The Regeneration Effect of H2SO4 on V-W-TiO2 SCR Catalyst Deactivated by Alkali Metal

The sodium content in Zhundong coal is extremely high, which can accelerate the deactivation of the V-W-TiO2 selective catalytic reduction (SCR) catalysts. Sulfuric acid solution (H2SO4) washing has been verified as a famous method to regenerate the de-NOx performance for catalyst which has been poisoned by alkali metals. However, the performance of the regenerated catalyst in practice still needs to be investigated. In the present study, the resistance to sulfur dioxide (SO2) and the mechanical strength of the regenerated catalyst were experimentally studied as well as the continuous operation performances under several conditions. The results indicate that the de-NOx activity of H2SO4 regenerated catalyst is chemically stable below 300 °C and thermally stable below 450 °C. However, the catalytic activity of the regenerated catalyst could suffer a decline during operating under the SCR atmosphere at 450 °C, which is different from the fresh catalyst. Besides, the regenerated catalyst shows good SO2 resistance, whereas the mechanical strength is likely to be affected by the H2SO4 washing treatment.

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Deactivation of Cu/SSZ-13 NH3-SCR Catalyst by Exposure to CO, H2, and C3H6

Catalysts ◽

10.3390/catal9110929 ◽

2019 ◽

Vol 9 (11) ◽

pp. 929 ◽

Cited By ~ 1

Author(s):

Auvray ◽

Mihai ◽

Lundberg ◽

Olsson

Keyword(s):

Flow Reactor ◽

Catalytic Reduction ◽

Plug Flow ◽

Acid Sites ◽

Drift Spectroscopy ◽

Scr Catalyst ◽

Nh3 Scr ◽

Scr Catalysts ◽

Nh3 Oxidation ◽

Diffuse Reflectance Infrared

Lean nitric oxide (NOx)-trap (LNT) and selective catalytic reduction (SCR) are efficient systems for the abatement of NOx. The combination of LNT and SCR catalysts improves overall NOx removal, but there is a risk that the SCR catalyst will be exposed to high temperatures and rich exhaust during the LNTs sulfur regeneration. Therefore, the effect of exposure to various rich conditions and temperatures on the subsequent SCR activity of a Cu-exchanged chabazite catalyst was studied. CO, H2, C3H6, and the combination of CO + H2 were used to simulate rich conditions. Aging was performed at 800 °C, 700 °C, and, in the case of CO, 600 °C, in a plug-flow reactor. Investigation of the nature of Cu sites was performed with NH3-temperature-programed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) of probe molecules (NH3 and NO). The combination of CO and H2 was especially detrimental to SCR activity and to NH3 oxidation. Rich aging with low reductant concentrations resulted in a significantly larger deactivation compared to lean conditions. Aging in CO at 800 °C caused SCR deactivation but promoted high-temperature NH3 oxidation. Rich conditions greatly enhanced the loss of Brønsted and Lewis acid sites at 800 °C, indicating dealumination and Cu migration. However, at 700 °C, mainly Brønsted sites disappeared during aging. DRIFT spectroscopy analysis revealed that CO aging modified the Cu2+/CuOH+ ratio in favor of the monovalent CuOH+ species, as opposed to lean aging. To summarize, we propose that the reason for the increased deactivation observed for mild rich conditions is the transformation of the Cu species from Z2Cu to ZCuOH, possibly in combination with the formation of Cu clusters.

