THESIS
2015
xvi, 202 pages : illustrations (some color) ; 30 cm
Abstract
Ammonia is an important source of malodor associated with the transportation,
processing and storage of organic, biological wastes; power plants and new diesel
engine vehicles. In this study, supported catalysts including vanadia/titania catalysts
and bifunctional catalysts, as well as their aerogel catalysts were designed, prepared,
modified and tested for selective catalytic oxidation of Ammonia (NH
3-SCO).
Vanadia supported on titania catalysts were tested via the reactions with a wide
concentration range of NH
3 from 40 ppm to 2175 ppm in synthetic air at temperatures
ranging from 25 ℃ to 250 ℃. The results showed a near 100% conversion for low
concentrations of NH
3 (40 ppm) and a still high reaction rate with moderate
conversion for high concentrations of NH
3 (2175 ppm). Van...[
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Ammonia is an important source of malodor associated with the transportation,
processing and storage of organic, biological wastes; power plants and new diesel
engine vehicles. In this study, supported catalysts including vanadia/titania catalysts
and bifunctional catalysts, as well as their aerogel catalysts were designed, prepared,
modified and tested for selective catalytic oxidation of Ammonia (NH
3-SCO).
Vanadia supported on titania catalysts were tested via the reactions with a wide
concentration range of NH
3 from 40 ppm to 2175 ppm in synthetic air at temperatures
ranging from 25 ℃ to 250 ℃. The results showed a near 100% conversion for low
concentrations of NH
3 (40 ppm) and a still high reaction rate with moderate
conversion for high concentrations of NH
3 (2175 ppm). Vanadia supported on titania
presented a monolayer form of supported catalyst when the surface vanadium coverage
approached and even surpassed the theoretical vanadium atom monolayer coverage
(7-8 V/nm
-2) using Micro-Raman, XRD and XPS. The mechanism of NH
3-SCO
over vanadia/titania catalysts was demonstrated to follow a direct oxidation pathway
involving hydrazinium-type intermediate. Vanadia/titania aerogel catalysts of large
surface area (800 cm
2/g) obtained using the ethanol supercritical drying method
presented a much higher ammonia reaction rate with the same selectivity of N
2
(100 %) at each reaction temperature. More importantly, hydrophobic aerogel
catalysts maintained reactivity for NH
3-SCO under a highly humid reaction condition
compared with vanadia/titania catalysts. Bifunctional catalysts based on
copper-vanadia/titania and ceria-vanadia/titania were also studied for NH
3-SCO, and showed promoted catalysis involving both direct oxidation and internal selective
catalytic reduction (iSCR) pathways. Supported catalysts including vanadia/titania
catalysts and bifunctional catalysts, as well as their aerogel catalysts, are able to
convert NH
3 to N
2 at lower temperatures (< 100 ℃).
This work provides a series of high catalytic selective catalysts for ammonia
remediation at low temperatures and humid conditions, which are suitable for
environmental applications for both indoor malodor treatments and practical
situations such as landfills, lavatories and drainage.
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