• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.560-567
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• 2020

In this study, we investigated that the effect of alkali metals [Na(Sodium) and K(Potassium)], known as representative deactivating substances among exhaust gases of various industrial processes, on the NH₃-SCR (selective catalytic reduction) reaction of V/W/TiO₂ catalysts. NO, NH₃-TPD (temperature programmed desorption), DRIFT (diffuse reflectance infrared fourier transform spectroscopy analysis), and H₂-TPR analysis were performed to determine the cause of the decrease in activity. As a result, each alkali metal acts as a catalyst poisoning, reducing the amount of NH₃ adsorption, and Na and K reduce the SCR reaction by reducing the L and B acid points that contribute to the reaction activity of the catalyst. Through the H₂-TPR analysis, the alkali metal is considered to be the cause of the decrease in activity because the reduction temperature rises to a high temperature by affecting the reduction temperature of V-O-V (bridge oxygen bond) and V=O (terminal bond).

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.468-475
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• 2015

Various methods to degrade explosives efficiently in natural soil and water that include trinitrotoluene (TNT) have been studied. In this study, TNT in water was degraded by reduction with palladium (Pd) catalyst impregnated onto alumina (henceforth Pd-Al catalyst) and formic acid. The degradation of TNT was faster when the temperature of water was high, and the initial TNT concentration, pH, and ion concentration in water were low. The amounts of Pd-Al catalyst and formic acid were also important for TNT degradation in water. According to the experimental results, the degradation constant of TNT with unit mass of Pd-Al catalyst was $8.37min^{-1}g^{-1}$. The degradation constant of TNT was higher than the results of previous studies which used zero valent iron. 2,6-diamino-4-nitrotoluene and 2-amino-4,6-dinitrotoluene were detected as by-products of TNT degradation showing that TNT was reduced. The by-products of TNT were also completely degraded after reaction when both Pd-Al catalyst and formic acid existed. Even though there are several challenges of Pd-Al catalyst (e.g., deactivation, poisoning, leaching, etc.), the results of this study show that TNT degradation by Pd-Al catalyst and formic acid is a promising technique to remediate explosive contaminated water and soil.

• Journal of the Korean Applied Science and Technology
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• v.29 no.4
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• pp.594-598
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• 2012

Polymer electrolyte membrane fuel cell(PEMFC) performance degrades seriously when sulfur dioxide and hydrogen sulfide are contaminated in the fuel gas at anode and air source at cathode, respectively. This paper reveals the effect of the combined sulfur impurity poisoning on both PEMFC cathode and anode parts through measuring electrical performance on single FC operated under 1 ppm to 10 ppm impurity gases. The severity of $SO_2$ and $H_2S$ poisoning depended on concentrations of impurity gases under optimum operating conditions($65^{\circ}C$ of cell temperature and 100 % relative humidity). Sulfur adsorption occured on the surface of Pt catalyst layer on MEA. In addition, MEA poisoning by impurity gases were cumulative. After four consecutive poisonings with 1, 3, 5 to 10 ppm, the fuel cell performance of PEMFC was decrease upto 0.54 V(76 %) from 0.71 V.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.503-509
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• 2016

Fuel cell is a device for producing electricity by using the hydrogen produced by the fuel processor. At this time, CO is also created by the fuel processor. The resulting CO enters the stack where is produce electricity and leads to the adsorption of anode catalyst, finally the CO poisoning occurs. Stack which occurred CO poisoning has a reduction in performance and shelf life are gradually fall because they do not respond to hydrogen. In this paper, experiments that using a PROX reactor to prevent CO poisoning were carried out for removing the CO concentration to less than 10ppm range available in the fuel cell. Furthermore experiments by the PROX reaction was designed and manufactured with a water-cooling heat exchange reactor to maintain a suitable temperature control due to the strong exothermic reaction.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.180-183
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• 2007

CO in the reformed gas for proton exchange membrane fuel cell(PEMFC) has a strong tendency to adsorb on the surface of the catalyst and thus to block the sites that hydrogen needs for reactions. Even part per million levels of CO can cause serious poisoning. This CO poisoning can overcome to bleed trace amounts of air into the anode. In this study, we indicated the alteration of stack performance in various CO concentration and then bled a small amount of air. The performance of stack was reduced by increasing CO amount, and recovered by air bleeding. But the air-bleeding have an impact on performance of anode should be further explored.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.35-43
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• 1998

