Figure reducing agent with efficiency for NOx


Figure 1 shows the catalytic conversion NO by NH3
is shown as a function of temperature. Cu/SUZ-4
showed higher activity than Cu/ZSM-5 at higher temperature. Though the NH3-SCR
activity of Cu/ZSM-5 decreased rapidly after 400°C due to NH3
oxidation, Cu/SUZ-4 kept high activity even at above 600°C. From NH3-TPD, Cu/SUZ-4 gave NH3 desorption at higher
temperatures. This would be consistent with NH3-SCR results
observed, strong acid probably contributed to the appearance of high SCR
activity. UV-Vis results indicated that copper states on both catalysts
would be a mixture of Cu2+ species interacting with oxygen of
zeolite structure and Cu2+ cations in CuO particles.

Results and discussion

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two Cu catalysts, Cu/SUZ-4 and Cu/ZSM-5, were prepared by solution ion-exchange
at 80°C for 1 h. According to the chemical analysis of Cu/SUZ-4 and Cu/ZSM-5
contained 1.49 and 1.68 wt.% Cu, respectively. Standard NH3-SCR tests were performed with reaction mixtures containing 240
ppm of NH3, 200 ppm of NO, 7 vol% of O2,
5 vol% of H2O and balance N2. The total gas flow was 135
sccm and the gas hourly space velocity (GHSV) was estimated to be 80,000 h-1
for 50 mg of catalyst. NH3 oxidation conducted in the same manner
without supplying NO gas. The IR spectra of CO and NO adsorbed catalyst
were recorded with quartz cell using CaF2 windows. Before recording
the spectra, sample was pre-treated in vacuum or air flow at 400°C and cooled



Selective catalytic reduction (SCR) is technology that has
been extensively studied and successfully commercialized to reduce NOx emission
1. Up to now, NH3 is successful reducing agent with efficiency for
NOx removal achieved 80-90%. Main attention has been paid to SCR catalyst based
on copper exchanged zeolites because of high
activities for NOx reduction. However,
the high-temperatures catalytic activity of Cu-based catalysts is still to be
improved 2. SUZ-4 has been reported to give high thermal stability and excellent catalytic
properties. SUZ-4 is synthetic zeolite with three-dimensional pore
having straight ten-membered ring intersected by two eight-membered channels. In this paper, we present an analysis of structure
and catalytic properties on NH3-SCR catalyst using Cu/SUZ-4 (10 and
8 membered ring) and Cu/ZSM-5 (10 membered ring).



The structure and catalytic properties of copper exchanged
SUZ-4 (Cu/SUZ-4) and ZSM-5 (Cu/ZSM-5) have been studied using various
characterization including XRD,
UV-Vis, ICP-AES, NH3-TPD and FTIR. Catalytic activity test
showed that Cu/SUZ-4 is more active
as NH3-SCR catalyst at high temperature with maximum NO conversion 92%. Several
aspects contribute to overall performance of the catalyst, such as zeolite
structure, nature of the copper location and different activities of catalyst
for undesired side reaction. The
characterization of the two catalysts indicates that copper ion presence at two
different cationic locations on SUZ-4.


*e-mail [email protected], fax +81-03-5286-3850

1Department of Applied Chemistry, School of
Advanced Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku
169-8555, Japan 2Research Institute for Science and Engineering,
Waseda University

Astri Andarini Budiawati1, Masahiko
Matsukata1, 2, *

Enhanced NH3-SCR
performance over copper-exchanged SUZ-4 zeolite


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