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Combination of LNT and SCR for NOx reduction in passenger car applications

Combustion Engines ◽

10.19206/ce-116945 ◽

2014 ◽

Vol 157 (2) ◽

pp. 60-67

Author(s):

Teuvo MAUNULA

Keyword(s):

Catalytic Reduction ◽

Nox Reduction ◽

Main Reaction ◽

Maximum Temperature ◽

Lean Nox Trap ◽

Particulate Emissions ◽

Passenger Cars ◽

Experimental Conditions ◽

Scr Catalyst ◽

Scr Catalysts

The removal of NOx and particulate emissions in light-duty diesel vehicles will require the use of aftertreatment methods like Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR) with urea and Lean NOx Trap (LNT) (Euro 6 and beyond). A new concept is the combination of LNT + SCR, which enables on-board synthesis of ammonia (NH3), which reacts with NOx on the SCR catalyst. The main application for this kind system will be lighter passenger cars, where LNTs may be used instead of full urea-SCR system. That particular combinatory system was investigated by developing platinum (Pt) and rhodium (Rh) containing LNTs and SCR catalysts in this study. In the use conditions, the maximum temperature may reach temperatures up to 800 °C and NOx reduction reactions should proceed without NO2 assistance in the SCR position after LNT and DPF. PtRh/LNT with the total loadings of 85 g/cft (2.8 g/L) and higher resulted in a high NOx efficiency above 80–90% with a broad operation window in the laboratory simulations. In the experimental conditions, a higher NH3 concentration after LNT was essential to simulate well the operation of SCR catalysts. The developed Cu-SCR catalyst showed a high hydrothermal durability up to the ageing temperature of 800 °C and a wide operation window without the NO2 assistance (NO only in feed). Fe-SCR and V-SCR catalysts were more dependent on NO2. A studied concept had an air injection after LNT to keep SCR condition always in lean side, where the SCR reaction was promoted by oxygen resulting in high reduction selectivity to nitrogen (N2) without NH3 emissions. The simulations in reaction conditions and system design resulted in the proposals for the optimal design and main reaction mechanism in DOC + DPF + LNT + SCR systems.

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The Deactivation of Industrial SCR Catalysts—A Short Review

Energies ◽

10.3390/en13153870 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3870 ◽

Cited By ~ 3

Author(s):

Agnieszka Szymaszek ◽

Bogdan Samojeden ◽

Monika Motak

Keyword(s):

Nitrogen Oxides ◽

Power Plants ◽

Alkali Metals ◽

Mechanical Stability ◽

Catalytic Reduction ◽

Short Review ◽

Nh3 Scr ◽

Scr Catalysts ◽

Honeycomb Monolith ◽

The Common

One of the most harmful compounds are nitrogen oxides. Currently, the common industrial method of nitrogen oxides emission control is selective catalytic reduction with ammonia (NH3-SCR). Among all of the recognized measures, NH3-SCR is the most effective and reaches even up to 90% of NOx conversion. The presence of the catalyst provides the surface for the reaction to proceed and lowers the activation energy. The optimum temperature of the process is in the range of 150–450 °C and the majority of the commercial installations utilize vanadium oxide (V2O5) supported on titanium oxide (TiO2) in a form of anatase, wash coated on a honeycomb monolith or deposited on a plate-like structures. In order to improve the mechanical stability and chemical resistance, the system is usually promoted with tungsten oxide (WO3) or molybdenum oxide (MoO3). The efficiency of the commercial V2O5-WO3-TiO2 catalyst of NH3-SCR, can be gradually decreased with time of its utilization. Apart from the physical deactivation, such as high temperature sintering, attrition and loss of the active elements by volatilization, the system can suffer from chemical poisoning. All of the presented deactivating agents pass for the most severe poisons of V2O5-WO3-TiO2. In order to minimize the harmful influence of H2O, SO2, alkali metals, heavy metals and halogens, a number of methods has been developed. Some of them improve the resistance to poisons and some are focused on recovery of the catalytic system. Nevertheless, since the amount of highly contaminated fuels combusted in power plants and industry gradually increases, more effective poisoning-preventing and regeneration measures are still in high demand.

