NOx Capacity Research Articles

The mineral phase reconstruction of copper slag as Fenton-like catalysts for catalytic oxidation of NOx and SO2: Variation in active site and radical formation pathway

Herein, the copper slag through CaO-thermal treatment was used as a heterogeneous catalyst to activate H2O2 into free radicals to remove NOx and SO2. The NOx removal capacity of modified copper slag exhibited a volcano-type tendency with increased calcination temperatures. Because of the iron phase transformation and decrease in surface exposure Cu species by adjusting surface properties, the copper slag delivers a higher NOx capacity and H2O2 utilization rate than raw copper slag and bare H2O2. In addition, the interaction of multi-phases of modified copper slag was illustrated by simulation experiments. Moreover, the possible formation pathway of free radicals in the alkaline medium was proposed based on the electron paramagnetic resonance (EPR) as well as chemical quenching experiments. The surface-bound hydroxyl radical through ≡Fe3+ sites is decisive for free radical formation in alkaline conditions. Our findings shed new light on the feasibility of SO2 and NOx removal by metallurgical slag via mineral phase reconstruction as a novel heterogeneous catalyst.

Integration of an Oxidation Catalyst with Pd/Zeolite-Based Passive NOx Adsorbers: Impacts on Degradation Resistance and Desorption Characteristics

Fully ion-exchanged Pd/SSZ-13 model passive NOx adsorbers (PNA) exhibit significant NOx storage capability, achieving NOx-to-Pd ratios of 1, and NOx desorption at higher temperatures, where downstream NOx reduction catalysts are active, under simulated exhaust conditions. However, CO has been found to induce PNA degradation, which limits the potential for practical application. In this study, in an attempt to understand the consequences of limiting CO exposure, we integrated a model Pt/Al2O3 diesel oxidation catalyst (DOC) with a Pd/SSZ-13 PNA and performed NOx adsorption and temperature-programmed desorption (TPD) cycles with the PNA, the DOC, and the DOC+PNA integrated system. Despite the high initial NOx-to-Pd ratio, Pd/SSZ-13 experienced significant degradation over 15 adsorption and desorption cycles when including CO, with the NOx-to-Pd ratio dropping from 0.98 to 0.75. CO oxidation over the DOC+PNA integrated system lights off at significantly lower temperature compared to the PNA, limiting the PNA CO exposure at temperatures above 200 °C. As a result, the durability of the DOC+PNA integrated system is enhanced, and only a 0.02 decrease in NOx-to-Pd ratio was observed over the 15 test cycles. A further benefit with integration of the PNA with the DOC was a lower temperature NOx release, within a more practical temperature window. This is due to the enhanced oxidation activity of the DOC+PNA integrated system and consequently an early onset of NO2 formation, which was found to trigger the low temperature NOx release. Low temperature NOx adsorption and TPD experiments with controlled exposure of CO and NO2 reveal two types of NOx storage mechanisms, one of which is destabilized by the presence of NO2, leading to the evolution of a lower temperature NOx release. Overall, integrating the PNA with a highly active low temperature CO oxidation catalyst was beneficial by lowering the NOx release temperature window and leading to significantly less NOx capacity loss.

Deactivation and regeneration studies on Pd-containing medium pore zeolites as passive NOx adsorbers (PNAs) in cold-start applications

Two Pd-containing medium pore zeolite frameworks, MFI and MWW, have been evaluated as passive NOx adsorbers (PNAs) in automotive applications. The NOx adsorption/desorption behavior of Pd-containing standard ZSM-5 and MCM-22 zeolites with analogous physico-chemical properties (Si/Al~10–12, 1%wt Pd, crystal size of ~200–400 nm), has been first studied. Pd/ZSM-5 shows better low-temperature NOx capacity than Pd/MCM-22 (0.83 and 0.55 μmol NOx/μmol Pd), but, in contrast, Pd/MCM-22 is able to desorb NOx at remarkable lower temperatures (~50 °C fewer). In order to evaluate the influence of the textural properties of the MWW-type materials on the NOx adsorption/desorption behavior, a delaminated DS-ITQ-2 and nano-MCM-22, have also been prepared. The deactivation of the different Pd-containing medium pore zeolites and their posterior regeneration have been systematically studied by subjecting the samples to CO-ageing treatments at different temperatures (from 150 to 650 °C) and hydrothermal treatments at 750 °C, respectively. Pd/ZSM-5 is able to almost fully recovery the former NOx adsorption capacity, whereas Pd/MWW materials only recuperate half of their initial NOx adsorption capacity, fact that can be explained by the larger critical sizes of part of the agglomerated metal particles on the external surface of these materials. • Different NOx adsorption/desorption is observed for MFI and MWW structures. • MFI mostly recovers initial NOx uptake after ageing/hydrothermal treatments. • CO‐aged MWW‐type materials show larger metal sintering compared to MFI.

