Aspects of the Role of Hydrogen in H2-Assisted HC–SCR Over Ag–Al2O3

Kannisto, Hannes; Ingelsten, Hanna Härelind; Skoglundh, Magnus

doi:10.1007/s11244-009-9359-1

Cited by 34 publications

(19 citation statements)

References 27 publications

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“…It can be clearly seen in Figure 4A It has been reported that Ag has lower binding energy with increasing oxidation state due to its core-level photo- The Journal of Physical Chemistry C Article emission. 18,28 According to this empirical rule, supported silver species for all samples are mostly close to the +1 oxidation state, just like Ag + ion in AgNO 3 solid, even though silver metal XRD peaks were found for "150 r/min" and "Al 2 O 3 mill + AgNO 3 mill" samples. Figure 4B shows the Fourier transforms of k 3 -weighted EXAFS oscillations at the Ag K-edge.…”

Section: Resultsmentioning

confidence: 88%

Water Effect on Preparation of Ag/Al₂O₃ Catalyst for Reduction of NOx by Ethanol

Deng

2016

J. Phys. Chem. C

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Alumina-supported silver catalysts (Ag/Al 2 O 3 ) derived from wet impregnation, a semiwet method, and water-free ball-milling were investigated for the selective catalytic reduction of NOx by ethanol. It was found that Ag/Al 2 O 3 catalysts with the highest NO x reduction efficiency can be obtained via wet impregnation and the semiwet method but not by water-free ball milling. To optimize the preparation parameters and discern the effect of water in the production of Ag/Al 2 O 3 catalysts, the resulting series of alumina-supported silver samples were characterized by means of XRD, BET, XAS (XANES and EXAFS), in situ DRIFTS, and NMR. The results indicated that silver species were oxidized and highly dispersed on the large surface area Al 2 O 3 obtained from wet impregnation and the semiwet method. In situ DRIFTS revealed that the vital intermediate enolic species were correspondingly predominant on the surfaces of catalysts prepared by these methods, while the inactive intermediate acetate species were significantly formed on Ag/Al 2 O 3 catalysts prepared by water-free ball milling. Solid state 1 H NMR suggested that the water employed in the wet methods enhances the exchange of Ag + with protons from hydroxyl groups on the alumina surface, which leads to silver species being highly dispersed and forming active Ag−O−Al entities.

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Section: Resultsmentioning

confidence: 88%

Water Effect on Preparation of Ag/Al₂O₃ Catalyst for Reduction of NOx by Ethanol

Deng

2016

J. Phys. Chem. C

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“…NO and O2 form NOx surface species (nitrates and nitrites). Strongly adsorbed nitrate is known to self-inhibit the NOx reduction at low temperature [22,23]. For activation of HC, the O2 partially oxidizes the HC to form oxygenated HC surface components.…”

Section: Introductionmentioning

confidence: 99%

Studies on H2-Assisted Liquefied Petroleum Gas Reduction of NO over Ag/Al2O3 Catalyst

Yadav

Thakur

et al. 2017

Bull. Chem. React. Eng. Catal.

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Hydrocarbon-Selective catalytic reduction (HC-SCR) is one of the potential methods to remove NOx emissions from diesel engine, lean burn petrol engines and natural gas engines exhaust. Ag/Al2O3 is a good catalyst for HC-SCR of NOx under lean-burn conditions. Further, addition of small amount of H2 is effective for enhancing HC-SCR activity. This effect is unique to silver and to specific Ag/support combinations, namely, Ag/γ-Al2O3. Various HC reductants, such as: octane, decane, dodecane and propane, have been reported in the literatures. Only a single study on LPG as a reductant over Cu-ZSM catalyst was reported. There was no work reported on H2 assisted LPG over Ag/Al2O3 catalyst. Thus, this gap in the literature is filled with the present investigation of NO reduction over 2 wt.% Ag/Al2O3 catalyst using LPG reductant. The fresh and used catalyst was characterized by various techniques like low temperature N2-adsorption, XRD, XPS and SEM. There was practically no change in the characteristics of the fresh and used catalyst. Two different reductants of CO and LPG were compared for SCR of NO over the catalyst without and with H2-assisted. The experiments were performed in a fixed bed tubular flow reactor under the following conditions: 100mg catalyst; 0.13% NO, 2.5% LPG/CO, 1% H2, 10% O2, rest Ar; total flow rate 60 mL/min; temperature ambient 400 o C and pressure 1 atm. Around 100% conversion of NO was achieved using LPG reductant. Light off temperature of NO reduction significantly reduced by H2assisted LPG reductant. The maximum conversion of NO with CO was limited to 35.15% at temperature of 224 o C and above. Whereas, 97.79 % NO conversion was achieved at 365 o C with LPG reductant. While, the maximum conversions with H2-LPG and H2-CO reductants were 100 and 99.46% at 117 and 220 o C, respectively. Therefore, H2-LPG-SCR of NOx over 2 wt.% Ag/Al2O3 catalyst system can be used to get 100% reduction at low temperature.

