Ammonia distribution, selective catalytic

It appears interesting to investigate vanadia doped sulfated Ti-pillared clay for the selective catalytic reduction of NO by anmionia and to compare their performance with sulfated Ti-pillared clay and vanadia doped Ti-pillared clay. In this work, all the catalysts were synthesized under identical conditions and were characterized by different techniques. These techniques included surface area measurement, pore size distribution, X-ray diffraction. X-ray photoelectron spectroscopy, TPD-NH3 and chemical analysis of Ti retained by the clay. The catalysts were then tested in the selective catalytic reduction of NO by ammonia in the presence of oxygen at different temperatures. 

The most important secondary measures include the effective selective catalytic reduction (SCR) and the less effective selective non-catalytic reduction (SNCR). The major drawbacks with SCR are the high capital and operating costs, the large bulky catalytic reactor, NOx/NH3 analytical equipment as well as an ammonia or urea storage and distribution system. SNCR on the other hand has a lower capital cost, but is less effective in NOx reduction. 

Ammonia TPD is very simple and versatile. The use of propylamine as a probe molecule is starting to gain some popularity since it decomposes at the acid site to form ammonia and propene directly. This eliminates issues with surface adsorption observed with ammonia. The conversion of the TPD data into acid strength distribution can be influenced by the heating rate and can be subjective based on the selection of desorption temperatures for categorizing acid strength. Since basic molecules can adsorb on both Bronsted and Lewis acid sites, the TPD data may not necessarily be relevant for the specific catalytic reaction of interest because of the inability to distinguish between Bronsted and Lewis acid sites. 

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