Article

TPD Study of Mordenite-Type Zeolites for Selective Catalytic Reduction of NO by NH 3

Research Center for Catalytic Technology, Department of Chemical Engineering, School of Environmental Engineering, Pohang University of Science and Technology (POSTECH)/Research Institute of Science and Technology (RIST), P.O. Box 125, Pohang 790-600, Korea
Journal of Catalysis - J CATAL 01/1996; 161(2):597-604. DOI: 10.1006/jcat.1996.0222

ABSTRACT The effect of the adsorption of NO and NH3on catalytic activity has been examined by temperature-programmed desorption over a series of cation-exchanged mordenite catalysts for selective catalytic reduction (SCR) of NO by NH3. The catalytic activity observed in a packed-bed flow reactor was well correlated with the cation content of the catalyst and its adsorption properties, making it possible to elucidate the role of metals and acidity in this reaction system. The amount of NH3and NO adsorbed on the catalyst surface proportionally increased with the degree of cation exchange of the catalyst, especially at the Brønsted acid site (H+) and the metal site (Cu2+). SCR activity also gradually increased with the acidity of the catalyst and/or its degree of catalyst cation exchange. Surface acidity of the mordenite catalysts appears to be a dominant factor in the high performance of the SCR reaction system. The common activation energy is observed to be about 12 kcal/mole for NaHM and CuHM catalysts, independent of their cation content on the catalyst surface. The active sties of this catalytic system are both the Brønsted acid site and the metal site. Furthermore, the reaction occurred in a Langmuir–Hinshewood manner with a dual-site catalysis mechanism.

0 Bookmarks
 · 
15 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: A catalyst based on MnO(x)/TiO(2) was prepared by sol-gel method for low-temperature selective catalytic reduction (SCR) of NO with NH(3). Focusing on the effects of the operating parameters, the SCR reaction was investigated at temperatures from 353 to 523K under steady and transient states. Under the optimal conditions, the efficiency of NO removal could exceed 90% at temperature of 423K. Furthermore, within the range investigated, the reaction order of NO, NH(3), O(2) was determined to be 1, 0, and 0.5, respectively. Apparent activation energy was also calculated to be 38kJ/mol, lower than that for most of the catalysts reported by previous investigations.
    Journal of Hazardous Materials 08/2007; 145(3):488-94. · 3.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: MnO(2) nanotubes, nanorods, and nanoparticles were prepared using a hydrothermal method, after which the different activities for selective catalytic reduction (SCR) of nitrogen oxides (NO(x)) were compared. MnO(2) nanorods performed the highest activity for reduction of NO(x) under a gas hourly space velocity of 36,000 h(-1) with conversion efficiencies of above 90% between 250 and 300 °C; it also had the highest removal efficiency of 98.2% at 300 °C. From the analysis of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and temperature-programmed reduction, we can ascribe the high activity of MnO(2) nanorods to low crystallinity, more lattice oxygen, high reducibility, and a large number of strong acid sites. The apparent activation energy of the SCR reaction on the surface of nanorods was calculated to be 20.9 kJ/mol, which favored the reaction better than the other catalysts.
    Journal of hazardous materials 01/2011; 188(1-3):105-9. · 4.14 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Polymers synthesized via anionic polymerization have proved important to our fundamental understanding of the processing, that is rheology and crystallisation, of bulk commodity polymers. The role of monodisperse hydrogenated polybutadienes as models for linear and branched polyethylene is examined. Systematic studies of the effects of long-chain branching, using well-defined "comb" materials have improved our understanding of how the number and length of branches affect the rheological properties and how these features impact on their crystallization behaviour. A combination of techniques including rheology, Small Angle X-ray Scattering (SAXS), and birefringence measurements have provided insight into role of linear long chains in the formation of oriented morphologies during the crystallization of hydrogenated polybutadiene blends of controlled polydispersity leading to the development of a quantitative model. (C) 2010 Elsevier Ltd. All rights reserved.
    European Polymer Journal. 01/2011; 47(4):447-464.