M. J. B. Souza

Textural Properties of Nickel, Palladium and Titanium Oxides Supported on MCM‑41 Materials and Their Application on Oxidative Desulfurization of Dibenzothiophene

Textural and catalytic properties of nickel, palladium or titanium oxides supported on MCM-41 materials were evaluated in this paper. The results indicated that the MCM-41 material with well defined and highly ordered hexagonal structure was obtained. After metal ions impregnation and calcinations, the structure of MCM-41 was preserved and formed metallic oxide particles, however the decreased of surface area of these structures occurred. The catalysts studied showed maximum conversion levels of dibenzothiophene in the range of 50-65%.

Synthesis, structure, and morphology of bifunctional catalysts based on zirconia modified by molybdenum oxide

The preparation of Pt/MoOx-ZrO2 materials has been carried out by polymeric precursor method and with molybdenum loadings in the range 10–20 wt %. The synthesized samples were calcined at 600, 700, and 800°C. The structure and texture of the calcined Pt/MoOx-ZrO2 materials were characterized by x-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy, and N2 adsorption measurements. XRD of the calcined samples revealed the formation of crystalline ZrO2, Pt metal, and Zr(MoO4)2. Crystalline Zr(MoO4)2 was also detected by FTIR spectra. A decrease in the specific surface area was observed by nitrogen adsorption experiments when the temperatures of calcination and molybdenum loading increased.

Effect of the Acid Treatment of Montmorillonite Clay in the Oleic Acid Esterification Reaction

, several solid catalysts have been studied for the production of biodiesel. In this scenario there are the clays, especially those of the smectite group, because it is a natural raw material, abundant in nature, easy operation and excellent physicochemical properties. These clays in their natural form do not have the appropriate properties acidic esterification process and, therefore, have not been studied for this purpose. However, suitable acid treatments can make these solid potential catalysts for biodiesel production by esterification route. Thus, in the present work, montmorillonite clay was treated with sulfuric acid at different concentrations to obtain a material with higher acidity and applied in the oleic acid esterification reaction. The treatment process with sulfuric acid was used because it is a relatively cheap and simple process.

Preparation and characterization of Pt-dealuminated Y zeolite by TG/DTA and TPR

Monometallic catalysts containing Pt supported on dealuminated Y zeolite were prepared by impregnation with a solution containing H2PtCl6·6H2O cationic complexes. The catalysts were calcined and characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), simultaneous thermogravimetry/differential thermal analysis (TG/DTA), temperature programmed reduction, physisorption of nitrogen, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The XRD results showed that zeolite Y maintained its crystalline structure throughout the dealumination and metal incorporation processes. However, the relative crystallinity of the various samples was reduced upon impregnation. Furthermore, the XRD diffractograms, the SEM and TEM micrographs, and EDX spectra for the impregnated samples presented evidence for the presence of Pt oxides. The adsorption isotherms of the nitrogen physisorption showed the existence of micropores and mesopores within the Pt/Y zeolite. Temperature programmed reduction profiles suggest that the reduction temperature of Pt depends on the location of the metal within the zeolitic structure. The reduction peaks can be attributed to cations located in the large cavities, sodalite cages, or hexagonal prisms. The TG/DTA analyses showed the endothermic decomposition of the Pt complexes deposited on the zeolite during impregnation.

Yield of aromatics from naphthenics upon catalytic cracking

Cis- and trans-decalin were reacted over cracking catalysts to study the formation of aromatics in a particular fraction of the liquid products obtained in the fluid catalytic cracking process (FCC). A batch, fluidized bed CREC riser simulator reactor was used at 673 and 723 K and contact times varied from 3 to 15 s. Cis-decalin was much more reactive. Despite differences induced and measured in their accessibility indices, the catalysts led to similar activity profiles, suggesting that diffusion restrictions do not prevail. Products were C1-C12 hydrocarbons while coke was very low. Isomerization, cracking, hydrogen transfer, ring opening, ring contraction and alkylation reactions occurred and products from the various reactions were observed at very short reaction times. Bicyclic C10 naphthenics and alkyl-substituted C7-C11 aromatics or naphtheno-aromatics were the most important products. A reaction mechanism with three initial routes (isomerization, ring opening and direct hydrogen transfer reactions) was proposed.

