NO Removal Activity Research Articles

Simultaneous Removal of NO and Hg(0) from Flue Gas over Mn-Ce/Ti-PILCs.

A series of Mn-Ce/Ti-PILCs (PILCs, pillared interlayered clays) catalysts were prepared via impregnation method in simultaneous removal of NO and elemental mercury in simulated flue gas. The physicochemical properties of these catalysts have been examined by some characterization methods, such as H2-TPR, nitrogen adsorption, XRD and XPS. Mn(6%)-Ce(6%)/Ti-PILCs exhibited superior NO conversion (>95%) and Hg(0) removal efficiency (>90%) at low temperature (250 °C). The results indicated that the elemental mercury had little impact on NO removal efficiency, while the presence of NH3 and NO in SCR system inhibited the Hg(0) removal. NO and Hg(0) removal activity was strongly affected by the transform between surface adsorbed oxygen and lattice oxygen. The species ratio of Mn(4+)/Mn(3+) and Ce(4+)/Ce(3+) on the catalyst surface contributed to the NO conversions and Hg(0) removal. Mn-Ce/Ti-PILCs displayed a broad prospect for controlling the emission of NO and mercury. On the basis of the results obtained, a mechanism for the simultaneous removal of NO and Hg(0) was proposed for the Mn-Ce/Ti-PILCs catalysts: -NH2 + NO → N2 + H2O, -OH + 1/2 Hg(ad) →1/2 HgO + 1/2 H2O.

Ultrasound-assistant preparation of Cu-SAPO-34 nanocatalyst for selective catalytic reduction of NO by NH3

The influence of the various preparation methods of Cu-SAPO-34 nanocatalysts on the selective catalytic reduction of NO with NH3 under excess oxygen was studied. Cu-SAPO-34 nanocatalysts were prepared by using four techniques: conventional impregnation (IM), ultrasound-enhanced impregnation (UIM), conventional deposition precipitation (DP) using NaOH and homogeneous deposition precipitation (HDP) using urea. These catalysts were characterized in detail by various techniques such as N2-sorption, XRD, TEM, H2-TPR, NH3-TPD and XPS to understand the catalyst structure, the nature and the dispersed state of the copper species, and the acid sites for NH3 adsorption. All of the nanocatalysts showed high activities for NO removal. However, the activities were different and followed the sequence of Cu-SAPO-34 (UIM)>Cu-SAPO-34 (HDP)>Cu-SAPO-34 (IM)>Cu-SAPO-34 (DP). Based on the obtained results, it was concluded that the NO conversion on Cu-SAPO-34 nanocatalysts was mainly related to the high reducibility of the isolated Cu2+ ions and CuO species, the number of the acid sites and the dispersion of CuO species on SAPO-34.

Enhanced visible-light-driven photocatalytic removal of NO: Effect on layer distortion on g-C3N4 by H2 heating

We report a simple strategy for realizing the tunable structure distortion of graphitic carbon nitride (g-C3N4) layers by H2 post calcination to improve the intrinsic electronic structure and the photocatalytic performances of g-C3N4 samples. In comparison with the O2 or N2 post treatment, the H2-modified g-C3N4 develops new optical absorption above 460nm and enhances photocatalytic activity for NO removal. The combined characterization results reveal that H2 heating induced the structure distortion of g-C3N4 layers is originated from the creation of amino groups within the structure and generation of the strong hydrogen bonding interactions between layers. The distorted structure allows n–π* electron transitions in g-C3N4 to increase visible-light absorption. The structure distortion also enables more electrons to be available for initiating the photocatalytic reaction and the separation of photogenerated charge carriers in g-C3N4. This work provides a simple strategy for realizing the tunable structure distortion of g-C3N4 layers to adjust its electronic structure and photocatalysis.

Facile synthesis of porous graphene-like carbon nitride (C6N9H3) with excellent photocatalytic activity for NO removal

We reported the possible synthesis of a new porous graphene-like carbon nitride (C6N9H3) by simply adding hydrochloric acid in the precursor of block g-C3N4. The formation of the porous graphene-like C6N9H3 can be attributed to the change in the thermal condensation modal of the precursor and the acidic condition induced by Cl− and H+. The photocatalytic activity of the samples was evaluated by the removal of NO under visible light illumination. We found that the porous graphene-like C6N9H3 exhibited enhanced photocatalytic activity compared to the block g-C3N4. We also researched the removal mechanism and found that the removal of NO in our systems was due to the synergic effect of h+ and O2−. This study could shed light on the design of efficient photocatalysts and facilitate a deep understanding of the NO removal mechanism through photocatalytic technology.

