Showing papers by "Elisabete Moreira Assaf published in 2013"
TL;DR: In this paper, the effect of nickel content on NiO-MgO-ZrO 2 catalysts was investigated and the results showed that high nickel content favored the formation of large Ni° particles during the reforming reaction, thus lowering the catalytic performance.
122 citations
TL;DR: In this paper, Nanocapsular hydrotalcites (layered double hydroxides) were synthesized by the sol-gel method and used as precursors of nano-structured mixed oxides containing various nickel loads.
114 citations
TL;DR: In this paper, the authors compared the catalysts 5Ni-5Ca/Al (I) and 5Ni−5Ca/(Al) (C) for ethanol steam reforming and showed that 5Ni•5Ca•Al is less selective to ethylene production and therefore was characterized by the following techniques: energy dispersive X-ray spectroscopy (EDX), XRD, temperature programmed reduction (TPR), Xray absorption near edge structure (XANES), specific surface area by the BET method, scanning electron microcopy (SEM) and isoprop
82 citations
TL;DR: In this article, the authors used NiO, LaNiO 3 and La 2 NiO 4 in the steam reforming of glycerol and showed that the deposition of carbon on the catalyst during the reaction fell steadily as the proportion of La 2 O 3 in the support increased.
65 citations
TL;DR: In this paper, a single step polymerization of NiO/Y 2 O 3 /ZrO 2 mixtures was used to synthesize catalysts for the Fischer-Tropsch process, and they were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), physisorption of N 2 (BET), and XPS.
Abstract: Catalysts composed of NiO/Y 2 O 3 /ZrO 2 mixtures were synthesized by the polymerization method in a single step. They were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), physisorption of N 2 (BET) and X-ray photoelectron spectroscopy (XPS) and then tested in the oxidative reforming of a model biogas (1.5CH 4 :1CO 2 ) in the presence of oxygen (1.5CH 4 + 1CO 2 + 0.25O 2 ) at 750 °C for 6 h. It was observed that the catalysts Ni20YZ and Ni40YZ performed better in catalytic processes than NiO/ZrO 2 and NiO/Y 2 O 3 , synthesized under the same conditions. The formation of Y 2 O 3 –ZrO 2 and NiO–Y 2 O 3 solid solutions increased the rates of conversion of the reactants (CH 4 and CO 2 ) into synthesis gas (H 2 + CO). The formation of oxygen vacancies (in samples containing ZrO 2 and Y 2 O 3 ) seemed to promote removal of the coke deposited on the nickel surface during the oxidative reforming of model biogas. The H 2 /CO ratios in the reaction products formed on the best catalysts were 1:1, which is desirable for their direct use in the STD and in the Fischer–Tropsch processes.
57 citations
TL;DR: In this paper, the use of copper catalysts supported on ceria and/or titania for water-gas shift reaction (WGSR) was evaluated, which showed good performance, fulfilling the goal of CO in reducing levels for hydrogen fuel cell applications.
51 citations
TL;DR: In this article, the performance of Ni and Co catalysts supported on alumina to convert acetic acid into hydrogen was investigated for the steam reforming of bio-oil derived from biomass pyrolysis.
49 citations
TL;DR: The immobilized Candida antarctica lipase was employed in enzymatic esterifications of oleic acid with aliphatic alcohols for the biodiesel production and a new method was developed to quantify esters produced (biodiesel) by 1H NMR based on the α-CH2 protons.
Abstract: Biodiesel can be obtained by esterification reactions of free fatty acids with enzymatic catalysts (lipases). In this study, the immobilized Candida antarctica lipase was employed in enzymatic esterifications of oleic acid with aliphatic alcohols (methanol, ethanol, n-propanol, n-butanol). Some features that influence the enzymatic esterification reaction, such as amount of biocatalysts, reaction time, hydration level and biocatalyst turnover were evaluated. The products were determined by GC-FID and 1H NMR analyses and these analytical methods were compared. The enzymatic catalyst (C. antarctica lipase) was efficient providing high yields of biodiesel (above 90 %) in less than 24 h to ethanol, n-propanol and n-butanol, whereas for methanol, the enzyme was inactive after ten cycles of reaction. Two new quantitative easy methods were also developed to quantify esters produced by 1H NMR based on the α-CH2 protons of oleic acid and esters. The quantification method used in the enzymatic reactions by 1H NMR showed effective with small differences in comparison with GC-FID analyses. C. antarctica lipase was employed in enzymatic esterifications of oleic acid with aliphatic alcohols (methanol, ethanol, n-propanol, n-butanol) for the biodiesel production. A new method was developed to quantify esters produced (biodiesel) by 1H NMR based on the α-CH2 protons.
45 citations
12 citations
TL;DR: Ceria-supported copper catalysts (Ce1−xCuxO2, with x (mol) = 0, 0.01, 0.,05, and 0.10) were prepared in one step through the polymeric precursor method.
8 citations
TL;DR: In this article, a 10 %Co supported on CexZr1−xO2 (0 < x < 1) was used to catalyze oxidative ethanol reforming reactions, which was characterized by temperature-programmed reduction, X-ray diffraction and N2 physisorption.
Abstract: Catalysts containing 10 %Co supported on CexZr1−xO2 (0 < x < 1) were used to catalyze oxidative ethanol reforming reactions. The catalysts were characterized by temperature-programmed reduction, X-ray diffraction and N2 physisorption. Catalytic tests were conducted at 773 K and molar feed ratios of H2O/Ethanol/O2 = 3/1/0.16 and 3/1/0.20. The mixed oxide provides enhanced resistance to carbon formation because the insertion of Zr4+ causes a distortion in the CeO2 lattice, leading to a higher fraction of cerium species on the surface and favoring the oxidation and gasification reactions of carbon and CO. The addition of oxygen improved the oxidative properties of the reactive systems, with a high formation of CO2.