Catalytic oxidation of nitrogen containing compounds for nitrogen determination

• Published in: Catalysis today 2019-02, Vol.323, p.159-165
• Main Authors: Karakas, Gurkan, Sevinc, Alper
• Format: Article
• Language: English
• Subjects: Acetonitrile; Fe/Al2O3 catalytic combustion; High temperature catalytic oxidation; Nitrogen determination
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2018.04.058

[Display omitted] •The catalytic oxidation of acetonitrile over Pt, Fe, Cu and Cu-Ce/Al2O3 catalysts were studied.•Oxidation of acetonitrile to N2, N2O and NO takes place by different reaction routes depending on catalyst structure.•Direct oxidation of cyanide and isocyanide species is favored over Pt/Al2O3 catalyst.•High temperature catalytic oxidation activity of catalyst samples were tested for various nitrogenous components.•Fe/Al2O3 catalyst has promising high temperature catalytic oxidation activity for quantitative NO determination. The high temperature catalytic oxidation (HTCO) performance of Al2O3 supported Pt, Cu, Cu-Ce and Fe catalysts were systematically studied with a perspective of selective oxidation of nitrogenous compounds to nitric oxide for quantitative determination of bound nitrogen. The catalyst samples were prepared via impregnation and characterized by XRD and BET. In addition, temperature programmed reaction experiments with acetonitrile and oxygen were conducted to evaluate the catalytic activity and selectivity toward N2, N2O and NO. The catalyst samples were also tested for model components; urea, EDTA, pyridine, glutamic acid and ammonium sulfate representing different functional groups. The conversion of acetonitrile was tended to increase in the order of Cu-Ce/Al2O3>Cu/Al2O3>Pt/Al2O3>Fe/Al2O3 at around 500 °C and almost complete conversion of acetonitrile was achieved at 700 °C over the all catalyst samples studied. Temperature programmed reaction experiments indicated that two reaction routes, direct oxidation of cyanide species and oxidation of ammonia formed by hydrolysis of cyanide species determine NO selectivity. Direct oxidation of cyanide species is favored over Pt/Al2O3 catalyst which exhibit highest NO yield (93%) at 700 °C. The second route, hydrolysis of cyanide species to ammonia which is further oxidized to N2, NO and NO2 was evidenced by TPR-FTIR analyses over Fe/Al2O3, Cu/Al2O3 and Cu-Ce/Al2O3 catalysts. Among these catalysts, highest NO yield (90%) was observed over Fe/Al2O3 at 700 °C which is comparable to Pt/Al2O3 catalyst. For Cu and Cu-Ce/Al2O3 catalyst, lower yields were obtained due to higher N2 selectivity. Similar results were obtained from benchmark tests performed by model nitrogen components representing different functional groups. Pt/Al2O3 and Fe/Al2O3 catalysts possessed higher oxidation activities and nitrogen recoveries than Cu and Cu-Ce catalysts. As a result, Fe/Al2O3 catalyst is highly eff