Effect of Aging Atmosphere on Catalytic Activity for NO–CO–C3H6–O2 Reaction of CeO2-Containing Oxide Supported Pd Catalysts

The catalytic activity for CO, hydrocarbon and NO removal on Al2O3 and CeO2 based oxides supported Pd catalysts were studied under switching of aging condition between air and N2 atmosphere. For CeO2-containing Pd catalysts, the deterioration of catalytic activities by aging in N2 was improved by oxidative treatment. Based on results of XPS and FT-IR measurements, it was presumed that the catalytic activity of Pd catalysts was strongly affected by the adsorbed form of CO on Pd, which occurs owing to a change of the chemical state of Pd.

Roles of Cr3+ doping and oxygen vacancies in SrTiO3 photocatalysts with high visible light activity for NO removal

The photocatalytic degradation of nitrogen monoxide (deNOx) in the gas phase was investigated in a continuous reactor using a strontium titanate-based semiconductor, CaAl2O4:(Eu, Nd)/Cr-doped SrTiO3, and CaAl2O4:(Eu, Nd)/oxygen vacancy-induced SrTiO3 catalysts. Cr doping and oxygen vacancies generation could narrow the band gap of SrTiO3 and affect the photocatalytic performance to varying degrees. The photocatalytic activity of SrTiO3 toward LED light (445nm)-induced photocatalytic deNOx can be greatly improved by the nonstoichiometric synthesis of SrTiO3, mainly due to oxygen deficiency generation. CaAl2O4:(Eu, Nd)/Cr-doped SrTiO3 composites possessed superiority in NO removal under persistent fluorescence irradiation (440nm) after the mercury lamp with wavelength larger than 290nm was turned off.

Effect of Y doping on oxygen vacancies of TiO2 supported MnOX for selective catalytic reduction of NO with NH3 at low temperature

A Y-doped TiO 2 -supported MnO X has been developed by partly substituting the Ti 4+ of the catalyst with Y 3+ to promote oxygen vacancies for charge compensation. The aim of this study was to improve the activity of low-temperature SCR of NO with NH 3 in the presence of excess oxygen by means of increasing the amount of oxygen vacancies. Analysis by PL spectra, XPS and EPR showed that Y doping increased the amount of oxygen vacancies and superoxide ions. The catalytic activity of NO removal was promoted by Y doping. ► NO removal is enhanced on the Y-doped MnO X /TiO 2 catalysts for low-temperature SCR. ► Y doping can increase oxygen vacancies for charge compensation on the catalysts. ► Oxygen vacancies by Y doping are responsible for the high catalytic activity.

Investigation of the physicochemical properties of CuO–CoO binary metal oxides supported on γ-Al2O3 and their activity for NO removal by CO

The dispersion and physicochemical behaviors of CuO–CoO binary metal oxides supported on γ-Al2O3 were characterized by XRD, LRS, XPS, H2-TPR, and in situ FT-IR techniques. Their activities were evaluated by NO–CO model reaction. The results indicated that (a) for lower loadings, CuO and CoO were able to be highly dispersed on the surface of γ-Al2O3 support; (b) the interaction between dispersed CuO and CoO upon γ-Al2O3 was discussed in the view of incorporation model. According to this model and obtained results, the surface dispersed Cu–O–Co species were considered to exist on the surface of γ-Al2O3; (c) CO or/and NO adsorption FT-IR results evidenced that the surface dispersed copper species could be reduced to lower valence by CO and the NO adsorption species converted with the increase in the temperature; (d) the surface dispersed Cu–O–Co species could be reduced to active Cu-□-Co species by CO among the mixture atmosphere. The formation of the surface synergetic oxygen vacancy (SSOV) was a crucial factor in the process of the NO–CO reaction. And a possible reaction pathway was tentatively proposed to discuss the NO–CO reaction based on all of these results.

