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

Sylwia Górecka,Kamil Górecki,Dagmar Fridrichová,Kateřina Pacultová,Tereza Bílková,Radim Žebrák,Lucie Obalová

doi:10.3390/ma14216581

Abstract

Copper-containing mixed metal oxides are one of the most promising catalysts of selective catalytic oxidation of ammonia. These materials are characterized by high catalytic efficiency; however, process selectivity to dinitrogen is still an open challenge. The set of Cu-Zn-Al-O and Ce/Cu-Zn-Al-O mixed metal oxides were tested as catalysts of selective catalytic oxidation of ammonia. At the low-temperature range, from 250 °C up to 350 °C, materials show high catalytic activity and relatively high selectivity to dinitrogen. Samples with the highest Cu loading 12 and 15 mol.% of total cation content were found to be the most active materials. Additional sample modification by wet impregnation of cerium (8 wt.%) improves catalytic efficiency, especially N2 selectivity. The comparison of catalytic tests with results of physicochemical characterization allows connecting the catalysts efficiency with the form and distribution of CuO on the samples’ surface. The bulk-like well-developed phases were associated with sample activity, while the dispersed CuO phases with dinitrogen selectivity. Material characterization included phase composition analysis (X-ray powder diffraction, UV-Vis diffuse reflectance spectroscopy), determination of textural properties (low-temperature N2 sorption, scanning electron microscopy) and sample reducibility analysis (H2 temperature-programmed reduction).

Highlights

Ammonia (NH3 ) is a colorless gas with a characteristic expressive odor
The production of NH3 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 or selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR)

Summary

Introduction

Ammonia (NH3 ) is a colorless gas with a characteristic expressive odor. Its emissions are estimated at approximately 5600 kt y−1 [1]. NH3 contributes to the acidification of soil and water due to its deposition, eutrophication in aquatic ecosystems and the excess of nitrogen It participates in the formation of acid rains and photochemical smog or ozone depletion [2,3,4]. The production of NH3 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)

Methods

Discussion

Conclusion