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Research of Microwave - Ethanol Auxiliary V2O5-WO3/TiO2 SCR Catalyst Regeneration Experiment

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1015.619 ◽

2014 ◽

Vol 1015 ◽

pp. 619-622

Author(s):

Zhuang Kun Wang

Keyword(s):

Catalytic Reduction ◽

Physical Structure ◽

Catalyst Regeneration ◽

Practical Significance ◽

Regeneration Process ◽

Recovery Method ◽

Scr Catalyst ◽

Scr Catalysts ◽

Element Enrichment ◽

Scr System

Using selective catalytic reduction (SCR) that takes NH3 as the reducing agent to remove NOx is one of the most often used coal-fired flue gas denitration technology that of the highest denitration efficiency. As the core of the SCR system, catalyst is the important factors that affect the whole SCR system denitration efficiency. As the growth of the running time, catalyst tends to lose active energy because of the surface channel jam and toxic element enrichment and deactivation. Each year the deactivation catalyst regeneration process, can save a lot of money, thus help to avoid pollution of the environment. So study of the SCR catalyst regeneration technology is around the corner, which is of great practical significance for lowering the cost of the SCR system, promoting the application of the SCR technology, and protecting the environment. In this paper, the research takes vanadium series SCR catalysts as the object to study the regeneration technology of catalyst, new physical structure recovery method, and effect of regeneration process in the treatment on the performance of catalyst.

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Effect of Alkali Metal Deposition on Activity of De-NOx SCR Catalysts

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.955-959.698 ◽

2014 ◽

Vol 955-959 ◽

pp. 698-701

Author(s):

Pei Qing Cao ◽

Chang An Wang ◽

Zhi Qiang Liu ◽

Yong Bo Du ◽

Yong Gang Zhao ◽

...

Keyword(s):

Alkali Metal ◽

Metal Content ◽

Catalytic Effect ◽

No Reduction ◽

Metal Deposition ◽

Impregnation Method ◽

Scr Catalyst ◽

Scr Catalysts ◽

Zhundong Coal ◽

Sodium And Potassium

Zhundong coal has a huge proved reserve and many excellent properties. However, the alkali metal content in Zhundong coal is apparently high, which can accelerate the deactivation of De-NOx SCR catalysts. In the present study, the effect of alkali metal deposition on activity of SCR catalysts through solution impregnation method was experimentally investigated. The results indicate that alkali metal deposition on the catalyst surface significantly deactivates the capacity of SCR catalysts. NaOH presents the most intense poisonousness. The catalytic effect on NO reduction reduces with the increase of alkali metal content on catalyst surfaces. In addition, potassium establishes more obvious poisonousness on SCR catalyst than sodium. There is interaction effect between sodium and potassium on deactivating the SCR catalyst.

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Heterogeneous Mercury Reaction on a Selective Catalytic Reduction (SCR) Catalyst

Catalysis Letters ◽

10.1007/s10562-007-9317-0 ◽

2007 ◽

Vol 121 (3-4) ◽

pp. 219-225 ◽

Cited By ~ 111

Author(s):

Yujin Eom ◽

Seok Ho Jeon ◽

Thanh An Ngo ◽

Jinsoo Kim ◽

Tai Gyu Lee

Keyword(s):

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Scr Catalyst

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Modeling of a Urea SCR Catalyst With Automotive Applications

Dynamic Systems and Control ◽

10.1115/imece2002-32104 ◽

2002 ◽

Cited By ~ 30

Author(s):

Devesh Upadhyay ◽

Michiel Van Nieuwstadt

Keyword(s):

Catalytic Reduction ◽

Chemical Properties ◽

Lumped Parameter Model ◽

Scr Catalyst ◽

Weighted Residuals ◽

Method Of Weighted Residuals ◽

Lumped Parameter ◽

1D Model ◽

Continuously Stirred Tank Reactor ◽

Three State Model

A zero order lumped parameter control oriented model of a Selective Catalytic Reduction (SCR) catalyst is presented. The lumped parameter model is developed using two approaches. in the first approach it was assumed that the catalyst behaves as an Isothermal Continuously Stirred Tank Reactor (ICSTR). The second approach involved deriving the lumped parameter model from a 1D model using the method of weighted residuals. Both approaches led to a three state model, with the gas phase concentrations of NOx and NH3 and the surface coverage fraction as the states. The model depends on chemical properties specific to the SCR catalyst; consequently model validation requires knowledge of these parameters, either via laboratory-based experiments or as supplied by the catalyst supplier. We present an alternate approach that allows estimation of the essential parameters through a minimization of the l2 errors between measured and simulated results.

