• Clean Technology
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• v.26 no.1
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• pp.79-87
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• 2020

The bio-oil produced from the fast pyrolysis of lignocellulosic biomass contains a high amount of oxygenates, causing variation in the properties of bio-oil, such as instability, high acidity, and low heating value, reducing the quality of the bio-oil. Consequently, an upgrading process should be recommended ensuring that these bio-oils are widely used as fuel sources. Catalytic fast pyrolysis has attracted a great deal of attention as a promising method for producing upgraded bio-oil from biomass feedstock. In this study, the fast pyrolysis of tulip tree was performed in a bubbling fluidized-bed reactor under different reaction temperatures, with and without catalysts, to investigate the effects of pyrolysis temperature and catalysts on product yield and bio-oil quality. The system used silica sand, ferric oxides (Fe₂O₃ and Fe₃O₄), and H-ZSM-5 as the fluidized-bed material and nitrogen as the fluidizing medium. The liquid yield reached the highest value of 49.96 wt% at 450 ℃, using Fe₂O₃ catalyst, compared to 48.45 wt% for H-ZSM-5, 47.57 wt% for Fe₃O₄ and 49.03 wt% with sand. Catalysts rejected oxygen mostly as water and produced a lower amount of CO and CO₂, but a higher amount of H₂ and hydrocarbon gases. The catalytic fast pyrolysis showed a high ratio of H₂/CO than sand as a bed material.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.1
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• pp.24-30
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• 2004

Analysis model for the two-phase catalytic reactor is presented. With the progress in development of micro thermofluidic devices, needs fur understanding of the phenomena in two phase reaction in cm scale has been arisen. To investigate thermal and reactive performance of down scaled two phase reactor simple analysis model that is a kind of lumped flow model is proposed. Analysis model presented is based on the experiment on mm scale model reactor. Target experiment is catalytic decomposition of 70wt％ hydrogen peroxide with existence of perovskite L $a_{0.8}$S $r_{0.2}$Co $O_3$ catalyst. It is composed of balance equations of mass and energy. Each phase is considered to be a species fur the simplicity. Axial diffusion and transversal distribution of properties are neglected. Two phase catalytic reaction is modeled as successive gasification of liquid lump around catalyst and reaction in gas phase. Heat transfer is modeled by model function ofNu number. Modeled Nu is expressed as Nu=N $u_{0}$ (1＋ $a_1$( $a_2$ $T^{-}$ $a_3$)exp( $a_4$ $T^{-1}$)exp( $a_{5}$ z). Transfer coefficients are determined by the comparison of experimental results. With the model, heat transfer characteristics are investigated. Also by the mass transfer coefficient, characteristics in mass transfer is investigated. With the result basic understanding on design and analysis of mm scale two-phase reactive device is obtained. Also it can be further applied to micro scale reactive device fabricated by micromachining.ing..

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.4
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• pp.443-448
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• 2010

The objective of this study was to assess the catalytic activities of manganese oxide (MnO, $MnO_2$, $Mn_2O_3$, and $Mn_3O_4$) catalysts for odors (acetaldehyde and propionaldehyde) removal. We used a fixed bed reactor as the experimental apparatus and the catalytic performance were carried out over the temperature range of $200{\sim}470^{\circ}C$. The properties and performance of catalysts were characterized by the X-ray diffraction (XRD) and Brunauer Emmett Teller (BET). The catalytic activities of manganese oxide catalysts for acetaldehyde combustion were in the order of MnO < $MnO_2$ < $Mn_2O_3$ < $Mn_3O_4$, and it is similar to that of propionaldehyde combustion. We also confirmed that the reactions have well followed the kinetic model of Power-Rate Law and the reaction order (n) is 1 for both of the acetaldehyde and propionaldehyde combustion. In addition, the reaction activation energy of acetaldehyde and propionaldehyde combustion over $Mn_3O_4$ were found to be $72.42\;kJmol^{-1}$ for 487~503 K and $51.14\;kJmol^{-1}$ for 473~533 K, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.2-2
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• 2011

