Assessment of copper-iron catalyst supported on activated carbon for low-temperature nitric oxide reduction by hydrogen

Optimization of an active phase composition in the low-temperature nitric oxide reduction catalyst In the first research studies series a selection of the quantitative composition of catalyst active phase composition (iron, copper and manganese) deposited on mineral-carbon support was carried out. It was found on the basis of the selection studies series that the best results were attained when copper and manganese were used as catalyst components. The quantitative composition of the denitrogention catalyst was estimated using a statistical method of experiment planning and metals content changed in the range 0.5 - 1.5wt % for both metals. Catalyst activity in nitric oxide reduction by ammonia was determined in the dependence on an active phase composition in the temperature range 100 - 200°C, at GHSV (Gas Hour Space Velocity) 6 000 and 10 000 Nm3/m3h, NO concentration 400 ppm, NH3/NO ratio 1:1. A graphic presentation of the obtained results was made using the UNIPLOT program. The highest activity in nitric oxide reduction by ammonia presented copper - manganese catalysts prepared by the impregnation of mineral-carbon support with active metals salts solutions and calcination after each metal impregnation with copper (up to 1.5 wt %) and manganese (up to 1.5 wt %).

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Ultra-Low Amounts of Palladium (0.005-0.05 Wt% Pd) Supported on Titania: Remarkable Low-Temperature Activity for NO Reduction with CO and Structure-Function Property Relationships in Methane Oxidation

10.26434/chemrxiv.13489380.v1 ◽

2020 ◽

Author(s):

Konstantin Khivantsev ◽

Libor Kovarik ◽

Nicholas R. Jaegers ◽

János Szanyi ◽

Yong Wang

Keyword(s):

Nitric Oxide ◽

Carbon Monoxide ◽

Methane Oxidation ◽

Steam Reforming ◽

Methane Steam Reforming ◽

Oxide Reduction ◽

Water Steam ◽

Methane Steam ◽

Anatase Titania ◽

Nitric Oxide Reduction

Atomically dispersed Pd +2 cations with ultra-dilute loading of palladium (0.005-0.05 wt%) were anchored on anatase titania and characterized with FTIR, microscopy and catalytic tests. CO infrared adsorption produces a sharp, narrow mono-carbonyl Pd(II)-CO band at ~2,130 cm-1 indicating formation of highly uniform and stable Pd+2 ions on anatase titania. The 0.05 wt% Pd/TiO2 sample was evaluated for methane combustion under dry and wet (industrially relevant) conditions in the presence and absence of carbon monoxide. Notably, we find the isolated palladium atoms respond dynamically upon oxygen concentration modulation (switching-on and switching off). When oxygen is removed from the wet methane stream, palladium ions are reduced to metallic state by methane and catalyze methane steam reforming instead of complete methane oxidation. Re-admission of oxygen restores Pd+2 cations and switches off methane steam reforming activity. Moreover, 0.05 wt% Pd/TiO2 is a competent CO oxidation catalyst in the presence of water steam with 90% CO conversion and TOF ~ 4,000 hr-1 at 260 ⁰C. More importantly, we find that diluting 0.05 wt% Pd/titania sample with titania to ultra-low 0.005 wt% palladium loading produces a remarkably active material for nitric oxide reduction with carbon monoxide under industrially relevant conditions with >90% conversion of nitric oxide at 180 ⁰C (~460 ppm NO and 150 L/g*hr flow rate in the presence of >2% water steam) and TOF ~6,000 hr-1. Pd thus outperforms state-of-the-art rhodium containing catalysts with (15-20 times higher rhodium loading; rhodium is ~ 3 times more expensive than palladium). Furthermore, palladium catalysts are more selective towards nitrogen and produce significantly less ammonia relative to the more traditional rhodium catalysts due to lower Pd amount nd lower water-gas-shift activity. Our study is the first example of utilizing ultra-low (0.05 wt% and less) noble metal (Pd) amounts to produce heterogeneous catalysts with extraordinary activity for nitric oxide reduction. This opens up a pathway to study other Pd, Pt and Rh containing materials with ultra-low loadings of expensive noble metals dispersed on titania or titania-coated oxides for industrially relevant nitric oxide abatement.

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