Production d'hydrogène par reformage à la vapeur et craquage catalytique de bio-huiles sur catalyseurs monolithes

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Lean NOx Removal by a Bifunctional (EtOH + NH3) Mixture Dedicated to (Ag/Al2O3 + NH3-SCR) Dual-Bed Catalytic System: Comparison Between WO3/CeZrO2 and Cu–FER as NH3-SCR Catalyst

International audienceIn a previous study, a drastic enhancement of the NOx conversion in EtOH-SCR process was achieved by means of ammonia and ethanol co-feeding over Ag/Al2O3 catalyst to avoid the NO2/NOx ratio dependency of conventional implemented urea-SCR technology. The ammonia activation was mainly attributed to the availability of hydrogen H* species resulting from EtOH dehydrogenation, which promoted the H2 assisted NH3-SCR over Ag/Al2O3. Additional conversion gain was reached with a dualbed configuration in which a NH3-SCR catalyst (WO3/CexZr1-xO2) was added downstream to the silverbased sample (Ag/Al2O3 + NH3-SCR catalyst). This study deals with the influence of the SCR catalyst formulation on the catalytic performances of the dual-bed system. Oxide-based sample (WO3/CexZr1-xO2) and exchanged copper zeolite (Cu2.5-FER) were selected as model NH3-SCR catalysts. Results shows that WO3/CexZr1-xO2 in more appropriate in dual-bed configuration for (EtOH+NH3)-SCR process because ammonia and ethanol (or its by-products) strongly interacted together on Cu2.5-FER

Hydrogen production by sequential cracking of biomass-derived pyrolysis oil over noble metal catalysts supported on ceria-zirconia

International audienceConversion of crude pyrolysis bio-oil for H2 production is investigated using a sequential process which alternates (i) cracking reaction steps, during which the bio-oil is converted to syngas and carbon stored on the catalyst and (ii) regeneration steps allowing to combust coke under an air flow. The performances of Pt and Rh catalysts supported on ceria-zirconia in powder form or deposited on cordierite monoliths are comparatively studied. From these data and calculated thermodynamic equilibrium, the co-existence of thermal and catalytic processes is demonstrated. A stable hydrogen productivity up to ca. 18 mmol of H2 g−1 of bio-oil (50% H2 in the gas stream) with a minimized methane formation (ca. 6%) is obtained with the monolith configuration. Both Pt and Rh-based catalysts allow a good control of carbon formation, the coke being fully combusted during the regeneration step. Slow deactivation phenomena and selectivity changes along time on stream, mostly observed for platinum powder samples, are related to changes in catalyst structure and to the peculiar role of oxygen stored in the zirconia-ceria support. The heat balance evaluation of the sequential cracking/regeneration cycle shows that the process could be auto-thermal, i.e., minimizing the energy input, being competitive with conventional steam-reforming process under the same operating temperature

Hydrogen production from crude pyrolysis oil by a sequential catalytic process

International audienceA sequential process aiming at hydrogen production was studied over two Ni-based catalysts, using crude beech-wood oil as the feed. The process alternates cracking/reforming steps, during which a H2 + CO rich stream is produced and carbon is stored on the catalyst, with regeneration steps where the carbon is combusted under oxygen. The two catalysts exhibited good performances for H2 production from bio-oil, the gaseous products stream consisting in 45–50% H2. The regeneration step was found fast and efficient, the coke being readily combusted and the catalyst activity fully recovered. A positive heat balance between the endothermic cracking/reforming reactions and the exothermic coke combustion suggests that an autothermal process could be designed. Comparison of the thermal decomposition of bio-oil (empty reactor) with the catalytic cracking revealed that they are first decomposed into primary light gases (CO, CO2, CH4, C2+) and soots. These compounds are further reformed onto the catalyst by the steam contained in bio-oil, and equilibrated via the WGS reaction. The key roles of the catalyst are therefore (i) to improve the overall bio-oil gasification into syngas, (ii) to promote steam reactions and increase hydrogen production by steam reforming and WGS and (iii) to control and determine the nature of the coke formed during the cracking/reforming step. A Ni/Al2O3 catalyst with large Ni particles was found to promote the formation of carbon filaments, whereas on a Ni–K/La2O3–Al2O3 catalyst, with a lower Ni loading and highly dispersed Ni, the carbon was essentially deposited as an amorphous carbon layer

Influence of Sodium and/or Phosphorus Addition on the Deactivation of Cu-FER Zeolites for SCR of NOx with NH3

International audienceThis work investigates the effect of sodium and phosphorus on the DeNOx performances of model Cu-FER SCR catalysts with two copper loadings (2.8wt% and 6.1wt%). These inorganic elements, present in the Biodiesel fuels and lubricants, were added by wet-impregnation using two solvents: water or ethanol. Catalysts were evaluated in standard-SCR conditions as well as in NO and NH3 oxidation, and characterized by means of H2-TPR and NH3 adsorption monitored by FT-IR. It was evidenced that catalytic behaviors were highly influenced by the implemented impregnation route with a stronger impact of water as solvent. Whatever the studied catalysts, NH3 adsorption capacities decreased after addition of sodium and/or phosphorus. Interestingly, sodium and phosphorus acted differently on the poisoning of NH3 adsorption sites. Na mainly poisoned Brønsted acid sites and favored a back exchange with Cu 2+ species (especially when Na was added in water), while phosphorus directly interacted with copper species, mainly in exchange position. The deactivation observed at low temperature (250°C) was preferentially due to the decrease in NH3 adsorption together with the increase in the copper-phosphorus interaction, especially for copper species in exchange position

Study of hydrothermal aging impact on Na- and P-modified diesel oxidation catalyst (DOC)

SSCI-VIDE+CARE+FGA:SGI:AGFInternational audienceHydrothermal agin

Wet air oxidation in a catalytic membrane reactor: Model and industrial wastewaters in single tubes and multichannel contactors

International audienceRecent results on catalytic wet air oxidation applied to a membrane contactor are presented that give new insight following a series of previous publications. Model and industrial effluents are treated in both single tube and multichannel catalytic systems. Characterisation of the catalytic material (solid analyses, electron microscopy, EDS and EPMA) is carried out, in order to determine the catalyst distribution. Catalytic results show performances heavily dependent on the nature of the effluent and the operating conditions, and to a lesser extent on the catalytic membrane characteristics. At 80 8C, an industrial effluent is oxidised at a membrane surface related rate of 3.8 mmol/s/m2. This result is achieved using a membrane containing about 0.1 wt.% Pt. This allows a revised and improved technico-economical evaluation of the Watercatox process

Effect of Na, K, Ca and P-impurities on diesel oxidation catalysts (DOCs)

SSCI-VIDE+CARE+PAN:FGA:EIO:SGI:AGFInternational audienceBiodiesel impuritie