Diesel exhaust emission catalyst : synthesis, characterization and activity studies
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Date
2003-09
Authors
Khoo, Daw Deeng
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Abstract
The selective catalytic reduction with hydrocarbons as reducing agent (SCRHC)
has attracted lot of interest and is the most promising way to eliminate NOx from
the oxygen rich stream of diesel exhaust emissions. There is a need to develop a suitable
catalyst that could remove NOx and at the same time could circumvent the disadvantage
of packed bed reactor that results in high-pressure drop during the gas passage through
the catalytic bed, flow maldistribution causing loss of selectivity and high susceptibility
to fouling by diesel particulate.
In the present research, structured catalyst was developed with 0.99 of porosity,
to make the path of the gaseous emissions in structured reactors easier and has lowpressure
drop. CU/ZSM-5 catalyst was successfully coated over stainless steel wire
mesh by in-situ hydrothermal method. The total coverage after 3 times coating process
resulted in 140 gzsms/m2 and the thickness of coating was 4 !-lm. BET surface area of the
\\·i~c :::csh \\·as 311 m2/g (3 times coating). 5.7 wt% copper was loaded by ion exchange
processes in the structured ZSM-5 catalyst. No structural changes were found in the
catalyst after activity measurement and time on stream study of 48 hours.
Design of Experiments (DOE) was used in the activity studies of CU/ZSM-5
st:u.::ured catalyst. The response surface methodology (RSM) couple with Center
Composite Design (CCD) was used to obtain the optimum conditions for selective
~<it.al~1ic reduction of NO v.;ith iso-butane as reducing gas. The optimum conditions
were 1730 ppm of NO, 1280 ppm of iso-butane and 375°C reaction temperature with
94 % reduction of NO and 4.6 % SCR-HC selectivity.
Description
Keywords
To eliminate NOx from the oxygen rich stream , of diesel exhaust emissions