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Praserthdam, Piyasan,Chaisuk, Choowong,Mongkhonsi, Tharathon 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.1
The catalytic activity behavior for the selective catalytic reduction of NO by C_3H_6 under excess oxygen and the nature of surface species on the active sites of Pt/AI_2O_3 catalyst after adding a second metal(Fe, Sn, Co, Cr or W)were investigated. It has been found that an important role of second metals is on TONs of C_3H_6 and NO conversions and the nature of surface species produced on the catalyst surface at low temperature instead of the catalytic activity behavior towards the temperature programmed reaction. Although the introduction of each second metal distinctly disturbs the characteristic of surface species, the reaction mechanism is presumably similar. The observation of few surface species and the investigation about their reactivity indicate that few mechanisms are simultaneously proceeding at the same reaction condition.
Piyasan Praserthdam,Narongrat Poovarawan,Thidaya Thitiapichart,Kongkiat Suriye,Joongjai Panpranot,Wimonrat Limsangkass,Francisco José Cadete Santos Aires 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.1
Lanthanum (0.5, 0.6, 0.75, 0.9 and 1 wt%) was added as a second metal on the 9 wt% WO3/SiO2 catalysts by the incipient wetness impregnation method. The catalysts were tested in the metathesis reaction of ethylene and 2- butene using either pure 2% trans-2-butene and the mixture of 1% cis- and 1% trans-2-butene as the reaction feed and were characterized by X-ray diffraction (XRD), nitrogen physisorption (BET), inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy, ion-exchange titration, FT-Raman, ammonia temperature programmed desorption (NH3-TPD) and reactant temperature programmed desorption (reactant-TPD). An optimum lanthanum loading at 0.5 wt% could improve dispersion of tungsten active phase and adsorption properties of the reactants on the catalysts. The adsorption of the mixed cis/trans-2-butene isomer was much improved on the La- WO3/SiO2 catalysts with 0.5 wt% La.
Investigation of different modifiers for nanocrystal zirconia on W/ZrO2 catalysts via esterification
Supareak Praserthdam,Peangpit Wongmaneenil,Bunjerd Jongsomjit 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.6
The present work focused on investigation of different modifiers, such as Si, Al, Bi, and Pb on the tungstated zirconia catalysts. First, the different modifier precursors were introduced onto the nanocrystal zirconia having molar ratio (metal: Zr) at 0.01:1. Then, the 15 wt% of tungsten (W) was impregnated onto the modified zirconia. The physicochemical properties influenced by the modifiers were determined using the N2 physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and electron spin resonance (ESR). In order to measure the catalytic activity, esterification of acetic acid and 1-heptanol was performed. It was found that the modifiers apparently resulted in dramatically decreased activity due to decreased acidity of the catalysts. It can be proposed that the modifiers had three major roles; (i) inhibit the phase transformation, (ii) enhance the presence of F-center (electrons stabilized in oxygen vacancy), and (iii)increase strong interaction of adsorbed species on zirconia. The third effect was the key factor leading to pronounced decrease in acidity of the catalysts. 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Boonpai, Sirawat,Wannakao, Sippakorn,Panpranot, Joongjai,Praserthdam, Supareak,Chirawatkul, Prae,Praserthdam, Piyasan Techno-Press 2022 Advances in nano research Vol.12 No.3
The behavior of hydrogen species on the surface of the catalyst during the Lewis acid transformation to form Brønsted acid sites over the spherical silica-supported WO<sub>x</sub> catalyst was investigated. To understand the structure-activity relationship of Lewis acid transformation and hydrogen bonding interactions, we explore the potential of using the in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) with adsorbed ammonia and hydrogen exposure. From the results of in situ DRIFTS measurements, Lewis acid sites on surface catalysts were transformed into new Brønsted acid sites upon hydrogen exposure. The adsorbed NH<sub>3</sub> on Lewis acid sites migrated to Brønsted acid sites forming NH<sup>4+</sup>. The results show that the dissociated H atoms present on the catalyst surface formed new Si-OH hydroxyl species - the new Brønsted acid site. Besides, the isolated Si-O-W species is the key towards H-bond and Si-OH formation. Additionally, the H atoms adsorbed surrounding the Si-O-W species of mono-oxo O=WO<sub>4</sub> and di-oxo (O=)<sub>2</sub>WO<sub>2</sub> species, where the Si-O-W species are the main species presented on the Inc-SSP catalysts than that of the IWI-SSP catalysts.
