Catalytic Reduction Of Nitrogen Monoxide Research Articles

Catalytic reduction of nitrogen monoxide using iron–nickel oxygen carriers derived from electroplating sludge: Novel method for the collaborative emission decrease of polluting gases

The valorization of electroplating sludge (ES) for high added value presents greater economic and environmental benefits than conventional treatment methods such as thermal processing, solidification, and landfill. Inspired by the mechanism of chemical looping combustion (CLC), this study developed a novel cost-effective method for denitrification by preparing FeNi-OCs from ES to achieve the synergistic reduction of CO and NO emissions. The phase structure, micromorphology, and valence state changes of the FeNi-OC catalyst during the CO-catalyzed reduction of NO and the pathway for catalytic denitrification using FeNi-OCs were analyzed. Results showed that CO could reduce FeNi-OCs to FeNi, and the reduced FeNi was subsequently oxidized back to FeNi-OCs by NO, a process analogous to CLC. During experiments, the simultaneous consumption of CO and NO gases was observed at 350 °C. This phenomenon was highly pronounced at 600 °C, where the CO and NO concentrations decreased from initial values of 8550 and 470 ppm, respectively, to 6719 and 0 ppm, respectively, with conversion rates of 21.41 % and 100 %, respectively. Hence, synergistic emission reduction was achieved. Further experiments also indicated that the addition of 1.5 % ES during iron ore sintering could substantially reduce the CO and NO concentrations in the sintering flue gas from 1268.32 and 244.81 ppm, respectively, to 974.51 and 161.11 ppm, respectively.

Flue gas purification from NO using supported Cu–Mn and Cu–Mn–Nb catalysts synthesized by electroless metal deposition method

In the present work, granular fixed-bed catalysts with active Cu–Mn and Cu–Mn–Nb layers synthesized by electroless metal deposition method were prepared and tested for purification of a flue gas from nitrogen monoxide (NO) by CO. Lightweight expanded clay aggregate with i.d. of 2–4 mm and 8–10 mm was used as a substrate for deposition of the active layer. Elemental composition of the prepared catalytic layers was determined by means of inductively coupled plasma optical emission spectroscopy and energy-dispersive X-ray analysis. Field emission scanning electron microscopy and X-ray photoelectron spectroscopy were applied to investigate morphology of the active layers and the oxidation state of the main components (Mn, Cu and Nb), respectively. Additionally, X-ray diffraction analysis and energy-dispersive X-ray mapping were conducted to provide comprehensive information about the structure and dispersion of active components on the surface of the catalysts prepared. It was demonstrated that electroless metal deposition method allows preparation of a relatively uniform active layer with highly distributed active sites on the substrate surface, while the Cu0.012–Mn0.986Nb0.0012 active layer synthesized by electroless metal deposition can be successfully applied for selective catalytic reduction of NO with the use of CO as a reductant. The effective NO conversion (90–95%) was observed at temperatures of 300–400 °C and higher. X-ray photoelectron spectroscopy revealed that significant amount of Mn3+ and Mn4+ species and predominance of chemisorbed oxygen over the lattice oxygen should be responsible for NO conversion efficiency of the catalyst prepared.

Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.

Selective catalytic reduction of NO using acetone solvent vapors as the reducing agent over Cu2+ and/or Al3+ ions substituted MCM-41 catalysts

Selective catalytic reduction (SCR) of nitrogen monoxide (NO) using acetone solvent vapors as the reducing agent over mesoporous Cu–MCM-41, Al–MCM-41, Cu–Al–MCM-41 and CuO supported metal oxides such as CuO/Al2O3 and CuO/SiO2 was investigated in this study. The synthesized materials were characterized by using powder low-angle X-ray diffraction (XRD), N2 adsorption–desorption measurements, 27Al magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR), electron paramagnetic resonance spectroscopy (EPR) and inductively coupled plasma-mass spectrometer (ICP-MS) analysis. The presence of isolated Cu2+ ions and tetrahedrally coordinated Al3+ ions within the framework of Cu–Al–MCM-41 catalyst played a vital role in this deNOx reaction as confirmed by EPR and 27Al MAS-NMR spectroscopic studies, respectively. Among the various catalysts studied, bifunctional Cu–Al–MCM-41 was found to be the most effective catalyst for achieving maximum deNOx activity at lower temperatures of around 250–350°C. Besides, Cu–Al–MCM-41 catalyst also showed higher acetone oxidation than those of Cu–MCM-41, CuO/Al2O3 and CuO/SiO2 catalysts in the entire temperature range. For higher temperature of above 400°C, it was found that Cu–MCM-41 catalyst shows highest activity for the NO reduction but it shows less acetone incineration activity as compared to that of Cu–Al–MCM-41 catalyst. The study of simultaneous removal of NO and acetone solvent vapors using Cu–Al–MCM-41 and Cu–MCM-41 catalysts reveals the potential of using waste organic solvents from industry as the reducing agent of deNOx (SCR) process.