Electrodes using for the anode electrode of direct methanol fuel cell with Pt/C and Pt/Ru/C catalyst were prepared and characterized by SEM, TEM, thermal analysis and electrochemical analysis. The half cell tests were carried out with 1 M $H_2SO_4$ electrolyte and 1 M $CH_3OH$ in order to evaluate the electrode performance. The employed electrochemical methods were cyclic vol-tammetry and potentiodynamic polarization experiments. It was found that 20 w% polytetrafluoroethylene (PTFE) content in catalyst showed the best performance due to the best platinum utilization on PTFE-containing catalyst layer. It was found that Pt/Ru/C binary catalyst inhibited the poisoning of anode electrode showing improved performance compared to the Pt/C catalyst by the adsorption of oxygen containing species on the electrode surface at same time. The apparent activation energy for methanol oxidation on the Pt/Ru/C and Pt/C catalyst layer was 11.60 kJ/mol and 26.85 kJ/mol, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.6
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• pp.238-242
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• 2016

The effect of the alkali, alkali earth metal elements on selective catalytic reduction(SCR) catalyst deactivation behavior were investigated in terms of microstructure, surface area, pore volume and De-NOx test. Poisoned SCR catalyst were manufactured by injection of $K_2CO_3$, $Na_2CO_3$, $Ca(CH_3COO)_2{\cdot}H_2O$, $C_4H_6MgO_4{\cdot}4H_2O$, $H_3PO_4$ solutions in the new SCR catalyst at $350^{\circ}C$ for 6 hours. New and poisoned catalysts surface were similar. But specific surface area, pore volume decrease from Na, Mg, K, Ca, P compared to new SCR catalyst. Especially, Na poisoned catalyst surface area and pore size extremely decreased by $10.20m^2/g$, $0.061cm^2/g$. De-NOx test results of new and poisoned catalysts at $150{\sim}450^{\circ}C$ indicated that alkali metal (K, Na) poisoned SCR catalysts have the lowest De-NOx efficiency, alkali earth metal poisoned SCR catalysts (Ca, Mg) De-NOx efficiency are higher than alkali metal poisoned SCR catalysts. P poisoned SCR catalyst De-NOx efficiency is similar new SCR catalyst. It were considered that physical deactivation of SCR catalyst was affected by SCR catalyst surface area and pore volume change.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.38-46
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• 1991

Regeneration of Ni catalyst deactivated by carbon-deposition and sulfur-poisoning was studied. When a carbon-deposited catalyst was regenerated by hydrogen, the final recovery of catalytic activity for benzene hydrogenation was large but relatively long period of regeneration was required, and futhermore the deposited carbon could not be removed completely. In case of oxygen-treatment, the regeneration rate was high and the deposited carbon could be removed almost completely after a subsequent reduction treatment. When a sulfur-poisoned catalyst was regenerated by hydrogen and water vapor, the catalytic activity was not recovered. The regeneration treatment with oxygen at $650^{\circ}C$ recovered the catalytic activity up to 60 % of the initial value. When $Cl^-$ was added to oxygen, the activity was easily recovered to 45 % of the initial value even after treatment at $500^{\circ}C$. Sintering of the dispersed Ni particles was enhanced by water vapor but was hindered by oxygen and chlorine addition.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.714-720
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• 2011

Ethanol was used as reducing agent to remove $NO_x$ exhaust from the stationary source. Pre-treatment with sulfuric acid over $Ag/Al_2O_3$ catalyst was dedicated to overcome the $SO_2$ poisoning effect. The $NO_x$ reduction experiment was performed under the simulated condition of power plant The increased surface area with higher CPSI devoted to increase de-$NO_x$ yield. De-$NO_x$ yield of the $NO_x$ exhaust containing 20 ppm of $SO_2$ increased after acid treatment with 0.7% $H_2SO_4$ over 4.0% $Ag/Al_2O_3$, where the increased dispersion of Ag found from the results of XRD and XPS was the dominant factor for the increased de-$NO_x$ yield. However, the reason for the decreased de-$NO_x$ yield with the acid treatment of higher concentration (1.0% and 2.0%) of $H_2SO_4$ was found to be due to the formation of $Ag_2SO_4$ crystallites found from XRD result. Acid-treated $Ag/Al_2O_3$ catalyst showed maximum de-$NO_x$ yield at higher temperature than non-treated $Ag/Al_2O_3$ catalyst did.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.187-192
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• 2023

The use of biomass is increasing as a response to the convention on climate change. In Korea, a method applied to replace fossil fuels is using wood chips in a cogeneration plant. To remove air pollutants generated by burning wood chips, a selective denitrification facility (Selective catalytic reduction, SCR) is installed downstream. However, problems such as ash deposition and descaling of the equipment surface have been reported. The cause is thought to be unreacted ammonia slip caused by ammonia ions injected into the reducing agent and metal corrosion caused by an acidic environment. Element analysis confirmed that ash contained alkali metals and sulfur that could cause catalyst poisoning, leading to an increase in the size of ash particle and deposition. Measurement of the size of ash deposited inside the facility confirmed that the size of ash deposited on the catalyst was approximately three times larger than the size of generally formed ash. Therefore, it was concluded that a reduction in pore area of the catalyst by ash deposition on the surface of the catalyst could lead to a problem of increasing differential pressure in a denitrification facility.