• International Journal of Automotive Technology
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• v.8 no.3
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• pp.283-288
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• 2007

This paper presents the static characteristics of a urea-SCR system. The static characterization of the urea-SCR system was generated by sweeping urea flow rates at common engine torque/speed operating points. Several experiments were performed using engine operating points at different raw NOx emission levels, space velocities, and SCR catalyst temperatures. The recorded NOx emissions from the engine exhaust outlet and engine tailpipe are then compared. The urea-SCR static system results indicated that a $50{\sim}60%$ NOx conversion is achievable at most engine operating points using the stoichiometric $NH_3/NOx$ ratio, and a high 98% NOx conversion is possible by exceeding the stoichiometric $NH_3/NOx$ ratio. The effect of the pre-oxidation catalyst volume was also investigated and found to have a profound impact on experimental results, particularly the static NOx conversion.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.26-32
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• 2015

The purpose of this study is to investigate the de-NOx performance characteristics according to the $TiO_2$ crystal structures ratio of $V_2O_5$ SCR catalysts. The anatase(100%) SCR catalyst showed the highest desorption peak of 80ppm at about $250^{\circ}C$, and $NH_3$ was not desorbed at $500^{\circ}C$. It can be confirmed that there was many $NH_3$ desorbed at a high temperature among other various crystal structures, which is because the catalyst was more acidized to increase the intensity of acid sites as the content of subacid sulfate ions($NH_2SO_4$) in the rutile phase increases. The anatase/rutile(7%/93%) SCR had the smallest width of de-NOx performance drop according to thermal aging, and had strong durability against thermal aging.

• 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.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.76-83
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• 2010

Recently, as the current and future emission regulations go stringent, the research of NOx reduction has become a subject of increasing interest and attention in diesel engine. Selective Catalytic Reduction (SCR) is one of the effective technology to reduce NOx emission from diesel engine. Especially, Urea-SCR that uses urea as a reductant is becoming increasingly popular as a cost effective way of reducing NOx emissions from heavy duty vehicles. In this research, we designed urea injector and DCU (Dosing Control Unit) specially developed for controlling the Urea-SCR process onboard vehicles. As passenger and commercial diesel engine experiment, we grasped characteristics of NOx emission and SCR catalyst temperature level in advance. As a result, highest NOx emission level was shown in condition of low engine speed and high load. On the other hand, SCR catalyst temperature was highest at high engine speed and load. On the basis of these result, we conducted the NOx reduction test at steady engine operating conditions using the urea injector and DCU. It was shown that 74% NOx conversion efficiency on the average and 97% NOx conversion efficiency was obtained at high SCR catalyst temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6575-6580
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• 2013

Various modified SCR catalysts were prepared and tested to improve the strength of catalysts for use under severe conditions. The SCR catalysts were modified with a binder and dispersion agent, and tested at the fixed bed reactor. FT-IR and $H_2$-TPR were used to analyze the degree of hydrogen use and ammonia adsorption by the modified catalysts. In the case of the SCR catalysts coated with 2.3g of the binder, 4.7g of ethanol, and 0.1g of dispersion agent, the strength of catalyst was increased by approximately 12%. On the other hand, despite the enhancement of strength, the activities of the SCR catalysts were decreased by 2-10%. When the mixed solution composed of binder, dispersion agent and $SiO_2$ solution was precipitated on the catalyst, the $NO_x$ conversion of the catalyst was decreased slightly. The Bronsted acid site and Lewis acid site worked as the activators for the SCR reaction, and were decreased by $SiO_2$.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.119-123
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• 2012

This study presents the effect of oxygen on the $NH_3$ selective catalytic reduction (SCR) by Mn/$TiO_2$ catalyst. The lattice oxygen of catalysts is participate in the low temperature SCR, and the gaseous oxygen directly takes part in the rexoidtion of reduced catalyst. These redox properties of oxygen an play important role in SCR activity and the available capability of lattice oxygen depends on the manganese oxidation state of the catalyst surface. $MnO_2$ species has a higher redox property than that of $Mn_2O_3$ species on deposited $TiO_2$ surface and these manganese oxide states strongly depend on the $TiO_2$ surface area.