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Experimental and kinetic analysis of hydrothermal aging effects on ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407018814950 ◽

2018 ◽

Vol 233 (12) ◽

pp. 3030-3042

Author(s):

Tae Joong Wang ◽

In Hyuk Im

Keyword(s):

Adsorption Capacity ◽

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Adsorption Site ◽

Selective Catalytic Reduction Catalyst ◽

Aging Effects ◽

Hydrothermal Aging ◽

Ammonia Adsorption ◽

Fresh Catalyst ◽

Reduction Catalysts

Ammonia/urea selective catalytic reduction is an efficient technology to control NOx emission from diesel engines. One of its critical challenges is the performance degradation of selective catalytic reduction catalysts due to the hydrothermal aging experienced in real-world operations during the lifetime. In this study, hydrothermal aging effects on the reduction of ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst were investigated under actual engine exhaust conditions. Ammonia adsorption site densities of the selective catalytic reduction catalysts aged at two different temperatures of 750°C and 850°C for 25 h with 10% H2O were experimentally measured and compared to that of fresh catalyst on a dynamometer test bench with a heavy-duty diesel engine. The test results revealed that hydrothermal aging significantly decreased the ammonia adsorption capacity of the current commercial Cu-zeolite selective catalytic reduction catalyst. Hydrothermal treatment at 750°C reduced the ammonia adsorption site to 62.5% level of that of fresh catalyst, while hydrothermal treatment at 850°C lowered the adsorption site to 37.0% level of that of fresh catalyst. Also, in this study, numerical simulation and kinetic analysis were carried out to quantify the impact of hydrothermal aging on the reduction of ammonia adsorption capacity by introducing an aging coefficient. The kinetic parameter calibrations based on actual diesel engine tests with a commercial monolith Cu-zeolite selective catalytic reduction catalyst provided a highly realistic kinetic parameter set of ammonia adsorption/desorption and enabled a mathematical description of hydrothermal aging effect.

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Reduction of NOx Emission of a Diesel Engine with a Multiple Injection Pump by SCR Catalytic Converter

Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis ◽

10.11118/actaun201664041205 ◽

2016 ◽

Vol 64 (4) ◽

pp. 1205-1210 ◽

Cited By ~ 2

Author(s):

Vít Marek ◽

Lukáš Tunka ◽

Adam Polcar ◽

Dušan Slimařík

Keyword(s):

Diesel Engine ◽

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Catalytic Converter ◽

Nox Emission ◽

Multiple Injection ◽

Scr Catalyst ◽

Exhaust Gases ◽

Injection Pump ◽

Reduction Of Nox

This paper deals with reduction of NOx-emission of a diesel engine with multiple injection pump by SCR catalytic converter. Main aim of the measurement was the detection of SCR catalyst converter efficiency. Tests were realized at the Research and Development workplace of Zetor Tractor a.s. Used engine was equipped with a multiple injection pump with electromagnetic regulator of a fuel charge. During the experiment selective catalytic reduction and diesel particulate filter were used as an after treatment of harmful pollutants reduction. Testing cycle of the eight-point test was chosen and Non-Road Steady Cycle (NRSC) was maintained according to 97/68/EC directive. Results confirmed the dependencies between temperatures of SCR catalyst and exhaust gases and the volume of exhaust gases on efficiency of SCR catalyst. During the operation load of the engine, selective catalytic reduction reached efficiency over 90 %. Used after treatment system is suitable for reduction of harmful pollutants according to the Tier 4f norm.

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