Pd/Co3O4 catalyst for CH4 emissions abatement: study of SO2 poisoning effect

A catalyst with 0.7 wt% Pd load supported over Co₃O₄ oxide was investigated in the methane oxidation by operating under CH₄/O₂ stoichiometric conditions. The effect of the noble metal addition on the activity of bare Co₃O₄ was evaluated. Samples were characterized by BET, XRD, TPR and XPS analyses. The SO₂ poisoning of Pd catalyst and Co₃O₄ was studied by performing CH₄ oxidation tests under stoichiometric conditions in SO₂ (1 ppm or 10 ppm)_. Experiments evidenced that in our conditions the low amount of SO₂ doesn’t influence the Pd behaviour, whereas in presence of 10 ppm of SO₂ some deactivation occurs that becomes more evident above 450 °C at which the catalyst doesn’t reach 100% of methane conversion. Catalytic tests performed over Co₃O₄ and the Pd supported catalyst, after a treatment at 350 °C for 15 h in 10 ppm SO₂/He, suggest that Co₃O₄ is a sulphating support, as confirmed by XPS analysis. Therefore, an important role in lowering the sulphur poisoning of Pd may be played by Co₃O₄.     

Combined CO/CH4 oxidation tests over Pd/Co3O4 monolithic catalyst: Effects of high reaction temperature and SO2 exposure on the deactivation process

CO and CH₄ combined oxidation tests were performed over a Pd (70 g/ft³)/Co₃O₄ monolithic catalyst in conditions of GHSV = 100,000 h⁻¹ and feed composition close to that of emission from bi-fuel vehicles. The effect of SO₂ (5 ppm) on CO and CH₄ oxidation activity under lean condition (λ = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co₃O₄ catalytic sites via chemisorbed SO₃ and/or sulphates occurred upon exposure to SO₂. A treatment of regeneration to remove sulphate species was attempted by performing a heating/cooling cycle up to 900 °C in oxidizing atmosphere. Decomposition of PdO and Co₃O₄ phases at high temperature, above 750 °C, was observed. Moreover, sintering of Pd⁰ and PdO particles along with of CoO crystallites takes place.     

Mapping of diesel soot regeneration behaviour in catalysed silicon carbide filters

A range of different soot regeneration conditions has been explored using laboratory scale catalysed soot filters, loaded on a state-of-the-art common rail diesel engine. The concurrent effect of oxygen feed rate (manageable both by flow rate and by oxygen concentration) and of heat removal, strictly linked to exhaust flow rate and temperature, was investigated. It has been observed that oxygen plays a major role in defining the oxidising reaction rate and determining possibly dangerous thermal peaks. Nevertheless, especially at high flow rate, the heat removal capability of the gas flow significantly increases the differences between the reaction behaviour at different oxygen contents.     

Reduction of soot pollution from automotive diesel engine by ceramic foam catalytic filter

Recent progress in diesel technology demonstrates the possibility of reducing the particulate matter (PM) emissions level combining the high efficiency of common rail engine with exhaust gas after-treatment devices, such as diesel PM filter. Ceramic foam catalytic filter (CFCF), prepared by coating of ceramic foam (CFUF), results in lower temperature and shorter regeneration time due to the higher specific surface, lower pressure drop and good filtration efficiency with respect to CFUF.