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Tandem Mass Spectrometric Analysis Of Ammonium And Sodium Oligoperoxide Adducts With The Application Of Two-dimensional Correlation Spectroscopy And Computational ChemistryFrisch, Jessica Lynne 01 January 2012 (has links)
Oligoperoxides, H[OO(CH3)2C]nOOH, are formed as side products in the synthesis of the primary high explosive triacetone triperoxide (TATP). Previous tandem mass spectrometry (MSn ) experiments using a quadrupole ion trap reported that the openchained oligoperoxide adducts of ammonium or sodium resulted in different product ions in the mass spectra. Dissociation mechanisms were previously proposed based on MSn experiments, where n > 2; however, a dissociation pathway achieved by an MSn experiment, where n > 2, may not necessarily be the same pathway achieved in an MS2 experiment. For this dissertation research, the collision induced dissociation pathways were investigated for the open-chained oligoperoxides in MS2 experiments utilizing a quadrupole ion trap. Tandem mass spectral experiments were performed for the openchained oligoperoxides ranging from the trimer to the octamer (n=3-8), including both ammonium and sodium adducts. The dissociation pathways were proposed as a result of two-dimensional correlation spectroscopy applied to the mass spectral data, which was referred to as two-dimensional correlation mass spectrometry (2D-CMS). The 2DCMS method was first validated by analysis of simple and more complex kinetic models followed by simple and more complex molecules. To further aid in the elucidation of the dissociation mechanisms, computational chemistry was performed for the optimization of stable precursor and product ion structures and calculations of their relative energies and adduct dissociation energies.
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Influence of Framework n(Si)/n(Al) Ratio on the Nature of Cu Species in Cu-ZSM-5 for NH3-SCR-DeNOxJabłońska, Magdalena, Góra-Marek, Kinga, Bruzzese, Paolo Cleto, Palčić, Ana, Pyra, Kamila, Tarach, Karolina, Bertmer, Marko, Poppitz, David, Pöppl, Andreas, Gläser, Roger 05 August 2024 (has links)
Nanosized Cu-containing ZSM-5 catalysts with different n(Si)/
n(Al) ratio of 18.9–50.5 were prepared by ion-exchange. The
physico-chemical characterization clearly shows that the molar
ratio of framework T atoms influences the nature and distribution
of copper species. According to DR UV-Vis, TPR-H2, EPR, or
FT-IR spectroscopy analyses, the amount of aggregated copper
species increases with increasing the framework n(Si)/n(Al) ratio.
Thus, the activity of the Cu-containing ZSM-5 with n(Si)/n(Al)
ratio of 47.0—50.5 in the selective catalytic NO reduction with
NH3 (NH3-SCR-DeNOx) significantly decreases compared to the
other materials (n(Si)/n(Al) ratio of 18.9—19.6). The reaction
mechanism has been discussed in light of the results of 2D COS
(two-dimensional correlation spectroscopy) analysis of IR spectra
and catalytic properties of the zeolites. The results make
evident that enhanced activity of Cu-containing ZSM-5 in NH3-
SCR-DeNOx is correlated with the formation of different NOx
under the experimental conditions.
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