• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.73-82
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• 2012

The main and side reactions of the three selective catalytic reduction (SCR) reactions with ammonia over a vanadium-based catalyst have been investigated using synthetic gas mixtures in the temperature range of $170{\sim}590^{\circ}C$. The three SCR reactions are standard SCR with pure NO, fast SCR with an equimolar mixture of NO and $NO_2$, and $NO_2$ SCR with pure $NO_2$. Vanadium based catalyst has no significant activity in NO oxidation to $NO_2$, while it has high activity for $NO_2$ decomposition at high temperatures. The selective catalytic oxidation of ammonia and the formation of nitrous oxide compete with the SCR reactions at the high temperatures. Water strongly inhibits the selective catalytic oxidation of ammonia and the formation of nitrous oxide, thus increasing the selectivity of the SCR reactions. However, the presence of water inhibits the SCR activity, most pronounced at low temperatures. In this study, the experimental results are analyzed by means of a dynamic one-dimensional isothermal heterogeneous plug-flow reactor (PFR) model according to the Eley-Rideal mechanism.

• 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..

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.68-78
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• 2006

In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia$(NH_3)$ in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis cannot be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea. Hence the key factor to implementation of SCR technology on automobile is fast thermolysis, good mixing of Ammonia and gas, and reducing Ammonia slip. In this context, this study performs three-dimensional numerical simulation of urea injection of heavy-duty diesel engine under various injection pressure, injector locations and number of injector hole. This study employs Eulerian-Lagrangian approach to consider break-up, evaporation and heat and mass-transfer between droplet and exhaust gas with considering thermolysis and the turbulence dispersion effect of droplet. The SCR-monolith brick has been treated as porous medium. The effect of location and number of hole of urea injector on the uniformity of Ammonia concentration distribution and the amount of water at the entrance of SCR-monolith has been examined in detail under various injection pressures. The present results show useful guidelines for the optimum design of urea injector for reducing Ammonia slip and improving DeNOx performance.

• Clean Technology
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• v.22 no.4
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• pp.281-285
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• 2016

Cu wire catalyst was highly reactive toward catalytic wet peroxide oxidation of the highly refractory 1,4-dioxane. While complete removal of 1,4-dioxane could be achieved with the catalyst, the removed 1,4-dioxane could not totally mineralized into $CO_2$ and $H_2O$. In accordance with the disappearance of 1,4-dioxane, formaldehyde and oxalic acid were formed gradually with reaction time and they went through maxima. At around the time of maximum concentrations of these two intermediates acetaldehyde concentration was increased drastically and showed maximum value. With the disappearance of these three intermediates, formic acid together with ethylene glycol diformate began to increase gradually. The Cu wire catalyst was proved also to be highly stable against deactivation during the reaction.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.438-443
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• 2019

A new measurement method is suggested to quantify the phosphate poisoning of cathodic Pt catalyst for HT-PEMFC. To do that, hydrogen peroxide was used as an indicator to reduce the error which has been occurred in conventional electrochemical measurement such as CV or ORR RDE with high concentration of phosphate ions. As a result, the current density induced from the reaction of hydrogen peroxide decomposition increased proportionally to the concentration of phosphate ion while the conventional methods show has a significant error with high concentration of phosphate ion. Thus, it is confirmed that the suggested way is superior to the conventional measurement method for the quantification of phosphate ion poisoning in an atmosphere similar to the actual operation condition of HT-PEMFC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5376-5383
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• 2011

The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose $CO_2$ because $CO_2$ is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of $CO_2$ at low temperature. Metal oxides, which converts $CO_2$ to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of $CO_2$. As the results, the reduction area of $H_2$ was high value at 15 wt% of NiO and the decomposition area of $CO_2$ was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of $H_2$ was 28.47wt% and oxidation area by $CO_2$ was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. $CO_2$ decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.463-469
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• 2015

Bisphenol A (BPA) in aqueous solution was measured using HPLC technique, which was established by acetonitrile analysis and KDP solution analysis methods. In these experiments the decomposition characteristics of BPA were compared using the ozone alone, ozone/pH 10, and ozone/hydrogen peroxide processes. About 70% of 10 mg/L of BPA was removed during 60 min by the ozone alone process, while 10 mg/L of BPA was completely removed by the ozone/pH 10 and ozone/hydrogen peroxide processes in 40 min and 60 min, respectively. The final decomposition efficiency drawn from results of TOC and HPLC analyses showed that the ozone/hydrogen peroxide process was the best among them, whereas the concentrations of TOC and reaction intermediates when using the ozone/pH 10 process were higher than those of the ozone alone process after 60 min of reaction. The ozone/hydrogen peroxide process was the most efficient among them when oxidizing organic carbons in water to $CO_2$ and $H_2O$.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.813-822
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• 1996

In order to reduce carbon dioxide, one of the major greenhouse gases, a new type of copolymer, poly(alkylene carbonate) has been synthesized. The alternating copolymers have been obtained from carbon dioxide and various epoxides with zinc carboxylate as a catalyst. The number-average molecular weight of the polymer is about 50,000 and polydispersity is rather broad(5~10). The polymers are amorphous, and glass-clear materials that exhibit unusually facile and clean thermal decomposition behavior. Complete decomposition with no carbon residue is observed at elevated temperature even in an inert atmosphere. Terpolymers with bulkier epoxides improve the physical properties of the copolymer with simple epoxides. The decomposition properties of the polymer provide versatile applications such as ceramic, metal, and electronic binders and lost-foam casting. Further application of the polymer for the barrier film or the plasticizer will be investigated.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.65-71
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• 1996

Decomposition reaction of methanol was conducted on Ni-Cu/SiO$_2$catalysts with several variables. Variables used in this study are S.V(Space Velocity), partial pressure of methanol, reaction temperature, and composition rate of Ni-Cu. The range of S.V is 10,000-30,000h$\^$-1/, the temperature range is 150-400$^{\circ}C$ and values of Cu/(Ni＋Cu) are 0, 0.25, 0.5, 0.75, and 1. Over Ni/SiO$_2$, and Ni-Cu/SiO$_2$, the conversion rate of decomposition reaction of methanol arrived at 100% with increasing of temperature. At this time the selectivity of CO on Ni/SiO$_2$, was suddenly decreased, but on Ni-Cu/SiO$_2$, it was still sustained highly. The main products of reaction were CO and H$_2$, and by-products were CO$_2$ and CH$_4$mainly.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.25-30
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• 2007

The catalysts for decomposition reaction of acetaldehyde were investigated. The catalysts were prepared with transition metal Ni, Mo, Al on ${\gamma}-Al_2O_3$ support by impregnation method. Physio-chemical properties of catalysts were characterized by SEM-EDS, XRD, XPS, BET and TPR techniques. The conversion efficiency of catalysts for acetaldehyde was measured in the temperature range of $150{\sim}500^{\circ}C$ by GC through the micro reactor system. The 8 wt% $Ni/{\gamma}-Al_2O_3$ was found to be the most active catalyst of mono-metal catalysts tested, and the 1-3 wt% $Ni-Al/{\gamma}-Al_2O_3$ showed higher conversion efficiency than other bimetallic catalysts.