Single-walled carbon nanotubes (SWNTs) have been considered as a promising candidate for nextgeneration electronics due to its extraordinary electrical properties associated with one-dimensional structure. Since diversity in electronic structure depends on geometrical features, the major concern has been focused on obtaining the diameter, chirality, and density controlled SWNTs. Despite huge efforts, the controlled synthesis of SWNTs has not been achieved. There have been various approaches to synthesize controlled SWNTs by preparation of homogeneously sized catalyst because the SWNTs diameter highly depends on catalyst nanoparticles size. In this study, geometrically controlled SWNTs were synthesized using designed catalytic layers: (a) morphologically modified Al2O3 supporting layer (Fe/Al2O3/Si), (b) Mo capping layer (Mo/Fe/Al/Si), and (c) heat-driven diffusion and subsequent evaporation process of Fe catalytic nanoparticles (Al2O3/Fe/Al2O3/Si). These results clearly revealed that (a) the grain diameter and RMS roughness of Al2O3 supporting layer play a key role as a diffusion barrier for obtaining Fe nanoparticles with a uniform and small size, (b) a density and diameter of SWNTs can be simultaneously controlled by adjusting a thickness of Mo capping layer on Fe catalytic layer, and (c) SWNTs diameter was successfully controlled within a few A scale even with its fine distribution. This precise control results in bandgap manipulation of the semiconducting SWNTs, determined by direct comparison of Raman spectra and theory of extended tight binding Kataura plot. We suggest that these results provide a simple and possible way for the direct growth of diameter, density, and bandgap controlled SWNTs by precise controlling the formation of catalytic films, which will be in demand for future electronic applications.

• Journal of the Korean institute of surface engineering
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• v.40 no.3
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• pp.125-130
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• 2007

Many fundamental studies have been carried out regarding waste water and hazardous gas treatment technology using the photolysis effect of $TiO_2$. However, photolysis of both organic and organic-inorganic binders immobilizing $TiO_2$ makes permanent use impossible. In this study we manufactured a catalytic electrode by nickel-$TiO_2$ composite plating in order to immobilize $TiO_2$. The surface properties according to the current density changes of cathode and concentration changes of $TiO_2$ powder in nickel plating bath has been analysed with EDX, XRF, SEM, Raman spectrometer etc. The characterization of the catalytic electrode in decomposition of organic compound has been obtained by using UV-Visible spectrophotometer through analysing concentration changes of methyl orange solution containing the catalytic electrode vs. time with projecting UV-light in the solution. The study shows that a catalytic electrode of nickel-$TiO_2$ composite plating with high-efficiency in decompostion of organic compound has been formed under high concentration of $TiO_2$ powder and low current density of cathode.

• Clean Technology
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• v.18 no.1
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• pp.89-94
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• 2012

In this study, we investigated the activity of Pd and Pt supported on acidic Fe-ZSM5 supports for selective catalytic oxidation of ammonia ($NH_3$-SCO). Among the catalysts, Pt/Fe-ZSM5 catalyst exhibited superior $NH_3$-SCO activity to Pd/Fe-ZSM5 catalyst. We also tested Pt/Fe-ZSM5 catalysts with different Fe loading using ion-exchange method to prepare Fe-ZSM5 supports, which resulted in the increased catalytic performance with smaller Fe content: $NH_3$ was oxidized completely at low temperature ($250^{\circ}C$). The physicochemical properties of Fe-ZSM5 were investigated to figure out the relationship between the characteristics of the catalysts and the catalytic activity on $NH_3$-SCO by Inductively coupled plasma-atomic emissions spectrometer (ICP-AES), $N_2$ sorption, X-ray diffraction (XRD), temperature programmed desorption of $NH_3$ ($NH_3$-TPD) technique.

• Clean Technology
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• v.20 no.1
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• pp.28-34
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• 2014

In this study, we synthesized $TiO_2$ supports with nanosized crystalline structure by solvothermal method and prepared $TiO_2$ supported Pd-Cu catalysts. It was shown that the crystalline size of $TiO_2$ support in the catalyst influenced on the catalytic activity of nitrate reduction in water. The catalyst with the smaller crystalline size of $TiO_2$ support presented faster nitrate reduction rate, but had low nitrogen selectivity due to high pH environment of reaction medium during the reaction. Through injection of carbon dioxide as a pH buffer, the nitrogen selectivity increased by about 60%. Furthermore, we investigated that the relationships between the catalytic performance and the physicochemical properties of the prepared catalysts characterized by $N_2$ adsoprtion-desorption, X-ray diffraction (XRD), $H_2$-temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS).

