The effect of the chemical nature of the oxide support on the performance of cobalt Fischer–Tropsch catalysts is investigated. A series of supports is synthesized via monolayer coverage of porous γ-Al2O3 with various oxides representative of a wide range of Lewis acid–base character, as quantified by UV–vis spectroscopy coupled to alizarin adsorption. Incorporation of cobalt (20 wt %) results in model catalysts with identical porosities and similar Co particle sizes (>10 nm), allowing the study of support effects without overlap from diffusional or particle size factors. Under realistic reaction conditions, the initial TOF scales with the acidity of the oxide support, whereas the cobalt time yield and selectivity to industrially relevant C13+ hydrocarbons show a volcano dependence, with a maximum at an intermediate acid–base character. As inferred from in situ CO-FTIR, “selective” blockage of a few cobalt sites, though crucial for CO hydrogenation, by atoms from basic oxides and “unselective” site blockage via decoration of Co nanoparticles (strong metal–support interaction) with acidic, reducible oxides cause a decrease in reaction rate for supports with pronounced alkaline and acidic character, respectively. The extent of secondary isomerization reactions of α-olefin products, of relevance for chain reinsertion processes and product selectivity, also correlates with the support acidity. For a TiO x /Al2O3 as support, a remarkable C13+ productivity exceeding 0.09 molC gCo –1 h–1 is achieved, owing to the combination of optimal activity and selectivity. These results provide a unifying view of the support effects over a considerably broad study space and delineate a blueprint toward advanced Fischer–Tropsch catalysts.
In this memory effect study, hydrotalcite-type compounds in the lamellar double hydroxide-like (LDH)/zeolite A composite material were analyzed using X-Ray Diffration XRD) in situ experiments. Three samples were analyzed: Al,Mg-LDH, Al,Mg-LDH/ZA composite, and a physical mixture (50/50 wt%) of zeolite A and Al,Mg-LDH. The Al,Mg-LDH sample was treated at 500 °C in an O2 atmosphere and subsequently rehydrated. The Al,Mg-LDH/ZA composites had three treatments: one was performed at 300 °C in a He atmosphere, and two treatments were performed with an O2 atmosphere at 300 and 500 °C. In the physical mixture, two treatments were carried out under O2 flow at 500 °C and under He flow at 300 °C. Both went through the rehydration process. All samples were also analyzed by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The results show that the LDH phase in the Al,Mg-LDH/ZA compounds has memory effects, and thus, the compound can be calcined and rehydrated. For the LDH in the composite, the best heat treatment system is a temperature of 300 °C in an inert atmosphere.
Silicoaluminophosphate molecular sieves of SAPO-11 type (AEL structure) were synthesized by the hydrothermal method, from the residue of a fluorescent lamp as a source or Si, Al, and P in the presence of water and di-propyamine (DPA) as an organic template. To adjust the P2O5/SiO2 and Si/Al and ratios, specific amounts of silica, alumina, or alumina hydroxide and orthophosphoric acid were added to obtain a gel with molar chemical composition 1.0 Al2O3:1.0 P2O5:1.2 DPA:0.3 SiO2:120 H2O. The syntheses were carried out at a temperature of 473 K at crystallization times of 24, 48, and 72 h. The fluorescent lamp residue and the obtained samples were characterized by X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and BET surface area analysis using nitrogen adsorption isotherms. The presence of fluorapatite was detected as the main crystalline phase in the residue, jointly with considered amounts of silica, alumina, and phosphorus in oxide forms. The SAPO-11 prepared using aluminum hydroxide as Al source, P2O5/SiO2 molar ratio of 3.6 and Si/Al ratio of 0.14, at crystallization time of 72 h, achieves a yield of 75% with a surface area of 113 m2/g, showing that the residue from a fluorescent lamp is an alternative source for development of new materials based on Si, Al, and P.
This study describes the formation of new C-C bonds through the allylation reaction of different aldehydes promoted by beta zeolite. This environmentally friendly method was characterized by its efficiency, versatility, and chemoselectivity in the formation of different homoallylic alcohols. Homoallylic alcohols were obtained in good yields (80% to 96%), short reaction times (30 to 75 min) at room temperature, and without the need for additional purifications. In addition, water was used as a co-solvent, ensuring the method a development in the field of green chemistry. Moreover, it was found that the zeolite beta can be reused for up to one reaction cycle without loss of its efficiency.
Burning fossil fuels containing significant amounts of sulfur compounds generates toxic and pollutant products, and removal of these sulfur compounds is of substantial interest to the oil industry. New technologies, such as oxidative desulfurization, are being developed to achieve this, with the aim of increasing the removal of these contaminants at lower costs. In this work, commercial clays (K-10 and KSF), a natural clay (Poço A), and its pillarized form (Poço A PILC) were impregnated with 1% vanadium for the oxidation and extraction of dibenzothiophene (DBT) in commercial diesel charge. The catalysts were characterized by XRD, textural analysis, and SEM. The products obtained in the catalytic tests performed were analyzed by GC-FID gas chromatography. The vanadium-impregnated K-10 and KSF clays showed the best results regarding DBT oxidation, with yields of 33 and 58%, respectively. However, all clays yielded good results for extraction of the organic compound while avoiding oxidation.
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