• Polymer(Korea)
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• v.29 no.2
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• pp.122-126
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• 2005

The effect of Al-MCM-41 preparation methods on the catalytic degradation of linear low density polyethylene (LLDPE) was investigated. Al-MCM-41 catalysts were synthesized by direct method (Al-MCM-41-D) and post treatment method (Al-MCM-41-P) and their characteristics were elucidated by XRD, BET, $NH_3\;TPD,\;^{27}Al$ MAS NMR. TGA kinetic analysis showed that the catalytic activation energies of Al-MCM-41-D and Al-MCM-41-P were 191.54 and 114.26 kJ/mol, respectively. The higher catalytic activity of Al-MCM-41-P would be attributed to its smaller pore size as well as higher number of acid sites that are accessible.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.684-689
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• 2010

We synthesized a variety of SAPO catalysts with various structure directing agents by the hydrothermal method and applied them to the D-xylose dehydration. Single or mixtures of organic amines, viz. tetraethylammonium hydroxide(TEAOH), dipropylamine(DPA), diethylamine(DEA), morpholine and diethanolamine(DEtA) were used as structure directing agents. The $N_2$-isotherm, $NH_3$-temperature programmed desorption(TPD) and temperature programmed oxidation(TPO) were conducted to characterize SAPO catalysts. Among tested SAPO catalysts, the SAPO-34 synthesized with morpholine showed the highest furfural yield. The external surface area as well as the surface concentration of acid sites appeared to affect the catalytic activity for the dehydration of xylose into furfural.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.619-625
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• 2023

In order to solve problems caused by the heat load of hypersonic aircraft, this study examined the optimization of the Si/Al ratio of the catalyst and nickel ion exchange to improve the performance of the hydrocarbon decomposition reaction (endothermic reaction). It was confirmed that the catalysts prepared through Si/Al ratio optimization and nickel ion exchange showed about 10% improvement in heat absorption performance compared to thermal cracking at 4 MPa and 550 ℃. FT-IR and NH₃-TPD analyses were found to identify factors affecting activity changes, and it was observed that the Si/Al ratio of the HZSM-5 catalyst was closely correlated with acid site development and catalytic activity. In addition, TGA and O₂-TPO analyses were conducted to observe the carbon deposition inhibition properties of the nickel-added catalyst.

• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.623-628
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• 2004

Zeolite SUZ-4 was successfully synthesized with TEAOH (Tetraethyl ammonium hydroxide) as structure directing agent under a vigorous stirring condition. Well-defined zeolite SUZ-4 structure was only obtained under stirring of 250 rpm or more. The results imply that stirring plays a pivotal role for reproducible synthesis. Morphology of SUZ-4 crystal was controlled by adjustment of water concentrations. The physicochemical characterization of SUZ-4 and its hydrothermal stability using a steam treatment were investigated by using XRD, BET, and $NH_3-TPD$.

• Clean Technology
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• v.18 no.2
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• pp.162-169
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• 2012

Pt-Sn/${\theta}-Al_2O_3$ catalyst for n-butane dehydrogenation reaction was prepared by incipient wetness method. To confirm the physicochemical properties of Pt-Sn/${\theta}-Al_2O_3$ catalyst, the characterization was performed using X-ray diffraction (XRD), $N_2$ sorption analysis, temperature programmed desorption of $NH_3$ ($NH_3$-TPD), temperature programmed reduction of $H_2$ ($H_2$-TPR) techniques. Also, the catalytic activities of Pt-Sn/${\theta}-Al_2O_3$ for n-butane dehydrogenation was tested as a function of pretreatment temperature, pretreatment time, reaction temperature, and the partial pressure of n-butane and hydrogen. The sum of selectivities to n-butenes consisting of 1-butene, cis-2-butene, and trans-2-butene was almost constant 95% in the range of conversion of n-butane 5-55%. The activation energy calculated from Arrhenius equation was $82.4kJ\;mol^{-1}$ and the reaction orders of n-butane and hydrogen from Power's law were 0.70 and -0.20, respectively.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.620-629
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• 2022

