Selective catalytic reduction of NO with NH3 over natural zeolites and its application to stationary diesel engine exhaust
Introduction
NOx is the main source of photochemical smog and contributes devastatingly to acid rain. The reduction and/or elimination of NO emission can be considered one of the most important keys to solving environmental problems. The selective catalytic reduction (SCR) of NO has been generally used for stationary exhaust sources. The V2O5/TiO2 catalyst has been commercially used in the presence of NH3. The reaction mechanism has been studied by many researchers 1, 2, 3, 4, 5, 6, 7, 8, 9. More recently, other oxide catalysts 10, 11, 12and zeolites 13, 14, 15, 16, 17for NO removal by NH3 have been studied. A large number of zeolite based catalysts are also being developed 18, 19, 20, 21. Zeolites are able to contain low concentrations of various cations and have micropores for NH3 adsorption as the reductant. However, V2O5/TiO2 catalysts generally contain V2O5 of ca. 10 wt% This may cause environmental problems in catalyst disposal. In addition, synthetic zeolites may be expensive to use as SCR catalysts. In this work, natural zeolite catalysts exchanged with various cations including vanadium ions were developed for the selective reduction of NO. Furthermore, we have attempted the development of catalysts which contain low concentrations of vanadium oxide with a high activity for NO reduction in the presence of NH3 to be used for stationary diesel engine exhaust.
Section snippets
Zeolites and their cation exchange
Synthetic mordenite (MOR, JRC-Z-HM20) provided by the Catalysis Society of Japan was used. The first natural zeolite is Zeo 3S which mainly consists of clinoptilolite (HEU) and small amounts of crystallite and quartz (produced in Akita, Japan). The second is Izukalite which mainly consists of mordenite (MOR) and a small amount of quartz (produced in Shimane, Japan). The elemental composition of these zeolites are shown in Table 1, which were determined by ICP photoemission analysis.
The cation
NO conversion over cation exchanged mordenite (JRC-Z-HM20)
The catalytic reduction of NO in the presence of NH3 was carried out over synthetic mordenite exchanged with various cations. The catalysts used are shown in Table 1. The conversion of NO are found to be higher over Cu, Fe, Cr, V, Ni and Ce exchanged catalysts at space velocity (SV) 30 000 h−1 and at 350–500°C while the catalysts exchanged with H, Zn, Tl, Zr, Ti and Ag exhibited lower activities (Table 4). Fig. 2 shows the results at low SV 3000 h−1 over the catalysts which exhibit high
References (25)
- et al.
J. Catal.
(1980) - et al.
Appl. Catal.
(1990) - et al.
J. Catal.
(1977) - et al.
J. Catal.
(1996) - et al.
J. Catal.
(1996) - et al.
J. Catal.
(1997) - et al.
J. Catal.
(1997) - et al.
Catal. Today
(1992) - et al.
J. Catal.
(1973) - et al.
Catal. Today
(1988)
Catalysis (Shokubai)
Cited by (38)
Ion Exchange
2015, Progress in Filtration and SeparationEnhancement of the catalytic performance of H-clinoptilolite in propane-SCR-NO<inf>x</inf> process through controlled dealumination
2014, Chemical Engineering JournalCitation Excerpt :NO or NO2 has been the main chemical form of NOx used in the cited studies. Mishima et al. [10] proposed the use of natural zeolites for the abatement of NOx in stationary diesel exhaust gas streams. However, they considered NH3 as reductant, and this turns out to be costly and problematic due to safety requirements of ammonia for such installations.
Abatement of nitrous oxide over natural and iron modified natural zeolites
2011, Applied Catalysis A: GeneralCitation Excerpt :In the reduction of N2O with NH3, Coq et al. observed that BEA is the most efficient host zeolite [2–4] with the mononuclear species found to be the most active species. In addition to ZSM-5 and BEA, various synthetic and natural zeolitic materials such as mordenite (MOR), heulandite-clinoptilolite (HEU), ferrierite (FER) and chabazite (CHA) have also been investigated [7,27–30]. Among them, Fe-MOR and Fe-HEU show excellent performance in selective catalytic oxidation (SCO) of ammonia to nitrogen and SCR of NO with ammonia with similar activity as found for Fe-ZSM-5 [27,28,31].
NO removal by activated carbon-supported copper catalysts prepared by impregnation, polyol, and microwave heated polyol processes
2011, Applied Catalysis A: GeneralCitation Excerpt :Selective catalytic reduction (SCR) has been found to be an effective method for the removal of nitric oxides (NOx) [1–3].
Recent developments in novel sorbents for flue gas clean up
2010, Fuel Processing TechnologySelectivity, stability and repeatability of In<inf>2</inf>O<inf>3</inf> thin films towards NO<inf>x</inf> at high temperatures (≥500 °C)
2010, Sensors and Actuators, B: Chemical