NO removal by activated carbon-supported copper catalysts prepared by impregnation, polyol, and microwave heated polyol processes

The effect of HNO 3 pretreatment of activated carbon (AC)-supported copper catalysts for NO removal with NH 3 was studied. In addition, the effects of various preparation methods for Cu/AC catalysts, namely, impregnation (IM), polyol process (P), and microwave heated polyol process (MP), on the activity of NO removal with NH 3 were compared. HNO 3 pretreatment increased the number of carboxyl sites and promoted good dispersion of active sites. In addition, the chemical states of active phases were found to be affected when the catalysts were prepared by the microwave heated polyol process. More Cu 2O particles were observed on the Cu/AC-N-MP catalyst than on the Cu/AC-N-P catalyst. The experimental results indicated that HNO 3 pretreatment of the AC support led to increased catalytic activity for NO removal with NH 3. The catalytic activity of the Cu/AC catalysts for NO removal at 200 °C decreased in the following order: Cu/AC-N-MP > Cu/AC-N-P > Cu/AC-N-IM. The microwave heated polyol process is a facile method for the rapid synthesis of carbon-supported Cu catalysts for NO removal at low temperature.

In situ synthesized Cu-ZSM-5/cordierite for reduction of NO

ZSM-5 zeolites were directly synthesized on the surface of honeycomb cordierite substrates by hydrothermal method and certified by XRD and SEM techniques; the adhesion of ZSM-5 coatings was evaluated by ultrasonic vibration. Cu-ZSM-5/cordierite monolithic catalyst was prepared by ion-exchange and impregnation method and applied for the selective catalytic reduction (SCR) of NO by NH 3 using a simulated diesel exhaust. The results show that the cordierite surface is almost completely covered by ZSM-5 crystals and the crystallization time greatly impacts the loadings and adhesion of ZSM-5 coatings on substrate, the NO x removal rate over Cu-ZSM-5/cordierite is above 90% in a temperature range of 240–480 °C. Moreover, Cu-ZSM-5/cordierite prepared by different methods shows a wide temperature window (240–540 °C) with high NO removal activities.

DeNOx performance of Ag/Al2O3 catalyst by n-dodecane: Effect of calcination temperature

The effect of the calcination temperature of Ag/Al2O3 catalyst on NO removal activity by n-dodecane as a diesel simulant has been examined with respect to the Ag loading and C1/NO feed ratio under a feed gas condition containing both excess H2O and oxygen. The higher the catalyst calcination temperature and Ag loading, the higher deNOx activity that has been achieved in the reaction temperature range lower than 300°C. 56% of the NO conversion to N2 has been attained over Ag(2)-800 catalyst at 300°C when the C1/NO feed ratio to the reactor is 6. The amount of the metallic Ag formed on the catalyst surface responsible for the high deNOx performance in the temperature region lower than 300°C increases upon the increase of the catalyst calcination temperature from 550 to 800°C and of the Ag loading from 1 to 3wt.%, as determined by UV–vis and XPS. The –NCO species formed on the catalyst surface with acetate, formate and carbonate compounds produced from the partial oxidation of n-dodecane is a critical reaction intermediate for the present reaction system, as identified by in situ IR study. The formation of the –NCO species on the catalyst surface becomes apparent, particularly at 300°C as the catalyst calcination temperature increases.

Activity and characterization of Rh/Al 2O 3 and Rh–Na/Al 2O 3 catalysts for the SCR of NO with CO in the presence of SO 2 and HCl

SO 2 and HCl are major pollutants emitted from waste incineration processes. Both pollutants are difficult to remove completely and can enter the catalytic reactor. In this work, the effects of SO 2 and HCl on the performance of Rh/Al 2O 3 and Rh–Na/Al 2O 3 catalysts for NO removal were investigated in simulated waste incineration conditions. The characterizations of the catalysts were analyzed by BET, SEM/EDS, XRD, and ESCA. Experimental results indicated the 1%Rh/Al 2O 3 catalyst was significantly deactivated for NO and CO conversions when SO 2 and HCl coexisted in the flue gas. The addition of between 2 and 10 wt.% Na promoted the activity of the 1%Rh/Al 2O 3 catalyst for NO removal, but decreased the CO oxidation and BET surface area. The catalytic activity for NO removal was inhibited by HCl as a result of the formation of RhCl 3. Adding Na to the Rh/Al 2O 3 catalyst decreased the inhibition of SO 2 because of the formation of Na 2SO 4, which was observed in the XRD and ESCA analyses. SEM mapping/EDS showed that more S was residual on the surface of the Rh–Na/Al 2O 3 catalyst than Cl.

