Navegando por Autor "Araujo, Antonio S."
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Artigo Development of HZSM-5/AlMCM-41 hybrid micro–mesoporous material and application for pyrolysis of vacuum gasoil(Elsevier, 2013-05) Coriolano, Ana Catarina F.; Silva, Cristiano G.C.; Costa, Maria J. F.; Pergher, Sibele Berenice Castellã; Caldeira, Vinícius P. S.; Araujo, Antonio S.The pyrolysis of vacuum gasoil (VGO) was studied alone and in presence of HZSM-5/AlMCM-41 hybrid catalyst. This micro–mesoporous material was synthesized by the hydrothermal method using dual templates of tetrapropilamonium and cetyltrimethylammonium ions at different crystallization times. The obtained materials were washed and calcined for remotion of the organic templates. The characterization by X-ray diffraction, nitrogen surface area by the BET method, scanning and transmission electron microscopies, evidenced that typical MFI structure was embedded into the bulk of the MCM-41 matrix, in order to obtain the hybrid micro–mesoporous phase. The protonic form of the material was obtained by ion exchange with ammonium chloride solution and subsequent thermal treatment. The total acidity, as determined by n-butylamine adsorption, was equivalent to 0.75 mmol g−1, in the temperature range of 300–500 °C, corresponding to strong acid sites. For catalytic reaction, a physical mixture of 10% of catalyst/VGO was decomposed in a thermobalance at heating rates of 5; 10 and 20 °C min−1, from 100 to 550 °C. From TG/DTG data, applying the model-free kinetics, it was observed that the activation energy for the pyrolysis of VGO alone was ca. 125 kJ mol−1. For VGO physically mixed to both AlMCM-41 and HZSM-5, the value decreased to ca. 80–90 kJ mol−1, whereas for the hybrid, the value was the lowest, ca. 65 kJ mol−1, evidencing the efficiency of the combined effect of the acid sites, crystalline phase and microporosity of ZSM-5 zeolite with the accessibility of the mesoporous of the AlMCM-41 ordered material. For determination of the catalytic properties, the samples of VGO and catalyst/VGO were submitted to pyrolysis-GC–MS system at 500 °C using helium as gas carrier. The VGO alone suffers decomposition to a wide range of hydrocarbons, typically C17–C41, while in the presence of catalyst, light fraction of hydrocarbons, in the range of liquefied petroleum gas (C3–C5), gasoline (C6–C10) and diesel (C11–C16) were obtained, evidencing that the HZSM-5/AlMCM-41 hybrid material is an effective catalyst for pyrolysis of VGO.Artigo Influencia da ativaçao acida na estabilidade termica de hibridos vermiculita/epoxido(ABRATEC, 2010-04) Alves, Ana Paula de Melo; Germano, Ana Fernanda de S.; Arakaki, Luiza N. H.; Fonseca, Maria G. da; Araujo, Antonio S.Artigo Porous materials obtained by acid treatment processing followed by pillaring of montmorillonite clays(Elsevier, 2013-11) Bieseki, Lindiane; Treichel, Helen; Araujo, Antonio S.; Pergher, Sibele Berenice CastellãMontmorillonite clay was treated with hydrochloric acid and subsequently pillared with aluminum polyoxocations. The acid-treated samples were evaluated for the removal of structural elements (Al, Fe and Mg) and for conservation of the lamellar organization. The more severe the treatment, the greater the specific area obtained. Despite the loss of structural organization, all samples were pillared, with a displacement of peak (001) to 2θ lower angles. The pillaring of all acid-treated samples promoted an increase in the specific area of these materials. Pillared samples previously treated at 50 °C with HCl concentrations of 2 and 4 mol L− 1 underwent an increase in their specific areas of approximately 45%. Pillared samples treated with 4 mol L− 1 of HCl at 80 °C underwent the lowest percent increase in surface area, approximately 10%, compared to the untreated samples. All samples possessed greater uniformity in pore size. Acid treatment prior to pillaring promoted an increase in the number of acid sites of moderate strength compared to pillared natural clay.Artigo Use of a low-cost template-free ZSM-5 for atmospheric petroleum residue pyrolysis(Scielo, 2016-04) Pergher, Sibele Berenice Castellã; Caldeira, Vinícius P. S.; Santos, Anne G. D.; Costa, Maria J. F.; Araujo, Antonio S.To understand the physicochemical properties and catalytic activity during the pyrolysis of atmospheric petroleum residue, a templatefree ZSM-5 zeolite was synthesized using a direct method without additional seeds or an organic structure director and compared with conventionally synthesized ZSM-5. The crystallinities of the two zeolites were evaluated by XRD and FTIR and were quite similar; however, structural analyses using SEM and argon physisorption revealed that the zeolites diverged in particle diameter and in the external surface area of the micropores. The synthesis procedure without a template incorporated additional aluminum into the crystalline network, according to ICP-AES and TPD NH3 experiments. The catalytic pyrolysis performed over the template-free ZSM-5 generated results comparable to those for pyrolysis performed over the conventional ZSM-5 according to its hydrocarbon distribution. The selectivity to aromatics compounds was exactly the same for both ZSM-5 zeolites, and these values stand out compared to thermal pyrolysis. The template-free ZSM-5 produced 20% of light hydrocarbons (C4-C6), where such compounds are olefins and paraffins of great interest to the petrochemical industry. Therefore, template-free ZSM-5 is promising for industrial use due to its lowered synthesis time, low-cost and significant distribution to light hydrocarbons