Date

2017

Author

Sevinç, Alper

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High temperature catalytic oxidation (HTCO) of nitrogen containing compounds has great importance with regard to determination of the nitrogen in the environmental and industrial samples. The complete oxidation of bound nitrogen in different functional groups, ammonia, nitrates and organic nitrogen to nitric oxide is a crucial step for the determination of nitrogen in samples. The main goal of this work is catalyst screening for the complete oxidation of total bound nitrogen in the nitrogen containing compounds to nitric oxide. Four different catalyst samples, 10 % wt Cu/Al2O3, 3% wt Cu- 7 % wt Ce/Al2O3, 5 % wt Fe/Al2O3 and 1 % wt Pt/Al2O3, were synthesized by impregnation method. Characterization of the catalyst samples was performed by X-ray diffraction (XRD) and BET. High temperature catalytic oxidation (HTCO) experiments were conducted with compounds containing different nitrogen functional groups to observe the catalytic activities of the catalyst samples. Temperature vi programmed oxidation (TPO) studies were carried out to observe reaction mechanism of bound nitrogen at different temperatures. HTCO experiments showed that, water is as important oxidizing agent as oxygen for the oxidation of organic nitrogen to NO. According to conversion results of HTCO experiments, 5 % wt Fe/Al2O3 catalyst showed the best catalytic activity for conversion of bound nitrogen in tested model compounds to NO. 1 % wt Pt/Al2O3 catalyst also showed good catalytic activity for the model compounds oxidation except pyridine. 10 % wt Cu/ Al2O3 catalyst performed bad catalytic activity for conversions of bound nitrogen to NO for EDTA, glutamic acid and ammonium sulfate. 3% wt Cu- 7 % wt Ce /Al2O3 catalyst showed poor conversions of bound nitrogen to NO for compounds, EDTA, pyridine, ammonium nitrate and glutamic acid. TPO studies showed that complete conversion of bound nitrogen of acetonitrile to NO occurs at temperatures between 700-800 oC for the 5 % wt Fe/ Al2O3 and 1 % wt Pt/ Al2O3 catalysts. The results of TPO experiment over 10 % wt Cu/Al2O3 catalyst showed that N2 formation is seen up at temperatures to 900 oC. According to TPO experiment results over 3% wt Cu- 7 % wt Ce /Al2O3, it can be stated that N2 and N2O are the main nitrogen containing products at temperatures up to 900 oC. In this study, 5 % wt Fe/Al2O3 catalyst showed the best catalytic activity for high temperature oxidation of bound nitrogen to NO in the selected model compounds. Therefore; it can be stated for the future works that, alumina supported iron catalysts will be one of the first alternative to platinum containing catalysts in the nitrogen determination by using HTCO technique.

Subject Keywords

Nitrogen., Catalysts, Oxidation., Nitrogen compounds.

URI

http://etd.lib.metu.edu.tr/upload/12621483/index.pdf
https://hdl.handle.net/11511/26695

Collections

Graduate School of Natural and Applied Sciences, Thesis