Ammonia on H-ZSM

Figure 3 Variations with coverage of the differential heats of adsorption of ammonia on H-ZSM-5 (sample 1) measu-red at 150°C, (A), 200°C, (a), 250°C, (fe 300°C (0) and 400°C (+) The sample was outgassed at 400°C prior NH3 adsorp-tion. The meaning of the arrows is explained in the text.

Figure 1.10 Differential heats of adsorption as a function of coverage for ammonia on H-ZSM-5 (o) and H-mordenite ( ) zeolites [70], In both cases, the heats decrease with the extent of NH3 uptake, indicating that the strengths of the individual acidic sites on each catalyst are not uniform. On the other hand, the H-ZSM-5 sample has a smaller total number of acidic sites. Also, the H-mordenite sample has a few very strong sites, as manifested by the high initial adsorption heat at low ammonia coverage. These data point to a significant difference in acidity between the two zeolites. That may account for their different catalytic performance. (Reproduced with permission from Elsevier.)...

Figure 7.8 The relaxation of the aluminum tetrahedron upon adsorption of ammonia on H-ZSM-5. Adapted from ref [33].

Another instructive example of a reaction monitored in situ by transmission IR spectroscopy is the alkylation of the toluene ring by methanol reported by Lercher and coworkers [820,890,891 ]. This work was related to the investigation of adsorption and co-adsorption of toluene, methanol and ammonia on H-ZSM-5 and H, Na-ERI by the same group (vide supra and [127,652,814-821]). The authors used a continuously stirred tank reactor [892-895]. Some conclusions drawn by the authors from their results of combined IR spectroscopic and gas chromatographic experiments were reported as follows. 

Briiggemann TC, Vlachos DG, Kell FJ (2011) Microkinetic modeling of the fast selective catalytic reduction of nitrogen oxide with ammonia on H-ZSM-5 based on first principles. J. Catal. 283 178-191... 

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See also in sourсe #XX -- [ , ]

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