• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.20-28
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• 2015

This work investigated the size and shape effect of ${\gamma}$-alumina-supported metal oxides on the hydrocarbon selective catalytic reduction of nitrogen oxides. Several metal oxides including Ag, Cu and Ru were used as the catalysts, and n-heptane as the reducing agent. For the Ag/${\gamma}$-alumina catalyst, the $NO_x$ reduction efficiency in the range of $250{\sim}400^{\circ}C$ increased as the size of Ag decreased (20 nm>50 nm>80 nm). The shape effect of metal oxides on the $NO_x$ reduction was examined with spherical- and wire-shape nanoparticles. Under identical condition, higher catalytic activity for $NO_x$ reduction was observed with Ag and Cu wires than with the spheres, while spherical- and wire-shape Ru exhibited similar $NO_x$ reduction efficiency to each other. Among the metal oxides examined, the best catalytic activity for $NO_x$ reduction was obtained with Ag wire, showing almost complete $NO_x$ removal at a temperature of $300^{\circ}C$. For Cu and Ru catalysts, considerable amount of NO was oxidized to $NO_2$, rather than reduced to $N_2$, leading to lower $NO_x$ reduction efficiency.

• Clean Technology
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• v.22 no.4
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• pp.211-224
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• 2016

Three way catalyst has been used extensively for the exhaust gas treatment for the internal combustion gasoline engine. While, numerous research efforts have been directed to develop various technologies for the abatement of exhaust gas from diesel engine. Diesel engine operating under lean condition produces large amount of NOx and the corresponding catalytic technology employing vanadium supported titania using ammonia has been commercialized for heavy duty vehicle. Recently, the Cu catalyst supported on zeolite has been investigated for NOx abatement using ammonia because of its critical importance for ultra low emission vehicle. The current review shows the recent trend in research and development for zeolite based copper catalysts, which are mainly used as catalysts for selective catalytic reduction using ammonia, are one of the aftertreatment technologies for effectively removing nitrogen oxides from diesel exhaust.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.127-138
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• 2016

Diesel vehicles should be equipped with urea-selective catalytic reduction(SCR) system as a high-performance catalyst, in order to reduce harmful nitrogen oxide emissions. In this study, a three-dimensional Eulerian-Lagrangian CFD analysis was used to numerically predict the multiphase flow characteristics of the urea-SCR system, coupled with the chemical reactions of the system's transport phenomena. Then, the numerical spray structure was modified by comparing the results with the measured values from spray visualization, such as the injection velocity, penentration length, spray radius, and sauter mean diameter. In addition, the analysis results were verified by comparison with the removal efficiency of the nitrogen oxide emissions during engine and chassis tests, resulting in accuracy of the relative error of less than 5%. Finally, a verified CFD analysis was used to calculate the interanl flow of the urea-SCR system, thereby analyzing the characteristics of pressure drop and velocity increase, and predicting the uniformity index and overdistribution positions of ammonia.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.9.1-9.1
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• 2005

• 한국가스학회:학술대회논문집
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• 2005.05a
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• pp.227-227
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• 2005

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.187-191
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• 2001

In the paper, an approach to the development of the selective catalytic reduction process of NOx is presented. The reduction process can be efficiently controlled using a conventional combination of feed-forward and feed-back control structures. The aim of this paper is to test and verify an approach to the SCR process which is based on an industrial pilot plant of combustion and nitric oxide formation. The systems are based on measurements of a NOx removal ratio and the fuel flow rate, and NH$_3$slip which are usually available as a part of de-NOx control system.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.103-111
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• 2018

