To highlight the deactivation mechanisms encountered by minerals impurities from biodiesel, the effects caused by Na, P or (Na+P) additions were studied over a model Cu-FER catalyst. Na, P or (Na+P) were added by wet-impregnation in water in a wide concentration range up to 2 wt-%. The catalytic behaviors were evaluated by NH3/NO oxidation and standard/fast NH3-SCR reactions. In addition, a combination of several characterization techniques (ICP-AES, N2 adsorption/desorption, XRD, NH3-TPD, NO adsorption monitored by FTIR and H2-TPR) was applied to provide useful information regarding the deactivation mechanism caused by the minerals addition. Sodium and phosphorus interacted differently with the Cu-FER catalyst. Na addition induced a loss of Brønsted acid sites and a back-exchange of Cu 2+ with Na + , with formation of external CuO species, thus favoring the oxidation of NO and NH3. After phosphorus addition, the exchanged Cu 2+ species remained moderately affected, but direct interactions with copper were evidenced which were primarily responsible for catalyst deactivation toward the oxidation reactions. After equimolar addition of phosphorus and sodium, both Na and P effects were observed. For the NH3-SCR process, the ammonia adsorption ability, which depends on both acidity and copper units, appeared the main key parameter driving the catalytic activity at low temperature (T ≤ 250 °C). Phosphorus appeared to be the major responsible for catalyst deactivation after (Na+P) co-poisoning.

The aim of this paper is to evaluate the effect of the oxygenated compounds concentration on sooting propensities of Diesel and Biodiesel surrogates and to investigate the oxidative reactivity of soot obtained by combustion of these surrogates using an atmospheric axisymmetric co-flow diffusion flame burner. Methyl decanoate (MD) concentrations from 3 to 30 % (in mole %) are added to a Diesel surrogate made up of a binary mixture of 70 % of n-decane and 30 % of α-methylnaphthalene (α-MN). The sooting propensities of these mixtures are estimated through the Yield Sooting Indices (YSIs) in methane diffusion flames doped with 35,000 ppm of surrogate vapors. The characteristics of the soot volume fraction are extracted using the light extinction method (LEM). Additionally, soot generated from the combustion of the model Diesel and Biodiesel fuels were collected, sampled and characterized using physico-chemical techniques. MD addition is found to reduce sooting tendencies. This decrease is more pronounced when the concentration of oxygenate additives increases. On another side, the oxidative reactivity of soot generated from the diffusion flame burner is found to decrease when the Biodiesel percentage increases. Furthermore, soot generated from the combustion of Diesel and Biodiesel surrogates exhibited different behaviors. Biodiesel-derived soot particles were smaller and less reactive than Diesel-derived ones, the latter displaying less ordered graphite-like structures and higher amorphous carbon concentration.

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Abstract:The effect of the sodium addition mode was investigated on model Cu/FER selective catalytic reduction (SCR) catalysts with two copper loadings (2.8 wt. % and 6.1 wt. %) in order to compare samples with or without over-exchanged copper. Na was added by wet-impregnation using two solvents: water or ethanol. Catalysts were evaluated in Standard and Fast-SCR conditions, as well as in NO and NH 3 oxidation. They were characterized by H 2 -TPR, NO and NH 3 adsorption monitored by FT-IR. As expected, whatever the copper loading, ammonia adsorption capacity was decreased by Na additions. Interestingly, characterizations also showed that Na impregnation in water favors the migration of the Cu-exchanged species, leading to the formation of CuO extra-framework compounds. Consequently, for both copper loadings, Na impregnation in water led to a stronger catalyst deactivation than impregnation in ethanol. Finally, the NO x conversion at low temperature (250 • C) appeared mainly affected by the loss in NH 3 adsorption capacity whereas the deNO x deactivation at high temperature (500 • C) was rather governed by the decrease in the exchanged copper ratio, which also induced a partial inhibition of NO and NH 3 oxidation behaviors.

In this work a cobalt-free zeolite-based catalyst formulation is proposed for NO x CH 4 -SCR towards a commercial application of after-treatment system for heavy-duty vehicles moved by natural gas (lean-gas burn engines). PdCe-HMOR catalyst was characterised by H 2 -TPR, DRS UV-Vis and TEM/EDS. The effect of [CH 4 ]/ [NO] in the gas feed was studied in order to assess the catalytic performance under simulated dynamic engine conditions. The catalyst was also tested with a representative gas feed of real exhaust gases of a heavy-duty vehicle's engine (lean-burn conditions) powered by natural gas.