Effect of hydrocarbon slip on NO removal activity of CuZSM5, FeZSM5 and V 2O 5/TiO 2 catalysts by NH 3

The effect of C 3H 6 on the deNO x activity of CuZSM5, FeZSM5 and V 2O 5/TiO 2 catalysts by NH 3 has been examined. The catalytic NO removal activity decreased by the continuous inclusion of C 3H 6 into the reactor feed gas stream. The higher the feed concentration of C 3H 6, the more severe the retardation of the catalyst activity. The primary cause for the inhibition is the competitive adsorption of NH 3 and C 3H 6 onto the catalyst surface and the useless consumption of NH 3 by the side reaction, including the NH 3 oxidation and ammoxidation reactions during the course of NH 3/SCR reaction with C 3H 6.

Green synthesis of a self-assembled rutile mesocrystalline photocatalyst

This paper reports a simple and environmentally benign approach for the synthesis of photocatalytically active rutile TiO2 mesocrystals. It is a microwave-assisted hydrothermal method involving titanium(III) chloride as the only reactant. The resulting 1D rutile nanowires can easily assemble into 3D hierarchical architectures without the help of surfactants or additives. The average aspect ratio for the nanowires is 267. The BET specific surface area of the mesocrystals is 16 m2 g−1. The optical band energy of the product exhibits an obvious red-shift of 0.2 eV with aspect to that of pure rutile TiO2. This red-shift effect may be ascribed to the high aspect ratio of rutile nanowires. The products show excellent photocatalytic activity for NO removal in air and the activity is well maintained after three cycles. Gold modification on the rutile TiO2 results in a 50% improvement in the photocatalytic performance.

Effect of V 2O 5 additive on simultaneous SO 2 and NO removal from flue gas over a monolithic cordierite-based CuO/Al 2O 3 catalyst

A monolithic cordierite-based CuO/Al 2O 3 catalyst showed industrial potential for simultaneous SO 2 and NO removal from flue gases at 350–400 °C. However, it is still a challenge to prevent CuO from aggregation and to keep it in an active state during the removal and regeneration processes. This work shows that addition of V 2O 5 to the catalyst can significantly reduce CuO particle size and improve SO 2 removal activity, and maintain a high selective catalytic reduction (SCR) activity for NO removal. Furthermore, V 2O 5 additive prevents aggregation of SiO 2 in the cordierite with the coated Al 2O 3, and inhibits over reduction of the SO 2 removal product, CuSO 4, during the regeneration by NH 3, which are important to the catalyst's stability. V 2O 5 additive changes the regeneration product from Cu 3N to CuO and thus may avoid the temperature rise and NOx release in the subsequent removal process.

The characterization and activity of F-doped vanadia/titania for the selective catalytic reduction of NO with NH 3 at low temperatures

A F-doped vanadia/titania catalyst has been developed by partly substituting the lattice oxygen of the catalyst with fluorine, using NH 4F as a precursor. The aim of this novel design was to promote the activity of a catalyst with low vanadia loading in the low-temperature selective catalytic reduction of NO with NH 3. Analysis by N 2 physisorption, XPS, ICP, XRD, ESR and PL spectra showed that fluorine doping facilitated the formation of V 4+ and Ti 3+ ions mainly by charge compensation, promoted the distribution of vanadium on the catalyst surface, and increased the amount of surface superoxide ions. The catalytic activity of NO removal was promoted by F-doping. And the catalyst with [F]/[Ti] = 1.35 × 10 −2 showed the highest NO removal efficiency in SCR reaction at low temperatures.

Pt/La-Ba-Al2O3/H-ZSM-5 Catalyst for Treating Hydrogen-Powered Vehicle Exhaust

Abstract La-Ba-Al 2 O 3 (LBA) was prepared by the peptizing method, and Pt/LBA and Pt/LBA/H-ZSM-5 catalysts were prepared by impregnation. The catalyst activity for NO removal from the exhaust of a hydrogen-powered vehicle was evaluated. The specific surface area and pore volume of LBA were 144 m 2 /g and 0.45 ml/g, respectively. X-ray diffraction results showed that LBA had a γ-Al 2 O 3 structure and good thermal stability. The Pt/LBA/H-ZSM-5 catalyst exhibited excellent performance in the selective catalytic reduction of NO between 106 and 356 °C with a maximum NO conversion of 98.8% at 153 °C and N 2 selectivity of 81.3%.