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“…The spectra were recorded between 20 and 80° (2θ). The mean crystallite size (d) of the catalyst was calculated from the line broadening of the most intense reflection using the Scherrer"s formula in Equation (11). (11) where d is the mean crystallite diameter, 0.89 is the Scherrer constant, λ is X-ray wavelength (Cu Kα radiation) = 1.54056 Å, and  is effective line width of the observed X-ray reflection, calculated by the expression  2 =B 2 -b 2 ; where B is full width half maximum (FWHM) and b is instrumental broadening determined through the FWHM of the X-ray reflection at 2θ of crystalline SiO2.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

“…), precious metal (Ag/Al2O3, Au-Ag/Al2O3) and transition metals (V2O5-WO3/TiO2, Cu-ZSM-5, Fe-ZSM-5, etc.) [7][8][9][10][11][12]. PGM catalysts are highly active but they are costly, low abundance and vulnerable to further price increases with increasing demand.…”

Section: Introductionmentioning

confidence: 99%

Low Temperature Selective Catalytic Reduction (SCR) of NOx Emissions by Mn-doped Cu/Al2O3 Catalysts

Yadav

Kavaiya

Mohan

et al. 2017

Bull. Chem. React. Eng. Catal.

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The 15 mol% Cu/Al2O3 catalysts with different Mn doping (0.5, 1.0, 1.5, mol%) were prepared using PEG-300 surfactant following evaporation-induced self-assembly (EISA) method. Calcination of precursors were performed in flowing air conditions at 500 ºC. The catalysts were characterized by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope Energy Dispersive X-Ray (SEM-EDX), Fourier Transform Infra Red (FTIR), and N2 physisorption. The catalysts activities were evaluated for H2 assisted LPG-SCR of NO in a packed bed tubular flow reactor with 200 mg catalyst under the following conditions: 500 ppm NO, 8 % O2, 1000 ppm LPG, 1 % H2 in Ar with total flow rate of 100 mL/min. Characterization of the catalysts revealed that surface area of 45.6-50.3 m 2 /g, narrow pore size distribution (1-2 nm), nano-size crystallites, Cu 2+ and Mn 2+ phases were principal active components. Hydrogen enhanced significantly selective reduction of NO to N2 with LPG over 1.0 mol % Mn-Cu/Al2O3 giving 95.56 % NO reduction at 150 ºC. It was proposed that the synergistic interaction between H2 and LPG substantially widened the NO reduction temperature window and a considerable increase in both activity and selectivity. Negligible loss of catalyst activity was observed for the 50 h of stream on run experiment at 150 ºC. The narrow pore size distribution, thermal stability of the catalyst and optimum Mn doping ensures good dispersion of Cu and Mn over Al2O3 that improved NO reduction in H2-LPG SCR system.

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Aspects of the Role of Hydrogen in H2-Assisted HC–SCR Over Ag–Al2O3

Cited by 34 publications

References 27 publications

Water Effect on Preparation of Ag/Al₂O₃ Catalyst for Reduction of NOx by Ethanol

Water Effect on Preparation of Ag/Al₂O₃ Catalyst for Reduction of NOx by Ethanol

Studies on H2-Assisted Liquefied Petroleum Gas Reduction of NO over Ag/Al2O3 Catalyst

Low Temperature Selective Catalytic Reduction (SCR) of NOx Emissions by Mn-doped Cu/Al2O3 Catalysts

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Aspects of the Role of Hydrogen in H2-Assisted HC–SCR Over Ag–Al2O3

Cited by 34 publications

References 27 publications

Water Effect on Preparation of Ag/Al2O3 Catalyst for Reduction of NOx by Ethanol

Water Effect on Preparation of Ag/Al2O3 Catalyst for Reduction of NOx by Ethanol

Studies on H2-Assisted Liquefied Petroleum Gas Reduction of NO over Ag/Al2O3 Catalyst

Low Temperature Selective Catalytic Reduction (SCR) of NOx Emissions by Mn-doped Cu/Al2O3 Catalysts

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Water Effect on Preparation of Ag/Al₂O₃ Catalyst for Reduction of NOx by Ethanol

Water Effect on Preparation of Ag/Al₂O₃ Catalyst for Reduction of NOx by Ethanol