• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.104-110
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• 2010

Deactivation of SCR catalysts applied in coal, orimulsion, and LNG power plants in Korea were studied for the regeneration of the deactivated catalyst. The catalysts were characterized by XRD, ICP-AES, BET and SEM, and were examined for ammonia SCR. Deactivation of SCR catalyst applied in coal power plant was mainly caused by the blockade of the pore due to the deposition of sulfate and particulate related to the ingredients of the fuel. The surface area of SCR catalyst applied in orimulsion power plant decreased considerably by the accumulation of the compounds of vanadium, sulfur, and magnesium on the surface of the catalyst. The compounds of vanadium and sulfur were related to the ingredients of the fuel, and the compound of magnesium was related to the additive of the fuel. The activity of the deactivated catalyst for ammonia SCR, however, decreased slightly. Despite the long use for more than two-year, deactivation of SCR catalyst applied in LNG power plants hardly occurred.

• Environmental Engineering Research
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• v.10 no.1
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• pp.31-37
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• 2005

The selective catalytic experiments using both sulfated/sulfur-free titania and V2O5/TiO2 catalysts have been conducted for NO reduction by NH3 in a packed-bed, down-flow reactor. The sulfated and vanadia loaded titania exhibited higher activity for NO removal than the sulfur-free catalysts, where > 90% NO removal was achieved over the sulfated V2O5/TiO2 catalyst between 280∼500 C. The surface structure of vanadia species on the catalyst surface played a critical role in the high performance of catalysts in which the existence of monomeric/polymeric vanadate is revealed by Raman spectra studies. Water vapor and SO2 were added to the reacting system for the catalyst deactivation tests. At higher temperatures (T ≥ 350 C), little deactivation was observed over the sulfated V2O5/TiO2 catalysts, showing good durability against SO2 and water vapor, which is compared with deactivation at lower temperatures.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.69-78
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• 2018

A study has been carried out of the regenerability of a commercial Ni catalyst used in the steam reforming of the volatiles from biomass pyrolysis (gases and bio-oil), determining the evolution of the reaction indices (conversion, product yields and $H_2$ production) in successive reaction-regeneration cycles. The causes of catalyst deactivation (coke deposition and Ni sintering) have been ascertained characterizing the deactivated and regenerated catalysts by TPO, TEM, TPR and XRD. Catalyst activity is not fully recovered by coke combustion in the first cycles due to the irreversible deactivation by Ni sintering, but the catalyst reaches a pseudo-stable state beyond the fourth cycle, reproducing its behaviour in subsequent cycles.

• Clean Technology
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• v.22 no.2
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• pp.82-88
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• 2016

The loss of activity by coke is an important cause of catalyst deactivation during industrial operation. In this study, hydrogen ratio of reaction condition, which has influenced on coke formation over Pt-Sn catalyst, and regeneration of catalysts activity by coke burning, Pt sintering of coke burning as coke contents, effects of coke formation and deactivation with different Sn contents were confirmed. Pt-Sn-K catalyst supported on θ-alumina and γ-alumina was prepared progressively. Activity of regenerated catalyst for propane dehydrogenation was compared with fresh catalyst by coke burning, after propane dehydrogenation was carried out with different hydrogen ratio at 620 ℃ on fresh catalyst. Regenerated catalyst’s physical characterization such as BET, coke analysis and XRD was investigated. Through catalytic activity test and characterization, Sn contents of catalyst and hydrogen ratio in feed stream could affect coke formation on catalyst surface. Excessive coke makes loss of activity and Pt sintering during air regeneration process.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.61-69
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• 2002

To meet stringent LEV and ULEV emission standards, a considerable amount of development work was necessary to ensure suitable efficiency and durability of catalyst systems. The main challenge is to cut off the engine cold-start emissions. It is known that up to 80% of the total hydrocarbons(THC) are exhausted within the first five minutes in case of US FTP 75 cycle. Close-Coupled Catalyst(CCC) provides fast light-off temperature by utilizing the energy in the exhaust gas. However, if some malfunction occurred at engine operation and the catalyst temperature exceeds 1050$\^{C}$, the catalytic converter is deactivated and shows the poor conversion efficiency. This paper presents effEcts of engine operating conditions on catalytic converter temperature in a SI engine, which are the indications of catalytic deactivation. Exhaust gas temperature and catalyst temperature were measured as a function of air/fuel ratio, ignition timing and misfire rates. Additionally, light-off time was measured to investigate the effect of operating conditions. It was found that ignition retard and misfire can result in the deactivation of the catalytic converter, which eventually leads the drastic thermal aging of the converter. Significant reduction in light-off time can be achieved with proper control of ignition retard and misfire, which can reduce cold-start HC emissions as well.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.212-212
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• 2011