Adsorption of CO2 in presence of NOx and SOx on activated carbon textile for CO2 capture in post-combustion conditions

The influence of NOx and SO2 contaminants on CO2 capture by adsorption was investigated using a carbon fiber textile as an adsorbent. The study was made in a dynamic system, studying the contaminant alone and in binary or ternary mixtures. The results at short times showed that the CO2 capacity and kinetics were not impacted by the presence of NOx in the entrance gas whereas the NOx capacity was slightly impacted by the presence of CO2. In the presence of SO2, the CO2 capacity loss reached 10%. Moreover, with NOx and SO2 accumulation at the surface of the textile, the loss of CO2 capacity can reach 25% and SO2 adsorption is favored to the detriment of NO. For CO2 capture processes by adsorption de-SOx pretreatment is recommended.

Preheating Of Sunflower Blended Biodiesel for the Improvement of Performance Characteristics of a DI Diesel Engine under Various Loads

Due to fast depletion of fuel and for the huge demand of various engine fuels in large sectors and power generation, thse biodiesel which is derived from biological wastes can be a substitute of pure diesel oil. Diesel engine has the benefits of low fuel consumption, high potency, smart economical and dynamic performance. However at the identical time, the diesel engine has high NOx and soot emissions. And these two sorts of emissions provides a trade-off relationship which can bring difficulties to satisfy the necessities of emission rules of NOx and soot. This particular paper primarily reviews regarding using of preheated bio-diesel that contains 20 percentage of pure sunflower oil (biological name-Helianthus annuus) and analyses its performance characteristics for selected blend with completely variable loads. Various experiments were carried out by employing a four stroke single cylinder, direct injection, water cooled diesel engine with suitable specifications. Helianthus oil is mixed with bio diesel for fast burning inside the engine cylinder and by doing so , the Cetane number is quite high that leads to the ignition delay shorter. Therefore the overall content is preheated somewhat in order to lift its temperature so as to boost the burning process. Incorporating to this , it reduces the various emissions such as NOx, CO and smoke capacity by 2% to 3%. Various parameters are required to outline the analysis of combustion and performance characteristics of the test fuel like brake thermal efficiency(BTE),basic specific fuel consumption(BSFC), basic specific energy consumption (BSEC),temperature of the exhaust gas and emissions like NOx, unburn hydrocarbons(HC), carbon monoxide(CO) and smoke were carried out in the specified engine

Fast cycling in a non-isothermal monolithic lean NOx trap using H2 as reductant: Experiments and modeling

A combined experimental and modeling study of fast cycling NOx storage and reduction with H2 for emissions control of lean burn gasoline and diesel vehicles is conducted to provide mechanistic insight and detailed understanding to Toyota’s Di-Air technology. Experiments reveal NOx conversion enhancement over a model Pt/Rh/BaO/CeO2/Al2O3 lean NOx trap (LNT) catalyst for cycle times less than 10s (fast cycling) compared to the longer cycle times typical of conventional NSR. Increased cycle frequency results in the increase (decrease) of the cycle-averaged NOx conversion (NH3 selectivity) over a wide temperature range. The more frequent storage and regeneration of fast cycling increases the utilization of stored NOx capacity by decreasing NOx breakthrough during the lean phase. The decreased NH3 selectivity is in part a result of a combination of increased efficiency of the NH3 oxidation by oxygen stored on the ceria component and of the adsorption of NH3 on the support. A global kinetic model incorporated into a non-isothermal 1-D monolith reactor model is effective in capturing most of the experimental trends. Quantitative agreement requires treatment of the extent of mixing of the lean and rich feeds upstream of the reactor, as well as of mixing of the product stream in the downstream FTIR cell. The predicted axial temperature profile shows a front-monolith temperature rise as high as twice that measured in the middle-monolith under slower cycling. Under faster cycling a predicted 100°C front-monolith temperature rise contrasts to a measured near-constant middle-monolith temperature. Non-isothermal effects are especially important when catalyst temperatures exceed 450°C, which lowers the NOx storage capacity, resulting in an increased amount of slipped NOx during early lean phase.