A plasma-catalytic combined process was used as an attempt to improve the conversion efficiency of nitrogen oxides ($NO_x$) over a wide temperature range ($150{\sim}500^{\circ}C$) to cope with the exhaust gas whose temperature varies greatly. Since the catalytic $NO_x$ reduction is effective at high temperatures where the activity of the catalyst itself is high, the $NO_x$ reduction was carried out without plasma generation in the high temperature region. On the other hand, in the low temperature region, the plasma was created in the catalyst bed to make up for the decreased catalytic activity, thereby increasing the $NO_x$ conversion efficiency. Effects of the types of catalysts, the reaction temperature, the concentration of the reducing agent (n-heptane), and the energy density on $NO_x$ conversion efficiency were examined. As a result of comparative analysis of various catalysts, the catalytic $NO_x$ conversion efficiency in the high temperature region was the highest in the case of the $Ag-Zn/{\gamma}-Al_2O_3$ catalyst of more than 90%. In the low temperature region, $NO_x$ was hardly removed by the hydrocarbon selective reduction process, but when the plasma was generated in the catalyst bed, the $NO_x$ conversion sharply increased to about 90%. The $NO_x$ conversion can be maintained high at temperatures of $150{\sim}500^{\circ}C$ by the combination of plasma in accordance with the temperature change of the exhaust gas.

• Korean Chemical Engineering Research
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• v.44 no.5
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• pp.540-546
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• 2006

Effects of organic and inorganic additives on the SNCR reaction of NOx were investigated in a pilot scale flow reactor with a variation of operating parameters. NOx reduction efficiency increased with the increase of a residence time and an initial NOx concentration. NOx reduction reaction by urea solution started to appear about 850 and then reached to maximum value around $970^{\circ}C$. NOx reduction efficiency also increased with the increase of NSR (Normalized Stoichiometric Ratio) up to 2.0. Addition of ethanol and phenol as an organic additives shifted the optimum temperature window to lower region with decreasing the maximum NOx reduction efficiency. This might be due to the side reaction of hydrocarbon in ethanol structure. NaOH addition widened the temperature window and enhanced the NOx reduction efficiency about 10％ due to the chain reaction of NaOH and the reduction of $N_2O$.

• Clean Technology
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• v.29 no.2
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• pp.79-86
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• 2023

The homogeneous catalyst, Ru-MACHO-BH, selectively performs hydrogenation reactions only on the carbonyl group of α, β-unsaturated aldehyde compounds with extremely high reactivity and selectivity. However, the hydrogenation of α, β-unsaturated aldehydes involves a heterogeneous Diels-Alder reaction, resulting in the formation of significant amounts of byproducts, such as dimers. In this study, we used the Ru-MACHO-BH catalyst (Carbonyl hydrido (tetrahydroborato) [bis (2-diphenyl phosphino ethyl) amino] ruthenium(II)) to selectively hydrogenate the carbonyl group of a specific type of α, β-unsaturated aldehyde called methacryl aldehyde, leading to the synthesis of methallyl alcohol. Simultaneously, we applied diols to inhibit the formation of byproducts. The results demonstrate that monoethylene glycol can significantly reduce the formation of diols. Based on these results, we effectively suppressed the formation of dimers containing vinyl groups in methacryl aldehyde by using hydroquinone, which can efficiently inhibit the chemical interaction of vinyl groups. Consequently, the conversion rate of methacryl aldehyde was increased. Ultimately, by reducing the amount of the expensive homogeneous catalyst Ru-MACHO-BH to 1/10, we achieved a selectivity of over 90% and a yield of over 80% for the desired product, methallyl alcohol. These results provide a method to minimize yield reduction while reducing the usage of expensive catalysts, thereby improving cost-effectiveness. We expect that the reaction could be applied to various kinds of selective hydrogenation and has been successfully run on an industrial scale.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.928-935
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• 2010

A bag filter system was partially burnt down during a trial run of waste wood incineration boiler. This brought about unburned hydrocarbon which caused a rapid deactivation of low temperature SCR catalyst set up in two stage after the bag filter. The deactivated catalyst was investigated in order to trace the origin by several characterization methods such as XRD, EDX, BET, TGA, SEM. The deactivated catalyst was regenerated by different methods such as acid washing, water washing in ultrasonication, and calcination treatment under air condition. It is found the calcination treatment under air condition at $450^{\circ}C$ for 2 hours to be the best regeneration method. The catalytic activity was measured in the form of 2 cm ${\times}$ 2 cm ${\times}$ 10 cm (catalyst weight 10 g) honeycomb type. A deNOx efficiency of the regenerated catalyst showed 100% at $180^{\circ}C$ which is the same level of fresh one.