Low-temperature Catalytic Reduction of Nitrogen Monoxide with Carbon Monoxide on Copper Iron and Copper Cobalt Composite Oxides

Copper iron composite oxides (CuO/Fe2O3) and copper cobalt composite oxides (CuO/Co3O4) for the catalytic reduction of NO with CO at low temperature were prepared by co-precipitation. The catalytic activity and thermal stability of the catalysts were evaluated by a microreactor-GC system. The 100% conversion temperatures of NO are 80C for CuO/Fe2O3 and 90C for CuO/Co3O4. The catalysts possess high catalytic activity and favorable thermal stability for NO reduction with CO in a wide temperature range and long time range. A systematic study of the molar ratios of the reactants, the volume of NaOH, aging time, and calcination temperature/time was carried out to investigate the influence preparation conditions on the catalytic activity of the catalysts.

Catalytic reduction of nitrogen monoxide with propene over Nb/TiO2 mixed mechanically with Mn2O3

Selective catalytic reduction of nitrogen monoxide (NO) over a catalyst of mechanically mixed Nb/TiO2 and Mn2O3 (Mn2O3+Nb/TiO2) in an oxidizing atmosphere with propene (C3H6) was studied. The Mn2O3+Nb/TiO2 catalyst showed high activity for the reduction of NO to N2. The maximum conversion of NO to N2 was observed at 200∼300°C, with about 80% reduction of NO to N2. Mn2O3 enhanced the formation of NO2 from NO and the activation of propene to react with NO2 for reduction to N2.

Catalytic reduction of nitrogen monoxide by propene in the presence of excess oxygen over gold based ceria catalyst

The catalytic reduction of nitrogen monoxide by propene in the presence of excess oxygen over gold based ceria catalyst was studied. Adsorption and temperature programmed desorption of NO/O2 on Au/CeO2 reveal that the catalyst adsorbs and desorbs NO over a large range of temperature. A maximum of 26% conversion of NO x was obtained around 210 °C, with a selectivity of 50% to N2.

Enhancement of Activity of Ir Catalysts for the Selective Catalytic Reduction of NO by CO

Abstract The activity of Ir catalysts for selective catalytic reduction of nitrogen monoxide by carbon monoxide was drastically enhanced by combining iridium and tungsten oxide on a silica support.

Three-way catalyst-induced formation of ammonia—velocity- and acceleration-dependent emission factors

Ammonia (NH 3) is classified as a toxic air pollutant but its release from vehicles is not regulated. Herein we report on the efficiency of the catalytic reduction of nitrogen monoxide (NO) and the selectivity towards NH 3. Chemical ionization mass spectrometry (CIMS) has been applied to monitor NH 3 and NO emissions at a time resolution of 2 s. At real world driving, intense, catalyst-induced NH 3 formation was detected for a gasoline-fueled passenger car equipped with a Pd/Rh-based three-way-catalyst (TWC). Post-catalyst NH 3 emissions strongly depend on velocity and acceleration and varied by two orders of magnitude from 1 to 170 mg km −1. For most vehicle conditions, tail-pipe NH 3 emissions exceeded those of NO. Excellent NO conversion above 95% was noticed as soon as catalyst light-off occurred. Post-catalyst NO emissions were lowest when NH 3 formation was most intense and vice versa. This complementary behavior indicates that a TWC can be operated in a way that either NH 3 or NO emissions dominate. The NH 3/NO mixing ratio was mainly influenced by the air-to-fuel ratio. At fuel-rich combustion ( λ<1), highest NH 3/NO mixing ratios clearly above one were observed, whereas ratios at or below one were found at lean conditions ( λ > 1 ). Catalyst temperature effected the selectivity of the DeNOx process. Highest NH 3 selectivity up to 0.45 was found when operating the catalyst below 280 °C. Above this temperature, the selectivity was reduced to 0.02–0.05. The obtained results highlight those parameters, influencing the NH 3 output of a TWC vehicle at real world driving.

