10.1016/j.jcat.2012.12.002
Catalytic performance of sheet-like Fe/ZSM-5 zeolites for the selective oxidation of benzene with nitrous oxide
Fe/ZSM-5 zeolite nanosheets were prepared according to a literature procedure modified with the purpose of including Fe3+[25] and [26]. In a typical synthesis, 10.42 g of TEOS (tetraethylorthosilicate) was added to a solution containing 0.47 g of aluminum nitrate nonahydrate, 0.06 g of iron nitrate nonahydrate, and 20.0 g of distilled water. The mixture was stirred for 2 h. A solution containing 2.41 g of C16-6-6(Br)2 or C16-6-6(OH)2, 0.42 g sodium hydroxide (NaOH) and 15.7 g of demi-water was added to this mixture and shaken by hand for 5 min. After further stirring with a magnetic stirrer for 6 h at room temperature, the gel mixture was transferred to a Teflon-lined stainless-steel autoclave and heated at 140 degC for 9 days under tumbling (60 rpm). The zeolite product was filtered, washed with distilled water, and dried at 100 degC overnight. Using the OH form of the template, three different Si/Fe ratios were employed (Si/Fe = 84, 180 and 300). The as-synthesized zeolites were calcined at 580 degC for 4 h under a flow of air. The calcined samples were ion-exchanged into their ammonium form by triple ion-exchange with a 1 M aqueous solution of NH4NO3 at room temperature. The proton form of the zeolites was obtained by calcination at 550 degC under a flow of air for 4 h. The samples are denoted as Fe/ZSM-5-sheet(x, y) with x the anion of the template used (OH or Br) and y the Si/Fe ratio. Steam activation was carried out by heating an amount of sample in a flow of 10% water vapor (100 ml min-1) in artificial air at 700 degC for 3 h. The steamed samples are denoted by using the suffix "-st." A reference Fe/ZSM-5 catalyst was prepared by controlled hydrolysis of TEOS in the presence of tetrapropylammonium hydroxide (TPAOH) according to a literature procedure [10].
TEOS (tetraethylorthosilicate)
added to a solution
10.42 g
g
solution
aluminum nitrate nonahydrate
0.47 g
g
solution
iron nitrate nonahydrate
0.06 g
g
solution
f distilled water
20.0 g
g
mixture
stirred
2 h
h
solution
C16-6-6(OH)2
2.41 g
g
solution
sodium hydroxide (NaOH)
0.42 g
g
solution
demi-water
15.7 g
g
mixture
shaken by hand
5 min
min
gel mixture
stirring with a magnetic stirrer
6 h
h
gel mixture
heated
140 degC
degC
gel mixture
heated
9 days
days
gel mixture
tumbling
60 rpm
rpm
zeolite product
dried
100 degC
degC
Si/Fe
ratios
84, 180 and 300
as-synthesized zeolites
calcined
580 degC
degC
as-synthesized zeolites
calcined
4 h
h
aqueous solution of NH4NO3
1 M
M
zeolites
calcination
550 degC
degC
zeolites
calcination
4 h
h
flow
water vapor
10%
%
sample
heating
700 degC
degC
sample
heating
3 h
h
water vapor
100 ml min-1
ml min-1