Factors Affecting Mercury Oxidation by SCR Catalysts

2014 ◽  
Vol 986-987 ◽  
pp. 755-760
Author(s):  
Wen Du ◽  
Li Bao Yin ◽  
Yu Qun Zhuo ◽  
Qi Sheng Xu ◽  
Liang Zhang ◽  
...  
Keyword(s):  
Active Sites ◽  
Catalytic Reduction ◽  
Space Velocity ◽  
Injection Rate ◽  
Mercury Oxidation ◽  
Factors Affecting ◽  
Scr Catalysts ◽  
Negative Effect ◽  
Oxidation Efficiency ◽  
Scr System

The application of selective catalytic reduction (SCR) system may affect mercury speciation in coal-combustion flue gas. The factors affecting mercury oxidation efficiency by SCR catalysts have been evaluated in this research. The influencing factors investigated included hydrogen chloride (HCl), sulfur dioxide (SO2), ammonia (NH3) injection rate and space velocity. HCl had been found to promote mercury oxidation significantly. The Eley-Rideal mechanism was proven to be suitable to explain the reaction of Hg0 and HCl. NH3 injection had a strong negative effect to mercury oxidation. The deactivation of aged SCR catalysts was mainly due to loss of active sites.

scholarly journals New Insight into the In Situ SO2 Poisoning Mechanism over Cu-SSZ-13 for the Selective Catalytic Reduction of NOx with NH3

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1391
Author(s):  
Yu Qiu ◽  
Chi Fan ◽  
Changcheng Sun ◽  
Hongchang Zhu ◽  
Wentian Yi ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Zeolite Catalysts ◽  
So2 Poisoning ◽  
Negative Effect ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared ◽  
Sulfate Species

To reveal the nature of SO2 poisoning over Cu-SSZ-13 catalyst under actual exhaust conditions, the catalyst was pretreated at 200 and 500 °C in a flow containing NH3, NO, O2, SO2, and H2O. Brunner−Emmet−Teller (BET), X-ray diffraction(XRD), thermo gravimetric analyzer (TGA), ultraviolet Raman spectroscopy (UV Raman), temperature-programmed reduction with H2 (H2-TPR), temperature-programmed desorption of NO+O2 (NO+O2-TPD), NH3-TPD, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and an activity test were utilized to monitor the changes of Cu-SSZ-13 before and after in situ SO2 poisoning. According to the characterization results, the types and generated amount of sulfated species were directly related to poisoning temperature. Three sulfate species, including (NH4)2SO4, CuSO4, and Al2(SO4)3, were found to form on CZ-S-200, while only the latter two sulfate species were observed over CZ-S-500. Furthermore, SO2 poisoning had a negative effect on low-temperature selective catalytic reduction (SCR) activity, which was mainly due to the sulfation of active sites, including Z2Cu, ZCuOH, and Si-O(H)-Al. In contrast, SO2 poisoning had a positive effect on high-temperature SCR activity, owing to the inhibition of the NH3 oxidation reaction. The above findings may be a useful guideline to design excellent SO2-resistant Cu-based zeolite catalysts.

Modelling and parametric investigation of NOx reduction by oxidation precatalyst-assisted ammonia-selective catalytic reduction

2009 ◽  
Vol 223 (9) ◽  
pp. 1193-1206 ◽  
Author(s):  
S-C Jung ◽  
W-S Yoon
Keyword(s):  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Volume Ratio ◽  
Kinetic Scheme ◽  
Space Velocity ◽  
Gas Temperature ◽  
Scr System ◽  
Very High

Nitrogen oxide (NO x) reduction by the selective catalytic reduction (SCR) system assisted by an oxidation precatalyst is modelled and analytically investigated. The Langmuir—Hinshelwood SCR kinetic scheme with vanadium-based catalyst and ammonia (NH3) reductant in conjunction with the NO—NO2 conversion reaction over a platinum-based catalyst is used. The effects of the ratio of the oxidation precatalyst to the SCR monolith volume, the gas temperature, the space velocity, and the NH3-to-NO x concentration ratio on the de-NO x performance are parametrically examined. The oxidation precatalyst promotes NO x conversion at low temperatures. At intermediate temperatures, the NO x reduction is either activated or deactivated with increase in the space velocity. A higher oxidation precatalyst-to-SCR monolith volume ratio tends to promote the NO x reduction of higher space velocities. At high temperatures, the de-NO x efficiency is very high and insensitive to the space velocity. The NO x conversion efficiency depends on the NH3-to-NO x ratio at low temperatures.

scholarly journals Recent Progress in Atomic-Level Understanding of Cu/SSZ-13 Selective Catalytic Reduction Catalysts

Catalysts ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 140 ◽  
Author(s):  
◽  
Keyword(s):  
Selective Catalytic Reduction ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Short Review ◽  
Catalytic Performance ◽  
Catalyst Design ◽  
Catalyst Stability ◽  
Hydrothermal Aging ◽  
Scr Catalysts ◽  
Fast Scr

