Gold nanoparticles in environmental catalysis: Influence of the Fe-modified alumina supports on the catalytic behavior of supported gold nanoparticles in CO oxidation in the presence of ammonia

The preferable utilization of ammonia and carbon monoxide from industrial kiln gases is their processing into the initial components of solid state synthesis. The kiln gas of industrial synthesis of the nanostructured lithium–iron–phosphate LFP material contains both ammonia and carbon monoxide, and NH 3 can be processed into (NH 4 ) 2 HPO 4 , whereas CO should be transformed into CO 2 in order to be used for Li 2 CO 3 synthesis. This work focuses on the preparation of catalysts that can preferentially oxidize CO with a minimal NH 3 conversion in their rich mixtures. The Au nanoparticles (particle size below 3 nm) were supported on the θ-Al 2 O 3 modified with 1–5 wt.% Fe that resulted in the Au catalysts highly effective in CO oxidation at 200–250 °C in the presence of NH 3 . The TPR-H 2 and DRIFT spectroscopy revealed almost complete reduction of the gold precursor surface after calcination in air at 300 °C, as well as the presence of residual organic moieties in the samples. Variation in the procedure of modifying treatment and Fe precursor realized a different Fe 3+ environment and affected the catalytic behavior. The FeO x species of the exchange-bonded Fe 3+ ions favored NH 3 oxidation, whereas distribution of Fe 3+ as isolated ions decreased the activity in NH 3 oxidation. Compared to the Au/FeO x /θ-Al 2 O 3 and Au/θ-Al 2 O 3 samples, the Au/θ-Al 2− x Fe x O 3 catalysts were more active in CO oxidation. These catalysts exhibited the widest temperature window between the complete CO conversion and the detectable NH 3 conversion. The catalysts were thermally stable and maintained the activity both in CO and NH 3 oxidation after treatment at 500 °C.