Selective Catalytic Reduction of Nitrogen Monoxide with H&lt;sub&gt;2&lt;/sub&gt; or CO as Reductant in Presence of SO&lt;sub&gt;2&lt;/sub&gt;

Ir/SiO2 and Rh/SiO2 catalysts showed excellent activity for NO reduction with CO or H2 in the presence of O2 and SO2. Ir/SiO2 catalyzed NO reduction with both CO and H2, whereas Rh/SiO2 catalyzed reduction only with H2. The most important characteristic was that coexistence of O2 and SO2 is essential for NO reduction to occur. Surface science investigation using Ir(111) single crystal model catalyst revealed that the atomic sulfur was formed via disproportionation of SO2 and reacted with oxygen adsorbed on the surface to form SO2, which desorbed from the surface. Therefore, the iridium surface reverted to its initial metallic state. FT-IR measurements on Ir/SiO2 also indicated that the SO2 both stabilized and created Ir0 sites in the oxidizing atmosphere. The addition of Li and Ba to Ir/SiO2 and Zn to Rh/SiO2 was quite effective to enhance the catalytic activity for NO reduction in the presence of O2 and SO2 by acting as oxidation retardant to prevent deactivation of the active Ir and Rh metals supported on SiO2.

High Activity of Pt/AlPO4 Catalyst for Selective Catalytic Reduction of Nitrogen Monoxide by Propene in Excess Oxygen.

AbstractFor Abstract see ChemInform Abstract in Full Text.

High Activity of Pt/AlPO4 Catalyst for Selective Catalytic Reduction of Nitrogen Monoxide by Propene in Excess Oxygen

Abstract The activity of Pt(0.5 wt%)/AlPO4 for C3H6-SCR was found to be much higher than that of Pt(0.5 wt%)/Al2O3; although the selectivity toward N2O of both the catalysts were comparable, the maximal conversion of NO to N2 by Pt(0.5 wt%)/AlPO4 was higher than that by Pt(0.5 wt%)/Al2O3, and moreover the temperature window of the former located in lower side than that of the latter. The superiority of Pt(0.5 wt%)/AlPO4 was discussed on the basis of the results of XPS measurements.

Catalytic reduction of nitric monoxide by ethene over Nb/TiO2 in the presence of excess oxygen

Selective catalytic reduction of nitrogen monoxide over TiO2 with different niobium loadings (between 0 and 15wt.%) by ethene in an oxidizing atmosphere was studied. Nb/TiO2 catalyst showed high activity and selectivity for the reduction of NO to N2. The maximum conversion of NO to N2 was observed on the Nb (10wt.%)/TiO2. NO2 and N2O were hardly created at the temperature the selective catalytic reduction of NO to N2 occurred. On increasing the concentration of ethene, the catalytic activity for the reduction of NO to N2 was enhanced. The effect of water vapor on the catalytic activity was studied.

Optimum Preparation Conditions for Alumina Catalyst Containing Cobalt for the Selective Catalytic Reduction of Nitrogen Monoxide with Ethene in Excess Oxygen.

Alumina catalysts containing Co were prepared under various conditions of Co loading, Co salt and calcination temperature to elucidate the factors affecting the activity for the selective reduction of NO with ethene in excess oxygen, and the acctive Co species. The optimum calcination temperature was 800°C regardless the type of Co salt and the loading of Co, at which formation of CoAl2O4 was maximum, formation of Co3O4 was minimum and the γ-type stmcture of alumina was retained. The catalytically active component is CoAl2O4, which acts as a cocatalyst with γ-alumina to complete the reduction of NO.

Selective catalytic reduction of nitrogen monoxide with propene over CuCl/MCM-41 catalysts

Selective catalytic reduction of nitrogen monoxide with propene over two kinds of CuCl/MCM-41 catalysts prepared by a dispersion method has been studied. It was found that CuCl/AlMCM-41 exhibits substantially higher activity over CuCl/SiMCM-41. Characterization of these samples by H2-TPR, IR and XRD showed that the active copper species were mainly related to Cu2+ and Cu+ ions in CuCl/AlMCM-41 catalyst.