• Journal of the Korean Magnetic Resonance Society
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• v.8 no.2
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• pp.77-85
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• 2004

$^1$H-detected $^{15}$N NMR was employed to investigated the effect of mutation (Y14F) on the dynamic properties of catalytic residues in ${\Delta}^5$-3- ketosteroid isomerase (KSI) from Conamonas testosteroni. In particular, the backbone dynamics of the catalytic residues have been studied in free enzyme and its complex with a steroid ligand, 19-nortestosterone hemisuccinate, by $^{15}$N relaxation measurements. The relaxation data were analyzed using the model-free formalism to extract the model-free parameters (S$^2$, ${\tau}_e$, and R$_{ex}$). The results show that the mutation causes a significant decrease in the order parameter (S$^2$) for the catalytic residues of free Y14F KSI, presumably due to breakdown of the hydrogen bond network by mutation. In addition, the order parameters of Phe-14 and Asp-99 increased slightly upon ligand binding, indicating a slight restriction of the high-frequency (pico- to nanosecond) internal motions of the residues in the complexed Y14F KSI, while the order parameter of Tyr-55 decreased significantly upon ligand binding.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.317.2-317.2
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• 2013

Ultrathin oxide encapsulated metal-oxide hybrid nanocatalysts have been fabricated by a soft chemical and facile route. First, SiO2 nanoparticles of 25~30 nm size have been synthesized by modified Stobber's method followed by amine functionalization. Metal nanoparticles (Ru, Rh, Pt) capped with polymer/citrate have been deposited on functionalized SiO2 and finally an ultrathin layer of TiO2 coated on surface which prevents sintering and provides high thermal stability while maximizing the metal-oxide interface for higher catalytic activity. TEM studies confirmed that 2.5 nm sized metal nanoparticles are well dispersed and distributed throughout the surface of 25 nm SiO2 nanoparticles with a 3-4 nm TiO2 ultrathin layer. The metal nanoparticles are still well exposed to outer surface, being enabled for surface characterization and catalytic activity. Even after calcination at $600^{\circ}C$, the structure and morphology of hybrid nanocatalysts remain intact confirm the high thermal stability. XPS spectra of hybrid nanocatalyst suggest the metallic states as well as their corresponding oxide states. The catalytic activity has been evaluated for high temperature CO oxidation reaction as well as photocatalytic H2 generation under solar simulation. The design of hybrid structure, high thermal stability, and better exposure of metal active sites are the key parameters for the high catalytic activity. The maximization of metal-TiO2 interface interaction has the great role in photocatalytic H2 production.

• Journal of Microbiology and Biotechnology
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• v.29 no.9
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• pp.1375-1382
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• 2019

Phenylalanine hydroxylase from Chromobacterium violaceum (CvPAH) is a monomeric enzyme that converts phenylalanine to tyrosine. It shares high amino acid identity and similar structure with a subunit of human phenylalanine hydroxylase that is a tetramer, resulting in the latent application in medications. In this study, semirational design was applied to CvPAH to improve the catalytic ability based on molecular dynamics simulation analyses. Four N-terminal truncated variants and one single point variant were constructed and characterized. The D267P variant showed a 2.1-fold increased thermal stability compared to the wild type, but lower specific activity was noted compared with the wild type. The specific activity of all truncated variants was a greater than 25% increase compared to the wild type, and these variants showed similar or slightly decreased thermostability with the exception of the $N-{\Delta}9$ variant. Notably, the $N-{\Delta}9$ variant exhibited a 1.2-fold increased specific activity, a 1.3-fold increased thermostability and considerably increased catalytic activity under the neutral environment compared with the wild type. These properties of the $N-{\Delta}9$ variant could advance medical and pharmaceutical applications of CvPAH. Our findings indicate that the N-terminus might modulate substrate binding, and are directives for further modification and functional research of PAH and other enzymes.