at 650 °C (g-C<inf>3</inf>N<inf>4</inf>-650 °C). Moreover, the photocatalytic properties of metalfree g-C<inf>3</inf>N<inf>4</inf> photocatalyst materials were evaluated by degrading of MB dye solution under natural sunlight irradiation for 100 min. The results revealed that the highest photocatalytic activity was exhibited by the sample synthesized at 600 °C, which the apparent rate constant (kapp.) was 0.0291min-1. The orders of activities as:g-C<inf>3</inf>N<inf>4</inf>-600°C > g-C<inf>3</inf>N<inf>4</inf>-650 °C > g-C<inf>3</inf>N<inf>4</inf>-550 °C > g-C<inf>3</inf>N<inf>4</inf>-500°C > g-C<inf>3</inf>N<inf>4</inf>-450°C. Hence, the metal-free g-C<inf>3</inf>N<inf>4</inf> photocatalyst appears to be an attractivematerial for water or wastewater purification applications over activated by sunlight irradiation.

Choojun, Kittisak

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