Fabiana Magalhães Teixeira Mendes

• PhD
• Researcher at Instituto Nacional de Tecnologia

Ruthenium catalysts supported on zinc-promoted amorphous-niobium mixed oxides were prepared, characterized, and studied in the additive-free partial hydrogenation of benzene reaction. The amorphous matrix of Nb2O5 was responsible for a highly active Ru/Nb2O5 catalyst, although less selective than those containing zinc. The ZnO-containing supports w...

Commercially dense pure titanium sheets and porous titanium samples processed by powder metallurgy were treated with a mixture consisting of equal volumes of H2SO4 and H2O2 for 2 or 4 hours. Characterization was performed by scanning electron microscopy, energy dispersive X-ray spectroscopy, confocal scanning optical microscopy, X-ray diffraction,...

This work evaluates the performance of activated carbon obtained from sugarcane straw (SCAC) as an adsorbent for polyaromatic hydrocarbons (PAHs) present in model wastewater. Two commercial samples of activated carbons with different textural properties were also studied for comparison. The activated carbon prepared from sugarcane straw presents a...

Partial hydrogenation of benzene with ruthenium-supported catalysts is an interesting alternative route to produce cyclohexene, an intermediate in the production of nylon 6.6 and other fine chemicals. In this work, ruthenium chloride solution was added to xZnO/Al2O3 by wetness impregnation. The supports were derived from hydrotalcite compounds and...

Two catalysts, Cu/ZnO/Al 2 O 3 and Cu/ZrO 2 /Al 2 O 3 , were employed for acetic acid synthesis from ethanol and water. They were characterized by X-ray fluorescence, N 2 physisorption, N 2 O titration, in situ X-ray diffraction refined by the Rietveld method, in situ X-ray photoelectron spectroscopy, temperature-programmed reduction followed by X-...

Catalysts containing V-Mg-O species supported on activated carbon (AC), obtained from sugar-cane straw, were prepared and evaluated in the propane ODH reaction. Two conditions containing different molar amounts of Mg and V where prepared, one (condition II) with higher molar amounts of magnesium and vanadium than condition I, but the ratio of Mg/V...

NbxAlyNz thin films were deposited by magnetron sputtering reactive technique with (y/x+y) ratio varying from 0 to 0.4, in order to maintain aluminum atoms inside NbN matrix in solid solution. GAXRD analyses revealed that the crystalline phase obtained for NbxAlyNz thin films was B1-NbN with a lattice constant shrinkage as Al concentration at these...

A high surface area activated carbon was obtained from sugar cane straw by chemical activation with phosphoric acid and was used for the first time as a support for vanadium catalysts. This work aims to investigate the vanadium oxide species in a low surface density (up to 1 V atom nm⁻²) on this new support, especially applied to propane oxidation...

The dehydration of fructose to 5-hydroxymethylfurfural (HMF) is a way to produce a very versatile intermediate of the green chemistry. Heteropolyacid compounds are acid catalysts with singular properties (strong acidity and well-defined structure). This paper aims to analyze the activity of phosphotungstic acid (HPW) and Cs-exchanged phosphotungsti...

The 1-butyl-3-methylimidazolium chloride ionic liquid was employed as a structure-directing agent for the preparation of TiO2-TON zeolites under different crystallization conditions. By varying the crystallization parameters (i.e., time, structure-directing agent, and TiO2 content), the ionic liquid was determined to be a powerful structure-directi...

Activated carbon from sugarcane residues, bagasse and straw was obtained with phosphoric acid activation. All samples were characterized by N2 adsorption-desorption isotherm, scanning electron microscopy, coupled with energy dispersive microscopy, X-ray photoelectron spectroscopy and thermal analysis. The advantages of using a ball or hammer millin...

In order to produce gasoline directly from syngas, HZSM-5 can be added to the Fischer-Tropsch catalyst. However, this catalytic system shows an important deactivation rate. Aiming at describing this phenomenon, Fe-based catalysts and physical mixtures containing these catalysts and HZSM-5 were employed in this reaction. All these systems were chara...

Using ab initio calculations based on density functional theory (DFT), we propose a geometrical structure for MoOx monolayers recently grown on O/Cu3Au(1 0 0) substrates. The proposed structure reproduces the p(2 × 2) symmetry found by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED), as well as the intermediate oxidat...

Previous studies on the use of SO2 and CO2 as impregnating agent for sugar cane bagasse steam treatment showed comparative and promising results concerning the cellulose enzymatic hydrolysis and the low formation of the inhibitors furfural and hydroxymethylfurfural for the use of CO2 at 205°C/15 min or SO2 at 190°C/5 min. In the present study sugar...

Ternary physical mixtures comprised a Fischer–Tropsch catalyst, a methanol synthesis catalyst and a zeolite employed in the hydrocarbon synthesis from syngas. Two Fe-based catalysts (i.e., one promoted by K and the other by Ru), two HY zeolites with different acidities, a commercial HZSM-5 and Cu/ZnO/Al2O3 (methanol synthesis catalyst) were used in...

The direct synthesis of ethyl acetate from ethanol, a renewable raw material, was studied using PdO/SiO2 catalysts and the oxidative route. These catalysts were prepared by ionic exchange and also by impregnation. They were characterized by XPS, UV–vis, XRD, chemical analysis and BET. These catalysts were tested under different experimental conditi...