Alumina supported Pt(1%)/Ce0.6Zr0.4O2 monolith: Remarkable stabilization of ceria–zirconia solution towards CeAlO3 formation operated by Pt under redox conditions

A structured Pt(1wt%)/ceria–zirconia/alumina catalyst and the metal-free ceria–zirconia/alumina were prepared, by dip-coating, over a cordierite monolithic support. XRD analyses and Rietveld refinements of the structural data demonstrate that in the Pt supported catalysts ceria–zirconia is present as a Ce0.6Zr0.4O2 homogeneous solid solution and that the deposition over the cordierite doesn’t produce any structural modification. Moreover no Pt sintering occurs.By comparing the XRD patterns recorded on Pt/ceria–zirconia/alumina and ceria–zirconia/alumina after three redox cycles, it results that Pt, favouring the structural reorganization of the ceria–zirconia into one cubic solid solution, prevents any CeAlO3 formation. On the contrary, such phase due to the interaction between Ce3+ and the alumina present in the washcoat is detected when redox cycles are carried out on the ceria–zirconia metal free.Transmission electron microscopy (TEM) investigations of the redox cycled Pt/ceria–zirconia/alumina catalyst detected ceria–zirconia grains with diameter between 10 and 35nm along with highly dispersed Pt particles (2–3nm) strongly interacting with ceria.Scanning electron microscopy (SEM) and EDX analyses, recorded on the redox cycled Pt/ceria–zirconia/alumina washcoated monolith evidence a homogeneous distribution of the active components through the channels even after redox aging.Reduction behaviour and CO oxidation activity are in good agreement with the structural modification of the solid solution induced by the redox cycles and reflect the positive effect of Pt/ceria interaction on the catalytic performances.The effect of redox aging on the NO reduction by C3H6, in lean conditions, was investigated over the Pt/ceria–zirconia/alumina monolith. The catalyst shows at low temperature (290°C) good NO removal activity and appreciable selectivity to N2.

Effects of oxygen and hydrogen chloride on NO removal efficiency by Rh/Al 2O 3 and Rh–Na/Al 2O 3 catalysts

The influences of oxygen, hydrogen chloride, and sodium modification on the activity of the Rh/Al 2O 3 catalyst for NO removal were investigated in simulated waste incineration conditions. The characterizations of the catalysts were analyzed by SEM/EDS, XRD, and ESCA. Experimental results indicated that the Rh/Al 2O 3 catalyst has high stability and activity for NO removal over a range of 0–20% O 2. The addition of Na promoted the activity and N 2 selectivity of the Rh/Al 2O 3 catalyst, but an increase in NO 2 selectivity was observed when oxygen concentration and reaction time increased. The Rh/Al 2O 3 catalyst gradually deactivated on both NO and CO conversions when HCl concentration increased to 500 ppm because of the formation of RhCl 3. The Rh–Na/Al 2O 3 catalyst has a low activity for NO conversion, but 100% CO conversion still remained even though 500 ppm HCl was contained in the feed gas. The Na added to the Rh/Al 2O 3 catalyst can react with HCl to form NaCl, resulting in a suppressed deactivation for Rh active sites. Low HCl concentrations do not affect NO 2 selectivity of the Rh/Al 2O 3 catalyst but do decrease that of the Rh–Na/Al 2O 3 catalyst.

Characterization and reactivity of WO3–V2O5 supported on sulfated titanium pillared clay catalysts for the SCR-NO reaction

Vanadia and tungsten oxides supported on sulfated Titanium pillared clay were prepared and characterized by N-2 physisorption, XRD, XPS, NH3-TPD and H-2-TPR measurements. The effect of vanadium and tungsten oxides on the catalytic activity of sulfated Ti-pillared clay (STi-PILC) for NO reduction by ammonia was examined. Based on the temperature-programmed reduction, it was found that the sulfate stability depends on the loaded metal oxides and the reduction properties of SO42- or V2O5 in the sample were changed in the presence of WO3. The difference in reduction properties of sulfate strongly suggests some interaction of sulfate with tungsten and vanadia species on the surface of STi-PILC support. Vanadia enhanced the NO removal activity of STi-PILC, while no significant effect of tungsten was observed for WO3-V2O5/STi-PILC catalyst. When both tungsten and sulfate exist simultaneously on the surface of vanadia supported STi-PILC, the sulfate species seems to play a more important role for NO removal activity than tungsten. To cite this article: L. Khalfallah Boudali et al., C R. Chimie 12 (2009). (C) 2008 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.