Rapid Detection of Neutrophil Oxidative Burst Capacity is Predictive of Whole Blood Cytokine Responses.

BackgroundMaladaptive immune responses, particularly cytokine and chemokine-driven, are a significant contributor to the deleterious inflammation present in many types of injury and infection. Widely available applications to rapidly assess individual inflammatory capacity could permit identification of patients at risk for exacerbated immune responses and guide therapy. Here we evaluate neutrophil oxidative burst (NOX) capacity measured by plate reader to immuno-type Rhesus Macaques as an acute strategy to rapidly detect inflammatory capacity and predict maladaptive immune responses as assayed by cytokine array.MethodsWhole blood was collected from anesthetized Rhesus Macaques (n = 25) and analyzed for plasma cytokine secretion (23-plex Luminex assay) and NOX capacity. For cytokine secretion, paired samples were either unstimulated or ex-vivo lipopolysaccharide (LPS)-stimulated (100μg/mL/24h). NOX capacity was measured in dihydrorhodamine-123 loaded samples following phorbol 12-myristate 13-acetate (PMA)/ionomycin treatment. Pearson’s test was utilized to correlate NOX capacity with cytokine secretion, p<0.05 considered significant.ResultsLPS stimulation induced secretion of the inflammatory molecules G-CSF, IL-1β, IL-1RA, IL-6, IL-10, IL-12/23(p40), IL-18, MIP-1α, MIP-1β, and TNFα. Although values were variable, several cytokines correlated with NOX capacity, p-values≤0.0001. Specifically, IL-1β (r = 0.66), IL-6 (r = 0.74), the Th1-polarizing cytokine IL-12/23(p40) (r = 0.78), and TNFα (r = 0.76) were strongly associated with NOX.ConclusionNOX capacity correlated with Th1-polarizing cytokine secretion, indicating its ability to rapidly predict inflammatory responses. These data suggest that NOX capacity may quickly identify patients at risk for maladaptive immune responses and who may benefit from immuno-modulatory therapies. Future studies will assess the in-vivo predictive value of NOX in animal models of immune-mediated pathologies.

The nitric oxide ISO photocatalytic reactor system: Measurement of NOx removal activity and capacity

Abstract Although the NO removal-based air-purification ISO method ISO 22197-1:2007 is well established, its preconditioning requirements mean that only the initial activity of the photocatalyst under test is measured owing to the often-reported, gradual alteration of the surface kinetics for NO oxidation by air through the accumulation of surface HNO 3 . Herein, we compare the photocatalytic NO removal abilities of a number of different, common TiO 2 materials, surface-saturated with photogenerated HNO 3 , with their behaviours observed during the typical 5 h-long ISO standard test. It is found that all the TiO 2 materials studied eventually become largely NO to NO 2 converters after sufficient exposure to NO under irradiation (>5 h) due to the accumulation of surface HNO 3 . The UV exposure time, t *, necessary to reach this HNO 3 saturated condition is different for each different catalyst. As a consequence, an alternative preconditioning process for the ISO method is proposed which can be used to provide a more realistic measure of the photocatalytic activity of the underlying material and provide a measure of the NO x removing capacity of the photocatalytic material under test.

Combustion, performance and emissions characteristics of a biogas fuelled diesel engine with fish biodiesel as pilot fuel

Environmental concerns and reduction in the availability of petroleum fuels have driven interest in the search for alternative fuels for IC engines. In order to overcome the problems associated with the use of petroleum based diesel fuels, a renewable and eco-friendly biofuel can be used for partial replacement of diesel fuels. Hence in this work, feasibility of using fish oil biodiesel was investigated. The important fuel properties were evaluated. Experimental tests were carried out to evaluate the performance, emissions and combustion characteristics. A single cylinder 10 HP, constant speed, water cooled diesel engine was used for experimentation with B20 fish diesel as fuel. This study expanded to achieve diesel equivalent performance from diesel engines with maximum replacement of diesel with renewable fuels. In this context the study analysed the influence of B20 fish biodiesel as a pilot fuel in a biodiesel biogas dual fuel engine. The results of dual-fuel mode operation study are compared to those for B20 diesel operation at identical engine settings. Further for baseline comparison, the results of biodiesel and dual fuel mode of operation are compared to those of standard diesel run. Experiments were performed at various load conditions from 0 to 100% of maximum load at a constant speed of 1500 rpm. In general, B20 fish biodiesel is compatible with diesel in terms of performance and combustion characteristics. The exhaust emissions like CO and HC were significantly less, and NOx is slightly higher, than diesel fuel at all engine load conditions. Dual fuel mode of operations shows lower thermal efficiency and higher fuel consumption for other fuel mode of test run at all ranges of engine loads. Significantly lower in NOx and smoke capacity and HC, CO concentrations were considerably higher for dual fuel mode as compared to other fuels. In dual fuel mode, peak pressure and heat release rate were slightly higher compared to diesel and biodiesel mode of operation for all engine loads.