Cu/SSZ-13 Selective Catalytic Reduction (SCR) catalysts have been extensively studied for the past five-plus years. New and exciting fundamental and applied science has appeared in the literature quite frequently over this time. In this short review, a few topics specifically focused on a molecular-level understanding of this catalyst are summarized: (1) The nature of the active sites and, in particular, their transformations under varying reaction conditions that include dehydration, the presence of the various SCR reactants and hydrothermal aging; (2) Discussions of standard and fast SCR reaction mechanisms. Considerable progress has been made, especially in the last couple of years, on standard SCR mechanisms. In contrast, mechanisms for fast SCR are much less understood. Possible reaction paths are hypothesized for this latter case to stimulate further investigations; (3) Discussions of rational catalyst design based on new knowledge obtained regarding catalyst stability, overall catalytic performance and mechanistic catalytic chemistry.

scholarly journals The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

Catalysts ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 741 ◽  
Author(s):  
Wang ◽  
Hou ◽  
Yan ◽  
Zhang ◽  
Wang ◽  
...  
Keyword(s):  
Copper Sulfate ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Copper Ions ◽  
Acid Resistance ◽  
Temperature Program Reduction ◽  
Copper Species ◽  
Nh3 Scr ◽  
Scr Catalysts

To reveal the role of SO3 poisoning in Cu/SSZ-13 NH3-SCR catalysts, fresh and sulfated Cu/SSZ-13 catalysts were prepared in the presence or absence of SO3 flux. The deactivation mechanism is probed by the changes of structural, copper species, and selective catalytic reduction (SCR) activity. The variations concentrate on the changes of copper species as the Chabazite (CHA) framework of Cu/SSZ-13 catalysts could keep intact at high ratios of SO3/SOx. The thermal gravimetric analyzer (TGA) results reveal that the copper sulfate formed during sulfation and the amounts of sulfate species increased with an increase in the SO3/SOx ratio. In contrast to the changing trend of copper sulfate, temperature program reduction (H2-TPR), and electron paramagnetic resonance (EPR) results manifest that, since the number of active copper ions declines with an increase of the SO3/SOx ratio, the active sites transform to these inactive species during sulfation. Due to the combination of NH3-SCR activity and the kinetic tests, it is shown that the decreased number of active sites is responsible for the declined SCR activity at low temperature. As Cu/SSZ-13 catalysts show excellent acid-resistance ability, our study reveals that the Cu/SSZ-13 catalyst is a good candidate for NOx elimination, especially when SO3 exists.

scholarly journals Numerical Simulations of SCR DeNOx System for a 660MW coal-fired power station

2018 ◽  
Vol 38 ◽  
pp. 04009
Author(s):  
Deng Yongqiang ◽  
Mei Zhongming ◽  
Mao Yijun ◽  
Liu Nianping ◽  
Yin Guoming
Keyword(s):  
Numerical Simulations ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Structural Parameters ◽  
Escape Rate ◽  
Power Station ◽  
Factors Affecting ◽  
Operational Conditions ◽  
High Ammonia ◽  
Scr System

Aimed at the selective catalytic reduction (SCR) DeNOx system of a 660 MW coal-fired power station, which is limited by low denitrification efficiency, large ammonia consumption and over-high ammonia escape rate, numerical simulations were conducted by employing STAR-CCM+ (CFD tool). The simulations results revealed the problems existed in the SCR DeNOx system. Aimed at limitations of the target SCR DeNOx system, factors affecting the denitrification performance of SCR, including the structural parameters and ammonia injected by the ammonia nozzles, were optimized. Under the optimized operational conditions, the denitrification efficiency of the SCR system was enhanced, while the ammonia escape rate was reduced below 3ppm. This study serves as references for optimization and modification of SCR systems.

Adaptive and Efficient Ammonia Storage Distribution Control for a Two-Catalyst Selective Catalytic Reduction System

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Ming-Feng Hsieh ◽  
Junmin Wang
Keyword(s):  
Catalytic Reduction ◽  
Nox Reduction ◽  
Injection Rate ◽  
Nox Emissions ◽  
System A ◽  
Ammonia Slip ◽  
Ammonia Storage ◽  
In Series ◽  
Storage Distribution ◽  
Scr System

This paper presents an adaptive urea-SCR dosing control design for a two-catalyst SCR system. A novel SCR ammonia storage distribution control (ASDC) approach aiming to simultaneously increase the SCR NOx conversion efficiency and reduce the tailpipe ammonia slip was proposed and experimentally validated. Based on the insight into SCR operational principles, a high ammonia storage level at the upstream part of the catalyst can generally yield a higher NOx reduction efficiency while a low ammonia storage level at the downstream part of the catalyst can reduce the undesired tailpipe ammonia slip. To achieve such an ammonia storage distribution control, a two-catalyst (in series) SCR system with NOx and NH3 sensors was devised. Grounded in a newly developed SCR control-oriented model, an adaptive (with respect to the SCR ammonia storage capacity) controller was designed to control the urea injection rate for achieving different ammonia storages in the two catalysts. Experimental data from a US06 test cycle conducted on a medium-duty Diesel engine system showed that, with the similar total engine-out NOx emissions and NH3 (AdBlue) consumptions, the proposed ASDC strategy simultaneously reduced the tailpipe NOx emissions by 57% and the ammonia slip by 74% in comparison to those from a conventional controller.