Effect of water vapor on the deactivation of Pd-zeolite catalysts for selective catalytic reduction of nitrogen monoxide by methane

For the selective reduction of nitrogen oxides (NOx) by methane, Pd-MOR (Pd: 0.47 wt.%) showed stable activity in the absence of water vapor at 450°C for more than 30 h, while it showed a gradual decrease in NOx conversion in the presence of water vapor. Pd-ZSM-5 (Pd: 0.58 wt.%) showed a gradual decrease in NOx conversion even in the absence of water vapor and almost lost activity in 20 h in the presence of water vapor. CO adsorption measurement revealed that Pd-ZSM-5 tested in the presence of water suffered the severest decrease in Pd dispersion. Raman measurement clearly indicated that PdO is formed on the deactivated samples. These results suggested that deactivation of Pd-zeolite is caused by Pd agglomeration to form PdO and water vapor promotes the agglomeration.

Infrared study of catalytic reduction of nitrogen monoxide by propene over Ag/TiO 2–ZrO 2

The reaction mechanism of NO reduction by propene over silver-supported TiO 2–ZrO 2 catalyst was studied by means of in situ FT-IR, combined with catalytic activity studies. The catalytic activity studies suggested that silver plays an important role as the active species. In FT-IR measurements under a static condition, organic nitro (R-NO 2), nitrite (R-ONO), inorganic NO − 3, carbonate, formate and acetate species were detected when TiO 2–ZrO 2 or Ag/TiO 2–ZrO 2 was exposed to a gas mixture of NO+C 3H 6+O 2 at room temperature. In the case of Ag/TiO 2–ZrO 2, an intense IR band assigned to isocyanate (–NCO) species was observed by evacuation at temperatures above 300°C after being exposed to NO+C 3H 6+O 2. Under a dynamic condition, the isocyanate band was not detected on Ag/TiO 2–ZrO 2, but observed on TiO 2–ZrO 2. The isocyanate species was found to be highly reactive toward NO 2. A reaction mechanism has been proposed that organic nitro and nitrite compounds formed initially on TiO 2–ZrO 2 are converted on Ag sites to isocyanate, which is then reduced to N 2 by the reaction with NO 2 on Ag sites.

Bifunctional YFeO 3-Based Catalysts Used in the Selective Catalytic Reduction of Nitrogen Monoxide in the Presence of Excess Oxygen

The catalytic activity of YFeO 3-based catalysts in the lean-NO x process was studied for the sulfated perovskite YFeO 3, composites between YFeO 3 and the solid acid ZrO 2, as well as sulfated composites YFeO 3/ZrO 2. Moreover, a mechanical mixture between YFeO 3 and sulfated tetragonal zirconia (t-ZrO 2/SO 4) was studied. It is shown that the lean-NO x activity of YFeO 3 is improved by forming the composites YFeO 3/ZrO 2 as well as by sulfating samples, with the highest conversion rates of NO x into N 2 being about 30% at about 400°C. The disadvantage of these materials is that the activity decreases with increasing the oxygen content of the feed gas. However, the mechanical mixture between YFeO 3 and t-ZrO 2/SO 4 shows not only an improved high-temperature activity at about 400°C but also a pronounced low temperature (<300–350°C) activity. The latter clearly increases with increasing oxygen content, whereas the former decreases. The opposing effect of oxygen is explained by different reaction mechanisms.

Selective Removal of Cobalt Oxide from Cobalt-loaded Alumina Catalysts and Its Effect on the Activity for Selective Catalytic Reduction of Nitrogen Monoxide by Ethene in Excess Oxygen

Abstract The selective removal of Co3O4 from a cobalt-loaded alumina catalyst resulted in increased activity for the title reaction, indicating that Co3O4 inhibited the reaction but that the resudual CoAl2O4-like species acted as catalytically active species. CoAl2O4-like species were sufficiently active for the oxidation of NO to NO2 but much less active for the oxidation of ethene (a side reaction).

Palladium-exchanged MFI-type zeolites in the catalytic reduction of nitrogen monoxide by methane. Influence of the Si/Al ratio on the activity and the hydrothermal stability

Pd-exchanged MFI-type zeolites containing 3.7 and 0.7 framework aluminium atoms per unit cell (corresponding to Si/Al ratios of 25 and 131) were found active in the selective reduction of nitrogen monoxide in the presence of excess oxygen. Upon steaming at 800°C, both catalysts exhibited the total loss of their catalytic activity in the reduction of NO. Such a behaviour was ascribed to the complete aggregation of Pd ions into large metal particles on the external surface of the zeolite crystals. Both supports, although maintaining their crystallinity, are shown to experience extended dealumination upon steaming. Although the loss of Pd exchange capacity could partially explain the Pd migration and sintering, a mechanism involving the formation of mobile Pd hydroxyl entities condensing into PdO particles outside the zeolite crystallites is preferred.