Etude de catalyseurs poreux hautement structurés, Pd/Zéolithes Beta et Faujasite et Pd/Oxydes de titane et de Zirconium, vis-à-vis de l'oxydation totale du toluène

Dans ce travail, les performances catalytiques des catalyseurs poreux imprégnés de palladium ont été étudiées dans la réaction d'oxydation du toluène. Deux types de supports hautement structurés ont été utilisés: des zéolithes bêta (bea, si/al = 12) et faujasite (y, si/al = 2,4) a larges pores et des oxydes de titane, de zirconium, de titane-zirconium meso/macroporeux. Dans une première partie de ce travail, les zéolithes ont été préparées par échanges ioniques avec des cations h+, na+ et cs+ et avec 0,5% en masse de palladium. Les tests catalytiques effectués avec ses solides ont montré que les échantillons de zéolithe faujasite sont plus actifs que les échantillons de zéolithe beta. L'ordre d'activité catalytique a été relié à l'acido-basicite pour les échantillons pd/zéolithe faujasite et l'ordre est inverse pour les échantillons pd/zéolithe bêta qui suit plutôt l'ordre de la surface spécifique et de la dispersion des particules de palladium. Dans la deuxième partie de ce travail, l'effet de la calcination des oxydes poreux vis-a-vis de l'activité catalytique a été étudié. Parmi les catalyseurs les plus actifs, l'ordre suivant a été obtenu 0,5%pd/tio2-400 > 0,5%pd/zro2-600 >= 0,5%pd/tizr-600, les activités de ces solides ont été reliées aux dispersion, réductibilité des particules de palladium, à l'interaction pd-support et/ou à la surface spécifique élevée du catalyseur. Ces catalyseurs poreux ont été comparés avec des catalyseurs classiques 0,5%pd/ zro2 et 0,5%pd/ tio2, et les solides poreux se sont révélés plus actifs à cause de leurs surfaces spécifiques élevées et de la stabilité de leur support.DUNKERQUE-BU Lettres Sci.Hum. (591832101) / SudocSudocFranceF

CO2 reforming of methane over Ni and/or Ru catalysts supported on mesoporous KIT-6: Effect of promotion with Ce

International audienc

Evaluation of a Catalyst Durability in Absence and Presence of Toluene Impurity: Case of the Material Co₂Ni₂Mg₂Al₂ Mixed Oxide Prepared by Hydrotalcite Route in Methane Dry Reforming to Produce Energy

Ni, Co, Mg, and Al mixed-oxide solids, synthesized via the hydrotalcite route, were investigated in previous works toward the dry reforming of methane for hydrogen production. The oxide Co2Ni2Mg2Al2 calcined at 800 °C, Co2Ni2Mg2Al2800, showed the highest catalytic activity in the studied series, which was ascribable to an interaction between Ni and Co, which is optimal for this Co/Ni ratio. In the present study, Co2Ni2Mg2Al2800 was compared to a commercial catalyst widely used in the industry, Ni(50%)/Al2O3, and showed better activity despite its lower number of active sites, as well as lower amounts of carbon on its surface, i.e. less deactivation. In addition to this, Co2Ni2Mg2Al2800 showed stability for 20 h under stream during the dry reforming of methane. This good durability is attributed to a periodic cycle of carbon deposition and removal as well as to the strong interaction between Ni and Co, preventing the deactivation of the catalyst. The evaluation of the catalytic performances in the presence of toluene, which is an impurity that exists in biogas, is also a part of this work. In the presence of toluene, the catalytic activity of Co2Ni2Mg2Al2800 decreases, and higher carbon formation on the catalyst surface is detected. Toluene adsorption on catalytic sites, side reactions performed by toluene, and the competition between toluene and methane in the reaction with carbon dioxide are the main reasons for such results

Nuclear Magnetic Resonance and Calorimetric Investigations of Extraction Mode on Flaxseed Gum Composition

We discussed about the influence of extraction mode on the flaxseed gums composition and their thermal stabilities. In order to do so, flaxseed gum was extracted by both classical magnetic stirring method and ultrasonic-assisted extraction (UAE). As a function of time, protein content, gum yield, pH values were evaluated and samples were characterized by 1H and 13C nuclear magnetic resonance (NMR) experiments as well as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The flaxseed gum extracted in aqueous solution correspond to a mixture of different components, including polysaccharides, proteins and sometimes lignan derivatives. It is found that the protein and gum contents increase with the extraction duration for both the ultrasonic assisted and the traditional extraction while the pH decreases at the same time. As expected, compared to traditional magnetic stirring method, ultrasonic assisted extraction method can significantly enhance the yield of polysaccharides, lignans and proteins. The variation of pH is correlated to the increase of lignan molecules in the extracted samples. For thermic methods, SEM experiments showed that lignan derivatives which ester-bonded to polysaccharides associated to proteins are responsible to the formation of globular aggregates. Supplementary rod-like molecular organization were obtained from UAE and questions on the nature of the amphiphilic mesogen carbohydrate structures

Production of liquid bio-fuel from catalytic de-oxygenation: Pyrolysis of beech wood and flax shives

International audienceThis study presents a detailed analysis of the catalytic de-oxygenation of the liquid and gaseous pyrolytic products of two biomasses (beech wood and flax shives) using different catalysts (commercial HZSM-5 and H-Y, and lab-synthesised Fe-HZSM-5, Fe-H-Y, Pt/Al2O3 and CoMo/Al2O3). The experiments were all conducted in a semi-batch reactor under the same operating conditions for all feed materials. BET specific surface area, BJH pore size distribution and FT-IR technologies have been used to characterise the catalysts, while gas chromatography-mass spectrometry (GC-MS), flame ionisation detection (GC-FID) and thermal conductivity detection (GC-TCD) were used to examine the liquid and gaseous pyrolytic products. It was firstly seen that at higher catalyst-to-biomass ratios of 4:1, de-oxygenation efficiency did not experience any further significant improvement. Fe-HZSM-5 was deemed to be the most efficient of the catalysts utilised as it helped reach the lowest oxygen contents in the bio-oils samples and the second best was HZSM-5. It was also found that HZSM-5 and H-Y tended to privilege the decarbonylation route (production of CO), whilst their iron-modified counterparts favoured the decarboxylation one (production of CO2) for both biomasses studied. It was then seen that the major bio-oil components (carboxylic acids) underwent almost complete conversion under catalytic treatment to produce mostly unoxygenated aromatic compounds, phenols and gases like CO and CO2. Finally, phenols were seen to be the family most significantly formed from the actions of all catalysts