Nutchapon Chotigkrai,Phakpum Tannititam,Sunthon Piticharoenphun,Narit Triamnak,Supareak Praserthdam,Piyasan Praserthdam 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.4
The effect of Zn doping (0.5-3wt%) on Cu-exchanged mordenite (Cu-MOR) was investigated during thestepwise oxidation of methane to methanol. The strong interaction between Cu and ZnOx stabilized the highly-dispersedstate of Cu2+ but reduced the Cu2+ bounded to extra-framework oxygen (active site), as demonstrated by the H2-TPR and XPS results. The Cu/Al and Zn/Al ratios suggested that Zn preferably bonded to the sites in the 8-MR channel,which led to highly dispersed Cu2+ anchored onto the highly accessible sites (12-MR and 8-MR side pocket). Thereactivity indicated that highly dispersed Cu2+ can be gradually transformed into active Cu2+ species during contactwith methane. Bimetallic Cu-ZnOx was also able to activate methane, resulting in a product complex. Although ZndopedCu-MOR catalysts gave a lower methanol yield at 2 h, a higher methanol yield could be achieved at saturationmethane loading time. Interestingly, 3 wt% Zn doping on Cu-MOR showed superior activity due to the increase ofmethanol yield up to 20% at 5 h of methane loading time. This work paves the way for the design of highly dispersedCu2+ in the 12-MR channel of mordenite zeolite via the control of strong Cu-ZnOx interaction.
Influence of Fe or Zn Loading Method on Toluene Methylation over MFI - Type Zeolite Catalysts
Phatansari, Suphot,Praserthdam, Piyasan,Punsupsawat, Thana 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.4
Toluene methylation with methanol was investigated on MFI-type zeolite catalysts containing Fe or Zn within the range of 0-2% by weight as an active component. The catalytic performances were compared on catalysts to which Fe or Zn was introduced by different methods, i.e., ion-exchanged and incorporation methods. The prepared catalysts were characterized by XRD, XRF, BET, FTIR and pyridine adsorption technique on in-situ FTIR. The results showed that the incorporated samples, H-Fe, Al-silicate (Si/Fe=150) and H-Zn, Al-silicate (Si/Zn=150), exhibited catalytic activity and xylene selectivities approximately equivalent to those from the ion-exchanged samples, Fe(0.8)/H-MFI and Zn(1.0)/H-MFI, containing nearly the same amount of Fe or Zn. The higher p-xylene selectivity was achieved with H-Fe, Al-silicate (Si/Fe=150) and H-Zn, Al-silicate (Si/Zn=150) because of Bro¨nsted acid strengths weaker than Fe(0.8)/H-MFI and Zn(1.0)/H-MFI. Therefore, the isomerization of p-isomer produced primarily was suppressed on the incorporated catalysts better than the ion-exchanged ones.
Aromatization of Light Paraffins over Ga-containing MFI - type Catalyst
Phatansari, Suphot,Praserthdam, Piyasan,Sripusitto, Apisit 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.4
Aromatization of light paraffins such as propane and butane was investigated on MFI-type catalysts containing Ga as an active component. Even with less amount of Ga loading, Ga ion-exchanged MFI exhibited higher selectivity for aromatics, mainly benzene, toluene and xylene (BTX), than that of H-Ga-Silicate. This may be attributed to the presence of Al in Ga ion-exchanged MFI which increases the catalyst acidity. Further development was done by preparing H-Ga, Al-bimetallosilicate with the purpose of minimizing the catalyst preparation procedure. It has been found that H-Ga, Al-bimetallosilicate having Si/Ga ratio of 155 and Si/Al ratio of 40 exerted considerably high selectivity for aromatics, ca. 64% for BTX. This selectivity was comparable to that of H-Ga ion-exchanged MFI with the same amount of Ga loading. However, the bimetallosilicate catalyst can be prepared in only one step crystallization, which minimizes the catalyst preparation procedure.
Mongkhonsi, Tharathon,Praserthdam, Piyasan,Srihiranpullop, Sunee 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.5
The effect of K addition on the amount and dispersion of carbon deposition on metal sites and support sites was investigated on a physical mixture for hexane dehydrogenation. TPO, BET and ESR experiments were used for characterization. The K addition significantly decreases catalyst deactivation involving the amount of coke deposits and the density of carbon radicals on the metal and support sites because of ensemble and electronic effects, especially on the metal sites. Coke on the metal sites associated with carbonaceous species rich in hydrogen is less polymerized than coke on the support sites, corresponding to a more graphitic-like carbon.