• Resources Recycling
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• v.21 no.6
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• pp.65-73
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• 2012

Selective catalytic reduction(SCR) catalysts are obtained from de-NOx system of thermoelectric power plant. A process was developed for valuable metals such as vanadium and tungsten recovery from spent SCR catalyst by using soda roasting followed by water leaching. Spent SCR catalyst having $V_2O_5$(1.23 mass %) and $WO_3$(7.73 mass %). For getting soluble metal forms of the targeted metals like vanadium and tungsten soda roasting process was implemented. In soda roasting process, sodium carbonate added 5 equivalent ratio at roasted temperature $850^{\circ}C$ with 120 min roasted time for $544{\mu}m$ particle size of spent SCR catalyst. After soda roasting process moved to water leaching for roasted spent catalyst. Before leaching process the roasted spent catalyst was grinded up to $-45{\mu}m$ size. The leaching time is 30 min at $40^{\circ}C$ temperature, 10 % pulp density. The final leaching efficiency obtained 46 % of vanadium and 92 % of tungsten from present process.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.6
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• pp.519-525
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• 2010

Ethanol was used as reductant to remove $NO_x$ over Ag/$Al_2O_3$ catalyst via SCR from stationary emission source. Among the tested hydrocarbon reductants, ethanol showed highest de-$NO_x$ performance over the Ag/$Al_2O_3$ catalyst. De-$NO_x$ efficiency of about 83% was obtained in the condition of GHSV 20,000 $hr^{-1}$, $NO_x$ 200 ppm, CO 200 ppm, $O_2$ 13%, $H_2O$ 5% and mole ratio of ethanol/$NO_x$ = 2 between temperature of $300^{\circ}C$ and $400^{\circ}C$. While $SO_2$ presence in the $NO_x$ exhaust suppressed the catalytic activity, catalyst with acid (0.7% $H_2SO_4$) treatment of catalyst showed higher catalytic activity, where In-Situ DRIFT showed S presence over catalyst surface was increased after acid treatment of catalyst. From in-situ DRIFT and SCR results, it was concluded that sulfur presence over the surface of Ag/$Al_2O_3$ catalyst was the dominant factor to control the de-$NO_x$ reaction yield via HC-SCR from the exhausted gas including $SO_2$.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.859-869
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• 2005

The commercial $V_2O_5-WO_3/TiO_2$ catalysts which had been exposed to the off gas from incinerator for a long time were regenerated by physical and chemical treatment. The catalytic properties and NOx conversion reactivity of those catalysts were examined by analysis equipment and NOx conversion experiment. The characterization of the catalysts were performed by XRD(x-ray diffractometer), BET, POROSIMETER, EDX(energy dispersive x-ray spectrometer), ICP(inductively coupled plasma), TGA(thermogravimetric analyzer) and SEM (scanning electron microscopy). NOx conversion experiment were performed with simulated off gas of the incinerator and $NH_3$ was used as a reductant of SCR reaction. Among the regeneration treatment methods which were applied to regenerate the aged catalysts in this study, it showed that the heat treatment method had excellent regeneration effect on the catalytic performance for NOx conversion. The catalytic performance of the regenerated catalysts with heat treatment method were recovered over than 95% of that of fresh catalyst. For the regenerated catalysts with the acid solution(pH 5) and the alkali solution(pH 12), the catalytic performance were recovered over than 90% of that of fresh catalyst. From the characterization results of the regenerated catalysts, the specific surface area was recovered in the range of $85{\sim}95%$ of that of fresh catalyst. S and Ca element, which are well known as the deactivation materials for the SCR catalysts, accumulated on the aged catalyst surface were removed up to maximum 99%. Among the P, Cr, Zn and Pb elements accumulated on the aged catalyst surface, P, Cr and Zn element were removed up to 95%. But the Pb element were removed in the range of $10{\sim}30%$ of that of fresh catalyst.

• Clean Technology
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• v.29 no.4
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• pp.313-320
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• 2023

In order to increase the usability of H₂-SCR, the NOx removal characteristics with catalyst powder of PtNi/CeO₂-W-TiO₂ using Ce as a co-catalyst was synthesized and coated on a porous metal structure (PMS) were evaluated. Catalyst powder of PtNi/CeO₂-W-TiO₂(PtNi nanoparticles onto W-TiO₂, with the incorporation of ceria (CeO₂) as a co-catalysts) was synthesized and coated onto a porous metal structure (PMS) to produce a Selective Catalytic Reduction (SCR) catalyst. H₂-SCR with CeO₂ as a co-catalyst exhibited higher NOx removal efficiency compared to H₂-SCR without CeO₂. Particularly, at a 10wt% CeO₂ loading ratio, the NOx removal efficiency was highest at 90℃. As the amount of catalyst coating on PMS increased, the NOx removal efficiency was improved below 90℃, but it was decreased above 120℃. When the space velocity was changed from 4,000 h^-1 to 20,000 h^-1, the NOx removal efficiency improved at temperatures above 120℃. It was expected that the use of the catalyst could be reduced by applying the PMS with excellent specific surface area as a support.