Marcelo J. B. Souza

Synthesis, characterization and catalytic application of cerium-modified MCM-41

The nanostructured CeMCM-41 material was synthesized by the hydrothermal method, using cethyltrimethylammonium bromide as template. The sample was characterized by X-ray diffraction, energy-disperse X-ray, thermogravimetry, nitrogen adsorption isotherm and pore size distribution. The specific surface area of CeMCM-41 was equivalent to 850 m 2 g -1 , with the pore width and mesopore volume of 3.8 nm and 0.8 cm 3 g -1 , respectively. To evaluate the catalytic performance of the CeMCM-41, a mass of ca. 0.1 g was heated from room temperature up to 723 K at heating hate of 10°C min -1 using oxygen flowing at 50 ml min -1 . The CeMCM-41 was tested as catalyst for n-heptane oxidation, in a fixed-bed continuous-flow reactor, at 723 K and F/W ratio (molar flow of reactant per mass of catalyst) of 0.4-0.6 g h mol -1 . The obtained products were analyzed in a gas chromatograph coupled to a mass spectrometer. The GC-MS analysis revealed that the main oxidation products obtained were typically CO and CO 2 , with 12% of hydrocarbon conversion.

Systems involving cobalt and cerium oxides: characterization and catalytic behavior in the C6–C7 n-alkanes combustion

Abstract The objective of this work is to report the characterization and catalytic behavior of Co3O4, CeO2, and Co3O4–CeO2 catalysts in the C6–C7 n-alkanes combustion. X-ray diffraction indicated that crystalline oxides of Co3O4 and CeO2 are obtained by heat treatment at temperatures higher than 600xa0°C. The FTIR spectra are characteristic of cobalt and/or cerium oxides. The reactions were processed in a fixed bed continuous flow reactor, at 450xa0°C varying F/W ratio and n-alkanes. The results obtained showed that the catalysts give good activity in the C6–C7 n-alkanes combustion with high selectivity to carbon dioxide.

Kinetic study of isopropanol dehydration over silicoaluminophosphate catalyst

The catalytic dehydration of isopropanol has been studied over a solid acid silicoaluminophosphate type SAPO-5. The reaction was processed varying the temperature and weight hourly space velocity, using a fixed bed continous flow reactor. The isopropanol undergoes inter- and intramolecular dehydration, forming propylene and isopropyl ether, respectively. Nevertheless, the catalyst was selective to the olefin, with an activation energy of the order of 46.1 kJ/mol.

m-Xylene Isomerization in SAPO-11/HZSM-5 Mixed Catalyst

The catalytic isomerization of m-xylene was studied over a solid acid silicoaluminophosphate type SAPO-11, mixed to HZSM-5 zeolite. The reaction was processed varying the temperature and weight hourly space velocity, using a fixed bed continuous flow reactor. The m-xylene suffers isomerization to p-xylene and o-xylene by molecular displacement of methyl groups. The mixed catalyst was selective to p-xylene at 623 K and 2.5 h−1 with a maximum p/o ratio of 2.05. The ethylbenzene formation was not observed in the products. In this process an apparent activation energy of the order of 13.9 kJ mol−1 was obtained.

Hydrothermal synthesis and thermal characterization of niobium-aluminophosphate with AEL structure ☆

Abstract Niobium-aluminophosphate materials with AEL structure (NbALPO-11) were prepared by hydrothermal method, using pseudoboehmite, phosphoric acid, hydrated niobium oxalate, water and di-isopropylamine. The obtained materials were characterized by X-ray fluorescence, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, thermogravimetry and measurements of acidity. From the X-ray diffraction it was confirmed that niobium was incorporated in the framework at low Nb concentration. The obtained NbALPO-11 presented acidity of weak and medium strength, as verified by n -butylamine desorption. The characterization of the catalytic active sites was carried out by isopropanol dehydration at a temperature of 400°C, and space velocities of 1.6, 3.2, 4.8, 6.4 and 8.0 h −1 . The materials were active for this process where the main products were propene and di-isopropyl ether.

Hydrodesulfurization of thiophene over coblat and molybdenum sulfides supported on MCM-41 materials

In this work was studied the potential application of molybdenum suphides supported on SiMCM-41 and A1MCM-41 materials in the thiophene hydrodesulfurization. The SiMCM-41 and AIMCM-41 materials were synthesized by hydrothermal method using cethyltrimethylammonium bromide as template. The deposition of the active HDS species was performed by solvent excess impregnation of ammonium tetrathiomolybdate salt over the supports followed by calcination. Cobalt was used as promoter in order to obtain a Co/(Co+Mo) atomic ratio of 0.3. The materials presented activity in thiophene HDS.

n-Heptane oxidation over co3o4-ceo2 catalyst

The present study reports the catalytic behavior of Co3O4-CeO2 in the oxidation of n-heptane. The results obtained showed that the catalyst give good activity in n-heptane oxidation with high selectivity to carbon dioxide.

Fischer-Tropsch synthesis over Co/SiMCM-41 and Co/SiO2 materials: The role of support at different cobalt loadings

The conversion of synthesis gas to liquid products via Fischer-Tropsch synthesis (FTS) is an important process in the generation of clean fuels of sulfur and nitrogen compounds. Catalysts based on iron are very used in the conventional process due its cheap manufacture price. Recently the use of cobalt as promoter gave good results. In this work are presented new alternatives for FTS with the use of cobalt supported on molecular sieves of the type MCM-41. A comparative study with the usual catalysts based on silica was accomplished with different levels of cobalt.

Catalytic cracking of C5+ gasoline over hy zeolite

The catalytic conversion of a C5+ natural gasoline over the HY zeolite has been studied. The results show the formation of C2, C3 and C4 hydrocarbons with an apparent activation energy of ca. 39 kJ mol-1.

Synthesis, Characterization and Catalytic Properties of NBALPO-11

Niobium containing aluminophosphate materials with AEL structure were prepared by the hydrothermal method. The chemical composition of the hydrogel was: 1 DIPA: 1 Al2O3: (1-x) P2O5: x Nb2O5: 80 H2O, with x=0.025, 0.050, 0.075 and 0.100. The crystallization was carried out at temperature of 170°C for 72 h. The materials obtained were characterized by XRF, DRX, FTIR, TG and measurements of acidity. The characterization of the catalytic active sites were carried out in the isopropanol dehydration at temperature of 400°C, and WHSV of 1.6, 3.2, 4.8, 6.4 and 8.0 h-1 . The samples showed good catalytic activity with selectivity to propene.