We present the preparation, characterization and catalytic evaluation of gold-based catalysts over Al2O3, ZrO2 and 10% ZrO2/Al2O3 in selective CO oxidation. Oxidation and reduction pretreatments were evaluated using in situ X-ray diffraction, and the size of gold particles was determined. All catalysts contained gold particles in the range of 2–5 n...

The goal of this work is to prepare well-ordered molybdenum oxide films using oxygen implanted Cu3Au(100) substrate (CAOS, Cu3Au–Oxygen Substrate) and identify the structure of the different oxide phases. Those films were grown on an UHV chamber (2×10−10mbar background pressure) and prepared by electron beam deposition. The structure of the films w...

The kinetics of the Fischer-Tropsch reaction over a Co/Nb2O5 catalyst in a fixed bed reactor was investigated experimentally. Experiments were carried out under isothermal and isobaric conditions (T=543 K, P=2.1 MPa) and under different conditions of several H2/CO feed molar ratio (0.49–4.79), space velocities (0.2–3.8 h−1), mass of catalyst (0.3–1...

A series of Co/x%Nb2O5/Al2O3 catalysts were prepared by anchoring niobia on an Al2O3 support at different niobia concentrations. Characterization of the structure and nature of surface active sites was attempted in order to correlate the CO hydrogenation activity of these systems with those of the Co/Al2O3 and Co/Nb2O5 catalysts. The effect of the...

Cobalt was deposited by physical vapor deposition onto thin well-ordered niobia films in order to model niobia supported Co catalysts. Adsorption of CO on the Co/niobia surfaces was studied by temperature programmed desorption and infrared reflection absorption spectroscopy. Structural characterization was performed by photoelectron spectroscopy an...

Combining low energy electron diffraction, scanning tunneling microscopy, angular resolved photoelectron spectroscopy using synchrotron radiation and density functional theory calculations, we have studied the structure of thin niobia films grown on a Cu3Au(1 0 0) substrate. Nb deposition onto oxygen implanted Cu3Au(1 0 0) and subsequent oxidation...

This study involves the characterization of a series Co/x% Nb2O5/Al2O3 catalysts.The temperature-programmed surface reaction technique (TPSR) and in situ diffuse reflectance spectroscopy (DRS) results have shown a transient behavior of the catalysts, distinguishing very well the Co/Al2O3 from the Co/Nb2O5·Al2O3 catalysts.DRS and temperature-program...

Co/Nb2O2, Co-Ru/Nb2O5 and Co-Re/Nb2O5 catalysts were prepared and characterized by TPR. The catalysts were investigated on CO hydrogenation under 0.4, 2 and 4Mpa. The total pressure has an important effect on the product distribution. The selectivity toward diesel and C5+ hydrocarbons achieves a maximum at reaction pressure of 2.0Mpa. The catalysts...

Nickel supported species obtained by impregnation of Ni(acac)2 onto faujasite zeolite (NaX and NaY) were identified by XPS and the influence of the nature of the support has been correlated with the location of the species in/on the zeolite. In the case of NaX two species are formed, one characterized by binding energy of 856.3 eV and ascribed to N...

Ammonium oxalate complex of niobium was investigated as an aqueous precursor for the preparation of x% Nb2O5/Al2O3 (x=5, 10, 20 and 30wt.%) samples. Catalysts with the same Nb2O5 contents were also prepared from the traditional niobium oxalate/oxalic acid aqueous solution. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflect...

This chapter presents ethylene oligomerization with nickel-containing NaX zeolite. Nickel complex-containing zeolite materials Ni(MeCN)6(BF4)2/NaX and Ni(acac)2 have been prepared and characterized by X-Ray photoelectron spectroscopy (XPS). These materials are catalytically active for ethylene dimerization and 1-butene isomerization. The supported...

The promoting effect of Ru and Re addition to Co/Nb2O5 catalyst in the Fischer-Tropsch Synthesis was studied. The catalysts were characterized by TPR, XRD and H2 chemisorption. The Re and Ru addition increased both the activity and the C5+ selectivity by different mechanisms. Re prevented the cobalt agglomeration whereas Ru increased the Co° site d...

The hydrogenation of CO over Co/Nb2O5, Co/Al2O3 and niobia-promoted Co/Al2O3 catalysts was investigated after H2 reduction at 573 and 773K. The Co/5%Nb2O5/Al2O3 catalyst did not present strong metal support interaction after reduction at 773K. However, the increase of Nb2O5 content (Co/20%Nb2O5/Al2O3) changed the selectivity of CO hydrogenation, pr...

RhCu supported on alumina were selected for the dehydrogenation of cyclohexanol. Highly dispersed RhCu supported on alumina were obtained and characterized after reduction. The metallic surface area was determined by frontal H2 chemisorption and by N2O decomposition followed by TPR. The TPR method for surface oxide reduction after exposing the cata...

In this first part, we examined the structure and morphology of catalysts with low metal contents, which have been used in cyclohexanol dehydrogenation. The catalysts were prepared by successive wet impregnation after intermediate calcination. They were characterized by TPR, DRS, XPS, XRD and CO FT-IR in the oxide form. The results indicate a high...