In addition to the catalysts' activity and selectivity, the deactivation of catalysts during use is of practical importance. It is crucial to understand the phenomena of the deactivation to predict the loss of activity during catalyst usage so that the high operational costs associated with catalyst replacement can be reduced. In this study, the activity of Ru catalysts, such as nanoparticles (3~6 nm) and polycrystalline thin film (50 nm), have been investigated under CO oxidation and oxidative/reductive reaction conditions at various temperatures with the ambient pressure X-Ray photoelectron spectroscopy (APXPS). With APXPS, the surface oxides on the catalyst are measured and monitored in-situ. It was found that the Ru film exhibited faster oxidation-and-reduction compared to that of nanoparticles showing mild oxidative-and-reductive characteristics. Additionally, the larger Ru nanoparticles showed a higher degree of oxide formation at all temperatures, suggesting a higher stability of the oxide. These observations are in agreement with the catalytic activity of Ru catalysts. The loss of activity of Ru films is correlated with bulk oxide formation, which is inactive in CO oxidation. The Ru nanoparticle, however, does not exhibit deactivation under similar conditions, suggesting that its surface is covered with a highly active ultrathin surface oxide. Since the active oxide is more stable as nanoparticles than as a film, the nanoparticles showed mild oxidative/reductive behavior, as confirmed by APXPS results. We believe these simultaneous observations of both the surface oxide of Ru catalysts and the reactivity in real time enable us to pinpoint the deactivation phenomena more precisely and help in designing more efficient and stable catalytic systems.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.259-263
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• 2008

The catalytic activity of the used catalyst, $V_2O_5/TiO_2$, for MSW incinerators was investigated focusing on its regeneration. As the result of the experimental analysis, the NOx removal efficiency difference between the fresh catalyst and used catalyst is about 60% at $260^{\circ}C$ and 1, 2-dichlorobenzen (1, 2-DCB) removal efficiency difference is about 14% at $200^{\circ}C$, in honeycomb test. And the catalysts, both the fresh and used, were characterized by XRD, TGA, and ICP techniques in order to investigate the deactivation. On the basis of the results, it is found that the used catalyst is deactivated by ammonium-sulfates, heavy metals (Pb, As etc.), alkali metals (Ca), and phase transfer of $TiO_2$. Also calcination treatment under nitrogen and air condition was excellent than washing and calcination treatment.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.45-50
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• 2002

Use of a phenomenological model, developed far prediction of catalytic deactivation, is demonstrated in comparing harshness of different driving cycles that are currently used to rapidly age catalytic converters on engine test benches. The model shows that seemingly equivalent driving cycles cause the catalytic converters to reach significantly different levels of deactivation. The comparison of the model prediction with the limited vehicle data seems encouraging despite the simplicity of the model at the current stage of its infancy.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.963-968
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• 1999

The global environmental problems have been caused by the release of CFCs. Therefore, methods for safe destruction of recoverd CFCs will be eventually needed. The objective of this study was to develop and test a catalyst operating at a mild condition for the decomposition of CFC-113. In this work, catalytic oxidative decomposition of CFC-113 was carried out over aerosol $TiO_2/SiO_2(ATS)$ catalysts prepared by the sol-gel method. All ATS catalysts(Ti/Si mol ratio=1, 2, 2.33, 4) showed high initial activity. However, the deactivation of ATS catalysts was found that more remarkable due to an attack of fluorine and the destruction of ATS structure(Si-F reaction) from analyses of SEM-EDX, XRD than $TiO_2/SiO_2(ATS)$ catalyst prepared by the precipitation method. ATS catalysts prepared by more acidic prehydrolysis condition were found to have still more activity and longer life-time by increasing of acidity. The activity of ATS catalyst also depend on the content of $TiO_2$. There was reason that the acidity of the ATS catalyst was increased with the increased content of $TiO_2$ from 50 to 80 mol %. Solid superacid catalyst ($ATX/SO_4{^{2-}}$) modified with $H_2SO_4$ solution was prepared for high activity and lower deactivation. The reaction of $ATS/SO_4{^{2-}}$ catalyst also exhibited even higher activity and lower deactivation than the original ATS catalyst. It is suggested that the addition of the sulphate species clearly inhibit the deactivation.