Síntese e caracterização de materiais mesoporosos modificados com níquel para a captura de CO2

SBA-15 and MCM-48 mesoporous materials were successfully synthesized by the hydrothermal method and impregnated with nickel in proportions of 5-20 wt.% aiming to capture CO2. The materials were characterized by X-ray diffraction analysis, N2 adsorption and scanning electron microscopy. CO2> capture tests were conducted at pressures between 100 and 4000 KPa at a constant temperature of 298 K and showed that the adsorption capacities vary significantly with the textural properties of these materials with different contents of nickel, reaching maximum values of 14.89 and 9.97 mmol g-1 for MCM-48 and SBA-15, respectively.

Synthesis of LaNiO3 perovskite by the modified proteic gel method and study of catalytic properties in the syngas production

This work describes a study on the synthesis of LaNiO3 perovskites via the modified proteic gel method, varying collagen content and on the catalytic activity of LaNiO3 and LaNiO3/Al2O3 in the syngas (CO + H2) production. X-ray diffraction patterns revealed the formation of perovskite structure in all samples prepared by proteic gel synthesis method, varying collagen content and after calcinations at 700 oC for 2 h. LaNiO3/Al2O3 catalyst prepared by the impregnation method showed diffraction peaks due to the perovskite structure and to the support (Al2O3). This catalyst presented: specific surface of 46.1 m2 g-1, two reduction peaks in the temperature programmed reduction (TPR) profile and 46% of methane conversion (by the partial oxidation of methane using oxygen) after 18 h of reaction.

Determination of the acidity of MCM-41 with different Si/Al ratios by the temperature programmed Desorption of Pyridine

Mesoporous catalysts of MCM-41 type with different Si/Al ratios were synthesized by the hydrothermal method and characterized by X-ray diffraction, nitrogen adsorption and thermogravimetric analysis. Their acidic properties were determined via the temperature programmed desorption of pyridine. Vyazovkin kinetic models were used to correlate the total acidity as a function of the Si/Al ratio with the apparent activation energy for pyridine desorption. The results obtained indicated that the catalysts possessed weak and medium acidic sites. An increase in the Si/Al ratio led to an increase in the activation energy for pyridine desorption.

Catalytic cracking of isopropylbenzene over hybrid HZSM-12/M41S (M41S = MCM-41 or MCM-48) micro-mesoporous materials

ABSTRACT The catalytic cracking of isopropylbenzene was investigaded over hybrid ZSM-12/MCM-41 and HZSM-12/MCM-48 micro-mesoporous materials, in order to verify the effect of the acid site of the accessibility of mesoporous channels combined with the acid sites into the zeolite. The hybrid materials were synthesized by the hydrothermal method using the template mechanism. The obtained materials were characterized by X-ray diffraction and BET isotherms using nitrogen adsorption-desorption at 77 K. The X-ray diffraction patterns presented characteristic peaks of the microporous and mesoporous phases. These analysis revealed the formation of ordered hexagonal MCM-41 or cubic MCM-48 mesoporous phases, associated with the ZSM-12 structure. In order to generate acid sites, the materials were ion exchanged with ammonium chloride solution. The calcined hybrid materials were tested as catalyst for cracking of isopropyl-benzene, using a fixed bed reactor at 450 oC and nitrogen gas. The catalytic tests showed that the HZSM-12/AlMCM-41 and HZSM-12/MCM-48 hybrid materials have potential for use in cracking reactions, bening more active than the zeolite or the M41S alone. The catalytic activities of the hybrid materials can be associated with a synergistic effect between the acid sites present on the zeolitic phase and the mesoporous phase. In order to verify how the structure of the hybrid materials may affect and control their catalytic performances, the results were compared with HZSM-12 physically mixed with MCM-41 and MCM-48.

Oxidative desulfurization of thiophene on TiO2/ZSM-12 zeolite

In this work the hydrothermal synthesis of ZSM-12 zeolite was performed, varying the MTEACl/SiO2 ratio, where the synthesis temperature was 140 oC and the crystallization time was 144 hours. The catalysts were characterized by XRD, FTIR and TG. TiO2/ZSM-12 catalysts were used with titanium ions concentrations of 5, 10 and 15%. The oxidative desulfurization (ODS) reactions were performed using a model mixture containing n-heptane as solvent and thiophene as sulfur compound, H2O2 as an oxidizing agent, and acetonitrile as an extractor solvent at reaction temperatures of 30, 50 and 70 oC. The obtained results shows that TiO2/ZSM-12 with 15% of Ti catalyst has a better performance in the ODS reaction converting thiophene at about 60%.