Cu-Mg-Fe-O-(Ce) Complex Oxides as Catalysts of Selective Catalytic Oxidation of Ammonia to Dinitrogen (NH3-SCO)

Abstract

Multicomponent oxide systems 800-Cu-Mg-Fe-O and 800-Cu-Mg-Fe-O-Ce were tested as catalysts of selective catalytic oxidation of ammonia to dinitrogen (NH3-SCO) process. Materials were obtained by calcination of hydrotalcite-like compounds at temperature 800 °C. Some catalysts were doped with cerium by the wet impregnation method. Not only simple oxides, but also complex spinel-like phases were formed during calcination. The influence of chemical composition, especially the occurrence of spinel phases, copper loading and impregnation by cerium, were investigated. Materials were characterized by several techniques: X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), low-temperature nitrogen adsorption (BET), cyclic voltammetry (CV), temperature programmed reduction (H2-TPR), UV-vis diffuse reflectance spectroscopy and scanning electron microscopy (SEM). Examined oxides were found to be active as catalysts of selective catalytic oxidation of ammonia with high selectivity to N2 at temperatures above 300 °C. Catalysts with low copper amounts (up to 12 wt %) impregnated by Ce were slightly more active at lower temperatures (up to 350 °C) than non-impregnated samples. However, when an optimal amount of copper (12 wt %) was used, the presence of cerium did not affect catalytic properties. Copper overloading caused a rearrangement of present phases accompanied by the steep changes in reducibility, specific surface area, direct band gap, crystallinity, dispersion of CuO active phase and Cu2+ accessibility leading to the decrease in catalytic activity.

Ferrierite and Its Delaminated Forms Modified with Copper as Effective Catalysts for NH3-SCO Process

“…One of the most promising technologies for the elimination of ammonia from flue gases is based on selective catalytic oxidation of ammonia to dinitrogen, NH 3 -SCO [7,8]. In this case the role of the oxidising agent plays oxygen present in flue gases and therefore there is no need for additional reactant introduction to the gas stream.…”

Catalytic Oxidation of Ammonia over Cerium-Modified Copper Aluminium Zinc Mixed Oxides

“…The production of NH 3 is mostly related to agriculture; in developed countries, 80–90% of ammonia emissions come from animal husbandry, fertilizer manufacturing, and biomass fuel combustion. Another source of ammonia emissions is related to the industry, including energy production, transport, industrial processes (chemical, pharmacy, plastics) or selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) technology for NOx abatement [ 7 , 8 ].…”

“…Many catalysts have already been tested for NH 3 -SCO [ 7 ], e.g., transition metal oxides [ 6 , 8 , 11 , 12 , 13 ], rare earth oxides [ 8 , 14 ], supported noble metals [ 15 , 16 , 17 , 18 ] and transition metals [ 19 ], metal modified oxides [ 20 , 21 ], zeolites [ 22 , 23 , 24 ], mesoporous silica [ 25 ] and clays [ 26 ]. Most of those catalysts showed very good activity; however, ensuring high N 2 selectivity is still one of the main challenges.…”

“…Among all catalysts listed above, Cu-based materials show good efficiency, and they are still intensively studied. Many types of Cu-containing catalysts have been tested in the last years, showing high activity and selectivity in ammonia oxidation reactions [ 6 , 8 , 19 , 24 , 27 , 28 , 29 ]. The catalytic efficiency of such materials is usually affected by many factors, such as Cu content [ 8 , 29 , 30 , 31 ], preparation method [ 32 ], calcination temperature [ 6 , 30 , 31 ], particle size [ 32 ] or type of support [ 33 ].…”

“…Many types of Cu-containing catalysts have been tested in the last years, showing high activity and selectivity in ammonia oxidation reactions [ 6 , 8 , 19 , 24 , 27 , 28 , 29 ]. The catalytic efficiency of such materials is usually affected by many factors, such as Cu content [ 8 , 29 , 30 , 31 ], preparation method [ 32 ], calcination temperature [ 6 , 30 , 31 ], particle size [ 32 ] or type of support [ 33 ]. However, the copper oxide was often proved to be an active species in the NH 3 -SCO reaction [ 5 , 8 , 29 , 31 , 34 ].…”