By varying various experimental conditions such as heating rate, molar hourly space velocity (MHSV), and nitridation reaction temperature, vanadium oxynitride was prepared through temperature programmed reduction/nitridation reaction (TPRN) of vanadium pentoxide and ammonia, and characterization were performed. In order to investigate the physico-chemical properties of the prepared catalyst, N₂ adsorption-desorption analysis, X-ray diffraction analysis (XRD), hydrogen temperature programmed reduction (H₂-TPR), temperature programmed oxidation (TPO), ammonia temperature programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) was performed. Transformation of V₂O₅ with 5 m² g^-1 low specific surface area by reduction at 340 ℃ to V₂O₃ showed a high specific surface area value of 115 m² g^-1 by micropore formation. As the nitridation temperature increased beyond that, the specific surface area continued to decrease due to sintering. The nitridation reaction variable that had the greatest influence on the specific surface area was the reaction temperature, and the x + y value of VN_xO_y of a single phase approached from 1.5 to 1.0 as the nitridation reaction temperature increased. At a high reaction temperature of 680 ℃, the cubic lattice constant a was VN. close to the value. At 680 ℃, the highest nitridation temperature among the experimental conditions, the ammonia conversion rate was 93%, and no deactivation was observed.

• Clean Technology
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• v.23 no.2
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• pp.172-180
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• 2017

Thermodynamic evaluation indicates that nearly 100% conversion of elemental mercury to oxidized mercury can be attained by HCl of several tens of ppm level at the temperature window of SCR reaction. Cu-, Fe-, Mn-chloride loaded $V_2O_5-WO_3/TiO_2$ catalysts revealed good NO removal activity at the operating temperature window of SCR process. The catalysts with high desorption temperature indicating adsorption strength of $NH_3$ revealed higher NO removal activity. The HCl fed to the reaction gases promoted the oxidation of mercury. However, the activity for the oxidation of elemental mercury to oxidized mercury by HCl was suppressed by $NH_3$ inhibiting the adsorption of HCl to catalyst surface under SCR reaction condition containing $NH_3$ for NO removal. Metal chloride loaded $V_2O_5-WO_3/TiO_2$ catalysts showed much higher activity for mercury oxidation than $V_2O_5-WO_3/TiO_2$ catalyst without metal chloride under SCR reaction condition. This is primarily attributed to the participation of chloride in metal chloride on the catalyst surface promoting the oxidation of elemental mercury.

• Advances in nano research
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• v.9 no.3
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• pp.173-181
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• 2020

Adsorption and heterogeneous electro-Fenton process using iron-loaded ZSM-5 nano-zeolite were investigated for the removal of Tetracycline (TC) from wastewater. The nano-zeolite was synthesized hydrothermally and modified through impregnation. The zeolite was characterized by XRD, FT-IR, FE-SEM, N₂ adsorption-desorption, and NH₃-TPD techniques. The equilibrium data were best represented by the Freundlich isotherm. The pseudo-second-order kinetic model was the most accurate model for the adsorption of TC on the modified nano-zeolite. The effect of parameters such as pH of solution and current density were investigated for the heterogeneous electro-Fenton process. The results showed that the current density of 150 mA and pH of 3 led to the highest TC removal (90.35%) at 50 min. The nano-zeolite showed the appropriate reusability. Furthermore, the developed kinetic model was in good agreement with the removal data of TC through the electro-Fenton process.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.723-728
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• 2012

The production of biodiesel by transesterification of soybean oil was performed on $MoO_3$, $SnO_2$ and $CeO_2$ mixed oxides. The catalysts were characterized using XRD and $NH_3$-TPD. $MoO_3$ showed the highest activity among the three metal oxides. When 7 wt% of catalysts was introduced into the reactants, the highest activity was obtained and the water added to reactant decreased the catalytic activity. $MoO_3$ and $SnO_2$ mixed with 50:50 showed the highest activity and $CeO_2$ added with 20% on the $MoO_3-SnO_2$ mixed oxide also showed the highest activity. The catalytic activity showed to have a good relationship with the amount of acid site of catalysts. When the waste soybean oil was used as a reactant, the conversion was decreased about 30%.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.305-311
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• 2021

Effects of chitosan as a mesopore directing agent of SAPO-34 catalysts were investigated to improve the catalytic lifetime in DTO reaction. The synthesized catalysts were characterized by XRD, SEM, N₂ adsorption-desorption isotherm and NH₃-temperature programmed desorption (TPD). The modified SAPO-34 catalysts prepared by varying the added amount of chitosan showed the same cubic morphology and chabazite structure as the conventional SAPO-34 catalyst. As the added amount of chitosan increased to 3 wt%, the surface area, mesopore volume and concentration of weak acid sites of modified SAPO-34 catalysts increased. The modified SAPO-34 catalysts showed enhanced catalytic lifetime and high selectivity for light olefins in the DTO reaction. In particular, the SAPO-CHI 3 catalyst (3 wt%) exhibited the longest catalytic lifetime than that of the conventional SAPO-34. Therefore, it was confirmed that chitosan was a suitable material as a mesopore directing agent to delay deactivation of the SAPO-34 catalyst.