Comparison of different kinetic models for NOX storage on a lean NOX trap

The kinetics of NOX storage on a lean NOX trap (LNT) were studied using NOX breakthrough curves measured with a laboratory reactor. A much wider range of temperatures (125–450°C) was used than in most studies to facilitate discrimination between potential models. The breakthrough curves were run until the LNT was saturated to (i) enable NO oxidation to NO2 to be studied in the absence of NOX storage, (ii) to enable the effective NOX capacity as a function of temperature to be determined, and (iii) to provide a more demanding test for potential models.Breakthrough curves for 125 and 450°C were very similar, while curves at intermediate temperatures initially followed that for 125°C before breaking away from this curve at a point that became earlier with increasing temperature. Thus, the breakthrough curves have a temperature independent initial portion, followed by a temperature dependant portion. This was explained by there being two types of site: fast sites and slow sites. Fast sites are responsible for the initial part of the curve; both the rate of storage on these sites and the available capacity are independent of temperature. The rate of storage on slow sites, on the other hand, is temperature dependant, as is the available storage capacity. Slow sites are more abundant than fast sites. The performance of three NOX storage models for these sites was compared.The amount of NOX stored as a function of temperature was bell‐shaped. The models naturally predicted that storage was limited by kinetics at lower temperatures and nitrate stability at higher temperatures.

Receptor model source attributions for Utah's Salt Lake City airshed and the impacts of wintertime secondary ammonium nitrate and ammonium chloride aerosol

Communities along Utah's Wasatch Front are currently developing strategies to reduce daily average PM2.5 levels to below National Ambient Air Quality Standards during wintertime persistent stable atmospheric conditions, or cold-air pools. Speciated PM2.5 data from the Wasatch Front airshed indicate that wintertime exceedances of the PM2.5 standard are mainly driven by high levels of ammonium nitrate. Stable wintertime conditions foster the formation of ammonium nitrate aerosol when sufficient sources of NOx, ammonia, and oxidative capacity exist. However, this work demonstrates that secondary ammonium chloride aerosol can also be a significant source of secondary wintertime PM2.5 if sufficient sources of atmospheric chlorine exist. Two factor analysis techniques, positive matrix factorization (PMF) and Unmix, were used to identify contributors to PM2.5 at three monitoring stations along Utah's Wasatch Front: Bountiful, Lindon, and Salt Lake City. The monitoring data included chemically speciated PM2.5 data for 227, 227, and 429 days at each location, respectively, during the period from May 2007 through May 2011. PMF identified 10–12 factors and Unmix identified 4–5 factors for each of the locations. The wintertime PMF and Unmix results showed large contributions from secondary PM2.5 when PM2.5 concentrations exceeded 20 μg/m3. PMF identified both ammonium nitrate and ammonium chloride aerosol as significant secondary contributors to PM2.5 (10–15% of total PM2.5 from ammonium chloride) during wintertime pollution episodes. Subsequent ion balance analysis of the monitoring data confirmed the presence of significant ammonium chloride aerosol on these highly polluted days at all three monitoring sites. The directly emitted primary PM2.5 portions of the source attribution results were further compared to county-level emissions inventories and showed generally good agreement for Salt Lake City and Lindon during wintertime except for wood smoke and fugitive dust, which have higher contributions in the receptor modeling results than in the emissions inventories. Implications: The study suggests that secondary ammonium chloride aerosol can be a significant source of wintertime PM2.5 in an ammonia-rich environment, like the Wasatch Front airshed, if sufficient sources of atmospheric chlorine exist. During wintertime, cold-air-pool events, the source attribution results generally agree with the county emission inventories with the exception of wood smoke and cooking sources. At the Salt Lake City monitoring station, the estimated contributions from wood smoke and cooking are nearly double those of the corresponding inventory, suggesting that they are nearly as important as gasoline emissions.