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

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.

scholarly journals H2O and/or SO2 Tolerance of Cu-Mn/SAPO-34 Catalyst for NO Reduction with NH3 at Low Temperature

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 289 ◽  
Author(s):  
Guofu Liu ◽  
Wenjie Zhang ◽  
Pengfei He ◽  
Shipian Guan ◽  
Bing Yuan ◽  
...  
Keyword(s):  
Low Temperature ◽  
Reaction Temperature ◽  
Active Sites ◽  
Competitive Adsorption ◽  
Catalytic Reduction ◽  
Acid Sites ◽  
Impregnation Method ◽  
Spent Catalyst ◽  
Poisoning Effect ◽  
Negative Effect

A series of molecular sieve catalysts (Cu–Mn/SAPO-34) with different loadings of Cu and Mn components were prepared by the impregnation method. The deNOx activity of the catalyst was investigated during the selective catalytic reduction (SCR) of NO with NH3 in the temperature range of 120 °C to 330 °C, including the effects of H2O vapors and SO2. In order to understand the poisoning mechanism by the injection of H2O and/or SO2 into the feeding gas, the characteristics of the fresh and spent catalyst were identified by means of Brunner−Emmet−Teller (BET), X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and Thermal Gravity- Differential Thermal Gravity (TG-DTG). The conversion of NO by the catalyst can achieve at 72% under the reaction temperature of 120 °C, while the value reached more than 90% under the temperature between 180 °C and 330 °C. The deNOx activity test shows that the H2O has a reversible negative effect on NO conversion, which is mainly due to the competitive adsorption of H2O and NH3 on Lewis acid sites. When the reaction temperature increases to 300 °C, the poisoning effect of H2O can be negligible. The poisoning effect of SO2 on deNOx activity is dependent on the reaction temperature. At low temperature, the poisoning effect of SO2 is permanent with no recovery of deNOx activity after the elimination of SO2. The formation of (NH4)2SO4, which results in the plug of active sites and a decrease of surface area, and the competitive adsorption of SO2 and NO should be responsible for the loss of deNOx activity over Cu/SAPO-34.

scholarly journals CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131 ◽  
Author(s):  
Rola Mohammad Al Soubaihi ◽  
Khaled Mohammad Saoud ◽  
Myo Tay Zar Myint ◽  
Mats A. Göthelid ◽  
Joydeep Dutta
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Active Sites ◽  
Bond Activation ◽  
Dissociative Adsorption ◽  
High Catalytic Activity ◽  
Good Catalytic Activity ◽  
Pretreatment Conditions ◽  
Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

scholarly journals Spatial distribution of the Barbary Partridge (Alectoris barbara) in Sardinia explained by land use and climate

2021 ◽  
Vol 67 (4) ◽  
Author(s):  
Gianpasquale Chiatante ◽  
Marta Giordano ◽  
Anna Vidus Rosin ◽  
Oreste Sacchi ◽  
Alberto Meriggi
Keyword(s):  
Land Use ◽  
Conservation Status ◽  
Distance Sampling ◽  
Strong Relationship ◽  
European Population ◽  
Factors Affecting ◽  
Brood Rearing ◽  
Management Actions ◽  
Negative Effect ◽  
Study Sites

AbstractMore than half of the European population of the Barbary Partridge is in Sardinia; nonetheless, the researches concerning this species are very scarce, and its conservation status is not defined because of a deficiency of data. This research aimed to analyse the habitat selection and the factors affecting the abundance and the density of the Barbary Partridge in Sardinia. We used the data collected over 8 years (between 2004 and 2013) by spring call counts in 67 study sites spread on the whole island. We used GLMM to define the relationships between the environment (topography, land use, climate) both the occurrence and the abundance of the species. Moreover, we estimated population densities by distance sampling. The Barbary Partridge occurred in areas at low altitude with garrigue and pastures, avoiding woodlands and sparsely vegetated areas. We found a strong relationship between the occurrence probability and the climate, in particular, a positive relation with temperature and a negative effect of precipitation, especially in April–May, during brood rearing. Furthermore, dry crops positively affected the abundance of the species. We estimated a density of 14.1 partridges per km2, similar to other known estimates. Our findings are important both because they increase the knowledge concerning this species, which is considered data deficient in Italy, and because they are useful to plan management actions aimed to maintain viable populations if necessary.

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