Dynamics of N2O decomposition over HZSM-5 with low Fe content

被引:54
作者
Bulushev, DA [1 ]
Kiwi-Minsker, L [1 ]
Renken, A [1 ]
机构
[1] EPFL, LGRC, Swiss Fed Inst Technol, CH-1015 Lausanne, Switzerland
关键词
Fe-containing HZSM-5; N2O decomposition; transient response method; temperature-programmed desorption; surface oxygen loading from N2O;
D O I
10.1016/j.jcat.2003.11.012
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The dynamics of N2O decomposition to gaseous nitrogen and oxygen over HZSM-5 catalysts with a low iron content (200 and 1000 ppm) was studied by the transient response method in the temperature range 523-653 K. The active catalysts were prepared from HZSM-5 with Fe in the framework on its steaming at 823 K followed by thermal activation in He at 1323 K. Two main steps were distinguished in the dynamics of N2O decomposition. The first step represents N2O decomposition forming gaseous nitrogen and surface atomic oxygen. The second step is associated with surface oxygen recombination and desorption. At 523-553 K only the first step is observed. Above 573 K the decomposition of N2O to O-2 and N-2 in stoichiometric amounts starts at a rate increasing with time until a steady-state value is reached. This increase was assigned to the catalysis by adsorbed NO formed slowly on the catalyst surface from N2O, as indicated by temperature-programmed desorption. The catalytic effect of the adsorbed NO was also confirmed by transient experiments with forced addition of NO in the stream of N2O during its decomposition. A simplified kinetic model is proposed to explain the autocatalytic reaction. Catalyst pretreatment in O-2 did not affect N2O decomposition, but irreversible water vapor adsorption at 603 K resulted in a twofold decrease in surface oxygen loading from N2O and complete inhibition of the oxygen desorption. (C) 2003 Elsevier Inc. All rights reserved.
引用
收藏
页码:389 / 396
页数:8
相关论文
共 28 条
[1]   Co-ordination and oxidation changes undergone by iron species in Fe-silicalite upon template removal, activation and interaction with N2O:: an in situ X-ray absorption study [J].
Berlier, G ;
Spoto, G ;
Fisicaro, P ;
Bordiga, S ;
Zecchina, A ;
Giamello, E ;
Lamberti, C .
MICROCHEMICAL JOURNAL, 2002, 71 (2-3) :101-116
[2]   Evolution of iron states and formation of α-sites upon activation of FeZSM-5 zeolites [J].
Dubkov, KA ;
Ovanesyan, NS ;
Shteinman, AA ;
Starokon, EV ;
Panov, GI .
JOURNAL OF CATALYSIS, 2002, 207 (02) :341-352
[3]   Kinetic isotope effects and mechanism of biomimetic oxidation of methane and benzene on FeZSM-5 zeolite [J].
Dubkov, KA ;
Sobolev, VI ;
Talsi, EP ;
Rodkin, MA ;
Watkins, NH ;
Shteinman, AA ;
Panov, GI .
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, 1997, 123 (2-3) :155-161
[4]   Isothermal oscillations during N2O decomposition over Fe/ZSM-5:: effect of H2O vapor [J].
El-Malki, EM ;
van Santen, RA ;
Sachtler, WMH .
MICROPOROUS AND MESOPOROUS MATERIALS, 2000, 35-6 :235-244
[5]   Active sites in Fe/MFI catalysts for NOx reduction and oscillating N2O decomposition [J].
El-Malki, EM ;
van Santen, RA ;
Sachtler, WMH .
JOURNAL OF CATALYSIS, 2000, 196 (02) :212-223
[6]   The room temperature, stoichiometric conversion of N2O to adsorbed NO by Fe-MCM-41 and Fe-ZSM-5 [J].
Grubert, G ;
Hudson, MJ ;
Joyner, RW ;
Stockenhuber, M .
JOURNAL OF CATALYSIS, 2000, 196 (01) :126-133
[7]   Identification by isotopic exchange of oxygen deposited on Fe/MFI by decomposing N2O [J].
Jia, JF ;
Wen, B ;
Sachtler, WMH .
JOURNAL OF CATALYSIS, 2002, 210 (02) :453-459
[8]  
Kapteijn F, 1996, APPL CATAL B-ENVIRON, V9, P25
[9]   Active sites in HZSM-5 with low Fe content for the formation of surface oxygen by decomposing N2O:: is every deposited oxygen active? [J].
Kiwi-Minsker, L ;
Bulushev, DA ;
Renken, A .
JOURNAL OF CATALYSIS, 2003, 219 (02) :273-285
[10]   Nature of active sites in the oxidation of benzene to phenol with N2O over H-ZSM-5 with low Fe concentrations [J].
Kubánek, P ;
Wichterlová, B ;
Sobalík, Z .
JOURNAL OF CATALYSIS, 2002, 211 (01) :109-118