A comparative study of Pt/Ba/Al2O3 and Pt/Fe-Ba/Al2O3 NSR catalysts: New insights into the interaction of Pt–Ba and the function of Fe

The influence of the introduction of Pt and/or Fe on the structures, NOx storage property and sulfur removal performance of Ba/Al2O3 catalyst was studied. The techniques of TG/DTA, XRD, FT-IR, H2-TPR, EXAFS and DRIFTS were employed for the careful characterization of the catalysts. Two types of Ba species are identified, namely a well-spread monolayer of Ba species and a bulk BaAl2O4 phase. The addition of Fe inhibits the Ba dispersion by enhancing the bulk BaAl2O4 formation, thus slightly decreasing the SOx absorption and greatly suppressing the growth of the bulk BaSO4, and its addition also promotes the NOx storage by increasing the mobility of the stored NOx, contributing to the formation of bulk Ba(NO3)2. The introduction of Pt always re-disperses the bulk BaAl2O4 phase via a hydration process, and enhances both the NOx and SOx absorption capacity of the catalyst. Whereas the co-existence of Pt and Fe was detrimental for the NOx storage and sulfur removal as compared with Pt/Ba/Al2O3 catalyst, although it favors the reduction of BaSO4 phase. Based upon the EXAFS, in situ DRIFTS and repeated H2-TPR results, it is found that the interaction between Pt and Ba species is of great importance for NOx storage and sulfur removal. This Pt–Ba interaction not only accelerates the NOx spillover which is a key step during storage, but also facilitates the selective reduction of BaSO4 into H2S, favorable to sulfur removal and catalyst regeneration. The introduction of Fe to the Pt/Ba/Al2O3 catalyst decreases this Pt–Ba interaction by encapsulation of Pt in the matrix of Fe/FeOx lattice after repeated redox cycles, leading to the decrease of NOx storage capacity (NSC) of the catalyst, and making sulfur removal more difficult since Fe selectively catalyzes the reduction of BaSO4 into BaS.

Removal of NO by Reversible Adsorption on Fe−Mn Based Transition Metal Oxides

A series of Fe−Mn-based transition metal oxides were prepared and used for NO adsorption at 25 °C in the presence of O2. The sorbents were also characterized by BET surface area, TPD, XRD, and FTIR spectroscopy. Both TGA and chemiluminescent NO/NOx analyzer experiments showed that the mixed oxides were efficient and reversible sorbents for NO removal. The NOx capacity decreased in the order of Fe−Mn−Ti, Fe−Mn−Zr > Fe−Mn−Ce, Fe−Mn−Ni > Fe−Mn−Co > Fe−Mn−Cu, Fe−Mn. The maximum NOx capacity reached 42−45 mg/g of sorbent for the Fe−Mn−Ti and Fe−Mn−Zr oxides. SO2 and CO2 decreased the NOx adsorption amount only slightly. H2O decreased the NOx adsorption significantly, but the inhibition was reversible. TPD profiles indicated that NOx species could desorb at temperatures below 400 °C. The high efficiency for NO removal on these oxides was related to their high activities in NO oxidation to NO2 at 25 °C. FTIR spectra showed that the nitrate was the final species for NO adsorption. NO2 and nitrite were the interme...

Selective Adsorption of NOxfrom Hot Combustion Gases by Ce-Doped CuO/TiO2

CuO/TiO2 has been shown to be a superior sorbent for selective, reversible adsorption of NO from hot combustion gases. High NOx adsorption capacities at 200 and 300 °C were obtained with a 5% CuO/TiO2 sorbent, and the NOx desorbed rapidly at 450 °C. Doping with 2% Ce on the CuO/TiO2 sorbent further increased both uptake rates (50% increase in initial rate) and NOx capacity (by 30%). In a direct comparison with the most promising known sorbent, MnO/ZrO2 (1:1 molar ratio), reported by Eguchi et al. (J. Catal. 1996, 158, 420), the Ce-CuO/TiO2 sorbent showed both higher uptake rates (by 100% in initial rate) and higher NOx capacity (by 15%). The effects of CO2, H2O, and SO2 on NOx sorption on the Ce-CuO/TiO2 sorbent were studied at 200 °C. CO2 slightly decreased the initial uptake rate but increased the NOx capacity. H2O coadsorbed with NOx on different sites, both reversibly (i.e. desorbed at 450 °C). SO2 irreversibly adsorbed (likely to sulfate the surface of TiO2) and decreased the NOx capacity by approxim...